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WO2025101977A1 - Transmissions à poulies inversées, barbotin et configurations planétaires - Google Patents

Transmissions à poulies inversées, barbotin et configurations planétaires Download PDF

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Publication number
WO2025101977A1
WO2025101977A1 PCT/US2024/055233 US2024055233W WO2025101977A1 WO 2025101977 A1 WO2025101977 A1 WO 2025101977A1 US 2024055233 W US2024055233 W US 2024055233W WO 2025101977 A1 WO2025101977 A1 WO 2025101977A1
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WO
WIPO (PCT)
Prior art keywords
belt
transmission
segments
axis
segment
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/US2024/055233
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English (en)
Inventor
Thomas Libby
Riley SHEAR
Murphy BRASCO-KITCHELL
Elaine LOWINGER
Scott SCHERAGA
Alexander KERNBAUM
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
SRI International Inc
Original Assignee
SRI International Inc
Stanford Research Institute
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Filing date
Publication date
Application filed by SRI International Inc, Stanford Research Institute filed Critical SRI International Inc
Publication of WO2025101977A1 publication Critical patent/WO2025101977A1/fr
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H7/00—Gearings for conveying rotary motion by endless flexible members
    • F16H7/02—Gearings for conveying rotary motion by endless flexible members with belts; with V-belts
    • F16H7/023—Gearings for conveying rotary motion by endless flexible members with belts; with V-belts with belts having a toothed contact surface or regularly spaced bosses or hollows for slipless or nearly slipless meshing with complementary profiled contact surface of a pulley
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16G—BELTS, CABLES, OR ROPES, PREDOMINANTLY USED FOR DRIVING PURPOSES; CHAINS; FITTINGS PREDOMINANTLY USED THEREFOR
    • F16G5/00—V-belts, i.e. belts of tapered cross-section
    • F16G5/16—V-belts, i.e. belts of tapered cross-section consisting of several parts
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16G—BELTS, CABLES, OR ROPES, PREDOMINANTLY USED FOR DRIVING PURPOSES; CHAINS; FITTINGS PREDOMINANTLY USED THEREFOR
    • F16G5/00—V-belts, i.e. belts of tapered cross-section
    • F16G5/20—V-belts, i.e. belts of tapered cross-section with a contact surface of special shape, e.g. toothed
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16G—BELTS, CABLES, OR ROPES, PREDOMINANTLY USED FOR DRIVING PURPOSES; CHAINS; FITTINGS PREDOMINANTLY USED THEREFOR
    • F16G7/00—V-belt fastenings
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H55/00—Elements with teeth or friction surfaces for conveying motion; Worms, pulleys or sheaves for gearing mechanisms
    • F16H55/02—Toothed members; Worms
    • F16H55/17—Toothed wheels
    • F16H55/171—Toothed belt pulleys
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H55/00—Elements with teeth or friction surfaces for conveying motion; Worms, pulleys or sheaves for gearing mechanisms
    • F16H55/32—Friction members
    • F16H55/52—Pulleys or friction discs of adjustable construction
    • F16H55/56—Pulleys or friction discs of adjustable construction of which the bearing parts are relatively axially adjustable
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H9/00—Gearings for conveying rotary motion with variable gear ratio, or for reversing rotary motion, by endless flexible members
    • F16H9/02—Gearings for conveying rotary motion with variable gear ratio, or for reversing rotary motion, by endless flexible members without members having orbital motion
    • F16H9/04—Gearings for conveying rotary motion with variable gear ratio, or for reversing rotary motion, by endless flexible members without members having orbital motion using belts, V-belts, or ropes
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H9/00—Gearings for conveying rotary motion with variable gear ratio, or for reversing rotary motion, by endless flexible members
    • F16H9/02—Gearings for conveying rotary motion with variable gear ratio, or for reversing rotary motion, by endless flexible members without members having orbital motion
    • F16H9/04—Gearings for conveying rotary motion with variable gear ratio, or for reversing rotary motion, by endless flexible members without members having orbital motion using belts, V-belts, or ropes
    • F16H9/12—Gearings for conveying rotary motion with variable gear ratio, or for reversing rotary motion, by endless flexible members without members having orbital motion using belts, V-belts, or ropes engaging a pulley built-up out of relatively axially-adjustable parts in which the belt engages the opposite flanges of the pulley directly without interposed belt-supporting members
    • F16H9/16—Gearings for conveying rotary motion with variable gear ratio, or for reversing rotary motion, by endless flexible members without members having orbital motion using belts, V-belts, or ropes engaging a pulley built-up out of relatively axially-adjustable parts in which the belt engages the opposite flanges of the pulley directly without interposed belt-supporting members using two pulleys, both built-up out of adjustable conical parts
    • F16H9/20—Gearings for conveying rotary motion with variable gear ratio, or for reversing rotary motion, by endless flexible members without members having orbital motion using belts, V-belts, or ropes engaging a pulley built-up out of relatively axially-adjustable parts in which the belt engages the opposite flanges of the pulley directly without interposed belt-supporting members using two pulleys, both built-up out of adjustable conical parts both flanges of the pulleys being adjustable

Definitions

  • a transmission may be included to match properties of a motor, engine, turbine, or other torque generator (e.g., a torque-speed curve, an efficiency curve) to properties of an effector, a wheel, a generator, or some other intended application for a generated torque.
  • a transmission may be provided in an automobile to match the high rotational speed and relatively lower torque generated by an internal combustion engine to lower speed and higher torque requirements for driving the wheels of the automobile.
  • a transmission may be provided to couple an internal combustion engine to a generator such that both the internal combustion engine and the generator are operated according to respective efficient rotational speeds.
  • a transmission may have a set transmission ratio (the ratio of the rotation speed and/or applied torque at an input of the transmission to the rotation speed and/or delivered torque at an output of the transmission) or may have a controllable transmission ratio.
  • the transmission ratio of such a transmission may be controllable via electronic, mechanical, hydraulic, and/or other methodologies (e.g., via actuation of a clutch, slidable gear(s), split pulley, drum, turbine vane(s), hydraulic valve(s), or other elements of the transmission by a motor, solenoid, or other methodologies).
  • a transmission may have a discrete number of selectable transmission ratios (or “gears”) that can be selected by operating one or more clutches or other actuators.
  • a transmission may have a transmission ratio that is continuously controllable across a range of transmission ratios; such transmissions may be referred to as “continuously variable transmissions.”
  • Such variable transmissions may include split pulleys, toroidal drums, hydrostatic elements, or other actuatable components to permit continuous control of the transmission ratio across the range of transmission ratios.
  • CVTs Continuously variable transmissions
  • robotics variable gearboxes are rare.
  • High performance power electronics for motors reduce the need for ratio variation somewhat, but many applications can benefit from improved variable-ratio transmissions.
  • mobility applications e.g. bicycles, e-bikes, and motorscooters
  • Single speed approaches have typically low performance.
  • Multispeed discrete gearboxes in bicycles typically cannot be shifted under load, and often cannot be shifted while stopped.
  • multiple inner pulleys/sprockets can be arranged symmetrically or in some other arrangement to balance the masses thereof, reducing vibration or other effects that may accompany the use of a single inner pulley/sprocket.
  • Such multiple inner pulleys/sprockets can also be coupled to respective planet gears of a planetary gearset or other mechanism, allowing the achievable range of transmission ratios of a transmission to be set to a high ratio and/or tailored to a specific application.
  • These improvements additionally or alternatively include the use of a sprocket, rather than a pulley, to engage with the belt.
  • Such a sprocket includes a set of inward-facing teeth to engage with corresponding features of the belt (e.g., one or more teeth on each segment of a multi-segment belt).
  • the use of a sprocket, rather than a pulley, allows for increased efficiency (e.g., by reducing or avoiding slippage, wear, or other loss mechanisms that might occur when using pulleys).
  • an inner pulley/sprocket of the transmission could be coupled to a mechanism to control or otherwise adjust the eccentricity with which the inner pulley orbits the axis of rotation defined by an outer pulley of the transmission.
  • Transmission architectures described herein can accept radially inverted pulleys and belts while maintaining large transmission ratios and ratio ranges. Radially-inverted traction drives as described herein provide continuously variable ratios without complex and expensive belts (e.g., that include band packs or other elements configured to withstand tensile loads).
  • the belt of a transmission, coupling, or other mechanism as described herein may be configured in a variety of ways.
  • the belt is an A-belt configured to engage with the inward-facing teeth of an inverted sprocket.
  • the belt could be composed of a plurality of segments, each segment of which is configured to engage with a single tooth of the sprocket at a time.
  • the relative alignment of neighboring segments of such a multi-segment belt could be maintained by teeth formed in the side of such segments that are configured to engage with each other from segment to segment.
  • wires, flexures, or other straps could connect neighboring segments together to resist their moving out of alignment with each other.
  • Such straps could be disposed within channels or other features formed in the sides of the segments, allowing the segment to contact and engage with each other via rolling motion (e.g., substantially pure rolling motion) without exerting large compressive forces through the straps.
  • the straps of such a belt may be flexures formed as a piece with the belt segments.
  • neighboring belt segments may be coupled together by linkages, e.g., linkages coupled to respective belt segments at foci defined by elliptical rolling-motion contact surfaces of the segments via which the segments engage in rolling motion with each other and transmit compressive loads.
  • linkages e.g., linkages coupled to respective belt segments at foci defined by elliptical rolling-motion contact surfaces of the segments via which the segments engage in rolling motion with each other and transmit compressive loads.
  • Such improved multi-segment belts may be employed in an inverted transmission, coupling, or other mechanism (e.g., a mechanism as described herein) or in some other mechanism wherein it is desirable to maintain an alignment between segments of a multi- segment push-belt or other variety of multi-segment belt configured to transmit compressive forces along its length.
  • a transmission in a first aspect, includes: (i) a first split pulley rotatable about a first axis and including first and second half-pulleys; (ii) a second split pulley rotatable about a second axis and including third and fourth half-pulleys; (iii) an outer member defining a third axis, wherein the first split pulley and second split pulley are nested within the outer member; (iv) a first belt that is in contact with the first split pulley and the outer member, wherein a couple between the first and second half-pulleys exerts forces onto the first belt that are radially directed inward toward the first axis, and wherein the outer member exerts forces onto the first belt that are radially directed inward toward the third axis; and (v) a second belt that is in contact with the second split pulley and the outer member, wherein a couple between the third and fourth half-pulleys exerts forces onto
  • a transmission in a second aspect, includes: (i) a split pulley defining a first axis and including first and second half-pulleys; (ii) a sprocket defining a second axis and including a plurality of inward-facing teeth, wherein the split pulley is nested within the sprocket; and (iii) a belt, wherein the belt is in contact with the split pulley and the sprocket, wherein a couple between the first and second half-pulleys exerts forces onto the belt that are radially directed inward toward the first axis, and wherein the sprocket exerts forces onto the belt that are radially directed inward toward the second axis.
  • a transmission in a third aspect, includes: (i) a first sprocket rotatable about a first axis and including a first plurality of inward-facing teeth; (ii) a second sprocket rotatable about a second axis and including a second plurality of inward-facing teeth; (iii) an outer member defining a third axis, wherein the first sprocket and second sprocket are nested within the outer member; (iv) a first belt that is in contact with the first sprocket and the outer member, wherein the first sprocket exerts forces onto the first belt that are radially directed inward toward the first axis, and wherein the outer member exerts forces onto the first belt that are radially directed inward toward the third axis; and (v) a second belt that is in contact with the second sprocket and the outer member, wherein the second sprocket exerts forces onto
  • a transmission belt that includes a plurality of belt segments, wherein each belt segment of the transmission belt engages with neighboring segments of the transmission belt via contact surfaces shaped such that the belt segments engage with each other via rolling motion along the contact surfaces, wherein the plurality of belt segments include a first belt segment and a second belt segment, wherein the first and second belt segments include respective pluralities of geared teeth that are configured to oppose the first and second belt segments engaging with each other via non-rolling motion along the contact surfaces of the first and second belt segments.
  • a transmission belt that includes: (i) a plurality of belt segments, wherein each belt segment of the transmission belt engages with neighboring segments of the transmission belt via contact surfaces shaped such that the belt segments engage with each other via rolling motion along the contact surfaces; (ii) a first linkage; and (iii) a second linkage, wherein the plurality of belt segments include a first belt segment, a second belt segment, and a third belt segment, wherein the contact surface of the first belt segment defines a first focus and a second focus, wherein a first end of the first linkage is rotatably coupled to the first belt segment at the first focus and a second end of the first linkage is rotatably coupled to the second belt segment, and wherein a first end of the second linkage is rotatably coupled to the first belt segment at the second focus and a second end of the second linkage is rotatably coupled to the third belt segment.
  • a transmission belt that includes a plurality of belt segments, wherein each belt segment of the transmission belt engages with neighboring segments of the transmission belt via contact surfaces shaped such that the belt segments engage with each other via rolling motion along the contact surfaces, wherein the plurality of belt segments include a first belt segment and a second belt segment, wherein the first and second belt segments are coupled together via at least two flexible straps that are configured to oppose the first and second belt segments engaging with each other via non-rolling motion along the contact surfaces of the first and second belt segments, and wherein the first and second belt segments are disposed within recesses formed in the first and second belt segments relative to the contact surfaces of the first and second belt segments BRIEF DESCRIPTION OF THE DRAWINGS [0018]
  • Figure 1 depicts cross-sectional views of elements of several example transmissions.
  • Figure 2 is a cross-sectional perspective view of elements of an example variable transmission.
  • Figure 3 depicts a cross-sectional view of elements of an example transmission.
  • Figure 4 depicts a cross-sectional view of elements of an example transmission.
  • Figure 5A is a cross-sectional view of elements of an example variable transmission.
  • Figure 5B is a cross-sectional view of elements of the example transmission shown in Figure 5A.
  • Figure 5C is a cross-sectional view of elements of the example transmission shown in Figure 5A.
  • Figure 5D is a photograph of elements of a physical model configured similarly to the example transmission shown in Figure 5A.
  • Figure 5E is another photograph of the elements of the physical model shown in Figure 5D.
  • Figure 5F is another photograph of a physical model that includes the elements shown in Figure 5D.
  • Figure 6 is a cross-sectional view of elements of a belt.
  • Figure 7 is a cross-sectional view of elements of a belt and transmission.
  • Figure 8A is a cross-sectional view of elements of a belt of an example transmission.
  • Figure 8B is a cross-sectional view of elements of the belt of the example transmission shown in Figure 8A.
  • Figure 8C is a cross-sectional view of elements of the belt of the example transmission shown in Figure 8A.
  • Figure 9A is a perspective view of a segment of a belt.
  • Figure 9B is a cross-sectional view of the segment shown in Figure 9A.
  • Figure 10A is a cross-sectional view of segments of a belt.
  • Figure 10B is another view of segments of the belt depicted in Figure 10A.
  • Figure 10C is a cross-sectional view of segments of a belt.
  • Figure 10D is a cross-sectional view of segments of a belt.
  • Figure 11 is a cross-sectional view of segments of a belt.
  • Figure 12 depicts experimental results, according to an example embodiment.
  • Figure 13 depicts experimental results, according to an example embodiment.
  • Belt-based transmissions or other mechanical couplings include two or more pulleys and/or sprockets that engage with at least one belt.
  • the mechanism may be referred to as a belt-and-pulley transmission.
  • the transmission ratio of such a transmission may be static or variable. Power is transmitted from one pulley/sprocket to another via a length of the belt that travels between the pulleys/sprockets. This power can be transmitted as a tensile force along the belt, or via compressive forces along the belt.
  • Pulleys of conventional belt-and-pulley transmissions, couplings, or other mechanisms engage with a belt by exerting forces onto the belt, via contact surfaces of the pulleys, that are radially directed ‘outward’ relative to the axis of the pulley rotation. That is, the forces directed onto the belt of such a transmission by a pulley of such a transmission have radial components (relative to the geometry of the pulley) that are directed outward, away from the axis of rotation of the pulley.
  • the belt For conventional transmissions that transmit power compressively via a push belt, the belt includes bands or other elements that are in tension in order to counter these ‘outward’ forces exerted onto the belt, which result in a net tensile force over portions of the length of the belt, thus keeping the belt engaged with the pulley.
  • Such compressive transmissions are often preferred over transmissions that transmit power via tensile forces.
  • the power capacity and lifetime of such compressive transmissions is often limited by the cost and complexity of push belts that are capable of withstanding the increased tension of high-power applications.
  • Improved transmissions described herein have ‘radially inverted’ pulleys that exert forces that are radially directed ‘inward,’ relative to the axes of the pulleys’ rotation, onto a compressive, push-type belt. That is, the forces directed onto the belt of such improved transmissions by a pulley thereof have radial components (relative to the geometry of the pulley) that are directed inward, toward from the axis of rotation of the pulley. Accordingly, the belts of such transmissions are not under tension of a magnitude similar to the magnitude of the power-transmitting compression forces.
  • Such belts can thus include band-packs (or other elements configured to resist tensile forces applied to the belt) exhibiting significantly reduced cost and complexity, or even omit such complex and expensive elements entirely.
  • the pulleys can be nested within each other or otherwise configured such that they at least partially overlap.
  • Elements of a first pulley of such a transmission (which may be a split-pulley to permit variation in the transmission ratio) can be located within or between elements of a second pulley, which is split to permit the overlapping configuration.
  • one or both of the axes of rotation of the pulleys of such a transmission could move relative to each other and/or to a mechanism or system of which they are a part.
  • the first pulley in such a transmission may engage in trochoidal motion within the transmission, rotating about an axis of rotation that, itself, orbits about a central axis of rotation of the transmission and/or of a second pulley at a specified distance from the central axis of rotation.
  • the first pulley of such a transmission could be driven by an input member (e.g., via an off-center cam), and power can be extracted from the first pulley via an offset shaft coupling or some other mechanism.
  • both pulleys could have offset axes of rotation that do not move relative to a mechanism or system of which they are a part (e.g., an outer pulley could have a very wide throat or other opening to permit an axle of an inner pulley to pass through).
  • Such transmissions can be further improved by using multiple belts, and corresponding multiple pulleys, to transmit forces/torques from an input (e.g., an input that drives the pulley as respective planets in a planetary gearset) to an output (e.g., a planet carrier or other rectifier mechanism).
  • the power capacity, torque capacity, lifetime, cost, or other properties of the transmission can be improved.
  • These benefits may result from the distribution of loads across multiple belts/pulleys, reduced vibration or other variable loads by arranging the two (or more) inner pulleys in a balanced configuration to center the mass of the inner pulleys, planet carrier, belts, and/or other central rotating elements of the transmission on a common axis of rotation of such elements, or other factors.
  • Such transmission can be additionally or alternatively further improved by replacing some or all of the pulleys thereof with sprockets or other toothed elements.
  • sprockets can include sets of inward-facing teeth to engage with a belt while also exerting inward-directed forces thereon. The use of sprockets instead of pulleys can lead to increased efficiency, increased device lifetime, and other benefits.
  • a multi-segment belt of such a transmission could be configured to engage with a sprocket such that each segment of the belt has a single tooth or other feature that engages with one or more teeth of the sprocket at a time.
  • the eccentricity with which inner pulleys/sprockets thereof orbit a central axis of rotation could be variable, allowing the transmission to adjust to changes in the effective diameter of one or more pulleys thereof without changing the length of the belt(s) or the effective diameter of the sprocket(s).
  • the belt could include wires, flexures, or other types of flexible strap that are capable of sustaining tensile forces and that connect from one belt segment to the next, resisting movement of the belt segments away from the specified alignment.
  • the belt segments can include teeth or other interlocking features that engage with neighboring segments to resist movements away from the specified alignment.
  • the belt can include linkages that connect, via axles, bearings, or other rotatable means, neighboring belt segments at or near foci defined by the elliptical contact surfaces thereof.
  • Example Transmissions and Components Thereof A variety of transmissions provide a static or variable transmission ratio between an input and an output by transmitting forces from one (or more) pulleys and/or sprockets to another pulley and/or sprocket via one or more belts that are in contact with both.
  • a first transmission 100a includes first 110a and second 120a pulleys.
  • a belt 130a wraps around the pulleys 110a, 120a.
  • Outward forces (illustrated by the arrows in Figure 1) exerted from the pulleys 110a, 120a onto the belt 130a (e.g., exerted from the first pulley 110a in a direction radially away from an axis of rotation 115a of the first pulley 110a such that a radial component of the exerted force, relative to the geometry of the pulley 110a, is directed outward, away from the axis 115a of the pulley 110a) allow the belt 130a to resist slipping on contact surfaces of the pulleys 110a, 120a, allowing power (torques and/or rotations) applied to one of the pulleys to be transmitted, via the belt 130a, to the other pulley.
  • One or both of the pulleys 110a, 120a could be split pulleys and configured to allow the axial separation between the halves of the split pulleys to be adjusted, thereby controlling the transmission ratio of the transmission 100a.
  • the lower half of Figure 1 illustrates the transmission 100a in cross-section through the plane of the belt 130a
  • the upper half of Figure 1 illustrates the transmission 100a in cross- section through a plane passing through the axis of rotation 115a of the pulley 110a and depicts only the first pulley 110a and the portion of the belt 130a in contact therewith.
  • the pulleys of a belt-and-pulley transmission can be nested or otherwise made to partially overlap with each other to provide a variety of benefits.
  • Such benefits can include reduced size, increased transmission ratios, smaller changes in the axial separation of split pulley halves effecting greater changes in the transmission ratio of the transmission (where the transmission is a variable transmission utilizing split pulleys to adjust its ratio), increased speed in shifting the transmission ratio, or other benefits relative to a non-overlapping configuration.
  • Such an overlapping transmission can include an ‘outer’ pulley that is split into two halves, to allow the elements of an ‘inner’ pulley to be located between the outer two halves, allowing the belt to contact both the inner and outer pulleys despite their overlapping with each other.
  • the pulleys of such a nested transmission may rotate about axes that are static (i.e., that do not move in space relative to a ground, housing, or other structural elements of the transmission).
  • the axis of rotation of one or both of the pulleys e.g., the inner pulley
  • the axis of rotation of the inner pulley could move.
  • the axis of rotation of the inner pulley could orbit about the axis of rotation of the outer pulley, such that the inner pulley engages in a trochoidal motion.
  • a second transmission 100b depicted in Figure 1 is an example of such a nested- pulley transmission.
  • the second transmission 100b includes first 110b and second 120b pulleys.
  • a belt 130b wraps around the pulleys 110b, 120b.
  • Outward forces (illustrated by the arrows in Figure 1) exerted from the pulleys 110b, 120b onto the belt 130b (e.g., exerted from the first pulley 110b in a direction away from an axis of rotation 115b of the first pulley 110b such that a radial component of the exerted force, relative to the geometry of the pulley 110b, is directed outward, away from axis 115b of the pulley 110c) allow the belt 130b to resist slipping on contact surfaces of the pulleys 110b, 120b, allowing power (forces and/or rotations) applied to one of the pulleys to be transmitted, via the belt 130b, to the other pulley.
  • One of the pulleys (e.g., 110b) could be split into two half-pulleys disposed opposite elements of the other one of the pulleys (e.g., 120b) to allow both pulleys to rotate and for the belt 130b to pass from the contact surfaces of one pulley to the other.
  • Contact surfaces of the pulleys 110b, 120b in order to exert such radially ‘outward’ forces onto the belt 130b, have surface normals that are directed radially inward toward the respective axes of rotation of the pulleys 110b, 120b. Accordingly, the contact surfaces of the pulleys 110b, 120b are convex.
  • Both of the pulleys 110b, 120b could be split pulleys and configured to allow the axial separation between the halves of the split pulleys to be adjusted, thereby controlling the transmission ratio of the transmission 100b.
  • the lower half of Figure 1 illustrates the transmission 100b in cross-section through the plane of the belt 130b
  • the upper half of Figure 1 illustrates the transmission 100b in cross-section through a plane passing through the axis of rotation 115b of the pulley 110b and depicts only the first pulley 110b and the portion of the belt 130b in contact therewith (portions of the second pulley 120b over which the first pulley 110b may overlap are omitted from the upper portion of Figure 1).
  • the belt is a “push type” belt.
  • a method of power transmission through the belt could be selected in order to improve the efficiency, reduce the noise and vibration, or other features of the transmission.
  • the belt typically includes straps, band packs, hinges, multi-bar links, or other elements to transmit substantially static tensile loads along the belt.
  • the magnitude of these tensile loads is tailored to ensure that the normal force exerted by the pulleys onto the belt is sufficient to prevent slippage of the belt relative to the contact surfaces of the pulleys. Accordingly, increases in the power capacity of such a transmission are accompanied by increases in the tensile load the belt must withstand, increasing the cost, mass, volume, and/or complexity of the belt. Further, increases in the power transmitted through such a “push belt” result in decreases in the normal forces exerted on the belt (due to the increased compressive, power- transmitting forces cancelling more of the substantially static tensile forces within the belt), increasing the chance that the belt slips against the pulley(s) and leading to potential instability as the transmitted power increases.
  • the pulleys of an overlapping-pulley type belt-and-pulley transmission define an area that is completely enclosed by the effective circumferences of the pulleys. Accordingly, such an overlapping-pulley type transmission can be configured to exert forces onto a belt from the pulleys ‘inward’ toward their respective axes of rotation. The belt would thus be under compression everywhere, and so could omit (or include fewer, smaller, and/or less costly) tension-transmitting elements to maintain the integrity of the belt and/or the alignment of segments thereof.
  • a third transmission 100c depicted in Figure 1 is an example of such a nested- pulley transmission wherein the pulleys exert ‘inward’ forces onto a belt.
  • the third transmission 100c includes first 110c and second 120c pulleys.
  • a belt 130c is disposed within the area defined by the overlapping effective circumferences of the pulleys 110c, 120c.
  • Inward forces exerted from the pulleys 110c, 120c onto the belt 130c (e.g., exerted from the first pulley 110c in a direction toward an axis of rotation 115c of the first pulley 110c such that a radial component of the exerted force, relative to the geometry of the pulley 110c, is directed inward, toward the axis 115c of the pulley 110c) allow the belt 130c to resist slipping on contact surfaces of the pulleys 110c, 120c, allowing power (forces and/or rotations) applied to one of the pulleys to be transmitted, via the belt 130c, to the other pulley.
  • the belt 130c is in contact with the first pulley 110c along a first contact surface 131c and with the second pulley 120c via a second contact surface 133c.
  • the contact surfaces 131c, 133c of the pulleys 110c, 120c in order to exert such radially ‘inward’ forces onto the belt 130c, have surface normals that are directed radially inward toward the respective axes of rotation of the pulleys 110c, 120c. Accordingly, the contact surface 131c, 133c of the pulleys 110c, 120c are concave.
  • the lower half of Figure 1 illustrates the transmission 100c in cross-section through the plane of the belt 130c
  • the upper half of Figure 1 illustrates the transmission 100c in cross-section through a plane passing through the axis of rotation 115c of the pulley 110c and depicts only the first pulley 110c and belt 130c (portions of the second pulley 120c over which the first pulley 110c may overlap are omitted from the upper portion of Figure 1 for purposes of clearer illustration).
  • Most of the length of the belt 130c e.g., most of the discrete segments of a multi-segment belt
  • two portions 135c of the belt are ‘floating,’ such that they are not in contact with either pulley 110c, 120c.
  • These ‘floating’ portions are those portions of the belt that move between contact with one of the pulleys to contact with the other.
  • One of the pulleys e.g., 110c
  • One of the pulleys could be split into two half-pulleys that are positioned opposite elements of the other one of the pulleys (e.g., 120c). This configuration allows both pulleys to rotate and allows the belt 130c to pass from the contact surfaces of one pulley to the other.
  • Both of the pulleys 110c, 120c could be split pulleys and configured to allow the axial separation between the halves of the split pulleys to be adjusted, thereby controlling the transmission ratio of the transmission 100c.
  • Such a transmission exerting inward-facing forces onto a belt and thus reducing or eliminating the need for tension-sustaining elements of the belt, could be implemented in a variety of ways.
  • One or both of the pulleys could be split-pulleys, with the separation(s) between the half-pulleys of the split-pulley(s) being controllable to control a transmission ratio of the transmission.
  • both of the pulleys of a transmission as described herein could rotate about respective axes of rotation which are, themselves, nonmoving within the transmission.
  • one of the pulleys could be mechanically grounded while the axis of rotation of the other pulley could orbit about the axis of symmetry of the grounded pulley, with the orbiting of the axis of rotation being an input of the transmission and the overall rotation of the orbiting pulley about its axis being an output of the transmission (e.g., the transmission could be configured as a cycloidal variety of transmission).
  • one of the pulleys is configured to ‘orbit’ in this manner
  • a variety of mechanisms could be employed to drive the transmission and/or to rectify the motion of the orbiting pulley to provide an output, or vice versa.
  • the motion of the axis of rotation of the inner pulley could be driven by an input member coupled to an off-center cam that is rotatably coupled to the inner pulley.
  • a balancing mass could also be coupled to the cam and/or input member to offset the movement of the off-center mass of the inner pulley as the inner pulley’s axis of rotation orbits within the transmission.
  • the rotation of the inner pulley about its axis of rotation could be coupled (or ‘rectified’) to an output member using a set of individual pins (surrounded by bearings) penetrating into corresponding holes or other features in the inner pulley.
  • Other methods for coupling rotations/torques into/out of the elements of such a transmission are possible.
  • the configuration of a belt of such a transmission could also be selected from a variety of possibilities to access desired benefits or trade-offs.
  • the belt could have an “A”-shaped cross-section (i.e., with all contact surfaces via which the belt contacts the pulleys facing away from each other), with both split-pulleys exerting compressive local forces onto the belt (e.g., onto individual segments of the belt) in order to drive the belt and prevent slippage of the belt relative to the pulleys.
  • the belt could have an “M”- shaped cross-section (i.e., some of the belt’s pulley-contacting surfaces face toward each other, and some face away from each other), with one of the split-pulleys exerting compressive local forces onto the belt (e.g., the ‘inner’ pulley in contact with the belt contact surfaces that face away from each other) and the other exerting tensile/expanding local forces onto the belt in order to drive the belt and prevent slippage of the belt relative to the pulleys (e.g., the ‘outer’ pulley in contact with the belt contact surfaces that face toward each other).
  • the belt could have an “M”- shaped cross-section (i.e., some of the belt’s pulley-contacting surfaces face toward each other, and some face away from each other), with one of the split-pulleys exerting compressive local forces onto the belt (e.g., the ‘inner’ pulley in contact with the belt contact surfaces that face away from each other) and the other exert
  • FIG. 2 shows, in cross-section, elements of an example transmission 200 in which the pulleys exert radially ‘inward’ forces onto a belt and wherein the axis of one of the pulleys ‘orbits’ around the axis of rotation of the other pulley.
  • the transmission 200 includes an inner pulley 230, an outer split pulley 220, and a belt 240.
  • a first portion of the belt 240 (shown in the upper portion in Figure 2) is in contact with the inner pulley 230 and a second portion of the belt 240 (shown in the lower portion in Figure 2) is in contact with the outer split pulley 220.
  • An input member 210 couples torques/rotations into/out of the transmission 200, causing the inner pulley 230 to precess by rotating about a cam 215 that rotates about a central axis 201 (which is also the axis of symmetry of the belt-contacting surfaces of the outer split pulley 220) as the input member 210 rotates.
  • a counterweight 217 is also coupled to the input member 210 to compensate for the motion of the inner pulley’s 230 center of mass about the axis 201.
  • the outer split pulley 220 is mechanically coupled to a mechanical ground 260 (e.g., a housing) of the transmission 200 such that it is prevented from rotating relative to the ground 260.
  • An output member 270 couples torques/rotations out of/into the transmission 200 by being coupled, via a gear 275, to a toothed contact surface 235 of the inner pulley 230.
  • the inner pulley 230 of the example transmission 200 is non-split and so has a non-adjustable effective diameter with respect to its contact with the belt 240. Accordingly, the transmission 200 has a fixed transmission ratio.
  • the axial separation between the halves of the split outer pulley 220 could be statically set or could be continuously adjusted (e.g., to optimize a compression along the belt 240 and/or contact forces applied to the belt 240 across different torque and/or power conditions).
  • the inner pulley could also be split. In such an example, the axial distances between the halves of the inner and outer split pulleys could be adjusted to control the transmission ratio of the transmission and/or to control a level of compression in the belt.
  • the degree of eccentricity with which the inner pulley 230 precesses about the central axis 201 could be variable. This can allow the transmission ratio of the transmission 200 to be controllable by controlling the separation between halves of the split outer pulley 220 and adjusting the degree of eccentricity of the inner pulley 230 to account for the neither the length of the belt 240 nor the effective diameter of the inner pulley 230 being adjustable. [0066] Alternatively, such adaptations could allow the inner pulley 230 to be replaced with a sprocket having inward-facing teeth configured to engage with respective features (e.g., segments) of the belt 240.
  • the effective diameter of such a sprocket is non-variable, as is the length of the belt 240, so adjusting the degree of eccentricity of precession of such an inner sprocket about the central axis 201 can allow contact forces applied to the belt 240 to be maintained while varying the separation between halves of the split outer pulley 220 (thereby adjusting the effective diameter of the outer pulley with respect to its contact with the belt 240 and thus adjusting the overall transmission ration of the transmission 200).
  • the outer pulley 220 could be replaced with a sprocket having inward-facing teeth, the belt 240 reconfigured to be driven by such teeth, and the inner pulley 230 reconfigured as a split pulley.
  • the belt 240 has an “M”-shaped cross-section. Accordingly, as depicted in Figure 2, the outer split pulley 220 exerts tensile/expanding local forces onto the belt via contact surfaces on the belt that face toward each other while the inner split pulley 230 exerts compressive local forces onto the belt via contact surfaces on the belt the face away from each other.
  • a transmission as described herein, having nested or otherwise overlapping pulleys configured to exert ‘inward’ forces onto a belt could also be implemented using a belt having a “A”-shaped cross-section, or other cross-sectional shape.
  • the coupling between the inner member 210 and the inner pulley 230 and/or output member 270 and the inner pulley 230 could be modified.
  • the output member 270 could be rotatably coupled to the inner pulley 230 using an offset shaft coupling, a cycloidal transmission, or some other variety of coupling.
  • transmissions described herein are characterized as including inputs from which power is transmitted to outputs
  • these transmissions may additionally or alternatively be configured to be back-drivable or otherwise configured to permit bidirectional energy transmission and/or energy transmission from output(s) to input(s).
  • transmissions as described herein could be used to bidirectionally transfer energy between joints of a robot, e.g., to increase the overall efficiency of the robot by permitting energy to be harvested from one joint (e.g., a joint currently receiving energy from, e.g., contact with the ground) and applied to another joint (e.g., a joint currently being employed to exert force on a payload), or vice versa.
  • an inward-directed sprocket e.g., a sprocket having a set of inward-directed teeth
  • a belt of such a transmission or other mechanism instead of a pulley. This could be done, e.g., to increase the efficiency and/or lifetime of the mechanism, since the engagement of a sprocket with a belt is likely to exhibit less sliding motion than a pulley.
  • FIG. 3 depicts aspects of such a transmission or other mechanism.
  • the mechanism includes a belt 310, an outer sprocket 320 that engages with the segments 311a, 311b, 311c of the belt 310 via a set of inward-facing teeth such that the sprocket 320 exhibits an effective pitch line 321 with respect to its interaction with the belt (e.g., as though it were interacting with the belt as a pulley with an effective diameter equal to the diameter of the pitch line 321).
  • the mechanism also includes a pulley (not shown) that is nested within the sprocket 320 and that exerts forces onto the belt 310 that are oriented radially inward.
  • a first set of segments 311a of the belt 310 engage with the sprocket 320, a second set of segments 311b engage with the pulley.
  • a third set of segments 311c is in contact with neither and transmits, via compressive forces, torques between the sprocket 320 and pulley.
  • the transmission of Figure 3 could be configured similarly to transmission 200, with belt 310 and pulley corresponding to the belt 240 and inner pulley 230, respectively, and with the sprocket 320 replacing the outer pulley 220.
  • the pulley engages with the belt along a pitch line 331.
  • the effective diameter of the pulley could be adjusted, thereby controlling the transmission ratio of the mechanism by adjusting the diameter of the pitch line 331.
  • the location of the axis of rotation of the pulley and/or sprocket could be movable in order to compensate for the variation in effective diameter of the pulley as the length of the belt and effective diameter of the sprocket do not change.
  • Such a mechanism could be altered such that the outer belt-engaging element is a pulley and the belt-engaging element nested therein is a sprocket having inward-facing teeth, or such that both elements are sprockets that engage with the belt via inward-facing teeth.
  • the sprocket (outer or inner) could be configured as two separate sprockets flanking elements of a pulley (e.g., halves of a split pulley) disposed therebetween.
  • the sprocket could be a single sprocket centered between opposed halves of a pulley (e.g., of an adjustable split pulley).
  • each segment of the belt 310 has a respective single tooth via which it engages with the sprocket 320.
  • the teeth or other sprocket- engaging features of the segments could be configured in some other manner, e.g., with multiple teeth formed on each belt segment.
  • the shape of the belt teeth could be configured to facilitate efficient engagement/disengagement with the sprocket.
  • the belt segments could contact each other via contact surfaces that correspond to elliptic cylinders or some other geometry to facilitate their engaging with each other via rolling motion (e.g., substantially pure rolling motion), and the shape of the belt teeth could be specified based on that relative motion.
  • rolling motion e.g., substantially pure rolling motion
  • a transmission as described herein could include more than one inner pulley (or sprocket).
  • such a transmission could include multiple inner pulleys arranged uniformly about a center axis such that the motion of their centers of mass about the center axis cancel, thereby reducing vibration, the magnitude of reaction forces transmitted through bearings, or providing some other benefit.
  • Such a transmission could also include additional belts, each belt engaging with the outer pulley (or sprocket) and with a respective one of the inner pulleys (or sprockets). This has the benefit of distributing the load across multiple belts, allowing such a transmission to exhibit increased lifetime, reduced cost, reduced weight, reduced size, or other benefits.
  • Figure 4 schematically depicts elements of such a transmission 400.
  • the transmission 400 includes first 430a and second 430b belts that engage with an outer pulley 410 (depicted as the pitch circle at which the outer pulley 410 engages with the belts 430a, 430b) that exerts thereon forces that are directed radially inward toward a center 411 (e.g., an axis of rotation) of the outer pulley 410.
  • the first 430a and second 430b belts also engage with first 420a and second 420b inner pulleys, respectively, that are nested within the outer pulley 410.
  • the first 420a and second 420b inner pulleys exert forces on the respective first 430a and second 430b belts that are directed radially inward toward their respective axes of rotation 431a, 431b.
  • the belts 430a, 430b can experience compression everywhere along their lengths and can be configured as described herein to obtain various benefits, e.g., reduced cost, reduced weight, increased transmitted power limit, increased transmitted torque/compressive force limit, increased efficiency, and increased lifetime.
  • elements 410, 420a, 420b are described above as being pulleys (e.g., split pulleys), some or all of those elements could be configured as sprockets with inward- facing teeth (and the belt(s) 430a, 430b configured accordingly) in order to obtain the benefits above.
  • one of the outer element 410 or inner elements 420a, 420b are configured as sprockets and the opposite is/are configured as split pulley(s) to effect control of the transmission ratio of the mechanism 400.
  • the mechanism 400 could be configured to allow the distance of the axes of rotation 421a, 421b of the inner elements 420a, 420b from the center 411 to be adjusted (e.g., to maintain contact forces between the belts 430a, 430b and pulley(s) to prevent slippage).
  • one of the outer or inner elements could be configured as a pulley that engages with the belt along a midline of the belt (e.g., halves of an adjustable split pulley 220) that exert forces directed axially outward onto the belt to prevent slippage, while the opposite of the inner or outer elements is configured as two flanking sprockets that engage with the belt along two sets of teeth flanking the midline of the belt.
  • one of the outer or inner elements could be configured as a single sprocket that engages with the belt along a midline of the belt, while the opposite of the inner or outer elements is configured as two flanking half-pulleys (e.g., halves of an adjustable split pulley) that exert forces directed axially inward onto the belt to prevent slippage.
  • two flanking half-pulleys e.g., halves of an adjustable split pulley
  • the pulleys and sprocket exert ‘inward’ forces onto the belts, and the axes of rotation of the inner pulleys orbit about the central axis of the transmission 500 as a whole.
  • the transmission 500 includes a first inner split pulley 510a (comprising first 511a and second 511b half-pulleys) that rotates about a first axis of rotation 501a, a first belt 530a, a second inner split pulley 510b (comprising third 511c and fourth 511d half-pulleys) that rotates about a second axis of rotation 501b, a second belt 530b, and an outer sprocket 520 having a plurality of inward-facing teeth that engage with the belts 530a, 530b.
  • the cross-sectional depiction of the transmission 500 in Figure 5C includes all of the elements of the transmission 500, while the end-on view of Figure 5B omits the housing 560 and the cross-sectional view of Figure 5A omits the housing 560 and belts 530a, 530b for ease of illustration.
  • An input member 505 couples torques/rotations into/out of the transmission 500, causing the inner pulleys 510a, 510b to precess about a central axis 503 (which is also the axis of rotation of the input 505 and a central axis of rotational symmetry of the outer sprocket 520) as the input member 505 rotates.
  • the outer sprocket 520 is mechanically coupled to a mechanical ground 560 (e.g., a housing) of the transmission 500 such that it is prevented from rotating relative to the ground 560.
  • An output member 570 couples torques/rotations out of/into the transmission 500 by being coupled to a carrier 535 that is coupled to the inner pulleys 510a, 510b such that the carrier 535 rotates about the central axis 503 as the inner pulleys 510a, 510b orbit the central axis 503.
  • the axial separation between the half-pulleys 511a, 511b of the first inner split pulley 510b and the axial separation between the half-pulleys 511c, 511d of the second inner split pulley 510b could be adjusted in order to control the transmission ratio of the transmission 500.
  • the transmission 500 can be configured to adjust the distance from the central axis 503 at which the inner split pulleys 510a, 510b orbit the central axis 503 (i.e., to adjust the distance between the central axis 503 and the first 501a and second 501b axes of rotation).
  • a planetary gearset could be used to transmit torques while arms or other rigid mechanical member maintain fixed the distances between various gears of the planetary gearset.
  • the transmission 500 includes an example of such mechanisms.
  • the input member 505 is coupled (e.g., fused) to a sun gear 580 that rotates about the central axis 503.
  • Each inner split pulley 510a, 510b is coupled (e.g., fused via one of the respective half-pulleys) to a respective planet gear 590a, 590b that rotates about a respective one of the first 501a or second 501b axes of rotation.
  • First 585a and second 585b spur gears engage with the sun gear 580 and with respective planet gears 590a, 590b to transmit torques from the input member 505 to the inner split pulleys 510a, 510b.
  • Arms or other rigid members of the transmission 500 maintain the distances between the axis of rotation of the sun gear 580 and the axes of rotation of the spur gears 585a, 585b, and between each spur gear 585a, 585b and the respective planet gear 590a, 590a with which it engages.
  • this includes the spur gears 585a, 585b and sun gear 580 being rotatably coupled to the carrier 535 (e.g., via needle or other types of bearings).
  • This also includes the planet gears 585a, 585b (and corresponding split pulleys 510a, 510b) being rotatably coupled to respective arms 595a, 595b that, themselves, are able to be rotated about the axis of rotation of the respective spur gear 585a, 585b.
  • the distances between the spur gears 585a, 585b and the respective planet gears 590a, 590b are maintained at a set distance while still allowing the axes of rotation 501a, 501b of the planet gears 585a, 585b to move toward/away from the central axis 503 (e.g., to compensate for changes in the effective diameter of the split pulleys 510a, 510b).
  • Such distances could be actively controlled, e.g., by a mechanism that also acts in concert to adjust the axial separation between the half-pulleys of the inner split pulleys 510a, 510b.
  • springs, dampers, or other elements could be included to passively adjust the distances between the central axis 503 and the axes of rotation 501a, 501b, e.g., to maintain a set compressive force along the belts 530a, 530b, to maintain a set axial force applied to the belts 530a, 530b by the half-pulleys, to apply an amount of axial force to the belts 530a, 530b that depends on the load experienced by the transmission 500, and/or configured in some other way.
  • the transmission 500 includes two such planetary gearsets, one on either side of the split pulleys 510a, 510b and coupled to respective opposite half-pulleys thereof. This could be done, e.g., in order to reduce an amount of differential rotation of the half-pulleys of a single inner split pulley 510a, 510b, to balance a pattern of loads/torques within the transmission 500, to simplify the construction of the transmission 500 (e.g., to allow the transmission to lack splines or other elements to prevent differential rotation between half- pulleys of a single inner split pulley), or to provide some other benefit.
  • a single such planetary gearset is used, e.g., where the nested inner elements of the transmission are sprockets, where the nested inner elements of the transmission are pulleys (e.g., split pulleys) that exert axially outward-directed forces onto respective belts (and thus may be driven symmetrically from the middle, by a single planetary gearset), or in some other configuration.
  • the transmission 500 includes only two inner rotating elements and respective compressively loaded belts, a transmission as described herein could include more inner pulleys/sprockets and corresponding belts.
  • such a transmission could include three, four, or more (e.g., ten) inner pulleys/sprockets and corresponding belts.
  • Such additional elements could be provided to further distribute the load of such a transmission across more belts, thereby increasing lifetime, increasing power/torque capacity, reducing cost, reducing weight/size, and/or providing some other benefit.
  • Contact surfaces of the half-pulleys 511a, 511b of the first inner split pulley 510a exert respective forces onto the first belt 530a. Such forces may have components directed into/out of the plane of Figure 5A; such components are “tangential” components relative to the cylindrical geometry of the half-pulleys 511a, 511b.
  • Components of the forces directed parallel to the axis of rotation 501a of the first split pulley 510a are “axial” components relative to the cylindrical geometry of the first split pulley 510a.
  • Components of the forces directed perpendicular to the axis of rotation 501a of the first split pulley 510a and in the plane of Figure 5A are “radial” components relative to the cylindrical geometry of the first split pulley 510a.
  • the forces exerted by the first split pulley 510a are all radially directed ‘inward’ in that they all have radial components that are directed inward toward the axis of rotation 501a of the first split pulley 510a.
  • the pair of half-pulleys 511a, 511b forming the first split pulley 510a exert a pair of forces onto the first belt 530a that represent a compressive force couple between the half-pulleys 511a, 511b (since the axial components of the forces are directed toward each other) and a radially inward-directed force onto the belt 530a, as well as potentially a tangential force onto the belt 530a (e.g., to transmit torque between the first split pulley 510a and the sprocket 520).
  • such couples exerted in a radially inward direction onto a belt, may be exerted away from each other, onto contact surfaces of a belt that face toward each other, thereby exerting a tensile axial force onto the belt (as well as the inward- facing radial force and optionally a tangential force).
  • the belt- contacting surfaces of the first split pulley 510a have surface normals that are directed radially inward toward the first axis of rotation 501a.
  • the local surface normal of any portion of any of the contact surfaces of the first 511a or second 511b half-pulleys has a radial component that is in the plane of Figure 5A and that is directed inward toward the axis of rotation 501a.
  • the axial component of the local surface normal of any portion of any of the contact surfaces may have a direction that is appropriate to facilitate exertion of compressive forces onto the belt in order to maintain non-slipping contact between the belt 530a and the contact surface.
  • the contact surfaces of the half-pulleys 511a, 511b are concave.
  • Figures 5D, 5E, and 5F are photographs of a transmission assembled similarly to the transmission 500 depicted in Figures 5A, 5B, and 5C.
  • the pictured transmission includes two inner pulleys and one outer sprocket that exert forces ‘inward’ onto two belts that are everywhere in compression.
  • Figure 5D depicts the ‘inner’ elements of the transmission, including the belts, inner pulleys, mechanisms for transmitting torques from an input shaft to the rotation of the inner pulleys about their axes of rotation, mechanisms for transmitting torques from the orbiting of the inner pulleys about a central axis of rotation to an output shaft, and mechanisms allowing the eccentricity of inner pulleys orbiting to be adjusted to account for changes in the effective diameter of the inner pulleys.
  • Figure 5E depicts these same elements, with one of the inner pulleys and associated components (including the corresponding belt) removed.
  • Figure 5F depicts the transmission complete, including an outer housing in which the elements depicted in Figures 5D and 5E are disposed.
  • the outer housing includes an outer sprocket whose inward-facing teeth engage with the two belts of the transmission.
  • the belt of a transmission as described herein e.g., 100c, 200, 400, 500
  • having pulleys and/or sprockets that exert inward-facing forces onto the belt could be configured in a variety of ways to facilitate efficient, low-ripple transmission of power from one pulley/sprocket to another over extended periods of operational lifetime and for high magnitudes of transmitted power.
  • Such a belt could include a plurality of segments stacked together within the transmission, with (at a particular point in time) a first subset of the segments in contact with a first, inner pulley/sprocket, a second subset of the segments in contact with a second, outer pulley/sprocket, and a third subset of the segments that are not in contact with any pulley or sprocket but transmitting, via compressive loads, power from the first pulley/sprocket to the second pulley/sprocket (such a transmission would also include a fourth subset of the segments that are not in contact with any pulley/sprocket and that are not compressively transmitting power but merely transitioning back from the pulley/sprocket being driven to the driving pulley/sprocket).
  • a cross-sectional shape of the segments through a plane perpendicular to the axes of rotation of the pulley(s)/sprocket(s) could be circular, elliptical, or some other shape specified such that the segments engage with each other in rolling motion (e.g., pure or substantially pure rolling motion), increasing the efficiency of the transmission and increasing the operational lifetime of the belt and/or transmission.
  • rolling motion e.g., pure or substantially pure rolling motion
  • a cross-sectional shape of the segments through a plane perpendicular to the direction along which the belt transmits force could be “A”-shaped, “M”- shaped, or some other shape specified such that the segments contact pulleys of the transmission without slipping.
  • the particular configuration of the belt segments could be specified to obtain a desired size, volume, weight, cost, complexity of fabrication, lifetime, material composition or specification, transmission ratio or range of controllable transmission ratio, efficiency, generated vibration or noise vibration harshness, or some other desired constraint of the belt and/or of the transmission.
  • Figure 6 depicts a cross-section of a number of segments (including example segment 610) of an example belt 600 (e.g., an M-belt, an A-belt) as described herein.
  • the plane of the cross-sectional view is perpendicular to the length of the belt 600 and to the axes of rotation of the pulleys/sprockets with which the belt 600 is in contact.
  • Each segment has contact surfaces (e.g., surface 615 of segment 610) that contact and transmit forces to and from neighboring segments.
  • the shape of such contact surfaces e.g., 615) can be circular, elliptical, or other specified shapes such that the segments engage with each other via rolling motion (e.g., substantially pure rolling motion).
  • substantially all of the compressive force transmitted along the belt from one pulley/sprocket to the next could be transmitted via such contact surfaces that engage with each other via rolling motion (e.g., greater than 90% of the compressive force transmitted along the belt from one pulley/sprocket to the next could be transmitted via such rolling-motion contact surfaces).
  • the shape of the contact surfaces could also be specified to minimize velocity ripple, to stabilize sections of the belt that are “floating” between contact with one or the other pulley of a transmission, or to provide some other benefits.
  • the thickness of the segments could be reduced in order to decrease Hertzian contact forces, thereby increasing load and stiffness.
  • Figure 7 depicts a cross-section of a number of segments (including example segment 710) of an example belt 700 (e.g., an A-belt) as described herein.
  • the plane of the cross-sectional view is perpendicular to the length of the belt 700.
  • Each segment has contact surfaces that contact and transmit forces to and from neighboring segments.
  • the shape of such contact surfaces can be circular, elliptical, or other specified shapes such that the segments can engage with each other via substantially pure rolling motion.
  • the belt also includes constraint features configured to maintain the alignment of the segments relative to each other, to constrain the segments to engage in substantially pure rolling motion relative to each other, and to prevent segments of the belt from being ‘ejected’ from the belt when the segments are ‘floating’ between contact with either pulley/sprocket of a transmission.
  • the line of contact between the wedges and a pulley of the transmission is depicted by curve 720a, while the line of contact between adjacent wedges is depicted by curve 720b.
  • These contact points exert opposing forces onto the example segment 710, depicted by 725a and 725b, respectively. Being offset from each other, these forces can impart a skewing moment onto the example segment 710.
  • constraint features configured to constrain the wedges to engage in the substantially pure rolling relative to each other can exert compensating forces to counter the skewing moment, maintaining the segments in proper alignment with each other and with the pulley.
  • Such a configuration can greatly simplify belt design and reduce the total drive volume by as much as 40% for a given torque.
  • the geometry of the segments of a belt can be specified to improve the efficiency of a transmission containing the belt by making it more likely that the segments engage with each other in a rolling motion, e.g., in a substantially pure rolling motion. This reduces wear and noise, increases efficiency and belt lifetime, and increases the torque and/or energy capacity of the transmission.
  • the geometry of the belt segments can also be specified to increase the stability of the belt at the locations where the belt segments “float” from contact with one pulley to contact with the other, ensuring that large loads can be compressively transmitting across such ‘floating’ belt segments despite the lack of stabilizing forces exerted by either pulley/sprocket directly.
  • Figure 8A depicts segments (e.g., segments 850, 851, 853) of a belt 800.
  • a first subset 801a of the segments is in contact with no pulley (or ‘floating’)
  • a second subset 803a is in contact with a first pulley
  • a third subset 805a is in contact with a second pulley.
  • the second subset 803a is in contact with the first pulley along a first pitch line 810a of the first pulley, which defines the effective diameter of the first pulley with respect to its interaction with the belt 800
  • the third subset 805a is in contact with the second pulley along a second pitch line 820a of the second pulley, which defines the effective diameter of the second pulley with respect to its interaction with the belt 800.
  • the overall transmission ratio of the transmission is related to the ratio between the radii of the pitch lines 810a, 820a.
  • each belt segment When the belt segments have been configured to engage with each other via rolling motion (e.g., via substantially pure rolling motion by having contact surfaces that conform to circular or other elliptical cross-sections, as depicted in Figure 8A), these forces are transmitted from segment to segment, from the first pitch circle 810a to the second pitch circle 820a, along a straight line 859a.
  • Each belt segment is configured to engage with its neighbors such that it contacts the neighbors at points along the line 859a, thereby facilitating the transmission of forces along the line 859a. So, for example, a first belt segment 850 of the floating segments 801a contacts a first neighboring belt segment 851 at a first contact point 855 and a second neighboring belt segment 853 at a first contact point 857.
  • the belt and/or segments thereof may include straps, teeth, linkages, or other alignment features to ensure the alignment of the belt segments, and some portion of the transmitted force may be transmitted via such alignment features (with the direction and location of the force transmitted thereby acting to maintain the belt segments in proper alignment).
  • FIG 8B illustrates the configuration of the belt 800 when the transmission is set to have a torque ratio of 1.36:1.
  • the axes of rotation 815b, 815b of the first and second pulleys, respectively, as well as the locations of their respective pitch lines 810b, 820b in this configuration are depicted in Figure 8B.
  • Also depicted in Figure 8B is the location of the line 859b along which compressive forces are transmitted from the first pulley to the second pulley (or vice versa).
  • Figure 8C illustrates the configuration of the belt 800 when the transmission is set to have a torque ratio of 0.96:1.
  • the axes of rotation 815c, 815c of the first and second pulleys, respectively, as well as the locations of their respective pitch lines 810c, 820c in this configuration are depicted in Figure 8C.
  • Also depicted in Figure 8C is the location of the line 859c along which compressive forces are transmitted from the first pulley to the second pulley (or vice versa).
  • one or the other of the pulleys depicted in Figs 8A-C could be replaced with a sprocket having inward-facing teeth that engage with the belt 800 and that exert inward- facing forces thereon, directed toward an axis of the sprocket.
  • the effective diameter of the sprocket is fixed, and so the pitch line of the sprocket is also fixed.
  • the transmission ratio of a transmission including such a sprocket and pulley could be adjusted by controlling the effective diameter of an inward-directed pulley opposite the sprocket (and, optionally, adjusting an eccentricity of precession of the pulley in order to maintain compressive forces along the belt and/or contact forces applied to the belt).
  • the mechanics of transmission of forces/torques between the sprocket and pulley of such a transmission across different transmission ratios would be similar to that illustrated in Figures 8A-C.
  • a multi-segment belt as described herein could include features to maintain the segments of the belt in proper alignment despite shocks, vibration, particulates in the transmission, imperfections in the elements of the transmission (e.g., imperfections in the pulleys/sprockets, imperfections in the belt segments), or other processes or factors that might lead to the segments moving out of alignment with each other and/or with the pulleys/sprockets of a transmission.
  • Such features could, during normal operation of the transmission or other mechanism including such a belt, engage with each other in manners other than pure rolling motion (e.g., via some nonzero amount of sliding motion).
  • the segments could be shaped such that the majority of the compressive force through the belt is transmitted via other aspects of the segments (e.g., via larger surfaces shaped to engage with each other via substantially pure rolling motion), such that the non-pure rolling motion of the alignment features relative to each other do not significantly negatively impact efficiency or operational lifetime of the belt and/or transmission.
  • alignment features would act to counter small misaligning forces, rather than to maintain a large, static tension sufficient to counter the power-transmitting compression through the belt, the alignment features could be smaller, lighter, lower cost, or otherwise improved relative to the tensile band-packs of conventional push-type belts.
  • such alignment features could include sets of teeth formed to engage with corresponding teeth on neighboring belt segments.
  • Figures 9A and 9B depict, in perspective and cross-sectional view, respectively, a segment 900 of such a belt.
  • the segment 900 is configured to engage with neighboring segments of the belt via first contact surfaces 910; the first contact surfaces 910 correspond to an elliptic cylinder or other geometry such that the segments engage with each other, at the first contact surfaces 910, via rolling motion (e.g., substantially pure rolling motion) so as to reduce inefficiency, wear, heat generation, and noise during operation and to increase the load capacity of the belt and/or of a transmission or other mechanism that includes the belt.
  • rolling motion e.g., substantially pure rolling motion
  • the segment 900 also includes second contact surfaces 920 via which a pulley (e.g., a split pulley) can exert inward-facing forces into the belt segment 900, thereby allowing forces and/or torques to be exerted thereby onto the belt.
  • the segment 900 also includes a third contact surface 930 via which the belt segment 900 can engage with a sprocket (e.g., by being formed, as shown in Figs.9A and 9B, as a single tooth).
  • the belt segment 900 includes first 940 and second 950 sets of teeth configured to engage with corresponding sets of teeth of neighboring segments of a belt.
  • the first 940 and second 950 sets of teeth are formed such that they complement each other, and thus, a belt can be composed of identical copies of the belt segment 900 interlocking together.
  • a belt can be composed of identical copies of the belt segment 900 interlocking together.
  • the sets of teeth of a segment of such a belt could be configured in some other manner, e.g., such that the belt is composed of alternating first and second types of segments having respective different tooth configurations that interlock with each other. This could be done to balance forces (e.g., skewing forces) exerted onto a single belt segment from neighboring segments or to provide some other benefit.
  • a set of teeth of such a belt segment could be configured in a variety of ways, e.g., corresponding to a set of teeth arranged along the surface of a circular, ellipsoidal, or otherwise shaped gear.
  • such alignment features could include wires, flexures, or other types of flexible straps configured to connect between adjacent belt segments and to sustain tensile loads, thereby exerting forces to keep the neighboring segments in alignment.
  • Figure 10A depicts, in side view, the use of such straps to maintain the alignment of segments 1010 of a belt 1000.
  • the straps include a first strap 1020a that passes, alternatingly, over and under the segments 1010 of the belt 1000, while a second strap 1020b passes, alternatingly, under and over the segments 1010 of the belt 1000 opposite the first strap 1020a.
  • the straps 1020a, 1020b could be fused to the segments 1010, e.g., by spot welding, the use of bolts or other fixation hardware, by being part of a single continuous piece of material formed to include both the segments 1010 and the straps 1020a, 1020b (e.g., by 3D printing or other additive manufacturing methods, by casting, by subtractive manufacturing methods).
  • Such straps could be disposed within recesses formed in the surface of the belt segments, so that the bulk of any compressive forces transmitted from segment to segment is not transmitted transversely through the straps.
  • Fig. 10B depicts an example of a belt 1000 configured in this manner.
  • Each of the depicted belt segments contacts the neighboring segment via contact surfaces 1030 (e.g., a surface having an elliptic cylinder geometry, to facilitate the segments engaging with each other efficiently via rolling motion).
  • the straps 1020a, 1020b, 1020c are disposed within recesses 1040 recessed beneath the contact surfaces 1030, allowing compressive forces to be transmitted between the segments 1010 via the contact surfaces 1030 and not transversely through the straps 1020a, 1020b, 1020c.
  • the straps 1020a, 1020b, 1020c transmit relatively smaller-magnitude tensile forces longitudinally to maintain the relative alignment of the segments 1010.
  • Fig. 10c Also depicted in Fig. 10c is a configuration of straps such that a central first strap 1020a is flanked on either side by second 1020b and third 1020c straps. The first strap 1020a passes over/under the segments 1010 in a pattern opposite the pattern of the second 1020b and third 1020c straps. This could be done in order to balance the alignment forces exerted on the segments 1010 by the straps, reducing skewing or other unwanted behaviors of the segments.
  • a belt 1000 as depicted in Figure 10A could be fabricated in a variety of ways.
  • the straps and belt segments could be formed separately and then assembled together, e.g., by spot welding or otherwise fusing the straps at one or more points to each belt segment.
  • each segment could be formed from two (or more) discrete portions, allowing straps to be fixed (e.g., by spot welding) to the adjacent portions of neighboring segments at the desired level of pre-tensioning. After this fixation is completed, the segment portions can then be fixed to each other (e.g., by welding, bolts or other fixation hardware, or other means).
  • Fig.10C depicts first 1051a and second 1051b portions of a first belt segment 1050.
  • the first portion 1051a has been connected to a portion 1061a of a second belt segment 1060 via first 1080a and second 1080b straps prior to fixing the first 1051a and second 1051b portions together.
  • the second portion 1051b has been connected to a portion 1071a of a third belt segment 1070 via third 1080c and fourth 1080d straps prior to fixing the first 1051a and second 1051b portions together.
  • the straps could be formed as flexures or other elements from the same single, continuous piece of material as the belt segments.
  • Fig. 10D depicts a cross-sectional view through a portion of such a belt, showing the straps 1080 continuous with and passing between neighboring segments 1090 of the belt.
  • Such a configuration could be accomplished via by 3D printing or other additive manufacturing methods, by casting, by subtractive manufacturing methods, and/or by some other method.
  • the complete belt could be formed from a number of discrete portions formed in this manner and then fixed together (e.g., by bolting, welding, or otherwise adhering together two half-segments at the end of respective discrete belt portions).
  • alignment features could include rigid linkages that are rotatable coupled (e.g., via axles or other bearings) to neighboring belt segments at specified locations thereof such that the segments engage in rolling motion relative to each other. To maintain elliptic cylinders in contact with each other, two linkages, rotatably connecting to opposite foci of the elliptic cylinders, are sufficient.
  • Fig. 11 depicts first 1110a, second 1110b, and third 1110c segments of a belt 1100.
  • Each of the segments contacts neighboring segments via a contact surface that corresponds to at least a portion of an elliptic cylinder.
  • the first segment 1110a is coupled to the second segment 1110b via a first linkage 1120a and to the third segment 1110c via a second linkage 1120b.
  • the first linkage 1120a is rotatably coupled, at a first end, to the first segment 1110a at a first focus of the elliptic cylinder contact surface thereof and to the second linkage 1120b is rotatably coupled, at a first end, to the first segment 1110a at a second focus of the elliptic cylinder contact surface.
  • a second end of the first linkage 1120a is rotatably coupled to the second segment 1110b at a focus of the elliptic cylinder contact surface thereof and a second end of the second linkage 1120b is rotatably coupled to the third segment 1110c at a focus of the elliptic cylinder contact surface thereof.
  • the linkages 1120a, 1120b maintain the inter-focus distances between neighboring segments at a set distance.
  • This constraint in combination with the constraint that the belt 1100 is maintained under compression, exerts forces between neighboring belt segments to maintain their alignment and encourage them to engage in rolling motion with each other.
  • III. Experimental Results [00110] A transmission, coupling, or other mechanism as described herein, having ‘radially inverted’ pulleys and/or sprockets that exert forces ‘inward’ onto a compressive, push- type belt, was assessed experimentally across a variety of conditions and configurations in order to verify the benefits of such a transmission.
  • Figure 12 compares the efficiency of such a transmission across input torque levels for two different numbers of belt segments (42 and 21). As shown, larger numbers of belt segments and/or smaller belt segments resulted in increased efficiency, especially at lower torque levels.
  • Figure 13 depicts the input/output speed ratio of the transmission over time for both the 42 segment belt and the 21 segment belt.
  • Embodiments of the present disclosure may thus relate to one of the enumerated example embodiments (EEEs) listed below. It will be appreciated that features indicated with respect to one EEE can be combined with other EEEs.
  • EEE 1 is a transmission comprising: (i) a first split pulley rotatable about a first axis and comprising first and second half-pulleys; (ii) a second split pulley rotatable about a second axis and comprising third and fourth half-pulleys; (iii) an outer member defining a third axis, wherein the first split pulley and second split pulley are nested within the outer member; (iv) a first belt that is in contact with the first split pulley and the outer member, wherein a couple between the first and second half-pulleys exerts forces onto the first belt that are radially directed inward toward the first axis, and wherein the outer member exerts forces onto the first belt that are radially directed inward toward the third axis; and (v) a second belt that is in contact with the second split pulley and the outer member, wherein a couple between the third and fourth half-pulleys exerts forces onto the second
  • EEE 2 is the transmission of EEE 1, further comprising: (i) an input member, wherein rotation of the input member results in rotation of the first split pulley about the first axis, rotation of the second split pulley about the second axis, and movement of the first axis and second axis about the third axis; and (ii) an output member, wherein the output member is coupled to the first split pulley and second split pulley such that movement of the first axis and second axis about the third axis results in rotation of the output member and further such that a torque at the input member causes a torque to be realized at the output member.
  • EEE 3 is the transmission of any preceding EEE, wherein the transmission is configured such that a transmission ratio of the transmission is controllable by adjusting a separation between the first and second half-pulleys and a separation between the third and fourth half-pulleys.
  • EEE 4 is the transmission of any preceding EEE, wherein the outer member is a split pulley comprising fifth and sixth half-pulleys, and wherein the outer member exerting forces onto the first belt that are radially directed inward toward the third axis comprises a couple between the fifth and sixth half-pulleys exerting forces onto the first belt that are radially directed inward toward the third axis.
  • EEE 5 is the transmission of EEE 4, wherein the transmission is configured such that a transmission ratio of the transmission is controllable by adjusting a separation between the fifth and sixth half-pulleys.
  • EEE 6 is the transmission of any of EEEs 1-3, wherein the outer member is a sprocket comprising a plurality of inward-facing teeth.
  • EEE 7 is the transmission of EEE 6, wherein the first belt comprises a plurality of belt segments, wherein each belt segment of the first belt comprises a respective tooth, and wherein the plurality of inward-facing teeth of the sprocket engage with the first belt via at least one tooth of the first belt.
  • EEE 8 is the transmission of any of EEEs 6-7, further comprising: (i) a sun gear rotatable about the third axis; (ii) a first planet gear rotatable about the first axis and coupled to the first split pulley; (iii) a second planet gear rotatable about the second axis and coupled to the second split pulley; (iv) a first spur gear, wherein the first spur gear engages with the sun gear and the first planet gear; and (v) a second spur gear, wherein the second spur gear engages with the sun gear and the second planet gear.
  • EEE 9 is the transmission of EEE 8, further comprising: (i) a first rigid member configured to maintain a first distance between the sun gear and the first spur gear while permitting an axis of the first spur gear to move around the third axis; and (ii) a second rigid member configured to maintain second distance between the first planet gear and the first spur gear.
  • EEE 10 is the transmission of any preceding EEE, wherein the first belt comprises a plurality of belt segments, wherein each belt segment of the first belt engages with neighboring segments of the first belt via contact surfaces shaped such that the belt segments engage with each other via rolling motion along the contact surfaces.
  • EEE 11 is the transmission of EEE 10, wherein the first belt further comprises a first linkage and a second linkage, wherein the contact surfaces of the plurality of belt segments have shapes that conform to portions of an elliptic cylinder, wherein the plurality of belt segments comprise a first belt segment, a second belt segment, and a third belt segment, wherein the contact surface of the first belt segment defines a first focus and a second focus, wherein a first end of the first linkage is rotatably coupled to the first belt segment at the first focus and a second end of the first linkage is rotatably coupled to the second belt segment, and wherein a first end of the second linkage is rotatably coupled to the first belt segment at the second focus and a second end of the second linkage is rotatably coupled to the third belt segment.
  • EEE 12 is the transmission of EEE 10, wherein the plurality of belt segments comprise a first belt segment and a second belt segment, wherein the first and second belt segments are coupled together via at least two flexible straps that are configured to oppose the first and second belt segments engaging with each other via non-rolling motion along the contact surfaces of the first and second belt segments.
  • EEE 13 is the transmission of EEE 10, wherein the plurality of belt segments comprise a first belt segment and a second belt segment, wherein the first and second belt segments comprise respective pluralities of geared teeth that are configured to oppose the first and second belt segments engaging with each other via non-rolling motion along the contact surfaces of the first and second belt segments.
  • EEE 14 is the transmission of any preceding EEE, wherein the first belt experiences a net compressive force along the length of the first belt at every location along the length of the first belt.
  • EEE 15 is the transmission of EEE 14, wherein the first belt does not include a longitudinal band that is under tension.
  • EEE 16 is the transmission of any preceding EEE, further comprising: (i) a third split pulley rotatable about a fourth axis and comprising seventh and eighth half-pulleys; and (ii) a third belt that is in contact with the third split pulley and the outer member, wherein a couple between the seventh and eighth half-pulleys exerts forces onto the third belt that are radially directed inward toward the third axis, and wherein the outer member exerts forces onto the third belt that are radially directed inward toward the third axis.
  • EEE 17 is a transmission comprising: (i) a split pulley defining a first axis and comprising first and second half-pulleys; (ii) a sprocket defining a second axis and comprising a plurality of inward-facing teeth, wherein the split pulley is nested within the sprocket; and (iii) a belt, wherein the belt is in contact with the split pulley and the sprocket, wherein a couple between the first and second half-pulleys exerts forces onto the belt that are radially directed inward toward the first axis, and wherein the sprocket exerts forces onto the belt that are radially directed inward toward the second axis.
  • EEE 18 is the transmission of EEE 17, further comprising: (i) an input member, wherein rotation of the input member results in rotation of the split pulley about the first axis and movement of the first axis about the second axis; and (ii) an output member, wherein the output member is coupled to the split pulley such that movement of the first axis about the third axis results in rotation of the output member and further such that a torque at the input member causes a torque to be realized at the output member.
  • EEE 19 is the transmission of any of EEEs 17-18, wherein the transmission is configured such that a transmission ratio of the transmission is controllable by adjusting a separation between the first and second half-pulleys.
  • EEE 20 is the transmission of any of EEEs 17-19, wherein the belt comprises a plurality of belt segments, wherein each belt segment of the belt comprises a respective tooth, and wherein the plurality of inward-facing teeth of the sprocket engage with the belt via at least one tooth of the belt.
  • EEE 21 is the transmission of any of EEEs 17-20, further comprising: (i) a sun gear rotatable about the second axis; (ii) a planet gear rotatable about the first axis and coupled to the split pulley; and (iii) a spur gear, wherein the spur gear engages with the sun gear and the planet gear.
  • EEE 22 is the transmission of any of EEEs 17-21, wherein the belt comprises a plurality of belt segments, wherein each belt segment of the belt engages with neighboring segments of the belt via contact surfaces shaped such that the belt segments engage with each other via rolling motion along the contact surfaces.
  • EEE 24 is the transmission of EEE 22, wherein the plurality of belt segments comprise a first belt segment and a second belt segment, wherein the first and second belt segments are coupled together via at least two flexible straps that are configured to oppose the first and second belt segments engaging with each other via non-rolling motion along the contact surfaces of the first and second belt segments.
  • EEE 25 is the transmission of EEE 22, wherein the plurality of belt segments comprise a first belt segment and a second belt segment, wherein the first and second belt segments comprise respective pluralities of geared teeth that are configured to oppose the first and second belt segments engaging with each other via non-rolling motion along the contact surfaces of the first and second belt segments.
  • EEE 26 is the transmission of any of EEEs 17-25, wherein the belt experiences a net compressive force along the length of the belt at every location along the length of the belt.
  • EEE 27 is the transmission of EEE 26, wherein the belt does not include a longitudinal band that is under tension.
  • EEE 28 is a transmission belt comprising a plurality of belt segments, wherein each belt segment of the transmission belt engages with neighboring segments of the transmission belt via contact surfaces shaped such that the belt segments engage with each other via rolling motion along the contact surfaces, wherein the plurality of belt segments comprise a first belt segment and a second belt segment, wherein the first and second belt segments comprise respective pluralities of geared teeth that are configured to oppose the first and second belt segments engaging with each other via non-rolling motion along the contact surfaces of the first and second belt segments.
  • EEE 29 is a transmission belt comprising: (i) a plurality of belt segments, wherein each belt segment of the transmission belt engages with neighboring segments of the transmission belt via contact surfaces shaped such that the belt segments engage with each other via rolling motion along the contact surfaces; (ii) a first linkage; and (iii) a second linkage, wherein the plurality of belt segments comprise a first belt segment, a second belt segment, and a third belt segment, wherein the contact surface of the first belt segment defines a first focus and a second focus, wherein a first end of the first linkage is rotatably coupled to the first belt segment at the first focus and a second end of the first linkage is rotatably coupled to the second belt segment, and wherein a first end of the second linkage is rotatably coupled to the first belt segment at the second focus and a second end of the second linkage is rotatably coupled to the third belt segment.
  • EEE 30 is a transmission belt comprising a plurality of belt segments, wherein each belt segment of the transmission belt engages with neighboring segments of the transmission belt via contact surfaces shaped such that the belt segments engage with each other via rolling motion along the contact surfaces, wherein the plurality of belt segments comprise a first belt segment and a second belt segment, wherein the first and second belt segments are coupled together via at least two flexible straps that are configured to oppose the first and second belt segments engaging with each other via non-rolling motion along the contact surfaces of the first and second belt segments, and wherein the first and second belt segments are disposed within recesses formed in the first and second belt segments relative to the contact surfaces of the first and second belt segments.
  • EEE 31 is the transmission belt of EEE 30, wherein the at least two flexible straps are fused to the first and second belt segments and exert respective tensile forces along the lengths of the at least two flexible straps between the first and second belt segments.
  • EEE 32 is the transmission belt of any of EEEs 30-31, wherein the first belt segment comprises a first portion fused to a second portion, wherein the at least two flexible straps are coupled to the first portion, wherein the plurality of belt segments further comprise a third belt segment, wherein the first and third belt segments are coupled together via at least two additional flexible straps that are configured to oppose the first and third belt segments engaging with each other via non-rolling motion along the contact surfaces of the first and third belt segments, and wherein the at least two additional flexible straps are coupled to the second portion.
  • EEE 33 is a transmission comprising: (i) a first sprocket rotatable about a first axis and comprising a first plurality of inward-facing teeth; (ii) a second sprocket rotatable about a second axis and comprising a second plurality of inward-facing teeth; (iii) an outer member defining a third axis, wherein the first sprocket and second sprocket are nested within the outer member; (iv) a first belt that is in contact with the first sprocket and the outer member, wherein the first sprocket exerts forces onto the first belt that are radially directed inward toward the first axis, and wherein the outer member exerts forces onto the first belt that are radially directed inward toward the third axis; and (v) a second belt that is in contact with the second sprocket and the outer member, wherein the second sprocket exerts forces onto the second
  • EEE 34 is the transmission of EEE 33, further comprising: (i) an input member, wherein rotation of the input member results in rotation of the first sprocket about the first axis, rotation of the second sprocket about the second axis, and movement of the first axis and second axis about the third axis; and (ii) an output member, wherein the output member is coupled to the first sprocket and second sprocket such that movement of the first axis and second axis about the third axis results in rotation of the output member and further such that a torque at the input member causes a torque to be realized at the output member.
  • EEE 35 is the transmission of any of EEEs 33-34, wherein the outer member is a split pulley comprising first and second half-pulleys, and wherein the outer member exerting forces onto the first belt that are radially directed inward toward the third axis comprises a couple between the first and second half-pulleys exerting forces onto the first belt that are radially directed inward toward the third axis.
  • EEE 36 is the transmission of EEE 35, wherein the transmission is configured such that a transmission ratio of the transmission is controllable by adjusting a separation between the first and second half-pulleys.
  • EEE 37 is the transmission of any of EEEs 33-34, wherein the outer member is a third sprocket comprising a plurality of inward-facing teeth.
  • EEE 38 is the transmission of any of EEEs 33-38, wherein the first belt comprises a plurality of belt segments, wherein each belt segment of the first belt comprises a respective tooth, and wherein the plurality of inward-facing teeth of the first sprocket engage with the first belt via at least one tooth of the first belt.
  • EEE 39 is the transmission of any of EEEs 33-38, further comprising: (i) a sun gear rotatable about the third axis; (ii) a first planet gear rotatable about the first axis and coupled to the first sprocket; (iii) a second planet gear rotatable about the second axis and coupled to the second sprocket; (iv) a first spur gear, wherein the first spur gear engages with the sun gear and the first planet gear; and (v) a second spur gear, wherein the second spur gear engages with the sun gear and the second planet gear.
  • EEE 40 is the transmission of EEE 39, further comprising: (i) a first rigid member configured to maintain a first distance between the sun gear and the first spur gear while permitting an axis of the first spur gear to move around the third axis; and (ii) a second rigid member configured to maintain second distance between the first planet gear and the first spur gear.
  • EEE 41 is the transmission of any of EEEs 33-40, wherein the first belt comprises a plurality of belt segments, wherein each belt segment of the first belt engages with neighboring segments of the first belt via contact surfaces shaped such that the belt segments engage with each other via rolling motion along the contact surfaces.
  • EEE 42 is the transmission of EEE 41, wherein the first belt further comprises a first linkage and a second linkage, wherein the contact surfaces of the plurality of belt segments have shapes that conform to portions of an elliptic cylinder, wherein the plurality of belt segments comprise a first belt segment, a second belt segment, and a third belt segment, wherein the contact surface of the first belt segment defines a first focus and a second focus, wherein a first end of the first linkage is rotatably coupled to the first belt segment at the first focus and a second end of the first linkage is rotatably coupled to the second belt segment, and wherein a first end of the second linkage is rotatably coupled to the first belt segment at the second focus and a second end of the second linkage is rotatably coupled to the third belt segment.
  • EEE 43 is the transmission of EEE 41, wherein the plurality of belt segments comprise a first belt segment and a second belt segment, wherein the first and second belt segments are coupled together via at least two flexible straps that are configured to oppose the first and second belt segments engaging with each other via non-rolling motion along the contact surfaces of the first and second belt segments.
  • EEE 44 is the transmission of EEE 41, wherein the plurality of belt segments comprise a first belt segment and a second belt segment, wherein the first and second belt segments comprise respective pluralities of geared teeth that are configured to oppose the first and second belt segments engaging with each other via non-rolling motion along the contact surfaces of the first and second belt segments.
  • EEE 45 is the transmission of any of EEEs 33-44, wherein the first belt experiences a net compressive force along the length of the first belt at every location along the length of the first belt.
  • EEE 46 is the transmission of EEE 45, wherein the first belt does not include a longitudinal band that is under tension V.

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Abstract

Sont prévus des mécanismes de transmission variable et non variable qui comprennent des poulies « inversées radialement » et/ou des barbotins qui sont imbriqués les uns dans les autres ou alors se chevauchent afin d'exercer des forces « vers l'intérieur » sur une courroie de compression qui transmet de l'énergie entre les poulies/barbotins. En exerçant des forces « vers l'intérieur » sur la courroie, la courroie peut être soumise à une compression nette partout sur sa longueur, ce qui permet à la courroie d'être moins complexe et de présenter un coût inférieur, et aux transmissions de présenter une taille et un coût réduits et une capacité de puissance accrue par rapport à des transmissions qui utilisent des poulies/barbotins « non inversés radialement ». Au moins deux poulies ou barbotins « internes » peuvent être imbriqués à l'intérieur d'une seule poulie ou d'un seul barbotin « externe », exerçant des forces « vers l'intérieur » sur au moins deux courroies respectives dans une configuration planétaire, équilibrant la masse rotative d'un porte-satellites interne et augmentant la puissance nominale en distribuant la transmission d'une entrée à une sortie à travers au moins deux courroies.
PCT/US2024/055233 2023-11-08 2024-11-08 Transmissions à poulies inversées, barbotin et configurations planétaires Pending WO2025101977A1 (fr)

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US20180320766A1 (en) * 2016-01-29 2018-11-08 Sri International Compact infinitely variable transmission
WO2021101541A1 (fr) * 2019-11-20 2021-05-27 Sri International Courroie pour transmission à variation continue
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US20130337957A1 (en) * 2012-06-19 2013-12-19 John M. Vranish Segmented ground gear transmission (SGGT)
US20180320766A1 (en) * 2016-01-29 2018-11-08 Sri International Compact infinitely variable transmission
WO2021101541A1 (fr) * 2019-11-20 2021-05-27 Sri International Courroie pour transmission à variation continue
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