WO2025193733A1

WO2025193733A1 - Sprocket for toothed belt system

Info

Publication number: WO2025193733A1
Application number: PCT/US2025/019420
Authority: WO
Inventors: Bipinchandra Patel; Derek White; Marvin Miller; Elizabeth AMICI; Alexander Wang; Michael BRYNN; Leslee W. Brown
Original assignee: Gates Corp
Current assignee: Gates Corp
Priority date: 2024-03-13
Filing date: 2025-03-11
Publication date: 2025-09-18
Anticipated expiration: 2026-09-13

Abstract

Belt systems, such as toothed systems, having a belt and a wheel (e.g., a pulley, gear, sprocket, etc.) where the fit between the belt and wheel is mismatched. In some implementations, when the belt and wheel are engaged, the belt lands do not contact the tips of the wheel teeth. In other implementations, the groove depth of the wheel is less than the tooth height of the belt. Generally, when the belt and wheel of the belt systems are engaged, a pressure between the belt lands and the tips of the wheel teeth is reduced compared to other systems.

Description

SPROCKET FOR TOOTHED BELT SYSTEM

CROSS-REFERENCE

[0001] This application claims priority to U.S. provisional application no. 63/564,855 filed March 13, 2024 and to U.S. provisional application no. 63/654,242 filed May 31, 2024, the entire disclosures of which are incorporated herein by reference for all purposes.

TECHNICAL FIELD

[0002] This disclosure is directed to belt systems having a toothed sprocket and an engaging toothed belt.

BACKGROUND

[0003] On a belt drive, both the sprocket and the belt wear as the two contact each other as the system runs. Different systems may wear in different ways. In some applications, wear on the land of the belt, such as between the teeth of the belt, exposes the tensile cords, which can lead to premature belt failure.

SUMMARY

[0004] The present disclosure provides belt systems, having a toothed belt and a toothed wheel (e.g., a pulley, gear, sprocket, etc.), that do not have a “matching” fit between the belt and the wheel, thus reducing the pressure between the belt and the wheel. In particular, the tip of the wheel tooth has less contact, and in some implementations does not contact the land area of the belt, due to the shape (profile) of the groove between the wheel teeth. The groove of the wheel, between the teeth of the wheel, is shortened radially and/or longitudinally, so that the belt tooth “bottoms out” on either the wheel groove bottommost portion or on the groove sidewall. By not having the lands between the belt teeth contact the wheel teeth, the life of the belt is prolonged due to reduced land wear which prevents or delays stress on the load carrying cords of the belt.

[0005] This disclosure provides belt systems comprising a flexible, endless belt having a plurality of teeth each with a tip and with lands between adjacent teeth, and a toothed wheel having a plurality of teeth, each tooth having a tip, and grooves between adjacent teeth, each groove having a sidewall and a bottommost portion. When the belt and wheel are engaged, the belt lands do not contact the tips of the wheel teeth. Alternately, although the belt lands do contact the tips of the wheel, the pressure between the two is reduced, reducing the wear rate of one or both of the belt and the wheel.

[0006] In a particular implementation, described herein is a belt system comprising a flexible, endless belt having a plurality of teeth each with a tip and with lands between adjacent teeth, and a toothed wheel having a plurality of teeth, each tooth having a tip, and grooves between adjacent teeth, each groove having a sidewall and a bottommost portion. When the belt and wheel are engaged, the belt lands do not contact the tips of the wheel teeth. The distance between the belt lands and the tooth tips may be at least 1 mm, at least 2 mm, or 3 mm, or 4 mm, or 5 mm.

[0007] In some implementations, although the belt lands may contact the tips of the wheel tooth, the pressure between the two is reduced, reducing wear rate of one or both of the belt and the wheel. In some implementations, when the belt and wheel are engaged, the tips of the belt teeth contact the engaging and opposing tooth flanks and/or the sidewalls of the wheel grooves, in meshing engagement.

[0008] In yet another particular implementation, described herein is a belt system comprising a flexible, endless belt having a plurality of teeth with lands between adjacent teeth, each tooth having a tooth height, and a toothed wheel having a plurality of teeth and grooves between adjacent teeth, each groove having a groove depth. The groove depth is less than the tooth height.

[0009] These and other aspects of the toothed belt systems described herein will be apparent after consideration of the Detailed Description and Figures herein. It is to be understood, however, that the scope of the claimed subject matter shall be determined by the claims as issued and not by whether given subject matter addresses any or all issues noted in the Background or includes any features or aspects recited in the Summary.

BRIEF DESCRIPTION OF THE FIGURES

[0010] FIG. l is a perspective, cross-sectional view of a portion of a toothed belt.

[0011] FIG. 2 is an enlarged schematic side view of a toothed belt engaged with a toothed wheel such as a pulley, gear or sprocket. [0012] FIG. 3 is a schematic side view of engagement of a toothed belt with a toothed wheel such as a pulley, gear or sprocket, identifying various measurements.

[0013] FIG. 4 is an enlarged schematic side view diagram of two superimposed grooves from toothed wheels.

[0014] FIG. 5 is a schematic side view of the two grooves depicted in FIG. 4 having a belt tooth received in each groove.

[0015] FIG. 6 is a computer generated wear analysis on two belt teeth.

[0016] FIG. 7A and FIG. 7B are side view diagrams of two wheel grooves identifying the groove dimensions.

[0017] FIG. 8 is a graphical representation of before and after wear of a belt on two different toothed wheels.

DETAILED DESCRIPTION

[0018] As indicated above, the present disclosure is directed to revising the fit between a toothed belt and a toothed wheel (e.g., a pulley, gear, sprocket, etc.) of a system so that the pressure between the belt land and the wheel teeth tips is reduced or eliminated by shortening the height and/or width of the groove of the wheel. Sometimes, the land between belt teeth does not contact the tips of the wheel teeth. The belt tooth “bottoms out” on either the wheel groove bottommost portion or on the groove sidewall. This prolongs belt life by reducing the land wear of the belt which inhibits and thus prevents or delays stress on the load carrying cords of the belt.

[0019] Thus, described herein are various implementations that include dimensional changes to the wheel groove, which can be accomplished by various methods, including by the changing the profile of the wheel groove and/or by the application of coatings. Application of a coating, surface treatment, or surface finish on at least a portion of the wheel tooth or groove consequently changes the dimension of the groove.

[0020] In the following description, reference is made to the accompanying drawing that forms a part hereof and in which is shown by way of illustration at least one specific implementation. The following description provides additional specific implementations. It is to be understood that other implementations are contemplated and may be made without departing from the scope or spirit of the present disclosure. The following detailed description, therefore, is not to be taken in a limiting sense. While the present disclosure is not so limited, an appreciation of various aspects of the disclosure will be gained through a discussion of the examples, including the figures, provided below. In some instances, a reference numeral may have an associated sub-label consisting of an upper-case letter to denote one of multiple similar components. When reference is made to a reference numeral without specification of a sublabel, the reference is intended to refer to all such multiple similar components.

[0021 J Turning to the figures, FIG. 1 shows a generic belt 100 having a body 102 formed of a flexible material having a back side 104 and a front side 106 with a plurality of load carrying cords 108 within the body 102, the particular cords 108 in FIG. 1 bound in triplicate bundles although in other implementations the cords 108 may be single cords or bundled otherwise. The cords 108 may be, e.g., carbon cords, polymeric cords (e.g., polyester, aramid), fiberglass cords, etc. Defined in the front side 106 are a plurality of teeth 110; although trapezoidal teeth are depicted in this implementation of FIG. 1, the tooth shape is not limited thereto and can take any shape that is compatible with a sprocket, gear or other toothed wheel. Each individual tooth 110 extends either perpendicular to or angled/helical to the longitudinal length of the belt 100 so that the plurality of teeth 110 run along or around the length of the belt 100. In use, the teeth 110 on the front side 106 are in contact with a drive mechanism, e.g., a toothed gear or sprocket. Although not seen in FIG. 1, the belt 100 is an endless belt, having the form of a loop with no beginning and no end. The belt 100 may have a splice therein.

[0022] FIG. 2 shows a portion of a system 200 having a toothed belt 210 engaged with a toothed wheel 220. The belt 210 has a body formed of a flexible material having a back side 211 and an opposite front side having defined therein a plurality of teeth 212. The shape of the teeth 212 is not limited thereto and can take any shape that is compatible with the wheel 220. Each individual tooth 212 extends perpendicular or angled to the longitudinal length of the belt 210, so that the plurality of teeth 212 run along or around the length of the belt 210. A land 214 is present between adjacent teeth 212. Although not seen in FIG. 2, the belt 210 is an endless belt, having the form of a loop with no beginning and no end.

[0023] The wheel 220 has a plurality of teeth 222 around the circumferential surface, with a groove 224 present between adjacent teeth 222. Although concave grooves 224 with a rounded bottom are depicted in this implementation of FIG. 2, the groove shape is not limited thereto and can take any shape that is compatible with the teeth 222 of the corresponding belt. [0024] In use, the teeth 212 of the belt 210 are in contact with a drive mechanism, e.g., a toothed gear or sprocket, e.g., wheel 220, by engaging with the grooves 224 of the wheel 220, and the teeth 222 of the wheel 220 engaging with the lands 214 of the belt 210. In such a manner, the teeth 212, 222 and the land 214 and the groove 224 mesh.

[0025] In accordance with the design of the systems of this disclosure, the teeth of the wheel do not engage with the lands of the toothed belt, but rather, the tip of the belt tooth engages with (“bottoms out”) on the groove between wheel teeth. In some implementations, the teeth of the wheel engage with or abut the sidewalls or tip of the belt teeth rather than the land between the teeth. In some implementations, the top of the tooth may contact the bottom of the wheel groove.

[0026] As a tutorial in belt systems, when determining the dimensions of a belt and a wheel, the pitch line diametrical difference (PLDD), rather than the radial pitch line difference (PLD), is used to define a belt’s pitch line as influenced by the location of the load carrying cord. Turning to FIG. 3, a portion of a system 300 having a toothed belt 310 and a toothed wheel 320 is shown. It is noted that not all the teeth and the grooves in the wheel 320 are shown, as typically the teeth/grooves extend around the entire circumference of the wheel 320, nor is the belt 310 shown extending fully around the wheel 320. Rather, the details shown in FIG. 3 are sufficient to provide an understanding of the terminology and measurements used for determining fit. Belt fit relies on three belt properties, the belt pitch line diametrical difference (belt PLDD), the pitch stiffness (Kpitch), and zero tension pitch (ZTP).

[0027] FIG. 3 shows, for the belt 310, the Belt Pitch Line, which is the line where the linear speed of the belt 310 matches the tangential speed of the wheel 320, which is based on gear design, when the wheel pitch and belt pitch are equal. It is assumed that the Belt Pitch Line is coincident with the center of the load carrying cord within the belt. The pitch line can be defined by measurements, including the location of the load carrying cord(s). It is noted that because the Belt Pitch Line is determined by the position of the load carrying cord and is inherent to the belt, two belts with different cord locations placed on the same wheel of a particular outside diameter will have two separate (different) pitch diameters.

[0028] The distance from the belt land (e.g., land 214 of FIG. 2) to the Belt Pitch Line (which is also the minimum thickness of the belt) is called the belt Pitch Line Difference (PLD), which is measured by measuring the length of a rotating belt upright and inverted in measuring pulleys. The PLD is also a function of the location of the load carrying cord(s).

[0029] An imaginary circle, referred to as the Pitch Diameter for a particular combination of wheel and belt, can be defined by the wheel outside diameter increased by the belt pitch line diametrical difference (PLDD). That is, Pitch Diameter = Wheel Outside Diameter + Belt PLDD. This imaginary circle represents the location of the Belt Pitch Line as it travels around the wheel at the tension used to measure the Belt Pitch Line (the measuring tension).

[0030] The wheel or pulley pitch is the difference in the wheel’s outside diameter (OD) and the imaginary pitch diameter (PLD) based on the nominal pitch of the system. For convenience, both the belt pitch and the wheel pitch are described using the pitch line diametrical difference (PLDD), which is double the PLD. The wheel or pulley pitch is defined as the circumference of the Sprocket Pitch Circle, divided by the number of grooves in the sprocket. The Sprocket Pitch Circle is the circle defined by the Pitch Diameter. For wheels or pulleys that are not perfect circles, the wheel or pulley pitch would be defined using an offset of the pulley profile equal to half the PLDD divided by the intersection of the pulley grooves and the offset sprocket pitch closed curve.

[0031] Changing the fit of the belt 310 on the wheel 320 can change the relationship or interaction between the belt 310 and the wheel 320 during use. By optimizing the fit between the belt 310 and the wheel 320, which includes surface properties, the tension on the belt 310, as it progresses around the wheel 320, is more constant, the peak tooth load (force) is reduced, and the effective tension load is distributed over more teeth.

[0032] In accordance with the design of the systems of this disclosure, the grooves of the wheel are modified so that the wheel teeth only partially engage or do not engage with the lands of the toothed belt, but rather, the tip of the belt tooth engages with (“bottoms out” on) the groove between wheel teeth. The distance between the lands of the belt and the tip of the wheel tooth may be between 0 to 5 mm, e.g., at least 1 mm, and in some designs at least 2 mm, or 3 mm, or 4 mm.

[0033] For a wheel (e.g., pulley, sprocket, gear, idler, etc.), the dimensions and/or contour of the groove or tooth can be modified during the forming process of the wheel. For example, during the process of making the wheel, e.g., by casting, molding, machining, waterjet cutting, plasma cutting, hobbing, etc., the wheel dimensions can be modified. Additionally or alternately, the dimensions can be modified after formation of the wheel. For example, the dimensions can be increased after forming the wheel teeth by applying a coating onto at least a portion of the outer periphery or circumference of the wheel; a coating will increase the dimension on the order of micrometers. Example coating techniques include deposition (e.g., PVD, CVD, sputtering, any of these with or without plasma aid), plating (e.g., electrolysis, electroless), oxidation techniques, plasma spray. Example coating materials include diamondlike-carbon (DLC), tungsten carbide, silicon carbide, chromium carbide, boron nitride, titanium nitride, and chromium nitride.

[0034] Dimensions of the wheel teeth can be decreased after forming the wheel by removing a portion of the tooth, e.g., the tip of the tooth. Example material removal techniques include, but are not limited to, bead blasting, tumbling, oxidizing, milling, and chemicalmechanical polishing (CMP).

[0035] FIG. 4 shows the comparison of two grooves from toothed wheels, the grooves having different radial distances or depths but the same width. Both wheels are intended to be used with the same belt. The first wheel groove 400A (dotted) has a radial depth from the bottommost portion of the groove between the two shown teeth to the top of the teeth shown as A. The second wheel groove 400B (dashed) has a radial depth, from the bottommost portion of the groove between the two shown teeth to the top of the teeth shown as B; example depths A, B, for the grooves 400A, 400B, respectively, is 5.16, 4.80 units. The difference between the two depths is shown as X. Additionally, for the second wheel groove 400B (dashed), the bottommost portion of the groove is more flat, defined by a larger radius than the first wheel. By having a shallower groove area, or, by having a less deep groove, with the sidewalls of the groove the same, the area available for receiving the belt tooth is reduced. Because the radial distance of the groove area is reduced, the groove is too shallow for the entire belt tooth to fit within the groove; because of this, the belt land does not fully seat against the top of the wheel tooth.

[0036] In alternate implementations, the sidewall of the groove is altered, e.g., shortened in the longitudinal or circumferential direction of the wheel, resulting in a more narrow groove. With a more narrow groove, due to it typically being tapered, the belt tooth will not seat as far into the groove, but butt up to points on the sidewall. In yet other implementations, the sidewall of the groove has a different angle than the belt tooth (e g., the wheel groove has a smaller included angle than the angle of the sidewalls of the belt tooth).

[0037] FIG. 5 shows the same two wheel grooves of FIG. 4, called out as 500A (first, dotted wheel groove) and 500B (second, dashed wheel groove). The grooves 500A, 500B have the same profile sidewalls 504A, 504B, respectively, but with the groove 500B being less deep than the groove 500A.

[0038] Shown engaged with each of the grooves 500 is a toothed belt, with one Belt Tooth (the same tooth) shown in each of the grooves 500. The Belt Tooth is a trapezoidal shape having a rounded tip. The belt land, L, on each side of the Belt Tooth, is called out. The grooves 500 are concave, having an arcuate shape; in other implementations the grooves may be trapezoidal. For the first groove 500A, the lands L of the belt essentially touch the tips of the wheel teeth, whereas for the groove 500B, the lands L of the belt do not touch the tips of the wheel teeth, but rather, the distance X is between the belt lands L and the tips of the wheel teeth.

[0039] FIG. 6 shows two computer simulated belt teeth; the same belt tooth was run on a first toothed wheel (left) and on a second toothed wheel having a shallower groove profile (right) to obtain the simulated wear pattern. The shallower wheel groove (right) promotes belt tooth tip contact and inhibits belt land contact. The left side shows a belt tooth where the lands of the belt, on either side of the tooth, had a high amount of wear due to contact with the tips of the wheel teeth. The right side shows a belt tooth that engaged with a shallower wheel groove that had an altered tip radius. This shows that the tip of the belt tooth had a high amount of wear due to its contact with the bottommost portion of the wheel groove.

[0040] FIG. 7A shows a first wheel groove. Example dimensions for the groove of FIG. 7A are provided in Table 1 and Table 2.

Table 1

Table 2

[0041] FIG. 7B shows a wheel groove having a similar width as the groove of FIG. 7A yet a different wall profile and a shallower and flatter bottom. Example dimensions for the groove of FIG. 7B are provided in the figure.

[0042] FIG. 8 shows results from a wear test: curve 800 represents a belt tooth before being run/used, curve 802 represents the same tooth after a wear test run on a dynamometer having a first toothed wheel with the groove profile of FIG. 7A, and curve 804 represents the same tooth after a wear test run on a dynamometer having a second toothed wheel with the groove profile of FIG. 7B. The belt tooth represented by curve 804, which ran on a wheel with a shallower groove profile resulted in less wear in the land and leading flank areas. In turn, the reduced wear led to an increase in belt life.

[0043] Thus, described herein are various implementations that include dimensional changes and/or changed surface properties to belt systems, which can be accomplished by various methods, including by the application of coatings. Various features and details have been provided in the multiple designs described above. It is to be understood that any features or details of one design may be utilized for any other design, unless contrary to the construction or configuration. Any variations may be made.

[0044] The above specification and examples provide a complete description of the structure and use of exemplary implementations of the invention. The above description provides specific implementations. It is to be understood that other implementations are contemplated and may be made without departing from the scope or spirit of the present disclosure. The above detailed description, therefore, is not to be taken in a limiting sense. While the present disclosure is not so limited, an appreciation of various aspects of the disclosure will be gained through a discussion of the examples provided.

[0045J Unless otherwise indicated, all numbers expressing feature sizes, amounts, and physical properties are to be understood as being modified by the term “about,” whether or not the term “about” is immediately present. Accordingly, unless indicated to the contrary, the numerical parameters set forth are approximations that can vary depending upon the desired properties sought to be obtained by those skilled in the art utilizing the teachings disclosed herein.

[0046] As used herein, the singular forms “a”, “an”, and “the” encompass implementations having plural referents, unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.

[0047] Spatially related terms, including but not limited to, “bottom,” “lower”, “top”, “upper”, “beneath”, “below”, “above”, “on top”, “on,” etc., if used herein, are utilized for ease of description to describe spatial relationships of an element(s) to another. Such spatially related terms encompass different orientations of the device in addition to the particular orientations depicted in the figures and described herein. For example, if a structure depicted in the figures is turned over or flipped over, portions previously described as below or beneath other elements would then be above or over those other elements.

Claims

WHAT IS CLAIMED IS:

1. A belt system comprising: a flexible, endless belt having a plurality of teeth each with a tip and a land between adjacent teeth, each tooth having a height; a toothed wheel having a plurality of teeth, each tooth having a tip, and a plurality of grooves, each groove between adjacent teeth and having opposite sidewalls and a bottommost portion between the sidewalls, each groove having a depth less than the wheel tooth height; wherein when the belt and wheel are engaged, the belt lands do not contact the tips of the wheel teeth.

2. The belt system of claim 1, wherein when the belt and wheel are engaged, the tips of the belt teeth contact the bottommost portion of the wheel groove.

3. The belt system of claim 1, wherein when the belt and wheel are engaged, the tips of the belt teeth contact the sidewalls of the wheel groove.

4. The belt system of claim 3, wherein sidewalls of the belt teeth form a greater angle than the sidewalls of the wheel grooves.

5. The belt system of claim 3, wherein the wheel grooves are more narrow than the belt teeth.

6. The belt system of any of claims 1-5, wherein a distance between the belt lands and the tips of the wheel teeth is at least 1 mm.

7. The belt system of claim 6, wherein a distance between the belt lands and the tips of the wheel teeth is at least 2 mm.

8. The belt system of claim 1, wherein the belt comprises a body with a plurality of load carrying cords therein.

9. The belt system of claim 1, wherein each of the plurality of belt teeth is trapezoidal.

10. The belt system of claim 9, wherein each of the plurality of grooves is concave.

11. The belt system of claim 10, wherein each of the plurality of grooves is trapezoidal.

12. The belt system of claim 10, wherein each of the plurality of grooves is arcuate.