WO2025090714A1 - Joint structures for articulatable mechanisms, and related devices and methods - Google Patents

Abstract

A joint structure that is configured to provide articulation between two links coupled by the joint structure comprises a pair of complementary joint features. One of the pair of complementary joint features comprises an elongated slot defined by a pair of protrusions extending in a direction of elongation of the slot and defining side walls of the slot. Another of the pair of complementary joint features comprises a male gear feature terminating in a rounded head. The rounded head is received in and moveable relative to the slot, and through a range of motion of articulation of the joint structure, the rounded head remains at a position within the slot bounded by the pair of protrusions.

Description

JOINT STRUCTURES FOR ARTICULATABLE MECHANISMS, AND RELATED DEVICES AND METHODS

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Provisional Application No. 63/592,978, filed October 25, 2023, the entirety of which is incorporated by reference herein.

TECHNICAL FIELD

[0002] Aspects of the present disclosure relate to joint structures for articulatable mechanisms, and related devices and methods. In particular, aspects of the present disclosure relate to instruments with joint structures that are articulatable in response to forces transmitted by actuation elements extending through links coupled together at the joint structures.

INTRODUCTION

[0003] Various instruments, such as medical (e.g., surgical) or other industrial instruments, include articulatable mechanisms including joint structures that impart one or more degrees of freedom of movement to such instruments. These articulatable mechanisms can include one or more joint structures, each of which can articulate in one or more degrees of freedom, which can be the same or different.

[0004] Articulation can be controlled by one or more actuation elements, such as, for example, cables, coupled through various components to a manipulator system that receives inputs from a user, such as a surgeon or other operator, to orient portions of the instrument as desired. Such manipulator systems can include a teleoperated (e.g., computer-controlled) manipulator system. In other applications, the instrument and articulatable mechanism can be actuated manually. In some cases, it is desirable that an articulatable mechanism exhibit a relatively high stiffness in any given articulation position to facilitate the instrument’s ability to maintain a given position under reaction forces, such as those resulting from operation of an end effector, or working end component, of the instrument. [0005] An instrument can include one or more articulatable mechanisms, which can be used to couple an end effector coupled to the distal end portion of a shaft of the instrument so as to provide orientation in one or two-degrees of freedom (e.g., pitch and yaw) of the end effector. Other articulatable mechanisms can be provided along the length of the shaft to achieve various poses of the shaft of instrument. The one or more actuation elements extend from a transmission mechanism coupled to the shaft proximally of the articulatable mechanism, through the instrument shaft and to link(s) of the joint structure(s) of the articulatable mechanism. Forces transmitted by the one or more actuation elements impart articulating movement of the link(s) relative to each other about the joint structures, thereby allowing remote “steering” of the articulatable mechanism. For example, actuation elements can transmit forces through selective tensioning of flexible, cable-like actuation elements and/or through push/pull forces of stiffer, compressive rod-like actuation elements. Those having ordinary skill in the art have familiarity with various types of actuation elements used to transmit forces to articulate articulatable mechanisms.

[0006] Some articulatable mechanisms can include a joint structure having joint features that provide a gearing type of movement, and thus allow two opposing links coupled by the joint structure to have relative angular orientations that change according to a fixed relationship, and which prevent the links from sliding relative to one another during articulation. If over rotated, however, such articulatable mechanisms can be susceptible to dislocation, in which the joint features disengage and slip out of their fixed relationship. Dislocation therefore can become an issue at larger angular orientations of the joint structures (i.e. , when the links articulate relative to one another at larger angles). Pin gearing and involute gearing joint structures, for example, have previously been used to enforce the rolling constraint between the links of articulatable mechanisms. However, such joint structures can have more complicated intermeshing gear features that can be more prone to dislocation.

[0007] There exists a need to provide joint structures for articulatable mechanisms in instruments, having suitable strength and precision, with simplified designs for ease of manufacturing. There further exists a need to provide articulatable mechanisms that address joint dislocation issues.

SUMMARY

[0008] Exemplary embodiments of the present disclosure can solve one or more of the above-mentioned problems and/or can demonstrate one or more of the above- mentioned desirable features. Other features and/or advantages may become apparent from the description that follows.

[0009] In accordance with at least one exemplary embodiment, a joint structure that is configured to provide articulation between two links coupled by the joint structure comprises a pair of complementary joint features. One of the pair of complementary joint features comprises an elongated slot defined by a pair of protrusions extending in a direction of elongation of the slot and defining side walls of the slot. Another of the pair of complementary joint features comprises a male gear feature terminating in a rounded head. The rounded head is received in and moveable relative to the slot, and through a range of motion of articulation of the joint structure, the rounded head remains at a position within the slot bounded by the pair of protrusions.

[00010] In accordance with at least another exemplary embodiment, a joint structure is configured to provide articulation between two links coupled by the joint structure comprising a pair of complementary joint features. One of the pair of complementary joint features comprises an elongated slot bounded by a pair of protrusions extending in a direction of elongation of the slot and defining side walls of the slot. Another of the pair of complementary joint features comprises a male gear feature terminating in a rounded head. The male gear feature has a recessed region adjacent the rounded head. The rounded head is received in and moveable relative to the slot. Through a range of motion of articulation of the joint structure in a first direction from a neutral position, the rounded head remains within the elongated slot bounded by the pair of protrusions, and one of the pair of protrusions is respectively received in and moves along the recessed region. Through a range of motion of articulation of the joint structure in a second direction from the neutral position, the rounded head remains within the elongated slot and bounded by the pair of protrusions, and another of the pair of protrusions is respectively received in and moves along the recessed region.

[00011] In accordance with at least another exemplary embodiment, an articulatable mechanism comprises a first link and a second link coupled to each other by a pair of complementary joint features. The pair of complementary joint features is configured to permit articulation of the first link and second link relative to each other about a pivot axis. The pair of complementary joint features comprises a pair of protrusions extending from the first link in a direction perpendicular to the pivot axis and defining an elongated slot between the pair of protrusions. The pair of complementary joint features also comprises a pin extending from the second link and received in the elongated slot. The pin and the pair of protrusions are rotatable relative to each other to cause articulation of the first and second links relative to each other. Through a range of motion of articulation of the first and second links relative to each other, the pin is moveable in translation relative to the slot and remains within the slot bounded by the pair of protrusions.

[00012] In accordance with at least another exemplary embodiment, a link of an articulatable mechanism comprises a first end, a second end, a lateral surface extending between the first end and the second end, and a longitudinal axis extending between the first and the second end. The link also comprises a first pair of joint features extending in a first axial direction from the first end and positioned diametrically opposite one another, and a second pair of joint features extending in a second axial direction from the second end and positioned diametrically opposite one another. Each joint feature of the first pair of joint features comprises an elongated slot defined by a pair of protrusions extending in a direction of elongation of the slot and defining side walls of the slot. Each joint feature of the second pair of joint features comprises a semi-circular recessed region adjacent a circular pin, the circular pin protruding radially outwardly from the semi-circular recessed region. The first pair of joint features are configured to engage with a third pair of joint features on another link having a same configuration as the second pair of joint features, and the second pair of joint features is configured to engage with a fourth pair of joint features on another link having a same configuration as the first pair of joint features.

BRIEF DESCRIPTION OF DRAWINGS

[00013] The present disclosure can be understood from the following detailed description, either alone or together with the accompanying drawings. The drawings are included to provide a further understanding of the present disclosure, and they are incorporated in and constitute a part of this specification. The drawings illustrate one or more exemplary embodiments of the present disclosure and, together with the description, explain certain principles and operation. In the drawings,

[00014] FIG. 1 is a schematic view of an embodiment of an instrument comprising an articulatable mechanism;

[00015] FIG. 2 is a diagrammatic view of an embodiment of a computer-assisted medical system employing robotic technology and including the instrument of FIG. 1 ; [00016] FIGS. 3 and 4 are partial perspective views of an embodiment of a distal end portion of an instrument comprising an articulatable mechanism;

[00017] FIG. 5 is an isolated, perspective view of an embodiment of an articulatable mechanism comprising multiple links;

[00018] FIG. 6 is an isolated, perspective view of the articulatable mechanism of FIG. 5 illustrating the links of the articulatable mechanism articulated relative to one another;

[00019] FIG. 7A is a side view of an embodiment of an articulatable mechanism including first and second links coupled by a joint structure, in a neutral state of relative rotation of the first and second links about the joint structure;

[00020] FIG. 7B is a side view of the articulatable mechanism of FIG. 7A showing the first and second links partially rotated relative to one another about the joint structure;

[00021] FIG. 7C is a side view of the articulatable mechanism of FIG. 7A showing the first and second links fully rotated relative to one another about the joint structure; [00022] FIG. 8A is a side view of the articulatable mechanism of FIG. 7A showing bearing surfaces of the first and second links, in the neutral state of relative rotation of the first and second links about the joint structure;

[00023] FIG. 8B is a side view of the articulatable mechanism of FIG. 7A showing the bearing surfaces of the first and second links, when the first and second links are partially rotated relative to one another about the joint structure;

[00024] FIG. 8C is a side view of the articulatable mechanism of FIG. 7A showing the bearing surfaces of the first and second links, when the first and second links are fully rotated relative to one another about the joint structure;

[00025] FIG. 9 is a side view of the articulatable mechanism of FIG. 7A showing the pivot axis of the joint structure, when the first and second links are fully rotated relative to one another about the joint structure;

[00026] FIG. 10 is an isolated, enlarged perspective view of a first link of the articulatable mechanism of FIG. 5;

[00027] FIG. 11 is an isolated, enlarged perspective view of a second link of the articulatable mechanism of FIG. 5;

[00028] FIG. 12 is a partial perspective view of another embodiment of a distal end portion of an instrument comprising multiple articulatable mechanisms; and [00029] FIG. 13 is a schematic view illustrating aspects of motion of an articulatable mechanism according to various embodiments.

DETAILED DESCRIPTION

[00030] Various technical solutions, objects, and/or advantages will be set forth in part in the description which follows, and in part will be obvious from the description, or can be learned by practice of the present disclosure and/or claims. At least some of these can be realized and attained by the elements and combinations particularly pointed out in the appended claims.

[00031] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the claims; rather the claims should be entitled to their full breadth of scope, including equivalents. [00032] The present disclosure contemplates articulatable mechanisms, such as, but not limited to, for use in various remotely-actuatable instruments, such as, for example medical instruments. The articulatable mechanisms can include one or more joint structures coupling pairs of links together that include joint features that can provide desired stiffness and predictable movement, e.g., during articulation of the coupled links about the joint structure, while also providing a more robust dislocation tolerance (i.e. , providing a greater range of articulation before dislocation of the links, thereby making the joint structures less likely to dislocate from one another). Various embodiments of the present disclosure contemplate joint features that interact so as to mimic the movement of a pin-in-slot joint, or a revolute joint pair, which can provide desired accuracy and control over the joint movement (e.g., with reduced slipping or undesirable motion), while utilizing relatively simple surface profile geometries to enable ease of manufacture. Various embodiments of the present disclosure can utilize a joint feature profile that mimics a pin-in-slot joint for the control of positioning/timing of the joint structure articulation. With this configuration, the joint structure can provide a relatively large tolerance, thereby making it less likely that the joint features will dislocate from one another during articulation of the articulatable mechanism.

[00033] Utilizing an arrangement of mating joint features that mimic a pin-in-slot joint movement, as described above, the contemplated joint structures can provide a one-degree-of-freedom kinematic pair, which constrains the motion of the links coupled by the joint structure to rolling on each other, which kinematically results in rotation about two parallel axes, or in some embodiments rotation about a pivot axis that varies with a contact position of the joint features, as explained further below.

[00034] Thus, as illustrated schematically in FIG. 13, contemplated joint features in accordance with various embodiments can allow the links to roll on each other in a manner like contact of the rolling surfaces of two cylindrical shapes Ci and C2to thereby articulate the joint about two “virtual” pivot points pi and p2 respectively located at the centers of each cylindrical shape Ci and C2. The pivot points pi, P2 can therefore be thought of as being located on two parallel axes that are about 2R apart, where R is the radius of each cylindrical shape Ci and C2. [00035] The point P on FIG. 13 represents the center of the “mimicked pin,” which is associated with the cylindrical shape C2 at a distance L from the center of the cylindrical shape at pivot point P2. Point P is shown on the X axis (e.g., the X axis representing the center of the “mimicked slot,” which is associated with the cylindrical shape Ci), but in real life applications may not actually reside on the X axis and may lie along a different path. Although not wishing to be bound by a particular theory, it was determined that the joint features can be designed using a parameter L/R, to determine the “L” dimension of the pin location, such that the point P (i.e., the “mimicked pin”) will generally stay on or very close to the X axis (i.e., constrained within the “mimicked slot”) as C2 rolls on Ci. In various embodiments, as will be described further below, the parameter L/R (wherein R is the radius of C2and L is the distance between the center of C2 and the pin location P) can range between 1 .00 and 1 .30, with a L/R closer to 1 .00 being used for smaller ranges of motion (i.e., with less potential for error), and a L/R closer to 1 .30 being used for larger ranges of motion, such as, for example, as much as about 90 degrees (i.e., with more potential for error). In some embodiments, for example, when R=.O67 inches (wherein R is the radius of C2) and L=.O774 inches (wherein L is the distance between the center of C?and the pin location P), such that L/R=1 .155, the joint features experience very little deviation at a joint angle 9 of about 60 degrees (i.e., the joint has very little error while articulating from a neutral position through a range of about +/-60 degrees).

[00036] In other words, the joint features of the present disclosure function to constrain the rotation of the joint structure to closely approximate this rolling motion, while preventing translation or sliding linear motion (e.g., slipping or translation of one link relative to the other). In this manner, the joint features allow the joint structure to have substantially repeatable movements, which allow the links to substantially return to their original positions, also referred to herein as the “timing” of the joint structure.

[00037] Further, utilizing mating joint features that mimic a pin-in-slot joint movement can also increase the dislocation tolerance of the joint, as a depth of the mimicked pin and slot can be optimized to constrain the translation of the joint structure (e.g., using the parameter L/R), thereby preventing dislocation of the joint features even at larger angular orientations of the joint structure.

[00038] In various exemplary embodiments, an articulatable mechanism includes a first link and a second link coupled to each other at a joint structure. The joint structure, for example, comprises a pair of complementary joint features, also referred to herein as gear features. The pair of complementary joint features is configured to permit articulation of the first link and second link relative to each other about a pivot axis. One of the pair of complementary joint features, for example, can comprise an elongated slot bounded by a pair of protrusions extending in a direction of elongation of the slot and defining side walls of the slot (e.g., a female gear feature). While another of the pair of complementary joint features can comprise a male gear feature terminating in a rounded head. Thus, when arranged in the articulatable mechanism (to form the joint structure), the rounded head is received in and is moveable relative to the slot to cause articulation of the first and second links relative to each other. In various embodiments, through a range of motion of articulation of the joint structure from a neutral position through, for example, +/- 60 degrees, the rounded head can remain at a position within the slot bounded by the pair of protrusions.

[00039] In some embodiments, for example, the male gear feature can have a recessed region adjacent the rounded head. In such embodiments, through a range of motion of articulation of the joint structure in a first direction from a neutral position, the rounded head remains within the elongated slot bounded by the pair of protrusions, and one of the pair of protrusions is respectively received in and moves along the recessed region. Similarly, through a range of motion of articulation of the joint structure in a second direction from the neutral position, the rounded head remains within the elongated slot bounded by the pair of protrusions, and another of the pair of protrusions is respectively received in and moves along the recessed region.

[00040] The joint structures are therefore configured to mimic the movement of a pin-in-slot joint structure, while also providing a design that is resistant to dislocation. With this structure, for example, the contemplated joint structures can permit a controlled and relatively large range of articulation of the links relative to one another, via a relatively simple to manufacture gear arrangement, while also reducing the likelihood of joint dislocation during the relatively large range of articulation.

[00041] As will be explained in further detail below with respect to various embodiments, the respective complementary joint features are configured to mate and interact with each other in a manner that constrains the rotational movement of the joint structure to behave substantially as a pin-in-slot type of joint movement, which also behaves similar to a revolute gear, as those having ordinary skill in the art would understand. As such, references to the male and female joint features, or gear features, are also referred to herein as pins and slots, respectively, for ease of reference.

[00042] Referring now to FIG. 1 , a schematic side view of an embodiment of an instrument 100 (such as, for example, a medical instrument) is shown. The directions “proximal” and “distal” are used herein to define the directions as shown in FIG. 1 , with distal generally being in a direction further along a kinematic arm or closest to the worksite in the intended operational use of the instrument 100. While aspects of the present disclosure are discussed in the context of medial or surgical instruments with joint structures in the form of wrists supporting an end effector, or other working end component, of the instrument, embodiments of the present disclosure can be used with various instruments used in medical procedures. For example, such instruments include those used for diagnosis, therapy, and sensing, including, for example, imaging instruments such as endoscopes and other imaging instruments. Accordingly, medical instruments as used herein encompasses a variety of instruments used in surgical, diagnostic, and therapeutic applications. In addition, aspects of the disclosure can have non-surgical applications, such as in other remotely-actuatable instruments for inspection and other industrial uses, general robotic uses, manipulation of non-tissue work pieces, etc.

[00043] The instrument 100 includes a shaft 104 with a transmission mechanism 102 at a proximal end portion of the shaft 104 and a working end component 106 at a distal end portion 107 of the shaft. In an exemplary embodiment, the transmission mechanism 102 is configured to interface with a manipulating system, such as manipulating systems shown below in connection with FIG. 2. Alternatively, the transmission mechanism 102 can be configured to be operated manually such as for a manual, laparoscopic instrument, which can have a handle or other arrangement configured to be manipulated directly by a user.

[00044] The working end component 106 is coupled at the distal end portion 107 of the shaft 104 by an articulatable mechanism 105, which can include one or more articulatable joint structures to impart one or more degrees of freedom of movement to the working end component 106 relative to the shaft 104 (for example, to move the working end component 106 in one or more of pitch and yaw). Thus, an articulatable mechanism 105 can include two links coupled together by a joint structure, or a series of more than two links coupled by a series of joint structures. For ease and simplification, several of the embodiments discussed below show two links and a single joint structure referred to below as an articulatable mechanism, but the principles disclosed herein can be applied to articulatable mechanisms that have more than two links and more than one joint structure, as those having ordinary skill in the art would be familiar with. Moreover, articulatable mechanisms in accordance with exemplary embodiments can include a series of links connected with joint structures wherein one or more of the joint structures have the same or different axes about which they articulate the joined links.

[00045] Certain coordinated movements of multiple joint structures can enable, for example, articulating the working end component 106 relative to the shaft, longitudinal translations, combined movement in pitch and yaw directions, or other compound movements of the working end component 106 in multiple degrees of freedom relative to the instrument shaft 104. While a single actuation element 108 is shown in connection with FIG. 1 , other, additional actuation elements can also be operably coupled between the transmission mechanism 102 and the articulatable mechanism 105 to actuate articulation D of the articulatable mechanism 105 along various degrees of freedom associated with individual joint structures.

[00046] Operation of the working end component 106 can be controlled by manipulation of the transmission mechanism 102, either manually or through drives of a manipulating system (e g., the manipulating system shown in FIG. 2). The transmission mechanism 102 includes various mechanical and/or electromechanical devices that transmit motion, energy, and/or signals, e.g., from the manipulating system, or from inputs at the transmission mechanism 102 operable by a user, to the working end component 106. For example, one or more actuation elements (one actuation element 108 shown in FIG. 1 ) can extend from the transmission mechanism 102, through the shaft 104, and to the working end component 106, to operably couple the transmission mechanism 102 (or a component therein) to the working end component 106. Force applied to the actuation element 108 by the transmission mechanism 102 can actuate (e.g., close, open, or otherwise control) the working end component 106.

[00047] While the working end component 106 shown in FIG. 1 comprises a jaw mechanism including a pair of opposing jaw members, other working end component configurations, such as staplers, clip appliers, ligation tools, and other tools are considered within the scope of this disclosure. Furthermore, as illustrated in the embodiment of FIGS. 3 and 4, an exemplary instrument 200 can similarly include a working end component in the form of an imaging device, such as, for example, an endoscopic camera 206, which is coupled to a distal end portion 207 of a shaft 204 of the instrument 200 by articulatable mechanism 205. In this manner, the instrument 200 can similarly operate to position a distal end camera 206 for viewing of a work site and the operation of surgical instruments within a patient.

[00048] Moreover, more than one articulatable mechanism can also be incorporated within the instrument 100. As illustrated in the embodiment of FIG. 12, an exemplary instrument 300 can similarly include a jaw mechanism 306, which is coupled to a distal end portion 307 of a shaft 304 of the instrument 300 by articulatable mechanisms 305 and 309.

[00049] In various embodiments, actuation elements can comprise flexible members, such as polymer or metal (e.g., tungsten) solid or braided actuation elements, such as cables. Selective tensioning of the actuation elements can cause transmission of force to the links of an articulatable mechanism to cause articulation in a given direction. Those of ordinary skill in the art are generally familiar with such components and they are thus not described in detail here.

[00050] In various embodiments, the transmission mechanism 102 is configured to operably couple to and receive drive inputs from a manipulator system of a teleoperable, computer-assisted medical system that operates at least in part with robotic technology (sometimes referred to as a robotic surgical system). One embodiment of such a computer-assisted medical system is illustrated in the schematic diagram of FIG. 2, depicting a manipulator system 1000 comprising a plurality of manipulator arms 1002 to which the transmission mechanism 102 of instrument 100 can operably couple, a surgeon side console 2000 comprising various master inputs 52 and a surgeon viewer 2006 which can include video images of the remote worksite taken through an endoscopic imaging device, such as, for example, the camera 206 of instrument 200 of the embodiments of FIGs. 3 and 4, and/or other graphical information, and a vision/control console 4000 which can also have a display 4006 presenting similar images as the viewer 2006 or other information relating to a procedure.

[00051] The vision/control console 4000 also can in some embodiments comprise components that supply auxiliary functionality to instruments, such as via an auxiliary unit 80, which can be, for example, insufflation gas, vacuum for evacuation, electrosurgical energy, and similar flux supply units. Such units can be controlled through a controller integrated with the system and/or can be separately controlled at a stand-alone input unit 90, rather than through the surgeon console 2000. A non-limiting embodiment of a computer-assisted, teleoperable medical system with which the instrument 100 and various instrument embodiments described herein can be utilized are the da Vinci® Surgical Systems commercialized by Intuitive Surgical, Inc., of Sunnyvale, California.

[00052] In various other embodiments contemplated within the scope of the present disclosure, the medical instrument 100, 200, or 300 can be configured to be manually actuated, with the proximally located, transmission mechanism 102 having inputs that are configured to be manually actuated rather than coupled to a manipulator arm. Yet other embodiments contemplate the instrument can have both manually actuated inputs and inputs configured to be driven by drive outputs of a manipulator system.

[00053] Turning again to FIGS. 3 and 4, an exemplary embodiment of a joint structure 210 of an articulatable mechanism (e.g., wrist) 205 of a surgical instrument 200 is shown. For clarity purposes, FIGS. 3 and 4 only illustrate a distal end portion 207 of a shaft 204 of the instrument 200, which includes the articulatable mechanism 205 coupled thereto, which is comprised of a plurality of joint structures, with one such joint structure 210 of articulatable mechanism 205 labeled and which will be described further below. The other joint structures can have similar or different configurations. FIGS. 3 and 4 further illustrate a working end component, in the form of an endoscopic camera 206, coupled to the wrist 205 of the instrument 200. FIG. 4 also illustrates an embodiment of the instrument 200 that further includes a protective cover 209 positioned over the articulatable mechanism 205. As discussed above, the instrument 200, for example, can be used to insert the end of camera 206 through a cannula in small incisions in a patient undergoing a medical procedure and to operate the wrist 205 at a worksite inside the patient. However, those of ordinary skill in the art would appreciate that the joint structures in accordance with various embodiments described in further detail below can be used in instruments having other working end component configurations, such as any of those discussed above with reference to instruments 100 and 300 of FIGS. 1 and 12.

[0046] The lateral dimensions (e.g., diameters) of the shaft 204, articulatable mechanism (e.g., wrist) 205, and working end component of instrument 200 are generally selected according to the size of the cannula with which the instrument will be used. In an exemplary embodiment, a largest lateral dimension of the working end component, articulatable mechanism 205 and shaft 204 can range from about 3 mm to about 13 mm, for example, about 4 mm, about 5 mm, or about 8 mm to match the sizes of some existing cannula systems. Due to the size constraints of these components, it can be advantageous for the joint structures (e.g., joint structure 210) to conserve as much interior cross-sectional area as possible, so as to not interfere with the actuation elements and/or central lumens that route lines, cables and/or other components, e.g., such as to supply energy, light or the like as discussed above.

[00054] With reference to FIGS. 3 and 4, an articulatable mechanism can comprise a first link 212 and a second link 214 coupled at a joint structure 210. The joint structure 210 can be a two-piece joint in which the first link 212 and the second link 214 are directly in contact with one another through joint features, or gear features, of the joint structure 210. The joint structure 210 including links 212, 214 can be provided in a wrist or other articulatable mechanism of an instrument, such as wrist 105, 205 that supports a working end component or along a length of the shaft, such as shown at 309 in the instrument 300 of FIG. 12. The links 212, 214 can be coupled together by actuation elements 202 used to control the motion of the links 212, 214 about the joint structure 210, as discussed above for the exemplary embodiment of FIG. 1 , and to press the links 212, 214 against one another to hold them together, as those having ordinary skill in the art are familiar with. According to an embodiment, each link 212, 214 can include one or more passages 203 within a lateral wall 233, 235 (see, e.g., the isolated, enlarged view of link 214 in FIG. 11 ) to accommodate a corresponding number of actuation elements 202, such as, e.g., cables, passing through the links 212, 214, as further shown in the isolated view of the articulatable mechanism 205 in FIG. 5 described below.

[00055] According to an embodiment, a link can include more than one passage so as to route various numbers of actuation elements and/or to allow for selection of routing paths of actuation elements. For example, a link can include two actuation element passages, three passages, four passages, or a higher number of tendon passages. As those of ordinary skill in the art would understand, actuation elements can be routed in pairs on opposing (e.g., diametrically opposite) sides of links and work in a concerted fashion to rotate the links relative to the pivot axis PA about the joint structure 210 in opposite directions, with one cable (or portion of a cable if a common cable is used) being paid out and the other cable (or portion) drawn in. Furthermore, as illustrated in FIG. 5, in various embodiments, some actuation elements can be routed in a generally straight path (e.g., for cables that drive the joint structures) and some actuation elements can be routed in a spiral path (e.g., for cables that constrain the joint structures), as would be understood by those or ordinary skill in the art.

[00056] As further illustrated in FIG. 5, which shows the articulatable mechanism 205 comprised of a plurality of joint structures, with two different such joint structures 210 labeled, and in the enlarged, isolated view of FIG. 10, each link 212 has oppositely facing end faces 232, 232’ and a lateral wall 233 extending between end faces 232, 232’. Similarly, with further reference to the enlarged, isolated view of FIG. 11 , each link 214 has oppositely facing end faces 234, 234’ and a lateral wall 235 extending between the end faces 234, 234’. A longitudinal axis f is defined by each link that extends centrally through each of the links 212, 214. In various embodiments, each of the first and second links 212, 214 are generally annular in configuration with a central opening 236, 237 that is surrounded by the respective lateral walls 233, 235 (see also FIG. 6 in which the actuation elements are removed for ease of illustration). Although as shown in the isolated, enlarged views of FIGS. 10 and 11 , in some embodiments, links 212 and 214 can have similar structures, as further shown in FIGS 5 and 6, links 212 and 214 can also have different structures, for example, depending on their placement in the articulatable mechanism 205, as would be understood by those of ordinary skill in the art.

[00057] Furthermore, while the links may have a generally annular configuration, the central openings 236, 237 are not limited to being circular and can have various shapes. In various embodiments, each central opening 236, 237 can be elongated in a direction perpendicular to or parallel to a pivot axis PA (see FIG. 9) of the first and second links 212, 214 relative to each other about the joint structure 210.

[00058] The term "link" is used herein in a general sense as the term is often used in describing a chain or vertebra-like structure. Those having ordinary skill in the art will appreciate that the link components of the articulatable mechanisms can have various shapes and configurations not limited to annular shapes.

[00059] To control the positioning/timing of the articulation of links 212, 214 relative to one another, while also providing a relatively large tolerance for dislocation of the links 212, 214 relative to one another, as discussed above, various embodiments of the present disclosure contemplate a joint feature profile that mimics a pin-in-slot joint between the links 212, 214. As best illustrated in the enlarged, isolated views of FIGS. 5-11 , the joint structures 210 connecting the links 212, 214 can therefore include respective joint features 222, 224 that intermesh with one another. For instance, with reference to FIGS. 5 and 10, each first link 212 can include a first pair of joint features 222 positioned diametrically opposite one another and extending in a first axial direction Ai away from the end faces 232. Each second link 214 can include a second pair of joint features 224 positioned diametrically opposite one another and extending in a second axial direction A2 away from the end faces 234. As will be further described below and shown in FIGS. 7A-7C and 9, the joint features 222 and 224 are complementary and configured to mate with each other through a range of rotational movement of the links 212, 214 relative to each other.

[00060] As illustrated in the isolated views of FIGS. 7A-7C, 10 and 11 , in various embodiments, each joint feature 222 of the first pair of joint features 222 includes an elongated slot 223 defined by a pair of protrusions 225 extending in a direction of elongation of the slot 223 and defining side walls 223’ of the slot 223. While each joint feature 224 of the second pair of joint features 224 includes a male gear feature 224 terminating in a rounded head 227. In this manner, the first pair of joint features 222 and the second pair of joint features 224 can matingly engage with each other so as to form the joint structure 210, such that the first and second links 212, 214 are rotatable relative to each other about the joint structure 210 and a pivot axis PA (see FIG. 9). [00061] In various embodiments, each of the first and second links 212 and 214 can further include additional joint features, for example, extending from the other one of their respective end faces 232’, 234’. For example, with reference to FIGS. 5 and 10, for a respective joint structure 210, the first link 212 can further include a third pair of joint features 242 extending from end face 232’ in an axial direction A2 opposite of the direction A1 of the first pair of joint features. In some embodiments, as shown in FIGS.

10 and 11 , the second and third pair of joint features 224, 242 can have the same configuration. Similarly, as shown in both FIGS. 5 and 11 , the second link 214 can further include a fourth pair of joint features 244 extending from the end face 234’ in the 1 axial direction Ai opposite to the direction A2 in which the second pair of joint features 224 extend, and the first and fourth pair of joint features 222, 244 can have the same configuration. In various embodiments, as shown in the figures, the pairs of joint features on opposite end faces of a link may be offset 90 degrees relative to each other to provide orthogonal axes of rotation of a link with respect to the mating link of the coupled links at the joint structure, while in other embodiments the joint features can be aligned and not rotationally offset.

[00062] As discussed above, the present disclosure contemplates the mating joint features of joint structures to cooperate and interact in a manner similar to a pin-in-slot joint. In this manner, as shown in FIGS. 7A-7C and 9-11 , each contemplated joint structure 210 includes a pair of complementary joint features 222, 224, or gear features, such that one of the pair of complementary joint features 222, 224 comprises the elongated slot 223 and another of the pair of complementary joint features comprises the rounded head 227. As discussed above, the elongated slot is defined by a pair of protrusions 225 extending in a direction of elongation of the slot 223, with each protrusion 225 of the pair of protrusions 225 comprises a tip portion 225’. The pair of protrusions therefore function to define side walls 223’ of the slot 223, such that the elongated slot 223 is open at one end and closed at an opposite end, with the closed end of the slot 223 having a surface profile complementary to the rounded head 227.

[00063] In this manner, the rounded head 227 can be received in and is moveable relative to the slot 223 so as to provide a pin-in-slot articulation of the joint structure 210, which also functions to increase a dislocation tolerance of the joint structure 210. For example, as progressively illustrated in FIGS. 7A, 7B, and 7C, through a range of motion of articulation of the joint structure 210 from a neutral position (see FIG. 7A) through an angle limit 0 of the range of motion (see FIG. 7C), the rounded head 227 will remain at a position within the slot 223 bounded by the pair of protrusions 225.

Although movement in only a first rotation direction Di is illustrated in FIGS. 7A-7C, it would be understood that the rounded head 227 is also moveable relative to the slot 223 in a second, opposite rotation direction D2from the neutral position of FIG. 7A through an opposite angle limit 6 of the range of motion (see FIG. 9), such that the joint structure 210 may move between first and second ends of the range of relative rotation. In some embodiments, for example, the rounded head 227 can remain at a position within the slot 223 bounded by the pair of protrusions 225 through a range of motion of articulation of the joint structure 210 from the neutral potion through +/- 60 degrees. [00064] As illustrated in FIG. 9, as joint structure 210 moves through the range of motion of articulation, the joint structure 210 pivots about a pivot axis PA that varies with a contact position on a radius of curvature of a pivot radius PR. FIG. 9 shows the pivot axis PA at a joint locked position of 60 degrees (i.e. , at an end of the link’s range of relative rotation). The pivot axis PA, however, will be understood to move along a contact point of the links 212, 214, which is set by the pivot radius PR shared by the links 212, 214 (i.e., the contact angle that the joint 210 is set to).

[00065] In various embodiments, for example, to help maintain the rounded head 227 at a position within the slot 223, the male gear feature 224 can include a recessed region 228 adjacent the rounded head 227, such that the rounded head 227 protrudes radially outwardly relative to the recessed region 228. In this manner, throughout the range of motion of articulation of the joint structure 210 (e.g., from neutral through +/- 60 degrees), the recessed region 228 can receive and guide a respective protrusion 225 of the pair of protrusions 225. In other words, through a range of motion of articulation of the joint structure 210 in the first direction Di from the neutral position, the rounded head 227 remains within the slot 223 and bounded by the pair of protrusions 225, and one of the pair of protrusions 225 is respectively received in and moves along the recessed region 228. While, through a range of motion of articulation of the joint structure 210 in the second direction D2 from the neutral position, the rounded head 227 remains within the slot 223 and bounded by the pair of protrusions 225, and another of the pair of protrusions 225 is respectively received in and moves along the recessed region 228.

[00066] In various embodiments, at both the first and second ends of the range of motion of articulation of the joint structure 210, respective outer circumferential portions 253, 255 of the joint features 222, 224 facing each other also contact each other (see e.g., FIG. 7C). In one exemplary embodiment, the outer circumferential portions 253, 255 can be angled (in other words sloped or canted) relative to inner circumferential portions of the end faces 232, 234 of the links 212, 21 .

[00067] As known in the art, a consequence of a configuration in which actuation elements hold links coupled by a joint structure together is that a compressive load is applied between the links. To address these compressive loads, the contemplated joint structures 210 can also include one or more features that are configured to provide load bearing surfaces to accommodate the compressive load. As best illustrated in the isolated views of FIGS. 8A-8C, which similar to FIGS. 7A-7C illustrate the joint structure 210 progressively moving through a range of motion of articulation from the neutral position (see FIG. 8A) through the angle limit 6 of the range of motion (see FIG. 8C), the links 212, 214 of the joint structure 210 can include respective bearing surfaces 252, 254 that are configured to be in rolling contact with one another throughout the range of motion of articulation. In various embodiments, for example, a respective bearing surface 252, 254 can be positioned radially inwardly of each joint feature 222, 224. For example, the bearing surfaces 252, 254 can each include a convex surface profile, such that the bearing surfaces 252, 254 can interact and roll along one another as the rounded head 227 moves relative to the slot 223. Reference is made to U.S. Patent Nos. 6,817,974 and 11 ,518,048 incorporated by reference herein, which describe configurations of rolling bearing surfaces and the interplay of the configuration of the same and emanation locations of actuation elements and effect on the kinematics of the overall articulation.

[00068] As mentioned above, because the slot 223 and the rounded head 227 of the male gear feature 224 are configured to cooperate and move relative to each other in a manner similar to a pin-in-slot joint, the rounded head 227 of the male gear feature 224 can also be considered as a pin that engages with the slot 223, which is formed by the pair of protrusions 225 of a female gear feature 222. Furthermore, since the joint features 222, 224 of the joint structure 210 mimic the movement of a pin-in-slot, revolute joint, joint structure 210 can provide a controlled and “timed” articulation range of motion between the first link 212 and the second link 214. For instance, joint structure 210 can provide a repeatable, maximum range of motion up to the angle limit 0 (at the first and second ends of the range of motion of articulation), while also preventing the first link 212 from dislocating from the second link 214. In various embodiments, the angle limit 0 can be increased to about 60 degrees, without also increasing the risk of dislocation of the links 212, 214.

[00069] Those of ordinary skill in the art would understand that the joint structures 210 and associated links 212, 214 discussed above and illustrated in FIGS. 3-11 are non-limiting and exemplary only, and that articulatable mechanisms, joint structures, and links in accordance with the present disclosure can have various configurations and/or shapes of joint features 222, 224 without departing form the scope of the present disclosure and claims. Furthermore, the contemplated articulatable mechanisms, joint structures, and links can include various other design features other than those discussed in the exemplary embodiments above.

[00070] Indeed, due to the contemplated surface profiles of reduced complexity, the joint structures and articulatable mechanisms (e.g., instrument wrists and other instrument joints and combinations thereof) including such joint structures can be designed to provide a desired amount of constrained, rolling motion, in a more efficient manner with fewer parts. As a result, the manufacturing cost and complexity for an articulatable mechanism, such as a wrist or other instrument articulatable, that includes one or more of such joint structures can be reduced while still achieving desired control over articulation.

[00071] The embodiments described herein can be well suited for use in medical applications. In particular, some embodiments are suitable for use in, for example, surgical, teleoperated surgical, diagnostic, therapeutic, and/or biopsy procedures. Such procedures could be performed, for example, on human patients, animal patients, human cadavers, animal cadavers, and portions or human or animal anatomy. Some embodiments can also be suitable for use in, for example, for non-surgical diagnosis, cosmetic procedures, imaging of human or animal anatomy, gathering data from human or animal anatomy, training medical or non-medical personnel, and procedures on tissue removed from human or animal anatomies (without return to the human or animal anatomy). Even if suitable for use in such medical procedures, the embodiments can also be used for benchtop procedures on non-living material and forms that are not part of a human or animal anatomy. Moreover, some embodiments are also suitable for use in non-medical applications, such as industrial robotic uses. In non-limiting embodiments, the techniques, methods, and devices described herein can be used in, or can be part of, a computer-assisted surgical system employing robotic technology such as the da Vinci® Surgical Systems commercialized by Intuitive Surgical, Inc., of Sunnyvale, California. Those skilled in the art will understand, however, that aspects disclosed herein can be embodied and implemented in various ways and systems, including manually operated instruments and computer-assisted, teleoperated systems, in both medical and non-medical applications. Reference to the daVinci® Surgical Systems are illustrative and not to be considered as limiting the scope of the disclosure herein.

[00072] As used herein and in the claims, terms such as computer-assisted or teleoperable in referencing manipulator systems, or the like should be understood to refer broadly to any system comprising one or more controllable kinematic structures (“manipulators”) that are movable and controllable at least in part through the aid of an electronic controller (with or without human inputs). Such systems can occasionally be referred to in the art and in common usage as robotically assisted systems or robotic systems. Such systems include systems that are controlled by a user (for example through teleoperation), by a computer automatically (so-called autonomous control), or by some combination of these. In examples in which a user controls at least some of the operations of the manipulator, an electronic controller (e.g., a computer) can facilitate or assist in the operation. The term “computer” as used in “computer-assisted manipulator systems” refers broadly to any electronic control device for controlling, or assisting a user in controlling, operations of the manipulator, and is not intended to be limited to things formally defined as or colloquially referred to as “computers.” For example, the electronic control device in a computer-assisted manipulator system could range from a traditional “computer” (e.g., a general-purpose processor plus memory storing instructions for the processor to execute) to a low-level dedicated hardware device (analog or digital) such as a discrete logic circuit or application specific integrated circuit (ASIC), or anything in between. Further, manipulator systems can be implemented in a variety of contexts to perform a variety of procedures, both medical and non-medical. Thus, although some examples described in greater detail herein can be focused on a medical context, the devices and principles described herein are also applicable to other contexts, such as industrial manipulator systems.

[00073] This description and the accompanying drawings that illustrate various aspects and embodiments should not be taken as limiting — the claims define the scope of protection. Various mechanical, compositional, structural, electrical, and operational changes can be made without departing from the spirit and scope of this description and the claims. In some instances, well-known structures, components, and techniques have not been shown or described in detail in order not to obscure the present disclosure. Like numbers in two or more figures that end in the same two digits but begin with a different series, such as 8xx, 10xx, etc. are as best as possible used to represent the same or similar elements.

[00074] Elements and their associated aspects that are described in detail with reference to one embodiment can, whenever practical, be included in other embodiments in which they are not specifically shown or described. For example, if an element is described in detail with reference to one embodiment and is not described with reference to a second embodiment, the element can nevertheless be claimed as included in the second embodiment.

[00075] Further, this description’s terminology is not intended to be limiting. For example, spatially relative terms — such as “beneath”, “below”, “lower”, “above”, “upper”, “proximal”, “distal”, and the like — can be used to describe one element’s or feature’s relationship to another element or feature as illustrated in the figures. These spatially relative terms are intended to encompass different positions (i.e. , locations) and orientations (i.e., rotational placements) of a device in use or operation in addition to the position and orientation shown in the figures. For example, if a device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be “above” or “over” the other elements or features. Thus, the exemplary term “below” can encompass both positions and orientations of above and below. A device can be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. Likewise, descriptions of movement along and around various axes includes various special device positions and orientations. In addition, the singular forms “a”, “an”, and “the” are intended to include the plural forms as well, unless the context indicates otherwise. And, the terms “comprises”, “comprising”, “includes”, and the like specify the presence of stated features, steps, operations, elements, and/or components but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and/or groups. Components described as coupled can be electrically or mechanically directly coupled, or they can be indirectly coupled via one or more intermediate components. Mathematical and geometric terms are not necessarily intended to be used in accordance with their strict definitions unless the context of the description indicates otherwise, because a person having ordinary skill in the art would understand that, for example, a substantially similar element that functions in a substantially similar way could easily fall within the scope of a descriptive term even though the term also has a strict definition.

[00076] Other embodiments in accordance with the present disclosure will be apparent to those skilled in the art from consideration of the specification and figures, and practice of the embodiments disclosed herein. It is intended that the specification and embodiments be considered as illustrative only, with the following claims being entitled to their fullest breadth, including equivalents, under the applicable law.

Claims

WHAT IS CLAIMED IS:

1 . A joint structure configured to provide articulation between two links coupled by the joint structure, the joint structure comprising: a pair of complementary joint features, wherein: one of the pair of complementary joint features comprises an elongated slot defined by a pair of protrusions extending in a direction of elongation of the slot and defining side walls of the slot, and another of the pair of complementary joint features comprises a male gear feature terminating in a rounded head, wherein the rounded head is received in and moveable relative to the slot, and wherein through a range of motion of articulation of the joint structure, the rounded head remains at a position within the slot bounded by the pair of protrusions.

2. The joint structure of claim 1 , wherein the elongated slot is open at one end and closed at an opposite end, the closed end having a surface profile complementary to the rounded head.

3. The joint structure of claim 2, wherein each protrusion of the pair of protrusions comprises a tip portion.

4. The joint structure of any one of claims 1 -3, wherein the rounded head of the male gear feature is moveable relative to the slot so as to provide a pin-in-slot articulation of the joint structure.

5. The joint structure of any one of claims 1 -3, wherein the male gear feature has a recessed region adjacent the rounded head, the rounded head protruding radially outwardly relative to the recessed region.

6. The joint structure of claim 5, wherein, through the range of motion of articulation of the joint structure, the recessed region receives and guides a respective protrusion of the pair of protrusions.

7. The joint structure of any one of claims 1 -3, wherein the range of motion of articulation of the joint structure is from a neutral position through +/- 60 degrees.

8. A joint structure configured to provide articulation between two links coupled by the joint structure, the joint structure comprising: a pair of complementary joint features, wherein: one of the pair of complementary joint features comprises an elongated slot bounded by a pair of protrusions extending in a direction of elongation of the slot and defining side walls of the slot, and another of the pair of complementary joint features comprises a male gear feature terminating in a rounded head, wherein the male gear feature has a recessed region adjacent the rounded head, wherein the rounded head is received in and moveable relative to the slot, and wherein through a range of motion of articulation of the joint structure in a first direction from a neutral position, the rounded head remains within the elongated slot bounded by the pair of protrusions, and one of the pair of protrusions is respectively received in and moves along the recessed region, and wherein through a range of motion of articulation of the joint structure in a second direction from the neutral position, the rounded head remains within the elongated slot and bounded by the pair of protrusions, and another of the pair of protrusions is respectively received in and moves along the recessed region.

9. The joint structure of claim 8, wherein the elongated slot is open at one end and closed at an opposite end, the closed end having a surface profile complementary to the rounded head.

10. The joint structure of claim 9, wherein each protrusion of the pair of protrusions comprises a tip portion.

11 . The joint structure of any one of claims 8-10, wherein the rounded head protrudes radially outwardly relative to the recessed region.

12. The joint structure of any one of claims 8-10, wherein the range of motion of articulation of the joint structure in the first direction from the neutral position and the second direction from the neutral position is +/- 60 degrees.

13. An articulatable mechanism comprising: a first link and a second link coupled to each other by a pair of complementary joint features, the pair of complementary joint features configured to permit articulation of the first link and second link relative to each other about a pivot axis, the pair of complementary joint features comprising: a pair of protrusions extending from the first link in a direction perpendicular to the pivot axis and defining an elongated slot between the pair of protrusions, and a pin extending from the second link and received in the elongated slot, wherein the pin and the pair of protrusions are rotatable relative to each other to cause articulation of the first and second links relative to each other, and wherein through a range of motion of articulation of the first and second links relative to each other the pin is moveable in translation relative to the slot and remains within the slot bounded by the pair of protrusions.

14. The articulatable mechanism of claim 13, wherein the pair of complementary joint features comprise a first pair of joint features extending in a first axial direction from the first link and positioned diametrically opposite one another and a second pair of joint features extending in a second axial direction from the second link and positioned diametrically opposite one another.

15. The articulatable mechanism of claim 14, wherein each of the first link and the second link further comprises oppositely facing end faces, a lateral wall extending between the end faces, and a longitudinal axis extending between the end faces, wherein the first pair of joint features extends from one of the end faces of the first link, and wherein the second pair of joint features extends from one of the end faces of the second link.

16. The articulatable mechanism of claim 15, wherein each of the first and second links comprises a central opening surrounded by the lateral wall.

17. The articulatable mechanism of claim 16, wherein the central opening of each of the first and second links is elongated in a direction perpendicular to or parallel to the pivot axis of the articulation of the first link and second link relative to each other.

18. The articulatable mechanism of any one of claims 14-17, wherein each joint feature of the first pair of joint features comprises a pair of protrusions extending from the first link in a direction perpendicular to the pivot axis and defining an elongated slot between the pair of protrusions, each protrusion of the pair of protrusions comprising a tip portion.

19. The articulatable mechanism of claim 18, wherein each joint feature of the second pair of joint features comprises a pin extending from the second link in a direction perpendicular to the pivot axis, the pin comprising a rounded head protruding radially outwardly from a recessed region.

20. The articulatable mechanism of claim 19, wherein, through a range of motion of articulation of the first and second links relative to each other from a neutral position through +/- 60 degrees, in a first direction from the neutral position, one of the protrusions of the pair of protrusions is respectively received in and moves along the recessed region, and in a second direction from the neutral position, the other protrusion of the pair of protrusions is respectively received in a moves along the recessed region.

21 . The articulatable mechanism of any of claims 14-17, wherein the first link further comprises a third pair of joint features extending in the second axial direction from the first link.

22. The articulatable mechanism of claim 21 , wherein the first pair of joint features and the third pair of joint features are offset 90 degrees from each other around the first link and positioned diametrically opposite one another.

23. The articulatable mechanism of claim 13, further comprising at least one drive tendon coupling the first link and the second link.

24. The articulatable mechanism of claim 23, wherein the at least one drive tendon is configured to exert a force on at least one of the first and second links to cause articulation of the first link and second link relative to each other.

25. A medical instrument comprising: a shaft; the articulatable mechanism of claim 13 coupled to the shaft; and a working end component.

26. The medical instrument of claim 25, wherein the working end component comprises an imaging device.

27. The medical instrument of claim 25, wherein the working end component comprises a jaw mechanism.

28. The medical instrument of any one of claims 25-27, wherein the articulatable mechanism is coupled to an end portion of the shaft.

29. The medical instrument of claim 28, wherein the working end component is coupled to the articulatable mechanism.

30. A link of an articulatable mechanism, the link comprising: a first end, a second end, a lateral surface extending between the first end and the second end, and a longitudinal axis extending between the first and the second end; a first pair of joint features extending in a first axial direction from the first end and positioned diametrically opposite one another; and a second pair of joint features extending in a second axial direction from the second end and positioned diametrically opposite one another; wherein each joint feature of the first pair of joint features comprises an elongated slot defined by a pair of protrusions extending in a direction of elongation of the slot and defining side walls of the slot, wherein each joint feature of the second pair of joint features comprises a semicircular recessed region adjacent a circular pin, the circular pin protruding radially outwardly from the semi-circular recessed region, wherein the first pair of joint features are configured to engage with a third pair of joint features on another link having a same configuration as the second pair of joint features, and wherein the second pair of joint features is configured to engage with a fourth pair of joint features on another link having a same configuration as the first pair of joint features.