204 and the wrist 206, with the jaws 210, 212 of the end effector 204 in the closed position. The wrist 206 operatively couples the end effector 204 to the shaft 202. In some embodiments, however, a shaft adapter may be directly coupled to the wrist 206 and otherwise interpose the shaft 202 and the wrist 206. Accordingly, the wrist 206 may be operatively coupled to the shaft 202 either through a direct coupling engagement where the wrist 206 is directly coupled to the distal end of the shaft 202, or an indirect coupling engagement where a shaft adapter interposes the wrist 206 and the distal end of the shaft 202. As used herein, the term “operatively couple” refers to a direct or indirect coupling engagement between two components.

To operatively couple the end effector 204 to the shaft 202, the wrist 206 includes a first or “distal” clevis 402a and a second or “proximal” clevis 402b. The clevises 402a,b are alternatively referred to as “articulation joints” of the wrist 206 and extend from the shaft 202 (or alternatively a shaft adapter). The clevises 402a,b are operatively coupled to facilitate articulation of the wrist 206 relative to the shaft 202. As illustrated, the wrist 206 also includes a linkage 404 arranged distal to the distal clevis 402a and operatively mounted to the jaws 210, 212.

The proximal end of the distal clevis 402a may be rotatably mounted or pivotably coupled to the proximal clevis 402b at a first pivot axis P₁of the wrist 206. In some embodiments, an axle may extend through the first pivot axis P₁and the distal and proximal clevises 402a,b may be rotatably coupled via the axle. In other embodiments, however, such as is depicted in FIG. 4A, the distal and proximal clevises 402a,b may be engaged in rolling contact, such as via an intermeshed gear relationship that allows the clevises 402a,b to rotate relative to each other similar to a rolling joint.

First and second pulleys 406a and 406b may be rotatably mounted to the distal end of the distal clevis 402a at a second pivot axis P₂of the wrist 206. The linkage 404 may be arranged distal to the second pivot axis P₂and operatively mounted to the jaws 210, 212. The first pivot axis P₁is substantially perpendicular (orthogonal) to the longitudinal axis A₁of the shaft 202, and the second pivot axis P₂is substantially perpendicular (orthogonal) to both the longitudinal axis A₁and the first pivot axis P₁. Movement of the end effector 204 about the first pivot axis P₁provides “yaw” articulation of the wrist 206, and movement about the second pivot axis P₂provides “pitch” articulation of the wrist 206.

A plurality of drive cables, shown as drive cables 408a, 408b, 408c, and 408d, extend longitudinally within a lumen 410 defined by the shaft 202 (or a shaft adaptor) and extend at least partially through the wrist 206. The drive cables 408a-d may form part of the cable driven motion system housed within the drive housing 208 (FIG. 2), and may comprise cables, bands, lines, cords, wires, woven wires, ropes, strings, twisted strings, elongate members, belts, shafts, flexible shafts, drive rods, or any combination thereof. The drive cables 408a-d can be made from a variety of materials including, but not limited to, a metal (e.g., tungsten, stainless steel, nitinol, etc.), a polymer (e.g., ultra-high molecular weight polyethylene), a synthetic fiber (e.g., KEVLAR®, VECTRAN®, etc.), an elastomer, or any combination thereof. While four drive cables 408a-d are depicted in FIG. 4A, more or less than four may be employed, without departing from the scope of the disclosure.

The drive cables 408a-d extend proximally from the end effector 204 and the wrist 206 toward the drive housing 208 (FIG. 2) where they are operatively coupled to various actuation mechanisms or devices that facilitate longitudinal movement (translation) of the drive cables 408a-d within the lumen 410. Selective actuation of the drive cables 408a-d applies tension (i.e., pull force) to the given drive cable 408a-d in the proximal direction, which urges the given drive cable 408a-d to translate longitudinally within the lumen 410.

In the illustrated embodiment, the drive cables 408a-d each extend longitudinally through the proximal clevis 402b. The distal end of each drive cable 408a-d terminates at the first or second pulleys 406a,b, thus operatively coupling each drive cable 408a-d to the end effector 204. In some embodiments, the distal ends of the first and second drive cables 408a,b may be coupled to each other and terminate at the first pulley 406a, and the distal ends of the third and fourth drive cables 408c,d may be coupled to each other and terminate at the second pulley 406b. In at least one embodiment, the distal ends of the first and second drive cables 408a,b and the distal ends of the third and fourth drive cables 408c,d may each be coupled together at corresponding ball crimps (not shown) mounted to the first and second pulleys 406a,b, respectively.

In at least one embodiment, the drive cables 408a-d may operate “antagonistically”. More specifically, when the first drive cable 408a is actuated (moved), the second drive cable 408b naturally follows as coupled to the first drive cable 408a, and when the third drive cable 408c is actuated, the fourth drive cable 408d naturally follows as coupled to the third drive cable 408c, and vice versa. Antagonistic operation of the drive cables 408a-d can open or close the jaws 210, 212. More specifically, selective actuation of the drive cables 408a-d in other known configurations or coordination will cause the jaws 210, 212 to open or close. Antagonistic operation of the drive cables 408a-d can further cause the end effector 204 to articulate at the wrist 206. More specifically, selective actuation of the drive cables 408a-d in known configurations or coordination can cause the end effector 204 to articulate about one or both of the pivot axes P₁, P₂, thus facilitating articulation of the end effector 204 in both pitch and yaw directions, either individually or simultaneously. Antagonistic operation of the drive cables 408a-d advantageously reduces the number of cables required to provide full wrist 206 motion, and also helps eliminate slack in the drive cables 408a-d, which results in more precise motion of the end effector 204.

In the illustrated embodiment, the end effector 204 is able to articulate (move) in pitch about the second or “pitch” pivot axis P₂, which is located near the distal end of the wrist 206. Thus, the jaws 210, 212 open and close in the direction of pitch. In other embodiments, however, the wrist 206 may alternatively be configured such that the second pivot axis P₂facilitates yaw articulation of the jaws 210, 212, without departing from the scope of the disclosure.

In some embodiments, an electrical conductor 412 may also extend longitudinally within the lumen 410, through the wrist 206, and terminate at an electrode 414 to supply electrical energy to the end effector 204. In some embodiments, the electrical conductor 412 may comprise a wire, but may alternatively comprise a rigid or semi-rigid shaft, rod, or strip (ribbon) made of a conductive material. The electrical conductor 412 may be entirely or partially covered with an insulative covering (overmold) made of a non-conductive material. Using the electrical conductor 412 and the electrode 414, the end effector 204 may be configured for monopolar or bipolar RF operation.

In the illustrated embodiment, the end effector 204 comprises a combination tissue grasper and vessel sealer that includes a knife 420 (FIG. 4B), alternately referred to as a “cutting element” or “blade.” The knife is aligned with and configured to traverse a guide track 422 (FIG. 4B) defined longitudinally in one or both of the upper and lower jaws 210, 212. The knife 420 may be operatively coupled to the distal end of a drive rod 416 that extends longitudinally within the lumen 410 and passes through the wrist 206. Longitudinal movement (translation) of the drive rod 416 correspondingly moves the knife 420 within the guide track(s) 422. Similar to the drive cables 408a-d, the drive rod 416 may form part of the actuation systems housed within the drive housing 208 (FIG. 2). Selective actuation of a corresponding drive input will cause the drive rod 416 to move distally or proximally within the lumen 410, and correspondingly move the knife 420 in the same longitudinal direction.

FIG. 4B is a partial isometric view of the distal end of the surgical tool 200 with the first jaw 210 (FIG. 4A) removed. With the first jaw 210 removed, the guide track 422 defined in the second jaw 212 is visible extending from a proximal end 422a to a distal end 422b. In some embodiments, the first jaw 210 may include a similar or complimentary guide track (not shown) in opposition to the guide track 422 when the first and second jaws 210, 212 are closed. The knife 420 (partially visible) is illustrated in a “zero” or “home” position wherein the knife 420 is disposed within a knife housing 424 adjacent the proximal end 422a of the guide track 422. The knife housing 424 may be constructed of a non-conductive material and as a separate component. When the knife 420 is disposed within the knife housing 424, the end effector 204 may be safely handled for cleaning or maintenance. In operation, the knife 420 may be selectively moved distally out of the knife housing 424 along the guide track 422 by longitudinally moving the drive rod 416 as described above.

FIG. 5 is a bottom view of the drive housing 208, according to one or more embodiments. As illustrated, the drive housing 208 may include a tool mounting portion 502 used to operatively couple the drive housing 208 to a tool driver of a robotic manipulator. The tool mounting portion 502 may releasably couple the drive housing 208 to a tool driver in a variety of ways, such as by clamping thereto, clipping thereto, or slidably mating therewith. In some embodiments, the tool mounting portion 502 may include an array of electrical connecting pins, which may be coupled to an electrical connection on the mounting surface of the tool driver. While the tool mounting portion 502 is described herein with reference to mechanical, electrical, and magnetic coupling elements, it should be understood that a wide variety of telemetry modalities might be used, including infrared, inductive coupling, or the like.

The tool mounting portion 502 includes and otherwise provides an interface 504 configured to mechanically, magnetically, and/or electrically couple the drive housing 208 to the tool driver. As illustrated, the interface 504 includes and supports a plurality of drive inputs, shown as drive inputs 506a, 506b, 506c, 506d, 506e, and 506f. Each drive input 506a-f comprises a rotatable disc configured to align with and couple to a corresponding actuator or “drive output” of a tool driver, such that rotation (actuation) of a given drive output drives (rotates) a corresponding one of the drive inputs 506a-f. Each drive input 506a-f may provide or define one or more surface features 508 configured to align with mating surface features provided on the corresponding drive output. The surface features 508 can include, for example, various protrusions and/or indentations that facilitate a mating engagement. In some embodiments, some or all of the drive inputs 506a-f may include one surface feature 508 that is positioned closer to an axis of rotation of the associated drive input 506a-f than the other surface feature(s) 508. This may help to ensure positive angular alignment of each drive input 506a-f.

In some embodiments, actuation of the first drive input 506a may be configured to control rotation of the shaft 202 about its longitudinal axis A₁. The shaft 202 may be rotated clockwise or counter-clockwise depending on the rotational actuation of the first drive input 506a. In some embodiments, actuation of the second, third, fourth, and fifth drive inputs 506b-e may be configured to operate movement (axial translation) of the drive cables 408a-d (FIG. 4A), which results in the actuation of the wrist 206 (FIG. 4A) and/or articulation (operation) of the end effector 204 (FIG. 4A). In some embodiments, actuation of the sixth drive input 506f may be configured to advance and retract the drive rod 416 (FIG. 4A), and thereby correspondingly advance or retract the knife 420 (FIG. 4B) at the end effector 204. Each of the drive inputs 506a-f may be actuated based on user inputs communicated to the tool driver coupled to the interface 504, and the user inputs may be received via a computer system incorporated into the robotic surgical system.

FIG. 6 is an exposed isometric view of the interior of the drive housing 208, according to one or more embodiments. Several component parts that may be otherwise contained within the drive housing 208 are not shown in FIG. 6 to enable discussion of the depicted component parts. As illustrated, the drive housing 208 houses and otherwise contains a plurality of capstan assemblies operable to operate surgical tool 200 (FIG. 2). In particular, a first capstan assembly 602a is contained (housed) within the drive housing 208. As illustrated, the first capstan assembly 602a may include a drive gear 604a, which may be operatively coupled to or extend from the first drive input 506a (FIG. 5) such that actuation of the first drive input 506a results in rotation of the drive gear 604a. In the illustrated embodiment, the drive gear 604a comprises a worm gear, e.g., a crossed helical or screw gear, which may be configured to mesh and interact with a driven gear 606a secured within the drive housing 208 and operatively coupled to the shaft 202 such that rotation of the driven gear 606a correspondingly rotates the shaft 202. Accordingly, actuation of the first capstan assembly 602a, via actuation of the first drive input 506a, will drive the driven gear 606a and thereby control rotation of the elongate shaft 202 about the longitudinal axis A₁.

The drive housing 208 may further contain or house a second capstan assembly 602b, which may include a drive gear 604b operatively coupled to or extending from the sixth drive input 506f (FIG. 5) such that actuation of the sixth drive input 506f results in rotation of the drive gear 604b. The drive gear 604b is a rotary pinion gear arranged to intermesh with a longitudinally driven gear 606b positioned within the drive housing 208. In the illustrated embodiment, the driven gear 606b comprises a rack gear longitudinally translatable within the drive housing 208 as acted upon by the drive gear 604b. The drive rod 416 may be operatively coupled to the driven gear 606b and extend distally therefrom to the end effector 204 (FIGS. 2 and 4). Accordingly, actuation of the second capstan assembly 602b, via actuation of the sixth drive input 506f, will cause the driven gear 606b to longitudinally translate and correspondingly advance or retract the drive rod 416 and the knife 420 (FIG. 4B) coupled to the end of the drive rod 416 at the end effector 204.

The drive housing 208 further contains or houses third, fourth, fifth, and sixth capstan assemblies 602c, 602d, 602e, and 602f, alternately be referred to as “drive cable” capstan assemblies since they are operable to actuate the drive cables 408a-d, as described below. While four “drive cable” capstan assemblies 602c-f are depicted in FIG. 6, alternative embodiments may include more or less than four, depending on how many drive cables 408a-d are used.

In the illustrated embodiment, the third capstan assembly 602c is actuated through operation (rotation) of the second drive input 506b (FIG. 5), the fourth capstan assembly 602d is actuated through operation (rotation) of the third drive input 506c (FIG. 5), the fifth capstan assembly 602e is actuated through operation (rotation) of the fourth drive input 506d (FIG. 5), and the sixth capstan assembly 602f is actuated through operation (rotation) of the fifth drive input 506e (FIG. 5). As illustrated, each capstan assembly 602c-f includes a drive gear 604c, 604d, 604e, and 604f that is coupled to or extends from the corresponding drive input 506b-e, respectively, such that actuation (rotation) of the drive input 506b-e correspondingly rotates the associated drive gear 604c-f, respectively.

Moreover, each drive gear 604c-f is positioned to mesh and interact with a corresponding driven gear 606c, 606d, 606e, and 606f rotatably mounted within the drive housing 208. Each driven gear 606c-f includes or is otherwise coupled to a corresponding cable pulley 608c, 608d, 608e, and 608f, and each cable pulley 608c-f is configured to be operatively coupled to (e.g., has wrapped there around, at least partially) a corresponding one of the drive cables 408a-d. In the illustrated embodiment, the first drive cable 408a terminates at cable pulley 608d ultimately driven by actuation of the fourth capstan assembly 602d, the second drive cable 408b terminates at cable pulley 608f ultimately driven by actuation of the sixth capstan assembly 602f, the third drive cable 408c terminates at cable pulley 608c ultimately driven by actuation of the third capstan assembly 602c, and the fourth drive cable 408d terminates at cable pulley 608e ultimately driven by actuation of the fifth capstan assembly 602e.

Accordingly, actuation of the fourth capstan assembly 602d (via operation of the third drive input 506c of FIG. 5) will correspondingly control movement of the first drive cable 408a; actuation of the sixth capstan assembly 602f (via operation of the fifth drive input 506e of FIG. 5) will correspondingly control movement of the second drive cable 408b; actuation of the third capstan assembly 602c (via operation of the second drive input 506b of FIG. 5) will correspondingly control movement of the third drive cable 408c; and actuation of the fifth capstan assembly 602e (via operation of the fourth drive input 506d of FIG. 5) will correspondingly control movement of the fourth drive cable 408d.

Couplers for Biasing Mechanisms

Still referring to FIG. 6, each of the second, fourth, fifth and sixth capstan assemblies 602b and 602d-f may include a coupler 610 thereon for facilitating connection to a biasing member (see FIG. 10). The couplers 610 are operatively coupled to or extend from the respective third, fourth, fifth and sixth drive input 506c-f (FIG. 5) such that actuation of the respective drive input 506c-f results in rotation of the respective coupler 610 along with the respective drive gear 604d-f and 604b. The couplers 610 include one or more hooks 612, which may be used to couple the biasing mechanism to the capstan assemblies 602b and 602d-f.

Although not shown in FIG. 6, an additional coupler 610 (not shown) may also be secured to, or form part of, the third capstan assembly 602c. A castellated peg 614 is provided, operatively coupled to or extending from the third drive gear 604 such that actuation of the second drive input 506b results in rotation of the castellated peg 614 along with the third drive gear 604c. In some embodiments, the castellated peg 614 is an integral part of the second drive input 506b. The castellated peg 614 may transmit torque to the additional coupler 610 coupled thereto such that the additional coupler 610 rotates along with the castellated peg 614, the third drive gear 604c and the second drive input 506b.

FIG. 7A is an exposed isometric view of the interior of the drive housing 208, illustrating a chassis plate 704, which may be secured to the drive housing 208 in a fixed position with fasteners 706, ultrasonic welding, adhesives or other attachment mechanisms. Each of the respective capstan assemblies 602a-f protrude through the chassis plate 704 such that the chassis plate 704 does not interfere with the rotation of the capstan assemblies 602a-f. The second capstan assembly 602b forms part of a knife drive mechanism 710, which is supported between the drive housing 208 and the chassis plate 704. The chassis plate 704 may include mounting posts 712 defined thereon, to which biasing members (FIG. 10) or other components may be mounted in a fixed position with respect to knife drive mechanism 710.

FIG. 7B is a perspective cross sectional view of the knife drive mechanism 710 supported by the drive housing 208 and the chassis plate 704. Specifically, the sixth drive input 506f is radially supported by a first or lower bearing set 714 and a second or upper bearing set 716. In the illustrated embodiment, the first and second bearing sets 714, 716 are ball bearing sets having an outer race fixedly coupled to the bottom of the drive housing 208 and the chassis plate 704, respectively, and an inner race coupled to the sixth drive input 506f. In other embodiments, roller bearings, plastic bearings, bushings or other types or rotary bearings may be provided as the first and second bearing sets 714, 716. In still other embodiments, a plastic material of the drive housing 208 and the chassis plate 704 may engage the sixth drive input 506f and serve as the first and second bearing sets 714, 716. The bearing sets 714, 716 are both arranged to rotate about a rotational axis A₃of the second capstan assembly 602b and prevent any tilting of the second capstan assembly 602b when subjected to radial loads. The drive gear 604b is coupled to the sixth drive input 506f between the lower and upper bearing sets 714, 716 such that drive gear 604b rotates in a drive plane B₁orthogonal to the rotational axis A₃. The drive plane B₁generally bisects the drive gear 604b.

The drive gear 604b is intermeshed with the driven gear 606b on the drive plane B₁and moves longitudinally within the drive plane B₁. The drive rod 416 is coupled to the driven gear 606b within the drive plane B₁such that the drive rod 416 is aligned with both the drive gear 604b and the driven gear 606b. The drive rod 416 is rotatably coupled to the longitudinally driven gear 606b about a longitudinal axis A₄, which extends centrally through the drive rod 416 and lies within the drive plane B₁. The longitudinal axis A₄may be considered to lie within the drive plane B₁even if the longitudinal axis A₄does not lie directly on the drive plane B₁that bisects the drive gear 604b, For example, in some embodiments, the longitudinal axis A₄may be considered to lie within the drive plane B₁where the longitudinal axis lies between planes defined by upper and lower surfaces of the drive gear 604b. Where the drive rod 416 translates and rotates at a height within the interface between the teeth of the drive gear 604b and the longitudinally driven gear 606b, the drive rod may be considered to be aligned with the drive plane B₁. The alignment of the drive rod 416 within the drive plane B₁prevents any forces imparted to the drive rod 416 in operation from being transmitted to the second capstan assembly 602b and thereby inadvertently tilting the second capstan assembly 602b away from the rotational axis A₃. Supporting the drive gear 604b between the bearing sets 714, 716, rather than above or below both bearing sets 714, 716, prevents loads applied through the driven gear 606b to the drive gear 604b from creating bending moments that could tilt the capstan assembly 602b and lead to inaccurate movement of the knife 420 (FIG. 4B).

FIG. 8A is front perspective view of the knife drive mechanism 710 independent of the drive housing 208 and the chassis plate 704 (FIG. 7B). The drive gear 604b includes a plurality of circumferentially spaced teeth 802 capable of being operatively intermeshed with a plurality of longitudinally spaced teeth 804 on the driven gear 606b (e.g., the rack gear). An elongated bore 806 extends longitudinally through the driven gear 606b and receives the drive rod 416 therein. As described in greater detail below, the drive rod 416 is secured within the elongated bore 806 to permit rotation of the drive rod 416 with respect to the driven gear 606b and such that the drive rod 416 translates longitudinally along with the driven gear 606b.

In operation, the sixth drive input 506f may be rotated, e.g., by a tool driver, in a first angular direction, as indicated by the arrow A₀. The drive gear 604b and the coupler 610 are thereby induced to also rotate in the direction of arrow A₀. The first and second bearing sets 714, 716 support the rotational motion of the second capstan assembly 602b about the rotational axis A₃. Rotation of the drive gear 604b in the first angular direction A₀drives the driven gear 606b and the drive rod 416 longitudinally in a distal direction, as indicated by arrow B₀. The knife 420 is thereby driven distally through the guide track 422 (FIG. 4B). The sixth drive input 506f may then rotated in a second angular direction, as indicated by the arrow C₀. The drive gear 604b is thereby induced to also rotate in the direction of arrow C₀, and the driven gear 606b and the drive rod 416 are thereby driven in a proximal direction, as indicated by arrow Do. The knife 420 is thereby drawn proximally and back through the guide track 422 (FIG. 4B).

FIG. 8B is a rear perspective view of the knife drive mechanism 710 illustrating a coupling 810 between the longitudinally driven gear 606b and the drive rod 416. The driven gear 606b includes an opening 812 extending between an exterior surface and the elongated bore 806. The opening 812 has a length “L” defined between a distal wall 814 and a proximal wall 816 of the opening 812. A rotating collar 818 may be crimped or otherwise secured to drive rod 416. In some embodiments, the rotating collar 818 may be affixed to the drive rod 416 by welding, adhesives, brazing, fasteners or set screws, overmold or other attachment mechanisms recognized in the art. The rotating collar 818 may be able to engage the distal and proximal walls 814, 816 to prevent minimal (or no) longitudinal motion between the drive rod 416 and the driven gear 606b. The rotating collar 818 and the drive rod 416 may be free to rotate within the longitudinal bore in the direction of arrows E₀.

FIGS. 9A and 9B are cross-sectional side views of the drive rod 416 extending within the longitudinal bore 806 of the driven gear 606b. FIG. 9A illustrates the drive rod 416 in an initial rotational position wherein the knife 420 is arranged in an upward orientation with respect to the driven gear 606b, and FIG. 9B illustrates the drive rod 416 in an second rotational position wherein the knife 420 is arranged in an downward orientation with respect to the driven gear 606b. The ability of the drive rod 416 to rotate freely within the driven gear 606b allows for unlimited roll of the end effector 204 (FIG. 4A), and prevents torsional loading of the drive rod 416 in operation which may increase the operational life and efficiency of the surgical tool 200 (FIG. 2). The drive rod 416 is rotatable about a longitudinal axis A₄, and in some embodiments, the longitudinal axis A₄may lie within the drive plane B₁(FIG. 7B).

The drive rod 416 may be constructed of a plurality of elongated members connected in series. Specifically, the drive rod 416 includes a series of longitudinally spaced rods and tubes coupled to one another to form the drive rod 416. The drive rod 416 includes a flexible rod 902 at a distal end thereof, to which the knife 420 is coupled (fixed). When assembled into the surgical tool 200, the flexible rod 902 extends through the wrist 206 and permits articulation of the end effector 204 with respect to the shaft 202 (FIG. 2). A proximal end of the flexible rod 902 extends into an inner lumen of an intermediate tube 904, and a proximal end of the intermediate tube 904 extends into the inner lumen of an outer tube 906. In some embodiments, a stiffening rod 908 may extend within the outer tube 906 to provide an appropriate stiffness to the proximal end of the drive rod 416. In one or more embodiments, the flexible rod 902, intermediate tube 904, outer tube 906 and stiffening rod 908 may be constructed from a variety of materials including, but not limited to, a metal (e.g., stainless steel, titanium, tungsten, nitinol, etc.) a polymer (e.g., ultra-high molecular weight polyethylene), a carbon fiber material or any combination thereof.

The flexible rod 902, intermediate tube 904 and the outer tube 906 may be fixedly joined to one another such that longitudinal motion therebetween is prohibited. In some embodiments, the flexible rod 902, intermediate tube 904 and the outer tube 906 may be joined to one another by crimping, welding, adhesives, brazing, fasteners or set screws, overmolding, etc. Once assembled, the drive rod 416 may be coupled to the driven gear 606. The rotating collar 818 may be inserted into the opening 812, and thereafter, the drive rod 416 may be inserted through the longitudinal bore 806 and through the rotating collar 818. The longitudinal position of the drive rod 416 within the longitudinal bore 806 may be adjusted to accommodate any tolerance stack-up that may have occurred assembling the drive rod 416. Once the longitudinal position is adjusted, the rotating collar 818 may be crimped, welded or otherwise fastened to the outer tube 906 of the drive rod 416 as described above.

FIG. 10 is a perspective view of a dual pinion knife drive mechanism 1000 including a passive secondary input assembly 1002, according to one or more additional embodiments. The secondary input assembly 1002 is generally rotatable about an axis A_sparallel to and spaced from the rotational axis A₃of the second capstan assembly 602b. The dual pinion drive mechanism 1000 includes the second capstan assembly 602b, which drives the longitudinal translation of a driven gear 1004 in a manner similar to which the second capstan assembly drives the driven gear 606b (FIG. 8A) as described above. The driven gear 1004 also includes longitudinally spaced teeth 1006 on an opposite lateral side thereof such that the teeth 1006 of the driven gear 1004 are intermeshed with both the drive gear 604b of the second capstan assembly 602b and a rotary pinion gear 1008 of the passive secondary input assembly 1002.

The passive secondary input assembly 1002 is supported on a stationary axle 1010, which may be affixed to a drive housing 208 (FIG. 6) in a stationary manner. The rotary pinion gear 1008 and a coupler 610 may be rotationally coupled to the stationary axle 1010 such that the rotary pinion gear 100 and the coupler 610 rotate in response to the longitudinal translation of the driven gear 1004. In some embodiments, the coupler 610 of the passive secondary input assembly 1002 may be coupled to a biasing member 1012. As illustrated, the biasing member 1012 is coupled to the coupler 610 by hooks 612 and imparts a bias on the coupler 610 and rotary pinion gear 1008 in the angular direction of arrow F₀. The bias of the biasing member 1012 may be transmitted through the rotary pinion gear 1008, the driven gear 1004 and the drive rod 416 to the knife 420 (FIG. 4B). This bias may increase a maximum firing load that may be applied by the knife 420 to cut tissue in operation. In other embodiments, the biasing member 610 may be coupled to the coupler 610 to impart a bias on the coupler 610 in an opposite angular direction as illustrated by the arrow Go. A bias in the opposite angular direction may serve to return the knife 420 to the proximal end 422a of the drive track 422 (FIG. 4B), e.g., in the event the surgical tool 200 (FIG. 2) is removed from the tool driver.

In some example embodiments, the biasing member 1012 is a constant-force spring or constant-torque spring extending between and operably coupling a spool 1014 to the coupler 610. The constant-force spring may generally be constructed of a pre-stressed flat strip of spring material formed into virtually constant-radius coils around the spool 1014. The biasing member 1012 may be reverse wound onto the coupler 610 such that, when released, torque is applied to the input assembly 1002 as the biasing member 1012 returns to its natural curvature. In some embodiments, the biasing member 1012 may be provided without the spool 1014. The biasing member 1012 may be housed in a cavity (not shown), which may introduce friction and change the torque provided to the input assembly 1002. In some embodiments, the biasing member 1012 may be pre-stressed to provide near constant torque to the input assembly 1002, or even negative torque in some instances. Negative gradients of up to 50% may be achieved

The biasing member 1012 may be constant force spring that applies a constant force to a rotational or linearly translating member, or a constant torque spring that applies a constant torque to a rotational member to provide a constant force on a driven member of the surgical tool 200. For example, the biasing member 1012 as illustrated may apply a constant force or constant torque to the input assembly 1002 such that a constant force is imparted to the drive rod 416 through the rotary pinion gear 1008 and the driven gear 1004. In other embodiments (not shown) a biasing member may apply a constant force to a linearly translating member, such as the longitudinally driven gear 1004, or the drive rod 416 itself to impart a constant force to the drive rod 416.

In some embodiments, the constant-force spring may comprise strips of spring-steel, aluminum, titanium, a polymer, an elastomer, a fiber mesh, or any combination of the foregoing. The strips may be generally relaxed when fully coiled around the spools 1014, and when the strips are extended or deflected by a loading force, the internal stress in the strips resists the loading force at a nearly constant rate. In other embodiments, the biasing member 1012 may comprise a torsion spring that progressively increases resistance rate with further deflection. The spool 1014 may be supported on a mounting post 712 of the chassis plate 704 (FIG. 7A). In other embodiments (not shown), an additional biasing member 1012 may be mounted on a spool 1014 and may be coupled to the coupler 610 of the second capstan assembly 602b (or any other capstan assembly described herein) without departing from the scope of the disclosure.

In operation, the sixth drive input 506f may be rotated, e.g., by a tool driver, in the first angular direction A₀, as described above, to translate the driven gear 1004 in the distal longitudinal direction B₀. The distal longitudinal motion of the driven gear 1004 induces the rotary pinion gear 1008 and the coupler 610 to rotate in the angular direction of arrow F₀. Rotation of the coupler 610 in the angular direction F₀unwinds the biasing member 1012 from the coupler 610 and allows the biasing member 1012 to wind around the spool 1014 under the internal stresses of the biasing member 1012. The sixth drive input 506f may then be rotated in the second angular direction C₀, as described above, to translate the driven gear 1004 in the proximal direction D₀. The rotary pinion gear 1008 and the coupler 610 may thereby be induced to rotate in the angular direction indicated by arrow Go, winding the biasing member from the spool 1014 to the coupler 610. In operation, the drive gear 604b and the rotary pinion gear 1008 rotate together in the same plane B₂in which the drive rod 416 translates. In other embodiments, the drive gear 604b and the rotary pinion gear 1008 may rotate in different planes. In either case, the passive secondary input assembly 1002 stabilizes and biases the driven gear 1004 to ensure accurate motion of the knife 420.

FIG. 11 is a perspective view of a dual pinion knife drive mechanism 1100 including an active secondary input assembly 1102, according to one or more additional embodiments. The active secondary input assembly 1102 may be identical, or a mirror image of, the second capstan assembly 602b. The sixth drive input 506f of the second capstan assembly 602b may be operated to drive the driven gear 1004 longitudinally as described above.

The active secondary input assembly 1102 may include a drive input 1104, which may be rotated by a tool driver to drive rotation of a rotary pinion gear 1108 in a manner similar to the sixth drive input 506f and the drive gear 604b. In some embodiments, the drive input 1104 may be operated such that the rotary pinion gear 1108 imparts a distal force on the driven gear 1004 whenever the drive gear 604b imparts a distal force on the driven gear 1004. In this manner, the active secondary input assembly 1102 may effectively double the cutting force which may be imparted to the drive rod 416 and the knife 420, as well as double the retraction force which may be applied in a proximal direction to return the knife 420 to a “zero” or “home” position. In some embodiments, the drive input 1104 may be operated such that the rotary pinion gear 1108 imparts a proximal bias to the driven gear 1004 when the drive gear 604b imparts a distal force to the driven gear. In this manner, the rotary pinion gear 1108 may engage a distally facing flank of the teeth 1006 while the drive gear 604b engages a proximally facing flank of the teeth, eliminating all backlash in the operation of the dual pinion knife drive mechanism 1100.

In FIGS. 10 and 11, the second capstan assembly 602b and the passive and active secondary input assemblies 1002, 1102 are illustrated without a first or lower bearing set 714 (FIG. 7B). It should be appreciated that in some embodiments, a first or lower bearing set 714 may be included without departing from the scope of the disclosure. In each of the embodiments of the knife drive mechanism 710, 1000, 1100 described above, the drive rod 416 is aligned in a plane with the drive gear 604b and rotary pinion gears 1008, 1108 which engage the driven gear 606b, 1004.