# Patent

## Title
Surgical stapling instrument incorporating an uneven multistroke firing mechanism having a rotary transmission

## Abstract

A surgical stapling and severing instrument particularly suited to endoscopic procedures incorporates a handle that produces separate closing and firing motions to actuate an end effector. In particular, the handle produces multiple firing strokes in order to reduce the required amount of force required to fire (i.e., staple and sever) the end effector. Varying the center of rotation, circumferential length, and depth of cam lobes in a cam disk that interacts with the firing trigger via a drive wedge allows optimization. In particular, mechanical advantages during specific firing strokes mitigates increased force to fire at the end effector, enabling a more uniform tactile force at the firing trigger.

## Background
CROSS REFERENCE TO RELATED APPLICATION
The present application is related to a co-pending and commonly-owned application entitled “SURGICAL STAPLING INSTRUMENT INCORPORATING A MULTISTROKE FIRING MECHANISM HAVING A ROTARY TRANSMISSION” to Frederick E. Shelton IV, Michael Earl Setzer, and Douglas B. Hoffman, filed on even date herewith, the disclosure of which is hereby incorporated by reference in its entirety.
FIELD OF THE INVENTION
The present invention relates in general to surgical stapler instruments that are capable of applying lines of staples to tissue while cutting the tissue between those staple lines and, more particularly, to improvements relating to stapler instruments and improvements in processes for forming various components of such stapler instruments that accomplish firing with multiple strokes of a trigger.
BACKGROUND OF THE INVENTION
Endoscopic surgical instruments are often preferred over traditional open surgical devices since a smaller incision tends to reduce the post-operative recovery time and complications. Consequently, significant development has gone into a range of endoscopic surgical instruments that are suitable for precise placement of a distal end effector at a desired surgical site through a cannula of a trocar. These distal end effectors engage the tissue in a number of ways to achieve a diagnostic or therapeutic effect (e.g., endocutter, grasper, cutter, staplers, clip applier, access device, drug/gene therapy delivery device, and energy device using ultrasound, RF, laser, etc.).
Known surgical staplers include an end effector that simultaneously makes a longitudinal incision in tissue and applies lines of staples on opposing sides of the incision. The end effector includes a pair of cooperating jaw members that, if the instrument is intended for endoscopic or laparoscopic applications, are capable of passing through a cannula passageway. One of the jaw members receives a staple cartridge having at least two laterally spaced rows of staples. The other jaw member defines an anvil having staple-forming pockets aligned with the rows of staples in the cartridge. The instrument includes a plurality of reciprocating wedges which, when driven distally, pass through openings in the staple cartridge and engage drivers supporting the staples to effect the firing of the staples toward the anvil.
An example of a surgical stapler suitable for endoscopic applications is described in U.S. Pat. No. 5,465,895, which advantageously provides distinct closing and firing actions. Thereby, a clinician is able to close the jaw members upon tissue to position the tissue prior to firing. Once the clinician has determined that the jaw members are properly gripping tissue, the clinician can then fire the surgical stapler with a single firing stroke, thereby severing and stapling the tissue. The simultaneous severing and stapling avoids complications that may arise when performing such actions sequentially with different surgical tools that respectively only sever or staple.
One specific advantage of being able to close upon tissue before firing is that the clinician is able to verify via an endoscope that a desired location for the cut has been achieved, including a sufficient amount of tissue has been captured between opposing jaws. Otherwise, opposing jaws may be drawn too close together, especially pinching at their distal ends, and thus not effectively forming closed staples in the severed tissue. At the other extreme, an excessive amount of clamped tissue may cause binding and an incomplete firing.
Generally, a single closing stroke followed by a single firing stroke is a convenient and efficient way to perform severing and stapling. However, in some instances, it would be desirable for multiple firing strokes to be required. For example, surgeons are able to select from a range of jaw sizes with a corresponding length of staple cartridge for the desired length of cut. Longer staple cartridges require a longer firing stroke. Thus, a hand-squeezed trigger to effect the firing is required to exert a larger force for these longer staple cartridges in order to sever more tissue and drive more staples as compared to a shorter staple cartridge. It would be desirable for the amount of force to be lower and comparable to shorter cartridges so as not to exceed the hand strength of some surgeons. In addition, some surgeons not familiar with the larger staple cartridges may become concerned that binding or other types of malfunction have occurred when an unexpectedly higher force is required.
One approach to lower the required force for a firing stroke is a ratcheting mechanism that allows a firing trigger to be stroked multiple times, as described in U.S. Pat. Nos. 5,762,256 and 6,330,965. However, it is believed that the conversion of the reciprocating motion of the firing trigger directly into a solid rack by a pawl constrains the design options for a desired amount of firing motion during each firing stroke. In addition, these known surgical stapling instruments with multiple-stroke firing mechanisms do not have the advantages of a separate closure and firing action.
Consequently, a significant need exists for a surgical stapling instrument that uses multiple firing strokes to achieve a desired length of severing and stapling with a desired relationship of firing stroke travel to longitudinal firing motion produced for an end effector, but more particularly, to one that optimizes force and travel for each stroke.
BRIEF SUMMARY OF THE INVENTION
The invention overcomes the above-noted and other deficiencies of the prior art by providing a surgical stapling and severing instrument having a rotary transmission that transfers a sequence of multiple firing strokes. In particular, recognizing that the end effector of such an instrument requires different levels of force during the firing, a rotary transmission of a firing mechanism varies the mechanical advantage during certain strokes as compared to others, optimizing the firing for a more uniform force requirement. Thereby, the handle need not require an excessive number of firing strokes merely to handle the worst-case number of strokes wherein the largest forces are required.
In another aspect of the invention, a surgical instrument has an end effector that is responsive to a longitudinal firing motion to perform a surgical operation. A user causes movement in a firing actuator to create the firing motion that is selectively transferred by a firing mechanism. Specifically, a cam disk has a plurality of cam lobes about at least a portion of its circumference that are respectively engaged by a drive wedge coupled to the firing actuator when making a firing motion. The cam disk is coupled to a rack by gear engagement to translate this intermittent rotational motion into the longitudinal firing motion. The moment arm and radial spacing of the cam lobes are advantageously varied to address the amount of force required during a respective stroke. Increasing the mechanical advantage during a specific stroke wherein significant resistance is encountered in the end effector (e.g., tissue severing, firing bar friction, staple forming) allows for a minimum number of multiple strokes to be used with each stroke having a similar feel to the surgeon.
These and other objects and advantages of the present invention shall be made apparent from the accompanying drawings and the description thereof.



BRIEF DESCRIPTION OF THE FIGURE
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention, and, together with the general description of the invention given above, and the detailed description of the embodiments given below, serve to explain the principles of the present invention.
FIG. 1 is a perspective view of a surgical stapling and severing instrument having an open end effector.
FIG. 2 is a left side elevation view in cross section along lines 2—2 of the open end effector of FIG. 1.
FIG. 3 is a perspective view of the open end effector of FIG. 1.
FIG. 4 is an exploded, perspective view of an implement portion of the surgical stapling and severing instrument of FIG. 1.
FIG. 5 is an exploded, perspective view of a handle of the surgical stapling and severing instrument of FIG. 1.
FIG. 6 is a left side view in elevation of the handle of the surgical stapling and severing instrument of FIG. 1 in an open condition with a left portion of a handle housing removed to expose a firing mechanism including a rotary transmission for multiple firing strokes.
FIG. 7 is a right side view in elevation of the handle of FIG. 6 with a right portion of the handle portion removed to expose a closure mechanism and anti-backup features.
FIG. 8 is a downward perspective view of the handle of FIG. 7.
FIG. 9 is a side elevation view of the handle of FIG. 6 with the closure trigger closed and the firing trigger omitted to expose a firing drive wedge and cam lobes in a cam disk.
FIG. 10 is a downward perspective view of the firing drive wedge and cam lobes of FIG. 9.
FIG. 11 is an aft perspective view of a rotary transmission firing mechanism of the handle of FIG. 1.
FIG. 12 is a side elevation view of the handle of FIG. 6 in a closed and fired condition with a small idler gear of the rotary transmission firing mechanism omitted to expose an anti-backup pendulum contacting a solid rack.
FIG. 13 is a side view of a cam disk for a rotary transmission firing mechanism incorporating uneven firing strokes to optimize firing forces at the firing trigger for the surgical stapling and severing instrument of FIG. 1.
FIG. 14 is an illustrative diagram of force of fire versus firing travel for a multiple firing stroke instrument having even firing strokes.
FIG. 15 is an illustrative diagram of force of fire versus firing travel for a multiple firing stroke instrument having an uneven firing stroke optimized for firing forces experienced at the firing trigger.
FIG. 16 is a depiction of a straight rack having unevenly spaced rack teeth sections for a linear transmission firing mechanism incorporating uneven firing strokes to optimize firing forces at the firing trigger for the surgical stapling and severing instrument of FIG. 1.
FIG. 17 is a depiction of a linked rack having unevenly spaced rack teeth sections for a linear transmission firing mechanism incorporating uneven firing strokes to optimize firing forces at the firing trigger for the surgical stapling and severing instrument of FIG. 1.
FIG. 18 is a depiction of a tapered rod linear firing mechanism with a screen door lock drive that incorporates uneven firing strokes to optimize firing forces at the firing trigger for the surgical stapling and severing instrument of FIG. 1.



DETAILED DESCRIPTION OF THE INVENTION
Turning to the Drawings, wherein like numerals denote like components throughout the several views, FIGS. 1–4 depict a surgical stapling and severing instrument 10 that is capable of practicing the unique benefits of the present invention. The surgical stapling and severing instrument 10 incorporates an end effector 12 having an anvil 14 pivotally attached to an elongate channel 16, forming opposing jaws for clamping tissue to be severed and stapled. The end effector 12 is coupled by a shaft 18 to a handle 20. An implement portion 22, formed by the end effector 12 and shaft 18, is advantageously sized for insertion through a trocar or small laparoscopic opening to perform an endoscopic surgical procedure while being controlled by a surgeon grasping the handle 20. The handle 20 advantageously includes features that allow separate closure motion of the end effector 12 from firing, as well as enabling multiple firing strokes to effect firing (i.e., severing and stapling) of the end effector 12 while indicating the degree of firing to the surgeon.
To these ends, a closure tube 24 of the shaft 18 is coupled between a closure trigger 26 and the anvil 14 to cause closure of the end effector 12. Within the closure tube 24, a frame 28 is coupled between the elongate channel 16 and the handle 20 to longitudinally position and support the end effector 12. A rotation knob 30 is coupled with the frame 28, and both elements are rotatably coupled to the handle 20 with respect to a rotational movement about a longitudinal axis of the shaft 18. Thus, the surgeon can rotate the end effector 12 by turning the rotation knob 30. The closure tube 24 is also rotated by the rotation knob 30 but retains a degree of longitudinal movement relative thereto to cause the closure of the end effector 12. Within the frame 28, a firing rod 32 is positioned for longitudinal movement and coupled between the anvil 14 of the end effector 12 and a multiple-stroke firing trigger 34. The closure trigger 26 is distal to a pistol grip 36 of the handle 20 with the firing trigger 34 distal to both the pistol grip 36 and closure trigger 26.
In endoscopic operation, once the implement portion 22 is inserted into a patient to access a surgical site, a surgeon refers to an endoscopic or other diagnostic imaging device to position tissue between the anvil 14 and elongate channel 16.
Grasping the closure trigger 26 and pistol grip 36, the surgeon may repeatedly grasp and position the tissue. Once satisfied as to the location of the tissue relative to the end effector 12 and the amount of tissue therein, the surgeon depresses the closure trigger 26 fully toward the pistol grip 36, clamping the tissue in the end effector 12 and locking the closure trigger 26 in this clamped (closed) position. If not satisfied with this position, the surgeon may release the closure trigger 26 by depressing a release button 38 (FIG. 4), whose operation is described more fully below, and thereafter repeat the procedure to clamp tissue.
If clamping is correct, the surgeon may proceed with firing the surgical stapling and severing instrument 10. Specifically, the surgeon grasps the firing trigger 34 and pistol grip 36, depressing the firing trigger 34 a predetermined number of times. The number of firing strokes necessary is ergonomically determined based on a maximum hand size, maximum amount of force to be imparted to the instrument during each firing stroke, and the longitudinal distance and force needed to be transferred through the firing rod 32 to the end effector 12 during firing. As will be appreciated in the discussion below, individual surgeons may choose to cycle the firing trigger 34 a different angular range of motion, and thus increase or decrease the number of firing strokes.
In FIG. 1, the closure release button 38 is obscured by a retraction lever 40 that would rotate distally over the top of the handle 20, exposing the closure release button 38, when the stapling and severing instrument 10 is being fired. After depressing the closure release button 38 to disengage a rotary transmission firing mechanism 42 within the handle 20, the surgeon may draw the retraction lever 40 proximally to assist retraction of the firing rod 32 from the end effector 12.
Implement Portion Including an E-Beam End Effector.
The advantages of a handle 20, capable of providing multiple-stroke firing motion, has application to a number of instruments, with one such end effector 12 being depicted in FIGS. 1–4. The end effector 12 responds to the closure motion from the handle 20 that is transferred longitudinally and distally by the closure tube 24. The elongate channel 16 engages the anvil 14 in a pivoting fashion to form opposing jaws, which are engaged to the frame 28 forming a rigid attachment to the handle 20. The closure tube 24 engages the anvil 14 distal to the pivotal connection between the anvil 14 and elongate channel 16. Thus, a distal movement of the closure tube 24 relative to the frame 28 effects closure and a proximal movements relative to the frame 28 effects opening of the end effector 12.
With particular reference to FIG. 4, the implement portion 22 also includes components that respond to a firing motion from the handle 20, specifically the firing rod 32 that couples a longitudinal motion between the firing mechanism 42 in the handle 20 and the implement portion 22. In particular, the firing rod 32 (shown disassembled in FIG. 5) rotatably engages a firing trough member 46 within a longitudinal recess 48 in frame 28. Firing trough member 46 moves longitudinally within frame 28 in direct response to longitudinal motion of firing rod 32. A longitudinal slot 50 in the closure tube 24 operably couples with the rotation knob 30 (not shown), the longitudinal slot 50 further allowing the rotation knob 30 to engage the frame 28 at a small longitudinal slot 52 therein to effect rotation. The length of the longitudinal slot 50 in the closure tube 24 is sufficiently long as to allow relative longitudinal motion with the rotation knob 30 to accomplish closure motions respectively.
The distal end of the frame trough member 46 is attached to a proximal end of a firing bar 56 that moves with the frame 28, to distally project an E-beam 60 into the end effector 12. The end effector 12 includes a staple cartridge 62 that is actuated by the E-beam 60 that causes staples to be driven up from staple apertures 64 of the cartridge 62 into contact with staple forming grooves 68 of the anvil 14, creating formed “B” shaped staples. With particular reference to FIG. 3, the staple cartridge body 86 further includes a proximally open, vertical slot 70 for passage of a vertically oriented cutting surface provided along a distal end of E-beam 60 to cut tissue while being stapled.
The illustrative end effector 12 is described in greater detail in five co-pending and commonly-owned U.S. patent applications, the disclosure of each being hereby incorporated by reference in their entirety: (1) “SURGICAL STAPLING INSTRUMENT HAVING A SINGLE LOCKOUT MECHANISM FOR PREVENTION OF FIRING”, Ser. No. 10/441,424, to Frederick E. Shelton, Mike Setser, Bruce Weisenburgh, filed 20 Jun. 2003; (2) “SURGICAL STAPLING INSTRUMENT HAVING SEPARATE DISTINCT CLOSING AND FIRING SYSTEMS”, Ser. No. 10/441,632, to Frederick E. Shelton, Mike Setser, Brian J. Hemmelgarn, filed 20 Jun. 2003; (3) “SURGICAL STAPLING INSTRUMENT HAVING A SPENT CARTRIDGE LOCKOUT”, Ser. No. 10/441,565, to Frederick E. Shelton, Mike Setser, Bruce Weisenburgh, filed 20 Jun. 2003; (4) “SURGICAL STAPLING INSTRUMENT HAVING A FIRING LOCKOUT FOR AN UNCLOSED ANVIL”, Ser. No. 10/441,580, to Frederick E. Shelton, Mike Setser, Bruce Weisenburgh, filed 20 Jun. 2003; and (5) “SURGICAL STAPLING INSTRUMENT INCORPORATING AN E-BEAM FIRING MECHANISM”, Ser. No. 10/443,617, to Frederick E. Shelton, Mike Setser, Bruce Weisenburgh, filed 20 Jun. 2003.
It should be appreciated that although a nonarticulating shaft 18 is illustrated herein, applications of the present invention may include instruments capable of articulation, such as described in five co-pending and commonly owned U.S. patent applications, the disclosure of each being hereby incorporated by reference in their entirety: (1) “SURGICAL INSTRUMENT INCORPORATING AN ARTICULATION MECHANISM HAVING ROTATION ABOUT THE LONGITUDINAL AXIS”, Ser. No. 10/615,973, to Frederick E. Shelton, Brian J. Hemmelgarn, Jeff Swayze, Kenneth S. Wales, filed 9 Jul. 2003; (2) “SURGICAL STAPLING INSTRUMENT INCORPORATING AN ARTICULATION JOINT FOR A FIRING BAR TRACK”, Ser. No. 10/615,962, to Brian J. Hemmelgarn, filed 9 Jul. 2003; (3) “A SURGICAL INSTRUMENT WITH A LATERAL-MOVING ARTICULATION CONTROL”, Ser. No. 10/615972, to Jeff Swayze, filed 9 Jul. 2003; (4) “SURGICAL STAPLING INSTRUMENT INCORPORATING A TAPERED FIRING BAR FOR INCREASED FLEXIBILITY AROUND THE ARTICULATION JOINT”, Ser. No. 10/615,974, to Frederick E. Shelton, Mike Setser, Bruce Weisenburgh, filed 9 Jul. 2003; and (5) “SURGICAL STAPLING INSTRUMENT HAVING ARTICULATION JOINT SUPPORT PLATES FOR SUPPORTING A FIRING BAR”, Ser. No. 10/615,971, to Jeff Swayze, Joseph Charles Hueil, filed 9 Jul. 2003.
Multi-Stroke Firing Handle.
In FIGS. 5–8, the handle 20 responds to actuation of the closure trigger 26 and firing trigger 34 to generate respectively the closure and firing motions to the implement portion 22. With regard to the closure motion, the closure trigger 26 includes an upper portion 76 that includes three lateral apertures, a forwardly positioned pin hole 78, a lower, aft pivot hole 80, and a center cutout 82. Three rods laterally oriented between and engaged to right and left half shells 84, 86 of a handle housing 88 (with the right half shell 84 shown in FIGS. 5–6 and the left half shell 86 shown in FIG. 7). In particular, an aft rod 90 passes through the aft pivot hole 80 of the upper portion 76 of the closure trigger 26, and thus the closure trigger 26 pivots about the aft rod 90. A front rod 92, which is distally positioned to the aft rod 90, and a top rod 94, which is above the front rod 92, pass through the center cutout 82, which is shaped to constrain movement of the closure trigger 26 by contacting the front and top rods 92, 94 at each extreme of trigger travel. Thus, the center cutout 86 includes a vertical portion, whose bottom surface contacts the front rod 92 when the closure trigger 26 is forward (distal), and includes an upper, proximally sloped portion, whose top and forward surfaces contact the top rod 94 respectively when the closure trigger 26 is at its forward, relaxed position and its proximal, actuated position.
A closure yoke 96, which engages the closure tube 24, is longitudinally slidingly received within the handle housing 88 and is engaged at its distal end to a proximal end of the closure tube 24, thus transferring longitudinal closure motion to the closure tube 24 and hence to the anvil 14 for closing the end effector 12. This engagement allows rotation of the closure tube 24 while the closure yoke 96 does not rotate. Above this engagement, a lateral pin hole 100 is coupled to a closure link 102 by a front pin 104, with the other end of the closure link 102 coupled to the pin hole 78 of the closure trigger 26 via an aft pin 106.
A triangular spacer 120 includes holes 122–126 to receive the rods 90–94 and is to the left of the upper portion of the closure trigger 26. To the left of the triangular spacer 120, a cam disk 130 rotatingly receives the front rod 92 and includes a semi-circular slot 132 that receives the aft and top rods 90, 94. A central hole 134 receives front pin 92. To the left of the cam disk 130, a rod hole 136 at an upper end 138 of the firing trigger 34 receives the top rod 94. A distally opened recess 140 in the firing trigger below the rod hole 136 is registered to receive the front rod 92, allowing the firing trigger 34 to be drawn distally during firing. Frictional, downward engagement of the cam link 102 (See FIG. 8) to the firing trigger 34 during actuation of the closure trigger 26 causes the firing trigger 34 to be partially drawn distally, staging the firing trigger 34 for grasping.
With particular reference to FIGS. 5, 9, and 10, the cam disk 130 presents a series of cam lobes 142–144 (FIG. 9) about the forward portion (when in its unfired state as depicted), specifically along its left side, that are respectively engaged by the firing trigger 34 to impart a top-to-front rotation to the cam disk 130. This rotation is transferred through a gear train 150 (FIG. 10) of the rotary transmission firing mechanism 42, beginning with a gear portion 152 about a lower portion of the right side of the cam disk 130 that engages a small idler gear 154, which thus rotates top to the rear at an increased rate relative to the cam disk 130. A large idler gear 156 is connected by an idler axle 158 to the small idler gear 154 and thus rotates in the same direction and rate. A second small gear 160 is enmeshed to the larger idler gear 156, and is thus rotated top to the front at a greater rate. A fine-toothed large gear 162 is connected by a second axle 164 to the second small gear 160 and thus rotates in the same direction and rate as the second small gear 160. The gear train 150 thus amplifies the motion of the cam disk 130 by including a double gear reduction feature to provide additional longitudinal firing motion. The fine-toothed large gear 162 engages a gear segment 168 on an underside of a solid rack 170 whose distal end engages the proximal end of the firing rod 32. The rack 170 has its distal portion longitudinally slidingly received within the closure yoke 96 and its proximal portion longitudinally slidingly received between right and left shell halves 84, 86 of the handle housing 88.
The selective engagement of the firing trigger 34 to the cam lobes 142–144 provides further longitudinal travel by enabling multiple firing strokes of the firing trigger 34. To prepare the gear train 150 for firing, the cam disk 130 is urged toward its unfired position by a gear train retraction spring 172 attached to a leftward projecting integral pin 174 formed within an annular recess 176 at a lower proximal edge of the cam disk 130 (FIGS. 9–10). The gear train retraction spring 172 has its other end attached to a pin 178 integral to the handle housing 88.
With particular reference to FIGS. 5, 9, 11, below and distal to the upper end 128 of the firing trigger 34 is a drive wedge pin hole 180. A drive wedge 182 is held against the left side of the firing trigger 34 by a drive wedge pin 184, between which is placed a standoff finger 186 that contacts a center, uncammed circumferential surface of the cam disk 130. A mousetrap-style spring 188 between the upwardly and proximally directed standoff finger 186 and the downwardly and proximally directed drive wedge 182 urges the drive wedge 182 upward into engagement with the cam lobes 142–144.
Below the drive wedge pin hole 180, the drive wedge 182 also has a lower and proximal pin hole 190 and the firing trigger 34 includes a lower pin hole 192. An opposing tension spring 194 is attached between a rightward extending pin 196 in the lower pin hole 192 and the pin hole 190 to urge the drive wedge 182 downward, thereby preventing the drive wedge 182 from rotating too far upwardly when the firing trigger 34 is cycled distally between strokes (see FIG. 10 that has the firing trigger 34 hidden).
With particular reference to FIG. 12, when the drive wedge 182 is drawn away from one of the cam lobes 142–144 between firing strokes, the cam disk 130 would tend to rotate top to the rear by the action of the gear train retraction spring 172 but for the action of an anti-backup lever 200. Lateral pins 202, 204 of the anti-backup pendulum 200 engage respectively right and left of shell halves 84, 86 of the handle housing 88. Above the pins 202, 204, an anti-backup tension spring 206 is attached to an integral pin 208 of the right half shell 88 distal to the anti-backup pendulum 200. With particular reference to FIG. 5, a lower foot 210 of the anti-backup pendulum 200 makes frictional contact with an upper surface 212 of the solid rack 170. When the lower foot 210 of the anti-backup pendulum 200 is drawn proximally by a retracting solid rack 170, the anti-backup lever 20 approaches a perpendicular engagement to the solid rack 170 that increases the frictional force, locking the solid rack 170, which is sufficient to overcome the backdriving force provided by the gear train retraction spring 172. When the solid rack 170 is driven distally by the firing trigger 34, the lower foot 210 is pushed distally, reducing the friction and allowing firing. Excessive forward movement of the lower foot 210 is prevented by the idler axle 158 and by the urging from the anti-backup tension spring 206.
In FIG. 12, the release button 38 is pivoted upward about its aft pivot pins 220, 222, raising its distal arm 224 above a proximally directed arm 226 of the anti-backup pendulum 200 allowing distal movement of the lower foot 210 for locking the rack 170 between firing strokes. A clamp locking lever 230 rocks about its lateral pivot pins 232, 234 to effect this raising of the release button 38. In particular, a proximally and upwardly projecting arm 236 of the clamp locking lever 230 slidingly abuts an undersurface of the distal arm 224 of the release button 38. A distally projecting locking arm 238 of the clamp locking lever 230 locks the closure yoke 96 in its clamped condition. In particular, a tab 240 extending down between the proximally and upwardly projecting arm 236 and the distally projecting locking arm 238 is urged proximally by a tension spring 242 that is also attached to the right half shell 84 of the handle housing 88 at a pin 244. With reference to FIGS. 6–7, the distally projecting locking arm 238 rests upon a step 246 presented on a top, proximal portion of the closure yoke 96, allowing the closure yoke 96 to be distally moved to transfer the closure motion. A clamp locking notch 248 distally and upwardly open recess of the step 246 receives the distally projecting locking arm 238 when the closure yoke 96 reaches its distal actuated position (FIG. 8, 9). Thus, the surgeon may release the closure trigger 26 with the end effector 12 remaining clamped.
With reference to FIGS. 5–8, 12, in addition to the afore-described anti-backup feature and closure clamping feature, a firing lockout feature is provided by a firing lockout lever 250.With the surgical stapling and severing instrument 10 in its initial open and unfired state, the firing lockout lever 250 responds to the closure yoke 96 being retracted by blocking distal, firing movement of the solid rack 170, as shown particularly in FIGS. 7 and 8. The firing lockout lever 250 includes a distally extending arm 252 having a distally ramped upper surface 254 that is aligned with a right edge 256 along the proximal portion of the solid rack 170. A recessed right edge 258 along the remaining distal portion of the solid rack 170 allows the distally ramped upper surface 254 of the firing lockout lever 250 to rotate upward, pivoting about its proximal lateral pins 260, 262 urged by a tension spring 264 connected to a vertical tab 266 that is perpendicularly and proximally attached to the distally extending arm 252. The other end of the tension spring 264 is connected to an integral pin 268 formed in the right half shell 84 of the handle housing 88 aft of the vertical tab 266.
As shown in FIG. 8, the distally ramped surface 254 blocks distal movement of the solid rack 170 by being wedged upward by a step 270 formed across the proximal end of the closure yoke 96, open proximally and upwardly to receive the downwardly pivoting distally extending arm 252 of the firing lockout lever 250. With the closure yoke 96 moved distally to close the end effector 12 as shown in FIG. 12, the right edge 256 of the solid rack 170 is allowed to pass over the distally ramped surface 254 that responds thereto by moving the distally extending arm 252 downward to engage a lower step 272 formed in the closure yoke 96 proximal to the higher and more distal step 270. The engagement of the firing lockout lever 250 to the lower step 272 has a benefit of preventing retraction (proximal movement) of the closure yoke 96 until the solid rack 170 is retracted. Thus, initiating retraction of the firing mechanism 42 advantageously occurs prior to unclamping of the end effector 12, which may otherwise cause binding in the firing mechanism 42. Moreover, enough frictional contact may exist between the lower step 272 and the firing lockout lever 250 to advantageously require a two-step procedure to return the surgical stapling and severing instrument 10 to its open and retracted condition. In particular, once the firing mechanism 42 has been retracted by depressing the release button 38, a slight squeeze on the closure trigger 26 would tend to allow the firing lockout lever 250 to raise to its firing lockout position. Thereafter, the release of the closure trigger 26 may proceed with the firing lockout lever 250 aligned for engagement of the higher step 270 when the closure yoke 96 is fully retracted and thus the end effector 12 opened.
It should further be appreciated that the rack 170 may be advantageously formed of links that allow a portion proximal to the firing mechanism 42 to be curved into the handle, allowing for a more compact design. Such a linked rack is described in greater detail in co-owned “SURGICAL STAPLING INSTRUMENT INCORPORATING A FIRING MECHANISM HAVING A LINKED RACK TRANSMISSION”, Ser. No. 10/673,930, to Jeffrey S. Swayze, Frederick E. Shelton IV, filed 29 Sep. 2003.
Uneven Firing Strokes.
Having the firing trigger 34 interact with a rotary transmission firing mechanism 150 upstream of the solid rack 170 presents an opportunity for further optimization of multiple firing strokes. With reference to FIG. 13, a cam disk 330 facilitates uneven firing strokes so that mechanical advantage may be increased for specific firing strokes that are expected to encounter increased resistance with other strokes having less mechanical advantage to decrease the number of firing strokes required. In addition, the tactile feedback given to the surgeon is more uniform, avoiding a misperception that binding has occurred or full travel achieved when a stroke requires a greater firing force than a preceding stroke required.
The firing trigger 34, via an operational relationship with the drive wedge 182, interacts with three cam lobes 342–344 about a different center of rotation than the cam disk 330 that includes the cam lobes; thereby, enhanced control of how the cam disk 330 rotates by actuation of the firing trigger 34 may be achieved. The spacing of the cam lobes 342–344, their depth (as shown by their respective radial distances R1–R3 from the front pin 92), and their overall shape allow desired variation in stroke distance and mechanical advantage.
As depicted in FIGS. 14–15, the force to fire requirements vary as a function of the longitudinal firing travel due to changes in the load. In FIG. 14, the firing travel distance has been divided into three firing strokes of equal distance. During a first stroke, the force ramps upward during a first portion of the stroke and then becomes relatively constant with a slow increase. During the second stroke and into the third stroke, this slow increase in force required continues, followed by a drop off as full firing travel is approached. These changes in force required are related to various factors, such as the amount of tissue being severed, staples being driven, and mechanical friction encountered in the firing mechanism 42 and implement portion 22. The surgeon experiences a highest level of work performed (i.e., force over a distance) during the second stroke, as related to the Area2 being larger than the adjacent Area 1 and Area3. If the amount of force required is too high for the intended population of surgeons, then additional strokes may be required for this even firing rotary transmission firing mechanism 42.
In FIG. 15, uneven firing strokes are used to advantageously vary the longitudinal amount of firing travel between strokes, as shown by the end of the first stroke at D*1, which is more than D1 of FIG. 14, and the second stroke at D*2, which is less than D2 of FIG. 14. The amount of work required by the surgeon during each stroke is approximately equal, which would tend to avoid exceeding the hand strength of some surgeons. Moreover, the surgeon is less likely to misinterpret the tactile feedback given by the surgeon with the average force to fire over each stroke seeming to be more constant. In particular, although not depicted, it should be appreciated that having to travel a shorter longitudinal distance during stroke 2 means that increased mechanical advantage is being employed to reduce the instantaneous force to fire felt at the firing trigger.
An illustrative rotary transmission firing mechanism 42 has been described as benefiting from an uneven firing stroke to optimize travel versus force required; however, it should be appreciated that a linearly coupled approach to converting firing trigger motion to a longitudinal firing motion may also benefit from uneven firing strokes. In FIG. 16, a depiction of a straight rack 400 is shown having unevenly spaced rack teeth sections 402, 404, 406. Specifically, in a distal rack teeth section 402, the three feet shown have a narrow longitudinal length. In a middle rack teeth section 404, the three teeth shown have a moderate longitudinal length. In a proximal rack teeth section 406, the three teeth shown have an extended longitudinal length. Thus, a pawl 408 forward and downwardly urged from a pivoting connection 410 to a top portion 412 of a firing trigger 414 tends to engage a given tooth later in the firing stroke when contacting teeth in the proximal rack teeth section 406 than in the distal rack teeth section 402. The mechanical advantage and degree to which the surgeon's hand has clenched as the pawl 408 engages the straight rack 400 thus varies depending upon the length of rack teeth for each section 402, 404, 406.
In FIG. 17, an application of uneven firing strokes is made to a linked rack firing mechanism 430, such as described in greater detail in commonly-owned and co-pending U.S. patent application Ser. No. 10/673,930, entitled “SURGICAL STAPLING INSTRUMENT INCORPORATING A FIRING MECHANISM HAVING A LIKED RACK TRANSMISSION” to Jeffrey S. Swayze and Frederick E. Shelton IV. In this instance, the length of a ramped slot 432, 434, 436 varies in the three links 438, 440, 442 that form a linked rack 444.
In FIG. 18, a screen door lock drive 500 incorporates uneven firing strokes with a tapered firing rod 502 that is engaged by a screen door lock-style dogleg plate 504 that is downwardly and forwardly urged about a pivot connection 506 at a top portion 508 of a firing trigger 510. The dogleg plate 504 has a distally projecting arm 512 connecting the pivot connection 506 to a downward arm 514 that includes an aperture 516 to receive the tapered rod 502. As the top portion 508 of the firing trigger 510 is moved distally to fire, the projecting arm 512 moves distally. Frictional contact of the tapered rod 502 to the aperture 516 causes the downward arm 514 to rotate the screen dog leg plate 504 top forward, causing the aperture 516 to no longer slide along the tapered rod 502 but instead to bind and engage, urging the tapered rod 502 to distally fire the instrument. The diameter of the tapered rod 502 thus dictates how much the dogleg plate 504 must rotate top forward before the binding occurs.
Thus, in each of these versions in FIG. 16–18 of a pawl-style engagement of a firing trigger to a straight portion of a firing rack, changing spacing of teeth results in uneven strokes and avoids the situation where the firing mechanism engages with the firing trigger closer to its most relaxed position when a stronger force is required. Instead, delaying engagement until the firing trigger has been brought closer to the pistol grip of the instrument insures that the amount of work (force over distance) expended during the given stroke may be comparable to other strokes. In addition, the force may be exerted with the firing trigger closer to the pistol grip where greater hand strength is generally available. Also, the arcing relative movement of the upper portion of the firing trigger versus the longitudinal distal movement of the rack also varies based on when the pawl engages the rack.
In use, the surgeon positions the end effector 12 and shaft 18 through the cannula of a trocar to a surgical site, positions the anvil 14 and elongates channel 16 as opposing jaws to grasp tissue to be stapled and severed. Once satisfied with the position of end effector 12, the closure trigger 26 is fully depressed toward the pistol grip 36 of the handle 20, causing a closure link 102 to advance a closure yoke 96 and thus a closure tube 24 to close the end effector 12. The distally moved closure yoke 96 presents a clamp locking notch 248 that receives a clamp locking lever 230, clamping the end effector 12. Stroking the firing trigger 34 multiple times effects firing of the firing rod 32 by sequentially engaging a drive wedge 182 that is coupled to the firing trigger 34 to cam lobes 342–344 on the cam disk 330. This ratcheting rotation is transferred through the rotary transmission firing mechanism 150 to distally advance the solid rack 170. With the closure yoke 96 advanced, the rack 170 is able to depress a firing lockout lever 250 out of the way. Between firing strokes, the anti-backup pendulum 100 is drawn into a perpendicular locking contact with the rack 170, opposing a retraction force imparted by the gear train retraction spring 172 connected to the cam gear 330. Once full firing travel is achieved, depressing the release button 38 first disengages the anti-backup pendulum 100, allowing the solid rack 170 to retract and secondly disengages the clamp locking lever 230 from the closure yoke 96 to remove one impediment from opening the end effector 12. The surgeon squeezes the closure yoke 26 to allow the firing lockout lever 250 to release from the closure yoke 96 and releases the closure trigger 26, allowing the closure yoke 96 to proximally move to where it holds up the firing lockout lever 250 to lockout the sold rock 170 from firing. Thereafter, the implement portion 22 of the surgical stapling and severing instrument 10 may be removed such as for replacing the staple cartridge 62 in preparation for another operation.
While the present invention has been illustrated by description of several embodiments and while the illustrative embodiments have been described in considerable detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications may readily appear to those skilled in the art.
It will be appreciated that the terms “proximal” and “distal” are used herein with reference to a clinician gripping a handle of an instrument. Thus, the end effector 12 is distal with respect to the more proximal handle 20. It will be further appreciated that for convenience and clarity, spatial terms such as “vertical” and “horizontal” are used herein with respect to the drawings. However, surgical instruments are used in many orientations and positions, and these terms are not intended to be limiting and absolute.
The present invention is being discussed in terms of endoscopic procedures and apparatus. However, use herein of terms such as “endoscopic”, should not be construed to limit the present invention to a surgical stapling and severing instrument for use only in conjunction with an endoscopic tube (i.e., trocar). On the contrary, it is believed that the present invention may find use in any procedure where access is limited to a small incision, including but not limited to laparoscopic procedures, as well as open procedures.
For instance, while a surgical stapling and severing instrument 10 is described herein that advantageously has separate and distinct closing and firing actuation, it nevertheless provides clinical flexibility. However, it should be appreciated that applications consistent with the present invention may include a handle that converts a single user actuation into a firing motion that closes and fires the instrument.
In addition, while a manually actuated handle is illustrated, a motorized or otherwise powered handle may benefit from incorporating a linked rack as described herein, allowing reduction of the size of the handle or other benefits. For instance, while partially stowing the linked rack into the pistol grip is convenient, it should be appreciated that the pivot connection between links allows for stowing the link parallel to the straight portion defined by the shaft and the barrel of the handle.

## Claims

1. A surgical instrument, comprising:
an end effector operably configured to respond to a firing motion;
a shaft attached to the end effector and including an elongate firing member coupled to the end effector for movement to longitudinally transmit the firing motion; and
a handle proximally attached to the shaft, comprising:
a cam member including a plurality of cam lobes, at least one of the cam lobes differing in shape from an adjacent cam lobe,
a firing actuator repeatably moveable in a firing direction and a return direction, and operatively configured to interact with a respective cam lobe during each firing stroke, and
a firing mechanism responsive to intermittent motion from the cam disk to produce the longitudinal firing motion to the end effector.

2. The surgical instrument of claim 1, wherein the cam member comprises a cam disk.

3. The surgical instrument of claim 2, wherein the handle further comprises a wedge coupled to the firing actuator and operably configured to sequentially engage a respective one of the plurality of cam lobes of the cam disk during each movement of the firing actuator in the firing direction.

4. The surgical instrument of claim 2, wherein the handle further comprises a rack connected to the firing member of the shaft and coupled by gear engagement with the cam disk to transmit an intermittent rotation of the cam disk as the longitudinal firing motion.

5. The surgical instrument of claim 4, wherein the rack is coupled by gear engagement with the cam disk comprised of a gear train.

6. The surgical instrument of claim 5, wherein the gear train comprises a gear reduction assembly relating the intermittent rotation of the cam disk to an increased longitudinal motion of the rack.

7. The surgical instrument of claim 6, further comprising a firing lockout mechanism responsive to the closure mechanism being unclosed to prevent movement of the rack.

8. The surgical instrument of claim 6, wherein the handle further comprises:
a firing lockout mechanism responsive to the closure mechanism being unclosed to prevent movement of the rack and responsive to the rack being at least partially fired to prevent opening of the closure mechanism;
a clamp lock mechanism responsive to closure motion of the closure mechanism to lock the closure mechanism;
an anti-backup mechanism operably configured to prevent retraction of the rack between firing strokes of the firing trigger; and
a release mechanism operably configured to unlock the anti-backup mechanism.

9. The surgical instrument of claim 6, wherein the end effector is operably configured to staple and sever tissue during firing.

10. The surgical instrument of claim 1, further comprising an anti-backup mechanism operably configured to prevent retraction of the firing mechanism between firing strokes of the firing actuator.

11. The surgical instrument of claim 10, wherein the firing lockout mechanism is operably configured to respond to the rack having been at least partially fired to block opening movement of the closure mechanism.

12. The surgical instrument of claim 11, wherein the release mechanism is further operably configured to unlock the clamp lock mechanism.

13. The surgical instrument of claim 1, wherein the end effector comprises a pair of opposing jaws responsive to a closure motion and a firing bar responsive to the firing member, the shaft operably configured to transmit the closure motion through a closure member to the end effector, the handle further comprising a closure mechanism operably configured to produce the closure motion.

14. The surgical instrument of claim 13, wherein the handle further comprises a clamp lock responsive to closure motion of the closure mechanism to lock the closure mechanism.

15. The surgical instrument of claim 1, wherein the handle further comprises a pistol grip, and the firing mechanism comprises a bendable rack stowable in the pistol grip when retracted.