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. A flexible rack transmits these firing strokes to a firing rod that reciprocates in an elongate shaft to actuate the end effector. The flexible rack advantageously stows into a pistol grip of the handle when retracted to minimize handle length.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     The present application is a continuation in part of U.S. pat. appln. Ser. No. 11/052,632, “MULTI-STROKE MECHANISM WITH AUTOMATED END OF STROKE RETRACTION” to Jeffrey S. Swayze et al., filed Feb. 7, 2005, which in turn was a continuation in part of U.S. pat. appln Ser. No. 10/673,930 entitled “SURGICAL STAPLING INSTRUMENT INCORPORATING A FIRING MECHANISM HAVING A LINKED RACK TRANSMISSION”, to Jeffrey S. Swayze, which issued as U.S. Pat. No. 6,905,057, the disclosures of both of which are hereby incorporated by reference in their entirety. 
     
    
     FIELD OF THE INVENTION  
       [0002]     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  
       [0003]     Endoscopic and laparoscopic surgical instruments are often preferred over traditional open surgical devices since a smaller incision tends to reduce the post-operative recovery time and complications. The use of laparoscopic and endoscopic surgical procedures has been relatively popular and has provided additional incentive to develop the procedures further. In laparoscopic procedures, surgery is performed in the interior of the abdomen through a small incision. Similarly, in endoscopic procedures, surgery is performed in any hollow viscus of the body through narrow endoscopic tubes inserted through small entrance wounds in the skin.  
         [0004]     Laparoscopic and endoscopic procedures generally require that the surgical region be insufflated. Accordingly, any instrumentation inserted into the body must be sealed to ensure that gases do not enter or exit the body through the incision. Moreover, laparoscopic and endoscopic procedures often require the surgeon to act on organs, tissues and/or vessels far removed from the incision. Thus, instruments used in such procedures are typically long and narrow while being functionally controllable from a proximal end of the instrument.  
         [0005]     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.).  
         [0006]     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.  
         [0007]     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.  
         [0008]     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, to effect the firing, a hand-squeezed trigger 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, comparable to that needed for 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 malfunction has occurred when an unexpectedly higher force is required.  
         [0009]     In U.S. Pat. No. 6,905,057, a multiple firing stroke handle for an endoscopic surgical stapling and severing instrument succeeds in reducing these firing forces by advancing a firing mechanism during each squeeze of the firing trigger, mechanically coupling this firing motion through a pawl into a linked rank. In addition to reducing the force required to squeeze the firing trigger, the linked rack stows into a pistol grip of the handle and advantageously reduces the length of the handle as compared to a rigid rack.  
         [0010]     Consequently, a significant need exists for a surgical stapling instrument which has a multiple stroke firing mechanism with a reduced handle length.  
       BRIEF SUMMARY OF THE INVENTION  
       [0011]     The invention overcomes the above-noted and other deficiencies of the prior art by providing a surgical stapling and severing instrument that advantageously incorporates a flexible firing member in a handle. The handle guides a distal portion of the flexible firing member longitudinally to translate a firing motion into a shaft firing member that translates in a shaft to actuate a distally attached end effector. The handle deflects a proximal portion of the flexible firing member from the longitudinal axis during retraction to advantageously reduce the required length of the handle.  
         [0012]     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 FIGURES  
       [0013]     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.  
         [0014]      FIG. 1  is a left isometric view of a surgical stapling and severing instrument in an initial state with the closure and firing trigger released and the end effector (staple lying assembly) open.  
         [0015]      FIG. 2  is a right isometric exploded view of the surgical stapling and severing instrument of  FIG. 1  with the staple applying assembly omitted.  
         [0016]      FIG. 3  is a right isometric view of a handle of the surgical stapling and severing instrument of  FIG. 2  in a clamped and partially fired state with a right shell of a handle housing and rotation knob removed to expose a first version of a flexible firing rack consistent with aspects of the invention.  
         [0017]      FIG. 4  is an aft right isometric view of the flexible firing rack and closure yoke of the surgical stapling and severing instrument of  FIG. 2 .  
         [0018]      FIG. 5  is a front left isometric view of the flexible firing rack of  FIG. 2 .  
         [0019]      FIG. 6  is an aft right isometric view of the flexible firing rack of  FIG. 2 .  
         [0020]      FIG. 7  is an aft view in elevation of the flexible firing rack of  FIG. 2 .  
         [0021]      FIG. 8  is a front left isometric view of an alternative flexible firing rack with top apertures for the surgical stapling and severing instrument of  FIG. 1 .  
         [0022]      FIG. 9  is a front left isometric view of another alternative flexible firing rack with sprocket holes for manual retraction for the surgical stapling and severing instrument of  FIG. 1 .  
         [0023]      FIG. 10  is an aft right isometric view of an alternative surgical stapling and severing instrument with a right handle shell and rotation knob omitted to expose a loop chain drive and a linked rack in an initial state.  
         [0024]      FIG. 11  is a right side view in elevation of the alternative surgical stapling and severing instrument of  FIG. 10  with the right handle shell and rotation knob omitted.  
         [0025]      FIG. 12  is an aft right isometric exploded view of the alternative surgical stapling and severing instrument of  FIG. 10  with the staple applying assembly omitted.  
         [0026]      FIG. 13  is a left side view in elevation of a handle of the alternative surgical stapling and severing instrument of  FIG. 10  with the right handle shell, main body of the closure yoke assembly, rotation knob, closure tube and closure trigger omitted to expose a closure yoke distally advanced (i.e., closed end effector) and the loop chain drive and linked rack in an initial, unfired state.  
         [0027]      FIG. 14  is a left side view in elevation of the portion of the handle of the alternative surgical stapling and severing instrument of  FIG. 13  after the loop chain drive has moved the linked rack to a fired state.  
         [0028]      FIG. 15  is an aft left isometric view of the firing trigger, loop chain drive, linked rack and manual retraction mechanism of the portion of the handle of  FIG. 14 .  
         [0029]      FIG. 16  is an aft left isometric view of the firing trigger, loop chain drive, and linked rack of  FIG. 15 .  
         [0030]      FIG. 17  is an aft right isometric exploded isometric view of the loop chain drive of  FIG. 16  including a ratchet gear coupling to the firing trigger.  
         [0031]      FIG. 18A  is a left side view in elevation taken in vertical and longitudinal cross section through an alternative flexible threaded cable firing mechanism in an initial unfired state for the surgical stapling and severing instrument of  FIG. 1 .  
         [0032]      FIG. 18B  is a left side view in elevation taken in vertical and longitudinal cross section through the alternative flexible threaded cable firing mechanism of  FIG. 18A  in a fully fired state.  
         [0033]      FIG. 18C  is a left side view in elevation taken in vertical and longitudinal cross section through the alternative flexible threaded cable firing mechanism of  FIG. 18B  after automatic firing retraction.  
         [0034]      FIG. 18D  is a forward view in elevation taken in vertical and transverse cross section through the alternative flexible threaded cable firing mechanism of  FIG. 18A .  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0035]     In  FIG. 1 , a surgical stapling and severing instrument  10  includes multi-stroke firing of an end effector, which in the illustrative version is a staple applying apparatus  12 . An upper jaw (anvil)  14  may be repeatably opened and closed about its pivotal attachment to a lower jaw  15  of an elongate (staple) channel  16  engaged to a replaceable staple cartridge  17 . The staple applying assembly  12  is proximally attached to elongate shaft  18 , forming an implement portion  19 . When the staple applying assembly  12  is closed, the implement portion  19  presents a small cross-sectional area suitable for insertion through a trocar by an externally connected and manipulated handle  21 . In  FIG. 2 , a flexible firing rack  22  incorporated into the handle  21  advantageously transfers firing motion to the implement portion  19  yet retracts to enable a reduced length handle  21 .  
         [0036]     In  FIGS. 1-3 , the handle  21  has user controls mounted on its handle housing  23 , such as a rotation knob  24  that rotates the elongate shaft  18  and staple applying assembly  12  about a longitudinal axis of the shaft  18 . A closure trigger  26 , which pivots in front of a pistol grip  27  about a closure trigger pin  28  engaged laterally across the handle housing  23 , is depressed to close the staple applying assembly  12 . A multiple stroke firing trigger  30 , which pivots in front of the closure trigger  26 , causes the staple applying assembly  12  to simultaneously sever and staple tissue clamped therein. Since multiple firing strokes are employed to reduce the amount of force required per stroke by the surgeon&#39;s hand, right and left indicator wheels  32 ,  33  (the former depicted in  FIG. 3 ) that turn on an axle  31  ( FIG. 3 ) rotate presenting indicia of the firing progress. For instance, full firing travel may require three full firing strokes and thus the indicator wheels  32 ,  33  rotate up to one-third of a revolution each per stroke. A manual firing release lever  34  allows retraction before full firing travel if desired and allows assistance to retract in the presence of binding or a failure in the retraction bias. The manual firing release lever  34  is normally downwardly biased by a coil spring  35  ( FIG. 3 ). A closure release button  36  is outwardly presented when the closure trigger  26  is clamped and partial firing has not occurred that would prevent unclamping the closure trigger  26 .  
         [0037]     In  FIG. 3 , the elongate shaft  18  has as its outer structure a longitudinally reciprocating closure tube  38  that pivots the anvil  14  to effect closure in response to proximal depression of the closure trigger  26  of the handle  21 . The elongate channel  18  is connected to the handle  21  by a frame  40  that is internal to the closure tube  38 . The frame  40  is rotatably engaged to the handle  21  so that twisting the rotation knob  24  causes rotation of the implement portion  19 . Each half shell of the rotation knob  24  includes an inward projection  41  that enters a respective longer side opening  42  in the closure tube  38  and projects inward to engage the frame  40  that determines the rotated position of the implement portion  19 . The longitudinal length of the longer opening  42  is sufficiently long to allow longitudinal closure motion of the closure tube  38 .  
         [0038]     An upper portion  44  of the closure trigger  26  pushes forward a closure yoke assembly  46  via a closure link  48 . The closure link  48  is pivotally attached at its distal end by a closure yoke pin  50  to the closure yoke assembly  46  and is pivotally attached at its proximal end by a closure link pin  52 . The closure trigger  26  is urged to the open position by a closure trigger tension spring  54  that is connected proximally to the upper portion  44  of the closure trigger  26  and to the handle housing  23  formed by right and left half shells  56 ,  58 . The right and left half shells  56 ,  58  each include a closure yoke guide post  59  that slides within respective horizontally elongate rectangular apertures  60  formed in each side of the closure yoke assembly  46 , with the post  59  at a distal position in the respective aperture  60  when the closure yoke assembly  46  is proximally positioned with the anvil  14  open and at a proximal position in the aperture  60  when the closure yoke assembly  46  is distally positioned with the anvil  14  closed.  
         [0039]     The upper portion  44  of the closure trigger  26  includes a proximal crest  62  with an aft notch  64 . The closure release button  36  and a pivoting locking arm  66  are connected by a central lateral pivot  68 . A compression spring  70  biases the closure release button  36  proximally (clockwise about the central lateral pivot  68  as viewed from the right). With the upper portion  44  back when the closure trigger  26  is released, the pivoting locking arm  66  rides upon the proximal crest  62  drawing in the closure release button  36 . When the closure trigger  26  reaches its fully depressed position, it should be appreciated that the aft notch  64  is presented below the pivoting locking arm  66 , which drops into and locks against the aft notch  64  under the urging of the compression spring  70 . With the firing components retracted, manual depression of the closure release button  36  rotates the pivoting locking arm  66  upward, unclamping the closure trigger  26 .  
         [0040]     Once the closure trigger  26  is proximally clamped, a firing rod  72  is distally moved from the handle  21  in response to the multiple stroke firing trigger  30  being drawn to the pistol grip  27  with the amount of firing travel visible to the surgeon on right and left indicator gauge wheels  32 ,  33 . The firing trigger  30  pivots about a firing trigger pin  74  that laterally traverses and is engaged to the right and left half shells  56 ,  58 .  
         [0041]     The flexible firing rack  22  is initially retracted, urged to remain in this position by a combination tension/compression spring  76  that is constrained within the pistol grip  27  of the handle  21 , with its nonmoving end  78  connected to the housing  23  and a moving end  80  connected to a downwardly flexed and proximal, retracted end  82  of a steel band  84  that may be molded into the flexible firing rack  22  ( FIGS. 6-7 ). Alternatively, the steel band  84  may underlie and attach to a front end  85  of the flexible firing rack  22  ( FIG. 3 ). As a further alternative, a proximally presented hook  86  on the flexible firing rack  22  ( FIGS. 4-5 ) may serve as an attachment for a retraction spring (not shown). In  FIGS. 5-6 , the front end  85  of the flexible firing rack  22  includes a female attachment receptacle  87  that engages a proximal end of the firing rod  72 . A toothed rack segment  88  ( FIGS. 2-5 ) is upwardly presented along a left edge of the flexible firing rack  22 .  
         [0042]     In  FIGS. 4-6 , in addition to incorporating a degree of downward flexibility into the flexible firing rack  22  by choice of material, a plurality of transverse slots  90  passing through a bottom portion accommodate the tighter radius of turn, enabling downward bending into the pistol grip  27 , thereby minimizing the longitudinal length of the handle  21 . Yet, the flexible firing rack  22  forms a sufficiently rigid rack structure in its upper portion when straightened by distal advancement into the closure yoke assembly  46  to transfer a significant firing force through the firing rod  72  in the implement portion  19 , yet readily retracts into the pistol grip  27 . It should be appreciated that the combination tension/compression spring  76  increases the amount of firing travel available while essentially reducing the minimum length by half over a single spring.  
         [0043]     In  FIG. 3 , a distal pinion spur gear  91  engages the toothed rack segment  88 , turned thereby during firing about a distal gear axle  92  whose lateral ends turn within receptacles in the handle half shells  56 ,  58 . A proximal dual gear  93  has a left large spur gear  94  that is turned on axle  31  by the distal pinion spur gear  91 . A coaxial right small ratchet gear  95  turns within a hub  96  that is attached to the manual firing release lever  34 . A clip spring  97  urges a pawl  98  within the hub  96  into contact with the ratchet gear  95  so that actuation of the manual firing release lever  34  back drives the dual gear  93 , the pinion spur gear  91 , and the flexible firing rack  22  while an unlocking cam surface  99  unlocks an anti-backup mechanism  100 .  
         [0044]     With particular reference to  FIGS. 2-3 , the anti-backup mechanism  100  prevents the combination tension/compression spring  76  from retracting the flexible firing rack  22  between firing strokes. A coupling slide tube  101  has a proximally open cylindrical cavity  102  shaped to receive the front end  85  of the flexible firing rack  22  with a narrower distal opening  103  that allows passage of the firing rod  72  to communicate the firing motion. A pair of lateral recesses  104  proximally placed on the coupling slide tube  101  engage respectively the pair of closure yoke guide posts  59  that have passed into the closure yoke assembly  46  to ground the coupling slide tube  101 . The firing rod  72  extends proximally out of a proximal end of the frame  40  and through a locking hole  105  of an anti-backup plate  106 . The through hole  105  is sized to slidingly receive the firing rod  72  when perpendicularly aligned but to bind when tipped. A lower tab attachment  107  extends proximally from a lower lip of the proximal end of the frame  40 , extending through an aperture  108  on a lower edge of an anti-backup plate  106 . This lower tab attachment  107  draws the lower portion of the anti-backup plate  106  proximate to the frame  40  so that the anti-backup plate  106  is perpendicular when the firing rod  72  is distally advanced and allowed to tip top aft into a binding state when the firing rod  72  attempts to retract. An anti-backup compression spring  110  is distally constrained by the proximal end of the frame  40  and distally abuts a top portion of the anti-backup plate  106 , biasing the anti-backup plate  106  to a locking state.  
         [0045]     Opposing the aft bias from anti-backup compression spring  110 , an anti-backup cam tube  112  slidingly encompasses the coupling slide tube  101  and abuts the anti-backup plate  106 . A proximally projecting anti-backup yoke  114  attached to the anti-backup cam tube  112  extends overtop of the closure yoke assembly  46 .  
         [0046]     To cause knife retraction at the end of full firing travel, a proximal end  116  of the flexible firing rack  22  includes a tang  118  ( FIGS. 4-5 ) that projects upwardly when the distal end  116  is advanced into a rack channel  120  formed in the closure yoke assembly  46 . This tang  118  is aligned to activate a bottom proximal cam  122  on an anti-backup release lever  124 . Alternatively or in addition, actuation of the manual release firing lever  34  distally moves the cam surface  99  on the hub  96  to distally move the bottom proximal cam  122  on the anti-backup release lever  124  to effect release. Structures formed in the right and left half shells  56 ,  58  constrain movement of the anti-backup release lever  124 . A pin receptacle  126  and circular pin  128 , formed respectively between right and left half shells  56 ,  58 , is received through a longitudinally elongate aperture  130  formed in the anti-backup release lever  124  distal to the bottom proximal cam  122 , thus allowing longitudinal translation as well as rotation about the circular pin  128 . In the right half shell  56 , a proximally open channel  132  includes a proximal horizontal portion that communicates with an upwardly and distally angled portion that receives a rightward aft pin  134  near the proximal end of the anti-backup release lever  124 , thus imparting an upward rotation as the anti-backup release lever  124  reaches the distal most portion of its translation. A blocking structure  136 , formed in the right half shell  56  proximal to the anti-backup release lever  124 , prevents proximal movement thereof once assembled to maintain rightward aft pin  134  in the proximally open channel  132 .  
         [0047]     It should be appreciated that the rack channel  120  of the closure yoke assembly  46  serves as a longitudinally aligned firing member guide that stabilizes a distal portion of the flexible firing rack  22 . In applications that do not include a distinct end effector closure mechanism, a longitudinally aligned firing member guide may be incorporated into the handle housing  23  as a stationary conduit.  
         [0048]     A distal end  138  of the anti-backup release lever  124  thus is urged distally and downwardly, causing a rightward front pin  140  to drop into distally open step structure  142  formed in the right half shell  56 , which is urged into this engagement by a compression spring  144  hooked to a leftward hook  146  on the anti-backup release lever  124  between the rightward front pin  140  and the longitudinally elongate aperture  130 . The other end of the compression spring  144  is attached to a hook  148  formed in the left half shell  58  in a more proximal and lower position just above the closure yoke assembly  46 . The compression spring  144  thus pulls the distal end  138  of the anti-backup release lever  124  down and aft, which results in the rightward front pin  140  locking into the distally open step structure  142  when distally advanced.  
         [0049]     Once tripped, the anti-backup release lever  124  remains forward holding the anti-backup plate  106  perpendicularly, thus allowing the flexible firing rack  22  to be retracted. When the closure yoke assembly  46  is subsequently retracted when unclamping the end effector  12 , an upwardly projecting reset tang  150  on the closure yoke assembly  46  contacts a bottom distal cam  152  of the anti-backup release lever  124 , lifting the rightward front pin  140  out of the distally open step structure  142  so that the anti-backup compression spring  1   10  can proximally push the anti-backup cam tube  112  and the anti-backup release lever  124  to their retracted positions. To effect the distal movement of the flexible firing rack  22 , the firing trigger  30  pivots about the firing trigger pin  74  that is connected to the housing  23 . An upper portion  160  of the firing trigger  30  moves distally about the firing trigger pin  74  as the firing trigger  30  is depressed towards pistol grip  27 , stretching a proximally placed firing trigger tension spring  162  proximally connected between a spring pin  163  attached to the upper portion  160  of the firing trigger  30  and the housing  23 .  
         [0050]     In  FIGS. 2-4 , the upper portion  160  ( FIGS. 2-3 ) of the firing trigger  30  engages the flexible firing rack  22  during each firing trigger depression by a side pawl mechanism  170  that also disengages when the firing trigger  30  is released. In particular, a ramped right-side track  172  formed by a plurality of proximally and rightwardly facing beveled surfaces  174  spaced along the flexible firing rack  22  are sequentially engaged by a side pawl slide assembly  176 . In particular, a pawl slide block  178  has right and left lower guides  180  that slide respectively in a left track  182  formed in a main body  183  of the closure yoke assembly  46  below the rack channel  120  and a right track  184  in a closure yoke rail  186  that parallels rack channel  120  and is attached to a rack channel cover  188  that closes a rightwardly open portion of the rack channel  120  in the main body  183  of the closure yoke assembly  46  that is distal to the travel of the pawl slide assembly  176 . A compression spring  190  is attached between a hook  192  on a top proximal position on the closure yoke rail  186  and a hook  193  on a distal right side of the pawl slide block  178 , which keeps the pawl slide block  178  drawn proximally into contact with the upper portion  160  of the firing trigger  30 .  
         [0051]     A pawl block  194  sits on the pawl slide  178  pivoting about a vertical aft pin  196  that passes through a left proximal comer of pawl block  194  and pawl slide  178 . A kick-out block recess  198  is formed on a distal portion of a top surface of the block  194  to receive a kick-out block  200  pivotally pinned therein by a vertical pin  202  whose bottom tip extends into a pawl spring recess  204  on a top surface of the pawl slide  178 . A pawl spring  206  in the pawl spring recess  204  extends to the right of the vertical front pin  202  urging the pawl block  194  to rotate counterclockwise when viewed from above into engagement with the ramped right-side track  172 . A small coil spring  208  in the kick-out block recess  198  urges the kick-out block  200  to rotate clockwise when viewed from above, its proximal end urged into contact with a contoured lip  210  formed in the closure yoke assembly  46  above the rack channel  120 .  
         [0052]     It should be appreciated that the stronger mechanical advantage of the pawl spring  206  over the small coil spring  208  means that the pawl block  194  tends toward engagement with the kick-out block  200  rotated clockwise. As the firing trigger  30  is fully depressed and begins to be released, the kick-out block  200  encounters a ridge  212  ( FIG. 4 ) in the contoured lip  210  as the pawl slide  178  retracts, forcing the kick-out block  200  to rotate clockwise when viewed from above and thereby kicking out the pawl block  194  from engagement with the flexible firing rack  22 . The shape of the kick-out block recess  198  stops the clockwise rotation of the kick-out block  200  to a perpendicular orientation to the contoured lip  210  maintaining this disengagement during the full retraction and thereby eliminating a ratcheting noise. The selection of the material of the flexible firing rack  22  may further dampen ratcheting noise.  
         [0053]     In  FIG. 8 , an alternative flexible firing rack  22   a  with longitudinally aligned rectangular top apertures  240  along a right portion of a top surface reduces rigidity enhancing downward flexing for stowing in the pistol grip  27  of the surgical stapling and severing instrument  10  ( FIG. 1 ).  
         [0054]     In  FIG. 9 , another alternative flexible firing rack  22   b  includes the top apertures  240  and in addition includes a bottom relieved portion  250  rather than traverse slots  90  to enhance downward flexibility.  
         [0055]     In  FIGS. 10-17 , an alternative surgical stapling and severing instrument  10 ′ is as described above for  FIGS. 1-4  with the exception of substitution of a linked rack  22   c,  similar to that described in the afore-referenced U.S. Pat. No. 6,905,057 instead of the flexible firing rack  22 ,  22   a - 22   b.  In addition, rather than the afore-described side pawl mechanism  170 , a chain drive  170   a  fires the linked rack  22   c.    
         [0056]     It should be appreciated that any patent, publication, or other disclosure material, in whole or in part, that is said to be incorporated by reference herein is incorporated herein only to the extent that the incorporated material does not conflict with existing definitions, statements, or other disclosure material set forth in this disclosure. As such, and to the extent necessary, the disclosure as explicitly set forth herein supersedes any conflicting material incorporated herein by reference. Any material, or portion thereof, that is said to be incorporated by reference herein, but which conflicts with existing definitions, statements, or other disclosure material set forth herein will only be incorporated to the extent that no conflict arises between that incorporated material and the existing disclosure material.  
         [0057]     With particular reference to  FIG. 12 , the linked rack  22   c  includes a distal long link  300  that reciprocates within the rack channel  120  of a closure yoke assembly  46   a,  the latter differing in that the main body  183  is attached to a right-side rack channel cover  188   a  that includes a recess  60   a  that engages the right side closure yoke guide post  59  of the right half shell  56 . A plurality of smaller rack links  301 - 305  proximal to the distal long link  300  have rounded adjacent ends that allow for the links  301 - 305  to rotate downwardly yet present a respective portion of a toothed rack segment  88   a  when in the rack channel  120 . Each link  300 - 305  is engaged to a looped bicycle-style drive chain  310  by a respective pair of long pins  312  that pass through chain link pivot holes  314  through a respective chain link  316  of the drive chain  310 . Other chain links  316  are pinned together by short link pins  312   a.    
         [0058]     A lower proximal idler wheel  318  rotates upon an axle  320  in an aft portion of the handle housing  23  adjacent to the closure release button  36  and to the right half shell  56 . A distal idler wheel  322  rotates upon an axle  324  proximal to a retracted position of the rack channel cover  188   a.  The drive chain  310  rotates at each looped end about these idler wheels  318 ,  322 . Above the lower proximal idler wheel  318 , an axle  326  passes within the drive chain  310  so that a retraction bias spur gear  328 , rotating about the axle  326 , engages and forms an approximately  90  degree comer in the drive chain  310 . A coil spring  329  has an inner end attached to the retraction bias spur gear  328  and an outer end attached to the right half shell  56  and is wound such that clockwise (when viewed from the right) firing of the drive chain  310  tightens the coil spring  329 , providing a retraction bias to the chain drive  170   a.    
         [0059]     A firing trigger  30   a  has an upper portion  160   a  that is coupled during each firing depression by a firing trigger ratchet assembly  330 . In particular, arcing gear teeth  332 , which are radially equidistant from the firing trigger axle  74 , engage a trigger spur gear  334  that free wheels on a ratchet axle  336 . A disk  338  that is attached to a right side of the trigger spur gear  334  also freely rotates on the ratchet axle  336  and presents a ratchet pawl  340  to a ratchet gear  342  that is attached to rotate with the ratchet axle  336 . A spur gear  344  is also attached to rotate with the ratchet axle  336  and is positioned under the chain drive  310  to engage the chain drive  310  and constrain its movement into a dogleg shape. The ratchet gear  342  ( FIG. 11 ) is shaped such that the firing trigger ratchet assembly  330  converts the clockwise rotation (CW) (when viewed from the right) of the arcing gear teeth  332  and thus counter clockwise rotation (CCW) of the trigger spur gear  334  into a CCW rotation of the ratchet axle  336  and spur gear  344  and thus the drive chain  310 . Forming the disk  338  and ratchet pawl  340  from a molded polymer may advantageously provide economy for a surgical stapling and severing instrument of limited operational life as well as reducing ratchet noise.  
         [0060]     In use, the surgical stapling and severing instrument  10 ′ is initially unclamped and unfired in  FIGS. 10-11 . Once clamped, the firing trigger  30   a  is depressed a plurality of times, moving the linked rack  22   c  from a retracted position ( FIG. 13 ) to a distally fired position ( FIGS. 14-15 ) by the chain drive  170   a.  In particular, the firing trigger ratchet assembly  330  allows the firing trigger  30   a  to distally advance the top portion of a drive chain  310 , which winds the retraction coil spring  329 . The anti-backup mechanism  100  is tripped after full firing travel by the tang  118  on the most proximal link  305  contacting the anti-backup release lever  124 . The firing trigger ratchet assembly  330  allows the drive chain  310  to be rotated in a retraction direction without coupling to the firing trigger  30   a.  Alternatively, the manual retraction release lever  34  may be actuated, moving the anti-backup release lever  124  to a released position and backdriving gears  93 ,  91  that retract the linked rack  22   c  by engaging the tooth rack segment  88   a.    
         [0061]     In  FIGS. 18A-18D , a flexible threaded cable firing mechanism  400  for an additional alternative surgical stapling and severing instrument  10 ″ advantageously enables a length of firing travel that would not necessarily require a longer handle. In  FIG. 18A , distal and proximal handle grounding structures  402 ,  404  encompass a cylindrical firing sleeve  406  that has a central bore  408  including an inner diameter (ID) threaded portion  410  along a distal end  412  that includes an increased diameter distal head  414  that initially abuts the distal handle grounding structure  402 . A central portion  416  of the cylindrical firing sleeve  406  has a constant radius for reciprocally sliding a small amount through the distal and proximal handle ground structures  402 ,  404 . A proximal hub end  418  of the cylindrical firing sleeve  406  has a slightly increased radius that is initially spaced proximally from the proximal handle grounding structure  404  and may be moved into abutment with the same. A compression spring  420  encompasses the central portion  416  of the cylindrical firing sleeve  406 , contacting a proximal surface of the distal handle grounding structure  402  and a distal surface of an aft directed bevel gear  422  encompassing and attached to the central portion  416  of the cylindrical firing sleeve  406 , providing a proximal bias to the cylindrical firing sleeve  406 .  
         [0062]     A flexible rod  424  passes through the central bore  408  and includes outer diameter (OD) threads  426  that engage the ID threaded portion  410  of the cylindrical firing sleeve  406 . A cable coupling  428  is attached at its proximal end to the flexible rod  424  and at its distal end to the firing rod  72 . An anti-rotation pin  430  extends laterally from the cable coupling  428  to longitudinally slide along a pin guide  432  grounded to the handle (not shown) while preventing rotation of the flexible rod  424 . A cable sheath  433  for reduced friction may cover a portion of the flexible rod  424  proximal to a portion that is capable of reaching the ID threaded portion  410 .  
         [0063]     A left bevel gear  434  is coupled by a one-way clutch (e.g., ratchet) to a firing trigger (not shown) to turn the aft directed transverse bevel gear  422  and thus the cylindrical firing sleeve  406  in a first direction. Given the corresponding direction of turns of the threads  410 ,  426 , the flexible rod  424  distally translates from the cylindrical firing sleeve  406 , distally moving the cable coupling  428  and the firing rod  72 . The rotation in the first direction of the cylindrical firing sleeve  406  winds a retraction coil spring  436  that encompasses and has an inner end attached to a distal portion of the proximal hub end  418  and has an outer end  437  ( FIG. 18D ) grounded to the handle housing (not shown). Between firing strokes when the firing trigger is uncoupled from the left bevel gear  434 , the retraction coil spring  436  is prevented from turning the cylindrical firing sleeve  406  in the opposite second direction by a ratchet mechanism  438 . In particular, a ratchet gear  440  encompassing a central portion of the proximal hub end  418  is form proximally adjacent to the retraction coil spring  436 . A most proximal lateral surface  442  has a reduced radius. A pawl  444  is grounded to the handle (not shown). With the cylindrical firing sleeve  406  retracted as in  FIG. 18A , the pawl  444  engages the ratchet gear  440  preventing rotation in the second direction.  
         [0064]     In  FIG. 18B , as the flexible rod  424  approaches full distal travel, a cable stop  446  attached to the flexible rod  424  distally advances sufficiently to contact the proximal surface of the cylindrical firing sleeve  406 , translating the cylindrical firing sleeve  406  distally and compressing the compression spring  420 . The increased diameter distal head  414  contacts a distally ramped proximal edge  448  of a rocker latch  450  that pivots about pivotal connection  452  grounded to the housing (not shown). It should be appreciated that the rocker latch  450  is biased inwardly and thus the ramped proximal catch  448  rotates to longitudinally capture a proximal edge of the increased diameter distal head  414  of the cylindrical firing sleeve  406 . Distal translation of the cylindrical firing sleeve  406  moves the ratchet gear  440  out from under the ratchet pawl  444  allowing the retraction coil spring  436  to rotate the cylindrical firing sleeve  406  in the second direction, which in turn retracts the flexible rod  424 . In  FIG. 18C , the cable coupling  428  has retracted sufficiently to contact a proximally ramped release arm  454  of the rocker latch  450 , rotating the ramped proximal catch  448  out of engagement with the increased diameter distal  414  of the cylindrical firing sleeve  406  and allowing the compression spring  420  to urge the cylindrical firing sleeve  406  proximally, resetting the mechanism  400  to the state of  FIG. 18A .  
         [0065]     A right bevel gear  456  may be included that is part of a manual firing release mechanism  458  that releases the ratchet mechanism  438  (e.g., distally shifts cylinder firing sleeve  406 , displaces ratchet pawl  444 ) and rotates the cylinder firing sleeve to retract the flexible rod  424 . The right bevel gear  456  may include a pivot bias (not shown) that normally maintains the right bevel gear  456  out of contact with the aft directed transverse bevel gear  422 , whether retracted as in  FIG. 18A  or extended as in  FIG. 18B , but which distally translates the right bevel gear  456  sufficiently for engagement when a manual firing retraction lever (not shown in FIGS.  18 A-D) is actuated.  
         [0066]     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.  
         [0067]     For example, while the additional firing travel typical of multiple firing strokes illustrates particular advantages of a flexible firing member contained in the handle, it should be appreciated that aspects of the present invention may be applied to single firing stroke instruments.  
         [0068]     For another example, while a transverse cavity afforded by a pistol grip illustrates one location to retract a flexible firing member, applications consistent with the present invention may not include a pistol grip. For instance, the flexible firing member may be routed around a 180 degree bend with a retracted end closely parallel to a distal end.  
         [0069]     For yet another example, while a manually actuated firing trigger is illustrated for clarity, remotely actuated handles may benefit from a flexible firing member incorporated into a proximal portion equivalent to a handle that is positioned and/or held by a fixture or robotic manipulator.