turning to the drawings , wherein like numerals denote like components throughout the several views , fig1 - 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 ( fig4 ), 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 fig1 , after firing the surgical stapling and severing instrument 10 , a closure release lever 40 is activated to retract the firing mechanism . depressing the closure release lever 40 disengages a rotary transmission firing mechanism 42 within the handle 20 , enabling a spring 172 to retract the firing rod 32 from the end effector 12 . 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 fig1 - 4 . the anvil 14 of 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 slidingly engages the translating and closing anvil 14 to form opposing jaws , and the frame 28 fixedly engages the stationary channel 16 to form a rigid attachment to the handle 20 . the closure tube 24 engages the anvil 14 distal to the pin in slot 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 movement relative to the frame 28 effects opening of the end effector 12 . with particular reference to fig4 , the implement portion 22 also includes components that respond to a firing motion from the handle 20 , specifically of the firing rod 32 ( not shown in fig4 ) 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 fig5 ) rotatably engages a firing trough member 46 slidably located 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 . a tab is located in front of slot 50 on the closure tube 24 and the tab is bent down into slot 52 in the frame 28 to couple the closure tube 24 to the frame 28 . 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 drive 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 fig3 , 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 / 615 , 972 , 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 . in fig5 - 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 fig5 - 6 and the left half shell 86 shown in fig7 ). in particular , an aft rod 90 passes through the aft pivot hole 84 of the upper portion 80 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 86 , 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 92 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 82 of the closure trigger 26 via an aft pin 106 . a triangular spacer 120 includes holes 122 , 124 , 126 to receive the rods 90 , 92 , 94 respectively and is sandwiched between a cam disk 130 and the upper portion 80 of the closure trigger 26 . cam disk 130 rotates about 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 rod 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 . firing trigger 34 rotatably mounts onto rod 94 to sandwich cam disk 130 between the triangular spacer 120 and firing trigger 34 . a distally opened recess 140 in the firing trigger 34 below the rod hole 136 is registered to receive the front rod 92 , allowing the firing trigger 34 to be drawn distally during firing . actuation of the closure trigger 26 swings the cam link 102 downward into contact with drive wedge pin 184 extending inwardly from firing trigger 34 causing the firing trigger 34 to be partially drawn distally and staging the firing trigger 34 for grasping . with particular reference to fig5 , 9 , and 10 , the cam disk 130 presents a series of cam lobes 142 - 144 ( fig9 ) 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 ( counter - clockwise as viewed from the left ) rotation to the cam disk 130 . this rotation is transferred through a gear train 150 ( fig5 and 11 ) 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 120 that engages a small idler gear 154 , which thus rotates top to the rear ( clockwise ) 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 ( counter - clockwise as viewed from the left ) 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 120 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 clockwise 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 120 ( fig9 - 10 ). the gear train retraction spring 172 has its other end attached to a pin 178 integral to the handle housing 88 . activation of the firing trigger 34 rotates cam disk 130 counter - clockwise to elongate the retraction spring 172 . continued actuation of the firing trigger 34 wraps the elongated retraction spring 172 about the outer diameter of the cam disk 130 as it rotates and into the annular recess 176 ( not shown ). with particular reference to fig5 , 9 , 11 , below and distal to the upper end 128 of the firing trigger 34 is a drive wedge pin hole 180 and a proximal pin hole 190 . drive wedge pin 184 and pin 196 extend inwardly from holes 180 and 190 ( respectively ) in firing trigger 34 . drive wedge 182 and a standoff finger 186 are pivotally mounted on drive wedge pin 184 and operably connected by a mousetrap - style spring 188 . an opposing tension spring 194 between drive wedge 182 and pin 196 urge the drive wedge 182 , standoff finger 186 , and spring 188 clockwise ( fig1 ). when firing trigger 34 is actuated ( fig9 ), standoff finger 186 is brought into contact with a center , uncammed circumferential surface of the cam disk 120 , rotating the standoff finger 186 , spring 188 and drive wedge 182 counterclockwise . the counterclockwise motion of standoff finger 186 biases drive wedge 182 into firing engagement with the cam lobes 142 - 144 ( fig9 ). with particular reference to fig1 , 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 respective right and left 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 fig5 , 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 fig1 , 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 fig6 - 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 , which is a 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 ( fig8 , 9 ). thus , the surgeon may release the closure trigger 26 with the end effector 12 remaining clamped . with reference to fig5 - 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 fig7 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 fig8 , 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 fig1 , 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 fully 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 , which is incorporated herein by reference in its entirety . 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 elongate 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 142 - 144 on the cam disk 130 . 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 130 . once full firing travel is achieved , depressing the closure release lever 40 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 lock out 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 actuations , 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 .
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 the end effector .