Patent Publication Number: US-11660110-B2

Title: Motor-driven surgical cutting and fastening instrument with tactile position feedback

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application claiming priority under 35 U.S.C. § 120 to U.S. Patent Application Ser. No. 16/388,234, entitled MOTOR-DRIVEN SURGICAL CUTTING AND FASTENING INSTRUMENT WITH TACTILE POSITION FEEDBACK, filed Apr. 18, 2019, which issued on Jun. 21, 2022 as U.S. Pat. No. 11,364,046, which is a continuation application claiming priority under 35 U.S.C. § 120 to U.S. patent application Ser. No. 15/093,028, entitled MOTOR-DRIVEN FASTENING ASSEMBLY, filed Apr. 7, 2016, which issued on May 28, 2019 as U.S. Pat. No. 10,299,817, which is a continuation application claiming priority under 35 U.S.C. § 120 to U.S. patent application Ser. No. 13/656,257, entitled MOTOR-DRIVEN SURGICAL CUTTING AND FASTENING INSTRUMENT WITH TACTILE POSITION FEEDBACK, filed Oct. 19, 2012, which issued on Jun. 21, 2016 as U.S. Pat. No. 9,370,358, which is a continuation application claiming priority under 35 U.S.C. § 120 to 13/151,501, entitled MOTOR-DRIVEN SURGICAL CUTTING AND FASTENING INSTRUMENT WITH TACTILE POSITION FEEDBACK, filed Jun. 2, 2011, which issued on Oct. 23, 2012 as U.S. Pat. No. 8,292,155, which is a continuation application claiming priority under 35 U.S.C. § 120 to U.S. patent application Ser. No. 11/344,024, entitled MOTOR-DRIVEN SURGICAL CUTTING AND FASTENING INSTRUMENT WITH MECHANICAL CLOSURE SYSTEM, filed Jan. 31, 2006, which issued on May 29, 2012 as U.S. Pat. No. 8,186,555, the entire disclosures of which are hereby incorporated by reference herein. 
     The present application is also related to the following U.S. patent applications, filed on Jan. 31, 2006, which are incorporated herein by reference: 
     MOTOR-DRIVEN SURGICAL CUTTING AND FASTENING INSTRUMENT WITH USER FEEDBACK SYSTEM; U.S. patent application Ser. No. 11/343,498, now U.S. Pat. No. 7,766,210; 
     MOTOR-DRIVEN SURGICAL CUTTING AND FASTENING INSTRUMENT WITH LOADING FORCE FEEDBACK; U.S. patent application Ser. No. 11/343,573, now U.S. Pat. No. 7,416,101; 
     MOTOR-DRIVEN SURGICAL CUTTING AND FASTENING INSTRUMENT WITH TACTILE POSITION FEEDBACK; U.S. patent application Ser. No. 11/344,035, now U.S. Pat. No. 7,422,139; 
     MOTOR-DRIVEN SURGICAL CUTTING AND FASTENING INSTRUMENT WITH ADAPTIVE USER FEEDBACK; U.S. patent application Ser. No. 11/343,447, now U.S. Pat. No. 7,770,775; 
     MOTOR-DRIVEN SURGICAL CUTTING AND FASTENING INSTRUMENT WITH ARTICULATABLE END EFFECTOR; U.S. patent application Ser. No. 11/343,562, now U.S. Pat. No. 7,568,603; 
     SURGICAL CUTTING AND FASTENING INSTRUMENT WITH CLOSURE TRIGGER LOCKING MECHANISM; U.S. patent application Ser. No. 11/343,321, now U.S. Patent Application Publication No. 2007/0175955; 
     GEARING SELECTOR FOR A POWERED SURGICAL CUTTING AND FASTENING STAPLING INSTRUMENT; U.S. patent application Ser. No. 11/343,563, now U.S. Patent Application Publication No. 2007/0175951; 
     SURGICAL INSTRUMENT HAVING RECORDING CAPABILITIES; U.S. patent application Ser. No. 11/343,803, now U.S. Pat. No. 7,845,537; 
     SURGICAL INSTRUMENT HAVING A REMOVABLE BATTERY; U.S. patent application Ser. No. 11/344,020, U.S. Pat. No. 7,464,846; 
     ELECTRONIC LOCKOUTS AND SURGICAL INSTRUMENT INCLUDING SAME; U.S. patent application Ser. No. 11/343,439, now U.S. Pat. No. 7,644,848; 
     ENDOSCOPIC SURGICAL INSTRUMENT WITH A HANDLE THAT CAN ARTICULATE WITH RESPECT TO THE SHAFT; U.S. patent application Ser. No. 11/343,547, now U.S. Pat. No. 7,753,904; 
     ELECTRO-MECHANICAL SURGICAL CUTTING AND FASTENING INSTRUMENT HAVING A ROTARY FIRING AND CLOSURE SYSTEM WITH PARALLEL CLOSURE AND ANVIL ALIGNMENT COMPONENTS; U.S. patent application Ser. No. 11/344,021, now U.S. Pat. No. 7,464,849; 
     DISPOSABLE STAPLE CARTRIDGE HAVING AN ANVIL WITH TISSUE LOCATOR FOR USE WITH A SURGICAL CUTTING AND FASTENING INSTRUMENT AND MODULAR END EFFECTOR SYSTEM THEREFOR; U.S. patent application Ser. No. 11/343,546, now U.S. Patent Application Publication No. 2007/0175950; and 
     SURGICAL INSTRUMENT HAVING A FEEDBACK SYSTEM; U.S. patent application Ser. No. 11/343,545, now U.S. Pat. No. 8,708,213. 
    
    
     BACKGROUND 
     The present invention generally concerns surgical cutting and fastening instruments and, more particularly, motor-driven surgical cutting and fastening instruments. 
    
    
     
       DRAWINGS 
       Various embodiments of the present invention are described herein by way of example in conjunction with the following figures, wherein 
         FIGS.  1  and  2    are perspective views of a surgical cutting and fastening instrument according to various embodiments of the present invention; 
         FIGS.  3 - 5    are exploded views of an end effector and shaft of the instrument according to various embodiments of the present invention; 
         FIG.  6    is a side view of the end effector according to various embodiments of the present invention; 
         FIG.  7    is an exploded view of the handle of the instrument according to various embodiments of the present invention; 
         FIGS.  8  and  9    are partial perspective views of the handle according to various embodiments of the present invention; 
         FIG.  10    is a side view of the handle according to various embodiments of the present invention; 
         FIG.  11    is a schematic diagram of a circuit used in the instrument according to various embodiments of the present invention; 
         FIGS.  12 - 13    are side views of the handle according to other embodiments of the present invention; 
         FIGS.  14 - 22    illustrate different mechanisms for locking the closure trigger according to various embodiments of the present invention; 
         FIGS.  23 A-B  show a universal joint (“u-joint”) that may be employed at the articulation point of the instrument according to various embodiments of the present invention; 
         FIGS.  24 A-B  shows a torsion cable that may be employed at the articulation point of the instrument according to various embodiments of the present invention; 
         FIGS.  25 - 31    illustrate a surgical cutting and fastening instrument with power assist according to another embodiment of the present invention; 
         FIGS.  32 - 36    illustrate a surgical cutting and fastening instrument with power assist according to yet another embodiment of the present invention; 
         FIGS.  37 - 40    illustrate a surgical cutting and fastening instrument with tactile feedback to embodiments of the present invention; 
         FIGS.  41 - 42    illustrate a proportional sensor that may be used according to various embodiments of the present invention; 
         FIG.  43    is a perspective view of a surgical cutting and fastening instrument that can employ various end effector embodiments and staple cartridge embodiments of the present invention; 
         FIG.  44    is a perspective view of an end effector embodiment of the present invention in a closed position; 
         FIG.  45    is a perspective view of the end effector of  FIG.  44    in an open position; 
         FIG.  46    is an exploded assembly view of an end effector embodiment of the present invention; 
         FIG.  47    is a cross sectional view of an end effector embodiment of the present invention supporting a staple cartridge therein with some of the components thereof omitted for clarity; 
         FIG.  48    is a partial top view of a staple cartridge that may be employed in connection with various embodiments of the present invention; 
         FIG.  49    is a partial cross-sectional view of a staple cartridge and end effector embodiment of the present invention illustrating the firing of staples into tissue clamped in the end effector; 
         FIG.  50    is a bottom perspective view of a portion of an end effector embodiment of the present invention supporting a staple cartridge therein; 
         FIG.  51    is a partial perspective view of an end effector embodiment of the present invention supporting a staple cartridge therein; 
         FIG.  52    is a perspective view of a distal drive shaft portion of various embodiments of the present invention; 
         FIG.  53    is a cross-sectional view of the distal drive shaft portion of  FIG.  52   ; 
         FIG.  54    is a cross-sectional view of the distal drive shaft portion and closure nut with the closure nut in an open position; 
         FIG.  55    is another cross-sectional view of the distal drive shaft portion and closure nut with the closure nut in the closed position; 
         FIG.  56    is a perspective view of a tapered clutch member of various embodiments of the present invention; 
         FIG.  57    is a cross-sectional view of the tapered clutch member of  FIG.  56   ; 
         FIG.  58    is a perspective view of a clutch plate of various embodiments of the present invention; 
         FIG.  59    is a cross-sectional view of the clutch plate of  FIG.  58   ; 
         FIG.  60    is a perspective view of a closure nut of various embodiments of the present invention; 
         FIG.  61    is a cross-sectional view of the closure nut of  FIG.  60   ; 
         FIG.  62    is a side elevational view of various end effector embodiments of the present invention in an open position; 
         FIG.  63    is an enlarged partial cut away view of the end effector of  FIG.  62   ; 
         FIG.  64    is another enlarged partial cutaway view of the end effector of  FIG.  62   ; 
         FIG.  65    is a side elevational view of an end effector of the present invention in an open position clamping a piece of tissue therein; 
         FIG.  66    is an enlarged partial cut away view of the end effector of  FIG.  65   ; 
         FIG.  67    is a side elevational view of various end effector embodiments of the present invention prior to being actuated to a closed position; 
         FIG.  68    is an enlarged partial cut away view of the end effector of  FIG.  67   ; 
         FIG.  69    is a side elevational view of various end effector embodiments of the present invention in a closed position; 
         FIG.  70    is an enlarged partial cut away view of the end effector of  FIG.  69   ; 
         FIG.  71    is another enlarged partial cut away view of the end effector of  FIGS.  69  and  70   ; 
         FIG.  72    is a cross-sectional view of the end effector of  FIGS.  69 - 71    after the knife assembly has been driven to its distal-most position; 
         FIG.  73    is a cross-sectional view of the end effector of  FIGS.  69 - 71   ; 
         FIG.  74    is a partial enlarged view of a portion of an end effector of the present invention; 
         FIG.  75    is a cross-sectional view of a control handle of various embodiments of the present invention; 
         FIG.  76    is a partial cross-sectional view of a portion of another end effector embodiment of the present invention in an open position; and 
         FIG.  77    is a partial cross-sectional view of the end effector of  FIG.  76    in a closed position. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS.  1  and  2    depict a surgical cutting and fastening instrument  10  according to various embodiments of the present invention. The illustrated embodiment is an endoscopic instrument and, in general, the embodiments of the instrument  10  described herein are endoscopic surgical cutting and fastening instruments. It should be noted, however, that according to other embodiments of the present invention, the instrument may be a non-endoscopic surgical cutting and fastening instrument, such as a laparoscopic instrument. 
     The surgical instrument  10  depicted in  FIGS.  1  and  2    comprises a handle  6 , a shaft  8 , and an articulating end effector  12  pivotally connected to the shaft  8  at an articulation pivot  14 . An articulation control  16  may be provided adjacent to the handle  6  to effect rotation of the end effector  12  about the articulation pivot  14 . In the illustrated embodiment, the end effector  12  is configured to act as an endocutter for clamping, severing and stapling tissue, although, in other embodiments, different types of end effectors may be used, such as end effectors for other types of surgical devices, such as graspers, cutters, staplers, clip appliers, access devices, drug/gene therapy devices, ultrasound, RF or laser devices, etc. 
     The handle  6  of the instrument  10  may include a closure trigger  18  and a firing trigger  20  for actuating the end effector  12 . It will be appreciated that instruments having end effectors directed to different surgical tasks may have different numbers or types of triggers or other suitable controls for operating the end effector  12 . The end effector  12  is shown separated from the handle  6  by a preferably elongate shaft  8 . In one embodiment, a clinician or operator of the instrument  10  may articulate the end effector  12  relative to the shaft  8  by utilizing the articulation control  16 , as described in more detail in U.S. patent application Ser. No. 11/329,020, filed Jan. 10, 2006, entitled SURGICAL INSTRUMENT HAVING AN ARTICULATING END EFFECTOR, now U.S. Pat. No. 7,670,334, which is incorporated herein by reference. 
     The end effector  12  includes in this example, among other things, a staple channel  22  and a pivotally translatable clamping member, such as an anvil  24 , which are maintained at a spacing that assures effective stapling and severing of tissue clamped in the end effector  12 . The handle  6  includes a pistol grip  26  towards which a closure trigger  18  is pivotally drawn by the clinician to cause clamping or closing of the anvil  24  toward the staple channel  22  of the end effector  12  to thereby clamp tissue positioned between the anvil  24  and channel  22 . The firing trigger  20  is farther outboard of the closure trigger  18 . Once the closure trigger  18  is locked in the closure position as further described below, the firing trigger  20  may rotate slightly toward the pistol grip  26  so that it can be reached by the operator using one hand. Then the operator may pivotally draw the firing trigger  20  toward the pistol grip  12  to cause the stapling and severing of clamped tissue in the end effector  12 . In other embodiments, different types of clamping members besides the anvil  24  could be used, such as, for example, an opposing jaw, etc. 
     It will be appreciated that the terms “proximal” and “distal” are used herein with reference to a clinician gripping the handle  6  of an instrument  10 . Thus, the end effector  12  is distal with respect to the more proximal handle  6 . 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 closure trigger  18  may be actuated first. Once the clinician is satisfied with the positioning of the end effector  12 , the clinician may draw back the closure trigger  18  to its fully closed, locked position proximate to the pistol grip  26 . The firing trigger  20  may then be actuated. The firing trigger  20  returns to the open position (shown in  FIGS.  1  and  2   ) when the clinician removes pressure, as described more fully below. A release button on the handle  6 , when depressed may release the locked closure trigger  18 . The release button may be implemented in various forms such as, for example, as a slide release button  160  shown in  FIG.  14   , and/or button  172  shown in  FIG.  16   . 
       FIG.  3    is an exploded view of the end effector  12  according to various embodiments. As shown in the illustrated embodiment, the end effector  12  may include, in addition to the previously-mentioned channel  22  and anvil  24 , a cutting instrument  32 , a sled  33 , a staple cartridge  34  that is removably seated in the channel  22 , and a helical screw shaft  36 . The cutting instrument  32  may be, for example, a knife. The anvil  24  may be pivotably opened and closed at a pivot point  25  connected to the proximate end of the channel  22 . The anvil  24  may also include a tab  27  at its proximate end that is inserted into a component of the mechanical closure system (described further below) to open and close the anvil  24 . When the closure trigger  18  is actuated, that is, drawn in by a user of the instrument  10 , the anvil  24  may pivot about the pivot point  25  into the clamped or closed position. If clamping of the end effector  12  is satisfactory, the operator may actuate the firing trigger  20 , which, as explained in more detail below, causes the knife  32  and sled  33  to travel longitudinally along the channel  22 , thereby cutting tissue clamped within the end effector  12 . The movement of the sled  33  along the channel  22  causes the staples of the staple cartridge  34  to be driven through the severed tissue and against the closed anvil  24 , which turns the staples to fasten the severed tissue. In various embodiments, the sled  33  may be an integral component of the cartridge  34 . U.S. Pat. No. 6,978,921, entitled SURGICAL STAPLING INSTRUMENT INCORPORATING AN E-BEAM FIRING MECHANISM, which is incorporated herein by reference, provides more details about such two-stroke cutting and fastening instruments. The sled  33  may be part of the cartridge  34 , such that when the knife  32  retracts following the cutting operation, the sled  33  does not retract. 
     It should be noted that although the embodiments of the instrument  10  described herein employ an end effector  12  that staples the severed tissue, in other embodiments different techniques for fastening or sealing the severed tissue may be used. For example, end effectors that use RF energy or adhesives to fasten the severed tissue may also be used. U.S. Pat. No. 5,709,680 entitled ELECTROSURGICAL HEMOSTATIC DEVICE, and U.S. Pat. No. 5,688,270 entitled ELECTROSURGICAL HEMOSTATIC DEVICE WITH RECESSED AND/OR OFFSET ELECTRODES, which are incorporated herein by reference, disclose an endoscopic cutting instrument that uses RF energy to seal the severed tissue. U.S. patent application Ser. No. 11/267,811, now U.S. Pat. No. 7,673,783, and U.S. patent application Ser. No. 11/267,383, now U.S. Pat. No. 7,607,557, which are also incorporated herein by reference, disclose an endoscopic cutting instrument that uses adhesives to fasten the severed tissue. Accordingly, although the description herein refers to cutting/stapling operations and the like below, it should be recognized that this is an exemplary embodiment and is not meant to be limiting. Other tissue-fastening techniques may also be used. 
       FIGS.  4  and  5    are exploded views and  FIG.  6    is a side view of the end effector  12  and shaft  8  according to various embodiments. As shown in the illustrated embodiment, the shaft  8  may include a proximate closure tube  40  and a distal closure tube  42  pivotably linked by a pivot links  44 . The distal closure tube  42  includes an opening  45  into which the tab  27  on the anvil  24  is inserted in order to open and close the anvil  24 , as further described below. Disposed inside the closure tubes  40 ,  42  may be a proximate spine tube  46 . Disposed inside the proximate spine tube  46  may be a main rotational (or proximate) drive shaft  48  that communicates with a secondary (or distal) drive shaft  50  via a bevel gear assembly  52 . The secondary drive shaft  50  is connected to a drive gear  54  that engages a proximate drive gear  56  of the helical screw shaft  36 . The vertical bevel gear  52   b  may sit and pivot in an opening  57  in the distal end of the proximate spine tube  46 . A distal spine tube  58  may be used to enclose the secondary drive shaft  50  and the drive gears  54 ,  56 . Collectively, the main drive shaft  48 , the secondary drive shaft  50 , and the articulation assembly (e.g., the bevel gear assembly  52   a - c ) are sometimes referred to herein as the “main drive shaft assembly.” 
     A bearing  38 , positioned at a distal end of the staple channel  22 , receives the helical drive screw  36 , allowing the helical drive screw  36  to freely rotate with respect to the channel  22 . The helical screw shaft  36  may interface a threaded opening (not shown) of the knife  32  such that rotation of the shaft  36  causes the knife  32  to translate distally or proximately (depending on the direction of the rotation) through the staple channel  22 . Accordingly, when the main drive shaft  48  is caused to rotate by actuation of the firing trigger  20  (as explained in more detail below), the bevel gear assembly  52   a - c  causes the secondary drive shaft  50  to rotate, which in turn, because of the engagement of the drive gears  54 ,  56 , causes the helical screw shaft  36  to rotate, which causes the knife driving member  32  to travel longitudinally along the channel  22  to cut any tissue clamped within the end effector. The sled  33  may be made of, for example, plastic, and may have a sloped distal surface. As the sled  33  traverse the channel  22 , the sloped forward surface may push up or drive the staples in the staple cartridge through the clamped tissue and against the anvil  24 . The anvil  24  turns the staples, thereby stapling the severed tissue. When the knife  32  is retracted, the knife  32  and sled  33  may become disengaged, thereby leaving the sled  33  at the distal end of the channel  22 . 
     As described above, because of the lack of user feedback for the cutting/stapling operation, there is a general lack of acceptance among physicians of motor-driven endocutters where the cutting/stapling operation is actuated by merely pressing a button. In contrast, embodiments of the present invention provide a motor-driven endocutter with user-feedback of the deployment, force, and/or position of the cutting instrument in the end effector. 
       FIGS.  7 - 10    illustrate an exemplary embodiment of a motor-driven endocutter, and in particular the handle thereof, that provides user-feedback regarding the deployment and loading force of the cutting instrument in the end effector. In addition, the embodiment may use power provided by the user in retracting the firing trigger  20  to power the device (a so-called “power assist” mode). As shown in the illustrated embodiment, the handle  6  includes exterior lower side pieces  59 ,  60  and exterior upper side pieces  61 ,  62  that fit together to form, in general, the exterior of the handle  6 . A battery  64 , such as a Li ion battery, may be provided in the pistol grip portion  26  of the handle  6 . The battery  64  powers a motor  65  disposed in an upper portion of the pistol grip portion  26  of the handle  6 . According to various embodiments, the motor  65  may be a DC brushed driving motor having a maximum rotation of, approximately, 5000 RPM. The motor  64  may drive a 90° bevel gear assembly  66  comprising a first bevel gear  68  and a second bevel gear  70 . The bevel gear assembly  66  may drive a planetary gear assembly  72 . The planetary gear assembly  72  may include a pinion gear  74  connected to a drive shaft  76 . The pinion gear  74  may drive a mating ring gear  78  that drives a helical gear drum  80  via a drive shaft  82 . A ring  84  may be threaded on the helical gear drum  80 . Thus, when the motor  65  rotates, the ring  84  is caused to travel along the helical gear drum  80  by means of the interposed bevel gear assembly  66 , planetary gear assembly  72  and ring gear  78 . 
     The handle  6  may also include a run motor sensor  110  in communication with the firing trigger  20  to detect when the firing trigger  20  has been drawn in (or “closed”) toward the pistol grip portion  26  of the handle  6  by the operator to thereby actuate the cutting/stapling operation by the end effector  12 . The sensor  110  may be a proportional sensor such as, for example, a rheostat or variable resistor. When the firing trigger  20  is drawn in, the sensor  110  detects the movement, and sends an electrical signal indicative of the voltage (or power) to be supplied to the motor  65 . When the sensor  110  is a variable resistor or the like, the rotation of the motor  65  may be generally proportional to the amount of movement of the firing trigger  20 . That is, if the operator only draws or closes the firing trigger  20  in a little bit, the rotation of the motor  65  is relatively low. When the firing trigger  20  is fully drawn in (or in the fully closed position), the rotation of the motor  65  is at its maximum. In other words, the harder the user pulls on the firing trigger  20 , the more voltage is applied to the motor  65 , causing greater rates of rotation. 
     The handle  6  may include a middle handle piece  104  adjacent to the upper portion of the firing trigger  20 . The handle  6  also may comprise a bias spring  112  connected between posts on the middle handle piece  104  and the firing trigger  20 . The bias spring  112  may bias the firing trigger  20  to its fully open position. In that way, when the operator releases the firing trigger  20 , the bias spring  112  will pull the firing trigger  20  to its open position, thereby removing actuation of the sensor  110 , thereby stopping rotation of the motor  65 . Moreover, by virtue of the bias spring  112 , any time a user closes the firing trigger  20 , the user will experience resistance to the closing operation, thereby providing the user with feedback as to the amount of rotation exerted by the motor  65 . Further, the operator could stop retracting the firing trigger  20  to thereby remove force from the sensor  100 , to thereby stop the motor  65 . As such, the user may stop the deployment of the end effector  12 , thereby providing a measure of control of the cutting/fastening operation to the operator. 
     The distal end of the helical gear drum  80  includes a distal drive shaft  120  that drives a ring gear  122 , which mates with a pinion gear  124 . The pinion gear  124  is connected to the main drive shaft  48  of the main drive shaft assembly. In that way, rotation of the motor  65  causes the main drive shaft assembly to rotate, which causes actuation of the end effector  12 , as described above. 
     The ring  84  threaded on the helical gear drum  80  may include a post  86  that is disposed within a slot  88  of a slotted arm  90 . The slotted arm  90  has an opening  92  its opposite end  94  that receives a pivot pin  96  that is connected between the handle exterior side pieces  59 ,  60 . The pivot pin  96  is also disposed through an opening  100  in the firing trigger  20  and an opening  102  in the middle handle piece  104 . 
     In addition, the handle  6  may include a reverse motor (or end-of-stroke sensor)  130  and a stop motor (or beginning-of-stroke) sensor  142 . In various embodiments, the reverse motor sensor  130  may be a limit switch located at the distal end of the helical gear drum  80  such that the ring  84  threaded on the helical gear drum  80  contacts and trips the reverse motor sensor  130  when the ring  84  reaches the distal end of the helical gear drum  80 . The reverse motor sensor  130 , when activated, sends a signal to the motor  65  to reverse its rotation direction, thereby withdrawing the knife  32  of the end effector  12  following the cutting operation. 
     The stop motor sensor  142  may be, for example, a normally-closed limit switch. In various embodiments, it may be located at the proximate end of the helical gear drum  80  so that the ring  84  trips the switch  142  when the ring  84  reaches the proximate end of the helical gear drum  80 . 
     In operation, when an operator of the instrument  10  pulls back the firing trigger  20 , the sensor  110  detects the deployment of the firing trigger  20  and sends a signal to the motor  65  to cause forward rotation of the motor  65  at, for example, a rate proportional to how hard the operator pulls back the firing trigger  20 . The forward rotation of the motor  65  in turn causes the ring gear  78  at the distal end of the planetary gear assembly  72  to rotate, thereby causing the helical gear drum  80  to rotate, causing the ring  84  threaded on the helical gear drum  80  to travel distally along the helical gear drum  80 . The rotation of the helical gear drum  80  also drives the main drive shaft assembly as described above, which in turn causes deployment of the knife  32  in the end effector  12 . That is, the knife  32  and sled  33  are caused to traverse the channel  22  longitudinally, thereby cutting tissue clamped in the end effector  12 . Also, the stapling operation of the end effector  12  is caused to happen in embodiments where a stapling-type end effector is used. 
     By the time the cutting/stapling operation of the end effector  12  is complete, the ring  84  on the helical gear drum  80  will have reached the distal end of the helical gear drum  80 , thereby causing the reverse motor sensor  130  to be tripped, which sends a signal to the motor  65  to cause the motor  65  to reverse its rotation. This in turn causes the knife  32  to retract, and also causes the ring  84  on the helical gear drum  80  to move back to the proximate end of the helical gear drum  80 . 
     The middle handle piece  104  includes a backside shoulder  106  that engages the slotted arm  90  as best shown in  FIGS.  8  and  9   . The middle handle piece  104  also has a forward motion stop  107  that engages the firing trigger  20 . The movement of the slotted arm  90  is controlled, as explained above, by rotation of the motor  65 . When the slotted arm  90  rotates CCW as the ring  84  travels from the proximate end of the helical gear drum  80  to the distal end, the middle handle piece  104  will be free to rotate CCW. Thus, as the user draws in the firing trigger  20 , the firing trigger  20  will engage the forward motion stop  107  of the middle handle piece  104 , causing the middle handle piece  104  to rotate CCW. Due to the backside shoulder  106  engaging the slotted arm  90 , however, the middle handle piece  104  will only be able to rotate CCW as far as the slotted arm  90  permits. In that way, if the motor  65  should stop rotating for some reason, the slotted arm  90  will stop rotating, and the user will not be able to further draw in the firing trigger  20  because the middle handle piece  104  will not be free to rotate CCW due to the slotted arm  90 . 
       FIGS.  41  and  42    illustrate two states of a variable sensor that may be used as the run motor sensor  110  according to various embodiments of the present invention. The sensor  110  may include a face portion  280 , a first electrode (A)  282 , a second electrode (B)  284 , and a compressible dielectric material  286  (e.g., EAP) between the electrodes  282 ,  284 . The sensor  110  may be positioned such that the face portion  280  contacts the firing trigger  20  when retracted. Accordingly, when the firing trigger  20  is retracted, the dielectric material  286  is compressed, as shown in  FIG.  42   , such that the electrodes  282 ,  284  are closer together. Since the distance “b” between the electrodes  282 ,  284  is directly related to the impedance between the electrodes  282 ,  284 , the greater the distance the more impedance, and the closer the distance the less impedance. In that way, the amount that the dielectric  286  is compressed due to retraction of the firing trigger  20  (denoted as force “F” in  FIG.  42   ) is proportional to the impedance between the electrodes  282 ,  284 , which can be used to proportionally control the motor  65 . 
     Components of an exemplary closure system for closing (or clamping) the anvil  24  of the end effector  12  by retracting the closure trigger  18  are also shown in  FIGS.  7 - 10   . In the illustrated embodiment, the closure system includes a yoke  250  connected to the closure trigger  18  by a pin  251  that is inserted through aligned openings in both the closure trigger  18  and the yoke  250 . A pivot pin  252 , about which the closure trigger  18  pivots, is inserted through another opening in the closure trigger  18  which is offset from where the pin  251  is inserted through the closure trigger  18 . Thus, retraction of the closure trigger  18  causes the upper part of the closure trigger  18 , to which the yoke  250  is attached via the pin  251 , to rotate CCW. The distal end of the yoke  250  is connected, via a pin  254 , to a first closure bracket  256 . The first closure bracket  256  connects to a second closure bracket  258 . Collectively, the closure brackets  256 ,  258  define an opening in which the proximate end of the proximate closure tube  40  (see  FIG.  4   ) is seated and held such that longitudinal movement of the closure brackets  256 ,  258  causes longitudinal motion by the proximate closure tube  40 . The instrument  10  also includes a closure rod  260  disposed inside the proximate closure tube  40 . The closure rod  260  may include a window  261  into which a post  263  on one of the handle exterior pieces, such as exterior lower side piece  59  in the illustrated embodiment, is disposed to fixedly connect the closure rod  260  to the handle  6 . In that way, the proximate closure tube  40  is capable of moving longitudinally relative to the closure rod  260 . The closure rod  260  may also include a distal collar  267  that fits into a cavity  269  in proximate spine tube  46  and is retained therein by a cap  271  (see  FIG.  4   ). 
     In operation, when the yoke  250  rotates due to retraction of the closure trigger  18 , the closure brackets  256 ,  258  cause the proximate closure tube  40  to move distally (i.e., away from the handle end of the instrument  10 ), which causes the distal closure tube  42  to move distally, which causes the anvil  24  to rotate about the pivot point  25  into the clamped or closed position. When the closure trigger  18  is unlocked from the locked position, the proximate closure tube  40  is caused to slide proximately, which causes the distal closure tube  42  to slide proximately, which, by virtue of the tab  27  being inserted in the window  45  of the distal closure tube  42 , causes the anvil  24  to pivot about the pivot point  25  into the open or unclamped position. In that way, by retracting and locking the closure trigger  18 , an operator may clamp tissue between the anvil  24  and channel  22 , and may unclamp the tissue following the cutting/stapling operation by unlocking the closure trigger  20  from the locked position. 
       FIG.  11    is a schematic diagram of an electrical circuit of the instrument  10  according to various embodiments of the present invention. When an operator initially pulls in the firing trigger  20  after locking the closure trigger  18 , the sensor  110  is activated, allowing current to flow there through. If the normally-open reverse motor sensor switch  130  is open (meaning the end of the end effector stroke has not been reached), current will flow to a single pole, double throw relay  132 . Since the reverse motor sensor switch  130  is not closed, the inductor  134  of the relay  132  will not be energized, so the relay  132  will be in its non-energized state. The circuit also includes a cartridge lockout sensor  136 . If the end effector  12  includes a staple cartridge  34 , the sensor  136  will be in the closed state, allowing current to flow. Otherwise, if the end effector  12  does not include a staple cartridge  34 , the sensor  136  will be open, thereby preventing the battery  64  from powering the motor  65 . 
     When the staple cartridge  34  is present, the sensor  136  is closed, which energizes a single pole, single throw relay  138 . When the relay  138  is energized, current flows through the relay  136 , through the variable resistor sensor  110 , and to the motor  65  via a double pole, double throw relay  140 , thereby powering the motor  65  and allowing it to rotate in the forward direction. 
     When the end effector  12  reaches the end of its stroke, the reverse motor sensor  130  will be activated, thereby closing the switch  130  and energizing the relay  134 . This causes the relay  134  to assume its energized state (not shown in  FIG.  13   ), which causes current to bypass the cartridge lockout sensor  136  and variable resistor  110 , and instead causes current to flow to both the normally-closed double pole, double throw relay  142  and back to the motor  65 , but in a manner, via the relay  140 , that causes the motor  65  to reverse its rotational direction. 
     Because the stop motor sensor switch  142  is normally-closed, current will flow back to the relay  134  to keep it closed until the switch  142  opens. When the knife  32  is fully retracted, the stop motor sensor switch  142  is activated, causing the switch  142  to open, thereby removing power from the motor  65 . 
     In other embodiments, rather than a proportional-type sensor  110 , an on-off type sensor could be used. In such embodiments, the rate of rotation of the motor  65  would not be proportional to the force applied by the operator. Rather, the motor  65  would generally rotate at a constant rate. But the operator would still experience force feedback because the firing trigger  20  is geared into the gear drive train. 
       FIG.  12    is a side-view of the handle  6  of a power-assist motorized endocutter according to another embodiment. The embodiment of  FIG.  12    is similar to that of  FIGS.  7 - 10    except that in the embodiment of  FIG.  12   , there is not slotted arm connected to the ring  84  threaded on the helical gear drum  80 . Instead, in the embodiment of  FIG.  12   , the ring  84  includes a sensor portion  114  that moves with the ring  84  as the ring  84  advances down (and back) on the helical gear drum  80 . The sensor portion  114  includes a notch  116 . The reverse motor sensor  130  may be located at the distal end of the notch  116  and the stop motor sensor  142  may be located at the proximate end of the notch  116 . As the ring  84  moves down the helical gear drum  80  (and back), the sensor portion  114  moves with it. Further, as shown in  FIG.  12   , the middle piece  104  may have an arm  118  that extends into the notch  12 . 
     In operation, as an operator of the instrument  10  retracts in the firing trigger  20  toward the pistol grip  26 , the run motor sensor  110  detects the motion and sends a signal to power the motor  65 , which causes, among other things, the helical gear drum  80  to rotate. As the helical gear drum  80  rotates, the ring  84  threaded on the helical gear drum  80  advances (or retracts, depending on the rotation). Also, due to the pulling in of the firing trigger  20 , the middle piece  104  is caused to rotate CCW with the firing trigger  20  due to the forward motion stop  107  that engages the firing trigger  20 . The CCW rotation of the middle piece  104  cause the arm  118  to rotate CCW with the sensor portion  114  of the ring  84  such that the arm  118  stays disposed in the notch  116 . When the ring  84  reaches the distal end of the helical gear drum  80 , the arm  118  will contact and thereby trip the reverse motor sensor  130 . Similarly, when the ring  84  reaches the proximate end of the helical gear drum  80 , the arm will contact and thereby trip the stop motor sensor  142 . Such actions may reverse and stop the motor  65 , respectively, as described above. 
       FIG.  13    is a side-view of the handle  6  of a power-assist motorized endocutter according to another embodiment. The embodiment of  FIG.  13    is similar to that of  FIGS.  7 - 10    except that in the embodiment of  FIG.  13   , there is no slot in the arm  90 . Instead, the ring  84  threaded on the helical gear drum  80  includes a vertical channel  126 . Instead of a slot, the arm  90  includes a post  128  that is disposed in the channel  126 . As the helical gear drum  80  rotates, the ring  84  threaded on the helical gear drum  80  advances (or retracts, depending on the rotation). The arm  90  rotates CCW as the ring  84  advances due to the post  128  being disposed in the channel  126 , as shown in  FIG.  13   . 
     As mentioned above, in using a two-stroke motorized instrument, the operator first pulls back and locks the closure trigger  18 .  FIGS.  14  and  15    show one embodiment of a way to lock the closure trigger  18  to the pistol grip portion  26  of the handle  6 . In the illustrated embodiment, the pistol grip portion  26  includes a hook  150  that is biased to rotate CCW about a pivot point  151  by a torsion spring  152 . Also, the closure trigger  18  includes a closure bar  154 . As the operator draws in the closure trigger  18 , the closure bar  154  engages a sloped portion  156  of the hook  150 , thereby rotating the hook  150  upward (or CW in  FIGS.  12 - 13   ) until the closure bar  154  completely passes the sloped portion  156  passes into a recessed notch  158  of the hook  150 , which locks the closure trigger  18  in place. The operator may release the closure trigger  18  by pushing down on a slide button release  160  on the back or opposite side of the pistol grip portion  26 . Pushing down the slide button release  160  rotates the hook  150  CW such that the closure bar  154  is released from the recessed notch  158 . 
       FIG.  16    shows another closure trigger locking mechanism according to various embodiments. In the embodiment of  FIG.  16   , the closure trigger  18  includes a wedge  160  having an arrow-head portion  161 . The arrow-head portion  161  is biased downward (or CW) by a leaf spring  162 . The wedge  160  and leaf spring  162  may be made from, for example, molded plastic. When the closure trigger  18  is retracted, the arrow-head portion  161  is inserted through an opening  164  in the pistol grip portion  26  of the handle  6 . A lower chamfered surface  166  of the arrow-head portion  161  engages a lower sidewall  168  of the opening  164 , forcing the arrow-head portion  161  to rotate CCW. Eventually the lower chamfered surface  166  fully passes the lower sidewall  168 , removing the CCW force on the arrow-head portion  161 , causing the lower sidewall  168  to slip into a locked position in a notch  170  behind the arrow-head portion  161 . 
     To unlock the closure trigger  18 , a user presses down on a button  172  on the opposite side of the closure trigger  18 , causing the arrow-head portion  161  to rotate CCW and allowing the arrow-head portion  161  to slide out of the opening  164 . 
       FIGS.  17 - 22    show a closure trigger locking mechanism according to another embodiment. As shown in this embodiment, the closure trigger  18  includes a flexible longitudinal arm  176  that includes a lateral pin  178  extending therefrom. The arm  176  and pin  178  may be made from molded plastic, for example. The pistol grip portion  26  of the handle  6  includes an opening  180  with a laterally extending wedge  182  disposed therein. When the closure trigger  18  is retracted, the pin  178  engages the wedge  182 , and the pin  178  is forced downward (i.e., the arm  176  is rotated CW) by the lower surface  184  of the wedge  182 , as shown in  FIGS.  17  and  18   . When the pin  178  fully passes the lower surface  184 , the CW force on the arm  176  is removed, and the pin  178  is rotated CCW such that the pin  178  comes to rest in a notch  186  behind the wedge  182 , as shown in  FIG.  19   , thereby locking the closure trigger  18 . The pin  178  is further held in place in the locked position by a flexible stop  188  extending from the wedge  184 . 
     To unlock the closure trigger  18 , the operator may further squeeze the closure trigger  18 , causing the pin  178  to engage a sloped backwall  190  of the opening  180 , forcing the pin  178  upward past the flexible stop  188 , as shown in  FIGS.  20  and  21   . The pin  178  is then free to travel out an upper channel  192  in the opening  180  such that the closure trigger  18  is no longer locked to the pistol grip portion  26 , as shown in  FIG.  22   . 
       FIGS.  23 A-B  show a universal joint (“u-joint”)  195 . The second piece  195 - 2  of the u-joint  195  rotates in a horizontal plane in which the first piece  195 - 1  lies.  FIG.  23 A  shows the u-joint  195  in a linear (180°) orientation and  FIG.  23 B  shows the u-joint  195  at approximately a 150° orientation. The u-joint  195  may be used instead of the bevel gears  52   a - c  (see  FIG.  4   , for example) at the articulation point  14  of the main drive shaft assembly to articulate the end effector  12 .  FIGS.  24 A-B  show a torsion cable  197  that may be used in lieu of both the bevel gears  52   a - c  and the u-joint  195  to realize articulation of the end effector  12 . 
       FIGS.  25 - 31    illustrate another embodiment of a motorized, two-stroke surgical cutting and fastening instrument  10  with power assist according to another embodiment of the present invention. The embodiment of  FIGS.  25 - 31    is similar to that of  FIGS.  6 - 10    except that instead of the helical gear drum  80 , the embodiment of  FIGS.  23 - 28    includes an alternative gear drive assembly. The embodiment of  FIGS.  25 - 31    includes a gear box assembly  200  including a number of gears disposed in a frame  201 , wherein the gears are connected between the planetary gear  72  and the pinion gear  124  at the proximate end of the drive shaft  48 . As explained further below, the gear box assembly  200  provides feedback to the user via the firing trigger  20  regarding the deployment and loading force of the end effector  12 . Also, the user may provide power to the system via the gear box assembly  200  to assist the deployment of the end effector  12 . In that sense, like the embodiments described above, the embodiment of  FIGS.  23 - 32    is another power assist, motorized instrument  10  that provides feedback to the user regarding the loading force experienced by the cutting instrument. 
     In the illustrated embodiment, the firing trigger  20  includes two pieces: a main body portion  202  and a stiffening portion  204 . The main body portion  202  may be made of plastic, for example, and the stiffening portion  204  may be made out of a more rigid material, such as metal. In the illustrated embodiment, the stiffening portion  204  is adjacent to the main body portion  202 , but according to other embodiments, the stiffening portion  204  could be disposed inside the main body portion  202 . A pivot pin  209  may be inserted through openings in the firing trigger pieces  202 ,  204  and may be the point about which the firing trigger  20  rotates. In addition, a spring  222  may bias the firing trigger  20  to rotate in a CCW direction. The spring  222  may have a distal end connected to a pin  224  that is connected to the pieces  202 ,  204  of the firing trigger  20 . The proximate end of the spring  222  may be connected to one of the handle exterior lower side pieces  59 ,  60 . 
     In the illustrated embodiment, both the main body portion  202  and the stiffening portion  204  includes gear portions  206 ,  208  (respectively) at their upper end portions. The gear portions  206 ,  208  engage a gear in the gear box assembly  200 , as explained below, to drive the main drive shaft assembly and to provide feedback to the user regarding the deployment of the end effector  12 . 
     The gear box assembly  200  may include as shown, in the illustrated embodiment, six (6) gears. A first gear  210  of the gear box assembly  200  engages the gear portions  206 ,  208  of the firing trigger  20 . In addition, the first gear  210  engages a smaller second gear  212 , the smaller second gear  212  being coaxial with a large third gear  214 . The third gear  214  engages a smaller fourth gear  216 , the smaller fourth gear being coaxial with a fifth gear  218 . The fifth gear  218  is a 90° bevel gear that engages a mating 90° bevel gear  220  (best shown in  FIG.  31   ) that is connected to the pinion gear  124  that drives the main drive shaft  48 . 
     In operation, when the user retracts the firing trigger  20 , a run motor sensor (not shown) is activated, which may provide a signal to the motor  65  to rotate at a rate proportional to the extent or force with which the operator is retracting the firing trigger  20 . This causes the motor  65  to rotate at a speed proportional to the signal from the sensor. The sensor is not shown for this embodiment, but it could be similar to the run motor sensor  110  described above. The sensor could be located in the handle  6  such that it is depressed when the firing trigger  20  is retracted. Also, instead of a proportional-type sensor, an on/off type sensor may be used. 
     Rotation of the motor  65  causes the bevel gears  66 ,  70  to rotate, which causes the planetary gear  72  to rotate, which causes, via the drive shaft  76 , the ring gear  122  to rotate. The ring gear  122  meshes with the pinion gear  124 , which is connected to the main drive shaft  48 . Thus, rotation of the pinion gear  124  drives the main drive shaft  48 , which causes actuation of the cutting/stapling operation of the end effector  12 . 
     Forward rotation of the pinion gear  124  in turn causes the bevel gear  220  to rotate, which causes, by way of the rest of the gears of the gear box assembly  200 , the first gear  210  to rotate. The first gear  210  engages the gear portions  206 ,  208  of the firing trigger  20 , thereby causing the firing trigger  20  to rotate CCW when the motor  65  provides forward drive for the end effector  12  (and to rotate CCW when the motor  65  rotates in reverse to retract the end effector  12 ). In that way, the user experiences feedback regarding loading force and deployment of the end effector  12  by way of the user&#39;s grip on the firing trigger  20 . Thus, when the user retracts the firing trigger  20 , the operator will experience a resistance related to the load force experienced by the end effector  12 . Similarly, when the operator releases the firing trigger  20  after the cutting/stapling operation so that it can return to its original position, the user will experience a CW rotation force from the firing trigger  20  that is generally proportional to the reverse speed of the motor  65 . 
     It should also be noted that in this embodiment the user can apply force (either in lieu of or in addition to the force from the motor  65 ) to actuate the main drive shaft assembly (and hence the cutting/stapling operation of the end effector  12 ) through retracting the firing trigger  20 . That is, retracting the firing trigger  20  causes the gear portions  206 ,  208  to rotate CCW, which causes the gears of the gear box assembly  200  to rotate, thereby causing the pinion gear  124  to rotate, which causes the main drive shaft  48  to rotate. 
     Although not shown in  FIGS.  25 - 31   , the instrument  10  may further include reverse motor and stop motor sensors. As described above, the reverse motor and stop motor sensors may detect, respectively, the end of the cutting stroke (full deployment of the knife/sled driving member  32 ) and the end of retraction operation (full retraction of the knife/sled driving member  32 ). A similar circuit to that described above in connection with  FIG.  11    may be used to appropriately power the motor  65 . 
       FIGS.  32 - 36    illustrate a two-stroke, motorized surgical cutting and fastening instrument  10  with power assist according to another embodiment. The embodiment of  FIGS.  32 - 36    is similar to that of  FIGS.  25 - 31    except that in the embodiment of  FIGS.  32 - 36   , the firing trigger  20  includes a lower portion  228  and an upper portion  230 . Both portions  228 ,  230  are connected to and pivot about a pivot pin  207  that is disposed through each portion  228 ,  230 . The upper portion  230  includes a gear portion  232  that engages the first gear  210  of the gear box assembly  200 . The spring  222  is connected to the upper portion  230  such that the upper portion is biased to rotate in the CW direction. The upper portion  230  may also include a lower arm  234  that contacts an upper surface of the lower portion  228  of the firing trigger  20  such that when the upper portion  230  is caused to rotate CW the lower portion  228  also rotates CW, and when the lower portion  228  rotates CCW the upper portion  230  also rotates CCW. Similarly, the lower portion  228  includes a rotational stop  238  that engages a lower shoulder of the upper portion  230 . In that way, when the upper portion  230  is caused to rotate CCW the lower portion  228  also rotates CCW, and when the lower portion  228  rotates CW the upper portion  230  also rotates CW. 
     The illustrated embodiment also includes the run motor sensor  110  that communicates a signal to the motor  65  that, in various embodiments, may cause the motor  65  to rotate at a speed proportional to the force applied by the operator when retracting the firing trigger  20 . The sensor  110  may be, for example, a rheostat or some other variable resistance sensor, as explained herein. In addition, the instrument  10  may include a reverse motor sensor  130  that is tripped or switched when contacted by a front face  242  of the upper portion  230  of the firing trigger  20 . When activated, the reverse motor sensor  130  sends a signal to the motor  65  to reverse direction. Also, the instrument  10  may include a stop motor sensor  142  that is tripped or actuated when contacted by the lower portion  228  of the firing trigger  20 . When activated, the stop motor sensor  142  sends a signal to stop the reverse rotation of the motor  65 . 
     In operation, when an operator retracts the closure trigger  18  into the locked position, the firing trigger  20  is retracted slightly (through mechanisms known in the art, including U.S. Pat. Nos. 6,978,921 and 6,905,057, which are incorporated herein by reference) so that the user can grasp the firing trigger  20  to initiate the cutting/stapling operation, as shown in  FIGS.  32  and  33   . At that point, as shown in  FIG.  33   , the gear portion  232  of the upper portion  230  of the firing trigger  20  moves into engagement with the first gear  210  of the gear box assembly  200 . When the operator retracts the firing trigger  20 , according to various embodiments, the firing trigger  20  may rotate a small amount, such as five degrees, before tripping the run motor sensor  110 , as shown in  FIG.  34   . Activation of the sensor  110  causes the motor  65  to forward rotate at a rate proportional to the retraction force applied by the operator. The forward rotation of the motor  65  causes, as described above, the main drive shaft  48  to rotate, which causes the knife  32  in the end effector  12  to be deployed (i.e., begin traversing the channel  22 ). Rotation of the pinion gear  124 , which is connected to the main drive shaft  48 , causes the gears  210 - 220  in the gear box assembly  200  to rotate. Since the first gear  210  is in engagement with the gear portion  232  of the upper portion  230  of the firing trigger  20 , the upper portion  232  is caused to rotate CCW, which causes the lower portion  228  to also rotate CCW. 
     When the knife  32  is fully deployed (i.e., at the end of the cutting stroke), the front face  242  of the upper portion  230  trips the reverse motor sensor  130 , which sends a signal to the motor  65  to reverse rotational directional. This causes the main drive shaft assembly to reverse rotational direction to retract the knife  32 . Reverse rotation of the main drive shaft assembly causes the gears  210 - 220  in the gear box assembly to reverse direction, which causes the upper portion  230  of the firing trigger  20  to rotate CW, which causes the lower portion  228  of the firing trigger  20  to rotate CW until the lower portion  228  trips or actuates the stop motor sensor  142  when the knife  32  is fully retracted, which causes the motor  65  to stop. In that way, the user experiences feedback regarding deployment of the end effector  12  by way of the user&#39;s grip on the firing trigger  20 . Thus, when the user retracts the firing trigger  20 , the operator will experience a resistance related to the deployment of the end effector  12  and, in particular, to the loading force experienced by the knife  32 . Similarly, when the operator releases the firing trigger  20  after the cutting/stapling operation so that it can return to its original position, the user will experience a CW rotation force from the firing trigger  20  that is generally proportional to the reverse speed of the motor  65 . 
     It should also be noted that in this embodiment the user can apply force (either in lieu of or in addition to the force from the motor  65 ) to actuate the main drive shaft assembly (and hence the cutting/stapling operation of the end effector  12 ) through retracting the firing trigger  20 . That is, retracting the firing trigger  20  causes the gear portion  232  of the upper portion  230  to rotate CCW, which causes the gears of the gear box assembly  200  to rotate, thereby causing the pinion gear  124  to rotate, which causes the main drive shaft assembly to rotate. 
     The above-described embodiments employed power-assist user feedback systems, with or without adaptive control (e.g., using a sensor  110 ,  130 , and  142  outside of the closed loop system of the motor, gear drive train, and end effector) for a two-stroke, motorized surgical cutting and fastening instrument. That is, force applied by the user in retracting the firing trigger  20  may be added to the force applied by the motor  65  by virtue of the firing trigger  20  being geared into (either directly or indirectly) the gear drive train between the motor  65  and the main drive shaft  48 . In other embodiments of the present invention, the user may be provided with tactile feedback regarding the position of the knife  32  in the end effector, but without having the firing trigger  20  geared into the gear drive train.  FIGS.  37 - 40    illustrate a motorized surgical cutting and fastening instrument with such a tactile position feedback system. 
     In the illustrated embodiment of  FIGS.  37 - 40   , the firing trigger  20  may have a lower portion  228  and an upper portion  230 , similar to the instrument  10  shown in  FIGS.  32 - 36   . Unlike the embodiment of  FIGS.  32 - 36   , however, the upper portion  230  does not have a gear portion that mates with part of the gear drive train. Instead, the instrument includes a second motor  265  with a threaded rod  266  threaded therein. The threaded rod  266  reciprocates longitudinally in and out of the motor  265  as the motor  265  rotates, depending on the direction of rotation. The instrument  10  also includes an encoder  268  that is responsive to the rotations of the main drive shaft  48  for translating the incremental angular motion of the main drive shaft  48  (or other component of the main drive assembly) into a corresponding series of digital signals, for example. In the illustrated embodiment, the pinion gear  124  includes a proximate drive shaft  270  that connects to the encoder  268 . 
     The instrument  10  also includes a control circuit (not shown), which may be implemented using a microcontroller or some other type of integrated circuit, that receives the digital signals from the encoder  268 . Based on the signals from the encoder  268 , the control circuit may calculate the stage of deployment of the knife  32  in the end effector  12 . That is, the control circuit can calculate if the knife  32  is fully deployed, fully retracted, or at an intermittent stage. Based on the calculation of the stage of deployment of the end effector  12 , the control circuit may send a signal to the second motor  265  to control its rotation to thereby control the reciprocating movement of the threaded rod  266 . 
     In operation, as shown in  FIG.  37   , when the closure trigger  18  is not locked into the clamped position, the firing trigger  20  rotated away from the pistol grip portion  26  of the handle  6  such that the front face  242  of the upper portion  230  of the firing trigger  20  is not in contact with the proximate end of the threaded rod  266 . When the operator retracts the closure trigger  18  and locks it in the clamped position, the firing trigger  20  rotates slightly towards the closure trigger  20  so that the operator can grasp the firing trigger  20 , as shown in  FIG.  38   . In this position, the front face  242  of the upper portion  230  contacts the proximate end of the threaded rod  266 . 
     As the user then retracts the firing trigger  20 , after an initial rotational amount (e.g., 5 degrees of rotation) the run motor sensor  110  may be activated such that, as explained above, the sensor  110  sends a signal to the motor  65  to cause it to rotate at a forward speed proportional to the amount of retraction force applied by the operator to the firing trigger  20 . Forward rotation of the motor  65  causes the main drive shaft  48  to rotate via the gear drive train, which causes the knife  32  and sled  33  to travel down the channel  22  and sever tissue clamped in the end effector  12 . The control circuit receives the output signals from the encoder  268  regarding the incremental rotations of the main drive shaft assembly and sends a signal to the second motor  265  to caused the second motor  265  to rotate, which causes the threaded rod  266  to retract into the motor  265 . This allows the upper portion  230  of the firing trigger  20  to rotate CCW, which allows the lower portion  228  of the firing trigger to also rotate CCW. In that way, because the reciprocating movement of the threaded rod  266  is related to the rotations of the main drive shaft assembly, the operator of the instrument  10 , by way of his/her grip on the firing trigger  20 , experiences tactile feedback as to the position of the end effector  12 . The retraction force applied by the operator, however, does not directly affect the drive of the main drive shaft assembly because the firing trigger  20  is not geared into the gear drive train in this embodiment. 
     By virtue of tracking the incremental rotations of the main drive shaft assembly via the output signals from the encoder  268 , the control circuit can calculate when the knife  32  is fully deployed (i.e., fully extended). At this point, the control circuit may send a signal to the motor  65  to reverse direction to cause retraction of the knife  32 . The reverse direction of the motor  65  causes the rotation of the main drive shaft assembly to reverse direction, which is also detected by the encoder  268 . Based on the reverse rotation detected by the encoder  268 , the control circuit sends a signal to the second motor  265  to cause it to reverse rotational direction such that the threaded rod  266  starts to extend longitudinally from the motor  265 . This motion forces the upper portion  230  of the firing trigger  20  to rotate CW, which causes the lower portion  228  to rotate CW. In that way, the operator may experience a CW force from the firing trigger  20 , which provides feedback to the operator as to the retraction position of the knife  32  in the end effector  12 . The control circuit can determine when the knife  32  is fully retracted. At this point, the control circuit may send a signal to the motor  65  to stop rotation. 
     According to other embodiments, rather than having the control circuit determine the position of the knife  32 , reverse motor and stop motor sensors may be used, as described above. In addition, rather than using a proportional sensor  110  to control the rotation of the motor  65 , an on/off switch or sensor can be used. In such an embodiment, the operator would not be able to control the rate of rotation of the motor  65 . Rather, it would rotate at a preprogrammed rate. 
     The various embodiments of the present invention have been described above in connection with cutting-type surgical instruments. It should be noted, however, that in other embodiments, the inventive surgical instrument disclosed herein need not be a cutting-type surgical instrument. For example, it could be a non-cutting endoscopic instrument, a grasper, a stapler, a clip applier, an access device, a drug/gene therapy delivery device, an energy device using ultrasound, RF, laser, etc. 
       FIG.  43    depicts a surgical cutting and fastening instrument  2010  that is capable of practicing various unique benefits of the end effectors and drive arrangements of the present invention. The surgical instrument  2010  depicted in  FIG.  43    comprises a handle  2006 , a shaft assembly  2008 , and an articulating end effector  2300  pivotally connected to the shaft assembly  2008  at an articulation pivot  2014 . In various embodiments, the control handle houses a drive motor  2600  and control system generally represented as  2610  therein for controlling the opening and closing of the end effector  2300  and the cutting and stapling of the tissue clamped therein. An articulation control  2016  may be provided adjacent to the handle  2006  to effect rotation of the end effector  2300  about the articulation pivot  2014 . The handle  2006  of the instrument  2010  may include a closure trigger  2018  and a firing trigger  2020  for actuating the end effector  2300 . The end effector  2300  is shown separated from the handle  2006  preferably by an elongate shaft  2008 . In one embodiment, a clinician or operator of the instrument  2010  may articulate the end effector  2300  relative to a proximal portion of the shaft  2008  by utilizing the articulation control  2016 , as described in more detail in U.S. patent application Ser. No. 11/329,020, filed Jan. 10, 2006, entitled SURGICAL INSTRUMENT HAVING AN ARTICULATING END EFFECTOR, now U.S. Pat. No. 7,670,334. Other articulation arrangements could also be employed. 
     As will be discussed in further detail below, various end effector embodiments include an anvil  2340 , which is maintained at a spacing that assures effective stapling and severing of tissue clamped in the end effector  2300 . In various exemplary embodiments, the handle  2006  may include a pistol grip  2026  towards which a closure trigger  2018  is pivotally drawn by the clinician to cause clamping or closing of the anvil  2340  toward cartridge  2500  seated in an elongate channel  2302  of the end effector  2300  to thereby clamp tissue positioned between the anvil  2340  and the staple cartridge  2500 . A firing trigger  2020  may be situated farther outboard of the closure trigger  2018 . In various embodiments, once the closure trigger  2018  is locked in the closure position as further described below, the firing trigger  2020  may rotate slightly toward the pistol grip  2026  so that it can be reached by the operator using one hand. Then the operator may pivotally draw the firing trigger  2020  toward the pistol grip  2026  to cause the stapling and severing of clamped tissue in the end effector  2300 . Those of ordinary skill in the art will readily appreciate however, that other handle and drive system arrangements may be successfully employed in connection with various embodiments described herein and their equivalent structures without departing from the spirit and scope of the present invention. 
     It will be appreciated that the terms “proximal” and “distal” are used herein with reference to a clinician gripping the handle  2006  of an instrument  2010 . Thus, the end effector  2300  is distal with respect to the more proximal handle  2006 . 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. 
       FIGS.  43 - 47    illustrate a unique and novel end effector  2300  of various embodiments of the present invention adapted for use with a staple cartridge  2500 , the basic operation of which is known in the art. For example, U.S. Pat. No. 6,978,921, entitled SURGICAL STAPLING INSTRUMENT INCORPORATING AN E-BEAM FIRING MECHANISM, provides more details about the construction of such staple cartridges. 
     In general, such staple cartridges  2500  include a cartridge body  2502  that is divided by a central, elongated slot  2508  which extends from the proximal end  2504  of the cartridge body  2502  towards its tapered outer tip  2506 . See  FIG.  46   . The cartridge body  2502  may be fabricated from a polymeric material and be attached to a metal cartridge pan  2510 . A plurality of staple-receiving pockets  2512  are formed within the cartridge body  2502  and are arranged in six laterally spaced longitudinal rows or “lines” of staples  2514 ,  2516 ,  2518 ,  2520 ,  2522 ,  2524 . See  FIG.  48   . Positioned within the pockets  2512  are staple—supporting drivers  2532  which support staples  2534  thereon. Depending upon the location (line) of staple-receiving pockets  2512 , the staple supporting drivers  2532  may support one or two staples  2530  thereon. The cartridge body  2502  further includes four longitudinal slots  2503 ,  2505 ,  2507 ,  2509  extending from its proximal end  2504  to its tapered outer tip  2506  for receiving corresponding sled cams  2328  formed on a wedge sled  2326  in the end effector  2300 , the construction and operation of which will discussed in further detail below. See  FIG.  47   . As the sled cams  2328  are advanced through their respective slots  2503 ,  2505 ,  2507 ,  2509  in the cartridge body  2502  from proximal end  2504  to distal end  2506 , they contact the staple-supporting drivers  2532  associated with those slots and force the staple-supporting drivers  2532  and the staples  2534  that they support upward out of the cartridge body  2502 . See  FIG.  49   . As the ends of the legs  2536  of the staple 2   534  contact the pockets  2350  formed in the bottom surface  2341  of the anvil  2340 , they are folded over to close the staples  2534 . 
     Various end effectors of the present invention include an elongate channel  2302  that is sized to removably receive and support the cartridge body  2502  and pan  2510  of a disposable cartridge  2500  therein. A knife screw  2304  is rotatably supported in the elongate channel  2302 . The knife screw  2304  has a distal end  2306  that has a distal thrust bearing  2308  attached thereto that is rotatably supported by a distal bearing housing  2310  formed in the distal end  2303  of the elongate channel  2302 . See  FIG.  46   . The knife screw  2304  has a central drive portion  2312  with a helical thread formed thereon. The knife screw  2304  further has a smooth extension portion  2314  and a knife screw gear  2316  formed thereon or otherwise attached thereto. A proximal thrust bearing  2318  is formed or attached to the proximal end  2317  of the knife screw  2304 . The proximal thrust bearing  2318  is rotatably housed within a proximal bearing housing  2319  supported in a distal spine tube segment  2058 . The distal spine tube segment  2058  has a pair of columns  2059  formed on its distal end that are adapted to be received in vertical slots  2307  formed in the proximal end  2305  of the elongate channel  2302 . The columns  2059  may be retained within the slots  2307  in the elongate channel  2302  by friction, adhesive, or by the distal end of the shaft tube  2009 . See  FIGS.  43  and  46   . 
     Various embodiments of the present invention further include a knife assembly  2320  that has a knife/sled bearing  2322  that is threaded onto the threaded portion  2312  of the knife screw  2304 . The knife assembly  2320  supports a vertically extending blade  2324  and a wedge sled  2326  that supports the four sled cams  2328 . The reader will understand that, as the knife screw  2304  is rotated in a clockwise direction, the knife assembly  2320  and the wedge sled  2326  is advanced toward the distal end  2303  (direction “A”) of the elongate channel  2302  and, when the knife screw  2304  is rotated in a counterclockwise direction, the knife assembly  2320  and wedge sled  2326  is moved toward the proximal end  2305  of the channel member  2302  (direction “B”). In addition, the knife assembly  2320  has a pair of laterally extending deflector tabs  2330  protruding therefrom, the purpose of which will be discussed below. 
     In various embodiments of the present invention, an anvil  2340  is pivotally coupled to the proximal end  2305  of the channel member  2302  by a pair of trunnion tabs  2342  that are sized to be received in oval-shaped pivot holes  2700  provided through the side walls  2309  of the elongate channel  2302 . In various embodiments, the anvil  2340  may be stamped from sheet metal or other material such that the trunnion tabs  2342  are substantially rectangular or square shaped. In other embodiments, the anvil  2340  may be molded or machined from other materials such that it is rigid in nature and the trunnion tabs or pins are substantially round. As can be seen in  FIGS.  49  and  73   , the bottom surface  2341  of the anvil  2340  has a series of staple forming pockets  2350  formed therein. It will be understood that the staple forming pockets  2350  serve to close the staples  2534  as the ends of the staple legs  2536  are forced into contact therewith. In addition, a longitudinal clearance slot  2343  may be provided in the bottom surface  2341  of the anvil  2340  for receiving the upper end of the knife assembly  2320  and the guide tabs  2330  therethrough such that the laterally extending guide tabs  2330  serve to urge the anvil  2340  down onto the elongated channel  2302  as the knife assembly  2320  and wedge sled  2326  are driven through the cartridge  2500  to cut the tissue and deploy the staples  2534 . 
     A drive assembly for operating various embodiments of the end effector  2300  will now be described. In various embodiments, a distal drive shaft portion  2402  extends through a drive shaft hole  2061  in the distal spine tube  2058 . See  FIG.  46   . The distal drive shaft portion  2402  may extend directly to a drive motor arrangement  2600  in the control handle  2006  or it may be articulated to enable the end effector  2300  to be pivoted relative to the shaft or closure tube assembly that connects the end effector  2300  to the control handle  2006 . 
     As can be seen in  FIGS.  52 - 55   , in various embodiments of the present invention the distal drive shaft portion  2402  has a clutch-receiving portion  2404  and a closure thread  2406  formed thereon. A clutch assembly  2410  is slidably received on the clutch—receiving portion  2404  of the drive shaft portion  2402 . In various embodiments, the clutch assembly  2410  includes a collet-like tapered clutch member  2412  that has a drive gear  2414  integrally formed on its proximal end  2413 . See  FIGS.  56  and  57   . The drive gear  2414  meshes with a transfer gear  2450  that in turn meshes with the knife screw gear  2316 . See  FIGS.  50  and  51   . Thus, when the clutch assembly  2410  drivingly engages the distal drive shaft portion  2402 , the drive gear  2414  rotates the transfer gear  2450  which, in turn rotates the knife screw gear  2316 . 
     A series of four tapered sections  2416  are formed on the distal end  2415  of the tapered clutch member  2412 . A series of male splines  2418  are formed in the interior of the tapered sections  2416 . See  FIGS.  56  and  57   . The male splines  2418  are adapted to selectively engage a female spline section  2408  formed on the distal drive shaft portion  2402  as will be discussed in further detail below. See  FIGS.  52 - 55   . The clutch assembly  2410  further includes a clutch plate  2420  that is received on the tapered sections  2416  of the tapered clutch member  2412 . As can be seen in  FIGS.  58  and  59   , the clutch plate  2420  has a proximal hub portion  2422  and a distal hub portion  2424  that is separated by a flange portion  2426 . A cylindrical distal hole portion  2428  extends through the distal hub portion  2424  and a tapered proximal hole  2430  extends through the flange portion  2426  and the proximal hub portion  2422 . The hole portions  2428 ,  2430  enable the clutch plate  2420  to be slidably received on the drive shaft  2402  and slide onto the tapered clutch member  2412 . A clutch opening spring  2432  is provided between a flange portion  2417  formed on the tapered clutch member  2412  and the flange portion  2426  of the clutch plate  2420  and a thrust bearing  2434  is also journaled on the clutch-receiving portion  2404  adjacent to the clutch plate  2420 . See  FIGS.  63  and  64   . 
     Also in various embodiments, a closure nut  2440  is received on the distal drive shaft portion  2402 . As can be seen in  FIGS.  54 ,  55 ,  60  and  61   , the closure nut  2440  has a threaded hole portion  2442  extending partially therethrough to enable it to be threaded onto the closure thread  2406  on the distal drive shaft portion  2402 . As can be further seen in those Figures, the closure nut  2440  has an upstanding closure ramp  2444  protruding therefrom. The top of the closure ramp  2444  terminates in a radiused portion  2446  that extends to an upstanding closure tab  2448  that is adapted to engage a downwardly protruding closure hook  2346  formed on the proximal end  2345  of anvil  2340 . 
     More specifically and with reference to  FIG.  63   , the proximal end  2345  of the anvil  2340  has an anvil closure arm portion  2347  protruding proximally therefrom that terminates in a downwardly extending closure hook  2346 . As can also be seen in that Figure, the bottom surface of the anvil closure arm  2347  has a tab relief groove  2348  therein for receiving the closure tab  2348  when the closure nut  2440  is advanced to its most distal position (shown in  FIGS.  69 - 72   ). Also in various embodiments, a closure lock spring  2460  is attached to the bottom of the elongate channel  2302 , by mechanical fastener arrangements or adhesive. The closure lock spring  2460  has an upper portion  2462  that terminates in an upstanding retainer lip  2464 . In addition, longitudinally extending retainer arm  2466  is rigidly attached to the upper portion  2462  of the closure lock spring  2460 . See  FIG.  46   . 
     Various embodiments of the present invention employ an anvil  2340  that is capable of moving axially and laterally relative to the elongate channel  2302  prior to being advanced to the closed position. More specifically and with reference to  FIGS.  62 - 72   , in various embodiments, the elongate channel  2302  is stamped or otherwise formed from sheet metal or the like and the pivot holes may be punched therein. Such construction leads to reduced manufacturing costs for the end effector. Other embodiments may be machined from rigid materials such as 2416 stainless steel such that the trunnion pins are substantially round in cross-section. Regardless of which manufacturing method is employed to manufacture the anvil  2340  and the resulting shape of the trunnion tabs  2342 , as can be seen in  FIGS.  63 ,  66 ,  68 ,  70 , and  74   , the pivot holes  2700  are oval or oblong and serve to afford the trunnion tabs  2342  with the ability to move axially back and forth and up and down in their corresponding pivot hole  2700 . As can be seen in  FIG.  74   , the trunnion tabs  2342  may have a length “X” of, for example, approximately 0.060 inches and a height “Y” of, for example, approximately 0.050 inches. The pivot holes  2700  have a proximal wall portion  2702 , a distal wall portion  2704 , an upper wall portion  2706  and a lower wall portion  2708 . In various embodiments, for example, the distance “L” between the proximal wall  2702  and the distal wall  2704  may be approximately 0.120 inches and the distance “H” between the upper wall portion  2706  and lower wall portion  2708  may be approximately 0.090 inches. See  FIG.  74   . Those of ordinary skill in the art will appreciate that these distances and tolerances may, in connection with various embodiments, be somewhat dictated by the manufacturing tolerances attainable by the processes used to manufacture the anvil  2340  and the elongate channel  2302 . In other embodiments, however, the distances “H”, “L”, “X”, and “Y” may be sized relative to each other to enable the anvil  2340  to travel along a closing path that is relatively substantially parallel to the top surface of a cartridge  2500  supported in the elongate channel  2302 . Such arrangement serves to prevent or minimize the likelihood of tissue from being rolled out of between the anvil and the cartridge during clamping. Thus, these dimensions are merely exemplary and are not intended to be limiting. The trunnion tabs  2342  and the pivot holes  2700  may have other sizes, shapes and dimensions relative to each other that differ from such exemplary dimensions given herein that nevertheless enable those components to operate in the unique and novel manner of various embodiments of the present invention as described herein. 
     This ability of the trunnion tabs  2342  to travel within their respective pivot hole  2700  in the side walls of the  2309  of the elongate channel  2302  can be appreciated from reference to  FIGS.  62 - 68   . As can be seen in each of those Figures, the closure nut  2440  is in its distal-most open position. When in that position, the retainer lip  2464  of the closure lock spring is biased under the closure nut  2440  and does not restrict the travel thereof.  FIGS.  62  and  63    illustrate the trunnion tabs  2342  adjacent the proximal end wall portions  2702  of the pivot holes.  FIGS.  65  and  44    illustrate the trunnion tabs  2342  after they have crept somewhat midway between the proximal end wall portion  2702  and the distal end wall portion  2704  of the pivot hole  2700 .  FIGS.  67  and  68    illustrate the trunnion tabs  2342  after they have crept to a position adjacent the distal end wall portions  2704  of the pivot holes  2700 . Thus, in various embodiments, the trunnion tabs  2342  are loosely received within their respective pivot holes  2700  and capable of moving axially, laterally and vertically or in combinations of such directions therein. 
       FIGS.  69 - 72    illustrate the anvil  2340  in a closed position. As can be seen in  FIG.  70   , the trunnion tabs  2342  are in abutting contact with a proximal end wall portion  2702  of the pivot hole  2700 . When in that position (i.e., when the trunnion tabs  2342  are held in abutting contact with proximal end wall portion  2702 ), the staple-forming pockets  2350  in the bottom surface  2341  of the anvil  2340  are in axial registration with corresponding staple-receiving pockets  2512  in the cartridge  2500  seated in the elongate channel  2302  such that when the staples  2534  are fired, they are correctly formed by the corresponding pockets  2350  in the anvil  2340 . The anvil  2340  is locked in that position by the retainer lip  2464  portion of the closure lock spring  2460  as will be discussed in further detail below. 
     Also in various embodiments, the anvil  2340  is capable of moving laterally relative to the elongate channel due to manufacturing tolerances in the fabrication of the trunnion tabs  2342  and the pivot holes  2700 . As can be seen in  FIGS.  44 - 46 ,  62 ,  65 ,  69 , and  73   , in various embodiments, the anvil  2340  is provided with a pair of downwardly extending tissue stops  2344 . During the clamping process, the tissue stops  2344  essentially perform two functions. One of the functions consists of orienting the tissue  2900  within the end effector  2300  so as to prevent the tissue  2900  from extending axially into the end effector  2300  such that it extends beyond the innermost staple pockets  2512  in the cartridge  2500  when seated in the elongate channel  2302 . See  FIG.  65   . This prevents tissue  2900  from being cut that is not stapled. The other function performed by the tissue stops  2344  is to axially align the anvil  2340  relative to the elongate channel  2302  and ultimately to the cartridge  2500  received therein. As the anvil  2340  is closed, the tissue stops  2344  serve to contact corresponding alignment surfaces  2720  on the side of the elongate channel  2302  and serve to laterally align the anvil  2340  relative to the elongate channel  2302  when the anvil  2340  is closed and clamping tissue  2900  such that the staple-forming pockets  2350  in the bottom surface  2341  of the anvil  2340  are laterally aligned with the corresponding staple-receiving pockets  2512  in the cartridge  2500 . See  FIGS.  69  and  73   . 
     The operation of various embodiments of the present invention will now be described with reference to  FIGS.  62 - 71   .  FIGS.  62 - 68    illustrate the closure nut  2440  in an open position. As can be seen in those Figures, when in the open position, the closure nut  2440  is located such that the hook arm  2346  is permitted to move to various positions relative thereto that enable the anvil  2340  to pivot open to permit tissue  2900  to be inserted between the anvil  2340  and the elongated channel  2302  and cartridge  2500  seated therein. When in this position, the distal end  2467  of the retainer arm  2466  that is attached to the closure lock spring  2460  is in contact with a ramp surface  2321  formed on the proximal end of the knife assembly  2320 . See  FIG.  64   . As the knife assembly  2320  moves proximally, the end of the retainer arm  2466  contacts the ramp surface  2321  on the proximal end of the knife assembly  2320  and serves to cause the retainer arm  2466  to bias the upper portion  2462  of the closure lock spring  2460  downward toward the bottom of the elongate channel  2302 . When the knife assembly  2320  moves distally away from the retainer arm  2466 , the upper portion  2462  of the closure lock spring  2460  is permitted to spring upward to enable the retainer lip  2464  to engage the closure nut  2440  as will be further discussed below. 
     The reader will appreciate that when the end effector  2300  is in the open positions depicted in  FIGS.  62 - 68   , the user can install a disposable cartridge assembly  2500  in the elongate member  2302 . Also, when in those positions, the anvil  2340  may be able to move axially, laterally and vertically relative to the elongate channel  2302 . In various embodiments, when the drive shaft  2402  is rotated in a first direction, the closure thread  2406  thereon threadably drives the closure nut  2440  in the proximal direction (direction “B” in  FIG.  50   ) until the closure threads  2406  disengage the threaded hole  2442  in the closure nut  2440 . See  FIG.  55   . As the closure nut  2440  is driven proximally, the closure hook  2346  on the anvil closure arm  2347  rides up the ramp  2444  of the closure nut  2440  until it rides into the radiused portion  2446  and contacts the closure tab  2448 . Such movement of the closure nut  2440  serves to “pull” the anvil  2340  to the closed position. See  FIGS.  69 - 71   . When in that position, the trunnion tabs  2342  are in abutting contact with the proximal end portion  2702  of the pivot holes  2700  and the retainer lip  2464  of the closure lock spring has engaged the distal end  2441  of the closure nut  2440  to retain the anvil  2340  in the fully closed and axially aligned position. When also in that position, by virtue of the contact of the tissue stops  2344  with the alignment surfaces  2720  on the side walls  2309  of the elongate channel  2302 , the anvil  2340  is laterally aligned with the elongate channel  2302  so that the staple forming pockets  2350  in the anvil  2340  are laterally aligned with corresponding the staple-receiving pockets  2512  in the cartridge  2500 . 
     As the closure nut  2440  is driven in the proximal direction, the proximal end  2449  of the closure nut  2440  contacts the thrust bearing  2434  which forces the clutch plate  2420  in the proximal direction against the force of clutch opening spring  2432 . Further travel of the closure nut  2440  in the proximal direction drives the clutch plate  2420  onto the tapered sections  2416  of the tapered clutch member  2412  which causes the male splines  2418  therein to engage the female splines  2408  on the distal drive shaft portion  2402 . Such engagement of the male splines  2418  in the tapered clutch member  2412  with the female splines on the distal drive shaft portion  2402  causes the tapered clutch member  2412  and the drive gear  2414  to rotate with the distal drive shaft portion  2402 . Drive gear  2414 , in turn, rotates the knife screw gear  2316  which causes the knife screw to rotate and drive the knife assembly distally (“A” direction). 
     As the knife assembly  2320  is driven distally, it cuts the tissue and the cams  2328  on the wedge sled  2326  serve to drive the staple supporting drivers  2532  upward which drive the staples  2534  toward the anvil  2340 . As the legs  2536  of the staples  2534  are driven into the corresponding staple-forming pockets  2350  in the anvil  2340 , they are folded over. See  FIG.  49   . 
     When the knife assembly  2320  moves distally, the distal end  2467  of the retainer arm  2466  is no longer in contact with the ramp surface  2321  of the knife assembly  2320  which enables the retainer arm  2466  and the upper portion  2462  of the closure lock spring  2460  to spring upwardly which further enables the retainer lip  2464  on the closure lock spring  2460  to retainingly engage the distal end  2441  of the closure nut  2440  to prevent it from moving distally. See  FIGS.  70  and  71   . By virtue of its contact with the closure nut  2440  which is in contact with the thrust bearing  2434 , the retainer lip  2464  serves to retain the clutch assembly  2410  engaged with the distal drive shaft portion  2402  until the knife assembly  2320  once again returns to contact the distal end  2467  of the retainer arm  2464 . After the knife assembly  2320  has been driven to its final distal position as shown in  FIG.  72   , it activates a conventional sensor or contact  2313  mounted within the elongate channel  2302  and signals the control motor to stop driving the drive shaft  2402 . See  FIG.  76   . Those of ordinary skill in the art will understand that a variety of different control arrangements could be employed to control the drive shaft  2402 . For example, when the knife assembly  2310  reaches its distal-most position and activates the sensor  2313 , the control system  2610  housed within the handle  2006  could automatically reverse the drive motor  2600  therein and cause the drive shaft portion  2402  and knife screw to reverse direction (e.g., move in the proximal “B” direction). In various other embodiments, the control system  2610  may simply stop the drive motor  2600  and then require the surgeon to activate a button  2030  to cause the motor  2600  to reverse. In still other arrangements, the control system  2610  may institute a predetermined timed delay between the time that the reversing sensor  2313  is activated and the time that the motor  2600  is reversed. 
     As the knife assembly  2320  moves in the proximal direction on the knife screw  2304 , the closure threads  2406  on the drive shaft  2402  begin to screw back into the threaded hole portion  2442  in the closure nut  2440 . During this process, the ramp surface  2321  of the knife assembly  2320  again contacts the distal end  2467  of the retainer arm  2466  which serves to bias the upper portion  2462  of the closure lock spring  2460  toward the bottom of the elongate channel  2302  to permit the retainer lip  2464  to disengage from the distal end  2441  of the closure nut  2440  thereby permitting the clutch opening spring  2432  to bias the clutch assembly  2410  and closure nut  2440  distally. As the closure nut  2440  moves distally, the closure hook  2346  on the anvil  2340  rides up the ramp  2444  on the closure nut  2440  until the closure nut  2440  reaches the open position wherein the closure tab  2448  is received within the tab relief groove  2348  in the bottom surface  2341  of the anvil  2340  and the closure nut  2440  moves the anvil assembly  2372  to the open position. A second conventional sensor or contact  2315  is mounted within the proximal end portion  2305  of the elongate channel  2302  for sensing when the closure nut  2440  is in the open position and communicates with the motor to cause it to stop. See  FIG.  46   . 
     As indicated above, a variety of different motor/control arrangements may be employed to power the drive shaft portion  2402 . For example, in various embodiments when the closure trigger  2018  is actuated, that is, drawn in by a user of the instrument  2010 , the motor  2600  may commence the above described closing process. A third sensor  2315 ′ may be used in the elongate channel member  2302  to sense when the closure nut  2404  has moved into the closed position (shown in  FIG.  70   ). When the third sensor  2315 ′ senses that the closure nut  2440  is in that position, the sensor  2315 ′ may cause the motor  2600  to stop rotating. Thereafter, if the surgeon is satisfied with the clamping of the tissue in the end effector  2300 , the surgeon may actuate the firing trigger  2020  or other actuator arrangement to activate the motor  2600  to rotate the drive shaft  2402  which drives the knife screw  2304  in the above-mentioned manner. 
     Another drive arrangement is depicted in  FIGS.  75 - 77   . In this embodiment, a closure wedge  2440 ′ is axially moved by a manual drive assembly  2800 . More specifically and with reference to  FIG.  75   , the proximal end  2802  of the drive shaft  2402 ′ is has a drive gear  2810  attached thereto. Although a variety of different gear and motor arrangements may be employed, the drive gear  2810  may be oriented for selective meshing engagement with a gear train or transmission assembly generally designated as  2820  that is ultimately driven my motor  2600 . The drive shaft  2402 ′ is movably supported by a proximal spine tube segment  2820  that is pivotally coupled to the distal spine tube segment  2058  as described in various of the U.S. patent applications incorporated by reference herein above and rigidly attached to the housing portions  2007  of the handle  2006 . In other arrangements wherein the end-effector is not capable of articulating travel, the distal spine tube  2058  may be longer and rigidly coupled to the sections  2007  of the handle  2006 . Regardless of which spine tube arrangement is employed, the drive shaft  2402 ′ is axially and rotatably received therein such that the drive shaft  2402 ′ can move axially in the distal and proximal directions and also rotate when engaged with the motor  2600 . 
     Various methods may be employed to mechanically move the drive shaft  2402 ′ in the distal and proximal directions. For example, as shown in  FIG.  75   , a thrust bearing assembly  2830  may be attached to the drive shaft  2402 ′ for selective contact by a control linkage assembly  2840 . As can be seen in that Figure, the control linkage assembly  2840  may be linked to the closure trigger  2018  and capable of biasing the drive shaft  2402 ′ in the proximal (“B”) direction when the closure  2018  is pivoted in the proximal direction, the control linkage assembly contacts the thrust bearing and pulls the drive shaft  2402  in the proximal direction. 
     Turning next to  FIGS.  76  and  77   , as can be seen in these Figures, the distal end  2406 ′ of the drive shaft is rotatably supported within a closure wedge  2440 ′ that is similar in construction as closure nut  2440  as described above. In particular, the closure wedge  2440 ′ has a proximal hole  2442 ′ and a distal hole portion  2443 ′ that is larger in diameter than the proximal hole portion  2442 ′. The distal end  2406 ′ of the drive shaft  2402 ′ is rotatably supported in the distal hole portion  2443 ′ by  a bearing  2445 ′. The distal end portion  2406 ′ of the drive shaft  2406 ′ is longer than the hole  2403 ′ such that as the drive shaft  2402 ′ moves distally and proximally, it cannot become disengaged from the wedge  2440 ′. The wedge  2440 ′ also has a closure ramp portion  2444 ′, a radiused portion  2446 ′, and a closure tab  2448 ′ formed thereon. As can be seen in  FIGS.  76  and  77   , a drive gear  2414 ′ is attached to the drive shaft  2402 ′ and is adapted to mesh with the transfer gear  2450  that is in meshing engagement with the knife screw gear  2316 . 
     In these embodiments, when the user wishes to close the anvil  2340 , the user moves the closure trigger  2018  toward the handle  2006 . This action causes the control linkage assembly  2840  to move the drive shaft  2402 ′ in the proximal direction and pull the wedge  2440 ′ proximally. As the wedge  2440 ′ moves proximally, the closure hook  2346  on the proximal end  2345  of the anvil  2340  rides up the ramp portion  2444 ′ thereon until the it is seated in the radiused portion  2446 ′ of the wedge  2440 ′. The wedge  2440 ′ gets biased proximally until the retainer lip  2464  engages the distal end  2441 ′ of the wedge  2440 ′ as shown in  FIG.  77   . When in that position, the trunnion tabs  2342  of the anvil  2340  are in engagement with the proximal end portion  2702  of pivot holes  2700  as described above. Also when in that position, the drive gear  2414 ′ is now in meshing engagement with the transfer gear  2450  (not shown in  FIG.  77   ) that is in meshing engagement with the knife screw gear  2316 . Thus, when the drive shaft  2402 ′ is rotated by activating the control motor, the drive gear  2414 ′ serves to drive the transfer gear  2450  and the knife screw gear  2316  to drive the knife assembly  2320  in the above described manner. The closure lock spring  2460  and the motor control sensors in the elongate channel operate in the above described manner. 
     After the drive motor  2600  has reversed the rotation of the drive shaft  2402 ′ which drives the knife assembly  2320  proximally back to its starting position wherein the ramp surface  2321  contacts the distal end  2467  of the retainer arm  2466 , the lip  2464  of the closure lock spring  2460  is biased downwardly to permit the wedge  2440 ′ to move distally. The user can then release the closure trigger  2018  which is spring biased to the unactuated position shown in  FIG.  43   . As the closure trigger  2018  returns to the unactuated position, the control linkage assembly  2840  permits the drive shaft  2402 ′ and wedge  2440 ′ to move distally and open the anvil  2340  in the above-described manner. 
     The reader will understand that various embodiments of the present invention provide vast improvements over prior end effectors and end effector drive arrangements. In particular, the various unique and novel drive system of various embodiments of the present invention permit the anvil and elongated channel components of the end effector to be manufactured utilizing materials and processes that are more economical than other materials and processes used in the past without sacrificing performance. In addition, by providing an anvil that can travel along a closing path that is substantially parallel to the elongate channel and staple cartridge housed therein, reduces the likelihood that the tissue will be rolled out of position during the initial closing of the anvil. 
     The invention which is intended to be protected is not to be construed as limited to the particular embodiments disclosed. The embodiments are therefore to be regarded as illustrative rather than restrictive. Variations and changes may be made by others without departing from the spirit of the present invention. Accordingly, it is expressly intended that all such equivalents, variations and changes which fall within the spirit and scope of the present invention as defined in the claims be embraced thereby. 
     Although the present invention has been described herein in connection with certain disclosed embodiments, many modifications and variations to those embodiments may be implemented. For example, different types of end effectors may be employed. Also, where materials are disclosed for certain components, other materials may be used. The foregoing description and following claims are intended to cover all such modification and variations. 
     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 materials 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.