Patent Publication Number: US-11638583-B2

Title: Motorized surgical system having a plurality of power sources

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation patent application claiming priority under 35 U.S.C. § 120 to U.S. patent application Ser. No. 16/540,670, entitled MOTORIZED SURGICAL CUTTING AND FASTENING INSTRUMENT, filed Aug. 14, 2019, now U.S. Patent Application Publication No. 2020/0038020, which is a continuation patent application claiming priority under 35 U.S.C. § 120 to U.S. patent application Ser. No. 14/135,996, entitled MOTORIZED SURGICAL CUTTING AND FASTENING INSTRUMENT, filed Dec. 20, 2013, which issued on May 26, 2020 as U.S. Pat. No. 10,660,640, which is a continuation patent application claiming priority under 35 U.S.C. § 120 to U.S. patent application Ser. No. 12/031,556, entitled MOTORIZED SURGICAL CUTTING AND FASTENING INSTRUMENT, filed Feb. 14, 2008, which issued on Jan. 28, 2014 as U.S. Pat. No. 8,636,736, the entire disclosures of which are hereby incorporated by reference herein. 
     The present application incorporates by reference the following related, co-owned U.S. nonprovisional patent applications that were filed on Feb. 14, 2008:
         MOTORIZED SURGICAL CUTTING AND FASTENING INSTRUMENT HAVING A MAGNETIC DRIVE TRAIN TORQUE LIMITING DEVICE, U.S. patent application Ser. No. 12/031,542, now U.S. Pat. No. 8,459,525;   MOTORIZED SURGICAL CUTTING AND FASTENING INSTRUMENT HAVING HANDLE BASED POWER SOURCE, U.S. patent application Ser. No. 12/031,567, now U.S. Pat. No. 8,657,174;   SURGICAL CUTTING AND FASTENING INSTRUMENT HAVING RF ELECTRODES, U.S. patent application Ser. No. 12/031,573;   MOTORIZED CUTTING AND FASTENING INSTRUMENT HAVING CONTROL CIRCUIT FOR OPTIMIZING BATTERY USAGE, U.S. patent application Ser. No. 12/031,580, now U.S. Pat. No. 8,622,274.       

    
    
     BACKGROUND 
     Surgical staplers have been used in the prior art to simultaneously make a longitudinal incision in tissue and apply lines of staples on opposing sides of the incision. Such instruments commonly include a pair of cooperating jaw members that, if the instrument is intended for endoscopic or laparoscopic applications, are capable of passing through a cannula passageway. One of the jaw members receives a staple cartridge having at least two laterally spaced rows of staples. The other jaw member defines an anvil having staple-forming pockets aligned with the rows of staples in the cartridge. Such instruments typically include a plurality of reciprocating wedges that, when driven distally, pass through openings in the staple cartridge and engage drivers supporting the staples to effect the firing of the staples toward the anvil. 
     An example of a surgical stapler suitable for endoscopic applications is described in published U.S. Pat. No. 7,000,818, entitled, SURGICAL STAPLING INSTRUMENT HAVING SEPARATE DISTINCT CLOSING AND FIRING SYSTEMS, the disclosure of which is herein incorporated by reference. In use, a clinician is able to close the jaw members of the stapler upon tissue to position the tissue prior to firing. Once the clinician has determined that the jaw members are properly gripping tissue, the clinician can fire the surgical stapler, thereby severing and stapling the tissue. The simultaneous severing and stapling steps avoid complications that may arise when performing such actions sequentially with different surgical tools that respectively only sever or staple. 
     In addition, it is also known in the prior art to include electrodes in the end effector that can be used to emit/receive RF energy to form a hemostatic line along the cut line. U.S. Pat. No. 5,403,312, entitled ELECTROSURGICAL HEMOSTATIC DEVICE (hereinafter the “&#39;312 Patent”), which is incorporated herein by reference, discloses an electrosurgical instrument with an end effector that compresses tissue between one pole (or electrode) of a bipolar energy source on one interfacing surface, and a second pole (or electrode) on a second interfacing surface. The RF energy applied through the compressed tissue in the end effector, which cauterizes the tissue. The end effector described in the &#39;312 Patent also includes staples for stapling the tissue compressed in the end effector. 
     Motor-powered surgical cutting and fastening instruments, where the motor powers the cutting instrument, are also known in the prior art, such as described in published U.S. Pat. No. 7,422,139, entitled MOTOR-DRIVEN SURGICAL CUTTING AND FASTENING INSTRUMENT WITH TACTILE POSITION FEEDBACK, which is incorporated herein by reference. 
     SUMMARY 
     In one general aspect, embodiments of the present invention are directed to surgical cutting and fastening instruments. The instruments may be endoscopic instruments, such as linear endocutters or circular cutters, or laparoscopic instruments. The instruments may be comprised of staples and/or RF electrodes for fastening tissue clamped in the end effector. 
     Several embodiments disclosed herein are pertinent to cordless motor-powered instruments. The instruments may be powered by a power pack comprising a DC power source, such as one or more series-connected battery cells. A cell selection switch may control how many of the battery cells are being used to power the motor at a given time to control the power available to the motor. This allows the operator of the instrument to have greater control over both the speed and the power of the motor. In another embodiment, the instrument may comprise a power regulator, including, for example, a DC-to-DC converter, that regulates the voltage supplied to the motor. Further, the voltage set point for the power regulator could be set so that the voltage delivered from the power source is less than the voltage at which the power source delivers maximum power. That way, the power source (e.g., a number of series-connected battery cells) could operate on the “left” or increasing side of the power curve, so that increases in power would be available. 
     In addition, according to various embodiments, the power source may comprise secondary accumulator devices, such as rechargeable batteries or supercapacitors. Such secondary accumulator devices may be charged repeatably by replaceable batteries. A charge management circuit may control the charging of the secondary accumulator devices and provide various status signals, such as an alert, when the charging of the secondary accumulator devices is complete. 
     In other embodiment, a power pack comprising the secondary accumulator devices may be removable from the instrument and connectable to a remote charger base. The charger base may charge the secondary accumulator devices, such as from the AC electrical mains or a battery. The charger base may also comprise a processor and memory unit. Data stored in a memory of the removable power pack may be downloaded to the charger base, from which it may be uploaded for later use and analysis, such as by the user (e.g., physician), the manufacturer or distributor of the instrument, etc. The data may comprise operating parameters, such as charge cycle information, as well as ID values for various replaceable components of the instrument, such as the staple cartridge. 
     In various embodiments, a surgical stapling system comprising a surgical instrument and a plurality of power sources is disclosed. The surgical instrument comprises an end effector, an elongate shaft extending from the end effector, a firing member, and a motor. The end effector comprises an elongate channel, an anvil movable relative to the elongate channel from an open position toward a closed position to capture tissue therebetween, and a staple cartridge removably positioned in the elongate channel. The staple cartridge comprises a plurality of staples removably stored therein. The firing member is moveable between an unfired position and a fired position. The staples are deployable from the staple cartridge based on the firing member moving toward the fired position. The motor is configured to drive the firing member between the unfired position and the fired position. Each power source is removably coupleable with the surgical instrument. Each power source is configured to supply power to the motor. The plurality of power sources comprises a first power source comprising first power cells configured to supply power to the motor and a second power source comprising second power cells configured to supply power to the motor. The first power cells are connected in series. The second power cells are connected in series. The number of first power cells and the number of second power cells are different. 
     In various embodiments, a surgical fastening system comprising a surgical instrument and a plurality of power packs is disclosed. The surgical instrument comprises an end effector, an elongate shaft extending from the end effector, a firing member, and a motorized system. The end effector comprises a first jaw, a second jaw, and a fastener cartridge removably positioned in the first jaw. The first jaw and the second jaw are configurable between an open configuration and a closed configuration. The fastener cartridge comprises a plurality of fasteners removably stored therein. The firing member is moveable between a starting position and an ending position. The fasteners are deployable from the fastener cartridge based on the firing member moving toward the ending position. The motorized system is configured to drive the firing member between the starting position and the ending position. Each power pack is removably coupleable with the surgical instrument. Each power pack is configured to supply power to the motorized system. The plurality of power packs comprises a first power pack comprising first battery cells configured to supply power to the motorized system and a second power pack comprising second battery cells configured to supply power to the motorized system. The first battery cells are coupled in series. The second battery cells are coupled in series. The number of first battery cells and the number of second battery cells are different. 
     In various embodiments, a surgical stapling system comprising a surgical instrument and a plurality of power sources is disclosed. The surgical instrument comprises an end effector, a firing member, and a motor. The end effector comprises an elongate channel, an anvil rotatable relative to the elongate channel from an open position toward a clamped position to capture tissue therebetween, and a staple cartridge removably positioned in the elongate channel. The staple cartridge comprises a plurality of staples removably stored therein. The firing member is moveable between a proximal position and a distal position. The staples are deployable from the staple cartridge based on the firing member moving toward the distal position. The motor is configured to drive the firing member between the proximal position and the distal position. Each power source is removably coupleable with the surgical instrument. Each power source is configured to supply power to the motor. The plurality of power sources comprises a first power source comprising first power cells and a second power source comprising second power cells. The first power cells define a first voltage potential. The second power cells define a second voltage potential. The first voltage potential and the second voltage potential are different. 
     In addition, the instrument may comprise a torque-limiting device to limit the torque supplied by the motor, to limit thereby actuation forces that may damage components of the instrument. According to various embodiments, the torque-limiting devices may be an electromagnetic or permanent magnet, or mechanical clutch devices connected (either directly or indirectly) to the output pole of the motor. 
     In another general aspect, the present invention is directed to RF instruments (i.e., surgical cutting and fastening instruments with electrodes at the end effector for applying RF energy to the tissue held by the end effector) with new types of electrode configurations. In general, the new electrode configurations include combinations of smaller active electrodes and larger return electrodes. The smaller active electrodes are used to concentrate the therapeutic energy at the tissue, while the larger return electrodes preferentially are used to complete the circuit with minimal impact on that tissue interface. The return electrodes typically have greater mass and thereby are able to stay cooler during electrosurgical application. 
     In addition, the end effector, according to various embodiments, may comprise a number of co-linear, segmented active electrodes. The segmented electrodes could be energized synchronously or, more preferably, in sequence. Activating the segmented electrodes in sequence provides the advantages of (1) decreased instantaneous power requirements due to a smaller targeted area of tissue coagulation and (2) allowing other segments to fire if one is shorted out. 
     In addition, a number of mechanisms for activating the RF electrodes and for articulating the end effector are disclosed herein. 
    
    
     
       FIGURES 
       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 - 14  and  17    are schematic diagrams of circuits used to power the motor of the instrument according to various embodiments of the present invention; 
         FIG.  15    is a block diagram illustrating a charge management circuit according to various embodiments of the present invention; 
         FIG.  16    is a block diagram illustrating a charger base according to various embodiments of the present invention; 
         FIG.  18    illustrates a typical power curve of a battery; 
         FIGS.  19 - 22    illustrate embodiments of an electromagnetic, clutch-type torque-limiting device according to various embodiments of the present invention; 
         FIGS.  23 - 25 ,  27 - 28 , and  59    are views of the lower surface of the anvil of the instrument according to various embodiments of the present invention; 
         FIGS.  26 ,  53 ,  54 , and  68    are cross-sectional front views of the end effector according to various embodiments of the present invention; 
         FIGS.  29 - 32    show an embodiment of the end effector having RF electrodes according to various embodiments of the present invention; 
         FIGS.  33 - 36    show another embodiment of the end effector having RF electrodes according to various embodiments of the present invention; 
         FIGS.  37 - 40    show another embodiment of the end effector having RF electrodes according to various embodiments of the present invention; 
         FIGS.  41 - 44    show another embodiment of the end effector having RF electrodes according to various embodiments of the present invention; 
         FIGS.  45 - 48    show another embodiment of the end effector having RF electrodes according to various embodiments of the present invention; 
         FIGS.  49 - 52    show another embodiment of the end effector having RF electrodes according to various embodiments of the present invention; 
         FIGS.  55  and  56    show side views of the end effector according to various embodiments of the present invention; 
         FIG.  57    is a diagram of the handle of the instrument according to another embodiment of the present invention; 
         FIG.  58    is a cut-away view of the handle of the embodiment of  FIG.  57    according to various embodiments of the present invention; 
         FIGS.  60 - 66    illustrate a multi-layer circuit board according to various embodiments of the present invention; 
         FIG.  67    is a diagram illustrating an end effector according to various embodiments of the present invention; and 
         FIGS.  69  and  70    are diagrams of an instrument comprising a flexible neck assembly according to various embodiments of the present invention. 
     
    
    
     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. More details regarding RF devices may be found in the &#39;312 Patent. 
     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 published U.S. Pat. No. 7,670,334, entitled SURGICAL INSTRUMENT HAVING AN ARTICULATING END EFFECTOR, 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 , having a hook portion  150 , as shown in  FIG.  7    or any of the mechanisms described in published U.S. Patent Application Publication No. 2007/0175955, which is incorporated herein by reference. 
       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 proximal end of the channel  22 . The anvil  24  may also include a tab  27  at its proximal 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. Pat. Nos. 7,673,783 and 7,607,557, which are also incorporated herein by reference, disclose endoscopic cutting instruments that use 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 proximal 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 proximal spine tube  46 . Disposed inside the proximal spine tube  46  may be a main rotational (or proximal) 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 proximal 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 proximal 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 shaft  36 , allowing the helical drive screw shaft  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  traverses 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 . 
       FIGS.  7 - 10    illustrate an exemplary embodiment of a motor-driven endocutter. The illustrated embodiment 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, a number of battery cells connected in series may be used to power the motor  65 . 
     The motor  65  may be a DC brushed driving motor having a maximum rotation of approximately 25,000 RPM with no load. The motor  65  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  110 , 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 proximal end of the helical gear drum  80  so that the ring  84  trips the switch  142  when the ring  84  reaches the proximal end of the helical gear drum  80 . 
     In operation, when an operator of the instrument  10  pulls back the firing trigger  20 , biased to rotate in a CCW direction by a spring  222 , 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 proximal 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 proximal 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 . 
     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 proximal end of the proximal 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 proximal closure tube  40 . The instrument  10  also includes a closure rod  260  disposed inside the proximal 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 proximal 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 proximal 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 proximal 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 proximal closure tube  40  is caused to slide proximally, which causes the distal closure tube  42  to slide proximally, 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 therethrough. 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  138 , 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  140  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. 
     Additional configurations for motorized surgical instruments are disclosed in published U.S. Pat. No. 7,422,139, entitled MOTOR-DRIVEN SURGICAL CUTTING AND FASTENING INSTRUMENT WITH TACTILE POSITION FEEDBACK, which is incorporated herein by reference. 
     In a motorized surgical instrument, such as one of the motorized endoscopic instruments described above or in a motorized circular cutter instrument, the motor may be powered by a number of battery cells connected in series. Further, it may be desirable in certain circumstances to power the motor with some fraction of the total number of battery cells. For example, as shown in  FIG.  12   , the motor  65  may be powered by a power pack  299  comprising six (6) battery cells  310  connected in series. The battery cells  310  may be, for example, 3-volt lithium battery cells, such as CR 123A battery cells, although in other embodiments, different types of battery cells could be used (including battery cells with different voltage levels and/or different chemistries). If six 3-volt battery cells  310  were connected in series to power the motor  65 , the total voltage available to power the motor  65  would be 18 volts. The battery cells  310  may comprise rechargeable or non-rechargeable battery cells. 
     In such an embodiment, under the heaviest loads, the input voltage to the motor  65  may sag to about nine to ten volts. At this operating condition, the power pack  299  is delivering maximum power to the motor  65 . Accordingly, as shown in  FIG.  12   , the circuit may include a switch  312  that selectively allows the motor  65  to be powered by either (1) all of the battery cells  310  or (2) a fraction of the battery cells  310 . As shown in  FIG.  12   , by proper selection, the switch  312  may allow the motor  65  to be powered by all six battery cells or four of the battery cells. That way, the switch  312  could be used to power the motor  65  with either 18 volts (when using all six battery cells  310 ) or 12 volts (such using four of the second battery cells). In various embodiments, the design choice for the number of battery cells in the fraction that is used to power the motor  65  may be based on the voltage required by the motor  65  when operating at maximum output for the heaviest loads. 
     The switch  312  may be, for example, an electromechanical switch, such as a micro switch. In other embodiments, the switch  312  may be implemented with a solid-state switch, such as transistor. A second switch  314 , such as a push button switch, may be used to control whether power is applied to the motor  65  at all. Also, a forward/reverse switch  316  may be used to control whether the motor  65  rotates in the forward direction or the reverse direction. The forward/reverse switch  316  may be implemented with a double pole-double throw switch, such as the relay  140  shown in  FIG.  11   . 
     In operation, the user of the instrument  10  could select the desired power level by using some sort of switch control, such as a position-dependent switch (not shown), such as a toggle switch, a mechanical lever switch, or a cam, which controls the position of the switch  312 . Then the user may activate the second switch  314  to connect the selected battery cells  310  to the motor  65 . In addition, the circuit shown in  FIG.  12    could be used to power the motor of other types of motorized surgical instruments, such as circular cutters and/or laparoscopic instruments. More details regarding circular cutters may be found in published U.S. Pat. Nos. 8,317,074 and 7,500,979, which are incorporated herein by reference. 
     In other embodiments, as shown in  FIG.  13   , a primary power source  340 , such as a battery cell, such as a CR2 or CR123A battery cell, may be used to charge a number of secondary accumulator devices  342 . The primary power source  340  may comprise one or a number of series-connected battery cells, which are preferably replaceable in the illustrated embodiment. The secondary accumulator devices  342  may comprise, for example, rechargeable battery cells and/or supercapacitors (also known as “ultracapacitors” or “electrochemical double layer capacitors” (EDLC)). Supercapacitors are electrochemical capacitors that have an unusually high energy density when compared to common electrolytic capacitors, typically on the order of thousands of times greater than a high-capacity electrolytic capacitor. 
     The primary power source  340  may charge the secondary accumulator devices  342 . Once sufficiently charged, the primary power source  340  may be removed and the secondary accumulator devices  342  may be used to power the motor  65  during a procedure or operation. The accumulating devices  342  may take about fifteen to thirty minutes to charge in various circumstances. Supercapacitors have the characteristic they can charge and discharge extremely rapidly in comparison to conventional batteries. In addition, whereas batteries are good for only a limited number of charge/discharge cycles, supercapacitors can often be charged/discharged repeatedly, sometimes for tens of millions of cycles. For embodiments using supercapacitors as the secondary accumulator devices  342 , the supercapacitors may comprise carbon nanotubes, conductive polymers (e.g., polyacenes), or carbon aerogels. 
     As shown in  FIG.  14   , a charge management circuit  344  could be employed to determine when the secondary accumulator devices  342  are sufficiently charged. The charge management circuit  344  may include an indicator, such as one or more LEDs, an LCD display, etc., that is activated to alert a user of the instrument  10  when the secondary accumulator devices  342  are sufficiently charged. 
     The primary power source  340 , the secondary accumulator devices  342 , and the charge management circuit  344  may be part of a power pack in the pistol grip portion  26  of the handle  6  of the instrument  10 , or in another part of the instrument  10 . The power pack may be removable from the pistol grip portion  26 , in which case, when the instrument  10  is to be used for surgery, the power pack may be inserted aseptically into the pistol grip portion  26  (or other position in the instrument according to other embodiments) by, for example, a circulating nurse assisting in the surgery. After insertion of the power pack, the nurse could put the replaceable primary power source  340  in the power pack to charge up the secondary accumulator devices  342  a certain time period prior to use of the instrument  10 , such as thirty minutes. When the secondary accumulator devices  342  are charged, the charge management circuit  344  may indicate that the power pack is ready for use. At this point, the replaceable primary power source  340  may be removed. During the operation, the user of the instrument  10  may then activate the motor  65 , such as by activating the switch  314 , whereby the secondary accumulator devices  342  power the motor  65 . Thus, instead of having a number of disposable batteries to power the motor  65 , one disposable battery (as the primary power source  340 ) could be used in such an embodiment, and the secondary accumulator devices  342  could be reusable. In alternative embodiments, however, it should be noted that the secondary accumulator devices  342  could be non-rechargeable and/or non-reusable. The secondary accumulators  342  may be used with the cell selection switch  312  described above in connection with  FIG.  12   . 
     The charge management circuit  344  may also include indicators (e.g., LEDs or LCD display) that indicate how much charge remains in the secondary accumulator devices  342 . That way, the surgeon (or other user of the instrument  10 ) can see how much charge remains through the course of the procedure involving the instrument  10 . 
     The charge management circuit  344 , as shown in  FIG.  15   , may comprise a charge meter  345  for measuring the charge across the secondary accumulators  342 . The charge management circuit  344  also may comprise a non-volatile memory  346 , such as flash or ROM memory, and one or more processors  348 . The processor(s)  348  may be connected to the memory  346  to control the memory. In addition, the processor(s)  348  may be connected to the charge meter  345  to read the readings of and otherwise control the charge meter  345 . Additionally, the processor(s)  348  may control the LEDs or other output devices of the charge management circuit  344 . The processor(s)  348  can store parameters of the instrument  10  in the memory  346 . The parameters may include operating parameters of the instrument that are sensed by various sensors that may be installed or employed in the instrument  10 , such as, for example, the number of firings, the levels of forces involved, the distance of the compression gap between the opposing jaws of the end effector  12 , the amount of articulation, etc. Additionally, the parameters stored in the memory  346  may comprise ID values for various components of the instrument  10  that the charge management circuit  344  may read and store. The components having such IDs may be replaceable components, such as the staple cartridge  34 . The IDs may be for example, RFIDs that the charge management circuit  344  reads via a RFID transponder  350 . The RFID transponder  350  may read RFIDs from components of the instrument, such as the staple cartridge  34 , that include RFID tags. The ID values may be read, stored in the memory  346 , and compared by the processor  348  to a list of acceptable ID values stored in the memory  346  or another store associated with the charge management circuit, to determine, for example, if the removable/replaceable component associated with the read ID value is authentic and/or proper. According to various embodiments, if the processor  348  determines that the removable/replaceable component associated with the read ID value is not authentic, the charge management circuit  344  may prevent use of the power pack by the instrument  10 , such as by opening a switch (not shown) that would prevent power from the power pack being delivered to the motor  65 . According to various embodiments, various parameters that the processor  348  may evaluate to determine whether the component is authentic and/or proper include: date code; component model/type; manufacturer; regional information; and previous error codes. 
     The charge management circuit  344  may also comprise an i/o interface  352  for communicating with another device, such as described below. That way, the parameters stored in the memory  346  may be downloaded to another device. The i/o interface  352  may be, for example, a wired or wireless interface. 
     As mentioned before, the power pack may comprise the secondary accumulators  342 , the charge management circuit  344 , and/or the f/r switch  316 . According to various embodiments, as shown in  FIG.  16   , the power pack  299  could be connected to a charger base  362 , which may, among other things, charge the secondary accumulators  342  in the power pack. The charger base  362  could be connected to the power pack  299  by connecting aseptically the charger base  362  to the power pack  299  while the power pack is installed in the instrument  10 . In other embodiments where the power pack is removable, the charger base  362  could be connected to the power pack  299  by removing the power pack  299  from the instrument  10  and connecting it to the charger base  362 . For such embodiments, after the charger base  362  sufficiently charges the secondary accumulators  342 , the power pack  299  may be aseptically installed in the instrument  10 . 
     As shown in  FIG.  16   , the charger base  362  may comprise a power source  364  for charging the secondary accumulators  342 . The power source  364  of the charger base  362  may be, for example, a battery (or a number of series-connected batteries), or an AC/DC converter that converters AC power, such as from electrical power mains, to DC, or any other suitable power source for charging the secondary accumulators  342 . The charger base  362  may also comprise indicator devices, such as LEDs, a LCD display, etc., to show the charge status of the secondary accumulators  342 . 
     In addition, as shown in  FIG.  16   , the charger base  362  may comprise one or more processors  366 , one or more memory units  368 , and i/o interfaces  370 ,  372 . Through the first i/o interface  370 , the charger base  362  may communicate with the power pack  299  (via the power pack&#39;s i/o interface  352 ). That way, for example, data stored in the memory  346  of the power pack  299  may be downloaded to the memory  368  of the charger base  362 . In that way, the processor  366  can evaluate the ID values for the removable/replaceable components, downloaded from the charge management circuit  344 , to determine the authenticity and suitability of the components. The operating parameters downloaded from the charge management circuit  344  may also stored in the memory  368 , and then may then be downloaded to another computer device via the second i/o interface  372  for evaluation and analysis, such as by the hospital system in which the operation involving the instrument  10  is performed, by the office of the surgeon, by the distributor of the instrument, by the manufacturer of the instrument, etc. 
     The charger base  362  may also comprise a charge meter  374  for measuring the charge across the secondary accumulators  342 . The charge meter  374  may be in communication with the processor(s)  366 , so that the processor(s)  366  can determine in real-time the suitability of the power pack  299  for use to ensure high performance. 
     In another embodiment, as shown in  FIG.  17   , the battery circuit may comprise a power regulator  320  to control the power supplied by the power savers  310  to the motor  65 . The power regulator  320  may also be part of the power pack  299 , or it may be a separate component. As mentioned above, the motor  65  may be a brushed DC motor. The speed of brushed DC motors generally is proportional to the applied input voltage. The power regulator  320  may provide a highly regulated output voltage to the motor  65  so that the motor  65  will operate at a constant (or substantially constant) speed. According to various embodiments, the power regulator  320  may comprise a switch-mode power converter, such as a buck-boost converter, as shown in the example of  FIG.  17   . Such a buck-boost converter  320  may comprise a power switch  322 , such as a FET, a rectifier  324 , an inductor  326 , and a capacitor  328 . When the power switch  322  is on, the input voltage source (e.g., the power sources  310 ) is directly connected to the inductor  326 , which stores energy in this state. In this state, the capacitor  328  supplies energy to the output load (e.g., the motor  65 ). When the power switch  322  is in the off state, the inductor  326  is connected to the output load (e.g., the motor  65 ) and the capacitor  328 , so energy is transferred from the inductor  326  to the capacitor  328  and the load  65 . A control circuit  330  may control the power switch  322 . The control circuit  330  may employ digital and/or analog control loops. In addition, in other embodiments, the control circuit  330  may receive control information from a master controller (not shown) via a communication link, such as a serial or parallel digital data bus. The voltage set point for the output of the power regulator  320  may be set, for example, to one-half of the open circuit voltage, at which point the maximum power available from the source is available. 
     In other embodiments, different power converter topologies may be employed, including linear or switch-mode power converters. Other switch-mode topologies that may be employed include a flyback, forward, buck, boost, and SEPIC. The set point voltage for the power regulator  320  could be changed depending on how many of the battery cells are being used to power the motor  65 . Additionally, the power regulator  320  could be used with the secondary accumulator devices  342  shown in  FIG.  13   . Further, the forward-reverse switch  316  could be incorporated into the power regulator  320 , although it is shown separately in  FIG.  17   . 
     Batteries can typically be modeled as an ideal voltage source and a source resistance. For an ideal model, when the source and load resistance are matched, maximum power is transferred to the load.  FIG.  18    shows a typical power curve for a battery. When the battery circuit is open, the voltage across the battery is high (at its open circuit value) and the current drawn from the battery is zero. The power delivered from the battery is zero also. As more current is drawn from the battery, the voltage across the battery decreases. The power delivered by the battery is the product of the current and the voltage. The power reaches its peak around at a voltage level that is less than the open circuit voltage. As shown in  FIG.  18   , with most battery chemistries there is a sharp drop in the voltage/power at higher current because of the chemistry or positive temperature coefficient (PTC), or because of a battery protection device. 
     Particularly for embodiments using a battery (or batteries) to power the motor  65  during a procedure, the control circuit  330  can monitor the output voltage and control the set point of the regulator  320  so that the battery operates on the “left” or power-increasing side of the power curve. If the battery reaches the peak power level, the control circuit  330  can change (e.g., lower) the set point of the regulator so that less total power is being demanded from the battery. The motor  65  would then slow down. In this way, the demand from the power pack would rarely if ever exceed the peak available power so that a power-starving situation during a procedure could be avoided. 
     In addition, according to other embodiments, the power drawn from the battery may be optimized in such a way that the chemical reactions within the battery cells would have time to recover, to thereby optimize the current and power available from the battery. In pulsed loads, batteries typically provide more power at the beginning of the pulse that toward the end of the pulse. This is due to several factors, including: (1) the PTC may be changing its resistance during the pulse; (2) the temperature of the battery may be changing; and (3) the electrochemical reaction rate is changing due to electrolyte at the cathode being depleted and the rate of diffusion of the fresh electrolyte limits the reaction rate. According to various embodiments, the control circuit  330  may control the converter  320  so that it draws a lower current from the battery to allow the battery to recover before it is pulsed again. 
     According to other embodiments, the instrument  10  may comprise a clutch-type torque-limiting device. The clutch-type torque-limiting device may be located, for example, between the motor  65  and the bevel gear  68 , between the bevel gear  70  and the planetary gear assembly  72 , or on the output shaft of the planetary gear assembly  72 . According to various embodiments, the torque-limiting device may use an electromagnetic or permanent magnetic clutch. 
       FIGS.  19  to  22    show a sample electromagnetic clutch  400  that could be used in the instrument  10  according to various embodiments. The clutch  400  may comprise a horseshoe-shaped stator  402  having magnetic disks  404 ,  406  at each end. The first disk  404  may be connected to an axially movable, rotatable pole piece  408 , such as the output pole of the motor  65 . The second magnetic disk  406  may be connected to an axially stationary, rotatable pole piece  410 , such as an input pole to a gear box of the instrument  10 . In the views of  FIGS.  19  and  20   , the first pole piece  408  is axially pulled away from the second pole piece  410  by a clearance  412  such that the magnetic disks  404 ,  406  are not engaged. A wire coil (not shown), which may be wrapped around the stator  402  may be used to create the electromagnetic flux needed to actuate the clutch  400 . When the coil conducts an electrical current, the resulting magnetic flux may cause the two magnetic disks  404 ,  406  to attract, causing the first pole piece  408  to move axially toward the second pole piece  410 , thereby causing the two magnetic disks  404 ,  406  to become engaged, as shown in  FIGS.  21  and  22   , such that the two pole pieces  408 ,  410  will rotate together until the torque exceeds the friction torque generated between the faces of magnetic disks  404  and  406 . 
     The attractive force between the two disks  404 ,  406  and the corresponding torque capacity of the clutch  400  could be controlled by controlling the diameter of the disks  404 ,  406 , the coefficient of friction between the contacting faces of magnetic disks  404  and  406 , and by using magnetic materials for the disks  404 ,  406  that saturate at a known and controllable flux density. Therefore, even if there was an operating condition where more current was passed through the coil, the magnetic material of the disks  404 ,  406  would not generate a greater attractive force and subsequent limiting torque. 
     Utilization of such a clutch has many additional potential benefits. Being electrically controlled, the clutch  400  could be quickly deactivated by removing current from the wire to limit the amount of heat generated within the clutch  400  and within the motor  65 . By disconnecting the motor from the rest of the drive train, via the clutch  400 , most of the stored inertial energy in the drive train would be disconnected, limiting shock if the output were to be blocked suddenly. In addition, by being electrically controlled, some limited slipping could be designed-in to aid in reducing shocks when restarting the drive train under load. Further, because the magnetic saturation properties of one or more of the components (e.g., the magnetic disks  404 ,  406 ) within the clutch could be used to control the torque limit instead of coil current, the clutch  400  would be less sensitive to changes in system voltage. The torque limit in such embodiments would be primarily a function of the physical dimensions of the components of the clutch (e.g., the magnetic disks  404 ,  406 ) and would not require voltage regulators or other external components for proper operation. 
     In another embodiment, rather than using an electromagnetic clutch, the torque-limiting device may comprise a permanent magnet (not shown). The permanent magnet may be connected, for example, to the first, axially-movable, pole piece  408 , and attract the axially-fixed second pole piece  410 , or vice versa. In such embodiments, one of the disks  404 ,  406  could be made of a permanent magnet and the other one of a magnetic material like iron. In a slight variation, the stator  402  could be made in the form of a permanent magnet, causing the magnetic disks  404  and  406  to be attracted to each other. Because of the permanent magnet, the two disks  404 ,  406  would be engaged always. Using a permanent magnet would not provide as accurate as torque control as the electromagnetic clutch configuration described above, but it would have the advantages of: (1) not requiring controls or control logic to control the current through the coil; (2) being more compact that the electromagnetic clutch configuration; and (3) simplifying design of the instrument  10 . 
     As mentioned previously, the end effector  12  may emit RF energy to coagulate tissue clamped in the end effector. The RF energy may be transmitted between electrodes in the end effector  12 . A RF source (not shown), comprising, for example, an oscillator and an amplifier, among other components, which may supply the RF energy to the electrode, may be located in the instrument itself, such as in the handle  6  for a cordless instrument  10 , or the RF source may be external to the instrument  10 . The RF source may be activated as described further below. 
     According to various embodiments, the end effector  12  may comprise multiple sections (or segments) of electrodes. For example, as shown in the example of  FIG.  23   , the lower surface of the anvil  24  (i.e., the surface facing the staple cartridge  34 ) may comprise three co-linear RF segments. In this example, each segment has the same length (e.g., 20 mm), although in other embodiments there may be more or fewer segments, and the segments may have different lengths. In the example of  FIG.  23   , there are three pairs of active or “anode” terminals or electrodes  500  lined up longitudinally along each side of the channel length on the lower surface of the anvil  24 . In particular, in the illustrated embodiment there is a pair of distal electrodes  500   1 , a pair of middle electrodes  500   2 , and a pair of proximal electrodes  500   3  on each side of the knife channel  516 . The metallic outer portion or channel  22  of the end effector  12  or the metallic anvil  24  may serve as the counter-electrode (or cathode) for each of the three upper active electrodes (or anodes)  500 . The upper electrodes  500  may be coupled to the RF source. When energized, RF energy may propagate between the upper electrodes  500  and the counter electrode, coagulating tissue clamped between the electrodes. 
     The electrodes  500  may be energized simultaneously or in various orders, such as sequentially. For embodiments where the electrodes  500  are energized according to a sequence, the sequence may be automatic (controlled, for example, by a controller (not shown) in communication with the RF source) or by selection by the user. For example, the proximal electrodes  500   3  could be energized first; then the middle electrodes  500   2 ; then the distal electrodes  500   1 . That way, the operator (e.g., the operating surgeon) can selectively coagulate areas of the staple line. The electrodes in such an embodiment could be controlled by a multiplexer and/or a multiple output generator, as described further below. That way, the tissue under each electrode  500  could be treated individually according to the coagulation needs. Each electrode in the pair may be connected to the RF source so that they are energized at the same time. That is, for the distal pair of active electrodes  500   1 , each, being on opposite sides of the knife channel, may be energized by the RF source at the same time. Same for the middle pair of electrodes  500   2  and the proximal pair of electrodes  500   3 , although, in an embodiment where the electrode pairs are energized in sequence, the distal pair is not energized at the same time as the middle and proximal pairs, and so on. 
     Further, various electrical parameters, such as impedance, delivered power or energy, etc., could be monitored and the output to particular electrodes  500  could be modified to produce the most desirable tissue effect. Additionally, another advantage is in the case of a metal staple or other electrically conductive object left from a previous instrument firing or surgical procedure that may cause a short of the electrodes. Such a short situation could be detected by the generator and/or multiplexer, and the energy could be modulated in a manner appropriate for the short circuit. 
     In addition, energizing the electrodes  500  in sequence reduces the instantaneous power required from the RF source in comparison to a design that would has one set of electrodes as long as the combined length of the three segmented electrodes  500  shown in  FIG.  23   . For example, for electrode configurations as shown in the &#39;312 Patent, it has been demonstrated that it would require fifty to one-hundred watts to coagulate successfully forty-five mm lines on either side of the cut line. By using smaller active electrodes (e.g., the upper electrodes  500 ) that have less surface area than the larger return electrodes (e.g., the metallic anvil  24 ), the smaller active electrodes  500  can concentrate the therapeutic energy at the tissue while the larger, return electrode is used to complete the circuit with minimal impact on the tissue interface. In addition, the return electrode preferably has greater mass and thereby is able to stay cooler during electrosurgical application. 
     The electrodes  500  may be surrounded by an electrically insulating material  504 , which may comprise a ceramic material. 
       FIG.  24    shows another embodiment having segmented RF electrodes. In the embodiment shown in  FIG.  24   , there are four co-linear segmented electrodes  500   1-4  of equal length (15 mm in this example). Like the embodiment of  FIG.  23   , the electrodes  500  of  FIG.  24    could be energized simultaneously or sequentially. 
       FIG.  25    shows yet another embodiment, in which the segmented electrodes have different lengths. In the illustrated embodiment, there are four co-linear segmented electrodes, but the most distal electrodes  500   1 ,  500   2  are 10 mm in length, and the two proximate electrodes  500   3 ,  500   4  are 20 mm in length. Having short distal electrodes may provide the advantage of concentrating the therapeutic energy, as mentioned above. 
       FIG.  59    shows an embodiment having fifteen pairs of segmented RF electrodes  500  on a circuit board  570 , or other type of suitable substrate, on the lower surface of the anvil  24  (i.e., the surface facing the channel  22 ). The various electrode pairs are energized by the RF source (or generator)  574 . The multiplexer  576  may distribute the RF energy to the various electrode pairs as desired under the control of a controller  578 . According to various embodiments, the RF source  574 , the multiplexer  576 , and the controller  578  may be located in the handle  6  of the instrument. 
     In such an embodiment, the circuit board  570  may comprise multiple layers that provide electrical connections between the multiplexer  576  and the various electrode pairs. For example, as shown in  FIGS.  60  to  63   , the circuit board may comprise three layers  580   1-3 , each layer  580  providing connections to five of the electrode pairs. For example, the upper most layer  580   3  may provide connections to the most proximate five electrode pairs, as shown in  FIGS.  60  and  61   ; the middle layer  580   2  may provide connections to the middle five electrode pairs, as shown in  FIGS.  60  and  62   ; and the lowest layer  580   1  may provide connections to the most distal five electrode pairs, as shown in  FIGS.  60  and  63   . 
       FIG.  64    shows a cross-sectional end view of the anvil  24  according to such an embodiment. The circuit board  570 , adjacent to the staple pockets  584 , comprises three conducting layers  580   1-3 , having insulating layers  582   1-4  therebetween.  FIGS.  65  and  66    show how the various layers  580   1-3  may be stacked to connect back to the multiplexer  576  in the handle. 
     An advantage of having so many RF electrodes in the end effector  12 , as shown in  FIG.  67   , is that, in the case of a metal staple line  590  or other electrically conductive object left in the tissue  592  from a previous instrument firing or surgical procedure that may cause a short of the electrodes, such a short situation could be detected by the generator and multiplexer, and the energy could be modulated in a manner appropriate for the short circuit. 
       FIG.  27    shows another end effector  12  with RF electrodes. In this embodiment, the end effector  12  only comprises distal electrodes  500   1 , with the metallic anvil  24  serving as the return electrode. The distal electrodes  500   1  do not span the entire length of the anvil  24 , but only a fraction of the length. In the illustrated embodiment, distal electrodes  500   1  are only approximately 20 mm in length along a 60 mm anvil, so that the distal electrodes  500   1  only cover approximately the most distal ⅓ of the anvil length. In other embodiments, the distal electrodes  500   1  could cover the most distal 1/10 to ½ of the anvil length. Such embodiments could be used for spot coagulation, as described in U.S. Pat. No. 5,599,350, which is incorporated herein by reference. 
       FIG.  28    shows yet another embodiment of the end effector  12  with RF electrodes. In this embodiment, an active electrode  500  is positioned at the distal tip of the anvil  24 , insulated by the anvil  24  by an electrically non-conductive insulator  504 , which may be made of ceramic material. Such an embodiment may be used for spot coagulation. 
       FIGS.  29  to  32    illustrate other embodiments of the end effector  12  that may be useful for spot coagulation. In these embodiments, the anvil  24  comprises a pair of electrodes  500   1 ,  500   2  at the distal end of the anvil  24  and along a lateral side of the anvil  24 .  FIG.  29    is front-end view of the anvil  24  according to such an embodiment,  FIG.  30    is a side view,  FIG.  31    is an enlarged fragmentary front-end view, and  FIG.  32    is a top view. In such an embodiment, the metallic anvil  24  may act as the return electrode. The active electrodes  500   1 ,  500   2  may be insulated from the anvil  24  by electrically non-conductive insulators  504 , which may comprise ceramic material. 
       FIGS.  33  to  36    show an embodiment where the anvil  24  comprises two distal electrodes  500   1 ,  500   2  located at the top, center of the anvil  24 . Again, the metallic anvil  24  may act as the return electrode, and the active electrodes  500   1 ,  500   2  may be insulated from the anvil  24  by electrically non-conductive insulators  504 . 
       FIGS.  37  to  40    show an embodiment where one active electrode  500   1  (e.g., the active electrode) is positioned on the anvil  24 , and another active electrode  500   2  is positioned on the lower jaw  22 , and preferably on the cartridge  34 . The metallic anvil  24  may serve as the return electrode. The anvil electrode  500   1  is insulated from the anvil  24  by an insulator  504 . The electrode  500   2 , being positioned in the cartridge  34 , which is preferably made from a non-conductive material such as plastic, is insulated from the metallic channel  22  by the cartridge  34 . 
       FIGS.  41  to  44    show an embodiment where the anvil  24  has two active electrodes  500   1 ,  500   2  at the very most distal end of the anvil  24  that extend completely from the upper surface of the anvil  24  to the lower surface. Again, the metallic anvil  24  may act as the return electrode, and the active electrodes  500   1 ,  500   2  may be insulated from the anvil  24  by electrically non-conductive insulators  504 . 
       FIGS.  45  to  48    show an embodiment where the cartridge  34  has two active electrodes  500   1 ,  500   2  at the very most distal end of the staple cartridge  34 . In such an embodiment, the metallic anvil  24  or the metallic channel  22  may act as the return electrode. In this illustrated embodiment, the electrodes  500   1 ,  500   2  are connected to insulator inserts  503 , but in other embodiments, the insulator inserts  503  could be omitted and the plastic cartridge  34  may serve as the insulator for the electrodes  500   1 ,  500   2 . 
       FIGS.  49  to  52    show an embodiment having one active electrode  500   1  at the very most distal end of the anvil  24  and another active electrode  500   2  at the very most distal end of the cartridge  34 . Again, in such an embodiment, the metallic anvil  24  or the metallic channel  22  may act as the return electrode. In this illustrated embodiment, the electrode  500   2  is connected to insulator inserts  503 ,  505 , but in other embodiments, the insulator inserts  503 ,  505  could be omitted and the plastic cartridge  34  may serve as the insulator for the electrode  500   2 . 
       FIG.  57    is a side view and  FIG.  58    is a cross-sectional side of the handle  6  according to other embodiments of the present invention. The illustrated embodiment only includes one trigger, the closure trigger  18 . Activation of the knife, staple drivers, and/or RF electrodes in this embodiment may be achieved through means other than a separate firing trigger. For example, as shown in  FIG.  57   , actuation of the knife, staple drivers, and/or RF electrodes may be activated by a push-button switch  540  or other type of switch that is in a position that is convenient for the operator. In  FIG.  57   , the switch  540  is shown at the most proximate portion of the handle  6 . In another embodiment, the switch may be positioned near the distal end of the handle  6  so that pulling of the nozzle  539  activates the switch to cause actuation of the instrument. In such an embodiment, a switch (not shown) may be placed under or near the nozzle  539  so that movement of the nozzles toggles the switch. 
     Alternatively, actuation of the knife, staple drivers, and/or RF electrodes may be activated by voice or other sound commands detected by a microphone  542 . In other embodiments, the handle  6  may comprise a RF or sonic transceiver  541 , which may receive and/or transmit RF or sonic signals to activate the instrument. Also, as shown in  FIG.  58   , a foot pedal or switch  544  could be used to activate the instrument  10 . The foot pedal  544  may be connected to the handle  6  by a cord  545 . Also, the handle  6  may comprise a dial control  546  or some other suitable control device for controlling actuation of the segmented RF electrodes (see, for example,  FIGS.  23  and  24   ). Using such a control device  546 , the operator may serially activate the various pairs of RF electrodes  500  in the end effector  12 . 
     The instrument  10  shown in  FIGS.  57  and  58    also includes many feedback systems for the user. As mentioned above, the instrument  10  may comprise the speaker  543  for audibleizing commands or instructions to the operator. In addition, the handle  6  may comprise visual indicators  548 , such as LEDs or other light sources that provide visual feedback regarding actuation of the various segmented RF electrodes. For example, each of the visual indicators  548  could correspond to one of the segmented RF electrode pairs. The corresponding visual indicator  548  may be activated when the segmented RF electrode pair is activated. In addition, the handle  6  may comprise an alphanumeric display  550 , which may be an LED or LCD display, for example. The display  550  may be connected to a circuit board  552  inside the handle  6 . The handle  6  may also comprise a vibrator  554  in the pistol grip portion  26  that may provide vibrational feedback to the operator. For example, the vibrator  554  could vibrate each time that one of the segmented pairs of the RF electrodes in the end effector  12  is activated. 
       FIG.  26    is a cross-sectional view of the end effector  12  according to various embodiments where the electrodes are on the upper jaw (or anvil)  24 . In the illustrated embodiment, the active electrodes  500  are positioned adjacent the knife slot  516 . The metal anvil  24  may serve as the return electrode. Insulators  504 , which may be made of ceramic, insulate the electrodes  500  from the metallic anvil  24 . The embodiment of  FIG.  68    is similar to that of  FIG.  26   , except that electrodes  500  are made smaller, such that a portion of the insulators  504  can extend between the respective electrodes  500  and the edges of the knife channel  516 . 
       FIG.  53    is a cross-sectional end view of the end effector  12  according to another embodiment. In this embodiment, like the embodiment of  FIG.  26   , the active electrodes  500   1 ,  500   2  are on the anvil  24  on opposite sides of the knife channel. The electrodes  500   1 ,  500   2  are insulated from the metallic anvil by insulators  504 , which again preferably comprise ceramic material. In this embodiment, however, the insulators  504  are made very thin (compare with  FIG.  26   ). Making the insulators  504  very thin provides the potential advantage that the anvil  24  may include a relatively large metal section  520  above the electrodes  500 , thereby potentially supporting a slimmer anvil profile for a given anvil stiffness, or a stiffer profile for a given anvil cross-sectional dimension. The insulators  504  may be cast in or sputter coated onto the anvil  24 . 
       FIG.  54    illustrates another embodiment. In this embodiment, the active electrodes  500   1 ,  500   2  are sputter coated or bonded to the insulators  504 , which may also be sputter coated or bonded to the anvil  24 . Like the embodiment of  FIG.  53   , this design allows for more anvil material above the electrodes. In such an embodiment, the electrodes  500   1 ,  500   2  may comprise silver, which is a good conductor of electricity and has antimicrobial properties. 
       FIG.  55    shows a side view of the end effector according to another embodiment. In this embodiment, a thin film of electrically insulating material  530  is deposited on the face of the cartridge  34 . The insulating film  530  preferably comprises a heat- and arc-resistant material, such as ceramic. This would tend to increase the resistance of the cartridge  34  to arc-tracking and shorting, permitting more firings between changes of the cartridge  34 . In addition, if the cartridge  34  was a poor electrical conductor, it would support quicker heating of tissue and reduce the overall energy requirements. The active electrodes (not shown in  FIG.  55   ) may be in the anvil  24 , as described in embodiments above. 
       FIG.  56    shows an embodiment that is similar to that shown in  FIG.  55   , except that in  FIG.  56   , a thin layer  532  of slightly electrically conductive material is deposited on top of the insulating film  530 . The conductivity of the thin, slightly conductive layer  532  may be lower than the conductivity of the tissue clamped in the end effector  12  for treatment. As such, the thin, slightly conductive layer  532  would provide a reduced-conductivity path to provide additional heating of the clamped tissue. This would tend to reduce the time required to heat the tissue and achieve coagulation. 
     As described above, the instrument  10  may comprise an articulation pivot  14  for articulating the end effector  12 . 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 published U.S. Pat. No. 7,670,334, entitled SURGICAL INSTRUMENT HAVING AN ARTICULATING END EFFECTOR, which is incorporated herein by reference. In other embodiment, rather than a control device that is integrated with the instrument  10 , the end effector  12  may be articulated by a separate instrument, such as gripper, that is inserted into the patient so that its operative portion is near the end effector  12  so that it can articulate the end effector  12  as desired. The separate instrument may be inserted through a different opening as the end effector  12 , or through the same opening. Also, different operators can operate the separate instruments, or one person can operate both instruments, to articulate the end effector  12 . In another passive articulation scenario, the end effector  12  may be articulated by carefully pushing it against other parts of the patient to achieve the desired articulation. 
     In another embodiment, the end effector  12  may be connected to the handle by a flexible cable. In such an embodiment, the end effector  12  could be positioned as desired and held in position by use of another instrument, e.g., a separate gripper instrument. In addition, in other embodiments, the end effector  12  could be positioned by a separate instrument and clamped by a second separate instrument. In addition, the end effector  12  could be made sufficiently small, such as 8 to 9 mm wide by 10 to 11 mm tall, so that a pull-to-close mechanism could be used to clamp the end effector from the handle  6 . The pull-to-close mechanism could be adapted from that described in U.S. Pat. No. 5,562,701, entitled CABLE-ACTUATED JAW ASSEMBLY FOR SURGICAL INSTRUMENTS, which is incorporated herein by reference. The cable could be disposed in or along a flexible endoscope for use, for example, in upper or lower gastro-intestinal tract procedures. 
     In yet another embodiment, as shown in  FIGS.  69  and  70   , the instrument  10  may comprise a flexible neck assembly  732  enabling articulation of the end effector  12 . When an articulation transmission assembly  731  coupled to the shaft  8  is rotated, it may cause remote articulation of the flexible neck assembly  732 . The flexible neck assembly  732  may comprise first and second flexible neck portions  733 ,  734 , which receive first and second flexible band assemblies  735 ,  736 . Upon rotation of the articulation transmission assembly  731 , one of the first and second flexible transmission band assemblies  735 ,  736  is moved forwardly and the other band assembly is moved rearwardly. In response to the reciprocating movement of the band assemblies within the first and second flexible neck portions  733 ,  734  of the flexible neck assembly  732 , the flexible neck assembly  732  bends to provide articulation. A further description of the flexible neck is described in U.S. Pat. No. 5,704,534, which is incorporated herein by reference. 
     The devices disclosed herein can be designed to be disposed of after a single use, or they can be designed to be used multiple times. In either case, however, the device can be reconditioned for reuse after at least one use. Reconditioning can include any combination of the steps of disassembly of the device, followed by cleaning or replacement of particular pieces, and subsequent reassembly. In particular, the device can be disassembled, and any number of the particular pieces or parts of the device can be selectively replaced or removed in any combination. Upon cleaning and/or replacement of particular parts, the device can be reassembled for subsequent use either at a reconditioning facility, or by a surgical team immediately prior to a surgical procedure. Those skilled in the art will appreciate that reconditioning of a device can utilize a variety of techniques for disassembly, cleaning/replacement, and reassembly. Use of such techniques, and the resulting reconditioned device, are all within the scope of the present application. 
     Preferably, the various embodiments of the invention described herein will be processed before surgery. First, a new or used instrument is obtained and if necessary cleaned. The instrument can then be sterilized. In one sterilization technique, the instrument is placed in a closed and sealed container, such as a thermoformed plastic shell covered with a sheet of TYVEK. The container and instrument are then placed in a field of radiation that can penetrate the container, such as gamma radiation, x-rays, or high-energy electrons. The radiation kills bacteria on the instrument and in the container. The sterilized instrument can then be stored in the sterile container. The sealed container keeps the instrument sterile until it is opened in the medical facility. 
     It is preferred that the device is sterilized. This can be done by any number of ways known to those skilled in the art including beta or gamma radiation, ethylene oxide, steam and other methods. 
     While the present invention has been illustrated by description of several embodiments and while the illustrative embodiments have been described in considerable detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications may readily appear to those skilled in the art. The various embodiments of the present invention represent vast improvements over prior staple methods that require the use of different sizes of staples in a single cartridge to achieve staples that have differing formed (final) heights. 
     Accordingly, the present invention has been discussed in terms of endoscopic procedures and apparatus. However, use herein of terms such as “endoscopic” should not be construed to limit the present invention to a surgical stapling and severing instrument for use only in conjunction with an endoscopic tube (i.e., trocar). On the contrary, it is believed that the present invention may find use in any procedure where access is limited, including but not limited to laparoscopic procedures, as well as open procedures. Moreover, the unique and novel aspects of the various staple cartridge embodiments of the present invention may find utility when used in connection with other forms of stapling apparatuses without departing from the spirit and scope of the present invention.