Patent Publication Number: US-2023136300-A1

Title: Surgical stapler with removable power pack

Description:
This application claims priority from provisional application Ser. No. 62/962,388, filed Jan. 17, 2020 and, from provisional application Ser. No. 62/876,586, filed Jul. 19, 2019. The entire contents of each of these applications are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This application relates to surgical staplers and removable power packs loadable into the surgical staplers to effect firing of the staples. 
     2. Background 
     Surgical staplers are used in various medical applications where a device is needed to join and dissect anatomical tissue. However, there are drawbacks and costs associated with use of surgical staplers. Currently staplers are either fully disposable, reusable or partially reusable. Due to contamination during the surgical procedure, e.g., exposure to the patient&#39;s body fluids, the staplers are required to be sterilized after use, a time consuming and expensive process, with possible risks of infection if not properly sterilized as contaminants adhered to the surgical stapler from a previous use could be transferred to another patient. To avoid the risks of resterilization, some surgical staplers are disposed after use in the surgical procedure. These staplers can be reloaded to fire multiple cartridges of staples, but after the procedure, the staplers are discarded. However, the practice of using single use disposable surgical staplers is costly. 
     In certain procedures, high forces are required to fire the staples through tissue into contact with the anvil for formation. This is compounded when multiple rows of staples are fired either simultaneously or sequentially from the stapler. Therefore, powered staplers have been introduced to reduce the force requirements of the user. Such powered staplers have motor driven mechanisms (assemblies) to advance components within the stapler to fire the staples from the cartridge through tissue. Such powered staplers, if reusable, are subject to the same aforementioned costs and risk of resterilization. However they suffer from additional drawbacks since the sterilization process and/or heat or chemicals used in the sterilization process can damage the electronic components of the drive assemblies, which may shorten the lifespan of the surgical stapler or adversely affect its function if resterilization compromises the function of the motor or drive assembly. If the stapler is disposable, the stapler becomes more costly since the electronic components, which add to the cost of the stapler, are also discarded with the stapler. 
     It would be advantageous to provide a cost effective, efficient, simple to use and advanced assemblies for powering surgical instruments which overcome the drawbacks of manual actuation without suffering from the disadvantages of current power driven staplers. 
     Further, it would be advantageous to provide such surgical instruments which include systems to evaluate various parameters and functionalities to improve operation of the instruments and improve the surgical procedures and outcomes. 
     SUMMARY 
     The present invention overcomes the deficiencies and disadvantages of the prior art. The present invention advantageously provides surgical staplers that overcome the drawbacks discussed above by having a fully enclosed and removable power pack. The surgical staplers according to the present disclosure may be used multiple times without the need to sterilize the power pack between uses because the power pack is fully enclosed and sealed by the surgical stapler handle assembly or housing, thereby preventing contact between the power pack and the patient and/or patient&#39;s bodily fluids or the like. Thus, the surgical staplers of the present disclosure advantageously reduce the time, resources and/or costs for preparing the surgical stapler for its next use. The present disclosure also provides power packs that are cost effective, efficient and easily loadable into surgical staplers where they engage structure in the housing to effect varied functions of the stapler. 
     In accordance with one aspect of the present invention, a power pack removably loadable into a compartment of a surgical fastener applier is provided. The power pack has a) a first motor and b) a first drive mechanism having a first engagement member, the first drive mechanism operably connected to the motor and the first engagement member removably engageable with a firing mechanism of the surgical fastener applier when the power pack is loaded into the compartment to effect movement of the firing mechanism from a first position to the second position. A rotatable screw is rotatable by the motor to effect linear movement of the first engagement member and an encoder is positioned within the power pack to detect movement of the rotatable screw to determine a firing position of the firing mechanism. 
     In some embodiments, the encoder is mounted to the rotatable screw to detect a rotational position of the screw to determine the axial position of the first engagement member which in turn detects the axial position of the firing mechanism of the surgical stapler, the encoder rotatable with rotation of the rotatable screw and rotatable relative to a code wheel fixedly mounted within the power pack. 
     In other embodiments, the encoder is connected to the first drive mechanism and moves linearly with linear movement of the first drive mechanism to detect a linear position of the first drive mechanism to thereby detect a position of the firing mechanism. The encoder can be mounted to a collar of the first drive mechanism, the collar including a region forming the first engagement member. 
     In some embodiments, the power pack includes a second motor, a second rotatable screw operatively connected to and rotatable by the second motor and a second drive mechanism operatively connected to the second rotatable screw and having a second engagement member removably engageable with an articulating mechanism in the housing of the surgical fastener applier to effect movement of the articulation mechanism to effect articulation of first and second jaws of the surgical stapler from a linear position to an angled position. A second encoder is positioned within the power pack to detect movement of the second rotatable screw to determine an articulation position of the articulation mechanism. 
     In accordance with another aspect of the present invention, a surgical fastener applier is provided comprising a housing containing a compartment therein, an elongated member extending distally from the housing, and a first jaw and a second jaw at a distal portion of the elongated member, at least the first jaw movable with respect to the second jaw to clamp tissue between the first and second jaws. A firing mechanism is positioned within the housing, the firing mechanism movable between a first position and a second position, wherein movement to the second position effects firing of fasteners into the tissue clamped between the first and second jaws. A power pack is removably loadable into the compartment, the power pack having a) a first motor and a first engagement member removably engageable with the firing mechanism when the power pack is loaded into the compartment to effect movement of the firing mechanism from the first position to the second position; and b) a second motor and a second engagement member removably engageable with an articulating mechanism in the housing of the surgical fastener applier to effect movement of an articulation mechanism to effect articulation of the first and second jaws from a linear position to a position angled with respect to a longitudinal axis of the elongated member. A firing position is determined based on a first motor count of the first motor and an articulation position is determined based on a second motor count of the second motor. 
     In some embodiments, an encoder communicates the motor counts to a microprocessor within the power pack for adjustment of a motor speed. In some embodiments, a predetermined time for completion of a firing stroke of the firing mechanism is preset. In some embodiments, if an amperage of the first motor increases above a predetermined threshold, a speed of the motor is slowed and the present time is adjusted accordingly. 
     In accordance with another aspect of the present invention, a power pack removably loadable into a compartment of a surgical fastener applier is provided. The power pack has a first motor and a first engagement member removably engageable with a firing mechanism within the housing of the surgical fastener applier when the power pack is loaded into the compartment, the first engagement member movable axially in response to rotation of a first screw operatively connected to the first motor. At least one thrust bearing limits axial movement of the first screw. Linear movement of the first engagement member effects movement of the firing mechanism from the first position to the second position. A first load cell is engageable by the bearing to measure a force during firing. 
     In some embodiments, the power pack includes a second motor and a second engagement member removably engageable with an articulation mechanism within the housing when the power pack is loaded into the compartment, the second engagement member movable axially in response to rotation of a second screw operatively connected to the second motor, wherein linear movement of the second engagement member effects movement of the articulation mechanism to effect articulation of the first and second jaws and at least one bearing limits axial movement of the second screw. A second load cell is engageable by the bearing to measure an articulation force. 
     In accordance with another aspect of the present invention, a surgical fastener applier is provided comprising:
         a housing containing a compartment therein, the compartment having an openable cover to provide access to the compartment for removably loading a power pack having a motor;   an elongated member extending distally from the housing;   a first jaw and a second jaw adjacent a distal portion of the elongated member, at least the first jaw movable with respect to the second jaw to clamp tissue between the first and second jaws; and   a fastener firing mechanism positioned within the housing, the firing mechanism movable by the motor of the power pack loaded into the compartment, the firing mechanism movable between a first position and a second position, wherein in the second position, the firing mechanism effects firing of fasteners into the tissue clamped between the first and second jaws;   wherein the motor of the power pack received in the compartment is not actuable unless the cover is closed.       

     In some embodiments, the cover includes a member movable into contact with an activation switch in the power pack when the cover is closed. In some embodiments, the power pack has a printed circuit board in communication with the switch. 
     In accordance with another aspect of the present invention, a surgical fastener applier is provided comprising:
         a housing containing a compartment therein, the compartment having an openable cover to provide access to the compartment for removably loading a power pack having a motor;   an elongated member extending distally from the housing;   a first jaw and a second jaw adjacent a distal portion of the elongated member, at least the first jaw movable with respect to the second jaw to clamp tissue between the first and second jaws;   a fastener firing mechanism positioned within the housing, the firing mechanism movable by the motor of the power pack loaded into the compartment, the firing mechanism movable between a first position and a second position, wherein in the second position, the firing mechanism effects firing of fasteners into the tissue clamped between the first and second jaws; and   a power pack having an reader, such as an RFID reader, for detecting a type of staple cartridge prior to loading the staple cartridge in the instrument, the staple cartridge having an a code or tag, such as an RFID tag.       

     In some embodiments, the power pack presets the motor to correspond to the type of staple cartridge detected. The type of staple cartridge detected can be a length of a linear array of staples within the cartridge and/or a size of the staples within the cartridge. 
     In some embodiments, a motor in the power pack for firing staples cannot be actuated if the reader detects the staple cartridge has already been fired. 
     In some embodiments, the surgical fastener applier has a window adjacent the housing exhibiting a desired clamp force dependent on the type of cartridge and/or the type of cartridge selected. 
     In accordance with another aspect of the present invention, a surgical fastener applier is provided comprising:
         a housing containing a compartment therein, the compartment having an openable cover to provide access to the compartment for removably loading a power pack having a motor, a first switch and a second switch;   an elongated member extending distally from the housing;   a first jaw and a second jaw adjacent a distal portion of the elongated member, at least the first jaw movable with respect to the second jaw to clamp tissue between the first and second jaws;   a fastener firing mechanism positioned within the housing, the firing mechanism movable by the first motor of the power pack loaded into the compartment, the firing mechanism movable between a first position and a second position, wherein in the second position, the firing mechanism effects firing of fasteners into the tissue clamped between the first and second jaws, the firing mechanism actuated by the first switch; and   an articulation mechanism movable between a first position to a second position to angle the first and second jaws to an angled position with respect to a longitudinal axis of the elongated member, the articulation mechanism actuated by a second switch;   wherein the first switch cannot be activated if the second switch is activated and the second switch cannot be activated if the first switch is activated.       

     In some embodiments, the power pack has a first drive mechanism engageable with the firing mechanism, and the power pack cannot be removed from the compartment if the first drive mechanism in not in a home position. In some embodiments, the power pack has a second drive mechanism engageable with the articulation mechanism, and the power pack cannot be removed from the compartment if the articulation mechanism in not in a home position. 
     In some embodiments, opening of the jaws disables a firing mode. In some embodiments, closing of the jaws disables an articulation mode. 
     In accordance with another aspect of the present disclosure, a surgical fastener applier is provided comprising:
         a housing containing a compartment therein;   an elongated member extending distally from the housing;   a first jaw and a second jaw at a distal portion of the elongated member, at least the first jaw movable with respect to the second jaw to clamp tissue between the first and second jaws;   a firing mechanism positioned within the housing, the firing mechanism movable between a first position and a second position, wherein movement to the second position effects firing of fasteners into the tissue clamped between the first and second jaws; and   a power pack removably loadable into the compartment, the power pack having a) a first motor and a first engagement member removably engageable with the firing mechanism when the power pack is loaded into the compartment to effect movement of the firing mechanism from the first position to the second position, the first engagement having a home position and an advanced position; and b) a second motor and a second engagement member removably engageable with an articulating mechanism in the housing of the surgical fastener applier to effect movement of an articulation mechanism to effect articulation of the first and second jaws from a linear position to a position angled with respect to a longitudinal axis of the elongated member, the second engagement member having a home position and an advanced position, wherein the power pack can be loaded into the compartment only if the first and second engagements are in the home position.       

     In some embodiments, the power pack can be removed from the compartment only if the first and second engagement members are in the home position. 
     In some embodiments, neither a firing switch nor an articulation switch can be activated if the cover is not in the closed position. 
     In accordance with another aspect of the present invention, a method for powering a surgical stapler is provided comprising:
         a) providing a surgical stapler having first and second jaws, an elongated shaft and a housing containing a compartment;   b) loading a reusable power pack into a homing cradle so an articulation mechanism and a firing mechanism within the power pack are in a home position, the power pack having a first motor for firing staples and a second motor for articulation of the jaws; and   c) after step (b) removing the power pack from the homing cradle and placing the power pack into the compartment of the housing; and   d) wherein the powertrain cannot be loaded into the compartment if the articulation mechanism and the firing mechanism are not in the home position.       

     In some embodiments, the firing mode cannot be effected if a cover of the compartment is not in the closed position. In some embodiments, the power pack cannot be removed from the compartment if the articulation mechanism and the firing mechanism are not in the home position. In some embodiments, a switch for actuating the firing mechanism cannot be actuated if a switch for the articulation mechanism is activated. In some embodiments, a switch for actuating the articulation mechanism cannot be actuated if a switch for the firing mechanism is activated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that those having ordinary skill in the art to which the subject invention appertains will more readily understand how to make and use the surgical apparatus disclosed herein, preferred embodiments thereof will be described in detail hereinbelow with reference to the drawings, wherein: 
         FIG.  1    is a perspective view of a first embodiment of the surgical stapler of the present disclosure having a removable power pack; 
         FIG.  2 A  is a side view of the surgical stapler of  FIG.  1   ; 
         FIG.  2 B  is a bottom view of the surgical stapler of  FIG.  1   ; 
         FIG.  2 C  is a front view of the surgical stapler of  FIG.  1 A : 
         FIG.  3 A  is a perspective view of the surgical stapler of  FIG.  1    showing the handle compartment cover in the open position and further showing the power pack prior to insertion into the handle compartment; 
         FIG.  3 B  is front view of the surgical stapler of  FIG.  3 A  showing the handle compartment cover in the open position; 
         FIG.  3 C  is a front view of the power pack of  FIG.  3 A ; 
         FIG.  3 D  is a top perspective view of the surgical staple of  FIG.  3 A  showing the compartment for receiving the power pack; 
         FIG.  4 A  is a top view of the motor and drive mechanism (assembly) of the power pack of  FIG.  3 A ; 
         FIG.  4 B  is a side view of the motor and drive mechanism of the power pack of  FIG.  4 A ; 
         FIG.  4 C  is a top view of the power pack of  FIG.  3 A ; 
         FIG.  4 D  is a side view of the motor and drive mechanism of  FIG.  4 A  shown engaged with the rod of the firing assembly of the surgical stapler of  FIG.  1   ; 
         FIG.  4 E  is a perspective view of the motor and drive mechanism of the power pack of  FIG.  3 A ; 
         FIG.  4 F  is a cross-sectional view taken along line AY-AY of  FIG.  4 C  showing the power pack engaging the firing rod of the surgical stapler of  FIG.  1   ; 
         FIG.  4 G  is a side view of the power pack of  FIG.  3 A ; 
         FIG.  4 H  is a cross-sectional view taken along line AT-AT of  FIG.  4 G ; 
         FIG.  4 I  is a top view of the surgical stapler of  FIG.  1   ; 
         FIG.  5 A  is a schematic view illustrating transition from rotational movement to linear movement to effect a function of the surgical stapler; 
         FIG.  5 B  is a schematic view of an alternate embodiment illustrating transition from rotational movement to linear movement to rotational movement to effect a function of the surgical stapler; 
         FIG.  6 A  is a side view of the surgical stapler of  FIG.  1    showing the handle compartment cover in the open position and further showing the power pack in the process of being inserted in the compartment of the handle; 
         FIG.  6 B  is a bottom view of the surgical stapler of  FIG.  6 A ; 
         FIG.  6 C  is a cross-sectional view taken along line A-A of  FIG.  6 B ; 
         FIG.  6 D  is a close up view of the area of detail AR of  FIG.  6 C ; 
         FIG.  7 A  is a top view of the surgical stapler of  FIG.  1    with the power pack fully inserted into the compartment in the handle and the cover in the closed position; 
         FIG.  7 B  is a cross-sectional view taken along line A-A of  FIG.  7 A ; 
         FIG.  7 C  is a close up view of the area of detail B of  FIG.  7 B  showing the firing mechanism at the distal end for firing staples; 
         FIG.  8 A  is a top view of the surgical stapler of  FIG.  1    showing the power pack fully inserted and the cover of the handle compartment in the closed position, the view the same as  FIG.  7 A  but having section line E-E; 
         FIG.  8 B  is a cross-sectional view taken along line E-E of  FIG.  8 A , the view being the same as  FIG.  7 B  but having section lines F-F and identified area of detail B; 
         FIG.  8 C  is a side view of the surgical stapler of  FIG.  1    showing the power pack fully inserted in the handle compartment and the compartment cover closed; 
         FIG.  8 D  is a cross-sectional view taken along line J-J of  FIG.  8 C ; 
         FIG.  9    is a cross-sectional view taken along line F-F of  FIG.  8 B ; 
         FIG.  10    is a close up view of the area of detail G of  FIG.  8 B ; 
         FIG.  11    is a close up view of the area of detail H of  FIG.  9   ; 
         FIG.  12    is a close up view of the detail K of  FIG.  8 D ; 
         FIG.  13 A  is a side view of an alternate embodiment of the surgical stapler showing the power pack of  FIG.  3 A  prior to insertion into the handle compartment; 
         FIG.  13 B  is a side view similar to  FIG.  13 A  showing the power pack of  FIG.  3 A  inserted into the handle compartment; 
         FIG.  13 C  is a side view of another alternate embodiment of the surgical stapler showing the power pack of  FIG.  3 A  prior to insertion into the handle compartment; 
         FIG.  13 D  is a side view similar to  FIG.  13 C  showing the power pack of  FIG.  3 A  inserted into the handle compartment; 
         FIG.  14 A  is a side view illustrating an alternate embodiment having a power pack for effecting both firing and articulation of the surgical stapler, the power pack shown fully inserted into the compartment of the handle of the surgical stapler and the compartment cover shown in the closed position; 
         FIG.  14 B  is a top view of the surgical stapler of  FIG.  14 A ; 
         FIG.  14 C  is a cross-sectional view taken along line C-C  FIG.  14 B ; 
         FIG.  14 D  is a side view of the surgical stapler of  FIG.  14 A , the view being the same as  FIG.  14 A  but having section line M-M; 
         FIG.  14 E  is cross-sectional view taken along line M-M of  FIG.  14 D ; 
         FIG.  14 F  is a cross-sectional view taken along line N-N of  FIG.  14 D ; 
         FIG.  15 A  is a close up view of the area of detail D of  FIG.  14 C ; 
         FIG.  15 B  is a close up view of the area of detail O of  FIG.  14 E : 
         FIG.  15 C  is a top view of the power pack of  FIG.  14 A  for effecting both firing and articulation of the surgical stapler; 
         FIG.  15 D  is a cross-sectional view taken along line AW-AW of  FIG.  15 C ; 
         FIG.  15 E  is a side view of the power pack of  FIG.  14 A ; 
         FIG.  15 F  is a cross-sectional view taken along line AT-AT of  FIG.  15 E ; 
         FIG.  16 A  is a top view of the surgical stapler of  FIG.  14 A , the view being the same as  FIG.  14 B  but having section line E-E; 
         FIG.  16 B  is a side view of the surgical stapler of  FIG.  14 A , the view being the same as  FIG.  14 C  but having section line F-F and identified area of detail G; 
         FIG.  16 C  is a cross-sectional view taken along line F-F of  FIG.  15 C ; 
         FIG.  16 D  is a close up view of the area of detail H of  FIG.  16 C ; 
         FIG.  17    is a side view of the surgical stapler of  FIG.  14 A , the view being the same as  FIG.  14 A  but having section line J-J; 
         FIG.  18 A  is a cross-sectional view taken along line J-J of  FIG.  17   ; 
         FIG.  18 B  is a close up view of the area of detail BA of  FIG.  18 A ; 
         FIG.  19 A  is a top cutaway view of the power pack of  FIG.  14 A ; 
         FIG.  19 B  is an enlarged view of the area of detail AK of  FIG.  19 A ; 
         FIG.  19 C  is an enlarged view of the area of detail AL of  FIG.  19 A ; 
         FIG.  20    is a cross-sectional side view of the surgical stapler of  FIG.  14 A , the view being the same as  FIG.  14 C  but having identified areas of detail Q, R and S; 
         FIG.  21 A  is an enlarged view of the area of detail Q of  FIG.  20   ; 
         FIG.  21 B  is an enlarged view of the area of detail R of  FIG.  19 A ; 
         FIG.  21 C  is an enlarged view of the area of detail S of  FIG.  19 A ; 
         FIG.  22 A  is a top view of the motor and drive mechanism (assembly) of the power pack of  FIG.  14 A  for effecting staple firing and articulation; 
         FIG.  22 B  is a side view of the motor and drive mechanism of the power pack of  FIG.  14 A ; 
         FIG.  22 C  is a side view of the motor and drive mechanism of  FIG.  14 A  shown engaged with the articulation rod of the articulation assembly of the surgical stapler of  FIG.  14 A ; 
         FIG.  22 D  is a perspective view of the motor and drive mechanism (assembly) of the power pack of  FIG.  14 A ; 
         FIG.  23 A  is a cross-sectional side view of the surgical stapler of  FIG.  14 A , the view being the same as  FIG.  18 A  but having and identified area of detail AU; 
         FIG.  23 B  is an enlarged view of the area of detail AU of  FIG.  23 A ; 
         FIG.  24 A  is a top view of the motor and drive mechanism (assembly) of the power pack of an alternate embodiment having a belt drive; 
         FIG.  24 B  is a side view of the motor and drive mechanism of  FIG.  24 A ; 
         FIG.  24 C  is a perspective view of the motor and drive mechanism of  FIG.  24 A ; 
         FIG.  24 D  is a front view of the motor and drive mechanism of  FIG.  24 A ; 
         FIG.  25 A  is a top view of the motor and drive mechanism (assembly) of the power pack of an another alternate embodiment having a belt drive; 
         FIG.  25 B  is a side view of the motor and drive mechanism of  FIG.  25 A ; 
         FIG.  25 C  is a perspective view of the motor and drive mechanism of  FIG.  25 A ; 
         FIG.  25 D  is a front view of the motor and drive mechanism of  FIG.  25 A ; 
         FIG.  26 A  is a top view of the motor and drive mechanism (assembly) of the power pack of another alternate embodiment having a belt drive; 
         FIG.  26 B  is a side view of the motor and drive mechanism of  FIG.  26 A ; 
         FIG.  26 C  is a perspective view of the motor and drive mechanism of  FIG.  26 A ; 
         FIG.  26 D  is a front view of the motor and drive mechanism of  FIG.  26 A ; 
         FIG.  27 A  is a top view of the motor and drive mechanism (assembly) of the power pack of an alternate embodiment having a belt drive; 
         FIG.  27 B  is a side view of the motor and drive mechanism of  FIG.  27 A ; 
         FIG.  27 C  is a perspective view of the motor and drive mechanism of  FIG.  27 A ; 
         FIG.  27 D  is a front view of the motor and drive mechanism of  FIG.  27 A ; 
         FIG.  27 E  is a view similar to  FIG.  27 B  showing engagement with the stapler firing rod; 
         FIG.  28 A  is a top view of an alternate embodiment of the surgical instrument containing the power pack of  FIG.  3 A  within the handle compartment, the surgical instrument being a circular stapler; 
         FIG.  28 B  is a side view of the circular stapler of  FIG.  28 A ; 
         FIG.  28 C  is a perspective view of the circular stapler of  FIG.  28 A ; 
         FIG.  28 D  is a front view of the circular stapler of  FIG.  28 A ; 
         FIG.  29 A  is a top view of an alternate embodiment of the surgical instrument containing the power pack of  FIG.  3 A  within the handle compartment, the surgical instrument being an open surgery linear stapler; 
         FIG.  29 B  is a side view of the linear stapler of  FIG.  29 A ; 
         FIG.  29 C  is a perspective view of the linear stapler of  FIG.  29 A ; 
         FIG.  29 D  is a front view of the linear stapler of  FIG.  29 A ; 
         FIG.  30 A  is a top view of an alternate embodiment of the surgical instrument containing the power pack of  FIG.  3 A  within the handle compartment, the surgical instrument being a flexible endoscopic linear stapler; 
         FIG.  30 B  is a side view of the linear stapler of  FIG.  30 A ; 
         FIG.  30 C  is a perspective view of the linear stapler of  FIG.  30 A ; 
         FIG.  30 D  is a front view of the linear stapler of  FIG.  30 A ; 
         FIG.  31 A  is a top view of an alternate embodiment of the surgical instrument containing the power pack of  FIG.  3 A  within the handle compartment, the surgical instrument being an endoscopic clip applier; 
         FIG.  31 B  is a side view of the clip applier of  FIG.  31 A ; 
         FIG.  31 C  is a perspective view of the clip applier of  FIG.  31 A ; 
         FIG.  31 D  is a front view of the clip applier of  FIG.  31 A ; 
         FIG.  32 A  is a top view of an alternate embodiment of the surgical instrument containing the power pack of  FIG.  3 A  within the handle compartment, the surgical instrument being an endoscopic grasper; 
         FIG.  32 B  is a side view of the endoscopic grasper of  FIG.  32 A ; 
         FIG.  32 C  is a perspective view of the endoscopic grasper of  FIG.  32 A ; 
         FIG.  32 D  is a front view of the endoscopic grasper of  FIG.  32 A ; 
         FIG.  33 A  is a top view of an alternate embodiment of the surgical instrument containing the power pack of  FIG.  3 A  within the handle compartment, the surgical instrument being an endoscopic scissor; 
         FIG.  33 B  is a side view of the endoscopic scissor of  FIG.  33 A ; 
         FIG.  33 C  is a perspective view of the endoscopic scissor of  FIG.  33 A ; 
         FIG.  33 D  is a front view of the endoscopic scissor of  FIG.  33 A ; 
         FIG.  34 A  is a top view of an alternate embodiment of the surgical instrument containing the power pack of  FIG.  3 A  within the handle compartment, the surgical instrument being a fastener applier; 
         FIG.  34 B  is a side view of the fastener applier of  FIG.  34 A ; 
         FIG.  34 C  is a perspective view of the fastener applier of  FIG.  34 A ; 
         FIG.  34 D  is a front view of the fastener applier of  FIG.  34 A ; 
         FIG.  35    is a perspective view of an alternate embodiment of the surgical instrument of the present invention having a replaceable battery pack; 
         FIG.  36    is a perspective view of another alternate embodiment of the surgical instrument of the present invention having a replaceable battery pack; 
         FIG.  37 A  is a perspective view of another alternate embodiment of the surgical instrument of the present invention having a replaceable battery pack; 
         FIG.  37 B  is a side view of the surgical instrument of  FIG.  37 A ; 
         FIG.  37 C  is a perspective view of the surgical instrument of  FIG.  37 A  showing the power pack and battery pack within the compartment of the surgical instrument; 
         FIG.  38    is a concept diagram of readying the power train for use in accordance with one embodiment of the present invention; 
         FIG.  39    is a concept diagram illustrating the relationship between instrument jaw position and articulation and firing enabling; 
         FIGS.  40 A,  40 B and  40 C  shown the steps of use of the instrument of the present invention; 
         FIG.  41 A  is a side view of one embodiment of the handle portion of the surgical instrument of the present invention illustrating the clamping handle in the open position so the firing switch cannot be activated; 
         FIG.  41 B  is a side view of the clamping handle in the closed position so the firing switch can be activated; 
         FIGS.  42 A- 43 C  illustrate alternate embodiments of the surgical instrument of the present invention having measurement devices to provide feedback, wherein: 
         FIG.  42 A  is a side view of the surgical instrument; 
         FIG.  42 B  is a perspective view of the surgical instrument; 
         FIG.  42 C  is a top view of the surgical instrument; 
         FIG.  42 D  is a cross-sectional view taken along line A-A of  FIG.  42 C ; 
         FIG.  42 E  is an enlarged view of the area of detail B of  FIG.  42 D ; 
         FIG.  42 F  is an enlarged view of the area of detail C of  FIG.  42 D ; 
         FIG.  43 A  is a cross-sectional view identical to the cross-sectional view of  FIG.  42 D  illustrated to identify the areas of detail E and F; 
         FIG.  43 B  is an enlarged view of the area of detail E of  FIG.  43 A ; 
         FIG.  43 C  is an enlarged view of the area of detail F of  FIG.  43 A ; 
         FIG.  44 A  is a cross-sectional view identical to the cross-sectional view of  FIG.  42 D  illustrated to identify the areas of detail H and I; 
         FIG.  44 B  is an enlarged view of the area of detail I of  FIG.  44 A ; 
         FIG.  44 C  is an enlarged view of the area of detail H of  FIG.  44 A ; 
         FIGS.  45 A- 45 F  illustrate an alternate embodiment of the surgical instrument of the present invention having a feedback feature (measurement device) in the power pack, wherein: 
         FIG.  45 A  is a top view of the surgical instrument with the power pack being loaded into the instrument; 
         FIG.  45 B  is a cross-sectional view taken along line J-J of  FIG.  45 A  showing the power pack being loaded into the instrument; 
         FIG.  45 C  is an enlarged view of the area of detail K of  FIG.  45 B ; 
         FIG.  45 D  is a top view of the surgical instrument with the power pack loaded into the instrument; 
         FIG.  45 E  is a cross-sectional view taken along line L-L of  FIG.  45 A  showing the power pack in the instrument; 
         FIG.  45 F  is an enlarged view of the area of detail M of  FIG.  45 E ; 
         FIG.  46    is a perspective view of components within the handle assembly in accordance with an alternate embodiment; 
         FIG.  47    is a perspective view of the components of  FIG.  46    (with the handle housing removed); 
         FIG.  48    is a sectional view of the components of  FIG.  46    (with the handle housing removed); 
         FIG.  49    is an enlarged side view illustrating a cam slot arrangement for closing the jaws of the instrument, the cartridge jaw shown in the open (unclamped) position; 
         FIG.  49    is top view of the jaw assembly; 
         FIG.  50    is a cross-sectional view taken along line K-K of  FIG.  49    showing the cartridge jaw in the open unclamped position; 
         FIG.  51    is an enlarged view of the area of detail designated in  FIG.  50   ; 
         FIG.  52    is a block diagram depicting various measurement devices; 
         FIG.  53    is a flow chart depicting utilization of a dummy cartridge to measurement; 
         FIG.  54    is a flow chart depicting motor speed adjustment based on measurements. 
         FIG.  55    is a perspective view of an alternate embodiment of the power pack of the present invention; 
         FIG.  56    is a top view of the power pack of  FIG.  55   ; 
         FIG.  57 A  is a cross-sectional view taken along line A-A of  FIG.  56   ; 
         FIG.  57 B  is an enlarged view of the area of detail B of  FIG.  57 A ; 
         FIG.  57 C  is an enlarged view of the area of detail C of  FIG.  57 A ; 
         FIG.  58    is a perspective of the deployment (firing) screw assembly of the power pack of  FIG.  55   ; 
         FIG.  59    is a side view of the assembly of  FIG.  58   ; 
         FIG.  60 A  is an enlarged view of the area of detail D of  FIG.  59   ; 
         FIG.  60 B  is a cross-sectional view taken along line E-E of  FIG.  60 A ; 
         FIG.  61 A  is an enlarged view of the area of detail F of  FIG.  59   ; 
         FIG.  61 B  is a cross-sectional view taken along line G-G of  FIG.  61 A ; 
         FIG.  62 A  is a cross-sectional view taken along line H-H of  FIG.  56   ; 
         FIG.  62 B  is an enlarged view of the area of detail I of  FIG.  62 A ; 
         FIG.  62 C  is an enlarged view of the area of detail K of  FIG.  62 A ; 
         FIG.  63    is a perspective of the articulation screw assembly of the power pack of  FIG.  55   ; 
         FIG.  64    is a side view of the assembly of  FIG.  63   ; 
         FIG.  65 A  is an enlarged view of the area of detail L of  FIG.  64   ; 
         FIG.  65 B  is a cross-sectional view taken along line M-M of  FIG.  65 A ; 
         FIG.  66 A  is an enlarged view of the area of detail N of  FIG.  64   ; 
         FIG.  66 B  is a cross-sectional view taken along line O-O of  FIG.  66 A ; 
         FIG.  67    is side view of the power pack in accordance with an alternate embodiment of the present invention having an encoder; 
         FIG.  68    is an exploded view of the deployment screw assembly and encoder of the power pack of  FIG.  67   ; 
         FIG.  69 A  is a cross-sectional view taken along line P-P of  FIG.  68   ; 
         FIG.  69 B  is an enlarged view of the area of detail Q of  FIG.  69 A ; 
         FIG.  69 C  is a cross-sectional view taken along line R-R of  FIG.  69 A ; 
         FIG.  69 D  is an enlarged view of the area of detail S of  FIG.  69 C ; 
         FIG.  70    is a perspective view of the deployment screw assembly and encoder of the power pack of  FIG.  67   ; 
         FIG.  71    is an enlarged view of the area of detail BK of  FIG.  70   ; 
         FIG.  72    is a side view of the power pack of  FIG.  67    showing section line T-T; 
         FIG.  73 A  is a cross-sectional view taken along line T-T of  FIG.  72   ; 
         FIG.  73 B  is an enlarged view of the area of detail V of  FIG.  73 A ; 
         FIG.  74    is side view of the power pack of an alternate embodiment of the present invention having an encoder; 
         FIG.  75    is a cross-sectional view taken along line W-W of  FIG.  74   ; 
         FIG.  76 A  is a cross-sectional view taken along line Y-Y of  FIG.  74   ; 
         FIG.  76 B  is an enlarged view of the area of detail X of  FIG.  75   ; 
         FIG.  76 C  is an enlarged view of the area of detail Z of  FIG.  76 A ; 
         FIG.  77    is a perspective view of an alternate embodiment of the surgical instrument of the present invention having a cover to activate a switch of the power pack, the cover shown in an open position; 
         FIG.  78    is an enlarged view of the area of detail CB of  FIG.  77   ; 
         FIG.  79    is a top perspective view of the instrument of  FIG.  77   ; 
         FIG.  80    is an enlarged view of the area of detail CG of  FIG.  79   ; 
         FIG.  81    is a side view of the surgical instrument of  FIG.  77   ; 
         FIG.  82 A  is a rear view of the surgical instrument of  FIG.  81   ; 
         FIG.  82 B  is a cross-sectional view taken along line CD-CD of  FIG.  81   ; and 
         FIG.  83    illustrates a firing profile graph with line A representing motor speed, line C representing the measured force and line B representing the optimal force. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The present disclosure provides power packs, containing a battery and power train, which are loadable into a surgical stapler to power various functions of the surgical stapler to reduce the forces exerted by the clinician otherwise required if manual force was utilized. The present disclosure also provides surgical staplers designed to receive the power pack and to interact with the power pack to effect firing of the staplers. In some embodiments, the power pack can be used to effect articulation of the jaw assembly of the stapler to pivot the jaw assembly with respect to the longitudinal axis of the stapler. Each of these embodiments is discussed in detail below. 
     The power pack can also be utilized for powering endoscopic linear staplers, other types of staplers as well as other surgical instruments. Examples of these instruments are also discussed below. 
     The loadable power packs of the present disclosure are mountable into the handle housing of the surgical instrument, and are maintained in a sterile environment within the surgical instrument so they can be removed and reused. This enables the power pack to be removed from the stapler and reused in another procedure and/or instrument without the complexities, time, costs and risks of resterilization of the power pack. The sealed environment of the battery and power train within the housing also enables certain features/components to be used which might not otherwise be practical if sterilization of the internal power pack was required. Thus, by preventing contact between the power pack and the patient and/or bodily fluids and the external environment, resterilization is not required. The power pack can be used with surgical instruments discarded after use (fully disposable instruments), partially disposable surgical instruments or with fully reusable/sterilizable instruments with the advantage that the power pack need not be discarded or sterilized. Thus, the surgical stapler of the present disclosure advantageously reduces the time, resources and/or costs for preparing the surgical stapler for its next use. 
     The power packs are easily loadable in the surgical instrument, preferably the handle assembly or housing of the instrument, to easily and securely engage structure in the housing to effect movement of such structure in the instrument. The power packs are also easily disengageable from the structure for removal from the housing for subsequent reuse. The power packs can be configured so they can be loadable and engageable in various types of surgical instruments. The power pack is fully enclosed and sealed by the handle housing so there is no need to sterilize the power pack between uses. The power pack can include a replaceable battery pack so the battery can be changed during a surgical procedure. 
     In some embodiments the power packs includes sensors, encoders or measurement devices to assess/detect certain functions of the surgical instruments. In some embodiments, automatic adjustments are made via a microprocessor in the power pack to account for such assessment and detection. 
     Referring now to the drawings and particular embodiments of the present disclosure, wherein like reference numerals identify similar structural features of the devices disclosed herein, there are illustrated several embodiments of the surgical instruments and removable power pack of the present disclosure. 
     With reference to  FIGS.  1 - 23 B , the power pack is used with endoscopic linear staplers which are inserted through trocars and fire linear rows of surgical staples from a cartridge through tissue into contact with an anvil which forms the individual staples. The staplers include an openable compartment in the handle housing that enables easy loading of the power pack within the stapler. The staplers also provide a tight seal to protect the power pack from contaminants so that the power pack does not need to be sterilized for multiple uses. 
     The power pack is engageable with a staple drive (staple firing) mechanism of the surgical stapler so that once it is loaded in the stapler, actuation of the motor within the power pack effects firing of the staples through tissue. In some embodiments, the power pack is engageable with an articulation mechanism wherein actuation of the motor effects articulation of the stapler. The powered articulation can be in addition to the powered staple firing or alternatively the stapler could have powered articulation and manual staple firing. A specific embodiment of such powered articulation included with powered firing is shown in  FIGS.  14 A- 23 B  and discussed in detail below. 
     The term “surgical fasteners” as used herein encompasses staples having legs which are deformed by an anvil, two part fasteners wherein a fastener or staple component with legs is received and retained in a second component (retainer), and other types of fasteners which are advanced through tissue of a patient in performing surgical procedures. 
     The term “proximal” as used herein denotes the region closer to the user and the term “distal” as used herein denotes the region further from the user. The terms “top” or “upper” and “bottom” or “lower” refer to the orientation of the instruments as shown in the orientation of the instrument in  FIG.  2 A , with the cover being on the top and the handle extending at the bottom. 
     Turning first to  FIGS.  1 - 12   , a first embodiment of the surgical stapler and removable power pack are illustrated. In this embodiment, the power pack, which contains a battery, motor, drive mechanism and stapler engagement structure, effects firing of the surgical fasteners (staples). 
     The surgical stapler, also referred to herein as the or surgical fastener applying instrument or surgical fastener applier, is designated generally by reference numeral  1  and includes a proximal portion  1   a , a distal portion  1   b  and an elongated or endoscopic portion  6  (also referred to as an elongated tubular portion or shaft) extending between the proximal portion  1   a  and the distal portion  1   b . A handle assembly  2  with a housing  4  (also referred to herein as a handle housing) is positioned at the proximal portion  1   a  and is configured to house and protect internal mechanisms of the stapler including the removable power pack when loaded (mounted) therein. At the distal portion  1   b  are opposing members, i.e., jaws,  8   a ,  8   b , configured to clamp and constrain tissue during operation of the surgical stapler. At least one of the jaws is movable with respect to the other jaw from an open position to receive tissue between the jaws and a closed position to clamp tissue between the jaws. Thus, one of the jaws can be stationary and the other jaw movable with respect to the stationary jaw or alternatively both jaws can move, e.g., pivot, toward each other. In the embodiment of  FIG.  1   , jaw  8   b , which contains at least one row of surgical fasteners (staples) is movable with respect to non-pivoting (stationary) jaw  8   a  which contains an anvil with staple forming pockets. Jaws  8   a ,  8   b  are collectively referred to herein as jaws  8 . The fasteners are fired (advanced) from jaw  8   b  by linear movement of a firing mechanism which engages staple drivers within the jaw  8   b  which move transverse to the longitudinal axis, i.e., transverse to the direction of movement of the firing mechanism, to sequentially advance (from proximal to distal) the staples in the linear rows of staples from the jaw  8   b  and through tissue to engage the anvil pockets on jaws  8   a  for formation of the staples. Such firing of the staples is illustrated in  FIG.  7 C  and discussed below. 
     The elongated tubular member  6  extends distally from the housing  4  and is configured to fit through a surgical port (trocar) used for laparoscopic surgery. The endoscopic portion  6  can be of varying dimensions and in some embodiments is configured to fit through a 10 mm trocar, although other dimensions for fitting through other size trocars are also contemplated such as trocars ranging from 5 mm to 15 mm. It is advantageous to minimize the diameter of the endoscopic portion to minimize the size of the patient&#39;s incision. With the jaws  8  in the clamped position, the outer diameter of the elongated member  6  is maintained as the cross-sectional dimension of the closed jaws  8  preferably does not exceed the cross-sectional dimension (i.e., diameter) of the tubular member  6 . 
     The surgical stapler  1  can in some embodiments include a joint  10  that provides for the articulation of the opposing members  8 , i.e., pivoting of the jaw assembly (jaws  8 ) to angular positions with respect to the longitudinal axis of elongated member  6 . 
     Articulation can be achieved by linear motion of elongated members extending through the endoscopic portion  6  which are slidable to angle the jaw assembly. A rotational member or knob  12  is configured to rotate, with respect to the handle assembly, the elongated member  6  and connected jaws  8  about the axis of the elongated member  6  to change the position of the jaws  8 . Articulation is effected by manual manipulation of a lever adjacent the handle  2 . A handle lever  14 , linked to an axially movable clamping bar, is pivotable from a first position to a second position closer to stationary handle  16  to effect movement of the jaw  8   b  toward the jaw  8   a  from an open (unclamped) position to a clamping position, also referred to as a closed position of the jaws  8 . Release of handle lever  14  returns the jaw  8   b  to its open position. Stationary handle  16  for grasping by the user is ergonomically designed for comfort of use. In summary, the surgical stapler operates by manual pivoting of the lever  14  toward stationary handle  16  to clamp the tissue between jaws  8 , followed by powered firing of the staples from jaw  8   b , through the clamped tissue and into contact with the staple forming pockets of the anvil of jaw  8   b . Prior to firing, the jaws  8  can be rotated to a desired orientation by rotation of endoscopic portion  6  via knob  12  and/or articulated about joint  10 , via movement of the elongated articulation members, to a desired angled position with respect to the longitudinal axis of endoscopic portion  6 . In the embodiment of  FIG.  1   , articulation is performed by manual manipulation of a lever (not shown) which is operatively connected to an internal elongated member within tubular member  6  which extends to joint  10 . A force applied to the internal elongated member pivots/articulates the jaws  8  about the joint  10 . In later described embodiments ( FIG.  14 A ), powered articulation is provided. 
     The housing  4  of the handle assembly  2  of the surgical stapler is configured to receive the loadable/removable power pack  18  in a receptacle (compartment)  20  as shown in  FIGS.  3 A and  3 D . The receptacle includes a base  25   a  and side walls  25   b  and  25   c  having one or more guides  23  that cooperate with corresponding guiding structures  28  on the outer wall of the housing  19  of power pack  18  for proper alignment of the power pack  18  in the handle assembly  2  during insertion into the receptacle  20 . In the embodiment of  FIG.  3 A , the guides  28  on power pack housing  19  are in the form of a pair of ribs or projections  28  extending transversely to a longitudinal axis of the power pack  18  for receipt within grooves formed between guides, e.g., ribs or projections,  23  of the compartment  20 , also extending transversely with respect to a longitudinal axis of the stapler  1 . In the illustrated embodiment, the ribs  23  are on opposing sides of the power pack  18  and are axially offset from each other, although in alternate embodiments they can be axially aligned. Additionally, a different number of ribs (axially or non-axially aligned) can be provided (with corresponding receiving structure in the compartment  20 ). It should be appreciated that alternatively, the grooves could be provided on the power pack  18  and the ribs provided in the compartment  20  to provide the guiding structure for the power pack  18 . The guiding structure also helps to retain power pack  18  in position within the compartment  20 . The power pack  18  has front and rear concave regions  19   a ,  19   b  to reduce its overall size. 
     The handle assembly  2  includes a cover  22  for opening and closing the receptacle  20 . The compartment cover  22  is shown as being hingedly attached to the housing  4 , but may alternatively be fully removable or attached in some other manner such as a slidable connection or the like. The cover  22  is shown pivotable mounted to a top portion of the housing  4  (in the orientation of  FIG.  2 A ) for top loading of the power pack, although alternatively, side or bottom loading can be provided. The cover  22  is shown pivotable from a closed position of  FIG.  2 A  to an open position of  FIG.  3 A  to enable loading of power pack into the compartment  20  of the housing  4 . In some embodiments, the cover  20  is spring loaded to an open position so it remains open for loading of the power pack  18 . Once loaded, the cover  22  is pivoted about hinge  22   a  to its closed position. A latch can be provided to latch the cover  22  to the housing  4  in the closed position. When the cover  22  is in an open position, e.g., as shown in  FIG.  3 A , the power pack  18  may be removed from the receptacle  20  or inserted into the receptacle  20 . 
     When the cover  22  is in a closed position, the seal of the cover  22  is in contact with the rim of the housing  2  such that the receptacle  20 , and the power pack  18  if inserted into the receptacle  20 , is sealed from the environment exterior to the surgical stapler. The top seal  24  can be attached to the cover  22  and in some embodiments can be in the form of an elastomer that is compressed by the housing, e.g., tightly fits slightly within the housing or is pressed on the rim of the housing  2 . In other embodiments, the elastomer seal  24  can be on the housing  2 , i.e., extending around the perimeter of the rim of the compartment  20 , and is compressed by the cover  22  to seal between the cover  22  and housing  4 . Other seals can also be provided within the surgical stapler to seal/protect the power pack  18  from contaminants, e.g., body fluids. These seals are discussed in more detail below. 
     Turning now to the power pack of the present disclosure, and with reference to  FIGS.  4 A- 4 I , the power pack  18  includes a motor assembly, battery and electronics contained within housing  19 . More specifically, as shown in  FIGS.  4 A- 4 E , the power pack  18  includes a powering assembly including a motor  32  connected to a planetary gear box  34  configured to gear down the output of the motor  32  for proper drive speeds for firing staples from jaw  8   b  through the tissue into contact with the anvil of jaw  8   a . The planetary gear box  34  drives a lead screw  36  through one or more gears operatively connected to the motor shaft. More specifically, upon rotation of the motor shaft by motor  32  in a first direction, gear  38  is rotated in the same first direction, causing rotation of the gear  30  in a second opposite direction due to the intermeshed teeth of gears  30  and  38 . Lead screw  36  is operatively connected to gear  30  so that rotation of gear  30  causes rotation of lead screw  30  in the same direction. The power pack  18  includes a battery  33  which can be rechargeable outside the stapler when the power pack  18  is removed. The power pack  18  in some embodiments can include a power switch which is activated, i.e., turned on, by the clinician to start the motor and effect staple firing. In other embodiments, the motor can automatically turn on when the power pack is fully loaded or upon actuation of another control on the stapler housing  4 . In some embodiments, the motor can automatically turn off when the power pack is removed from the stapler housing. 
     Connected to the end of lead screw  36  (the end opposite the connection to the gear  30 ) is a drive mechanism  40 . The drive mechanism  40  is configured to move in a linear motion (in an axial direction) along the lead screw  36  in response to rotation of the lead screw  36 . For example, the drive mechanism  40  may include internal threads that engage external threads of the lead screw  36  and may include slides engaged in a track that prevent the drive mechanism  40  from rotating and therefore cause the drive mechanism  40  to move linearly (axially) in response to rotation of the lead screw  36 . As depicted in  FIGS.  4 A- 4 G , the power pack  18  has a compact configuration as the lead screw  36  extends alongside, slightly spaced from, the motor  32  and gear box  34 , i.e., both the motor  32 /gear box  34  and lead screw  36  extending longitudinally with the lead screw  36  parallel to the motor  32 . The drive mechanism  40  is connected to a proximal end of lead screw  36  and extends proximally of the proximal end of the motor  32  in the illustrated embodiment. 
     The power pack  18  can have features/structure to constrain the motor  32 . In the embodiment of  FIG.  4 F , such feature is in the form of proximal rails  27   a  and distal rails  27   b  spaced apart axially within the housing  19 . Motor  32  is seated within proximal rails  27   a  and gear box  34  is seated within rails  27   b , the rails  27   a ,  27   b  retaining the motor and preventing axial and rotational movement within the housing  19 . Bearing or bushings  27   c  and  27   d  can also be provided to constrain the lead screw  36  at opposing ends, while allowing rotation thereof, thereby also constraining the motor. Other features can additionally or alternatively be provided to restrain the motor from axial movement while allowing rotation of the lead screw. 
     The drive mechanism  40  includes a first output flag or yoke  42 , which is discussed in more detail below, configured to engage a staple firing mechanism, e.g., firing rod  46 , extending longitudinally within the handle  4 . The staple firing rod  46  is operatively connected to a firing rod in the endoscopic portion  6  which is operatively engageable with a series of staple drivers in jaw  8   b  to advance the fasteners (staples) from the fastener jaw  8   b . Alternatively, the firing rod  46  can extend through the endoscopic portion  6  and itself engage the stapler drivers as shown in  FIG.  7 C . Thus, as the motor  32  generates rotational motion of the lead screw  36  through the planetary gear box  34  and the gears  38 ,  30 , the drive mechanism  40  moves in linear motion along the lead screw  36 . Such linear motion effects linear movement of the firing rod  46  (due to the engagement by the flag  42 ) which advances the staple driving mechanism to advance (fire) the staples out from jaw  8   b  through tissue and into contact with the anvil in jaw  8   a . As noted above, the firing rod  46  can be a single element extending through the endoscopic portion  6  (see e.g.,  FIG.  7 C ) and terminating adjacent jaws  8  or alternatively can be attached to one or more components intermediate the firing rod  46  and jaws  8 . In  FIG.  7 C , camming surface  46   a  of firing rod  46  engages staple drivers  47  to sequentially fire staples  51  as the firing rod  46  is advanced. 
     The power pack  18  can also include in some embodiments one or more sensors to indicate the position of the firing rod  46  to indicate to the clinician the status of staple firing. The embodiment of  FIG.  4 F  illustrates an example of such sensors if they are provided. The power pack  18  has within the housing a proximal sensor  39   a  and a distal sensor  39   b  to sense the position of yoke  42  of the drive mechanism  40 . Thus, sensor  39   a  senses the initial position of the yoke  42  (and thus the initial position of the firing rod  46 ) and at the end of the firing stroke, sensor  39   b  would indicate the end (final) position of the yoke  42  (and thus the final positon of the firing rod  46 ) which would indicate completed firing of the fasteners. The power pack  18  could also include an audible or visual indicator (viewable though the power pack housing  19  and instrument handle housing  4 ) actuated by the sensor to indicate to the clinician the position of the flag  42  and thus the completion or status of the firing stroke to fire the fasteners. The power pack  19  can also include sensors to detect the position of the articulation flag in the embodiments discussed below which have powered articulation. The sensor can include a potentiometer to determine the location during the firing stroke. It can also include an encoder to detect the position along the stroke. Alternatively, the stroke can also be identified by motor count. The power pack  18  in all other respects is identical to power pack  18  of  FIG.  3 A . 
     It is also contemplated that in alternate embodiments, the sensor(s) can be carried by the handle housing rather than (or in addition to) the power pack and utilized to detect the positioning of the flag  42  and/or firing rod  46  and/or detect the position of the articulation flag and/or articulation rod in the embodiments discussed below which have powered articulation. 
     It is also contemplated that a sensor(s) can be provided to detect the position of the clamping rod for clamping the jaws. The sensor can be provided in (or supported by) the power pack or alternatively the sensor(s) can be carried by the handle housing rather than (or in addition to) the power pack and utilized to detect the positioning of the jaws by detecting the position of the flag engaging the jaw clamping rod and/or detecting the position of the jaw clamping rod in the embodiments which have powered clamping. 
     Note the sensor can be provided in some embodiments; in other embodiments, no sensor is provided. 
     The power pack in some embodiments has a battery pack that is removably mounted in or on the power pack. This is discussed in more detail in conjunction with  FIGS.  35 - 37 C . 
     Turning now to the loading of the power pack  18  into the surgical stapler  1 , as seen in  FIGS.  6 A- 6 D , the power pack  18  is in the process of being inserted into the receptacle  20  of housing  4 . As shown, handle compartment cover  22  is open to provide access to compartment  20 . The output flag  42  of the power pack  18  as noted above is driven by the motor assembly and is configured to engage and interact with structure within the handle assembly  2 , e.g., firing rod  46 , to control operation of the surgical stapler  1  when the power pack  18  is fully inserted into the receptacle  20 . As can be appreciated in  FIG.  6 D , the output flag  42  is not fully engaged with the flange  44  of the firing rod  46 . Also shown in  FIG.  6 D  is the clamp bar  49  which is positioned within and concentric with firing rod  46 . The clamp bar  49  is operatively connected to the pivotable handle  14  of stapler  1  via linkage  14   a  (pin  14   b  connects one end of handle  14  to the distal end of clamp bar  49 ). In this manner, movement of pivotable handle  14  toward stationary handle  16  causes the operatively connected jaw clamping mechanism, e.g., clamp rod  49 , to be advanced distally to pivot jaw  8   b  toward jaw  8   a  to clamp tissue between the two jaws  8 . Note that for clamping, clamp bar  49  slides linearly within a lumen of firing rod  46 ; for staple firing, firing rod  46  moves linearly over clamp bar  49 . 
     The output flag  42  of power pack  18  is configured to engage a bossed end  44  of the firing rod  46  when the power pack  18  is fully inserted into the receptacle  20  of the handle assembly  2 . As shown, the output flag (yoke)  42  has a receiving or mounting feature or member (also referred to as the engagement feature (member) or firing rod engagement feature (member) in the form of two arms  43   a  and a slot  43   b  therebetween, configured to frictionally (and releasably) engage the bossed end  44 , the feature aligning with the bossed end  44  during insertion. (The aforedescribed guiding structure on the power pack  18  and internal wall of the compartment  20  aid such alignment). 
       FIGS.  8 A,  8 B and  10    show the power pack  18  fully inserted into the compartment  20  of stapler  1 . In this position, the output flag  42  is engaged with the bossed end  44  of the firing rod  46 . Note the firing rod  46  is able to rotate when the first output flag  42  of the power pack  18  is engaged with the bossed end  44 . When the power pack  18  is secured to the firing rod  46  by the first output flag  42 , linear motion generated at the first output flag  42  by the motor actuated drive assembly is transferred to the firing rod  46 , which moves linearly to actuate the staple firing mechanism. That is, rotation of the gear  30  effects axial (linear) movement of the drive screw  36  which effects axial (linear) movement of the connected drive mechanism  40  to effect axial (linear) movement of the associated drive mechanism (rod) engaging member (i.e., flag  42 ). It should be appreciated that flag  42  provides one example of the releasable attachment (engagement member) of the motor assembly to the firing rod  46 , it being understood that other mounting (engagement) members or features are also contemplated to engage the firing rod to advance it axially. 
     In use, the cover  22  of stapler  1  is opened and the power pack  18  is inserted into receptacle  20  of sterile handle assembly  2  (of sterile stapler  1 ), with the output flag  42  of the power pack  18  engaging a corresponding feature, e.g., boss  44  of elongated drive rod  46 , in the handle assembly  2  as discussed above. Then, the cover  22  is closed to seal the power pack  18  within the receptacle  20  from the external environment and the surgical stapler  1  may be actuated, i.e., manually clamped, articulated and/or rotated if desired, and the motor actuated to effect staple firing. After applications of fasteners and release (unclamping of the jaws from tissue), the cover  22  can be opened and the power pack  18  removed and charged while the stapler and handle assembly are resterilized if the stapler is a reusable instrument or the stapler and handle assembly are disposed of if the stapler is a single use disposable instrument. The power pack  18 , due to its sealed configuration discussed above, can be reused without requiring sterilization by insertion into the receptacle  20  of a resterilized handle assembly or a sterile handle assembly of an unused disposable handle assembly. Thus, as can be appreciated, the removable power pack  18  does not need to be subjected to the sterilization process and, therefore, contact between the harsh temperatures and/or chemicals of the sterilization process is advantageously avoided. Also, by being able to reuse the power pack without sterilization, significant cost savings are achieved compared to if the power pack is not resterilizable, is disposed of along with the disposable stapler. 
     Note that in the embodiment of  FIGS.  1 - 12    (and  FIGS.  14 - 23 B  discussed below), rotational motion caused by the motor is translated into linear motion. This is shown schematically in  FIG.  5 A  wherein the drive rod in the handle housing is engaged by the motor driven drive assembly of the power pack  18  (or power pack  90  which is discussed below) moves linearly (axially) to effect linear (axial) movement of the drive member in the stapler, e.g., extending through the endoscopic portion, which effects staple firing. Alternatively, or in addition, a drive assembly of the power pack engages a drive rod in the housing which moves linearly to effect linear movement of a drive rod to effect clamping of the jaws and/or a drive assembly of the power pack engages a drive rod in the housing which moves linearly to effect linear movement of a drive member to effect articulation of the jaw assembly. Alternatively, the intermediate drive member could be omitted and the drive rods directly effect respective clamping and articulation. 
     In an alternate embodiment, shown schematically in  FIG.  5 B , linear motion is converted back to rotational movement. That is, the handle housing has a receptacle (compartment) to receive power pack  18  (or power pack  90 ) which has one or more engagement features to engage or couple to a firing rod for firing staples, a clamping rod for clamping the jaws about tissue and/or an articulation rod to articulate the jaws to angular positions with respect to the longitudinal axis. The drive rod is connected at its distal end to a block in the stapler having a female thread or a slotted guide engagement to prevent rotation of the block and enable linear movement. (The drive rod could alternatively be attached to other structure). The block is connected to a male lead screw which is engaged at its proximal end via threaded engagement to the distal end of the block. The lead screw is connected at its distal end to a component that requires rotation to effect operation of the stapler, such as effecting staple firing, clamping and/or articulation. A bearing can be provided to keep the lead screw on center and control axial motion. In use, actuation of the motor advances the drive assembly of the power pack linearly which is engaged with and advances the drive rod in the handle housing linearly (axially). Linear movement of the drive rod causes linear movement of the block positioned in the endoscopic portion (or alternatively positioned in the handle housing.) Linear movement of the block causes rotation of the male lead screw to engage a staple firing component(s) to effect staple firing. Alternatively, or in addition, the drive assembly, or a separate drive assembly (assemblies), engages a drive rod in the housing which moves linearly to effect linear movement of a block to cause rotation of the lead screw to move a jaw clamping component(s) to effect clamping of the jaws and/or engages a drive rod in the housing which moves linearly to effect linear movement of a block to cause rotation of the lead screw to move an articulation component(s) to effect articulation of the jaws. 
     In the embodiment of  FIGS.  1 - 12   , the power pack  18  actuates the firing rod  46  to fire the staples while other steps are performed manually. In summary, in this embodiment, in use, the jaws  8   a ,  8   b  are moved to the closed (clamped) position manually by a hand actuated lever or control. Also, in this embodiment, the jaws  8  are articulated with respect to the longitudinal axis of the endoscopic portion manually by a hand actuated lever or control. Thus, the clinician would manually clamp the jaws, manually rotate the endoscopic portion and attached jaws  8 , and manually articulate the jaws by manipulation of controls at the proximal end of the stapler  1 , e.g., at the handle  4 . 
       FIGS.  1 - 12    show one embodiment of an endoscopic linear stapler that can be used with the power pack  19  of the present disclosure. However, the power pack  18  is not limited to such endoscopic staplers. For example,  FIGS.  13 A and  13 B  illustrate another endoscopic linear stapler, designated by reference numeral  100 , that can be powered by power pack  18 . Stapler  100  has a handle  102  manually pivotable towards stationary handle  103  for clamping of the jaws  108   a ,  108   b , an endoscopic portion  106  extending from the handle housing  101 , a jaw assembly  104  containing jaws  108   a ,  108   b  and connector  107   a  extending proximally from shaft or tube  107  for attachment to the endoscopic portion  106  so that the jaw assembly  104  can be replaced multiple times in a single surgical procedure to provide additional rows of staples to tissue. The stapler  100  also includes a rotation knob  109  for rotation of the endoscopic portion  106 , with respect to the handle housing, to rotate the attached jaws  108   a ,  108   b . The stapler  100  can also include an articulation knob to articulate the jaws. Power pack  18  is shown in  FIG.  13 A  prior to loading within the handle housing  101  and shown in  FIG.  13 B  fully loaded (inserted) within the handle housing  101 . A cover (not shown) can be provided to seal the power pack  18  from the external environment. As in the embodiment of  FIGS.  1 - 12   , the flag  42  extending from lead screw  36  engages a firing rod within the handle housing  101  to effect movement of a firing rod to fire the staples when the motor of the power pack  18  is actuated. Power pack  90  having articulation described below can also be utilized with stapler  100 . 
       FIGS.  13 C and  13 D  illustrate another endoscopic linear stapler that can receive the power pack  18 . Endoscopic linear stapler  110  has a handle  112  manually pivotable toward stationary handle  113  for clamping of the jaws  118   a ,  118   b , an endoscopic portion  116  extending from the handle housing  111 , and a jaw assembly at the distal end of the endoscopic portion  116 . The stapler  110  also includes a rotation knob  119  for rotation of the endoscopic portion  116  to rotate the jaws  118   a ,  118   b . The stapler  110  can also include an articulation knob to articulate the jaws  118   a ,  118   b . Power pack  18  is shown in  FIG.  13 C  prior to loading within the handle housing  112  and shown in  FIG.  13 D  fully loaded (inserted) within the handle housing  112 . A cover (not shown) can be provided to seal the power pack  18  from the external environment. As in the embodiment of  FIGS.  1 - 12   , the flag  42  extending from lead screw  36  engages a firing rod within the handle housing  111  to effect movement of a firing rod to fire the staples when the motor of the power pack  18  is actuated. Power pack  90  having articulation described below can also be utilized with stapler  110 . 
       FIGS.  30 A- 30 D  illustrate another type of endoscopic linear stapler that can receive and be powered by the power pack  18 . Stapler  260  has a handle  266  manually pivotable towards stationary handle  264  for clamping of the jaws, an endoscopic portion  268  extending from the handle housing  267 , and a jaw assembly containing jaws  272   a ,  272   b . The endoscopic portion  268  is flexible which enables use in various endoscopic procedures. The stapler  260  also includes a rotation knob  270  for rotation of the endoscopic portion  268  to rotate the jaws  272   a ,  272   b . Power pack  18  is shown fully loaded (inserted) within the handle housing  262  and cover  263  closed to seal the power pack  18  from the external environment. As in the embodiment of  FIGS.  1 - 12   , the flag  42  extending from lead screw  36  engages a firing rod within the handle housing  262  to effect movement of a flexible firing rod extending through flexible endoscopic portion  268  to fire the staples when the motor of the power pack  18  is actuated. Power pack  90  having articulation described below can also be utilized with stapler  260 . 
     The power pack  18  is also not limited to use with endoscopic linear staplers, nor is it limited to use with staplers.  FIGS.  28 A- 29 D  illustrate two examples of different staplers. As in the endoscopic linear staplers discussed herein, these staplers can also have a knife bar to cut tissue between the rows of staples applied to the tissue. 
     By way of example, the power pack  18  can be used with a circular stapler that applies circular arrays of staples such as shown in  FIGS.  28 A- 28 D . Surgical stapling instrument  220  can receive and be powered by the power pack  18  of the present disclosure. Stapler  220  has a handle  226  manually pivotable towards stationary handle  264  for clamping of the jaws, an elongated tubular portion  228  extending from the handle housing  222 , and a jaw assembly having an anvil (jaw)  232  and a cartridge (jaw)  235  containing circular arrays of fasteners (staples). The anvil  232  has a proximal clamping surface  233  and is movable by anvil rod  234  toward the cartridge  235  to clamp tissue between the anvil clamping surface  233  and distal clamping surface  236  of cartridge  235  by manual movement of handle  226  toward stationary handle  224 . The stapler  220  also includes a rotation knob  230  for rotation of the elongated portion (shaft)  228  to rotate the jaws  232 ,  235 . Power pack  18  is shown fully loaded (inserted) within the handle housing  222  and cover  223  is shown closed to seal the power pack  18  from the external environment. As in the embodiment of  FIGS.  1 - 12   , the flag  42  extending from lead screw  36  engages a firing rod within the handle housing  222  to effect movement of a firing rod extending through elongated portion  228  to fire the circular arrays of staples when the motor of the power pack  18  is actuated. Power pack  90  having articulation described below can also be utilized with stapler  220 . 
     By way of another example, the power pack can be used with a linear stapler that applies transverse rows of staples in a linear direction, i.e., parallel to the longitudinal axis of the stapler, such as shown in  FIGS.  29 A- 29 D . Surgical stapling instrument  240  can receive and be powered by the power pack  18  of the present disclosure. Stapler  240  has a handle  246  manually pivotable towards stationary handle  244  for clamping of the jaws, an elongated tubular portion  248  extending from the handle housing  242 , and a jaw assembly containing an anvil (jaw)  252  and a cartridge (jaw)  255  containing linear rows of fasteners (staples) arranged perpendicular to the longitudinal axis of the stapler  240 . The proximal anvil clamping surface  253  of anvil  252  and distal clamping surface  256  of cartridge  255  are brought into approximation by manual movement of handle  246  toward stationary handle  244  which advances cartridge  255  toward anvil  252 . (Alternatively the anvil could be retracted toward the cartridge). The stapler  240  also includes a rotation knob  250  for rotation of the elongated portion (shaft)  248  to rotate the elongated portion  248  and jaws  252 ,  255 . Power pack  18  is shown fully loaded (inserted) within the handle housing  242  and cover  243  is shown closed to seal the power pack  18  from the external environment. As in the embodiment of  FIGS.  1 - 12   , the flag  42  extending from lead screw  36  engages a firing rod within the handle housing  242  to effect movement of a firing rod extending through elongated portion  248  to fire the staples from cartridge  255  when the motor of the power pack  18  is actuated. Power pack  90  having articulation described below can also be utilized with stapler  240 . 
     The power pack  18  can also be used with single firing instruments that fire a single staple, clip, tack, etc. into body tissue. Two examples of such instruments are illustrated in  FIGS.  31 A- 31 D  and  FIGS.  34 A- 34 D . Turning first to the instrument  280  of  FIGS.  31 A- 31 D , by way of example, surgical clip applying instrument  280  can receive and be powered by the power pack  18  of the present disclosure. Stapler  280  has a handle  286  manually pivotable towards stationary handle  284  for loading a clip into the jaws, an elongated tubular portion  288  extending from the handle housing  282 , and a pair of pivotable jaws  292  which support a clip therebetween. Closing of the jaws  292  crimps the clip about tissue. The clip applier  280  also includes a rotation knob  290  for rotation of the elongated portion (shaft)  288  to rotate the jaws  292 . Power pack  18  is shown fully loaded (inserted) within the handle housing  282  and cover  283  is shown closed to seal the power pack  18  from the external environment. As in the embodiment of  FIGS.  1 - 12   , the flag  42  extending from lead screw  36  engages a rod within the handle housing  282  operably connected to a clip closing mechanism to effect movement of the clip closing mechanism to close the jaws to apply to tissue a surgical clip supported by the jaws  292 . The power pack  18  can also have a motor powered drive assembly for advancing the clip into the jaws  292 , the drive assembly engageable with a clip feed mechanism. 
     Another example of a single firing instrument is illustrated in  FIGS.  34 A- 34 D  and designated generally by reference numeral  340 . Instrument  340  can receive and be powered by the power pack  18  of the present disclosure. Instrument  340  has a handle  346  manually pivotable towards stationary handle  344  for angling the surgical tack and an elongated tubular portion  348  extending from the handle housing  342 . Tacker support  345  is pivotable relative to the longitudinal axis by movement of handle  346  which is operably connected to an elongated member which pivots support  345 . The instrument  340  also includes a rotation knob  350  for rotation of the elongated portion (shaft)  348 . Power pack  18  is shown fully loaded (inserted) within the handle housing  342  and cover  343  is shown closed to seal the power pack  18  from the external environment. As in the embodiment of  FIGS.  1 - 12   , the flag  42  extending from lead screw  36  engages a rod within the handle housing  342  operably connected to a tack firing mechanism to effect advancement of the tack  347  into tissue. The power pack  18  can also be provided with a motor powered drive assembly to pivot support  345 . 
     In the embodiments of  FIGS.  1 - 12   , a gear mechanism is driven by the motor to rotate the lead screw to advance the drive mechanism to effect firing of the staples. In the alternate embodiments of  FIGS.  24 A- 27 D , a belt drive mechanism is used to effect firing. The belt drive mechanism is contained in the power pack  18  in the same manner as the gear mechanism of the foregoing embodiments, and thus the power pack for the belt drive would include the housing  19  of the configuration of  FIG.  1    and loaded in the stapler  1  in the same manner as power pack  18  described above. The belt drives of  FIGS.  24 A- 27 D  are described below for use with stapler  1  of  FIG.  1 A  but can be used in the other surgical staplers and instruments disclosed wherein which are designed to receive power pack  18  or power pack  90  for powered actuation. 
     Turning first to the embodiment of  FIGS.  24 A- 24 D , the belt drive assembly (mechanism) includes a motor  148  connected to a planetary gear box  150  configured to gear down the output of the motor  148  for proper drive speeds for firing staples from jaw  8   a  through the tissue into contact with the anvil of jaw  8   b . The planetary gear box  150  drives a lead screw  144  via the drive belt operatively connected to the motor shaft. More specifically, upon rotation of the motor shaft by motor  148 , first rotatable disc  152  (also referred to as the first wheel or pulley) is rotated in a first direction, causing movement of belt  156  and rotation of second rotatable disc  154  (also referred to as the second wheel or pulley). Note the two discs  152 ,  15  are spaced apart and not in contact. Lead screw  144  is operatively connected to disc  154  so that rotation of disc  154  causes rotation of lead screw  144  in the same direction. The power pack  18  includes a battery which can be rechargeable outside the stapler when the power pack  18  is removed. The motor  148  is actuated in the various ways described above with regard to power pack  18  of  FIG.  3 A . A tensioner can be provided such as tensioner  158 , illustratively in the form of a tension disc or wheel, to apply a force against the belt  156 . In the orientation of  FIGS.  24 C  and  24 D, the tensioner  158  is positioned underneath the drive belt  156  and applies an upward tensioning force against the belt  156  in a direction toward discs  152 ,  154 . Other types of mechanisms to apply a tensioning force to the belt are also contemplated for use in the embodiments of  FIGS.  24 A- 27 D  if such tensioning of the drive belt  156  is desired. 
     Connected to the end of lead screw  144  (the end opposite of the connection to the disc  154 ) is a drive mechanism  142 . The drive mechanism  142 , like drive mechanism  40  of  FIG.  3 A , is configured to move in a linear motion (in an axial direction) along the lead screw  144  in response to rotation of the lead screw  144 . For example, as in the drive mechanism  40 , drive mechanism  142  may include internal threads that engage external threads of the lead screw  144  and may include slides engaged in a track that prevent the drive mechanism  142  from rotating and therefore cause the drive mechanism  142  to move linearly in response to rotation of the lead screw  144 . As shown, the lead screw  144  extends alongside, slightly spaced from, the motor  148  and gear box  150 , i.e., both the motor  148 /gear box  150  and lead screw  144  extending longitudinally with the lead screw  144  parallel to the motor  148 . The drive mechanism  142  extends proximally of the proximal end of the motor  148  in the illustrated embodiment. 
     The drive mechanism  142 , like drive mechanism  140  of  FIG.  3 A , includes a first output flag or yoke  146  with slot  143  configured to engage a staple firing rod  46  extending longitudinally within the handle  4 . The flag  146  is the same as flag  42  of  FIG.  4 A  and engages the staple firing rod  46  in the same manner as flag  42 . Therefore, for brevity, further discussion of flag  146  and it engagement with firing rod  46  is not provided as the structure and function of flag  42 , and alternative firing rod engagement features, are fully applicable to flag  146  of  FIGS.  24 A- 24 D . In brief, as the motor  148  generates rotational motion of the lead screw  144  through the drive belt, the drive mechanism  144  moves in linear motion along the lead screw  144  to effect linear movement of the firing rod  46  which advances the staple driving mechanism to advance (fire) the staples out from jaw  8   b  through tissue and into contact with the anvil in jaw  8   a.    
       FIGS.  25 A- 25 D  illustrate an alternate embodiment of a belt drive mechanism. Belt drive mechanism (assembly)  160  is identical to belt drive  140  except for the different sized discs (wheels). That is, assembly  160  has a motor  168  connected to a planetary gear box  170  configured to gear down the output of the motor  168 . The planetary gear box  170  drives a lead screw  164  through the belt drive operatively connected to the motor shaft. Upon rotation of the motor shaft by motor  168 , first disc  172  is rotated in a first direction, causing movement of belt  176  and rotation of second disc  174  in the same direction. Lead screw  164  is operatively connected to disc  174  so that rotation of disc  174  causes rotation of lead screw  164  in the same direction. A tensioner  178  like tensioner  158  can be provided to apply tension to the belt  176 . The drive mechanism  162 , like drive mechanism  40  of  FIG.  3 A , includes a first output flag or yoke  166  with slot  163  configured to engage a staple firing rod  46  in the same manner as flag  42 . Rotation of the motor shaft generates rotational motion of the lead screw  164  through the drive belt, causing the drive mechanism  162  to move in linear motion along the lead screw  164  to effect linear movement of the firing rod  46  which advances the staple driving mechanism to advance (fire) the staples out from jaw  8   b  through tissue and into contact with the anvil in jaw  8   a.    
     The belt drive  160  differs from belt drive  140  of  FIG.  24 A  in that second disc  174  which is operatively connected to lead screw  164  is larger in diameter than first disc  172 . Consequently, instead of providing a one to one ratio of the discs as in discs  154  and  152  of  FIG.  24 A , a greater ratio of disc  174  to disc  172  is provided which varies the output of motor  168 . That is, the rotational output of lead screw  164  is less than the rotational output of the motor shaft due to the differing degree of rotation of discs  174 ,  178  due to the varying sizes. In all other respects, mechanism  160  is identical to mechanism  140 . 
       FIGS.  26 A- 26 D  illustrate an alternate embodiment of a belt drive mechanism. Belt drive mechanism (assembly)  180  is identical to belt drive  140  of  FIG.  24 A  except for the configuration of the drive belt and discs. That is, assembly  180  has a motor  188  connected to a planetary gear box  190  configured to gear down the output of the motor  188 . The planetary gear box  190  drives a lead screw  184  through the belt drive operatively connected to the motor shaft. Upon rotation of the motor shaft by motor  188 , first disc (wheel or pulley)  192  is rotated in a first direction, causing movement of belt  196  and rotation of second disc (wheel or pulley)  194 . Lead screw  184  is operatively connected to disc  194  so that rotation of disc  194  causes rotation of lead screw  184  in the same direction. A tensioner  198  like tensioner  158  can be provided to apply tension to the belt  196 . The drive mechanism  182 , like drive mechanism  140  of  FIG.  3 A , includes a first output flag or yoke  186  with slot  183  configured to engage a staple firing rod  46  in the same manner as flag  42 . Rotation of the motor shaft generates rotational motion of the lead screw  184  through the drive belt, causing the drive mechanism  182  to move in linear motion along the lead screw  184  to effect linear movement of the firing rod  46  which advances the staple driving mechanism to advance (fire) the staples out from jaw  8   b  through tissue and into contact with the anvil in jaw  8   a.    
     The belt drive  180  differs from belt drive  140  of  FIG.  24 A  in that discs  192 ,  194  have teeth to engage ribs or treads on belt  196 . As shown, the toothed discs  192 ,  194  are spaced apart so their teeth/projections do not intermesh—the teeth of disc  192  engage belt  196  and the teeth of disc  194  engage belt  196 . Rotation of disc  192  moves drive belt  194  in the same direction due to its engagement with the teeth, which causes rotation of toothed disc  194  in the same direction due to engagement with its teeth to rotate lead screw  184 . In all other respects, mechanism  180  is identical to mechanism  140 . 
       FIGS.  27 A- 27 E  illustrate an alternate embodiment of a belt drive mechanism. Belt drive mechanism (assembly)  200  is identical to belt drive  180  except for the different sized discs. That is, assembly  200  has a motor  208  connected to a planetary gear box  210  configured to gear down the output of the motor  208 . The planetary gear box  210  drives a lead screw  204  through the belt drive operatively connected to the motor shaft. Upon rotation of the motor shaft by motor  208 , first disc (wheel or pulley)  212  is rotated in a first direction, causing movement of belt  216  and rotation of second disc (wheel or pulley)  214 . Lead screw  204  is operatively connected to disc  214  so that rotation of disc  214  causes rotation of lead screw  204  in the same direction. A tensioner  218  like tensioner  198  can be provided to apply tension to the belt  216 . The drive mechanism  202 , like drive mechanism  140  of  FIG.  3 A , includes a first output flag or yoke  206  with slot  203  configured to engage a staple firing rod  46  in the same manner as flag  42 . Rotation of the motor shaft generates rotational motion of the lead screw  204  through the drive belt, causing the drive mechanism  202  to move in linear motion along the lead screw  204  to effect linear movement of the firing rod  46  which advances the staple driving mechanism to advance (fire) the staples out from jaw  8   b  through tissue and into contact with the anvil in jaw  8   a.    
     The belt drive  200  differs from belt drive  180  of  FIG.  24 A  in that second toothed disc  214  which is operatively connected to lead screw  204  is larger in diameter than first toothed disc  172 . Consequently, instead of providing a one to one ratio of the discs as in discs  194  and  192 , a greater ratio of disc  214  to disc  212  is provided which varies the output of motor  208 . That is, the rotational output of lead screw  204  is less than the rotational output of the motor shaft due to the differing degree of rotation of discs  214 ,  212  due to the varying sizes. In all other respects, mechanism  200  is identical to mechanism  180 . 
     It should be appreciated that the foregoing belt drive mechanisms can be used as an alternative to the gear mechanism in power pack  18  as well as an alternative to one or both of the gear mechanisms of power pack  90  discussed below. 
     In the foregoing embodiments, the power pack  18  was described for powering staple firing. In an alternate embodiment, the power pack can include a drive mechanism for effecting articulation. This motor powered articulation can be in addition to the motor powered staple firing, or alternatively, the power pack can be used solely for powered articulation. The embodiment of  FIGS.  14 A- 23 B  illustrate a surgical stapler and power pack which powers both staple firing and articulation. If only for articulation, the power pack described below (power pack  90 ) would not include the gear mechanism engageable with the firing rod  46  for staple firing. 
     With initial reference to  FIGS.  14 A- 14 C , surgical stapler  61  is identical to surgical stapler  1  of  FIG.  1 A  except for the power pack mounted in the stapler  61  and the articulation rod in the stapler  61  which is engaged by the power pack. Thus, like stapler  1 , stapler  61  has a handle assembly  63 , an endoscopic portion  66  extending distally therefrom and a pair of jaws  68   a ,  68   b , (collectively “jaws  68 ”) with at least one of the jaws movable relative to the other jaw, e.g., jaw  68   b  containing the staples (fasteners) movable toward stationary jaw  68   a  containing the anvil pockets. Handle  72  like handle  14  of stapler  1  is pivotable toward stationary handle  70  to approximate jaws  68   a ,  68   b  to clamp tissue between the closed jaws  68   a ,  68   b . Handle assembly  63  includes a housing  64  and cover  62  which is identical to cover  22  of stapler  1 , i.e., pivotably mounted to the housing  64  to move from a closed to an open position for top loading (or alternatively other directional loading) a power pack into the compartment within the housing  64 . The compartment, like compartment  25  described above, retains the power pack and can include guiding structure for alignment of the power pack similar to guiding structure  28  described above to receive guides  90   a ,  90   b  of power pack  90 . Stapler  61  also includes a rotation knob  74  which functions in the same manner as rotation knob  12  of stapler  1  described above to rotate tubular portion (shaft)  66 . The jaw assembly, i.e., jaws  68   a ,  68   b , articulate about joint  69  to move the jaws  68   a ,  68   b  to angular positions with respect to the longitudinal axis of stapler  61 . 
     The power pack in the embodiment of  FIGS.  14 A- 23 B  is designated by reference numeral  90  and has a motor assembly and drive mechanism for firing staples which is identical to that of the power pack  18  of  FIG.  3 A . However, power pack  90  differs from power pack  18  in that it additionally has a motor assembly and drive mechanism for articulating the jaws. The addition of the articulation assembly can be appreciated by a comparison of the cross-sectional view of  FIG.  4 H , which only effects firing of the fasteners (staplers), and the cross-sectional view of  FIG.  15 F  which effects firing of fasteners and articulation of the jaw assembly. 
     More specifically, with reference to  FIGS.  15 A- 15 F and  18 B , the powered staple firing assembly like the firing assembly of power pack  18  of  FIG.  4 H , includes a motor  83  connected to a planetary gear box  85  configured to gear down the output of the motor in the same manner as motor  32  and gear box  34  of power pack  18 . The planetary gear box  85  drives a lead screw  86  through one or more gears operatively connected to the motor shaft. More specifically, upon rotation of the motor shaft by the motor  83  in a first direction, gear  81  is rotated in the same first direction, causing rotation of the gear  84  in a second opposite direction due to the intermeshed teeth of gears  81  and  84 . Lead screw  86  is operatively connected to gear  84  so that rotation of gear  84  causes rotation of lead screw  86  in the same direction. The power pack  18  includes a battery  33  which can be rechargeable outside the stapler when the power pack  18  is removed. The power pack  90  in some embodiments can include a power switch which is activated, i.e., turned on, by the clinician to start the motor and effect staple firing. In other embodiments, the motor can automatically turn on when fully loaded or upon actuation of another control on the stapler housing  4 . 
     Connected to the end of lead screw  86  (the end opposite the connection to the gear  84 ) is a drive mechanism  80  which is configured to move in a linear motion (in an axial direction) along the lead screw  86  in response to rotation of the lead screw  86 . Drive mechanism  80  includes a flag or yoke  82  identical to yoke  42  of power pack  18  discussed above, which engages flange or boss  76  of firing rod  75  within housing  64  of stapler  61 . The connection of the flag  82  to the firing rod  76 , the motor and gear mechanism, and the drive mechanism  80  of power pack  90  are the same as the power pack  18  and therefore the aforedescribed functions and features/components of power pack  18  for staple firing are fully applicable to the function and features/components of power pack  90  for staple firing so for brevity are not fully repeated herein. It should also be appreciated that the alternative mechanisms for motor powered stapled firing, such as the various belt drive mechanisms discussed above and/or illustrated in the Figures, can also be used in the power pack  90  to effect staple firing. Additionally, the various sensors discussed above with regard to sensing the firing stroke can also be provided in power pack  90  for the same uses. 
     Power pack  90  also has an articulation assembly, shown in detail in  FIGS.  22 A- 22 D . The articulation assembly includes a powering assembly including a motor  96  connected to a planetary gear box  93  configured to gear down the output of the motor  96 . The planetary gear box  93  drives a lead screw  98  through gears  91 ,  92  operatively connected to the motor shaft. More specifically, upon rotation of the motor shaft by motor  96  in a first direction, gear  91  is rotated in the same first direction, causing rotation of the gear  92  in a second opposite direction due to the intermeshed teeth of gears  92  and  91 . Lead screw  98  is operatively connected to gear  92  so that rotation of gear  92  causes rotation of lead screw  98  in the same direction. The power pack  90  in some embodiments can include a power switch which is activated, i.e., turned on, by the clinician to start the motor and effect articulation. 
     Connected to the end of lead screw  98  (the end opposite the connection to the gear  92 ) is a drive mechanism  95  configured to move in a linear motion (in an axial direction) along the lead screw  98  in response to rotation of the lead screw  98 . For example, the drive mechanism  95 , like drive mechanisms  40  and  80  described above, may include internal threads that engage external threads of the lead screw  98  and may include slides engaged in a track that prevent the drive mechanism  95  from rotating and therefore cause the drive mechanism  95  to move linearly (axially) in response to rotation of the lead screw  98 . As depicted, the power pack  90  has a compact configuration as the lead screw  98  extends alongside, slightly spaced from, the motor  96  and gear box  93 , i.e., both the motor  96 /gear box  93  and lead screw  98  extending longitudinally with the lead screw  98  parallel to the motor  96 . The drive mechanism  95  is connected to a proximal end of lead screw  98 . The drive mechanism  95  has an articulation rod engagement feature in the form of a flange or yoke  94  extending therefrom having legs  99   a  and a recess  99   b  to engage an articulation rod  79  within the housing  63 . In the illustrated embodiment (see e.g.,  FIGS.  15 B and  22 C ), the articulation rod  79  includes a flange  78  which is engageable by the flag  94 . The output flag  94  can engage the bossed end  78  of the articulation tube  79  in substantially the same manner as the output flag  42  engages the bossed end  44  of the firing rod  46  as discussed above. 
     The articulation assembly of the power pack  90  is oriented in the opposite direction from the staple firing assembly to minimize the space required in the power pack  90 , thereby providing the power pack with a compact configuration. As can be appreciated by reference to  FIGS.  15 A and  15 F , the drive assembly  80  and associated flag  82  are at a proximal end of the assembly for firing staples with the lead screw  86  extending distally toward the gears  81 ,  84 . The driving assembly  95  with associated flag  94  of the assembly for articulation are at a distal end with the lead screw  98  extending proximally toward gears  91 ,  92 . Also as can be appreciated by reference to the orientation of  FIGS.  15 A and  15 F , the articulation assembly is above (closer to the cover  22 ) than the firing assembly, and the articulation assembly in the illustrated embodiment is positioned axially proximal of gears  81 ,  84  and axially distal of drive mechanism  80 , radially spaced from lead screw  86 . 
     The power pack  90 , like power pack  18  can have features/structure to constrain the motors  84  and  96 . In the embodiment of  FIG.  15 D , such feature is in the form of proximal rails  97   a  and distal rails  97   b  spaced apart axially within the housing of the power pack  90 . Gear box  93  is seated within proximal rails  97   a  and motor  96  is seated within distal rails  97   b , the rails  97   a ,  97   b  retaining the motor and preventing axial and rotational movement within the housing of power pack  90 . Bearing or bushings  98   a ,  98   b  can also be provided to constrain the lead screw  98  at opposing ends, while allowing rotation thereof, thereby also constraining the motor. Other features can additionally or alternatively be provided to restrain the motor from axial movement while allowing rotation of the lead screw. 
     The power pack  90  can include guides, e.g., projections  90   a ,  90   b , either axially aligned or axially offset, similar to guides  28  of power pack  18  for alignment with guiding structure in the compartment of stapler  61 . This can prevent misloading of the power pack. 
     In use, with the cover  62  of stapler  61  in the open position, power pack  90  is loaded into the compartment of the handle housing  63 . The cover  62  is closed to seal the power pack  90  from contaminants in same manner as cover  22  of stapler  1 . Upon loading of the power pack  90 , flag  82  of the drive mechanism  80  of the staple firing assembly engages flange  76  of firing rod  75  and flag  94  of drive mechanism  95  of the articulation assembly engages flange or bossed end  78  of articulation rod  79 . Actuation of the motor  96  effects linear motion of the flag  94  which moves the articulation rod  79  linearly (axially). The articulation rod  79  is either directly coupled to the joint  69 , or coupled to another member or multiple members which are coupled to the joint  69 . When moved linearly, the articulation rod  79  effects movement of the jaws  68 A,  68   b  of the stapler  61  to angular positions with respect to the longitudinal axis of the stapler  61 . Note the articulation drive assembly operates in a similar manner as the firing drive assembly of power pack  18  in that when the power pack  90  is secured to the tube  79  by the second output flag  94 , linear motion generated at the second output flag  94  is transferred to linear motion of the tube  79 . 
     Actuation of the motor  83  effects linear motion of the flag  82  which moves the firing rod  75  linearly (axially). The firing rod  75  either extends through the elongated portion  66  for engagement of the firing mechanism in the jaw  68   b  or is coupled to another elongated component(s) extending through the endoscopic portion  66  to engage the firing mechanism in the jaw  68   b . Note that the articulation rod or tube  79  can be configured to receive the firing rod  75  so that the firing rod  75  can move within the tube  79  to effect firing and the articulation rod  79  can slide linearly over the firing rod to effect articulation. 
     After use, the cover  62  can be opened and the power pack  90  removed and charged while the handle assembly  63  (and stapler  61 ) is sterilized or disposed of if the stapler is a disposable instrument. The power pack  90 , like power pack  18  described above, may be reused without requiring sterilization by being inserted into the receptacle of the now-sterilized handle assembly  63  or a different sterile handle assembly. Thus, the removable power pack  90 , like power pack  18 , does not need to be subjected to the sterilization process and, therefore, contact between the harsh temperatures and/or chemicals of the sterilization process is advantageously avoided. 
     One or more seals are utilized for sealing power pack  18  and power pack  90  within the handle assembly  2  or  63  so that the power pack remains sterile and is not exposed to bodily fluids during surgical procedures. For example, as discussed above, in the stapler  1  of  FIG.  1   , the top seal  24  is positioned at the interface between the cover  22  and the housing  4  of the handle assembly  2  where the cover  22  closes for sealing the opening into the receptacle  20  and, therefore, power pack  18  from the environment when positioned therein. Similarly, in the stapler  61  of  FIG.  14 A , the top seal is positioned at the interface between the cover  62  and the housing  64  of the handle assembly  63  wherein the cover  62  closes for sealing the opening into the receptacle and, therefore, power pack  90  from the environment when positioned therein. As shown in  FIGS.  21 A- 21 C , further seals can be provided to further seal the receptacle and thus the power pack. An O-ring  56  is placed around the articulation rod  79  to seal the space around the rod  79 . A flexible trigger seal  58  surrounds the lever  72  for sealing the internal components of the handle assembly  63  throughout the range of positions of the movable lever  72 . Thus, all of the openings into the receptacle of the handle assembly  63  are sealed from the external environment. The O-ring seal  56  and trigger seal  58  can also be used in stapler  1  so the openings into the receptacle  20  of handle assembly  2  are sealed from the external environment. Elastomeric seal  59   a  seals cover  62  from U-channel  59  within the handle which supports the power pack  90 . Additional seals can be provided to prevent flow of body fluid through the endoscopic portion  66  (and endoscopic portion  6 ). Other types of seals and seals in different locations are also contemplated. 
       FIGS.  35 - 37 C  illustrate alternate embodiments of the power pack having a removable battery pack. Each of the power packs (power trains)  406 ,  420  and  430  in the embodiments of  FIGS.  35 - 37 C  can have a motor assembly and drive mechanism for firing staples which is identical to that of the power pack  18  of  FIG.  3 A  or alternatively can have a motor and drive mechanism for firing staples and additionally a motor assembly and drive mechanism for articulating the jaws as in power pack  90  of  FIG.  14 A  described above. The surgical staplers for receiving power packs  406 ,  420  or  430  are the same as the surgical stapler  1  (except for the compartment and cover) so that it has been labeled with like reference numerals. The power packs  406 ,  420  and  430  could also be used with the other surgical staplers described herein or with other surgical instruments such as those described herein. Therefore, further discussion of the surgical staplers is not provided herein as the description of the stapler  1  components (e.g., shaft  6 , jaws  8   a ,  8   b , handle  12 , etc.) and its functions, as well the description of other staplers, are fully applicable to the stapler receiving power packs  406 ,  420  or  430 . 
     Turning first to the embodiment of  FIG.  35   , the power pack  406  has an upper surface  412  having a cavity  410  to slidably receive card-like battery pack  408 . Battery pack  408  is slid into the cavity and engages a contact within the housing to enable actuation of the motor to power the drive mechanism within the power pack  406  to effect staple firing and/or jaw articulation in the same manner as described above (via engagement by the flag or yoke). Power pack  406  is placed into the cavity  404  of housing  402  in a similar manner as described above, e.g., top loaded into the compartment, and the hinged cover  407  is closed to seal the power pack  406  from the external environment. Cover  407  differs from cover  22  in that it includes a spring loaded latch  409  received in latch cavity  405  of housing  402  to retain the cover  407  in the closed position. The latch  409  is released by pressing latch  409  to disengage the latch  409  so the cover  407  can be opened to access the power pack  406 . Raised surface (tab)  414  on one or both sides of the power pack  406  aligns with a recess in the compartment  404  for alignment of the power pack  406  during insertion. 
     In use, the battery pack  408  can be aseptically preloaded in the power pack  406 , either by a user or packaged with the battery pack  408  preloaded, and the power pack  406  is aseptically preloaded into the surgical instrument. During a surgical procedure, in the event of a battery failure, the cover  407  can be opened and the power pack  406  can be removed intraoperatively from compartment  404 , the battery pack  408  removed from cavity  410 , a new (second) charged battery (battery pack) aseptically placed in cavity  410  and the power pack  406  with the replacement battery pack reloaded into compartment  404 . In an alternative use, during a surgical procedure, in the event of a battery failure, the cover  407  can be opened and with the power pack  406  remaining in compartment  404 , the battery pack  408  is removed from cavity  410  of the power pack  406  and a new (second) charged replacement battery (battery pack) aseptically placed in cavity  408  while the power pack  406  remains loaded (positioned) within the compartment  404  of the surgical instrument. 
     In the alternate embodiment of  FIG.  36   , the stapler  1  is the same as in  FIG.  35   , the difference being the power pack and battery pack. More specifically, power pack  420  has an outer upper surface  422  extending proximally from wall  428 , on which the battery pack  424  is mounted. Wall  425  of battery pack  424  can be placed in abutment with wall  428 , and the power pack  420  and battery pack  424  can be dimensioned so that the battery pack  424  becomes part of the outer contour of the power pack  420 , e.g., the upper surface  427  of the power pack can be substantially flush with the upper surface  429  of the power pack  420 , although in alternate embodiments the upper surface can be below or above the upper surface  429 . Power pack  422  can have an alignment tab  426  on one or both sides to aid insertion/alignment. The battery pack  424  can include an engagement feature  420  interacting with the power pack/to secure the battery pack  424  on the power pack  420 . 
     In use, as with power pack  406  described above, the battery pack  420  can be preloaded, i.e., pre-mounted, onto the power pack  406  (by the user or prepackaged) and can be removed and replaced with another (second) charged battery (battery pack) during a surgical procedure by first removing the power pack  406  from the compartment  404  of stapler  1  or alternatively the battery pack  420  can be removed from the power pack  406  and replaced by another charged battery pack while the power pack  406  remains in the compartment  404 . 
     In the alternate embodiment of  FIGS.  37 A- 37 C , the battery pack  440  is mounted into a cavity (receptacle) in the power pack  430 . Note the stapler  1  of  FIGS.  37 A- 37 C  is the same as in  FIG.  35   , the difference being the power pack and battery pack. Power pack  430  has a cavity  432  extending along its length dimensioned to receive battery pack  440 . The power pack  430  and battery pack  440  can be dimensioned so that the battery pack  440  becomes part of the outer contour of the power pack  430 . Irregular gripping surface or tab  442  on side wall  443  of battery pack  440  is received in cutout  432  on the side wall of power pack  430 . The gripping surface can be grasped by the user to facilitate removal as the battery pack  440  is removed from the power pack  430 . In some embodiments, a gripping surface or tab like surface  442  can also be provided on the opposing side wall (received in another cavity like cavity  432  positioned on the opposing side) for facilitating grasping both sides of the battery pack  440  for removal from the power pack. 
     In the loaded position, the battery pack can protrude slightly above the plane of the top edges  404   a  of the compartment  402  as shown in  FIG.  37 C  or alternatively can be flush or below the plane of the compartment edges  404   a . In any case, the power pack and mounted battery pack  440  are placed sufficiently within the compartment  402  so that the cover  407  can be completely closed to seal the power pack  430  and battery pack  440  from the external environment. 
     In use, the battery pack  440  can be preloaded in the power pack  430 , either by a user or packaged with the battery pack  440  preloaded. During a surgical procedure, in the event of a battery failure, the cover  407  can be opened, power pack  430  removed from compartment  404 , the battery pack  440  removed from cavity  434 , a new (second) charged battery (battery pack) aseptically placed in cavity  434  and the power pack  440  with a replacement battery pack reloaded into compartment  404 . In an alternative use, during a surgical procedure, in the event of a battery failure, the cover  407  can be opened and with the power pack  430  remaining in compartment  404 , the battery pack  440  is removed from cavity  434  of the power pack  440  and a new (second) charged battery (battery pack) aseptically placed in cavity  434  while the power pack  430  remains loaded (positioned) within the compartment  404 . 
     Note the battery packs disclosed herein can include custom cells or alternatively off the shelf batteries. The use of the term battery pack as used herein encompasses different types of batteries and different housings for the batteries which are mounted on or inserted either fully or partially into the power pack housing (which contains the powertrain therein) to operatively connect with the motor in the power pack. 
     The battery packs can be retained, e.g., locked, in or on the power pack housing in various ways such as a latch, spring loaded engagement, frictional engagement, interlocking tabs, etc., and such mountings can also include a release button for disengaging/removing the battery pack from the power pack. 
     As noted above, the power pack  90  can be used with the other staplers disclosed herein, e.g. circular staplers, linear staplers, as well as other instruments wherein two powered functions are desired. The first motor assembly can effect linear motion of a first elongated member to effect a first function of the stapler, e.g., clamping, articulation, firing, and the second motor assembly can effect linear motion of a second elongated member to effect a second different function of the stapler, e.g., clamping, articulation, firing. In the embodiment of  FIG.  14 A , one function is articulation and another function is staple firing. Note the power pack  90  can also be used with surgical instruments other than surgical staplers such as those illustrated in  FIGS.  33 A and  34 A . 
       FIGS.  38 - 41    illustrate an alternate embodiment of the stapling instrument having an encoder with switching devices to effect articulation and firing. Operation of the instrument is illustrated schematically in the concept diagrams of  FIGS.  38 - 40   . 
     Initially, with reference to  FIG.  38   , the powertrain (also referred to herein as the power pack) is inserted into a homing cradle. The powertrain has an external homing switch engaged with the homing cradle. The replaceable battery can be inserted into the cradle either before or after the battery is loaded into the powertrain. A DC to DC converter can be provided to boost battery voltage from for example 7.6V to 18V. A safety (thermosensor) can be provided on the battery pack to prevent overheating. For example, a battery life indicator (e.g., a gas gauge) can be provided as part of a battery management system to prevent battery overheating. A circuit board in the charger monitors the thermosensor so if the temperature exceeds a predetermined threshold, it automatically shuts down the charge to the battery. Indicator lights providing battery status can be provided. Within the homing cradle, the enable switch is allowed. The powertrain powers up and the unit goes through a homing sequence so that the articulation motor and the firing motor are both in the home position. A screen can be provided on one or more of the powertrain or the cradle to indicate the articulation and firing are in the home positions and the system is ready for use (enabled), i.e., ready for loading into the surgical instrument compartment for powering the surgical functions of the instrument. The switches are enabled within the homing cradle but cannot be actuated within the cradle. A screen/window can also be provided on the instrument, e.g., instrument housing, to indicate the home position. 
       FIG.  39    illustrates schematically how the surgical functions are enabled/disabled based on the position of the instrument jaws. This is achieved through software in the powertrain (power pack). With the powertrain loaded in the compartment, if the instrument jaws are open, the firing mechanism, i.e., the firing switch, is disabled. This ensures that the staples cannot be advanced from the staple receiving jaw and the knife bar cannot be advanced distally unless the jaws are properly clamped on tissue. In the open position of the instrument jaws, the articulation mechanism, i.e., the articulation switch, is enabled so that the cartridge and anvil jaw assemblies can be articulated by actuation of the articulation motor to various angles with respect to the longitudinal axis of the surgical instrument. 
     With continued reference to the diagram of  FIG.  39   , with the powertrain loaded in the compartment, if the instrument jaws are moved to the closed (tissue clamping position), the firing mechanism, i.e., the firing switch, is enabled. This enables the firing motor to be actuated so the firing mechanism and cutting blade can be advanced distally to fire the staples and cut tissue clamped between the jaws. In the closed position of the instrument jaws, the articulation mechanism, i.e., the articulation switch, is disabled so that the cartridge and anvil jaw assemblies cannot be articulated. 
     The foregoing is shown in the stapler of  FIGS.  41 A and  41 B , wherein in the open position of the jaws ( FIG.  41 A ), the manually actuated clamping handle  514  is in the open position with the engagement surface  510  spaced from the switch  512 . When the clamping handle  514  is moved to the closed position ( FIG.  41 B ), the engagement surface  510  comes into contact with the switch  512  to complete the circuit for activation of the firing mode. In this clamped position, the firing button  518  can be actuated to effect staple firing. With the engagement surface  510  spaced from the switch  512 , the circuit is open such that actuation of the firing button  518  will not actuate the motor and thus not initiate firing. Alternatively, the switch can be in the “closed position” in both handle positions with the software detecting the clamped position of the handle. 
     The steps for loading the powertrain and using the instrument will now be described in conjunction with the flow chart of  FIGS.  40 A- 40 C . The powertrain is inserted into the homing cradle followed by insertion of the battery into the homing cradle. This moves the articulation and firing motors into the home position. If the screen indicates completion of the homing sequence, i.e., ready for use, the powertrain and charged battery are removed from the cradle and placed into the compartment of the instrument housing as described above with respect to the other staplers. Once the powertrain is properly seated in the compartment, the compartment cover can be closed which then enables subsequent actuation of the switches. If not properly seated, the switches are not enabled. In some embodiments, as described below, closing of the cover automatically activates an enable switch. 
     To use the stapler, the clamping handle is closed to move the jaws to the closed position for insertion through the trocar. Once inserted, if articulation is desired, the handle is unclamped to move the jaws to the open position and the articulation switch, e.g., a rocker switch or other switches preferably accessible on either side of the instrument, is pivoted to move the jaws from the  0  position to the left or right. The encoder via a motor count detects the articulated position of the jaws which in some embodiments can be visually displayed on an instrument or power pack screen. After reaching the articulated position of the jaws, tracked via the motor count, the articulation switch is released to maintain the jaws in this position. In some embodiments a double pump articulation switch can be utilized to bring articulation back to zero automatically. 
     Next, the jaws are clamped via the manually actuated handle, which enables activation of the firing mode. With the jaws closed, the firing switch is actuated, to advance the firing rod and knife bar to apply staples and cut tissue. A motor count tracks the position of the firing rod. That is, the motor encoder detects motor location within a full stroke, i.e., informs what portion of the cycle (revolutions) of the complete cycle the firing mechanism is in along the firing stroke. The count correlates to the amount of spins of the driveshaft, effectively controlling the distance of the drive mechanism, e.g., collar. The number of revolutions is tied into a predetermined (selected) speed and a predetermined time. The motor speed can be automatically adjusted during use. Note as the motor operates, if there is a spike in amperage, the central processing unit will slow down the motor rpm, and the time cycle will be adjusted accordingly, along with the encoder detection of the full stroke. 
     In some embodiments, to effect firing, the firing trigger needs to be pressed a first time as a pre-actuation mode and then pressed a second time to advance the firing rod and knife bar. After application of staples, the firing rod and knife bar are retracted to the home position. The articulation switch is then actuated to return the articulation motor and thus the jaws to the home position. The jaws are closed by the clamping handle and the instrument is removed from the patient&#39;s body through the trocar. Note an abort switch can be provided to reverse motor rotation to retract the firing mechanism and knife bar during the procedure. 
     After removal of the instrument, the jaws are open and the spent cartridge is removed. If additional staples are required a fresh cartridge is loaded into the cartridge receiving jaws and the instrument jaws are closed and the instrument is inserted through the trocar (returning to block  7  of the diagram of  FIG.  40   —“manually pull handle to clamp jaws and insert through trocar.”) 
     As noted above, in some embodiments, a switch is located on the power pack which is actuated by the instrument cover when the cover is closed. This is shown in  FIGS.  77 - 82 B . Instrument  900 , like instrument  61  of  FIG.  14 A  described above, has an elongated member  902 , a pair of jaws  907 ,  905  at a distal portion and rotation knob  914 . Pivotable handle  924  is movable toward stationary handle  922  to close the jaws for clamping onto tissue. A clamp release button  926  releases the clamp lever to open (unclamp) the jaws, Pivotable cover  912  has a projection or boss  934  extending at a proximal region which engages activation (power enable) switch  932  on the power module (power pack)  950  when the cover  912  is moved from its open position of  FIG.  77    to the closed position. The power module  950  can be the same as power pack  700  discussed below or any of the other power packs disclosed herein. In this manner, when the motors within the power pack cannot be activated unless the cover  912  is in the closed position. Power pack  950  includes a screen  952  like screen  704  disclosed herein. A pair of articulation buttons/switches  930 , symmetrical about the axis, are disposed on each side of the instrument housing  920  to articulate the jaws  905 ,  907  in either direction, e.g., button  905  articulates the jaws to the left and the button on the opposing side (not shown) articulates the jaws to the right. In alternate embodiments, the opposite buttons can articulate the jaws to left and right. Once the cover is closed and boss  934  engages the power enable switch  932 , the firing mechanism can be activated via switch  928  which in communication with the motor operatively connected to the drive mechanism within the power pack. The electromechanical switch  934  is mounted to PCB board which is fixed within the power pack which communicates with the CPU within the power pack. 
     The cover can have a seal about its periphery and/or a seal around the periphery of the opening to the compartment can be provided, as discussed above, to seal the power pack within the compartment to prevent entry of contaminants. 
     Below is a chart summarizing the safety mechanisms of the surgical instrument in accordance with some embodiments: 
     
       
         
           
               
               
             
               
                   
               
             
            
               
                 Pre-loading 
                 Can&#39;t activate switch when powertrain in cradle 
               
               
                 of power train 
                 Thermosensor in battery pack monitored by electronics in charger to shut 
               
               
                 into instrument 
                 down charger if overheating 
               
               
                   
                 Viewable screen indicates ready/not ready condition of powertrain 
               
               
                   
                 Can&#39;t activate switch if powertrain not properly loaded and instrument 
               
               
                   
                 compartment cover not fully closed 
               
               
                   
                 Loading into instrument prevented if firing and articulation not in home 
               
               
                   
                 position 
               
               
                 Once 
                 Opening of jaws breaks circuit to disable firing mode 
               
               
                 powertrain 
                 Closing of jaws disables articulation mode 
               
               
                 loaded 
                 Cant actuate firing switch if articulation switch activated 
               
               
                   
                 Can&#39;t actuate articulation switch if firing button activated 
               
               
                   
                 Encoder following error if resistance in firing 
               
               
                   
                 Encoder detects proper functioning of motor 
               
               
                   
                 Encoder detects position and completion of firing stroke via motor count 
               
               
                   
                 Encoder detects articulated jaw position via motor count 
               
               
                   
                 Fire button needs to be depressed first as initial step before firing 
               
               
                   
                 Copycat position so can resume where left off if power pack replaced 
               
               
                   
                 Firing abort button to cease advancement of firing rod and retract to home 
               
               
                   
                 position 
               
               
                 Removal of 
                 Can&#39;t remove powertrain if articulation driver not in home position 
               
               
                 Powertrain 
                 Can&#39;t remove powertrain if staple driver not in home position 
               
               
                   
               
            
           
         
       
     
       FIGS.  68 - 76 C  illustrate two embodiments utilizing an encoder to measure either rotational movement of the ball screw ( FIGS.  68 - 73   ) or linear movement of the collar/drive mechanism ( FIGS.  74 - 76 B ). This provides a failsafe if the motor loses communication with the CPU. 
     Turning first to  FIG.  68   , the deployment screw  818  has a collar  830  extending therefrom which functions like collar  94  of the deployment screw of  FIGS.  22 A- 22 D  in that it forms an engagement member for engaging and advancing the firing rod (firing mechanism) in the housing of the surgical stapler. This collar configuration is similar to that of collar  756  of  FIG.  59 A  of application Ser. No. 16/792,110, filed May 15, 2020, the entire contents of which are incorporated herein by reference. 
     Deployment screw  818  differs from these deployment screws in that it supports an electromechanical encoder  810 . More particularly, the encoder  810  is mounted to encoder holder  812  which has a post  813  inserted into opening  826  at a proximal (back) end of screw  818 . Other ways to mount the encoder to the screw are also contemplated. Code wheel  814  is mounted in opening  816   a  of proximal chassis  816 . When the motor is actuated to rotate the deployment screw  818  as described herein to advance the collar  756  and firing mechanism, the static (fixed) code wheel  814  reads the discrete positions of the encoder and sends a signal to the CPU within the power pack indicative of such reading/position. Such rotation count determines the location of the firing mechanism and thus the location of the I-beam firing the staples from the cartridge. Note the number of discrete positions can vary and in some embodiments there are 64 discrete positions. 
     In the alternate embodiment of  FIGS.  74 - 76 B , encoder  846  is fixably attached to collar  846  of deployment screw  848 . (Deployment screw  848  and collar  846  are otherwise the same as screw  818  and collar  830 ). As the collar  846  moves axially distally when the deployment screw is actuated by the motor as described in the embodiments above, the positon of the collar  846  is detected by scale  850 . Scale  850  is attached to the chassis  856  of the power pack housing, and runs along the length of the stroke. The detected axial position of the encoder is sent to the PCB within the power pack for determination of firing mechanism location. Note in this embodiment, the encoder  846  us positioned in an indentation at a proximal end of the collar  852  adjacent nut  854 , but can alternatively be mounted to the collar in other ways/locations. 
     Note an encoder similar to that of  FIG.  68 - 73  or  74 - 76 B  can also be utilized with the articulation screw to determine the positions of the articulation mechanism and thus the articulation angle of the jaws. The encoder could be mounted for example to the articulation screw or collar. 
     A screen can be provided on the top of the powertrain to indicate the firing, clamping and/or articulation modes/positions. The screen can be visible through a clear window in the housing of the instrument. An example of the screen is shown in  FIGS.  55  and  57 A  wherein screen  704  is on a proximal portion of the housing  706  of power pack  700 . The screen in this embodiment angles toward the user. It is covered when instrument compartment cover  702  is closed, and cover  702  has a transparent portion or window (such as window  913  of cover  912  of  FIG.  79   ) so that the screen  704  is visible when the cover  702  is closed. As can be appreciated, the screen can be provided in other positions and portions of the power pack  700 . The screen  704  can show various features and parameters via numeric designations light or other indicators. For example, the screen can show one or more of firing position, articulation position (degree of articulation), the type (staple size and length) of cartridge selected, battery life, clamping position, tissue range, confirmation of home positon of articulation mechanism and/or firing mechanism when loaded and/or when ready for removal from the instrument compartment, confirmation that the cover is in the fully closed position, and/or other conditions of the motor or other components of power pack or instrument. 
     In alternate embodiments of the present invention, the surgical instruments have features to aid staple size selection. These instruments can also provide motor speed adjustments to accommodate different tissue thicknesses. 
     These features include a measurement device such as a force gauge, a strain gauge pressure sensor or other gauges/sensors to measure one or more of i) the clamping force on tissue clamped between the instrument jaws; ii) the clamping pressure on the tissue clamped between the jaws and/or iii) tissue density within the jaws of the instrument. The gauges/sensors can be placed on various locations of the instrument, including proximal and distal portions. Alternatively, the sensors/gauges can be placed on the loadable power pack. These variations are discussed in detail below with reference to  FIGS.  42 A- 45 F . Note that the instruments of  FIGS.  42 A- 44 C  show several gauges/sensors within the instrument to illustrate examples of possible locations for the gauges/sensors. It is not intended that all of the depicted gauges/sensors need to be in a single instrument as it is contemplated that only one of the gauges/sensors is in the instrument. However, it is also contemplated that more than one gauge/sensor can be provided in the instrument. 
     In some embodiments a screen is located in the handle housing (see screen  613  of  FIG.  42 D ) or on the power module to provide a visual indicator to the clinician of the measured parameter(s). For example, clamping forces, tissue or clamping pressures, and/or tissue densities measured or calculated by the sensors/gauges as disclosed herein can be displayed on the power module TTF, LCD or Human Machine Interface screen to give real-time feedback to the surgeon. This real-time feedback can be used along with tactile manual clamping. This can induce faster learning for the surgeon on acceptable tissue being clamped. 
     Turning first to  FIGS.  42 A- 42 F , several different possible locations for the force measurement device are provided. For brevity of the drawings, as noted above,  FIG.  42 D  and identical  FIG.  43 A  show in a single drawing multiple possible locations for the gauges/sensors. Note only one of these locations can be utilized or alternatively, gauges/sensors can be placed on more than one of the identified locations, as well as in other locations. These locations can be on a movable part related to clamping of the jaws or on a joint where there is a transfer of force. As used herein, the term measurement device will be used to denote gauges or sensors or other devices to measure one or more of clamping force, clamping pressure, tissue density and/or other parameter. 
     The instrument  600  of  FIGS.  42 A- 43 C  is identical to the instrument of  FIG.  14 A  described above except for the measurement features and the cam pin/slot arrangement for opening and closing the jaws. 
     The cartridge jaw  607  is shown in the open position in  FIGS.  42 A,  42 B and  42 D , spaced from anvil (or anvil jaw)  605 , i.e., the cartridge received in cartridge receiving channel of cartridge jaw  607  is spaced from anvil forming surface  605   a  of anvil  605 . The anvil forming surface  605   a  deforms the staples fired from the cartridge jaw  607 . In the open (unclamped) position, the clamp pin  604  is at a distal end of clamp pin slot  603  (see  FIG.  51   ). In this position, the clamp rod (clamp shaft)  620  and the clamp laminates  616  are in the distal position. Clamp laminates  616  connect clamp rod  620  to the distal clamp adapter  622  via hook engagement of hook  616   a  at the distal end of clamp laminates  616  and a hook at the proximal end of the clamp adapter  622 . The clamp laminates  616  can be fixedly attached to the clamp rod  620  and clamp adapter  622  or alternatively floatably attached to these components. The flexibility of the clamp laminates  616  allows for articulation of the jaws  605 ,  607 . 
     Upon manual clamping of the handle  609 , i.e. movement toward stationary handle  611 , to effect closure of the cartridge jaw  607 , the clamp rod  620 , which is operatively connected to the clamping handle  609 , is pulled proximally, thereby pulling the attached clamp adapter  622  proximally. This moves the through pin  604  which is attached to clamp adapter  622 , proximally within the cam slot  603  to move the cartridge jaw  607  toward the anvil jaw  605  to a clamped (closed) position as the cartridge jaw  607  pivots about pivot pin  624 . The clamp pin  604  translates in the slot  603  relative to the location of the clamp rod position. The cartridge jaw  607  rotates around the pivot pin  624  relative to the location of the clamp pin  604  in the cam slot. The pin/slot arrangement is shown in  FIGS.  49 - 51   . Further details of the clamp pin/slot structure for closing and opening the jaws are described in application Ser. No. 16/792,110 and provisional application Ser. No. 62/900,146, filed Sep. 13, 2019, the entire contents of which are incorporated herein by reference. 
     In the embodiments of  FIGS.  42 E and  42 F , the measuring device is placed distal of the handle housing  602 . More specifically, in  FIG.  42 E . the load pin (clamp pin)  604 , which is movable within the cam slot  603  as described above based on the axial movement of the clamp rod  620 , measures force as the cartridge jaw  607  is moved to the closed position. 
     In an alternate embodiment, the load cell  606  is located in the distal clamp adapter  610 . The load cells herein can form transducers for converting force into a measurable electrical signal. The distal clamp adapter  610  is actuated, i.e., moved axially, by the clamp laminates  616  which are connected to the clamp rod  620  which is movable to close and open the cartridge jaw  607 . Note the laminates have slots which interact with the wall of the clamp rod  620  to move with the clamp rod, thus they are floatably connected to the clamp shaft. The load cell  606  is shown located at a proximal portion of the clamp adapter  610  where it is hooked to the clamp laminates  616 , however it could be located at other regions of the clamp adapter  610 . Axial movement of the clamp rod  620  moves the clamp adapter  610  to measure force as the cartridge jaw  607  is moved to the closed position. 
     In an alternate embodiment, the load cell  608  is located at a distal end of the clamp rod  620 . It is shown at the distalmost end of the clamp rod  620 , where the clamp rod  620  is hooked to the clamp laminates  616 , but alternately can be located at other regions of the clamp rod  620 . Axial movement of the clamp rod  620  measures force as the cartridge jaw  607  is moved to the closed position. 
     Note these load cells  604 ,  606  and  608  are positioned at the distal region of the instrument adjacent and proximal of the instrument jaws  605 ,  607  and proximal of the jaw pivot pin  624 . Note load cell  604  provides an example of the measurement device on a load cell pin of the instrument; load cells  606 ,  608  provide an example of the measurement device on an axially movable part tied into jaw movement placed under load during clamping of the jaws on tissue. In this manner, clamping pressure or clamping force can be measured. Tissue density can also be measured. 
     The measurement device can alternatively be positioned further proximally of the jaws  605 ,  607  as shown for example in  FIG.  42 F . As shown, strain gauge  626  is located in the clamp shaft (clamp rod)  620  distal of the handle seal. That is, it is adjacent the handle  602  and distal thereof (and distal of the rotation knob  615 ). The clamp shaft  620  is movable axially to effect jaw opening and closing and thereby enabling gauge  626  to measure the force. Alternatively, the strain gauge can be located in a proximal region of the clamp shaft  620  proximal of the handle seal as shown for example in  FIG.  43 B  discussed below. 
     In the foregoing embodiments, the measurement devices are positioned distal of the handle housing  602 . In the alternate embodiments of  FIGS.  43 A- 44 C , the measurement devices are positioned in the handle portion with  FIG.  43 B  illustrating the measurement device within the handle housing  602  and located in/on the axially movable clamp rod  620  and  FIGS.  43 C,  44 B and  44 C  illustrating the measurement device on the manually actuated clamping handle or linkage. 
     More specifically,  FIG.  43 B  illustrates strain gauge  630  positioned in the proximal region of the axially movable clamp rod  620  within the handle housing  602 . Thus, the gauge  630  is positioned proximal of the handle seal.  FIG.  43 C  illustrates a) strain gauge  638  located at the proximal end of the proximal clamp adapter  632 ; and b) strain gauge  634  located at the distal end of the clamp adapter  632 . Proximal clamp adapter  632  is actuated by the clamp pivot plate  640 . Strain gauge  634  is actuated by the proximal lip of the clamp rod  620  which is attached to proximal clamp adapter  632 . The clamp adapter  632 , clamp rod  620  and clamp pivot plate  640  are shown in the enlarged view of  FIGS.  46 - 48   . 
     In alternate embodiments, the load pin can be located at one or more of the pin locations on the clamp pivot plate  640 . The pivot plate  640  is connected at one end to link or clamp yoke  645  via pin  642   a  and at the other end to clamp adapter  632  via pin  642   c . Link  645  is connected to clamping handle  609  at the opposing end. Pin  642   b , positioned between pins  642   a  and  642   c  connects to the adapter  632 . Pins  642   a ,  642   b ,  642   c  form load pins for force measurement based on movement of the pivot plate during clamping of the jaws  607 ,  605  initiated by manual movement of handle  603 . It should be appreciated that only one, only two or all three load pins  642   a ,  642   b  and  642   c  could be used in a single instrument. When clamping handle  609  is moved toward stationary handle  611 , it causes movement of yoke  645  which pivots the plate  640  clockwise about pivot pin  642   b  to move the proximal clamp adapter  632  proximally to effect proximal movement of the clamp rod  620  which moves the cam pin  604  ( FIG.  51   ) proximally within cam slot  603  to move cartridge jaw  607  toward anvil jaw  605  to clamp the jaws. 
     In the embodiment of  FIG.  44 A , the load pin  646  is located at the clamp pivot location, i.e., it connects handle  603  with the clamp yoke (link)  645 . Movement of handle  609  effects movement of clamp yoke  645  as described above. In  FIG.  44 C , the load cell  648  is located in or on the clamp yoke  645  which can be in the form of a split yoke or complete yoke. It is outside the sterile portion of the handle housing  602   a  and is positioned on yoke  645  between the handle  609  and the pivot plate  640 . The load cell can alternatively be positioned in other regions of the link  645 . 
     As in the embodiments above, when provided on the instrument, the measurement device, e.g., the force gauge/strain gauge can be in line with the clamp linkage of the disposable instrument and/or in line with the clamp rod. It can be in the front of the clamp stroke, in the middle or in the back at or near the proximal clamp adapter. It can be inside or outside the handle housing. It can also be offset from the clamp rod such as below or side by side with the clamp bar. It could also be in line in the tube, distal of the handle so it does not need to rotate. It can also be inside the distal jaws of the instrument. 
     As noted above, the load cell can in alternative embodiments be located in the removable power pack as shown in  FIGS.  45 A- 45 F . The force gauge/strain gauge  654  is inside the reusable power module  652  and connected to the clamp linkage of the disposable instrument either through a split clamp linkage or at end of the clamp linkage stroke supported with a spring. As described above, the power module  654  is loaded into the compartment of the handle housing  602   a  and cover  656  seals the compartment. The measurement device e.g., load cell  654 , within power module  652  measures clamp linkage linear movement/distance to determine the theoretical gap between the jaws for force measurement. That is, the load cell  654  mates with the clamp rod  620  as it drops into the linkage and translates with the clamp rod  620  during axial movement of the clamp rod  620  to measure clamp force. This can be used together with strain gauge/force gauge reading to calculate tissue density through the entire clamp stroke. 
     The force gauge is powered from power module and communicates with the power module microprocessor. 
       FIGS.  56 - 66 B  illustrate another alternate embodiment wherein the load cell is positioned in the power pack. In this embodiment, the deployment screw  710  and articulation screw  750  are supported by axial bearings and thrust bearings. 
     Thrust (axial) bearings and radial bearings on opposing ends of the screw  710  provide centering and axial alignment of the screw  710  during use. These thrust and radial bearings function in the same manner as thrust bearings  768 ,  780  and radial bearings  757 ,  782  of screw  754  of the embodiment of  FIG.  59 B  of co-pending application Ser. No. 16/792,110, filed May 15, 2020, the entire contents of which are incorporated by reference as noted above. As shown. thrust bearing  716  is mounted at the distal end of screw  710  and thrust bearing  736  is mounted at the proximal end of the screw  710 , proximal of collar  712 , to resist any axial force applied to the rotating screw  710  and maintain its axial position. Radial bearings  724 ,  734  are provided to resist radial loads (forces that are perpendicular to the direction of the screw) and are located on the respective distal and proximal ends of the screw  710  with radial bearing  724  distal of thrust bearing  716  and radial bearing  734  proximal of thrust bearing  736 . The thrust bearings  716 ,  736  are slip fit over the outer diameter of the deployment screw  710  ( FIG.  59   ), at distal and proximal ends, respectively, and thus float relative to the screw  710 . They are sandwiched together with the chassis. The radial bearings are press fit into openings in distal plate  744  and proximal plates as in application Ser. No. 16/792,110. The deployment screw  710  has a reduced diameter portion at the proximal end ( FIG.  57 C ) and distal end ( FIG.  57 B ) to form a shoulder  713  and  715 , respectively, at the larger diameter portions which abut, i.e., contact, thrust bearings  736 ,  716 , respectively. Thus, the thrust bearings  716 ,  736  can rotate freely within the housing, but are constrained by the steps (shoulders) of the ball screw  710  so they cannot move along the axis of the screw. The belt  723  and pulley  722  of the deployment (firing) mechanism are shown in  FIG.  57 B  and are the same as in the foregoing embodiments. 
     Collar  712  has mounted thereto a pair of left and right track bearings  714  which function in the same manner as left track bearings  779  and a pair right track bearings  778 , e.g., traveling along tracks in the  760 ,  762 , described in detail in the Ser. No. 16/792,110 application, thereby preventing rotation out of the track as forces are translated linearly along shaft as the nut translates forward and backward. The tracks can be attached to or integrated (monolithic) with the chassis. The collar  712 , like collar  756  of FIG. 59A of the Ser. No. 16/792,110 application includes a blade/tab extending inwardly from the wall which engages a circumferential recess (groove) in the deployment disk of the stapler which is attached to (or extends from) the firing rod of the stapler. In this manner, axial movement of collar  712  (via ball screw  710  when actuated by the motor) moves the deployment disk axially, the collar traveling along the respective left and right tracks (runners) via respective left and right bearings  714 . 
     The deployment screw  710  includes a load cell or strain gauge  730  at the proximal end which is sandwiched between distal and proximal plates  738   b ,  738   a . The deployment screw  710  further includes a load cell or strain gauge  720  at the distal end which is sandwiched between distal and proximal plates  718   b ,  718   a . These load cells behind the thrust bearings measure force during firing. This can prevent the motor from being faulted. If the load cell detects an energy spike, a signal is sent to the microprocessor within the power pack  700  to slow down the motor. 
     The articulation screw  750  has distal thrust and axial bearings  762 , 763  ( FIG.  62 B ) and proximal thrust and axial bearings  772 , 776  ( FIG.  62 C ), similar to the thrust and axial bearings of the articulations screw  752  of FIG. 60A of the Ser. No. 16/792,110 application. Articulation screw has a load cell or strain gauge  760  ( FIG.  62 B ) at the distal end which is sandwiched between distal and proximal plates  764   b ,  764   a . The articulation screw  750  further includes a load cell or strain gauge  770  at the proximal end which is sandwiched between distal and proximal plates  774   a ,  774   b . These load cells behind the thrust bearings measure articulation force. This can prevent the motor from being faulted. If the load cell detects an energy spike, a signal is sent to the microprocessor within the power pack  700  to slow down the motor. 
     The present invention can also provide a system that indicates to the user acceptable ranges for fastener application. Forces, tissue or clamping pressures, and/or tissue densities measured or calculated by the sensors/gauges as disclosed herein can are displayed on the power module TTF, LCD or Human Machine Interface screen on the instrument housing to give real-time feedback to the surgeon. Based on forces, measured pressure and densities pre-calculated from tissue testing which provide a baseline and maximum and interim values, the Human Machine Interface (HMI) screen will indicate if the measurement is within an optimal range for acceptable staple line outcome. This can be understood with reference to the diagram of  FIG.  52   .  FIG.  52    shows the gauges can be provided a) in the clamp linkage (which includes components effecting mechanical clamping of the jaws (e.g., the manual clamp handle, cam pivot plate, adapter, clamp rod etc.) and/or b) in the power module, e.g., the component(s) therein tied into clamp rod movement; and/or c) in the instrument jaws. For (a) and (b) the clamp linkage movement, e.g., linear or pivotal movement is measured; for (c) the jaw movement toward the opposing jaw is measured. This can provide sufficient information for force determination. However, the information can also be used to determine tissue density as depicted in the optional last boxes of the diagram of  FIG.  52   . 
       FIG.  54    provides a flow chart depicting one embodiment of a system where the instrument determines if the staple size is appropriate based on the preset ranges where the values are pre-calculate/predetermined. More particularly, the jaws are clamped on tissue in the manners discussed herein and a parameter, e.g., clamping force, pressure and/or tissue density is measured utilizing one or more of the measurement devices disclosed herein. The measured parameter is compared by the microprocessor (e.g., a microprocessor in the power module) to the pre-set range. If the measured parameter is within the acceptable range, then firing is enabled and articulation is disabled. The microprocessor, based on the measured parameter, will then account for motor speed accordingly. That is, the microprocessor will control and adjust the motor speed, i.e., the microprocessor using AI will control or change the firing speed of the deployment motor based on the range detected whereas thin tissue will fire at faster speeds, medium tissue at nominal speeds and thick tissue will fire at slower speeds to enable tissue fluid to egress and reduce the forces on the stapler system. 
     If the measured parameter is outside the acceptable range, then firing is disabled and the instrument recommends, e.g., via a screen or other indicator on the instrument or power module, alternative size staple load either smaller or larger in size. 
     Note the Human Machine Interface screen will indicate whether it is in the acceptable range (thin/less dense/low pressure or medium/average density/nominal pressure or thick/more dense/high pressure). It is contemplated that in some systems, the optimal force/pressure/density of tissue would be staple load size agnostic and the same ranges would apply to all load sizes. In other systems, a staple size selector switch on the power module is provided so the forces/pressure/density would be staple load size specific and in certain applications provide more precise indications/motor controls. 
     In some embodiments, if a strain gauge reading records a force/pressure or tissue density within a predetermined range so the stapling function is indicated, i) the power module microprocessor will enable the firing sequence of the device to deploy staples and ii) the power module microprocessor will disable the articulation functionality of the device. On the other hand, if a strain gauge reading records a force/pressure or tissue density outside a predetermined range so the stapling function is not indicated, the power module microprocessor will disable the firing sequence of the device putting it in a lockout condition not allowing staple firing. 
     In some embodiments, the surgeon will be provided the option to override the device. 
     A gauge in the form of a cartridge can be provided in some embodiments so the surgeon can load and clamp on tissue prior to selecting a cartridge load size. This cartridge load gauge enables the surgeon to select a proper cartridge size without potentially wasting the wrong size cartridge. The surgeon will load the gauge (dummy cartridge) into the instrument. Then the surgeon palpates tissue with the jaws to determine staple height size and the device will indicate an optimal cartridge size such as via an output on the screen. The surgeon then removes the dummy cartridge and inserts the indicated staple cartridge in the cartridge jaw. These steps are shown in the flow chart of  FIG.  53   . 
     A clamp indicator in the window/can be provided to show where in the range the tissue falls based on the cartridge selected. The firing speed via AI (machine inference) can be controlled based on the cartridge selected and/or clamp indication measurements. 
     In some embodiments, the power pack can have a reader, such as an RFID reader, for detecting a type of staple cartridge prior to loading the staple cartridge in the instrument. The staple cartridge can have a code or tag, such as an RFID tag, and would be held adjacent the loaded power pack for detection of the type of cartridge, i.e., the size of the staples in the cartridge and/or the length of the arrays of staples within the cartridge. When detected, a signal is sent to the control module within the power pack to indicate which cartridge size is selected so the clamp force can be adjusted accordingly, and in some embodiments, indicated in the window/screen of the power module. The microprocessor can also preset the motor to correspond to the type of cartridge selected. The control module can be configured so that if a cartridge is loaded without its chip being read by the RFID reader, then the instrument cannot be actuated, e.g., cannot be fired. It can also be configured, so that the reader will detect if the cartridge has been fired (spent), i.e., devoid of staples, and if spent, the instrument cannot be actuated e.g., cannot be fired. The RFID tag can be on the plastic cartridge cover to minimize interference or assembled into the cartridge. Note alternatives to RFID readers to identify cartridge type, e.g., size, are also contemplated, with such identifiers communicating with the microprocessor in the power pack to adjust the clamping and/or firing parameters. 
     The logic circuit in some embodiments could be as follows: 1) load the power pack (in the home position) into the instrument compartment (the instrument cannot be actuated unless a power pack is loaded); 2) close the cover to enable the switch for articulation and the switch for firing (an enable mode); 3) select a cartridge and hold it adjacent the power pack to activate the load cells and to send a signal to the microprocessor confirming the cartridge has not been previously fired and to set the firing speed and adjust for other parameters, e.g., staple line length and firing stroke; 4) once all is active, place the cartridge in the instrument jaw; 5) the articulation switch and firing switch can be activated for performing the surgical procedure. 
     In some embodiments, a supercapacitor on the PCB can be provided to store enough energy to maintain microprocessor memory if the battery is exchanged or if the wrong size cartridge is utilized (wasted). 
     The load cell can be utilized in some embodiments for data acquisition to provide post procedure evaluation. In the manual option, the sales/OR staff will download case data from the power module via data transfer interface (e.g., USB). Data will be sent to HQ for trending and optimization for future cases. The feedback can be used to provide surgeons with ideal load selection. Note this would require staff present to input outcomes. In an alternative automatic option, the sales/OR staff will connect to the device via Bluetooth/wireless on their iPad or other mobile device and the data will be sent from the sales staff iPad (or other device) for trending and optimization for future cases. Other data collected and stored for such uses can further include biometrics, number of devices fired by the power pack; the length of the surgical procedures, forces generated, tissue information, operation of the stapling components and power pack components and other parameters of the tissue, surgical procedure, stapling instruments and/or power pack. 
     The foregoing measurement devices were discussed for use in surgical staplers. They can be used in open and endoscopic and laparoscopic staplers. However, they can also be used to measure pressure, force and/or tissue density in other instruments with clampable jaws such as graspers, energy devices, shears, clip appliers (where the measurement would prompt the surgeon to check clip closure based on force feedback of clip deployment). 
     Note the output can be digital. The output can be serial. It can be measured by voltage output. 
     A firing profile graph can be shown through HMI on the power module, visible through an instrument screen. High/low lines as with a statistical process control chart (SPC) will allow the surgeon to maintain a “safe” firing speed. That is, the graph will provide an indication to the surgeons where they are during the stroke. For example, if force is too high, they may want to take action to reduce the force or pause firing. An example of a chart is provided in  FIG.  83   . In the chart, line A represents motor speed, line C represents the measured force and line B represents the optimal force. As shown, for example, if the force spikes, the motor speed is slowed accordingly. 
     In the foregoing embodiments, use of the power pack of the present disclosure to fire staples such as in endoscopic linear staplers, open surgery linear staplers, circular staplers, as well as firing single clips or tacks were disclosed as examples. It should be appreciated that the power packs of the present disclosure can also be used to power functions of other surgical instruments.  FIGS.  33 A- 34 D  illustrate two examples of such instruments. 
     In  FIGS.  32 A- 32 D  an endoscopic scissors, designated generally by reference numeral  300 , can receive and be powered by the power pack  18  (or power pack  90 ) of the present disclosure. Scissors  300  has a handle  306  manually pivotable towards stationary handle  304  to effect closing of the jaws, an elongated tubular portion  308  extending from the handle housing  302 , and a pair of pivotable jaws  312  with cutting edges. Closing of the jaws  312  severs tissue between the jaws. The scissors  300  include a rotation knob  310  for rotation of the elongated portion (shaft)  308  to rotate the jaws  312 . Power pack  18  is shown fully loaded (inserted) within the handle housing  302  and cover  303  is shown closed to seal the power pack  18  from the external environment. As in the embodiment of  FIGS.  1 - 12   , the flag  42  extending from lead screw  36  engages a rod within the handle housing  302  operably connected to a jaw closing mechanism to effect movement of jaws  312  toward each other to sever tissue between the jaws  312 . Either one or both jaws  312  can be movable. 
     In  FIGS.  33 A- 33 D  an endoscopic grasper, designated generally by reference numeral  320 , can receive and be powered by the power pack  18  (or power pack  90 ) of the present disclosure. Grasper  320  has a handle  326  manually pivotable towards stationary handle  324  to effect closing of the jaws  332 , an elongated tubular portion  328  extending from the handle housing  322 , and a pair of pivotable jaws  332  with grasping surfaces that can include teeth, roughened surfaces, ribs, etc. Closing of the jaws  332  grasps tissue between the grasping surfaces of jaws  332 . Either one of the jaws can be movable, i.e., pivotable, or both jaws can be movable (pivotable) toward and away from each other, for movement between closed and open positions. The graspers  320  includes a rotation knob  330  for rotation of the elongated portion (shaft)  328  to rotate the jaws  332 . Power pack  18  is shown fully loaded (inserted) within the handle housing  322  and cover  323  is shown closed to seal the power pack  18  from the external environment. As in the embodiment of  FIGS.  1 - 12   , the flag  42  extending from lead screw  36  engages a rod within the handle housing  322  operably connected to a jaw closing mechanism to effect movement of jaws  332  to close the jaws to grasp tissue between the jaws  332 . It should be appreciated that the aforedescribed variations of the power packs can also be used with the surgical instruments of  FIGS.  32 A and  33 A . 
     The power packs  18  and  90  disclosed herein can be used in surgery where the clinician manually clamps the jaws and actuates the motor or motors to provide powered staple firing and/or powered jaw articulation. It is also contemplated that the power packs  18  and  90  can be used with robotic driven surgical staplers wherein clamping, motor actuation and any other functions of the instrument are performed robotically, including remote robotic control. 
     The staplers disclosed herein, or certain components thereof, can be made of environmental friendly biodegradable materials. For example, the handle can be made of biodegradable material. Such material can include for example corn based lactic acid. The packaging for the surgical staplers and/or the packaging for the power packs and/or the battery packs can also be composed of biodegradable materials to minimize the carbon footprint. 
     Although the apparatus and methods of the subject disclosure have been described with respect to preferred embodiments, those skilled in the art will readily appreciate that changes and modifications may be made thereto without departing from the spirit and scope of the present disclosure as defined by the appended claims. 
     Additionally, persons skilled in the art will understand that the elements and features shown or described in connection with one embodiment may be combined with those of another embodiment without departing from the scope of the present invention and will appreciate further features and advantages of the presently disclosed subject matter based on the description provided. 
     Throughout the present invention, terms such as “approximately,” “generally,” “substantially,” and the like should be understood to allow for variations in any numerical range or concept with which they are associated. For example, it is intended that the use of terms such as “approximately” and “generally” should be understood to encompass variations on the order of 25%, or to allow for manufacturing tolerances and/or deviations in design. 
     Although terms such as “first,” “second,” “third,” etc., may be used herein to describe various operations, elements, components, regions, and/or sections, these operations, elements, components, regions, and/or sections should not be limited by the use of these terms in that these terms are used to distinguish one operation, element, component, region, or section from another. Thus, unless expressly stated otherwise, a first operation, element, component, region, or section could be termed a second operation, element, component, region, or section without departing from the scope of the present disclosure. 
     Each and every claim is incorporated as further disclosure into the specification and represents embodiments of the present disclosure. Also, the phrases “at least one of A, B, and C” and “A and/or B and/or C” should each be interpreted to include only A, only B, only C, or any combination of A, B, and C.