Patent Publication Number: US-2023143166-A1

Title: Surgical stapler with removable power pack

Description:
This application claims priority from provisional application Ser. No. 62/553,297, filed Sep. 1, 2017 and from provisional application Ser. No. 62/616,045, filed Jan. 11, 2018. 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 more particularly, to surgical staplers having removable power packs 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. 
     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 disclosure, a surgical fastener applier is provided comprising a housing containing a compartment therein and an elongated member extending distally from the housing. A first jaw and a second jaw are positioned at a distal portion of the elongated member, wherein at least the first jaw is movable with respect to the second jaw to clamp tissue between the first and second jaws. A firing mechanism is positioned within the housing and is movable between a first position and a second firing position, wherein in the second position, the firing mechanism effects firing of fasteners into the tissue clamped between the first and second jaws. A cover on the housing is openable to access the compartment within the housing and a power pack is removably loadable into the compartment, the power pack having a motor and an engagement member removably engageable with the firing mechanism within the compartment when the power pack is loaded into the compartment to effect movement of the firing mechanism from the first position to the second firing position. 
     In some embodiments, a first seal to seal about the cover in the closed position is provided to protect the power pack positioned within the housing and/or the apparatus includes a second seal to block passage of body fluids from the elongated member into the compartment. 
     In some embodiments, the power pack has a housing and one of the housing or the compartment has at least one external rib and another of the housing or the compartment has at least one groove to receive the rib to guide the power pack within the compartment. Other guide structures could alternatively be provided. 
     In some embodiments, the power pack includes a second engagement member removably engageable with an articulating mechanism of the surgical fastener applier 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 power pack can include a second motor and the second motor can effect linear movement of the articulation mechanism of the surgical fastener applier. 
     In some embodiments, the power pack includes a gear mechanism powered by the motor, wherein rotation of a motor shaft of the motor effects rotation of the gear mechanism which effects linear movement of the firing mechanism of the surgical fastener applier. In other embodiments, the power pack includes a drive belt powered by the motor, wherein rotation of a motor shaft of the motor effects rotation of a first disc which moves the drive belt to effect linear movement of the firing mechanism of the surgical fastener applier. 
     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 and a jaw assembly including a first jaw and a second jaw at a distal portion of the elongated member wherein at least the first jaw is movable with respect to the second jaw. A jaw clamping mechanism is movable between a first position and second position to move at least the first jaw toward the second jaw to clamp tissue between the first and second jaws. A firing mechanism is movable between a first position and a second firing position to fire fasteners into the tissue clamped between the first and second jaws. An articulation mechanism is movable between a first position and a second position to articulate the jaw assembly from a linear position to a second position angled with respect to a longitudinal axis of the elongated member. A cover on the housing is movable from a closed position to an open position to access the compartment. A power pack is loadable into the compartment, the power pack having a motor and an engagement member engageable with the articulation mechanism to effect movement of the articulation mechanism from the first position to the second position. 
     In some embodiments, the power pack includes a gear mechanism for moving a drive mechanism linearly to move the articulation mechanism linearly to articulate the jaw assembly. In other embodiments, the power pack includes a drive belt for moving a drive mechanism linearly to move the articulation mechanism linearly to articulate the jaw assembly. 
     In accordance with another aspect of the present disclosure, a method for powering a surgical stapler is provided comprising the steps of:
         providing a surgical stapler having a housing containing a compartment and a cover movable between a closed position and an open position;   loading a power pack having a drive mechanism into the compartment when the cover is in the open position, wherein the step of loading the power pack releasably engages the drive mechanism with a firing mechanism in the housing;   closing the cover to seal the compartment from an external environment;   actuating the motor to move the drive mechanism linearly to thereby move the firing mechanism linearly to advance a plurality of staples into body tissue; and   after advancing the staples, opening the cover and removing the power pack from the compartment to release the engagement of the drive mechanism from the firing mechanism.       

     In some embodiments, the surgical stapler has first and second jaws movable from an open position to a closed by position by manual movement of a handle. 
     In some embodiments, the step of loading a power pack into the compartment releasably engages a second drive mechanism of the power pack with an articulation mechanism in the housing. 
     In accordance with another aspect of the present invention, a power pack is provided removably loadable into a housing of a surgical instrument, the power pack comprising a motor having a motor shaft, a rotatable disc operably connected to the motor shaft, a drive mechanism operably connected to the rotatable disc, and an engagement member linearly movable by the drive mechanism. The engagement member is configured to removably engage an axially movable member in the housing of the surgical instrument, wherein actuation of the motor causes linear movement of the engagement member to effect movement of the axially movable member in an axial direction. 
     In some embodiments, the rotatable disc is engageable with a drive belt to move the drive mechanism in an axial direction. In some embodiments, the rotatable disc is a gear for moving the drive mechanism axially. 
     In some embodiments, a second engagement member is provided which is configured to engage a second axially movable member in the housing of the surgical instrument. A second motor and second rotatable disk can be provided for moving the second engagement member axially. 
     In some embodiments, the first motor is configured to drive a plurality of staples through tissue and the second motor is configured to articulate jaws of the surgical instrument to an angled position with respect to the instrument. In some embodiments, the first motor is configured to move the jaws of the surgical instrument between an open and closed position. 
     In accordance with another aspect of the present disclosure, a surgical instrument 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. An advancing mechanism is positioned within the housing and is movable between a first position and a second position. A cover on the housing is openable to access the compartment within the housing. A power pack is loadable into the compartment, the power pack having a motor and an engagement member engageable with the advancing mechanism within the compartment when the power pack is loaded into the compartment to effect movement of the advancing mechanism from the first position to the second position. 
     In some embodiments, the advancing mechanism is operably connected to at least one of the first and second jaws, wherein movement of the jaw advancing mechanism effects closing of the first and second jaws. In other embodiments, movement of the advancing mechanism effects firing of at least one fastener into the tissue clamped between the first and second jaws. 
     In some embodiments, the power pack has a second motor and a second engagement member engageable with a second advancing mechanism positioned within the housing of the instrument when the power pack is loaded into the compartment to effect movement of the second advancing mechanism from the first position to the second position. 
     In accordance with another aspect of the present disclosure, a surgical instrument is provided comprising a housing containing a compartment therein configured to receive a power pack, 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 firing position, wherein in the second position, the firing mechanism effects firing of at least one fastener into the tissue clamped between the first and second jaws. A cover is mounted on the housing movable from a closed position to an open position to access the compartment within the housing, the cover in the closed position sealing the compartment from the external environment to protect a power pack when loaded therein. A first seal is provided to prevent flow of body fluids into the compartment from the elongated member to protect the power pack when loaded in the compartment. 
     In some embodiments, the housing contains a firing rod positioned therein to removably receive an engagement member of the power pack when loaded therein for motorized advancement of the firing rod to effect firing of at least one fastener supported in the instrument. 
    
    
     
       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.  1 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 ; and 
         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 ; and 
         FIG.  34 D  is a front view of the fastener applier of  FIG.  34 A . 
     
    
    
     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 instances, 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. 
     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. 
     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  23  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 . 
     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. 
     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 . 
     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. 
     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.