Patent Publication Number: US-11653922-B2

Title: Surgical stapling device with firing lockout mechanism

Description:
FIELD 
     The disclosure is directed to surgical stapling devices having staple cartridges and, more particularly, to surgical stapling devices with lockout mechanisms to prevent firing of the stapling device when a knife is not present in the staple cartridge. 
     BACKGROUND 
     Surgical stapling devices for simultaneously stapling and cutting tissue are well known in the art and include a tool assembly and a drive assembly. The tool assembly includes an anvil assembly and a cartridge assembly having a channel member and a staple cartridge that is received within the channel member. Typically, the staple cartridge includes a cartridge body that supports staples, pushers, and an actuation sled. The actuation sled is movable through the cartridge body from a retracted position to an advanced position into sequential engagement with the pushers to sequentially eject the staples from the cartridge body. 
     In some stapling devices, a knife is supported on the actuation sled and is movable with the actuation sled through the cartridge body. The drive assembly is positioned proximally of the actuation sled and is movable in relation to the anvil and cartridge assemblies to advance the actuation sled and knife through the staple cartridge to move the tool assembly between open and clamped positions, to eject the staples from the cartridge body, and to cut tissue clamped between the anvil and cartridge assemblies. After the stapling device is fired, the actuation sled and knife remain in a distal portion of the staple cartridge. 
     When a stapling device is fired with a staple cartridge that does not have an actuation sled and/or a knife present in a proximal portion of the staple cartridge, staples will not be ejected from the staple cartridge and tissue will not be cut. A continuing need exists for a lock mechanism of simple construction that can prevent advancement of a drive assembly of a stapling device through the staple cartridge when a sled and/or knife is not present in the proximal portion of the staple cartridge. 
     SUMMARY 
     This disclosure is directed to a stapling device having a tool assembly including a cartridge assembly, an anvil assembly, and a drive assembly. The anvil assembly supports a lockout mechanism that prevents advancement of the drive assembly when the cartridge assembly does not have an actuation sled or knife present in a proximal portion of the cartridge assembly. 
     Aspects of this disclosure are directed to a surgical stapling device that includes an elongate body, a tool assembly, and a drive assembly. The elongate body has a proximal portion and a distal portion. The tool assembly is supported on the distal portion of the elongate body and includes a cartridge assembly and an anvil assembly that are coupled together to facilitate movement of the tool assembly between open and clamped positions. The cartridge assembly includes a staple cartridge having a cartridge body, staples, pushers, and an actuation sled and knife assembly. The actuation sled and knife assembly includes an actuation sled and a knife supported on the actuation sled for movement between raised and lowered positions. The actuation sled and knife assembly is movable within the cartridge body from a retracted position to an advanced position to eject the staples from the cartridge body and to cut tissue clamped between the cartridge and anvil assemblies. The anvil assembly includes a lockout mechanism that is linearly movable from a locked position to an unlocked position. The actuation sled and knife assembly is positioned to urge the lockout mechanism to its unlocked position when the actuation sled and knife assembly is in its retracted position. The drive assembly is positioned proximally of the actuation sled and knife assembly and is movable in relation to the tool assembly between a retracted position and an advanced position to move the tool assembly between the open and clamped positions and to move the actuation sled and knife assembly from its retracted position to its advanced position. The lockout mechanism is positioned to prevent movement of the drive assembly from its retracted position to its advanced position when the lockout mechanism is in its locked position. 
     In aspects of the disclosure, the lockout mechanism includes a lockout member that is movable between the locked and unlocked positions. 
     In some aspects of the disclosure, the lockout mechanism includes a biasing member that is positioned to urge the lockout member to the locked position. 
     In certain aspects of the disclosure, the anvil assembly includes an anvil plate that supports a housing that defines an opening, and the lockout member and the biasing member are positioned within the housing. 
     In aspects of the disclosure, the lockout member is movable through the opening in the housing between the locked and unlocked positions. 
     In some aspects of the disclosure, the anvil assembly includes an anvil plate that defines a central knife slot that defines a longitudinal axis, and the lockout member extending across at least a portion of the central knife slot when the lockout member is in the locked position. 
     In certain aspects of the disclosure, the drive assembly includes a working member that has an I-beam configuration and includes a first beam, a second beam, and a vertical strut that connects the first beam to the second beam. 
     In aspects of the disclosure, the vertical strut is positioned to translate through the central knife slot of the anvil plate as the drive assembly moves between its retracted and advanced positions. 
     In some aspects of the disclosure, the lockout member has a distally facing cam surface that defines a plane that forms an acute angle with the longitudinal axis of the central knife slot of the anvil plate. 
     In certain aspects of the disclosure, the distally facing cam surface engages the vertical strut of the drive assembly as the drive assembly is moved from the advanced position to its retracted position to move the lockout member from the locked position to the unlocked position. 
     In aspects of the disclosure, the lockout member includes a proximally facing stop surface that defines a plane that is substantially perpendicular to the longitudinal axis of the central knife slot of the anvil plate. 
     In some aspects of the disclosure, the knife of the actuation sled and knife assembly is positioned to engage the lockout member when the actuation sled and knife assembly is in a retracted position to retain the lockout member in the unlocked position. 
     Other aspects of the disclosure are directed to a tool assembly that includes a cartridge assembly, an anvil assembly, and a lockout mechanism. The cartridge assembly includes a staple cartridge having a cartridge body, staples, pushers, and an actuation sled and knife assembly. The actuation sled and knife assembly includes an actuation sled and a knife that is supported on the actuation sled for movement between raised and lowered positions. The actuation sled and knife assembly is movable within the cartridge body from a retracted position to an advanced position to eject the staples from the cartridge body and to cut tissue clamped between the cartridge and anvil assemblies. The anvil assembly is coupled to the cartridge assembly to facilitate movement of the tool assembly between open and clamped positions. The lockout mechanism is supported on the anvil assembly and is linearly movable from a locked position to an unlocked position. The actuation sled and knife assembly is positioned to urge the lockout mechanism to its unlocked position when the actuation sled and knife assembly is in its retracted position. 
     Still other aspects of the disclosure are directed to a tool assembly that includes a cartridge assembly, an anvil assembly, and a lockout mechanism. The cartridge assembly includes a staple cartridge having a cartridge body, staples, pushers, and an actuation sled and knife assembly. The actuation sled and knife assembly includes an actuation sled and a knife. The actuation sled and knife assembly is movable within the cartridge body from a retracted position to an advanced position to eject the staples from the cartridge body and to cut tissue clamped between the cartridge and anvil assemblies. The anvil assembly is coupled to the cartridge assembly to facilitate movement of the tool assembly between open and clamped positions. The lockout mechanism is supported on the anvil assembly and is linearly movable from a locked position to an unlocked position. The actuation sled and knife assembly is positioned to urge the lockout mechanism to its unlocked position when the actuation sled and knife assembly is in its retracted position. 
     Other features of the disclosure will be appreciated from the following description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various aspects of the disclosure are described herein below with reference to the drawings, wherein: 
         FIG.  1    is side perspective view of a stapling device according to aspects of the disclosure including a tool assembly in an open position; 
         FIG.  2    is a side perspective view of the tool assembly of the stapling device shown in  FIG.  1    with a staple cartridge separated from a channel member of a cartridge assembly of the tool assembly; 
         FIG.  3    is an enlarged view of the indicated area of detail shown in  FIG.  2    illustrating a proximal portion of the cartridge assembly; 
         FIG.  4    is a side perspective view of an actuation sled and knife assembly of the staple cartridge shown in  FIG.  2   ; 
         FIG.  5    is an exploded view of the staple cartridge of the cartridge assembly shown in  FIG.  2   ; 
         FIG.  5 A  is a side perspective, exploded view of the actuation sled and knife assembly of the staple cartridge shown in  FIG.  5   ; 
         FIG.  6    is a side perspective view of an anvil assembly of the tool assembly shown in  FIG.  2   ; 
         FIG.  7    is an enlarged view of the indicated area of detail shown in  FIG.  6    illustrating a lockout mechanism; 
         FIG.  8    is a side perspective view of a lockout member of the lockout mechanism shown in  FIG.  7   ; 
         FIG.  9    is a top perspective view of the lockout member of the lockout mechanism shown in  FIG.  7   ; 
         FIG.  10    is a top view of a proximal portion of the anvil assembly shown in  FIG.  6   ; 
         FIG.  11    is an enlarged view of the indicated area of detail shown in  FIG.  10   ; 
         FIG.  12    is a perspective view from a first side of a distal portion of a drive assembly of the stapling device shown in  FIG.  1   ; 
         FIG.  13    is a perspective view from a second side of the distal portion of the drive assembly shown in  FIG.  12   ; 
         FIG.  14    is an enlarged view of the indicated area of detail shown in  FIG.  2   ; 
         FIG.  15    is a side perspective of the proximal portion of the tool assembly of the stapling device shown in  FIG.  1    with the anvil assembly and the cartridge assembly shown in phantom as a working member of the drive assembly is advanced from a retracted position to a position to move the tool assembly to the clamped position; 
         FIG.  16    is a schematic view illustrating the positions of the lockout mechanism, the working member of the drive assembly, and knife of the actuation sled and knife assembly prior to engagement of the knife with the lockout mechanism; 
         FIG.  17    is a side perspective view of the working member of the drive assembly and the actuation sled and knife assembly as the drive assembly lifts the knife of the actuation sled and knife assembly from a lowered position to a raised position; 
         FIG.  18    is a schematic view illustrating the positions of the lockout mechanism, the working member of the drive assembly, and knife of the actuation sled and knife assembly with the knife engaged with the lockout mechanism to move the lockout mechanism from a locked position to an unlocked position; 
         FIG.  19    is a top view of a proximal portion of the anvil assembly and the drive assembly as the drive assembly returns to its retracted position after the stapling device has been fired with the lockout mechanism retained in the unlocked position by the drive assembly; and 
         FIG.  20    is a top view of the proximal portion of the anvil assembly and the distal portion of the drive assembly shown in phantom with the drive assembly in its retracted position and the lockout mechanism in the locked position. 
     
    
    
     DETAILED DESCRIPTION 
     The disclosed surgical stapling device will now be described in detail with reference to the drawings in which like reference numerals designate identical or corresponding elements in each of the several views. However, it is to be understood that aspects of the disclosure are merely exemplary of the disclosure and may be embodied in various forms. Well-known functions or constructions are not described in detail to avoid obscuring the disclosure in unnecessary detail. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the disclosure in virtually any appropriately detailed structure. 
     In this description, the term “proximal” is used generally to refer to that portion of the device that is closer to a clinician during use of the stapling device in its customary manner, while the term “distal” is used generally to refer to that portion of the device that is farther from the clinician during use of the stapling device in its customary manner. In addition, the term “clinician” is used generally to refer to medical personnel including doctors, nurses, and support personnel. Further, directional terms such as front, rear, upper, lower, top, bottom, and similar terms are used to assist in understanding the description and are not intended to limit the disclosure. 
     The disclosed surgical stapling device includes a tool assembly and a drive assembly for actuating the tool assembly. The tool assembly includes a cartridge assembly having a staple cartridge and an anvil assembly that supports a lockout mechanism. The staple cartridge includes a cartridge body and an actuation sled and knife assembly that includes an actuation sled and a knife. The actuation sled and knife assembly is movable in relation to the cartridge body to eject staples from the cartridge body and to cut tissue. The anvil assembly supports a lockout mechanism that includes a lockout member that is linearly movable between a locked position and an unlocked position. The drive assembly is movable from a retracted position to an advanced position to move the actuation sled and knife assembly from its retracted position to its advanced position. In the locked position, the lockout member obstructs movement of the drive assembly from its retracted position towards its advanced position. 
       FIG.  1    illustrates a surgical stapling device according to aspects of the disclosure shown generally as stapling device  10 . The stapling device  10  includes a handle assembly  12 , an elongate body  14 , and a tool assembly  16 . The elongate body  14  defines a longitudinal axis “X” ( FIG.  1   ). The handle assembly  12  includes a body  18  that defines a hand grip  18   a , a plurality of actuator buttons  20 , and a rotation knob  22 . The rotation knob  22  is rotatably supported on a distal portion of the body  18  of the handle assembly  12  and supports the elongate body  14  to facilitate rotation of the elongate body  14  and the tool assembly  16  in relation to the handle assembly  12  about the longitudinal axis “X”. The actuator buttons  20  control operation of the various functions of the stapling device  10  including articulation, clamping, firing, and cutting of tissue. 
     The tool assembly  16  includes an anvil assembly  24  and a cartridge assembly  26  that are that are coupled together to facilitate movement of the tool assembly  16  between open and clamped positions. Although the stapling device  10  is illustrated as an electrically powered stapling device, it is envisioned that the disclosed tool assembly  16  would also be suitable for use with manually powered surgical stapling devices and robotically operated stapling systems. U.S. Pat. No. 9,055,943 discloses a surgical stapling device including a powered handle assembly, U.S. Pat. No. 6,241,139 discloses a surgical stapling device including a manually actuated handle assembly, and U.S. Pat. No. 9,962,159 discloses a stapling device that is configured for use with a robotic system. 
       FIGS.  2 - 5    illustrate the cartridge assembly  26  ( FIG.  1   ) which includes a staple cartridge  28  and a channel member  30  that defines a recess  30   a  that receives the staple cartridge  28 . In aspects of the disclosure, the staple cartridge  28  is releasably supported within the recess  30   a  of the channel member  30  and is replaceable to facilitate reuse of the stapling device  10 . 
     The staple cartridge  28  includes a cartridge body  32 , an actuation sled and knife assembly  34  ( FIG.  4   ), pushers  36  ( FIG.  5   ), staples  38  ( FIG.  5   ), and a base plate  40 . The cartridge body  32  defines a central knife slot  42  and staple receiving pockets  44 . In aspects of the disclosure, the staple receiving pockets  44  are aligned in rows that are positioned on each side of the central knife slot  42 . Although three rows of staple receiving pockets  44  are shown on each side of the central knife slot  42 , it is envisioned that the cartridge body  32  may define one or more rows of staple receiving pockets  44  on each side of the central knife slot  42 . Each of the staple receiving pockets  44  receives one of the staples  38  and one of the pushers  36 . The pushers  36  support the staples  38  and are engaged by an actuation sled  34   a  of the actuation sled and knife assembly  34  as the actuation sled and knife assembly  34  is advanced through the cartridge body  32  to eject the staples  38  from the cartridge body  32 . The base plate  40  is secured to the bottom of the cartridge body  32  to prevent the pushers  36  and staples  38  from falling from the cartridge body  32  prior to firing of the stapling device  10  ( FIG.  1   ). 
       FIGS.  4 - 5 A  illustrate the actuation sled and knife assembly  34  ( FIG.  5 A ) which includes the actuation sled  34   a , a knife  66 , and a biasing member  68  ( FIG.  5 A ). The actuation sled  34   a  supports the knife  66  and is movable within the cartridge body  32  ( FIG.  5   ) from a retracted position to an advanced position. The actuation sled  34   a  includes a body  50  ( FIG.  5 A ) that has a central portion  52  and cam surfaces  54  that are positioned on opposite sides of the central portion  52  of the body  50 . The cam surfaces  54  define ramps that are positioned to engage the pushers  36  as the actuation sled  34   a  moves from its retracted position towards its advanced position to sequentially eject the staples  38  from the cartridge body  32 . 
     The central portion  52  of the actuation sled  34   a  supports the knife  66  and includes spaced walls  56  and a housing  58 . Each of the spaced walls  56  defines a circular recess  60  ( FIG.  5 A ). The housing  58  extends distally of and is positioned between longitudinal axes defined by the spaced walls  56 . The housing  58  defines a recess  62  that is aligned with the central knife slot  42  of the cartridge body  32 . 
     The knife  66  has a body  70  that has a Z-shaped configuration and includes an elongate arm  72 , a first portion  74  that extends downwardly from a distal end of the elongate arm  72 , and a second portion  76  that extends upwardly from a proximal end of the elongate arm  72 . The first portion  74  of the body  70  of the knife  66  supports a pivot member  78  that is received within the circular recesses  60  in the spaced walls  56  of the actuation sled  34   a  such that the knife  66  is pivotably supported on the actuation sled  34   a  between raised and lowered positions. In the raised position of the knife  66 , the first portion  74  of the body  70  of the knife  66  is received within the recess  62  of the housing  58  of the central portion  52  of the actuation sled  34   a . The second portion  76  of the body  70  of the knife  66  defines a distally facing cutting edge  80  that is shielded within the central knife slot  42  of the cartridge body  32  when the knife  66  is in the lowered position and extends above the central knife slot  42  when the knife  66  is in the raised position. The body  70  of the knife  66  also includes a protrusion  82  that extends laterally of the elongate arm  72 . In aspects of the disclosure, the protrusion  82  is positioned on the proximal portion of the elongate arm  72  of the knife  66 . 
     The biasing member  68  of the actuation sled and knife assembly  34  is received within the recess  62  of the housing  58  of the central portion  52  of the actuation sled  34   a  and engages the first portion  74  of the body  70  of the knife  66  at a position above an axis defined by the pivot member  78  of the knife  66  to urge the knife  66  towards the lowered position. In aspects of the disclosure, the biasing member  68  includes a coil spring although it is envisioned that other types of biasing mechanisms or members could be used in place of the coil spring. 
       FIGS.  6  and  7    illustrate the anvil assembly  24  which includes an anvil cover  90  and an anvil plate  92 . The anvil cover  90  includes a mounting portion  94 , and a cover portion  96  ( FIG.  15   ) that extends distally from the mounting portion  94  along the anvil plate  92 . The mounting portion  94  includes spaced extensions  98  that define bores  100  and extend downwardly from the anvil plate  92  towards the channel  30  of the cartridge assembly  26 . The anvil plate  92  includes a tissue engaging surface  102  that is in juxtaposed relation to the staple cartridge  28  when the tool assembly  16  is in a clamped position ( FIG.  1   ). The tissue engaging surface  102  defines a plurality of staple deforming recesses  104 . The distal edge of the spaced extensions  98  define tissue stops  98   a  that are positioned slightly distal of the proximal-most staple deforming recesses  104 . The anvil plate  92  has a side opposite to the tissue engaging surface  102  that defines an elongated recess  91  ( FIG.  16   ). The anvil cover  90  is secured to the anvil plate  92 , e.g., by welding or crimping, such that the cover portion  96  ( FIG.  15   ) of the anvil cover  90  encloses the elongated recess  91  of the anvil plate  92  to define a channel  93  ( FIG.  16   ) within the anvil assembly  24 . The anvil plate  92  also defines a central knife slot  108  that extends through the tissue engaging surface  102  of the anvil plate  92  and communicates with the elongated recess (not shown) of the anvil plate  92 . 
     The bores  100  in the extensions  98  of the anvil cover  90  receive pivot members  112  ( FIG.  2   ) that extend through the bores  100  into bores (not shown) defined in a proximal portion of the channel member  30  ( FIG.  2   ) to pivotably secure the anvil assembly  24  to the cartridge assembly  26 . In aspects of the disclosure, the cartridge assembly  26  can pivot towards the anvil assembly  24  between the open and clamped positions. It is envisioned that the tool assembly  16  ( FIG.  2   ) could also be configured to pivot toward the cartridge assembly  26 . 
     The anvil assembly  24  includes a lockout mechanism  114  ( FIG.  7   ) illustrated in  FIGS.  6 - 11    that is supported on the anvil plate  92  between the extensions  98  of the mounting portion  94  of the anvil assembly  24  proximally of the tissue engaging surface  102  of the anvil plate  92 . In aspects of the disclosure, the lockout mechanism  114  is supported on an outer surface  102   a  of the anvil plate  92  that is contiguous with the tissue engaging surface  102  of the anvil plate  92 . The lockout mechanism  114  includes a lockout member  116  and a biasing member  118 . The lockout member  116  is received within a housing  120  secured to the surface  102   a  of the anvil plate  92  and defines a cavity  122 . In aspects of the disclosure, the housing  120  has a rectangular configuration and defines an opening  124  ( FIG.  7   ) that faces the central knife slot  108 . 
     The lockout member  116  includes a body  125  that has a first end portion that is received within the cavity  122  of the housing  120  supported on the anvil plate  92  of the anvil assembly  24  and a second end portion that extends transversely through the opening  124  of the housing  120  towards the central knife slot  108  of the anvil assembly  24 . The first end portion of the body  125  of the lockout member  116  supports wings  128  that extend distally and proximally from the body  125 . The wings  128  extend from the body  125  within the cavity  122  defined by the housing  120  to prevent the lockout member  116  from passing entirely through the opening  124 . In a locked position of the lockout mechanism  114 , the wings  128  engage an inner wall  120   a  ( FIG.  11   ) of the housing  120  that defines the opening  124 . The second end portion of the body  125  of the lockout member  116  includes a distally facing cam surface  126  and a proximally facing stop surface  127 . The distally facing cam surface  126  defines a plane that forms an acute angle with a longitudinal axis defined by the central knife slot  108  of the anvil plate  92 . The proximally facing stop surface  127  defines a plane that is substantially perpendicular to the longitudinal axis of the central knife slot  108  of the anvil plate  92 . 
     The biasing member  118  of the lockout mechanism  114  is positioned within the cavity  122  of the housing  120  to urge the lockout member  116  from an unlocked position spaced outwardly of the central knife slot  108  of the anvil assembly  24  towards a locked position. In the locked position, the lockout member  116  extends at least partially across the central knife slot  108  of the anvil assembly  24  to obstruct advancement of the drive assembly  130 . In aspects of the disclosure, the biasing member  118  is secured to a post  129  supported on the anvil assembly  24  within the cavity  122  of the housing  120  such that the biasing member  118  is positioned in compression between the post  129  and the lockout member  116 . In some aspects of the disclosure, the lockout member  116  defines a bore  129   a  ( FIG.  8   ) that receives one end of the biasing member  118 . In aspects of the disclosure, the biasing member  118  includes a coil spring although the use of other types of biasing members is envisioned. 
       FIGS.  12  and  13    illustrate a drive assembly  130  of the stapling device  10  ( FIG.  1   ) which includes a resilient and/or flexible drive beam  132  and a working member  134 . The resilient drive beam  132  has a proximal portion (not shown) that is coupled to a drive rod (not shown) supported within the elongate body  14  of the stapling device  10  ( FIG.  1   ) and a distal portion that is coupled to the working member  134 . In aspects of the disclosure, the resilient drive beam  132  is formed from laminated sheets of material, e.g., steel, that are welded to the working member  134 . Alternately other materials of construction and securement techniques are envisioned. 
     The working member  134  of the drive assembly  130  has an I-beam configuration and includes a first beam  138 , a second beam  140 , and a vertical strut  142  that connects the first beam  138  to the second beam  140 . The vertical strut  142  defines a cutout  142   a  ( FIG.  13   ) that is positioned beneath the first beam  138  and receives the second portion  76  ( FIG.  4   ) of the knife  66  when the knife  66  is moved to its raised position. The working member  134  is positioned proximally of the actuation sled  34   a  ( FIG.  12   ) and is movable through the tool assembly  16  between retracted and advanced positions to move the actuation sled and knife assembly  34  through the tool assembly  16  ( FIG.  1   ) from its retracted position to its advanced position. As the working member  134  moves through the cartridge assembly  26 , the first beam  138  is received within the channel  93  ( FIG.  16   ) defined within the anvil assembly  24  ( FIG.  6   ), the second beam  140  is engaged with the cartridge assembly  26 , and the vertical strut  142  moves through the central knife slots  42  ( FIG.  3   ) and  108  ( FIG.  6   ) of the cartridge body  32  and the anvil plate  92 , respectively. 
     The vertical strut  142  defines a cam channel  152 . The cam channel  152  ( FIG.  13   ) is angled upwardly and proximally from a central portion of the vertical strut  142  and is positioned to receive the protrusion  82  of the knife  66  ( FIG.  4   ) when the drive assembly  130  is moved from its retracted position towards its advanced position to move the knife  66  from its lowered position to its raised position. 
       FIG.  14    illustrates the drive assembly  130  in its retracted position. When the drive assembly  130  is in its retracted position, the tool assembly  16  is in the open position with the cartridge assembly  26  pivoted away from the anvil assembly  24 , and the working member  134  of the drive assembly  130  is aligned with the anvil assembly  24 . The actuation sled and drive assembly  34  is supported in the cartridge assembly  26  and is misaligned with the drive assembly  130 . In the retracted position of the drive assembly  130 , the lockout member  116  of the lockout mechanism  114  extends at least partially across the central knife slot  108  ( FIG.  6   ) of the anvil assembly  24  and is positioned within the cutout  142   a  of the vertical strut  142 . 
       FIGS.  15  and  16    illustrate the proximal portion of the tool assembly  16  as the drive assembly  130  is advanced from its retracted position towards a clamped position in the direction of arrow “A”. As the working member  134  of the drive assembly  130  is advanced towards its clamped position, the working member  134  moves into engagement with the tool assembly  16  to move the tool assembly  16  from the open position ( FIG.  1   ) to the clamped position. In the clamped position of the drive assembly  130 , the vertical strut  142  of the working member  134  of the drive assembly  130  is still spaced from the central portion of the actuation sled  34   a  of the actuation sled and knife assembly  34  such that the actuation sled and knife assembly  34  remains in its retracted position. The lockout member  116  of the lockout mechanism  114  also remains in the locked position and extends at least partially across the central knife slot  108  ( FIG.  6   ) of the anvil assembly  24  into the cutout  142   a  of the vertical strut  142 . 
       FIGS.  16  and  17   .  16  illustrate a schematic view of the drive assembly  130  and the actuation sled and knife assembly  34  as the drive assembly  130  advances from the clamped position to move the knife  66  from the lowered position ( FIG.  15   ) to the raised position ( FIG.  17   ). When the drive assembly  130  moves from its clamped position towards its advanced position, the protrusion  82  ( FIG.  4   ) on the knife  66  is received in the cam channel  152  ( FIG.  13   ) in the vertical strut  142  of the drive assembly  130 . As the drive assembly  130  continues to advance, the protrusion  82  of the knife  66  moves upwardly through the cam channel  152  to pivot the knife  66  about the pivot member  78  ( FIG.  4   ) in the direction of arrow “B” in  FIG.  17    from the lowered position to the raised position. When the knife  66  is in the raised position, the vertical strut  142  of the working member  134  of the drive assembly  130  is positioned in abutting relation to the central portion  52  of the actuation sled  34   a  such that further advancement of the drive assembly  130  advances the actuation sled and knife assembly  34  through the cartridge body  32  ( FIG.  5   ) of the staple cartridge  28 . 
       FIG.  18    illustrates the interaction between the knife  66  and the lockout mechanism  114  as the knife  66  moves from the lowered position to the raised position. When the knife  66  is moved in the direction of arrow “C” in  FIG.  18    from the lowered position to the raised position, the second portion  76  ( FIG.  17   ) of the body  70  of the knife  66  engages the distally facing cam surface  126  of the lockout member  116  to urge the lockout member  116  in the direction of arrow “D” against the urging of the biasing member  118  from the locked position extending at least partially across the central knife slot  108  of the anvil assembly  24  further into the housing  120  of the lockout mechanism  114  to the unlocked position. When the lockout member  116  of the lockout mechanism  114  is moved to the unlocked position upon movement of the knife  66  to the raised position, the drive assembly  130  is free to move from its clamped position to its advanced position to advance the actuation sled and knife assembly  34  through the cartridge body  32  ( FIG.  5   ) to eject the staples  38  from the staple cartridge  28  ( FIG.  5   ) and to cut tissue clamped between the anvil assembly  24  and the cartridge assembly  26 . It is noted that the lockout member  116  is retained in the unlocked position as the drive assembly  130  moves through the cartridge body  32  of the staple cartridge  28  via engagement with the flexible drive beam  132  of the drive assembly  130 . 
       FIGS.  19  and  20    illustrate the drive assembly and the anvil assembly  24  as the drive assembly  130  is moved from its advanced position back to its retracted position. When the drive assembly  130  moves from its advanced position back to its retracted position in the direction of arrows “E” in  FIG.  19   , the actuation sled and knife assembly  34  remains in its advanced position and the flexible drive beam  132  engages the lockout member  116  of the lockout mechanism  114  to retain the lockout member  116  in the unlocked position. When the working member  134  moves proximally past the lockout member  116  of the lockout mechanism  114 , the lockout member  116  is moved by the biasing member  118  back to the locked position. In the locked position, the lockout member  116  moves back into the cutout  142   a  of the vertical strut  142  of the working member  134  of the drive assembly  130  such that the proximally facing stop surface  127  is positioned at least partially across the central knife slot  108  of the anvil assembly  24  to prevent readvancement of the drive assembly  130 . 
     In some aspects of the disclosure, depending on the configuration of the drive assembly, the distally facing cam surface  126  of the lockout member  116  may be positioned to engage the vertical strut  142  of the drive assembly  130  as the drive assembly is moved from the advanced position to its retracted position to move the lockout member  116  from the locked position to the unlocked position. 
     When the staple cartridge  28  does not include an actuation sled and knife assembly  34  or a knife  66 , the lockout member  116  cannot be moved from the locked position ( FIG.  20   ) to the unlocked position as described above. As such, the stapling device  10  ( FIG.  1   ) cannot be fired. The disclosed lockout mechanism  114  prevents refiring of the stapling  10  ( FIG.  1   ) with a spent staple cartridge  28  ( FIG.  5   ) and also prevents firing of a stapling device  10  that includes a staple cartridge that does not have a knife present. 
     Persons skilled in the art will understand that the devices and methods specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary embodiments. It is envisioned that the elements and features illustrated or described in connection with one exemplary embodiment may be combined with the elements and features of another without departing from the scope of the disclosure. As well, one skilled in the art will appreciate further features and advantages of the disclosure based on the above-described embodiments. Accordingly, the disclosure is not to be limited by what has been particularly shown and described, except as indicated by the appended claims.