Patent Abstract:
A surgical stapling and severing instrument particularly suited to endoscopic articulates an end effector by having a geared articulation mechanism that converts rotational motion from a handle portion. A firing bar longitudinally translates between the handle portion and the end effector. The firing bar head is thickened in order to present an undistorted cutting edge and engagement features to the opposing jaws of the end effector. The firing bar also advantageously includes a thinned or tapered proximal portion in the form of a strip or band that negotiates the articulation mechanism.

Full Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   The present application is related to four co-pending and commonly-owned applications filed on even date herewith, the disclosure of each is hereby incorporated by reference in their entirety, these four applications being respectively entitled:
         (1) “SURGICAL INSTRUMENT INCORPORATING AN ARTICULATION MECHANISM HAVING ROTATION ABOUT THE LONGITUDINAL AXIS” to Kenneth S. Wales, Douglas B. Hoffman, Frederick E. Shelton IV, and Jeff Swayze;   (2) “SURGICAL STAPLING INSTRUMENT INCORPORATING AN ARTICULATION JOINT FOR A FIRING BAR TRACK” to Douglas B. Hoffman;   (3) “SURGICAL STAPLING INSTRUMENT HAVING ARTICULATION JOINT SUPPORT PLATES FOR SUPPORTING A FIRING BAR” to Kenneth S. Wales and Joseph Charles Hueil; and   (4) “A SURGICAL INSTRUMENT WITH A LATERAL-MOVING ARTICULATION CONTROL” to Kenneth S. Wales.       

   FIELD OF THE INVENTION 
   The present invention relates in general to surgical stapler instruments that are capable of applying lines of staples to tissue while cutting the tissue between those staple lines and, more particularly, to improvements relating to stapler instruments and improvements in processes for forming various components of such stapler instruments that include an articulating shaft. 
   BACKGROUND OF THE INVENTION 
   Endoscopic surgical instruments are often preferred over traditional open surgical devices since a smaller incision tends to reduce the post-operative recovery time and complications. Consequently, significant development has gone into a range of endoscopic surgical instruments that are suitable for precise placement of a distal end effector at a desired surgical site through a cannula of a trocar. These distal end effectors engage the tissue in a number of ways to achieve a diagnostic or therapeutic effect (e.g., endocutter, grasper, cutter, staplers, clip applier, access device, drug/gene therapy delivery device, and energy device using ultrasound, RF, laser, etc.). 
   Positioning the end effector is constrained by the trocar. Generally these endoscopic surgical instruments include a long shaft between the end effector and a handle portion manipulated by the clinician, this long shaft enables insertion to a desired depth and rotation about the longitudinal axis of the shaft, thereby positioning the end effector to a degree. With judicious placement of the trocar and use of graspers, for instance, through another trocar, often this amount of positioning is sufficient. Surgical stapling and severing instruments, such as described in U.S. Pat. No. 5,465,895, are an example of an endoscopic surgical instrument that successfully positions an end effector by insertion and rotation. 
   More recently, U.S. Appl. Ser. No. 10/443,617, “SURGICAL STAPLING INSTRUMENT INCORPORATING AN E-BEAM FIRING MECHANISM” to Shelton et al., filed on 20 May 2003, describes an improved “E-beam” firing bar for severing tissue and actuating staples. Some of the additional advantages include affirmatively space the jaws of the end effector, even if slightly too much or two little tissue is clamped for optimal staple formation. Moreover, the E-beam firing bar includes engages the end effector and staple cartridge in a way that enables several beneficial lockouts to be incorporated. 
   Depending upon the nature of the operation, it may be desirable to further adjust the positioning of the end effector of an endoscopic surgical instrument rather than being limited to insertion and rotation. In particular, it is often desirable to orient the end effector at an axis transverse to the longitudinal axis of the shaft of the instrument. The transverse movement of the end effector relative to the instrument shaft is conventionally referred to as “articulation”. This articulated positioning permits the clinician to more easily engage tissue in some instances. In addition, articulated positioning advantageously allows an endoscope to be positioned behind the end effector without being blocked by the instrument shaft. 
   While the aforementioned non-articulating stapling and severing instruments have great utility and may be successfully employed in many surgical procedures, it is desirable to enhance their operation with the ability to articulate the end effector, thereby giving greater clinical flexibility in their use. 
   Approaches to articulating a stapling and severing tend to be complicated by integrating control of the articulation along with the control of closing the end effector to clamp tissue and firing (i.e., stapling and severing) the end effector within the small diameter constraints of an endoscopic instrument. Generally, the three control motions are all transferred through the shaft as longitudinal translations. For instance, U.S. Pat. No. 5,673,840 discloses an accordion-like articulation mechanism (“flex-neck”) that is articulated by selectively drawing back one of two connecting rods through the implement shaft, each rod offset respectively on opposite sides of the shaft centerline. 
   Another example of longitudinal control of an articulation mechanism is U.S. Pat. No. 5,865,361 that includes an articulation link offset from a camming pivot such that pushing or pulling longitudinal translation of the articulation link effects articulation to a respective side. Similarly, U.S. Pat. No. 5,797,537 discloses a similar rod passing through the shaft to effect articulation. 
   While these longitudinally controlled articulation mechanisms have provided certain advantages to surgical instruments such as for endoscopic stapling and severing, it is believed that an alternative articulation motion would provide additional design flexibility. In particular, advantageous approaches are described in the four above cross-referenced and co-pending applications wherein a rotational motion relative to a longitudinal axis of the shaft transfers an articulating motion to an articulation mechanism coupling the end effector to the shaft. 
   What would be further desirable is to retain the advantages of an E-beam firing bar in a surgical stapling and severing instrument in combination with a rotationally controlled articulation mechanism. Consequently, a significant need exists for such an instrument incorporating a firing beam that advantages severs clamped tissue, engages the jaws of the end effector for affirmatively-controlled stapling, yet is coupled for firing motion through an articulation mechanism. 
   SUMMARY OF THE INVENTION 
   The invention overcomes the above-noted and other deficiencies of the prior art by providing a firing bar that is effective in longitudinally actuating an end effector and also has a tapered proximal portion that is effective in flexing through an articulating shaft. Thereby, the clinical advantages of an articulating surgical instrument are realized without degrading consistent operation of the end effector. 
   On one aspect of the invention, a surgical instrument has a handle portion that produces an articulation motion and a firing motion that are transferred through a shaft having a longitudinal axis. An articulation mechanism coupling the shaft to an end effector and responsive to the articulation motion to rotate the end effector from the longitudinal axis of the shaft. A firing mechanism responds to the firing motion and is coupled for movement through the articulation mechanism and end effector. In particular, the firing mechanism has an actuating portion having a first thickness and positioned in the end effector and an articulation portion proximally attached to the actuating portion and having a second thickness less than the first thickness for articulating movement through the articulation mechanism. Thereby the firing mechanism is effective at both actuating the end effector and articulating through the articulation mechanism. 
   In another aspect of the invention, a surgical instrument has a handle portion that produces a firing motion, a closing motion, and an articulation motion, with all threw separately transferred down a shaft. An end effector is pivoted by an articulation mechanism responsive to the articulation motion. The end effector includes an elongate channel coupled to the shaft and including a channel slot. An anvil is pivotally coupled to the elongate channel and is responsive to the closing motion from the shaft and has an anvil channel. A firing device has a distally presented cutting edge longitudinally received between the elongate channel and the anvil and includes a thinned strip portion transitioning through the articulation mechanism. 
   In yet another aspect of the invention, a surgical instrument has a handle portion operably configured to produce a rotational articulation motion and a longitudinal firing motion, which are transferred through a shaft. An articulation mechanism responds to the rotational articulation motion to articulate an end effector. A firing bar responds to the longitudinal firing motion of the handle portion. The firing bar includes an elongate strip longitudinally positioned for movement through the articulation mechanism and has a firing bar head distally connected to the elongate strip and positioned for longitudinal movement in the end effector. 
   These and other objects and advantages of the present invention shall be made apparent from the accompanying drawings and the description thereof. 

   
     BRIEF DESCRIPTION OF THE FIGURES 
     The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention, and, together with the general description of the invention given above, and the detailed description of the embodiments given below, serve to explain the principles of the present invention. 
       FIG. 1  is a perspective view of an articulating surgical instrument in a nonarticulated position. 
       FIG. 2  is a perspective view of an articulating surgical instrument in an articulated position. 
       FIG. 3  is a perspective view of an opened end effector of the articulating surgical instrument of  FIGS. 1–2 . 
       FIG. 4  depicts a side elevation view in section of the end effector of  FIG. 3  of the surgical instrument of  FIG. 1 , the section generally taken along lines  4 — 4  of  FIG. 3  to expose portions of a staple cartridge but also depicting the firing bar along the longitudinal centerline. 
       FIG. 5  depicts a side elevation view in section of the end effector of  FIG. 4  after the firing bar has fully fired. 
       FIG. 6  depicts a side elevation view in section of a handle portion of a proximal end of the surgical instrument of  FIG. 1  including a rotating articulation control. 
       FIG. 7  depicts a perspective, exploded view of the handle portion of the proximal end of the surgical instrument of  FIG. 1 . 
       FIG. 8  depicts a perspective view looking downward, forward and to the right of a distal portion of the handle portion of the surgical instrument of  FIG. 1  partially cutaway to expose a rotating articulation control mechanism. 
       FIG. 9  depicts a perspective view looking upward, rearward and to the right of the distal portion of the handle portion of  FIG. 8 , partially cutaway to expose the rotating articulation control mechanism and have a rotating articulation control knob disassembled. 
       FIG. 10  depicts a top perspective detail view of a spur gear articulation mechanism and end effector of the surgical instrument of  FIG. 1  with firing and frame portions removed. 
       FIG. 11  depicts a perspective, exploded view of an implement portion of the surgical instrument of  FIG. 1  including a spur gear articulation mechanism. 
       FIG. 12  depicts a top sectional view of the spur gear articulation mechanism of  FIG. 11 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Turning to the Drawings, wherein like numerals denote like components throughout the several views,  FIGS. 1–3  depict a surgical instrument, which in the illustrative embodiment is more particularly a surgical stapling and severing instrument  10 , that is capable of practicing the unique benefits of the present invention. In particular, the surgical stapling and severing instrument  10  is sized for insertion, in a nonarticulated state as depicted in  FIG. 1 , through a trocar cannula passageway to a surgical site in a patient for performing a surgical procedure. Once an articulation mechanism  11  and a distally attached end effector  12  are inserted through the cannula passageway, the articulation mechanism  11  may be remotely articulated, as depicted in  FIG. 2 , by an articulation control  13 . Thereby, the end effector  12  may reach behind an organ or approach tissue from a desired angle or for other reasons. For instance, a firing mechanism, advantageously depicted as an E-beam firing bar  14  (depicted in  FIG. 3 ), that severs clamped tissue, engages an elongate channel  16  and a pivotally attached anvil  18 . 
   The surgical and stapling and severing instrument  10  includes a handle portion  20  connected to an implement portion  22 , the latter further comprising a shaft  23  distally terminating in the articulating mechanism  11  and the end effector  12 . The handle portion  20  includes a pistol grip  24  toward which a closure trigger  26  is pivotally drawn by the clinician to cause clamping, or closing, of the anvil  18  toward the elongate channel  16  of the end effector  12 . A firing trigger  28  is farther outboard of the closure trigger  26  and is pivotally drawn by the clinician to cause the stapling and severing of clamped tissue in the end effector  12 . Thereafter, a release button  30  is depressed to release the clamped tissue. 
   An outmost closure sleeve  32  of the shaft  23  longitudinally translates in response to the closure trigger  26  to pivotally close the anvil  18 . Specifically, a distal portion, or closure ring  33 , of the closure sleeve  32  with respect to the articulation mechanism  11  is indirectly supported by a frame  34  of the implement portion  22  (partially visible at the articulation mechanism  11 ). At the articulation mechanism  11 , a proximal portion, or closure tube  35 , of the closure sleeve  32  communicates with the distal portion (closure ring)  33 . The frame  34  is flexibly attached to the elongate channel  16  via the articulation mechanism  11 , enabling articulation in a single plane. The frame  34  also longitudinally slidingly supports a firing drive member  36  that communicates a firing motion from the firing trigger  28  to the firing bar  14 . Only the firing bar  14  of the firing drive member  36  is depicted  FIG. 3 , but the firing drive member  36  is described below further detail with regard to various versions of a rotationally controlled articulation mechanism  11 . 
   It will be appreciated that the terms “proximal” and “distal” are used herein with reference to a clinician gripping a handle of an instrument. Thus, the end effector  12  is distal with respect to the more proximal handle portion  20 . It will be further appreciated that for convenience and clarity, spatial terms such as “vertical” and “horizontal” are used herein with respect to the drawings. However, surgical instruments are used in many orientations and positions, and these terms are not intended to be limiting and absolute. 
   E-Beam Firing Bar 
     FIGS. 3–5  depict the end effector  12  employing the E-beam firing bar  14  to perform a number of functions. In  FIG. 3 , the firing bar  14  is proximally positioned, allowing an unspent staple cartridge  37  to be installed into the elongate channel  16 . In particular, an upper pin  38  of the firing bar  14  resides within a recess, depicted as an anvil pocket  40  allowing the anvil  18  to be repeatedly opened and closed. With the end effector closed as depicted in  FIG. 4 , the firing bar  14  is advanced in engagement with the anvil  18  by having the upper pin  38  enter a longitudinal anvil slot  42 . A lower most pin, or firing bar cap  44 , engaged a lower surface of the elongate channel  16  by having the firing bar  14  extend through a channel slot  45 . A middle pin  46  slidingly engages a top surface of the elongate channel  16 , cooperating with the firing bar cap  44 . Thereby, the firing bar  14  affirmatively spaces the end effector  12  during firing, overcoming pinching that may occur with a minimal amount of clamped tissue and overcoming staple malformation with an excessive amount of clamped tissue. 
   During firing, a distally presented cutting edge  48  between the upper pin  38  and middle pin  46  of the firing bar enters a proximally presented vertical slot  49  of the staple cartridge  37 , severing tissue clamped between the staple cartridge  37  and the anvil  18 . As shown in  FIG. 4 , the middle pin  46  actuates the staple cartridge  37  by entering into a firing slot within the staple cartridge  37 , driving a wedge sled  41  into upward camming contact with staple drivers  43  that in turn drive a plurality of staples  47  out of staple apertures  51  in the staple cartridge  37  into forming contact with staple pockets  53  on an inner surface of the anvil  18 .  FIG. 5  depicts the firing bar  14  fully distally translated after completing severing and stapling tissue. 
   Two-Axis Handle 
   With reference to  FIGS. 6–7 , the handle portion  20  is comprised of first and second base sections  50  and  52 , which are molded from a polymeric material such as a glass-filled polycarbonate. The first base section  50  is provided with a plurality of cylindrical-shaped pins  54 . The second base section  52  includes a plurality of extending members  56 , each having a hexagonal-shaped opening  58 . The cylindrical-shaped pins  54  are received within the hexagonal-shaped openings  58  and are frictionally held therein for maintaining the first and second base sections  50  and  52  in assembly. 
   A housing cap  60  has a bore  62  extending completely through it for engaging and rotating the implement portion  22  about its longitudinal axis. The housing cap  60  includes an inwardly protruding boss  64  extending along at least a portion of the bore  62 . The protruding boss  64  is received within a longitudinal slot  66  formed at a proximal portion of the closure sleeve  32  such that rotation of the housing cap  60  effects rotation of the closure sleeve  32 . It will be appreciated that the boss  64  further extends through frame  34  and into contact with a portion of the firing drive member  36  to effect their rotation as well. Thus, the end effector  12  (not shown in  FIGS. 3–4 ) rotates with the housing cap  60 . 
   A proximal end  68  of the frame  34  passes proximally through the housing cap  60  and is provided with a circumferential notch  70  that is engaged by opposing channel securement members  72  extending respectively from the base sections  50  and  52 . Only the channel securement member  72  of the second base section  52  is shown. The channel securement members  72  extending from the base sections  50 ,  52  serve to secure the frame  34  to the handle portion  20  such that the frame  34  does not move longitudinally relative to the handle portion  20 . 
   The closure trigger  26  has a handle section  74 , a gear segment section  76 , and an intermediate section  78 . A bore  80  extends through the intermediate section  78 . A cylindrical support member  82  extending from the second base section  52  passes through the bore  80  for pivotally mounting the closure trigger  26  on the handle portion  20 . A second cylindrical support member  83  extending from the second base section  52  passes through a bore  81  of firing trigger  28  for pivotally mounting on the handle portion  20 . A hexagonal opening  84  is provided in the cylindrical support member  83  for receiving a securement pin (not shown) extending from the first base section  50 . 
   A closure yoke  86  is housed within the handle portion  20  for reciprocating movement therein and serves to transfer motion from the closure trigger  26  to the closure sleeve  32 . Support members  88  extending from the second base section  52  and securement member  72 , which extends through a recess  89  in the yoke  86 , support the yoke  86  within the handle portion  20 . 
   A proximal end  90  of the closure sleeve  32  is provided with a flange  92  that is snap-fitted into a receiving recess  94  formed in a distal end  96  of the yoke  86 . A proximal end  98  of the yoke  86  has a gear rack  100  that is engaged by the gear segment section  76  of the closure trigger  26 . When the closure trigger  26  is moved toward the pistol grip  24  of the handle portion  20 , the yoke  86  and, hence, the closure sleeve  32  move distally, compressing a spring  102  that biases the yoke  86  proximally. Distal movement of the closure sleeve  32  effects pivotal translation movement of the anvil  18  distally and toward the elongate channel  16  of the end effector  12  and proximal movement effects closing, as discussed below. 
   The closure trigger  26  is forward biased to an open position by a front surface  130  interacting with an engaging surface  128  of the firing trigger  28 . Clamp first hook  104  that pivots top to rear in the handle portion  20  about a pin  106  restrains movement of the firing trigger  28  toward the pistol grip  24  until the closure trigger  26  is clamped to its closed position. Hook  104  restrains firing trigger  28  motion by engaging a lockout pin  107  in firing trigger  28 . The hook  104  is also in contact with the closure trigger  26 . In particular, a forward projection  108  of the hook  104  engages a member  110  on the intermediate section  78  of the closure trigger  26 , the member  110  being outward of the bore  80  toward the handle section  74 . Hook  104  is biased toward contact with member  110  of the closure trigger  26  and engagement with lockout pin  107  in firing trigger  28  by a release spring  112 . As the closure trigger  26  is depressed, the hook  104  is moved top to rear, compressing the release spring  112  that is captured between a rearward projection  114  on the hook  104  and a forward projection  116  on the release button  30 . 
   As the yoke  86  moves distally in response to proximal movement of the closure trigger  26 , an upper latch arm  118  of the release button  30  moves along an upper surface  120  on the yoke  86  until dropping into an upwardly presented recess  122  in a proximal, lower portion of the yoke  86 . The release spring  112  urges the release button  30  outward, which pivots the upper latch arm  118  downwardly into engagement with the upwardly presented recess  122 , thereby locking the closure trigger  26  in a tissue clamping position. 
   The latch arm  118  can be moved out of the recess  122  to release the anvil  18  by pushing the release button  30  inward. Specifically, the upper latch arm  118  pivots upward about pin  123  of the second base section  52 . The yoke  86  is then permitted to move proximally in response to return movement of the closure trigger  26 . 
   A firing trigger return spring  124  is located within the handle portion  20  with one end attached to pin  106  of the second base section  52  and the other end attached to a pin  126  on the firing trigger  28 . The firing return spring  124  applies a return force to the pin  126  for biasing the firing trigger  28  in a direction away from the pistol grip  24  of the handle portion  20 . The closure trigger  26  is also biased away from pistol grip  24  by engaging surface  128  of firing trigger  28  biasing front surface  130  of closure trigger  26 . 
   As the closure trigger  26  is moved toward the pistol grip  24 , its front surface  130  engages with the engaging surface  128  on the firing trigger  28  causing the firing trigger  28  to move to its “firing” position. When in its firing position, the firing trigger  28  is located at an angle of approximately 45° to the pistol grip  24 . After staple firing, the spring  124  causes the firing trigger  28  to return to its initial position. During the return movement of the firing trigger  28 , its engaging surface  128  pushes against the front surface  130  of the closure trigger  26  causing the closure trigger  26  to return to its initial position. A stop member  132  extends from the second base section  52  to prevent the closure trigger  26  from rotating beyond its initial position. 
   The surgical stapling and severing instrument  10  additionally includes a reciprocating section  134 , a multiplier  136  and a drive member  138 . The reciprocating section  134  comprises a wedge sled, or wedge sled, in the implement portion  22  (not shown in  FIG. 6-7 ) and a metal drive rod  140 . 
   The drive member  138  includes first and second gear racks  141  and  142 . A first notch  144  is provided on the drive member  138  intermediate the first and second gear racks  141 ,  142 . During return movement of the firing trigger  28 , a tooth  146  on the firing trigger  28  engages with the first notch  144  for returning the drive member  138  to its initial position after staple firing. A second notch  148  is located at a proximal end of the metal drive rod  140  for locking the metal drive rod  140  to the upper latch arm  118  of the release button  30  in its unfired position. 
   The multiplier  136  comprises first and second integral pinion gears  150  and  152 . The first integral pinion gear  150  is engaged with a first gear rack  154  provided on the metal drive rod  140 . The second integral pinion gear  152  is engaged with the first gear rack  141  on the drive member  138 . The first integral pinion gear  150  has a first diameter and the second integral pinion gear  152  has a second diameter that is smaller than the first diameter. 
   Rotational Articulation Control 
   With reference to  FIGS. 6–9 , the handle portion  20  advantageously incorporates the articulation control  13  that both rotates the implement portion  22  about the longitudinal axis of the surgical instrument  10  and articulates the end effector  12  to an angle with the longitudinal axis. A hollow articulation drive tube  200  is concentrically located within the closure sleeve  32  and is operably coupled to an actuation lever  202  such that rotation of actuation lever  202  rotates tube  200  about the longitudinal axis and causes perpendicular rotation or articulation of the closure ring  250  and end effector  12 . This articulation of the closure ring  250  corresponds to the degree and direction of rotation of actuator lever  202  viewed and manipulated by the clinician. In the illustrative version, the relationship is one to one, with the degree of rotation of the actuator lever  202  corresponding to the degree of articulation from the longitudinal axis of the shaft  23 , thus providing an intuitive indication to the clinician. It will be appreciated that other angular relationships may be selected. 
   The articulation control  13  includes a pair of mirrored articulation transmission housings  204  that are attached to the housing cap  60 . Moreover, the articulation transmission housing  204  includes longitudinally aligned external tabs  206  that a clinician twists to effect rotation of the articulation transmission housing  204 , and thus of the end effector  12 , about the longitudinal axis of the implement portion  22 . The actuator lever  202  is attached to a cylindrical articulation body  208  that resides within a cylindrical recess  210  opening generally upward and perpendicular to the shaft  23 . The lowermost portion of the articulation body  208  includes prongs  212  that snap fit into an opening  214  in the articulation transmission housing  208  near to the shaft  23 , the prongs  212  preventing the articulation body  208  from being withdrawn from the cylindrical recess  210 . 
   Annularly presented gear teeth  216  are located about the lower portion of the articulation body  208  and mesh with teeth  218  on an articulation yoke  220 . The articulation yoke  220  straddles an articulation rectangular window  222  formed in the closure sleeve  32 . Closure sleeve  32  is slidably moveable within the articulation control  13  (in the longitudinal direction) to close and open the end effector  12 . The articulation drive tube  200  moves longitudinally with the closure sleeve  32  relative to the fixed articulation control  13 . Window  222  provides clearance for a boss  224  inwardly presented from the articulation yoke  220  that passes through the rectangular window  222  to engage a slot  226  in the articulation drive tube  200 , longitudinally positioning the articulation drive tube  200  for rotational motion. The hollow articulation drive tube  200  extends longitudinally within the closure sleeve  32  from the articulation mechanism  11  and terminates distally before the locking tabs  227  of the closure sleeve  32 . The tabs  227  are inwardly bent behind the proximal face of the articulation drive tube  200  and thereby retaining the articulation drive tube  200  in the shaft  23 . 
   It should be appreciated that the articulation transmission housing  204  is operatively associated to the closure tube  35  of the shaft  23 . The housing cap  60  retains the articulation yoke  220  in the articulation transmission housing  204  and retains the articulation control  13  within the handle portion  20  by presenting proximally an outer diameter circular groove  228  that engages a circular inward lip  230  at the distal opening of the assembled base sections  50 ,  52 . 
     FIGS. 10 and 11  depict the gear articulation mechanism  11  of  FIGS. 1–2  in the form of a spur gear articulation mechanism  240 , which is generally the same as described above but with additional articulation driving components on the other side of the articulation mechanism  240  to thereby increase performance. Articulation mechanism  240  has a rotatable hollow articulation drive tube  242  that is concentrically located within closure sleeve  32  and has a distally projecting gear section  244  about a first circumference portion  246 . Gear section  244  meshes with a spur gear  248  attached to and proximally projecting from closure ring  250  which pivots about pins  253  extending through first and second pivot points  252 ,  260  projecting distally from the closure sleeve  32 . Thus, an articulation pivot axis passes through both the first and second pivot points  252 ,  260  and pins  253  rotatably couple closure ring  250  to the closure sleeve  32 . Rotation of drive  242  engages the gears  242  and  248  and articulates closure ring  250  about first and second pivot points  252 ,  260 . 
   To increase the effective surface area of gear contact between the hollow articulation drive tube  242  and the closure ring  250 , a second circumference portion  254  of the hollow articulation drive tube  242  has a recessed distally projecting gear section  256  extending therefrom. Gear section  256  is operably coupled to a second spur gear  258  attached to and proximally projecting from an opposite lateral side of the closure ring  250  by a reversing gear  262  pivotally supported by the frame  34 . Reversing gear  262  engages both the recessed distally projecting gear section  256  on one side and the second spur gear  258  of the closure ring  250  on the other. 
   When the closure trigger  26  is actuated, both the hollow articulation drive tube  242  and pivotally attached closure tube  250  of the closure sleeve  32  are moved distally to close the anvil  18 . The closure tube  35  of the closure sleeve  32  is spaced away from the closure ring  33  by pivot points  252 ,  260  pinned to pivot holes  264  and  266  centered in spur gears  248 ,  258 , and a frame opening  268  that extends therethrough. The frame opening  268  provides clearance so that the proximal edges of the closure ring  33  and the distal edges of the closure tube  35  of the closure sleeve  32  do not collide during articulation. 
     FIG. 11  depicts in disassembled form an implement portion  270  that includes the spur gear articulation mechanism  240 . A frame  272  is longitudinally attachable to the handle portion  20  (depicted in  FIGS. 1 and 2 ) with a bushing  274  on its proximal end for rotatingly engagement thereto. A frame trough  276  formed by an opening  278  longitudinally aligned with the center of the frame  272  is longer than a firing connector  280  that slides longitudinally within the frame trough  276 . The proximal end of the firing connector  280  rotatingly engages the distal end of the metal drive bar  140  (depicted in  FIG. 6 ). The distal end of the firing connector  280  includes a slot  282  that receives a proximal end of the firing bar  14 , attached therein by pins  284 . A more distal portion of the firing bar  14  is positioned within a lower groove  286  in a firing bar slotted guide  288  that is distally engaged with an articulating frame member  290  and the frame  272 . 
   Articulating frame member  290  has a channel-anchoring member  292  that distally attaches to an attachment collar  294  of a proximal portion in the elongate channel  16 . The firing bar  14  passes through a lower slot  295  in the articulating frame member  290 . The articulating frame member  290  is spaced away from the distal end of the frame  272  by the firing bar slotted guide  288  and flexibly attached thereto for articulation by a resilient connector  296 . A widened proximal end  298  of the resilient connector  296  engages a distally communicating top recess  300  in the distal end of the frame  272  and a widened distal end  302  of the resilient connector  296  engages a proximally communicating top recess  304  in the articulating frame member  290 . Thereby, the elongate channel  16  is attached to the handle portion  20 , albeit with a flexible portion therebetween. 
   The elongate channel  16  also has an anvil cam slot  306  that pivotally receives an anvil pivot  308  of the anvil  18 . The closure ring  250  that encompasses the articulating frame member  290  includes a distally presented tab  310  that engages an anvil feature  312  proximate but distal to the anvil pivot  308  on the anvil  18  to thereby effect opening. When the closure ring  250  is moved forward, its distally presented closing face  314  contacts a ramped cylindrical closing face  316 , which is distal to tab  312  of the anvil  18 . This camming action closes the anvil  18  downward until the closing face  314  of the closure ring  250  contacts a flat cylindrical face  318  of the anvil  18 . 
   Tapered Firing Bar 
     FIG. 12  depicts the articulation mechanism  240  along the articulation pivot axis illustrating flexible support structures between the shaft  23  and the end effector  12  and a construction of the firing bar  14  that advantageously performs severing yet is flexible enough for articulation. The hollow articulation drive tube  242  engages the spur gear  248  of the closure ring  33  (only the spur gear  248  of the closure ring  33  being depicted). Omitted from this view are the proximal portion, or closure tube  35 , of the closure sleeve  32  that longitudinally position for articulation the spur gear  248 . 
   Resilient support in the articulation mechanism  240  allow articulation about the articulation pivot axis includes a pair of support plates  400 ,  402  that provide lateral guides to a proximal portion of the firing bar, depicted as an elongate tapered firing bar strip  404  aligned for flexing about the articulation pivot axis. This tapered firing bar strip  404  transitioned to a thicker distal portion, depicted as a firing bar head  406 , that includes the cutting edge  48 , upper pin  38 , middle pin  46  and firing bar cap  44 . The thinner portion of firing bar strip  404  is easier to bend than the thicker portion  406 , thereby reducing the force to articulate the end effector. This thicker firing bar head  406  has increased thickness to resist deflection from tissue clamping loads during firing, thereby ensuring an effective severing and actuation of the staple cartridge  37 . 
   Operation 
   A closed end effector  12  and shaft  23  of an implement portion  22  of a surgical stapling and severing instrument  10  are inserted through a cannula passageway of a trocar to a surgical site for an endoscopic or laparoscopic procedure. The articulation control  13  is rotated as desired about the longitudinal axis of the shaft  23  to effect a corresponding rotation of the end effector  12 . Advantageously, the actuator lever  202  of the articulation control  13  is pivoted to create a rotation articulation motion in an articulation drive tube  200 ,  242  that is converted into an articulation motion at a geared connection in an articulation mechanism  11 ,  240  thereby positioning the end effector  12  in a desired position. The firing bar  14  is advanced through the implement portion  22  to actuate the end effector  12 , advantageously assisted through the articulation mechanism  11 ,  240  by including the elongate tapered firing bar strip  404  that flexes with reduced resistance. 
   While the present invention has been illustrated by description of several embodiments and while the illustrative embodiments have been described in considerable detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications may readily appear to those skilled in the art. 
   The present invention has been discussed in terms of endoscopic procedures and apparatus. However, use herein of terms such as “endoscopic”, should not be construed to limit the present invention to a surgical stapling and severing instrument for use only in conjunction with an endoscopic tube (i.e., trocar). On the contrary, it is believed that the present invention may find use in any procedure where access is limited to a small incision, including but not limited to laparoscopic procedures, as well as open procedures. 
   For another example, although the E-beam firing beam  14  has advantages for an endoscopically employed surgical severing and stapling instrument  10 , a similar E-Beam may be used in other clinical procedures. It is generally accepted that endoscopic procedures are more common than laparoscopic procedures. Accordingly, the present invention has been discussed in terms of endoscopic procedures and apparatus. However, use herein of terms such as “endoscopic”, should not be construed to limit the present invention to a surgical stapling and severing instrument for use only in conjunction with an endoscopic tube (i.e., trocar). On the contrary, it is believed that the present invention may find use in any procedure where access is limited to a small incision, including but not limited to laparoscopic procedures, as well as open procedures. 
   For yet another example, although an illustrative handle portion  20  described herein is manually operated by a clinician, it is consistent with aspects of the invention for some or all of the functions of a handle portion to be powered (e.g., pneumatic, hydraulic, electromechanical, ultrasonic, etc.). Furthermore, controls of each of these functions may be manually presented on a handle portion or be remotely controlled (e.g., wireless remote, automated remote console, etc.). 
   As yet an additional example, although a simultaneous stapling and severing instrument is advantageously illustrated herein, it would be consistent with aspects of the invention rotationally controlled articulation with other types of end effectors, such as grasper, cutter, staplers, clip applier, access device, drug/gene therapy delivery device, and a energy device using ultrasound, RF, laser, etc. 
   For example, although a spur gear articulation mechanism  240  is illustrated herein, it that other articulation mechanisms may be included, such as those described in the aforementioned co-pending applications. 
   As an additional example, for articulation mechanisms that obstruct the longitudinal axis of the shaft, the support plates and tapered firing bar strip may be offset from the longitudinal axis.

Technology Classification (CPC): 0