Abstract:
A surgical stapling and severing instrument particularly suited to endoscopic use includes a proximal portion that is manipulated external to a patient to position an attached elongate shaft and end effector to a desired surgical site inside of the patient. An articulation joint pivotally attaches the end effector to the elongate shaft to give further clinical flexibility in reaching tissue at a desired angle. A closure tube assembly includes a single pivoting portion that overrides the articulation joint in order to distally translate to the end effector to close, yet pass over an articulated shaft by having a multiple pivot frame ground encompassed therein to accommodate the longitudinal change in closure sleeve pivot. Thereby, additional clinical flexibility in positioning the end effector is achieved without losing the ability for separate closure and firing motions transferred by the shaft.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   The present invention is a continuation-in-part of commonly owned U.S. patent application Ser. No. 11/061,908 now U.S. Pat. No. 7,559,450 entitled “SURGICAL INSTRUMENT INCORPORATING A FLUID TRANSFER CONTROLLED ARTICULATION MECHANISM” to Kenneth Wales and Chad Boudreaux filed on 18 Feb. 2005, the disclosure of which is hereby incorporated by reference in its entirety. 

   FIELD OF THE INVENTION 
   The present invention relates in general to surgical instruments that are suitable for endoscopically inserting an end effector (e.g., endocutter, grasper, cutter, staplers, clip applier, access device, drug/gene therapy delivery device, and an energy device using ultrasound, RF, laser, etc.) to a surgical site, and more particularly to such surgical instruments with 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.). 
   The positioning of 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. patent Ser. No. 10/443,617, “SURGICAL STAPLING INSTRUMENT INCORPORATING AN E-BEAM FIRING MECHANISM” to Shelton IV et al., filed on 20 May 2003, which is hereby incorporated by reference in its entirety, describes an improved “E-beam” firing bar for severing tissue and actuating staples. Some of the additional advantages include the ability to affirmatively space the jaws of the end effector, or more specifically a staple applying assembly, even if slightly too much or too little tissue is clamped for optimal staple formation. Moreover, the E-beam firing bar engages the end effector and staple cartridge in a way that enables several beneficial lockouts to be incorporated. 
   These surgical stapling and severing instruments include a shaft having a frame that guides a firing bar that performs the firing. A closure tube slides overtop of the frame and firing bar to effect closure of the jaws of the staple applying assembly. Thereby, a separate closure and firing capability are provided that allow increased clinical flexibility. The surgeon may repeatedly close and reposition tissue until satisfied with placement. 
   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. 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 is typically accomplished by a pivot (or articulation) joint being placed in the extended shaft just proximal to the staple applying assembly. This allows the surgeon to articulate the staple applying assembly remotely to either side for better surgical placement of the staple lines and easier tissue manipulation and orientation. This articulated positioning permits the clinician to more easily engage tissue in some instances, such as behind an organ. In addition, articulated positioning advantageously allows an endoscope to be positioned behind the end effector without being blocked by the instrument shaft. 
   Approaches to articulating a surgical stapling and severing instrument tend to be complicated by integrating control of the articulation along with the control of closing the end effector to clamp tissue and fire the end effector (i.e., stapling and severing) 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, in co-pending and commonly owned U.S. patent application Ser. No. 10/615,973 “SURGICAL INSTRUMENT INCORPORATING AN ARTICULATION MECHANISM HAVING ROTATION ABOUT THE LONGITUDINAL AXIS” to Frederick E. Shelton IV et al, the disclosure of which is hereby incorporated by reference in its entirety, a rotational motion is used to transfer articulation motion as an alternative to a longitudinal motion. 
   Consequently, a significant need exists for a surgical stapling and severing instrument having a shaft that includes a separate closure tube that separately opens and closes the jaws, yet is capable of articulating. 
   BRIEF SUMMARY OF THE INVENTION 
   The invention overcomes the above-noted and other deficiencies of the prior art by providing a surgical instrument that includes a shaft having a frame ground that pivotally attaches to an end effector via a double pivoting connection. The end effector in turn includes a pivotal upper jaw or anvil that pivots to close and clamp tissue in response to longitudinal movement of a closure tube that slides over the frame. In order to longitudinally translate to cause this closure over an articulated joint, the frame ground has a double pivoting joint of its own. 
   In one aspect of the invention, a surgical instrument includes a proximal portion that is manipulated external to a patient to position an attached elongate shaft and end effector to a desired surgical site inside of the patient. A closure tube includes a pivoting joint that overrides the articulation joint in order to distally translate to close the end effector, yet pass over an articulated shaft. An articulation joint pivotally attaches the end effector to the elongate shaft to give further clinical flexibility in reaching tissue at a desired angle. To accommodate the longitudinally moving pivot point of the closure tube, a double pivoting frame ground has a link that is pivotally attached at its proximal and distal ends respectively to a proximal frame portion that is attached to the handle portion and a distal frame portion that is attached to the end effector. Thereby, additional clinical flexibility in positioning the end effector is achieved without losing the ability for separate closure and firing motions transferred by the shaft. 
   In another aspect of the invention, a surgical instrument includes an articulating end effector that performs severing and stapling of clamped tissue between a closed anvil and elongate channel or lower jar containing a staple cartridge. A double pivoting frame ground includes a link that assists in articulating a firing bar that reciprocates within the elongate shaft of the surgical instrument. 
   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 front top perspective view of a surgical stapling and severing instrument shown with an open end effector, or staple applying assembly, and with the staple cartridge removed. 
       FIG. 2  is a front top perspective view of the surgical stapling and severing instrument of  FIG. 1  with an articulation mechanism actuated by a fluidic actuation control. 
       FIG. 3  is a perspective disassembled view of an elongate shaft and articulation mechanism of the surgical stapling and severing instrument of  FIG. 1 . 
       FIG. 4  is a perspective disassembled view of distal portions of an implement portion of the surgical stapling and severing instrument of  FIG. 1 , including the staple applying assembly and articulation mechanism. 
       FIG. 5  is a top perspective view of the staple applying assembly of  FIGS. 1 and 4  with a lateral half of a staple cartridge removed to expose components driven by a firing motion. 
       FIG. 6  is a front perspective view of an implement portion of the surgical instrument of  FIG. 1  with a double pivot closure sleeve assembly and end effector removed to expose a single pivot frame ground articulated by a fluidic articulation mechanism. 
       FIG. 7  is perspective detail view of an alternative articulation joint for the surgical instrument of  FIG. 1  depicting a double pivoting closure sleeve assembly at a proximal position with a single pivot frame ground. 
       FIG. 8  is a bottom right perspective exploded view of the alternative articulation joint of  FIG. 7  including a double pivoting fixed-wall dog bone link and a frame ground incorporating rail guides for a lateral moving member (T-bar). 
       FIG. 9  is top left perspective exploded view of a further alternative articulation joint for the surgical instrument of  FIG. 1 , including an alternate solid wall support plate mechanism incorporated into a lower double pivot link to support a firing bar and including a rail guided laterally moving member (T-bar). 
       FIG. 10  is a top diagrammatic view of an alternate articulation locking mechanism for the surgical instrument of  FIG. 1  with a closure sleeve assembly removed to expose a backloading disengaged T-bar for automatic articulation lock engagement and disengagement. 
       FIG. 11  is a top diagrammatic view of an additional alternative articulation mechanism for the surgical instrument of  FIG. 1 , a spring biased rack on a T-bar with locking features that engage due to backloading from an end effector. 
       FIG. 12  is an alternative T-bar and frame ground incorporating lateral guidance for the surgical instrument of  FIG. 1 . 
       FIG. 13  is yet an additional alternative T-bar and frame ground incorporating lateral guidance for the surgical instrument of  FIG. 1 . 
       FIG. 14  is a left top perspective disassembled view of an alternative articulation mechanism including a double pivoting frame assembly and single pivoting closure sleeve assembly for the surgical instrument of  FIG. 1 .  FIG. 15  is a left bottom perspective view of the alternative articulation mechanism of  FIG. 14 . 
       FIG. 16  is a front perspective view of an alternative implement portion having a multiple pivot closure sleeve assembly for the surgical stapling and severing instrument of  FIG. 1 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Overview Of Articulating Shaft. 
   Turning to the Drawings, wherein like numerals denote like components throughout the several views,  FIG. 1  depicts a surgical instrument, which in the illustrative versions 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 (not shown) for performing a surgical procedure. Once an implement portion  12  is inserted through a cannula passageway, an articulation mechanism  14  incorporated into a distal portion of an elongate shaft  16  of the implement portion  12  may be remotely articulated, as depicted in  FIG. 2 , by an articulation control  18 . An end effector, depicted in the illustrative version as a staple applying assembly  20 , is distally attached to the articulation mechanism  14 . Thus, remotely articulating the articulation mechanism  14  thereby articulates the staple applying assembly  20  from a longitudinal axis of the elongate shaft  16 . Such an angled position may have advantages in approaching tissue from a desired angle for severing and stapling, approaching tissue otherwise obstructed by other organs and tissue, and/or allowing an endoscope to be positioned behind and aligned with the staple applying assembly  20  for confirming placement. 
   Handle. 
   The surgical and stapling and severing instrument  10  includes a handle portion  22  proximally connected to the implement portion  12  for providing positioning, articulation, closure and firing motions thereto. The handle portion  22  includes a pistol grip  24  toward which a closure trigger  26  is pivotally and proximally drawn by the clinician to cause clamping, or closing, of the staple applying assembly  20 . 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 clamped in the staple applying assembly  20 . Thereafter, a closure release button  30  is depressed to release the clamped closure trigger  26 , and thus the severed and stapled ends of the clamped tissue. The handle portion  22  also includes a rotation knob  32  coupled for movement with the elongate shaft  16  to rotate the shaft  16  and the articulated staple applying assembly  20  about the longitudinal axis of the shaft  16 . The handle portion  22  also includes a firing retraction handle  34  to assist in retracting a firing mechanism (not depicted in  FIGS. 1-2 ) should binding occur, so that opening of the staple applying assembly  20  may occur thereafter. 
   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 surgical stapling assembly  20  is distal with respect to the more proximal handle portion  22 . 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. 
   An illustrative multi-stroke handle portion  22  for the surgical stapling and severing instrument  10  of  FIGS. 1-2  is described in greater detail in the co-pending and commonly-owned U.S. patent application entitled “SURGICAL STAPLING INSTRUMENT INCORPORATING A MULTISTROKE FIRING POSITION INDICATOR AND RETRACTION MECHANISM” to Swayze and Shelton IV, Ser. No. 10/674,026, the disclosure of which is hereby incorporated by reference in its entirety, with additional features and variations as described herein. While a multi-stroke handle portion  22  advantageously supports applications with high firing forces over a long distance, applications consistent with the present invention may incorporate a single firing stroke, such as described in co-pending and commonly owned U.S. patent application “SURGICAL STAPLING INSTRUMENT HAVING SEPARATE DISTINCT CLOSING AND FIRING SYSTEMS” to Frederick E. Shelton IV, Michael E. Setser, and Brian J. Hemmelgarn, Ser. No. 10/441,632, the disclosure of which is hereby incorporated by reference in its entirety. Implement Portion (Articulating Elongate Shaft And Staple Applying Assembly). 
   In  FIGS. 3-5 , the implement portion  12  advantageously incorporates the multiple actuation motions of longitudinal rotation, articulation, closure and firing within a small diameter suitable for endoscopic and laparoscopic procedures. The staple applying assembly  20  (“end effector”) has a pair of pivotally opposed jaws, depicted as an elongate channel  40  with a pivotally attached anvil  42  ( FIGS. 1-2 ,  4 - 5 ). Closure and clamping of the anvil  42  to the elongate channel  40  is achieved by longitudinally supporting the elongate channel  40  with a frame assembly  44  ( FIG. 3 ) rotatingly attached to the handle portion  22  over which a double pivot closure sleeve assembly  46  longitudinally moves to impart a closing and opening motion respectively to a distal and proximal motion to the anvil  42 , even with the staple applying assembly  20  articulated as in  FIG. 2 . 
   With particular reference to  FIG. 3 , the frame assembly  44  includes a single pivot frame ground  48  whose proximal end is engaged to the rotation knob  32 , with a right half shell  50  thereon shown in  FIG. 3 . It should be appreciated that a proximal end of the closure sleeve assembly  46 , specifically of a closure straight tube  52 , encompasses the proximal end of the frame ground  48 , passing further internally to the handle portion  22  to engage closure components (not shown) that longitudinally translate the closure sleeve assembly  46 . A circular lip  54  at the proximal end of the closure straight tube  52  provides a rotating engagement to such components. Engaging components of the rotation knob  32  pass through a longitudinal slot  56  on a proximal portion of the straight closure tube  52  to engage an aperture  58  proximally positioned on the frame ground  48 . The longitudinal slot  56  is of sufficient length to allow the closure longitudinal translation of the closure sleeve assembly  46  at various rotational angles set by the rotation knob  32  to the closure sleeve assembly  46  and the frame ground  48 . 
   The elongate shaft  16  supports the firing motion by receiving a firing rod  60  that rotatingly engages firing components of the handle portion  22  (not shown). The firing rod  60  enters a proximal opening  62  along the longitudinal centerline of the frame ground  48 . The distal portion of the frame ground  48  includes a firing bar slot  64  along its bottom that communicates with the proximal opening  62 . A firing bar  66  longitudinally translates in the firing bar slot  64  and includes an upwardly projecting proximal pin  68  that engages a distal end  70  of the firing rod  60 . 
   The elongate shaft  16  supports articulation by incorporating a rectangular reservoir cavity  72 , one lateral portion depicted in a distal portion of the rotation knob  32 . A bottom compartment  74  that resides within the rectangular reservoir cavity  72  has laterally spaced apart left and right baffles  76 ,  78 . An articulation actuator  80  slides laterally overtop of the bottom compartment  74 , its downward laterally spaced left and right flanges  82 ,  84 , which are outboard of the baffles  76 ,  78 , each communicating laterally to left and right push buttons  86 ,  88  that extend outwardly from the respective shell halves of the rotation knob  32 . The lateral movement of the articulation actuator  80  draws left and right flanges  82 ,  84  nearer and farther respectively to the left and right baffles  76 ,  78 , operating against left and right reservoir bladders  90 ,  92  of a fluidic articulation system  94 , each bladder  90 ,  92  communicating respectively and distally to left and right fluid conduits or passageways  96 ,  98  that in turn communicate respectively with left and right actuating bladders  100 ,  102 . The latter oppose and laterally pivot a T-bar  104  of the articulation mechanism  14 . 
   The frame assembly  44  constrains these fluidic actuations by including a top and distal recessed table  106  of the frame ground  48  upon which resides the fluid passages  96 ,  98  and actuating bladders  100 ,  102 . The T-bar  104  also slidingly resides upon the recessed table  106  between the actuating bladders  100 ,  102 . Proximal to the T-Bar  104 , a raised barrier rib  108  is aligned thereto, serving to prevent inward expansion of the fluid passages  96 ,  98 . The frame assembly  44  has a rounded top frame cover (spacer)  110  that slides overtop of the frame ground  48 , preventing vertical expansion of the fluid passages  96 ,  98  and actuating bladders  100 ,  102 , as well as constraining any vertical movement of the T-bar  104 . In particular, the frame cover  110  includes features that enable it to also provide an articulation locking member  111 , described in greater detail below as part of an articulation locking mechanism  113 . 
   A distal end (“rack”)  112  of the T-bar  104  engages to pivot a proximally directed gear segment  115  of an articulated distal frame member  114  of the articulation mechanism  14 . An articulated closure tube  116  encompasses the articulated frame member  14  and includes a horseshoe aperture  118  that engages the anvil  42 . A double pivoting attachment is formed between the closure straight tube  52  and articulating closure ring  116  over the articulating mechanism  14 , allowing longitudinal closure motion even when the articulating mechanism  14  is articulated. In particular, top and bottom distally projecting pivot tabs  118 ,  120  on the closure straight tube  52  having pin holes  122 ,  124  respectively are longitudinally spaced away from corresponding top and bottom proximally projecting pivot tabs  126 ,  128  on the articulating closure ring  116  having pin holes  130 ,  132  respectively. An upper double pivot link  134  has longitudinally spaced upwardly directed distal and aft pins  136 ,  138  that engage pin holes  122 ,  130  respectively and a lower double pivot link  140  has longitudinally spaced downwardly projecting distal and aft pins  142 ,  144  that engage pin holes  124 ,  132  respectively. 
   With particular reference to  FIG. 4 , the articulating closure ring  116  is shown for enhanced manufacturability to include a short tube  146  attached to an articulating attachment collar  148  that includes the proximally projecting pivot tabs  126 ,  128 . Similarly, the straight closure tube  52  is assembled from a long closure tube  150  that attaches to an aft attachment collar  152  that includes the distally projecting pivot tabs  118 ,  120 . The horseshoe aperture  118  in the short closure tube  146  engages an upwardly projecting anvil feature  154  slightly proximal to lateral pivot pins  156  that engage pivot recesses  158  inside of the elongate channel  40 . 
   The illustrative version of  FIG. 4  includes a dog bone link  160  whose proximal pin  157  pivotally attaches to the frame ground  48  in a frame hole  161  and whose proximal pin  159  rigidly attaches to a proximal undersurface  162  of the articulating frame member  114 , thereby providing pivotal support therebetween. A bottom longitudinal knife slot  163  in the dog bone link  160  guides an articulating portion of the firing bar  66 . The articulating frame member  114  also includes a bottom longitudinal slot  164  for guiding a distal portion of the firing bar  66 . 
   Staple Applying Apparatus (End Effector). 
   With reference to  FIGS. 4-5 , the firing bar  66  distally terminates in an E-beam  165  that includes upper guide pins  166  that enter an anvil slot  168  in the anvil  42  to verify and assist in maintaining the anvil  42  in a closed state during staple formation and severing. Spacing between the elongate channel  40  and anvil  42  is further maintained by the E-beam  164  by having middle pins  170  slide along the top surface of the elongate channel  40  while a bottom foot  172  opposingly slides along the undersurface of the elongate channel  40 , guided by a longitudinal opening  174  in the elongate channel  40 . A distally presented cutting surface  176  of the E-beam  164 , which is between the upper guide pins  166  and middle pin  170 , severs clamped tissue while the E-beam actuates a replaceable staple cartridge  178  by distally moving a wedge sled  180  that causes staple drivers  182  to cam upwardly driving staples  184  out of upwardly open staple holes  186  in a staple cartridge body  188 , forming against a staple forming undersurface  190  of the anvil  42 . A staple cartridge tray  192  encompasses from the bottom the other components of the staple cartridge  178  to hold them in place. The staple cartridge tray  192  includes a rearwardly open slot  194  that overlies the longitudinal opening  174  in the elongate channel  40 , thus the middle pins  170  pass inside of the staple cartridge tray  192 . 
   The staple applying assembly  20  is described in greater detail in co-pending and commonly-owned U.S. patent application Ser. No. 10/955,042, “ARTICULATING SURGICAL STAPLING INSTRUMENT INCORPORATING A TWO-PIECE E-BEAM FIRING MECHANISM” to Frederick E. Shelton IV, et al., filed 30 Sep. 2004, the disclosure of which is hereby incorporated by reference in its entirety. 
   Articulation Locking Mechanism. 
   In  FIGS. 3-4  and  6 - 8 , an articulation locking mechanism  200  is advantageously incorporated to maintain the staple applying assembly  20  at a desired articulation angle. The articulation locking mechanism  200  reduces loads on the left and right actuating bladders  100 ,  102 . In particular, a compression spring  202  ( FIG. 3 ) is proximally positioned between a proximal end  204  of the articulation locking member  111  and the handle portion  22 , biasing the articulation locking member  111  distally. With particular reference to  FIG. 4 , two parallel slots  206 ,  208  at a distal end  210  of the articulation locking member  111  receive respectively upwardly projecting guide ribs  212 ,  214  on the frame ground  48 . The guide ribs  212 ,  214  are longitudinally shorter than the parallel slots  206 ,  208 , allowing a range of relative longitudinal travel. Thereby, with particular reference to  FIG. 8 , selective abutting engagement of a distal frictional surface, depicted as a toothed recess  216  distally projecting from the articulation locking member  111 , is engaged to a corresponding locking gear segment  217  in a brake plate  218  received into a top proximal recess  220  of the articulating frame member  114 . Distal and proximal holes  221 ,  222  in the brake plate  218  receive distal and proximal pins  223 ,  224  that upwardly project from the top proximal recess  220 . 
   With particular reference to  FIG. 6 , the elongate shaft  16  is depicted in an articulated position with the closure sleeve assembly  46  removed from around the frame assembly  44  and without the elongate channel  40  and anvil  42 . Articulation actuator  80  is shown moved laterally to the left to compress right proximal reservoir bladder  90  and expand distal right actuation bladder  100  moving T-bar  104  to the position shown. Thus, lateral movement of the articulation actuator  80  articulates the distal frame  114  clockwise about the single pivot frame ground  48  as shown. The articulation actuator  80  advantageously also automatically engages and disengages the articulation locking mechanism  200 . In particular, a toothed detent surface  225  along a proximal top surface of the articulation actuator  80  receives an upwardly projecting locking pin  226  from the proximal end  204  of the articulation locking member  111 . The engagement of the locking pin  226  within the root of the toothed detent surface  225  provides sufficient distal movement of the articulation locking member  111  for locking engagement of the locking gear segment  217  in the brake plate  218 . Lateral movement by an operator of the compression member  272  proximally urges the locking pin  226  proximally, and thus disengages the articulation locking member  111  from the brake plate  218 . When the operator releases the articulation actuator  80 , the locking pin  226  is urged by the compression spring  202  into the adjacent detent in detent surface  225  to lock the locking mechanism  111 , and thereby the staple applying assembly  20 , and constrains the articulation mechanism  14  at a desired articulation position by constraining and expanding the inflated shape of the proximal left and right reservoir bladders  90 ,  92 . 
   Portions of the articulation lock mechanism  200  are described in greater detail in commonly-owned U.S. Pat. No. 5,673,841 “SURGICAL INSTRUMENT” to Dale R. Schulze and Kenneth S. Wales, et al., filed 10 Mar. 1996, the disclosure of which is hereby incorporated by reference in its entirety. 
   Alternatively or additionally, an orifice may be provided within parallel fluid bladders  236 ,  238  to control the flow rate between the proximal actuating bladders  100 , 102  and distal reservoir bladders  90 ,  92 . In  FIGS. 16 ,  18 , the fluid passageways  258 ,  264  may be sized to provide resistance to changing the angle of articulation, serving as the orifices or as a fluid flow rate limiting structure. 
   In  FIG. 10 , an alternate locking mechanism  2000  of an articulation mechanism  2002  of a surgical instrument  2004  is normally unlocked and is activated by cocking a laterally moving T-bar  2006  due to back loading. A slot  2008  is located in a frame ground  2010  to receive and guide a rib  2012  extending down from the T-bar  2006 . A slender longitudinal section  2014 , which is orthogonally attached to the rib  2012  deflects if an end effector  2016  is backloaded. For instance, as the end effector  2016  is forced to the right as depicted at arrow  2018 , for instance, its proximal gear segment  2020  acts upon a rack  2022  of the T-bar  2006 , imparting a nonorthogonal backdriving force, as depicted at arrow  2024 . Thus, the slender longitudinal section  2014  bends, cocking rib  2012  in slot  2008 . This cocking produces opposing binding forces, as depicted by arrows  2026 ,  2028 , that lock the T-bar  2006  and prevent further articulation. Unlocking occurs when actuation of the articulation bladders uncocks the laterally moving T-bar  2006 . Thereafter, the rib  2016  may assist in guiding the T-bar  2006 . 
   In  FIG. 11 , yet an additional articulation locking mechanism  2100  for a surgical instrument  2102  is depicted that is normally unlocked and activated by the proximal force vector from the  20  degree pressure angle from gear teeth  2104  of an end effector  2106  and rack teeth  2108  of a T-bar  2110 . When the end effector  2106  is backloaded, as depicted by nonorthogonal arrow  2112 , the longitudinal vector of the pressure angle, depicted as arrow  2114 , moves the T-bar  2110  proximally. This longitudinal force vector is applied to a stiff spring  2118  behind a rack  2120  of the T-bar  2110 . When the spring  2118  deflects as T-bar  2110  moves proximally, locking teeth  2126  projecting proximally from the rack  2120  are brought into engagement with locking elements  2122  which are proximally and laterally aligned on a ground frame  2124  and brought into engagement with locking teeth  2126  projecting proximally from the rack  2120 . The locking teeth  2126  and locking elements  2122  disengage when the proximal force vector is reduced or eliminated by removing the back loading of the end effector  2106 , allowing T-bar  2110  to move distally under urging from spring  2118 . 
   Double Pivot Closure Sleeve and Single Pivot Frame Ground Combination. 
   With reference to  FIGS. 3-4  and  7 , the implement portion  12  advantageously incorporates the double pivot closure sleeve assembly  46  that longitudinally translates over and encompasses a single pivot frame ground  48 . These mechanisms and their operation will now be described in further detail. With particular reference to  FIG. 7 , the articulation mechanism  14  is depicted in an articulated state with the closure sleeve assembly  46  retracted proximally to an anvil open state. With the anvil  42  open, actuation of the articulation control  18  causes the articulated closure ring  116  to pivot about the upwardly directed distal pin  136  and downwardly directed distal pin  142  respectively of the upper and lower double pivot closure links  134 ,  140 . The frame ground  48  pivots around a single pin, depicted as the proximal pin  1808  that joins frame ground  48  to distal frame member  114 . With the anvil  42  open, the proximal pin  147  of frame ground  48  is aligned with the distal most position of upper and lower double pivot links  134 ,  140  of the closure sleeve assembly  46 . This positioning allows easy pivoting and rotation of the staple applying assembly  20  while the anvil  42  is open. When the closure sleeve assembly  46  is moved distally to pivot anvil  42  closed, the closure straight tube  52  moves distally about frame ground  48  and the articulated closure ring  116  moves distally along the articulated distal frame member  114  axis as urged by pivot links  134 ,  140 . Dual pivoting pins  136 ,  138  and  142 ,  144  on links  134 ,  140  facilitate engagement with closure straight tube  52  and articulated closure ring  116  as they are urged towards the distal closure position when the device is articulated (not shown). At the distal closure position, the frame ground pivot pin (“proximal pin”)  147  is vertically aligned with proximal pivot pins  138 ,  144  at full articulation or may fall at any point between distal pins  136 ,  142  and proximal pins  138 ,  144  while working effectively. 
   Solid Firing Bar Support. 
   In  FIG. 8 , the articulation mechanism  14  of  FIG. 7  is partially exploded and viewed from the bottom, showing a solid wall firing bar support design (dog bone link  160 ) that offers advantages over conventional flexible support plates. Support plates are used to bridge the gap and guide and support the firing bar  66  through a single frame ground pivot articulation joint  1801 . Flexible firing bars are known, but the incorporation of solid wall firing bars such as those shown in  FIGS. 4 ,  8  and  9  offer unique advantages. Referring now to  FIG. 8 , frame ground  48  includes a frame knife slot  1802  that runs along the bottom of frame ground  48  and a distal knife slot  164  runs along the bottom of an articulating distal frame member  114  for the sliding reception of the firing bar  66  (not shown) therein. Frame ground  48  described above includes a direct single pivotal connection  1808  with the distal frame member  114 . The fixed wall dog bone link  160  that is rotatably connected on proximal pin end  157  and movably connected on distal pin end  159  includes left and right lateral guides  1818 ,  1820 , defining therebetween a guidance slot  1822  for sliding passage of a firing bar  66  ( FIG. 4 ). 
   Thus, to bridge the gap between frame ground  48  and the distal frame member  114 , the fixed wall pivoting dog bone link  160  is pivotally attached to frame ground  48  and slidingly attached to frame member  114 . Proximal pin  157  of the pivoting dog bone  160  is pivotally received in a bore  1824  in frame ground  48  enabling pivotal dog bone  160  to pivot about bore  1824 . The distal pin  159  extends upwards from pivotal dog bone  160  and is slidingly received in a slot  1826  in distal frame  114 . Articulation of staple applying assembly  20  to an angle of such as 45 degrees from the longitudinal axis pivots pivoting dog bone  160  in bore  1824  at its proximal pin  157 , and distal pin  159  slides in slot  1826  to bend firing bar  66  to two spaced apart angles that are half of the angle of the staple applying assembly  20 . Unlike previously referenced flexible support plates that bend the firing bar  66  to a 45 degree angle, the fixed wall pivoting dog bone  160  bends the firing bar  66  to two spaced apart angles of such as 22.5 degrees each. Bending the flexible firing bar or bars  66  to half the angle cuts the bend stress in the firing bars  66  to one half of that found in conventional articulation supports. Reducing the bending stress in the firing bars  66  reduces the possibility of permanently bending or placing a set in the firing bars, reduces the possibilities of firing jams, ensures lower firing bar retraction forces, and provides smoother operation of the firing system. 
   In  FIG. 9 , a surgical instrument  1900  includes a double closure pivot/single frame pivot articulation joint  1902  wherein an alternate solid wall support plate mechanism  1904  replaces the lower double pivot link  140  and dog bone link  1812 . Left and right firing bar supports  1906 ,  1908  extend upwardly from a lower double pivot link  1910  of a closure sleeve assembly  1912 . Clearance  1914  is provided in a frame ground  1916  for the firing bar supports  1906 ,  1908  to travel as the closure sleeve assembly  1912  moves distally to close the anvil  42  (not shown in  FIG. 9 ) and proximally to open anvil  42 . Like the above described pivoting dog bone  1812 , the alternate lower double pivoting link  1910  also bends and supports the firing bar  66  (not shown in  FIG. 9 ) to have two spaced apart bend angles that are up to one half of the bend angle of the staple applying assembly  20 . 
   Lateral Member Guide Mechanisms. 
   With further reference to  FIG. 9 , left and right upward flanges  1918 ,  1920  on the frame ground  1916  include distal and proximal lateral pin guides  1922 ,  1924  that pass laterally through holes in a T-bar  1926 , assisting in minimizing binding in an articulation mechanism  1928 . As another example, in  FIG. 7 , the T-bar  104  advantageously includes a dovetail lateral guide  1930  that laterally slides within a dovetail channel  1932  formed therein. As yet a further example, in  FIG. 12 , a raised rib  1934  on a frame ground  1936  is received within a rectangular slot  1938  formed in a T-bar  1940 . To further facilitate non-binding lateral translation, distal and proximal lateral bearing tracks each include a respective plurality of ball bearings  1946 ,  1948 . As yet a further example, in  FIG. 13 , a plurality of frame lateral grooves  1950 - 1954  are formed in a frame ground  1956  with corresponding T-bar lateral grooves  1958 - 1962  in a T-bar  1964 . Slide rollers  1966 - 1970  reside trapped within respective pairs of lateral grooves  1950 / 1958 ,  1952 / 1960 ,  1954 / 1962 . These are by no means an exhaustive list of lateral guidance members that prevent unwanted cocking or rotation of the T-bar  1940 . 
   Double Pivot Frame Ground and Single Pivot Closure Combination. 
   In  FIGS. 14-15 , an alternate frame ground and closure mechanism  2200  includes a surgical instrument  2202  that includes double pivoting frame assembly  2204 . In particular, a frame ground  2206  is connected to distal frame member  2208  by a dual pivot frame dog bone  2210  having a proximal pivot pin  2212  pivotally engaging a proximal bore  2214  in frame ground  2206  and a distal pivot pin  2216  engaging a distal bore  2218  of distal frame member  2208 . A guidance slot  2220  is located on the underside of dog bone  2210  for the guidance of a firing bar  66  (not shown in  FIGS. 14-15 ) therein. Knife slot  2222  is located in distal frame member  2208 . As shown, articulation of the closure ring  2230  to a  45  degree angle articulates distal frame member  2208  to a 45 degree angle and articulates frame dog bone  2210  to half that angle. Consequently, firing bar  66  is subjected to the two shallow half bends that are spaced apart and obtains all the benefits listed above. 
   Outermost closure sleeve assembly  2224  is different in that only one pivot axis of the double pivoting design of the frame assembly  2204  accommodates its longitudinal closure motion. As shown, a closure tube shaft  2226  has a clevis  2228  at a distal end. Clevis  2228  is pivotally engaged with a closure ring  2230 . Closure ring  2230  has a proximal gear  2232  formed at a distal end and pin  2234  pivotally engages an upper tang  2236  of clevis  2228  and a lower arm  2238  engages with a lower tang  2240  of clevis  2228 . Holes  2242  in the clevis  2228  receive lateral guides pins  2243  and slidably attach a T-bar  2244  therein to engage proximal gear  2232  of the closure ring  2230 . Thus, this alternate mechanism  2200  uses a reversed single/dual pivot alternate concept from the previously described mechanism. That is, the alternate closure mechanism has a single pivot and the alternate frame ground has a dual pivot, unlike the previously described dual pivot closure mechanism with a single pivot frame ground. 
   It should be appreciated in light of the present disclosure that a dual pivoting frame link between proximal and distal frame portions has a number of advantages. While not an inclusive list, these advantages include facilitating guidance of firing members through the articulation with a wider radius of bending, Thereby allowing for reduced force to fire, reduced likelihood of binding and failure, and/or allowing for use of a stronger but more rigid firing member. Applications consistent with aspects of the invention may incorporate a closure tube assembly that also has multiple pivoting points, or a flexible cylindrical portion at the articulation joint. In addition, a plurality of articulation joints may be serially attached one to the other so that no one articulation joint is required to impart a large angular deflection. Alternatively, the articulating closure sleeve may be longitudinally fixed, serving as a cover, with the firing bar effecting closure, cutting and stapling. The double pivoting frame link serves to facilitate movement of the firing bar. 
   It should further be appreciated that while guiding the firing bar as depicted has certain advantages, a double pivoting connection may be formed by one or more frame links offset from the path of the articulating firing bar. It should further be appreciated that the one or more firing links may include at least a portion of resilient material along its length to further facilitate articulation. 
   It should further yet be appreciated that incorporating articulation actuators to position the proximal frame ground portion, distal frame ground portion, and the double pivoting frame link therebetween may instead actuate the closure sleeve, allowing the frame ground assembly to be passively articulated in response to articulation of the close sleeve assembly. 
   Laterally Moving Articulation Mechanism 
   In  FIG. 16 , an implement portion  2412  for a surgical instrument  2402  includes multiple pivot closure assembly  2204 . Outermost closure sleeve assembly  2424  is attached to a closure tube shaft  2426  by a flexible closure joint  2425  that encompasses a single pivot frame articulation joint (not shown in  FIG. 16 ). Alternatively, a flex-neck type frame articulation joint may be encompassed. The multiple pivot closure assembly  2446  is laterally flexible by having left and right vertical slits  2427 ,  2429  formed into a resilient material (e.g., polymer, silicone). Top and bottom bands  2451  of material maintain longitudinal length of the flexible closure joint  2425  and transfer a firing motion. 
   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. 
   For example, while a hydraulically powered articulation approach is disclosed herein, it should be appreciated that applications consistent with aspects of the present invention may be mechanically or electrically powered. 
   As another example, an end effector of a surgical instrument may include various types of actuating members that may be coupled to receive a selective reciprocating longitudinal motion carried by a sleeve assembly over an articulating shaft.