Abstract:
A surgical instrument particularly suited to endoscopic use articulates an end effector by including an articulation mechanism in an elongate shaft that incorporates an electrically actuated polymer (EAP) articulation locking mechanism actuator. Thereby, additional options for articulation become feasible, especially those that are actively powered and would otherwise dissipate heat and power if required to maintain position. Alternatively, a mechanically actuated articulation mechanism may be designed with reduced strength, and thus size, since the EAP articulation lock mechanism assists in preventing back driving after articulation. Versions of a. EAP articulation locking mechanism lock a pivoting articulation joint and others lock a flexible neck articulation joint.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. provisional application Ser. No. 60/591,694, entitled “SURGICAL INSTRUMENT INCORPORATING AN ELECTRICALLY ACTUATED ARTICULATION MECHANISM” to Shelton IV, filed 28 Jul. 2004. 
    
    
     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.). 
     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. Pat. 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 affirmatively spacing 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. 
     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, 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. The connecting rods ratchet through a series of discrete positions. 
     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. 
     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 Kenneth Wales 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. 
     While these mechanically communicated articulation motions have successfully enabled an endoscopic surgical stapling and severing instrument to articulate, development trends pose numerous challenges and barriers to entry into the market. Conflicting design objects include a shaft of as small a diameter as possible to reduce the size of the surgical opening, yet with sufficient strength to perform the several motions (e.g., closing, firing, articulation, rotation, etc.). However, these generally known articulation mechanisms have to remain robust enough to withstand being back driven by loads on the end effector. 
     Consequently, a significant need exists for an articulating surgical instrument that incorporates an articulation mechanism that reduces the required diameter of actuation components passing through the shaft of the instrument, yet robustly remains at the selected articulation angle thereafter. 
     BRIEF SUMMARY OF THE INVENTION 
     The invention overcomes the above-noted and other deficiencies of the prior art by providing a surgical instrument having an articulating shaft attached between a handle and an end effector. An electroactive polymer (EAP) actuator disengages an articulation lock during articulation and then reengages. Thereby, even a relatively weak articulation actuation mechanism may be employed with the articulation joint being locked thereafter, eliminating the need for the articulation actuation mechanism to be strong enough after actuation to prevent being backdriven. Thereby a shaft of advantageously small diameter may be achieved, yet have the functionality of remotely controllable actuation. 
     In one aspect of the invention, a surgical instrument includes a pivoting articulating joint attached between an end effector and a distal end of an elongate shaft. A locking member attached to one side of the pivoting articulating joint is resiliently urged toward locking engagement with the other side of the joint even when articulated. An electrical unlocking actuator opposes the locking member to cause disengagement so that a change in the articulation angle may be made. Then the locking member is allowed to reengage, preventing backdriving. 
     In another aspect of the invention, a surgical instrument includes a flexible articulation joint having vertical rows of left and right ribs allowing lateral bending to either side. Locking strips are positioned within recesses in the ribs such that when the flexible articulation joint is articulated to one side, the longitudinal length of the locking strip may be changed to force blocking features thereon to be inserted between the ribs, maintaining them in their spaced condition. 
     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 rear perspective view of an endoscopic surgical stapling instrument for surgical stapling and severing in an open, unarticulated state. 
         FIG. 2  is a perspective view of a laminate Electroactive Polymer (EAP) composite. 
         FIG. 3  is a perspective view of an EAP plate actuator formed from a stack formed from an adhesively affixed plurality of laminate EAP composites of  FIG. 2 . 
         FIG. 4  is a perspective view of a cutaway along a longitudinal axis of a contracting EAP fiber actuator. 
         FIG. 5  is a front view in elevation taken in cross section along lines  5 - 5  of the contracting EAP fiber actuator of  FIG. 4 . 
         FIG. 6  is a front right perspective view of an EAP actuated articulation joint for the surgical instrument of  FIG. 1  with a flex closure sleeve assembly and a pivoting frame assembly and a closed staple applying assembly. 
         FIG. 7  is a front right perspective view of the EAP actuated articulation joint and closed staple applying assembly of  FIG. 6  with a flexible closure sleeve assembly removed and a single pivot frame assembly partially exploded. 
         FIG. 8  is a front right exploded perspective view of the EAP actuated articulation joint and staple applying assembly of  FIG. 6 . 
         FIG. 9  is a detail view of the exploded single pivot frame assembly including EAP fiber actuators of  FIG. 7 . 
         FIG. 10  is a right side view in elevation taken in cross section along lines  10 - 10  of  FIG. 6  through a pivot axis of the EAP actuated articulation joint and looking right to see a pair of EAP fiber actuators. 
         FIG. 11  is top view taken in cross section along lines  11 - 11  of  FIG. 11  through a longitudinal axis of the EAP actuated articulation joint looking down to see a lower moment arm and lower EAP fiber actuators. 
         FIG. 12  is a front view in elevation taken in cross section along lines  12 - 12  of  FIG. 10  along the lateral EAP fiber actuators. 
         FIG. 13  is a top view of the EAP actuated articulation joint of  FIG. 11  with the right upper and lower EAP fiber actuators contracted to articulate the staple applying assembly to the left. 
         FIG. 14  is front right perspective view of an additional alternative EAP actuated articulation joint that includes a double pivot closure sleeve assembly in a proximal position opening the anvil of the end effector. 
         FIG. 15  is front right exploded view of the additional alternative EAP actuated articulation joint of  FIG. 14  including the double pivot closure sleeve assembly and a single pivot frame assembly. 
         FIG. 16  is right side view in elevation of the alternative EAP actuated articulation joint taken in cross section along lines  16 - 16  of  FIG. 14  with firing components included. 
         FIG. 17  is a top view of the alternative EAP actuated articulation joint in an unarticulated condition taken in cross section along lines  17 - 17  of  FIG. 14 . 
         FIG. 18  is a top view of the alternative EAP actuated articulation joint in a leftward articulated condition taken in cross section along lines  17 - 17  of  FIG. 14 . 
         FIG. 19  is yet another alternative EAP actuated articulation joint in a slightly articulated condition with a contracting EAP fiber actuator positioned to straighten the joint. 
         FIG. 20  is a right front perspective view of a partially exploded single pivot articulation joint that advantageously includes an EAP articulation locking mechanism that is biased to be normally locked. 
         FIG. 21  is a right front perspective view in detail of a proximal portion of the EAP articulation locking mechanism in a proximal frame ground of the single pivot articulation joint. 
         FIG. 22  is a top view of the single pivot articulation joint of  FIG. 20 . 
         FIG. 23  is a right side view in elevation of the single pivot articulation joint of  FIG. 22  taken in cross section along a longitudinal centerline of lines  23 - 23 . 
         FIG. 24  is a top view of the single pivot articulation joint of  FIG. 23  taken in cross section along lines  24 - 24  to show a gear segment on an upper pivot tang locked by the EAP articulation locking mechanism in an unarticulated condition. 
         FIG. 25  is a top view of the single pivot articulation joint of  FIG. 23  taken in cross section along a centerline of lines  25 - 25  looking down upon a lower pivot tab of a proximal frame ground that is partially articulating an end effector to the left while the EAP articulation locking mechanism is activated to an unlocked condition. 
         FIG. 26  is a front view in elevation of a distal frame ground of the single pivot articulation mechanism of  FIG. 24  taken in cross section along lines  26 - 26  depicting attachment of EAP fiber actuators that articulate the joint. 
         FIG. 27  is a front view in elevation of the proximal frame ground of the single pivot articulation joint of  FIG. 24  taken in cross section along lines  27 - 27  to expose EAP stack actuators and locking pins of the EAP actuated locking mechanisms. 
         FIG. 28  is a top view taken in cross section along an interface between an upper pivot tang of a distal frame ground and an upper pivot tab of a proximal frame ground of a single pivot articulation joint advantageously incorporating lengthened EAP fiber actuators acting upon rounded moment arms in combination with the EAP articulation locking mechanism. 
         FIG. 29  is a front view in elevation taken generally in cross section through the proximal frame ground and EAP articulation locking mechanism but also showing more distally viewed moment arms and lengthened EAP fiber actuators connected thereto. 
         FIG. 30  is a top view of a single pivot articulation joint taken in cross section along a top surface of an upper pivot tab of a proximal frame ground to illustrate expansive EAP stack actuators employed against a moment arm distally attached to the upper pivot tab to effect articulation used in conjunction with the normally locked EAP articulation locking mechanism activated in preparation for articulation. 
         FIG. 31  is a front view in elevation of the single pivot articulation joint of  FIG. 30  taken in cross section through upper and lower tip pins from the moment arms and through the EAP stack actuators. 
         FIG. 32  is a top view of the single pivot articulation joint of  FIG. 30  taken in cross section along a top surface of the upper pivot tab of the proximal frame ground after articulation of the distal frame ground to the left but before deenergizing the EAP articulation locking mechanism to effect articulation locking. 
         FIG. 33  is a front view in elevation of the single pivot articulation joint of  FIG. 31  taken in cross section through the upper and lower tip pins from the moment arms and through the expanded left and compressed right EAP stack actuators. 
         FIG. 34  is a right side view in elevation of a surgical instrument with a closure sleeve assembly cutaway to expose an EAP actuated articulation mechanism that articulates a flexible articulating frame ground. 
         FIG. 35  is a top view of the surgical instrument of  FIG. 34  articulating to the left. 
         FIG. 36  is a front right perspective view of the articulating frame ground of  FIG. 34  that incorporates EAP plate actuators and locking strips. 
         FIG. 37  is a top view of the articulating frame ground of  FIG. 34  in a left articulated state with a left EAP locking strip shown in phantom in an unlocked actuated state and a locked relaxed state. 
         FIG. 38  is a top view of the articulating frame ground of  FIG. 34  in a left articulated state taken in cross section through the EAP plate actuators and EAP locking strips. 
         FIG. 39  is a front view in elevation of the articulating frame ground of  FIG. 37  taken in cross section through lines  39 - 39  through the lateral guide pins. 
         FIG. 40  is a top view of an alternate articulating frame ground taken in cross section through a plurality of EAP rib spreader actuators. 
         FIG. 41  is a right perspective partially exploded view of an additional alternative articulating frame ground having a plurality of EAP fiber actuators. 
         FIG. 42  is a front view in elevation of the additional alternative articulating frame ground of  FIG. 41  taken in cross section along lines  42 - 42 . 
         FIG. 43  is a top view of an alternative single pivot articulation joint with a transverse EAP articulation locking mechanism for the surgical instrument of  FIG. 1 . 
         FIG. 44  is a side view in elevation of the alternative pivot articulation joint of  FIG. 43  taken in cross section along a longitudinal centerline of lines  44 - 44 . 
         FIG. 45  is a front view in elevation of the alternative pivot articulation joint of  FIG. 44  taken in cross section along transverse lines  45 - 45 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Overview Of Articulating Shaft. 
     In  FIG. 1 , a surgical instrument, depicted as a surgical severing and stapling instrument  10 , has at its distal end an end effector of a staple applying assembly  12 , spaced apart from a handle  14  by an elongate shaft  16 . The staple applying assembly  12  includes a staple channel  18  for receiving a replaceable staple cartridge  20 . Pivotally attached to the staple channel  18  is an anvil  22  that clamps tissue against the staple cartridge  20  for stapling and severing. When the staple applying assembly  12  is closed, its cross sectional area, as well as the elongate shaft  16  are suitable for insertion through a small surgical opening, such as through a cannula of a trocar (not shown). 
     Correct placement and orientation of the staple applying assembly  12  is facilitated by controls on the handle  14 . In particular, a rotation knob  30  causes rotation of the shaft  16  about its longitudinal axis, and hence rotation of the staple applying assembly  12 . Additional positioning is enabled at an articulation joint  32  in the shaft  16  that pivots the staple applying assembly  12  in an arc from the longitudinal axis of the shaft  16 , thereby allowing placement behind an organ or allowing other instruments such as an endoscope (not shown) to be oriented behind the staple applying assembly  12 . This articulation is advantageously effected by an articulation control switch  34  on the handle  14  that transmits an electrical signal to the articulation joint  32  to an Electroactive Polymer (EAP) actuator  36 , powered by an EAP controller and power supply  38  contained within the handle  14 . In particular, the electrical signal disengages an articulation lock by activating an EAP lock actuator (not shown in  FIG. 1 ) during articulation. 
     Once positioned with tissue in the staple applying assembly  12 , a surgeon closes the anvil  22  by drawing a closure trigger  40  proximally toward a pistol grip  42 . Once clamped thus, the surgeon may grasp a more distally presented firing trigger  44 , drawing it back to effect firing of the staple applying assembly  12 , which in some applications is achieved in one single firing stroke and in other applications by multiple firing strokes. Firing accomplishes simultaneous stapling of at least two rows of staples while severing the tissue therebetween. 
     Retraction of the firing components may be automatically initiated upon full travel. Alternatively, a retraction lever  46  may be drawn aft to effect retraction. With the firing components retracted, the staple applying assembly  12  may be unclamped and opened by the surgeon slightly drawing the closure trigger  40  aft toward the pistol grip  42  and depressing a closure release button  48  and then releasing the closure trigger  40 , thereby releasing the two stapled ends of severed tissue from the staple applying assembly  12 . 
     It should be appreciated that herein spatial terms such as vertical, horizontal, etc. are given with reference to the figures assuming that the longitudinal axis of the surgical instrument  10  is horizontal with the anvil  22  of the staple applying assembly  12  aligned vertically on top and the triggers  40 ,  44  aligned vertically on the bottom of the handle  14 . However, in actual practice the surgical instrument  10  may be oriented at various angles and as such these spatial terms are used relative to the surgical instrument  10  itself. Further, proximal is used to denote a perspective of a clinician who is behind the handle  14  who places the end effector  12  distal, away from himself. Handle. 
     In  FIG. 1 , the staple applying assembly  12  accomplishes the functions of clamping onto tissue, driving staples and severing tissue by two distinct motions transferred longitudinally down the shaft  16  over a shaft frame (not shown in  FIG. 1  but described below regarding  FIG. 7 ). This shaft frame assembly is proximally attached to the handle  14  and coupled for rotation with the rotation knob  30 . An illustrative multi-stroke handle  14  for the surgical stapling and severing instrument  10  of  FIG. 1  is described in greater detail in the co-pending and co-owned U.S. patent applications entitled “SURGICAL STAPLING INSTRUMENT INCORPORATING A MULTISTROKE FIRING POSITION INDICATOR AND RETRACTION MECHANISM” to Swayze and Shelton, Ser. No. 10/674,026, and entitled “SURGICAL STAPLING INSTRUMENT INCORPORATING A MULTI-STROKE FIRING MECHANISM WITH AUTOMATIC END OF FIRING TRAVEL RETRACTION”, Ser. No. 11/052,632, filed on Feb. 7, 2005 to Kevin Doll, Jeffrey S. Swayze, Frederick E. Shelton IV, Douglas Hoffman, and Michael Setser, the disclosures of which are hereby incorporated by reference in their entirety, with additional features and variations as described herein. 
     While a multi-stroke handle  14  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. 
     Electroactive Polymers. 
     Electroactive polymers (EAPs) are a set of conductive doped polymers that change shape when an electrical voltage is applied. In essence, the conductive polymer is paired to some form of ionic fluid or gel and electrodes. Flow of the ions from the fluid/gel into or out of the conductive polymer is induced by the voltage potential applied and this flow induces the shape change of the polymer. The voltage potential ranges from 1V to 4 kV depending on the polymer and ionic fluid used. Some of the EAPs contract when voltage is applied and some expand. The EAPs may be paired to mechanical means such as springs or flexible plates to change the effect that is caused when the voltage is applied. 
     There are two basic types of electroactive polymers and multiple configurations of each type. The two basic types are a fiber bundle and a laminate version. The fiber bundle consists of fibers around 30-50 microns. These fibers may be woven into a bundle much like textiles and are often called EAP yarn because of this. This type of EAP contracts when voltage is applied. The electrodes are usually a central wire core and a conductive outer sheath, which also serves to contain the ionic fluid that surrounds the fiber bundles. An example of a commercially available fiber EAP material is manufactured by Santa Fe Science and Technology and sold as PANION™ fiber and is described in U.S. Pat. No. 6,667,825, which is hereby incorporated by reference in its entirety. 
     The other type is a laminate structure, which consists of a layer of EAP polymer, a layer of ionic gel and two flexible plates that are attached to either side of the laminate. When a voltage is applied the square laminate plate expands in one direction and contracts in the perpendicular direction. An example of a commercially available laminate (plate) EAP material is from Artificial Muscle Inc, a division of SRI Laboratories. Plate EAP material is also available from EAMEX of Japan and is referred to as thin film EAP. 
     It should be noted that EAPs do not change volume when energized; they merely expand or contract in one direction while doing the opposite in the transverse direction. The laminate version may be used in its basic form by containing one side against a rigid structure and using the other much like a piston. It may also be adhered to either side of a flexible plate. When one side of the flexible plate EAP is energized, it expands flexing the plate in the opposite direction. This allows the plate to be flexed either direction depending on which side is energized. 
     An EAP actuator usually consists of numerous layers or fibers bundled together to work in cooperation. The mechanical configuration of the EAP determines the EAP actuator and its capabilities for motion. The EAP may be formed into long stands and wrapped around a single central electrode. A flexible exterior outer sleeve will form the other electrode for the actuator as well as contain the ionic fluid necessary for the function of the device. In this configuration, when the electrical field is applied to the electrodes, the strands of EAP shorten. This configuration of EAP actuator is called a fiber EAP actuator. Likewise, the laminate configuration may be placed in numerous layers on either side of a flexible plate or merely in layers on itself to increase its capabilities. Typical fiber structures have an effective strain of 2-4% where the typical laminate version achieves 20-30% utilizing much higher voltages. 
     In  FIG. 2 , a laminate EAP composite  100  is depicted being formed from a positive plate electrode layer  102  attached to an EAP layer  104 , which in turn is attached to an ionic cell layer  106 , which in turn is attached to a negative plate electrode layer  108 . In  FIG. 3 , a plurality of five laminate EAP composites  100  are affixed in a stack by adhesive layers  110  therebetween to form an EAP plate actuator  120 . It should be appreciated that opposing EAP actuators  120  may be formed that can selectively bend in either direction. 
     In  FIGS. 4-5 , a contracting EAP fiber actuator  140  includes a longitudinal platinum cathode wire  142  that passes through an insulative polymer proximal end cap  144  through an elongate cylindrical cavity  146  formed within a plastic cylinder wall  148  that is conductively doped to serve as a positive anode. A distal end of the platinum cathode wire  142  is embedded into an insulative polymer distal end cap  150 . A plurality of contracting polymer fibers  152  are arranged parallel with and surrounding the cathode wire  142  and have their ends embedded into respective end caps  144 ,  150 . The plastic cylinder wall  148  is peripherally attached around respective end caps  144 ,  150  to enclose the cylindrical cavity  146  to seal in ionic fluid or gel  154  that fills the space between contracting polymer fibers  152  and cathode wire  142 . When a voltage is applied across the plastic cylinder wall (anode)  148  and cathode wire  142 , ionic fluid enters the contracting polymer fibers  152 , causing their outer diameter to swell with a corresponding contraction in length, thereby drawing the end caps  144 ,  150  toward one another. 
     EAP Actuated Articulation Joint. 
     In  FIGS. 6-13 , a surgical severing and stapling instrument  200  includes an EAP actuated articulation joint  202  that is formed in its elongate shaft  204  proximate to the end effector, which is illustrated by the surgical stapling and severing assembly  12  that advantageously responds to separate closure and firing motions that are transferred longitudinally by the elongate shaft  204 . The EAP actuated articulation joint  202  advantageously adds the desirable clinical flexibility of articulating the staple applying assembly  12 . 
     In the illustrative version of  FIGS. 6-13 , the EAP actuated articulation joint  202  is more particularly a flexible closure and pivoting frame articulation joint  210 , which in  FIG. 6  is shown to include a flexible closure sleeve assembly  212  having a proximal closure tube  214  and distal closure ring  216  connected by a flexible closure tube  218 . Left and right longitudinal rows of vertical slits  220 ,  222  formed in the flexible closure tube  218  allow flexing to the right or to the left for articulation, yet an uninterrupted top longitudinal band  224  transfers a longitudinal closure motion regardless of the amount of such flexing. It should be appreciated that an identical uninterrupted bottom longitudinal band runs along the bottom of the flexible closure tube  218  (not shown) and is opposite to and cooperates with the top longitudinal band  224  in transferring this motion. In particular, a top portion of the distal closure ring  216  includes a horseshoe aperture  226  that engages an anvil closure feature  228  of the anvil  22 . In  FIG. 7 , the anvil  22  includes laterally projecting pivot pins  230  at its proximal end that pivotally engage pivot apertures  232  formed near the proximal end of the elongate channel  18  ( FIGS. 7-8 ). The slightly more distal anvil closure feature  228  thus imparts a closing motion when the flexible closure sleeve assembly  212  moves distally and imparts an opening motion when moving proximally. The flexible closure tube  218  may bend along the length of the left and right longitudinal rows of vertical slits  220 ,  222 , thus accommodating an encompassed single pivot frame assembly  234  of the flexible closure and pivoting frame articulation joint  210  when articulated. 
     With particular reference to  FIGS. 7-9 , the single pivot frame assembly  234  includes a proximal frame ground  236  with distally projecting top and bottom pivot tabs  238 ,  240 , each having a respective top and bottom pivot pin hole  242 ,  244 . Corresponding top and bottom pivot tangs  246 ,  248  project proximally from a distal frame ground  250 , each tang  246 ,  248  with respective top and bottom pivot pin holes  252 ,  254  pivotally engaging the proximal frame ground  236 . In particular, the vertically aligned top pivot pin holes  242 ,  252  and bottom pivot pin holes  244 ,  254  are respectively engaged by top and bottom frame pivot pins  256 ,  258  ( FIG. 10 ). 
     In  FIG. 8 , an implement portion  260  of the surgical instrument  200  formed by the elongate shaft  16  and staple applying assembly  12  further includes a firing bar  270  that longitudinally translates through the proximal frame ground  218 , through the flexible closure and pivoting frame articulation joint  210 , and through a firing slot  272  in the distal frame ground  250  into the staple applying assembly  12 . Distal and proximal square apertures  274 ,  276  formed on top of the distal frame ground  250  define a clip bar  278  therebetween that receives a top arm  280  of a clip spring  282  whose lower, distally extended arm  284  asserts a downward pressure on a raised portion  286  along an upper portion of the firing bar  270  corresponding to the empty/missing cartridge lockout portion of firing travel. 
     With particular reference to  FIG. 8 , a distally projecting end of the firing bar  270  is attached to an E-beam  288  that assists in spacing the anvil  22  from the staple cartridge  20 , severs tissue, and actuates the staple cartridge  20 . The staple cartridge  20  includes a molded cartridge body  290  that holds a plurality of staples resting upon staple drivers  292  within respective upwardly open staple apertures  294 . A wedge sled  296  is driven distally by the E-beam  28   21 ′ 8 , sliding upon a cartridge tray  298  that holds together the various components of the replaceable staple cartridge  20 . The wedge sled  296  upwardly cams the staple drivers  292  to force out the staples into deforming contact with the anvil  22  while a cutting surface  300  of the E-beam  288  severs clamped tissue. It should be appreciated that upper pins  302  of the E-beam  288  engage the anvil  22  during firing while middle pins  304  and a bottom foot  306  engage respective top and bottom surfaces of a longitudinal slot  308  formed in the elongate channel  18 , with a corresponding longitudinal opening  310  in the cartridge tray  298  and a rearwardly open vertical slot  312  in the cartridge body  290 . Thereafter, the firing bar  270  is retracted proximally, retracting as well the E-beam  288 , allowing the anvil  22  to be opened to release the two stapled and severed tissue portions (not shown). 
     The staple applying assembly  12  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. 
     With particular reference to  FIGS. 9-13 , an EAP actuator system  400  advantageously actuates the single pivot frame assembly  234  in response to an electrical articulation signal (not shown) received from the handle  14 . In the illustrative version of  FIGS. 7-13 , top left and top right EAP fiber actuators  402 ,  404  attach horizontally to each lateral side of a top distally projecting moment arm  406  attached to the top pivot tab  238 . The outer ends of the top left and top right EAP fiber actuators  402 ,  404  are attached to respective upper left and right lateral attachment points  406 ,  408  of an inner diameter  410  of the distal frame ground  250 . Similarly, bottom left and bottom right EAP fiber actuators  412 ,  414  attach horizontally to each lateral side of a bottom distally projecting moment arm  416  attached to the top pivot tab  238 . The outer ends of the bottom left and bottom right EAP fiber actuators  412 ,  414  are attached to respective lower left and right lateral attachment points  418 ,  420  of the inner diameter  410  of the distal frame ground  250 . The attachments points  406 ,  408 ,  418 ,  420  are shown to pass through the distal frame ground  250  in  FIG. 12  with the left attachment points  406 ,  418  visible on the exterior of the distal frame ground  250  in  FIG. 9 . Activating one pair of EAP actuators, such as in  FIG. 13 , and in particular reference to the upper and lower right EAP fiber actuators  404 ,  414 , causes them to contract, drawing the upper and lower moment arms  406 ,  416  toward the right side of the distal frame ground  250 , thereby stretching the upper and lower EAP fiber actuators  402 ,  412 , collapsing the left longitudinal row of vertical slits  220 , and expanding the right longitudinal row of vertical slits  222 . 
     In  FIGS. 14-18 , a surgical severing and stapling instrument  500  includes an alternative EAP actuated articulation joint  502  that includes a double pivot closure sleeve assembly  504  ( FIGS. 14-15 ) and a single pivot frame assembly  506  ( FIGS. 15-18 ). In  FIG. 14 , the staple applying assembly  12  is depicted with the replaceable staple cartridge  20  removed and the anvil  22  open. Thus, the double pivot closure sleeve assembly  504  is at its proximal position with its distal pivoting axis aligned with a pivoting axis of the frame assembly  506 . It should be appreciated that with the closure sleeve assembly  504  moved distally to close the anvil  22 , a proximal pivot axis of the closure sleeve assembly  504  also pivots in order to translate over an articulated frame assembly  506 . 
     With particular reference to  FIG. 15 , the double pivot closure sleeve assembly  504  includes a proximal closure tube  510  whose distal end is keyed to attach to a proximal closure ring  512  having upper and lower distally projecting tangs  514 ,  516 . A distal closure tube  518 , which includes a horseshoe aperture  520  to engage the anvil closure feature  228  on the anvil  22 , is proximally pinned to a distal closure ring  522  having upper and lower proximally projecting tangs  524 ,  526 . An upper double pivot link  528  includes upwardly projecting distal and proximal pivot pins  530 ,  532  that engage respectively an upper distal pin hole  534  in the upper proximally projecting tang  524  and an upper proximal pin hole  536  in the upper distally projecting tang  514 . A lower double pivot link  538  includes downwardly projecting distal and proximal pivot pins  540 ,  542  that engage respectively a lower distal pin hole  544  in the lower proximally projecting tang  526  and a lower proximal pin hole  546  in the lower distally projecting tang  516 . 
     With particular reference to  FIGS. 15-18 , the single pivot frame assembly  506  includes a proximal frame ground  550  whose distal end includes a pivot pin hole  552  centered and proximal to a distally open pivot recess  554  defined between left and right moment arms  556 ,  558 . A dog bone link  560  includes a proximal pin  562  that upwardly engages the pivot pin hole  552  in the proximal frame ground  550  and a center bar  564  that pivots between the left and right moment arms  556 ,  558 . A distal pin  566  of the dog bone link  560  is rigidly attached into a lower proximal bore  568  in a distal frame ground  570  having distal lateral guides  572  that engage proximal guides  574  in the elongate channel  18 . 
     An EAP actuation system  580  includes left and right EAP stack actuators  582 ,  584  that selectively expand to assert an articulation force on the center bar  564  of the dog bone link  560 , which passively compresses the other EAP stack actuator. In  FIG. 18 , the right EAP stack actuator  582  has expanded, pivoting the dog bone link  560 , and thus the staple applying assembly  12 , to the left and passively compressing the left EAP stack actuator  584 . 
     In  FIG. 19 , yet another alternative EAP actuated articulation joint  600  for a surgical instrument  602  includes a single pivoting frame assembly  604  wherein a proximal frame ground  606  is engaged to a distally projecting tang  608  from a distal frame ground  610  at a pivot pin  612 . The distally projecting tang  608  is recessed on a right lateral side to define a half teardrop shaped pulley  614  on the right side of the pivot pin  612 . Attached to a distal point of the half teardrop shaped pulley  614  is a distal end of a contracting EAP fiber actuator  616  that follows the contour thereof and passes into the proximal frame ground  606 . The contracting EAP fiber actuator  616  may be sufficiently long so that, for even a small percentage contraction in a length a significant rotation may be achieved. It should be appreciated that a counter rotating mechanism may be incorporated on a left side of the depicted tang  608  on a similar but reversed mechanism formed on the other side of the EAP articulation joint  600 . 
     Longitudinal Articulation Locking Mechanism for Pivoting Articulation Mechanism. 
     In  FIGS. 20-27 , a longitudinal EAP actuated articulation lock  700  is incorporated into a pivoting articulation joint  702  for a surgical instrument  704 . For clarity, a single pivoting frame assembly  706  is depicted with a proximal frame ground  708  having distally extended upper and lower pivot tabs  710 ,  712  that are pivotally engaged to proximally directed upper and lower tangs  714 ,  716  of a distal frame ground  718  that is attached to an end effector  720 . An upper inner hole  722  in the upper pivot tab  710  is aligned under an upper outer hole  724  in the upper tang  714 , which are pivotally pinned together by upper pivot pin  726 . A lower inner hole  728  in the lower pivot tab  712  is aligned above a lower outer hole  730  in the lower tang  716 . Holes  728 ,  712  are pivotally pinned together by a lower pivot pin  732 . Upper and lower moment arms  734 ,  736  extend distally respectively from the upper and lower pivot tabs  710 ,  712 . The upper moment arm  734  may be urged to the left toward an upper left attachment point  738  formed in the distal frame ground  718  by a generally horizontal upper left EAP fiber actuator  740 . The upper moment arm  734  may be urged to the right toward an upper right attachment point  742  formed in the distal frame ground  718  by a generally horizontal upper right EAP fiber actuator  744 . The lower moment arm  736  may be urged to the left toward a lower left attachment point  746  formed in the distal frame ground  718  by a generally horizontal lower left EAP fiber actuator  748 . The lower moment arm  736  may be urged to the right toward a lower right attachment point  750  formed in the distal frame ground  718  by a generally horizontal lower right EAP fiber actuator  752 . 
     Closure of the anvil  22  may occur by action of a closure mechanism that is not shown, such as an EAP actuator that acts upon the anvil pivot. Alternatively, a firing motion may first close the anvil prior to further motion effecting stapling and severing. As a further alternative, a closure sleeve assembly or other longitudinally coupled mechanism (not shown) may impart a closing motion to the anvil  22 . 
     An upper EAP actuated articulation locking mechanism  800  advantageously unlocks the pivoting articulation joint  702  to allow articulating movement. The EAP actuated articulation locking mechanism  800  then relaxes to a locked state, providing a stable locked position that does not require power dissipation, and thus component heating, between changes in an amount of articulation. An upper locking bolt assembly  802  is shown in a rectangular upper lock recess  804  formed in the proximal frame ground  708  proximal to and vertically farther from the longitudinal centerline than the upper pivoting tab  710 . A locking bolt  806  extends a locking tip  808  out of a distal slot  810 , formed in the upper lock recess  804 , into engagement in a nearest tooth root  812  of a gear segment  814  formed about a proximal surface about the upper pivot tang  714  of the distal frame ground  718 . The locking bolt  806  proximally terminates in cross plate  816  that slides longitudinally in the rectangular upper lock recess  804  between the urging of a proximally positioned compression spring  818  and upper left and right EAP stack actuator  820 ,  822  that may be activated to expand longitudinally, compressing the compression spring  818  as the lock bolt  806  is moved proximally, thereby disengaging the locking tip  808  from the gear segment  814 , allowing the pivoting articulation joint  702  to be repositioned. An upper lock cover  824  closes the upper lock recess  804 . 
     For additional locking support, in  FIG. 23 , a lower EAP actuated articulation locking mechanism  830 , that is identical to the upper locking mechanism  800 , acts on the opposite site against lower pivot tang  716 . It should further be appreciated that a similar locking mechanism may be incorporated into a distal portion of an elongate shaft rather than a proximal end. Further, a double pivoting coupling may include a lock at each pivot. 
     In use, an unarticulated end effector  720  and pivoting articulation joint  702  ( FIGS. 20-24 ) are inserted to a surgical site. With EAP locking mechanisms  800 ,  830  typically deenergized, the locking tip  808  attached to the proximal frame ground  708  engages the gear segment  814  of the distal frame ground  718 , locking the single pivot frame assembly  706 . When desired, EAP stack actuators  820 ,  822  are energized to longitudinally lengthen, unlocking the EAP articulation locking mechanisms  800 ,  830 . While unlocked, the articulation joint  702  may be articulated, such as by contracting upper and lower right EAP fiber actuators  744 ,  752  to pivot the end effector  720  to the left ( FIG. 25 ), presenting a different tooth root  812  to the locking tip  808  so that when deenergized the EAP articulation locking mechanism  800  will lock to the articulation condition of the surgical instrument  704 . 
     In  FIGS. 28-29 , an alternative EAP articulation system  900  for a single pivot articulation joint  901  is depicted for use in conjunction with the EAP articulation locking mechanism  800  previously described. Upper and lower pairs of left and right EAP fiber actuators  902 ,  904 ,  906 ,  908  are lengthened by incorporating upper and lower rounded moment arms  910 ,  912  distally respectively on upper and lower pivot tabs  914 ,  916  of a proximal frame ground  918 . An upper left attachment point  920  in a distal frame ground  922  is slightly higher than an upper right attachment point  924 . A lower left attachment point  926  is also slightly higher than a lower right attachment point  928 , corresponding to the upper and lower left EAP fiber actuators  902 ,  906  wrapping respectively around a higher portion of the corresponding upper and lower rounded moment arms  910 ,  912  than the upper and lower right EAP fiber actuators  904 ,  908  ( FIG. 29 ). Thereby, the lengthened EAP fiber actuators  902 - 908  in combination with the length and contour of the moment arms  910 ,  912  may be selected for a desired performance characteristic. 
     In  FIGS. 30-33 , an additional alternative EAP articulation system  1000  for a single pivot articulation joint  1001  is depicted for use in conjunction with the EAP articulation locking mechanism  800  previously described. Instead of EAP fiber actuators that effect articulation, upper and lower pairs of left and right EAP stack actuators  1002 ,  1004 ,  1006 ,  1008  respectively oppose and laterally move upper and lower longitudinal tracks  1010 ,  1012 . A distally projecting upper moment arm  1014  attaches to an upper pivot tab  1016  of a proximal frame ground  1018 . An upper inwardly directed tip pin  1020  at a distal end of the upper moment arm  1014  longitudinally slidingly engages the upper longitudinal track  1010 , and thus responds to the differential contraction and expansion of the upper left and right EAP stack actuators  1002 ,  1004  that are laterally constrained by a distal frame ground  1022 . A distally projecting lower moment arm  1024  attaches to an upper pivot tab  1026  of the proximal frame ground  1018 . A lower inwardly directed tip pin  1030  at a distal end of the upper moment arm  1024  longitudinally slidingly engages the lower longitudinal track  1012 , and thus responds to the differential contraction and expansion of the lower left and right EAP stack actuators  1006 ,  1008  that are laterally constrained by the distal frame ground  1022 . 
     In  FIGS. 30-31 , the EAP articulation locking mechanism  800  is activated to disengage the locking tip  808  from the gear segment  814  in preparation for articulation. In  FIGS. 32-33 , the upper and lower left EAP stack actuators  1002 ,  1006  have been energized to expand, laterally moving rightward the upper and lower longitudinal tracks  1010 ,  1012 , thereby compressing the upper and lower EAP stack actuators  1004 ,  1008  and moving distal frame ground  1022  correspondingly against the reaction force from the upper and lower inwardly directed tip pins  1020 ,  1030 , which in the illustrative articulation is to the left. 
     Surgical Instrument with EAP Actuated Flexneck Articulation Joint. 
     In  FIG. 34 , a surgical instrument  1200  advantageously incorporates an EAP actuated articulation joint  1202  that is integral to an articulating frame assembly  1204  of an elongate shaft  1206  that transfers separate closure and firing motions from a handle  1208  to an end effector  1210 , depicted as a staple applying assembly  1212  having a closeable anvil  1214  that is pivotally attached to an elongate channel  1216  that holds a replaceable staple cartridge  1218 . The handle  1208  includes a closure trigger  1220  that is squeezed proximally toward a pistol grip  1222  to effect closure of the anvil  1214 . It should be appreciated that a closure sleeve assembly  1223  or other closure means (e.g., EAP actuated anvil, internal longitudinally translating member, etc.) that is not shown acts upon an anvil closure feature  1224  to effect opening and closing of the anvil  1214 . Once closed and clamped, a more distal firing trigger  1226  is squeezed toward the pistol grip  1222  to effect firing of a firing member  1228  longitudinally down the elongate shaft  1206  to cause severing of tissue and stapling of the severed ends. Once the firing trigger  1226  is released, a closure release button  1230  is depressed along with a slight depression of the closure trigger  1220  to release clamping components followed by release of the closure trigger  1220  to open the anvil  1214  and allow release of the stapled and severed tissue. A rotation knob  1232  allows selective rotation about a longitudinal axis of the elongate shaft  1206 . 
     The articulating frame assembly  1204  includes a proximal frame ground  1240  proximally and rotatably attached to the handle  1208  and distally attached to an articulating frame ground  1242  that in turn is attached to a distal frame ground  1244  that supports the end effector  1210 . An articulation control  1246  on the handle  1208  advantageously allows selection of articulation of the articulating frame ground  1242  by activating appropriate electrical signals thereto, such as depicted in  FIG. 35  when a leftward articulation has been selected by articulation control  1246 . It should be appreciated that the articulation control  1246  may advantageously include manual and/or automatic disengagement of an articulation lock for the articulating frame ground  1242 . 
     In  FIGS. 36-39 , the articulating frame ground  1242  incorporates an EAP actuating system  1300  that uses left and right EAP plate actuators  1302 ,  1304  that pass through respective left and rectangular actuator recesses  1306 ,  1308  ( FIGS. 38-39 ) in each lateral side of a generally cylindrical resilient frame body  1310 . A rectangular knife slot  1312  is formed in the resilient frame body  1310  aligned between the left and right rectangular actuator recesses  1306 ,  1308  for guiding a firing bar  1314  that is a distal portion of the firing member  1228 . 
     Continuous top and bottom longitudinal bands  1320  ( FIGS. 36-37 ) of the resilient frame body  1310  maintain a longitudinal amount of travel for the firing bar  1314  when the articulating frame ground  1242  is either straight or articulated. The resilient frame body  1310  is advantageously formed from a homogenous material that does not significantly compress along its longitudinal axis. Left and right pluralities of longitudinally aligned vertical recesses  1322 ,  1324  intersect respectively with the left and right EAP actuator recesses  1306 ,  1308 . Each vertical recess  1322 ,  1324  includes a rectangular through hole  1326  that passes from top to bottom through the resilient frame body  1310  parallel with and laterally offset from both the rectangular knife slot  1312  and the appropriate one of either the left or right rectangular actuator recess  1306 ,  1308 . Each rectangular through hole  1326  communicates laterally with a narrowed lateral gap  1328 . Adjacent vertical recesses  1322 ,  1324  define therebetween a rib  1330  that has a narrow inner wall  1332 , which allows lateral bending of the continuous top and bottom longitudinal bands  1320 , and a thicker curved outer slice  1334  that supports the respective one of the EAP plate actuators  1302 ,  1304  and limits the amount of articulation that may be achieved in that direction before the narrowed lateral gaps  1328  collapse fully as one or both EAP plate actuators  1302 ,  1304  are activated to bend in a selected direction. In  FIG. 37 , for instance, the left EAP plate actuator  1302  is activated to actuate to the left with the right EAP plate actuator  1304  stretching in response. It should be appreciated that the left and right EAP plate actuators  1302 ,  1304  may alternatively contract or expand when electrically activated to create a pull or a push respectively within the left and right rectangular actuator recesses  1306 ,  1308 . 
     In  FIGS. 38-39 , the articulating frame ground  1242  advantageously includes an EAP articulation locking mechanism  1350  that selectively holds the resilient frame body  1310  in an articulated left or an articulated right condition. To that end, a left locking passage  1352  is defined passing through the left plurality of rectangular through holes  1326  proximate to their leftmost outer portion, allowing a left ridged EAP locking strip  1354  to pass therethrough. Similarly, a right locking passage  1356  is defined as passing through the right plurality of rectangular through holes  1326  proximate to their rightmost outer portion, allowing placement of a right ridged EAP locking strip  1358 . Along their respective outermost surface  1360  of both the left and right ridged EAP locking strips  1354 ,  1358 , a plurality of longitudinally spaced vertical blocking ridges  1362  are longitudinally spaced and sized to define, in conjunction with the geometry of the ribs  1330  to lock at a desired articulation amount. In particular, when the flexible frame ground  1242  articulates toward the opposite side of a respective ridged EAP locking strip  1354 ,  1358 , the ribs  1330  on that side arc away from one another, as depicted in  FIG. 38  in articulating to the left. Once the ribs  1330  have reached a spacing sufficient for locking (i.e., wider than the longitudinal width of the vertical blocking ridges  1362 ), the right ridged EAP locking strip  1358  is biased outwardly to snap its ridges  1362  between adjacent thickened thicker curved outer slices  1334  of adjacent ribs  1330 . Activating the right ridged EAP locking strip  1358  causes contraction that unlocks the right ridged EAP locking strip  1358 . In  FIG. 39 , lateral upper and lower guide pins  1370 ,  1372 , that pass above and below the rectangular knife slot  1312 , preserve lateral alignment. 
     In  FIG. 40 , the articulating frame ground  1242  incorporates an EAP actuating system  1400  that uses a plurality of left and right EAP rib spreader plate actuators  1402  that each reside between an opposing pair of distally and proximally open rectangular recesses of a resilient frame body  1408 . Each opposing pair of distally and proximally open rectangular actuator recesses  1404 ,  1406  respectively are formed in an adjacent pair (proximal/distal) of laterally defined ribs  1410 . Each rib  1410  includes a vertical slot  1412  that is open outwardly laterally along its height with a wider rectangular through hole  1414  more inwardly positioned that narrows into an outer vertical slot  1416 . Each rib  1410  thus includes a thin inner wall  1418  that connects to upper and lower longitudinal continuous bands  1420 . A rectangular knife slot  1422  is formed laterally along the longitudinal centerline. Left and right ridged EAP locking strips  1354 ,  1358 , as described above, advantageously relax to an expanded curved shape on the expanded side of the articulating frame ground  1242  to lock, with longitudinal alignment maintained by lateral guide pins  1370 . 
     In  FIGS. 41-42 , the articulating frame ground  1242  incorporates a further alternative EAP actuating system  1500  into a resilient frame body  1502  that includes longitudinally aligned EAP fiber actuators  1504  arranged in left and right vertical stacks  1506 ,  1508  that pass through a respectively left and right plurality of lateral ribs  1510 , each having a thin inner vertical wall  1512  that connects to continuous longitudinal top and bottom bands  1514  to facilitate lateral bending thereof. Each rib  1510  widens laterally to a thick outer slice  1516  that is dimensioned for the limitation on articulation to that side. Each thick outer slice  1516  includes a vertical aligned longitudinal through hole  1518  for allowing the EAP fiber actuators  1504  to pass through. Distal and proximal lateral covers  1520 ,  1522  longitudinally flank the ribs  1510  to cover respective termination ends of the EAP fiber actuators  1504 . A laterally centered knife slot  1524  is formed in the resilient frame body  1502  for the firing bar  1314 . Contracting a selected vertical stack  1506 ,  1508  of EAP fiber actuators  1504  causes articulation to that side with the nonactuated vertical stack  1506 ,  1508  passively elongating in response thereto. 
     Transverse Articulation Locking Mechanism for Pivoting Articulation Mechanism. 
     In  FIGS. 43-45 , a transverse EAP actuated articulation lock  1700  is incorporated into a pivoting articulation joint  1702  for a surgical instrument  1704 . For clarity, a single pivoting frame assembly  1706  is depicted with a proximal frame ground  1708  having distally extended upper and lower pivot tabs  1710 ,  1712  that are pivotally engaged to proximally directed upper and lower tangs  1714 ,  1716  of a distal frame ground  1718  that is attached to an end effector (not shown in  FIGS. 43-45 ). An upper inner hole  1722  in the upper pivot tab  1710  is aligned under an upper outer hole  1724  in the upper tang  1714 , which are pivotally pinned together by upper pivot pin  1726 . A lower inner hole  1728  in the lower pivot tab  1712  is aligned above a lower outer hole  1730  in the lower tang  1716 . Holes  1728 ,  1712  are pivotally pinned together by a lower pivot pin  1732 . Upper and lower moment arms  1734 ,  1736  extend distally respectively from the upper and lower pivot tabs  1710 ,  1712 , urged laterally by EAP fiber actuators (not shown) as described above regarding  FIGS. 20-27 . 
     An upper EAP actuated articulation locking mechanism  1800  advantageously unlocks the pivoting articulation joint  1702  to allow articulating movement. The EAP actuated articulation locking mechanism  1800  then relaxes to a locked state, providing a stable locked position that does not require power dissipation, and thus component heating, between changes in an amount of articulation. An upper locking hook assembly  1802  is shown in a rectangular upper lock recess  1804  formed in the proximal frame ground  1708  proximal to and vertically farther from the longitudinal centerline than the upper pivoting tab  1710 . An EAP locking hook latch  1806  originates at its proximal end within an upper horizontal slot  1807  formed in the proximal frame ground  1708  communicating with the proximal end of the rectangular upper lock recess  1804 . An upper vertical pin passes through the proximal frame ground  1708 , the upper horizontal slot  1807  constraining the proximal end of the upper EAP locking hook latch  1806  therein. The upper EAP locking hook latch  1806  is formed of an EAP plate actuator that is configured to bend its distal end upwardly and outwardly, as shown in phantom at  1806   a  in  FIG. 44 , pulling an inwardly directed locking tip  1808  out of a nearest peripherally spaced through hole  1812  in a rounded locking plate  1814 . The rounded locking plate  1814  is formed about a proximal surface about the upper pivot tang  1714  of the distal frame ground  1718  which rotates under a distal portion of the upper lock recess  1804 . An upper lock cover  1824  closes the upper lock recess  1804 . 
     For additional locking support, in  FIGS. 43-44 , a lower EAP actuated articulation locking mechanism  1830 , that is identical to the upper locking mechanism  1800 , acts on the opposite site against lower pivot tang  1716 . It should further be appreciated that a similar locking mechanism may be incorporated into a distal portion of an elongate shaft rather than a proximal end. Further, a double pivoting coupling may include a lock at each pivot. 
     In use, distal frame portion  718  and pivoting articulation joint  1702  ( FIGS. 43-44 ) are inserted through a cannula to a surgical site. With EAP locking mechanisms  1800 ,  1830  typically deenergized, the locking tip  1808  attached to the proximal frame ground  1708  engages the center through hole  1814  of the distal frame ground  1718 , locking the single pivot frame assembly  1706 . When desired, the EAP locking hook latches  1806  are energized to bend outwardly within the lock recesses  1804 , unlocking the EAP articulation locking mechanisms  1800 ,  1830 . While unlocked, the articulation joint  1702  may be articulated, such as by actuating a mechanical linkage or EAP actuator. When articulated to the desired angle, the EAP articulation locking mechanisms  1800 ,  1830  are deenergized and thereby locked. 
     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.