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) actuator for remotely articulating the end effector. In particular, a flexible neck to a frame of the elongate neck may be laterally urged to the left or right by EAP actuators and advantageously locked into an articulated state.

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. patent Ser. No. 10/443,617, “SURGICAL STAPLING INSTRUMENT INCORPORATING AN E-BEAM FIRING MECHANISM” to Shelton 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 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. 
     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 sufficient strength to perform the several motions (e.g., closing, firing, articulation, rotation, etc.). 
     In addition, even though further reduction in cross-sectional size would be desirable, another conflicting desire is to incorporate yet additional functionality at the end effector. For instance, one such additional function is deploying a buttress at the staple site. A buttress is a pair of thin foam or fabric strips that are placed on the anvil and on the cartridge and are stapled into place on either side of the tissue that is transected. It adds structural integrity to the staple line for either extremely thin or thick tissues. Another would be additional enhancements to prevent firing with an improperly closed end effector, empty staple cartridge, missing cartridge, performing a therapeutic or diagnostic treatment by sending energy or fluid to the end effector, etc. Creating sufficient room in the shaft of the instrument to facilitate such additional function creates an incentive to modify how the end effector is articulated. 
     Consequently, a significant need exists for an articulating surgical instrument that incorporates an articulation mechanism that requires less mechanical mechanisms passing through the shaft of the instrument. 
     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 disposed in an articulation joint of the shaft is responsive to an electrical signal passed through the shaft to effect articulation. Thereby a shaft of advantageously small diameter may be achieved yet with the functionality of remotely controllable actuation. 
     In one aspect of the invention, a surgical instrument includes an articulating joint attached between an end effector and a distal end of an elongate shaft. An electrical actuator is positioned to actuate the articulation joint in response to an electrical signal remotely produced in a handle proximally attached to the elongate shaft. 
     In another aspect of the invention, a surgical instrument has an elongate shaft having a frame assembly and an encompassing and a longitudinally, slidingly received closure sleeve assembly. A staple applying assembly includes an elongate channel, a staple cartridge engaged in the elongate channel, and an anvil pivotally attached to the elongate channel presenting a staple forming surface to the staple cartridge. An articulation joint is formed in the frame assembly. In particular, a distal frame portion is attached to the elongate channel and a proximal frame portion is pivotally attached to the distal frame portion. A handle attached to a proximal end of the elongate shaft selectively communicates an electrical signal to the elongate shaft to an electroactive polymer actuator connected to the articulation joint that responds thereto to perform articulation of the staple applying assembly. Thus, a surgical stapling and severing instrument is provided that may approach tissue from a desired angle. 
     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 right side view in elevation of a surgical instrument with a closure sleeve assembly cut away to expose an EAP actuated articulation mechanism that articulates a flexible articulating frame ground. 
         FIG. 1A  is a top view of the surgical instrument of  FIG. 1  articulating to the left. 
         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 laterally flexible closure sleeve assembly and a flexible neck 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 flexible neck 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 front right perspective view of the articulating frame ground of  FIG. 1  that incorporates EAP plate actuators and locking strips. 
         FIG. 10  is a top view of the articulating frame ground of  FIG. 1A  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. 11  is a top view of the articulating frame ground of  FIG. 1A  in a left articulated state taken in cross section through the EAP plate actuators and EAP locking strips. 
         FIG. 12  is a front view in elevation of the articulating frame ground of  FIG. 10  taken in cross section through lines  12 - 12  through the lateral guide pins. 
         FIG. 13  is a top view of an alternate articulating frame ground for the surgical instrument of  FIG. 1  taken in cross section through a plurality of EAP rib spreader actuators. 
         FIG. 14  is a right perspective partially exploded view of an additional alternative articulating frame ground having a plurality of EAP fiber actuators for the surgical instrument of  FIG. 1 . 
         FIG. 15  is a front view in elevation of the additional alternative articulating frame ground of  FIG. 14  taken in cross section along lines  15 - 15 . 
         FIG. 16  is a top view taken in longitudinal cross section of a firing bar passing through an articulation joint of a surgical instrument with the firing bar advantageously laterally guided by support plates of inwardly actuated EAP plate actuators with one sliding end. 
         FIG. 17  is a top view taken in longitudinal cross section of the firing bar passing through an articulated articulation joint of the surgical instrument of  FIG. 16 . 
         FIG. 18  is a top view taken in longitudinal cross section of a firing bar passing through an articulated articulation joint of a surgical instrument with the firing bar advantageously laterally guided by support plates of outwardly actuated EAP plate actuators with one sliding end. 
         FIG. 19  is a top view taken in longitudinal cross section of a firing bar passing through an articulation joint of a surgical instrument with the firing bar advantageously laterally guided by outwardly actuated EAP support plates having constrained but longitudinally floating hooked ends. 
         FIG. 20  is a top view taken in longitudinal cross section of a firing bar passing through an articulation joint of a surgical instrument with the firing bar advantageously laterally guided by outwardly actuated EAP support plates each having one fixed hooked end and one end springedly longitudinally constrained. 
         FIG. 21  is a top view taken in longitudinal cross section of a firing bar passing through an articulation joint of a surgical instrument with the firing bar advantageously laterally guided by outwardly actuated EAP support plates with each having both ends springedly longitudinally constrained. 
         FIG. 22  is a top view of a flexible articulation joint incorporating the EAP support plates of  FIGS. 43-46 . 
         FIG. 23  is a front view in elevation of the flexible articulation joint of  FIG. 22  taken through lines  23 - 23 . 
         FIG. 24  is a top view of the flexible articulation joint of  FIG. 22  articulated to the left. 
         FIG. 25  is a front right perspective view of a flexible articulation joint incorporating the EAP support plates of  FIGS. 16-19  and also including left and right EAP plate articulation actuators. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Surgical Instrument With EAP Actuated Flexneck Articulation Joint. 
     In  FIG. 1 , 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 that is 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 the selection of articulating the articulating frame ground  1242  by activating appropriate electrical signals thereto, such as depicted in  FIG. 1A  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 . 
     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  1206  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 variation 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 range from 1V to 4 kV depends 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 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 serve 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, is 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. It 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 manufactured by Artificial Muscle Inc, a division of SRI Laboratories. Plate EAP material is also available from EAMEX of Japan and 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 would expand, flexing the plate in the opposite direction. This allows the plate to be flexed in either direction, depending on which side is energized. 
     An EAP actuator usually is made up 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 filed is applied to the electrodes, the strands of EAP would 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 as being formed from a positive plate electrode layer  1302  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 be selected to 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. 6-7 , 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. 6-8 , 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  and bottom longitudinal band (not shown) transfer a longitudinal closure motion regardless of an amount of such flexing. 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  FIGS. 7-8 , 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 . 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 laterally flexible frame assembly  234  of the flexible closure and pivoting frame articulation joint  210  when articulated. 
     In  FIGS. 6-8 , the laterally flexible frame assembly  234  includes a proximal frame ground  236  that includes a distally open cylindrical end  237  with top slot  238  that engages a top key tab  239  on a proximal end of a flexible frame member  240 . A distal end of the flexible frame member  240  in turn has a distally presented top key tab  241  that is received within a top slot  242  in a proximally open cylindrical end  243  of a distal frame ground  250 . Left and right vertical slots  244 ,  245  in the flexible frame member  240  allow for EAP actuators  245  that are inserted into these slots  244 ,  245  to assert an articulation motion to the flexible frame assembly  234 . 
     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  288 , 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 the 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. 
     As an alternative to the flexible frame assembly  234 , in  FIGS. 9-12 , 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. 11-12 ) 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. 9-10 ) 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. To advantageously allow forming of the resilient frame body  1310  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. 10 , 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. 11-12 , 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 passing through the right plurality of rectangular through holes  1326  proximate to their rightmost outer portion, allowing 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. 11  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 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. 12 , lateral upper and lower guide pins  1370 ,  1372  pass above and below the rectangular knife slot  1312  to preserve lateral alignment. 
     In  FIG. 13 , the articulating frame ground  1242  incorporates an EAP actuating system  1400  that uses a left plurality left and right EAP rib spreader plate actuator  1402  that resides 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. 14-15 , 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 of articulation to that side. Each thick outer slice  1516  includes vertical aligned longitudinal through holes  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. 
     EAP Support Plates For Firing Bar. 
     In  FIG. 16 , an articulation joint  2000  for a surgical instrument  2002  includes a pair of EAP support plates  2004 ,  2006  that laterally support a firing bar  2008  to minimize binding and buckling when articulated. Each support plate  2004 ,  2006  includes a structural member  2010  (e.g., rigid polymer, metal) that includes a laterally widened end  2012  that is captured within a correspondingly sized recess  2014  in a first frame ground  2016  and a straight end  2018  that is slidingly received within a second frame ground  2020 . A longitudinally expansive EAP laminate  2022  covers an internal surface of each support plate  2004 ,  2006 . 
     In  FIG. 17 , the articulation joint  2000  is articulated to one lateral side, causing the firing bar  2008  to overshoot an articulated longitudinal axis  2024  and come into contact with support plate  2006 . Lateral support therefrom prevents a blow out of the firing bar  2008  out of the articulation joint  2000  and/or allows fabrication of a more flexible firing bar  2008  with thus reduced force to articulate. In addition, the EAP laminates  2022  on each support plate  2004 ,  2006  are activated as necessary to control the amount of curvature of both to preserve a desired spacing therebetween for the firing bar  2008 . The straight ends  2018  slide in the second frame ground portion  2020  to accommodate the reduced travel required of the inner support plate  2004  as compared to the outer support plate  2006 . The EAP laminate  2022  may further provide cushioning and low surface friction characteristics that assist in laterally guiding the firing bar  2008 . 
     In  FIG. 18 , an alternative articulation joint  2100  for a surgical instrument  2102  includes a pair of EAP support plates  2104 ,  2106  that laterally support a firing bar  2108  to minimize binding and buckling when articulated. Each support plate  2104 ,  2106  includes a structural member  2110  (e.g., rigid polymer, metal) that includes a laterally widened end  2112  that is captured within a correspondingly sized recess  2114  in a first frame ground  2116  and a straight end  2118  that is slidingly received within a second frame ground  2120 . A longitudinally expansive EAP laminate  2122  covers an outer surface of each support plate  2104 ,  2106 . The articulation joint  2100  is articulated to one lateral side, causing the firing bar  2108  to overshoot an articulated longitudinal axis  2124  and come into contact with support plate  2106 . Lateral support therefrom prevents a blow out of the firing bar  2108  out of the articulation joint  2100  and/or allows fabrication of a more flexible firing bar  2108  with thus reduced force to articulate. In addition, the EAP laminates  2122  on each support plate  2104 ,  2106  are activated as necessary to control the amount of curvature of both to preserve a desired spacing therebetween for the firing bar  2108 . The straight ends  2118  slide in the second frame ground portion  2120  to accommodate the reduced travel required of the inner support plate  2104  as compared to the outer support plate  2106 . Placement of the EAP laminates  2122  away from contact from the firing bar  2108  may have advantages such as reducing wear to the EAP laminates  2122 . 
     In  FIG. 19 , an additional alternative articulation joint  2200  for a surgical instrument  2202  includes a pair of EAP support plates  2204 ,  2206  that laterally support a firing bar  2208  to minimize binding and buckling when articulated. Each support plate  2204 ,  2206  includes a structural member  2210  (e.g., metal) that includes a first outwardly tabbed end  2212  that is constrained and longitudinally free floating within a first inwardly open recess  2214  in a first frame ground  2216  and a second outwardly tabbed end  2218  that is constrained and longitudinally free floating within a second inwardly open recess  2220  of a second frame ground  2222 . A longitudinally expansive EAP laminate  2224  covers an inner surface of each support plate  2204 ,  2206 . 
     In  FIG. 20 , yet an additional alternative articulation joint  2300  for a surgical instrument  2302  includes a pair of EAP support plates  2304 ,  2306  that laterally support a firing bar  2308  to minimize binding and buckling when articulated. Each support plate  2304 ,  2306  includes a structural member  2310  (e.g., metal) that includes a first outwardly tabbed end  2312  that is fixed with an inwardly open slot  2314  in a first frame ground  2316  and a second outwardly tabbed end  2318  that is constrained and longitudinally free floating within an inwardly open recess  2320  of a second frame ground  2322 . A longitudinally expansive EAP laminate  2324  covers an inner surface of each support plate  2304 ,  2306 . A pair of compression springs  2326 ,  2328  are longitudinally aligned within the inwardly open recess  2320  biasing the second outwardly tabbed end  2318  of each support plate  2304 ,  2306  to a neutral position therein. 
     In  FIG. 21 , yet a further alternative articulation joint  2400  for a surgical instrument  2402  includes a pair of EAP support plates  2404 ,  2406  that laterally support a firing bar  2408  to minimize binding and buckling when articulated. Each support plate  2404 ,  2406  includes a structural member  2410  (e.g., metal) that includes a first outwardly tabbed end  2412  that is constrained but longitudinally free floating with a first inwardly open recess  2414  in a first frame ground  2416  and a second outwardly tabbed end  2418  that is constrained and longitudinally free floating within a second inwardly open recess  2420  of a second frame ground  2422 . A longitudinally expansive EAP laminate  2424  covers an inner surface of each support plate  2404 ,  2406 . A pair of compression springs  2426 ,  2428  are longitudinally aligned within the first inwardly open recess  2414  biasing the first outwardly tabbed end  2412  of each support plate  2404 ,  2406  to a neutral position therein. Another pair of compression springs  2430 ,  2432  are longitudinally aligned within the second inwardly open recess  2420  biasing the second outwardly tabbed end  2418  of each support plate  2404 ,  2406  to a neutral position therein. 
     In  FIGS. 22-25 , yet a further alternative articulation joint  2500  for a surgical instrument  2502  that incorporates EAP support plates  2504 ,  2506  resides on each lateral side of a firing bar  2508  in a knife slot  2510  of a resilient frame body  2512  of an articulating frame ground  2514  and is proximally coupled to a proximal frame ground  2516  and distally coupled to a distal frame ground  2518 . A left EAP plate actuator  2520  passes through a left plurality of lateral ribs  2522  formed in the resilient frame body  2512 . A right EAP plate actuator  2524  passes through a right plurality of lateral ribs  2526 . Each EAP plate actuator  2520 ,  2524  extends proximally into the proximal frame ground  2516 , includes an outer EAP laminate layer  2528  attached to an inner plate  2530  and is configured to actuate when electrically energized to bend the distal frame round  2518  toward the other side. The resilient frame body  2512  includes proximal inwardly open recesses  2532  that grip proximal, outwardly curved ends  2534  of each support plate  2504 ,  2506 . Distal straight ends  2536  of each support plate  2504 ,  2506  are allowed to slide out of the knife slot  2510  to adjust for changes in travel for articulation, as depicted in  FIG. 24 . 
     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.