Abstract:
A surgical stapler, preferably in a single use disposable form, comprises a combination of a staple feeding mechanism and a staple forming mechanism secured in a frame and an actuating trigger functionally connected to both the staple feeding mechanism and the staple forming mechanism, wherein the staple feeding mechanism includes a rail to guide contained staples serially to a staple forming position and a shuttle in association with the rail as a movable staple retaining cover, the shuttle being functionally connected to the trigger for movement in the same direction and the same time as the staples. This structure provides a reliable surgical stapler in which staples are not likely to jam the staple feeding mechanism.

Description:
FIELD OF THE INVENION 
     This invention relates to a surgical stapler for implanting staples into the skin and/or tissue for wound closure after a traumatic injury or a purposeful incision in a surgical procedure. 
     BACKGROUND OF THE INVENTION 
     It has become a preferred procedure to use staples for wound closure rather than thread or filament sutures. Surgeons choose staples because of the speed with which an incision can be closed as compared with the time consuming placing and tying of thread or filament sutures. 
     Many surgical staplers have been designed with various features to improve the profile of the stapler to increase visibility for the surgeon during the placing of the staples and to improve the reliability of the stapler with respect to serial delivery of contained staples without jamming. See, for example, U.S. Pat. Nos. 4,014,492, 4,109,844, 4,179,057, 4,202,480, 4,256,251, 4,375,866, 4,407,286, 4,489,875 and 4,527,725. The above patents describe staplers using preformed staples without a forming anvil, staplers having a stationary forming anvil, and staplers having a movable or retractable forming anvil as well as a wide variety of feeding mechanisms to deliver each staple to the delivery point where the staple is deformed during implantation into the skin and/or tissue. 
     In the effort to increase the angle formed between the bottom of a stapler and the skin or tissue surfaces being joined for the purpose of improving visibility for the surgeon, it has become increasingly difficult to retain jam-free delivery of the staples, particularly in those staplers where the staples are stored on a covered retaining track or rail and fed serially thereon to the forming jaws and forming anvil. The increased angle of the stack of staples stored in such a feeding mechanism of a stapler and the pressure of the biasing means, e.g., a spring biased pusher, tend to cause the stack of staples to buckle and jam the stapler, i.e., a following staple tends to push under a leading staple like a wedge and cause a jam in the feeding mechanism. The present invention provides a novel structure to prevent this problem as explained more fully hereinafter. 
     BRIEF SUMMARY 
     The surgical stapler of the present invention, preferably in a single use disposable form, comprises a combination of a staple feeding mechanism and a staple forming mechanism secured in a frame. An actuating trigger is functionally connected to both the staple feeding mechanism and the staple forming mechanism. The staple feeding mechanism includes a rail to guide contained staples serially to a staple forming position and a shuttle in association with the rail as a movable staple retaining cover. The shuttle is functionally connected to the trigger for movement in the same direction and the same time as the staples. This structure provides a reliable surgical stapler in which staples are not likely to jam the staple feed mechanism. While the invention is described in terms of an entire stapler, an important feature of the invention resides in the provision of a movable staple retaining cover or shuttle in the staple feeding mechanism to avoid frictional forces which can result in jamming of staples in the feeding mechanism. Such a movable shuttle is applicable to staplers other than the specific embodiment of the detailed description which follows hereinafter, and it can be adapted to most staplers which use a feeding mechanism based on a rack of staples retained on a rail. 
     As mentioned previously, the difficulty in feeding a rack of staples through a surgical stapler increases with the increase in the angle at which the staples are contained on the rail by the cover. That is, as the angle formed by the leg of a staple and a plane perpendicular to the longitudinal axis of the rail becomes larger, the frictional forces between the crowns of the staples positioned on a retaining track or rail and a fixed cover increase to a point such that at a 45 degree angle it becomes impossible to feed a rack of 40 staples without creating a jam in the feeding mechanism. The movable cover or shuttle of the surgical stapler of the present invention overcomes this problem completely because the shuttle is linked to move with the staples as they are advanced on the rail and therefore there is no friction between the staple crowns and the underside of the shuttle. 
     The specific advantages of the present surgical stapler will be described and explained more fully in the following detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The surgical stapler of the present invention will be described in more detail with reference to the accompanying drawings which show an illustrative and preferred specific embodiment of the invention. 
     In the drawings: 
     FIG. 1 is a perspective view of the surgical stapler of the present invention showing the surgical stapler appoximately in the position of use after having implanted surgical staples to close an incision. 
     FIG. 2 is a side view of the surgical stapler partly in section to show the arrangement of the pawl and pawl pad. 
     FIG. 3 is a partial view of the stapler showing the attitude of the pawl and pawl spring during the closing movement of the trigger when a staple is being deformed and implanted in tissue. 
     FIG. 4 is a partial view of the stapler showing the attitude of the pawl and pawl spring at the point of full closure of the trigger (dotted) and during the return movement of the trigger. 
     FIG. 5 is an enlarged partial view in section of the stapler showing the positions of the various parts when the trigger is in the full open position. 
     FIG. 6 is an enlarged partial view partly in section of the stapler showing the positions of the various parts when the trigger is in the full closed position. 
     FIG. 7 is a side view in section of the jaw, anvil and staple showing the relationship of these three parts when in position to begin deformation of the staple. 
     FIG. 8 is a front view partly in section of the jaw, anvil and staple in the same relative positions as in FIG. 7. 
     FIG. 9 is a font view of the jaw, anvil and staple showing the relationship of these three parts when deformation of the staple has been completed. 
     FIG. 10 is a perspective view of a combination of the bottom, rail, staples, shuttle and staple pusher. 
     FIG. 11 is a perspective exploded partial view of the anvil, jaw, compression spring and cover block showing the relationship of these parts. 
     FIG. 12 is a perspective and exploded view of the staple guiding and feeding elements of the stapler. 
    
    
     DETAILED DESCRIPTION 
     With reference to the accompanying drawings, the same part is identified by the same reference numeral in all figures of the drawings. 
     In FIG. 1, a specific and preferred embodiment of the surgical stapler of the present invention, indicated generally by reference numeral 20, is shown in an attitude of use after having implanted staples 10 to close an incision 11. The surgical stapler 20 includes a frame 21 and a trigger 22. 
     FIGS. 2, 3 and 4 show the arrangement of elements to provide for unidirectional movement of the trigger 22 throughout its closing movement as well as throughout its return movement. This is important to prevent malfunction of the stapler either by jamming or by releasing a staple before it is fully deformed and implanted. In FIG. 2, the trigger 22 is in its full open position with respect to the frame 21 and the arrrow shows the direction of closing movement. Pawl 23 is shown mounted on trigger 22 by pivot pin 26 and pawl spring 25 is positioned to bias pawl 23 when contacted by either of the ears of pawl 23. Pawl spring 25 is shown as an integrally molded part of trigger 22, but could be a separate leaf spring fastened to trigger 22. Pawl pad 24 is made of a resilient material and may be formed as part of frame 21 or may be a separate part fastened into frame 21 and positioned as shown to be contacted by pawl 23 during the closing movement of trigger 22 as shown in FIG. 3. During this closing movement of the trigger 22, the point of pawl 23 is forced against the resilient pawl pad 24 by the biasing action of pawl spring 25 against an ear of pawl 23. While the pawl 23 is shown as having a single point, it could have multiple points, e.g., a saw tooth configuration, at the point of contact with pawl pad 24. While the closing movement of trigger 22 is in no way hampered by the contact of pawl 23 against pawl pad 24, it is obvious from FIG. 3 that movement in the opposite direction would be prevented by pawl 23 digging into the surface of pawl pad 24. When trigger 22 reaches full closure position as shown in FIG. 4 (dotted), the pawl 23 reaches the step in the pawl pad 24 and turns on pivot pin 26 for the return movement of trigger 22 during which the pawl 23 is biased such that no closing movement is possible until the return movement is completed. 
     FIG. 5 shows the relative positions of the parts of the staple feeding assembly and the staple forming assembly when the trigger 22 is in the full open position and FIG. 6 shows the relative positions of the same parts when the trigger 22 is in the full closed position. As shown, the frame 21 provides a biasing spring 28 as an integral part of frame 21, but this could be provided by a separate leaf spring or the like fastened to frame 21. The biasing spring 28 biases the moving anvil 29 out of the path of staples 10 as shown in FIG. 5. When the trigger 22 is moved to the full closed position as in FIG. 6, the cam surface 30 of the staple forming jaw 31 tilts the moving anvil 29, which is non-planar, i.e., is a combination of two planar sections, about the fulcrum formed by the intersection of the two planes to position the forming end of the anvil 29 into the path of the staples 10. When the trigger 22 is again moved to the full open position (FIG. 5), the cam surface 32 on the staple forming jaw 31 assists the biasing spring 28 in tilting the moving anvil 29 out of the path of staples 10. A window 32a in the anvil 29 is positioned opposite the cam surface 32 when the anvil 29 is under the influence of cam surface 30. 
     The frame 21 includes an open window 43 which together with strap 44 on the cover block 34 serves to locate the cover block 34 within the frame 21 during assembly. The frame 21 has a cut out 45 at the tip to match a similar contour of the cover block 34 and provide clearance for the moving anvil 29. The frame 21 is preferably molded from plastic, e.g., a clear or pigmented polycarbonate, particularly when the surgical stapler 20 is made as a single use disposable device. 
     The trigger 22 rotates around the pivot pin 27 within the frame 21. The nose 22a of the trigger 22 bears on the top of staple forming jaw 31, and compression spring 33, positioned in a well in cover block 34, biases jaw 31 to the upward or withdrawn position and thereby the trigger 22 to the full open position (FIG. 5). 
     Cover block 34 provides a base for assembling the individual elements that make up the staple feeding mechanism and the staple forming and implantation mechanism. As shown in FIGS. 5, 6, 11 and 12, the cover block 34 includes contours into which fit the staple forming jaw 31 and forming anvil 29, both of which are retained in place by strap 44. Cover block 34 also provides a well to position compression spring 33 for biasing forming jaw 31 and the trigger 22. The staple deforming legs 47 of the jaw 31 are part of the single piece jaw 31 and are shaped to force the staple 10 around the forming anvil 29 (as shown in FIGS. 8 and 9) in the final closing movement of the trigger 22. The staple feeding mechanism (see FIGS. 10 and 12) composed of the shuttle 38, pusher 40, saddle spring 41, rail 39 and bottom 42 is assembled in combination with cover block 34. The cantilever spring 48 is provided as part of rail 39 for retention of the first staple prior to the movement into place of the forming end of anvil 29. Cover block 34 includes as an integral part the staple stripper block 45 which prevents any tendency of a formed staple 10 being drawn into the stapler 20. 
     The cover block 34 provides a pair of holes 38 (see FIG. 12) which function as bearings for the pivot pin 27 about which the trigger 22 rotates. The hub 35 of the trigger 22 is provided with a keyway 36 to accomodate a tang 37 of shuttle 38. The keyway 36 and tang 37 cooperate to impart linear motion to the shuttle 38 from the rotary motion of the trigger 22. During the closing motion of the trigger 22, the hub 35 (as seen in FIGS. 5 and 6) rotates counterclockwise and consequently the keyway 36 moves the tang 37 and the shuttle 38 toward the rear of the surgical stapler 20. In this same part of the cycle of operation of the stapler, i.e., the closing of the trigger 22, the anvil 29 is tilted into the path of the next staple 10 to be dispensed and then the jaw 31 which is moving downward contacts and forms the staple 10 around the anvil 29 as the staple 10 is implanted. While the trigger 22 is closing, the staples 10 on the rail 39 do not move, i.e., they do not advance toward the front of the stapler 20. Such advance of the staples 10 takes place only during the return or opening movement of the trigger 22 and then only after the jaw 31 has been retracted sufficiently to cause the anvil 29 to tilt out of the way and release the implanted staple 10. When this release takes place, the pusher 40 under the influence of saddle spring 41, which is conneced to the pusher ear 46, moves the row of staples 10 on rail 39 a distance equal to the thickness of a staple 10 so that the next staple 10 is placed in position to be formed and implanted. Throughout this return or opening movement of the trigger 22, the hub 35 (as seen in FIGS. 5 and 6) rotates clockwise and consequently the keyway 36 moves the tang 37 and the shuttle 38 toward the front of the surgical stapler 20. Therefore, during that part of the return or opening movement of the trigger 22 that the staples 10 are being moved on rail 39 by pusher 40, the shuttle 38 is constantly moving in the same direction as the staples 10. For this reason, the staples 10 are less likely to jam because friction between the crowns of the staples 10 and the retaining cover member, i.e., the shuttle 38, has been eliminated. In addition, the motion of the shuttle 38 assists the pusher 40 in uniform movement of staples 10. 
     The frame 21, trigger 22, pawl pad 24, cover block 34, pusher 40 and bottom 42 may all be molded of plastic, e.g., a clear or pigmented polycarbonate, particularly for a single use disposable stapler. However, the pawl 23, anvil 29, jaws 31, shuttle 38, rail 39 as well as the compression spring 33 and the saddle spring 41 are preferably made of stainless steel. 
     While the surgical stapler of the present invention could be made as a reuseable device by providing for the reloading of staples after the initial supply has been exhausted, it is preferred to provide the stapler as a single use disposable device. Consequently, some of the parts described in the detailed description have been designed knowing that reloading is not intended. 
     If desired, the surgical stapler described could be modified to make disassembly and reloading of staples possible. It is believed that such modifications do not require specific description because they would be obvious to a designer skilled in this art. For example, in the disposable form of the surgical stapler 20 of this invention, the pivot pin 27 does not pass through either side of the frame 21 but is held in place in the trigger 22 hub 35 and cover block 34 holes 38 by the inside surfaces of the frame 21 with the cover block 34 assembly cemented into the frame 21. In a reusable version, the pivot pin 27 could pass through the sides of frame 21 and be held in place by suitable means so that the cover block 34 assembly would be retained within frame 21 without cementing and could be removed for reloading with a new supply of staples 10 or replaced with a preloaded cover block 34 assembly as a cartridge.