Improved latch mechanism for surgical instruments

Abstract: A surgical instrument including a handle and a trigger is designed to be closed and latched by the operator, and includes a latch mechanism. The latch mechanism includes a latch on the grip, a latch knob including a latching notch on the trigger and a latch guide on the trigger to guide the latch hook into the latching notch.

Description: The present invention relates, in general, to a latch mechanism and, more particularly, to an improved latch mechanism for use in surgical instruments. Background of the Invention In many surgical instruments, end effectors are employed to, for example, grasp tissue. Such end effectors may be activated by moving a trigger mechanism or by closing a scissor type handle or, as in the surgical instrument illustrated in Figure 1, by grasping a first member such as trigger 30 and pulling it toward a second member such as grip 28. In Figure 1, pulling trigger 30 toward grip 28 acts to move closure tube 20 in a distal direction, closing jaws 16 and 17. Once the end effector jaws have closed on the tissue, it may be advantageous to leave the jaws on the tissue for some period of time. For example, it may be necessary to leave the jaws closed in order to treat the tissue by applying electrical energy to the end effector. It may also be advantageous to manipulate tissue gripped by the end effectors. It would, therefore, be advantageous to use a latching mechanism on the trigger or handle to hold the end effector closed. In prior devices, a number of latching mechanisms have been used, including ratchet devices which allow the surgeon to adjust the pressure applied by the end effector. However, in some instruments, especially endoscopic instruments with small end effectors, it may be advantageous to utilize a single latch which is activated by closing the trigger and released by squeezing the trigger a second time. In addition, it may be advantageous to provide a latch for use on surgical instruments wherein an audible click indicates that the instrument is latched. Such a latch mechanism is known from EP 0418761 A European Patent Application EP 0565049A1 to the United States Surgical Corporation discloses a surgical instrument locking mechanism comprising a latch release spring which is adapted to ride against an upwardly projecting cam member on the instrument trigger. As the trigger is moved, the latch release spring is brought into locking engagement within a triangular recess cut into the cam member on the trigger. This allows the jaws of the instrument to lock in place. To unlock the jaws the latch release spring contacts a triangular release cam which moves the spring over the cam and releases the latch release spring from the triangular recess. Summary of the Invention The present invention provides a surgical instrument including a latch mechanism, said latch mechanism comprising: a latch attached to and extending from a first handle of said surgical instrument; a latch knob including a guide surface and a latching notch on a second handle of said surgical instrument, and characterised in that: said latch comprises a latch hook located at an end of a flexible body; and said latch knob is located in a recess on said second handle. In a surgical instrument wherein two handle elements such as a handle and a trigger are designed to be closed and latched by the operator, an embodiment of the present invention relates to a latch mechanism which includes a latch on one handle element, for example, a grip, of the surgical instrument, a latch knob including a latching notch on a second handle element, for example, a trigger, and a latch guide positioned on the second handle element to guide the latch hook into the latching notch. According to an embodiment of the present invention, the latch knob is mounted on a mounting surface attached to the trigger and includes at least one deflecting surface adapted to deflect the latch in a first direction. Further according to an embodiment of the present invention the latch guide includes at least one guide surface adapted to guide the latch into the latch notch. Further, according to an embodiment of the present invention, the latch is adapted to flex around a fixed axis. In operation a latch according to an embodiment of the present invention is deflected away from its centre point by the deflecting surface as the trigger moves in the direction of the grip. Once the latch is released by the deflecting surface, it moves in a direction opposite the first direction until it encounters the guide surface. As the trigger is released, the latch moves along the guide until it encounters the notch. The latch is held in the notch by the spring force exerted on the trigger. When the spring force in the trigger is released by, for example, closing the trigger, the latch moves out of the notch and springs back to its centred position. Brief Description of the Drawings The novel features of the invention are set forth with particularity in the appended claims. The invention itself, however, both as to organisation and methods of operation, together with further objects and advantages thereof, may best be understood by reference to the following description, taken in conjunction with the accompanying drawings in which: Figure 1 is a perspective view of a surgical instrument including a latch mechanism according to the present invention. Figure 2 is a side elevational view of the surgical instrument illustrated in Figure 1 shown in a first, unclamped position. Figure 3 is a side elevational view of the surgical instrument illustrated in Figure 1 shown in a second, clamped position. Figure 4 is an enlarged perspective view of a latch mechanism according to the present invention. Figures 5A, 6A, 7A and 8A are fragmentary side views of the latching mechanism illustrating the relationship of the various elements during the closing and opening of the instrument. Figure 5B is an end view of the latch mechanism in a first, open position as seen along view line 5B-5B of Figure 5A. Figure 6B is a cross-sectional view of the latch mechanism in a second, position as seen along section line 6B-6B of Figure 6A. Figure 7B is a cross-sectional view of the latch mechanism in a third, latched position as seen along section line 7B-7B of Figure 7A. Figure 8B is a cross-sectional view of the latch mechanism in a fourth, unlatched position as seen along section line 8B-8B of Figure 8A. Figure 9 is an enlarged perspective view of a latch mechanism according to the present invention. Detailed Description of the Invention Figure 1 is a perspective view of a surgical instrument 10 which may be, for example, a bipolar cutting and coagulating instrument. The device illustrated in Figure 1 includes a latching mechanism according to the present invention. In surgical instrument 10, upper jaw 16 and lower jaw 17 of end effector 12 are supported by upper wireform 14 and lower wireform 15, respectively. Wireforms 14 and 15 also act as conductors, supplying bipolar electrical energy to upper jaw 16 and lower jaw 17, respectively. Tissue stop 18 is positioned within closure tube 20. Rotation knob 22 is affixed to closure tube 20 to cause rotation of closure tube 20 with respect to handle 26. Handle 26 includes knife button 24, grip 28 and trigger 30. Electrical cord 34 is connected to handle 26 through strain relief 32. Latch knob 36 and latch guide 37 are positioned on trigger 30. Handle latch shield 38 is positioned on grip 28. Figure 2 is a side elevational view of the surgical instrument illustrated in Figure 1 shown with trigger 30 open. Figure 3 is a side elevational view of the surgical instrument illustrated in Figure 1 shown with trigger 30 closed and latched. As illustrated in Figures 2 and 3, bipolar forceps 10 have a first open position and a second, closed position. In the open position, illustrated in Figure 2, trigger 30 is biased open by a spring or other mechanism, allowing closure tube 20 to move to its proximal position. With closure tube 20 in its proximal position the spring force in wireforms 14 and 15 separate jaws 16 and 17 of the end effector 12. In Figure 2, latch 44 is illustrated in outline form inside of handle latch shield 38. As illustrated in Figure 3, movement of trigger 30 in direction A1, towards grip 28, forces closure tube 20 to move in direction A2, away from handle 26. As closure tube 20 moves in a distal direction, closure tube 20 forces wireforms 14 and 15 towards tissue stop 18. Wireforms 14 and 15, in turn, force jaws 16 and 17 to move in direction A3. When tissue 40 is positioned between jaws 16 and 17 of end effector 12, closing trigger 30 causes jaws 16 and 17 to close and grip the tissue. Jaws 16 and 17 hold the tissue while it is being treated by, for example, applying high frequency bipolar energy. Alternatively, or after treatment of the tissue, a knife 42 may be advanced into end effector 12. As illustrated in Figure 3, knife 42 advances in direction B2 when knife button 24 is advanced in direction B1. Tissue stop 18 acts to shield knife 42 when knife 42 is in its retracted or proximal position. Figure 4 is an enlarged, perspective view of a latch mechanism 25 according to the present invention. In Figure 4, latch 44 is shown without grip 28 and latch shield 38 for clarity. Tabs 58 are used to mount latch 44 to grip 28. Latch 44 is adapted to bend or flex along an axis which is substantially parallel to line A-A. Latch 44 is preferably constructed of a spring material such as metal. Thus, deflection of latch 44 results in an opposing spring force which acts to move latch 44 back toward its original or centered position. Latch hook 56 protrudes from latch 44 in a direction substantially parallel to line A-A. Latch hook 56 is positioned at a distance from grip 28 to enable it to engage latch knob 36 when trigger 30 is closed. The embodiment of latching mechanism 25 illustrated in Figure 4 includes an S-shaped latch 44 which may be particularly well adapted for the embodiment of the invention illustrated in Figure 4. In particular, the S-shape of latch 44 results in latch hook 56 being oriented along the surface of latch knob 36, thus facilitating movement of latch hook 56 along the surface of latch knob 36 and preventing the latch hook from catching on the back side of latch knob 36. Trigger 30 includes a recess 52. Recess 52 includes latch knob 36, latch guide 37 and mounting wall 54. In the embodiment illustrated in Figure 4, latch knob 36 includes a first end 60 which is affixed to mounting wall 54, a second end 62 opposite first end 60, a guide surface 64 and a latching notch 66. In the embodiment of the invention illustrated in Figure 4, latch guide 37 is positioned in recess 52, below latch knob 36. At least a portion of latch knob 36 is positioned distal of latch guide 37. Latch guide 37 includes at least a first guide surface 68 and may also include a second guide surface 70. Figures 5-8 illustrate a motion diagram for latch mechanism 25. In this diagram the motion sequence is: a). Fully close trigger 30 as illustrated in Figures 5 and 6; b) Release trigger 30, causing the mechanism to latch as illustrated in Figure 7; c) Reclosing trigger 30, causing the mechanism to unlatch and allowing the trigger to open as illustrated in Figure 8. As trigger 30 closes, ramped surface 64 deflects springy latch 44 to the side. When trigger 30 bottoms out latch hook 56 is spring loaded and ready to travel into latch notch 66. Releasing trigger 30 causes latch hook 56 to engage the latch notch 66. Squeezing trigger 30 allows latch 44 to deflect to the right, releasing latch hook 56. Releasing the trigger allows it to open along with the jaws. More particularly, Figures 5, 6, 7 and 8 are views of latching mechanism 25 according to the present invention wherein the operation of latching mechanism 25 is illustrated. As illustrated in Figure 5, the operation of latch mechanism 25 according to the present invention is initiated by the operator closing trigger 30 by pulling trigger 30 toward grip 28 along path C1. As trigger 30 nears the end of its close stroke, latch 44 touches latch knob 36 and is forced in a first direction by guide surface 64 of latch knob 36. As illustrated in Figure 6, upon further movement of trigger 30 in direction C1, latch hook 56 moves past guide surface 64 and snaps against first guide surface 68 of Latch guide 37 with an audible "click". Latch 44 is held against first surface 68 of latch guide 37 for so long as the operator maintains pressure in direction C1. As illustrated in Figure 7, when the operator releases pressure on trigger 30, the spring forces act to move trigger 30 in direction Dl. As trigger 30 moves in direction D1, latch 44 moves along surface 68, towards latching knob 36. When latch 44 reaches the end of surface 68, the spring forces in latch 44 move latch 44 past latch guide 37 and move latch hook 56 into latch notch 66. The combined spring forces on latch 44 and trigger 30 act to hold latch hook into latch notch 66 until counter pressure is applied to latch trigger 30 to force latch hook 56 out of latch notch 66. Thus, with latch hook 56 in latch notch 66, latching trigger 30 is latched in the closed position. As illustrated in Figure 8, trigger 30 is released by moving trigger 30 toward grip 28 and then releasing the pressure on trigger 30. Thus, trigger 30 is released by moving trigger 30 along path E1 in Figure 8. More particularly, to release trigger 30, pressure is applied on trigger 30 which forces latch hook 56 down and out of latching notch 66. Guide surface 70 works with the residual spring tension on latch 44 to move latch hook 56 out past latch knob 36 to its central position so that when trigger 30 is released, latch 44 is released, allowing trigger 30 to move away from grip 28. As illustrated in Figure 9, an orientation guide 100 may be included on, for example, trigger 30 to ensure that latch 44 is properly aligned with latch knob 36 as trigger 30 is closed. Although many orientation guides would be suitable for aligning the latch described, the orientation guide in Figure 9 includes a pair of surfaces 110 and 120 which are located on mounting wall 54 and are adapted to interact with latch shield 38 to position latch 44 opposite guide surface 64 of latching knob 36. Thus, as trigger 30 is closed, the walls of latch shield 38 move along surfaces 110 or 120 and latch 44 is centered above surface 64. This latching mechanism is particularly suitable for devices such as electrocautery devices where the surgeon may need to keep the jaws closed on tissue as RF energy is applied. The addition of an auditory sound to the latch also enhances the latch. This mechanism can also be utilized on other open and endoscopic surgical devices.

Claims: A surgical instrument including a latch mechanism (25), said latch mechanism (25) comprising: a latch (44) attached to and extending from a first handle (26) of said surgical instrument; a latch knob (36) including a guide surface (64) and a latching notch (66) on a second handle (30) of said surgical instrument, and characterised in that : said latch (44) comprises a latch hook (56) located at an end of a flexible body; and said latch knob (36) is located in a recess (52) on said second handle (30). A surgical instrument according to claim 1, wherein said flexible latch body is adapted to flex around an axis (A-A), and said latch hook (56) extends from said latch body in a direction substantially parallel to said axis (A-A). A surgical instrument according to claim 1 or claim 2, further comprising a latch guide (37) on said second handle (30) of said surgical instrument wherein said latch guide (37) comprises a first surface (68), said first surface (68) being sloped toward said latching notch (66). A surgical instrument according to claim 3 wherein said guide surface (64) is adapted to move said latch hook (56) in a first direction substantially perpendicular to said axis (A-A) and said latching notch (66) is arranged substantially parallel to said axis (A-A). A surgical instrument according to claim 3 wherein: said latch hook (56) is connected to and spaced from said first handle (26) such that said latch hook (56) is adapted to move in a first direction and a second, opposite direction; said latch knob (36) is connected to a mounting surface (54) of said second handle (30), said latch knob (36) extending from said mounting surface (36) in a direction which is substantially perpendicular to said first direction; said latch guide (37) is separated from said latching notch (66). A surgical instrument according to any preceding claim wherein: said first handle (26) includes first and second walls on either side of said latch hook (44).; and said second handle (30) includes an orientation guide (100). An endoscopic surgical instrument according to any preceding claim further comprising: a knife trigger (24) connected to a handle (26) of said surgical instrument; an end effector (12) connected to said handle through an elongated tube (20) where in said end effector comprises: a pair of grasping jaws (16, 17); and a knife (42) adapted to move between said jaws wherein said knife is connected to said knife trigger (24).

Inventors: HANSFORD CHARLES A, HUGHETT J DAVID, WALES KENNETH S, HANSFORD, CHARLES A., HUGHETT, J. DAVID, WALES, KENNETH S.
Applicants: ETHICON ENDO SURGERY INC, ETHICON ENDO-SURGERY, INC.
Application year: 1996
Main classification: A61B17
IPC codes: B25B7, A61B18, A61B1, A61B17