Activation assembly for surgical instruments and surgical instruments incorporating the same

Abstract

A surgical instrument includes a housing and a lever movable relative to the housing to manipulate an end effector assembly, and an activation assembly disposed within the housing. The activation assembly includes a button, a switch operably associated with the button, and a plunger mechanism including at least one plunger. Actuation of the lever moves the at least one plunger along the first section of the cam surface and at least onto the jog whereby the at least one plunger is urged to depress the button to activate the switch to provide a signal to initiate delivery of energy to the end effector assembly.

Description

ACTIVATION ASSEMBLY FOR SURGICAL INSTRUMENTS AND SURGICAL INSTRUMENTS INCORPORATING THE SAMECROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 604,145, filed November 29, 2023, which is incorporated herein by reference in its entirety.FIELD

[0002] The present disclosure relates to surgical instruments and, more particularly, to an activation assembly for surgical instruments such as, for example, to enable initiation of the supply of energy to an end effector assembly of the surgical instrument to treat tissue.BACKGROUND

[0003] A surgical forceps is a pliers-like surgical instrument that relies on mechanical action between its jaw members to grasp, clamp, and constrict tissue. Energy based surgical forceps utilize both mechanical clamping action and energy, e.g., monopolar Radio Frequency (RF), bipolar RF, micro wave, ultrasonic, light, thermal, combinations thereof, and / or other suitable energy, to heat tissue to thereby treat, e.g., coagulate, cauterize, or seal, tissue grasped between jaw members of the energy based surgical forceps. Typically, once tissue is treated, the surgeon has to accurately sever the treated tissue. Accordingly, many energy based surgical forceps are designed to incorporate a knife that is advanced between the jaw members to cut the treated tissue. As an alternative to a mechanical knife, an energy based tissue cutting element may be provided to statically or dynamically cut the treated tissue using energy, e.g., the same or different energy as used for treating the tissue.SUMMARY

[0004] As used herein, the term “distal” refers to the portion that is being described which is farther from an operator (whether a human user (surgeon, nurse, etc.) or a surgical robot), while the term “proximal” refers to the portion that is being described which is closer to the operator. Terms including “generally,” “about,” “substantially,” and the like, as utilized herein, are meant to encompass variations, e.g., manufacturing tolerances, material tolerances, use and environmental tolerances, measurement variations, design variations, and / or other variations, up to and including plus or minus 10 percent. Further, to the extent consistent, any or all of the aspects detailed herein may be used in conjunction with any or all of the other aspects detailed herein.

[0005] Provided in accordance with the present disclosure is a surgical instrument including a housing, an end effector assembly distally spaced from the housing, a lever, and an activation assembly. The lever includes a grasping portion disposed externally of the housing and an activation portion extending into the housing. The activation portion defines a cam surface including a first section, a second section, and a jog disposed between the first and second sections. The lever is coupled to the housing and the end effector assembly and is movable relative to the housing from an unactuated position, wherein the grasping portion of the lever is spaced from the housing, to an actuated position, wherein the grasping portion of the lever is approximated relative to the housing, to manipulate the end effector assembly. The activation assembly is disposed within the housing and includes a button, a switch operably associated with the button, and a plunger mechanism including at least one plunger defining a first end portion and a second end portion. Actuation of the lever from the unactuated position to the actuated position moves the cam surface relative to the first end portion of the at least one plunger such that the first end portion of the at least one plunger is moved along the first section of the cam surface and at least onto the jog, an onto the second section of the cam surface, whereby the cam surface urges the at least one plunger towards the button such that the second end portion of the at least one plunger depresses the button to activate the switch.

[0006] In an aspect of the present disclosure, actuation of the lever from the unactuated position to the actuated position moves the cam surface relative to the first end portion of the at least one plunger such that the first end portion of the at least one plunger is moved along the first section of the cam surface, onto the jog, and onto the second section of the cam surface, whereby the cam surface urges the at least one plunger towards the button such that the second end portion of the at least one plunger depresses the button to activate the switch.

[0007] In an aspect of the present disclosure, the second end portion of the at least one plunger depresses the button to activate the switch at an activation position of the lever between the unactuated and actuated positions of the lever, the second end portion of the at least one plunger is displaced from the button to enable deactivation of the switch at a deactivation position of the lever between the actuated and unactuated positions of the lever, and the activation position is disposed farther towards the actuated position as compared to the deactivated position to define a hysteresis distance therebetween.

[0008] In another aspect of the present disclosure, the hysteresis distance is at least about 8% of the distance between the unactuated and actuated positions of the lever and / or at least about 0.10 inches.

[0009] In another aspect of the present disclosure, the at least one plunger includes a first plunger and a second plunger. The first plunger defines the first end portion and the second plunger defines the second end portion.

[0010] In yet another aspect of the present disclosure, the first plunger is movable relative to the second plunger during a first portion of the movement of the lever from the unactuated position to the actuated position, and the first plunger and the second plunger are movable together during a second portion of the movement of the lever from the unactuated position to the actuated position.

[0011] In still another aspect of the present disclosure, the first plunger slidably receives a portion of the second plunger within an internal bore thereof. In such aspects, the first plunger is movable relative to the second plunger until the portion of the second plunger bottoms out within the internal bore. The first plunger and the second plunger are movable together after the portion of the second plunger bottoms out within the internal bore.

[0012] In still yet another aspect of the present disclosure, the first plunger is movable relative to the second plunger during at least a portion of the movement of the lever from the actuated position to the unactuated position. In aspects, this enables the second plunger to maintain the depression of the button to thereby maintain the activation of the switch during at least a portion of the movement of the first plunger relative to the second plunger as the lever moves from the actuated position to the unactuated position.

[0013] In another aspect of the present disclosure, the plunger mechanism further includes an outer shell slidably receiving the first and second plungers, the outer shell including a first cylinder having a first internal diameter and a second cylinder having a second internal diameter smaller than the first internal diameter. The first plunger is slidably disposed within the first cylinder and the second plunger is slidably disposed within the second cylinder.

[0014] In another aspect of the present disclosure, the plunger mechanism further includes a first spring configured to bias the first plunger towards the cam surface and a second spring configured to bias the second plunger away from the first plunger.

[0015] In still another aspect of the present disclosure, the lever is coupled to the housing about a pivot and a longitudinal axis of the at least one plunger intersects the pivot.

[0016] In yet another aspect of the present disclosure, the end effector assembly includes first and second jaw members. In such aspects, the lever is configured to manipulate the end effector assembly by moving at least one of the first or second jaw members relative to the other for grasping tissue therebetween in response to movement of the lever from the unactuated position to the actuated position.

[0017] In another aspect of the present disclosure, the first and second jaw members include first and second electrically conductive tissue contacting surfaces, respectively. Activation of the switch, in such aspects, provides the signal to initiate delivery of energy to the first and second electrically conductive tissue contacting surfaces at different potentials to seal tissue grasped between the first and second jaw members.

[0018] Another surgical instrument provided in accordance with aspects of the present disclosure includes a housing, a shaft extending distally from the housing, an end effector assembly disposed at a distal end portion of the shaft, a lever, and an activation assembly. The end effector assembly includes first and second jaw members, at least one of which is movable from a spaced apart position to an approximated position for grasping tissue between first and second tissue contacting surfaces of the respective first and second jaw members. The first and second tissue contacting surfaces are configured to conduct energy through tissue grasped therebetween to treat tissue. The lever includes a grasping portion disposed externally of the housing and an activation portion extending into the housing. The activation portion has an outer edge defining a cam surface including a first section, a second section, and a jog disposed between the first and second sections. The lever is coupled to the housing and the at least one of the first or second jaw members and is movable relative to the housing from an unactuated position. The grasping portion of the lever is spaced from the housing, to an actuated position, and the grasping portion of the lever is approximated relative to the housing, to move the at least one of the first or second jaw members from the spaced apart position to the approximated position. The activation assembly is disposed within the housing and includes a button, a switch operably associated with the button, and a plunger mechanism including first and second plungers and first and second springs. Activation of the switch provides a signal to initiate delivery of energy to the first and second tissue contacting surfaces for conduction through tissue grasped therebetween. The first spring biases the first plunger towards the cam surface and the second spring biases the second plunger away from the first plunger. Actuation of the lever from the unactuated position to the actuated position movesthe cam surface relative to the first plunger such that the first plunger is moved along the first section of the cam surface and at least onto the jog, whereby the cam surface urges the first plunger towards the second plunger to thereby urge the second plunger into the button to depress the button and activate the switch.

[0019] In an aspect of the present disclosure, actuation of the lever from the unactuated position to the actuated position moves the cam surface relative to the first plunger such that the first plunger is moved along the first section of the cam surface, onto the jog, and onto the second section of the cam surface, whereby the cam surface urges the first plunger towards the second plunger to thereby urge the second plunger into the button to depress the button and activate the switch.

[0020] In an aspect of the present disclosure, the second plunger depresses the button to activate the switch at an activation position of the lever between the unactuated and actuated positions of the lever, the second plunger is displaced from the button to enable deactivation of the switch at a deactivation position of the lever between the actuated and unactuated positions of the lever, and the activation position is disposed farther towards the actuated position as compared to the deactivated position to define a hysteresis distance therebetween.

[0021] In another aspect of the present disclosure, the hysteresis distance is at least about 8% of the distance between the unactuated and actuated positions of the lever and / or at least about 0.10 inches.

[0022] In still another aspect of the present disclosure, the second spring maintains the second plunger depressing the button such that the switch remains activated while the first plunger moves relative to the second plunger during movement of the lever from the actuated position to the deactivation position.

[0023] In yet another aspect of the present disclosure, the lever is coupled to the housing about a pivot and longitudinal axes of the first and second plungers intersect the pivot.BRIEF DESCRIPTION OF DRAWINGS

[0024] The above and other aspects and features of the present disclosure will become more apparent in view of the following detailed description when taken in conjunction with the accompanying drawings wherein like reference numerals identify similar or identical elements.

[0025] FIG. 1 is a side view of an electrosurgical system in accordance with the present disclosure including an electrosurgical forceps and an electrosurgical generator;

[0026] FIG. 2A is a side, cutaway view of the housing of the electrosurgical forceps of the system of FIG. 1 with all but a lever and activation assembly of the electrosurgical forceps removed;

[0027] FIG. 2B is a side, cutaway view of the housing of FIG. 2A including the lever and the activation mechanism with an outer shell of the activation assembly removed;

[0028] FIG. 3 is an enlarged view of the area of detail indicated as “3” in FIG. 2B;

[0029] FIGS. 4A-4D are enlarged, side, partial cross-sectional views progressively illustrating actuation of the lever to activate a switch of the activation assembly and return of the lever to enable deactivation of the switch of the activation assembly;

[0030] FIG. 5 is a graph illustrating lever displacement versus lever force during actuation and subsequent return of the lever; and

[0031] FIG. 6 is an enlarged view of the area of detail indicated as “6” in the graph of FIG. 5.DETAILED DESCRIPTION

[0032] The present disclosure provides an activation assembly for surgical instruments such as, for example, to enable initiation of the supply of energy to an end effector assembly of the surgical instrument to treat tissue. Although described herein with respect to initiating the supply of energy to jaw members of an electrosurgical forceps, the activation assembly of the present disclosure is equally applicable for use with any other suitable surgical instrument and / or for activating any other suitable energy or other feature.

[0033] Referring to FIG. 1 , an electrosurgical system 2 provided in accordance with the present disclosure includes an electrosurgical forceps 10 and an electrosurgical generator 18. Forceps 10 includes a housing 20, a handle assembly 30, a rotating assembly 40, a trigger assembly 50, an activation assembly 60, an end effector assembly 70, and a jaw drive assembly 80. End effector assembly 70 includes first and second jaw members 72, 74, at least one of which is movable relative to the other about a pivot (or other suitable structure(s)) between a spaced apart position and an approximated position to grasp tissue to enable sealing and / or dividing of the grasped tissue. End effector assembly 70 further includes a knife (not shown) operably coupled to trigger assembly 50 to enable selective translation of the knife between jaw members 72, 74 to cut tissue (e.g., previously sealed tissue) grasped between jaw members 72, 74. Alternatively, end effector assembly 70 may include an energy based cutting element, e.g., a cutting electrode (not shown), disposed on either or both of jaw members 72, 74 and operably coupled to trigger assembly 50 toenable the selective supply of energy to the cutting electrode to cut tissue (e.g., previously sealed tissue) grasped between jaw members 72, 74. Thus, trigger assembly 50 may, in knife based configurations, include a trigger 52 operably coupled to a knife drive assembly (not shown) and configured, in response to actuation thereof, to mechanically advance the knife between jaw members 72, 74. Alternatively, in cutting electrode based configurations, trigger 52 of trigger assembly 50 may be coupled to an underlying switch (not shown) operably connected to generator 18 and configured, in response to actuation thereof, to signal generator 18 to supply energy to the cutting electrode.

[0034] Forceps 10 further includes an outer shaft 12 that has a proximal end portion operatively engaged to a body 21 of housing 20 and a distal end portion operably engaged to end effector assembly 70. Forceps 10 also includes an electrosurgical cable 14 configured to connect forceps 10 to generator 18 to enable generator 18 to communicate with forceps 10 and control the supply of electrosurgical energy to end effector assembly 70 of forceps 10 for sealing tissue grasped between first and second jaw members 72, 74 and, in aspects, for cutting tissue disposed between or in contact with the cutting electrode of end effector assembly 70.

[0035] Continuing with reference to FIG. 1, handle assembly 30 includes a fixed handle 32 and a movable handle or lever 34. Fixed handle 32 is integrally associated with housing 20, depending from body 21 thereof, and lever 34 is movable relative to fixed handle 32 to actuate a jaw drive assembly 80 of forceps 10. More specifically, lever 34 is coupled to housing 20, e.g., pivotably secured to housing 20 via a pivot 35 (FIG. 2A), within housing 20 at a first coupling location 36 and coupled with jaw drive assembly 80 at a second coupling location 38. Jaw drive assembly 80 may include one or more linkages 82, a carriage 84, a compression spring 86, and a drive shaft 88. Lever 34 couples, e.g., pivotably connects, to linkage(s) 82 at second coupling location 38 and linkage(s) 82, in turn, cooperate to move carriage 84 against compression spring 86 in response to actuation of lever 34 towards fixed handle 32. Movement of carriage 84 distally against compression spring 86, in turn, regulates translation of drive shaft 88 through outer shaft 12 and relative to end effector assembly 70 to move either or both of jaw members 72, 74 relative to one another to grasp tissue between jaw members 72, 74 and regulate the closure force applied to tissue grasped between jaw members 72, 74.

[0036] Upon reaching a threshold closure force applied to tissue grasped between first and second jaw members 72, 74, further movement of carriage 84 distally against compression spring86, e.g., in response to further actuation of lever 34 towards fixed handle 32, compresses compression spring 86 rather than translating compression spring 86 distally (due to the resistive force applied by tissue inhibiting further closure of jaw members 72, 74) such that drive shaft 88 and, thus, first and second jaw members 72, 74 are maintained in position grasping tissue therebetween. In this manner, the closure force applied to tissue grasped between jaw members 72, 74 is regulated to maintain a closure force or closure force within a closure force range. In aspects, a return spring (not shown) is provided to bias lever 34 away from fixed handle 32, thereby biasing jaw members 72, 74 towards the spaced apart position.

[0037] Continuing with reference to FIG. 1, end effector assembly 70 is shown as a unilateral assembly, e.g., wherein second jaw member 74 is fixed relative to outer shaft 12 and first jaw member 72 is pivotable relative to second jaw member 74 and outer shaft 12; however, a bilateral assembly, e.g., wherein both first and second jaw members 72, 74 are pivotable relative to one another and outer shaft 12, is also contemplated. Further, in order to drive relative movement of either or both of jaw members 72, 74, drive shaft 88 may be operably coupled to either or both jaw members 72, 74 via a cam and slot mechanism, one or more linkages, a lead screw, or via any other suitable mechanism. Such mechanism may be configured to urge jaw members 72, 74 towards the approximated position in response to proximal movement of drive shaft 88 through outer shaft 12, distal movement of drive shaft 88 through outer shaft 12, rotation of drive shaft 88 relative to outer shaft 12, or in any other suitable manner.

[0038] Each jaw member 72, 74 of end effector assembly 70 includes an electrically conductive tissue contacting surface 73, 75, respectively. Jaw members 72, 74 are configured to grasp tissue between electrically conductive tissue contacting surface 73, 75 in the approximated position thereof. Electrically conductive tissue contacting surfaces 73, 75 are adapted to connect to generator 18, e.g., via suitable electrical lead wires, electrically conductive structures, or combinations thereof extending through outer shaft 12, housing 20, and electrosurgical cable 14 to enable energization of electrically conductive tissue contacting surface 73, 75 with electrosurgical, e.g., Radio Frequency (RF), energy at different potentials for conducting electrosurgical energy between electrically conductive tissue contacting surface 73, 75 and through tissue grasped therebetween to seal the tissue.

[0039] Either or both jaw members 72, 74 may further include one or more stop members (not shown) disposed on or otherwise associated with either or both tissue contacting surfaces 73, 75to maintain a minimum gap distance between tissue contacting surfaces 73, 75 (or to maintain a gap distance within a gap distance range between tissue contacting surfaces 73, 75) when jaw members 72, 74 are disposed in an approximated position, thus inhibiting electrical shorting. The stop member(s) may be insulative, partly insulative, and / or electrically isolated from either or both tissue contacting surfaces 73, 75. In aspects, the minimum gap distance or the gap distance range may be from about 0.001 inches to about 0.010 inches; in other aspects from about 0.001 inches to about 0.008 inches; and, in still other aspects from about 0.001 inches to about 0.006 inches. Other suitable gap distances and ranges are also contemplated. The gap distance may be determined as the maximum gap distance between the tissue contacting surfaces 73, 75.

[0040] Referring still to FIG. 1, rotating assembly 40 includes a rotation wheel 42 engaged with outer shaft 12 and rotatably disposed about a distal nose 24 of body 21 of housing 20 to enable a user to manually control the orientation of outer shaft 12 and thus, end effector assembly 70, relative to housing 20, e.g., by manipulating rotation wheel 42. In aspects, rotating assembly 40 is infinitely rotatable in either direction to similarly rotate end effector assembly 70 relative to housing 20. Alternatively, rotating assembly 40 may have a defined range of motion.

[0041] Activation assembly 60 is disposed within fixed handle 32 of housing 20 and is configured, in response to sufficient actuation of lever 34, e.g., about pivot 35 (FIG. 2A), to signal generator 18 to initiate the supply of electrosurgical energy to first and second jaw members 72, 74 for sealing tissue. With additional reference to FIG. 3 and as described in greater detail below, activation assembly 60 includes an activation button 62 including an underlying activation switch 64 and a plunger mechanism 66 operably coupled between lever 34 and activation button 62 such that, upon sufficient actuation of lever 34, activation button 62 is movable from an unactuated position to an actuated position to thereby transition underlying electrical switch 64 from a first state (e.g., an OFF state) to a second state (e.g., an ON state). Electrical switch 64, in turn, is adapted to electrically connect to generator 18, e.g., via one or more electrical lead wires extending from electrical switch 64 through housing 20 and electrosurgical cable 14, to enable communication of the state of electrical switch 64 to generator 18. Generator 18, more specifically, may be configured to read an output, e.g., the presence of a resistance, voltage, current, etc. and / or a value of the resistance, voltage, current, etc., established by the change in state of the electrical switch 64 to thereby detect the state of electrical switch 64 and, thus, to detect whether the user has activated activation button 62. For example, generator 18 may read the first state of electricalswitch 64 as corresponding to a deactivated state and the second state of electrical switch 64 as corresponding to an activated state. In aspects, activation button 62 is biased towards an unactivated position and, thus, electrical switch 64 is biased towards the deactivated state.

[0042] Turning to FIGS. 2A, 2B, and 3, lever 34 is described in greater detail. Lever 34, as noted above, is coupled to housing 20 within housing 20 at a first coupling location 36. For example, lever 34 may be pivotably secured to housing 20 within housing 20 via pivot 35 at first coupling location 36. Lever 34 is also coupled to jaw drive assembly 80 (FIG. 1) within housing 20 at a second coupling location 38.

[0043] Lever 34, more specifically, includes a grasping portion 310 positioned externally of housing 20 and an activation portion 320 extending from grasping portion 310 through a distally oriented slot 22 (FIG. 1) defined within housing 20 and into housing 20. Lever 34 may be monolithically formed, e.g., via molding, or may be formed in any other suitable manner. Grasping portion 310 includes a finger loop 312 configured to receive one or more fingers of a user to facilitate grasping and manipulation of grasping portion 310 of lever 34. Finger loop 312 may define an open loop (as shown) such as, for example, defining a shepherd’s hook configuration including a relatively longer proximal leg 314 and a relatively shorter distal leg 316 interconnected by an upper curved portion 318a and defining an open lower portion 318b. Alternatively, finger loop 312 may define a closed configuration, e.g., including an oval ring shaped body defining an oval shaped opening, although other configurations are also contemplated.

[0044] Activation portion 320 of lever 34 extends proximally from grasping portion 310 and, as noted above, through distally oriented slot 22 of housing 20 (see FIG. 1) and into housing 20. Activation portion 320 may include a body 322 defining a plate-like configuration having relatively broad opposing faces 324 (only one of which is shown) and a relatively narrow outer edge 326. Body 322 of activation portion 320 may connect with finger loop 312 of grasping portion 310 along a portion of narrow outer edge 326. However, other configurations of activation portion 320 are also contemplated. Further, pivot 35 may extend transversely from and / or through opposing faces 324 of body 322 to pivotably couple body 322 to housing 20 within housing 20 on either side of body 322 at first coupling location 36. Body 322 may likewise couple to jaw drive assembly 80 (FIG. 1) through or transversely from opposing faces 324 at second coupling location 38. First and second coupling locations 36, 38 are spaced apart from one another along body 322 of activation portion 320 of lever 34.

[0045] A portion of outer edge 326 of body 322 of activation portion 320 of lever 34 defines a cam surface 328. In aspects, cam surface 328 is defined by at least part of the portion of outer edge 326 of body 322 that extends between second coupling location 38 and finger loop 312, although other configurations are also contemplated. Cam surface 328 includes a proximal section 332, a distal section 334, and a jog 336 interconnecting proximal and distal sections 332, 334. Either or both of proximal and distal sections 332, 334 may define planar configurations, curved configurations, angled segments, combinations thereof, etc. and may define similar planes, curves, and / or angles, or different planes, curves, and / or angles. Jog 336 may be configured as a curved hump (as shown), planar ramp, combinations thereof, or may be configured to include any other suitable feature or combination of features that define a discontinuity between the planes, curves, and / or angles of proximal and distal sections 332, 334 of cam surface 328 while interconnecting proximal and distal sections 332, 334 to enable activation assembly 60 to move along proximal section 332 and at least onto jog 336. In aspects, activation assembly 60 traverses jog 336 onto distal section 334. In aspects, jog 336 protrudes asymmetrically from outer edge 326 between proximal and distal sections 332, 334 such that proximal section 332 of cam surface 328 is offset from distal section 334. For example, proximal section 332 may be recessed relative to distal section 334 of cam surface 328 in a direction towards activation assembly 60, although other configurations are also contemplated. In aspects, proximal and distal sections 332, 334 define radiused curvatures having different radii of curvature wherein the radius of curvature of either or both of proximal and distal sections 332, 334 is centered on the pivot axis of pivot 35. In additional or alternative aspects, the radii of curvature of proximal and distal sections 332, 334 is greater, e.g., multiple times greater, than that of jog 336 to facilitate tactile feedback as detailed below. Further, in aspects where jog 336 is radiused, the radius of curvature of jog 336 is displaced relative to the pivot axis of pivot 35, thus also facilitating tactile feedback by increasing the disruption between proximal and distal sections 332, 334.

[0046] As detailed below, the discontinuity provided by jog 336 is also configured to create tactile feedback as activation assembly 60 is moved onto and, in aspects where so provided, as activation assembly 60 traverses jog 336. This tactile feedback may be in the form of an abrupt change in resistance, e.g., as activation assembly 60 moves from proximal section 332 into contact with jog 336 and / over overcomes jog 336 onto distal section 334. The abrupt change in resistancemay be an increase, a decrease, a combination of one or more increases or one or more decreases, or any other suitable abrupt change that is readily discernible by way of tactile feedback.

[0047] Continuing with reference to FIGS. 2A, 2B, and 3, activation assembly 60 is described in greater detail. Activation assembly 60 is disposed within fixed handle 32 of housing 20 and includes, as noted above, an activation button 62 including an underlying electrical switch 64 (FIG. 3), and a plunger mechanism 66 operably coupled between cam surface 328 of activation portion 320 of lever 34 and activation button 62. Activation button 62 (including electrical switch 64) may be mounted on a printed circuit board (PCB) 65 that is secured within and in fixed relation relative to fixed handle 32 of housing 20.

[0048] Plunger mechanism 66 includes an outer shell 610, first and second plungers 620, 630, and first and second springs 640, 650. Outer shell 610 is secured, e.g., via fasteners, within and in fixed relation relative to fixed handle 32 of housing 20. Outer shell 610 defines a first open end 614 and a second open end 616 and includes first and second cylinders 615, 617, wherein first cylinder 615 defines a larger internal diameter than second cylinder 617 (and, in aspects, a larger external diameters (as shown)) such that an annular interior shoulder 618 is defined between first and second cylinders 615, 617. First and second open ends 614, 616 define reduced diameter openings as compared to the internal diameters of first and second cylinders 615, 617, respectively. Activation button 62 extends through second open end 616 of outer shell 610 and into second cylinder 617.

[0049] First plunger 620 includes a body 622, a collar 624, and a cap 626 and defines an internal bore 628 (FIGS. 4A-4D). First plunger 620 may be monolithically formed, e.g., via molding, or may be formed in any other suitable manner. Body 622 is slidably disposed within first cylinder 615, although a portion of body 622 of first plunger 620 also extends into and is slidable through second cylinder 617. Collar 624 is formed with or otherwise fixedly engaged to body 622 towards a first end of body 622. Collar 624 is disposed within first cylinder 615 and defines a diameter greater than the diameters of body 622, first open end 614 of shell 610, and internal annular shoulder 618 such that collar 624 is retained within first cylinder 615 between first open end 614 and annular shoulder 618. First spring 640 may be configured as a compression coil spring and is disposed about body 622 of first plunger 620 within first cylinder 615 between collar 624 and annular shoulder 618. Thus, urging first plunger 620 towards the second end of outer shell 610 compresses first spring 640 between collar 624 and annular shoulder 618 such that, uponrelease or removal of the urging, first spring 640 biases first plunger 620 back towards the first end of outer shell 610, e.g., until collar 624 abuts first open end 614.

[0050] Cap 626 is fixed relative to and extends from the first end of body 622 and collar 624 through first open end 614 of outer shell 610 such that cap 626 is exposed within fixed handle 32 of housing 20. As detailed below, cap 626 is configured to interact with cam surface 328 of activation portion 320 of lever 34. Cap 626 defines a dome shaped free end 627 configured to reduce friction and facilitate smooth sliding of cap 626 along cam surface 328, although other suitable configurations are also contemplated. Internal bore 628 (FIGS. 4A-4D) is defined within the second end of body 622 and extends partially through body 622 towards the first end of body 622.

[0051] Referring still to FIGS. 2A, 2B, and 3, second plunger 630 includes a body 632 and a collar 634. Second plunger 630 may be monolithically formed, e.g., via molding, or may be formed in any other suitable manner. Body 632 is slidably disposed within second cylinder 617, although a portion of body 632 of second plunger 630 also extends into and is slidable through first cylinder 615. A first end of body 632, more specifically, is slidably received within internal bore 628 (FIGS. 4A-4D) of body 622 of first plunger 620 and is slidable therethrough until the first end of body 632 abuts a base surface 629 of internal bore 628 (see FIGS. 4A-4D).

[0052] Collar 634 is formed with or otherwise fixedly engaged to body 632 at the second end of body 632. Collar 634 is disposed within second cylinder 617 and defines a diameter greater than the diameters of body 632, second open end 616, and body 622 of first plunger 620 such that collar 634 is retained within second cylinder 617 between second open end 616 and body 622 of first plunger 620. As noted above, activation button 62 extends through second open end 616 of outer shell 610 into second cylinder 617, thus enabling collar 634 to interact with activation button 62 to selectively activate and enable deactivation of activation button 62 and, thus, electrical switch 64. More specifically, movement of collar 634 towards the second end of outer shell 610, e.g., in response to corresponding movement of body 632, urges collar 634 into contact with activation button 62 to depress activation button 62 from the deactivated position to the activated position to thereby activate electrical switch 64.

[0053] Second spring 650 may be configured as a compression coil spring and is disposed about body 632 of second plunger 630 between collar 634 and the second end of body 622 of first plunger 620. Thus, urging of first plunger 620 about and relative to second plunger 630 towardsthe second end of outer shell 610, e.g., whereby the first end of body 632 is moved within internal bore 628 (see FIGS. 4A-4D) towards base surface 629 (see FIGS. 4A-4D) thereof, compresses second spring 650 between collar 634 and the second end of body 622 such that, upon release or removal of the urging, second spring 650 biases first and second plungers 620, 630 apart from one another, e.g., whereby second plunger 630 is biased towards the second end of outer shell 610 relative to first plunger 620. The spring constant of second spring 650, in aspects, is greater than the spring constant of first spring 640.

[0054] In aspects, activation assembly 60 is oriented within fixed handle 32 of housing 20 such that longitudinal axes defined by first and / or second plungers 620, 630 (which are coaxial with one another, in aspects) intersect pivot 35, e.g., wherein the longitudinal axes are perpendicular to the pivot axis of pivot 35. In this manner, when cam surface 328 of activation portion 320 of lever 34 interacts with cap 626 of first plunger 620, first plunger 620 and, ultimately second plunger 630 are urged along longitudinal axes thereof towards activation button 62, thus minimizing the input force required to move first and second plungers 620, 630 sufficiently so as to activate activation button 62. Other configurations are also contemplated.

[0055] Turning to FIGS. 1, 3, and 4A-4D, the operation of lever 34 and activation assembly 60 to activate electrical switch 64 to thereby initiate the supply of energy to jaw members 72, 74 to treat tissue and, subsequently, to deactivate electrical switch 64 to stop the supply of energy to jaw members 72, 74, e.g., once tissue treatment is complete or otherwise when it is desired to stop the supply of energy, is described.

[0056] Initially, as shown in FIG. 1 , manipulation portion 310 of lever 34 is disposed in an unactuated position spaced from fixed handle 32 of housing 20 and, correspondingly, jaw members 72, 74 are disposed in the spaced apart position. Actuation of manipulation portion 310 of lever 34 towards fixed handle 32 of housing 20 from the un-actuated position towards the actuated position, as detailed above, actuates jaw drive assembly 80 to move jaw members 72, 74 towards the approximated position. In addition, actuation of manipulation portion 310 of lever 34 towards the actuated position moves activation portion 320 of lever 34 proximally through slot 22 of fixed handle 32 of housing 20 and further into fixed handle 32 of housing 20. In this manner, cam surface 328 of activation portion 320 of lever 34 is moved distally relative to cap 626 of first plunger 620 such that cap 626 is moved along proximal section 332 of cam surface 328 towards jog 336 of cam surface 328. In aspects, cap 626 is maintained in spaced relation relative toproximal section 332 of cam surface 328 during at least a portion of the relative movement of cap 626 therealong, e.g., to inhibit friction therebetween. However, it is also contemplated that cap 626 slidably contact proximal section 332 of cam surface 328 during at least a portion of the relative movement of cap 626 therealong.

[0057] Referring also to FIG. 3, in the initial position of lever 34, and during the initial actuation of lever 34 towards fixed handle 32 of housing 20 from the un-actuated position towards the actuated position, but before cap 626 reaches jog 336, first and second plungers 620, 630 remain in their at-rest positions under the bias of first and second springs 640, 650, respectively. At this point, collar 634 of second plunger 630 is spaced apart from or minimally contacting activation button 62 such that activation button 62 and, thus, electrical switch 64 are maintained in the deactivated positions thereof. In addition, at this point, a gap (see FIG. 4A) is maintained between the first end of body 632 of second plunger 630 and base surface 629 of internal bore 628 of body 622 of first plunger 620 within internal bore 628.

[0058] Referring to FIG. 4 A, in conjunction with FIGS. 1 and 3, upon sufficient actuation of lever 34 towards fixed handle 32 of housing 20 from the un-actuated position towards the actuated position, cap 626 moves along proximal section 332 of cam surface 328 and into contact with jog 336. Cap 626 may initially move along a proximal portion of proximal section 332 in spaced relation relative to proximal section 332 (e.g., such that cap 626 and proximal section 332 are not in contact with one another, thereby reducing friction) and may subsequently move along a distal portion of proximal section 332 in contact with proximal section 332 prior to reaching jog 336. In this manner, movement of cap 626 into contact with proximal section 332 prior to reaching jog 336 may provide initial tactile feedback, e.g., via an increase in resistance, indicating that cap 626 is approaching jog 336.

[0059] The point at which cap 626 contacts jog 336 may correspond, for example, to a sufficiently approximated position of jaw members 72, 74 (e.g., wherein surfaces 73, 75 of jaw members 72, 74 define a jaw angle therebetween equal to or less than a predetermined jaw angle) and / or a sufficient pressure applied to tissue grasped between jaw members 72, 74 (e.g., wherein compression spring 86 is at least partially compressed from its initial condition or compressed beyond a predetermined compression). Further, when cap 626 contacts jog 336, the user may be provided with audible and / or tactile feedback. This feedback indicates that, although activation button 62 has not yet been activated, further actuation of lever 34 will activate activation button62 and, thus, initiate the supply of energy to jaw members 72, 74. Dome shaped free end 627 of cap 626 and jog 336 may be configured relative to one another such that suitable tactile feedback is provided to the user without requiring excess force or defining a hard stop to further movement of lever 34. In particular, dome shaped free end 627 of cap 626 and jog 336 may both be radiused with convex surfaces facing one another and, in further aspects, may contact one another at an angle of from about 30 degrees to about 60 degrees, thus providing the tactile feedback without requiring excess force or defining a hard stop. Other configurations are also contemplated.

[0060] With additional reference to FIGS. 4B and 4C, once cap 626 contacts jog 336, and upon further actuation of lever 34 towards fixed handle 32 of housing 20 towards the actuated position, cap 626 at least partially traverses jog 336. In aspects, full actuation of lever 34 moves cap 626 onto jog 336 but stops short of cap 626 reaching distal section. In other aspects, cap 626 traverses jog 336 and moves onto distal section 334 of cam surface 328. As cap 626 at least partially traverses jog 336, jog 336 urges cap 626 into outer shell 610 and towards the second end thereof. This urging of cap 626 into outer shell 610 correspondingly moves body 622 of first plunger 620 towards the second end of outer shell 610 against the bias of (and thereby compressing) first spring 640. This movement, in turn, moves body 622 of first plunger 620 about body 632 of second plunger 630 such that body 632 of second plunger 630 is approximated relative to and ultimately abuts base surface 629 of internal bore 628. This movement of body 622 of first plunger 620 also opposes the bias of (and thereby compresses) second spring 650.

[0061] Once body 622 of first plunger 620 is moved about body 632 of second plunger 630 such that body 632 of second plunger 630 abuts base surface 629 of internal bore 628, further movement of body 622 of first plunger 620 in the same direction similarly urges body 632 and, thus, collar 634 of second plunger 630 in the same manner. Accordingly, this further movement of body 622 of first plunger 620, in response to further actuation of lever 34 towards fixed handle 32 of housing 20 towards the actuated position such that cap 626 further moved over jog 336 or traverses jog 336 onto distal section 334 of cam surface 328, moves second plunger 630 such that collar 634 contacts and, ultimately, depresses activation button 62 (see FIG. 4C), thereby activating electrical switch 64 and initiating the supply of energy to jaw members 72, 74.

[0062] Referring also to FIG. 4D, as lever 34 is released or returned from the actuated position back towards the un-actuated position, activation portion 320 of lever 34 is moved distally relative to cap 626 such that cap 626 proximally traverses jog 336 (from a more-distal portion of jog 336or from distal section 334) back onto proximal section 332 of cam surface 328, thereby allowing first plunger 620 to return towards the first end of outer shell 610 under the bias of first spring 640. However, while first plunger 620 is moved back towards its initial position, second spring 650, having a greater spring constant than first spring 640, applies bias to second plunger 630 to bias second plunger 630 away from first plunger 620. Thus, although first plunger 620 is moved back towards its initial position, second plunger 630 is maintained in position via second spring 650 such that collar 634 is maintained in contact with and depressing activation button 62 (see FIG. 4D) to maintain the supply of energy to jaw members 72, 74. This hysteresis effect inhibits interruption of the supply of energy to jaw members 72, 74 despite slight release of lever 34 from the actuated position.

[0063] Upon further release or return of lever 34, first plunger 620 is further retuned towards the first end of outer shell 610 under the bias of first spring 640 and, ultimately, second plunger 630 is also returned back towards the first end of outer shell 610 to release activation button 62 (see FIG. 4A) and stop the supply of energy to jaw members 72, 74. At this point, first and second plungers 620, 630, no longer under urging from lever 34, are returned to their initial positions (see FIG. 4 A) and maintained there under the bias of first and second springs 640, 650, respectively.

[0064] Turning to FIGS. 5 and 6, in conjunction with FIGS. 4A-4D, graphs of lever displacement versus lever force during actuation and return of lever 34 are shown. During the initial stages of actuation of lever 34, the lever force required to move lever 34 is minimal. As lever 34 continues to be actuated, the force increases (for example, as a result of engagement of compression spring 86 of jaw drive assembly 80 (FIG. 1)). However, at this point, activation assembly 60 remains in its initial condition. In aspects, an initial increase in force may be encountered as cap 626 is moved into contact with proximal section 332 prior to reaching jog 336 (e.g., in aspects where cap 626 is spaced apart from proximal section 332 during an initial portion of the travel therealong).

[0065] As lever 34 is further actuated such that cap 626 moves into contact with jog 336 (FIG. 4A; indicated at “A” in FIG. 6), the lever force jumps owing to the need to at least partially traverse jog 336. Still further actuation of lever 34 requires this increased lever force to urge cap 626 to begin to traverse jog 336 (FIG. 4B; indicated at “B” in FIG. 6), thereby also providing tactile feedback to the user. However, at this point, activation has still not been initiated. This delay between the user feedback and the activation provides sufficient time for the user to confirm thatactivation is intended and intentionally continue actuation of lever 34 (after receipt and comprehension of the feedback provided by jog 336).

[0066] Still further actuation of lever 34 such that cap 626 further traverses jog 336 or, in aspects, after cap 626 traverses jog 336 onto distal section 334 of cam surface 328, actuates first and second plungers 620, 630 to thereby activate activation button 62 and electrical switch 64 to initiate the supply of energy to jaw members 72, 74 (see FIG. 4C; indicated at “C” in FIG. 6). The lever force increases slightly or remains substantially constant during the portion of actuation of lever 34 from “B” (at least partial traversal of jog 336) to “C” (activation of activation button 62) as shown in FIG. 6. Further, additional actuation range of motion of lever 34 after activation of activation button 62 (e.g., beyond “C” in FIG. 6) may be permitted without adverse effect.

[0067] Once activation button 62 is activated, lever 34 may be maintained in position, e.g., at “C” in FIG. 6, to thereby maintain the supply of energy to jaw members 72, 74 to complete the desired tissue treatment, e.g., tissue sealing. Upon release or return of lever 34 back towards the unactuated position, the lever force drops off significantly and the displacement versus force curve returns in the opposite direction. However, due to the hysteresis effect noted above, deactivation does not occur at the same lever displacement position as activation. Rather, lever 34 is required to be released or returned an additional hysteresis distance “x” before deactivation occurs (see FIG. 4D; indicated at “D” in FIG. 6). This helps ensure that premature or inadvertent deactivation of the supply of energy does not occur. More specifically, relatively minimal release of lever 34, e.g., less than the additional hysteresis distance “x,” which may occur unintentionally, does not result in deactivation. Rather, deactivation only occurs after lever 34 is released or returned a distance greater than the additional hysteresis distance “x.” Further release or return of lever 34 after deactivation returns activation assembly 60 to its initial condition (see FIG. 4A; indicated at “E” in FIG. 6).

[0068] In aspects, the hysteresis distance “x” may be at least about 5% of the full displacement distance of lever 34; in other aspects, the hysteresis distance “x” may be at least about 8% of the full displacement distance of lever 34; in still other aspects, the hysteresis distance “x” is at least about 10% of the full displacement distance of lever 34.

[0069] In aspects, the hysteresis distance “x” is at least about 0.08 inches; in other aspects, the hysteresis distance “x” is at least about 0.10 inches; in still other aspects, the hysteresis distance “x” is at least about 0.12 inches.

[0070] Aspects of this disclosure may be further described by reference to the following numbered paragraphs:

[0071] 1. A surgical instrument, comprising: a housing; an end effector assembly distally spaced from the housing; a lever including a grasping portion disposed externally of the housing and an activation portion extending into the housing, the activation portion defining a cam surface including a first section, a second section, and a jog disposed between the first and second sections, wherein the lever is coupled to the housing and the end effector assembly and is movable relative to the housing from an unactuated position, wherein the grasping portion of the lever is spaced from the housing, to an actuated position, wherein the grasping portion of the lever is approximated relative to the housing, to manipulate the end effector assembly; and an activation assembly disposed within the housing and including a button, a switch operably associated with the button, and a plunger mechanism including at least one plunger defining a first end portion and a second end portion, wherein activation of the switch provides a signal to initiate delivery of energy to the end effector assembly, wherein actuation of the lever from the unactuated position to the actuated position moves the cam surface relative to the first end portion of the at least one plunger such that the first end portion of the at least one plunger is moved along the first section of the cam surface and at least onto the jog, whereby the cam surface urges the at least one plunger towards the button such that the second end portion of the at least one plunger depresses the button to activate the switch.

[0072] 2. The surgical instrument according to paragraph 1, wherein actuation of the lever from the unactuated position to the actuated position moves the cam surface relative to the first end portion of the at least one plunger such that the first end portion of the at least one plunger is moved along the first section of the cam surface, onto the jog, and onto the second section of the cam surface to urge the at least one plunger towards the button such that the second end portion of the at least one plunger depresses the button to activate the switch.

[0073] 3. The surgical instrument according to paragraph 1 or 2, wherein: the second end portion of the at least one plunger depresses the button to activate the switch at an activation position of the lever between the unactuated and actuated positions of the lever, the second end portion of the at least one plunger is displaced from the button to enable deactivation of the switch at a deactivation position of the lever between the actuated and unactuated positions of the lever, andthe activation position is disposed farther towards the actuated position as compared to the deactivated position to define a hysteresis distance therebetween.

[0074] 4. The surgical instrument according to paragraph 3, wherein the hysteresis distance is at least about 8% of the distance between the unactuated and actuated positions of the lever.

[0075] 5. The surgical instrument according to paragraph 3 or 4, wherein the hysteresis distance is at least about 0.10 inches.

[0076] 6. The surgical instrument according to any preceding claim, wherein the at least one plunger includes a first plunger and a second plunger, the first plunger defining the first end portion and the second plunger defining the second end portion.

[0077] 7. The surgical instrument according to paragraph 6, wherein the first plunger is movable relative to the second plunger during a first portion of the movement of the lever from the unactuated position to the actuated position and wherein the first plunger and the second plunger are movable together during a second portion of the movement of the lever from the unactuated position to the actuated position.

[0078] 8. The surgical instrument according to paragraph 7, wherein the first plunger slidably receives a portion of the second plunger within an internal bore thereof, wherein the first plunger is movable relative to the second plunger until the portion of the second plunger bottoms out within the internal bore and, wherein the first plunger and the second plunger are movable together after the portion of the second plunger bottoms out within the internal bore.

[0079] 9. The surgical instrument according to any one of paragraph 6-8, wherein the first plunger is movable relative to the second plunger during at least a portion of the movement of the lever from the actuated position to the unactuated position.

[0080] 10. The surgical instrument according to paragraph 9, wherein the second plunger maintains the depression of the button to thereby maintain the activation of the switch during at least a portion of the movement of the first plunger relative to the second plunger as the lever moves from the actuated position to the unactuated position.

[0081] 11. The surgical instrument according to any one of paragraphs 6-10, wherein the plunger mechanism further includes an outer shell slidably receiving the first and second plungers, the outer shell includes a first cylinder having a first internal diameter and a second cylinder having a second internal diameter smaller than the first internal diameter, wherein the first plunger isslidably disposed within the first cylinder and wherein the second plunger is slidably disposed within the second cylinder.

[0082] 12. The surgical instrument according to any one of paragraph 6-11, wherein the plunger mechanism further includes first and second springs, the first spring configured to bias the first plunger towards the cam surface and the second spring configured to bias the second plunger away from the first plunger.

[0083] 13. The surgical instrument according to any preceding paragraph, wherein the lever is coupled to the housing about a pivot, and wherein a longitudinal axis of the at least one plunger intersects the pivot.

[0084] 14. The surgical instrument according to any preceding paragraph, wherein the end effector assembly includes first and second jaw members, and wherein the lever is configured to manipulate the end effector assembly by moving at least one of the first or second jaw members relative to the other for grasping tissue therebetween in response to movement of the lever from the unactuated position to the actuated position.

[0085] 15. The surgical instrument according to paragraph 14, wherein the first and second jaw members include first and second electrically conductive tissue contacting surfaces, respectively, and wherein activation of the switch provides the signal to initiate delivery of energy to the first and second electrically conductive tissue contacting surfaces at different potentials to seal tissue grasped between the first and second jaw members.

[0086] 16. A surgical instrument, comprising: a housings shaft extending distally from the housing; an end effector assembly disposed at a distal end portion of the shaft, the end effector assembly including first and second jaw members, at least one of the first or second jaw members movable relative to another of the first or second jaw members from a spaced apart position to an approximated position for grasping tissue between first and second tissue contacting surfaces of the respective first and second jaw members, wherein the first and second tissue contacting surfaces are configured to conduct energy through tissue grasped therebetween to treat tissue; a lever including a grasping portion disposed externally of the housing and an activation portion extending into the housing, the activation portion defining a cam surface including a first section, a second section, and a jog disposed between the first and second sections, wherein the lever is coupled to the housing and the at least one of the first or second jaw members and is movable relative to the housing from an unactuated position, wherein the grasping portion of the lever isspaced from the housing, to an actuated position, wherein the grasping portion of the lever is approximated relative to the housing, to move the at least one of the first or second jaw members from the spaced apart position to the approximated position; and an activation assembly disposed within the housing and including a button, a switch operably associated with the button, and a plunger mechanism, wherein activation of the switch provides a signal to initiate delivery of energy to the first and second tissue contacting surfaces for conduction through tissue grasped therebetween, the plunger mechanism including first and second plungers and first and second springs, the first spring biasing the first plunger towards the cam surface and the second spring biasing the second plunger away from the first plunger, wherein actuation of the lever from the unactuated position to the actuated position moves the cam surface relative to the first plunger such that the first plunger is moved along the first section of the cam surface and at least onto the jog, whereby the cam surface urges the first plunger towards the second plunger to thereby urge the second plunger into the button to depress the button and activate the switch.

[0087] 17. The surgical instrument according to paragraph 16, wherein actuation of the lever from the unactuated position to the actuated position moves the cam surface relative to the first plunger such that the first plunger is moved along the first section of the cam surface, onto the jog, and onto the second section of the cam surface to urge the first plunger towards the second plunger to thereby urge the second plunger into the button to depress the button and activate the switch.

[0088] 18. The surgical instrument according to paragraph 16 or 17, wherein: the second plunger depresses the button to activate the switch at an activation position of the lever between the unactuated and actuated positions of the lever, the second plunger is displaced from the button to enable deactivation of the switch at a deactivation position of the lever between the actuated and unactuated positions of the lever, andthe activation position is disposed farther towards the actuated position as compared to the deactivated position to define a hysteresis distance therebetween.

[0089] 19. The surgical instrument according to paragraph 18, wherein the hysteresis distance is at least about 8% of the distance between the unactuated and actuated positions of the lever.

[0090] 20. The surgical instrument according to paragraph 18 or 19, wherein the hysteresis distance is at least about 0.10 inches.

[0091] 21. The surgical instrument according to any one of paragraph 16-20, wherein, during movement of the lever from the actuated position to the deactivation position, the second springmaintains the second plunger depressing the button such that the switch remains activated while the first plunger moves relative to the second plunger.

[0092] 22. The surgical instrument according to any one of paragraphs 16-21, wherein the lever is coupled to the housing about a pivot, and wherein longitudinal axes of the first and second plungers intersect the pivot.

[0093] While several aspects of the disclosure have been shown in the drawings, it is not intended that the disclosure be limited thereto, as it is intended that the disclosure be as broad in scope as the art will allow and that the specification be read likewise. Therefore, the above description should not be construed as limiting, but merely as exemplifications of particular configurations. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.

Claims

WHAT IS CLAIMED IS:

1. A surgical instrument (10), comprising: a housing (20); an end effector assembly (70) distally spaced from the housing (20); a lever (34) including a grasping portion (310) disposed externally of the housing (20) and an activation portion (320) extending into the housing (20), the activation portion (320) defining a cam surface (328) including a first section (332), a second section (334), and a jog (336) disposed between the first and second sections (332, 334), wherein the lever (34) is coupled to the housing (20) and the end effector assembly (70) and is movable relative to the housing (20) from an unactuated position, wherein the grasping portion (310) of the lever (34) is spaced from the housing (20), to an actuated position, wherein the grasping portion (310) of the lever (34) is approximated relative to the housing (20), to manipulate the end effector assembly (70); and an activation assembly (60) disposed within the housing (20) and including a button (62), a switch (64) operably associated with the button (62), and a plunger mechanism (66) including at least one plunger (620, 630) defining a first end portion and a second end portion, wherein activation of the switch (64) provides a signal to initiate delivery of energy to the end effector assembly (70), wherein actuation of the lever (34) from the unactuated position to the actuated position moves the cam surface (328) relative to the first end portion of the at least one plunger (620, 630) such that the first end portion of the at least one plunger (620, 630) is moved along the first section (332) of the cam surface (328) and at least onto the jog (336), whereby the cam surface (328) urges the at least one plunger (620, 630) towards the button (62) such that the second end portion of the at least one plunger (620, 630) depresses the button (62) to activate the switch (64).

2. The surgical instrument according to claim 1, wherein actuation of the lever (34) from the unactuated position to the actuated position moves the cam surface (328) relative to the first end portion of the at least one plunger (620, 630) such that the first end portion of the at least one plunger (620, 630) is moved along the first section (332) of the cam surface (328), onto the jog (336), and onto the second section (334) of the cam surface (328) to urge the at least one plunger(620, 630) towards the button (62) such that the second end portion of the at least one plunger (620, 630) depresses the button (62) to activate the switch (64).

3. The surgical instrument (10) according to claim 1 or 2, wherein: the second end portion of the at least one plunger (620, 630) depresses the button to activate the switch (64) at an activation position of the lever (34) between the unactuated and actuated positions of the lever (34), the second end portion of the at least one plunger (620, 630) is displaced from the button (62) to enable deactivation of the switch (64) at a deactivation position of the lever (34) between the actuated and unactuated positions of the lever (34), and the activation position is disposed farther towards the actuated position as compared to the deactivated position to define a hysteresis distance (“x”) therebetween.

4. The surgical instrument (10) according to claim 3, wherein the hysteresis distance is at least about 8% of the distance between the unactuated and actuated positions of the lever (34).

5. The surgical instrument (10) according to claim 3 or 4, wherein the hysteresis distance is at least about 0.10 inches.

6. The surgical instrument (10) according to any preceding claim, wherein the at least one plunger (620, 630) includes a first plunger (620) and a second plunger (630), the first plunger (620) defining the first end portion and the second plunger (630) defining the second end portion.

7. The surgical instrument (10) according to claim 6, wherein the first plunger (620) is movable relative to the second plunger (630) during a first portion of the movement of the lever (34) from the unactuated position to the actuated position and wherein the first plunger (620) and the second plunger (630) are movable together during a second portion of the movement of the lever (34) from the unactuated position to the actuated position.

8. The surgical instrument (10) according to claim 7, wherein the first plunger (620) slidably receives a portion of the second plunger (630) within an internal bore (628) thereof, wherein the first plunger (620) is movable relative to the second plunger (630) until the portion of the secondplunger (630) botoms out within the internal bore (628) and, wherein the first plunger (620) and the second plunger (630) are movable together after the portion of the second plunger (630) bottoms out within the internal bore (628).

9. The surgical instrument (10) according to any one of claims 6-8, wherein the first plunger (620) is movable relative to the second plunger (630) during at least a portion of the movement of the lever (34) from the actuated position to the unactuated position.

10. The surgical instrument (10) according to claim 9, wherein the second plunger (630) maintains the depression of the buton (62) to thereby maintain the activation of the switch (64) during at least a portion of the movement of the first plunger (620) relative to the second plunger (630) as the lever (34) moves from the actuated position to the unactuated position.

11. The surgical instrument (10) according to any one of claims 6-10, wherein the outer shell (610) includes a first cylinder (615) having a first internal diameter and a second cylinder (617) having a second internal diameter smaller than the first internal diameter, wherein the first plunger (620) is slidably disposed within the first cylinder (615) and wherein the second plunger (630) is slidably disposed within the second cylinder (617).

12. The surgical instrument (10) according to any one of claims 6-11, wherein the plunger mechanism (66) further includes first and second springs (640, 650), the first spring (640) configured to bias the first plunger (620) towards the cam surface (328) and the second spring (650) configured to bias the second plunger (630) away from the first plunger (620).

13. The surgical instrument (10) according to any preceding claim, wherein the lever (34) is coupled to the housing (20) about a pivot (35), and wherein a longitudinal axis of the at least one plunger (620, 630) intersects the pivot (35).

14. The surgical instrument (10) according to any preceding claim, wherein the end effector assembly (70) includes first and second jaw members (72, 74), and wherein the lever (34) is configured to manipulate the end effector assembly (70) by moving at least one of the first orsecond jaw members (72, 74) relative to the other for grasping tissue therebetween in response to movement of the lever (34) from the unactuated position to the actuated position.

15. The surgical instrument (10) according to claim 14, wherein the first and second jaw members (72, 74) include first and second electrically conductive tissue contacting surfaces (73, 75), respectively, and wherein activation of the switch (64) provides the signal to initiate delivery of energy to the first and second electrically conductive tissue contacting surfaces (73, 75) at different potentials to seal tissue grasped between the first and second jaw members (72, 74).

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