Electrosurgical device

Abstract

Surgical instrument (1) comprising a handle (10) and an elongated shaft (12) extending from the handle (10) and defining a front direction and a rear direction, an end effector (14) arranged at the distal end of the elongated shaft (12), a blade assembly within the elongated shaft (12) wherein the blade assembly has a blade (340) arranged at its distal end, the blade (340) being located in the region of the end effector (14), the blade assembly being connected at its proximal end to a component (352) within the handle (10), a release mechanism arranged on the handle (10) and movable between a first position and a second position, wherein moving the release mechanism from its first position to its second position causes a longitudinal movement of the blade assembly to effect a longitudinal movement of the blade (340) relative to the end effector (14),wherein the release mechanism comprises: a release arm (24, 344) comprising a proximal end and a distal end, and pivotable about a first pivot axis (A) arranged between the proximal and distal ends; a frame (346) comprising a proximal end and a distal end, wherein the proximal end of the frame is connected to the distal end of the release arm (24, 344) by means of a second pivot axis (B); and a collar (348) directly connected to the distal end of the frame (346) by means of a third pivot axis (C), wherein the third pivot axis (C) is located in the forward direction in front of the second pivot axis (B), wherein the arrangement is such that the movement of the release mechanism from its first position to its second position is caused by pivoting the release arm (24, 344) about the first pivot axis (A), which causes the frame (346) to collar (348) moved relative to the release arm (24, 344),wherein the collar (348) is further connected to the component (352) such that moving the collar (348) causes the blade assembly to move longitudinally in the forward direction, and wherein a spring (350) is attached at one end to the release arm (24, 344) and at the other end to the collar (348) in order to pre-tension the release mechanism to its first position.

Description

Field of the InventionEmbodiments of the present invention described herein relate to an electrosurgical apparatus and, more particularly, to electrosurgical forceps wherein a mechanical blade provides a tissue cutting function in combination with electrosurgical electrodes that provide a tissue coagulation or sealing action.BACKGROUND OF THE INVENTION AND PRIOR ARTElectrosurgical instruments provide advantages over conventional surgical instruments because they can be used to coagulate and seal tissues. Such a prior art arrangement is known from US 2015 / 0 223 870 A1, which describes an endoscopic bipolar forceps comprising a housing and a shaft, the shaft having an electrosurgical end effector at its distal end, which end effector comprises two jaw elements for detecting tissue therebetween. Each jaw member is adapted to be connected to an electrosurgical energy source, thereby permitting sealing of tissue held between the jaw members. A drive assembly is received within the housing for moving the jaw members. A movable handle is also provided such that movement of the handle actuates the actuator assembly to move the jaw members relative to each other. A knife channel is part of the end effector to allow for forward and rearward movement of a blade in the knife channel to in turn allow for cutting tissue.Further arrangements according to the prior art include the following: US 2007 / 0 173 814 A1, US 2012 / 0 241 505 A1, US 2012 / 0 184 990 A1, EP 3 064 163 A1, WO 2016 / 100 650 A1, US 2012 / 0 083 784 A1, U.S. Pat. No. 5,730 740 A, U.S. Pat. No. 5,104,397 A, U.S. Pat. No. 4,800,880 A, WO 98 / 14 124 A1, U.S. Pat. No. 2012 / 0 109 186 A1, U.S. Pat. No. 5,352,235 A, WO 2014 / 074 807 A1, U.S. Pat. No. 7,846,161 B2, WO 2008 / 024 911 A2, U.S. Pat. No. No. 5,776,130 a, U.S. Pat. No. No, U.S. Pat. No. 7,766,910 B2, EP 2 628 459 A2, US 2014 / 0 221 999 A1, U.S. Pat. No. 7,083,618 B2, US 2009 / 0 248 020 A1, US 2015 / 0 209 103 A1, U.S. Pat. No. 5,797,938 A and U.S. Pat. No. 7,101,373 B2.Summary of the InventionEmbodiments of the present invention provide an improved surgical instrument having an end effector attached to the end of an elongate shaft extending from a handle. The end effector is capable of performing a variety of different operations including tissue acquisition, cutting and sealing and / or coagulation, and one of the functions is controlled by a trigger mechanism contained within the handle. In some embodiments, the end effector includes a blade assembly, wherein the triggering mechanism is formed as a three-pivot push crank mechanism arranged to longitudinally drive the blade assembly along a rotatable drive shaft contained within the elongated shaft. As such, the mechanism is configured to drive the blade assembly with sufficient force so that the blade is able to cut tissue without the user having to apply additional force to the trigger. Such an arrangement is particularly advantageous when the blade is used to cut thick tissue.A first aspect provides a surgical instrument whicha handle, andan elongated shaft extending from the handle and defining a forward direction and a rearward direction,an end effector disposed at the distal end of the elongated shaft,a blade assembly within the elongate shaft, the blade assembly having a blade disposed at its distal end, the blade disposed in the region of the end effector, the blade assembly being connected at its proximal end to a component within the handle,a trigger mechanism disposed on the handle and movable between a first position and a second position, wherein moving the trigger mechanism from its first position to its second position causes longitudinal movement of the blade assembly to cause longitudinal movement of the blade relative to the end effector,wherein the triggering mechanism comprises:a trigger arm comprising a proximal end and a distal end and pivotable about a first pivot axis disposed between the proximal and distal ends,a frame having a proximal end and a distal end, the proximal end of the frame being connected to the distal end of the trigger arm by a second pivot axis; anda collar directly connected to the distal end of the frame by means of a third pivot axis, wherein the third pivot axis is located in front of the second pivot axis in the front direction,wherein the arrangement is such that moving the trip mechanism from its first position to its second position is caused by pivoting the trip arm about the first pivot axis causing the frame to move the collar relative to the trip arm, the collar further connected to the component such that moving the collar causes the blade assembly to move longitudinally in the forward direction.By using this three-pivot arrangement, the trigger mechanism is optimized by providing good force translation in the first position, i.e., at the beginning of the movement, when the user's finger is fully extended and not so strong, and also when the trigger approaches its second position where larger forces are likely to need to be overcome. For example, where the drive assembly includes a blade at its distal end, forces due to strong tissue portions may have to be overcome by the triggering mechanism. Further, the end effector may be a pair of curved jaws, and so the trigger mechanism must be capable of pushing the blade along a curved path. As such, the trigger mechanism is capable of driving the blade to effectively cut tissue without the user having to exert a substantial force on the trigger arm.Pivoting the trigger arm may move the proximal end generally in the rearward direction and the distal end generally in the forward direction. As such, pivoting of the trip arm moves the collar generally in the forward direction.In some arrangements, the frame may include a generally H-shaped component, the H-shaped component including first and second elongate side arms with a cross strut therebetween. The distal end of the trigger arm may therefore be disposed between the proximal ends of the first and second side arms. The first and second side arms may each have a bearing at their proximal ends such that the trigger arm is pivotable relative thereto.The trip arm may further include first and second bosses capable of being snapped into the bearings at the proximal end of the first and second side arms.The collar may be disposed between the distal ends of the first and second side arms. The first and second side arms may each have a bearing at their distal end such that the frame is pivotable relative to the collar.The collar may further include first and second bosses capable of being snapped into the bearings at the distal end of the first and second side arms.The elongate shaft defines a central axis, and the third pivot axis is disposed on the central axis, the first and second pivot axes being offset with respect to the central axis, on opposite sides thereof. The second pivot axis may be closer to the central axis when the trip mechanism is in its second position compared to when it is in its first position.According to the invention, the triggering mechanism is biased into its first position. In this regard, a spring is provided, the spring being secured at one end to the trip arm and at the other end to the collar so as to bias the trip mechanism to its first position. To this end, the triggering mechanism is configured to be capable of overcoming the forces due to the spring to move to its second position. Conversely, the spring is strong enough to be able to retract the drive assembly without requiring user intervention. For example, where the drive assembly includes a blade, the spring must be strong enough to retract the blade through strong tissue.The trip arm may further comprise at least one aperture, wherein the spring passes through the at least one aperture before being attached to the trip arm.The spring may be disposed below the central longitudinal axis of the surgical instrument.The third pivot axis can be arranged at the same height as the central longitudinal axis of the surgical instrument.The instrument may further comprise a rotatable rotary wheel arranged on the handle, wherein a rotation of the rotary wheel causes a corresponding rotation of the end effector. This allows the user to change the angle of the end effector, thereby allowing the user to reach different tissue sections within a region without having to rotate the entire instrument.Where the drive assembly is a blade assembly, the end effector may include a pair of jaws having first and second jaw members opposite thereto, the blade being longitudinally movable therebetween. The first and second jaw members may be curved to form a curved path.To assist the triggering mechanism in pushing the blade about the curved path, the blade may be formed of at least two regions, the first region having a lateral flexibility greater than that of the second region, the first region being disposed distal from the second region. By making the blade progressively more flexible toward the distal end, this helps counteract the frictional forces acting on the blade, so that it is easier for the blade to follow the curved path between the jaws. Another way to help the blade around the curved path may be to coat at least a portion of the blade with a low friction coating.The surgical instrument may also include a drive shaft, the drive shaft being connected at its distal end to the end effector and at its proximal end to an actuation mechanism, the actuation mechanism being movable between a first position and a second position to effect longitudinal movement of the drive shaft, the longitudinal movement of the drive shaft causing at least one of the jaw members to move relative to the other from a first open position, in which the jaws are disposed in spaced relationship relative to each other, to a second closed position, in which the jaws cooperate to grasp tissue therebetween.The drive shaft may include an elongated slot to receive the blade assembly, wherein moving the trip mechanism from its first position to its second position causes the blade to advance longitudinally along the elongated slot and between the first and second jaws.In some arrangements, the end effector may comprise one or more electrodes, and the instrument comprises electrical connections suitable for connecting the instrument to an electrosurgical generator.Also, another aspect provides a surgical instrument thata handle, andan elongated shaft extending from the handle,an end effector disposed at the distal end of the elongated shaft,a drive assembly within the elongate shaft, the distal end of the drive assembly being disposed in the region of the end effector, the drive assembly being connected at its proximal end to a trigger mechanism disposed on the handle, the trigger mechanism being movable between a first position and a second position, wherein moving the trigger mechanism from its first position to its second position causes longitudinal movement of the drive assembly to cause the end effector to move over a range of movement from an initial position to an end position,wherein the triggering mechanism is further arranged such that for a constant force applied to the triggering mechanism, the force applied by the end effector changes in a non-monotone manner over its range of motion.As noted above, with such an arrangement, the force profile of the end effector can be optimized over its range of motion. For example, if the end effector is a blade, more force is needed at the beginning of the cut to overcome the elasticity of the tissue and to begin the cut than is needed at the middle of the cut. However, more force is again required at the end of the cut, as tissue may accumulate and thus represents a denser array of tissue that requires more force for cutting. Thus, for example, the arrangement may be such that, with a constant force applied to the trigger mechanism, the force applied by the end effector decreases as the end effector moves over a first portion of its range of motion and then increases over a second portion of its range of motion.With respect to the accurate force profile, the rate of decreasing the force applied by the end effector over the first portion of the range of motion of the end effector may decrease. Accordingly, the rate of increase of the force applied by the end effector over the second part of the range of movement of the end effector may increase. Such an arrangement yields a curved force profile over the range of movement of the end effector, which has been found to be particularly effective.Brief Description of the DrawingsEmbodiments of the invention will now be described further, by way of example only, and with reference to the accompanying drawings, wherein like reference numerals in the drawings refer to like parts, and wherein: FIG. 1 is a side view of an electrosurgical instrument according to an embodiment of the present invention; FIG. 2 is a side view of a handle of the electrosurgical instrument according to the embodiment of the present invention; FIG. 3 is an exploded view of an electrosurgical instrument according to the embodiment of the present invention; FIG. 4 is a cross-sectional view of the clamping mechanism of the electrosurgical instrument of FIG. 3 in an open configuration; FIG. 5 ashows a cross-sectional view of the clamping mechanism of the electrosurgical instrument from FIG. 3 in a closed arrangement; FIG. 5 bshows a cross-sectional view of the clamping mechanism of the electrosurgical instrument from FIG. 3 in a closed arrangement with tissue clamped therein; FIG. 6 is a cross-sectional view of a portion of the clamping mechanism of the electrosurgical instrument of FIG. 3 ; FIG. 7 is a perspective view of the clamping mechanism of the electrosurgical instrument of FIG. 3 ; FIGS. 8 a- f show the assembly of a portion of the electrosurgical instrument of FIG. 3 ; FIGS. 9 a- bare cross-sectional views of a portion of the electrosurgical instrument of FIG. 3 ; FIGS. 10a-c show a blade guide portion of the electrosurgical instrument of FIG. 3; FIG. 11 shows a snap-in part of the electrosurgical instrument from FIG. 3 ; FIG. 12 shows a blade angle alignment portion of the electrosurgical instrument of FIG. 3 ; FIGS. 13 a- b show cross-sectional views of the blade angle alignment portion of the electrosurgical instrument of FIG. 3 ; FIGS. 14a-b show a blade angle steering wheel portion of the electrosurgical instrument of FIG. 3; FIGS. 15 a- b show the rotational movement of the blade angle control wheel of the electrosurgical instrument of FIG. 3 ; FIGS. 16 a- d show the rotational movement of the end effector of the electrosurgical instrument from FIG. 3 ; FIG. 17 shows a cross-sectional view of the electrosurgical instrument of FIG. 3 and illustrates a wiring path; FIGS. 18 a- b show details of an electrical wiring path used in the electrosurgical instrument of FIG. 3 ; FIG. 19 shows further details of an electrical wiring path used in the electrosurgical instrument of FIG. 3 ; FIGS. 20 a- bare side views of a portion of the cutting mechanism of the electrosurgical instrument of FIG. 3 ; FIG. 21 is a cross-sectional view of a portion of the cutting mechanism of the electrosurgical instrument of FIG. 3 ; FIG. 22 is a cross-sectional view of another portion of the cutting mechanism of the electrosurgical instrument of FIG. 3 ; FIG. 23 is a partially transparent perspective view of the cutting mechanism of the electrosurgical instrument of FIG. 3 ; FIGS. 24a-c show the assembly of a portion of the cutting mechanism of the electrosurgical instrument of FIG. 3; FIGS. 25 a- c show cross-sectional views of the cutting mechanism and clamping mechanism of the electrosurgical instrument of FIG. 3 ; FIGS. 26a-f are cross-sectional views illustrating operation of the locking mechanism of the electrosurgical instrument of FIG. 3; FIG. 27 is a diagram illustrating the cutting mechanism of the electrosurgical instrument of FIG. 3 ; FIGS. 28a-b are line drawings illustrating the cutting mechanism of the electrosurgical instrument of FIG. 3; FIGS. 29a-b show a blade angle alignment portion of the electrosurgical instrument of FIG. 3; FIG. 30 is a perspective view of a portion of the clamping mechanism of the electrosurgical instrument of FIG. 3 ; FIG. 31 is a partial cross-sectional view of the cutting mechanism and clamping mechanism of the electrosurgical instrument of FIG. 3 ; FIG. 32 is a partial cross-sectional view of the cutting mechanism and clamping mechanism of the electrosurgical instrument of FIG. 3 ; FIG. 33 shows the blade angle control wheel member and electrode control switch of the electrosurgical instrument of FIG. 3; FIG. 34 shows the blade angle steering wheel portion of the electrosurgical instrument of FIG. 3 ; FIGS. 35 a- b show the handle of the electrosurgical instrument of FIG. held by users with different hands; FIGS. 36 a- c show the rotational movement of the end effector of the electrosurgical instrument from FIG. 3 ; FIG. 37 shows the rotational movement of the blade angle control wheel of the electrosurgical instrument of FIG. 3 ; FIG. 38 is a schematic perspective view of an example of an end effector; FIG. 39 is an enlarged perspective view of a portion of the end effector of FIG. 38 ; FIG. 40 is a schematic cross-sectional view of a portion of the end effector of FIG. 38 ; FIG. 41 is a schematic perspective view of an alternative end effector; FIG. 42 is an enlarged perspective view of a portion of the end effector of FIG. 41 , FIG. 43 is a schematic cross-sectional view of a portion of the end effector of FIG. 41 , FIG. 44 is a schematic cross-sectional view of a portion of another alternative end effector; FIG. 45 is an illustration of an electrosurgical system including a generator and an instrument according to embodiments of the invention; FIG. 46 further shows a snap-in part of the electrosurgical instrument from FIG. 3 ; and Figures 47a-e illustrate the distal end of the blade used in the electrosurgical instrument of Figure 3.DESCRIPTION OF THE EMBODIMENTSAn embodiment of the invention will now be described. First, a brief overview of the entire embodiment is provided, followed by detailed descriptions of certain aspects thereof.1. Overview of the Construction of the InstrumentFig. 1 shows an electrosurgical instrument 1 according to an example of the present invention. The instrument 1 includes a proximal handle 10, an outer shaft 12 extending in a distal direction away from the proximal handle 10, and a distal end effector 14 attached to a distal end of the outer shaft 12. End effector 14 may be, for example, a set of opposing jaws arranged to open and close and comprising one or more electrodes disposed on or formed by their opposing inner surfaces and having, in use, ports for receiving a radio frequency (RF) electrosurgical signal for sealing or coagulating tissue. The jaws 14 are further provided with a slot or other opening in the opposed inner surfaces through which a mechanical blade or the like may protrude upon activation by the user. In use, the handle 10 is activated by the user in a first manner to clamp tissue between the jaws 14 and in a second manner to supply RF current to the electrodes to coagulate the tissue. The clamping jaws 14 may be curved so that the active elements of the instrument 1 are always visible. This is important in vessel sealing devices used to operate on body regions that make the user's view of the device difficult during use. The handle 10 may be activated by the user in a third manner to cause the blade to protrude between the jaws 14, thereby cutting tissue pinched therebetween. Upon completion of the required cutting and sealing, the user can release the tissue from the jaws 14.As shown in Figure 2, the handle 10 includes a housing 20 of two shell moldings 300, 302 which accommodates all the components required for the actuation and rotation of the clamping jaws 14, the coagulation and cutting of tissue. The shell moldings in the joined device are ultrasonically welded after the internal components are arranged inside them. The handle 10 includes a clamping handle 22 for clamping tissue between the jaws 14, a trigger 24 for cutting tissue, a switch 26 for activating and deactivating the RF supply of electrodes in the jaws 14 for coagulation of tissue, and a rotary wheel 28 for rotating the jaws 14 for reaching tissue at different angles. The handle 10 is constructed such that the instrument 1 and all its functions can be operated with only one hand, all operating mechanisms being easily accessible.Figure 3 shows all the features of instrument 1 required to perform its functions, including those housed in the two shell mould parts 300, 302 of the housing 20. To clamp tissue between the jaws 14, a clamping mechanism is actuated using the clamping handle 22. The clamping handle 22 further includes a collar 304 that includes a hinge 306 that acts as a pivot about which the clamping handle 22 rotates. The hinge 306 may be, for example, two outwardly directed pins that snap into corresponding mold portions 308 integrally formed with the shell mold portions 300, 302 so as to provide an anchor point about which the clamping handle 22 rotates. The clamping mechanism further includes a collar ring molding 310, a spring 312, and an inner molding 314 as illustrated in FIGS. 4-7, all of which are aligned along a drive shaft 316.The collar ring 304 comprises a through-opening 318, in which the collar ring molded part 310 is received. The opening 318 has a larger diameter at the top than at the bottom, wherein the collar ring molding part 310 is arranged to be received in the lower part of the opening 318, as FIG. 8 a illustrates. When assembled, the collar ring molding 310 fits easily through the larger portion of the opening 318 such that the collar ring 304 is received between two flanges 800, 802, as shown in FIGS. 8 b- c. As can be seen from Figure 8d, the collar ring 304 is then forced upwardly to engage the smaller portion of the through hole 318 with the collar ring molding 310. When the hinge 306 is connected to the hinge mouldings 308 within the housing 20, the collar moulding 310 is retained in the lower part of the opening 318 where it can freely rotate within the opening 318.As shown in FIG. 6, the collar ring molding 310, the spring 312, and the inner molding 314 are held between protruding members 600, 602 so as not to be able to axially move beyond these protruding members 600, 602. In this regard, the protruding members 602 on the proximal end of the drive shaft 316 are compressible to allow the drive shaft 316 to pass through a channel 604 in the proximal end of the inner mold part 314. The drive shaft 316 is slid through the channel 604 until it reaches an opening 606, the protruding elements 602 then no longer being compressed so that they bear flush against the walls of the drive shaft 316. Instead, the protruding elements 602 are fanned out and press against the walls of the opening 606 such that the width of the protruding elements 602 extends beyond the diameter of the channel 604. Consequently, the drive shaft 316 cannot be retracted through the channel 604 and is locked in place.The distance between the protruding elements 600, 602 is selected such that the spring 312 is at least partially compressed between the collar ring molding part 310 and the inner molding part 314. This precompressing is essential to ensure that the proper clamping load is applied when the clamping mechanism is activated, as will be described in more detail below. Both the collar ring molding 310 and the inner molding 314 include cavities 608, 610 into which the spring 312 extends. In particular, a substantial portion of the length of the collar ring molding 310 receives the spring 312. This arrangement allows a longer spring 312 which is important to ensure that the spring 312 never reaches its block length during use.The main body of the drive shaft 316 lies within the outer shaft 12, with the distal end of the drive shaft 316 being connected to both the distal end of the outer shaft 12 and the jaws 14. The drive shaft 316 moves axially within the outer shaft 12 and this axial movement moves the jaws 14 from an open to a closed position, as shown in Figures 4 and 5a. The drive shaft 316 is coupled to the jaws 14 by, for example, a drive pin 400 in a cam slot 402, wherein movement of the drive pin 400 in the cam slot 402 moves the jaws 14 between the open and closed positions. The connection between the drive shaft 316, the outer shaft 12 and the clamping jaws 14 is effected such that a rotational movement of the drive shaft 316 is transmitted to the outer shaft 12 and the clamping jaws 14.The outer shaft 12 and the drive shaft 316 are connected at another point by a shaft molding 320. The shaft molding 320 is received in a socket 322 of the housing 20 and thus connects the outer shaft 12 to the housing 20. the outer shaft 12 is secured to the shaft molding 320 by any suitable means, such as by snap projections 900 that cooperate with corresponding grooves 902 in the shaft molding 320, as shown in FIG. 9 b. The drive shaft 316 is passed through the body of the shaft molding 320 through an opening (not shown) that fits the T-shaped cross-section of the drive shaft 316, as illustrated by FIG. 10a. The shaft forming part 320 is arranged so as to be free to rotate in the socket 322. The shaft molding 320 may include, for example, cylindrical flange members 904, 906 that rotate in concentric mating surfaces 908, 910 provided in the shell molding 300, 302. Thus, the shaft molding 320 rotates with the drive shaft 316, which in turn transmits this rotational movement to the outer shaft 12 and the jaws 14. The shaft molding 320 thus functions as a rotational guide and an axial guide for the drive shaft 316.The clamping handle 22 includes a latch member 324 arranged to cooperate with a latch molding 326 provided in the proximal end 328 of the housing 20. The snap-in molding 326 may be held in place by any suitable means, such as a molding pin 330 integrally formed with one of the shell molding portions 300, 302 as shown in FIG. 3, or simply by the molding walls 1100 integrally formed with the shell molding portion 300 as shown in FIG. 11.When the clamping handle 22 is pushed toward the housing 20 to close the jaws 14, the latch 324 enters the housing 20 via an opening 1102 and engages the latch molding 326 to hold the clamping handle 22 in this position. As seen in Figs. 26a-26f, the latch molding 326 includes a two-way spring 1104 and a cam path 1106 along which the latch member 324 moves. As shown in FIG. 46, the latch mechanism may also include an override component 4600 to allow the user to manually release the latch member 324 when it hangs up and a locking component 4602 to fully deactivate the latch mechanism. The override component 4600 and the locking component 4602 may be provided on the snap-fit part 326 or integrated into the interior of the housing 20.As described above, the handle 10 further comprises a rotary wheel 28, the rotary wheel 28 being arranged to grip the inner molding 314. To this end, the rotary wheel 28 and the inner mold part 314 have interengaging elements 1200, 1202, as can be seen from Figure 12. These interengaging members 1200, 1202 connect together such that the rotary wheel 28 and the inner mould part 314 rotate together, further allowing axial movement of the inner mould part 314 within the rotary wheel 28, as can be seen from Figures 13a-b. Thus, rotation of the rotary wheel 28 causes rotation of the inner die 314, thus rotating the drive shaft 316 and collar die 310. For stability purposes, the rotary wheel 28 includes cylindrical surfaces 1204 that rotatably slide on inner mating surfaces (not shown) integrally formed with respect to the shell mold portions 300, 302.To allow a user to rotate the jaws 14, the housing 20 has two apertures 332, 334 through which notched portions 336 of the rotary wheel 28 extend. The two openings 332, 334 are opposite each other on both sides of the handle and are trapezoidal. In particular, the trapezoidal apertures have parallel sides which are at right angles to the longitudinal axis of the handle, and one of the parallel sides may be longer than the other, the longer side being at the front end of the aperture and the shorter side at the rear end of the aperture. The notched portions 336 are appropriately chamfered to fit well with the thumb or fingers of the user. To do so, the notched portions 336 are cut at an angle to the plane of rotation as shown in Figures 14a-b. In particular, the angle of the beveled portion of the notched portions should substantially match the angle of the outer housing adjacent the rotary wheel 28.The rotary wheel 28 also comprises at least one stop element 1500 for limiting the degree of rotation, as is illustrated in FIGS. 15 a- b. The stopper member 1500 interacts with stopper members 1502, 1504 formed integrally with the housing 20. When the rotary wheel 28 is rotated, the stopper member 1500 is blocked by the stopper members 1502, 1504, thereby preventing further rotation. For example, the stop members 1502, 1504 may limit the rotation of the rotary wheel to 270°. Similarly, the shaft molding 320 also includes a stop member 1600 that interacts with stop members 1602, 1604 formed integrally with the housing 20, as seen in FIGS. 16 a-d. The stop member 1600 of the shaft molding 320 and its corresponding stop member 1602, 1604 are aligned with respect to the stop member 1500 of the rotary wheel 28 and its corresponding stop members 1502, 1504 such that rotation is restricted to the same extent. This means that, when the rotary wheel 28 is rotated, the radial point at which the stop element 1500 is blocked on the rotary wheel 28 corresponds to the radial point at which the stop element 1600 is blocked on the shaft molding 320. In FIGS. 15 band 16 a, the clamping jaws 14 have been rotated counterclockwise by 90°, for example, from a neutral orientation (which is illustrated in FIG. 16 b). This freedom of rotation means that the user can grasp tissue from different angles without having to rotate the entire instrument 1.As described above, the switch 26 is provided to enable or disable the RF signal supplied to the electrodes in the jaws 14 via suitable circuitry, such as two intrusion protected switches on a small printed circuit board (PCB) 338. As shown in Figure 17, the PCB 338 is connected to a connecting cable 1700 for receiving the RF output signal from a generator (not shown) and electrical leads 1702, 1704 for supplying the RF current to the electrodes in the jaws 14, such as an active electrode lead and a counter electrode lead. As shown in FIGS. 17 and 18 ab, the conduits 1702, 1704 are wound below and around the shaft molding 320 before entering a guide slot 1800 in the interior cavity 1802 of the shaft molding 320 and descending the outer shaft 12. Wrapping the shaft molding 320 with the conduits 1702, 1704 in this manner maintains the conduits 1702, 1704 in a compact arrangement to allow easy assembly and, at the same time, rotation of the drive shaft 316. At this time, the wires 1702, 1704 are unwound and rewound with the rotation of the drive shaft 316. In addition, one of the shell mold parts 300 also includes two molded compartments 1900, 1902 arranged in sequence to receive the line contacts 1904, 1906 connecting the active lines and return lines 1702, 1704 to the cabling 1908, 1910 of the intrusion-protected switches 338. The opposing shell molding 302 includes corresponding rib portions (not shown) to retain the contacts 1904, 1906 in the compartments 1900, 1902. Thus, the two line contacts 1904, 1906 are longitudinally separated such that only one contact can pass through each compartment 1900, 1902, thereby providing a physical barrier between each compartment 1904, 1906 and each line. This prevents the risk of damage to the insulation on one of the leads caused by the contacts 1904, 1906, and at the same time the contacts 1904, 1906 themselves are protected from fluids which can travel along the outer shaft 12 and into the housing 20.Referring to the cutting mechanism, a blade 340 for cutting tissue pinched between the jaws 14 is provided in a central path 342 along the length of the drive shaft 316. The mechanism for actuating the blade 340 along the path 342 and between the jaws 14 is actuated via the trigger 24. The trigger 24 actuates a drive assembly consisting of a trigger molding 344, a blade drive molding 346, a blade collar ring molding 348, a tension spring 350, and a blade molding 352. The drive assembly is disposed between the shaft molding 320 and the handle collar 304 of the clamping mechanism. As shown in Figures 20a-b, the drive assembly functions as an offset crank push mechanism, converting the user applied force on the trigger 24 into axial movement of the blade molding 352 along the drive shaft 316, which in turn drives the attached blade 340.As seen in FIGS. 21, 22, and 23, the blade molding 352 is arranged to be received in the blade collar ring molding 348. As shown in Figure 22, the blade collar ring molding 348 includes a lip rim 2200 that engages a recess 2202 that extends around the perimeter of the blade molding 352. As shown in Fig. 23, the blade molding 352 has a T-shaped opening 2300 for receiving the drive shaft 316 and the blade 340. The blade molding 352 further includes an internal cutout 2100, as shown in Figure 21, for the proximal end of the blade 340, the end of the blade 2102 being shaped to mate with the internal cutout 2100 of the blade molding 352 to allow for ease of assembly, as illustrated in Figures 24a-c. The blade molding 352 is independently rotatable relative to the blade collar ring molding 348 such that the two molding may rotate concentrically. Consequently, the blade molding 352 is capable of rotating with the drive shaft 316.The jaws 14 may be curved as described above. In order to allow the blade 340 to be slid around the curve while maintaining sufficient cutting ability, the frictional force of the blade 340 in the curved path must be minimized. The frictional force is a product of the coefficient of friction of the blade 340 in the web 342 and the force applied to the walls of the web 342 by the bending of the blade 340. This frictional force may be reduced, for example, by adding a friction reducing coating on both sides of the blade and / or, preferably, weakening the blade 340 to grade the flexibility of the distal end of the blade so that it may flex along the path 342 while remaining rigid in the direction of cutting force. The preferred weakening may be accomplished, for example, by providing one or more apertures 354 in the distal end as shown in Figures 3 and 47a-c, or by grading the thickness of the blade 340 as shown in Figure 47d. Alternatively, as shown in Figure 47e, patterned laser cut-outs 4712 or chemical etching could be used in the distal end to adjust flexural rigidity along the blade length, where the spacings of such cut-outs may be constant or may increase stepwise from the distal to proximal end.In use, blood and tissue may accumulate in the distal end of the instrument 1. In particular, blood and tissue may cause the blade 340 to stick inside the drive shaft 316. Therefore, the distal end of the drive shaft 316 may include cut-out portions 1000 to reduce the surface area of the drive shaft 316 to which blood and tissue may adhere, as shown in Figures 10b-c. The cut-out portions may be, for example, such that the distal end includes two side walls without a base or the distal end includes a base with bifurcated side walls.2. Operation of the instrumentHaving described the overall construction of the apparatus, the overall operation of electrosurgical instruments 1 in the application will now be explained. The following is a further detailed description of the structure and operation of certain aspects of the apparatus.As discussed above, the handle 10 of the electrosurgical instrument is arranged to i) clamp tissue between a set of jaws 14, ii) lock the jaws in place (if the user desires), iii) provide an RF signal to electrodes in the jaws 14 to coagulate tissue clamped therebetween, and iv) move a blade 340 between the jaws 14 to cut tissue clamped therebetween. The handle 10 may also rotate the jaws 14 to allow the user to clamp tissue at various angles without having to rotate the entire handle 10. As a result, tissue clamped between the jaws can be sealed using the same electrosurgical instrument before or while it is being cut. Moreover, this effect can be achieved by the instrument upon one-handed operation by the surgeon.2.1 Clamping MechanismTo clamp tissue between the jaws 14, the user pushes the clamping handle 22 toward the proximal end 328 of the housing 20 until the latch member 324 engages the latch molding 326 within the housing 20. This movement causes drive handle 22 to pivot about its hinge 306, as shown in Figs. 8e-f, and pushes the rim of collar ring 304 against flange 800 to displace collar ring molding 310, spring 312, and inner molding 314 along drive shaft 316 in the proximal direction, as shown in Figs. 4 and 5a. As described above, the inner mold 314 is fixed to the drive shaft 316 by means of protruding members 602. Thus, as the inner mold portion 314 is axially retracted, the drive shaft 316 is also moved axially, thereby moving the pin 400 into the cam slot 402 of the jaws 14, thereby closing the jaws 14. Thus, the force from the drive handle 22 is transmitted to the drive shaft 316 via the spring mechanism of the collar ring molding 310, spring 312 and inner molding 314.When tissue is pinched between the jaws 14, as shown in Figure 5b, the spring 312 acts to limit the force acting on the tissue. Once the axial movement of collar ring molding 310, spring 312 and inner molding 314 has ended and collar ring 304 continues to press against flange 800, the threshold compressive force of spring 312 is eventually reached such that spring 312 begins to compress between collar ring molding 310 and inner molding 314. As the spring 312 continues to compress, the drive handle 22 can be moved to the engaged position without applying even further force to the pinched tissue. That is, the force of the drive handle 22 is no longer transmitted to the drive shaft 316, but is effectively absorbed by the spring 312. Thus, the spring 312 ensures that the proper amount of force is transmitted to the jaws 14. Without spring 312, actuation of drive handle 22 causes a continued increase in the force transmitted to drive shaft 316 and, in turn, to jaws 14 and tissue. This could cause mechanical damage to the tissue as the user continues to push the drive handle 22 to engage it with the latch member 324.As discussed above, the cavities 608, 610 in the collar ring molding 310 and the inner molding 314 cooperate to allow for the provision of a larger spring 312. This allows for a greater spring stroke so that the spring 312 is not compressed to its rebound length during use. When the spring 312 reaches its retraction length, it would no longer absorb the force exerted by the drive handle 22, and the force would be transferred again to the jaws 14.2.2 Latching MechanismWhen tissue is pinched between the jaws 14, the jaws 14 can be locked in a closed position by engaging the latch member 324 on the drive handle with the latch molding 326 inside the housing 20, as shown in Figures 26a-f. As the latch 324 enters the housing 20 through the opening 1102, the latch 324 engages the latch moulding 326, pushing the moulding 326 down the housing 20 and thereby extending the spring 1104. As shown in Figs. 26b-c, the latch member 324 on the side of the cam path 1106 moves upward until it reaches its maximum position. At this point, the drive handle 22 cannot be further compressed, and the spring 1104 pulls the latch molding 326 inside the housing 20 upward again, such that the latch member 324 is inserted into the V-shaped compartment of the cam path 1106 to maintain the drive handle 22 in the compressed position and the jaws 14 in the closed position, as shown in FIG. 26 d.In this locked position, the user's hand is free to manipulate the other functions of the instrument 1, as will be explained below.To release the latch 324 from the housing 20 and open the jaws 14, the user must push the drive handle 22 toward the housing 20 to disengage the latch 324 from the pocket of the cam path 1106, as shown in Figure 26e. The force of spring 1104 continues to pull latch molding 326 up into housing 20 such that latch member 324 moves down in the opposite direction on the side of cam path 1106, as shown in Figs. 26e-f, and back out of aperture 1102. The snap-in molded part 326 then returns to its initial position inside the housing 20.2.3 Cutting MechanismWhen the jaws 14 are in a closed position, the user may wish to cut the tissue clamped therebetween. To cut the tissue, a blade 340 is advanced between the jaws 14 by actuation of the drive assembly.The drive assembly is a three pivot point assembly that functions as a push crank mechanism. As the user retracts the trigger 24 toward the housing 20, as shown in FIGS. 25 b- c, the trigger molding 344 is levered about a pivot point A that is anchored to the housing 20, such as in the form of outwardly facing pins 358 that are associated with corresponding molding 356 integrally formed with the shell molding 300, 302 of FIG. 3. This pushes the pivot point B connecting the trigger molding 344 and the drive molding 346 over its central position, thereby displacing the blade collar ring 348, the blade molding 352 and the blade 340 along the drive shaft 316 with a force sufficient for the blade 340 to cut the pinched tissue. In this connection, the force applied to the trigger 24 is transmitted to the blade collar 348 and the blade molding 352 via the trigger molding 344 and the drive molding 346. As pivot point B moves beyond the midpoint to its advanced position, the speed at which blade collar 348 and blade molding 352 are displaced along drive shaft 316 increases, thereby increasing the force acting on blade 340. Thus, the force with which the blade 340 cuts into the tissue increases without the user exerting additional force on the trigger 24.The shaft molding 320 functions as a stopping point for the blade collar ring 348 and the blade molding 352. Consequently, the pivot point B with respect to the drive shaft 316 always remains above the other two pivot points A, C.During actuation of the trigger 24, the force applied to the trigger 24 is sufficiently high to overcome the compressive force of the tension spring 350 to extend along the same plane as the drive shaft 316 to allow axial movement of the blade collar ring 348 and the blade molding 352. Upon release of the trigger 24, the tension spring 350 is compressed again to retract the drive assembly to its initial position. The tension of the tension spring 350 is sufficiently strong to retract the blade 340 through thick tissue without the need for the user to intervene.2.4 Shaft rotationDuring use, the user may have to access tissues from different angles without having to move the entire instrument 1. For this reason, the clamping jaws 14 are advantageously rotatable with respect to the handle 10 by the rotation wheel 28. This is particularly advantageous when the clamping jaws 14 are present on a curved path, as shown in Figs. 16a-d. As discussed above, the rotary wheel 28 is connected to the inner mold part 314 via intermeshing members 1200, 1202 such that the inner mold part 314 rotates with the rotary wheel 28. Because the end of the drive shaft 316 is connected to the inner die 314, the drive shaft 316 also rotates, thus also rotating the jaws 14 at their opposite end.To enable this rotational movement without compromising the function of the clamping mechanism, the collar ring molding 310 is independently rotatable within the handle collar 304, such that the collar ring molding 310 also rotates with the drive shaft 316. Similarly, the blade molding 352 is independently rotatable in the blade collar ring 348 to allow rotation of the drive shaft 316 without compromising the function of the cutting mechanism.For transmitting the rotational movement to the outer shaft 12, the shaft molding part 320 is rotatable in its mount 322. As described above, the shaft molding 320 functions as a rotation guide for controlling rotational movement with respect to the drive shaft 316 along the entire length of the instrument 1. in addition, the active lines and return lines 1702, 1704 are disposed within the housing 20 to prevent damage to these lines 1702, 1704 by the rotating components. As described above, the conduits 1702, 1704 are wound around the shaft molding 320 to allow the degree of rotation of the drive shaft 316. As a result, the wires 1702, 1704 are unwound and rewound around the shaft molding 320 as it rotates.2.5 Electrode ActivationWhen the jaws 14 are in a closed position, the user may wish to coagulate and seal the tissue clamped therebetween. To this end, the user initiates electrode activation using switch 26 on housing 20 which is suitably arranged so that the user can easily access switch 26 during which the device is operating with one hand. This provides an RF signal to the electrodes in the jaws 14 to coagulate and seal the tissue. The RF signal may have a clean or mixed waveform depending on the desired effect.Having reviewed the structure and operation of the entire apparatus, further detailed descriptions of the structure and operation of certain aspects thereof will now follow.3. Construction and Operation of Clamping MechanismAs described above, the proximal handle 10 of the electrosurgical instrument 1 includes a first mechanism for actuating an aspect of a distal end effector 14 such that the end effector 14 switches between first and second states. End effector 14 may be, for example, a set of opposing jaws 14 arranged to be opened and closed. The mechanism used to initiate movement of these jaws 14 is the so-called clamping mechanism, which comprises a drive handle 22 and two barrel shaped mould parts 310, 314 with a spring 312 compressed therebetween, all elements being lined up along an elongate rod 316 extending between the jaws 14 and the handle 10, as shown in Figures 4 and 5a-b.As can be seen from FIG. 8 a, the drive handle 22 comprises a collar ring 304 in which the collar ring molded part 310 is accommodated. Collar 304 includes an opening 318 shaped like a keyhole or number 8. The opening 318 consists of two openings 804, 806 adjacent to each other, wherein the upper opening 804 has a larger diameter than the lower opening 806.The collar ring molding 310 is a cylinder- or barrel-shaped component having two flange portions 800, 802 spaced longitudinally. The diameter of the proximal flange 800 is larger than that of the upper and lower openings 804, 806. The diameter of the distal flange 802 is smaller than the upper opening 804 but larger than the lower opening 806.During assembly, the collar ring molding 310 is first inserted through the upper opening 804, as shown in FIGS. 8 b- c. Because distal flange 802 is smaller than upper opening 804, it easily passes therethrough, while proximal flange 800 is large enough to prevent collar ring molding 310 from being fully advanced through upper opening 804. As seen in Figure 8d, collar ring 304 is then slid upwardly to engage lower aperture 806 with collar ring molding 310.After assembly, the collar ring molding 310 remains within the lower opening 806 of the collar ring 304 and is positioned with its two flanges 800, 802 on either side of the collar ring 304, as shown in FIG. 8e. Because the lower opening 806 is smaller in diameter than both flanges 800, 802, the collar molding 310 cannot be removed simply by sliding it through the lower opening 806. In contrast, the body of the collar ring molding 310 between the two flanges 800, 802 has a slightly smaller diameter than the lower opening 806. Thus, the collar ring molding 310 is received sufficiently loosely in the lower opening 808 to allow rotational movement.As can be seen from FIG. 8 e, the distance in the longitudinal direction between the two flanges 800, 802 is only slightly greater than the thickness of the collar ring 304, so that it is received in a precisely fitting manner between the flanges 800, 802. This ensures that the movement of the drive handle 22 is transmitted directly to the collar ring molding part 310 and subsequently to the other components of the clamping mechanism. This is particularly important to ensure that the jaws 14 are responsive to movement of the drive handle 22 and that there is no delayed response between actuation of the drive handle 22 and movement of the jaws 14.When the collar ring molding 310 and the drive handle 22 are assembled, the remaining components may be assembled.The drive shaft 316 is an elongated rod having one or more protruding members 602 disposed at the proximal end thereof, as shown in Fig. 6. The protruding members 602 are flexible protrusions that are fanned out from the surface of the drive shaft 316. That is, the protruding members 602 are deformable so that they can be pressed flush on the surface of the drive shaft 316, but return to their original position when released from a reaction force. This allows for easy passage of the drive shaft 316 through all of the components of the clamping mechanism during assembly, as described below.The collar ring molding part 310 has an inner cavity divided into two parts. The first part is a narrow channel or slot 607 for receiving the drive shaft 316, the distal end of the collar ring molding 310 including an opening 311, as shown in Figure 3, which matches the T-shaped cross section of the drive shaft 316. The diameter of the channel 607 is only slightly wider than that of the drive shaft 316 to provide a tight fit for better stability. Upon insertion of the drive shaft 316, the protruding members 602 are pressed flat to allow the drive shaft to be slid completely therethrough.The second portion is a chamber 608 large enough to receive one end of the spring 312. The chamber 608 can extend over any suitable portion of the length of the collar ring molding 310. The length of the chamber 608 can be, for example, about 25% of the length of the collar ring molding part 310 up to 75% of the length of the collar ring molding part 310.The chamber 608 is substantially larger than the collar ring molding channel 607 so that the drive shaft 316 is slid through the collar ring molding 310, the protruding elements 602 again extend outward to their original structure when they reach the chamber 608.The collar ring molding 310 and drive handle 22 assembly is slid along the drive shaft 316 until the collar ring molding 310 reaches a second set of protruding members 600. These protruding members 600 have a greater width than the opening 311 on the collar ring molding 310 to form an obstacle that prevents the collar ring molding 310 from moving further along the drive shaft 316. To this end, the protruding elements 600 must be sufficiently rigid so that the collar ring molding 310 cannot be slid past the protruding elements 600 by the application of force or inward pressing of the same.The drive shaft 316 is then slid through the center of the spring 312. Spring 312 preferably has a diameter only slightly larger than that of drive shaft 312 so as to provide a tighter fit between spring 312 and drive shaft 316. The spring 312 is then slid along the drive shaft 316 until the end of the spring 312 fills the collar annulus 608.The inner mold part 314 is a cylinder- or barrel-shaped component with an interior cavity divided into two sections. The first portion is a chamber 610 in which an end of the spring 312 is received such that the spring 312 is partially enclosed by the collar ring molding 310 and the inner molding 314. The second portion is a narrow channel or slot 603 for receiving the proximal end of the drive shaft 316. The channel 603 is divided into two parts 604, 606. The first portion of the channel 604 is shaped to allow the drive shaft 316 to pass therethrough, thereby pressing the flexible extensions 602 flat. To this end, the diameter of the first channel portion 604 is only slightly larger than that of the drive shaft 316 to provide a tight fit. The tight fit of the drive shaft 316 in both the collar ring molding channel 607 and the channel 603 of the inner molding means that the drive shaft 316 is held firmly in place. This increases the stability of the drive shaft 316 in the housing 20, which is essential in particular for ensuring maximum control of the end effector 14.The second part of the channel 606 provides a shoulder 605 into which the protruding elements 602 may extend. Consequently, when the drive shaft 316 passes through the channel 604 and enters the second channel portion 606, the flattened protruding members 602 fan back to their original uncompressed position. After the protruding members 602 are engaged with the shoulder 605 of the second channel part 606, the drive shaft 316 cannot be retracted through the first channel part 604 and is thus held in the inner molding 314. For this purpose, the diameter of the second channel part 606 must be sufficiently wide so that the protruding elements 602 extend beyond the diameter of the first channel part 604. To make this snap-fit connection, a protruding element 602 is required only on one side of the drive shaft 316.This snap-fit connection is configured such that any axial movement of the inner molded part 314 is transmitted to the drive shaft 316. Similarly, any rotational movement of the inner mold part 314, for example, by the rotary gear 28 formed around the inner mold part 314, is also transmitted to the drive shaft 316.To complete the assembly of the clamping mechanism, the drive shaft 316 is simply slid through the collar ring molding 310, the spring 312, and finally the inner molding 314 until the protruding elements 602 snap into the second channel portion 606.After being disposed along the drive shaft 316, the collar ring molding 310, the spring 312, and the inner molding 314 are disposed such that the spring 312 is partially enclosed by the collar ring molding 310 and the inner molding 314. By providing the collar ring mold portion chamber 608 and the inner mold portion chamber 610 in which a substantial portion of the spring 312 may be received, a longer spring 312 may be used without requiring additional space in the handle 10. The larger the collar ring mold portion chamber 608 and the inner mold portion chamber 610, the longer the spring 312. In addition, the distance between the protruding members 600, 602 means that the ends of the spring 312 are compressed by the end walls 612, 614 of the collar ring mold portion chamber 608 and the inner mold portion chamber 610, respectively, so that the spring 312 undergoes initial pre-compression upon installation. This is important to ensure that upon actuation of the handle 22 to activate the clamping mechanism, the proper force is applied to the jaws 14.Additionally, the inner mold part 314 may be received in another barrel shaped mold part, such as the rotary wheel 28, as shown in FIGS. 13 a- b. Here, the inner mold part 314 rotates with the rotary wheel 28, but is free to move axially within the interior cavity 1300 of the rotary wheel 28 between a first position as shown in FIG. 13 aand a second position as shown in FIG. 13 b. Thus, rotation of the rotary wheel 28 rotates the inner mold part 314 which in turn rotates the drive shaft 316 and the jaws 14.After all the components are assembled, the drive handle 22 can be installed in the housing 20. For this purpose, the drive handle 22 is connected to the housing at its joint 306. The hinge 306 may be, for example, two outwardly extending pins that mate with corresponding hinge moldings 308 integrally formed with the shell moldings 300, 302. This provides an anchor point about which the drive handle 22 can rotate.Thus, the above-described arrangement provides a mechanism for actuating the end effector 14 that can be easily and securely assembled without any additional components.In use, the user pushes the drive handle 22 toward the proximal end 328 of the housing 20, thereby rotating the drive handle 22 about its hinge 306. In this case, the collar ring 304 presses against the proximal flange 800, as a result of which the collar ring molded part 310 is moved in the longitudinal direction. This longitudinal movement translates spring 312, inner molding 314 and drive shaft 316 back toward the proximal end of handle 10, as seen in Figure 5a. Because the drive shaft 316 is connected to the jaws 14, for example by an assembly of pin 400 and cam slot 402, the jaws 14 are moved from the open to the closed position. The force from the drive handle 22 is transmitted via the spring mechanism of the collar ring molding 310, spring 312 and inner molding 314 to the drive shaft 316. This spring mechanism is particularly important because it acts to limit the force acting on any tissue being pinched between the jaws 14.Upon pressing the drive handle 22, the collar ring molding 310, the spring 312 and the inner molding 314 continue their axial movement until either the inner molding 314 reaches its extreme proximal position so that the jaws 14 are fully closed as shown in Figure 5a or the jaws 14 cannot be further closed due to tissue 500 being pinched therebetween as shown in Figure 5b, in which case the drive handle 22 is not fully actuated so that it is held in place by the latch member 324. As the user continues to push the drive handle 22 and the collar ring 304 continues to abut the flange 800, the threshold compressive force of the spring 312 is eventually achieved so that the spring 312 begins to compress between the collar ring molding 310 and the inner molding 314, as seen in FIG. 5 b.As the spring 312 is further compressed, the drive handle 22 can be moved to the engaged position without applying additional force to the pinched tissue 500. That is, the force of the drive handle 22 is no longer transmitted to the drive shaft 316, but is effectively absorbed by the spring 312. This ensures that the proper amount of force is transmitted to the jaws 14. Without the spring 312, actuation of the drive handle 22 continues to increase the force applied to the drive shaft 316, and thus to the jaws 14 and tissue 500. This could result in mechanical damage to the fabric 500 when the user presses the drive handle 22 to engage the latch member 324.For this reason, pre-compression of the spring 312 is important to ensure that the spring 312 absorbs the force of the handle 22 once the inner mold part 314 reaches its final axial position. Similarly, a longer spring 312 allows for a greater spring stroke so that the spring 312 is not fully compressed to its block length during use. When the spring 312 reaches its block length, it would no longer absorb the force exerted by the drive handle 22, and the force would be transferred again to the jaws 14.To maintain the jaws 14 in their closed position, the latch member 324 on the drive handle 22 must be engaged with the latch molding 326 inside the proximal end 328 of the housing 20, as shown in Figures 26a-f.FIG. 11 shows that the snap-fit part 326 is a single integrally molded component that includes a body portion 1108, a spring member 1104, and a cam path 1106. The proximal end 328 of the housing 20 has parallel walls 1100 defining a channel 1110 in which the body portion 1108 is received. The width of the channel 1110 is selected to hold the body portion 1108 within the channel 1110, but yet is capable of sliding up and down within the channel 1110 during use, as described below. To do so, the snap-fit part 326 is preferably made of a low friction material, such as polytetrafluoroethylene (PTFE), to allow the body portion 1108 to slide easily within the channel 1110 without remaining adhered. For further stability in the channel 1110, a shaped pin 330 may be provided in the housing 20 which engages a cam slot 331 provided on the body portion 1108 as shown in FIG. 46.The spring 1104 is placed at the end of the body portion 1108 and is arranged to bias the body portion 1108 upward in the channel 1110 toward the distal end of the housing 20. The spring 1104 may have any suitable configuration; for example, the spring 1104 may have a curved shape or a loop shape, as illustrated in FIG. 11. The cam path 1106 is a protruding molding formed on the body portion 1108. The cam path 1106 includes a first cam surface 1112, a groove 1114, and a second cam surface 1116 to form a V-shaped molding.The latch member 324 is comprised of an arm 1118 which extends from the bottom of the drive handle 22. Arm 1118 includes a pin 1120 disposed at its end and adapted to move along cam path 1106.In use, the latch 324 is inserted into the housing 20 via an opening 1102. The pin 1120 engages the snap-fit portion 326 such that the body portion 1108 is pulled down the channel 1110, thereby pulling apart the spring 1104. As shown in Figs. 26b-c, the pin 1120 moves along the side of the first cam surface 1112 until it reaches the top of the "V". At this point, the drive handle 22 cannot be further depressed and the spring 1104 pulls the body portion 1108 up again in the channel 1110 so that the pin 1110 abuts the groove 1114, thereby maintaining the drive handle 22 in the depressed position and maintaining the jaws 14 in the closed position, as shown in Figure 26d.Thus, to lock the drive handle 22, the user need only activate the drive handle in the fully depressed position, wait until the pin 1110 locks into the groove 1114, and then release the drive handle 22. In this locked position, the user's hand is free to perform other functions of the instrument 1, such as actuating the cutting mechanism using the trigger 24, rotating the jaws 14 using the rotary wheel 28, or actuating the electrodes in the jaws 14 using the switch 26.To release the latch 324 from the housing 20 and open the jaws 14, the user must push the drive handle 22 a further time towards the housing 20. This releases the pin 1120 from the groove 1114 as shown in FIG. 26e. As the pin 1120 exits the groove 1114, the force of the biased spring 1104 pulls the body portion 1108 back up in the channel 1110 such that the pin moves along the side of the second cam surface 1116 as shown in FIGS. 26 e- f. When the pin 1120 reaches the bottom of the second cam surface 1116, it further pushes the body portion 1108 upward in the channel 1110 so that the pin 1120 can again exit the aperture 1102. Body portion 1108 may then return to its original position in channel 1110.To release the drive handle 22, the user need only push the drive handle 22 toward the proximal end of the housing 20 and then return the drive handle 22 to its original open position.Further, the latch molding 324 may include an override button 4600 integrally formed on the body portion 1108, as shown in FIG. 46, where the override button 4600 is engaged such that the position of the cam path 1106 changes such that the pin 1120 automatically exits the groove 1114 and releases the drive handle 22. Thus, if the latch mechanism were to fail for any reason, the user would be able to release the drive handle 22 to open the jaws 14.The body portion 1108 may further be provided with an integral locking bar 4602 to allow the user to release the entire latch mechanism, the locking bar 4602 being movable between first and second positions to manually slide the body portion 1108 within the channel 1110. When the lock rod 4602 is in the first position, the body portion 1108 is in its normal position so that the latch mechanism operates as above. The user may then move the locking rod 4602 to its second position, thereby moving the body portion 1108 upward within the channel 1110, such that the pin 1120 may only pass through the second cam surface 1116 and thereby be prevented from engaging the groove 1114.Such a locking mechanism is also suitable for many end effectors. For example, such a latch member may be provided on the trigger 24 for the cutting mechanism to maintain the blade 340 in the activated position.Upon release of the latch 324, the drive handle 22 can be moved back to its original position. In doing so, the collar ring 304 releases the load applied to the proximal flange 800 and presses against the distal flange 802, thereby pulling the collar ring molding 310 back to its original axial position. Thus, spring 312, inner mold part 314 and drive shaft 316 are also axially retracted, which in turn resets jaws 14 to the open configuration.4. Arrangement and Operation of Cutting MechanismVarious features and aspects relating to the structure and operation of the cutting mechanism will now be described. As described above, the proximal handle 10 of the electrosurgical instrument 1 includes a second mechanism for actuating another aspect of a distal end effector 14. For example, the end effector 14 may be a set of opposing jaws 14 and a blade 340, the distal end of the blade 340 being arranged to slide between the jaws 14 to cut tissue clamped between these jaws 14. The mechanism used to trigger movement of the blade 340 disposed in a central path 342 of the drive shaft 316 is the so-called cutting mechanism. The cutting mechanism includes a drive arm 2000, a blade drive die 346, a blade collar ring die 348, a blade die 352, and a tension spring 350, all of which are coupled together to form a 3-pivot push crank mechanism, as shown in FIGS. 20 a- b, as well as FIGS. 31 and 32.The drive arm 2000 is formed of a trigger 24 and the trigger molding part 344, wherein the trigger 24 is a finger grip member for triggering the cutting mechanism, and the trigger molding part 344 is a collar ring having a C-shaped side profile and an opening 364 through which the drive shaft 316 is inserted. The point at which the trigger 24 and the trigger molding 344 meet forms a pivot point A about which the drive arm 2000 is rotated. This first pivot point A is anchored to the housing 20, for example by means of outwardly facing pins 358 connected to respective mould parts 356 integral with the shell mould parts 300, 302.The distal end of the drive arm 2000, i.e., the end of the trigger molding portion 344, is pivotally connected to the blade drive molding portion 346 to form a second pivot point B. The blade drive molding 346 is an H-shaped frame having two parallel arms and a strut therebetween. Thus, the parallel arms of the blade drive molding 346 are pivotally connected at one end to the trigger molding 344, for example, by outwardly facing pins 366 and mating connectors 368. At the opposite end, the parallel arms of the blade drive molding 346 are also pivotally connected to the blade collar ring molding 348 to form a third pivot point C, for example, by way of outwardly facing pins 372 and mating connectors 370.As shown in Figs. 21 to 23, the blade collar ring molding 348 is a cylindrical or barrel-shaped component having a chamber 2104 in which the blade molding 352 sits, the blade molding 352 being a cylindrical or barrel-shaped component having a body 362 fitted into the chamber 2104 of the blade collar ring molding 348. The blade molding 352 further includes a flange 360 having a diameter greater than that of the chamber 2104 such that the flange 360 abuts the distal lip edge 2200 of the blade collar ring molding 348 as shown in FIG. 22. As a result, flange 360 ensures that the correct end of blade molding 352 is inserted into the blade collar ring molding.The body 362 is provided with a small groove 2202 around its periphery to provide a shoulder that is engaged with the distal nose 2200 such that the blade molding 352 and the blade collar ring molding 348 are snap-fit together. The distal lip rim 2200 mates with the groove 2202 to retain the blade molding 352 within the blade collar ring molding 348 while the blade molding 352 is free to rotate within the chamber 2104. Thus, the blade molding 352 and the blade collar ring molding 348 are free to rotate concentrically.Once the blade collar ring molding 348 and the blade molding 352 are assembled, the blade 340 may be connected as shown in Figs. 24a-c. In this regard, the blade molding 352 includes a T-shaped opening 2300 extending along its length and shaped to receive both the blade 340 and the drive shaft 316, as shown in FIG. 23.The proximal end of blade 340 includes an engagement member 2102 which extends further than the general profile of the remaining portion of blade 340, i.e., it does not lie in the same axial plane. As shown in FIG. 24 c, the body 362 further includes a recess 2100 in which the engagement member 2102 is held. To allow placement, the proximal end of blade 340 is cut at a first point opposite to engagement member 2102 to provide a beveled edge 2400, and is cut at a second point adjacent to engagement member 2102 to provide a recessed portion 2402. Thus, the proximal end of blade 340 has an L-shaped profile.To locate the blade 340 in the array of blade molding 352 and blade collar ring molding 348, the blade 340 is oriented at an angle to the longitudinal axis of the instrument 1 opposite the T-shaped opening 2300 such that the engagement member 2102 and the beveled edge 2400 can be inserted into the interior cavity 2404 of the blade molding 352 as shown in Figures 24a-b. Then, the blade 340 is pulled down in line with the longitudinal axis to press the engaging member 2102 into the recess 2100 as shown in FIG. 24c. Thus, the engagement member 2102 is operatively hooked to the shoulder 2406 of the blade molding 352, thereby retaining the proximal end of the blade 340 in the internal cavity 2404.The drive shaft 316 can then be inserted through the T-shaped opening 2300 with the blade 340 received in the central track 342 as shown by FIGS. 22 and 23. Thus, longitudinal movement of the blade collar ring molding 348 and blade molding 352 assembly along the drive shaft 316 translates the blade 340 along the track 342.To complete the blade trigger assembly, a tension spring 350 extends between the blade collar ring molding 348 and the drive arm 2000, for example, by hooks 2002, 2004.In use, the user pulls the trigger 24 back toward the housing 20 as shown in Figs. 25b-c so that the drive arm 2000 is pivoted about the first pivot point A. This pushes the second pivot point B forward in the distal direction causing the drive molding 346 to push the array of blade collar ring molding 348 and blade molding 352 along the drive shaft. The load applied to the trigger 24 is therefore transmitted to the blade collar ring molding 348 and the blade molding 352 via the trigger molding 344 and the drive molding 346. Because the proximal end of blade 340 is held within blade molding 352 as described above, blade 340 slides along central path 342 with the array of blade collar ring molding 348 and blade molding 352. Because the blade molding 352 is independently rotatable within the blade collar ring molding 348, the drive shaft 316 can be rotated without interfering with the operation of the cutting mechanism.The operation of the mechanism is optimized to provide good force translation at the beginning of the extension of the blade 340 when the user's finger is extended and less powerful, and also at the end of the extension of the blade 340, where more forces act against the extension of the blade 340, such as the force of the spring 350, friction within the web 342 and the force required to penetrate thick tissue. As can be seen from FIG. 27, a constant force is applied to the trigger 24 by the user. The mechanism converts this trigger force into a high output force of the blade 340, which decreases as the blade 340 is displaced along the path 342, and increases again as the blade 340 reaches the jaws 14. Therefore, as the pivot point B moves from its retracted position to its advanced position, as shown in Figs. 28a-b, such that β > 90°, the speed at which the blade collar ring 348 and blade molding 352 are displaced along the drive shaft 316 is increased, thereby increasing the force of the blade 340. Thus, the mechanism is capable of continuing to drive blade 340 with sufficient force to effectively cut tissue clamped between jaws 14 without requiring the user to apply additional force to trigger 24.Further, the cutting mechanism may be required to push the blade 340 along a curved set of jaws 14, which increases the frictional forces opposing the displacement of the blade 340. The frictional force is a product of the coefficient of friction of the blade 340 within the web 342 and the force that the blade 340 exerts on the walls of the web 342 due to the deflection.To reduce this frictional force, the lateral flexibility of the distal end of the blade may be staggered. Such stepped flexibility may be achieved, for example, by preferably weakening the blade 340 so as to be capable of flexing along the web 342 while remaining rigid in the direction of the cutting force. Preferred weakening may be achieved, for example, by providing one or more apertures or slots 354 in the distal end, as shown in Figure 47a. Such apertures may be of constant or varying size or shape depending on the amount of flexibility required. For example, in FIG. 47 b, two adjacent apertures 4702, 4704 are provided with different sizes, with the larger aperture 4702 causing a higher degree of flexibility than the smaller aperture 4704. As another example, in Figure 47c, three apertures 4706, 4708, 4710 of varying size and shape are provided, with the largest aperture 4706 being located distalmost to effect increased flexibility in this region. A preferred weakening may also be achieved by grading the thickness of the blade 340 so that the distal end of the blade 340 is chamfered 4700 as shown in Figure 47d.Alternatively, patterned laser cuts 4712 or chemical etches may be used in the distal end to control the bending strength over a length of the blade 340, as shown in FIG. 47e, where the distance between such cuts may be constant or may increase stepwise from the distal to the proximal end.Preferably, the blade 340 is divided into at least three regions of varying flexibility, for example, a distal region, a central region, and a proximal region, the distal region having greater lateral flexibility than the central region, and the central region having greater flexibility than the proximal region. For example, the distal portion may be formed by a beveled end 4700 to provide the greatest amount of flexibility; the central portion may be formed with an opening 354 to provide a relatively lesser amount of flexibility; and the proximal portion may be formed by a solid rod to provide even less flexibility, as shown in Figure 47a. In another example shown in Figure 47b, the distal portion has a large aperture 4702 to provide the greatest amount of flexibility; the central portion includes a smaller aperture 4704 to provide reduced flexibility; and the proximal portion is again a solid rod having the least amount of flexibility. The distal portion, the middle portion and the proximal portion may be obtained using any suitable combination of the preferred weakening described above.Another way to reduce the frictional force due to the curved path is to apply a low friction coating to at least one side of the distal end of the blade 340. For example, the blade may be coated with a low friction or non-stick material, such as a PTFE composite or other low friction polymer composite, using, for example, physical vapor deposition (PVD) or chemical vapor deposition (CVD) techniques.5. Drainage openingsVarious other features and aspects relating to the structure of the drive shaft 316 will now be described. As described above, the drive shaft 316 is an elongated rod having a T-shaped cross section as shown in Fig. 10a. The drive shaft 316 includes a slot or track 342 along its length that is adapted to receive another elongate member, such as the blade 340 used in the cutting mechanism described above. In one application, sliding of blade 340 along the length of drive shaft 316 is effected to displace the distal end of blade 340 between jaws 14 to cut tissue clamped therebetween.Over time, blood and tissue may collect in the distal end of the instrument 1, particularly along the outer shaft 12 and the drive shaft 316. This accumulation of blood and tissue can cause the blade 340 to stick in the drive shaft 316, reducing the operation of the instrument 1, particularly the cutting mechanism. To prevent this, portions of the distal end of the drive shaft 316 are cut out to reduce the area of contact between the drive shaft 316 and the blade 340, and also the surface on which blood and tissue may stick.These cut-out portions may be openings, such as the elongated windows 1000 shown in FIGS. 10 b-c, such that the distal end of the drive shaft 316 includes a supporting base having bifurcated sidewalls. The cut-out portions may also extend to the base of the drive shaft 316 such that the distal end includes bifurcated side walls and an open bottom. To maximize the amount of drainage provided by these apertures 1000, the apertures preferably account for more than 50% of the depth of the drive shaft 316.Thus, these apertures 1000 provide drainage apertures between the central web 342 and the exterior of the drive shaft 316.6. Rotary wheel and switchVarious other features and aspects relating to the operation of the rotary wheel 28 (also referred to herein as a rotary wheel) will now be described. The rotary wheel 28 is provided to allow the user to rotate the outer shaft 12 on which the end effector 14 is mounted. To reduce the space required to create a more compact instrument, the interior volume 1300 of the rotary wheel 28 is also used to provide a moving space for the inner mold part 314 that forms part of the clamping mechanism described above. With such an arrangement, a more compact mechanism can be obtained.In detail, the rotary wheel 28 comprises a toothed plastic wheel having a plurality of notched portions 336 disposed about its outer diameter. The rotary wheel 28 has the appearance of a gear wheel with the notched cut-out portions arranged to receive a thumb of a user in an ergonomic manner. In this regard, and as shown in more detail in Figures 13a, 13b, particularly Figure 14a, the notched portions are, in use, at an angle to the rotational plane of the rotary wheel such that generally the rotary wheel or rotary wheel 28 has a slightly frustoconical shape which is wider at an end remote from the user than at the end near the user. The notched portions 336 each extend from the distal edge of the rotary wheel to the proximal edge and are curved or saddle-like in shape to receive a thumb of a user in use. As shown in detail in Figure 14a, the angular shape of the notched portions 336 generally matches the angle of the body of the instrument to achieve the frusto-conical shape of the rotary wheel 28. In Figure 14a, the dot-and-dash lines illustrate the angular shape of the notches 336 around the edge of the wheel 28, which can be viewed distally tangentially to the angle of the outer walls of the instrument at the point around the rotary wheel, and particularly the portion of the outer walls of the instrument immediately before the rotary wheel. Such an arrangement, in which the angled notches of the outer rim of the rotary wheel match the angle of the wall of the instrument around the rotary wheel, provides a comfortable and ergonomic shape that is easy to manipulate by the surgeon.As shown in one embodiment, with respect to the number of notched portions 336 around the outer diameter of the wheel 28, eight notched portions are evenly arranged around the outer diameter of the wheel. In other embodiments, a smaller or a larger number of notched portions may be used, for example only six or seven, or even nine or ten. If a larger turning wheel 28 is to be used, a larger number of notched portions 336 may be provided, and conversely if a smaller turning wheel is to be used, the number of portions may be less. In this regard, the actual size of each notched portion 336 should typically remain the same, as the notched portions have been ergonomically selected to enable a user's thumb to be comfortably received.With respect to the positioning of the rotary wheel 28 within the instrument, as shown in FIG. 2, the rotary wheel 28 is positioned vertically oriented below the switch 26 and spaced from the rotary wheel in a direction orthogonal to a longitudinal axis defined, for example, by the longitudinal direction of the drive shaft 316. In particular, the hand switch 26 lies directly on an axis orthogonal to this longitudinal axis, which also passes through the rotary wheel 28. Further, as shown in Figures 14a and 14b, the switch 26 is relatively large in size and extends across the rotary wheel from one side of the upper surface of the instrument to the other. The switch 26 is curved in nature to generally conform to the curved upper surface of the outer wall of the instrument and has ridges, grooves or other raised protrusions on its outer surface to assist the user in grasping the switch to press it with his thumb. The surface area of the switch 26 is relatively large, namely more than 3 cm 2 or even 5 cm 2. This provides a large surface area to allow ergonomic activation thereof by the user. The vertical orientation of the switch 26 immediately above the rotary wheel 28 also permits ergonomic activation. As explained elsewhere, switch 26, in use, serves to cause an RF coagulation signal to be supplied to the end effector for coagulating tissue therein.With regard to the ergonomy of the switch and the rotary wheel, Figures 35a and 35b are two corresponding representations of different users with hands of different sizes. As shown, because the switch 26 has a relatively large area, it is easily operated by users with hands of different sizes while simultaneously operating the clamping handle 22 (and the blade trigger 24, if desired).Returning to FIG. 12, as previously described, the rotary wheel 28 has an internal cavity 1300 that is received in the internal mold part 314 when in use. As previously described, the inner mold member 314 includes an inner mold member chamber 610 and has a T-shaped cut-through portion 1208 therein through which the drive shaft 316 is received and secured as previously described. The inner mold part 314 is snapped into the inner cavity of the wheel 28, and flanges 1206, as shown in Figures 12 and 29a and 29b, are provided around the outer edge of the cylindrical inner cavity 1300 of the rotary wheel 28 to retain the inner mold part 314 in place within the cavity once inserted therein. The inner cavity 1300 of the rotary wheel 28 is further provided with locking elements 1200 interacting with corresponding locking elements 1202 provided around the outer periphery of the inner cylindrical molding 314. The respective locking members 1200 and 1202 include respective raised step portions that circumferentially fit side by side around the inner surface of the cavity 1300 when the rotary wheel 28 and inner cylindrical molding 314 are in the correct rotational alignment relative to each other. The respective locking members 1200 and 1202 are provided such that, in use, the inner cylindrical molding 314 can slide side-to-side within the inner cavity of the wheel 28, but cannot rotate within the rotary wheel 28. Instead, the interacting locking members 1202 and 1200 act such that the inner mold part 314 rotates with the rotary wheel 28 as it is rotated. In this manner, any torque imparted to the rotary wheel 28 by the user 28 is transmitted to the inner mold part 314 and then to the drive shaft 316 to rotate the drive shaft that supports the end effector. FIGS. 29 aand 29 b show the inner mold part 314 inserted into the inner cavity of the rotary wheel 28 and illustrate how the inner mold part 314 can slide axially within the inner cavity 1300 of the wheel 28.Figures 13a and 13b further show in more detail how the inner molding 314 is able to move within the inner cavity 1300 of the wheel 28. As described above, the drive shaft 316 passes through the T-shaped opening 1208 in the inner mold part 314 and is secured therein by means of protruding snap-lock or snap-fit elements 602 provided on the end of the drive shaft. The locking elements 602 are in the form of spring metal tabs that are also capable of passing through the T-shaped opening 1208 in the inner mold part 314 and then being received in a second channel part 606 of the inner mold part that forms a cavity that allows the spring tabs to spring apart, thereby securing the drive shaft within the inner mold part. The inner mold part 314 is then pushed into the inner cavity of the rotary wheel 1208 and held in place by the locking protrusions 1206, as described above. The inner molding may move axially within the inner cavity 1300 to abut the inner surface of the distal wall of the wheel 28, as shown in Figure 13a, or, at its opposite extension end, abut the engagement members 1206 at the distal edge of the wheel. Thus, the inner mold part 314 is provided with an amount of axial sliding movement within the cavity of the rotary wheel 28 which is required as part of the mechanism to control the force exerted by the user on material contained within the jaws, as described above.The detent nature of the inner molding 314 in the inner cavity of the rotary wheel 28 improves assembly of the device unmint, and makes assembly of the device significantly easier and thus less expensive. To position the rotary wheel within the housing, as shown in Figure 33, the outer distal wall 1310 of the rotary wheel 28 is concentric with and aligned with an inner support wall 1320 provided as a protrusion from the housing of the device. This also permits easy and accurate assembly and positioning of the wheel 28 within the housing.7. Rotation Control of Drive ShaftAs explained above, the shaft 12 is rotatable with the end effector 14 thereon to allow the end effector 14 to be moved to desired rotational positions for cutting and coagulating tissue. However, in order that the cable connections to the end effector 14 are not loaded too much by rotating the shaft too far in one direction, so that the wiring is wound or twisted or under too much load, a mechanism for controlling the rotation of the shaft 12 is required, in particular in order to limit the amount of rotation and thus prevent excessive loading of the wiring. Moreover, positive control of the rotation of the shaft 12 improves ergonomic experience of the instrument in use and the user's perception of quality.To provide rotational control of the shaft, in one embodiment, an arrangement shown in Figures 15a and 15b and Figures 16a to 16d is employed. Referring to Figure 15, here, the rotary wheel 28 is provided with notched portions 36 on its proximal surface (i.e., rear surface facing the user) with a ring 1506 that slightly projects from the proximal surface that is concentric with the axis of the wheel 28. The ring 1506, in use, rests on guide stop members 1502 and 1504 which are protrusions on the inner surface of the outer housing which protrude to be able to contact the outer periphery of the ring 1506. Because of their positioning on the housing with respect to the axis of the ring, the stop member 1502 is smaller than the stop member 1504, but both stop members 1502 and 1504 have angled upper guide surfaces 1510 and 1512, respectively (see Figure 15a) which contact the outer circumferential surface of the ring 1506 forming part of the rotary wheel and assist in supporting and guiding the rotary wheel as it rotates.In addition to providing a guiding function, the stopper members 1502 and 1504 also function as a stopper member to prevent rotation of the rotary wheel beyond the angular position of the stopper members. In this regard, the ring 1506 is provided with a rectangular stop projection 1500 extending radially therefrom. When the rotary wheel 28 is rotated, the stopper protrusion 1500 abuts against corresponding stopper surfaces 1514 and 1516 of the stopper members 1502 and 1504. The stop surfaces are angled to be parallel to the rectangular stop protrusion 1500 when the stop position is positioned at an angle to abut it.The stop members 1502 and 1504 arranged as described above are positioned and of such length as to provide a known amount of rotation of the wheel 28 from the stop member 1500 to the stop member 1502. In the arrangement presently described and shown in Figures 15a and 15b, the stop members 1502 and 1504 are positioned on the housing a distance apart to allow the rotary wheel to rotate 270° from stop to stop. The amount of rotation can be varied easily by increasing or decreasing the distance between the stop parts, wherein the stop parts are adapted accordingly with respect to length and angle of the guide and stop surfaces in order to meet the rotary wheel and the stop parts substantially perpendicularly, respectively. For example, the stop members may be positioned and shaped to provide an angular rotation of the wheel between 250° and 300°.The above describes the rotation control applied to the rotary wheel (and then, via the rotary wheel, the shaft). Figures 16a-16d show another rotation control mechanism applied to the shaft at the opposite end of the shaft using the shaft molding 320. Here, the shaft molding is provided with a rectangular stopper 1600 protruding therefrom. The inner surface of the outer housing is further provided with respective shaped stop portions 1602 and 1604, shown as being in the form of a portion having steps providing respective stop surfaces providing parallel stop surfaces corresponding to the rectangular stop member 1600 at respective angular positions of the shaft molding 320. In the example shown, the shaped stop members are positioned on the housing and provide stop surfaces corresponding to the stop member 1600 to allow 270° rotation of the shaft 12 that moves the end effector 14 from stop to stop. In further embodiments, the shaped stop portions 1602 and 1604 may be positioned to provide stop surfaces to the stop member 1600 in other rotational angle positions of the molded portion 320 to provide a greater or lesser amount of rotation, for example from 180° to 360°, or more preferably from 250° to 300°, or most preferably 270°.The respective rotation control mechanisms provided in the rotary wheel 28 and the shaft molding 320 may be provided independently of each other, i.e., they need not both be provided in a particular embodiment, but only one or the other may be provided to provide rotation control of the shaft. However, it is advantageous with regard to the operation and quality perception of the device if both rotation control mechanisms are provided in one device and are aligned such that they provide stopping of the rotation at the correspondingly same points in both rotational directions. Such an arrangement means that the rotation of the shaft is stopped independently at both ends of the handle 10 and it becomes very difficult for a user to force further undesired rotation of the shaft beyond the allowed limits given by the stops.An alternative rotation control mechanism is shown in Figs. 36 and 37. Figure 36 again shows the shaft moulding 320, but here the moulding is provided with a ring 3220 on which are mounted a primary rectangular stop member 3202 extending radially therefrom and secondary position marker members 3204, 3206 and 3208, which are arranged substantially, preferably in orthogonal positions, equiangularly around the ring. The secondary position marker members 3204, 3206 and 3208 form small raised projections which are not large enough to engage the stop surfaces 3212 and 3214.The stop surfaces 3212 and 3214 are provided as integral molded parts with the outer housing and are positioned here to allow 180° rotation of the shaft molded part 320. In this regard, the stop member 320 abuts the stop surfaces 3212 and 3214 at the ends of the range of rotation to prevent further rotation of the shaft molding. Thus, as shown in Figures 36a-36c, the shaft molding 320 supporting the shaft 12 can rotate through 180° to allow rotational positioning of the end effector as desired.Further provided is a resilient protrusion 3216 comprising a substantially triangular cross-section plastic protrusion extending upwardly from the molding forming abutment surface 3214 such that its tip contacts an outer circumferential surface of the ring 3220. The secondary position markers in the form of the small raised projections press against the tip of the resilient projection as the shaft moulding 320 rotates, causing the tip of the resilient projection to move from its rest position to allow the corresponding projection to move past the tip. The effect of this operation is to provide some feedback to the user because the user has to apply more force to move the mechanism beyond the rotational positions in which the raised protrusions contact the tip of the resilient protrusion, because sufficient force has to be provided for the tip of the resilient protrusion to flex so that the protrusion can move past the tip. The result is that the user experiences an increase in the force required to rotate the shaft beyond the rotational positions of the raised protrusions, and thus an indication of the rotational position of the shaft and thus the end effector is provided intuitively to the user. Such a haptic feedback mechanism thus allows user-friendly and simple operation of the device.Figure 37 shows the corresponding rotary wheel 28 for the mechanism in Figure 36, here the rotary wheel is also provided with respective small stops 3222 arranged orthogonally at 90° intervals around the rotary wheel. A similar mechanism may be provided for the resilient protrusion 3216 extending from the housing to provide similar haptic feedback as in the case of the shaft molding 320. In such an arrangement, haptic feedback is provided about the rotational position of the shaft from both ends of the handle, and thus the perception of the device by the user is improved.8. Wiring HarnessAt this point, further features and aspects relating to the cabling within the handle 10 will be described. As described above, the switch knob 26 is provided to enable and disable the RF signal for operating the electrodes in the end effector 14 via suitable circuitry, for example, via two intrusion protected switches on a small printed circuit board (PCB) 338. As shown in FIG. 17, the PCB 338 is connected to a connecting line 1700 for receiving the RF output from a generator (not shown) and electrical wiring 1702, 1704 for providing the RF current to the electrodes in the jaws 14, for example a cable for the active electrode and one for the counter electrode.In the arrangement, the wiring 1702, 1704 is routed from the electrodes down the outer shaft 12, along the drive shaft 316, and up to the shaft molding 320, as shown by Figure 17. As shown in FIG. 9 b, the shaft molding 320 is a cylindrical or barrel-shaped component having an opening 912 at the distal end to receive the outer shaft 12. The outer shaft 12 is secured to the shaft molding 320, for example, by locking protrusions 900 that cooperate with corresponding grooves 902 in the shaft molding 320. Thus, as the shaft molding 320 rotates, the outer shaft 12 rotates therewith. The shaft molding 320 further includes another opening 914 at the proximal end, the opening 914 having a T-shape to receive the drive shaft 316, the drive shaft 316 extending through the interior cavity 1802 of the shaft molding 320 and down the length of the outer shaft 12. Thus, the drive shaft 316 is able to slide within the shaft molding 320 and the outer shaft 12, but any rotational movement of the drive shaft 316 is transmitted to the shaft molding 320 and then the outer shaft 12.As shown in FIG. 18 a, the electrode cables 1702, 1704 are routed from the interior cavity 1802 through an opening 1800 in the wall of the shaft molding 320 before winding over and around the body 1804 of the shaft molding 320. Winding the cables 1702, 1704 around the shaft molding 320 in this manner maintains the cables 1702, 1704 in a compact arrangement to prevent the cables 1702, 1704 from being detrimental to the assembly of the remainder of the instrument 1. Further, winding the cables 1702, 1704 around the shaft molding 320 means that when the shaft molding 320 rotates with the drive shaft 316, the cables 1702, 1704 unwind and rewind with rotation without spanning and thereby shorting the cables 1702, 1704. In particular, winding the cables 1702, 1704 in this particular manner allows up to 270° rotation as described with respect to FIGS. 15 aand 16 a- d.The electrical wiring 1702, 1704 is then routed along the top of the housing 20. In this regard, one of the shell mold parts 300 is provided with two compartments 1900, 1902 that are arranged side-by-side to receive the cable contacts 1904, 1906 that connect the active and return cables 1702, 1704 to the cabling 1908, 1910 of the intrusion-protected switches 338. All of the electrical cables 1702, 1704, 1908, 1910 are routed into and around the compartments 1900, 1902 such that only one contact 1904, 1096 is received in each compartment 1900, 1902. Guiding the cables may be facilitated by guiding portions 1912, 1914, 1916 guiding a set of the cables 1702, 1910 around the exterior of the compartments 1900, 1902. In each compartment, the respective active cable 1702 is aligned with cable 1908 in the longitudinal direction and the return cable 1704 is aligned with cable 1910 in the longitudinal direction.Thus, the two cable contacts 1904, 1906 are longitudinally separated such that only one contact can pass through each compartment 1900, 1902, thereby providing a physical barrier between each contact 1904, 1906 and the cabling. This eliminates the risk of damage to the insulation of one of the cables by the contacts 1904, 1906 themselves.The cables 1702, 1704, 1908, 1910 are all inserted into their respective compartments 1900, 1902 via small openings 1918, 1920, 1922, 1924 in the walls of the compartments. Preferably, the dimensions of the apertures 1918, 1920, 1922, 1924 are such that only one electrical cable fits through. The opposing shell molding 302 also includes corresponding rib members (not shown) to retain the contacts 1904, 1906 within the compartments 1900, 1902 to form a substantially sealed housing. This is important to minimize the permeability of the compartments 1900, 1902 to protect the contacts 1904, 1906 from any fluid that could permeate along the outer shaft 12 and into the housing 20 which would cause shorting of the contacts 1904, 1906.9. End effectorsExample end effectors that may be used with the device will now be described. The examples to be described are mentioned for completeness only, and it is clear that further end effector configurations can be used with the instrument, provided they are capable of being driven by the drive shaft 316. That is, embodiments of the invention are not limited to the specific end effectors described herein, but other end effector configurations may also be used.Figures 38-44 show exemplary instruments in which electrically conductive stop members are disposed on one or both of the sealing electrodes. Referring to Figure 38, an end effector, generally indicated at 3801, includes an upper jaw 3802 pivotally connected to a lower jaw 3803 about a pivot point 3804. Flanges 3805 are provided at the proximal end of upper jaw 3802, while flanges 3806 are provided at the proximal end of lower jaw 3803. The flanges 3805, 3806 each have slots 3807 through which a drive pin 3808 extends such that proximal and distal movement of the drive pin 3808 (via a drive mechanism (not shown)) causes the jaws 3802, 3803 to pivot between open and closed positions.A metallic clamping piece 3809 is provided on the inner surface of the upper jaw 3802, while a metallic clamping piece 3810 is provided on the inner surface of the lower jaw 3803. As the jaws 3802, 3803 pivot to their closed position, the metallic clips 3809, 3810 come close together to grasp tissue (not shown) between them.The upper clamping piece 3809 has a generally planar surface except for an elongated recess (not seen in Figure 38) running along its length. The lower clamping piece 3810 has a corresponding recess 3811, the recesses in the clamping pieces 3809, 3810 receiving the longitudinal movement of a blade (not shown). The lower clamping piece 3810 is further provided with a plurality of metallic stop members 3812 arranged along the length of the clamping piece and on both sides of the recess 3811. The stop members 3812 will now be described in more detail with reference to FIGS. 39 and 40.Each metallic stop member 3812 consists of the top bulge of a stop member 3813 received in an insulating member 3814 so as to house the stop member, which isolates it from the rest of the clamping piece 3810. Each isolation member 3814 and stop member 3813 is disposed in a corresponding opening 3851 provided in the clamping piece 3810 such that the upper portion of the isolation member forms an isolation ring 3816 around each stop member 3812.When the jaws 3802, 3803 are moved to their closed position (as shown in Figure 40), the stop members 3812 contact the upper clamping piece 3809, maintaining a distance between the upper and lower clamping pieces of between 20 μm and about 350 μm (0.00079 inches to about 0.014 inches). In use, an electrosurgical coagulation voltage is applied between the clamping pieces 3809, 3810, and the spacing between the clamping pieces ensures effective sealing of tissue grasped between the clamping jaws 3802, 3803. At the same time, electrical short-circuiting between the clamping pieces is prevented because the stopper members 3812 are electrically insulated so that they do not carry the same electrical potential as the rest of the clamping piece 3810. The metallic stops 3812 are rigid, allowing consistent separation of the surfaces of the clips, while it is feasible that the electrical potential of the stops 3813 is monitored to detect when they contact the upper clip 3809, to indicate the closing of the jaws.Figures 41-43 show an alternative arrangement in which the metal stop members 3812 are mounted directly on the lower clamping piece 3810 without the insulating members surrounding the stop members. In this arrangement, insulating members 3817 are provided on the upper clamping piece 3809, in corresponding relation to each of the stopper members. In this way, when the jaws 3802, 3803 are closed, the insulating members 3817 ensure that there is no electrical short between the upper clamping piece 3809 and the lower clamping piece 3810. The metallic stop members 3812 ensure that the proper separation of the jaws is maintained during application of electrosurgical energy to seal tissue captured between the jaws.Finally, FIG. 44 shows a further alternative in which the metal stop elements 3812 are again directly attached to the lower clamping piece 3810. In this arrangement, a counter metal holder 3818 is disposed opposite each stopper member, and each counter metal holder 3818 is surrounded by an insulating member 3819 to be insulated from the remaining upper clamping piece 3809. When the jaws are closed, metal-to-metal contact occurs between the stop members 3812 and the metal anvils 3818, the insulation of the anvils ensuring that electrical shorting between the clamping pieces 3809, 3810 is again prevented. Again, the electrical potential of each of the metal counter-holders may be monitored to detect when they assume the potential of the lower clamp, indicating the closing of the jaws.10. Electrosurgical SystemReferring to Figure 45, it is contemplated that instrument 1 is, in use, connected to an electrosurgical generator 4500 having a controllable radio frequency (RF) source therein (not shown) which, in use, generates an RF coagulation signal that coagulates or seals tissue when applied thereto via the electrodes of the end effector of instrument 1. Electrosurgical generator 4500 includes control input switches 4504 and 4502 to allow the generator to be turned on and off, respectively, and to allow control of the power of the RF coagulation signal supplied to instrument 1. In this regard, electrosurgical generator 4500 is a conventional one.The instrument 1, in use, is connected to the generator 4500 by a control and power supply line 4506 which includes separate electrical leads to allow an RF signal to be supplied to the end effector of the instrument 1 via the previously described internal cabling, and further to allow a control signal to be received from the switch 26 of the instrument 1 to cause the electrosurgical generator to output an RF coagulation signal for the instrument 1. In use, the surgeon activates the generator via an on-off switch 4504, and selects the coagulation or sealing signal strength to be generated by the internal RF source using buttons 4502. During a surgical procedure with the instrument, if a sealing or coagulation RF signal is required at the end effector, the surgeon controls the generator to generate such a signal by pressing the switch 26 of the instrument, then the generated RF signal is passed to the end effector via the electrical leads 4506. That is, pressing the switch 26 in use will cause an RF coagulation or sealing signal to be applied to the appropriate electrodes contained in the end effector.11. SummaryIn view of the above, therefore, embodiments of the invention provide an advanced electrosurgical forceps instrument that allows simple and ergonomic one-handed operation by the user, provides rotational flexibility of the end effector, controls the force applied by the end effector to the detected tissue to prevent application of excess force, and allows convenient mechanical cutting of the detected tissue while simultaneously providing electrosurgical coagulation or sealing of the tissue. Moreover, the instrument has been devised to be easily and inexpensively assembled while at the same time providing a compact instrument thanks to an efficient use of the available space in the respective internal activation mechanism.Various other modifications of the above-described embodiments, whether by addition, elimination or replacement, will be apparent to those skilled in the art to provide additional embodiments, each and all of which is within the scope of the appended claims.

Claims

A surgical instrument (1) comprising a handle (10), an elongate shaft (12) extending from the handle (10) and defining a forward direction and a rearward direction, an end effector (14) disposed at the distal end of the elongate shaft (12), a blade assembly within the elongate shaft (12), the blade assembly having a blade (340) disposed at its distal end, the blade (340) disposed in the region of the end effector (14), the blade assembly being connected at its proximal end to a component (352) within the handle (10), a trigger mechanism disposed on the handle (10) and movable between a first position and a second position, wherein moving the trigger mechanism from its first position to its second position causes longitudinal movement of the blade assembly, To effect longitudinal movement of the blade (340) relative to the end effector (14), the trigger mechanism comprising: a trigger arm (24, 344) comprising a proximal end and a distal end and being pivotable about a first pivot axis (A) disposed between the proximal and distal ends; a frame (346) comprising a proximal end and a distal end, the proximal end of the frame being connected to the distal end of the trigger arm (24, 344) by means of a second pivot axis (B); and a collar (348) directly connected to the distal end of the frame (346) by means of a third pivot axis (C), the third pivot axis (C) being located forward of the second pivot axis (B) in the forward direction, the arrangement being such that, moving the trip mechanism from its first position to its second position is caused by pivoting the trip arm (24, 344) about the first pivot axis (A) causing the frame (346) to move the collar (348) relative to the trip arm (24, 344), the collar (348) further connected to the component (352) such that moving the collar (348) causes the blade assembly to move longitudinally in the forward direction, and a spring (350) attached at one end to the trip arm (24, 344) and at the other end to the collar (348) so as to bias the trip mechanism to its first position.The surgical instrument (1) of claim 1, wherein pivoting the trigger arm (24, 344) moves the proximal end of the trigger arm (24) generally in the rearward direction and moves the distal end of the trigger arm (344) generally in the forward direction.The surgical instrument (1) of claim 2, wherein pivoting of the trigger arm (24, 344) moves the collar (348) generally in the forward direction.The surgical instrument (1) of any one of claims 1 to 3, wherein the frame (346) includes a generally H-shaped component.The surgical instrument (1) of claim 4, wherein the H-shaped component (346) includes first and second elongate side arms with a cross strut therebetween.The surgical instrument (1) of claim 5, wherein the distal end of the trigger arm (344) is disposed between the proximal ends of the first and second side arms.The surgical instrument (1) of claim 6, wherein the first and second side arms each have a bearing at their proximal ends such that the trigger arm (24, 344) is pivotable relative to the first and second side arms.The surgical instrument (1) of claim 7, wherein the trigger arm (24, 344) includes first and second lugs capable of being snapped into the bearings at the proximal end of the first and second side arms.The surgical instrument (1) of any one of claims 5 to 8, wherein the collar (348) is disposed between the distal ends of the first and second side arms.The surgical instrument (1) of claim 9, wherein the first and second side arms each have a bearing at their distal end such that the frame (346) is pivotable relative to the collar (348).The surgical instrument (1) of claim 10, wherein the collar (348) includes first and second lugs capable of being snapped into the bearings at the distal end of the first and second side arms.The surgical instrument (1) according to any one of the preceding claims, wherein the elongate shaft (12) defines a central axis, and the third pivot axis (C) is disposed on the central axis.The surgical instrument (1) of claim 12, wherein the first and second pivot axes (A, B) are offset with respect to the central axis, on opposite sides of the central axis.The surgical instrument (1) of claim 13, wherein the second pivot axis (B) is closer to the central axis when the trigger mechanism is in its second position compared to when the trigger mechanism is in its first position.The surgical instrument (1) of any preceding claim, wherein the trigger arm (24, 344) comprises at least one aperture, the spring (350) passing through the at least one aperture before being attached to the trigger arm (24, 344).The surgical instrument (1) according to any one of the preceding claims, wherein the spring (350) is arranged below the central longitudinal axis of the surgical instrument (1).Surgical instrument (1) according to claim 16, wherein the third pivot axis (C) is arranged at the same height as the central longitudinal axis of the surgical instrument (1).Surgical instrument (1) according to one of the preceding claims, further comprising a rotatable rotary wheel (28) arranged on the handle (10), wherein a rotation of the rotary wheel (28) causes a corresponding rotation of the end effector (14).The surgical instrument (1) of any preceding claim, wherein the end effector (14) comprises a pair of jaws having first and second jaw members opposite thereto, the blade (340) being longitudinally movable therebetween.The surgical instrument (1) of claim 19, wherein the first and second jaw members are curved to form a curved path.The surgical instrument (1) of claim 20, wherein the blade (340) is formed from at least two regions, the first region having a lateral flexibility greater than that of the second region, the first region being disposed distal from the second region.The surgical instrument (1) of claim 20 or 21, wherein at least a portion of the blade (340) is coated with a low friction coating.The surgical instrument (1) of any one of claims 19 to 22, further comprising: a drive shaft (316), the drive shaft (316) being connected at its distal end to the end effector (14) and at its proximal end to an actuation mechanism, the actuation mechanism being movable between a first position and a second position to cause longitudinal movement of the drive shaft (316), the longitudinal movement of the drive shaft (316) causing at least one of the jaw members to move relative to the other jaw member from a first open position, in which the jaws are disposed in spaced relation relative to each other, to a second closed position, in which the jaws cooperate to grasp intermediate tissue.The surgical instrument (1) of claim 23, wherein the drive shaft (316) includes an elongated slot (342) for receiving the blade assembly, wherein moving the trigger mechanism from its first position to its second position causes advancement of the blade longitudinally along the elongated slot (342) and between the first and second jaws.The surgical instrument (1) according to any one of the preceding claims, wherein the end effector (14) comprises one or more electrodes, and the surgical instrument (1) comprises electrical connections suitable for connecting the surgical instrument (1) to an electrosurgical generator.The surgical instrument (1) of any preceding claim, wherein the trigger arm (24, 344) and the frame (346) are of such a length and the first and second pivot axes (A, B) are positioned such that, for a constant force applied to the trigger mechanism, the force applied by the end effector (14) varies over its range of motion.The surgical instrument (1) of claim 26, wherein the arrangement is such that for a constant force applied to the trigger mechanism, the force applied by the end effector (14) decreases as the end effector (14) moves over a first portion of its range of motion and then increases as the end effector (14) moves over a second portion of its range of motion.The surgical instrument (1) of claim 27, wherein the rate of decreasing the force applied by the end effector (14) decreases over the first portion of the range of motion of the end effector.The surgical instrument (1) according to claim 27 or 28, wherein the rate of increase of the force applied by the end effector (14) increases over the second portion of the range of movement of the end effector.

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