WO2009046490A1

WO2009046490A1 - Control system for a grasping instrument

Info

Publication number: WO2009046490A1
Application number: PCT/AU2008/001492
Authority: WO
Inventors: John Silady
Original assignee: John Silady
Priority date: 2007-10-09
Filing date: 2008-10-09
Publication date: 2009-04-16
Also published as: AU2007221906B1

Abstract

A control mechanism for a grasping instrument; said instrument comprising an elongate hollow member provided with a tool at an outer end of said elongate hollow member; said mechanism including spring modulation of force applied to an inelastic tool activating element within said elongate hollow member; said force applied by displacement of an operating handle, and wherein said force is limited to the force exerted by said spring when said spring is at a maximum predetermined compression.

Description

CONTROL SYSTEM FOR A GRASPING INSTRUMENT

The present invention relates to devices for grasping and holding and, more particularly, to control mechanisms for such devices.

BACKGROUND

One preferred application of the present invention is in the field of laparoscopic surgery. Laparoscopic surgical procedures include the cutting, holding and cauterising of tissue. For these purposes a wide range of instruments have been devised operable at the end of an elongate shaft or flexible hollow member. A surgeon is able to activate the instrument at the end of the shaft by a mechanism graspable by the thumb and fingers in a manner similar to the operation of scissors.

The instrument at the end of the rod, which may take various forms including small cutters and holding jaws or forceps, are very small and easily damaged if excessive force is applied to the pivot pins and other components by the grasping action of the surgeon.

Another problem which must be addressed is that in the case of holding or clamping of tissue, the force applied should not be excessive, regardless of the degree of closure of the graspable mechanism in the hand of the operator. For these operations also, it is desirable that the mechanism can be locked at a desired intermediate or maximum available clamping force, while at the same time providing that this clamping force can _. be instantly released without any further significant increase in the force applied to the tissue being held. Still a further problem is that the instrument must be capable of being rapidly disengaged from the controlling mechanism so that an alternative instrument can be quickly attached.

Although these problems are identified in relation to laparoscopic surgery, they apply to other applications in which a delicate object needs be grasped with restricted force, and held securely until released.

It is an object of the present invention to address or at least ameliorate some of the above disadvantages. Notes

1. The term "comprising" (and grammatical variations thereof) is used in this specification in the inclusive sense of "having" or "including", and not in the exclusive sense of "consisting only of". 2. The above discussion of the prior art in the Background of the invention, is not an admission that any information discussed therein is citable prior art or part of the common general knowledge of persons skilled in the art in any country. 3. Note, the terms "proximate" and "distal" as used in this specification refer to the relationship of a described feature relative to the working end of an attached surgical or grasping instrument.

BRIEF DESCRIPTION OF INVENTION Accordingly, in one broad form of the invention, there is provided a grasping instrument control mechanism; said instrument including opposing jaws at an end of an elongate hollow member; said mechanism including a rotatable operating handle acting on a jaws activating element; characterized in that said rotatable operating handle includes an arc of pinion teeth centred on the centre of rotation of said operating handle; said pinion teeth engaging with a rack of teeth along a portion of a cylindrical spring-retaining body communicating with said jaws activating element; said cylindrical spring-retaining body urged into a retracted position by rotation of said operating handle from a non-operating position towards an operating position proximate a fixed handle, wherein rotation of said operating handle past a point of resistance to further closure of said opposing jaws causes partial compression of a compression spring within said cylindrical spring-retaining body without substantial further closure of said opposing jaws.

Preferably, said mechanism is secured within a housing; a base portion of said housing integral with said fixed handle; said operating handle rotatable about a pivot provided in said base portion; said operating handle rotatable between a position maximally distal from said fixed handle and a position proximate said fixed handle; said operating handle passing through said non-operating position.

Preferably, said cylindrical spring-retaining body and a cylindrical pawl-retaining body (44) are slidingly located in a bore of an outer cylindrical body; said outer cylindrical body fixed within said base portion.

Preferably, said cylindrical pawl-retaining body includes a spring compression rod extending from a distal end of said cylindrical pawl-retaining body; said compression spring retained in said cylindrical spring-retaining body between an annular shoulder at a proximate end of said spring- retaining body and a spring compression nut engaged with a threaded portion of said spring compression rod; said spring compression rod extending into, and through substantially the length of said cylindrical spring- retaining body.

Preferably, said cylindrical spring-retaining body abuts said cylindrical pawl-retaining body when said operating handle is in said non-operating position; said compression spring then being in a minimum compressed state. Preferably, an opposing pair of pawls are retained in a longitudinal slot provided in said cylindrical pawl- retaining body; said pawls shaped at respective proximate ends as jaws so as to close on a ball-end of said jaws activating element; said pawls shaped at respective distal ends to allow symmetrical rotation of one pawl relative to the other between a closed retaining position on said ball- end, and an open disengaging position.

Preferably, said outer cylindrical body is provided with a counterbore at a proximate end of said outer cylindrical body; said counterbore arranged to allow partial protrusion of said opposing pair of pawls from said slot; said protrusion enabled when said proximate ends of said pawls are brought into coincidence with said counterbore by rotation of said operating handle into a position maximally distal from said fixed handle; said pawls rotated into a protruding position through contact of said ball-end of said jaws activating element moving into said proximal direction for disassembly of said instrument from said control mechanism.

Preferably, said opposing pair of pawls are constrained in said closed retaining position when said cylindrical pawl- retaining body is retracted wholly within said bore of said outer cylindrical body by partial rotation of said operating handle towards said fixed handle; said pawls then closed on said ball end of said jaws activating element when said instrument is assembled to said control mechanism.

Preferably, said mechanism further includes a locking lever for releasably retaining said operating handle in a desired operating position in which resistance to further closure of said jaws is accompanied by a degree of compression of said compression spring; said locking lever including first and second teeth for engagement with an arc of locking teeth of said operating handle.

Preferably, said arc of pinion teeth and said arc of locking teeth are substantially arranged at opposing sides of said operating handle and substantially diametrically opposed about said centre of rotation of said operating handle; said locking lever projecting from said housing at a side of said fixed handle distal from said operating handle; said lever arranged for depressing in a direction of said fixed handle by a finger of the hand of a user.

Preferably, said locking lever is an extension of a locking lever plate; said locking lever and said locking lever plate rotating about a pivot provided in said base portion of said housing; said locking lever and locking lever plate biased towards a non-locking position by a spring loaded ball engaging with a hole (88) in said locking lever plate. Preferably, teeth of said arc of locking teeth of said operating handle are set at angles with respect to radii at respective ones of said teeth; said angles such that said teeth point in a direction opposite to said rotation of said operating handle towards said position proximate said fixed handle.

Preferably, said first and second teeth project from said locking lever plate; said first and second teeth generally angled in an opposite direction to said angles of said teeth of said arc of locking teeth of said operating handle .

Preferably, a first tooth of said first and second teeth is located at greater remove from said pivot of said locking plate than the second tooth of said first and second teeth.

Preferably, said jaws are locked in a said desired operating position by the steps of:

a. applying sufficient additional pressure to said operating handle to induce said partial compression of said compression spring,

b. simultaneously moving said locking lever (82) towards said fixed handle,

c. releasing pressure on said operating handle,

d. releasing pressure on said locking lever, said movement of said locking lever towards said fixed

^'handle rotating said first and second teeth into meshing engagement with teeth of said arc of locking teeth; and wherein relative angles of said first tooth and meshing teeth of said arc of locking teeth, act to lock said first tooth into locked engagement with said meshing teeth by bias of said operating handle to return said operating handle to said non-operating position due to said partial compression of said compression spring.

Preferably, said second tooth acts to release said locking position of said locking lever; relative angles of said second tooth and teeth of said arc of locking teeth arranged such that slight rotation of said operating handle towards said fixed handle by slight renewed pressure on said operating handle, acts to release engagement between said first tooth and said meshing teeth of said arc of locking teeth; said spring-loaded ball then acting to return said locking lever to said non-locking position.

Preferably, a said instrument is detachably connected to said control mechanism by an instrument connector element at a proximal end of said mechanism; said connector element comprising an externally threaded cylindrical body; said cylindrical body integral with a disc provided with a finger graspable periphery; said cylindrical body and said disc rotatable around a proximate end portion of said outer cylindrical body; said proximate end portion projecting from said housing.

Preferably, a distal end of said elongate hollow member of a said surgical instrument is provided with a captive nut for threaded engagement with said externally threaded cylindrical body; said distal end provided with a skirt locating within said nut; said skirt clamped to a proximate face of said outer cylindrical body when said captive nut is maximally advanced on said externally threaded cylindrical body, the arrangement being such that said instrument may be rotated 360 degrees relative said control mechanism by means of said finger graspable periphery.

Preferably, said operating handle includes an arcuate segment diametrically opposite said arc of pinion teeth; said mechanism including a conductive path for the transmission of high frequency electric currents for use in diathermy procedures; said path including a cable connector extending from said fixed handle and a spring-loaded conductive rod in contact with an arcuate edge of said arcuate segment.

In another broad form of the invention, there is provided a control mechanism for a grasping instrument; said instrument comprising an elongate hollow member provided with a tool at an outer end of said elongate hollow member; said mechanism including spring modulation of force applied to an inelastic tool activating element within said elongate hollow member; said force applied by displacement of an operating handle, and wherein said force is limited to the force exerted by said spring when said spring is at a maximum predetermined compression.

Preferably, a retractive force applied to said inelastic tool activating element in a distal direction causes a said tool to change from an inactive state to an activated state .

Preferably, said mechanism is secured within a housing; a base portion of said housing integral with a fixed handle; said operating handle rotatable about a pivot provided in said base portion; said operating handle rotatable between a position proximate said fixed handle and a position distal from said fixed handle.

Preferably, a cylindrical spring-retaining body and a cylindrical pawl-retaining body are slidingly located in a bore of an outer cylindrical body; said outer cylindrical body fixed within said base portion.

Preferably, rotational displacement of said operating handle towards said position proximate said fixed handle, is transmitted via an arc of pinion teeth to a rack; said rack provided along a portion of a side of said cylindrical spring-retaining body; rotation of said operating handle towards said position proximate said fixed handle rotating said arc of pinion teeth, thereby urging said cylindrical spring retaining body into a retracting linear motion in said distal direction.

Preferably, said cylindrical pawl-retaining body is provided with a spring compression rod extending from a distal end of said cylindrical pawl-retaining body.

Preferably, said spring is retained in said cylindrical spring-retaining body between an annular shoulder at a proximate end of said spring-retaining body and a spring compression nut; said spring compression nut engaged with a threaded portion of said spring compression rod; said spring compression rod extending into, and through substantially the length of said spring-retaining body.

Preferably, said cylindrical spring-retaining body abuts said cylindrical pawl-retaining body when said operating handle is in a non-force transmitting position; said spring then being in a minimum compressed state.

Preferably, rotation of said operating handle from said non-force transmitting position to a position proximate said fixed handle causes said spring to change from said minimum compressed state to said maximum predetermined compression; said operating handle then biased toward contra-rotation towards said non-force transmitting position.

Preferably, an opposing pair of pawls are retained in a longitudinal slot provided in said cylindrical pawl- retaining body; said pawls shaped at respective proximate ends as jaws so as to close on a ball-end of said inelastic tool activating element; said pawls shaped at respective distal ends to allow symmetrical rotation of one pawl relative to the other between a closed retaining position on said ball-end, and an open disengaging position.

Preferably, said opposing pair of pawls are constrained in said closed retaining position when said cylindrical pawl- retaining body is retracted wholly within said bore of said outer cylindrical body.

Preferably, said outer cylindrical body is provided with a counterbore at a proximate end of said cylindrical body; said counterbore arranged to allow partial protrusion of said opposing pair of pawls from said slot; said protrusion enabled when said proximate ends of said pawls are brought into coincidence with said counterbore by rotation of said operating handle into a position maximally distal from said fixed handle. Preferably, rotation of said operating handle into said position maximally distal from said fixed handle urges said spring-retaining body and said pawl-retaining body into said position bringing said proximate ends of said pawls into coincidence with said counterbore, thereby allowing assembly and disengagement of a said instrument from said control mechanism.

Preferably, said opposing pair of pawls are rotated into said open releasing position by said ball-end acting against said jaws at said proximate ends of said pawls; said ball-end acting against said jaws as a said instrument is disengaged from said control mechanism.

Preferably, said mechanism further includes a locking lever for releasably retaining said operating handle in a desired said force transmitting position; said locking lever including first and second teeth for engagement with an arc of locking teeth of said operating handle.

Preferably, said arc of pinion teeth and said arc of locking teeth are substantially arranged at opposing sides of said operating handle and substantially diametrically opposed about said pivot.

Preferably, said locking lever projects from said housing at a proximate side of said fixed handle; said lever arranged for depressing in a direction of said fixed handle by a finger of the hand of a user.

Preferably, said locking lever is an extension of a locking lever plate; said locking lever and said locking lever plate rotating about a pivot provided in said base portion of said housing; said pivot passing through a hole in said locking lever plate.

Preferably, said base portion of said housing is provided with a spring-loaded ball; said ball biased towards partly protruding from an inside surface of said housing; protrusion of said ball varying with locking and nonlocking positions of said locking lever and locking lever plate; said ball in a maximum protruded state when said locking lever is in a non-locking position.

Preferably, said locking lever plate is provided with a spring-loaded ball engaging element; said element arranged so that said spring-loaded ball biases said element into a position centred on said ball; said locking lever in said non-locking position when said element is centred on said ball.

Preferably, said engaging element is a hole trough said locking lever plate. Preferably, teeth of said arc of locking teeth are set at angles with respect to radii at respective ones of said teeth; said angles such that said teeth point in a direction opposite to said rotation of said operating handle towards said position proximate said fixed handle.

Preferably, said first and second teeth project from said locking lever plate; said first and second teeth generally angled in an opposite direction to said angles of said teeth of said arc of locking teeth.

Preferably, said grasping instrument is locked in a grasping state by movement of said locking lever towards said fixed handle followed by release of pressure by a user on said operating handle; said movement of said locking lever rotating said first and second teeth into meshing engagement with teeth of said arc of locking teeth; and wherein relative angles of said first tooth and meshing teeth of said arc of locking teeth act to lock said first tooth into locked engagement with said meshing teeth by said bias toward contra-rotation of said operating handle.

Preferably, said second tooth acts to release said locking position of said locking lever; relative angles of said second tooth and teeth of said arc of locking teeth arranged such that slight rotation of said operating handle towards said fixed handle by renewed depression of said operating handle, acts to release engagement between said first tooth and said meshing teeth of said arc of locking teeth; said spring-loaded ball then acting to return said locking lever to said non-locking position.

Preferably, said mechanism includes a conductive path for the transmission of high frequency electric currents for use in diathermy procedures; said path including a cable connector extending from said fixed handle and a spring- loaded conductive rod in contact with an arcuate edge of said toothed plate.

Preferably, a said instrument is detachably connected to said control mechanism by an instrument connector element at a proximate end of said mechanism.

Preferably, an instrument connector element comprises a cylindrical body provided with an external thread; said cylindrical body integral with a disc provided with a finger graspable periphery; said cylindrical body and said disc rotatable around a proximate portion of said outer cylindrical body; said proximate portion projecting from said housing. Preferably, a distal end of said elongate hollow member of a said surgical instrument is provided with a captive nut for threaded engagement with said external thread; said distal end provided with a skirt locating within said nut; said skirt clamped to a proximate face of said outer cylindrical body when said captive nut is maximally advanced on said external thread, the arrangement being such that said instrument may be rotated 360 degrees relative said control mechanism by means of said finger graspable periphery.

Preferably, said housing further includes a cover portion; said cover portion attached to said base portion of said housing by at least one securing fastener; a head portion of said fastener provided with at least one pair of holes for engagement with corresponding pins of a fastener driving tool; said holes arranged so that said tool is able to provide rotational driving force in a tightening direction only; ramp features in said holes forcing disengagement of said tool when rotated in a fastener loosening direction.

In a another broad form of the invention, there is provided a method for applying an operating force to a grasping instrument; said force limited so as to prevent damage to said instrument from excessive force applied by a user; said method including the steps of: (a) interposing a spring mechanism between an operating handle of a control mechanism of said instrument and an inelastic instrument activating element,

(b) arranging wire diameter and number of coils of a spring of said spring mechanism said such that said spring does not reach full compression when said operating handle is moved to a maximum operating position.

In a further broad form of the invention, there is provided a locking system for an operating handle of a control mechanism of a grasping instrument; said locking system including a locking lever operable between a default nonlocking position and an operating handle locking position; said locking lever provided with first and second locking teeth; wherein a first of said locking teeth meshes with teeth of an arc of locking teeth of said operating handle to bias said locking lever in said^' locking position when pressure applied to said operating handle is released; a second of said locking teeth operative in releasing said locking lever from said locking position when a renewed pressure is applied to said operating handle.

Preferably, said locking lever is biased towards said nonlocking position by a spring-loaded ball; said ball biased to protrude from a supporting surface adjacent to a pivot of said lever; said spring-loaded ball engaging edges of a locating element provided in said lever; said lever in said non-locking position when said spring-loaded ball is centred with said locating element.

Preferably, teeth of said arc of locking teeth are set at angles with respect to radii at respective ones of said teeth; said angles such that said teeth point in a direction opposite to rotation of said operating handle in an operating direction.

Preferably, said first and second teeth project from a locking lever plate attached to said locking lever; said first and second teeth generally angled in an opposite direction to said angles of said teeth of said arc of locking teeth.

Preferably, a locking meshing of teeth of said arc of locking teeth and said first tooth of said locking lever is maintained by a biasing of rotation of said operating handle towards a non-operating direction.

Preferably, a leading edge of said first tooth engages with a leading edge of a tooth of said arc of locking teeth to draw said first locking teeth into a maximum meshed position with said arc of locking teeth when said locking lever is moved towards said locking position and pressure is released from said operating handle. Preferably, a trailing edge of said second tooth is brought into engagement with a trailing edge of a tooth of said arc of locking teeth when renewed pressure is applied to said operating handle in said operating direction; said engagement releasing said first locking teeth from said maximum meshed position; said spring-loaded ball then urging said locking lever to return to said non-locking position.

In yet a further broad form of the invention, there is provided a retaining mechanism for a ball end of an inelastic tool activating element of a grasping instrument; said retaining mechanism including a pair of opposing pawls operating in slots provided in a pawl-retaining cylindrical body; said pawls shaped at distal ends to rotate one against the other between a first closed position and a second open position of said pawls; said pawls provided at respective proximal ends with jaws; said jaws clamping around said ball end when said pawl-retaining cylindrical body is fully retracted into an outer cylindrical body; said jaws opening to release said ball end when said pawl- retaining cylindrical body is advanced proximally within said outer cylindrical body sufficient to bring said proximal ends of -said pawls into- coincidence with a counterbore of said outer cylindrical body. In another broad form of the invention there is provided a fastening system for clamping a cover portion to a base portion of a housing of a control mechanism for a grasping instrument; said fastening system comprising at least one threaded fastener provided with a head portion; said head portion provided with at least a pair of elongated arcuate slots in an outer surface of said head portion; each of said slots shaped at one side with a ramped surface extending from said outer surface to the bottom of said slot, and shaped at the other side with a surface substantially normal to said outer surface.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the present invention will now be described with reference to the accompanying drawings wherein:

Figure 1 is a side view of a control mechanism for a grasping instrument according to a first preferred embodiment of the invention, showing an instrument control mechanism with an example of an attachable surgical instrument,

Figure 2 is a side view of the control mechanism with the surgical instrument attached, Figure 3 is a sectioned side view of the control mechanism and surgical instrument of Figure 1 with a surgical instrument in a detached position,

Figure 3B is an enlargement of a portion of the mechanism of Figure 3,

Figure 4 is a sectioned side view of the control mechanism and surgical instrument of Figure 1 with the surgical instrument attached but in a non-activated state,

Figure 4B is an enlargement of a portion of the mechanism of Figure 4,

Figure 4C is a further enlargement of portion of Figure 4B,

Figure 5 is a sectioned side view of the control mechanism and surgical instrument of Figure 1 with the surgical instrument attached in an activated, locked state,

Figure 5B is an enlargement of a portion of the mechanism of Figure 5,

Figures 6A to 6B are enlarged sectioned side views and end views of portions of the mechanism of Figures 1 to 5, Figure 7 is a side view of a second preferred embodiment of diathermy instrument control mechanism according to the invention,

Figure 8 is a sectioned side view of the diathermy control mechanism of Figure 7. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS First Preferred Embodiment

With reference to Figure 1 to 3, in a first preferred application of the present invention, control mechanism 10 according to the invention, comprises a control mechanism 11 to which may be attached for example, any one of a number of surgical instruments for grasping, cutting and cauterizing tissue. An example of such a surgical instrument 12 comprises an elongate hollow member or shaft 14 (as best seen in Figure 3) , at the end of which is the active surgical instrument tool 16 (in this example a pair of grasping forceps) . For grasping and cutting operations, the instrument is activated by applying retractive force to an inelastic tool activating element, in this instance an activating rod 18 extending from the instrument tool mechanism 20 through shaft 14. This retractive force causes the tool 16 to change from an inactive state to an activated state. Control mechanism 11 comprises a housing 22 made up of a base portion 24 and a cover portion 26. Integrally formed with base portion 24, is a fixed handle 28 extending from base portion 24 and ending in a scissor-like ring 30 for insertion of at least one finger of the hand of a user (not shown) . Referring now particularly to Figures 3 and 3B, base portion 24 is provided with a pivot 32 about which an operating handle 34 can rotate from a position proximate fixed handle 28 (as shown in Figure 2) and a position maximally distal from fixed handle 28 (as shown in Figure 3) , and passing through an intermediate non-operating position (as shown in Figure 4) . Operating handle 34 is likewise provided with a scissor-like ring 36 for insertion of the thumb of a user, so that the two handles may be operated with the one hand in similar fashion to the manner of use of a pair of scissors.

Mounted rigidly to base portion 24, is an outer cylindrical body 38, with a proximate end portion 40 projecting from the proximate end of the base portion 24. Slidingly located within the bore of outer cylindrical body 38 are a cylindrical spring-retaining body 42 and a cylindrical pawl-retaining body 44. (These features are more clearly shown in the enlarged detail views of Figures 6A to 6C) . Attached at, or integral with, the distal end of pawl-retaining body 44 is a spring compression rod 46 extending into, and substantially the length of spring- retaining body 42, when the distal end of pawl-retaining body 44 abuts the proximate end of spring-retaining body 42 (as shown in Figure 6A) . Spring compression rod 46 is threaded at its distal end and provided with a spring compression nut 48. A compression spring 50 is retained between compression nut 48 and annular shoulder 52 at the proximate end of the cylindrical spring-retaining body 42.

Cylindrical pawl-retaining body 44 is provided with a longitudinal slot 49. Retained within longitudinal slot 49 are opposing pawls 54 and 55 shaped at their proximate ends as jaws to close on a ball end 56 of the inelastic activating rod 18. As best seen in the enlarged views of Figures 6A to 6C, the distal ends of pawls 54 and 55 are shaped so as to allow rotation one against the other between the open position of Figure GA and the closed positions of Figures 6B and 6C.

Note that this rotation of the pawls is effected without the need for pivot pins or the like; the pawls are loose within the slot and are restrained by the outer cylindrical body 38 and the countefbore 63 at the proximate end 40 of body 38.

Still with reference to Figures 6A to 6C as well as Figure 3, a portion of the side of the distal end of cylindrical spring-retaining body 42 is machined to provide a toothed rack 58 which engages with an arc of pinion teeth 60. Arc of pinion teeth 60 is part of a toothed plate 62 rigidly attached to, or integral with operating handle 34, and provided with a hole 33 for pivot 32. Also part of toothed plate 62 is an arc of locking teeth 64, substantially diametrically opposite to the arc of pinion teeth 60, with both arcs of teeth centred on pivot 32. It will be understood that, with rotation of operating handle 34 about pivot 32 in the proximate, or operating direction (that is towards fixed handle 28), pinion teeth 60 meshing with toothed rack 58 will retract the cylindrical spring-retaining body 42 in the distal direction as can be seen in Figures 4, 5 and 6C. Similarly, if operating handle 34 is rotated in the distal, or non- operating, direction away from fixed handle 28, cylindrical spring-retaining body will be advanced in the proximate direction as can be seen in Figures 3 and 6A.

When operating handle 34 is in the maximum distal, non-operating position of Figure 3 or 6A, the cylindrical spring-retaining body 42 and cylindrical pawl-retaining body 44 are sufficiently advanced towards the proximate end 40 of outer cylindrical body 38, for the proximate ends of pawls 54 and 55 to coincide with the counterbore 63 at the proximate end of the outer body (see Figure 6A) . In this position, the pawls 54 and 55 can be forced by ball end 56 to rotate relative to each other to the open position shown in Figures 3 and 6A, as, in this instance, the surgical instrument is pulled away from the control mechanism.

Referring again to Figures 1 to 3, control mechanism 11 is provided with an instrument connector element 65 which comprises an externally threaded cylindrical body 66. Cylindrical body 66 is integral with a disc 68 provided with a finger graspable periphery. The cylindrical body and the disc are rotatable around the proximate end portion 40 of the outer cylindrical body 38, projecting from housing 22.

Each instrument 12 which may be attached to the control mechanism 11, is provided with a captive nut 69 at the distal end of elongate hollow shaft 14, for threaded engagement with the external thread of the instrument connector element 65. The distal end of elongate hollow shaft 14 is provided with a skirt 70 arranged for clamping to a proximate face 72 of the externally threaded cylindrical body 66. By this means, with skirt 70 locked against the instrument connector element 65 by captive nut 69, the complete instrument 12 may be rotated 360 degrees about the shaft axis relative to the control mechanism 11. Initial retraction of cylindrical pawl-retaining body 44 will force pawls 54 and 55 into the closed position shown in Figures 4, 5, and 6B, as the pawls are withdrawn into the main bore of outer cylindrical body 38. As the pawls are retracted further, the ball end 56 and inelastic activating rod 18 are also retracted.

It will be understood, that as long as the inelastic activating rod 18 remains free to move in the distal direction (as shown by the arrows of Figure 6B) , cylindrical pawl-retaining body 44 will move in unison with cylindrical spring-retaining body 42 (as shown in Figures 4 and 6B) . However, when the instrument 16 closes onto a portion of tissue, or some other item (as shown in Figure 5), further movement of activating rod 18 will be resisted to the extent dependent on the nature of the tissue or item. At some point the resistance to further movement of the activating rod 18 becomes such that the installed spring force of spring 50 is exceeded and while cylindrical spring-retaining body 42 may be urged to continue movement to its maximum retraction within housing 22, the actual force applied to the tissue will be modulated by spring 50, as can be seen in Figure 6C.

The maximum travel of cylindrical spring-retaining body 42 in the distal direction, the wire diameter and number of coils of spring 50 are arranged so that spring 50 cannot reach full compression. Thus the maximum force applied to activating rod 18 is limited to the maximum exerted by spring 50 when at a maximum predetermined compression, even up to the point where operating handle 34 comes into contact with fixed handle 28. Before this point is reached a scissor cutting tool or grasping forceps of an attached surgical instrument for example (if not impeded) , will have reached its limit of closure, but since the force never exceeds the maximum predetermined by the spring at it maximum permitted compression, damage to instrument tools

(or to delicate tissue or other items) is prevented. For many procedures using forceps such as the example shown in Figures 1 to 5, or other grasping devices, it is desirable that a desired degree of clamping force on a portion of tissue or item be maintained. For this purpose the control mechanism 11 of this embodiment of the invention is provided with a locking mechanism 80 as shown in Figures 3 to 5. Locking mechanism 80 is arranged to hold the operating handle 34 in any of a number of possible incremental positions in which at least some additional compressive force has been applied to spring 50 as a result the of retraction of cylindrical spring-retaining body 42 relative to the pawl retaining body; that is, by the rotation of operating handle 34 in the proximate, or operating direction and when further closure of the jaws 16 is impeded. It will be understood that when such an additional force (in addition to the minimum installed spring force) is present, spring 50 will act to urge contra-rotation of operating handle 34 towards the distal, non-operating position.

The locking mechanism 80 provides interaction between locking teeth 84 of a locking lever 82 and the arc of locking teeth 64 provided on the toothed plate 62 described above. As can best be seen in the enlarged views of Figures 3B, 4B, 4C and 5B, locking lever 82 includes a locking lever plate 83 provided with first and second locking teeth 84A and 84B. Locking lever plate 83 and locking lever 82 pivot about locking lever pivot 86 between the unlocked position shown in Figures 3B and 4B, the intermediate engaging position of Figure 4C, and the fully locked position of Figure 5B.

The teeth of the arc of locking teeth 64, are set at angles with respect to radii at respective ones of the teeth, such that the teeth point in a direction opposite to the rotation of the operating handle 34 for applying compressive force to spring 50, that is, towards fixed handle 28. The pair of locking teeth 84A and 84B of locking lever 82 are also angled but in the opposite direction. It can be seen from a comparison of Figures 4B, 4C and 5B, that a first depressing of the locking lever 82 into the locking position of Figure 5B, brings the locking teeth 84A and 84B projecting from locking lever plate 83, into meshing engagement with teeth of the arc of locking teeth 64.

It should be noted that the leading edges of teeth 84A and 84B are set at different angles. This is partly to accommodate the angular difference of the locking teeth 64 with which these two teeth mesh, but also because they are functionally distinct, with tooth 84A being the active tooth in establishing the locking engagement of the teeth, and tooth 84B being active in disengagement.

As best understood from the enlarged view of Figure 4C, the leading edge of first tooth 84A (which is at greater remove from pivot 86) and the leading edge of a tooth of the arc of locking teeth 64 with which it engages, are both at the same angle relative the rotation centres o.f pivot 86 of locking lever plate 83 and pivot 32 of toothed plate 62. This angle is such that the biased tendency of the operating lever to contra-rotate towards the distal, non-operating position, acts to pull tooth 84B into the maximum meshed position shown in Figure 5B.

This meshing is initiated by a user, having applied the desired clamping force to an item such as a piece of tissue for example, as follows: (a) applying sufficient additional pressure to the operating handle to induce at least some additional compression of the spring 50, (b) simultaneously moving the locking lever in towards the fixed handle 28, and (c) immediately releasing the force he or she is applying to the operating handle 34.

This meshing engagement of the locking teeth 64 with the locking tooth 84A of the locking lever 82, is retained in the locked state when the operating lever 34 is in an operating position, because the operating lever is biased toward contra-rotation into a non-operating position by the force of spring 50.

Base portion 24 of housing 22 is provided with a spring-loaded ball 90, which is biased towards partly protruding from an inside surface 92 of the base portion 24. The protrusion of ball 90 varies with the locking and non-locking positions of locking lever 82, with the ball in a maximum protruded state when the locking lever is in the non-locking position shown in Figures 3, 3B, 4 and 4B. The arrangement is shown in the enlargements of Figures 3B, 4B and 4C. Locking lever plate 83 is provided with a spring- loaded ball engaging element, which in this instance is a hole 88 through the plate. Hole 88 is arranged so that the spring-loaded ball 90 biases the hole (and thus the locking lever plate and lever) into the non-locking position in which the hole is centred on the ball (as is the situation in Figures 3, 3B, 4 and 4B) . When the locking plate 83 is in the locking position shown in Figure 4C, ball 90 is partially depressed but still partially intruding into hole 88, thus biasing the plate and lever back to the position in which the hole 88 is centred on the ball, that is in the position of Figures 3, 3B and 4B.

To release operating lever 34 from its locked state, only a very slight renewed pressure is required on the operating handle 34, that is a very light squeezing pressure between the thumb and fingers of a user. It is by this action that the locking lever second tooth 84B becomes the active component. Again with reference to Figure 4C, it can be seen that the abutting of the trailing edge of tooth 84B and the trailing edge of the tooth of the arc of locking teeth 64 with which it meshes, that the slightest rotation applied to the operating handle 34 (in the direction opposite the arrow on plate 62 in Figure 4C; that is towards the fixed handle) , will induce a very small degree of rotation of locking lever plate 83 (in the direction opposite to the arrow on the plate 83 in Figure 4C) . This is sufficient to release the engagement between the leading edges of tooth 84A and its corresponding tooth of the arc of locking teeth. This is enough for the spring- loaded ball 90 to immediately urge locking lever 82 back into its default unlocked position.

In Use

In use, a user is able to apply a desired closing force to the tool of a surgical instrument for example, without risk of damage to the instrument, or to some fragile item such as tissue. In the case of forceps, a desired clamping force can be instantly retained by the relatively short throw of the locking lever, and almost instantly released by applying an insignificant brief additional pressure to the operating handle when in the locking position. As well, any of a number of interchangeable tools for cutting and gripping tissue or other items may be rapidly attached and detached by means of the novel pawl mechanism incorporated in the control mechanism.

It should be noted that although the above description is focused on an instrument incorporating a shaft with an inelastic rod operating within that shaft, the principles of force modulation by the spring mechanism and of the operating handle locking/unlocking mechanism can be equally applied to a flexible sheath with internal inelastic cable (a Bowden cable) for operating a flexible instrument.

Again, it will be understood that although the above description of the grasping control mechanism is directed primarily at surgical instruments, the principles of providing a spring modulated force and grasping locking mechanism of the invention can clearly be applied to a range instruments or tools for grasping and holding delicate items.

Second Preferred Embodiment

In a second preferred embodiment and application of the invention, elements of the control mechanism described above are adapted to a control mechanism for diathermy endoscopic procedures. With reference to Figure 7, a diathermy laparoscopic control mechanism 100 again comprises a control mechanism

110 to which may be attached any one of a range of endoscopic surgical instruments such as the surgical instrument 112 with forceps 116 shown in Figure 7. As can be seen in Figure 8, surgical instrument 112 is identical to the exemplary surgical instrument 12 shown for the first embodiment above and is attached to the control mechanism

110 and activated in precisely the same manner as previously described.

Thus in this embodiment also, the force provided for a procedure at the tool (forceps 116 in this instance) is modulated and limited by the spring-loaded mechanism described in detail above.

For transmission of the high frequency electric currents used in diathermy procedures, the control mechanism 110 of this embodiment is provided with a cable connector 102 projecting from fixed handle 128. Current is passed via compression spring 104 to conductive rod 106. Inner tip 107 of conductive rod 106 is urged into conducting contact with toothed plate 162, affixed to operating handle 134. In this embodiment toothed plate 162 is provided with a smooth arcuate edge 164 substantially diametrically opposite the arc of teeth 160. Base portion 124, fixed handle 128, operating handle

134 the surgical instrument connector element 165 as well as the elongate hollow shaft 114 of the instrument are all formed of non-conductive insulating material. However, toothed plate 162 is conductive so that the conductive path between cable connector 102 and the tool of the surgical instrument is completed via toothed plate 162, cylindrical spring-retaining body 142 and spring 150, the cylindrical pawl-retaining body 144, pawls 154 and 155 and activating rod 118.

In both the embodiments described above, the base portion and cover portion of the housing for the control mechanism may be fastened together by at least one, preferably two fasteners as can be seen in Figures 1, 2 and 7. Preferably these fasteners are arranged to allow tightening only with a suitable tool, and are resistant to unscrewing.

As can be seen in the inset of Figure 7, a threaded fastener 119 is includes a head portion 120 in which is provided at least a pair of elongated arcuate slots 121 in an outer surface of the head portion. Each of these slots 121 is shaped at one side with a ramped surface 122 extending from the outer surface of the head portion to the bottom 123 of the slot, and shaped at the other side with a surface substantially normal to the outer surface. Thus the slots allow the insertion of a driving tool with projecting pins, which when rotated against the surfaces normal to the outer surface of the head portion urge the fastener to rotate, but when rotated in the opposite direction force the tool to disengage without inducing rotation.

The above describes only some embodiments of the present invention and modifications, obvious to those skilled in the art, can be made thereto without departing from the scope of the present invention.

Claims

CIAIMS l.A grasping instrument control mechanism (10); said instrument including opposing jaws (16) at an end of an elongate hollow member (14) ; said mechanism including a rotatable operating handle (34) acting on a jaws activating element (18); characterized in that said rotatable operating handle (34) includes an arc of pinion teeth (60) centred on the centre of rotation of said operating handle (34); said pinion teeth (60) engaging with a rack of teeth (58) along a portion of a cylindrical spring-retaining body (42) communicating with said jaws activating element (18); said cylindrical spring-retaining body (42) urged into a retracted position by rotation of said operating handle (34) from a non-operating position towards an operating position proximate a fixed handle (28), wherein rotation of said operating handle (34) past a point of resistance to further closure of said opposing jaws (16) causes partial compression of a compression spring (50) within said cylindrical spring-retaining body (42) without substantial further closure of said opposing jaws (16) .

2. The mechanism of claim 1 wherein said mechanism is secured within a housing (22) ; a base portion (24) of said housing (22) integral with said fixed handle (28) ; said operating handle (34) rotatable about a pivot (32) provided in said base portion (24) ; said operating handle (34) rotatable between a position maximally distal from said fixed handle (28) and a position proximate said fixed handle (28); said operating handle passing through said non-operating position.

3. The mechanism of claim 2 wherein said cylindrical spring-retaining body (42) and a cylindrical pawl- retaining body (44) are slidingly located in a bore of an outer cylindrical body (38); said outer cylindrical body (38) fixed within said base portion (24).

4. The mechanism of claim 3 wherein said cylindrical pawl-retaining body (44) includes a spring compression rod (46) extending from a distal end of said cylindrical pawl-retaining body (44); said compression spring (50) retained in said cylindrical spring- retaining body (42) between an annular shoulder (52) at a proximate end of said spring-retaining body (42) and a spring compression nut (48) engaged with a threaded portion of said spring compression rod (46) ; said spring compression rod (46) extending into, and through substantially the length of said cylindrical spring-retaining body (42) .

5. The mechanism of any one of claims 2 to 4 wherein said cylindrical spring-retaining body (42) abuts said cylindrical pawl-retaining body (44) when said operating handle (34) is in said non-operating position; said compression spring (50) then being in a minimum compressed state.

6. The mechanism of any one of claims 2 to 5 wherein an opposing pair of pawls (54) (55) are retained in a longitudinal slot (49) provided in said cylindrical pawl-retaining body (44) ; said pawls (54) (55) shaped at respective proximate ends as jaws so as to close on a ball-end (56) of said jaws activating element (18); said pawls (54) (55) shaped at respective distal ends to allow symmetrical rotation of one pawl relative to the other between a closed retaining position on said ball-end (56) , and an open disengaging position.

7. The mechanism of claim 6 wherein said outer cylindrical body (38) is provided with a counterbore (63) at a proximate end of said outer cylindrical body; said counterbore (63) arranged to allow partial protrusion of said opposing pair of pawls (54) (55) from said slot (49) ; said protrusion enabled when said proximate ends of said pawls (54) (55) are brought into coincidence with said counterbore (63) by rotation of said operating handle (34) into a position maximally distal from said fixed handle (28); said pawls

(54) (55) rotated into a protruding position through contact of said ball-end of said jaws activating element (18) moving into said proximal direction for disassembly of said instrument (12) from said control mechanism (10) .

8. The mechanism of claim 6 or 7 wherein said opposing pair of pawls (54) (55) are constrained in said closed retaining position when said cylindrical pawl- retaining body (44) is retracted wholly within said bore of said outer cylindrical body (38) by partial rotation of said operating handle (34) towards said fixed handle (28) ; said pawls (54) (55) then closed on said ball end of said jaws activating element (18) when said instrument is assembled to said control mechanism.

9. The mechanism of any one of claims 1 to 8 wherein said mechanism further includes a locking lever (82) for releasably retaining said operating handle (34) ^■ in a desired operating position in which resistance to further closure of said jaws (16) is accompanied by a degree of compression of said compression spring (50); said locking lever (82) including first and second teeth (84A) (84B) for engagement with an arc of locking teeth (64) of said operating handle (34) .

10. The mechanism of claim 9 wherein said arc of pinion teeth (60) and said arc of locking teeth (64) are substantially arranged at opposing sides of said operating handle (34) and substantially diametrically opposed about said centre of rotation of said operating handle (34) ; said locking lever (82) projecting from said housing (22) at a side of said fixed handle (28) distal from said operating handle (34) ; said lever (82) arranged for depressing in a direction of said fixed handle (28) by a finger of the hand of a user.

11. The mechanism of claim 9 or 10 wherein said locking lever (82) is an extension of a locking lever plate (83); said locking lever (82) and said locking lever plate (83) rotating about a pivot (86) provided in said base portion (24) of said housing (22); said locking lever (82) and locking lever plate (83) biased towards a non-locking position by a spring loaded ball (90) engaging with a hole (88) in said locking lever plate.

12. The mechanism of any one of claims 9 to 11 wherein teeth of said arc of locking teeth (64) of said operating handle (34) are set at angles with respect to radii at respective ones of said teeth; said angles such that said teeth point in a direction opposite to said rotation of said operating handle

(34) towards said position proximate said fixed handle (28) .

13. The mechanism of claim 11 or 12 wherein said first and second teeth (84A) (84B) project from said locking lever plate (83) ; said first and second teeth generally angled in an opposite direction to said angles of said teeth of said arc of locking teeth (64) of said operating handle (34) .

14. The mechanism of any one of claims 9 to 13 wherein a first tooth of said first and second teeth is located at greater remove from said pivot (32) of said locking plate than the second tooth of said first and second teeth.

15. The mechanism of any one of claims 9 to 14 wherein said jaws (16) are locked in a said desired operating position by the steps of:

a. applying sufficient additional pressure to said operating handle (34) to induce said partial compression of said compression spring,

b. simultaneously moving said locking lever (82) towards said fixed handle (28)

c. releasing pressure on said operating handle (34), d. releasing pressure on said locking lever (82),

e. said movement of said locking lever (82) towards said fixed handle (28) rotating said first and second teeth (84A) (84B) into meshing engagement with teeth of said arc of locking teeth (64); and wherein relative angles of said first tooth (84A) and meshing teeth of said arc of locking teeth, act to lock said first tooth into locked engagement with said meshing teeth by bias of said operating handle (34) to return said operating handle to said non-operating position due to said partial compression of said compression spring (50).

16. The mechanism of claim 15 wherein said second tooth (84B) acts to release said locking position of said locking lever (82) ; relative angles of said second tooth and teeth of said arc of locking teeth arranged such that slight rotation of said operating handle (34) towards said fixed handle (28) by slight renewed pressure on said operating handle (34), acts to release engagement between said first tooth (84A) and said meshing teeth of said arc of locking teeth

(64); said spring-loaded ball (90) then acting to return said locking lever (82) to said non-locking position.

17. The mechanism of any one of claims 3 to 8 wherein a said instrument (12) is detachably connected to said control mechanism by an instrument connector element (65) at a proximal end of said mechanism; said connector element comprising an externally threaded cylindrical body (66); said cylindrical body integral with a disc (68) provided with a finger graspable periphery; said cylindrical body and said disc rotatable around a proximate end portion (40) of said outer cylindrical body (38); said proximate end portion projecting from said housing (22) .

18. The mechanism of claim 17 wherein a distal end of said elongate hollow member (14) of a said surgical instrument (12) is provided with a captive nut (69) for threaded engagement with said externally threaded cylindrical body (66); said distal end provided with a skirt (70) locating within said nut (69); said skirt clamped to a proximate face (72) of said outer cylindrical body (38) when said captive nut is maximally advanced on said externally threaded cylindrical body, the arrangement being such that said instrument may be rotated 360 degrees relative said control mechanism by means of said finger graspable periphery.

19. The mechanism of claim 17 or 18 wherein said operating handle (134) includes an arcuate segment (164) diametrically opposite said arc of pinion teeth (160) ; said mechanism including a conductive path for the transmission of high frequency electric currents for use in diathermy procedures; said path including a cable connector (102) extending from said fixed handle (128) and a spring-loaded conductive rod (106) in contact with an arcuate edge of said arcuate segment (164).

20. A method for applying an operating force to a grasping instrument; said force limited so as to prevent damage to said instrument from excessive force applied by a user; said method including the steps of:

interposing a spring mechanism between an operating handle of a control mechanism of said instrument and a jaw activating element,

arranging wire diameter and number of coils of a spring of said spring mechanism said such that said spring does not reach full compression when said operating handle is rotated to a maximum operating position and past a point of resistance to further closure of opposing jaws of said instrument, wherein said spring mechanism includes a spring- retaining cylindrical body; a rack of teeth along a portion of said spring-retaining body meshing with teeth of an arc of pinion teeth of an operating handle of said control mechanism.

21. A control mechanism for a grasping instrument; said instrument comprising an elongate hollow member provided with a tool at an outer end of said elongate hollow member; said mechanism including spring modulation of force applied to an inelastic tool activating element within said elongate hollow member; said force applied by displacement of an operating handle, and wherein said force is limited to the force exerted by said spring when said spring is at a maximum predetermined compression.

22. The mechanism of claim 21 wherein a retractive force applied to said inelastic tool activating element in a distal direction causes a said tool to change from an inactive state to an activated state.

23. The mechanism of claim 21 or 22 wherein said mechanism is secured within a housing; a base portion of said housing integral with a fixed handle; said operating handle rotatable about a pivot provided in said base portion; said operating handle rotatable between a position proximate said fixed handle and a position distal from said fixed handle.

24. The mechanism of claim 23 wherein a cylindrical spring-retaining body and a cylindrical pawl-retaining body are slidingly located in a bore of an outer cylindrical body; said outer cylindrical body fixed within said base portion.

25. The mechanism of claim 24 wherein rotational displacement of said operating handle towards said position proximate said fixed handle, is transmitted via an arc of pinion teeth to a rack; said rack provided along a portion of a side of said cylindrical spring-retaining body; rotation of said operating handle towards said position proximate said fixed handle rotating said arc of pinion teeth, thereby urging said cylindrical spring retaining body into a retracting linear motion in said distal direction.

26. The mechanism of claim 24 or 25 wherein said cylindrical pawl-retaining body is provided with a spring compression rod extending from a distal end of said cylindrical pawl-retaining body.

27. The mechanism of claim 26 wherein said spring is retained in said cylindrical spring-retaining body between an annular shoulder at a proximate end of said spring-retaining body and a spring compression nut; said spring compression nut engaged with a threaded portion of said spring compression rod; said spring compression rod extending into, and through substantially the length of said spring-retaining body.

28. The mechanism of any one of claims 24 to 27 wherein said cylindrical spring-retaining body abuts said cylindrical pawl-retaining body when said operating handle is in a non-force transmitting position; said spring then being in a minimum compressed state.

29. The mechanism of claim 28 wherein rotation of said operating handle from said non-force transmitting position to a position proximate said fixed handle causes said spring to change from said minimum compressed state to said maximum predetermined compression; said operating handle then biased toward contra-rotation towards said non-force transmitting position.

30. The mechanism of any one of claims 24 to 29 wherein an opposing pair of pawls are retained in a longitudinal slot provided in said cylindrical pawl- retaining body; said pawls shaped at respective proximate ends as jaws so as to close on a ball-end of said inelastic tool activating element; said pawls shaped at respective distal ends to allow symmetrical rotation of one pawl relative to the other between a closed retaining position on said ball-end, and an open disengaging position.

31. The mechanism of claim 30 wherein said opposing pair of pawls are constrained in said closed retaining position when said cylindrical pawl-retaining body is retracted wholly within^' said bore of said outer cylindrical body.

32. The mechanism of claim 30 or 31 wherein said outer cylindrical body is provided with a counterbore at a proximate end of said cylindrical body; said counterbore arranged to allow partial protrusion of said opposing pair of pawls from said slot; said protrusion enabled when said proximate ends of said pawls are brought into coincidence with said counterbore by rotation of said operating handle into a position maximally distal from said fixed handle.

33. The mechanism of claim 32 wherein rotation of said operating handle into said position maximally distal from said fixed handle urges said spring- retaining body and said pawl-retaining body into said position bringing said proximate ends of said pawls into coincidence with said counterbore, thereby allowing assembly and disengagement of a said instrument from said control mechanism.

34. The mechanism of any one of claims 30 to 33 wherein said opposing pair of pawls are rotated into said open releasing position by said ball-end acting against said jaws at said proximate ends of said pawls; said ball-end acting against said jaws as a said instrument is disengaged from said control mechanism.

35. The mechanism of any one of claims 28 to 34 wherein said mechanism further includes a locking lever for releasably retaining said operating handle in a desired said force transmitting position; said locking lever including first and second teeth for engagement with an arc of locking teeth of said operating handle.

36. The mechanism of claim 35 wherein said arc of pinion teeth and said arc of locking teeth are substantially arranged at opposing sides of said operating handle and substantially diametrically opposed about said pivot.

37. The mechanism of claim 35 or 36 wherein said locking lever projects from said housing at a proximate side of said fixed handle; said lever arranged for depressing in a direction of said fixed handle by a finger of the hand of a user.

38. The mechanism of any one of claims 35 to 37 wherein said locking lever is an extension of a locking lever plate; said locking lever and said locking lever plate rotating about a pivot provided in said base portion of said housing; said pivot passing through a hole in said locking lever plate.

39. The mechanism of claim 38 wherein said base portion of said housing is provided with a spring- loaded ball; said ball biased towards partly protruding from an inside surface of said housing; protrusion of said ball varying with locking and nonlocking positions of said locking lever and locking lever plate; said ball in a maximum protruded state when said locking lever is in a non-locking position.

40. The mechanism of claim 39 wherein said locking lever plate is provided ^' with a spring-loaded ball engaging element; said element arranged so that said spring-loaded ball biases said element into a position centred on said ball; said locking lever in said non- locking position when said element is centred on said ball.

41. The mechanism of claim 40 wherein said engaging element is a hole trough said locking lever plate.

42. The mechanism of any one of claims 35 to 41 wherein teeth of said arc of locking teeth are set at angles with respect to radii at respective ones of said teeth; said angles such that said teeth point in a direction opposite to said rotation of said operating handle towards said position proximate said fixed handle.

43. The mechanism of any one of claims 35 to 42 wherein said first and second teeth project from said locking lever plate; said first and second teeth generally angled in an opposite direction to said angles of said teeth of said arc of locking teeth.

44. The mechanism of any one of claims 38 to 43 wherein a first tooth of said first and second teeth is located at greater remove from said pivot of said locking plate than the second tooth of said first and second teeth.

45. The mechanism of any one of claims 35 to 44 wherein said grasping instrument is locked in a grasping state by movement of said locking lever towards said fixed handle followed by release of pressure by a user on said operating handle; said movement of said locking lever rotating said first and second teeth into meshing engagement with teeth of said arc of locking teeth; and wherein relative angles of said first tooth and meshing teeth of said arc of locking teeth act to lock said first tooth into locked engagement with said meshing teeth by said bias toward contra-rotation of said operating handle.

46. The mechanism of claim 45 wherein said second tooth acts to release said locking position of said locking lever; relative angles of said second tooth and teeth of said arc of locking teeth arranged such that slight rotation of said operating handle towards said fixed handle by renewed depression of said operating handle, acts to release engagement between said first tooth and said meshing teeth of said arc of locking teeth; said spring-loaded ball then acting to return said locking lever to said non-locking position.

47. The mechanism of claim 34 wherein said mechanism includes a conductive path for the transmission of high frequency electric currents for use in diathermy procedures; said path including a cable connector extending from said fixed handle and a spring-loaded conductive rod in contact with an arcuate edge of said toothed plate.

48. The mechanism of any one of claims 21 to 47 wherein a said instrument is detachably connected to said control mechanism by an instrument connector element at a proximate end of said mechanism.

49. The mechanism of claim 48 wherein an instrument connector element comprises a cylindrical body provided with an external thread; said cylindrical body integral with a disc provided with a finger graspable periphery; said cylindrical body and said disc rotatable around a proximate portion of said outer cylindrical body; said proximate portion projecting from said housing.

50. The mechanism of claim 49 wherein a distal end of said elongate hollow member of a said surgical instrument is provided with a captive nut for threaded engagement with said external thread; said distal end provided with a skirt locating within said nut; said skirt clamped to a proximate face of said outer cylindrical body when said captive nut is maximally advanced on said external thread, the arrangement being such that said instrument may be rotated 360 degrees relative said control mechanism by means of said finger graspable periphery.

51. The mechanism of any one of claims 23 to 50 wherein said housing further includes a cover portion; said cover portion attached to said base portion of said housing by at least one securing fastener; a head portion of said fastener provided with at least one pair of holes for engagement with corresponding pins of a fastener driving tool; said holes arranged so that said tool is able to provide rotational driving force in a tightening direction only; ramp features in said holes forcing disengagement of said tool when rotated in a fastener loosening direction.

52. A method for applying an operating force to a grasping instrument; said force limited so as to prevent damage to said instrument from excessive force applied by a user; said method including the steps of:

53. interposing a spring mechanism between an operating handle of a control mechanism of said instrument and an inelastic instrument activating element,

54. arranging wire diameter and number of coils of a spring of said spring mechanism said such that said spring does not reach full compression when said operating handle is moved to a maximum operating position.

55. A locking system for an operating handle of a control mechanism of a grasping instrument; said locking system including a locking lever operable between a default non-locking position and an operating handle locking position; said locking lever provided with first and second locking teeth; wherein a first of said locking teeth meshes with teeth of an arc of locking teeth of said operating handle to bias said locking lever in said locking position when pressure applied to said operating handle is released; a second of said locking teeth operative in releasing said locking lever from said locking position when a renewed pressure is applied to said operating handle.

56. The locking system of claim 53 wherein said locking lever is biased towards said non-locking position by a spring-loaded ball; said ball biased to protrude from a supporting surface adjacent to a pivot of said lever; said spring-loaded ball engaging edges of a locating element provided in said lever; said lever in said non-locking position when said spring- loaded ball is centred with said locating element.

57. The locking system of claim 53 or 54 wherein teeth of said arc of locking teeth are set at angles with respect to radii at respective ones of said teeth; said angles such that said teeth point in a direction opposite to rotation of said operating handle in an operating direction.

58. The locking system of any one of claims 53 to 55 wherein said first and second teeth project from a locking lever plate attached to said locking lever; said first and second teeth generally angled in an opposite direction to said angles of said teeth of said arc of locking teeth.

59. The locking system of any one of claims 53 to 56 wherein a locking meshing of teeth of said arc of locking teeth and said first tooth of said locking lever is maintained by a biasing of rotation of said operating handle towards a non-operating direction.

60. The locking system of any one of claims 53 to 57 wherein a leading edge of said first tooth engages with a leading edge of a tooth of said arc of locking teeth to draw said first locking teeth into a maximum meshed position with said arc of locking teeth when said locking lever is moved towards said locking position and pressure is released from said operating handle.

61. The locking system of claim 58 wherein a trailing edge of said second tooth is brought into engagement with a trailing edge of a tooth of said arc of locking teeth when renewed pressure is applied to said operating handle in said operating direction; said engagement releasing said first locking teeth from said maximum meshed position; said spring-loaded ball then urging said locking lever to return to said nonlocking position.

62. A retaining mechanism for a ball end of an inelastic tool activating element of a grasping instrument; said retaining mechanism including a pair of opposing pawls operating in slots provided in a pawl-retaining cylindrical body; said pawls shaped at distal ends to rotate one against the other between a first closed position and a second open position of said pawls; said pawls provided at respective proximal ends with jaws; said jaws clamping around said ball end when said pawl-retaining cylindrical body is fully retracted into an outer cylindrical body; said jaws opening to release said ball end when said pawl- retaining cylindrical body is advanced proximally within said outer cylindrical body sufficient to bring said proximal ends of said pawls into coincidence with a counterbore of said outer cylindrical body.

63. A fastening system for clamping a cover portion to a base portion of a housing of a control mechanism for a grasping instrument; said fastening system comprising at least one threaded fastener provided with a head portion; said head portion provided with at least a pair of elongated arcuate slots in an outer surface of said head portion; each of said slots shaped at one side with a ramped surface extending from said outer surface to the bottom of said slot, and shaped at the other side with a surface substantially normal to said outer surface.

64. A control mechanism for a grasping instrument as herein described and with reference to the accompanying drawings .