GB2451025A

GB2451025A - A tool with a switch encircling a handpiece

Info

Publication number: GB2451025A
Application number: GB0818796A
Authority: GB
Inventors: Michael John Radley Young; Stephen Michael Radley Young
Original assignee: SRA Developments Ltd
Current assignee: SRA Developments Ltd
Priority date: 2005-07-08
Filing date: 2005-07-08
Publication date: 2009-01-14
Anticipated expiration: 2025-07-08
Also published as: GB0818796D0; GB2451025B; GB0514011D0; GB2428283B; GB2428283A

Abstract

A tool has a finger touch operated activation switch 7 encircling a handpiece 1 of the tool. The switch may be a fluid filled toroidal element transmitting fluid pressure to a membrane backed micro-switch, a pivotal nose shell or shroud (13, fig 2) mounted on a ball joint with electrical contacts, an electrical annular switch (34, fig 3) made of a ring of QTC material (e.g. metallic particles embedded in an elastomeric matrix in which quantum tunnelling occurs under compression), or contact strips on a PCB separated by QTC material. One embodiment allows a power level of the tool to be controlled. An operative element of the tool may be rotated to a desired orientation, and the switch may be coaxial with a longitudinal axis of the tool. The tool may be an ultrasonic surgical tool such as a laparoscope having an elongate shaft extending from the handpiece 1.

Description

SURGICAL TOOL ACTIVATION SWITCH

The present invention relates to an improved electrical switch arrangement of particular benefit in surgical tools, such as laparoscopic instruments. More particularly, but not exclusively, it relates to an improved switch arrangement for the activation of ultrasonically vibratable cutting and coagulating tools and the like, and to tools provided with such a switch arrangement.

An extremely important principle in the design of surgical tools and instruments, and of tools and instruments for laparoscopic ("keyhole") surgery in particular, is that they must be designed so that they are as easy as possible for a surgeon to manipulate. This applies both to bringing the tool into contact with body tissues to be treated and to carrying out the treatment, which may be cutting tissue, coagulating blood vessels against bleeding, stapling or otherwise joining tissues, or a range of other techniques.

For taparoscopic surgery in particular, a number of tools have been devised that carry out such treatment only when electrically activated, obviating the risk of damage to other tissues while the tool is being brought to bear on the tissue to be treated. Ultrasonically-vibratable tools have been found to be particularly suitable for laparoscopic surgery, generally comprising a handpiece provided with a source of ultrasonic vibrations, an elongate narrow waveguide connected thereto to transmit the ultrasonic vibrations, and a treatment had mounted to a distal tip of the waveguide, which may act on adjacent tissue when ultrasonically vibrated. The surgeon inserts the treatment head and waveguide into a patient's body through a narrow incision and moves the treatment head to the tissue to be treated, usually guided by endoscopic visualisation. When the treatment head is correctly engaged with the tissue, the ultrasonic vibrations are activated, and treatment is carried out.

Some ultrasonically-vibratable laparoscopic tools have treatment heads provided with a cutting edge that may be used to sever tissue when vibrated. Others are provided with jaw arrangements that are used to grip an element of tissue before being ultrasonically vibrated.

These can be used to coagulate or cut the gripped tissue, or both. Examples of such tools are illustrated in our UK Patents Nos. GB2333709, GB2348810, GB2365775, GB2371492 and GB2387782, and our pending UK Patent Applications Nos. GB0508505.5 and GB050432 1.1.

In each case, the treatment head operates substantially in a single plane, and so it is usually necessary to rotate the treatment head about a longitudinal axis of the waveguide so that it is correctly aligned with the tissue to be treated. Rotating the whole tool may be possible, but is likely to require excessive and unergonomic contortions of the surgeon's wrist and arm.

Arrangements have thus been proposed in which the waveguide and treatment head may be rotated relative to the handpiece of the tool, one example of which is described in our pending UK Patent Application No. 0500937.8.

While such arrangements may improve the ergonomics of manipulating such tools, it is still necessary to activate the tool selectably to make the required cut, etc. In some cases, a foot-operated switch linked to a power supply for the source of ultrasonic vibrations is used.

However, operation of such a pedal switch is inevitably less controllable and sensitive than would be a hand-operated switch, and the surgeon will usually prefer to concentrate on very fine hand-eye coordination without also having to move his or her feet. Handpieces of tools with jaws frequently comprise scissor grip mechanisms to operate the jaws, located where one might otherwise position a trigger switch on a pistol grip. In any case, many surgeons hold such tools somewhat like a paint-brush or a pen, with a forefinger oriented generally longitudinally of the tool towards a nose of the handpiece, to make fine adjustments to the position of the treatment head. Where the treatment head and waveguide are rotatable with respect to the handpiece, the nose of the handpiece is frequently rotated with them.

Thus, it has up to now been impossible to provide a convenient and practical finger-operated activation switch for such tools, particularly one that is compatible with ergonomically designed tools with fully rotatable treatment heads.

It is hence an object of the present invention to provide a switching arrangement for such a tool which may comfortably be operated by a finger of a user in any alignment or angular conformation of the tool. It is also an object of the present invention to provide an ultrasonically vibratable laparoscopic surgical instrument provided with such a switching arrangement.

According to a first aspect of the present invention, there is provided a tool comprising manually graspable handpiece means, elongate shaft means extending from a distal end thereof and defining a longitudinal axis of the tool, an operative element of the tool mounted to the shaft means and switch means encircling the handpiece means and adapted selectably to activate the operative element by manual pressure.

A finger contact element of the switch means may thus be accessible for use from substantially any direction generally radial to the axis of the tool.

Preferably, said finger contact element is substantially radially symmetrical about said tool axis.

Advantageously, said finger contact element has a generally annular form.

Said generally annular finger contact element may then extend generally coaxially around the longitudinal axis of the tool.

Preferably, the operative element of the tool is selectively rotatable about the tool axis to a desired orientation for operation.

Advantageously, a distal portion of the handpiece means is rotatable together with the operative element.

The finger contact element of the switch means may be mounted to said rotatable distal portion.

Preferably, said tool comprises a surgical tool.

Advantageously, said tool comprises a laparoscopic surgical tool.

The tool may comprise an ultrasonically-vibratable surgical tool.

The shaft means may then comprise a waveguide to transmit ultrasonic vibrations from a source thereof in the handpiece means to a selectably ultrasonically-vibratable operative element at a distal end thereof.

In a first embodiment of the invention, the switch means comprises resiliently deformable chamber means containing a pressure transmitting medium and operatively linked to pressure-sensitive switch means.

Preferably, said chamber means and said pressure-sensitive switch means are connected by passage means through which said medium may pass.

Advantageously, said pressure transmitting medium is a liquid.

Alternatively, said pressure transmitting medium is a gas, optionally a compressed gas.

Preferably, said chamber means has a generally toroidal form encircling the handpiece means.

An outer wall of the chamber means may then comprise the finger contact element of the switch means.

Said outer wall may be so resiliently deformable under digital pressure as to revert to its original shape once said digital pressure is removed.

In a second embodiment of the present invention, the switch means comprises at least one switch element comprising a material which is substantially electrically non-conductive when undeformed but substantially electrically conductive when compressed or otherwise deformed.

Preferably, said material is adapted to become substantially conductive under a pressure no more than that exertable by a human finger.

Said material may comprise a quantum tunnelling composite (QTC) material.

The switch means advantageously comprises at least one switch element of said material so disposed between first and second electrical contact means that compression of said element results in a conductive path being established between the electrical contact means.

Said compression may result from digital pressure on the finger contact element of the switch means.

The finger contact element may comprise a resiliently flexible membrane adjacent said at least one switch element.

Preferably, said at least one switch element extends around the handpiece means of the tool adjacent the shaft means.

Advantageously, said at least one switch element comprises a plurality of separate switch elements of said material arranged generally in a ring encircling the handpiece means.

Alternatively, said at least one switch element comprises a single generally annular switch element of said material extending around the handpiece means.

In either case, the finger contact means may comprise a generally annular membrane defining an outer wall of a generally toroidal chamber means containing said at least one switch element and said electrical contact means.

In a third embodiment of the present invention, the switch means comprises outer shell means so pivotably mounted to an internal core body of the handpiece means that digital pressure on the shell means directed generally radially inwardly towards the axis of the tool from substantially any angle urges first electrical contact means mounted to the shell means into contact with second electrical contact means mounted to the core body.

Preferably, an outer surface of the shell means comprises the finger contact element of the switch means.

Advantageously, the switch means is provided with means to bias said electrical contact means apart.

The shell means may be mounted to the core body by means of ball joint means adjacent a distal end thereof, and the electrical contact means may be disposed adjacent respective proximal margins of the shell means and the core body.

The shell means and the core body may each be generally radially symmetrical about the longitudinal axis of the tool.

According to a second aspect of the present invention, there is provided a switch arrangement mountable to a tool, comprising resiliently deformable generally toroidal chamber means containing a pressure transmitting medium, said chamber means being adapted to encircle handpiece means of a tool and being operatively linked to pressure-sensitive switch means.

According to a third aspect of the present invention, there is provided a switch arrangement mountable to a tool, comprising at least one switch element comprising a material which is substantially electrically non-conductive when undeformed but substantially electrically conductive when compressed or otherwise deformed, said at least one switch element being disposable around a circumference of handpiece means of a tool.

According to a fourth aspect of the present invention, there is provided a switch arrangement mountable to a tool, comprising generally radially symmetrical outer shell means so pivotably mounted to an inner core of handpiece means of the tool that digital pressure on the shell means directed generally radially inwardly towards the core from substantially any angle urges first electrical contact means mounted to the shell means into contact with second electrical contact means mounted to the core.

Embodiments of the present invention will now be more particularly described by way of example and with reference to the accompany drawings, in which: Figure 1 is a perspective view of a first handpiece for an ultrasonic surgical tool embodying the present invention; Figure 2 is a side elevation, partially sectioned, of a second handpiece for an ultrasonic surgical tool embodying the present invention; Figure 3 is a side elevation, partially sectioned, of a third handpiece for an ultrasonic surgical tool embodying the present invention; Figure 4 is a scrap cross-sectional view of part of an annular switch element of the handpiece shown in Figure 3; and Figure 5 shows, schematically, an annular switch contact element isolated from the handpiece shown in Figure 3.

Referring now to the Figures, and to Figure 1 in particular, a first handpiece I for an ultrasonic surgical tool comprises a main casing 2 with a nose shroud 3 mounted distally thereto. An elongate narrow waveguide 4 extends distally from the nose shroud 3, and is surrounded by a substantially coaxially-extending sheath 5 which isolates the waveguide 4 from tissues through which it may be passed. An ultrasonically-vibratable treatment head (not shown) is mounted to a distal end of the waveguide 4.

An electrical cable 6 extending from a proximal end of the main casing 2 is connected to an electrical power supply. An ultrasonic transducer (not shown) is provided within the main casing 2, operatively linked to a proximal end of the waveguide 4. The particular tool shown is provided with a transducer set up to generate torsional mode ultrasonic vibrations, which are believed to be preferable to longitudinal mode ultrasonic vibrations in most surgical applications, but the present invention is equally applicable to tools employing longitudinal mode vibrations.

The nose shroud 3 is rotatable with respect to the main casing 2 about a longitudinal axis of the waveguide 4, and is linked by known means to the waveguide 4 and optionally the sheath 5, so that manual rotation of the nose shroud 3 may be used to bring the treatment head into a desired angular alignment.

The nose shroud 3 is encircled by an annular switch arrangement comprising a generally toroidal hollow finger contact element 7 having a resiliently flexible outer wall cooperating with a corresponding annular recess to define a volume filled with a pressure transmission fluid (either gas or liquid). Digital pressure on the outer wall of the toroidal element 7 displaces fluid therefrom along a flexible pipe 8 leading from its interior to a switching mechanism 9 within the main casing 2. The switching mechanism comprises a membrane backed by a micro-switch assembly. Fluid entering through the pipe 8 displaces the membrane so as to activate the microswitch, which generates a simple electrical code signal, I for "on", 0 for "off". When the toroidal element 7 is released, its outer wall resiliently resumes its original shape, and the fluid returns thereto from switching mechanism 9, which is thus turned off. This is used to turn power to the ultrasonic transducer on and off, either as an on/off toggle arrangement, or with the transducer activated only while the toroidal element 7 remains compressed.

A second handpiece 11 for an ultrasonic surgical tool is shown in Figure 2. This comprises a main casing 12, containing an ultrasonic transducer powered by means of an electrical cable 16 leading to a suitable power supply, all substantially similar to the first handpiece I shown in Figure 1. A nose shroud 13 is mounted thereto, and an elongate narrow waveguide 14 extends distally therefrom, surrounded by a substantially coaxially-extending sheath 15, and having an ultrasonically-vibratable treatment head (not shown) mounted to its distal end.

The structure of the nose shroud 1 3 of the second handpiece 11 is however different to that of the nose shroud 3 of the first handpiece 1. An outer casing 17 of the nose shroud 13 is mounted pivotably adjacent its distal end to a fixed ball structure 18, (conveniently forming part of the sheath 15) which is rigidly connected to a generally conical internal body 19 of the nose shroud 13. A first annular electrical contact 20 is provided on an inwardly-facing surface of the outer casing 17, adjacent its proximal margin, and a second annular electrical contact 21 is provided on an outwardly-facing surface of the internal body 19, opposing the first annular electrical contact 20.

Thus, digital pressure on any part of the outer casing 17 causes it to pivot about the fixed ball 18, bringing a portion of the first annular electrical contact 20 into conductive contact with a corresponding portion of the second annular electrical contact 21. An annular resilient membrane 22 extends between the outer casing 17 and the internal body 19 so as to bias the outer casing 17 back towards its equilibrium position; thus, when digital pressure on the outer casing 1 7 is removed, contact is broken between the annular electrical contacts 20, 21.

As above, this make/break switch arrangement may be used to activate the transducer only when the switch contact is made, or may be used in an on-off toggle switch arrangement.

A third handpiece 31 for an ultrasonic surgical tool is shown in Figure 3. Again, this comprises a main casing 32 containing an ultrasonic transducer powered by means of an electrical cable 36. A nose shroud 33 is mounted to the main casing 32, and has provision for a waveguide, sheath and treatment head (all omitted for clarity) to extend distally therefrom.

Externally, the third handpiece 31 closely resembles the first 1, having an annular switch arrangement encircling the nose shroud 33. However, this is an electrical annular switch arrangement 34, provided with switch leads 35 leading to a power supply for the transducer.

Figure 4 shows a portion of the electrical annular switch 34 in more detail. A shallow annular groove 36 encircles the nose shroud 33, and is covered by a corresponding annular cover 37 of a flexible resilient material, such as a silicone elastomer. This defines a generally toroidal volume with a generally lenticular cross-section, within which is located a pressure-sensitive contact arrangement comprising a quantum-tunnelling composite (QTC) material.

QTC materials (also known as quantum tunnelling conductive metal-polymer composites) are a relatively recent development, possessing the property of varying in electrical resistance by many orders of magnitude in response to relatively small imposed compressive forces, typically no more than fifteen Newtons. They have been developed by the University of Durham and Peratech Ltd of Darlington, and are the subject of a number of patent applications, such as International Patent Applications Nos. PCT/GB98/00206 and Conventional metal-polymer composites have been known for over 40 years, and comprise metal particles having a generally rounded shape embedded in a matrix of a non-conductive polymer (usually an elastomer). Normally, they are non-conductive, but if they can be compressed far enough to bring sufficient metal particles into contact to form a conductive path, they become (relatively poor) conductors (an effect known as "percolation"). The forces required are considerable, certainly far beyond anything exertable manually.

QTC materials comprise micron-size metallic particles embedded in an elastomeric matrix, but the particles have an irregular form, with numerous spikes extending outwardly therefrom. High charge densities are generated at the tips of these spikes. As a result, when two such particles approach, conduction by quantum tunnelling of electrons occurs, between nearby spikes, without the particles even needing to come into contact. The degree of conduction is very sensitive to the separation of the spikes and the number of spikes that come sufficiently close to spikes from other particles for quantum tunnelling to occur. Thus, it is possible to form a composite with such a volume fraction of spiky metal particles that it is effectively non-conductive under normal conditions, but under only minor compression becomes highly conductive. QTC elements are available, the resistance of which falls from I I2 f = to I Q under only fingertip pressure. QTC materials can thus form the basis not only of simple onloff switches, but also of proportional switches in which some function of a device can be varied continuously by varying finger pressure on the switch. QTC materials are easy to form into a desired shape. As well as simple pellets or pills, they can be formed into sheets, wires, tubes and so forth, which vary in conductivity with any imposed deformation.

In the annular switch arrangement 34 shown in Figures 3 and 4, the QTC material is disposed as a series of generally cylindrical QTC beads 38 strung on a circular loop 39 of metal wire, as shown in Figure 5. (NB the QTC beads 38 are arranged all round the loop 39, but some are omitted from Figure 5 for clarity). A conventional copper contact strip 40 extends along a floor of the entire groove 36. The loop 39 is connected to one switch lead 35 and the contact strip 40 to the other.

Thus, digital pressure anywhere on the annular cover 37 will bring an adjacent QTC bead 38 into contact with the contact strip 40, and then will compress the QTC bead 38, causing it to become electrically conductive and establishing a conducting path between the loop 39 and the contact strip 40. When the digital pressure is released, the QTC bead 38 reverts to being non-conductive, (it is hence immaterial whether or not it remains in physical contact with the contact strip 40).

This switch arrangement may thus be used as a straightforward on/off switch, as described above, or may also be used to control a power level of the tool, if desired.

The arrangement of QTC beads 38 strung on a conductive wire loop 39, shown in Figure 5, could be replaced by a simple loop of QTC wire having a conductive coaxial core. The QTC material would conduct locally where deformed, e.g. by finger pressure, establishing a conducting path between the coaxial core of the wire and the contact strip 40. However, the surgical tools described typically have a nose shroud 33 with a diameter of around twenty-five millimetres. A loop of QTC wire bent round into a circle of such a diameter would already be under considerable stress, possibly already sufficient to cause it to become conductive. Thus, digital pressure might do no more than reduce its resistance slightly further. Hence, for a reliable on/off switch, the arrangement of Figure 5, where the QTC beads 38 are under substantially no stress until pressed, is preferred.

For each of the handpieces I, 11, 31 shown, a surgeon may hold the tool in a comfortable and ergonomically sound grip, and the respective switch element will always be conveniently accessible for fingertip operation, whatever the orientation of a remainder of the tool.

In a further switch arrangement (not illustrated), a band of PCB (printed circuit board) material encircles a nose shroud of a tool such as those described above. Two circumferential contact strips of electrically conductive material supported on the PCB extend around the band, and are separated by a circumferentially extending strip of QTC material (or by a series of separate QTC elements arranged in a circumferential array). When finger pressure is exerted on the QTC strip or one QTC element, it becomes locally conductive, creating a conductive patch between the circumferential contact strips, and forming the basis of a switch mechanism, for example to turn the tool on and off.

A third circumferential contact strip may also be provided, separated from a first of the other two by a further circumferentially-extending strip of QTC material (or corresponding array of QTC elements). Pressure on this further QTC strip, etc, thus creates a conductive path between the contact strips that adjoin it, forming the basis for a second output of the switch mechanism, for example to control a power level of the tool.

While the tools above are described as having a single switch arrangement, alternative layouts are envisaged in which an annular on-off switch of any of the above types is supplemented by a second switch arrangement, for example adapted to toggle a power output of the tool between a plurality of predetermined levels. Conveniently, this second switch arrangement is also an annular switch arrangement encircling a nose shroud of the tool, spaced from the first (onloff) switch.

While the above switch arrangements are shown mounted to ultrasonically vibratable lararoscopic surgical tools, other laparoscopic tools, for example selectably providing electrothermal or radio-frequency treatment, would also benefit. It is possible that such switches would also be of use in non-surgical tools of similar shape.

Claims

I. A tool comprising manually graspable handpiece means, elongate shaft means extending from a distal end thereof and defining a longitudinal axis of the tool, an operative element of the tool mounted to the shaft means and switch means encircling the handpiece means and adapted selectably to activate the operative element by manual pressure.
2. A tool as claimed in claim I, wherein a finger contact element of the switch means is accessible for use from substantially any direction generally radial to the axis of the tool.
3. A tool as claimed in claim 2, wherein said finger contact element is substantially radially symmetrical about said tool axis.
4. A tool as claimed in either claim 2 or claim 3, wherein said finger contact element has a generally annular form.
5. A tool as claimed in claim 4, wherein said annular finger contact element extends generally coaxially around the longitudinal axis of the tool.
6. A tool as claimed in any one of the preceding claims, wherein the operative element of the tool is selectively rotatable about the tool axis to a desired orientation for operation.
7. A tool as claimed in ant one of the preceding claims, wherein a distal portion of the handpiece means is rotatable together with the operative element.
8. A tool as claimed in any one of claims 2 to 7, wherein the finger contact element of the switch means is mounted to said rotatable distal portion.
9. A tool as claimed in any one of the preceding claims, wherein said tool comprises a laparoscopic surgical tool.
10. A tool as claimed in any one of the preceding claims, wherein the shall means comprises a waveguide to transmit ultrasonic vibrations from a source thereof in the handpiece means to a selectably ultrasonically-vibratable operative element at a distal end thereof.
II. A tool as claimed in any one of the preceding claims, wherein the switch means comprises resiliently deformable chamber means containing a pressure transmitting medium and operatively linked to a pressure-sensitive switch means.
12. A tool as claimed in claim 11, wherein said chamber means and said pressure-sensitive switch means are connected by passage means through which said medium may pass.
13. A tool as claimed in any one of the preceding claims, wherein the switch means comprising at least one switch element of a material which is substantially electrically non-conductive when undeformed but substantially electrically conductive when compressed or otherwise deformed.
14. A tool as claimed in claim 13, wherein said material is adapted to become substantially conductive under a pressure no more than that extertable by a human finger.
15. A switch arrangement mountable to a surgical tool, comprising generally radially symmetrical outer shell means so pivotably mounted to an inner core of handpiece means of the tool that digital pressure on the shell means directed generally radially inwardly towards the core from substantially any angle urges first electrical contact means mounted to the shell means into contact with second electrical contact means mounted to the core. * ** * * * * ** S... * . ***.

S

55*555 * S * * S S... S * S... *...* * I

15. A tool as claimed in claim 14, wherein the material comprises a quantum tunnelling composite (QTC) material.

16. A tool as claimed in any one of claims 13 to 15, wherein the switch means comprises at least one switch element of said material so disposed between first and second electrical contact means that compression of said element results in a conductive path being established between the electrical contact means.

17. A tool as claimed in claim 16, wherein the compression results from digital pressure on the finger contact element of the switch means.

18. A tool as claimed in any one of claims 2 to 17, wherein the finger contact element comprises a resiliently flexible membrane adjacent said at least one switch element.

19. A tool as claimed in any one of claims 16 to 18, wherein said at least one switch element comprises a plurality of separate switch elements of said material arranged generally in a ring encircling the handpiece means.

20. A tool as claimed in any one of claims 16 to 19, wherein said at least one switch element comprises a single generally annular switch element of said material extending around the handpiece means.

21. A tool as claimed in any one of claims 16 to 20, wherein the finger contact means may comprise a generally annular membrane defining an outer wall of a generally torodial chamber means containing said at least one switch element and said electrical contact means.

22. A tool as claimed in any one of the preceding claims, the switch means comprises outer shell means so pivotably mounted to an internal core body of the handpiece means that digital pressure on the shell means directed generally radially inwardly towards the axis of the tool from substantially any angle urges first electrical contact means mounted to the shell means into contact with second electrical contact means mounted to the core body.

23. A tool as claimed in claim 22, wherein an outer surface of the shell means comprises the finger contact element of the switch means.

24. A tool as claimed in either claim 22 or claim 23, wherein shell means is mounted to the core body by means of ball joint means adjacent a distal end thereof, and the electrical contact means may be disposed adjacent respective proximal margins of the shell means and the core body.

25. A tool as claimed in any one of the preceding claims, in further axis of the tool comprising a switch arrangement detachably mountable to the tool, comprising resiliently deformable generally toroidal chamber means containing a pressure transmitting medium, said chamber means being adapted to encircle handpiece means of a tool and being operatively linked to pressure-sensitive switch means. * S

Amendments to the claims have been filed as follows I. A surgical tool comprising manually graspable handpiece means, elongate shaft means extending from a distal end thereof and defining a longitudinal axis of the tool, an operative element of the tool mounted to the shaft means and switch means encircling the handpiece means and adapted selectably to activate the operative element by manual pressure, wherein said switch means comprises outer shell means so pivotably mounted to an internal core body of the handpiece means that digital pressure on the shell means directed generally radially inwardly towards the axis of the tool from substantially any angle urges first electrical contact means mounted to the shell means into contact with second electrical contact means mounted to the core body.

2. A surgical tool as claimed in claim 1, wherein an outer surface of the shell means comprises a finger contact element of the switch means. * S. * . I

3. A surgical tool as claimed in either claim 1 or claim 2, wherein the shell means is S...

mounted to the core body by means of ball joint means adjacent a distal end thereof, ****..

and the first and second electrical contact means are disposed adjacent respective proximal margins of the shell means and the core body.

S..... * .

4. A surgical tool as claimed in any one of claims 1 to 3, wherein the switch means is provided with means to bias said first and second electrical contact means apart.

5. A surgical tool as claimed in any one of the preceding claims, wherein a finger contact element of the switch means is accessible for use from substantially any direction generally radial to the axis of the tool.

6. A surgical tool as claimed in claim 5, wherein said finger contact element is substantially radially symmetrical about said tool axis.

7. A surgical tool as claimed in either claim 5 or claim 6, wherein said finger contact element has a generally annular form.

8. A surgical tool as claimed in claim 7, wherein said annular finger contact element extends generally coaxially around the longitudinal axis of the tool.

9. A surgical tool as claimed in any one of the preceding claims, wherein the operative element of the tool is selectively rotatable about the tool axis to a desired orientation for operation. S... * S S...

10. A surgical tool as claimed in any one of the preceding claims, wherein a distal portion S.....

of the handpiece means is rotatable together with the operative element. *. * S S...

* : *.: 11. A surgical tool as claimed in claim 10, wherein the finger contact element of the switch means is mounted to said rotatable distal portion.

12. A surgical tool as claimed in any one of the preceding claims, wherein said tool comprises a laparoscopic surgical tool. 2-4

13. A surgical tool as claimed in any one of the preceding claims, wherein the shaft means comprises a waveguide to transmit ultrasonic vibrations from a source thereof in the handpiece means to a selectably ultrasonically-vibratable operative element at a distal end of the shaft means.

14. A surgical tool substantially as described herein with reference to Figure 2 of the accompanying drawings.