WO2002084119A1

WO2002084119A1 - Actuator with hydraulics

Info

Publication number: WO2002084119A1
Application number: PCT/GB2002/001588
Authority: WO
Inventors: William John Metheringham; Kamlesh Prajapati
Original assignee: Newlands Technology Limited
Priority date: 2001-04-10
Filing date: 2002-04-10
Publication date: 2002-10-24
Also published as: GB0108927D0

Abstract

The movement of an electrostrictive or magnetostrictive element (1) of an actuator is enhanced by means of hydraulic fluid (8) in a reservoir (6), expansion of the element causing displacement of the fluid so as in turn to displace a piston or plunger (4) by a greater distance than the dimension change of the element. The element either compresses the fluid reservoir at (9) to expel fluid into a bore (2) of the element (1) containing the piston (4) (Figure 1) or extends into the reservoir (Figure 2 not shown) such that the end itself of the element displaces the fluid. The actuator may be incorporated into an electric wet razor in which case the element, its associated bias and energising coils and magnets and a power supply are all provided in a handle part, whilst the fluid reservoir is provided in a (disposable) blade unit.

Description

ACTUATORWITH HYDRAULICS

Field of the Invention

In its broadest sense, this invention concerns actuators, particularly but not ex- clusively magnetostrictive or electrostrictive actuators. More specifically, the invention concerns actuators associated with hydraulics acting as a means to amplify the movements of the operative element of the actuator, and pumps incorporating magnetostrictive or electrostrictive actuators. Background to the Invention Magnetostrictive devices are devices employing materials that exhibit a change of dimension in the presence of an applied magnetic field. Such devices are immensely useful and versatile but suffer from the disadvantage that the magnitude of change in dimension is small for any given applied magnetic field. Similarly, electrostrictive devices whose dimension changes in the presence of an electric field, exhibit a small but definite dimension change when operated. There is thus a need, especially for certain applications, for a means of amplifying the dimension change,

It has been discovered that the extent of movement of a field-responsive element of such an actuator can be amplified if the element is caused to displace a volume of fluid in such a way that the displaced fluid in turn moves a piston or the like over a greater distance than the change of dimension of the element itself.

The properties of the fluid (eg its compressibility, viscosity, resistance to deterioration etc) need to be taken into account, as also is the choice of vibration frequency of the energising coil(s) and therefore of the device itself.

The actuator may form part of an electric vibrating razor. The fluid reservoir and piston may be incorporated in a disposable blade portion for vibration upon activation of energising coils or the like in the handle portion. Summary of the Invention

The invention therefore provides an actuator of the kind having an operative element exhibiting a dimension change in the presence of an applied field, the element being arranged to displace a volume of fluid when activated by a said field. Preferably said displaced volume of fluid in turn displaces piston means. Displacement of the piston means would be through a greater distance than the dimension change exhibited by the said element, whereby to amplify the dimension change.

The element may be of tubular configuration. The tube may conveniently be encircled or surrounded by magnetic or electric biasing means, such as one or more permanent magnets, electromagnets or electric coils. The applied magnetic or electric field may be created by one or more further coils or by means of the coil(s) provided for biasing. The frequency of the applied field may be variable.

Where the element is of tubular configuration, having a longitudinal bore there- through, the piston means may advantageously be located for reciprocal sliding movement in the bore.

The element is preferably positioned with one end adjacent a wall of a fluid reservoir, the said wall having an aperture in fluid communication with the bore in the element. The said one wall of the fluid reservoir preferably has a greater surface area than the adjacent end of the said element.

The said end of the element may bear against the said wall of the fluid reservoir, in which case the reservoir is at least partially deformable in the direction of the longitudinal axis of the bore. In this way, an increase in length of the element can change the volume of the reservoir and expel fluid into the bore, thereby displacing the piston means.

Alternatively, the said end of the element may be mounted for sliding movement into and out of the reservoir such that upon expansion of the element the said end itself expels fluid into the bore, thereby displacing the piston means. Sealing means provide for the tube to move in an out of the reservoir without loss of fluid. Suitable fluids include alcohols, for example ethanol, but it is contemplated that non-Newtonian fluids might also be usable; these would transmit shock loads, while not passing on slow movements.

The invention also contemplates an electric razor incorporating an actuator according to any of the above paragraphs, the piston means operating a blade unit to vi- brate said blade. ln such a razor, the electric coil(s) and/or magnet(s) are conveniently mounted in a handle portion; the fluid reservoir is then provided in a blade unit which may be disposable.

Preferred embodiments of the invention provide an actuator comprising a con- tainer containing fluid, the element being arranged to expel a volume of the fluid from the container in response to the application of the field.

Preferably, the container is deformable. Further preferred features of the container are the subject of dependent claims. Thus, in certain embodiments the expansion or contraction of the operative elements or element 1 causes deformation of the con- tainer to either expel fluid from it, or draw fluid back into it. In alternative embodiments, the element or elements may be arranged to expand into the container itself to displace fluid, or to drive some other member to displace the fluid.

A particularly preferred embodiment provides an actuator which further comprises expandable containment means arranged to receive the expelled volume of fluid from the container. Preferably, the expandable containment means is arranged and dimensioned such that the dimension change of the element or elements 1 is amplified. Preferably, the expandable containment means comprises bellows.

Further preferred embodiments provide pumps incorporating the actuators. In such pumps, rather than the displaced volume of fluid being expelled into expandable containment means or driving some piston means in a bore, the expelled fluid is ejected from a valve, nozzle, pinhole or other such orifice. The use of magnetostrictive elements in such pumps enables them to deliver highly reproducible and precise amounts of fluids. As such, these pumps are particularly useful in the pharmaceutical field. However, many other applications are possible. Preferred features of these pumps are the subject of some of the dependent claims. For example, in preferred embodiments the pump comprises means for maintaining a substantially constant volume of fluid in the container even though volumes of fluid are repeatedly being ejected from the container by operation of the operative element 1. Brief Description of the Drawings

The invention will now be described with reference to the following drawings, in which:

Figure 1 is a schematic drawing of a first embodiment of an actuator according to the invention;

Figure 2 is a schematic drawing of a second embodiment;

Figure 3 is a schematic drawing of a third embodiment;

Figure 4 is a schematic drawing of a further embodiment;

Figure 5 is a schematic drawing of yet a further embodiment; Figure 6 is a schematic drawing of a pump embodying the present invention;

Figure 7 is a schematic drawing of a further pump;

Figure 8 is a schematic drawing of yet another pump embodying the present invention;

Figure 9 is a schematic drawing of another pump; Figure 10 is a schematic drawing of a further pump embodying the invention;

Figure 1 1 is a schematic drawing of a further embodiment which produces an aerosol spray; and

Figure 12 is a schematic drawing of another actuator embodying the present invention. Detailed Description of the Illustrated Embodiments

In Figure 1 an actuator is shown comprising a magnetostrictive or electrostrictive element 1 of tubular configuration having a central bore 2 therethrough and carrying coil(s) and/or magnet(s) 3 to bias the material of the element and to apply a magnetic or electric energising field to cause the length of the element to change accord- ingly.

A piston or plunger 4 is located for oscillatory movement within the bore 2. One end 5 of the element is located adjacent a wall of a reservoir 6 having an aperture 7 of corresponding dimension to the bore 2 and aligned with the bore. The reservoir 6 and the portion of the bore 2 not occupied by the piston 4 is filled with fluid 8. The sides 9 of the reservoir are sufficiently flexible that exertion of a compres- sive force in the general direction of the axis of the bore 2 will cause the reservoir to contract and expel fluid into the bore 2. The resilience of the reservoir/fluid system ensures that the reservoir is restored to its previous shape once the pressure is re- moved. Also, because the system is effectively sealed, expansion of the reservoir when the element contracts allows fluid to be drawn from the bore so that the piston withdraws into the bore.

The reservoir could alternatively be constructed so that the wall contacted by the element is sufficiently flexible that, upon depression by the element, it is capable of displacing an adequate volume of fluid into the bore 2 to achieve the desired amplification of movement of the element.

The upper end 10 of the element 1 and the lower end 1 1 of the reservoir 6 are anchored so that any change in length of the element 1 as a result of an applied field is translated into compression or expansion of the reservoir 6. The effect of this is that fluid 8 passes backwards and forwards between the reservoir and the bore, in accordance with the frequency of the applied field, thereby causing the piston to oscillate.

In operation of the device, expansion of the element 1 causes the end 5 to compress the reservoir, thereby expelling a volume of fluid into the bore, as previously mentioned. However, since the reservoir wall is of larger cross-section than the end of the element the volume of fluid displaced for a given change in length of the element is larger than the volume displaced by movement of the element itself. Since this larger volume of fluid passes into the narrower cross-section bore, the movement of the piston 4 is amplified. A similar explanation applies to expansion of the reservoir when the element contracts in length. In the second embodiment of the invention shown in Figure 2, corresponding parts are indicated by reference numerals increased by 20 as compared to Figure 1. In this embodiment, the end 25 of the element 21 extends into an aperture 27 in the reservoir. The element is sealed by an O-ring 29 or other seal which simultaneously prevents fluid 28 escaping the reservoir while still allowing the element to move into and out of the reservoir. Operation of the actuator so as to increase the length of the element causes the end 25 to enter the fluid reservoir and displace a volume of fluid corresponding to the cross-section of the end of the element. The displaced fluid passes into the bore but because the bore diameter is smaller than the element diameter, the fluid displaces the piston further than the linear expansion of the element alone, thereby amplifying the movement of the element. A similar explanation applies to contraction of the element.

It is possible that other configurations will be desirable for certain applications. For example, a magnetostrictive or electrostrictive element, together with its coil(s) and/or magnet(s) could be immersed in a fluid such that displacement of the fluid as the element expands and contracts could be translated into increased linear movement of a piston or plunger. In addition, instead of a direct connection between the piston or plunger and a component operated by the actuator, increased movement can be achieved by a system of gears and/or levers.

If necessary, restoring means, such as a spring or the like, may be provided to ensure rapid return of the piston from the extended position. This restoring means may be part of the actuator or part of a device operated by the actuator.

The actuator may have particular application to electric razors of the wet type. In this case, the element, its coil(s) and/or magnet(s) and a power supply (such as a rechargeable or disposable battery or batteries or a mains electric input) are provided in a handle part (not shown). The reservoir, the fluid and the piston are provided in a blade unit. The blade unit may be disposable as a whole or the blade itself may be replaceable.

Although reference has been made to magnetostrictive or electrostrictive materials for the elements, it is preferred to use magnetostrictive material. Although rare- earth materials are commonly employed in magnetostrictive elements and devices, it is preferred to use so-called "Giant Magnetostrictive Materials" (or GMM), such as Terfe- nol-D.

Returning to Fig 1 , in the embodiment shown in that figure the sides 9 of the reservoir (i.e. container for the fluid) are flexible to permit compression of the reser- voir as the element 1 expands. In addition to being flexible, in alternative embodiments the side or sides 9 of the container 6 may be sprung such that the element 1 is maintained in compression (in the art this is known as arranging the element in a pre- stressed condition) between the upper anchorage 10 and the end of the container 6 which is in contact with the lower end 5 of the element 1. Moving on to Fig 3, this shows a further embodiment which includes a fluid container 6 having a flexible, sprung sidewall 9. An upper wall 61 of the container 6 is a substantially rigid circular plate having a central circular aperture 7. The container 6 also has a substantially rigid circular lower wall 62, and the upper and lower walls are connected by a flexible concave sidewall 9. The sidewall 9 is formed from resilient material and is arranged to act as a spring, tending to urge the upper and lower walls 61 , 62 apart. In the Figure, the sidewalls 9 are shown in a state of compression. The actuator also comprises a housing 50 which is substantially rigid and includes an upper wall 51 and a lower wall 52. A tube 40 is fixed inside the circular aperture 7 in the upper wall 61 of the container 6, and extends from the container along a longitudinal axis. The bore 41 of the tube 40 is thus in communication with the fluid 8 contained in the reservoir 6. A plug member 4 is arranged inside the tube 40, forming a sliding seal and is thus able to move along the axis of the tube in response to fluid 8 being expelled from or drawn into the container 6.

In this embodiment the tube 40 is centred on the circular upper wall 61 of the container 6. Magnetostrictive elements 1 a and 1 b are arranged symmetrically on opposite sides of the tube 40. Each of these elements 1 a, 1 b is in the form of a block (i.e. body) of magnetostrictive material. In this example with two operative elements, the elements are diametrically opposed on either side of the tube 40. In alternative embodiments, 3 or more elements may be used, and in such cases these elements should be spaced evenly around the central bore.

Each element 1 a, 1 b is maintained in compression between the upper wall 51 of the housing 50 and the upper wall 61 of the container 6 by means of the sprung side- wall 9 of the container. A typical pre-stress load for a magnetostrictive element is 70 N. A solenoid 3 is arranged around the elements 1 a, 1 b and is operable to generate a magnetic field. On application of this magnetic field the elements 1 a and 1 b exhibit a dimension change, namely their lengths increase in the direction parallel to the longitudinal axis of the tube 40. As the upper ends of the elements 1a, 1 b are constrained by the upper wall 51 of the housing 50, and the lower wall 62 is constrained by the lower wall 52 of the housing, this expansion under applied field drives the rigid upper wall 61 of the container 6 downwards, further compressing the side walls. The downwards motion of the upper wall 61 alone reduces the volume of the container and causes fluid 8 to be expelled into the bore 41. Advantageously, however, the concave nature of the sidewall 9 means that the sidewall is urged further inwards, radially, as the container 6 is compressed by the action of the elements 1 a, 1 b and results in an increased volume of fluid 8 being displaced.

Moving on to Fig 4, a further embodiment comprises an actuator having a substantially rigid housing 50 inside which a single operative element 1 is arranged to drive a dished upper wall 61 of a fluid container 6. The actuator further includes field generating means 3 for controlling a dimension of the element 1. In this embodiment the sides 9 of the container 6 are substantially rigid and changes in the volume of the container 6 are achieved solely by means of deflections of the dished upper surface 61 by the element 1. The dished upper surface 61 has a degree of resilience, and maintains the element 1 in compression against the upper wall 51 of the housing 50. The single element 1 is arranged generally in the centre of the upper container wall 61. A lower wall 62 of the container is held in contact with a lower wall 52 of the housing. The container 6 also comprises re-entrant tube means 63, which extends from the lower wall 62 into the volume of the container to form a bore 41. A piston 4 is arranged inside the bore 41 and forms a sliding seal. As in other embodiments, the tube means 63 will typically have circular cross section, although other shapes may be employed together with suitably shaped pistons to form an adequate fluid seal.

Using a single operative element 1 , which does not itself have a bore, simplifies construction and the re-entrant tube means 63 helps to reduce the overall length of the actuator.

It will be apparent from the descriptions of the preceding and subsequent em- bodiments that the terms upper and lower are being used only in a relative sense, and are not intended to limit the devices to any particular orientation with respect to the vertical.

Fig 5 shows a further embodiment which is broadly similar to that shown in Fig 2. In the embodiment of Fig 5, however, rather than the electrostrictive or magne- tostrictive element 1 being arranged to expand directly into the container 6 to displace fluid 8, the operative elements 1 drive a separate member into the fluid. This separate member is a carrier member which comprises a tubular portion 40, a flange portion 42 and a substantially annular fluid displacing portion 43. A central bore 41 runs through the 3 portions of the carrier member. A plurality of magnetostrictive elements 1 are circumferentially arranged around the tubular portion 40. Their dimensions in a direction parallel to the longitudinal access of the bore 41 are controlled by magnetic field generated by surrounding solenoid 3. A spring 44 is arranged between the flange portion 42 and a rigid upper wall 61 of the container 6 and acts to maintain all of the elements 1 in compression. In this embodiment the spring is a return spring, in the form of a wave spring, but other forms of springs may of course be used in alternative embodiments.

As the lengths of the elements 1 increase in the axial direction in response to field applied by the coil 3, the elements 1 , which are constrained between an upper anchorage 10 and a shoulder on the carrier member, drive the fluid displacing portion 43 of the carrier member against the bias spring 44 down into the container 6, thereby displacing fluid 8 up into the bore 41. This in turn causes the piston 4 to move upwards. The area of the lower face of the fluid displacing portion 43 is greater than the area of the bore 41 , and so the distance moved by the piston 4 is greater than the increase in length of each element 1 in response to the applied field. An "O" ring 29 forms a seal between the upper wall 61 of the container 6 and the fluid displacing portion 43.

Fig 6 shows a pump embodying the present invention. The pump comprises a fluid container 6 having a deformable upper wall 61 , and substantially rigid sidewalls 9 and lower wall 62. The container 6 contains fluid 8. The upper wall 61 has an aperture 7 in fluid communication with a tube 40 which extends from the container 6. A valve 71 is arranged at an end of the tube 40. In this embodiment the valve is a one-way valve which is arranged to open in response to the pressure of the fluid 8 behind it exceeding a predetermined magnitude. In other embodiments, controlled valves may be used, and may be electrical or electronic valves.

Operative elements 1 , whose dimensions change in response to an applied field, are arranged on either side of the tube 40. The upper ends of these elements 1 are anchored 10, and the lower wall 62 of the container 6 is also anchored 1. Field is applied to the elements 1 by means of field generators 3. The applied field causes the length of the elements 1 in the direction parallel to the longitudinal access of the tube 40 to increase, thereby exerting a downwards force on the upper wall 61 of the container 6. This depresses the upper wall 61 and expels fluid 8 from the container into the bore 41 of the tube 40. Rapid application of a field of sufficient magnitude to the elements 1 causes fluid 8 to be expelled from the valve 71.

Inside the container 6 is a plate 81 and a spring 82. As the stock of fluid 8 in the container 6 is depleted by repeated operation of the expanding members (the elements 1) the spring 82 moves the plate 81 upwards so that the remaining fluid 8 completely fills the tube 40 up to the non return valve 71 and the portion of the volume enclosed by the container 6 on the side of the plate 81 opposite the spring 82. Thus, the spring 82 maintains the fluid 8 at a positive pressure. Clearly, the spring constant must be such that this pressure is not so high that is causes fluid to leak out of the valve 71. In this embodiment, correct operation of the pump in response to application of applied field relies on a rapid expansion of the elements 1 so that fluid is expelled from the valve 71 rather than the expansion of the elements 1 , and the resultant deflection of the upper wall 61 , simply being accommodated by a further compression of the spring 82.

In alternative embodiments where atomisation of the fluid 8 on exit from the tube 40 is needed, and the tube has a very narrow bore 41 , then the valve may not be required. It will be apparent that in the embodiment shown in Fig 6 the spring 82 and plate 81 are an example of a means for reducing the volume of the reservoir as its contents are depleted. They also represent one possible means of pressurizing the contained fluid. Fig 7 illustrates a pump similar to that shown in Fig 6, except for the fact that rather than the expanding members 1 deforming the container 6 to expel fluid 8, the expanding members 1 drive a separate member into the reservoir to achieve the same result. In this example, a single expanding member 1 is used, and takes the form of a cylinder having a bore 2. One end of the cylinder is anchored against a fixed anchorage 10, and the opposite end is in contact with a member which comprises a flange portion 42 and a fluid displacing portion 43. The member has a central bore 41 which is in fluid communication with the bore 2 of the expanding member 1. Thus, in this example the member driven by the expanding element 1 has a top hat form. Lower faces of the flange portion 42 are in contact with a spring 44 which urges the member in the upwards direction in the figure, and so maintains the expanding member 1 in a compression and in contact with the upper anchorage 10. Excitation means 3 are operable to cause the element 1 to expand in length (in a direction along the axis of the bore 2). This in turn urges the member against the bias spring 44 down into the container 6, forcing fluid 8 to be expelled from the container into the bore 2, and then out of the valve 71. Once again, the spring 82 and plate 81 reduce the effective volume of the container 6 as the fluid stock is depleted.

Fig 8 shows another pump embodying the present invention. In this embodiment a single magnetostrictive element 1 in the form of a tube having a bore 2 is ar- ranged to deflect a wall 61 of a fluid container 6 in response to application of a magnetic field by suitable means 3. The container 6 contains 2 fluids. The first fluid 8 is the fluid to be pumped out of the valve 71. This fluid 8 is separated from the second fluid 84 by a flexible membrane 83. This second fluid 84 is supplied to the volume beneath the membrane 83 via a tube 73 and valve 72 from some suitable means. The supply of this second fluid is represented by the arrow 74. After a volume of the fluid 8 has been expelled from the valve 71 by expansion of the element 1 , a corresponding volume of fluid 84 is supplied to the container 6 via the valve 72 to maintain the total volume of fluids inside the container. The valve 72 in this example is a one-way valve. It may be arranged to open in a response to a predetermined pressure differential, or alterna- tively maybe directly controllable. It may be an electrical or electronically controlled valve. The membrane and second fluid supply utilised in the pump showing Fig 8 perform a similar function to the spring and plate in Fig 7, but the use of the membrane avoids the problem of maintaining a fluid tight seal between the plate 81 and sides 9 of the container 6. In alternative embodiments, rather than a membrane 83 the second fluid 84 may be contained within a flexible, expanding "bag" which gradually expands until it occupies all of the space inside the container 6 when all of the stock of fluid 8 has been expelled from the pump.

It will be apparent that in the pump shown in Fig 8 the supply of the second fluid 84 beneath the membrane 83 (alternatively into a sealed bag) provides the advantage that the stock of fluid 8 to be pumped is not diluted or contaminated in any way. This arrangement may be particularly suitable for the pumping and/or controlled delivery of fluids such as pharmaceutical compositions.

Moving on to Fig 9, in this further embodiment the axially expanding element 1 has a generally tubular construction comprising a main body portion 40 having a bore 2, a flange portion 42, and a fluid displacing portion 43 which is driven into the body of fluid 8 on expansion. In this example these portions are integral parts of the element 1 . Again, a bias spring 44 engaging the flange portion 42 and a surface of the container 6 is used to maintain the element 1 in compression between the container and a fixed anchorage point 10. Repeated actuation of the element 1 results in precisely determinable and equal quantities of fluid 8 being expelled from the pump (in this case via the valve 71 ). After each operation, the stock of fluid 8 inside the container 6 is replenished from a separate source by means of a supply tube 73 and valve 72 arranged in a sidewall 9 of the container.

Fig 10 illustrates a pump which is very similar in operation to that shown in Fig 9, except for the fact that the total volume of fluid contained in the container 6 is maintained by means of a supply of a second fluid 84 beneath a membrane 83.

Fig 1 1 shows a further embodiment, in the form of a pump which produces an atomised spray of a liquid 8. The liquid 8 is contained inside a flexible bag 85 which is sealed to an inside surface of an upper wall 61 of a fluid container 6. The volume inside the container 6 but outside the bag 85 is filled with a second fluid 84. The upper wall 61 of the container 6 is generally circular and substantially rigid, and includes a pinhole 63. A lower wall 62 of the container 6 is also generally circular and substantially rigid, and includes an aperture 64 through which a second fluid 84 is supplied from a separate reservoir 90 via a valve 72. A sidewall 9 of the container 6 is concave and acts as a spring biasing the top and bottom walls 61 , 62 apart. An actuating element in the form of a block 1 is maintained in compression between the lower wall 62 of the container and a wall 52 of a housing by the action of the sprung sidewall 9. Coils 3 are operable to provide an applied magnetic field to the element 1 which in turn causes its length (in the vertical direction in this figure) to increase, thereby pushing the lower wall 62 up- wards, compressing the sidewalls 9 (making them curve further inwards) and exerting an increased pressure on the fluid 8 inside the bag 85. This pressure increase is communicated by the second fluid 84. This compression forces fluid 8 out of the pinhole 63. The escaping fluid is in the form of an atomised spray. It will be apparent that in other embodiments, the form of exit aperture from the container 6 may be selected so that an atomised spray, or jet of fluid, or stream of gel or paste may be suitably emitted. When the applied field is removed, the element 1 returns to its original dimensions (assisted by the spring wall 9, which also keeps the element 1 in contact with the wall 52 of the housing). Rather than air being drawn into the bag 85 via the pinhole 63, the volume of expelled fluid 8 is replenished by a corresponding volume of the second fluid 84 from the reservoir 90.

Moving on to Fig 12, this shows another actuator embodying the present invention. The actuator includes a housing 50, which contains an actuating elementl . On application and removal of an applied field (by means not shown in the figure) the horizontal dimension of the element 1 changes in the direction shown by the arrow 1 10. The housing 50 accommodates a container 6 which has rigid front and back walls 61 ,62 and flexible, sprung sidewalls 9. The front wall 61 is connected to a front wall of the housing 51 , and includes an aperture 7 through which fluid 8 is expelled when the expansion of the element 1 urges the back wall 62 towards the front wall 61 thereby reducing the volume of the container 6. The expelled fluid is received by expandable con- tainment means 100 which in this example takes the form of sprung side portions 101 and end portion 102. Preferably the spring side portions 101 are in the form of stainless steel or beryllium copper bellows.

The expandable containment means is sealed to the container 6 so that all of the expelled volume of fluid 8 from the container 6 is received by the containment means, which in turn expands. In this example the surface area of the back wall 62 of the container 6 is much larger than the cross sectional area of the bellows 101 and hence results in amplified movement i.e. the distance moved by the end portion 102 in response to actuation of the element 1 is much greater than the dimension change of the element 1 in the horizontal direction in this figure. In alternative embodiments, other forms of expandable containment means may be used. Just as one example, the expandable containment means may take the form of a flexible membrane sealing the aperture 7 in the front plate 61 of the container 6. As the fluid is expelled from the container 6 the membrane deforms to accommodate the expelled fluid. This deformation may be coupled to drive a wide variety of mechanisms. Thus, it will be apparent that certain embodiments of the present invention provide an amplifier which uses a piston. The amplification of the movement occurs whether there is a piston sitting on top of the fluid or not.

In certain embodiments an actuator is used to move fluid, without a piston to pump fluid and for example can be used to create an atomised spray or jet of fluid or to move a gel or paste. In certain embodiments a means of maintaining a constant volume of fluid or gel or paste in a reservoir is provided, through a one-way valve, or by having the fluid arranged in a bag or separated by a membrane from a second reservoir that refills the first. Alternatively, it is possible to have a spring or some other means that reduces the volume of the reservoir as the contents are depleted. The actuators which include a piston may be used to drive movement of fluid, and so the present invention contemplates use of such actuators in pumps.

Embodiments of the present invention may be used in razors, and the pumps could force lubricating gel or fragrance onto the skin, instead of driving the blade itself (for example in a wet shave device). Alternatively, the pumps could be used in an elec- trie razor in conjunction with some other means of driving the blade. In embodiments where magnetostrictive elements are used, it is preferable to have the element maintained in a pre-stressed condition, for example by means of sprung walls of the container or by means of separate bias springs.

Some embodiments use a tubular expanding element, but it may be more con- venient (and indeed permit simplified construction of more robust devices) to use a single block or a variety of continuous blocks of material.

In the pump embodiment shown in Figs 6, 7, 8, 10 and 11 it will be clear when the stock of fluid 8 has run out.

It will be apparent that whilst some of the above descriptions of preferred em- bodiments have referred just to the operation of the actuators and pumps in response to expansion of the operative elements 1 , in many cases the operation of the devices on contraction of the elements (when the applied filed is removed) will be similar. Thus, many of the embodiments of the present invention provide amplified reciprocating motion which may be used to drive a number of applications.

Claims

1. An actuator having an operative element exhibiting a dimension change in the presence of an applied field, the element being arranged to displace a volume of fluid when activated by a said field.

2. An actuator in accordance with claim 1 , further comprising piston means arranged to be displaced by said displaced volume of fluid.

3. An actuator according to Claim 2 in which the displacement of the piston means is greater than the dimension change exhibited by the said element, thereby amplifying movement of the element.

4. An actuator according to any preceding claim wherein the element is of tubular configuration, including a longitudinal bore.

5. An actuator according to any preceding claim wherein the element is encircled or surrounded by magnetic or electric field generating means, such as one or more permanent magnets, electromagnets or electric coils.

6. An actuator according to Claim 5 wherein said field generating means comprise means for applying an electric or magnetic bias field to said element.

7. An actuator according to Claim 5 or Claim 6 wherein said field generating means comprise means for applying an electric or magnetic energising field to said element.

8. An actuator according to Claim 7 wherein said energising field is variable.

9. An actuator according to Claim 2 or Claim 3 wherein the piston means is mounted for reciprocal sliding movement in a bore.

10. An actuator in accordance with Claim 9 herein said bore is a bore in said element.

1 1 . An actuator according to Claim 10 wherein one end of the element is positioned adjacent a wall of a fluid reservoir, the said wall having an aperture in fluid communication with the bore in the element.

12. An actuator according to Claim 1 1 wherein the said wall of the fluid reservoir has a greater surface area than the adjacent end of the said element.

13. An actuator according to Claim 12 wherein the said end of the element bears against the said wall of the fluid reservoir, said reservoir being at least partly com- pressible in the direction of the bore of said element such that an increase in length of the element in the said direction causes a change in the volume of the reservoir, thereby to expel fluid into the bore and to displace the piston means.

14. An actuator according to Claim 11 wherein the said end of the element is mounted for sliding movement into and out of the reservoir such that an increase in length of the element in the direction of the bore causes the said end of the element to expel fluid into the bore and to displace the piston means.

15. An actuator according to Claim 14 further comprising sealing means to permit the tube to move in an out of the reservoir without loss of fluid.

16. An electric razor comprising a shaving blade and a magnetostrictive ac- tuator connected thereto to provide a reciprocating motion of the blade.

17. An electric razor incorporating an actuator according to any of Claims 1 to 15.

18. An electric razor according to Claim 17 wherein the displaced volume of fluid is arranged in turn to displace piston means and the piston means is adapted to vi- brate a blade unit.

19. An electric razor incorporating an actuator according to Claim 5 wherein said field generating means and power supply means therefor are mounted in a handle portion.

20. An electric razor according to Claim 19 wherein the fluid reservoir is provided in a blade unit which may be disposable.

21. An actuator according to any one of Claim 1 , 2 or 3 wherein the element is immersed in fluid in said reservoir.

22. An actuator according to any of Claims 1 to 15 and 2 , wherein the dis placed fluid in turn displaces piston means and the displacement of said piston means is coupled to a device to be actuated by means of levers, gears and the like further to enhance amplification of the dimension change of said element.

23. An actuator in accordance with Claim 1 comprising a container contain ing said fluid, the element being arranged to expel a volume of said fluid from the container in response to the application of said field.

24. An actuator in accordance with Claim 23 further comprising means for generating said applied field.

25. An actuator in accordance with Claim 23 or Claim 24 wherein the con- tainer is deformable, and the element is arranged to deform the container in response to the applied field to expel the volume of fluid.

26. An actuator in accordance with Claim 25 wherein the container comprises a sprung sidewall arranged to be compressed on expansion of the element.

27. An actuator in accordance with Claim 26 wherein the side wall is con- cave such that it bows further inwards into the container on compression.

28. An actuator in accordance with Claim 26 or Claim 27 wherein the sprung sidewall is arranged to maintain the element in a pre-stressed state.

29. An actuator in accordance with Claim 23 or Claim 24 wherein the element is arranged to expand into said container to displace said volume of fluid.

30. An actuator in accordance with Claim 23 or Claim 24 wherein the element is arranged to drive a fluid-displacing member in the container to displace said volume.

31. An actuator in accordance with any one of Claims 23 to 30 further comprising spring means arranged to maintain the element in compression.

32. An actuator in accordance with any one of Claims 23 to 31 further comprising expandable containment means arranged to receive said expelled volume of fluid from the container.

33. An actuator in accordance with Claim 32 adapted such that said dimension change of the element results in a larger change in a dimension of the expandable containment means, thereby providing amplification.

34. An actuator in accordance with Claim 32 or Claim 33 wherein the expandable containment means comprises bellows, sealed at one end and in fluid communication with the container at the opposite end.

35. An actuator in accordance with Claim 34 wherein the bellows are di- mensioned such that to accommodate the fluid volume expelled from the container as a result of said dimension change of the element, the sealed end of the bellows is displaced by a distance greater than said dimension change.

36. A pump comprising an actuator in accordance with any one of Claims 1 to 1 5, or 21 or 22, or 23 to 35.

37. A pump comprising an actuator in accordance with any one of Claims 23 to 31 further comprising a valve in fluid communication with the container and operable to permit release of fluid expelled from the container.

38. A pump comprising an actuator in accordance with any one of Claims 23 to 31 further comprising an aperture through which the volume of fluid expelled from the container is ejected.

39. A pump in accordance with Claim 38 wherein the aperture is a pinhole or nozzle arranged in a wall of the container.

40. A pump in accordance with any one of Claims 37 to 39, or comprising an actuator in accordance with any one of Claims 23 to 31 , further comprising means for maintaining a substantially constant volume of fluid in the container.

41. A pump in accordance with Claim 40 wherein the means for maintaining comprises a reservoir of fluid arranged to supply fluid via valve means, to a volume inside the container, said volume being separated from the volume occupied by the pumped fluid by partition means.

42. A pump in accordance with Claim 41 wherein the partition means comprises a flexible membrane or bag means.

43. A razor incorporating a pump in accordance with any one of Claims 36 to 42, the pump being arranged to pump shaving gel, fragrance, lubricating fluid or other such fluids to the skin.

44. A pump in accordance with any one of Claims 36 to 42 wherein the fluid in the container is a pharmaceutical composition.

45. A razor incorporating an actuator in accordance with any one of Claim 1 to 15, 21 ,22 or 23 to 35, the actuator being arranged to vibrate a blade unit.

46. An actuator substantially as described with reference to the accompanying drawings.

47. A razor incorporating an actuator substantially as described with reference to the accompanying drawings.

48. A pump substantially as described with reference to the accompanying drawings.

49. A pump in accordance with any one of Claims 35 to 43 further comprising means for pressurising the fluid in the container.