WO 2007/073212 PCT/NZ2006/000335 TITLE OF THE INVENTION IMPROVEMENTS IN SHEARING EQUIPMENT BACKGROUND TO THE INVENTION This invention relates to improvements in shearing equipment. More particularly the invention relates to a shearing handpiece intended to form part of portable shearing equipment. There is a commercial opportunity for lightweight portable shearing equipment comprising a motor driven handpiece and associated power pack. Readily portable shearing equipment of this type has a wide range of applications. For example, it enables operations such as dagging to be carried out away from a shearing shed. The operation can be readily carried out in a holding pen or, indeed, in a race adjacent a shearing shed so that the dagging operation can be carried out prior to the animal entering the shearing shed for shearing. One major advantage of being able to carry out say a dagging operation away from the shearing shed is that it does not require animals to be herded from the field, which may be quite some distance from the shearing shed. Thus, even temporary races or pens can be set up in the immediate vicinity of the animals so that the dagging or other cleaning/cleaning of wool operations can be carried out. Another advantage of such portable shearing equipment is that it provides a means for small holdings of sheep (e.g. on a lifestyle block) to be dagged and/or shorn by the owner of the sheep without having to outlay a significant sum of money to purchase shearing equipment intended for handling large flocks of sheep. Also it can mean that a lifestyle block owner does not need to rely on the services of contract shearers visiting the property. At the same time, portable shearing equipment can have application with contract shearers visiting small holdings or having to deal with small mobs of sheep. 1 WO 2007/073212 PCT/NZ2006/000335 Portable shearing equipment is known. However, the handpieces are often bulky and heavy and, therefore, can lead to fatigue and potential injury to the user. A further problem that has been associated with portable shearing handpieces is one of vibration and the handpiece becoming unacceptably hot. Traditional or known handpieces are time proven. SUMMARY OF THE INVENTION it is, therefore, an object of the present invention to provide a shearing handpiece which is driven by an electric motor mounted to the handpiece, and which does not suffer from the problems that have hitherto been associated with shearing equipment of a portable nature. Broadly according to one aspect of the invention there is provided a portable shearing handpiece including a barrel, a cutting head mounted on the barrel and a reciprocable drive within the barrel and coupled to the cutting head, the handpiece being characterised by an electric motor mounted with the barrel, the electric motor having a drive shaft which is coupled to the reciprocable drive. In the preferred form the motor is mounted to the handpiece barrel by a mount which extends within a cavity in the barrel, said output shaft extending through the mount, a distal end of the shaft projecting from the mount and being coupled to the reciprocable drive. Preferably the mount includes a bearing through which extends the shaft. Preferably the bearing is a needle or ball roller bearing. In a preferred form the shaft is further carried by a bearing adjacent the armature of the electric motor. 2 WO 2007/073212 PCT/NZ2006/000335 The mount is fixed by mechanical fastening means to the barrel. Preferably the mount is screw threaded into the barrel or could be circlipped in place or fixed in place by a set screw. According to a second broad aspect of the invention there is provided a conversion unit for motorising a shearing handpiece, the conversion unit including an electric motor coupled to an adaptor unit, the adaptor unit having a mount which in use is locatable within a cavity in the barrel of a shearing handpiece and a drive shaft coupled to the motor, the drive shaft extending through the mount to be drivingly engageable with a reciprocable drive of the shearing handpiece, there being fixing means for fixing the adaptor to the handpiece. Preferably the drive shaft is a single length shaft which extends through the armature of the motor. The shaft is mounted for rotation by a first bearing adjacent the armature and a second bearing adjacent a distal end of the shaft which is coupled to the reciprocable drive of the handpiece. In a preferred form the mount of the adaptor unit is of tubular form and mounts, at an end distal from the motor, the second bearing. Preferably the second bearing is a needle or ball roller bearing. According to one preferred form the fixing means is a screw thread form at the distal end of the tubular mount and is adapted to engage with an existing screw thread form within the barrel of the handpiece. In another form the adaptor unit could be circlipped or set screwed in place. In the preferred form a cam of the reciprocable drive of the handpiece is attached to an end of the shaft which projects from the tubular mount. Preferably the adaptor unit forms a part of the body of the electric motor. 3 WO 2007/073212 PCT/NZ2006/000335 BRIEF DESCRIPTION OF THE DRAWINGS In the following more detailed description of the invention according to one preferred embodiment, reference will be made to the accompanying drawings in which: Figure I is an elevation view of the shearing handpiece, Figure 2 is a cross-sectional illustration of the shearing handpiece shown in Figure 1, Figure 3 is an elevation view of a second embodiment, Figure 4 is an elevation view of the motor shaft of the embodiment shown in Figure 3, Figure 5 is an elevation view of the adapter of the embodiment of Figure 3, and Figure 6 is a plan view of the adapter shown in Figure 5. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION In the preferred form of the invention the handpiece is formed by adapting a known shearing handpiece. As is known in the art, the shearing handpiece 10 will have a barrel I0a within which there is a cavity in which a reciprocable drive is located. This drive is of a conventional nature being a fork 11 pivotally mounted in the cavity. The fork provides the reciprocating motion of the cutting head i.e. shearing blade B movable over the comb C. According to the present invention, the fork arrangement is retained in the shearing handpiece and operates in the normal manner thus further description is not required for the purposes of the present invention. 4 WO 2007/073212 PCT/NZ2006/000335 In the shearing handpiece 10 there will generally be a spindle which is rotatably mounted between bearings and/or bushes, which are mounted in the handpiece barrel. Also, mounted in the barrel is a so-called inner back-half joint. The inner end of the spindle is coupled to a cam 12 from which projects a pin (offset to the axis of the spindle) this pin engaging with the fork 11. Thus, as the cam 12 rotates the fork is caused to oscillate. According to the preferred form of the present invention in which an electric motor conversion unit is combined with an existing handpiece, the inner back-half joint of the handpiece is removed and discarded. The front bearing or bush (which may or may not be combined with the inner back-half joint) is also removed and discarded. According to the present invention, the motive power for the handpiece is an electric dc motor 14. This is attached directly to the handpiece 10 by an adaptor 21. The motor is coupled via an electric conductor cable to a power pack (not shown). The power pack, according to a preferred embodiment of the invention can be formed as part of a knap sack type arrangement, be attached to a harness or waist belt arrangement. In either case the power pack in the preferred form of the invention can be readily worn on the body of the person carrying out a shearing operation. In the preferred form of the invention, a readily accessible on-off switch is provided with the power pack. Preferably the power cord leading from the motor to the power pack is coupled to a junction box which incorporates the on-off switch. In a more preferred form of the invention, the on-off switch is attached to one of the straps or part of the harness. It is placed in a convenient position whereby it can be accessed and operated by the hand of the person carrying out the shearing operation which is opposite to the hand in which the user grasps the handpiece. In this way the user can, without releasing a grip on the handpiece, turn the handpiece on or off.
WO 2007/073212 PCT/NZ2006/000335 According to an alternative embodiment the power cord could be adopted to connect to a dc power supply such as a vehicle battery. In this way a power pack will not be required. The motor 14 is of a conventional construction and includes a body 15 within which is rotatably the armature 16. The armature 16 is mounted with a shaft 17. The inner end of the shaft (relative to the body 15) is mounted in a "back" bearing 18 located in a suitable mounting in the end wall 19 of the housing 15. It will be appreciated that the drawings, so far as Figure 2 is concerned, is largely schematic and does not show other conventional elements of the construction of the motor 14. The drawing, however, illustrates how the shaft 17 is of a length whereby it extends from the back bearing 18 through to a front bearing 20 and projects beyond the front bearing 20 to be engaged with the cam 12. An adaptor 21 couples the motor 14 to the handpiece 10. This adaptor 21 includes a tubular mount part 22 which engages within the hollow interior of the barrel of the handpiece 10. As can be seen in Figure 2, the forward or distal end of this tubular element 22 includes a mounting portion 23 into which the front bearing 20 is engaged. An adaptor 21 extends from the tubular mount 22 to a connector part 24 which engages within the housing 15 of the motor 14. In the preferred form of the invention, as illustrated, a transition part 25 between the connector part 24 the tubular mount 22 is of a frusto conical form. A shoulder 26 between the frusto conical transition portion 25 and the tubular mount 22 provides an abutment surface which engages against the end of the barrel of the handpiece 10 or a washer/spacer of a correct thickness when the mount 22 is fully engaged in 6 WO 2007/073212 PCT/NZ2006/000335 the barrel. The worker/spacer will ensure correct penetration of the mount 22 and ensure the power cord is in correct position. The transition part 25 thus effectively forms a front wall part of the body of the motor 14. The connector part 24 can be screw threaded into the housing 15 or more preferably can simply be a push fit into the end of the housing 15 to be fastened therein by the use of one or more mechanical fasteners such as a set screw 27. In one form of the invention the set screw 27 can also be used to fix a coupling 28 for the power cord 29. As a result, the power cord will extend from the end of the motor 14 adjacent the adaptor 21. However, according to another form of the invention, the power cord can be coupled to the motor at the end wall 19 and in such arrangement the end wall 19 can be removable to provide access to the brushes of the motor for purposes of servicing. Also, this would provide for ready servicing/replacement of the back bearing 18 if this is required. The adaptor 21 is fixed into the barrel handpiece 10 by suitable means. For example, a circlip or other mechanical fastening could be used to fix the adaptor 21 to the rear end of the barrel. In the form of the invention as illustrated, however, the distal end 23 of the tubular mount 22 is provided a screw thread form 30 which can screw into a corresponding screw thread form already in existence within the barrel of the handpiece 10. This existing screw thread form is used for mounting of the inner back-half joint. Thus, to assemble the motor 14 to the handpiece 10 it is simply a matter of positioning the tubular mount 22 within the barrel and then rotating the mount 22 to cause the distal end 23 to threadingly engage into the existing thread within the barrel. When tightened up the shoulder 26 of the adaptor 21 will engage against the end of the barrel. 7 WO 2007/073212 PCT/NZ2006/000335 Prior to the adaptor 21 being inserted into and fixed in the barrel of the handpiece 10, the cam 12 with its associated pin 13 will be fixedly mounted to the distal end 27 of the shaft 17. As a result, it will be appreciated by those skilled in the art that the motor can be easily and readily fitted to, or removed from the handpiece. Thus with the preferred form of the invention where an existing handpiece is used, it is a simple matter of removing the inner back-half joint with forward bearing from the barrel of the handpiece and then inserting and fixing in-place the adaptor 21 with its associated motor 14. In this way a very tidy and aesthetically pleasing mounting of the motor to the handpiece can take place. In the preferred form of the invention, the motor is a high torque motor capable of operating at about 1500 to 2800 rpm. Ideally, the motor is able to operate on one 1 2V 7amp hour batteries. In a preferred form of the invention, the motor is a 1 2V dc motor rated at between about 85-95 watts drawing in the vicinity of 6 amps under normal load. By way of one example a prototype has been tested using a motor of a type that has been found to be particularly useful for the direct driven motorised shearing handpiece, is a rear driving motor taken from the four wheel steer worm gear and rack and pinion of a Nissan Skyline car. Such a motor has the desired torque characteristics, is able to provide the operational rpm required, yet is compact, relatively lightweight and thus when mounted to the handpiece does not unduly impact on the balance of the handpiece. A further prototype has used a car fan motor which also exhibits good operating characteristics but has the advantage of being shorter in length though of greater diameter. However, it has proven to provide good balance of the handpiece and of a suitable weight. 8 WO 2007/073212 PCT/NZ2006/000335 It is preferred that the power cable be attached to the motor in the vicinity of its forward end (i.e. where the housing 15 joins with the adaptor 21) as this assists in providing good balance characteristics. However, with a car fan motor which is shorter the power cable preferably connects in through the rear part of the motor casing. In the preferred form of the invention the forward bearing 20 can be a single needle roller bearing but to get desirable surface area against the shaft a pair of needle roller bearings can be used. This is important when converting an existing handpiece (as described above) because the compactness of the bearing enables the mount 22 to carry the bearing yet still be of a size to screw into the existing screw thread in the barrel. In operation, a prototype of the motorised shearing handpiece of the invention has proven to have low vibration and does not overheat. This is believed to be in part due to the shaft 17 only being located by end bearings 18 and 20 thereby reducing frictional resistance and hence heat generation from the bearings. The handpiece has, in testing, proven to be extremely easy to use in a conventional manner without giving rise to undue fatigue or leading to possible use injury to the user. This is, as previously mentioned, due in large part to the low vibrational and heat characteristics of the handpiece. Also, the power pack is not unduly heavy, nor cumbersome to wear, and a good operational period between charging of the batteries is achievable. If required, the power pack can incorporate its own onboard charger unit, though in an alternative arrangement the power pack would be connected to a charger and in turn adapted for connecting to a power supply such as main supply or the battery of a vehicle. As described above the invention is in its preferred form a motorised conversion unit that can be readily fitted to an existing shearing handpiece without the need for any 9 WO 2007/073212 PCT/NZ2006/000335 modification to the handpiece other than removal of components from the handpiece. The conversion unit as described is particularly suited for performing a motorised conversion on a Sunbeam Supergrip or any Heiniger handpiece. It will be appreciated by those skilled in the art, however, that the adaptor portion of the unit can be of different configuration to suit other existing handpieces. The invention is, therefore, not limited solely to the adaptor unit as described herein. Figures 1 and 2 show an old style handpiece fitted with a motor. In Figure 3 there is shown a later model handpiece 10 to which has been fitted a different type of motor 14' namely a car fan motor as mentioned above. This type of motor can equally be incorporated in the embodiment of Figures 1 and 2. With a handpiece 10' of this type the cam 12 is mounted to a shaft 37 of the handpiece which is retained when the inner back-half joint is removed. This shaft 37 has its own bearing 38 which is a sealed roller bearing. Thus, as shown in Figure 4 a shorter shaft 17' is used in the conversion unit. Figure 4 shows the inner end 31 of shaft 17' has a threaded bore 32 into which the threaded end of the handpiece shaft is fitted. The other or outer end 33 of shaft 17' shows a slot 34 the purpose of which is hereinafter described. Between end parts 31 and 33 is a knurled length 35 which engages through the armature of the motor. Figure 5 show's the adapter 21' which is effectively bell housing 36 which, as with the first embodiment, has a generally frusto-conical part 25 and a connector part which push fits into the housing 15' of motor 14'. It also has the mount 22 which in this embodiment is press fitted into the handpiece to fit the motor conversion to the handpiece. A set screw 39 engages in threaded bore 40 to fix the handpiece 10 to the adapter 21'. In this form of the invention the handpiece bearing 38 simply engages with the distal end of the tubular mount 22. 10 WO 2007/073212 PCT/NZ2006/000335 It will be appreciated by those skilled in the art that the invention is also applicable to a purpose built handpiece. With a purpose built handpiece the mounting portion of the adaptor as described herein could actually form part of the handpiece body. It will be readily apparent to those skilled in the art how a purpose built handpiece could be constructed to include the end mounted motor with a shaft extending through to a bearing at or adjacent the cam drive of the fork. The invention is open to modification. One modification which provides a useful additional advantage of the invention is that a slot can b e formed in the end of the shaft 17 which is engaged in the back bearing 18. this slot is exposed and thus can be accessed by the blade of a screw driver. Consequently when the shearer is setting up the handpiece by adjusting the sweep of the cutter blade B the shearer can inert the screw driver in the slot and rotate shaft 17. This manual rotation of the shaft results in movement of the blade B over to comb C thereby enabling the shearer to visually check the limits of the sweep and ensure that it is correctly adjusted. Another aspect of the construction shown in Figure 3 of the drawings can be the inclusion of a wave washer 41 between the inner end of the mount 22 and the sealed roller bearing 38. Also a wave washer can be provided between the back bearing 18 and the end cover plate or wall 19 of the motor housing. A further element that can be usefully included is a backwards seal in the mount 22 to stop oil getting into the motor. Other modifications and improvements will be apparent to those skilled in the art and fall within the scope of the invention as defined in the claims. The present invention thus provides a simple yet effective motorised shearing handpiece and in particular one which can employ a standard handpiece with little or no modification thereto. The conversion is one which is ergonomically suitable for 11 WO 2007/073212 PCT/NZ2006/000335 its intended purpose and one in which heat build up and vibration is kept down. By being a direct drive there is no use of planetary gears which typically results in heat build up. 12