Field of the Invention The invention relates to hand-held power tools, for instance, vegetation cutters such as grass trimmers, brush cutters and other hand-held devices having large electric or petrol motors as sources of significant vibration. In particular, the invention relates to devices arranged to limit this vibration transmitted from the hand-held device to the operator. Background

Vibrating tools, in particular hand-held tools, represent an occupational health risk to the operator following continuous use. Symptoms such as numbness and tingling may be symptoms of common disorders such as Vibration White Finger ("Raynaud's Syndrome") caused by prolonged exposure to vibration through the hand or arms. Further, carpal tunnel syndrome may result from the extra gripping force needed to hold and control such vibrating tools. Portable petrol or electric driven grass trimmers are identified as a type of tool whose operator may be subjected to large magnitude of hand- arm vibration ("HAV").

Vibration may cause complex vascular, neurological and muscular skeletal disorders, collectively known as hand-arm vibration syndromes ("HAVS"). For instance, a petrol engine driven grass trimmer powered by a 32.8cc engine and using a string as the cutting element is a frequently used device for workers to cut back long grass in wide open areas or adjacent to road ways. Workers operating such tools on large scale projects may therefore be subjected to HAV for days or weeks at a time and so being subjected to the excessive vibration caused. Summary of Invention

In a first aspect the invention provides a handle adaptor arranged to mount a handle to a vibrating power tool said adaptor comprising: a vibration isolator, said vibration isolator including at least two vibration dampers each for damping vibration along a respective axis; wherein said respective axes corresponding to said vibration dampers are perpendicular to each other.

Accordingly, by providing vibration dampers on perpendicular axes, the handle and consequently the operator may be substantially isolated from vibration transmitted along these axes from the tool.

This may provide 2 advantages. First, a vibrating tool is likely to transmit vibration along at least 2 principal axes. Thus, the handle adaptor provides isolation against both components of the vibration along 2 principal axes. Hence it is a more effective means of isolating the operator from the transmitted vibration. Second, whilst a vibrating tool may have components of vibration along principal axes, the magnitude of these components will vary from device to device. By providing the handle adaptor with at least 2 vibration dampers along perpendicular axes, the handle adaptor is flexible enough to be used on a variety of devices irrespective of the magnitude of components along the principal axes. It therefore becomes a more universally applicable device for a wider range of devices.

In a second aspect the invention provides a handle adaptor for a hand-held tool having a shaft, comprising: a shaft engagement assembly for securing the handle adaptor to the shaft; a handle engagement member having a projection, the projection being adapted to allow a handle to be removably mounted thereto; and a vibration isolator spatially separating the handle engagement member from the shaft engagement assembly; wherein said vibration isolator is arranged to reduce transmission of vibration from the shaft to the handle.

It follows that the use of the adaptor provides for attachment of handles or other such device mounted parallel to a shaft of said grass trimmer. By example, an applicable grass trimmer may have a total vibration level (a^) on the handle of 1 1.30 ms ^"2 . This compares to a recommended exposure limit value (ELV) of

2 * *

5.0 ms ^" for daily vibration exposure of eight hours of application. The handle adaptor according to the present invention is directed to reduce the vibration total level (a _hV ). For the exemplary grass trimmer having a^ of 1 1.30 ms ^"2 , one embodiment of the present invention significantly lowered the hand-arm vibration level to 2.69 ms ^"2 . It had significantly reduced the vibration total value by 76% compared to the existing commercial handles. In one embodiment, the handle adaptor may have three vibration dampers each for damping vibration along a respective axis; wherein said respective axes corresponding to said vibration dampers are perpendicular to each other. Thus, whilst in a broad form the invention may accommodate a two dimensional isolation of vibration, an alternative embodiment includes isolation in three dimensions. Said three axes may be principal axes arranged to isolate each component of the applied vibration.

The vibration dampers may be vibration mounts of a visco-elasatic material such as rubber, silicone or other fatigue resistant dampening material.

The handle adaptor, according to the present invention, may be useful for a range of powered tools including grass trimmers, brush cutters, angle grinders, sanders, or other powered tool generating significant vibration through its usage. This is consistent with the advantage of the handle adaptor according to the present invention being adaptable to a range of applications. Each power tool will have the applied vibration with the principal components of that vibration having different magnitudes. With at least 2 or possibly 3 vibration dampers arranged along principal axes, a single handle adaptor may be usable on different power tools with little or no adjustment. The handle adaptor according to the present invention may be selectively removable. This may allow separate sale of the handle adaptor and so applied to existing power tools. To this end, the handle adaptor may include a shaft bracket arranged to mount to a shaft. Alternatively, such a bracket may be attachable to an existing handle of, for instance, an angle grinder or sander, with a handle engagement portion arranged to receive a handle on the handle adaptor to replace that of the powered tool. In a further embodiment the handle engagement portion may have a permanently fixed handle mounted thereto. Alternatively, the handle adaptor may be permanently mounted to the power tool and so manufactured at the same time as the power tool and sold as a single unitary device.

Brief Description of Drawings It will be convenient to further describe the present invention with respect to the accompanying drawings that illustrate possible arrangements of the invention. Other arrangements of the invention are possible and consequently, the particularity of the accompanying drawings is not to be understood as superseding the generality of the preceding description of the invention.

Figure 1 is an isometric view of a handle adaptor according to one embodiment of the present invention;

Figure 2 is a photograph of a grass trimmer having a handle mounted thereto using a handle adaptor according to a further embodiment of the present invention. Detailed Description

Figure 1 shows an adaptor for mounting to a vibrating tool (not shown). The adaptor includes a shaft mounting bracket 8 which comprises two clamping members held together by bolts 1 1. The shaft mounting bracket 8 is arranged to mount to a shaft of the vibrating tool so as to clamp the adaptor securely to the tool.

The adaptor includes a vibration isolator which separates a handle engagement member 4 from the shaft engagement bracket 8. In one embodiment, such as that shown in Figure 1 , the handle engagement member 4 may be shaped so that an engagement part of the handle engagement member 4 is parallel to a shaft of the vibrating tool once the bracket 8 is mounted to the shaft. Thus, a handle that can engage the parallel member would effectively be positioned in precisely the same orientation as if mounted directly to the shaft of the vibrating tool.

Separation of the shaft engagement bracket 8 from the handle engagement member 4 is achieved by a vibration isolator. The vibration isolator includes three damping mounts, or vibration dampers, 1, 2, 6, which are mounted between a bottom plate 7 which is mounted to the shaft engagement bracket 8, and the top plate 3 to which the handle engagement member 4 is mounted. The top and bottom plates 3, 7, have angled portions so as to align each of the three damping mounts 1, 2, 6, along corresponding axes 12, 13, 14. The three axes 12, 13, 14, are principal axes, being perpendicular to each other and meeting at a vertex 15 at the handle engagement portion so that damping along each of said principal axes 12, 13, 14, aligns with the point of engagement of a handle to be mounted to the handle engagement member 4.

Thus, in one embodiment of the present invention, vibration transmitted from the shaft of the vibrating tool is transmitted to the damping mounts 1 , 2, 6, which in turn dampen the vibration along principal axes so as to provide an isolation of vibration to the handle engagement member 4 and so minimize transmitted vibration to an operator of the vibrating tool. Figures 2 shows a further embodiment of the present invention whereby a handle 23 is mounted to the handle engagement member 24. The handle engagement member 24 is mounted to the vibration isolator 16, which includes three damping mounts 20, 21 , 22, aligned along principal axes so as to dampen vibration in three dimensions. The vibration absorber separates the handle engagement member 24 from a shaft engagement bracket 18 which in turn is mounted to a shaft 17 of a vibrating tool, in this case, a grass trimmer. Alternatively, other power/vibrating tools may benefit from the handle adaptor according to the present invention such as brush cutters, angle grinders, sanders or chain saws.