GB2093393A

GB2093393A - Shock-absorbing handle

Info

Publication number: GB2093393A
Application number: GB8105390A
Authority: GB
Original assignee: AF Hydraulics Ltd
Current assignee: AF Hydraulics Ltd
Priority date: 1981-02-20
Filing date: 1981-02-20
Publication date: 1982-09-02
Also published as: GB2093393B

Abstract

A hydraulic percussive tool has a body 1 which at the front end receives a cutting tool retained by a pivotal latch member 2. A handle assembly 5 at the rear end of the tool comprises a handle member 6 which is of rectangular cross-section and projects at both sides of the body 1 to provide side handles thereof. The handle member 6 is completely encapsulated within an elastomeric sleeve 7 with a central clamping section 7a and end sections 7b, 7c which respectively provide shock absorbing and electrically-insulating hand grips. The clamping section 7a is also of rectangular cross-section and has an effective thickness in the direction of the tool axis which is considerably greater than the thickness in the lateral direction. It is closely contained under a light degree of compression within a rectangular recess at the rear end of the body 1, and it is retained therein by clamping member 9 fixed to the end of the body by fixing bolts 10 which pass through aligned clearance holes 11 and 12 in the sleeve 7 and the handle member 6. <IMAGE>

Description

SPECIFICATION Hand-held percussive tool This invention relates to hand-held percussive tools such as roadbreakers and picks.

Hand-held percussive tools are commonly provided with side handles providing hand grips adjacent the rear end of the tool body, i.e. the end opposite to that in which the cutting tool is in use mounted. With the advent of tools of higher power, particularly hydraulically-operated tools, and the development of legislative rules governing working conditions the requirement for shockabsorbing handles for such tools has arisen.

Associated with this there is a frequent requirement for electrical insulation of the handles to protect the user in the event the cutting tool strikes a live electrical cable.

As regards shock-absorbing mounting of the handles the problem arises that maximum flexibility is required in the handle plane which also contains the longitudinal axis of the tool, i.e.

the working or percussive axis, whereas relatively low flexibility is required in the plane normal to that axis.

The main object of the invention is to provide a percussive tool with handles having a shockabsorbing mounting which fulfills the foregoing conflicting requirements as to flexibility in said handle and normal planes. A subsidiary object is to provide such a tool which can readily be designed with insulated side handles and wherein the shock absorbing mounting contributes to the electrical insulation.

According to the invention a percussive tool has side handles provided by a handle member which projects at both sides of the tool body to provide side handles, and which is clamped to the body through a surrounding sleeve of elastomeric material which has a greater effective thickness in the axial direction, i.e. the direction of the tool axis, than in a lateral direction at right angles to the handle member.

Preferably the handle member and the sleeve are of rectangular cross-section with the major axis of the section aligned with said lateral direction. The handle member desirably has a degree of inherent flexibility coupled with the requisite strength and to this end it is conveniently provided by a high tensile steel bar.

The external periphery of the elastomeric sleeve is preferably closely received in a rectangular recess at the rear end of the tool body, within which it is contained under slight compression by a clamping member bolted to the end of the body.

The fixing bolts for this member may pass through clearance holes in the sleeve and handle member.

The elastomeric sleeve preferably extends over the full length of and around the ends of the handle member so that the latter is completely encapsulated and the elastomeric material provides shock-absorbing handgrips and electrical insulation for the handles relative to the tool body.

In this case the ends of the sleeve at the side of the body are conveniently of increased thickness and circular external section to provide comfortable handgrips.

An operating lever for manual control of tool operation may be pivoted on the handle clamping member so as to extend behind one of the handgrips for movement by the operator from a normal OFF position to an ON position in which it lies against that handgrip, the end of this lever being provided with an electrically insulating sleeve. A pushrod, through which the lever operates a control valve of the tool, may pass through clearance holes in the handle member and the sleeve outside and adjacent the tool body.

The invention will now be further described with reference to the accompanying drawings which illustrate, by way of example, a preferred embodiment of the invention. In the drawings: Figure 1 is a side view of a percussive tool embodying a shock-absorbing handle mounting in accordance with the invention and partly sectioned in longitudinal plane containing side handles of the tool; Figure 2 is a fragmentary sectional view on the line Il-Il in Figure 1; and Figure 3 is a rear end view of the tool.

The tool comprises a body 1 the front end of which in use receives a cutting tool retained by a latch member 2, and which contains the hydraulic operating mechanism including a striker/piston 3 and a control valve 4. The tool-holding and hydraulic arrangements form no part of the invention, which is concerned solely with the rear end mounting of the handle assembly 5, and hence they will not be described in detail herein.

Although the invention is specifically described and illustrated as employed with a hydraulicallyoperated percussive tool it is to be appreciated that it can usefully be employed with all hand-held percussive tools, for example pneumatic as well as hydraulic.

The handle assembly 5 comprises a handle member 6 which projects at both sides of the body 1 and extends diametrically thereof. This handle member 6 is of high tensile steel, which provides a considerable degree of inherent flexibility coupled with adequate strength, and is of rectangular cross-section. This rectangular section has a major axis A disposed laterally of the body 1 in a plane normal to the longitudinal tool axis B. The handle member 6 is completely encapsulated within an elastomeric sleeve 7 with a central clamping section 7a and end sections 7b, 7c which respectively provide shock-absorbing handgrips. The end sections 7b and 7c thus extend around and cover the ends of the steel handle member 6 to provide electrical insulation and thus protect the operator in the event the cutting tool should strike a live electrical cable.

The clamping section 7a of the elastomeric sleeve is also of rectangular cross-section as shown particularly in Figure 2 and it has an effective thickness C in the direction of the tool axis B which is considerably greater than the thickness D in the direction of the lateral axis A.

The words "considerably greater" are used in the sense of the flexibility characteristics of a closelycontained elastomeric material, the flexibility of which varies as the square of the thickness. Thus the described form of the sleeve section 7a, coupled with its length relative to the thicknesses C and D, results in flexible mounting of the handle member 6 relative to the body 1 which gives a considerable degree of flexibility in the axial plane of the handle member 6 which also contains the tool axis B and relatively little flexibility, in fact an apparent stiffness, in the normal lateral plane containing the axis A.

The sleeve section 7a is closely contained under a light degree of compression, sufficient to provide an adequate friction grip and hence lateral location of the handle 75, within a longitudinal section recess 8 at the rear end of the tool body 1.

It is so retained by a clamping member 9 which is fixed to the end of the body by two fixing bolts 10 which pass through aligned clearance holes 11 and 12 formed respectively in the sleeve section 7a and in the handle member 6.

The end sections 7b and 7c of the sleeve are of increased thickness to provide circular-section shock-absorbing handgrips. The clamping member 9 is a box-section casting in which an operating lever 13 is pivotally mounted at 14 so as to project behind the handgrip 7c. This lever is provided by a cranked metal rod 1 5 the projecting end of which is covered by an electrically insulating sleeve 16 and which can be grasped by the operator for movement from the OFF position (shown in full lines in Figure 1) to the ON position (shown in broken lines) in which it engages the rear side of the handgrip 7.The lever 13 operates the hydraulic control valve 4 through a pushrod 17 which passes through aligned clearance holes 1 8 and 19 formed respectively in the sleeve and handle member alongside but adjacent the body 1 within a cut away rear end region of the body.

A rectangular plate 20 let into a recess at the outer side of the clamping member 9 is retained therein by drive rivets 21. This shrouds the lever pivot and provides a stop which defines the normal resting position of the lever 1 3.

The elastomeric material from which the sleeve 7 is moulded around the handle member 6 is conveniently polyurethene, and the specific arrangement described and illustrated, wherein the dimensions C and D are respectively 7 mm and 4 mm and the combined length of the sleeve is 67 mm provides, for example, extremely satisfactory shock-absorbing characteristics for a tool with a percussive power of say 40 foot pounds per blow at a frequency of 1000/2000 blows per minute.

Claims

1. A percussive tool having a handle member which projects at both sides of a body of the tool to provide side handles therefor, said handle member being clamped to the tool body through a surrounding sleeve of elastomeric material which has a greater effective thickness in the axial direction, i.e. the direction of the tool axis, than in a lateral direction at right angles to the handle member.

2. A percussive tool according to claim 1, wherein the handle member and the sleeve are of rectangular cross-section with the major axis of the section aligned with said lateral direction.

3. A percussive tool according to either one of the preceding claims, wherein the handle member has a degree of inherent flexibility coupled with the requisite stength.

4. A percussive tool according to claim 3, wherein the handle member is provided by a high tensile steel bar.

5. A percussive tool according to any one of the preceding claims, wherein the external periphery of the elastomeric sleeve is closely received in a rectangular recess at the rear end of the tool body, within which it is contained under slight compression by a clamping member bolted to the end of the body.

6. A percussive tool according to claim 5, wherein the bolts fixing the clamping member to the tool body pass through clearance holes in the sleeve and handle member.

7. A percussive tool according to any one of the preceding claims, wherein the elastomeric sleeve extends over the full length of and around the ends of the handle member so that the latter is completely encapsulated with the elastomeric material providing shock absorbing hand grips and electrical insulation for the side handles relative to the tool body.

8. A percussive tool according to claim 7, wherein the ends of the elastomeric sleeve at the sides of the tool body are of increased thickness and circular external section.

9. A percussive tool according to any one of claims operation is pivoted on said clamping member and extends behind one of the side handles for movement by the operator from a normal OFF position to an ON position in which it lies against the side handle.

10. A percussive tool according to claims 7 and 9, wherein said operating lever has an electricallyinsulating sleeve.

11. A percussive tool according to claim 9 or claim 10, wherein a pushrod through which said lever operates a control valve of the tool passes through clearance holes in the handle member and the sleeve outside and adjacent the tool body.

12. A percussive tool having a shock absorbing side handle arrangement constructed and arranged as substantially herein particularly described with reference to the accompanying drawings.