GB2234464A

GB2234464A - Percussive tool

Info

Publication number: GB2234464A
Application number: GB9016360A
Authority: GB
Inventors: Michael Graham
Original assignee: Thor Tools Ltd
Current assignee: Thor Tools Ltd
Priority date: 1989-08-02
Filing date: 1990-07-25
Publication date: 1991-02-06
Also published as: GB9016360D0

Abstract

A percussive tool such as a hand-held hammer drill in which the various components are held together against the action of a reciprocating piston by at least one connector. Shock absorbing means such as springs, associated with each connector, are provided within the body of the tool.

Description

PERCUSSIVE TOOL This invention relates to a percussive tool, and in particular to a hand held percussive tool such as a light hammer drill.

A light hammer drill is a tool which is used in the construction and similar industries for the drilling of holes in concrete, stone and other similarly hard substances. It comprises a reciprocating piston which not only impacts the drilling tip but also imparts a rotational movement thereto. Due to the reciprocating motion of the piston giving the impacting load to the drilling tip, alternating loads are applied to the connectors such as bolts which hold the component parts of the tool body together. The alternating peak loads create alternating stresses which in turn may cause fatigue failure of the connectors.

It is an object of the present invention to provide a tool in which the above disadvantage is reduced or overcome.

In accordance with the invention a percussive tool comprises a plurality of body components held together against the percussive action of an internal reciprocating piston by at least one connector having a shock absorbing means associated therewith within the body of the tool, said means dampening the alternating loads applied to the connector.

In one construction according to the invention two connectors are provided, each connector comprising an elongated bolt, positioned one at each side of and parallel to the central longitudinal axis of the tool, two shock absorbing springs, one for each bolt, being positioned, and preferably held in compression, between a shoulder or other suitable locating surface formed within the tool body and the bolt head. The spring may alternatively be located between a nut at the end of the bolt opposite the head and a locating surface, or at any other suitable position within the tool body.

One embodiment of the invention will now be described by way of example with reference to the accompanying drawings, Figures 1 and 2 respectively showing a side view and a top view, each part sectionalised, of a light hammer drill according to the invention.

As illustrated the drill 1 comprises four main body components: a head 2, which incorporates a chuck 3 for holding a drilling tip (not shown), two intermediate components 4 and 5, and a handle 6. These components house many other internal components including a pneumatically driven reciprocating piston but details of this will not be described since they are conventional and do not form part of the present invention.

As can be seen in the drawing the four body components 2, 4, 5 and 6 are held in line by two long bolts 8 and 9, one on each side of the drill 1 and located within holes extending through each component.

In particular the head 2 is provided with two flanges 10 and 11, each formed with a part of each hole and each part being formed with a counterbore 12, 13, which houses the head 14 or 15 of the bolt located therein and a helical spring 16 or 17 positioned about the shank of the bolt between the underside of the head and the shoulder 18 or 19 formed at the base of the counterbore 12 or 13.

The holes continue through the intermediate components and into two further flanges 20 and 21, formed one on each side of the handle 6. The bolts located in the holes are held in position by nuts 22 and washers 23 adjacent the external flange surface of the handle.

In use of the drill, as the piston reciprocates internally of the body, the alternating peak loads on the two bolts 8 and 9 are kept to a minimum by means of the shock absorbing springs i6 and 17. The likelihood of a bolt failing due, for example, to fatigue stress, and the subsequent separation of the various components of the tool is therefore reduced.

In the specific embodiment described and illustrated, the springs are helical but alternately may comprise disc-type springs or rubber or other elastomeric sleeve-shaped buffers. The reduction in the stresses on the bolts ensure that fatigue failures are kept to a minimum.

Further, as the piston reciprocates the springs open and close but because they are housed within counterbores within the head, entrapment of the operator's fingers or of any clothing is prevented.

This is particularly important when the tool is hand held. Further, by enclosing the shock absorbing springs into the body of the tool, damage thereto is substantially reduced, especially as the tools are often used in an environment where external damage can easily occur.

Claims

CLAIMS:

1. A percussive tool comprising a plurality of body components held together against the percussive action of an internal reciprocating piston by at least one connector having shock absorbing means associated therewith within the body of the tool, said means dampening the alternating loads applied to the connector.

2. A percussive tool according to claim 1 wherein two connectors are provided, one on each side of and parallel to the central longitudinal axis of the tool.

3. A percussive tool according to claim 2 wherein each connector comprises an elongated bolt.

4. A percussive tool according to claim 3 wherein the shock absorbing means comprises two springs, one for each bolt, positioned between a locating surface within the tool body and the bolt head.

5. A percussive tool according to claim 3 wherein the shock absorbing means comprises two springs, one for each bolt, positioned between a locating surface within the tool body and a nut at the end of the bolt.

6. A percussive tool according to claim 4 or 5 wherein the spring is held in compression.

7. A percussive tool according to any one of claims 4, 5 or 6 wherein each bolt is located within a hole extending for substantially the whole of the length of the bolt shank and the spring is located in a counterbore formed at an end of the hole.

8. A percussive tool according to any one of the preceding claims wherein the shock absorbing means comprise a helical spring, a disc-shaped spring, or a rubber or elastomeric buffer.

9. A percussive tool substantially as described herein with reference to and as illustrated in the accompanying drawings.