GB2209134A

GB2209134A - Electric power tool and adapter

Info

Publication number: GB2209134A
Application number: GB8820481A
Authority: GB
Inventors: William James Lowe
Original assignee: Individual
Current assignee: Individual
Priority date: 1987-08-27
Filing date: 1988-08-30
Publication date: 1989-05-04
Also published as: AU2321388A; WO1989001848A1; EP0375720A1; GB8820481D0; GB8720234D0

Abstract

An electric power tool, or an adapter to fit onto an electric portable drill comprises a housing (11) penetrated at one end by a shaft (12 or 26) and at the other end by a socket (14) for a hexagonal shanked chisel at the other. A rotary-to-linear vibrating motion conversion means within the housing comprises a camming face on the end of the shaft and a complementary camming face on a slider (21) which is biased by a spring (23) to keep the faces in contact and which has a hexagonal projection (24) which enters the socket (14) to engage the chisel.

Description

ELECTRIC POWER TOOL AND ADAPTER FIELD OF THE INVENTION The present invention concerns electric power tools and adapters therefor to perform chiselling operations.

BACKGROUND OF THE INVENTION Power tools are well known but rely on rotary cutting edges for the main part. There are a lot of times when an operation similar to chiselling would be preferable as when forming a groove in plasterwork for electric wiring or "plugging" a wall (chasing out cement between bricks to install a wooden insert to receive nails or screws). It would also be handy to have a power driven chisel for wood work which would be useful even when carving works of art from wood. One of the great advantages of chiselling rather than rotary cutting of plaster or wood is that rotary cutting produces a mist of fine dust particles whereas chiselling tends to produce larger heavier particles which fall to the ground.

SUMMARY OF THE INVENTION According to one aspect of the present invention there is provided an adapter for a portable electric drill comprising a shaft for being gripped by a chuck of the electric drill, the shaft at the end remote from the drill entering a housing, a socket for a chisel at the remote end of the housing, and a means for converting the rotary motion of the shaft into a reciprocating motion of the chisel when the housing is held nonrotational.

According to another aspect of the present invention there is provided a power tool comprising an electric motor, a housing providing a socket for a chisel and a means for converting the rotary motion of the motor's shaft into a reciprocating motion of the chisel.

Conveniently the said means generates the reciprocating motion co-axially with the shaft.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a view half in section of an adapter according to the present invention, Figure 2 is a detail of a modification of Figure 1 for the adaptor to form a permanent part of a power tool, Figure 3 is a detail of a modification to the adapter of Figure 1, Figure-4 is a perspective view of a camming device used in the embodiments of Figures 1 and 2, and Figures 5 to 7 illustrates various forms of chisels that can be used with the invention.

DESCRIPTION OF EXEMPIARY EMBODIMENTS Referring to Figure 1, there is a housing 11 of generally cylindrical shape. From one end projects a shaft 12 and at the other end there is a socket 14 to receive a chisel (not shown) such as those shown in Figures 5 to 7 with a hexagonal shank, the chisel being a frictional sliding fit in the socket. The housing is made in two parts, a body 15 and a cap 16 screwed or otherwise attached to the body (if screwed, the thread is preferably left-handed). The shaft is stepped so it can be inserted through the body to project from the body and be secured in and projecting from the body by a circlip 17 or other means, is journalled by an Oilite bush 18 (Oilite is a trademark), and its end within the body is formed as a camming face 19 as illustrated in Figure 4.This camming face co-operates with a complementary camming face 20 on a reciprocating slider 21 to form a means for converting the rotary motion of the shaft into a non-rotational reciprocating sliding movement. This slider is journalled in the body by an Oilite bush 22, is spring loaded by a spring 23 to bring the camming faces into engagement, and is stopped from rotating by a hexagonal projection 24 fitting in the socket 14 from the inside of the housing. This projection acts as a hammer on the end of a chisel.

Of course, the chisel does not necessary have to have a hexagonal shank it is sufficient to it to be non-circular so it is non-rotational is a complementary hole and other things described as hexagonal could also be non-circular.

Hardened tool steel is used for the shaft, slider and the cap, the body can be of steel, aluminium or any other material. The body and the cap conveniently have bands of knurling 25 or other roughening to facilitate being gripped by hand. The body can be made of a plastics material as can the cap provided that suitable provision is made for wear, the cap could have hardened tool steel inserts.

In Figure 2, the body 15 forms part of a casing of an electric motor whose shaft 26 projects into the body and into a sleeve 27. The shaft 26 and the sleeve are joined non-rotationally by a pin or screw 28 inserted through a hole 29 in the body, to form the equivalent of the shaft 12 in Figure 1.

It will be appreciated that whilst the spring 23 holds the slider 21, the chisel itself returns only due to pressure of a work-piece on the chisel holding the chisel against the slider. Thus in the absence of a work-piece, the chisel will be clear of the slider and whilst this might improve safety in that the chisel will not vibrate when removed from a workpiece whilst the shaft is still be rotated before the motor comes to a rest after switching off, for fine work such as carving wood figurines it would be desirable to have the chisel fully retracted to enable the operator to visualise the cut before switching on. Figure 3 shows a modification to attach the chisel to the slider.

A chisel 30 slides in the socket 14 in the cap 16.

The socket however widens out where the slider slides and the slider is larger in cross-section than the chisel and is provided with a recess 31 fitted with a liner 32 into which the chisel will grip frictionally and thus be fast with the slider although removable therefrom by a jerk.

Figure 4 illustrates a camming face. The camming face is formed on the end of a drum-shaped part 33 of the shaft with a central blind bore 34 and is dropforged with a plurality (say four) camming ramps 35 with say a 3 millimetre rise. The camming face on the slider would be complementary.

Figures 5 to 7 show various forms of chisels which can be used with the invention. Figure 5 shows a conventional plugging chisel. Figure 6 shows a conventional wood chisel but modified with at least one grip 36 ( a sideways projection from the chisel) to enable the chisel to be held pushed back by a finger of the operator (which finger would of course be vibrated during operation but would give a restoring bias). Figure 7 shows a conventional metal or masonry chisel.

As illustrated, the shaft 12 is located relative to the housing by a step on the shaft and the circlip 17 engaging the inside and outside of the housing respectively, the step and the inside of the housing forming a face-toface thrust bearing. Theoretically this is adequate, since there is no substantial axial force at this point. However in some prototypes, there has been overheating at this point. This can be overcome either by having the bush 18 long enough to space the step slightly from the inside of the housing so the step rubs on the end of the bush not on the inside of the housing or by using a rotary-andthrust roller or other bearing in place of the bush.

Claims

1. An adapter for a portable electric drill comprising a shaft (12) for being gripped by a chuck of the electric drill, the shaft at the end remote from the drill entering a housing (11), a socket (14) for a chisel at the remote end of the housing, and a means (19 and 20) for converting the rotary motion of the shaft into a reciprocating motion of the chisel when the housing is held non-rotational.

2. A power tool comprising an electric motor (15), a housing (15) providing a socket (14) for a chisel and a means (19 and 20) for converting the rotary motion of the motor's shaft (26) into a reciprocating motion of the chisel.

3. An adapter according to claim I or a tool according to claim 2 wherein the housing contains a slider (21) with a projection (24) extending non-rotationally into the internal end of the socket (14) for abutment with the chisel to provide the reciprocating motion thereof.

4. An adapter or tool according to claim 3 wherein the slider is biassed towards the shaft.

5. An adapter or tool according to claim 3 or 4 wherein the said means are a camming face (19) on the shaft and a complementary camming face (20) on the slider.

6. An adapter or tool according to claim 3, 4 or 5 wherein the socket is stepped with the chisel fitting into a reduced cross-section part and the slider's projection into a larger cross-section part, the proåecticn having a larger cross-section that the chisel and being recessed to receive the end of the chisel and the recess having a liner so the chisel will be a tightish fit in the lining.

7. An adapter or tool according to any one of the preceding claims wherein the socket is sized so that chisels are a frictional sliding fit in the socket.

8. An adapter substantially as herein described with reference to Figure 1 of the accompanying drawings

9. A power tool substantially as herein described with reference to Figure 2 of the accompanying drawings taken in combination with Figure 1.