GB2213757A

GB2213757A - Power tool suspension

Info

Publication number: GB2213757A
Application number: GB8827976A
Authority: GB
Inventors: Knut Christian Schoeps
Original assignee: Atlas Copco AB
Current assignee: Atlas Copco AB
Priority date: 1987-12-04
Filing date: 1988-11-30
Publication date: 1989-08-23
Anticipated expiration: 2008-11-30
Also published as: SE8704864D0; IT8848616A0; IT1224797B; FR2624248B1; SE457424B; JPH01193183A; FR2624248A1; GB8827976D0; DE3840163A1; GB2213757B

Description

4 1 m A- 2 137 1 POWER TOOL SUSPENSIONS This invention relates to power

tool suspensions. A power tool suspension provides connection of a power tool to a weight-balancing lift, and generally comprises a yoke attached to the tool housing, with a shackle which is coupled to the balancing unit by means of a wire, cord, chain or the like. The invention is especially concerned with suspension of power tools having a pistol grip.

It is known to use a yoke in arrangement for suspending a pneumatically or electrically powered machine -10 tool from a balancing unit via a shackle on a cord or wire, the yoke being pivotalIy mountdd on the tool housing and having a shape which offers a single conhection point for the shackle.

The known arrangement provides comfortable handling'of the tools and also some protection against rough handling of the tools. The known arrangement does not, however, utilise fully the capability of the balancing unit to make work still more comfortable and more efficient. This is due to the fact that the line of the lifting force applied by the balancing unit on the tool always extends through the connection point between the yoke and the tool, which usually means that the line of the lifting force extends through the centre of gravity of the tool only when the tool is hanging free when idle. As soon as the tool is to be applied to an object, the centre of gravity will generally be moved more 2 or less out of the lifting force line by forces applied through the handle of the tool. With heavy tools and more complicated application movements of the tool, the known arrangement causes tiresome and efficiency-impairing extra 5 work.

An object of the present invention is to provide an improved power tool suspension.

According to the present invention, there is provided a power tool suspension, comprising a power tool having a fore-and-aft operational axis, and a yoke mounted on the tool and comprising with respect to the centre of gravity of the tool forward and rear mounting portions pivotally mounted on the tool on a fore-and-aft yoke axis substantially parallel with said operational axis, and a curved portion interconn- ecting the mounting portions.

Embodiments of the invention will now be described by way of example, with reference to the accompanying drawings in.which:

Fig. 1 is a side view of one embodiment of a power tool suspension according to the present invention; Fig. 2 is a rear end view of the same power tool suspension as Fig. 1, but shown with the pistol grip extending horizontally from the tool housing; Fig. 3 is a perspective view of the yoke of the power tool suspension and, shown separated from the yoke, a bearing ring for rotational support of the yoke on a tool housing.

j i I 3 Fig. 4 shows a fragmentary cross-section through the bearing ring of Fig. 3 when mounted on the tool housing shown in Fig. 1 and cooperating with a surrounding part of the yoke; and Fig. 5 is a fragmentary side view of a second embodiment of a power tool suspension according to the invention.

In Figs. 1, 2 and 5, a tool 1 comprises a housing 2 which encloses a motor (not shown) for rotating an output spindle 3 which is intended to support and rotate an exchangeable screw or nut socket 4. In operation generally, the tool is held manually by means of a pistol grip 5 to which is attached a pressure air connection through a hose 6 and which houses a conventional throttle valve (not shown) operable by a trigger 7 and a reversing lever 8.

To assist operation of the tool 1, a suspension device 9 connects the tool to a balancing unit 10, which is'shown schematically in Fig. 1 on a smaller scale. The balancing unit 10 is itself suspended in a usual manner and is adapted to counteract the weight of the tool by-a spring force deployed within the balancing unit 10. The suspension device 9 comprises a yoke 11 attached to the tool housing 2, and a running loop or shackle 12 cooperating with the yoke 11. 25 The yoke 11 comprises a curved orcrest-shaped portion 14 which extends lengthwise over a considerable 4 part of the tool housing 2 in the application or operational direction of the tool, i.e. in the direction in which the tool is normally moved to come into engagement with a work piece (not shown). In the power tool shown in the drawings, the direction of application means the direction in which the output shaft 3 of the tool extends.

The yoke 11 is pivotally mounted on the tool housing 2 about a yoke axis substantially parallel with the fore-and-aft application direction or operational axis of the tool in that the yoke axis coincides with the rotational axis of the output shaft 3 of the tool.

The pivotal mounting of the yoke 11, which is made of rigid metal wire, has been accomprl'ished in that the yoke at one end is formed with a circular loop 15 (journalled on a substantially cylindrical portion 16 of the tool housing 2; and at the other end in that the yoke 11 cooperates with a bearing plate 17 on the rear end wall of the tool housing. Foi this purpose the rear end of the yoke is returned to form a bearing stub axle 18 which is arranged to cooperate with a bore in the bearing plate 17. The latter is made of,for example, sheet steel. The stub axle 18 is located axially in the plate 17, for example by means of a retaining washer, as shown, or by the stub axle 18 being screw threaded in the plate 17.

The entire yoke 11 including the loop 15 and the stub axle 18, is formed in one piece of stiff metal wire as is apparent in Fig. 3.

A i 1 'i In Figi.1, 3 and 4 it is to be seen that a ring 19, preferably of plastic, is arranged to guide and facilitate movement of the loop 15. As being shown in Fig. 4, the ring is formed with a circumferential groove for receiving the loop 15. The ring 19 is dimensioned so as to enable a simple mounting by being slid on to the front end of the tool housing.

In Fig. 5 there is shown an embodiment which as far as the yoke 11 is concerned differs from the one shown in the previous figures. In this figure, the same reference numerals are used for those parts which correspond with the previously described parts. The loop 15 is smaller to cooperate with a reduced diameter front portion of the tool housing 2, and without any ring 19.

A common feature of the yokes 11 in Figs. 1 and 5 i that the crest-formed portion 14 of the yoke has a substantially constant radius Rl, R2 over a main part of its length, and that the radius Rl, R2 exceeds the largest distance between the yoke and the pivot axis thereof.

The essential difference between the yokes in these figures is that the centre of gravity 20 of the tool in Fig. 5 has been chosen as a centre for the radius R2 defining the curve of the crest- formed portion 14.

From Fig. 2, it is evident that the tool (by a manually applied force) may be inclined sideways without making the line of the lifting force transferred to the 6 yoke move very far from the centre of gravity 20. This is to be compared with the case of previously proposed tools in which the shackle 12 is connected to an ear at the top side of the tool, i.e. on the left hand side of the tool 5 housing in Fig. 2.

As the tool is brought into various inclinations as regards the rotation axis of the output spindle, the crest-formed portion 14 of the yoke makes it possible for shackle 12 to slide along the yoke to positions where the lift force line will be fairly close to the centre of gravity 20, or, especially in the embodiment according to Fig. 5, even through the centre of gravity. Thus, during handling of the tool whilst applied in various different positions, there is obtained a good relief of the tool weight from the pistol grip 5.

It is to be noted that the fore-and-aft pivotal axis of the yoke does not have to coincide with rotation axis of the tool. By means of alternative bearing means for the ends of the yoke, the yoke axis may be moved closer to the centre of gravity 20 of the tool so as to further facilitate sideways inclinations of the tool.

The shape of the yoke and the range of movement of the shackle 12 thereon might have to be adapted to one dominating working direction, for example an upwardly inclined or a downwardly inclined direction. In order to adapt the yoke to such applications, which means that the range of movement v 11 I- 7 of the shackle has to be limited the yoke is provided with one or more stop members in a modification within the scope of the appended claims which are lockable in suitable places along the yoke.

4 8

Claims

WE CLAIM 1. A power tool suspension, comprising a power tool (1) having a

fore-and-aft operational axis, and a yoke (11) mounted on the tool (1) and comprising with respect to the centre of gravity of the tool forward and rear mounting portions (15,18)-pivotally mounted on the tool (1) on a fore-and-aft yoke axis substantially parallel with said operational axis, and a curved portion (14) interconnectinq the mounting portions (15,18). 2. A power tool suspension as claimed in Claim 1, including a counter-balance means (10) attached to the curved portion (14) of the yoke (11) by means of a sliding shackle (12). 3. A power tool suspension as claimed in Claim 1 or 2, wherein the said forward (15) rear (18) and curved (14) portions of the yoke (11) are formed in one piece from stiff wire or the like. 4. A power tool suspension as claimed in any one of the preceding claims, wherein the forward portion (15) of the yoke (11) is a circular loop embracing a cylindrical forward portion (16) of the tool (1). 5. A power tool suspension as claimed in Claim 4, wherein the circular loop (15) engages a ring (19) dimensioned to slide onto said cylindrical forward portion (16).

1 Z 9 1 6. A power tool suspension as claimed in any one of the preceding claims, wherein the rear portion (18) of the yoke (11) is a stub shaft (18) which projects forwards from a rear end of said curved portion (14) and is journalled in a bearing plate (17) secured to a rear end portion of the tool. 7. A-power tool suspension as claimed in any one of the preceding claims, wherein at least a major part of the curved portion (14) of the yoke (11) has a curvature of radius greater than the largest distance from the yoke axis of any point on said curved portion (14) measured normal to the yoke axis.

8. A power tool suspension as claimed in claim 7, wherein the curved portion (14) is part-circular.

9. A power tool suspension as claimed in Claim 8, wherein the centre of curvature of said curved portion (14) co-incides with the centre of gravity (20) of the tool (1).

10.1 A power tool suspension substantially as hereinbefore described with reference to and as shown in Figs. 1 to4 or these Figs. as modified by Fig. 5 of the accompanying drawings.

Published 1989 at The Patent Offtee, State House, 68171 High Holbom, London WCIR 4T?. Further copies may be obtained from The Patent Oftice.

Suleo Dranon, St II&r7 Lr!37, Oil pine' wn, Ment LMAM.D. Printed by Multiplex techniques ltd, St Mar7 Cray, Kent, Con. 1/87