GB2291744A

GB2291744A - Switch actuating mechanism for electrically powered tools

Info

Publication number: GB2291744A
Application number: GB9415019A
Authority: GB
Inventors: Adrian Coussins
Original assignee: ATCO QUALCAST Ltd
Current assignee: ATCO QUALCAST Ltd
Priority date: 1994-07-26
Filing date: 1994-07-26
Publication date: 1996-01-31
Anticipated expiration: 2014-07-26
Also published as: GB2291744B; FR2723250A1; GB9415019D0; FR2723250B1; DE19527207A1

Description

1 SWITCH ACTUATING MECHANISM FOR ELECTRICALLY POWERED TOOLS 2291744 A

portable electrically powered tool is frequently provided with two carrying handles such that, in use, it can be supported by the user separately grasping each handle. For example, with a hedgetrimmer, the user may grasp a rear handle with one hand and a front handle with the other hand.

For safety, it is also desirable that the tool should have two-handed switching, i.e. a first on/off switch actuated by one hand, and a second on/off switch actuated by the other hand. In this manner, as soon as one hand is removed from supporting the tool, the tool is automatically switched off. For convenience, the actuating buttons for the two switches are generally located in or adjacent the respective handles of the tool.

For certain tools it can also be convenient to provide the option of fitting auxiliary handles.From the manufacturer's viewpoint, it is desirable that the auxiliary handles should be fitted without modifying the basic structure of the tool. The manufacturer is then able to offer a basic version of the tool without auxiliary handles and a more expensive version with auxiliary handles. In one particular construction for a hedgetrimmer, auxiliary side handles are fitted to the cross-piece of a front T-handle such that the single T- handle is converted to a pair of opposite handed D-handles.

A disadvantage of this conversion is that it would be expected that an additional on/off switch would be required if the advantages of twohanded switching were to be retained in the version fitted with side handles.

According to the present invention, the advantage of two-handed switching is retained for an electric power tool when fitting an auxiliary handle to the tool by incorporating a mechanical linkage in the auxiliary handle, the arrangement being such that the linkage is 2 movable from a first position to a second position in response to actuation of a first manually operable actuating member associated with the auxiliary handle, the movement of the linkage being transmitted to an on/off switch located in a portion of the tool to which the auxiliary handle is attached. In this manner, the auxiliary handle can be fitted without requiring additional switches or associated electrical wiring.

In one particular embodiment, the portion of the tool to which the auxiliary handle is fitted comprises a basic handle which co-operates with the auxiliary handle to form a more complete handle. The basic handl e may, for examp] e, compri se a T-handl e whi ch co-operates wi th the auxiliary handle to form a closed loop handle. In particular, the T hand] e may have a hol 1 ow cross-pi ece open at both ends, and the 1 i nkage may then include a lever that projects into an open end of the crosspiece to co-operate with a switch actuating mechanism in the crosspiece when the auxiliary handle is fitted.

Pref erabl y, the on/of f swi tch i s actuabl e by a second manual 1 y operabl e actuating member when the auxiliary handle is not fitted, and the movement of the linkage is transmitted to the switch through the auxiliary mechanism associated with the second manually operable member.

A hedgetrimmer embodying the invention will now be described by way of example only with reference to the accompanying drawings in which:

Fig. 1 is a perspective view from above of the main body of the hedgetrimmer; Fig. 2 is a diagrammatic end view of the cross-piece of the front Thandle of the hedgetrimmer shown in Fig. 1 with the end cap removed to show the internal parts of the actuating button; Fig. 3 is a plan view of the actuating button provided in the T-handle of Fig. 1; f 3 Fig. 4 is an end view of the actuating button; Fig. 5 is a front elevation view of the actuating button; Fig. 6 is a magnified section on line A-A in Fig. 5; and Fig. 7 is an exploded sectional view of the components of an auxiliary handle fitted to the hedgetrimmer shown in Fig. 1.

Referring to these drawings, Fig. 1 shows the main body of a hedgetrimmer housing an electric motor for driving a conventional pair of elongate reciprocating cutter blades (not shown). The protective housing 10 is formed with a front T-handle 11 and a rear loop handle 12.

The rear loop handle 12 is hollow and has an associated internal on/off microswitch with an actuating button (not visible in the drawing) which can be actuated by the user when grasping the rear handle.

The front T-handle is also hollow and includes an internal on/off microswitch which is actuated by depressing an actuating button 13. Referring to Figs. 2-6, the button 13 protrudes through a slot in the bottom wall of the T-handle cross-piece 18. Inside the cross-piece, the button consists of a flat base strip 15 with upstanding channel- section guide walls 16 at each end, a central depth stop 60 and a laterally protruding ramp 17. The ramp 17 co-operates with the actuating button of the microswitch (not shown) to operate the switch in a conventional manner.

The guide walls 16 co-operate with corresponding guide walls 19 in the handle moulding to maintain alignment of the button such that it can move vertically up and down within the cross-piece 18. The arrangement is such that if the button 13 is depressed at either end, instead of at the centre, the base strip 15 is tilted but the vertical movement at the centre is still sufficient for the ramp 17 to actuate the microswitch.

4 The button 13 is depressed against a resilient bias (not shown) so that it automatically returns to the off position when the button is released.

As shown in Fig. 1, the hedgetrimmer is fitted with a pair of auxiliary side handles 20, 20a. The side handles 20 and 20a are identical and cooperate with the T-handle 11 to form a pair of opposed D-handles which can be grasped by one hand while the other hand is holding the rear handle 12. Since the handles are identical, only the handle 20 10 will be described now in detail.

The handle 20 is shown in Fig. 7 and is formed in two parts, an outer part 21 and an inner part 22. The two parts are coupled together by a screw 23 which is inserted through an opening 40 in the inner part 22 to engage a stub 24 in the outer part 21. Once screwed together, the two parts are then screwed to the main body 10 of the hedgetrimmer by inserting screws into the screw holes 41, 42. In particular, the screw inserted into screw hole 41 will be screwed into the hole 43 in a mounting 44 secured within the cross-piece 18 of the T-handle 11.

An actuating button 25 protrudes from a slot 45 in the wall 46 of the inner part of handle 20, and depression of the actuating button 25 produces movement of a linkage 26. The linkage 26 consists of an arm 27 pivotally connected to a rocking lever 28 at a pivot 47, the tip 29 of the rocking lever 28 projecting from an end face 30 of the inner part 22 into an offset plug-in portion 48 of the handle and being movable between the two positions shown in dashed outline when the linkage 26 is actuated by depressing the button 25. The plug-in portion 48 of the handle 20 fits within the hollow cross-piece 11 of the T-handle so that the tip 29 of the rocking lever will lie beneath the end portion 49 (Fig. 5) of the base strip 15 forming part of the actuating button 13. In this manner, actuation of the linkage 26 has the effect of tilting the button 13 as if it had been manually depressed at the end 49, and consequently the microswitch is actuated in the same manner as during normal operation of the button 13 without the side handle 20 fitted.

-r I f Button 25 consists of a flat base strip 50 with opposed pairs of upstanding guide walls 51 at each end. When the button 25 i s depressed, a central protuberance 52 on the underside of base strip 50 presses the free end 56 of the linkage arm 27 downwards against the bias of a spring 55. Because the rocking lever 28 has a fixed pivot mounting 54, the effect of the resulting upward movement of the pivot 47 when arm 27 is pressed down is to produce an anti-clockwise rotary movement of the rocking lever about the pivot 54. The top 29 of the rocking lever therefore moves from right to left as viewed in Fig. 7, and thereby lifts the end 49 of button 13 in the T-handle.

A manufacturer is therefore able to produce a basic hedgetrimmer with a rear handle 12 and a front T-handle 11, as well as a more expensive model f i tted wi th the aux i 1 i ary si de handl es 20, 20a. Both model s wi 11 have two-handed switching, and the more expensive model can be manufactured without the need for additional switches or associated electrical wiring. A removable cap would be placed over each open end of the T-handle cross-piece 18 when manufacturing the basic model without side handles 20, 20a.

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Claims

1. A portable electrically powered tool comprising first and second carrying handles each with an associated onjoff switch, and means for fitting a third handle, the third handle having an internal mechanical linkage movable from a first position to a second position in response to actuation of a manually operable actuator; the arrangement being such that, with the third handle fitted to the tool, the said movement of the mechanical linkage actuates one of the two on/off switches.

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2. A tool according to claim 1 in which the third handle when fitted to the tool combines with the first handle to form a composite handle.

3. A tool according to claim 2 in which the f irst handle is a Tshaped handle and the composite handle is a closed loop handle.

4. A tool according to claim 3 in which the linkage includes a rocking lever projecting from an end face of the third handle into an open end of the cross-piece of the T-shaped handle to cooperate with an actuating mechanism of the on/off switch associated with the T-shaped handle.

5. A tool according to any one of the preceding claims wherein the tool comprises a hedgetrimmer.

6. A hedgetrimmer substantially as herein described with reference to the accompanying drawings.

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