GB2246021A

GB2246021A - Actuating mechanisms

Info

Publication number: GB2246021A
Application number: GB9013556A
Authority: GB
Inventors: Adrian Coussins
Original assignee: QUALCAST GARDEN PROD
Current assignee: QUALCAST GARDEN PROD
Priority date: 1990-06-18
Filing date: 1990-06-18
Publication date: 1992-01-15
Anticipated expiration: 2010-06-18
Also published as: DE4119937C2; GB9013556D0; GB2246021B; DE4119937A1

Abstract

An actuating mechanism transmits motion in a first direction from an operating lever (13) to an actuating button (12) of a switch unit (11). The mechanism includes a resilient strip (20) which must be selectively interposed between the lever (13) and the button (12) before the switch unit (11) can be actuated, the strip (20) being constrained for movement in a second direction transverse to the first direction whereby a free end of the strip (20) is deflected to transmit the necessary load from the lever (13) to the actuating button (12). The resilient strip (20) permits overtravel of the operating lever (13). <IMAGE>

Description

A r__ -4- c, 1 ACTUATING MECHANISMS 1 This invention relates to an

actuating mechanism, and particularly a switch actuating mechanism for attachment to the handle of an electrical appliance, such as an electric lawnmower.

For safety reasons, a switch attached to the handle of an electrical appliance may have an operating lever which must be continuously held against a resilient bias when supplying current to the appliance. If for any reason the lever is released, the switch opens and the supply of current is cut off. In one particular system, the operating lever is grasped by the user and squeezed against the handle. If the user releases his grip, the lever automatically moves away from the handle under its resilient bias, and the appliance is switched off.

A problem with this arrangement is that the design of the operating lever must be matched to the design of the handle. Accordingly, even small differences in the handle design may prevent comfortable operation of the lever. Where an appliance, such as a lawnmower, is provided with a range of handles, it would be an advantage if the same operating lever could be used with different handles.

Another problem is that the full force of the operating lever is applied to the switch unit. This may produce high wear and, if the lever is forced back beyond the position at which the switch is actuated, can damage the switch and/or distort the lever.

A critical factor is the amount of movement of the operating lever which is necessary to actuate the switch. Once the movement has been completed, the lever should lie against the handle so that the user is able to grip the handle and the lever in one hand. If the actuating 1 1 1 1 2 movement is completed too soon, the lever will be spaced-an uncomfortable distance from the handle. On the other hand, the movement must be completed before the lever reaches the handle.

According to one aspect of the present invention, this problem is overcome by selectively inserting a resilient drive transmitting,energy absorbing, member in the path of the operating lever, the member being constrained against rotating with the lever, and the lever deflecting the member in a first plane to actuate the switch. Preferably the lever also deflects the member in a second plane to allow overtravel movement of the lever after actuating the switch.

In a preferred embodiment, the member comprises a resilient arm which forms part of a manually operable push button constrained for movement in one direction only to insert the arm in the path of the operating lever. With the button in its non-actuated state, the operating lever is free to rotate with zero loading. The button is preferably retained in its actuated state against a resilient bias by an interlock mechanism between the arm and the lever, the interlock being maintained only while the lever is deflecting the arm against its resilient bias.

The invention will be further described, by way of example only, with reference to the accompanying drawings in which:

Fig. 1 is a schematic plan view of a switch mechanism embodying the invention; Fig. 2 is a schematic elevation in the direction of the arrow 'W' in Fig. 1; and 3 Fig. 3 is a schematic elevation in the direction of the arrow "B" in Fig. 1.

The drawings illustrate a switch actuating mechanism for attachment to the handle of a lawnmower. Only those parts of the mechanism necessary for an understanding of the invention have been illustrated.

The components of the actuating mechanism are retained in a two-part housing 10 which is clamped around the lawnmower handle (not shown). In Fig. 1 the top half of the housing has been removed to show the operation of the switch mechanism.

The bottom half of the housing 10 carries a self-contained switch unit 11. The switch 11 is actuated by depressing a push-button 12 against a resilient bias.

An operating lever 13 is pivotally mounted on the housing 10 for movement between the rest position shown in full outline and an operative position shown in dashed outline. The lever include a cylindrical hub 14 which pivots freely about a sleeve 30 upstanding from the base of the housing 10. An operating lever arm 15 extends tangentially from a bottom portion of the hub 14, the arm 15 having an upstanding end piece 16 of generally triangular crosssection for engaging a return spring (not shown).

With the lever 13 in its rest position, the lever arm 15 lies closely adjacent and generally parallel to the edge wall 17 of the housing 10. When the operating lever 13 is moved to its operative position, rotation of the hub 14 about its pivot swings the arm 15 downwardly (as viewed in Fig. 1) toward the actuating button 12 of the switch 11.

However, as best shown in Fig. 2, the arm 15 is free to i \ 1 4 swing beneath the actuating button 12 so that the switch 11 cannot be actuated by movement of the operating lever 13 alone.

The hub 14 has a central bore carrying a spring 19. A push-button 18 has a flat top 24, a hollow stem 25 slidable in the bore of the hub 14, and a pair of legs 26,27 which cooperate with upstanding portions 28,29 of the housing 10 to prevent rotation of the button 18. To actuate the switch 11, the push-button 18 must first be depressed against the bias of the spring 19 so that a resilient plastic strip 20 extending from the leg 27 is interposed in the path of the lever arm 15. The height of the resilient strip 20 is such that a bottom section of the strip is then aligned with the lever arm 15 while a top section of the strip is aligned with the actuating button 12. Accordingly, when the lever arm 15 engages the bottom section of the strip 20, the strip is not only deflected about the fixed leg 27 such that the top section is urged against the button 12 to actuate the switch 11, but the bottom section is also twisted relative to the top section.

The switch 11 is actuated when the operating lever 13 has been pulled back through approximately half its permitted range of movement. However, if further movement of the operating lever 13 is required to bring the lever into a comfortable position against the handle of the lawnmower, this overtravel movement is permitted because the lever arm 15 is able to continue its travel beneath the depressed actuating button 12 and against the bias of the resilient strip 20 by continuing to bend or twist the bottom section of the strip 20 relative to the top section.

Once the push-button 18 has been depressed against the 35 spring 19, it will be retained in its actuated state so 1 long as sufficient pressure is applied to the operating lever 13 to maintain an interlock between a catch 31 at the base of the strip 20 and a detent 32 in the opposing face of the lever arm 15.

With the button 18 depressed, the resilient strip 20, ot concealed" within the housing 10, absorbs part of the load when the the operating lever is actuated and thereby protects the switch unit 11 and the operating lever from undue stress. At the same time, it permits overtravel of the operating lever so that the same actuating mechanism can be fitted to a range of handles having different shapes.

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Claims

1. An actuating mechanism wherein motion is transmitted from a first moving part to a second moving part, and wherein a resilient member fixed at one end is interposed between the two moving parts, its resilience being such as to transmit the necessary load from the first moving part to the second moving part when the mechanism is actuated.

2. A mechanism according to claim 1 wherein the free end of the resilient member is selectively interposed in the path of the first moving part.

3. A mechanism according to claim 1 or claim 2 in which the two moving parts are movable in separate parallel planes, and the free end of the resilient member comprises a resilient strip bridging the two planes.

4. A mechanism according to claim 3 in which the first moving part engages a first portion of the strip to bend the strip about its fixed end and to bend the first portion relative to a second portion spaced from the first portion, the second moving part being engaged by the second portion of the strip.

5. A mechanism according to claim 4 in which the parts have limited movement and in which overtravel of the first moving part is accomodated by continuing to bend the first portion of the strip relative to the second portion after the second moving part has reached the limit of its movement.

b 7 6. An electric switch mechanism including an actuating mechanism according to any one of the preceding claims in which the first moving part comprises a manually operable lever and the second moving part comprises an actuating member of a switch unit.

1 --- 11 k CLAIMS 1. An actuating mechanism wherein motion is transmitted in a first direction from a first moving part to a second moving part, and wherein an elongate resilient member is selectively interposed between the two moving parts, the resilient member being constrained for movement in a second direction transverse to the first direction whereby a free end of the resilient member is deflected to transmit the necessary load from the first moving part to the second 10 moving part.

AMENDMENTS TO THE CLAIMS 1 HAVE BEEN FILED AS FOLLOWS 2. A mechanism according to claim 1 in which the two parts are movable along respective paths offset from one another.

3. A mechanism according to claim 2 in which the two moving parts each have limited movement and in which overtravel of the first moving part is accommodated by continuing to bend a portion of the free end of the resilient member after the second moving part has reached the limit of its movement.

4. An electric switch mechanism including an actuating mechanism according to any one of the preceding claims in which the first moving part comprises a manuallyoperable lever and the second moving part comprises an actuating member of a switch unit.

5. A switch mechanism according to claim 4 wherein the resilient member is interposed between the lever and the switch actuating member in response to actuation of a manually operable push-button whereby the lever is free to rotate with reduced or substantially zero loading with the button in its non-actuated state.

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6. A switch mechanism according to claim 5 wherein the button forms an integral part of the resilient member.

7. A switch mechanism according to claim 6 wherein the button is retained in its actuated state against a resilient bias by an interlock mechanism between the said resilient member and the lever, the interlock being maintained for so long as the lever is deflecting the resilient member against its resilient bias.

8. A switch mechanism according to claim 6 or claim 7 wherein the pushbutton is non-rotatable and is slidably mounted in a hub portion of the lever.

9. An electric lawnmower comprising a handle for manoeuvring the mower over the ground and an electric switch mechanism according to any one of the claims 4-7 fitted to the handle, the arrangement being such that the lever is moved to a position alongside the handle when 20 actuating the switch unit.

10. A switch mechanism substantially as herein described with reference to the accompanying drawings.

Published 1991 at The Patent Office, Concept House. Cardiff Road, Newport, Gwent NP9 I RH. Further copies may be obtained fmm Sales Branch, Unit 6. Nine Mile Point. CwnifeWach. Cross Keys. Newport, NP1 7HZ. Printed by Multiplex techniques lid. St Mary Cray. Kent.