EP0626706A1

EP0626706A1 - Electrical switch

Info

Publication number: EP0626706A1
Application number: EP94303703A
Authority: EP
Inventors: Roger Louis Hambidge; Reginald Jeffrey Collings
Original assignee: Delta Schoeller Ltd
Current assignee: Stoneridge Pollack Ltd
Priority date: 1993-05-27
Filing date: 1994-05-24
Publication date: 1994-11-30
Also published as: GB9310996D0

Abstract

In order to reduce movement of a switch push button, a rocker switch has first and second tappets for engagement with first and second ends of the rocker. The tappets are mounted for movement with an operating member and pivot between inward and outward positions. A tappet presetting member projects from the rocker to preset the tappets so that with the rocker in a first position the first tappet is in its inward position to engage the rocker. Movement of the operating member thus causes the first tappet to move the rocker to its second position while the second tappet is in its outward position and free from the rocker. With the rocker in its second position, the second tappet is preset in its inward position to engage the rocker. When moved by the operating member it moves the rocker to its first position while the first tappet is in its outward position free from the rocker.

Description

This invention relates to electrical switches.
Electrical switches are known having contacts; a rocker mounted for pivotal movement between first and second stable positions, said contacts being closed in the first position of the rocker and open in the second position; an operating member, and means for translating successive movements of the operating member in one direction, into rocking movement of the rocker. Examples include push button switches in which repeated presses of the push button causes the rocker to rock between its first and second positions so closing and opening the contacts alternately. Further contacts may be included, e.g. to provide a change over facility.
In one example, the tappet is biased more or less centrally and the rocker has a camming surface. No matter which position the rocker is in, when the tappet has retracted with the push button, ready for the next push operation, the camming surface presents a surface to the tappet which surface will guide the tappet to an abutment on the rocker such as to rock the rocker the other way.
A problem with that arrangement is that it takes a substantial movement of the push button to move the tappet from its central position along the camming surface and into engagement with the relevant abutment.
A solution to the problem is proposed in EP-A1-0 232 765. Here the rocker is formed with a resilient web which engages the tappet beyond the axis of rotation of the tappet. Instead of remaining more or less central, the tappet is preset by the web towards one or other end of the rocker so as to meet the abutment after less travel of the push button.
In accordance with a first aspect of the invention, an alternative solution is provided in which said means for translating successive movements of the operating member in one direction, into rocking movement of the rocker comprises: first and second tappets for engagement with first and second spaced ends of the rocker, said tappets being mounted for movement with the operating member and for pivotal movement in relation to the operating member for movement between inward and outward positions; and a tappet presetting member projecting from the rocker and movable therewith, operative on the tappets, between the rocker and their pivot, to preset the tappets so that with the rocker in the first position the first tappet is preset in its inward position to engage the rocker, when moved by the operating member, so as to move the rocker to its second position, said second tappet being in its outward position freeing the rocker for such movement, and so that with the rocker in the second position the second tappet is preset in its inward position to engage the rocker, when moved by the operating member, so as to move the rocker to its first position, said first tappet being in its outward position freeing the rocker for such movement.
Although the tappet presetting member operates on the tappets between its pivot and the rocker, which in the prior art proposals would move the tappet the wrong way, correct operation is obtained by use of two tappets so that one moves into an operative position as the other moves out of an operative position. The invention may be embodied in different kinds of switches, e.g push button switches, pull switches etc. A push button switch, for example, has a much better "feel" when operated, than a switch having the prior art arrangement in which the tappet slides along the camming surface before reaching the abutment.
Conveniently , the tappet presetting member may be resilient, e.g. a flexible blade.
The rocker may operate the contacts in any convenient manner. In a preferred embodiment, one contact is mounted on a snap action blade spring. In that form, moving the rocker to the first position causes the blade spring to snap one way closing the contacts. Moving the rocker to the second position causes the blade spring to snap the other way, so opening the contacts.
In accordance with a second additional or alternative aspect of the invention, there is provided an electrical switch wherein one contact is mounted on a snap action blade spring having two slots therein defining one central and two outer legs extending between two end portions, the blade being so formed that the outer legs have a different extent from the central leg. This arrangement pretensions the spring so that it snaps from a curve one way to a curve the other without the need for external members to restrain it. That enables the spring to be welded or riveted to a conductive support so as to ensure good electrical contact between the two. Previously, the end of a snap spring has been restrained by a V-shaped notch, necessary in the conductive support to allow hinge-like movement, but providing poor and unreliable electrical contact between the spring and the support.
Conveniently, the blade spring is formed from a flat sheet of material, wherein the outer legs are, or the inner leg is, formed with a permanent bend or bends so as to shorten their or its extent thus to bend the other resiliently. The permanent bends may be S-shaped for example.
In order to operate the blade spring the rocker may be formed at one end to engage the outer legs and at the other end to engage the central leg, so that rocking from one to the other of said first and second positions causes the spring to snap between a position in which its contact engages the other contact and a position in which the contacts are separated.
One embodiment of the invention will now be described with reference to the accompanying drawings, in which:

Figure 1 is a pictorial view of the main components of a switch embodying the invention;
Figure 2 is a detail plan view of a blade spring of the switch of Figure 1; and
Figures 3 to 6 show elevations of the components of Figure 1, in a series of stages in a cycle of operation.

Referring to the drawings, the switch operates to make or break electrical connection between two conductive L- shaped posts 2 and 4. An arm 6 of the post 2 serves as a fixed contact of the switch. Movable contact 8 is mounted at one end of a blade spring 10 which is mounted at its other end on an arm 12 of the post 4 by any suitable means e.g. riveting, welding, soldering etc. which ensures good electrical contact between the two.
The blade spring 10 has two slots 14 extending longitudinally between two end areas 16 and 18, so forming a central leg 20 and two outer legs 22. The outer legs are shortened by an S-shaped bend permanently formed approximately in the middle of each outer leg 20, so as to force the central leg into a curve as seen in Figure 1. Bending the spring will cause the central leg 20 to snap from one side to the other of the outer legs 22, as will be explained in more detail, so that the spring has two stable positions: one shown in Figures 1, 3 and 4 in which the contacts 6 and 8 are closed, and the other shown in Figures 2 and 5 in which the contacts 6 and 8 are open.
Switching is controlled by a rocker 26 mounted separately from the blade spring by a pair of trunnions 28 (only one of which is shown in the drawings) which are received by bearings (not shown) so that the rocker can pivot about an axis 30 between a first position shown in Figures 1, 3 and 4, and a second position shown in Figures 2 and 5. At one side of the pivotal axis 30, the rocker is provided with two projections 32 for engagement with respective ones of the outer legs 20 of the blade spring. On the other side of the pivotal axis 30, the rocker is formed with a projection 34 for engagement with the central leg 22.
Starting from the position shown in Figure 2 in which the contacts 6 and 8 are open, rocking the rocker clock wise, as seen in that Figure, causes the projection 34 to bear on the central leg 22 of the blade spring. The central leg snaps to the other side of the outer legs into the position shown in Figure 3, so closing the contacts 6 and 8. The rocker rests in its first position as shown in Figure 3.
If the rocker is now pivoted back in an anticlockwise direction to its second position shown in Figures 5 and 2, the projections 32 bear on the outer legs 22 causing these to snap to the other side of the central leg so that the blade spring resumes its initial position, shown in Figure 5, in which the contacts 6 and 8 are open.
The rocker is pivoted back and forth by a pair of tappets 36 and 38.
Referring to Figure 2, with the contacts 6 and 8 open, the blade spring has its central leg 22 higher than the two outer legs 20. This places the rocker stably in the position illustrated, inclined so that its left end (as seen in Figure 2) is lower than the right end. A resiliently flexible member in the form of a blade or web 40 is mounted fixedly on the rocker and extends radially from its pivotal axis 30. The blade may be made separately from the rocker or, in a preferred example, is moulded integrally with the rocker from plastics material.
The tappets 36 and 38 form part of a tappet assembly 39 mounted for movement together on a pair of trunnions 42 and 44. Also mounted for movement with the tappets 36 and 38 is a follower member 46 in the general form of a box open at the top and bottom as seen in the drawings. Sides 48 and 50 of the box are wasted so as to provide internal follower surfaces 52 and 54 for engagement with the blade 40 between the pivotal axis 55 of the tappet assembly and the rocker. At rest as illustrated in Figure 2, the blade acts to position the tappet assembly so that the tappet 38 projects between two guide walls 56 and 58 of the rocker 26 and so that the tappet 36 is clear of the rocker.
The trunnions 42 and 44 of the tappet assembly are mounted slidably in channels (not shown) so that the tappet assembly can both pivot about the axis 55 and move rectilinearly towards and away from the rocker 26. At rest the tappet assembly is urged by springs (not shown) away from the rocker to a home position illustrated in Figure 2. Movement of the tappet assembly towards the rocker is controlled by an operating member (not shown) which may be a push button or a pull-cord arrangement, for example. Pressing, say, the push button thus urges the tappet assembly against the bias towards the rocker until the tip 80 of the tappet 38 engages an inclined surface 82 of the rocker between the walls 56 and 58. As the push button is depressed further, the tip of the tappet slides downwardly and outwardly along the surface 82 until it reaches an abutment surface 84 which prevents further outward movement because the tappet 36 is clear, the rocker is free to respond to further depression of the push button which causes the tappet to rock the rocker to the first position illustrated in Figure 3 against a bias provided by engagement of the blade 40 with the surface 52. As explained above, movement of the rocker to the position shown in Figure 3 closes the contacts 6 and 8. Ideally the tappet assembly is positioned by the blade 40 precisely to engage the rocker at the end of the surface 82 and in engagement with the abutment surface 84, so that no sliding movement of the tappet is necessary along the surface 82.
Releasing the push button allows it to retract by the trunnions sliding in the channels under the action of the bias, and also allows the bias provided by blade 40 to pivot the tappet assembly anticlockwise (as shown) about its axis 55 to the position shown in Figure 4. In this position, the tappet 38 is aligned between the walls 56 and 58 of the rocker and the tappet 36 is positioned clear of the rocker.
On its other side, the rocker is formed with a surface 90 and abutment surface 92 similar to the surfaces 82 and 84. As will be apparent, subsequent operation of the push button will engage the tappet 38 with the abutment surface 92. Further depression of the tappet assembly will tilt the rocker to the position shown in Figure 5 against a bias provided by engagement of the blade 40 with the surface 54. As explained above, this movement of the rocker opens the contacts 6 and 8.
Release of the push button allows the tappet assembly to retract from the rocker by the trunnions sliding in their channels under action of the bias. The bias provided by the blade 40 also rotates the tappet assembly from the position shown in Figure 5 to that shown in Figure 2 ready to repeat the cycle when the push button is next pressed.

Claims

An electrical switch, having at least two contacts, a rocker mounted for pivotal movement between first and second stable positions, said contacts being closed in the first position of the rocker and open in the second position, an operating member, and means for translating successive movements of the operating member in one direction, into rocking movement of the rocker, said means comprising: first and second tappets for engagement with first and second spaced ends of the rocker, said tappets being mounted for movement by the operating member and for pivotal movement in relation to the operating member for movement between inward and outward positions; and a tappet presetting member projecting from the rocker and movable therewith, operative on the tappets, between the rocker and their pivot, to preset the tappets so that with the rocker in the first position the first tappet is preset in its inward position to engage the rocker, when moved by the operating member, so as to move the rocker to its second position, said second tappet being in its outward position freeing the rocker for such movement, and so that with the rocker in the second position the second tappet is preset in its inward position to engage the rocker, when moved by the operating member, so as to move the rocker to its first position, said first tappet being in its outward position freeing the rocker for such movement.
A switch as claimed in claim 1, wherein the tappet presetting member is resilient.
A switch as claimed in claim 2, wherein the tappet presetting member is a flexible blade.
A switch as claimed in any preceding claim, wherein one contact is mounted on a snap action blade spring.
A switch as claimed in claim 4, wherein the blade spring has two slots therein defining one central and two outer legs extending between two end portions, the blade being so formed that the outer legs have a different extent from the central leg.
A switch as claimed in claim 5, wherein the blade spring is formed from a flat sheet of material, wherein the outer legs are, or the inner leg is, formed with a permanent bend or bends so as to shorten their or its extent thus to bend the other resiliently.
A switch as claimed in claim 5 or 6, wherein the rocker is formed at one side of its pivot to engage the outer legs and at the other side of the pivot to engage the central leg, so that rocking from one to the other of said first and second positions causes the spring to snap between a position in which its contact engages the other contact and a position in which the contacts are separated.
An electrical switch wherein one contact is mounted on a snap action blade spring having two slots therein defining one central and two outer legs extending between two end portions, the blade being so formed that the outer legs have a different extent from the central leg.
A switch as claimed in claim 8, wherein the blade spring is formed from a flat sheet of material, wherein the outer legs are, or the inner leg is, formed with a permanent bend or bends so as to shorten their or its extent thus to bend the other resiliently.
A switch as claimed in claim 8 or 9, including an operating member in the form of a rocker which is formed at one side of a pivot to engage the outer legs and at the other side of the pivot to engage the central leg, so that rocking from one to the other of said first and second positions causes the spring to snap between a position in which its contact engages another contact and a position in which the contacts are separated.
A switch as claimed in any of claims 8 to 10, wherein one end of the blade spring is fixed to a conductive support member.