NZ218566A - Slow break, fast make rocker activated switch - Google Patents

Description

© 21 856 n O NEW ZEALAND PATENTS ACT. 1953 No.: 218566 Date: 9th December 1986 COMPLETE SPECIFICATION "Improvements in/or relating to electrical switch £ear" u XI/We. PPL HOLDINGS LIMITED, a New Zealand company, of 14 Hazeldean Road, Christchurch, New Zealand hereby declare the invention for which X / we pray that a patent may be granted to XJfe/us, and the method by which it is to be performed, to be particularly described in and by the following statement: - 218566 Background to Invention The design of a satisfactory electrical switch requires consideration of a number of criteria which will influence the operation of the switch. Normally a design needs to incorporate a number of compromises. One of the difficulties is to produce a comparatively small switch will have a rating satisfactory for use in all normal domestic and light industrial use.

The switch should have an electrical and mechanical design to eliminate or substantially reduce contact bounce and movement. The contact make and break action should preferably be a slow break and a fast make.

We have developed design criteria which we believe provides a switch in accordance with the present invention having outstanding performance characteristics.

Accordingly the present invention consists in a switch comprising a switch housing, electrical terminals located ' — in said switch housing, fixed contacts electrically connected to the terminals and located within the switch housing in a separate but adjacent-configuration, a movable contact member movable to make or break an electrical connection between at least two of the fixed contacts and switch operating means movably supported in the housing and operable to change the position of the movable contact member to make or break the electrical connection between at least two of the fixed contacts, characterised in that the movable contact member has a base section with abutment sections extending from either end of the base section and at The Present Tnvention least one contact arm projecting out from an abutment section, said movable contact member being pivotally supported on one fixed contact provided as a fixed line contact and operable in association with the other fixed contact provided as an point arcing contact, and in that said switch operating means includes a movable plunger biased to exert a force on the top face of the base section of the movable contact member and abutment faces separate from the plunger to engage the abutment sections on the movable contact member so that movement of the operating means changes the position of the plunger and brings an abutment face into contact with an abutment section of the movable contact member before movement of the plunger to an over centre position to cause a slow break action and with continued movement of the plunger over centre of the fixed line contact pivotally supporting the movable contact member causes a quick make action, the plunger and the pivot contact establishing forces such that the contact pressure is sufficient for good electrical One preferred form of the present invention and a modifdcation thereof will now be described with reference to the accompanying drawings in which: Figure 1 is a cross section through a switch according to the present invention.

Figure 2 is a top plan view diagrammatically including a schematic of the contact configuration of the switch.

Figure 3 is an outside elevation of a switch module according to the present invention and, Figure 4 is a cross section through a modified switch according to the present invention.

Drawing Description connection. 218 5 6 6 The Preferred Embodiment A switch 1 has a switch body moulded from any suitable plastics material. Electrical terminals 3, 4 and 5 are located in the switch housing 2. The centre terminal 4 is electrically connected to a line contact 6. Terminal 3 is electrically connected to a fixed arcing contact 7 and terminal 5 is electrically connected to a fixed arcing contact 8. The arcing contacts 7 and 8 are substantially equidistant on either side of the centre line through the 1ine contact 6.

The line contact 6 provides a pivot support for a movable contact 9. The length and design of the line contact 6 may be varied within a designers choice but would ordinarily be in the order of 3-4mms. The material selected for the pivot line contact 6 should be good electrical conducting material and reasonably hard. A 10% nickel/silver alloy is an acceptable design choice.

Each of the fixed arcing contacts 7 and 8 are preferably dome type contacts and would again ordinarily be formed from the 10% nickel/silver alloy.

The movable contact member 9 has a base section 10, two abutment sections 11 extending upwardly from the base section 10 and two contact carrying arms 12 one extending out from each abutment section. The base 10 desirably has a shallow V or chevron configuration symmetrically about the centre line thereof. The under surface of the arms 12 provide electrical contact with the fixed contact 7 and 8 and should be inlayed with a 10% silver cadmium oxide.

There is no need for any inlay of contact material at the engagement between the movable contact 9 and the line contact 6. This is possible because the arrangement and design of the switch according to the present invention eliminates bounce at the line contact 6. 218566 The switch operating means is provided by a switch rocker 13 having a central hollow stem 14 projecting down to a position adjacent the upper surface of the movable contact 9 so that in use, the lower part of the stem provides an abutment face which will contact the abutment section of the movable contact. Fitted within the hollow interior of the stem is a plunger assembly 15 having a plunger head 16 and a biasing spring 17 to exert an outward force on the plunger. The end 18 of the plunger head 16 is rounded or semi-spherical in shape.

Stops 19 and 20 are provided in the switch housing against which the skirt 21 of the switch rocker 13 will abut to restrict movement of the switch rocker. Desirably the plunger head 16 has a certain freedom of movement within the hollow stem to facilitate the plunger changing position while still maintaining a force upon the top surface of the base of the movable contact member.

The switch as depicted in figure 1, shows an electrical connection between terminals 4 and 5 through the line contact 6 and the arcing contacts 8 and 12.

When an operator applies a force to the switch rocker 13 the plunger head 18 will move along the base 10. That movement will bring the abutment face of the stem into contact with the abutment section 11 of the movable contact closest to the arcing contact 7. Continued movement will force the movable contact to move away breaking the electrical connection between the arcing contacts 8 and 12.

This allows a slow breaking action.

Continued movement of the switch-rocker and hence the plunger along the base 10 causes the plunger to move over centre of the pivot line connection between 1S 00Y bOO RECEIVED the line contact 6 and the under surface of the base 10. This over centre action causes the switch to assume a configuration with the movable contact 12 in electrical contact with the arcing contact 7. This over centre action and the force created by the plunger coupled with the shape of the plunger head ensures that there is a rapid closing action with the force created between the plunger and the pivot contact such that the contact pressure is sufficient for a good electrical connection but not high enough to induce contact bounce during operation. The freedom of movement of the plunger within the support housing facilitates a rapid change of configuration to assist with the action of the switch. Also, the domed end of the plunger allows variation as to the point at which the force is applied during the operation of the switch but still maintaining a point of contact throughout the operation of the switch.

It should be noted that with a switch according to the present invention there is stability in configuration of the contact points with the line contact 6 at the pivot with the movable contact and the point arcing contacts between the arms 12 and the arcing contact 7 and 8 having a generally triangular configuration as schematically illustrated in figure 2 of the drawings.

Under the operation of the switch there is no point where the contact is not under a controlled movement designed to achieve the slow break and fast make as set out above.

The force of the plunger and the arrangement of the components is designed to ensure there is a minimum of contact bounce. The mass of the movable contact member and the location of the pressure applied to the plunger are important contributing factors in achieving these objectives. 21 85 66 In a modification of the above described invention the line contact 6 can be formed from a suitable inverted v. folded in conducting material and arranged to operate against an insert of appropriate contact material such a silver cadmium alloy on the under surface of the movable contact to achieve an acceptable contact configuration.

The switch also can be used in an escutcheon form where the switch body is associated with a socket or other fitting to be switched.

The present invention in a further modified form can be used with a switch module which switches some electrical operation directly. An example of this type of switch is illustrated in figure 4 where the switch is employed in association with an electrical socket outlet. In this instance, the fixed contacts are associated with the electric conductors coming from the socket. The arrangement in figure 4 has a fixed dome contact 7a mounted on one conductor and the other conductor has the line contact 6a formed therein.

As this is only a single switch operation, the movable contact 9a has a configuration without the second contact arm extending from the abutment section 11 otherwise the switch configuration is similar to that previously described. The rocker and plunger assembly similar to that previously described is mounted in an escutcheon that will clip into association in the housing of the socket to be switched. The escutcheon carries the stops and the pivot for the rocker and thus is a completed assembly that can be readily snapped into position once the movable contact member 9a has been fitted in place. Thus the assembly of the unit is quick and easy and takes advantage of the switching features which have been previously described. 218566 In a yet further modification of a switch according to the present invention, the same general configuration of the switch is used but in place of one of the arcing contacts and terminal a biased plunger operates against the switch rocker so that the switch rocker can only be activated while pressure is maintained by the user holding the switch closed. 19 OCT 1380 2.1?^ c

Claims (7)

WHAT WE CLAIM IS:

1. A switch comprising a switch housing, electrical terminals located in said switch housing, fixed contacts electrically connected to the terminals and located within the switch housing in a separate but adjacent configuration, a movable contact member movable to make or break an electrical connection between at least two of the fixed contacts and switch operating means movably supported in the housing and operable to change the position of the movable contact member to make or break the electrical connection between at least two of the fixed contacts, characterised in that the movable contact member has a base section with abutment sections extending from either end of the base section and at least one contact arm projecting out from an abutment section, said movable contact member being pivotally supported on one fixed contact provided as a fixed line contact and operable in association with the other fixed contact provided as an point arcing contact, and in that said switch operating means includes a movable plunger biased to exert a force on the top face of the base section of the movable contact member and abutment faces separate from the plunger to engage the abutment sections on the movable contact member so that movement of the operating means changes the position of the plunger and brings an abutment face into contact with an abutment section of the movable contact member before movement of the plunger to an over centre position to cause a slow break action and with continued movement of the plunger over centre of the fixed line contact pivotally supporting the movable contact member causes a quick make action, the plunger and the pivot contact establishing fore such that the contact pressure is sufficient for good electrical connection. - 10 - 218566

2. A switch as claimed in Claim 1 wherein the base section has a shallow V configuration.

3. A switch as claimed in any one of the preceding claims wherein the switch operating means comprises a switch rocker movably mounted within the switch housing, a central hollow stem incorporated in said switch rocker with the lower part of the outer face of the stem providing the abutment faces, a biasing spring in the hollow stem and a plunger slidably mounted in the hollow stem against the action of the biasing spring.

4. A switch as claimed in any one of the preceding claims wherein the plunger has a rounded end for contact against the top surface of the base of the movable contact member.

5. A switch as claimed in any one of the preceding claims wherein the mass of the movable contact member is kept to a minimum consistent with the electrical load to be carried thereby.

6. A switch as claimed in any one plunger is arranged to allow a rapid the movable contact member to assist still maintaining a force on the top contact member. of the preceding claims wherein the change of configuration relative to with the action of the switch while surface of the base of the movable

7. A switch as claimed in any one of the preceding claims wherein two separate movable contacts are arranged within a single housing in a parallel configuration with two separate plungers operated by a switch rocker to-change the position of the movable contact members. 6 DATED THIS DAY OF 19KO A.J. PAPK ?> SOM C: f!;: ! I u u i.; - PER AGENTS FOR THE APPLICANTS