GB2199189A

GB2199189A - Electrical toggle switch

Info

Publication number: GB2199189A
Application number: GB08728687A
Authority: GB
Inventors: David Langman Cook
Original assignee: PDL Holdings Ltd
Current assignee: PDL Holdings Ltd
Priority date: 1986-12-09
Filing date: 1987-12-08
Publication date: 1988-06-29
Also published as: NZ218566A; GB8728687D0; AU8218987A

Abstract

An electrical toggle switch has a movable contact (9) pivotally supported on a fixed line contact (6) with the movable contact shaped to include abutment sections (17, 18) on either side of a base section (10) which is in contact with the fixed contact and at least one contact arm (12) projecting from an abutment section to extend over a second arcing fixed contact (7 or 8). A switch operating toggle (13) has a biased plunger (16) to retain pressure on the movable contact and abutment faces provided by the toggle stem (14) to engage the abutment sections (17, 18) of the movable contact. In use, engagement between an abutment face and an abutment section generates force to cause a slow break action of the arcing contacts and the over centre action of the plunger in relation to the fixed line contact causes a quick close action with the contact pressure sufficient for good electrical connection but not high enough to induce contact bounce during operation. The fixed line contact (6) can be provided by a V-bend integral with a terminal and associated with a single fixed contact (7). Plural contact sets can be operated simultaneously by side-by-side movable contacts (9). A retractive switch can be provided by replacing one arcing fixed contact with a biassed plunger. <IMAGE>

Description

IMPROVEMENTS IN/OR RELATING TO ELECTRICAL SWITCH GEAR 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.

The Present Invention 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 two of the fixed contacts and switch operating means movably supported in the housing and operable to change the position of the movable contact to make or break the electrical connection between the fixed contacts, characterised in that the movable contact 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 being pivotally supported on a fixed line contact engaging the base section and said switching operating means including a movable plunger biased to exert a force on the top face of the base section of the movable contact and abutment faces separate from the plunger to engage the abutment sections on the movable contact so that movement of the operating member changes the position of the plunger and brings the abutment face in contact with the abutment section to cause a slow break action and continued movement of the plunger over centre of the fixed line contact pivotally supporting the movable contact member causing a quick make action with the plunger and the pivot contact establishing forces such that the contact pressure is sufficient for good electrical connection.

Drawing Description One preferred form of the present invention and a modification 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.

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 line 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.

The switch operating means is provided by a toggle 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 toggle 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 toggle and hence the plunger along the base 10 causes the plunger to move over centre of the pivot line connection between 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.

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.

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 rocker so that the rocker can only be activated while pressure is maintained by the user holding the switch closed.

Another switch configuration for specialised use adopting the geometry for the switch above described is an intermediate switch. In this instance, in the body of the switch two pivots contacts are positioned to support two movable contacts acted upon by the plunger and rocker assembly as previously described, although in this instance, the plunger will have a different configuration because it is necessary to operate the two separate movable contacts. The fixed contacts are carried on a Z-shaped carrier and have contacts top and bottom so that when one set of switches is opening another set is closing, thus effectively achieving the change over circuits usually requiring a substantial space for the switch but with the present design able to be confined into a switch body similar to that illustrated.

Claims

CLAIMS:

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 two of the fixed contacts and switch operating means movably supported in the housing and operable to change the position of the movable contact to make or break the electrical connection between the fixed contacts, characterised in that the movable contact 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 being pivotally supported on a fixed line contact engaging the base section and said switching operating means including a movable plunger biased to exert a force on the top face of the base section of the movable contact and abutment faces separate from the plunger to engage the abutment sections on the movable contact so that movement of the operating member changes the position of the plunger and brings the abutment face in contact with the abutment section to cause a slow break action and continued movement of the plunger over centre of the fixed line contact pivotally supporting the movable contact member causing a quick make action with the plunger and the pivot contact establishing forces such that the contact pressure is sufficient for good electrical connection.

2. A switch as claimed in Claim 1 wherein the fixed line contact about which the movable contact pivots and the break contacts form a triangular configuration.

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

4. A switch as claimed in any one of the preceding claims wherein the switch operating means comprises a toggle movably mounted within the switch housing, a central hollow stem incorporated in said toggle 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.

5. 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.

6. A switch as claimed in any of the preceding claims wherein the mass of the moving contact member is kept low consistent with the electrical load to be carried thereby.

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

8. 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 toggle to change the position of the movable contact members.