GB2240879A

GB2240879A - Electric switch

Info

Publication number: GB2240879A
Application number: GB9102546A
Authority: GB
Inventors: David Alexander Paul Wheeler
Original assignee: EMESS PLC
Current assignee: EMESS PLC
Priority date: 1990-02-08
Filing date: 1991-02-06
Publication date: 1991-08-14
Also published as: GB9002859D0; GB9102546D0

Abstract

An electric switch has a face plate (10) with an aperture (12) in which is located a dolly (34) which is pivotally mounted and operates a contact blade (26) mounted in a switch housing (17) secured to the face plate. Opposite walls of the aperture carry pegs (15) engageable within openings (38) formed in a rim (36) on the dolly and the rim locates in a trough defined by the wall of the aperture (12), an upstanding lip (13) and a web connecting the lip (13) to the wall of the aperture (12). The pegs (15) are engaged within the openings (38) by pressing the dolly into the aperture (12) from the front face of the face plate. <IMAGE>

Description

ELECTRIC SWITCH This invention relates to an electric switch of the kind comprising a face plate, a switch housing secured to the rear face of the face plate and an operating member or dolly located and movable within an aperture formed in the face plate.

The object of the invention is to provide a switch of the kind specified in a simple and convenient form.

According to the invention in an electric switch of the kind specified the aperture in the face plate is partly closed by an upstanding lip extending towards the front face of the face plate and which is connected to the face plate by a web thereby forming a trough with the adjacent wall of the aperture, and the operating member or dolly defines a peripheral rim which locates within said trough.

An example of a switch in accordance with the invention will now be described with reference to the accompanying drawings in which: Figure 1 is an exploded perspective view of the switch, Figure 2 is a view in the direction of the arrows A of Figure 1, And Figure 3 is a view showing the assembled relationship of two parts of the switch.

Referring to the drawing the switch comprises a face plate 10 which is provided with spaced apertures 11 for the reception of screws whereby the switch can be secured to a mounting box. Formed in the face plate is a substantially square aperture 12 which as will be seen more clearly from Figure 2, is partly closed by an upstanding lip 13 which is connected to the remaining portion of the face plate by a web, the lip and the web forming with the adjacent wall of the aperture, a trough 14.

A pair of opposite sides of the aperture are formed with inwardly projecting pegs 15 the upper surfaces of which as shown in Figure 3, are cylindrical and the under surfaces of which define a "V" groove. The web which forms the base wall of the trough is formed with apertures during the moulding of the face plate, the apertures being formed by the parts of the moulding tool which form the pegs 15. Depending from the under surface of the face plate are a pair of latch members 16 only one of which is shown, these being provided to secure a switch housing 17 to the face plate. Each latch member is located at the end of a resilient tongue 16A.

The switch housing 17 is of hollow rectangular form and formed in the base wall are 3 recesses, the outer recesses 18 accommodating contact blocks 19 respectively on the upper ends of which are located silver contacts 20. The contact blocks are provided with laterally extending threaded holes for the reception of cable securing screws 21 which when the blocks are in position are accessible through openings in the side walls of the recesses. Blind axial drillings are provided in the contact blocks to accommodate electrical conductors, the conductors being retained by tightening the screws and the conductors passing through holes formed in the base walls of the recesses.

The central recess mounts a contact block 23 which is similarly provided with a threaded hole for a cable retaining screw 24 but in this case the contact block has a triangular section head defining a pivot edge 25. Also provided is a contact blade 26 having a flat central portion 27 which pivots upon the edge 25, and side portions 28 which are connected to the ends of the central portion by inclined portions 29. The central portion of the blade has lateral extensions 30 which locate between locating posts 31 which are formed integrally with and extend upwardly from the base wall of the housing.

A pair of opposite side walls of the housing 17 define projections 32 for engagement with the respective ones of the latch members 16. The projections 32 are bounded by guide ribs 33 which co-operate with the end faces of the latch members 16 and the resilient tongues 16A which support the members, to locate the housing relative to the face plate.

Located in the aperture is an operating member or dolly 34 having a main body portion 35 and a peripheral rim 36. The rim is spaced from the main portion of the body and locates with clearance within the trough 14 as shown in Figure 2. A pair of opposite sides of the rim 36 is provided with integral projections 37 and each projection and the adjacent portion of the rim is cut away to form an opening defining a part cylindrical bearing surface 38 and a tongue 39 of triangular form the apex of which is directed towards the surface 38. A slot 40 extends along the rim to ensure that the projection 37 can deform. The main body portion of the dolly is provided with a blind bore to accommodate a spring 41 and an actuating plunger 42.

In order to assemble the switch the dolly 34 is pressed into the aperture 12 from the front surface of the face plate and the projections 37 engage the pegs 15 and are deformed inwardly but as the movement of the dolly into the aperture continues, the projections spring outwardly below the pegs to secure the dolly in position whilst at the same time allowing pivotal movement of the dolly relative to the face plate. The tongues 39 locate in the "V" grooves of the pegs as shown in Figure 3.

The switch housing after the various parts have been assembled therein is then positioned under the face plate and moved towards the rear face of the face plate, this movement being guided by the ribs 33. During this movement inclined surfaces on the latch members 16 ride over inclined surfaces on the projections 32 until the latch members engage beneath the projections to secure the housing relative to the face plate thereby completing the assembly of the switch.

The plunger 42 co-operates with the central portion 27 of the contact blade to provide the overcentre action which ensures rapid movement of the contact blade to achieve a switching operation as the dolly is moved between its extreme angular positions. Moreover, the inner edges of the body portion 35 of the dolly and which extend parallel to the pivot axis of the dolly can engage with the inclined portions 29 of the contact blade to effect operation of the switch in the event of breakage of the spring biasing the plunger.

The rim 36 of the dolly is located in the trough and provides an arc shield and also the lip acts as a barrier to prevent a blade or the like being pushed into the switch housing.

The switch as described is a single pole two way switch but it will be understood that a double pole switch or a so-called intermediate switch could be constructed.

The switch mechanism is sufficiently small in relation to the size of the standard face plate that up to four switch mechanisms can be provided. In this case the mechanisms would be disposed towards the corners respectively of the face plate. Three such switch mechanisms can be disposed on the face plate in a triangular configuration and of course two switch mechanisms would be disposed in side by side relationship or in any other convenient relationship.

Claims

1. An electric switch comprising a face plate, a switch housing secured to the rear face of the face plate, an operating member or dolly located and movable within an aperture formed in the face plate, said aperture being partly closed by an upstanding lip extending towards the front face of the face plate and which is connected to the face plate by a web thereby forming a trough with the adjacent wall of the aperture, and the operating member or dolly defining a peripheral rim which locates within said trough.

2. A switch according to Claim 1, including pivot means defined by the face plate and dolly said pivot means being engageable upon insertion of said dolly into the aperture from the front surface of the face plate.

3. A switch according to Claim 2, in which said pivot means comprises a pair of inwardly extending oppositely disposed pegs on said wall of the aperture, and a pair of shaped openings at least in part formed in said rim.

4. A switch according to Claim 3, in which said pegs define "V" grooves facing the web of the trough and cylindrical surf aces on the portion thereof facing away from the web of the trough, the opening defining complementary cylindrical surfaces and tongues for engagement in said "V" groove respectively.

5. A switch according to Claim 3 or 4, in which the openings are partly formed in projection respectively on said rim.

6. A switch according to any one of the preceding claims, in which said switch housing is clipped to the rear surface of the face plate.

7. An electric switch comprising the combination and arrangement of parts substantially as hereinbefore described with reference to the accompanying drawings.