AU781435B2 - Improvements in and relating to a domestic electrical switch - Google Patents

Description

Regulation 3.2

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

Name of Applicant: Cdrard Indutrie Pty Ltd Actual Inventor: William Muir Halliday V Address for Service: MADDERNS, 1st Floor, 64 Hindmarsh Square, Adelaide, South Australia, Australia Invention title: IMPROVEMENTS IN AND RELATING TO A DOMESTIC ELECTRICAL SWITCH Details of Associated Provisional Application No: PR 0007 dated 11 th September 2000 The following statement is a full description of this invention, including the best method of performing it known to us.

I PatAU131) TECHNICAL FIELD This invention relates to electrical switches, and particularly to switches known in the trade as the "dolly" type for use in alternating current circuits.

BACKGROUND TO THE INVENTION Dolly actuated switches for use in household electrical circuits are well known in the art. Such switches have a quick break action and provide a convenient means for manually controlling individual electrical circuits.

Conventional dolly type switches incorporate a pivotally mounted dolly which has a yoke or stem which acts directly on a profiled bridge member which in turn acts upon the electrical contacts. It is well known that arcing between the bridge and the contacts can have a destructive effect on the internal components of the switch, and may, for example, result in contamination or discolouration of the switch dolly which is aesthetically displeasing.

It is desirable therefore that electrical dolly type switches be designed in a manner so that the operating dolly of the switch is shielded from the potentially damaging effect of any arcing which occurs at the switch contact surfaces, and thereby reduce the likelihood of the operating dolly being discoloured over a period of time.

It is an object of the present invention therefore to provide an improved electrical 25 switch of the dolly type which is designed to minimise the destructive effects of contact arcing on componentry of the switch, in particular the operating dolly.

S It is another object of the present invention to provide an improved electrical domestic switch which incorporates a novel arc shield which can be quickly and readily assembled in the switch between the operating dolly and the bridge member without interfering with the working action of the switch.

SUMMARY OF THE INVENTION Broadly according to this invention therefore, an improved electrical switch includes: a base having an open upper end; an operating dolly pivotally mounted in the base and projecting through said open upper end; mutually spaced apart electrical contacts, each of which is connected to a respective conductor; a pivotal bridge selectively engageable with said electrical contacts and movable between contact engaging and contact disengaging positions, and a bridge actuator operably connected to said operating dolly for effecting movement of said bridge between said positions, characterised by: an apertured arc shield insert disposed between said bridge and said operating dolly said bridge actuator passing through a central aperture formed in the arc shield insert, said arc shield insert being arranged to shield at least a portion of the operating dolly from the destructive effects of contact arcing.

Preferably, the apertured arc shield insert is located in a recess formed within said base.

Preferably, the apertured arc shield insert is removably located in said recess.

eooee: Preferably the apertured arc shield insert has an outer perimeter shape which is complementary to the shape of the recess in which it locates within the base.

eoe* In a preferred embodiment of the invention, the insert is adapted to engage with a snap fit in said base.

Preferably the central aperture formed in the arc shield insert is bordered along each of its opposite ends by upwardly converging walls integrally moulded therewith.

Preferably the arc shield insert is moulded of resilient plastics material.

Preferably the arc shield insert is shaped and configured so that it can be inserted within the base in either of two different orientations. This substantially facilitates the assembly of the switch. It is an advantage of the present invention that the arc shield component of the switch can be readily assembled within the base through its open upper end, as well as readily disassembled therefrom.

BRIEF DESCRIPTION OF THE DRAWINGS In order to more fully explain the present invention, a preferred embodiment thereof will now be described in some further detail with reference to and as illustrated in the accompanying drawings wherein: Fig 1 is an "exploded" perspective view of a two-way, four terminal electrical switch made in accordance with a preferred embodiment of the invention; while Fig 2 is a sectional view taken through the switch assembly shown in Fig 1.

o• DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to Figs 1 and 2 of the drawings, there is shown a two-way, four terminal domestic electrical switch 10 which includes a moulded plastic base or housing 11 which supports three fixed terminals 12, each having an electrical contact surface 13.

•25 A pivotal moulded plastic operating dolly 15 is pivotally mounted in the base 11 and has a portion thereof projecting through its open upper end. The dolly 15 has associated therewith a spring-loaded yoke 17 which projects downwardly away from S the dolly 15 and acts upon a pivotal bridge 18 which is arranged to selectively engage the contact surfaces 13.

In accordance with this invention, there is provided an arc shield insert 20 removably located in a recess 21 formed in the bore of the base 11 and disposed between the bridge 18 and the operating dolly 15. In this embodiment the arc shield insert is a moulded plastics plate which has an inner periphery which defines a central aperture 23 and an outer peripheral edge which is shaped complementary to the recessed portion 21 within the base 11. As can be seen from Fig 2, the plate 20 overlies portions of the bridge 18 and the contact surfaces 13 and separates the actuating dolly from the contact surfaces.

The insert 20 is formed with upwardly converging cupped wall portions 25 at opposite ends of the central aperture 23 and which are shaped so that they do not interfere with the movement of the bridge 18 when it is actuated by the dolly between its open and closed positions. The wall portions 25 are also designed to enhance protection for the operating dolly componentry from any possible arcing damage.

In this embodiment the yoke 17 has its upper end releasably attached to a coil spring 28 which is held in place by means of a central boss 29 formed on the inner surface of the dolly In this embodiment the arc shield insert 20 snap-fittingly locates within the base 11 by means of outwardly projecting resilient flexible tongues 31 which partially locate in apertures 32 formed in the wall 33 of the base 11. With this configuration the insert 20 can be inserted in position in one of two different orientations. This arrangement serves to simplify the assembly of the insert 25 The operation of the switch is self-evident and is moved from an open position to a e0 closed position by applying finger pressure to the outer face of the operating dolly so that it is caused to rotate about its pivot axis which passes through aligned holes e:eee formed in the wall 33 of the base 11, such movement causing the bridge 18 to pivot about its fulcrum to selectively engage with a contact surface 13.

The switch is particularly effective in switching alternating current circuits of domestic voltages.

While the present invention has been described in terms of a preferred embodiment in order to facilitate a better understanding of the invention, it should be appreciated that various modifications can be made without departing from the principles of the invention. Therefore, the invention should be understood to include all such modifications within its scope.

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Claims (9)

1. An electrical switch including: a base having an open upper end; an operating dolly pivotally mounted in the base and projecting through said open upper end; mutually spaced apart electrical contacts, each of which is connected to a respective conductor; a pivotal bridge selectively engageable with said electrical contacts and movable between contact engaging and contact disengaging positions; and a bridge actuator operably connected to said operating dolly for effecting movement of said bridge between said positions, characterised by an apertured arc shield insert disposed between said bridge and said operating dolly, said bridge actuator passing through a central aperture formed in the arc shield insert, said arc shield insert being arranged to shield at least a portion of the operating dolly from the destructive effects of contact arcing.

2. An electrical switch according to claim 1 wherein the apertured arc shield insert is located in a recess formed within said base.

3. An electrical switch according to claim 2 wherein the apertured arch shield insert is removably located in said recess.

4. An electrical switch according to any one of claims 2 or 3, wherein the apertured arc shield insert has an outer perimeter shape which is complementary to the shape of the recess in which it locates within the base.

An electrical switch according to any one of claims 1 to 4 wherein the apertured arc shield insert is adapted to engage with a snap fit in said base.

6. An electrical switch according to any one of claims 1 to 5 wherein the central aperture formed in the arc shield insert is bordered along each of its opposite ends by upwardly converging walls integrally moulded therewith.

7. An electrical switch according to any one of claims 1 to 6 wherein the apertured arc shield is moulded of resilient plastics material.

8. An electrical switch according to any one of claims 1 to 7 wherein the apertured arc shield insert is shaped and configured so that it can be inserted within the base in either of two different orientations.

9. An electrical switch substantially as herein disclosed with reference to the accompanying drawings. DATED this 10 th day of September, 2001. GERARD INDUSTRIES PTY LTD By its Patent Attorneys 20 MADDERNS *e