GB2078012A - Electrical changeover switch - Google Patents

Abstract

Each fixed contact carrying member (16) of an electrical changeover switch is of generally L-shape, one contact carrying arm (16a) of the member being slidably located in a groove (14) in a switch body (12) and the other arm (16d) having a through hole (16e), removal of the fixed contact carrying member (16) from the body (12) in a direction opposite that of insertion in the groove (14) being prevented by a terminal screw (18) passing through the hole (16e) and screwthreadly secured to a nut (20) located in a recess (22) in the body (12) and removal of the fixed contact carrying member (16) from the body (12) in a direction opposite that of screw insertion being prevented by a portion (16c) of arm (16a) engaging in a notch (24) in the switch body (12). <IMAGE>

Description

SPECIFICATION Electrical changeover switch The present invention relates to change over switches of the type having two pairs of fixed contacts and a contact carrying member movable from a first position in which electrical connection is made between one pair of fixed contacts to a second position in which electrical connection is made between the other pair of fixed contacts.

In one method of assembly of change over switch, four terminal posts are first held in fixed mutual relationship in a jig and a switch body is then moulded about the posts. Each post is internally threaded to receive a terminal screw and has a protruding peg. Next four fixed contact carrying members each having a peg receiving aperture, are placed over respective pegs and the ends of the pegs deformed or rivetted to securely retain the contact carrying members to the terminal posts. Finally the movable contact carrying member and actuating mechanism are assembled and retained in the switch body.

It is an aim of the invention to provide an improved method of construction of change over switch which avoids the previously mentioned moulding and rivetting operations.

According to one aspect of the present invention, there is provided a change over switch in which each fixed contact carrying member is of generally Lshape, one contact carrying arm of the member being slidably located in a groove in a body of the switch and the other arm having a through hole, removal of the fixed contact carrying member in a direction opposite that of insertion in the groove being prevented by a terminal screw passing through the hole and screwthreadedly secured to a nut located in a recess in the body, removal of the fixed contact carrying member from the body in a direction opposite that of screw insertion being prevented by a portion of said one arm engaging in a notch in said body.

An embodiment of the invention will now be described by way of example only, with reference to the accompanying drawing, which is a perspective exploded view of a change over switch according to the present invention.

Referring to the Figure, the change over switch 10 includes a body 12 of moulded plastics material having two pairs of mutually facing slots 14 each slidably receiving a respective one of four fixed contact carrying members 16. Each member 16 is of a generally L-shape and one arm 16a supports a fixed contact 1 6b. On opposite sides of the fixed contact the arm 1 6a is recessed to provide two projections 1 6c. The other arm 1 6d has a through hole 16e through which a respective one of four terminal clamp screws 18 extends each screw being screwthreadedly secured to a respective one of four hexagonal nuts 20 located in four complementary shaped recesses 22 in the body 12.

When the fixed contact carrying members are assembled in the body, removal of the members 16 is a direction opposite that of insertion in their respective grooves is prevented by the terminal screws and nuts, and removal of the members in a direction opposite that of screw insertion into the nuts is prevented by one of the projections 1 6e of each member engaging in a notch 24 provided by the switch body.

Located between the pairs of fixed contacts is a movable contact carrying assembly 26 which includes an electrically conductive arm 28 carrying two contacts 30 each positioned in use between a respective pair of fixed contacts, an integral plunger and support unit 32, a pair of shaped springs 34 acting between the unit and the arm 28 to provide a snap action during the change over operation, and a helical return spring 36.

The body 12 and assembly 26 are enclosed in a transparent shroud 38 which slides over the body and is retained thereon by means of projections (not shown) on a side of the body remote from the terminal screws being press fitted into openings (not shown) in an inner face of the shroud.

The transparent shroud 38 when assembled contains the snap action mechanism 26 and also prevents the removal of the stationary members 16 in the event of the terminal screws being removed.

The shroud also includes guides 38a which cooperate with protectors 32a on unit 32 to guide the mechanism 26 for rectilinear movement.

1. An electrical change over switch having fixed and movable contacts, in which each fixed contact carrying member is of generally L-shape, one contact carrying arm of the member being slidably located in a groove in a body of the switch and the other arm having a through hole, removal of the fixed contact carrying member in a direction opposite that of insertion in the groove being prevented by a terminal screw passing through the hole and screwthreadedly secured to a nut located in a recess in the body, removal of the fixed contact carrying member from the body in a direction opposite that of screw insertion being prevented by a portion of said one arm engaging in a notch in said body.

2. The switch of Claim 1, including a shroud member slidably fitted to the switch body to enclose a movable contact carrying assembly, the shroud preventing removal of the fixed contact carrying members in the event that the terminal screws are absent.

3. The switch of Claim 2, wherein the shroud includes guides for guiding the movable contact carrying assembly.

4. An electrical change over switch substantially as herein described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Electrical changeover switch The present invention relates to change over switches of the type having two pairs of fixed contacts and a contact carrying member movable from a first position in which electrical connection is made between one pair of fixed contacts to a second position in which electrical connection is made between the other pair of fixed contacts. In one method of assembly of change over switch, four terminal posts are first held in fixed mutual relationship in a jig and a switch body is then moulded about the posts. Each post is internally threaded to receive a terminal screw and has a protruding peg. Next four fixed contact carrying members each having a peg receiving aperture, are placed over respective pegs and the ends of the pegs deformed or rivetted to securely retain the contact carrying members to the terminal posts. Finally the movable contact carrying member and actuating mechanism are assembled and retained in the switch body. It is an aim of the invention to provide an improved method of construction of change over switch which avoids the previously mentioned moulding and rivetting operations. According to one aspect of the present invention, there is provided a change over switch in which each fixed contact carrying member is of generally Lshape, one contact carrying arm of the member being slidably located in a groove in a body of the switch and the other arm having a through hole, removal of the fixed contact carrying member in a direction opposite that of insertion in the groove being prevented by a terminal screw passing through the hole and screwthreadedly secured to a nut located in a recess in the body, removal of the fixed contact carrying member from the body in a direction opposite that of screw insertion being prevented by a portion of said one arm engaging in a notch in said body. An embodiment of the invention will now be described by way of example only, with reference to the accompanying drawing, which is a perspective exploded view of a change over switch according to the present invention. Referring to the Figure, the change over switch 10 includes a body 12 of moulded plastics material having two pairs of mutually facing slots 14 each slidably receiving a respective one of four fixed contact carrying members 16. Each member 16 is of a generally L-shape and one arm 16a supports a fixed contact 1 6b. On opposite sides of the fixed contact the arm 1 6a is recessed to provide two projections 1 6c. The other arm 1 6d has a through hole 16e through which a respective one of four terminal clamp screws 18 extends each screw being screwthreadedly secured to a respective one of four hexagonal nuts 20 located in four complementary shaped recesses 22 in the body 12. When the fixed contact carrying members are assembled in the body, removal of the members 16 is a direction opposite that of insertion in their respective grooves is prevented by the terminal screws and nuts, and removal of the members in a direction opposite that of screw insertion into the nuts is prevented by one of the projections 1 6e of each member engaging in a notch 24 provided by the switch body. Located between the pairs of fixed contacts is a movable contact carrying assembly 26 which includes an electrically conductive arm 28 carrying two contacts 30 each positioned in use between a respective pair of fixed contacts, an integral plunger and support unit 32, a pair of shaped springs 34 acting between the unit and the arm 28 to provide a snap action during the change over operation, and a helical return spring 36. The body 12 and assembly 26 are enclosed in a transparent shroud 38 which slides over the body and is retained thereon by means of projections (not shown) on a side of the body remote from the terminal screws being press fitted into openings (not shown) in an inner face of the shroud. The transparent shroud 38 when assembled contains the snap action mechanism 26 and also prevents the removal of the stationary members 16 in the event of the terminal screws being removed. The shroud also includes guides 38a which cooperate with protectors 32a on unit 32 to guide the mechanism 26 for rectilinear movement. CLAIMS

1. An electrical change over switch having fixed and movable contacts, in which each fixed contact carrying member is of generally L-shape, one contact carrying arm of the member being slidably located in a groove in a body of the switch and the other arm having a through hole, removal of the fixed contact carrying member in a direction opposite that of insertion in the groove being prevented by a terminal screw passing through the hole and screwthreadedly secured to a nut located in a recess in the body, removal of the fixed contact carrying member from the body in a direction opposite that of screw insertion being prevented by a portion of said one arm engaging in a notch in said body.

2. The switch of Claim 1, including a shroud member slidably fitted to the switch body to enclose a movable contact carrying assembly, the shroud preventing removal of the fixed contact carrying members in the event that the terminal screws are absent.

3. The switch of Claim 2, wherein the shroud includes guides for guiding the movable contact carrying assembly.

4. An electrical change over switch substantially as herein described with reference to the accompanying drawings.