GB2083709A

GB2083709A - Temperature-sensitive switch for electrically heated appliances

Info

Publication number: GB2083709A
Application number: GB8134268A
Authority: GB
Original assignee: INTER CONTROL Hermann Koehler Electrik GmbH and Co KG
Current assignee: INTER CONTROL Hermann Koehler Electrik GmbH and Co KG
Priority date: 1979-02-06
Filing date: 1979-05-17
Publication date: 1982-03-24
Also published as: DE2904341C2; DE2904341A1; GB2083709B

Abstract

In a temperature-sensitive switch comprising a movable contact (4) mounted on one end of a resilient contact carrier (33) which is secured at its other end to an insulating switch mounting (1), a fixed contact (5) secured to the switch mounting and normally engaged by the movable contact to connect an electrically heated appliance to an electric current source and a snap-over bimetallic plate (38) operable on the contact carrier (33) to shift the movable contact out of engagement with the fixed contact and so break the supply circuit to the appliance when the temperature of the latter reaches a predetermined value, the contact carrier (33) is formed with longitudinal slots (43, 44) which define lateral lugs (41, 42) bent over at their free ends (45, 46) and serving to secure the bimetallic plate (38) against lateral displacement. <IMAGE>

Description

SPECIFICATION Temperature-sensitive switch for electrically heated appliances This invention relates to temperature-sensitive switches for monitoring electrically heated appliances, of the kind comprising a switch mounting of electrically insulating material, a resilient contact carrier secured at one end to said mounting and carrying at its free end a movable contact which cooperates with a fixed contact rigidly secured to said mounting, means for electrically connecting said contacts in an electrical supply circuit to an appliance to be monitored and a snap-over bimetallic plate disposed on one side of said contact carrier and operable thereon to shift said movable contact in a direction away from said fixed contact when the temperature to be monitored reaches a predetermined value.

The object of the present invention is to enable the bimetallic plate to be located on the contact carrier without the necessity to provide a central aperture.

Such an arrangement has the advantage that the effective life of the plate without a central aperture is substantially longer than that of a plate in which an aperture is provided.

According to the invention, this is achieved by providing the contact carrier with a central circular protuberance and two longitudinally extending slots adjacent its side edges.

The slots in the contact carrier are preferably formed so as to define, in the longitudinal direction of the contact carrier, along the outer edges thereof, two resilient lugs each of which is bent outward at its free end.

Furthermore, the two resilient lugs are bent slightly outward in the direction of the central protuberance at a point adjacent the closed ends of the slots.

The bimetallic plate is so disposed on the contact carrier as to be held in one direction by the L-shaped lugs and in the other by the resilient lugs located on the long sides of the contact carrier.

The lateral resilient lugs on the contact carrier prevent lateral displacement of the bimetallic plate in both its switch positions, since the resilient lugs, by reason of their being prebent, resiliently follow movement of the marginal zone of the plate and are thus continuously applied against the marginal zone thereof. When the plate becomes heated, it instantly alters its direction of curvature. In doing so, its centre engages the unpressed protuberance in the centre of the contact carrier while its marginal zone engages the L-shaped lugs on the contact carrier.

Consequently, the contact carrier positively adopts the curvature of the bimetallic plate and the contacts are opened.

By shifting the ends of the slots, it is possible to vary the stiffness of the contact carrier so that, for example, any downward pressure on the bimetallic plate due to excessive spring force in the contact carrier can be avoided by extending the slots in the direction of the fixed end of the contact carrier.

As a result of this measure, the cross-section of the contact carrier is weakened over a relatively considerable part of its length, so that its spring force is reduced.

A further advantage of the invention is the easy connection of the bimetallic plate to the contact carrier. When the plate is pushed transversely onto the contact carrier, only one lateral resilient lug is pressed downwards to enable the edge of the plate to be pushed beneath the L-shaped lugs. The shape of the rest of the contact carrier is unaffected so that the risk of twisting and possibly lasting deformation is avoided.

The invention will now be described in greater detaii hereinafter with reference to the accompanying diagrammatic drawings in which: Figure 1 shows one embodiment of the switch according to the invention, at rest; Figure 2 shows the switch of Figure 1 with its contacts open; Figure 3 shows the contact carrier as a single component, viewed from the side; and Figure 4 shows the contact carrier as an individual component, viewed from above.

In the embodiment shown in Figures 1 to 4, a contact carrier 33 has one end secured by means of a rivet 32 to an insulating mounting 1. At its free end, the resilient contact carrier 33 has a movable contact 4 which cooperates with a fixed contact 5 secured to insulating mounting 1. The contact carrier 33 is thus pretensioned in the direction of the contactS. The latter is constructed as a rivet, by means of which an electrical terminal 6 is secured to the insulating mounting 1. Similarly, a second electrical terminal 7 is also fixed to the mounting 1 by means of the rivet 32.

A bimetallic snap-action disc 38 is disposed above the contact carrier 33 and maintained in position with respect thereto, by L-shaped lugs 39 and 40 which are stamped out of the contact carrier 33 and by resilient lugs 41 and 42 disposed on the longer sides of the contact carrier.

As can be seen in Figures 3 and 4 slots 43 and 44 are formed between the outer edges of the contact carrier 33 and the resilient lugs 41 and 42 which latter are freely movable at their ends 45, 46 which are also bent upwards.

Furthermore, the two resilient lugs 41, 42 are upwardly inclined from points 48, 49 on the contact carrier 33, adjacent the ends 50, 51 of the slots 43,44.

The bent-up ends 45, 46 of the lateral lugs 41, 42 on the contact carrier 33 prevent any lateral slipping of the disc 38 in its two switch positions, since the lugs 41, 42 are pre-bent and resiliently follow the movement of the disc and thus bear continuously against the marginal zone thereof.

When the disc 38 becomes heated, it instantly snaps over. In doing so its centre bears against a protuberance 47 at the centre of the contact carrier 33 while its marginal zone engages the L-shaped lugs 39, 40 on the contact carrier 33. In consequence, the contact carrier 33 is constrained to follow the movement of the disc 38, so that the contacts 4 and 5 are opened.

By shifting the ends 50, 51 of the slots 43,44 it is possible to vary the stiffness of the contact carrier 33. Extending the slots 43,44 for example, dimi nishes the spring force, since the cross-section of the contact carrier 33 is weakened over a greater amount of its length.

Claims

1. A temperature-sensitive switch for monitoring electrically heated appliances, comprising a switch mounting of electrically insulating material, a resilient contact carrier secured at one end of said mounting and carrying at its free end a movable contact which cooperates with a fixed contact rigidly secured to said mounting, means for electrically connecting said contacts in an electrical supply circuit to an appliance to be monitored and a snap-over bimetallic plate disposed on one side of said contact carrier and operable thereon to shift said movable contact in a direction away from said fixed contact when the temperature to be monitored reaches a predetermined value, said contact carrier being formed with longitudinal slots which define lateral lugs which are bent over at their free ends and serve to secure the bimetallic plate against lateral displacement.

2. A switch according to Claim 1,wherein said contact carrier is formed with a central protuberance on its side remote from said switch mounting and said lugs are inclined at a small angle to the plane of the contact carrier on the same side as said protuberance, from a point adjacent the closed ends of said slots.

3. A switch according to Claim 1 or 2, wherein the stiffness of said contact carrier is dependent upon the extent of said slots.

4. Atemperature-sensitive switch, substantially as hereinbefore described with reference to and as shown in the accompanying drawing.