GB2269480A

GB2269480A - Thermal switch

Info

Publication number: GB2269480A
Application number: GB9313625A
Authority: GB
Inventors: Hans-Peter Morbitzer
Original assignee: Electrovac AG
Current assignee: Electrovac AG
Priority date: 1992-07-16
Filing date: 1993-07-01
Publication date: 1994-02-09
Also published as: ITMI931497A0; ITMI931497A1; IT1264906B1; DE4321960A1; GB9313625D0; FR2693838A1

Description

2269480 Thermal switch -- The invention relates to a thermal switch having

a temperature sensor. which is formed by a thermostatic bimetal element with snap action and is in connection via a transfer element with a contact system.

Thermal switches of this type are known per se. In the event of deformation of the temperature sensor due to increasing temperature. the transfer element is moved in the direction of the contact element and thereby deforms the latter in such a way that an interruption of the circuit occurs by opening of the contacts. If the temperature drops,, a cooling of the temperature sensor occurs. the transfer element moves then in the direction of the temperature sensor,, the contacts close and the circuit is closed again.

For many applications it is desirable that the circuit is interrupted at a certain temperature and that no closing of the contacts takes place even during the subsequent cooling.

The a im of the invention Is to provide a thermal switch, operating as a circuit-breaker, which ensures a permanent separation of the contacts after opening in the case of increasing temperature and remains in the open position even during subsequent cooling.

The invention achieves the aim by providing a clamping latch interacting with the transfer element.

The invention is further characterised in that the clamping latch has a base area and,, adjoining the latter, one or more tongue-shaped elements. the tongue-

Claims

shaped element or elements acting on the transfer element. Further

features and advantages according to the invention are characterised in Claims 3 to 14. 35 The invention is now described in more detail with reference to an exemplary embodiment, with the assistance of the attached drawings.

Fig. 1 shows a section through a thermal switch according to the invention; Fig. 2 shows a view f rom below of the thermal switch according to the invention as shown in Fig. 1; Fig. 3 shows diagrammatic representations of various clamping elements in cross-section; and Fig. 4 shows various embodiments of clamping elements in a view from above.

The thermal switch 1 represented in Fig. 1 essentially comprises a housing 2, preferably of ceramic, a plate-shaped thermostatic bimetal disc 3, arranged in the bottom region of the housing, and power supply leads 4, which are arranged on the housing on both sides and are in connection with the contact 6a and a contact carrier 5, carrying the contact 6b. The thermostatic bimetal disc 3 bears a transfer element 7,, which is arranged essentially centrally with respect to the deformable contact carrier 5 and is guided displaceably. Arranged inside the housing 2 or on the housing is a clamping element 8,, which is in contact with the transfer element 7 in such a way that, upon deformation (represented by dashed lines in Fig. 1) of the thermostatic bimetal disc 3 due to heating, it readily allows a movement of the transfer element in the direction of the contact carrier 5, but on the other hand reliably pre- vents sliding back of the transfer element after cooling of the thermostatic bimetal disc. As a result, the contacts 6a, 6b remain permanently interrupted. The clamping element itself comprises a base area 9, via which the fastening in the switch is performed, and a tongue-shaped element 104. which adjoins the latter and acts on the transfer element 7, consequently allowing or preventing movement of the latter.

Fig. 2 shows a view from below of the thermal switch according to the invention, the clamping element 8 being represented with a tongue-shaped element 10 divided into two-, and the tongue-shaped element having two lugs 10a. 10b. which are spatially separate from each other and are in contact with the outer regions of the transfer element 7. The base area 9 may be connected by 3 welding, clamping, riveting or screwing to the power supply lead 4, or else to the housing 2. Figs. 4a-g show various.embodiments of the clamping element,. base area 9 being designed in the form of a ring embracing the transfer element 7,, and there being arranged on both sides of the transfer element a tongue-shaped element, apart f rom in Fig. 4c, which has at least one tongueshaped element only on one side of the transfer element. The clamping elements represented in Figs. 4a to 4g may have, in particular in the transitional region from the tongue-shaped element to the, for example, annular base area, flexible locations 11. or cross-sectional weakenings 12, such as for example round, oval, or angular holes, which serve the purpose of permitting facilitated yielding of the element in the case of movement of the transfer element under increasing temperature in the opening direction of the contacts. A tapering of the tongue-shaped element in the transitional region, re presented in Fig. 4d, fulfils the same purpose.

Fig. 4g shows a tongue-shaped element, likewise having lugs, but the lugs in this case running together at their outer ends and acting on the transfer element only by a tip in each case. Such a design is favourable if a particularly shock-resistant latching effect is to be achieved.

The transfer element itself may be made smooth on its surface areas which are in contact with the tongueshaped element, the clamping effect in this case being regulated by the angle of the two surface areas with respect to each other. or else it has a surface favouring the clamping effect. For example. such a surface may be roughened by sand blasting or else be coated with small particles of hard material (Fig. 3d). Furthermore. the transfer element may have at least one detent or else, if applicable, a fine toothing, into which the clamping element engages and thereby allows only a movement in one direction.(Fig. 3b).

The lug-shaped element may also be a lever rounded off in its contact region (Fig. 3c) or a spring 4 (Fig. 3e). This spring may then be laid into a groove of the housing, for example as represented in Fig. 3f.

The clamping element represented in Figures 4 is designed as a clamping disc. The material used does not have to be a spring material,, instead the residual elasticity of any desired flexible material should suffice. In the case of these designs. the tongue-shaped elements may be pre-bent, but do not have to be. The clamping element is also roughened on its surface, for example by sand blasting, or else also provided with small particles. SiC, ' S'0211 A1203 etc. are envisaged as the coating material for the clamping element and similarly for the transfer element. The surfaces may, , however, also be roughened by pickling or etching.

It will of course be understood that the present invention has been described above purely by way of example, and that modifications of detail can be made within the scope of this invention.

A PATENT CLAIMS 1. Thermal switch having a temperature sensor,, which is formed by a thermostatic bimetal element with snap action and is in connection via a transfer element with 5 a contact system, characterised in that a clamping latch (8) interacting with the transfer element (7) is provided.
2. Thermal switch according to Claim 1, characterised in that the clamping latch (8) has a base area (9) and, adjoining the latter. one or more tongue-shaped elements (10a,, 10b), the tongue-shaped element or elements acting on the transfer element (7).
3. Thermal switch according to one of the preceding claims, characterised in that the clamping latch (8) is arranged with its base area (9) on the housing (2) of the thermal switch (1).
4. Thermal switch according to one of the preceding claims, characterised in that the clamping latch (8) is arranged with its base area (9) on the base plate or on a contact part.
5. Thermal switch according to one of Claims 1 to 4 characterised in that the clamping latch (8) has, prefer ably at the transition from the tongue-shaped element (10) to the base area (9), flexible locations (11) or cross-sectional weakenings (12).
6. Thermal switch according to one of Claims 2 to 5. characterised in that the base area (9) and the tongueshaped element (10) are connected together via a joint.
7. Thermal switch according to one of Claims 2 to 6,, 30 characterised in that the tongue-shaped element points in the direction of the contact system.
8. Thermal switch according to one of Claims 1 to 7, characterised in that the clamping latch (8) is formed by a spring element, such as for example a leaf spring.
9. Thermal switch according to Claim 8,, characterised in that the spring is arranged with its one end in an opening of the housing and the other end interacts with the transfer element (7).

6
10. Thermal switch according to one of Claims 1 to 9 characterised in that the transfer element (7) has a roughened, preferably sand-blastedt surface.
11. Thermal switch according to one of Claims 1 to 9, characterised in that the transfer element (7) has at least one detent.
12. Thermal switch according to one of Claims 1 to 9 characterised in that the transfer element has a fine toothing in the region of engagement with the clamping latch.
13. Thermal element according to one of Claims 1 to 12, characterised in that the tongue-shaped element of the clamping latch acts on one side of the transfer element.
14. Thermal element according to one of Claims 1 to 12, characterised in that the base area of the clamping latch embraces the transfer element and. on each side of the transfer element. a tongue-shaped element interacts with the latter.
15. A thermal switch substantially as hereinbefore described with reference to and as shown in the accompanying drawings.