GB2181896A

GB2181896A - Circuit-breaker for protection of a radiant heating means against overheating

Info

Publication number: GB2181896A
Application number: GB08624965A
Authority: GB
Inventors: Rudi Brunner; Georg Pfeiffer
Original assignee: AKO Werke GmbH and Co KG
Current assignee: AKO Werke GmbH and Co KG
Priority date: 1985-10-17
Filing date: 1986-10-17
Publication date: 1987-04-29
Also published as: AT398672B; DE3536981C2; GB2181896B; GB8624965D0; DE3536981A1; ATA177086A

Abstract

A circuit-breaker for providing protection against overheating of a radiant heating-means, particularly of a hob, comprises a rod 12 in a tube 11 as a temperature sensor. The temperature sensor is shorter than the diameter of the area 4 occupied by a heating element 3. In order to hold the free end of the temperature sensor 7 at the required distance from the heating element 3, a supporting member 39 is provided. This is gripped at the free end or is displaceable on the tube 11. <IMAGE>

Description

SPECIFICATION Circuit-breaker for protection of a radiant heating means against overheating This invention relates to a circuit-breaker device for protection of a radiant heating means against overheating, which device comprises a switch and a rod-shaped temperature sensor wherein a rod extends in a tube, a limit stop being constructed between the tube and the rod at the end remote from the switch, the temperature sensor being shorter than the diameter of the area occupied by the heating element and extending over turns of a heating element which is disposed on an insulating support, and the temperature sensor being mounted, at its end adjacent to the switch, on the surrounding edge of the insulating support.

Such a circuit-breaker for providing protection against overheating is described in the DE-GM 81 03 514. In the DE-GM 61 03 514, the rod-shaped temperature sensor projects into an open channel formed on the insulating support for this purpose. This weakens the insulation effect. The end of the temperature sensor remote from the switch is not fixed to the insulating support. Fixing the free end there would be unfavourable because the tube of the temperature sensor should expand under the action of heat.

In the DE-OS 31 43 692, a circuit-breaker for providing protection against overheating is described, the temperature sensor of which extends over the whole length of the insulating support. Its two ends are mounted on the surrounding edge of the insulating support.

The temperature sensor is situated above the heating element. Here the tube consists of quartz ware and the rod expands on an increase in temperature.

In the case of the circuit-breaker for providing protection against overheating according to the DE-OS 31 02 919, both ends are likewise mounted in the edge surrounding the heating element. The length of the temperature sensor is greater than the diameter of the heating element acting on it.

In the known circuit-breakers for protection against overheating, the length of the tube is adapted to the size of the heating element. It is therefore necessary for circuit-breakers for protection against overheating having temperature sensors of different lengths to be kept ready for heating surfaces of different sizes.

This makes manufacture, stocking and adjustment difficult.

It is the object of the invention to construct a circuit-breaker of the type initially mentioned for providing protection against overheating wherein the length of the temperature sensor is independent of the diameter of the heating element or of the insulating support and wherein the end of the temperature sensor which is then free is securely mounted on the insulating support.

According to the invention, the above problem is solved in a circuit-breaker of the type initially mentioned wherein a supporting member is disposed on the temperature sensor and holds the temperature sensor with spacing from the insulating support and the heating element.

This circuit-breaker is suitable for heating elements of different diameters. Circuit-breakers having temperature sensors of different lengths do not, therefore, have to be kept ready for different sizes of heating element. It has been found that a uniform adjustment of the circuit-breakers when used for different sizes of heating element leads, at most, to slight differences in the cut-out temperatures.

A saving in material is achieved as a result of the fact that the tube and the rod can be shorter than in the prior art. It is also advantageous that no special formations have to be provided on the insulating support itself in order to fix the end of the temperature sensor remote from the switch. The supporting member, which is part of the circuit-breaker guarantees the necessary spacing of the temperature sensor from the heating element and insulating support respectively. With the supporting member, the circuit-breaker can simply be mounted on the insulating support.

In a development of the invention, the supporting member surrounds the tube in the form of a sleeve and is displaceable in relation to this.

In other developments of the invention, the supporting member is gripped between the end of the tube and the end of the expansion rod. It is thus fixed to the temperature sensor without any additional construction means.

In a further development of the invention, an extension is formed on the supporting member whereby the latter is anchored in the insulating support. Such anchoring is recommended in the case of a gripped supporting member when the tube does not expand appreciably in comparison with the rod under the action of heat, but not when the tempera ture sensor is designed so that the tube expands under the action of heat and the rod transmits this expansion to the switch.

Such anchoring is also desirable in the case of a supporting member surrounding the tube in the form of a sleeve because, as a result, the supporting member, which is displaceable in relation to the tube, can be located at a desired point of the insulating support. Here, a heat expansion of the tube does not lead to distortion because this tube is mounted for displacement on the supporting member.

The anchoring of the supporting member in the insulating support is not necessary in all cases. It is sufficient if the supporting member stands on the insulating support.

In a further development of the invention, the supporting member bears against a glass ceramic plate covering the insulating support.

As a result, the effect is achieved that the spacing of the end of the temperature sensor remote from the switch is not only not too little but also is not too great.

The supporting member preferably consists of ceramic. Special measures for the electrical insulation of the temperature sensor from the heating element are then superfluous. The supporting member may, however, also consist of metal. Care must then be taken to ensure that the supporting member does not touch the heating element.

The invention is illustrated by way of example in the accompanying drawings, in which: Figures 1a to c are similar views which show the same circuit-breaker for providing protection against overheating associated respectively with three heating elements of different diameters, Figure 2 shows a supporting member on the limit stop of the circuit-breaker of Fig. 1, Figure 3 is a front view of a second example of a supporting member, Figure 4 is a side view of the supporting member of Fig. 3, Figure 5 is a front view of a third example of a supposing member, Figure 6 is a side view of the embodiment of Fig.5, Figure 7 is a front view of a fourth embodiment of a supporting member, Figure 8 is a side view of the supporting member of Fig. 7, Figure 9 is a front view of a fifth embodiment of a supporting member, Figure 10 is a side view of the supporting member of Fig. 9, Figure 11 is a front view of a sixth embodiment of a supporting member, Figure 12 is a side view of the supporting member of Fig. 11, Figure 13 is a front view of a supporting member mounted for displacement, and Figure 14 is a side view of the supporting member of Figure 13.

In the embodiment shown in Figure 1, a circuitbreaker 1 for providing protection against overheating is shown on an insulating support 2. Disposed at the bottom of the insulating support 2 is a coiled heating element 3 which is laid in the form of a spiral in a plurality of turns. The heating element 3 occupies a circular area 4. The heating element 3 is surrounded by an encircling edge 5 of the insulating support 2.

The circuit-breaker 1 for providing protection against overheating comprises a switch 6 and a rodshaped temperature sensor 7. The switch 6 is situated outside the edge 5. It is secured to a dish in which the insulating support 2 is seated. At its end adjacent to the switch 6, the temperature sensor 7 extends through a recess 8 in the edge 5. It extends radially in relation to the area 4 and only reaches as far as a central region 9 of the area 4 in which the turns of the heating element are less dense than in the region surrounding the central region 9.

A glass-ceramic plate 10 extends over the edges 5 of a plurality of insulating supports 2 (see Figs. 3 to 12).

The temperature sensor 7 comprises a quartz tube 11 with very low coefficient of thermal expansion. Extending in the quartz tube 11 is a rod 12 with high coefficient of thermal expansion. The ends of the quartz tube 11 and of the rod 12 remote from the switch 6 are supported against one another.

A limit stop is formed there. Disposed on this is a supporting member 13.

As can be seen from Fig. 1, the same circuitbreaker 1 can be used with insulating supports 2 or heating elements 3 of different diameters. Accordingly, it extends more or less into the central region 9.

In the example shown in Fig. 2, a head 14 is formed on the rod 12, onto which head a disc 15 is welded. Gripped between the end face of the tube 11 and the disc 15 is an internai flange 16 of a sleeve 17. The sleeve 17 consists of ceramic. The head 14 is countersunk in it. After assembly, it stands with its outer circumference 18 on the central region 9. The diameter of the sleeve 17 is such that the end of the temperature sensor 7 remote from the switch 6 is guaranteed the necessary spacing from the insulating support 2 or the heating element 3.

In the embodiment shown in Figs. 3 and 4, a supporting member 13, which is formed from a block 19 which likewise consists of ceramic, is gripped between the disc 15 and the quartz tube 11. The block 19 comprises a recess 20 which is open upwards for the introduction of the block 19 between the disc 15 and the quartz tube. The block 19 projects, with its front edge 21, beyond the head 14 so that the necessary electrical insulation spacing between the head 14 and the heating element 3 is guaranteed. Formed on a bearing portion 22 of the block 19 is a dowel-like extension 23. With this, the block 19 is anchored in the insulating support 2. At the same time, it stands with its bearing surface 24 on the insulating support 2. The recess 20 is so dimensioned that when the rod 12 is bearing against its lower edge 25 and the bearing surface 24 is seated on the insulating support 2, the necessary spacing of the temperature sensor 7 from the insulating support 2 is guaranteed. This can also be ensured by the fact that the disc 15 stands on the bearing portion 22. It is also possible to construct the block 19 so that its top 26 reaches as far as the glass-ceramic plate 10.

In the embodiment shown in Figures 5 and 6, a supporting member 13 which is formed from a metal strap 27 is welded to the head 14 instead of the disc 15. The quartz tube 11 is at the side of the strap 27 remote from the head 14. The strap 27 comprises spikes 28 with recesses 29. The strap 27 is a simple stamped metal part.

The spikes 28 are pressed so far into the insulating support 2 that the necessary spacing of the temperature sensor 7 is guaranteed.

The recesses 29 prevent the strap 27 from creeping out of the insulating support 2.

In the embodiment shown in Figures 7 and 8, the supporting member 13 is formed from a wire loop 30 which is gripped, by a bend 31 in the form of a ring or part of a ring, between the disc 15 and the quartz tube 11.

The bend 31 changes over into legs 32 at the ends of which hooks 33 are formed.

Like the strap 27, the wire loop 30 is pressed with its hooks 33 so far into the insulating support 2 that the necessary spacing of the end of the temperature sensor 7 remote from the switch, from the insulating support 2 or the heating element 3 is guaranteed. The hooks 33 prevent the legs 32 from creeping out of the insulating support 2.

In the embodiment shown in Figs. 9 and 10, the supporting member 13 is formed from a shaped part 34 bent out of sheet metal.

This shaped part comprises a central portion 35, the height of which corresponds to the spacing between the insulating support 2 and the glass-ceramic plate 10 which comprises a bore at the prescribed height of the temperature sensor 7. The rod 12 extends through the bore. The surround of the bore is gripped between the disc 15 and the tube 11.

A bearing-surface portion 36 is bent off the central portion 35 at the bottom and rests on the insulating support 2. Bent round at the end of the bearing-surface portion 36 is a toothed extension 37 which is anchored in the insulating support 2.

Bent round at the top on the central portion 35 is a bearing portion 38 which bears flat against the glass-ceramic plate 10.

In the embodiment shown in figures 11 and 12, the supporting member 13 consists of a ring 39 which may consist of ceramic or metal. The ring 39 is gripped, at its inner circumference, between the disc 15 and the quartz tube 11. The outer circumference of the ring 39 stands, on the one hand, on the insulating support 2. On the other hand, it bears against the glass-ceramic plate 10. This embodiment is particularly suitable when the axis of the temperature sensor 7 is intended to extend centrally between the insulating support 2 and the glass-ceramic plate 10.

In the embodiment shown in Figs. 13 and 14, the supporting member 13 is formed by a bearing sleeve 40. This surrounds the tube 11, particularly in the region of its end remote from the switch. The internal diameter of the bearing sleeve 40 is so dimensioned that the bearing sleeve 40 is displaceable on the tube 11. Formed on the bearing sleeve 40 as an extension is a pin 41 whereby the bearing sleeve 40 can be fixed at any desired point of the insulating support 2. A base 42 of the bearing sleeve 40 forms the bearing surface 24. During the mounting on the insulating support 2, a particularly favourable point, for example one which is free of heating coil, can be selected for the arrangement of the bearing sleeve 40.At the same time, as a result of the displaceable arrangement, the effect is achieved that a heat expansion of the tube 11 does not have a distorting effect on the bearing sleeve 40. The bearing sleeve 40 preferably consists of ceramic.

Numerous other examples, resulting, in particular, from a combination of component features of the embodiments described, lie within the scope of the invention. Thus the strap 27 shown in Figs. 5 and 6 may, for example, be so constructed that it bears against the glassceramic plate 10 in accordance with the embodiments in Figs. 9, 10 or 11, and 12. The ring 39 shown in Figs. 11 and 12 may also have a square outside circumference.

It is also possible, in the embodiment shown in Figs. 5 and 6, to construct bearing surfaces 24 on the strap 27 beside the spikes 28, with which surfaces the strap 27 stands on the insulating support 2.

The recess 20 shown in the embodiment of Figs. 3 and 4 may also be provided in the other embodiments in order to simplify the mounting of the supporting member on the temperature sensor 7.

The fact that the sensitivity of the quartz tube 11 to fracture is reduced by the comparatively short formation of the temperature sensor 7 is also favourable. Since the end of the temperature sensor 7 remote from the switch is not mounted on the edge 5, a subsequent alignment, which would otherwise be necessary in order to avoid distortion of the temperature sensor 7, is superfluous.

Claims

1. A circuit-breaker for protection of a radi ant heating means against overheating, comprising a switch and a rod-shaped temperature sensor wherein a rod extends in a tube, a limit stop being constructed between the tube and the rod at the end remote from the switch, the temperature sensor being shorter than the diameter of the area occupied by the heating element and extending over turns of a heating element which is disposed on an insulating support, the temperature sensor being mounted, at its end adjacent to the switch, on the surrounding edge of the insulating support, and a supporting member being disposed on the temperature sensor to hold the temperature sensor spaced apart from the insulating support and the heating element.

2. A circuit-breaker as claimed in Claim 1, wherein the supporting member surrounds the tube like a sleeve and is displaceable in relation to the tube.

3. A circuit-breaker as claimed in Claim 1, wherein the supporting member is gripped between the end o the tube and the end of the rod.

4. A circuit-breaker as claimed in Claim 1 or 3, wherein the supporting member is gripped between the end of the tube and a shim disposed at the end of the rod.

5. A circuit-breaker as claimed in any one of the preceding Claims, wherein an extension is constructed on the supporting member and is anchored in the insulating support.

6. A circuit-breaker as claimed in Claim 5, wherein a bearing surface is provided beside the extension.

7. A circuit-breaker as claimed in any one of the preceding Claims, wherein the supporting member stands up on the insulating support.

8. A circuit-breaker as claimed in any one of the preceding Claims, wherein the supporting member bears against a plate covering the insulating support.

9. A circuit-breaker as claimed in any one of the preceding Claims, wherein the supporting member lies in the central region of the area occupied by the heating element.

10. A circuit-breaker as claimed in any one of the preceding Claims, wherein the supporting member consists of ceramic and projects beyond the limit stop in the longitudinal direction of the temperature sensor.

11. A circuit-breaker as claimed in any one of the preceding Claims 1 to 9, wherein the supporting member consists of metal and is welded or screwed to the end of the rod as a limit stop.

12. A circuit-breaker as claimed in any one of the preceding Claims, wherein the supporting member is formed from a wire loop which is disposed with a bend on the limit stop and is anchored by hooks in the insulating support.

13. A circuit-breaker as claimed in any one of the preceding Claims, wherein the supporting member is provided with a recess open at one side for insertion between the end of the tube and of the rod.

14. A circuit-breaker as claimed in any one of the preceding Claims, wherein the supporting member is formed by a ring.

15. A circuit breaker device for protecting a radiant heating means against overheating, substantially as described herein with reference to the accompanying drawings.