EP0285927A2 - Thermostat - Google Patents

Abstract

The invention proposes a thermostat having a support supporting at least two connections, a moving contact (supported by an elastic connecting member operated by a bimetallic strip) being electrically connected to one connection and a stationary mating contact being electrically connected to the other connection, and it being possible to connect a low-resistance connection of the contact to the mating contact, under the influence of a small bimetallic plate, in which a block-shaped retaining part (19) rests with a resting surface (21) on at least one side of the support, in that a switching member (24), supporting the contacts or a contact (16), rests on the surface opposite the resting surface, at a distance from the support (2) and in that rivet structures (9, 27), for solid riveting of at least one contact (14, 16) or the switching member (24), are constructed on the retaining part (19). <IMAGE>

Description

The invention relates to a temperature switch with a carrier carrying at least two connections, with one connection being a movable contact carried by a bimetal-controlled elastic connecting element and the other connection being electrically connected to a stationary mating contact and wherein under the action of a bimetal plate a low-resistance connection of the contact with the Counter contact is switchable.

Such so-called open switches are known in a variety of configurations. For example, the elastic connecting element carrying the movable contact can itself consist of bimaterial or, as is even more the case with more recent designs, there is a separate bimetal plate which acts on the connecting element for switching the movable switching contact. Furthermore, the switch can be designed as a so-called non-clocking switch, in which a high-resistance, heat-generating resistor is provided in parallel to the switchable electrical connection from one connection via a contact, the counter contact to the other connection, for example in the form of a thick-film resistor, a PTC element or the like , which is subsequently applied to the carrier or is otherwise provided or attached to an existing switch as an additional part. The known carriers have complicated shapes, on the one hand to carry the circuit diagram in a suitable manner, and on the other hand to provide recesses or other configurations for the additional high-resistance resistor. If the carrier is a ceramic part, it must first be shaped as such by pressing and then sintered. This leads to the fact that these individually shaped and sintered complicated carrier parts are quite imprecise and require large tolerances, so that either reworking or adjustments are required. For example, ceramic carrier parts of this type are reworked with diamond disks, which in turn are expensive. Alternatively, the carrier parts can consist of suitable thermosets. Then they can be manufactured true to size, but they have the disadvantage of insufficient thermal resistance. In addition, these thermosets exhibit poor expansion behavior, which acts on fastenings and rivets in such a way that damage can occur here. Switches with thermoset support parts can therefore only be used at low temperatures. In both of the aforementioned cases, connections and contacts, in particular the connecting part for the movable contact, are riveted directly to the support part with rivets. If the rivet forms the stationary counter-contact to a movable contact, the rivet loosens due to the different temperature expansion behavior of the carrier and the rivet, this in turn can lead to higher contact resistances from the contact surface of the contact rivet to the connecting tab riveted through them, which in turn leads to an additional stronger warming results.

The invention has for its object to provide a switch of the generic type that avoids the aforementioned problems and in particular enables simple construction and manufacture. In this case, a precise fastening of the switching mechanism, in particular with regard to the coordination of the movable contact and counter-contact, is intended to be carried out by the movable ones Contact carrying link and possibly additional active switching element without post-processing and readjustments for high-temperature resistant switches.

According to the invention, the stated object is achieved in a switch of the type mentioned in the introduction in that a block-shaped holding part with a support surface rests on at least one side of the support, that one of the contacts or a contact-carrying switching element rests on the surface opposite the support surface at a distance from the support and that rivet designs for riveting at least one contact or of the switching element are formed on the holding part. It follows from the overall configuration according to the invention that the block-shaped holding part connects the corresponding contact with the connecting element associated with it, it follows that the holding part itself is electrically conductive. It is therefore preferably made of a suitable metal and is designed as a rotating part on which the fastening pins for fastening the connecting part, contact or such a load-bearing connecting part are formed by means of rivets. According to the invention, in addition to the carrier, a separate holding part is provided for the corresponding elements of the switch, but with which rivet attachments and devices for fixing said elements are formed in one piece using rivets. With the holding part according to the invention, the accuracy requirements are therefore removed from the carrier, while the holding part used according to the invention is a dimensionally stable, high-temperature-resistant part.

The object according to the invention designed in this way now advantageously offers the possibility of designing the carrier in a completely cuboid and thus simple outer contour. The carrier can be formed from a carrier plate or a plurality of stacked carrier plates of cuboid shape. In any case, with such a cuboid configuration of the carrier when it is manufactured from aluminum oxide ceramic, the procedure is as follows den: A large-area plate made of aluminum oxide ceramic is pre-pressed, from which the cuboid carrier parts are then punched out and sintered. This process is praiseworthy, it is not necessary to press the individual parts in their complicated shape, as is the case in the prior art, but simple flat plates are produced, which can thereby be manufactured much more dimensionally. Although these cuboid or plate-shaped parts also have a shrinkage, they can be taken into account with sufficient accuracy. In particular, there are no curvatures as in the case of complicated shapes with elevations and depressions that are used in the prior art. Carrier parts made of aluminum oxide ceramic are hard and have good thermal conductivity.

To make the switch self-retaining, a resistance track can be printed on the ceramic carrier, preferably on its side facing away from the switching mechanism. In the case of a carrier composed of two or more carrier plates, the resistance can preferably be arranged between them and thus protected.

PTC elements are oxide-ceramic resistance elements, which are usually designed as cuboid plates. The solution according to the invention therefore creates the possibility of producing the carrier immediately from PTC material or, if there are several layers, of producing one of the layers from PTC material. It is avoided that if the two connections can be bridged by a high-resistance resistor in addition to the actual switching mechanism, separate additional complicated devices with clamping devices or the like must be provided here. It has been found that when PTC material is used as the carrier, a plate thickness of 2 mm is sufficient to form a sufficiently stable carrier. It can also be done in the configuration of the switch according to the invention in such a way that aluminum oxide ceramic with PTC material be is layered and sintered together and suitable metallizations are provided.

In a further preferred embodiment it is provided that the bimetallic plate rests directly on the surface of the holding part and is penetrated by a wider section of a rivet attachment, the height of the wider section of the rivet attachment being penetrated, the height of the wider section of the rivet attachment being at least the thickness of the Corresponds to the bimetallic disc, while the connecting element rests on the wider shoulder of the rivet attachment and surrounds a thinner section thereof. This ensures that the bimetallic sheet can be fixed and riveted directly with a separate elastic connecting link, without it being clamped in its attachment point in a disadvantageous manner, which would adversely affect its switching behavior (for example DE-GM 86 25 990). To avoid this latter disadvantage, it has already been proposed that small tabs are provided on the connecting members carrying the contact, under which the bimetallic plates have been arranged (for example EP-OS 58 372). These designs had the disadvantage that the complicated hooks, which are easily damaged, had to be provided in addition. In a further embodiment it is provided that the connections at least partially encompass the carrier and, if appropriate, the holding part laterally by means of tabs. In this way, a relative definition of the individual parts is achieved by riveting before final fastening and thus this is made easier.

In such switches, a high current flow - and thus low resistance - through the movable contact, which is designed in particular as a switching element in the form of a spring, is sought, which requires large cross sections and a high spring strength, which the high-temperature bimetal position (when opening ) counteracts, but this counterforce may not be sufficient, particularly with extensive miniaturization. In a preferred embodiment it is therefore provided that by means of a weaker counter-spring which counteracts the spring action of the switching element, the additional spring thus supports in particular the bimetal effect. The counter spring contributes in an extremely advantageous manner to the enlargement of the cross-sectional area available for the leakage flux and thus to the reduction of the resistance without increasing the force to be returned by the bimetallic element, it rather reduces it.

In a further development it can be provided that the counter spring is connected at one end to the connecting member and engages with its opposite end on the carrier. This configuration further improves and supports the switching process against the spring force of the connecting element carrying the movable contact, in that the bimetallic element can be supported on the carrier at a location remote from the clamping point of the connecting element, and thus better use of force can be made. This is particularly the case if such a bimetallic element is provided in addition to the bimetallic snap disk clamped with the connecting member. With this configuration, too, the cross section of the connecting and transmission link can be increased with only one bimetallic snap disc compared to the configuration mentioned above.

• Fig. 1 eine Seitenansicht der bevorzugten Auführungs­form des Schalters;
• Fig. 2 eine Aufsicht auf den Schalter der Figur 1;
• Fig. 3 eine Stirnansicht entsprechend der Pfeile III-III;
• Fig. 4 eine Stirnansicht entsprechend der Pfeile III und IV in den Figuren 1 und 2.
• Fig. 5 eine verfrößerte Darstellung des Festlegungsbe­reichs von Übertragungsglied für den beweglichen Kontakt und Bimetallelement;
• Fig. 6 eine andere bevorzugte Ausgestaltung in Seiten­ansicht, in Schließstellung;
• Fig. 7 die Ausgestaltung der Fig.6 in Öffnungsstellung;
• Fig. 8 eine Aufsicht auf die Ausgestaltung der Figuren 6 und 7;
• Fig. 9 eine weitere bevorzugte Ausgestaltung der Er­findung und
• Fig. 10 eine Aufsicht auf die Ausgestaltung der Fig.9 entsprechend der Aufsicht der Fig.8.

Further advantages and features of the invention result from the claims and from the following description, in which an embodiment of the switch according to the invention is explained in detail with reference to the drawing. It shows:

• Figure 1 is a side view of the preferred embodiment of the switch.
• Figure 2 is a plan view of the switch of Figure 1;
• Fig. 3 is an end view corresponding to the arrows III-III;
• 4 shows an end view corresponding to the arrows III and IV in FIGS. 1 and 2.
• Figure 5 is an enlarged view of the area of attachment of the transfer member for the movable contact and bimetallic element.
• 6 shows another preferred embodiment in side view, in the closed position;
• 7 shows the configuration of FIG. 6 in the open position;
• 8 shows a top view of the configuration of FIGS. 6 and 7;
• 9 shows a further preferred embodiment of the invention and
• 10 is a top view of the embodiment of FIG. 9 corresponding to the top view of FIG. 8.

The illustrated embodiment of the switch 1 according to the invention has a flat cuboid carrier 3 made of insulating material or high-resistance material. The carrier 2 preferably consists of hard aluminum oxide ceramic, which has good thermal conductivity. If the switch is to be designed as a non-clocking but self-adhesive switch, the support 2 can be provided with a resistive force, for example it can be printed or even be made of a suitable PTC material.

In the exemplary embodiment shown, the carrier consists of two carrier plates 2a and 2b, one of which (2b) has a lateral fastening projection 2c with fastening openings 3. Instead, the carrier 2 could also be formed in one piece in the form of a one-piece cuboid. In addition, the attachment lug 2c on the carrier 2 can also be omitted if care is taken in a suitable manner for fixing the switch 1, for example by means of suitable fastening breakthroughs on the connections 4, 6 of the switch corresponding to the opening 3 (not shown here).

At both ends 7, 8, the connections 4, 6 are fixed by rivets 9, 11 which protrude through the carrier 2 or are formed integrally therewith. The connection 6 monitors the rivet 11 and carries on its connection end 12 the end 13 facing away from a stationary counter contact 14 for a movable contact 16 of the switch 1. The connection 6 furthermore has lateral straps 17 which at least partially encompass the carrier 2 and through which a certain fixation is effected before the riveting by means of the rivet 11, so that the riveting process is facilitated. The terminal 6 is flat from the mating contact to its terminal end 12, but could also be crimped instead, similar to how the other terminal 4 in the illustrated embodiment is crimped up by means of a crimping. In any case, it is desirable that the two connections 4, 6 lie in one plane. The connection 4 is basically fixed to the support 2 via the rivet pin 9 projecting through the support 2 in the same way as the connection 6. The rivet pin 9 is formed in one piece on a block-shaped holding part 19 which rests on the side 2 of the support which is also the stationary counter contact 14 is arranged. In the present case, this is the upper side of the carrier 2, the side of the carrier 2 opposite the rivet area of the connection 4. The block-shaped holding part 19 lies with its lower contact surface 21 on the carrier 2 and carries on its surface 22 opposite the contact surface 21 Bimetallic plate 23 and over this an elastic, the movable contact 16 supporting link 24 in the form of a flat spring. Bimetal plate 23 and connecting member 24 are riveted to the pot-shaped holding part 19 by a rivet head 26.

In particular, the bimetallic disc 23 is not firmly clamped and inserted between the block 19 and the connecting member 24 stuck, but only adequately fixed, as can be seen from Figure 5. A bimetallic plate 23 and Ver connecting member 24 protruding pin extension 27 of the holding part 19 is formed with sections of larger and smaller diameters. The bimetallic plate 23 has an opening which corresponds to the section with the larger diameter of the pin 27 and surrounds it. This section with a larger diameter just as high or slightly higher than the thickness of the bimetallic plate 23, so that, as said, this is not jammed between the surface 22 of the holding part 19 and the connecting member 24, but can freely perform its switching function without loosening it is or rattles.

The connection 4 also has the carrier 2 and here also the holding part 19 laterally encompassing tabs 28 for better fixing of the parts before final fixing by rivets. The movable contact 16 itself is welded to the connecting member 24, since riveting is problematic here.

The connections 4, 6 also have tapers 31, which serve as predetermined bending points, in order to avoid disadvantageous force transmission to the rivet points of the switch 1 and thus damage the same in the event of voltages or the like. The switch itself works in the usual way. It is shown in its low-temperature position, in which the contact 16 and counter-contact 14 are pressed against one another under the action of the elastic connecting member and are in contact with one another, so that there is a low-resistance electrical connection between the connections 4 and 6. The bimetallic plate 23 is bent in its low temperature position with its free end 29 downward from the connecting member 24 and in particular largely relieved of stress due to the clamping described. If the temperature rises above the changeover temperature of the bimetallic plate 23, it folds upward, so that its convex side is directed downward toward the carrier 2. The bimetallic plate 23 is supported on the surface 22 of the holding part 19 and lifts the ver with its free end 29 Binding member 24 and thus the movable contacts 16 from the stationary counter contact 14, so that the low-resistance connection between the terminals 4 and 6 is interrupted. In the event that the carrier 2 consists of PTC material, or has such (for example in the form of one of the two carrier parts 2a, 2b), there is still a high-resistance electrical connection between the terminals 4, 6, which leads to the fact that at very low current flow, the PTC part heats up and thus generates heat which acts on the bimetallic plate 23 by radiation and conduction via the relatively massive holding part 19, so that it is held in its high temperature position and thus the switch remains open until the power supply is external is interrupted.

In the embodiments of FIGS. 6 to 10, the same features and elements are denoted by the same reference symbols as in the embodiments described above. In this respect, reference is also made to the above explanations, so that they are not repeated.

6 to 8, in addition to the bimetallic snap disk 23, a further bimetallic element 31 is provided, which is clamped at its end 32, like the bimetallic element 23 and the connecting member 24 carrying the movable contact 16, and in any case preferably between the holding part 19 and the rivet head 26 The free end 33 of the bimetal element 31, on the other hand, is bent into a U-shape, so that the free leg 34 of the U-shaped fold 36 extends essentially parallel to the clamped leg 37, but directly above the upper side of the carrier 2. Between the two legs 34, 37 protrudes the free end of the bimetal element 23. The bimetal element 31 could also be provided instead of the bimetal element 23 and not only in addition.

When the temperature rises, the free end 34 of the bimetallic element 31 bends, which bends under due to the U-shaped fold a strong internal tension is present, comes to rest on the upper side of the carrier 2 and then presses itself away from the latter when the temperature rises further, and in this way lifts the connecting part 24 of the movable contact 16 from the stationary counter-contact 14 or supports lifting it off the bimetal element 23.

With this configuration, the transmission element 24 with the cross section necessary for sufficient current transmission (through which the required low resistance is achieved), but the relatively large spring force associated therewith, can nevertheless be lifted safely and reliably with its movable contact 16 from the stationary counter contact 14. The cross section can in particular be designed such that the disk 23 could not lift the contact 16 from the counter contact 14 alone, but this is now made possible by the preferred embodiment explained.

In the embodiment of FIG. 9, in the manufacture of the connecting member 24, lugs 41 are punched out in one piece with the latter, which have a web 42 extending laterally from the connecting member 24 and a web 42 which is connected to the connecting part 24 only via the web 42 and extends parallel to the latter Counter spring section 43 has. The web 42 is bent perpendicular to the plane of the connecting member 24. The counter-spring section is also perpendicular to the web 42 and thus in turn bent parallel to the connecting member 24 below it. Furthermore, with its free end region 44 relative to the connecting region, the distance determined by the width of the web 42 is bent further away from the connecting member 24, the distance of the free end region 44 of the counter spring from the connecting member 24 being greater in the relieving state than the height of the holding part 19 after clamping of the connecting member 24. In the manner already described, this presses under its own spring action with the movable contact 16 carried by it against the stationary counter-contact 14 and at the same time prestresses the counter-spring parts 43, the spring force of which is set so that it is less than the spring force of the connecting member 24th

The bimetallic element 23 is clamped in the same way as in the above embodiments and engages between the space given by the webs 42. When the temperature rises, the bimetallic member 23 jumps over, presses against the connecting member 24 and in the process lifts the contact 16 from the mating contact 14. It is supported in the configuration of FIGS. 9 and 10 by the counter-spring parts 43 which, due to their prestressing, press against the spring action of the connecting member 24. The joint is then interrupted by the jointly acting force of the bimetallic element and counter spring parts 43 that have jumped over. In this embodiment, too, the cross section of the connecting member 24 can be made larger and thus a higher current flow can be achieved than would be the case if only the force of the bimetallic disk 23 were available for lifting off.

Claims (16)

1. Temperature switch with a carrier carrying at least two connections, with one connection a movable contact carried by a bimetal-controlled elastic connecting element and with the other connection a stationary mating contact being electrically connected and a low-resistance connection of the contact with the mating contact being switchable under the action of a bimetal plate characterized in that on at least one side of the support (2) a block-shaped holding part (19) with a support surface (21) rests that on the surface opposite the support surface one of the contacts or a contact (16) carrying switching element (24) rests at a distance from the carrier (2) and that rivet designs (9, 27) for riveting at least one contact (14, 16) or the switching element (24) are formed on the holding part (19). 2. Switch according to claim 1, wherein the movable contact (16) is attached to a separate from the bimetallic plate (23) connecting member (24), characterized in that bimetallic plate (23) directly on the surface (22) of the holding part (19th ) rests and is penetrated by a wider section of a rivet attachment (27), the The height of the wider section of the rivet attachment (27) corresponds at least to the thickness of the bimetallic disc (23), while the connecting member (24) rests on the wider shoulder of the rivet attachment (27) and surrounds a thinner section thereof. 3. Switch according to claim 1 or 2, characterized in that the connections (4, 6) at least partially embrace the support (3) and optionally the holding part (19) laterally by means of tabs (17, 28). 4. Switch according to the preamble of claim 1 and in particular according to one of claims 1 to 3, characterized in that the outer contour of the carrier (2) forms a completely flat cuboid. 5. Switch according to claim 4, characterized in that the carrier has at least one supporting part made of light metal oxide, in particular aluminum oxide ceramic. 6. Switch according to one of the preceding claims, characterized in that the carrier (2) has at least one support part made of PTC material. 257. Switch according to one of the preceding claims, characterized in that the movable contact (16) is welded to the elastic connecting member (24). 8. Switch according to one of the preceding claims, characterized in that the carrier (2) consists of at least two superposed supporting parts (2a, 2b). 9. Switch according to one of the preceding claims, characterized in that the connections (4, 6) weakening, tapering or the like (31) have such points. 10. Switch according to one of the preceding claims, characterized in that at least with a part (2b) of the carrier (2), a connecting part (2c) is integrally formed. 11. Switch according to one of the preceding claims, characterized in that at least one of the spring action of the switching element (24) is provided with an opposing, weaker counter spring (43). 12. Switch according to claim 11, characterized in that the counter spring (43) is connected at one end (at 42) to the connecting member (24) and engages with its opposite end (44) on the carrier (2). 13. Switch according to claim 11 or 12, characterized in that the bimetallic element (23) projects with its free end in a free space between the connecting member (24) and counter spring (43). 14. Switch according to one of the preceding claims, characterized by a between clamping (26) of the movable contact part (16,24) and its contact head (16) on the carrier (2) acting under the effect of its bimetallic property, the movable contact (16) to the mating contact ( 14) lifting bimetallic element (31). 15. Switch according to claim 14, characterized in that the bimetallic element (31) at one end (32) with the connecting part (24) of the movable contact (16) is clamped and with its other free end (34) is bent into a U-shape and there attacks with the fold (36) on the carrier (2). 16. Switch according to one of the preceding claims, characterized in that the rivet formations (9, 27) are integrally formed with the holding part (19).

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