EP0224950A2 - Thermostatic switch with a bimetallic element - Google Patents

Abstract

The bimetallic switch consists of a flat, electrically insulating support (1), at least two electrical connection parts (3, 4) attached to the support (1), one of which has a fixed contact (10) arranged on the support and one with a contact spring ( 8) has a connection which is attached at one end to the carrier (1) and carries at its other end a movable contact piece (9) which cooperates with the fixed contact (10). The carrier (1) is a thin aluminum oxide ceramic plate.

Description

Technical field: -

The invention relates to a bimetallic switch with the features specified in the preamble of claim 1.

State of the art:

Such a switch is described in DE-29 16 516 A1. It is a thermal switch, which is arranged on a circuit board as a carrier. One or more heating resistors can be provided on the circuit board, with the help of which the thermal switch can operate as a relay or timing relay.

The known switch has the disadvantage that the printed circuit board tends to warp due to thermal stress, which means that the thermal switch cannot function properly, at least its switching temperature can be changed.

Disclosure of the Invention:

The invention has for its object to provide a bimetallic switch of the type mentioned, which can be manufactured in a very flat design, remains dimensionally stable even with different temperatures and is versatile and adaptable.

This object is achieved by a bimetallic switch with the features specified in claim 1. Advantageous developments of the invention are the subject of the dependent claims.

The new bimetallic switch uses a thin aluminum oxide ceramic plate as a carrier, which is also referred to as a wafer in semiconductor technology. The preparation of such aluminum _{'oxidkeramikplatten} with extraordinary breaking strength is prior art. Despite their advantages, which are described below, they have not been used as a carrier for bimetallic circuit breakers.

As a result of their strength, the aluminum oxide ceramic plates used as carriers for the thermal bimetallic switches can be considerably thinner than the carriers made of injection-molded plastic, which have been frequently used for small, open thermal switches, and thinner than printed circuit boards. It follows that the carrier used according to the invention has only a relatively low thermal capacity, which has a favorable effect on the response speed of the switch. There is such an aluminum Oxide ceramic carrier also and especially in the form of a thin plate, highly heat-resistant: it can be used up to considerably higher temperatures than plastic carrier or printed circuit boards and does not warp. Another advantage is its low thermal expansion coefficient compared to plastics. In addition, an aluminum oxide ceramic plate can be produced more dimensionally from the outset than a plastic injection molded part, so that fewer tolerance problems occur when producing a bimetal switch with an aluminum oxide ceramic plate as a carrier.

In addition, an aluminum oxide ceramic plate can not only be provided with conductor tracks and equipped with electrical components like a printed circuit board, but resistors and other active or passive circuit elements up to complete circuits can also be integrated in the carrier plate, as a result of which the switch becomes a compact, inexpensive hybrid component .

A particularly simple but important design for practical use of the switch according to the invention is characterized in that that the aluminum oxide ceramic carrier carries the generic elements of the bimetallic switch on one side, while it is provided with a resistance layer on its opposite side (the underside) and is thus designed as a thick-film resistor. If the resistance layer is arranged in such a way that it electrically bridges the switch, then such a switch can be used as an overtemperature switch, which does not close again automatically after a predetermined temperature has been exceeded, but remains open because, after the switch has been opened, the current only remains over the resistance layer flows, which heats up and generates so much heat and transfers it to the bimetallic element that it remains above its switching temperature. In its design according to the invention, such a switch is considerably more compact and cheaper than the switch described in DE-PS 32 31 136, which also remains open after its switching temperature has been exceeded.

In another embodiment of the switch, two can on the underside of the carrier plate Sheet resistors may be provided, one of which is electrically bridging the switch and one is arranged as a series resistor, which is accordingly connected to one of the two electrical connecting parts assigned to the two switching contacts and, on the other hand, to a third electrical connecting part; In the embodiment according to the invention, such a switch is distinguished from a comparable switch as described in DE-GM 84 11 838 by a more compact and less expensive structure.

For other applications, more than two film resistors can of course also be formed on the carrier plate.

In a further embodiment, a fuse wire could be arranged in series with the switch contacts on the aluminum oxide ceramic plate. In an overtemperature protection switch, such a fuse wire provides additional security in the event that the switch contacts are not separated despite the switching temperature being exceeded, e.g. because they stick; in such a case, the fuse wire heats up to above its melting temperature and breaks the circuit.

An aluminum oxide ceramic plate is also ideally suited for equipping it with sensors that generate an electrical output signal. The output signal of such a sensor can be used to control a heating resistor provided on the carrier plate, which heats the bimetal element and thereby actuates the switch.

The necessary electrical connection parts of the bimetallic switch could be attached to the carrier by drilling holes in the carrier, e.g. by means of a laser beam, and the connection parts are screwed or riveted to the carrier at the holes drilled in this way. However, it is more advantageous to metallize the carrier in places, preferably on its underside, and to form the connecting parts in the form of a fork so that they can be attached to the carrier with their fork, in separate metallized areas, after which they are soldered to the carrier. The soldering can be carried out according to inexpensive, automatic processes customary in electronics production, e.g. by passing the carrier plates over a wave pool.

The possibility of metallizing an aluminum oxide ceramic plate leads to a further advantage of the invention: namely, the fixed contact can also be formed by selective metallization of the top of the carrier, in particular by a printing process.

Alternatively, one can use the electrical connection parts at the same time as a carrier for the fixed contact of the switch or as a carrier for one end of the contact spring to be fixed on the carrier. The connection between the fixed contact and the one connecting part and between the contact spring and the other connecting part can be carried out in the usual way by spot welding, the welding process also being able to take place after the electrical connecting parts have been fastened to the carrier plate because of the temperature resistance of the aluminum oxide ceramic. Another, particularly advantageous way of attaching the connecting parts to the carrier is to use the reflow method. For this purpose, a solder metal is pressed onto the carrier at the provided fastening points, on which the connection parts, which are best designed for this purpose for a fork, are clamped and then soldered in a soldering furnace.

Another advantage of the invention is that; that it is possible to start with larger alumina ceramic plates in the manufacture of the thermobimetal switches, to form a whole number of thermobimetal switches on these plates side by side and only to separate the plates along predetermined dividing lines between the thermobimetal switches in a final manufacturing step.

Depending on the purpose of the switch, the contact spring itself can be made from a bimetal (for use as an overcurrent switch), or a separate bimetal element can be provided for actuating the contact spring. In the latter case, it is best to use a bimetallic snap disc, which is arranged between the contact spring and the carrier. A snap disk is a disk which is curved by embossing and which, owing to its curvature, can assume two oppositely curved, stable shapes, the transition between the two shapes taking place suddenly. To hold and center the bimetallic snap disk, hooks and tabs could be provided on or under the contact spring, which the Hold the bimetallic snap disc on its edge and at least partially grasp it. However, it is more advantageous to provide a plastic pin that is guided through a hole in the bimetallic snap disk with play and is either attached to the contact spring and projects through a hole in the carrier with play or is attached to the carrier and with play through a hole in the Contact spring protrudes, expediently this pin between the contact spring and the bimetallic snap disc has a collar through which the two are kept at a distance. Alternatively, the contact spring can be provided with an extension, for example by means of a deep-drawing process which engages with play through a hole in the bimetallic snap disk and through a hole in the carrier.

It is important to keep the bimetal snap disk and the contact spring at a distance if you want to prevent the heat of the contact spring from being transferred to the bimetal snap disk. For this purpose, it is advisable to provide an insulating plastic part between the contact spring and the bimetal snap disk, which either fits into a hole in the bimetal disk or inserted into a hole in the contact spring, possibly connected to both. In order to prevent the heat transfer between the contact spring and the bimetallic snap disk as much as possible, this plastic part - and corresponding to the collar of the bolt described above - is formed as large as possible so that it can thermally insulate the bimetal snap disk from the contact spring.

The best way to prevent heat transfer from the contact spring to the separate bimetal disc is to place the bimetal disc on the side of the carrier facing away from the contact spring.

The contact spring and the bimetal element can be arranged on the same side of the carrier. For many applications, however, it is cheaper to arrange the contact spring on one side and the bimetallic element on the opposite side of the carrier, because the bimetallic element is then protected from thermal influence by the current-carrying contact spring by the intermediate carrier. In this case, the necessary operative connection between the bimetallic element and the contact spring is expediently established by an actuating element which is arranged in a hole in the carrier between the bimetallic element and the contact spring.

The actuating element could be a plunger which is guided axially, ie movably in the longitudinal direction of the plunger, in an opening in the carrier designed as a bore. This plunger could be attached to the bimetallic element to prevent it from being lost. However, it is cheaper to attach it to the contact spring in order to influence the switching behavior of the bimetal element as little as possible. Another particularly advantageous possibility is not to attach the plunger to the contact spring or to the bimetal element, but to arrange it loosely between them in a bore in the carrier; Due to the loose arrangement, the heat transfer from the contact spring to the bimetal element via the plunger is reduced to a minimum. In order to secure the plunger against losing despite its loose arrangement, it is best to form it at one end with a head whose diameter is larger than the diameter of the hole in the carrier. This head also improves the thermal shielding between the contact spring and the bimetal element. To ensure that the plunger cannot slide out of the carrier in the direction in which its head is pointing, the diameter of the bore in the carrier should not be significantly larger than the diameter of the plunger below its head. This ensures that the plunger is not can slide obliquely past the contact spring out of the bore of the carrier, rather it is always enclosed between the contact spring on one side and the bimetallic element on the other side. In order to improve the guidance of the plunger and its centering on the contact spring, it can be advantageous to provide the plunger with an extension above its head and to allow this extension to pass through a hole provided at a corresponding point in the contact spring.

An embodiment of the thermal bimetallic switch according to the invention is particularly advantageous in which the actuating element, which is enclosed between the bimetallic element on one side and the contact spring on the other side and is arranged in a hole in the carrier, is a ball, which preferably consists of glass or a ceramic material. Such a ball not only has the advantage of being a particularly poor thermal bridge between the contact spring and the bimetallic element, it is also extremely easy to install. By sieving out the balls, it can be ensured in a simple and inexpensive manner that the balls used are only slightly less in diameter decide that these diameter tolerances do not lead to any noticeable scatter in the switching temperature. The carrier made of an aluminum oxide ceramic also contributes significantly to low scattering of the switching temperature, because it can be manufactured to a very good size and does not warp even after prolonged use and frequent changes in temperature, but maintains its shape in a stable manner. The combination of a carrier made of a thin aluminum oxide ceramic plate with a loose ball as the actuating element between the bimetallic element and the contact spring is therefore particularly advantageous in order to achieve low variation in the switching temperatures of thermobimetal switches in a series, in view of the fact that such switches are manufactured in large quantities advantage is not to be underestimated. Last but not least, it is the very thin aluminum oxide ceramic carrier that makes the use of such balls possible and interesting, because the smaller the balls are, the greater the advantages; however, the diameter of the balls must be greater than the thickness of the aluminum oxide ceramic carrier. Its thickness is preferably between 1.0 and 1.5 mm; the diameter of the balls is preferably chosen to be twice the thickness of the carrier. Such small balls - especially if they are made of ceramic or glass - are so light and have one low heat capacity so that they do not affect the switching temperature of the bimetal element.

In principle, the bimetallic element could be a bimetallic spring soldered on one side to the underside of the carrier, but it is more advantageous to use a bimetallic snap disk instead, which is held by holders which are attached to the carrier and encompass the edge of the bimetallic element and / or a stop for the edge form the bimetallic element, loose - but captive - is held on the carrier. Suitable brackets for the bimetallic snap disk are, for example, brackets attached to the top of the carrier by soldering, which are turned over to the underside of the carrier and hold the bimetal disc there, similar to photo corners. At least one of the brackets is expediently an integral part of one of the two electrical connection parts of the switch and therefore does not have to be installed separately. In combination with such a holder, which is an integral part of one of the two electrical connection parts, one preferably uses one with a pin as a further holder, with which it is captively inserted, in particular latched, into a bore in the carrier. This second holder can be an injection molded part made of plastic. Of course, it is also possible for the bimetallic disc to be inserted into the carrier only, particularly by means of it Hold brackets. The brackets must secure the bimetal disc against sliding out in all directions. This can be achieved with only two brackets if the respective bimetal element is provided on one edge with two mutually opposite recesses, in each of which a nose of the brackets engages. Conversely, one could of course also provide the bimetallic element with a nose on opposite edges and let it engage in recesses of the two mutually opposite holders. However, the previously mentioned option is cheaper.

Another advantage of using a carrier made of a thin aluminum oxide ceramic plate is that both electrical connections of the switch can be arranged at one and the same end of the carrier without difficulty; for this purpose, a conductor track printed on the carrier leads from the fixed contact to that end of the carrier at which the connection part for the contact spring is also located.

Another advantage of using a thin aluminum oxide ceramic plate as a carrier is that the thermobimetal switch can be easily provided with an adjustable resistor. You can do that apply a resistance layer on the underside of the carrier, which is connected at one end to one of the electrical connection parts of the switch. A slide, for example a spring clip guided on the support itself, can be slid over this resistance layer, which slides on the top of the support on a conductor track which leads to a further electrical connection part of the switch.

A particularly advantageous development of the bimetallic switch according to the invention consists in providing under the carrier a further aluminum oxide ceramic plate which is connected to the carrier in a sandwich-like manner to form a structural unit. This makes it possible to combine a larger number of electrical components, in particular sheet resistors, with the switch without increasing the base area of the switch, or to provide a well-protected resistance layer in the space between the two aluminum oxide ceramic plates. If the two aluminum oxide ceramic plates are not arranged one on top of the other, but at a short distance from one another, then one can advantageously arrange a resistance layer on one of the two mutually facing sides of the two plates, which on the one hand forms a potentiometer with one of the firmly attached to the Plates attached connecting parts and on the other hand is connected to an electrical contact part designed as a slide. In this way, the slide and the resistance layer are arranged in a well-protected manner and the slide is guided precisely and can be supported on the resistance layer on the opposite aluminum oxide ceramic plate in order to generate a contact pressure which is always sufficient.

An arrangement of two aluminum oxide ceramic plates lying directly on top of one another is particularly suitable for a further development of the switch according to the invention, in which a recess open to the contact spring is provided under the contact spring in the assembly formed from the two plates, in which the bimetallic element designed as a snap disk is loose but through the boundaries of the recess are held captive. In this type of training, separate mounts such as hooks or tabs or the like can be dispensed with on the carrier. The recess can be formed, for example, by providing a through hole in the upper aluminum oxide ceramic plate which is somewhat larger in the lower region than the diameter of the bimetallic snap disc and is narrowed at the upper edge by a collar or inwardly projecting projections so that the Bimetallic snap disc cannot fall out of the hole upwards. After this Inserting the bimetallic disc into the hole in the top plate from below covers the hole with the lower aluminum oxide ceramic plate so that the bimetallic snap disc cannot fall out downwards. The lower aluminum oxide ceramic plate can be formed at this point without any recess. But you can also provide an upwardly open blind hole in the lower plate, the diameter of which corresponds to the diameter of the adjacent hole in the upper plate; The bimetallic snap disc is then in the recess, which extends into both plates. It is also advantageous to make the hole in the lower plate larger in diameter than the adjacent hole in the upper plate and to refrain from narrowing the hole in the upper plate at the upper edge; one can then store the bimetallic disc in the blind hole of the lower plate and prevent the bimetallic disc from being lost by the narrower hole in the upper plate. Instead of a blind hole, a through hole can of course also be arranged in the lower plate, which is narrowed at the lower edge by a collar or inwardly projecting projections.

In the case of a bimetallic switch in which the bimetallic snap disk is in the manner described is arranged in a recess in the alumina ceramic plates, the contact spring is expediently provided with a bump directed against the bimetal snap disk or with a pin in order to reduce the distance between the bimetal element and the contact spring which has become larger due to the recessed arrangement of the bimetal element.

The thermal bimetallic switch, in which the bimetallic snap disk is arranged in a recess in the aluminum oxide ceramic plates, can be developed particularly advantageously by arranging in this recess between the bimetal element and the contact spring a conventional snap disk, which has a uniform coefficient of thermal expansion, that is, one Snap disc that does not reverse the direction of its curvature due to the effects of temperature. Such an ordinary snap disc is inserted into the recess in such a way that its curvature points in the same direction as the curvature of the bimetal snap disc below its switching temperature. If the bimetallic snap disc is then heated above its switching temperature, the direction of its curvature changes abruptly and thus also forces a reversal of the curvature of the ordinary snap disc, which acts on the contact spring and lifts it up. The advantage of this arrangement lies in the fact that if the temperature drops below the switching temperature of the bimetal element, it springs back to its original shape, but not the usual snap disk; rather, it continues to hold the switch open until it is reset by hand. Keeping this open after a fault is mandatory in many applications for safety reasons.

Brief description of the drawings:

• 1 shows a side view of a bimetallic switch,
• 2 shows the same switch in plan view,
• Fig. 3 shows the same switch in the view of the bottom,
• 4 shows a second bimetallic switch in a partially sectioned side view,
• 5 shows the switch from FIG. 4 in a top view,
• 6 shows a third bimetallic switch in a partially sectioned side view,
• 7 shows the switch from FIG. 6 in plan view,
• 8 shows a fourth thermobimetal switch in a partially sectioned side view,
• 9 shows the switch from FIG. 8 in plan view,
• 10 shows a fifth bimetallic switch in a partially sectioned side view,
• 11 shows a top view of the switch from FIG. 10,
• 12 shows a detail in a longitudinal section through the support of the thermobimetal switch, another embodiment of a holder for a bimetallic snap disk,
• 13 shows the holder from FIG. 12 in a section parallel to the support of the switch,
• 14 shows a sixth thermobimetal switch in a partially sectioned side view,
• 15 shows the switch from FIG. 14 in a top view,
• 16 shows a seventh thermobimetal switch in a partially sectioned side view,
• 17 shows the switch from FIG. 16 in a top view,
• Fig. 18 shows an eighth bimetallic switch in a partially sectioned side view, and
• 19 shows a ninth thermobimetal switch in a partially sectioned side view.

Detailed description of the drawings with ways of carrying out the invention:

In the various exemplary embodiments, identical or corresponding parts of the thermal bimetallic switches are designated with the same reference numbers.

The switch shown in FIGS. 1 to 3 consists of a thin, rectangular support 1 made of an aluminum oxide ceramic, which has an elongated hole 2 in the middle. The elongated carrier 1 is metallized at its two ends on the underside 1 a and there are therefore attached two connecting lugs 3 and 4, each of which has a soldering eye 5 at one end and is fork-shaped at its other end. The prongs 6 of the fork which rest against the metallized underside 1a of the carrier are soldered to the carrier 1 in the immersion bath. The prongs 7 of the fork resting on the top of the carrier 1 are not soldered to the carrier 1.

On one terminal lug 3, one end of a contact spring 8 is welded by spot welding, which carries a contact piece 9 at its free end. Opposite this movable contact piece 9, a fixed contact 10 is welded onto the other connecting lug 4. The contact spring 8 has a hole 11 approximately in the middle, in which a pin 12 made of plastic is held captive. The bolt 12 rests with a head 13 on the top of the contact spring 8 and extends downward through the contact spring. Its shaft is guided through a central hole 14 in the middle of a bimetallic snap disk 15, which is arranged between the carrier 1 and the contact spring 8, and through the elongated hole 2 of the carrier 1. Between the contact spring 8 and the bimetallic snap disk 15, the bolt 12 is provided with an extended collar 16, which on the one hand provides a certain distance and on the other hand provides thermal shielding between the contact spring 8 and the bimetallic snap disk 15.

On the underside 1a of the carrier 1 there is a sheet resistor 17, which is connected by conductor tracks 18 to the two connecting lugs 3 and 4 and thus bridges the switch electrically. If the bimetallic snap disk 15 speaks due to the occurrence of a temperature which is above its switching temperature, then it raises the contact spring 8 and current only flows through the sheet resistor 17, which heats up as a result-the bimetal snap disk 15 heats and prevents it from entering into it Starting position back jumps in which the switch would close.

The bimetallic snap disc 15 is hardly influenced by the current heat which is generated in the contact spring 8. This is ensured on the one hand by the shielding by the collar 16, but on the other hand also by the contact of the bimetallic snap disc 15 with the carrier 1, as a result of which heat can flow away from the bimetal element onto the carrier 1.

The thermal bimetallic switch shown in FIGS. 4 and 5 differs from that shown in FIGS. 1 to 3 primarily in that the bimetallic snap disk 15 is not arranged on the upper side of the carrier 1 between the carrier and the contact spring 8, but on the The underside of the carrier 1 is held loosely by a holder 20 which is an integral part of the one connecting lug 3 to which the contact spring 8 is also attached. This terminal lug 3 is formed like a fork like the terminal lug shown in FIG. 1. The immovable end of the contact spring 8 is under the upper prong 7 of the fork of the connecting lug 3, and both are soldered to the carrier 1. The lower prong 6 of the fork 3 is over the center of the carrier 1 is also extended and formed into a structure 20 which is similar to a pan, in the bottom of which a large recess 21 is provided which extends almost from edge to edge. At their edges are four upstanding, directed against the underside 1a of the carrier, parallel to the four edges of the carrier 1 side walls 22, 23, 24 and 25, of which the two walls 24 and 25 parallel to the narrow sides of the carrier 1 are the underside Touch 1a of the wearer. The structure 20 serves as a holder for the bimetallic snap disk 15, which is inserted before the connecting lug 3 is attached to the carrier 1. The large recess 21 ensures that the bimetallic snap disk 15 can reach the ambient temperature unhindered.

In order to be able to transmit the snap movement of the bimetallic snap disk 15 to the contact spring 8 when the switching temperature is exceeded, a continuous, cylindrical hole 26 is provided in the center of the carrier 1, in which a cylindrical plunger 27 with a lenticular head 28 is inserted. The plunger can be a Act on plastic injection molding. The shaft diameter of the plunger should be only slightly smaller than the diameter of the hole 26, in order to ensure that the plunger 27 is guided in the hole 26 largely without play.

The contact spring extending over the head 28 of the plunger 27 ensures that the plunger. 27 is movable, but is held captive.

The stem length of the plunger 27 is dimensioned such that when the temperature of the bimetallic snap disc is below its switching temperature and the bimetal snap disc is curved downward, as shown in FIG. 4 in solid lines, the plunger 27 does not extend all the way down to the bimetal snap disc. However, if the temperature of the bimetallic snap disc exceeds its switching temperature, then its curvature reverses, as shown in dashed lines in Fig. 4, and thereby it raises the plunger 27 and this the contact spring 8, so that the contact piece 9 provided at the tip of the Fixed contact 10 is lifted.

The thermobimetal switch shown in FIGS. 6 and 7 differs from the switch shown in FIGS. 4 and 5 essentially in the off Formation of the connection lugs and the holder for the bimetallic snap disc. The two connecting lugs 3 and 4 are not fork-shaped, but angled twice at the ends intended for attachment to the carrier 1 to form an approximately C-shaped structure on one side. With this approximately C-shaped structure, the connecting lugs 3 and 4 grip the carrier 1 from the side and are soldered to it. The immovable end of the contact spring 8 is in turn located between the carrier and the bent leg 30 of the terminal lug 3 lying thereon, and the corresponding leg 31 of the opposite terminal lug carries the fixed contact 10.

The holder for the bimetallic snap disk 15 is formed only in part by the connecting lug 3, and this is provided with a step-like angled extension 32; Opposite this there is a second through hole 33 in the carrier 1, into which a holding part 34 is inserted from above; it is a pin with a flat head 35 resting on the upper side of the carrier 1 and a shaft 36 which has a flat recess 37 below the carrier 1, which the extension 32 of the connecting lug 3rd is facing. The bimetallic snap disk 15 lies with one end in the gap formed between the underside 1a of the carrier and the extension 32 and with its opposite end in the recess 37 of the pin 34. In order to keep the bimetal snap disk 15 captive, there is a recess at one end 38 is provided, in which the pin 34 engages, so that the bimetallic snap disk cannot pivot out of the recess 37 to the side. At the opposite edge of the bimetallic snap disk, pivoting out of the area of the extension 32 is prevented by the fact that the bimetal snap disk there has an edge 39 parallel to the narrow side of the support 1, which extends almost over the entire width of the support 1 and at a short distance from the vertical wall 32a of extension 32 angled toward support 1.

The bracket 34 designed as a pin allows the bimetal snap disk -15 to be easily installed. The pin can simply be plugged into its hole and is held captive in it by the contact spring 8 extending over it. However, it is preferably ensured that it is stuck in its hole 33, for example by closely matching its diameter to the diameter of the hole.

The thermobimetal switch shown in FIGS. 8 and 9 differs from the switch depicted in FIGS. 4 and 5 essentially by the different design of the connecting lugs and the holder of the bimetallic snap disk. The two connecting lugs 3 and 4 are of essentially the same design, essentially the same as the connecting lug 4 in FIGS. 4 and 5. Neither of the two connecting lugs 3 and 4 is used to hold the bimetallic snap disk 15. Rather, two separate brackets 40 are provided for this , which are cone-shaped in a similar manner to the holder 34 in FIG. 6. The two holders 40 have a flat head 45, which rests on the top of the carrier 1, a shaft 46, with which they can pass through their respective hole 43 in Extend the carrier 1, a collar 44, which abuts the underside 1a of the carrier, and a wedge-shaped recess 47 in the shaft 46 below the collar 44. The holders 40 can be injection-molded parts made of plastic, which are initially produced without the head 45 , inserted from below to the collar 44 in their respective hole 43 and then by thermoplastic deformation of their upwardly projecting end a head 45 captively attached to the carrier 1. The two brackets are arranged so that the two wedge-shaped Recesses 47 are at the same height to accommodate the two opposite edges 49 of the bimetallic snap disk 15, both of which are provided with a recess 48 - corresponding to the recess 38 in FIG. 7 - into which the holders 40 engage and prevent the bimetallic snap disk 15 from being lost .

In a further modification of the switch shown in Fig. 4, the switch shown in Fig. 8 between the bimetallic snap disc 15 and the contact spring 8 has a plunger 27 which has a cylindrical extension 41 above its head 28, which with some play through a hole in the Contact spring 8 passes through and thereby leads to improved centering.

The thermal bimetallic switch shown in FIGS. 10 and 11 has a connecting lug 4 which essentially looks like the connecting lug 4 in FIGS. 1 to 3, and has a connecting lug 3 which looks essentially like that in FIGS. 1 to 3, but additionally has an extension 32 which serves to hold the bimetallic snap disk 15 like the connecting lug 3 shown in FIG. 6 The switch shown in FIG. 6 has a further peg-shaped holder 54, which has a longitudinally slotted shaft 56, which is undercut near its one end, into a through hole 33. the carrier 1 is engaged. The bracket 54 is inserted from below up to a collar 55 in the hole ₃₃ . A flat head 57 adjoins the collar 55. The bimetallic snap disk 15 is provided in the area of action of the holder 54 with a recess 38 as in the example in FIGS. 6 and 7, in which the holder 54 engages with the collar 55.

Instead of the bracket 54 in FIG. 10 and instead of the bracket 34 in FIG. 6 and instead of the brackets 40 in FIG. 8, one could also use brackets as shown in FIGS. 12 and 13. These brackets differ from the bracket shown in FIG. 6 in that a semicircular projection facing the bimetallic snap disk 15 and engaging in its recess 38 is provided in the recess 37.

The one shown in FIGS. 10 and 11 differs from the previous exemplary embodiments Thermobimetal switch is still essential in that the movement of the bimetallic snap disk 15 is transmitted to the contact spring 8 not by a plunger but by a small ball. The ball 58 is located in the cylindrical hole 26 of the carrier, the diameter of which is somewhat larger than the diameter of the ball 58. In addition, the diameter of the ball 58 is selected and matched to the position of the contact spring 8 and the bimetallic snap disk 15 such that the ' Ball is held captive both in the closed and in the open switch in the cage formed by the bimetallic snap disk, the hole 26 in the carrier and the contact spring 8. The diameter of the ball 58 is preferably approximately twice the thickness of the carrier 1. The ball expediently consists of glass or of a ceramic material. Such balls can be manufactured very precisely and are easy to use and favor tightly tolerated switching temperatures for switches in a series.

The thermobimetal switch shown in FIGS. 14 and 15 differs from the switch shown in FIGS. 1 to 3 essentially in that its bimetallic snap disk 15 is heated by a fixed resistor 60. The location of this fixed resistor is indicated in Fig. 14 by a circle. The fixed resistor could - as indicated in FIG. 15 - be a wire resistor. The fixed resistor is connected as a series resistor of the switch; Therefore, the electrical current runs from the terminal lug 3 first over the extension 61 located on the underside 1a of the carrier to one end of the fixed resistor 60, then via the fixed resistor 60 to a conductor track 62 which runs back on the underside 1a of the carrier to that end of the Carrier 1, to which the connecting lug 3 is fastened, is turned over at that end to the upper side of the carrier 1 and extends as a frame-shaped structure 63 along one edge of the carrier 1 initially in the direction of the opposite connecting lug 4 and then runs to the opposite longitudinal edge of the carrier 1 and at this back in the direction of the connecting lug 3. At this end the frame-shaped structure 63 is soldered to the carrier 1 and also fixes the contact spring 8, the immovable end of which is between the frame-shaped structure 63 and the carrier 1. The frame-shaped structure 63 is expediently a sheet which is formed in one operation from the same sheet from which the connecting lug 3 is also produced. The latter still owns a tab 64, which rests on the top of the carrier 1, but has no direct connection to the contact spring 8. The tab 64 and the extension 61 together form a fork which is attached to the carrier 1.

The interior 65 of the frame-shaped structure 63 serves to receive the bimetallic snap disk 15, under which there is an opening 66 b in the support 1, through which the heat generated by the fixed resistor 60 can be transferred to the bimetallic snap disk 15. As soon as it reaches its switching temperature due to the heating by means of the fixed resistor, it snaps, acts on a downward bulge 67 of the contact spring 8 and lifts it, whereby the switch is opened and at the same time the current flow through the fixed resistor 60 is interrupted. Such a switch can be used as a time switch which opens after a period of time predetermined by the heating power. The fixed resistor 60 could also be a fuse wire as a fuse against overcurrent. 16 and 17, two mutually identical aluminum oxide ceramic plates 1 and 1 'are sandwiched together to form a structural unit. The An End flag 4 is similar to that shown in Fig. 4 and Fig. 5, but it has a further extension 71, which is inserted into the space between the two plates 1 and 1 '. The other connecting lug 3 does not encompass the plates 1, 1 ', it is only inserted with an extension 70 into the space between the two plates 1, 1'. The two extensions 70, 71 keep the plates 1, 1 'parallel to each other at a short distance. Otherwise, the arrangement of the contact spring 8, the bimetallic snap disk 15 and the plunger 27 connecting them are solved in the same way as in FIG. 4.

On the top of the lower plate 1 'there are two electrical resistance layers 72 and 73 which run parallel to one another in the longitudinal direction of the plate 1' and are in contact with two electrical conductor tracks 74 and 75 running on the same plate 1 ', one of which has a conductor track 74 is connected to the extension 70 of the terminal lug 3, while the other conductor track leads to an electrical connecting part 76. In order to be able to make the position of the resistance layers 72 and 73 and the conductor tracks 74 and 75 clear, the upper plate 1 with the contact spring 8 has partially broken away in FIG. 17.

A slide 77 is also provided, which is designed as a bracket, which is guided displaceably on the longitudinal edges of the lower plate 1 'and is bent around the underside of the lower plate 1' and with its two free ends 78 and 79 in engages the space between the two plates 1 and 1 '- The two free ends 78 and 79 are designed as corrugated contact springs, one of which makes contact with the resistance layer 72 and the other with the resistance layer 73, both of which make contact with the opposite one Support the underside of the top plate 1.

The current runs from the connection lug 3 via its extension 70 to the conductor 74, from there to the resistance layer 72, via the slide 77 to the resistance layer 73 and from there via the conductor 75 to the electrical connection part 76, which is part of a bracket 80, which encompasses the two plates 1 and 1 ', is soldered from the top of the upper plate 1 with the end of the contact spring 8 to the plate 1 and is located on the underside of the lower plate 1' in a pan-shaped holder 20 for the bimetallic snap disc 15 (as in Fig. 4) continues. This bracket 80 has no direct connection with the connecting lug 3, the extension 70 is passed through a window 81 of the bracket 80.

The resistance layers 72 and 73 form a series resistance of the switch as in the example according to FIGS. 14 and 15, but the resistance is through this time the slider 77 designed variable.

Of course, it is also possible to design such a variable resistor as a parallel resistance.

In the bimetallic switch shown in FIG. 18, two aluminum oxide ceramic plates 1 and 1 'which are identical to one another are placed directly on top of one another. In the upper plate 1, a hole 82 is provided under the contact spring 8, which is narrowed at its upper edge by a collar 83. In the recess formed by this hole 82 there is a bimetallic snap disk 15, which is secured against falling out by the collar 83 and which snaps over when its switching temperature is exceeded and the contact spring 8 lifts off. The recess forms the holder for the bimetallic snap disk, and because this is arranged sunk, a bulge 67 is provided in the contact spring 8, which is directed against the bimetal snap disk.

The thermobimetal switch shown in FIG. 19 differs from that shown in FIG. 18 in that the hole 82 of the upper plate 1 continues into a recess 85 in the lower alumina ceramic plate 1 ', which, however, is one has a slightly larger diameter and is designed as a blind hole. The bimetallic snap disk 15 now lies in the blind hole 85. Above this is an ordinary snap disk 86, which does not consist of a bimetal and therefore does not snap when the temperature changes, but when subjected to mechanical action. The two snap disks 15 and 86 are held in the blind hole 85 in that the overlying hole 82 in the upper plate 1 is somewhat narrower than the blind hole 85 underneath. When the bimetal snap disk 15 is heated above its switching temperature, it jumps into the opposite shape, this also forces the usual snap disk 86 to snap, which thereby lifts the contact spring 8. Such a switch does not close automatically after the temperature has dropped below the switching temperature of the bimetallic snap disk 15, since the ordinary snap disk 86 remains in its shape until it is reset from the outside, for example by hand.

Claims (32)

1. A bimetallic switch which carries a flat, electrically insulating carrier, a contact spring which is fastened at one end to the carrier and at the other end carries a contact piece which can move by the action of a bimetal element and which cooperates with a fixed contact, and at least two electrical contacts fastened to the carrier Has connection parts, one of which is electrically connected to the fixed contact arranged on the carrier and one to the contact spring,
characterized in that the carrier (1) is a thin aluminum oxide ceramic plate (wafer). 2. Thermobilmetallschalter according to claim 1,
characterized in that the carrier (1) is metallized in places. 3. thermobimetal switch according to claim 2,
characterized in that the electrical connection parts (3, 4) are fork-shaped, are placed in separate metallized areas with the fork on the carrier (1) and are soldered to it. 4. thermobimetal switch according to claim 1,
characterized in that the carrier (1), in particular on its underside (1a), is provided with conductor tracks (18). 5. bimetallic switch according to claim 4,
characterized in that the carrier (1) is additionally equipped with electrical components (60) and / or sensors, in particular coated with one or more sheet resistors (17). 6. Thermobi_metallschalter according to claim 5,
characterized in that the carrier (1) has a resistor (17) which connects the switch electrically bridged, and / or carries a series resistor (60) which on the one hand with one of the two connection parts (3, 4) assigned to the two switching contacts (9, 10) and on the other hand with a third connection point on the carrier (1) or with the contact spring " (8) is connected. 7. bimetallic switch according to claim 5,
characterized in that the carrier (1) carries a fusible wire (60) electrically connected in series with the switch contacts (9, 10). 8. thermobimetal switch according to claim 5,
characterized in that it is designed as a hybrid switch by forming an electronic circuit on the carrier (1). 9. bimetallic switch according to claim 1,
characterized in that a bimetallic snap disc (15) is arranged between the latter and the carrier (1) for actuating the contact spring (8), and in that a pin (12) made of plastic is provided for centering and securing this bimetallic snap disc (15) with play through a hole (14) in the bimetallic snap disc (15) carried out and is either attached to the contact spring (8) and projects with play through a hole (2) of the carrier (1) or is attached to the carrier (1) and projects with play through a hole in the contact spring (8). 10. Thermobimetal switch according to claim 1,
characterized in that a bimetal snap disc (15) is arranged between the latter and the carrier (1) for actuating the contact spring (8), for centering and securing the contact spring (8) is provided with an extension, in particular formed by deep drawing, which with play through a hole (14) of the bimetallic snap disc (15) and through a hole (2) of the carrier. 11. A bimetallic switch according to claim 9,
characterized in that the bolt (12) between the contact spring (8) and the bimetallic snap disc (15) has a collar (16) which keeps the two at a distance. 12. Thermobimetal switch according to claim 9,
characterized in that a plastic part (12) insulating these two from one another is inserted either in a hole in the bimetallic disc (15) or in a hole (11) in the contact spring (8). 13. A bimetallic switch according to claim 11 or 12, characterized in that the collar (16) of the bolt (12) or the plastic part for thermal shielding of the bimetallic snap disc (15) against the contact spring (8) is formed over a large area. 14. Thermobimetal switch according to claim 1,
characterized in that the fixed contact (10) and the contact spring (8) with the movable contact piece (9) are arranged on one side of the carrier (1), while on the side of the carrier (1) facing away from them the bimetal element (15) It is arranged that a hole (26) is provided in the carrier (1) between the contact spring (8) and the bimetallic element (15), in which an actuating element (27, 58) is arranged, which movement of the bimetallic element (15) transfers to the contact spring (8). 15. Thermobimetal switch according to claim 14,
characterized in that the actuating element is a plunger (27) which is axially movably guided in the cylindrical hole (26) of the carrier (1). 16. Thermobilmetallschalter according to claim 15,
characterized in that the plunger (27) has a head (28) or collar lying between the carrier (1) and the contact spring (8), the diameter of which is larger than the diameter of the hole in the carrier (1). 17. Thermobimetal switch according to claim 16,
characterized in that in the contact spring (8) there is a hole (42) aligned with the hole (26) in the carrier (1), through which the plunger (27) engages with an extension (41). 18. Thermobimetal switch according to claim 14,
characterized in that the actuating element is a ball (58) which is held loosely in a cage formed by the contact spring (8), the bimetallic element (9) and the hole (26) in the carrier (1). '19. Thermobimetal switch according to claim 18,
characterized in that the ball (58) is made of glass or a ceramic material. 20. A bimetallic switch according to claim 14,
characterized by the bimetal element (15) is a disc, the brackets (20,32,34,40,54), which are attached to the carrier (1) and encompass the edge of the bimetal element (15) and / or a stop for the edge of the bimetal element (15) forms, loose - but captive - is held on the carrier (1). 21. Thermobimetal switch according to claim 20, there
characterized in that at least one of these brackets (20, 32) is an integral part of one of the electrical connection parts (3, 4). 22. Thermobimetal switch according to claim 20, there
characterized in that at least one of these mountings (34, 40, 54) has a pin with which it is captively inserted, in particular snapped into a hole (33, 43) in the carrier (1). 23. Thermobimetal switch according to claim 20,
characterized in that the bimetallic element (15) is provided on its edge with one or more recesses (38, 48) into which one of the brackets (34, 40, 54) engages. 24. Thermobimetal switch according to claim 1,
characterized in that a further aluminum oxide ceramic plate (1 ') is provided under the carrier (1) and is connected to the carrier (1) in a sandwich-like manner to form a structural unit. 25. Thermobimetal switch according to claim 24,
characterized in that the two aluminum oxide ceramic plates (1, 1 ') are arranged at a short distance from one another, that at least on one of the two mutually facing sides of the two plates (1', 1) there is a resistance layer (72, 73) which is used for Forming a variable resistor is connected on the one hand to one of the connection parts (3 or 4) fixedly attached to the plates (1, 1 ') and on the other hand to an electrical contact part (77) designed as a slide. 26. Thermobimetal switch according to claim 24,
characterized in that in the structural unit formed by the two adjoining aluminum oxide ceramic plates (1, 1 ') under the contact spring (8) there is provided a recess (82, 85) which is at least open towards the contact spring (8) and in which the al.s Snap disk formed bimetallic element (15) is held loose but captive. 27. Thermobimetal switch according to claim 26,
characterized in that the recess (82) is a through hole in the upper plate (1) which is narrowed on the upper side by projections or a collar (83) and is covered on the lower side by the lower plate (1 '). 28. A bimetallic switch according to claim 26.
characterized in that in the lower plate (1 ') through a blind hole (85) which is open at the top or through a through hole which is delimited on the underside by projections or a collar, part of the recess (82, 85) in the structural unit (1 , 1 ') is formed. 29. Thermobimetal switch according to claim 28,
characterized in that the clear width of the hole (53) in the lower plate (1 ') is greater than that of the upper plate (1). - 30. Thermobimetal switch according to claim 26,
characterized in that the contact spring (8) over the hole (82) of the upper aluminum oxide ceramic plate (1) has a bulge ( ₆₇ ) or carries a pin, which are directed against the bimetallic element (15). 31. A bimetallic switch according to claim 26.
characterized in that in the recess (82, 85) between the bimetallic element (15) and the contact spring (8) there is a conventional snap disk (86) having a uniform coefficient of thermal expansion. 32. bimetallic switch according to claim 1,
characterized in that the aluminum oxide ceramic plate (1) is between 1 mm and 1.5 mm thick.

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