EP0858090B1 - Thermostat switch with a bimetal switch device - Google Patents

Abstract

The switch has a bimetal switch mechanism (12) which is arranged in a housing (11) with a first housing part (14) of insulating material and a second housing part (17). The bimetal switch mechanism is connected to a first electrode (16) coming out from the first housing part (14). The first electrode (16) cooperates with a second electrode (19) which is provided on the inside of the other housing part (17). The bimetal switch mechanism has a spring part (23) which works against a bimetal plate (29). The spring part carries a movable contact (28) which cooperates with the second electrode. A holder extension (25) is provided on the side of the spring part (23). The first electrode (16) is fastened to the holder extension (25).

Description

The present invention relates to a temperature-dependent switch with a bimetallic switching mechanism, which is arranged in a housing having a first housing part made of insulating material and a second housing part, wherein the bimetallic switching mechanism is connected to a led out of the one housing part of the first electrode and a second Electrode cooperates, which is provided on the inside of the other housing part.

Such a switch is known from WO 92/20086.

The known switch has a two-part housing made of insulating material, in the opposite end faces each introduces a stripped wire. Inside the housing, a cavity is provided at the bottom of which a wire is freely accessible from above.

At the opposite end of the cavity, a pad is provided on the upper side of the second wire terminates, so that the two wire ends to each other have a height difference. Attached to the end of the second wire is a bimetallic tab having a movable contact at its free end which cooperates with the end of the first wire. Depending on its temperature, the bimetal tongue brings the movable contact into abutment with the wire end or lifts it off.

The lid of the two-piece housing is hinged to the base and is to be welded by ultrasound to the base, whereby a tight seal against the environment is achieved.

In the known switch is advantageous that it has small dimensions and because of the insulating housing has a low susceptibility to leakage currents and is not very stable to pressure. Furthermore, the air gaps in the interior of the housing are sufficiently large, so that the required isolation distance is achieved.

Since the known switch is connected to strands, it can indeed be processed well, since the strands, however, emerge at opposite ends of the housing, this switch is not well suited for automatic assembly, because this usually parallel strands are required.

The known switch is associated with a whole series of other disadvantages, which include above all the power supply via the bimetallic switching tongue. The current self-heating of the bimetallic switching tongue, which is even desirable here, namely that affects the switching behavior such that the predetermined by the design of the bimetallic switching switching temperature can change depending on the current. Furthermore, the properties of the bimetal tongue are unpredictably influenced by their welding at the end of the second wire.

The known switch can thus be used only conditionally for the monitoring of the temperature of a device to be protected, because its switching temperature can change unpredictably on the one hand by the assembly work and on the other is influenced by the height of the flowing current.

Furthermore, the known switch has only a low contact reliability, because no geometrically reproducible contact conditions prevail between the bare wire end and the movable contact. Namely, the contact surface depends in particular on the type and extent of the curvature of the bimetallic switching tongue, which in turn is influenced by the mechanical stresses during welding and the respective weld itself in a non-reproducible manner. Further, a special copper wire is required to provide resistance to abrasion.

Another disadvantage of the known switch is that the housing is welded with ultrasound. The inventors of the present application have in fact recognized that the Bimetal switching tongue in the known switch by the use of ultrasound in an unpredictable manner with respect to their switching behavior changes.

Another temperature-dependent switch, which also has very small dimensions, is known from DE-AS-2 121 802. This switch has a two-part metal housing from the lower part and with respect to this by an insulating electrically insulated cover part. The bimetal derailleur here consists of a spring washer with a movable contact and a bimetallic disk slipped over it.

The spring washer and the bimetallic disc are freely inserted in the lower part, so are not subject to mechanical stress. In the low temperature position of the switching mechanism, the spring washer is supported with its edge inside of the lower part and presses the movable contact inside against the cover part, so that an electrically conductive connection between the lower part and the cover part is made. In this switching position, the bimetal disc is completely unloaded.

If now the temperature increases beyond the transition temperature of the bimetallic disc out, this jumps to its other configuration and then supports with its edge inside of the lid part, being electrically insulated from the lid part by the intermediate insulating foil.

With its central region, the bimetallic disc now pushes the movable contact against the force of the spring washer away from the cover part, thereby opening the electrical connection between the cover part and the lower part.

In this switching mechanism are the major disadvantages, as they are present in the switch known from WO 92/20086, not to find. The bimetallic disc is not subject to mechanical stress when it is in its low temperature position, and it is also not responsible for the management of the electric current, so that no current self-heating is recorded. On the other hand, the spring washer is only responsible for making the electrical contact and to carry the current, so that the spring washer can be designed substantially in terms of good current carrying properties. But this allows the electrical properties as well as the responsible for the temperature-dependent switching properties in this switch can be set separately from each other, these properties are further not changed by the assembly of the known switch.

However, this switch also has some disadvantages associated with having a two-piece metal housing. Firstly, there may be problems in the assembly of the known switch when the insulating slip, so that the required insulation between the lower part and cover part is not made or the bimetal disc is not sufficiently isolated in its high temperature position relative to the cover part. Particular problems are caused by leakage currents as well as insufficient air gaps for the insulation.

Next, the housing of the known switch for some applications is not tight enough, the lid part is in fact held only by a Krimprand on the lower part, wherein the insulating film provides a seal, which is not always sufficient and may even be completely missing in incorrect assembly.

Another disadvantage of the very pressure-resistant metal housing is that it still has to be isolated from the device to be protected in many applications. The connection technique is carried out in the known switch so that crimped connections are provided on both housing parts, to which the pigtails still need to be connected by the user, which is often regarded as a disadvantage because of the not possible automation.

DE 43 37 141 A1 discloses a similarly constructed switch which has the same advantages as the switch known from DE-AS-2 121 802. In this switch, however, the insulating film is glued to the cover part prior to assembly, so that the disadvantages associated with the slipping of the insulating film are avoided.

Further, this switch has an outer shoulder on the housing, on which sits an annular end of a terminal lug, at the other end a first pigtail is soldered. The second pigtail is soldered directly to the cover part.

Although most of the above-mentioned disadvantages have been eliminated in this switch, so the connection technology of the strands on the switch is very expensive, which is also considered a disadvantage. Furthermore, this switch has relatively large dimensions.

Overall, it is in the two switches described above with metal housing of disadvantage that often the required security against leakage currents and the required size of the air gaps in the connection contacts is not given or has already been exploited to the extent that the known switches can not be further miniaturized.

From DE 36 12 251 and JP 01-286221 A, a temperature-dependent switch is known, the bimetallic switching mechanism comprises a bimetal disc and a working against this spring tongue, which is connected at one end to a first electrode and at its second End carries a movable contact part, which cooperates with the second electrode. Below its response temperature, the bimetallic disc is free of stress, but if it is above its switching temperature, it pushes against the force of the spring tongue away from the movable contact of the second electrode, thus opening the switch. The further the bimetal disc removes the movable contact from the second electrode, the greater the restoring force of the spring tongue, so that the bimetal disc is exposed to a high mechanical load in its high-temperature position, which leads to a shift in the switching temperature over time can.

Against this background, it is an object of the present invention to provide a switch of the type mentioned above with small dimensions, which combines the advantages of the switches discussed above and still avoids their disadvantages, with a reproducible switching behavior can be achieved in particular with a simple structure and simple assembly should.

According to the invention, this object is achieved in the switch mentioned above in that the bimetal derailleur comprises a working against a bimetal disc spring washer which carries a movable contact, which cooperates with the second electrode, and that on the spring washer laterally a holding lug is provided to which it is attached to the first electrode, wherein the spring washer in its one switching position with its free edge region at least partially on a projecting shoulder, which is provided in the first housing part.

The object underlying the invention is completely solved in this way.

The inventors of the present application have in fact recognized that it is also possible for a temperature-dependent switch with insulating housing to use a switching mechanism with spring washer and working against this bimetal disc.

The quite surprising solution of the object underlying the invention now makes it possible to combine the advantages of the free bimetal disc and the spring washer provided for the current flow with a housing made of insulating material, in which the distances between the electrodes and especially their mutual isolation sufficient are large so that the switch itself can be further miniaturized.

It is possible to manufacture a housing part made of metal, which is held by a raised edge of the other, made of insulating material housing part, wherein the edge is hot-stamped or heat-welded to provide a corresponding seal.

It has been found that the spring washer can be replaced in the derailleurs, as used in the above-described switches with metal housing, by a spring washer having a holding lug, with which it is attached to the one electrode. This attachment serves on the one hand the electrical connection and on the other hand, the mechanical support, which does not adversely affect the spring characteristics so far that the overall switching behavior is deteriorated.

It is advantageous that the shoulder forms, so to speak, a second abutment, so that can reach approximately the properties of a freely inserted spring washer. The movable contact is now pressed in a predetermined orientation against the second electrode, so that a good, reproducible contact is achieved. The spring washer now works not like a cantilever spring tongue, but like a spring washer with a bulge. The bulge, which is also referred to as a holding approach, can be designed so that the spring washer still has a snap behavior. Since the shoulder is formed protruding, under her so there is still free space, the spring washer can be pushed down by the rest through the bimetallic disc down, so that comparable mechanical conditions are achieved as in the initially discussed switches with metal housing.

Especially important for the desired, reproducible switching behavior is a freely inserted bimetal disc, which is not responsible for the current flow but only for a temperature-dependent switching. In this way, it is now possible even with a switch with housing made of insulating material to adjust the properties of the bimetallic disc prior to their assembly, whereby these properties are not adversely affected by the assembly itself.

In a further development, it is preferred if the second housing part is made of insulating material and on its inside the second electrode is arranged, which is led out of the housing.

The advantage here is that, as in the generic switch, the housing is made entirely of insulating material, so that no further insulation measures are required if the new switch is mounted on a device to be protected. It is also advantageous that it is now possible to ultrasonically weld the two housing parts without causing irreproducible changes in the switching behavior, because a free bimetal disc is not influenced by ultrasound, as the inventors of the present application were able to determine. Furthermore, the two electrodes, which can be formed flat, give the housing a good stability.

Thus, however, the new switch described so far has both the advantages associated with a tightly sealed housing made of insulating material as well as with a freely inserted, not responsible for the power supply bimetal disc.

It is then preferred if the bimetal disc is supported in its one switching position with its edge on a projecting shoulder, which is provided in the second housing part.

Here it is advantageous that in a simple manner a contact with the second electrode is prevented, which is provided on the inside of the second housing part. Since this shoulder is also projecting, there is also a sufficient air gap between the second electrode and the edge of the bimetallic disc.

In a development, it is preferred if the second electrode is a sheet metal part, which is held on the inside of the second housing part, and to which an outwardly leading pigtail is connected, for which an insulation channel is provided in the housing, which is preferably partially in the first and partially extends into the second housing part.

This measure is particularly advantageous in terms of ease of installation, the isolation channel may e.g. be provided half each in the two housing parts. After assembly, the pigtail is then surrounded on all sides by insulating material in the insulation channel, so that leakage currents are reliably avoided.

On the other hand, it is also preferred if the first electrode is a sheet metal part, which is held on the inside of the first housing part is, and to which an outwardly leading pigtail is connected, for which in the housing an isolation channel is provided, which preferably extends partially into the first and partially into the second housing part.

With this measure, the same advantages are associated with as with the insulation channel for the second electrode, being ensured by the combination of the two isolation channels for a particularly secure insulation of the external connections. The two sheet metal parts also give the case a good pressure stability.

In a further development, it is preferred if the two insulation channels run parallel to each other on opposite outer sides of the housing and open into an end face of the housing.

The advantage here is that a large distance between the two connection strands is achieved, whereby the still possible air gaps are determined not by the thickness but by the width of the housing, which is usually greater than the thickness. In other words, a very flat switch can be realized by this arrangement of the pigtails or the insulation channels, in which nevertheless the required lengths of the possible air gaps can be maintained. Another advantage is that the two pigtails are guided side by side from the housing, which is for further, in particular automatic connection technology advantage.

Generally, it is preferred if both housing parts are made essentially of solid material in which geometric adapted recesses for receiving the switching mechanism and the electrodes are provided.

By this measure, the best possible insulation against leakage currents and a reduction in the number of air gaps is achieved, being taken care of by the special arrangement of the insulation channels simultaneously large air gaps.

Finally, it is still preferable if the two housing parts are hinged together.

Here is an advantage that the new switch itself can be easily mounted. The two housing parts can be automatically equipped with the respective electrode, to which then the respective pigtail is soldered or welded. Then, the spring part, the movable contact and the bimetallic disc still have to be inserted into the one housing part, wherein the spring part may possibly be fastened together with the associated electrode in the housing part or welded to the electrode. Then the two housing parts are folded up and welded together with ultrasound.

In summary, it should be noted that the new switch is thus easy to assemble, the assembly can be done automatically. The new switch also combines the advantages of the generic switch with insulating housing with those of the known switch with metal housing, yet a safe and reproducible switching behavior is achieved and due to the good insulation inside the switch smallest dimensions can be achieved.

Further features and advantages will become apparent from the description of the accompanying drawings.

It is understood that the features mentioned above and those yet to be explained not only in the particular combination given, but also in other combinations or alone, without departing from the scope of the present invention.

Fig. 1

eine schematische Schnittdarstellung in Seitenansicht des neuen Schalters; und

Fig. 2

eine Draufsicht auf den neuen Schalter aus Fig. 1, wobei die Gehäuseteile aufgeklappt aber bereits bestückt sind.

An embodiment of the invention is illustrated in the accompanying drawings and will be explained in more detail in the following description. Show it:

Fig. 1

a schematic sectional view in side view of the new switch; and

Fig. 2

a plan view of the new switch of FIG. 1, wherein the housing parts are unfolded but already equipped.

In Fig. 1, 10 denotes a temperature-dependent switch having a housing 11 made of insulating material, in which a bimetallic switching mechanism 12 is arranged.

The housing 11 is formed in two parts and comprises a first housing part 14, on the inside 15 of which a first electrode 16 is arranged. Furthermore, a second housing part 17 is provided, on the inside 18 of which a second electrode 19 is arranged.

The second electrode 19 is held by a pin 21 on the housing part 17, while the first electrode 19 is held by a pin 22 on the housing part 14.

The pin 22 also holds a spring member 23, which is a spring washer 24 integrally formed therewith retaining lug 25, wherein the retaining lug 25 rests on the first electrode 16 and is held together with this by the pin 22.

The spring washer 24 lies with its edge region 26, which is not occupied by the holding lug 25, on an inner, projecting shoulder 27, which is arranged on the inside of the first housing part 14.

The spring washer 24 carries approximately centrally a movable contact 28, which presses against the second electrode 19 in the switching position shown in Fig. 1.

About the movable contact 28, a bimetal disc 29 is slipped, the edge 31 is unloaded in the switching position shown. However, this edge 31 is assigned a projecting shoulder 32 on the second housing part 17.

In the switching position shown in Fig. 1, the first and second electrodes 16, 19 via the movable contact 28 and the spring member 23 are electrically connected to each other. How the external connection of the new switch 10 takes place will be explained below in connection with FIG. 2.

Now, if the temperature is increased in the new switch 10 until the transition temperature of the bimetallic disc 29 is reached, this snaps from the convex shown in its concave shape, while supporting itself with its edge 31 on the shoulder 32, at the same time lifts the movable contact 28 of the second electrode 19, so that the electrical connection between the two electrodes 16, 19 is interrupted. Since the shoulder 27 protrudes from a bottom 33 of the first housing part 14, the movable contact 28 can escape downwards, so that a sufficient air gap between the movable contact 28 and the first electrode 19 is adjusted to provide sufficient insulation.

In Fig. 2, the switch of Fig. 1 is shown shortly before the end of its assembly, wherein the two housing parts 14, 17 are adjacent to each other.

It can be seen first that in the second housing part 17, a keyhole-like recess 34 is provided, at the bottom, which corresponds to the inner side 18, the second electrode 19 is arranged, which has the shape of a T with asymmetrically arranged transverse bar. At the downwardly projecting portion 19 'of the second electrode 19, a pigtail 35 is soldered, for which an isolation channel 36 is provided, which extends in each half in the first and the second housing part 14, 17.

It can be seen at the top in FIG. 2 that the first electrode 16 has an L-shape, to the lower part 16 'of which a pigtail 37 is also soldered or welded. The pigtail 37 extends in an isolation channel 38, which extends in half in the two housing parts 14, 17 each.

It can also be seen that the two housing parts 14, 17 are hinged together by webs 39.

Now, if the housing part 17 is folded onto the housing part 14, the two pigtails 35, 37 are completely in the associated isolation channels 36, 38 to lie, which are now arranged with sufficient distance from each other on opposite outer sides 41, 42 of the housing 11, but in a common end face 43 open, so that the connecting leads 35, 37 extend parallel to each other on the same side of the housing 11.

It can also be seen above in FIG. 2 that the spring part 23 has a keyhole-like shape, its outer contour 45 partially coinciding with that of the bimetallic disk 29. Dashed is still the shoulder 27 indicated.

The first electrode 16 and the spring part 23 are arranged in a recess 46, which also has approximately the shape of a keyhole, wherein furthermore the L-shaped configuration of the first electrode 16 in the region 16 'is taken into account.

At 48 finally a profiled, peripheral edge of the second housing part 17 is arranged, which comes when folding the two housing parts 14, 17 with a corresponding peripheral edge 49 of the first housing part 14 into abutment and can be welded thereto by ultrasound.

Returning to Fig. 1, it should be noted that the thickness of the first electrode 16 keeps the spring member 23 at a certain distance from the inside 15 of the housing member 14, leaving sufficient space for the movable contact 28 to move downwardly in the direction of the bottom 33 dodge. The spring member 23 is almost completely guided along its circumference, so that it has substantially the snap properties of a spring washer, as used in known switches with metal housing.

Of course, it is possible not to weld the pigtails 35, 37 with the respective electrodes 16, 19, but only aufzupressen, which can be achieved by appropriate design of the isolation channels 36, 38. Further, the spring member 23 may be welded to both the first electrode 16 as well as held by a clamp connection at this. It can be seen that the connecting leads 35, 37 are responsible for the external connection of the switch 10 because of their connection to the electrodes 14, 19.

In Fig. 2, the two housing parts 14, 17 are shown as if they were made of solid material, wherein the corresponding geometrically adapted recesses 34, 46 for the electrodes 16, 19 and the bimetallic switching mechanism 23 and the isolation channels 36, 38 for the pigtails 35, 37 are provided. Due to the many projecting webs in the two housing parts 14, 17 is provided for a very good insulation between the two connecting leads 35, 37 and the other electrically conductive parts in the new switch 10. Of course, the housing parts 14, 17 are not milled out of solid material, but poured or sprayed accordingly.

In this case, it is then possible to inject the two electrodes 16, 19 so that they become an integral part of their respective housing part 14 or 17.

Claims (8)

1. A temperature-dependent switch having a bimetallic switching mechanism (12) arranged in a housing (11) having a first housing part (14) made from insulating material, and a second housing part (17), whereby said bimetallic switching mechanism (12) is connected with a first electrode (16) extending out of said one housing part (14), and coacts with a second electrode (19) provided internally at said other housing part (17),
   characterized in that said bimetallic switching mechanism (12) comprises a spring disc (23) working against a bimetallic disc (29) and carrying a movable contact (28) that coacts with said second electrode (19), and that there is provided laterally on the spring disc (24) a retaining extension piece (25) at which it is attached to said first electrode (16), whereby said spring disc (24) in its one switch position braces with its free rim region (26) at least partly against a projecting shoulder (26) which is provided in said first housing part (14).
2. The switch of claim 1, characterized in that said second housing part (17) is fabricated from insulating material and has arranged on its inner side (18) said second electrode (19) that extends out of said housing (11).
3. The switch of claim 1 or claim 2, characterized in that said bimetallic disc (29), in one of its switch positions, braces at its rim (31) against a projecting shoulder (32) that is provided in said second housing part (17).
4. The switch of anyone of claims 1 through 3, characterized in that said second electrode (19) is a sheet-metal part which is retained internally at said second housing part (17) and to which is connected a connecting lead (35), extending outwardly, and for which there is provided in said housing (11) an insulation channel (36) which preferably extends partly into said first and partly into said second housing part (14, 17).
5. The switch of anyone of claims 1 through 4, characterized in that said first electrode (36) is a metal-sheet part which is retained internally on said first housing part (14) and to which is connected a connecting lead (37), extending outwardly, and for which there is provided in the housing (11) an insulating channel (38) which preferably extends partly into said first and partly into said second housing part (14, 17).
6. The switch of claims 4 and 5, characterized in that said two insulation channels (36, 38) are running parallel to one another on opposite outer sides (41, 42) of said housing (11), each channel opening in an end face (43) of said housing (11).
7. The switch of anyone of claims 1 through 6, characterized in that both housing parts (14, 17) are manufactured substantially from solid material, in which housing part geometrically adapted recesses (34, 46) are provided to receive the switching mechanism (12) and said electrodes (14, 19).
8. The switch of anyone of claims 1 through 7, characterized in that said two housing parts (14, 17) are hinged to one another.

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