EP0938117B1 - Switch - Google Patents

Abstract

The switch has electrical connections (11,14) that connect with a power circuit. Internally there is a fixed contact (29) that is engaged by a movable contact (28) that is on the tip of a bimetallic leaf spring (22). This is fixed at one end to a cantilever spring (21). At a specific temperature the bimetallic element responds to open the contacts.

Description

The present invention relates to a switch having a first and at least one second external terminal and a temperature-dependent switching mechanism, which produces an electrically conductive connection for an electrical current to be conducted through the switch as a function of its temperature between the two external terminals, wherein the switching mechanism is a switching element, the temperature changes its geometric shape between a closed and an open position and in its closed position the current flowing through the switch leads, and includes an actuator which is permanently connected electrically and mechanically in series with the switching element.

Such a switch is from the US 4,636,766 A as well as out US 5,196,820 known.

The known switch comprises as a switching element, a U-shaped bimetallic element with two legs of different lengths. On the long leg, a movable contact member is fixed, which cooperates with a switch-fixed mating contact, which in turn is in an electrically conductive connection with one of the two outer terminals.

The shorter leg of the U-shaped bimetallic element is attached to the free end of a lever arm formed as an actuator, which is connected at its other end fixed to the housing and is in electrically conductive communication with the other of the two outer terminals. The actuator is another bimetallic element, which is tuned to the U-shaped bimetallic element, which deform the two bimetallic elements in opposite directions with temperature changes and thus maintain the contact pressure between the movable contact part and the housing-fixed mating contact.

This switch is intended as a breaker for high currents, which lead to a strong heating of the flowed through bimetal elements, whereby ultimately the movable contact part is lifted from the fixed counter-contact. Influences of the ambient temperature are compensated by the aforementioned opposing deformation of the bimetallic elements.

In this construction, it is above all a disadvantage that two bimetallic elements are required whose temperature behavior must be exactly matched to one another, which is structurally complicated and cost-intensive to implement. In order to compensate for manufacturing tolerances, the known switch is also mechanically adjusted after assembly, which represents a further disadvantage.

Since the two bimetallic elements are designed geometrically very different, they also have different long-term stabilities, so that actually from time to time a readjustment would be required. However, this is no longer possible in use, so that overall the long-term stability and thus the functional reliability leaves something to be desired.

Another disadvantage of this construction is the high height required by the U-shaped bimetallic element.

The well-known current-dependent switch is therefore structurally complex, expensive and not very reliable.

Another, from the EP 0 103 792 B1 known, current-dependent switch has as a switching member on a bimetallic spring tongue, which is attached to the one outer terminal and carries at its free end a movable contact part, which cooperates with a mating contact, which is arranged at the free end of an elongated spring element, the other end is attached to the other external terminal. The switch is connected with its external terminals in series with an electrical device, that the operating current of this switch flows through the bimetallic spring tongue. In general, the well-known Switch further thermally coupled to the electrical device so that it can follow the temperature changes.

If the temperature of the device exceeds an impermissible value, the bimetallic spring tongue lifts the moving contact away from the mating contact, interrupting the flow of current and protecting the electrical device against further heating. In this open position, however, the bimetal spring tongue can also be brought by an increased current flow, since the bimetallic spring tongue heats up through the electrical current flowing therethrough. The electrical properties of the bimetal spring tongue can now be adjusted in coordination with the mechanical properties and the transition temperature so that it is in its closed position in which it directs the operating current of the electrical device when both the ambient temperature is below the switching temperature as well the operating current is below a response current. Now increases the operating current beyond the permissible value, so heats up the bimetal spring tongue very quickly and reaches its critical temperature, whereupon it goes into its open position.

This switch provides protection against both over temperature and overcurrent.

Because of the elastic bearing of the mating contact contact and mating contact rub during the switching operations together, whereby contamination and deposits are abraded by the contact surfaces, which ensures a low contact resistance and thus a good electrical connection. The elastic Storage of the mating contact further ensures a low mechanical load on the bimetal spring tongue, since the mating contact gives limited. As a result, irreversible deformations of the bimetallic spring tongue are avoided. Since such mechanical deformations can lead to a shift of the switching temperature, this arrangement provides a total of high reliability.

In the known switch, however, has the disadvantage that it has a relatively high space requirement for the switching function of the temperature-dependent switching mechanism because of the elastic deflection of the mating contact and the jumping of the bimetallic spring tongue in the open position. Another disadvantage is that the bimetallic spring tongue as all bimetallic elements in the transition from the closed to the open position passes through a so-called creep, in which due to a temperature increase or decrease the bimetallic element deforms creeping, but without its eg Convex low-temperature position already in its concave high-temperature position umzuschnappen. This creep phase occurs whenever the temperature of the bimetallic element approaches either the top or the bottom of the transition temperature and leads to significant conformational changes. In particular, as a result of aging or long-term operation, the creep behavior of a bimetallic element can also change beyond.

During the opening movement, the creep can cause the pressure of the contact against the mating contact to decrease, which results in undefined switching states. During the closing movement, the contact may be during the slow phase gradually approach the mating contact, which can cause the danger of an arc.

At one of the US 4,389,630 A known bimetallic switch, this creep phase of the bimetallic element is suppressed by the fact that the bimetallic disk used there is depressed in the central region or held down at the edge, with abutments are provided which mitwirkirken the Umschnappvorgang. The contact pressure increases continuously with increasing temperature until it opens.

This is achieved in that the bimetal disc is fixed to the free end of a spring element, wherein the connection point between the spring element and bimetal disc is supported by a housing-fixed nose. In this way, the bimetal disc is under mechanical bias, which suppresses the creep phase.

This construction is on the one hand structurally complex, with a further disadvantage is that the bias of the bimetallic disc adversely affects the life, reproducibility and long-term stability of the switching temperature. Nevertheless, if the bimetallic disc has a larger creep phase, this would affect the function of the switch.

These problems associated with the creep behavior of a bimetallic element are in a current-dependent switch, as in the above-mentioned US 4,636,766 , of the US 4,389,630 or the EP 0 103 792 is described, solved in that the bimetallic spring tongue is provided with knockouts, the Stealth phase, although not complete, but suppress it to a large extent. These knockouts or other mechanical effects on the bimetallic element are complex and expensive measures, which also significantly reduces the life of these bimetallic elements. Another disadvantage of the required stamping is the fact that not only different material compositions and thicknesses but also different knockouts must be used for different performance classes and response temperatures.

Overall, therefore, in these switches in addition to the space required for the switching process itself, especially the complex and thus expensive switching device of disadvantage, which must also be designed individually for different types of switches in each case.

Another construction with a movable mating contact also shows the US 4,319,214 , The bimetallic switching mechanism comprises a mating contact mounted on a spring arm and a movable contact part mounted on a bimetallic arm. The bimetallic arm is either attached directly to the lower housing part or it is supported by a further bimetallic arm, which in turn is attached to the lower housing part. In any case, the bimetal is provided with an embossment for adjusting the defined snap point, wherein either the bimetallic arm itself or the other bimetallic arm is associated with an abutment about which pivots the corresponding bimetallic arm with temperature changes.

In the embodiment with the two bimetallic arms they are matched in their switching behavior and bend if necessary, increase the temperature around the counter-bearing, wherein the movable contact part is moved away from the mating contact, but which is adjusted as a result of the spring action of the spring arm. Upon reaching the switching temperature of the bimetallic arm snaps around the embossing and possibly the abutment, whereby the movable contact member is lifted from the mating contact, which is prevented by a stop it to follow the contact part even further.

In these two constructions, on the one hand, it is a disadvantage that the only limited creep phase of the bimetal arm must be exactly matched to the spring force of the spring arm and the spatial position of the stop, to prevent the spring arm reaches the stop during the creep phase , which would lead to an unwanted opening of the contacts before reaching the critical temperature.

To avoid this, the bimetallic arms must be additionally provided with the creep-limiting imprints, and also support approximately centrally on a counter-bearing, around which they bend accordingly.

By these measures, the bimetallic arms are exposed to strong mechanical loads, which also have a disadvantageous effect on the life, reproducibility and stability of the switching temperature. Because of tolerable within very narrow limits tolerances this switch is also expensive and expensive.

Another disadvantage is the wandering mating contact, which is not only structurally complex, but also because of the required stroke increases the height undesirable.

In the embodiment with the two bimetallic arms is also still a disadvantage that they must be exactly matched with respect to their temperature behavior as in the generic switch mentioned above, to set the switching temperature.

In all switches described so far from the prior art, the creep phase is therefore kept as low as possible, for which increasing or compensating pressure and additional embossing are used.

In this context is from the DE 21 21 802 C another temperature-dependent switch is known in which the derailleur comprises a spring washer which is supported in the closed state of the switch with its edge on a first terminal electrode and a centrally supported movable contact presses against a stationary counter-contact, which is provided at a second terminal electrode. The two terminal electrodes form in the known switch an encapsulated metallic housing and are electrically isolated from each other by an insulating.

About the movable contact a bimetallic snap disk is slipped, which is below its switching temperature loosely inside the known switch, so is exposed to no mechanical stress. The operating current of the device to be protected in this switch flows only through the spring washer, the bimetallic snap disk is not loaded by the operating current.

In this switch, the creep phase of the bimetallic snap disk affects much less than in the aforementioned switches, so that here relatively inexpensive switching elements are used, which also have a long life.

When the bimetallic snap-action disc is heated beyond its switching temperature, it suddenly jumps from its convex to a concave shape at the end of the creep phase, supporting itself with its edge on the lid of the housing and pressing against its center area against the force of the spring washer movable contact away from the mating contact, whereby the circuit is interrupted.

So that now can not flow through the bimetallic snap disk to the spring washer, an additional insulating washer is provided between bimetallic snap disk and lid of the housing, which prevents this unwanted current flow.

Although this switch is technically extremely reliable and has great economic success, it is constructively too complicated for certain applications. Depending on the switching temperature, convexity and thickness of the bimetallic snap disk, for example, always a specially tuned spring washer must be used, which is a total of consuming and expensive. Another disadvantage is seen in the additional insulation between bimetallic snap disk and lid of the switch.

Another disadvantage is in certain applications in that this switch is not current-dependent, since the bimetallic snap disk at no time performs the operating current. Now, however, it is well known to provide the switch with a series resistor through which the operating current flows and which heats up when the current flow is too high and brings the bimetal Schriappscheibe for jumping. These design variants are technically very reliable, but compared to the switch mentioned above, they have the disadvantage that the series resistor can not react as quickly and sensitively as the current-carrying bimetallic element of the aforementioned switch.

Against this background, it is an object of the present invention to provide a current-dependent switch of the type mentioned, in which with a cheap and simple construction high reliability and long life is achieved.

In the switch mentioned above, this object is achieved in that the switching element comprises a spring element whose force is largely independent of temperature, and the switching member has a temperature-dependent actuating force which is greater than the restoring force of the spring element in its creep phase, regardless of its geometry change in the creep phase, the switching element compared to the spring element is to be regarded as rigid, so that the contact pressure is exerted solely by the force of the spring element.

The object underlying the invention is completely solved in this way. The inventor of the present application has namely recognized that the from the DE 21 21 802 C known mechanical and electrical parallel arrangement of temperature-neutral spring element and switching element in an electrical and modified mechanical series circuit and can be used in the generic switch to unite a number of advantages in the thus created new switch.

The electrical series connection of the spring element and switching element results in a current-dependent switch, since the switching element, which is preferably a bimetallic element or a trimetal element, can heat up very quickly due to its low thermal mass at too high current flow or even at short current peaks , Due to the mechanical series connection, so the interaction of the spring force of the spring element with that of the switching element, beyond the creep phase of the switching element can be compensated. If the switching element changes its geometry during the slow phase, this is compensated directly by the spring element. This makes it possible for the first time, even with a so-called current-dependent switch to allow a large creep phase of the switching element, because the spring element can compensate for the "unwanted" changes in shape during the creep phase. However, this means that a simpler to produce and therefore cheaper switching device can be used, which also has a longer life, as can be dispensed with the pre-stamping and a larger hysteresis is allowed, so that the slow phase can be exploited to the maximum.

But this is not only low geometric demands on the switching element but also lower demands on the spring element to provide, because the latter must now only ensure that the switching element below its transition temperature, So during the slow phase, remains in electrical contact with one of the external terminals. Different types of switches in terms of power class and response temperature can now be designed with substantially the same spring element but different switching elements, which - as already mentioned - are to provide these components of the rear derailleur much lower geometric and mechanical conditions, so that they are generally easier and cheaper to produce ,

With respect to the life of the switching device here arise the same advantages as in accordance with the loosely inserted bimetallic snap disk DE 21 21 802 However, with a high current sensitivity is achieved. Overall, more importance can be placed on the electrical properties and the switching temperature in the new switch, the mechanical spring force of the switching device plays in the new switch for the first time in the art a minor role, it must only be so large that the switching element by the spring element not compressed too much. The switching process itself is effected after completion of the creep phase solely by the switching device, which is now always biased in its closed position. This biased switching device still has a whole series of other advantages, so it does not vibrate in the magnetic field and has no risk of arc, because gradually opening or closing contacts are prevented by the bias.

But this is only a very small pre-stamping of the bimetallic element required by the only still ensures the snap effect for the sudden contact separation must become. A stronger emphasis, as previously used to support or suppress the creep phase, is no longer necessary. As a result, the mechanical loads are reduced and thus significantly increases the service life and reliability and reproducibility of the switching point.

The temperature-neutral spring element exerts on the bimetallic element no more hindering its deformation pressure, it is similar in the creep phase, the deformation of the bimetallic element by their own deformation such that movable contact part and fixed mating contact with each other so securely in abutment that for a low contact resistance is ensured, the contact pressure remains below the switching temperature largely independent of the temperature constant.

The creep phase of the bimetallic element is therefore no longer suppressed as in the prior art, but balanced, so to speak, the bimetallic element can namely deform almost unhindered in the slow phase, the changes in geometry are compensated by the spring element so that the Switch remains securely closed.

For this purpose, the temperature-dependent actuating force of the bimetallic element is chosen so that it is greater than the largely temperature-independent actuating force of the spring element in the creep phase, which thus merely "leads" the thus "rigid" bimetallic element.

A big advantage of the new switch is its simple design, in addition to the housing-fixed mating contact is only one Bimetallic element required, the spring element is temperature-neutral and therefore inexpensive. Overall, bimetallic element and spring element must still be matched with respect to the rest of the force, but no longer also in terms of their temperature behavior, because the rear derailleur is, so to speak, self-sufficient. As a result, a standard spring element for all temperature ranges is possible, whereby a significant rationalization effect is achieved. By this construction, a low overall height is also feasible, with no new individual adaptation is required at different switching temperatures, only the bimetallic element must be designed with the same spring characteristics but other switching temperatures.

Another advantage is that tolerances and fluctuations in the switching temperature are compensated by the leadership by the temperature-neutral spring element.

In a further development, it is preferred if the spring element is connected at its first end to the first connection element and at its second end to the switching element, wherein preferably by the spring element, the switching element in its closed position with its free end against a connected to the second connection element Counter contact is pressed and lifts in its open position its free end of the mating contact, which is further preferably arranged switch fixed, wherein also preferably the switching member carries at its free end a movable contact part, which cooperates with the mating contact.

By these measures, individually and in combination initially a structurally very simple construction of the new switch is provided. Due to the fixed connection between switching element and spring element associated with the insertion of the loose bimetallic snap disc disadvantages are avoided. Another advantage is that no additional insulation is required; If the contact part has lifted from the mating contact, there is no danger of an unwanted current path. Another advantage is that the switching element is exposed in its open position no mechanical stress, which increases the long-term stability of the new switch. But this is also no support of the switching device on the lid, etc. required by eg support warts, so that a planar cover and / or bottom is possible, which was not the case with previous switches.

Further, it is preferred if the switching element and the spring element welded together or are firmly connected by crimping, preferably wherein the free end of the switching element and the first end of the spring element lie on the same side of the connection between the spring element and switching element.

This measure is structurally advantageous because during assembly switching element and spring element only need to be superimposed and then firmly connected at one end to each other by welding or flanging, before then the spring element is still to be connected to the first external terminal. All in all, therefore, only two automatable steps are required here to finalize the new switch once the individual components have been manufactured and supplied. Overall, this leads to a very inexpensive switch, since expensive assembly work can be avoided.

A further advantage of this construction is overall in the small space requirements, by the "folded back" arrangement of the mating contact with respect to the connection between the switching element and spring element are on the one hand small dimensions in the longitudinal direction required. But also transversely to the longitudinal direction, ie in "switching direction", only small dimensions are required. During the creep phase, the switching member tends to lift the movable contact part of the mating contact, which is compensated by lowering the connection point between the spring element and switching element. When the switch now snaps over, the joint moves even further towards the mating contact, while simultaneously moving the movable contact in the opposite direction. The path between the attachment point of the spring element to the first outer terminal and the mating contact is thus used twice, once for the compensating movement of the junction between the switching element and spring element during the slow phase of the switching element and the other to lift the movable contact part of the mating contact.

Overall, this design leads to a switch with very low height, which in total only very little material is required, which in turn contributes to a cheap switch.

Further, it is preferable that the first external terminal is connected to a terminal electrode to which the spring member is fixed at its first end, and when preferably the second external terminal is connected to a second terminal electrode and the switching mechanism is disposed between the first and second terminal electrodes ,

This measure leads to a very simple construction; namely, there are only two parallel to be arranged terminal electrodes, between which the switching mechanism is arranged, that the spring element is fixed with its first end to one terminal electrode, while the mating contact is provided on the other terminal electrode.

Overall, it is advantageous if switching element, spring element and both terminal electrodes are punched out of strip material.

These measures are advantageous in terms of strip production because these four basic components of the new switch can be used e.g. supplied via four different bands and automatically connected in the manner described above so that the new switch is formed. A great advantage lies in the fact that neither the switching element nor the spring element must be supplied as bulk material, which is always associated with known switches with great problems in known switches, since the bulk material must be separated and aligned before assembly. When punching the individual components from endless belts, these problems naturally no longer arise. As a result, a complete tape production is possible without additional assembly, wherein at the terminal electrodes any connection techniques can be realized, e.g. Crimp connection, plug connection, solder connection, etc. Such freedom of application in the manufacture of a temperature-dependent switch was previously unknown.

It is preferred if the first and the second terminal electrode are held by a Isolierstoffträger, wherein Preferably, the second terminal electrode is an integral part of an insulating housing lower part by encapsulation, which is closed by the first terminal electrode.

This measure is structurally of great advantage, because the four basic components of the new switch, namely switching element, spring element and the two terminal electrodes can be assembled into a so-called open as well as a closed switch, without the construction of the four components themselves must be changed.

Another advantage of the new switch is that the cover part formed by the first terminal electrode and the bottom part formed by the second terminal electrode may be planar, planar electrodes, which was not previously possible in the prior art. However, this not only leads to a very low height of the new switch, these flat surfaces also create a prerequisite for Substratbedruckung to realize pre- or parallel resistors can be given to the new switch more functions.

Further advantages will become apparent from the description and 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

einen Längsschnitt durch den neuen Schalter;

Fig. 2

eine Draufsicht auf den Schalter gemäß Fig. 1;

Fig. 3

ein zweites Ausführungsbeispiel des neuen Schalters in einer Ansicht wie Fig. 2;

Fig. 4

das Schaltwerk des Schalters aus Fig. 1 in einer schematisierten, vergrößerten Darstellung, wobei das Schaltorgan in Schließstellung ist;

Fig. 5

eine Darstellung wie Fig. 4, jedoch während der Schleichphase des Schaltorganes; und

Fig. 6

eine Darstellung wie Fig. 4, wobei das Schaltorgan jedoch in seiner Öffnungsstellung ist.

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

Fig. 1

a longitudinal section through the new switch;

Fig. 2

a plan view of the switch according to Fig. 1 ;

Fig. 3

a second embodiment of the new switch in a view like Fig. 2 ;

Fig. 4

the rear derailleur of the switch off Fig. 1 in a schematic, enlarged view, wherein the switching member is in the closed position;

Fig. 5

a representation like Fig. 4 but during the slow phase of the switching element; and

Fig. 6

a representation like Fig. 4 However, the switching element is in its open position.

In Fig. 1 is shown generally at 10 a new switch, which is shown in schematic longitudinal section.

The new switch 10 has a first outer terminal 11 which is integrally connected to a flat terminal electrode 12. Further, a second external terminal 14 is provided, which is formed integrally with a second terminal electrode 15. The two terminal electrodes 12, 15 are on a Isolierstoffträger Held 16, which holds the two terminal electrodes 12, 15 spaced parallel to each other.

While the Isolierstoffträger 16 can basically be open on the side, is in Fig. 1 an embodiment shown in which the Isolierstoffträger 16 comprises a cup-shaped housing lower part 17 which is formed around the second terminal electrode 15 around by molding or casting such that the second terminal electrode 15 is an integral part of the housing lower part 17. The lower housing part 17 is closed by the first terminal electrode 12, which acts for this purpose as a cover part and is held captive by a indicated at 18, hot-welded edge of the insulating substrate 16.

Between the two terminal electrodes 12, 15, a temperature-dependent switching mechanism 19 is arranged, which comprises a mechanical and electrical series connection of a spring element 21 and a switching member 22 which are interconnected by a connection indicated at 23. The switching member 22 is in this case a bimetallic element.

The spring element 21 in this case has a largely temperature-independent actuating force, which means in the context of the present invention that the actuating force or spring force of the spring element 21 does not change appreciably in the range of the permissible operating temperature of the switch 10. The force of the bimetallic element, however, is strongly temperature-dependent and even in the so-called slow phase so great that the spring element 21 can not exert the deformation of the bimetallic element disabling pressure on the constant temperature in this spring system thus rigid bimetallic element.

The spring element 21 is with its first end 25 in Fig. 1 attached to the right of the first terminal electrode 12 and leads with its second end 26 in the connection 23 to the switching member 22. The switching member 22 carries at its free end 27 a movable contact member 28 which cooperates with a switch-fixed mating contact 29, which at the second terminal electrode 15 is formed.

Between the first and the second terminal electrode 12, 15, a PTC element indicated at 31 is still provided, which is arranged electrically parallel to the switching mechanism 19.

In his in Fig. 1 shown closed position, the switching mechanism 19 establishes an electrically conductive connection between the two external terminals 11, 14 and thereby closes the PTC element 31 short. A current flowing through the switch 10 now passes from the first external terminal 11 in the first terminal electrode 12 and from there via the spring element 21 in the switching member 22, from which it exits via the movable contact member 28, via the mating contact 29 and the second terminal electrode 15 to get to the second external terminal 14. If either the temperature of the switch 10 or of the switching element 22 and / or the current flowing through the switching element 22 increases, then the switching element 22 moves into its opening position, which will be described later, in which it lifts the movable contact part 28 away from the mating contact 29 , As a result, the flow of current through the switching mechanism 19 is interrupted, so that now a residual current can flow through the PTC element 31. This residual current heats the PTC element 31 so far that the temperature in the switch 10 remains above the response temperature of the switching element 22. In other words, the PTC element ensures a self-holding the once opened switch 10th

In Fig. 2 is a top view of the switch off Fig. 1 shown here, in which case the first and the second external terminal 11, 14 not as in Fig. 1 among themselves but adjacent to each other are indicated. In Fig. 2 It can be seen that the edge 18 of the housing lower part 17, the first terminal electrode 12 completely surrounds, so that the switch 10 is completely encapsulated.

In Fig. 2 It can also be seen that both the spring element 21 and the switching member 22 are formed as elongated tongues which are arranged in the plan view with each other so that both the first end 25 of the spring element 21 and the free end 27 of the switching member 22 in Fig. 2 to the right of connection 23.

In Fig. 3 another switch 10 is shown which does not have the square outline Fig. 2 but has a round outline. Otherwise, the switch 10 corresponds Fig. 3 however, the construction as he is in Fig. 1 shown in longitudinal section, wherein the same design features are denoted by the same reference numerals. It should only be mentioned that the spring element 21 and the switching member 22 are each formed as an oval discs.

Apart from the PTC element 31, which of course can be omitted at any time, if no self-holding function is desired, the new switch 10 comprises four basic components, namely the two electrodes 12, 15 and the spring element 21 and the switching member 22. All four components can be punched out of strip material and merged for the purpose of automatic assembly. For this purpose, first the connection 23 by welding ( Fig. 1 ) or flanging ( FIGS. 4 to 6 ), whereupon the spring element 21 is then welded at its first end 25 to the connection electrode 12. Due to the V-shaped design of the switching mechanism thereby comes the free end 27 of the switching member 22 via the mating contact 29 to lie. It should be mentioned that, of course, can be dispensed with the movable contact member 28 that is provided by the contact member 28, however, for a better contact resistance to the mating contact 29.

The two terminal electrodes 12, 15 are then still attached to the insulating substrate 16, whereby it is possible to spray around the housing lower part 17 around the terminal electrode 15 and then hang the terminal electrode 12 with the rear derailleur 19 attached thereto from above and through a hot edge 18 to be pressed fasten.

In Fig. 4 is schematically the rear derailleur 19 from Fig. 1 shown in enlarged scale in its closed position. The switching element 22 is located so far below its critical temperature that its creep has not yet used. The switching member 22 presses against the force of the spring element 21, the compound 23 in Fig. 4 to the top, so that adjusts a distance indicated at 33 to the first terminal electrode 12 and a distance indicated at 34 to the mating contact 29.

If now increases the temperature of the switching element 22 due to an increased current flow or due to an increased outside temperature, so first begins the creep phase of the Switching member 22, in which its spring force acting against the force of the spring element 21 decreases, so that the connection 23 in Fig. 4 is moved down, as it is in Fig. 5 is shown. However, the force of the bimetallic element is still so great that the force of the spring element 21 is not sufficient to hinder the deformations occurring in the creep phase. Regardless of its geometry change in the slow phase, the switching element compared to the spring element 21 is to be regarded as rigid, the contact pressure is exerted solely by the force of the spring element.

The distance 33 increases as the distance 34 decreases. However, the mechanical series circuit of spring element 21 and switching element 22 still pushes the movable contact member 28 against the mating contact 29. In comparison between the FIGS. 4 and 5 However, it can be seen that the movable contact part 28 in Fig. 5 has moved transversely to the mating contact 29. This friction is desirable, because in this way the contact surfaces between contact part 28 and mating contact 29 are cleaned, so that the electrical contact resistance is very low.

Increases now the temperature of the switching element 22 on, so it snaps in the direction of arrow 35 in its open position, the in Fig. 6 is shown. The connection 23 has reached even further down, wherein the switching element 22 has lifted the movable contact part 28 from the mating contact 29. In comparison between the FIGS. 4 and 6 It can be seen that the connection 23 between the terminal electrodes 12, 15 moves downward, while the movable contact member 28 moves in the reverse direction upwards, so that the light Distance between the two terminal electrodes 12, 15, so to speak, twice exploited.

In the in Fig. 6 shown position, the spring element 21 prevents contact between the connection 23 and the connection electrode 15. Should it be necessary for reasons of elasticity, the spring element designed so that it is the connection 23 in Fig. 6 would urükken on the terminal electrode 15, it may be provided between connection 23 and terminal electrode 15, an insulating part, as in Fig. 1 indicated at 36. When in Fig. 1 the switching element 22 reaches its open position, the spring element 21 presses the connection 23 onto the insulating element 36, which thus prevents contact with the connection electrode 15.

Claims (15)

1. A switch having a first and at least a second external terminal (11, 14) as well as a temperature-dependent switching mechanism (19) that makes, as a function of its temperature, an electrically conductive connection between said two external terminals (11, 14) for a current to be conducted through said switch (10), whereby said switching mechanism (19) includes a switching member (22) changing its geometrical shape between a closed position and an open position as a function of temperature, said switching mechanism in said closed position conducting said current flowing through said switch (10), said switching mechanism further comprising an actuating member permanently connected electrically and mechanically in series with said switching member (22),
   characterized in that said actuating member (19) comprises a spring element (21) having a largely temperature-independent displacing force and that said switching member (22) has a temperature-dependent displacing force which in said switching mechanism's creeping phase is greater than said displacing force of said spring element (21), whereby irrespective of its geometrical change in the creep phase the switching member (22) may be regarded as rigid by comparison with the spring element (21), such that contact pressure is exerted solely by the displacing force of the spring element (21).
2. The switch of claim 1, characterized in that the switching member (22) comprises a bimetallic element.
3. The switch of claim 1, characterized in that the switching member (22) comprises a trimetallic element.
4. The switch of anyone of claims 1 through 3, characterized in that the spring element (21) is joined at its first end (25) to said first external terminal (11) and at said second end (26) to the switching member (22).
5. The switch of claim 4, characterized in that in its closed position the switching member (22) is pressed with its free end (27), by said spring element (21), against a counter-contact (29) connected to said second external terminal (14), and, in its open position, said free end (27) lifts off from said counter-contact (29).
6. The switch of claim 5, characterized in that the counter-contact (29) is fixed immovable with respect to the switch.
7. The switch of claim 5 or 6, characterized in that the switching member (22) at its free end (27) carries a movable contact element (28) which co-acts with the counter-contact (29).
8. The switch of anyone of claims 1 through 7, characterized in that the switching member (22) and the spring element (21) are welded to one another.
9. The switch of anyone of claims 1 through 7, characterized in that the switching member (22) and the spring element (21) are joined permanently to one another, preferably by crimping.
10. The switch of anyone of claims 5 through 9, characterized in that the free end (27) of the switching member (22) and the first end (25) of the spring element (21) lie on the same side of the connection (23) between said spring element (21) and said switching element (23).
11. The switch of anyone of claims 1 through 10, characterized in that said first external terminal (11) is joined to a connection electrode (12) to which the spring element (21) is attached with its first end (25).
12. The switch of anyone of claims 1 through 11, characterized in that the second external terminal (14) is joined to a second connection electrode (15) and that the switching mechanism (19) is arranged between the first and second connection electrode (12, 15).
13. The switch of claims 11 and 12, characterized in that the second connection electrode (15) is an integral part, by injection-embedding, of an insulating lower housing part (17) which is closed off by the first connection electrode (12).
14. The switch of claims 11 and 12, characterized in that the first and the second connection electrode (12, 15) are held by an insulating support (16).
15. The switch of anyone of claims 11 through 14, characterized in that the switching member (22), the spring element (21) as well as both connection electrodes (12, 15) are stamped out from strip material.

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