WO2023227248A1

WO2023227248A1 - Overvoltage protection device with improved integrated overtemperature protection

Info

Publication number: WO2023227248A1
Application number: PCT/EP2023/025246
Authority: WO
Inventors: Robert IEREB; Simon ZEMAN
Original assignee: Eaton Intelligent Power Limited
Priority date: 2022-05-26
Filing date: 2023-05-25
Publication date: 2023-11-30
Also published as: GB202207786D0; GB2619066A

Abstract

An overvoltage protection device with integrated overtemperature protection (1 a..1 f) is disclosed, which comprises a housing (2), a varistor (3) arranged in the housing (2), a thermosensitive contact breaker (4, 4a..4f), which is arranged in the housing (2) and which is electrically connected in series with the varistor (3), and two terminals (5, 6) protruding through the housing (2), which are electrically connected to the series connection of the varistor (3) and the thermosensitive contact breaker (4, 4a..4f). The thermosensitive contact breaker (4, 4a..4f) is embodied as a bimetal contact breaker.

Description

Overvoltage protection device with improved integrated overtemperature protection

TECHNICAL FIELD

The invention relates to an overvoltage protection device with integrated overtemperature protection, wherein the overvoltage protection device comprises a housing, a varistor arranged in the housing, a thermosensitive contact breaker, which is arranged in the housing and which is electrically connected in series with the varistor, and two terminals protruding through the housing, which are electrically connected to the series connection of the varistor and the thermosensitive contact breaker.

BACKGROUND ART

Devices of the above kind are generally known in prior art. Unfortunately, the varistor degrades due to aging and due to the count of overvoltage protecting events over time and its leakage current and hence the power loss then increases. Overheating of the varistor caused by a leakage current flowing for a particular time duration may occur, which is not only dangerous for the varistor as such but also for other devices in the vicinity which may catch fire. Accordingly, current flow is interrupted by the thermosensitive contact breaker what protects the device varistor from overtemperature and hence also avoids danger for other devices in the vicinity of the varistor. In prior art, the thermosensitive contact breaker comprises two contacts which are soldered to each other. One of them is spring loaded by a helical spring and forced away from the other contact. Once the heat generated by the varistor liquefies the solder joint, the spring pulls apart the contact pair and cuts off the current. One drawback of such solutions is that the temperature when the thermosensitive contact breaker opens is not defined very well or needs considerable design effort to define it. Moreover, the known mechanism is comparably complex because of the need for a spring.

DISCLOSURE OF INVENTION

Accordingly, an object of the invention is the provision of an improved overvoltage protection device with integrated overtemperature protection. In particular, a simple solution shall be provided, which cuts off the current at a defined temperature without causing much design effort.

The object of the invention is solved by an overvoltage protection device with integrated overtemperature protection, wherein the thermosensitive contact breaker is embodied as a bimetal contact breaker.

In particular, the bimetal contact breaker may comprise a fixed contact, a bimetal bar with a fixed end and movable end and a movable contact formed by or attached to the movable end of the bimetal bar.

The type of bimetal element or bimetal bar well defines the temperature threshold where the thermosensitive contact breaker opens the current path and therefore cuts off the varistor from power. Moreover, the bimetal bar generates an opening force without other means and particularly without the use of a spring. Accordingly, the proposed overvoltage protection device with integrated overtemperature protection is less complex than known devices and provides a more reliable switching point at the same time. Also the design of the proposed overvoltage and overtemperature protection device is less complex.

In one embodiment, the bimetal bar can also trigger additional functions, for example optical, mechanical, or electrical remote and local signaling. For example, the bimetal bar can actuate a switch which turns on a signaling LED or turns on a signaling line to a superordinate control.

Further advantageous embodiments are disclosed in the claims and in the description as well as in the figures.

Advantageously, the varistor comprises a contact tab, which forms the fixed contact of the bimetal contact breaker or which the fixed contact or the fixed end of the bimetal bar is mounted to. By these measures a very good heat conduction from the varistor to the bimetal bar can be provided and thus a reliable function of the bimetal contact breaker can be achieved.

Advantageously, the fixed contact is soldered to the movable contact in the original cold state of the overvoltage protection device with integrated overtemperature protection. In this way, fast operation of the bimetal contact breaker is provided or supported because the contact pair of the bimetal contact breaker is kept close for a long time by the non-liquefied solder joint. During heat up of the bimetal bar, bending stress is generated in the same without a factual shape change. Once the temperature of the solder joint reaches a critical point, the same liquefies and causes a discharge of the bending stress within the bimetal bar and a sudden shape change and movement of its movable end. In turn, the bimetal contact breaker operates very fast, and a necessary distance between the fixed contact and the movable contact is obtained very fast as well. The properties of the solder joint, in particular its melting point, influence the temperature threshold when the bimetal contact breaker opens. In turn, said temperature threshold can be set by choosing a suitable solder material.

In another advantageous embodiment, the fixed end of the bimetal bar is welded to one of the terminals if the fixed contact is formed by the contact tab or if the fixed contact is mounted to the contact tab or is welded to a contact tab of the varistor.

In this way, unintentional separation from the bimetal bar from the terminal can be avoided when the bimetal bar is heated up. Similarly, the fixed end of the bimetal bar can be welded to a contact tab of the varistor and the fixed contact can be arranged on or formed by the terminal. If the fixed end of the bimetal bar is welded to a contact tab of the varistor, in particular a very good heat conduction from the varistor to the bimetal bar can be provided and thus a reliable function of the bimetal contact breaker can be achieved.

Beneficially, the overvoltage protection device with integrated overtemperature protection comprises a spark gap, which is arranged in the housing and which is electrically connected in series with the varistor and the thermosensitive contact breaker or in parallel with the varistor. The varistor is a voltage limiting element, whereas the spark gap is a voltage switching element. So, multiple functions can be integrated into an overvoltage protection device with integrated overtemperature protection by the proposed measures.

Advantageously, the spark gap comprises a contact tab, which forms the fixed contact or which the fixed contact of the bimetal contact breaker or the fixed end of the bimetal bar is mounted to or a parallel connection of the varistor and the spark gap comprises a common contact tab, which forms the fixed contact of the bimetal contact breaker or which the fixed contact or the fixed end of the bimetal bar is mounted to.

In particular in case of the common contact tab, by the propopsed measures a very good heat conduction from the varistor to the bimetal bar can be provided and thus a reliable function of the bimetal contact breaker can be achieved.

In one embodiment, the fixed end of the bimetal bar can be welded to a contact tab of the spark gap or to a common contact tab of the varistor and the spark gap if the same are connected in parallel. However, the function of the bimetal contact breaker is the same as already disclosed.

Advantageously, the bimetal bar can be preloaded, in particular bent, wherein the movable end of the bimetal bar is forced away from the fixed contact in the original cold state of the overvoltage protection device with integrated overtemperature protection. In other words, the bimetal bar in its cold state has a curved shape, wherein the movable end points away from the fixed contact. In one embodiment, during manufacturing of the overvoltage protection device with integrated overtemperature protection, the movable end of the bimetal bar is forced to the fixed contact, and the fixed contact is soldered to the movable contact. Once the solder solidifies, the bimetal bar is held in its preloaded position. Alternatively, it is also possible to first solder the fixed contact to the movable contact, to bend the bimetal bar and then to weld the fixed end of the bimetal bar to one of the terminals or to a contact tab of the varistor depending on where the movable contact is located. In yet another embodiment, the fixed contact is soldered to the the movable contact and the fixed end of the bimetal bar is welded to one of the terminals or to a contact tab of the varistor depending on where the movable contact is located in a first step. In a subsequent step, when the arrangement comprising the varistor and the bimetal contact breaker is built into the housing, the bimetal bar is bent by a part of the housing. By all these measures a fast opening of the bimetal contact breaker is further supported.

In another advantageous embodiment of the overvoltage protection device with integrated overtemperature protection, the same comprises an optical indicator, which is movably arranged at an opening or window of the housing, which is mechanically coupled to the movable end of the bimetal bar and which is caused to be moved from a first position indicating the on state of the bimetal contact breaker to a second position indicating the off state of the bimetal contact breaker by the bimetal bar when the bimetal contact breaker opens.

In this way, the operational state of the overvoltage protection device with integrated overtemperature protection can easily be checked from outside. The optical indicator may comprise symbols or colors on its surface. For example, the optical indicator may be colored green in a region, which is visible through an opening or window in the housing in the first position of the optical indicator, and may be colored red in a region, which is visible through said opening or window in the second position of the optical indicator.

Advantageously, the overvoltage protection device with integrated overtemperature protection can comprise a latching element, which holds the bimetal bar in its open position once the bimetal contact breaker opens. In this embodiment the bimetal bar can move from its closed position to its open position when it is heated, but it cannot move back when it cools down again. The latching element in particular may be made of an elastic material like elastic plastic or may be spring loaded.

In yet another advantageous embodiment, the overvoltage protection device with integrated overtemperature protection can comprise a blocking element made of an electrical insulator which is moved between the fixed contact and the movable contact when the bimetal contact breaker opens. For example, the blocking element can be spring loaded and can be forced between the fixed contact and the movable contact. On the one hand, a blocking element increases the creepage distance between the fixed contact and the movable contact, on the other hand, the blocking element impedes reclosing of the bimetal contact breaker. So, the blocking element provides a double function.

Beneficially, the blocking element can keep the bimetal contact breaker open even when the bimetal bar cools down again after opening. In this way, the bimetal contact breaker safely is kept open. Manual intervention to move the blocking element to its original position can be allowed. Then, the blocking element keeps the bimetal contact breaker open even when the bimetal bar cools down again after opening until manual intervention from outside. Generally, the varistor should not be operated any longer once the leakage current reaches a particular threshold level. However, in exceptional cases, the overvoltage protection device with integrated overtemperature protection can be put in operational state again by the proposed measures until a replacement is at hands. If no manual intervention is allowed or possible, one may also say that the blocking element is “irreversibly” moved between the fixed contact and the movable contact when the bimetal contact breaker opens. It is also to be noted that manual intervention, which is not intended by design, like disassembling or destroying the housing of the overvoltage protection device with integrated overtemperature protection, is not considered as manual intervention in the aforementioned sense.

Beneficially, the blocking element can comprise an optical indicator and form a combined blocking and indicator element, which is movably arranged at an opening or window of the housing, which is mechanically coupled to the movable end of the bimetal bar and which is caused to be moved from a first position indicating the on state of the bimetal contact breaker to a second position indicating the off state of the bimetal contact breaker by the bimetal bar when the bimetal contact breaker opens. In this way, again the operational state of the overvoltage protection device with integrated overtemperature protection can easily be checked from outside. The optical indicator again may comprise symbols or colors on its surface. For example, the optical indicator may be colored green in a region, which is visible through an opening or window in the housing in the first position of the combined blocking and indicator element, and may be colored red in a region, which is visible through said opening or window in the second position of the combined blocking and indicator element.

BRIEF DESCRIPTION OF DRAWINGS

The invention now is described in more detail hereinafter with reference to particular embodiments, which the invention however is not limited to.

Fig. 1 shows an oblique view of a first example of an overvoltage protection device with integrated overtemperature protection in its operational state; Fig. 2 shows the overvoltage protection device with integrated overtemperature protection of Fig. 1 in its defective state;

Fig. 3 shows an oblique view of an overvoltage protection device with integrated overtemperature protection with optical indicator in its operational state;

Fig. 4 shows the overvoltage protection device with integrated overtemperature protection of Fig. 3 in its defective state;

Fig. 5 shows an oblique view of an overvoltage protection device with integrated overtemperature protection with a latching element in its operational state;

Fig. 6 shows the overvoltage protection device with integrated overtemperature protection of Fig. 5 in its defective state;

Fig. 7 shows an oblique view of an overvoltage protection device with integrated overtemperature protection with a shiftable blocking element in its operational state;

Fig. 8 shows the overvoltage protection device with integrated overtemperature protection of Fig. 7 in its defective state;

Fig. 9 shows an oblique view of an overvoltage protection device with integrated overtemperature protection with a rotating blocking element in its operational state;

Fig. 10 shows the overvoltage protection device with integrated overtemperature protection of Fig. 9 in its defective state;

Fig. 11 shows a detailed view of an embodiment based on Figs. 9 and 10 and

Fig. 12 shows a circuit diagram of an embodiment with a spark gap.

DETAILED DESCRIPTION

Generally, same parts or similar parts are denoted with the same/similar names and reference signs. The features disclosed in the description apply to parts with the same/similar names respectively reference signs. Indicating the orientation and relative position is related to the associated figure, and indication of the orientation and/or relative position has to be amended in different figures accordingly as the case may be.

Figs. 1 and 2 show a first example of an overvoltage protection device with integrated overtemperature protection 1a, Fig. 1 in the original cold state ready for operation and Fig. 2 in defective state. The overvoltage protection device with integrated overtemperature protection 1a comprises a housing 2, a varistor 3 arranged in the housing 2, a thermosensitive contact breaker 4a, which is arranged in the housing 2 and which is electrically connected in series with the varistor 3, and two terminals 5, 6 protruding through the housing 2, which are electrically connected to the series connection of the varistor 3 and the thermosensitive contact breaker 4a.

The thermosensitive contact breaker 4a is embodied as a bimetal contact breaker and comprises a fixed contact 7, a bimetal bar 8a with a fixed end E1 and movable end E2 and a movable contact 9 formed by or attached to the movable end E2 of the bimetal bar 8a.

The varistor 3 is held in position in the housing 2 with optional holders 10, 11. The varistor 3 comprises two contact tabs, wherein the upper right contact tab at the same time forms the fixed contact 7 of the thermosensitive contact breaker 4a and wherein the lower left contact tab 12 is electrically connected to the terminal 6. It should be noted that the upper right contact tab does not necessarily form the fixed contact 7 but the fixed contact 7 can also be embodied as a separate part, which is electrically connected to the upper right contact tab of the varistor 3.

If the varistor 3 degrades due to aging and due to the count of overvoltage protecting events, its leakage current and hence the power loss increases. The leakage current heats up the varistor 3 and in turn also the bimetal bar 8a of the thermosensitive contact breaker 4a, e.g. by thermal radiation and/or thermal conductivity. Accordingly, the bimetal bar 8a bends and lifts the movable contact 9 from the fixed contact 7, i.e. it opens the contact pair. In turn, the current flow is interrupted and the device 1a is protected from overtemperature.

In an advantageous embodiment of the overvoltage protection device with integrated overtemperature protection 1a, the fixed contact 7 can be soldered to the movable contact 9 in the original cold state of the overvoltage protection device with integrated overtemperature protection 1a. In this way, fast operation of the bimetal contact breaker 4a is provided or supported because the contact pair of the same is kept close for a long time by the non-liquefied solder joint. So, during heat up of the bimetal bar 8a, bending stress is generated in the same without a factual shape change. Once the temperature of the solder joint reaches a critical point, the same liquefies and causes a discharge of the bending stress within the bimetal bar 8a and a sudden shape change and movement of its movable end E2. In turn, the bimetal contact breaker 4a operates very fast, and a necessary distance between the fixed contact 7 and the movable contact 9 is obtained very fast as well.

In this context, it is also of advantage if the fixed end E1 of the bimetal bar 8a is welded to the terminal 5. In this way, unintentional separation from the bimetal bar 8a from the terminal 5 can be avoided when the bimetal bar 8 is heated up. Of course, roles can change, and the fixed end E1 of the bimetal bar 8a can be welded to the contact tab of the varistor 3, and the fixed contact 7 can be arranged on or formed by the terminal 5. In one embodiment, the movable contact 9 is soldered to the fixed contact 7 on the terminal 5, in another embodiment it is not.

To provide or support a fast opening movement of the bimetal bar 8a, the same can be preloaded, in particular bent, wherein the movable end E2 of the bimetal bar 8a is forced away from the fixed contact 7 in the original cold state of the overvoltage protection device with integrated overtemperature protection 1a. In other words, the bimetal bar 8a of Fig. 1 in its cold state has a curved shape, wherein the movable end E2 points away from the fixed contact 7. In one embodiment, during manufacturing of the overvoltage protection device with integrated overtemperature protection 1a, the movable end E2 of the bimetal bar 8a is forced to the fixed contact 7, and the fixed contact 7 is soldered to the movable contact 9. Once the solder solidifies, the bimetal bar 8a is held in its preloaded position. Alternatively, it is also possible to first solder the fixed contact 7 to the movable contact 9, to bend the bimetal bar 8a and then to weld the fixed end E1 of the bimetal bar 8a to the terminal 5. In yet another embodiment, the fixed contact 7 is soldered to the the movable contact 9 and the fixed end E1 of the bimetal bar 8a is welded to the terminal 5 in a first step. In a subsequent step, when the arrangement comprising the varistor 3 and the bimetal contact breaker 4a is built into the housing 2, the bimetal bar 8a is bent by a part of the housing 8a.

Figs. 3 and 4 show a further embodiment of an overvoltage protection device with integrated overtemperature protection 1 b, which is similar to the overvoltage protection device with integrated overtemperature protection 1a of Figs. 1 and 2. Again, Fig. 3 shows the overvoltage protection device with integrated overtemperature protection 1 b in the original cold state ready for operation and Fig. 4 in its defective state. In contrast to the embodiment of Figs. 1 and 2, the overvoltage protection device with integrated overtemperature protection 1b comprises an opening or window 13 in its housing 2, and further on the overvoltage protection device with integrated overtemperature protection 1b comprises an optical indicator 14a. The optical indicator 14a is movably arranged at the opening or window 13 and is mechanically coupled to the movable end E2 of the bimetal bar 8b. The optical indicator 14a is caused to be moved from a first position indicating the on state of the bimetal contact breaker 4b (see Fig. 3) to a second position indicating the off state of the bimetal contact breaker 4b (see Fig. 4) by the bimetal bar 8b when the bimetal contact breaker 4b opens. The optical indicator 14a may comprise symbols or colors on its top surface. For example, the optical indicator may be colored green in a region, which is visible through the opening 13 in the first position of the optical indicator 14a, and may be colored red in a region, which is visible through the opening 13 in the second position of the optical indicator 14a. In this way, the operational state of the overvoltage protection device with integrated overtemperature protection 1 b can easily be checked from outside. It should be noted at this point that the housing 2 of the overvoltage protection device with integrated overtemperature protection 1a may comprise an opening 13 for checking the position of the bimetal bar 8a as well.

Figs. 5 and 6 show yet another embodiment of an overvoltage protection device with integrated overtemperature protection 1c, which is similar to the overvoltage protection device with integrated overtemperature protection 1a of Figs. 1 and 2. Again, Fig. 5 shows the overvoltage protection device with integrated overtemperature protection 1c in the original cold state ready for operation and Fig. 6 in its defective state. In contrast to the embodiment of Figs. 1 and 2, the overvoltage protection device with integrated overtemperature protection 1c comprises an opening or window 13 in its housing 2, and further on the overvoltage protection device with integrated overtemperature protection 1c comprises a latching element 15, which holds the bimetal bar 8c in its open position once the bimetal contact breaker 4c opens. In this embodiment the bimetal bar 8c can move from its closed position (Fig.5) to its open position (Fig. 6) when it is heated, but it cannot move back when it cools down again. This is achieved by the special shape of the movable end E2 of the bimetal bar 8c and the shape of the latching element 15. To further support the intended function, the latching element 15 may be made of an elastic material like elastic plastic or may be spring loaded. In the latter case, the latching element 15 in the given embodiment may move vertically but is pressed downwards by a spring. However, one easily understands, that the embodiment shown in Fig. 5 and 6 is not the only possible, and variations in the given context are possible.

Figs. 7 and 8 show yet another embodiment of an overvoltage protection device with integrated overtemperature protection 1 d, which is similar to the overvoltage protection device with integrated overtemperature protection 1a of Figs. 1 and 2. Again, Fig. 7 shows the overvoltage protection device with integrated overtemperature protection 1d in the original cold state ready for operation and Fig. 8 in its defective state. In contrast to the embodiment of Figs. 1 and 2, the overvoltage protection device with integrated overtemperature protection 1d again comprises an opening or window 13 in its housing 2. In addition, the overvoltage protection device with integrated overtemperature protection 1d comprises a blocking element 16a made of an electrical insulator, which is moved between the fixed contact 7 and the movable contact 9 when the bimetal contact breaker 4d opens. In this embodiment, the blocking element 16a is spring loaded and forced between the fixed contact 7 and the movable contact 9 by the spring 17, which is connected to the blocking element 16a via the connecting strip 18. When the bimetal contact breaker 4d opens, the blocking element 16a is pulled between the fixed contact 7 and the movable contact 9 and impedes reclosing of the bimetal contact breaker 4d.

In the given example, the blocking element 16a keeps the bimetal contact breaker 4d open even when the bimetal bar 8 cools down again after opening. Moreover, no manual intervention to unlock the overvoltage protection device with integrated overtemperature protection 1d is rendered possible in this embodiment. Accordingly, the blocking element 16a is “irreversibly” moved between the fixed contact 7 and the movable contact 9 when the bimetal contact breaker 4d opens.

Generally, the varistor 3 should not be operated any longer once the leakage current reaches a particular threshold level. However, in exceptional cases it could be useful to put the overvoltage protection device with integrated overtemperature protection 4d in operational state again until a replacement is at hands. For this reason, manual intervention to move the blocking element 16a to its original position can be allowed. For example, an additional opening can be provided on the right side of the housing 2 so that one can move the blocking element 16a upwards by external means, e.g. by use of a screwdriver.

It should be noted that the arrangement of the spring 17 and the use of the connecting strip 18 is not mandatory, but the spring 17 can also directly be mounted to the blocking element 16a and can be built into the housing 3 vertically.

In the embodiment of Figs. 7 and 8, the blocking element 16a has a double function. It not only impedes reclosing of the bimetal contact breaker 4d but it also indicates the switching state of the bimetal contact breaker 4d. For example, the blocking element 16a can be colored green on its top surface, so that a defective state of the overvoltage protection device with integrated overtemperature protection 1d is easily visible from outside when the blocking element 16a moves away from the opening 13. A blocking element 16a with an optical indication can also be considered as a combined blocking and indicator element.

Figs. 9 and 10 show a further embodiment of an overvoltage protection device with integrated overtemperature protection 1 e, which is similar to the overvoltage protection device with integrated overtemperature protection 1d of Figs. 7 and 8. Again, Fig. 9 shows the overvoltage protection device with integrated overtemperature protection 1e in the original cold state ready for operation and Fig. 10 in its defective state. In contrast to the embodiment of Figs. 7 and 8, the blocking element 16b made of an electrical insulator is shaped and operated differently. In detail, the blocking element 16b may swivel around an axle 19 and does not necessarily need a spring for its movement. Instead, the movable end E2 causes the blocking element 16b to be turned when the bimetal contact breaker 4e opens. In turn, a blocking part of the blocking element 16b is moved between the fixed contact 7 and the movable contact 9. Hence the bimetal contact breaker 4e cannot reclose again.

Fig. 11 shows a detailed view of a preferred embodiment. Here, the bimetal bar 8f comprises a notch 20 and the blocking element 16c comprises a nose 21 . When the bimetal contact breaker 4e opens, the nose 21 engages with the notch 20 and impedes a back rotation of the blocking element 16c and thus a reclosing of the bimetal contact breaker 4f. Fig. 11 in detail also shows an optical indicator 14c on the top of the blocking element 16c. Similar to other optical indicators disclosed before, the optical indicator 14c may comprise symbols and/or colors on its top side, which indicate the operational state of the overvoltage protection device with integrated overtemperature protection 1f through the window 13. Again, the blocking element 16c forms a combined blocking and indicator element.

Fig. 12 finally shows a circuit diagram of yet another overvoltage protection device with integrated overtemperature protection, which in addition comprises a spark gap 22, which is electrically connected in series with the varistor 3 and the thermosensitive contact breaker 4. The spark gap 22 may be built into any of the embodiments shown in Figs. 1 to 11 . One option is to weld the fixed end E1 of the bimetal bar 8a..8f to a contact tab of the spark gap 22. Whereas the varistor 3 is a voltage limiting element, the spark gap 22 is a voltage switching element. So, multiple functions can be integrated into an overvoltage protection device with integrated overtemperature protection 1 a..1 f. In Fig. 12, the spark gap 22 is electrically connected in series with the varistor 3. However, it may also be electrically connected in parallel with the varistor 3. In this case, one option is to weld the fixed end E1 of the bimetal bar 8a..8f to a common contact tab of the varistor 3 and the spark gap 22.

It should be noted that although it is not necessary to do so, the fixed contact 7 of the embodiments shown in Figs 3 to 11 like in the embodiment of Figs. 1 and 2 can optionally be soldered to the movable contact 9, 9f. Generally, it is of advantage to arrange the thermosensitive contact breaker 4 and in particular its bimetal bar 8a..8f close to the varistor 3 so that the latter heats the bimetal bar 8a..8f by thermal radiation and/or thermal conductivity. Hence it is also of advantage, if the fixed contact 7 or the fixed end E2 of the bimetal bar 8a..8f is arranged on a contact tab 12 of the varistor 3 or if a contact tab of the varistor 3 even forms the fixed contact 7 like this is the case in the examples disclosed in the Figs 1 to 11.

In case of a parallel connection of the varistor 3 and the spark gap 22, it is also of advantage to mount the fixed contact 7 or the fixed end E1 of the bimetal bar 8a..8f to a common contact tab of said parallel connection. It is also of advantage if said common contact tab even forms the fixed contact 7. In both ways, a good thermal conductivity between the varistor 3 and the bimetal bar 8a..8f can be provided as well. Alternatively, in case of a serial connection of the the varistor 3 and the spark gap 22, the fixed contact 7 or the fixed end E1 of the bimetal bar 8a..8f can be mounted to a contact tab of the spark gap 22, or the contact tab can also form the fixed contact 7.

One should also note that the overvoltage protection devices with integrated overtemperature protection 1 a..1 f in Figs. 1 to 11 are shown with an open housing 2 to allow an understanding of the function. However, in reality, the housings 2 of the overvoltage protection devices with integrated overtemperature protection 1 a..1 f usually is closed and can even be sealed.

It is noted that the invention is not limited to the embodiments disclosed hereinbefore, but combinations of the different variants are possible. In reality, the overtemperature protection device 1 a..1 f may have more or less parts than shown in the figures. Moreover, the description may comprise subject matter of further independent inventions.

It should also be noted that the term "comprising" does not exclude other elements and the use of articles "a" or "an" does not exclude a plurality. Also elements described in association with different embodiments may be combined. It should also be noted that reference signs in the claims should not be construed as limiting the scope of the claims. LIST OF REFERENCE NUMERALS

1 a..1 f overvoltage protection device with integrated overtemperature protection

2 housing

3 varistor

4, 4a..4f thermosensitive contact breaker I bimetal contact breaker

5, 6 terminal

7 fixed contact

8a..8f bimetal bar

9, 9f movable contact

10, 11 holder

12 contact tab of the varistor

13 opening / window

14a..14c optical indicator

15 latching element

16a. ,16c blocking element I combined blocking and indicator element

17 spring

18 connecting strip

19 axle

20 notch

21 nose

22 spark gap

E1 fixed end of bimetallic bar

E2 movable end of bimetallic bar

Claims

1 . Overvoltage protection device with integrated overtemperature protection (1 a..1f), comprising a housing (2), a varistor (3) arranged in the housing (2), a thermosensitive contact breaker (4, 4a..4f), which is arranged in the housing (2) and which is electrically connected in series with the varistor (3), and two terminals (5, 6) protruding through the housing (2), which are electrically connected to the series connection of the varistor (3) and the thermosensitive contact breaker (4, 4a..4f), characterized in that the thermosensitive contact breaker (4, 4a..4f) is embodied as a bimetal contact breaker.

2. Overvoltage protection device with integrated overtemperature protection (1a..1f) as claimed in claim 1 , characterized in that the bimetal contact breaker (4, 4a..4f) comprises a fixed contact (7), a bimetal bar (8a..8f) with a fixed end (E1 ) and movable end (E2) and a movable contact (9, 9f) formed by or attached to the movable end (E2) of the bimetal bar (8a..8f).

3. Overvoltage protection device with integrated overtemperature protection (1 a..1f) as claimed in claim 2, characterized in that the varistor (3) comprises a contact tab (12), which forms the fixed contact (7) or which the fixed contact (7) or the fixed end (E1 ) of the bimetal bar (8a..8f) is mounted to.

4. Overvoltage protection device with integrated overtemperature protection (1 a..1f) as claimed in claim 2 or 3, characterized in that the fixed contact (7) is soldered to the movable contact (9, 9f) in the original cold state of the overvoltage protection device with integrated overtemperature protection (1 a..1 f).

5. Overvoltage protection device with integrated overtemperature protection (1 a..1f) as claimed in claim 3 or 4, characterized in that fixed end (E1 ) of the bimetal bar (8a..8f) is welded to one of the terminals (5, 6) if the fixed contact (7) is formed by the contact tab (12) or if the fixed contact (7) is mounted to the contact tab (12) or is welded to a contact tab (12) of the varistor (3).

6. Overvoltage protection device with integrated overtemperature protection (1 a..1f) as claimed in any one of claims 1 to 5, characterized in a spark gap (22), which is arranged in the housing (2) and which is electrically connected in series with the varistor (3) and the thermosensitive contact breaker (4, 4a..4f) or in parallel with the varistor (3).

7. Overvoltage protection device with integrated overtemperature protection (1 a..1f) as claimed in claim 6, characterized in that the spark gap (22) comprises a contact tab, which forms the fixed contact (7) or which the fixed contact (7) or the fixed end (E1 ) of the bimetal bar (8a..8f) is mounted to or a parallel connection of the varistor (3) and the spark gap (22) comprises a common contact tab, which forms the fixed contact (7) or which the fixed contact (7) or the fixed end (E1 ) of the bimetal bar (8a..8f) is mounted to.

8. Overvoltage protection device with integrated overtemperature protection (1 a..1f) as claimed in any one of claims 2 to 7, characterized in that the bimetal bar (8a..8f) is preloaded, in particular bent, wherein the movable end (E2) is forced away from the fixed contact (7) in the original cold state of the overvoltage protection device with integrated overtemperature protection (1 a..1 f).

9. Overvoltage protection device with integrated overtemperature protection (1 a..1f) as claimed in any one of claims 2 to 8, characterized in an optical indicator (14a..14c), which is movably arranged at an opening or window (13) of the housing (2), which is mechanically coupled to the movable end (E2) of the bimetal bar (8a..8f) and which is caused to be moved from a first position indicating the on state of the bimetal contact breaker (4, 4a..4f) to a second position indicating the off state of the bimetal contact breaker (4, 4a..4f) by the bimetal bar (8a..8f) when the bimetal contact breaker (4, 4a..4f) opens.

10. Overvoltage protection device with integrated overtemperature protection (1 a..1f) as claimed in any one of claims 1 to 9, characterized in a latching element (15) which holds the bimetal bar (8a..8f) in its open position once the bimetal contact breaker (4, 4a..4f) opens.

11 . Overvoltage protection device with integrated overtemperature protection (1 a..1f) as claimed in any one of claims 1 to 10, characterized in a blocking element (16a..16c) made of an electrical insulator which is moved between the fixed contact (7) and the movable contact (9, 9f) when the bimetal contact breaker (4, 4a..4f) opens.

12. Overvoltage protection device with integrated overtemperature protection (1 a..1f) as claimed in claim 11 , characterized in that the blocking element (16a..16c) keeps the bimetal contact breaker open (4, 4a..4f) even when the bimetal bar (8a..8f) cools down again after opening.

13. Overvoltage protection device with integrated overtemperature protection (1 a..1f) as claimed in claim 12, characterized in that the blocking element (16a..16c) keeps the bimetal contact breaker (4, 4a..4f) open even when the bimetal bar (8a..8f) cools down again after opening until manual intervention from outside.

14. Overvoltage protection device with integrated overtemperature protection (1 a..1f) as claimed in any one of claims 11 to 13, characterized in that the blocking element (16a..16c) is spring loaded and forced between the fixed contact (7) and the movable contact (9, 9f).

15. Overvoltage protection device with integrated overtemperature protection (1 a..1f) as claimed in any one of claims 11 to 14, characterized in that the blocking element (16a..16c) comprises an optical indicator (14a..14c) and forms a combined blocking and indicator element, - which is movably arranged at an opening or window (13) of the housing (2), which is mechanically coupled to the movable end (E2) of the bimetal bar (8a..8f) and which is caused to be moved from a first position indicating the on state of the bimetal contact breaker (4, 4a..4f) to a second position indicating the off state of the bimetal contact breaker (4, 4a..4f) by the bimetal bar (8a..8f) when the bimetal contact (4, 4a..4f) breaker opens.