DK2775495T3 - Thermal contact with the insulation washer - Google Patents

Description

[0001] The present invention relates to a temperature-dependent switch with a housing that comprises a cover part having an upper side and a lower part having a raised, circumferential wall, wherein an insulating film is arranged between the lower part and the cover part and extends with its peripheral region as far as onto the upper side of the cover part, and the wall of the lower part is bent back onto the upper side and, as a result, holds the cover part with the insulating film interposed on the lower part, and with a temperature-dependent switching mechanism, which is arranged in the housing and which produces or opens, depending on its temperature, an electrically conductive connection between two contact areas provided externally on the housing.

[0002] Such a switch is known from DE 196 23 570 A1.

[0003] The known temperature-dependent switch is used in a manner known per se to monitor the temperature of a device. For this purpose, it is brought into thermal contact, for example over its outer surfaces, with the device to be protected so that the temperature of the device to be protected influences the temperature of the switching mechanism.

[0004] The switch is connected electrically in series into the supply circuit of the device to be protected via the connection lines soldered to its outer contact areas so that -below the response temperature of the switch - the supply current of the device to be protected flows through the switch.

[0005] The known switch has a deep-drawn lower part, in which an internally circumferential shoulder is provided, on which a cover part rests. The cover part is held fixedly on said shoulder by a raised and flanged rim of the lower part.

[0006] Since the cover part and the lower part are manufactured from an electrically conductive material, an insulating film is also provided between said cover part and said lower part, which insulating film extends parallel to the cover part and is raised upwards laterally so that its peripheral region extends as far as to the upper side of the cover part. The flanged rim, i.e. the bent-back wall of the lower part, in the process presses onto the cover part with the insulating film interposed.

[0007] The temperature-dependent switching mechanism in this case comprises a snap-action spring disc, which bears the movable contact part, and a bimetallic disc turned over the movable contact part. The snap-action spring disc presses the movable contact part towards a stationary counter contact internally on the cover part.

[0008] With its rim, the snap-action spring disc is supported in the lower part of the housing so that the electric current flows from the lower part through the snap-action spring disc and the movable contact part into the stationary counter contact and from there into the cover part.

[0009] A contact area which is arranged centrally on the cover part acts as first external connection. A contact area provided on the flanged rim of the lower part acts as second external connection. However, it is also possible for the second external connection not to be arranged on the rim but to be arranged laterally on the current-conducting housing or on the bottom side of the lower part.

[0010] It is known from DE 198 27 113 C2 to attach a so-called contact bridge to the snap-action spring disc, said contact bridge being pressed by the snap-action spring disc against two stationary counter contacts provided on the cover part. The current then flows from one stationary counter contact through the contact link into the other stationary counter contact so that the operating current does not flow through the snap-action spring disc itself.

[0011] This design is selected in particular when very high currents need to be switched which can no longer be conducted via the spring disc itself without any problems.

[0012] In both design variants, a bimetallic disc is provided for the temperature-dependent switching function, said bimetallic disc, when below its response temperature, lying in the switching mechanism free of forces, it being arranged geometrically between the contact part or the contact bridge, respectively and the snap-action spring disc.

[0013] Within the scope of the present invention, a bimetallic part is understood to mean a multilayered, active, sheet-like component part comprising two, three or four components connected to one another inseparably and having different coefficients of expansion. The connection of the individual layers of metals or metal alloys is cohesive or form-fitting and is achieved by rolling, for example.

[0014] Such bimetallic parts have a first stable geometric conformation in their low-temperature setting and a second stable geometric conformation in their high-temperature setting, between which they snap over in temperature-dependent fashion in the manner of a hysteresis. In the case of changes in temperature beyond their response temperature and below their return temperature, respectively, the bimetallic parts snap over into the respective other conformation. The bimetallic parts are therefore often referred to as snap-action discs, and can have an elongate, oval or circular form in plan view.

[0015] If the temperature of the bimetallic disc now increases as a result of a temperature increase in the device to be protected beyond the response temperature, the bimetallic disc changes its configuration and operates counter to the snap-action spring disc so that it lifts off the movable contact part from the stationary counter contact and the current transfer element from the two stationary counter contacts, respectively with the result that the switch opens and the device to be protected is disconnected and cannot heat up any further.

[0016] With these designs, the bimetallic disc is mounted free of mechanical forces when below its response temperature, wherein the bimetallic disc is not used for conducting the current either.

[0017] In this case it is advantageous that the bimetallic discs have a long mechanical life and that the switching point, i.e. the response temperature of the bimetallic disc, does not change even after many switching cycles.

[0018] If less stringent requirements are placed on the mechanical reliability or the stability of the response temperature, the bimetallic snap-action disc can also take on the function of the snap-action spring disc and possibly also of the current transfer element so that the switching mechanism only comprises a bimetallic disc, which then bears the movable contact part or has two contact areas instead of the current transfer element, so that the bimetallic disc not only ensures the closing pressure of the switch, but also conducts the current in the closed state of the switch.

[0019] Furthermore, it is known to provide such switches with a parallel resistor, which is connected in parallel with the external connections. This parallel resistor takes over part of the operating current when the switch is open and keeps the switch at a temperature above the response temperature, so that the switch does not automatically close again after cooling down. Such switches are referred to as self-holding.

[0020] It is furthermore known to provide such switches with a series resistor, through which the operating current flowing through the switch flows. In this way, ohmic heat is generated in the series resistor, which ohmic heat is proportional to the square of the current flowing. If the current intensity exceeds a permissible degree, the heat of the series resistor results in the switching mechanism being opened.

[0021] In this way, a device to be protected is already disconnected from its supply circuit when an excessively high current flow occurs which has not yet resulted in excessive heating of the device.

[0022] All of these different design variants can be realized using the switch according to the invention; in particular, the bimetallic disc can also take on the function of the snap-action spring disc.

[0023] Instead of a generally round bimetallic disc, a bimetallic spring which is clamped in at one end can also be used, which bears a movable contact part and a contact link, respectively.

[0024] However, it is also possible for temperature-dependent switches to be used which do not have a contact plate but rather a spring part as current transfer element, said spring part bearing the two counter contacts or the two counter contacts being formed on said spring part. The spring part can be a bimetallic part, in particular a bimetallic snap-action disc, which not only ensures the temperature-dependent switching function, but also at the same time ensures the contact pressure and conducts the current when the switch is closed.

[0025] DE 195 17 310 A1 discloses a temperature-dependent switch which has a comparable construction to that from DE 196 23 570 A1 mentioned at the outset, in which the cover part is manufactured from a positive temperature coefficient material, however, and can rest on an internally circumferential shoulder of the lower part, without an insulating film interposed, with said cover part being pressed onto said shoulder by the flanged rim of the lower part.

[0026] In this way, the positive temperature coefficient material cover is connected electrically in parallel with the two external connections so that it imparts a selfholding function to the switch.

[0027] Such positive temperature coefficient material resistors are also called PTC- resistors and are manufactured, for example, from semiconductive, polycrystalline ceramics such as BaTi03.

[0028] In the case of the temperature-dependent switch having a contact bridge and known from above-mentioned DE 198 27 113 C2 as well, the cover part is manufactured from a positive temperature coefficient material, so that it likewise has a self-holding function. In this case, two rivets are arranged on the cover part, the outer heads of said rivets forming the two external connections, and the inner heads of said rivets, as stationary counter contacts, interact with the contact bridge.

[0029] Finally, EP 0 740 323 discloses a temperature-dependent switch in accordance with the preamble of Claim 1.

[0030] In the known switches, the outer contact areas and the electrically conductive parts of the housing still need to be electrically insulated once connection lines have been soldered on.

[0031] As insulation and as pressure protection, the known switches are therefore often inserted into enveloping housings, or protective caps, which are used for mechanical and/or electrical protection and are often intended to protect the housing at the same time from the ingress of impurities. Examples of this are given, by way of example, in DE 91 02 841 U1, DE 92 14 543 U1, DE 37 33 693 A1 and DE 197 54 158.

[0032] In addition, DE 41 43 671 A1 discloses encapsulating the external connections by injection moulding with a single-component thermosetting plastic. It is known from DE 10 2009 039 948 to cast connection lugs with an epoxy resin.

[0033] The use of encapsulating housings or connection caps is often perceived as being excessively complex in terms of design and as unsatisfactory with respect to the thermal connection to the device to be protected, however.

[0034] Therefore, the known switches are often provided with an impregnating varnish or protective varnish after soldering of the connection lines.

[0035] In order to prevent varnish from entering the interior of the housing in the process, in the switch mentioned at the outset the cover part is provided with a bead, with which it penetrates the insulating film during flanging of the wall of the lower part. This ensures better sealing, but in many cases varnish nevertheless enters the interior of the housing.

[0036] In view of the above, the objet underlying the present invention is to eliminate, or at least reduce, the above-mentioned problems in the case of the known switch in a manner that is simple in design terms and inexpensive.

[0037] This object is achieved according to the invention in the case of the switch mentioned at the outset by the fact that the insulating film in its peripheral region comprises at least two radially extending slots.

[0038] The inventor of the present application has recognized that the problems with the tightness of the known switch can be attributed to the fact that the insulating film curls or becomes folded when bent back onto the upper side of the cover part, which results in it not being possible for the wall of the lower part to be bent back far enough onto the upper side of the cover part. In addition, this undulation of the insulating film on the upper side and on the circumferential end side of the cover part results in leakage paths for liquids occurring, so that, when the known switch is impregnated with protective varnishes, said varnishes can creep into the interior of the switch.

[0039] The flanged rim of the lower part does also not seal the upper side so well against other electrical insulation materials that it is in any case ensured that no liquid can pass into the interior of the switch during resinification.

[0040] Even when connection lines are soldered onto the upper side or the contact area provided there it cannot be completely ruled out that solder or corresponding liquids enter the interior of the switch.

[0041] Owing to the fact that the insulating film now has at least two radially extending slots in its peripheral region, the peripheral region is, so to speak, circumferentially divided into different sections, which are separated from one another by the slots. When the insulating film is laid onto the upper side of the cover part, the peripheral regions push one on top of the other at the slots so that the insulating film no longer becomes corrugated but bears flat against the end side and on the upper side.

[0042] In this way, the counter pressure of the insulating film during flanging of the raised wall of the lower part is reduced to such an extent that the bent-back wall with the insulating film slotted in this manner interposed ensures good sealing in the region of the flanged rim.

[0043] The object underlying the invention is achieved completely in this way.

[0044] In this case, it is preferred if the slots are distributed circumferentially uniformly over the peripheral region, wherein preferably at least three slots are provided distributed circumferentially over the peripheral region.

[0045] The uniform distribution of at least three slots provides three sections of the peripheral region, which ensures that the insulating film lays flat well on the upper side of the cover part and in addition prevents, in an unexpected manner, the insulating film from lying around the end side of the cover part in corrugated fashion.

[0046] It is particularly preferred here if at least ten slots are provided.

[0047] In this case, it is advantageous that the flat bearing arrangement of the insulating film is ensured better the more radial slots are provided in the peripheral region.

[0048] Owing to the increase in the number of slots, the individual regions of overlap of the sections of the peripheral region are also smaller, with the result that the material piles up less there.

[0049] Furthermore, it is preferred if at least one slot opens radially outwards in the form of a V.

[0050] The advantage with this measure consists in that material is removed from the peripheral region of the insulating film so that the individual sections of the peripheral region overlap to a lesser extent, preferably do not overlap any more at all.

[0051] In this case, it is preferred if the slot has an opening angle of at least 30°, wherein the opening angle is preferably between 30° and 90°, further preferably between 40° and 60°.

[0052] By virtue of opening angles within this range, it is ensured on the one hand-side that on the upper side of the cover part no or only a little material of the insulating film overlaps, but on the other hand-side sufficient insulation of the cover part with respect to the flanged rim of the lower part is provided.

[0053] In this case, it is particularly preferred if the slots have a depth which is less than the width of the peripheral region.

[0054] The advantage of this measure consists in that these slots do not pass around the upper side of the cover part as far as the end side of the cover part, which is advantageous in respect of the required electric voltage-proof.

[0055] A particularly effective sealing of the interior of the housing with respect to entering liquids and at the same time excellent electric voltage-proof are achieved if approximately twenty V-shaped slots are arranged distributed uniformly circumferentially, wherein the V-shaped slots have an opening angle of approximately 50° and extend over approximately half of the peripheral region that protrudes beyond the end side of the cover part.

[0056] It is furthermore preferred if the insulating film consists of polyimides, preferably of aromatic polyimides, such as Kapton®, for example.

[0057] Insulating films consisting of these materials are characterized by the fact that they are “drawable”, i.e. expand slightly when the cover part is inserted into the lower part, and that they can nevertheless be laid well around the end side of the cover part on the upper side thereof, wherein, in addition, the required electric voltage-proof is achieved.

[0058] It is generally preferred if an insulating protective film is arranged on the upper side and extends as far as beneath the peripheral region of the insulating film, wherein the protective film preferably extends beyond the slots beneath the peripheral region.

[0059] The advantage with this measure consists in that, in addition, a protective film is provided at the top on the upper side, said protective film preferably resting flat on the upper side, i.e. not effecting any undesired counter pressure when the raised wall of the lower part is bent back onto the upper side. If this protective film extends as far as beneath the peripheral region, so that the slots, so to speak, only begin above this protective film, according to the findings of the inventors, this ensures particularly effective mechanical sealing and electrical insulation between the lower part and the cover part and towards the outside.

[0060] The protective film in this case preferably consists of aromatic polyamides, further preferably of Nomex®.

[0061] Aromatic polyamides are characterized by a particularly good electric voltage-proof.

[0062] Generally it is preferred when a protective layer, preferably a protective paint, is applied at least to the upper side.

[0063] This measure is used once the connection lines have been soldered on in order to protect the prefabricated switch from the ingress of oils, etc. during use where it is wound into the winding of a motor, for example. In this case, conventional protective paints are used as protective paints, such as are also used for protecting equipped printed circuit boards.

[0064] It is generally preferred if the cover part and further preferably the lower part are manufactured from an electrically conductive material, wherein further preferably the switching mechanism bears a movable contact part, which interacts with a stationary counter contact, which is arranged on an inner side of the cover part and interacts with a contact area arranged on the upper side.

[0065] These measures result in a switch which is mechanically very pressure-tight and is simple to manufacture, wherein the contact area on the upper side of the cover part and the bent-back rim of the lower part each act as external connections of the switch.

[0066] The switching mechanism can in this case comprise a bimetallic part, which bears the movable contact part and therefore conducts the current through the switch.

[0067] The bimetallic part can in this case be a round, preferably circular, bimetallic snap-action disc, wherein it is also possible for an elongate bimetallic spring which is clamped in at one end to be used as bimetallic part.

[0068] It is preferred, however, if the switching mechanism additionally comprises a snap-action spring disc, which then bears the movable contact part and conducts the current through the closed switch and ensures the contact pressure in the closed state. In this way, the bimetallic part is relieved of the current conduction and of the mechanical loading in the closed state, which extends the life of the switch and ensures that the switching temperature has long-term stability.

[0069] The present invention is particularly suitable for round temperature-dependent switches, which therefore are round, circular or oval in plan view of the lower part, wherein other housing shapes can also make use of the invention if the corrugations avoided in accordance with the invention were to arrive in any case when the insulating film is turned over.

[0070] The invention is of particular advantage for temperature-dependent switches in which the lower part and the cover part are manufactured from metal, but the sealing effect of the radially slotted insulating film which is bent back onto the upper side can also be used in the case of other materials for the lower part and/or cover part.

[0071] Even if the electrically insulating effect of the insulating film is not required in certain designs, the sealing function can nevertheless be used.

[0072] Further features and advantages result from the description and the attached drawing.

[0073] It goes without saying that the features mentioned above and yet to be explained below can be used not only in the respectively cited combinations, but also in other combinations or on their own without departing from the scope of the present invention.

[0074] Embodiments of the invention are illustrated in the drawing and will be explained in more detail in the description below. In the drawing:

Fig. 1 shows a schematic sectional illustration in a side view of a temperature-dependent switch in a first embodiment;

Fig. 2 shows, in an illustration as in Fig. 1, a further embodiment of a temperature-dependent switch; and

Fig. 3 shows a schematic plan view of an insulating film before it is installed in the switches from Fig. 1 and Fig. 2.

[0075] Fig. 1 shows a temperature-dependent switch 10 schematically in a lateral section not true to scale, said switch comprising a housing 11, which comprises an electrically conductive pot-like lower part 12. An internally circumferential shoulder 14 is provided in the lower part 12, which is circular in plan view, and a plate-like, electrically conductive cover part 16 rests on said shoulder with an insulating film 15 interposed, said cover part closing the lower part 12.

[0076] The cover part 16 has a circumferential end side 17, which separates an upper side 18 from an inner side 19. The insulating film 15 extends along the inner side 19 and along the end side 17 and extends with its peripheral region 21 as far as onto the upper side 18.

[0077] The lower part 12 comprises a raised wall 22, which in this case is cylin-drically circumferential, the upper section 23 of said wall being bent back onto the upper side 18 and holding the cover part 16 on the lower part 12 with the insulating film 15 interposed.

[0078] The insulating film 15 therefore ensures electrical insulation of the cover part 16 with respect to the lower part 12. At the same time, the insulating film 15 ensures mechanical sealing between the cover part 16 and the lower part 12.

[0079] A temperature-dependent switching mechanism 24 is arranged in the housing 11 of the switch 10 formed by the lower part 12 and the cover part 16 and comprises a snap-action spring disc 25, which bears a movable contact part 26 centrally, with a freely inserted bimetallic snap-action disc 27 resting on said contact part.

[0080] The snap-action spring disc 25 is supported on a base 28 internally on the lower part 12, while the movable contact part 26, through a central opening 29 in the insulating film 15, is in bearing contact with a stationary counter contact 31, which is provided on the inner side 19 of the cover part 16.

[0081] Two contact areas 32, 33 which are formed firstly in a central region of the upper side 18 and secondly on the bent-back section 23 of the wall 22 are used for the external connection in the case of the switch 10 shown in Figure 1.

[0082] The lower part 12 has a flat bottom side 34, via which the switch 10 is thermally coupled to a device to be protected.

[0083] In this way, the temperature-dependent switching mechanism 24, in the low-temperature setting shown in Fig. 1, produces an electrically conductive connection between the two outer contact areas 32, 33, wherein the operating current flows via the stationary counter contact 31, the movable contact part 26, the snap-action spring disc 25 and the lower part 12.

[0084] Regions of the lower side 34 or of a circumferential face 35 of the lower part 12 can also act as outer contact area 32.

[0085] If, in the case of the switch 10 shown in Fig. 1, the temperature of the bimetallic snap-action disc 27 is increased beyond its response temperature via the thermal contact between the lower side 34 and the device to be protected, said bimetallic snap-action disc snaps over from the convex position shown in Fig. 1 into its concave position, in which it lifts off the movable contact part 26 counter to the force of the spring disc 25 from the stationary counter contact 31 and thus opens the circuit.

[0086] Fig. 2 shows a modification of the switch 10 from Fig. 1 as a further embodiment of the novel switch 10’, wherein identical reference numerals have been used for identical design features for the switches 10, 10’.

[0087] The snap-action spring disc 25 rests in this case with its rim 36 on the shoulder 14 of the lower part 12 and is held there by a spacer ring 37, on which in turn the insulating film 15 rests and the cover part 16 rests on said insulating film.

[0088] The snap-action spring disc 25 again bears the movable contact part 26, which interacts with the stationary counter contact 31 on the inner side 19 of the cover part 16.

[0089] The bimetallic snap-action disc 27 is arranged at the movable contact part 26 beneath the snap-action spring disc 25 and is free of forces in the closed state shown in Fig. 2.

[0090] If the temperature of the bimetallic snap-action disc 27 is increased beyond its response temperature, it presses with its rim 38 downwards against the rim 36 of the snap-action spring disc 25 and in the process lifts off the movable contact part 26 from the stationary counter contact 31.

[0091] If the temperature of the bimetallic snap-action disc 27 decreases below its return temperature, it presses with its rim 38 against a wedge-shaped shoulder 39, which is circumferential internally in the lower part 12, so that the snap-action spring disc 25 spring backs into its second geometrically stable conformation, as shown in Fig. 2.

[0092] In contrast to the switch 10 shown in Fig. 1, in the case of the switch 10’ shown in Fig. 2, an insulating protective film 41, for example consisting of Nomex®, is arranged on the upper side 18 of the cover part 16, said insulating protective film extending with its rim 42 radially outwards as far as to the insulating film 15. The protective film leaves a region 43 free in the centre, by means of which electrical contact can be made externally with the contact area 32 on the upper side 18.

[0093] The switch 10’ shown in Fig. 2 is shown in a state in which the raised wall 22 of the lower part 12 has not yet been completely bent back onto the upper side 18, wherein, for reasons of clarity, the edges 44 and 45 connecting the left-hand and right-hand regions in Fig. 2 of the raised wall 22 and the insulating film 15, respectively, are shown in broken form. As the section 23 of the wall 22 is bent back further, the insulating film 15 moves further downwards onto the upper side 18.

[0094] Each a slot 46 is indicated on the left and right in the peripheral region 21 of the insulating film 15, which is illustrated by crossed lines, which slots make up approximately half the width 48 of the peripheral region 21, with the result that the protective film extends radially outwards beyond the slots 46. These slots 46 are also provided in the insulating film 15 of the switch 10 shown in Fig. 1, but they cannot be seen in said figure owing to the position of the section.

[0095] The protective film 41 extends beyond the tips of the slots 46 in Fig. 2.

[0096] Fig. 3 shows a plan view of an insulating film 15, for example consisting of Kapton®, as can be used in the case of the switch shown in Fig. 1 and the switch shown in Fig. 2. The opening 29 is shown in the centre of the insulating film 15, with it being possible for the movable contact part 26 to come to bear with the stationary counter contact 31 through said opening.

[0097] The insulating film 15 is circular and has in total twenty slots 46, which extend radially inwards in the peripheral region 21 and open in the form of a V radially outwards with an opening angle 49 of 50°. The slots 46 are arranged so as to be uniformly distributed circumferentially.

[0098] The rim of the peripheral region 21 of the insulating film 15 is indicated by dashed lines in Fig. 3, said peripheral region coming to rest on the upper side 18 of the cover part 16 once the switches 10, 10’ from Fig. 1 and Fig. 2 have been fitted. It can be seen that the slots 46 have a depth 51 that corresponds approximately to half the width 48 of the peripheral region 21.

[0099] The slots 46 separate circumferential sections 52 of the peripheral region 21 from one another. When the peripheral region 21 is turned back along the dashed line, the sections 52 move onto the upper side 18, where they lie next to one another without, or at least without any notable overlap, with the result that they do not subject the bent-back upper section 23 of the wall 22 to any notable counter pressure. In this way, the section 23 can press the peripheral region 21 of the insulating film 15 and possibly of the protective film 41 onto the upper side 18 in such a way that good electrical insulation and mechanical sealing between the lower part 12 and the cover part 16 is achieved which is so good that an applied protective paint cannot enter the housing 11 between the lower part 12 and the cover part 16.

[00100] The protective paint 53 is indicated in Fig. 1.

Claims (18)

1. Temperature dependent contact with a housing (11) having a cover portion (16) having an upper side (18) and a underside (12) having a circumferential wall (22) drawn up, where between the bottom portion (12) and the lid part (16) is provided with an insulating foil (15) which extends with its edge region (21) to the upper side (18) of the lid part (16), and the wall (22) of the lower part (12) is folded over to the upper side (18) and thereby holding the lid part (16) with the insulating foil (15) in between on the lower part (12) and with a temperature-dependent coupling mechanism (24) arranged in the housing (11) and depending on its temperature, an electrical conductive connection between two contact surfaces (32, 33) provided outside the housing (11), characterized in that the insulating foil (15) in its edge region (21) has at least two radially extending cracks (46). Contact according to claim 1, characterized in that the cracks (46) are distributed evenly over the edge region (21). Contact according to claim 1 or 2, characterized in that at least 3 cracks (46) are provided peripherally distributed over the edge region (21). Contact according to claim 3, characterized in that at least 10 cracks (46) are provided. Contact according to one of claims 1 to 4, characterized in that at least one crack (46) opens V-shaped radially outwards. Contact according to claim 5, characterized in that the at least one crack (46) has an opening angle (49) of at least 30 °. Contact according to claim 6, characterized in that the opening angle (49) is between 30 ° and 90 °, preferably between 40 ° and 60 °. Contact according to one of claims 1 to 7, characterized in that the cracks (46) have a depth (51) which is less than the width (48) of the edge area (21). Contact according to one of claims 1 to 8, characterized in that the insulating film (15) consists of polyimides, preferably of aromatic polyimides. Contact according to one of claims 1 to 9, characterized in that an insulating protective foil (41) is provided on the upper side (18) which extends below the edge area (21) of the insulating foil (15). Contact according to claim 10, characterized in that the protective foil (41) extends beyond the cracks (46) below the edge region (21). Contact according to claim 10 or 11, characterized in that the protective film (41) consists of aromatic polyamides. Contact according to one of claims 1 to 12, characterized in that a protective layer (52), preferably a protective coating, is at least arranged on the upper side (18). Contact according to one of claims 1 to 13, characterized in that the lid part (16) is made of electrically conductive material. Contact according to one of claims 1 to 14, characterized in that the lower part (12) is made of electrically conductive material. Contact according to one of claims 1 to 15, characterized in that the coupling mechanism (24) carries a movable contact part (26) which works together with a stationary counter-contact (31) arranged on an inner side (19) of the lid part ( 16) and works with a contact surface disposed on the upper side (18). Contact according to claim 16, characterized in that the coupling mechanism (24) has a bimetal part (27). Contact according to claim 16 or 17, characterized in that the coupling mechanism (24) has a 1] eder snap disc (25).