TEMPERATURE-DEPENDENT SWITCH

Description

[0001] The present invention relates to a temperature-dependent switch according to claim 1.

[0002] A switch of this type is already known from DE 10 2007 063 650 B4.

[0003] Such temperature-dependent switches are used in a conventional manner to protect electrical devices from overheating. For this purpose, the switch is electrically connected in series with the device to be protected and its supply voltage, and is mechanically arranged on the device in such a way that it is thermally connected to it.

[0004] A temperature-dependent switching mechanism ensures that the switch's two stationary contacts are electrically connected below the switching mechanism's response temperature. Thus, the circuit is closed below the response temperature, and the load current of the device to be protected can flow through the switch.

[0005] If the temperature rises above a permissible value, the switching mechanism lifts the movable contact element from the mating contact, opening the switch and interrupting the load current of the protected device. The now de-energized device can cool down again. This also cools down the switch, which is thermally coupled to the device and would then normally close again automatically.

[0006] The switch known from DE 10 2007 063 650 B4 is a switch in which, in addition to the usual switching mechanism, a second switching mechanism is used, which switches at a higher switching temperature than the first switching mechanism. This additional, second switching mechanism serves as a safety element that opens the switch even if, for example, the first switching mechanism is fatigued or malfunctions for other reasons, or if a safety temperature is exceeded that is above the response temperature of the first switching mechanism.

[0007] The first switching mechanism is responsible for the usual opening and closing operations, whereas the second switching mechanism only becomes active when its own response temperature, which is higher than the response temperature of the first switching mechanism, is exceeded. The second switching mechanism can also provide a so-called latching function. It keeps the switch open even if the first switching mechanism snaps back into its low-temperature configuration and tries to close the switch when the temperature falls below its reset temperature. The second switching mechanism can then prevent the switch from resetting.

[0008] The so-called self-holding function of the switch known from DE 10 2007 063 650 B4 is achieved by the fact that the second switching mechanism has a temperature-independent bistable spring element that holds the second switching mechanism and thus the switch in the open position even when the temperature-dependent snap-action part of the second switching mechanism springs back to its low-temperature configuration. Thus, resetting does not occur automatically in the cooling position of the switch. Therefore, the device to be protected cannot automatically switch back on after being switched off.

[0009] This type of self-holding of the switch is a safety function designed to prevent damage, as is the case, for example, with electric motors used as drive units.

[0010] The switch known from DE 10 2007 063 650 B4 can therefore only be closed again by mechanical manipulation from the outside, for example by bringing the temperature-independent bistable spring part back into its first configuration by a targeted shock or by pressure exerted directly on the spring part from the outside.

[0011] However, such a mechanically triggered external reset of the switch is prone to errors, as vibrations that could cause the switch to close can also occur unintentionally, meaning that the switch may close again even when this is not intended. It is also disadvantageous to have to reset the switch manually, for example by inserting a bolt through the switch housing, which exerts pressure on the temperature-independent bistable spring element. Such openings in the housing can also allow contaminants to penetrate the interior of the switch, which in turn can impair its function.

[0012] Another switch with a self-holding function is known from DE 10 2013 101 392 A1. This switch has a single temperature-dependent switching mechanism with a temperature-independent bimetallic snap-action disc and a bistable spring disc, which carries a moving contact or a current-transfer element. When the bimetallic snap-action disc is heated to a temperature above its response temperature, it lifts the moving contact or the current-transfer element from one or two mating contacts against the force of the spring disc, thereby pressing the spring disc into its second stable configuration, in which the switching mechanism is in its high-temperature position. When the switch, and thus the bimetallic snap-action disc, cools down again, it springs back to its first configuration.However, due to its design, its edge cannot be supported on a counter bearing, so that the spring washer remains in the configuration in which the switch is open.

[0013] The switch known from DE 10 2013 101 392 A1 also remains in its open position after being opened once, even if it cools down again. However, tests conducted by the applicant have shown that this switch also closes again in the event of strong mechanical shocks, so that from a safety perspective, it may not be optimally suitable for some applications.

[0014] It is also known to equip such temperature-dependent switches with a so-called self-holding resistor, which is connected in parallel with the two stationary contacts of the switch so that it takes over part of the load current when the switch opens. This self-holding resistor then generates ohmic heat sufficient to keep the snap-action disc above its operating temperature.

[0015] A switch with this type of self-holding function is known from EP 0 951 040 B2. However, this type of self-holding, with a self-holding resistor connected in parallel with the switch, is only active as long as the electrical device is still switched on. As soon as the device is disconnected from the power supply circuit, no more current flows through the temperature-dependent switch, thus eliminating the self-holding function. Therefore, after the electrical device is switched on again, the switch would be closed again, allowing the device to heat up again, which could lead to subsequent damage.

[0016] Another temperature-dependent switch with a self-holding function is known from DE 10 2007 042 188 B3. This switch has a temperature-dependent, bistable snap-action disc and a temperature-independent, bistable spring disc. The spring disc is designed as a circular spring-action disc, to which the movable contact element is attached in the center. In the low-temperature position of the switch, the spring-action disc presses the movable contact element against the first stationary contact, which is arranged on the inside of a cover of the housing. With its edge, the spring-action disc presses against an inner base of a lower part of the housing, which acts as the second contact of the switch. In this way, the electrically conductive spring-action disc establishes an electrically conductive connection between the two stationary contacts of the switch.

[0017] In its low-temperature position, the bimetallic snap-action disc rests loosely against the moving contact. As the temperature of the bimetallic snap-action disc rises, it switches to its high-temperature position, where its edge presses against the inside of the housing's base, pressing its center against the spring-loaded snap-action disc, causing it to switch from its first to its second stable configuration, thereby lifting the moving contact element from the stationary contact and opening the switch.

[0018] When the switch temperature drops again, the bimetallic snap-action disc returns to its low-temperature position. Its edge engages the edge of the spring-action disc, and its center engages the upper part of the housing. However, the actuating force of the bimetallic snap-action disc is not sufficient to return the spring-action disc to its original configuration.

[0019] Only when the switch cools down significantly does the bimetallic snap-action disc bend further, so that it can finally press the edge of the spring-loaded snap-action disc down to the inner bottom of the base so far that the spring-loaded snap-action disc returns to its original configuration and closes the switch again.

[0020] The switch known from DE 10 2007 042 188 B3 therefore remains open after opening until it has cooled down to a temperature below room temperature, for which purpose a cold spray can be used, for example.

[0021] Although this switch meets the relevant safety requirements in many applications, it has been found that the tensioning of the bimetallic snap-action disc between the upper part of the housing and the edge of the spring-loaded snap-action disc can, in rare cases, cause the spring-loaded snap-action disc to spring back unintentionally. Furthermore, in practice, it is relatively difficult, or at least only possible with considerable effort, to manufacture a bimetallic snap-action disc with such thermal behavior. This is because, on the one hand, the bimetallic snap-action disc must exhibit very precise switching behavior when the switching temperature is reached, and, on the other hand, it must deflect even more in its low-temperature configuration when a temperature below room temperature is reached, than it already did when reaching its reset temperature and snapping back into its low-temperature configuration.

[0022] In this case, the bimetallic snap-action disc has three functions: 1. snapping into its high-temperature configuration when its switching temperature is reached, 2. snapping back into its low-temperature configuration when the switch-back temperature is reached, and 3. bending even more when cooling further below room temperature.

[0023] To achieve this, the thermal hysteresis behavior of the bimetallic snap-action disc must be designed over a very wide temperature range. Ensuring this while maintaining precise switching behavior is only possible with considerable effort.

[0024] US 2009 / 115566 A1 discloses a manually resettable thermostat comprising several individual thermostats stacked on top of each other, each with a manually resettable calibration temperature, forming an integrated assembly. The thermostat can be applied to a thermostat system requiring several different manually resettable calibration temperatures, thus saving space and simplifying the thermostat's operation.

[0025] EP 0 041 823 A1 discloses a temperature-dependent switch comprising two identically sized, bimetallic, part-spherical, heat-responsive actuating elements arranged in intermeshing contact relationship within an end portion of a housing. The first element changes from a first to a second curvature when its temperature rises above a first predetermined temperature and returns to its first curvature when its temperature falls below a second, lower predetermined temperature. The second element changes from a first to a second curvature when its temperature rises above a third predetermined temperature higher than the first temperature and remains in that curvature thereafter.A common force transmission bolt, mounted on the top element, transmits the movement of both elements to a pair of contacts at the other end of the housing, with the contacts being in a first state when both plates have the first curvature, and otherwise in a second state.

[0026] US 5,898,555 A relates to a motor protector for use in an electrical circuit supplying power to a motor to be protected, comprising two separate bimetallic disc-operated switches included in the protector, which are electrically connected in series with each other and to the power source and the motor. One of the two switches may comprise two bimetallic discs, the bimetallic discs having different operating and reset temperatures to provide a fail-safe feature.

[0027] Further exemplary temperature-dependent switches are known from DE 25 08 807 A1 and DE 10 2013 102006 A1.

[0028] Against this background, the object of the present invention is to further develop the temperature-dependent switch mentioned at the outset in such a way that it can be provided with a self-holding function in a structurally simpler manner which is not susceptible to mechanical vibrations.

[0029] According to the invention, this object is achieved by a switch according to claim 1, which has a first and a second stationary contact and at least one temperature-dependent switching mechanism with a movable contact element, wherein the at least one switching mechanism in its first switching position presses the contact element against the first contact and thereby establishes an electrically conductive connection between the two contacts via the contact element and in its second switching position keeps the contact element spaced from the first contact, wherein the at least one temperature-dependent switching mechanism has a first temperature-dependent snap part,which, when a first switching temperature is exceeded, snaps from its geometric low-temperature configuration into its geometric high-temperature configuration and, when a first switch-back temperature is subsequently undershot, snaps back from its geometric high-temperature configuration into its geometric low-temperature configuration, wherein the switch further comprises a second temperature-dependent snap-in part which, when a second switching temperature is exceeded that is equal to or higher than the first switching temperature, snaps back from its geometric low-temperature configuration into its geometric high-temperature configuration and, when a second switch-back temperature is subsequently undershot that is lower than the first switch-back temperature, snaps back from its geometric high-temperature configuration into its geometric low-temperature configuration,and wherein a snapping of the first snap part from its geometric low-temperature configuration into its geometric high-temperature configuration and / or a snapping of the second snap part from its geometric low-temperature configuration into its geometric high-temperature configuration brings the at least one switching mechanism from its first switching position into its second switching position. The second snap part is configured to keep the contact member spaced from the first contact even when the switch has heated above the first and second switching temperatures and subsequently cooled to a temperature between the first and second reset temperatures, wherein the at least one switching mechanism further comprises a temperature-independent spring part connected to the movable contact member,wherein the first snap part acts on the spring part when the first switching temperature is exceeded and thereby lifts the movable contact member from the first contact, wherein the second snap part is configured, in its high-temperature configuration, to exert an opening force on the movable contact member which keeps the contact member spaced from the first contact, and wherein the first snap part, in its low-temperature configuration, together with the spring part, exerts a closing force on the movable contact member which is opposite to the opening force and is smaller in magnitude than the opening force.

[0030] The switching process that causes the switch to open and thus interrupt the circuit can therefore be effected by both the first and second snap-action parts in the switch according to the invention. The two snap-action parts can therefore be designed such that they snap from their respective low-temperature configurations to their respective high-temperature configurations when similar switching temperatures are reached.

[0031] The first switching temperature (switching temperature of the first snap-action part) and the second switching temperature (switching temperature of the second snap-action part) can therefore be within a similar temperature range. The switch will therefore always open when one of the two switching temperatures is reached.

[0032] The self-holding function of the switch according to the invention is achieved by the additional second snap-in part. This second snap-in part keeps the movable contact member spaced from the first stationary contact even when the switch cools down below the reset temperature of the first snap-in part (first reset temperature) after opening, and the first snap-in part thus snaps back into its low-temperature configuration. In this case, the first snap-in part attempts to move the movable contact member back toward the first stationary contact of the switch in order to close the switch.However, this is prevented by the second snap part, whose switch-back temperature (second switch-back temperature) is lower than the switch-back temperature of the first snap part, since the latter is then still in its high-temperature configuration in which it keeps the movable contact member spaced from the first stationary contact against the force of the first snap part.

[0033] Even mechanical shocks cannot cause the second snap-action part to snap over if the switch has cooled to a temperature between the first and second reset temperatures after opening. The switch, and thus the circuit, will only close again when the switch and thus the second snap-action part have cooled to a temperature below the second reset temperature. Only then will the second snap-action part snap back into its low-temperature position, forcing the movable contact element back against the first stationary contact and closing the circuit.

[0034] The switch according to the invention is therefore a switch with a reversible self-holding function.

[0035] However, in contrast to the switch known from DE 10 2007 063 650 B4, the self-holding function can be deactivated more easily, namely by cooling the switch to a temperature below the second reset temperature. A mechanical reset of the second snap-in part, as proposed in the switch known from DE 10 2007 063 650 B4, is not necessary.

[0036] The switch according to the invention is also advantageous over the switch known from DE 10 2007 042 188 B3. In contrast to this previously known switch, the self-holding function according to the invention is not achieved by one and the same (single) snap-in part that must also cause the switch to open. Instead, with the switch according to the invention, the switch can be opened by the first snap-in part, whereas the self-holding function is achieved by the second (extra) snap-in part.

[0037] Thus, the switching hysteresis of the second snap-action part in the switch according to the invention must be designed over a similarly wide temperature range as the switching hysteresis of the single snap-action part in the switch known from DE 10 2007 042 188 B3. However, the second snap-action part of the switch according to the invention does not necessarily have to have such precise switching behavior, since the accuracy of the switching behavior in the switch according to the invention can be ensured via the first snap-action part. The two snap-action parts of the switch according to the invention can therefore be designed much more simply and manufactured more cost-effectively than the single snap-action part, which in the known switch must perform both the switching and the self-holding function.

[0038] According to the invention, the second switching temperature is equal to or higher than the first switching temperature.

[0039] In other words, the two snap parts of the switch according to the invention are designed in such a way that the switching temperature of the second snap part, which is essentially responsible for the self-holding function, is the same as or higher than the switching temperature of the first snap part.

[0040] If the first switching temperature is the same as, or at least similar to, the second switching temperature, both snap-action parts will snap from their low-temperature configuration to their respective high-temperature configurations simultaneously, or at least more or less simultaneously, when the switch is heated. However, it is more or less irrelevant which of the two snap-action parts snaps first, since the switch will open as desired anyway.

[0041] However, the two snap-in parts can also be designed such that the switching temperature of the second snap-in part is higher than the switching temperature of the first snap-in part. In this case, the first snap-in part is responsible for opening the switch, as it opens as soon as the first switching temperature is reached. This has the particular advantage that the first snap-in part, whose switching hysteresis is designed for a smaller or narrower temperature range than the switching hysteresis of the second snap-in part, can be designed with less effort for precise switching behavior when the switching temperature (first switching temperature) is reached exactly.

[0042] The switching temperature of the second snap-in part, i.e., the second switching temperature, can, for example, be designed in the range of the switch's overshoot temperature. However, the second switching temperature then no longer needs to be designed to a precise value required for safety reasons.

[0043] The "overshoot temperature," within which the second switching temperature can be located, is typically the temperature or temperature range to which the switch typically rises after it is turned off. Normally, the temperature still overshoots slightly after the switch is turned off, even if it is already open, because the switch continues to heat up due to the residual heat.

[0044] In a further embodiment of the switch according to the invention, it is provided that the second switching-back temperature is lower than room temperature, in particular lower than 15°C.

[0045] This has the advantage that after being opened once in a normal environment with room temperature (17-23°C), the switch does not automatically switch back on and close the circuit of the device to be protected. This prevents accidental switching back on.

[0046] In this case, the switch can only be closed again by (intentional) external exposure to cold. In principle, it is also possible to design the second snap-in part so that its reset temperature, i.e., the second reset temperature, is lower than 10°C. In such a case, the switch can only be reset by placing it in a refrigerator or by applying a cold spray.

[0047] According to the invention, it is provided that the at least one switching mechanism has a temperature-independent spring part which is connected to the movable contact member, wherein the first snap part acts on the spring part when the first switching temperature is exceeded and thereby lifts the movable contact member from the first contact.

[0048] Apart from the additional temperature-dependent second snap part, the temperature-dependent switching mechanism can therefore be designed in a conventional manner with a temperature-dependent (first) snap part and a temperature-independent spring part.

[0049] According to the invention, it is further provided that the second snap part is designed to exert an opening force on the movable contact member in its high-temperature configuration, which keeps the contact member spaced apart from the first contact, and that the first snap part, in its low-temperature configuration, together with the spring part, exerts a closing force on the movable contact member that is opposite to the opening force and is smaller in magnitude than the opening force.

[0050] This has the advantage that the self-holding function of the switch according to the invention is ensured in a mechanically simple manner. If the switch cools down to a temperature between the first and second reset temperatures after it has been opened, i.e., after the first and second switching temperatures have been exceeded, the movable contact element continues to be held at a distance from the first stationary contact by the second snap-action part. In this case, the second snap-action part exerts a spring force (referred to here as the "opening force") on the movable contact element that is greater than the closing force exerted on the movable contact element by the first snap-action part and the spring part together.

[0051] This can be achieved, for example, by ensuring that the spring constant of the second snap-in part is greater than the sum of the spring constants of the first snap-in part and the spring part. This can be achieved by appropriately shaping the second snap-in part, for example, by making it slightly thicker than the first snap-in part and the spring part.

[0052] According to a further embodiment, the spring part is a bistable spring part with two temperature-independent, stable geometric configurations.

[0053] Such a bistable design of the spring part has the advantage that the self-holding of the switch is further improved, since an accidental snapping of the spring part from one of its temperature-independent stable configurations to its other temperature-independent stable configuration is prevented.

[0054] Furthermore, it is preferred that the first and / or the second snap-action part is / are designed as a bi- or tri-metal snap-action disc.

[0055] According to a further embodiment, it is provided that the movable contact member has a first component and a second component connected thereto in a force-fitting, material-fitting or form-fitting manner, wherein the first snap-in part engages the first component and the second snap-in part engages the second component.

[0056] In this embodiment, the movable contact element is constructed in two parts. The two individual components of the movable contact element can be arranged one above the other. The first component can serve as the first contact mechanism, on which the first snap-in part is arranged. The second component can serve as the second contact mechanism, on which the second snap-in part is arranged. The two components of the movable contact element can be welded, soldered, or crimped together, for example.

[0057] The first snap-in part can be held captively on the first component or first contact mechanism of the movable contact element. The second snap-in part can be held captively on the second component or second contact mechanism. This has the advantage that the entire switching mechanism, including the first and second snap-in parts, can be prefabricated and inserted into the switch as a complete, pre-assembled unit.

[0058] If the switching mechanism further comprises a spring part, this can also be held captively on the first component or the first contact mechanism of the movable component.

[0059] According to one embodiment, the switch has a housing on which the first and second stationary contacts are provided and in which the at least one switching mechanism is arranged.

[0060] This measure is well known; it ensures that the switchgear is protected from the ingress of contaminants. The enclosure can be a separate switch housing or a pocket on the device to be protected from overheating.

[0061] Furthermore, it is preferred if the housing has a lower part closed by an upper part, wherein the first stationary contact or each of the two stationary contacts is arranged on an inner side of the upper part.

[0062] This measure is also known in terms of construction; in the switch according to the invention, it ensures that when the upper part is mounted on the lower part, the geometrically correct assignment between the first stationary contact or both stationary contacts and the movable contact element is simultaneously established.

[0063] According to a further embodiment of the switch according to the invention, it is provided that the movable contact member comprises a movable contact part that interacts with the first stationary contact, and that the spring washer interacts with the second stationary contact. It is particularly preferred that the spring part is designed as a bistable spring washer, which, at least in its first configuration, is electrically connected to the second stationary contact via its edge.

[0064] This principle is already known from DE 10 2007 042 188 B3. It ensures that the load current of the electrical device to be protected flows through the spring washer when the switch is closed. Thus, at least the first snap-in part is not subject to any current load in any position of the switch, which has a positive effect on its service life and switching behavior.

[0065] According to an alternative embodiment, the movable contact member comprises a current transmission member that interacts with both stationary contacts.

[0066] This has the advantage that the switch can carry significantly higher currents than the switch known from DE 10 2007 042 188 B3. In this case, the movable contact element creates an electrical short circuit between the two stationary contacts when the switch is closed, so that not only the two snap-action parts but also the spring part are no longer subject to the load current of the electrical device to be protected. Such a design is already known in principle from DE 10 2013 101 392 A1.

[0067] Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description. They show: Fig. 1 a schematic sectional view of an embodiment of the switch according to the invention in a first switching position; Fig. 2 a schematic sectional view of the Fig. 1 shown embodiment of the switch according to the invention in a second switching position; Fig. 3 a schematic sectional view of the Fig. 1 shown embodiment of the switch according to the invention in a third switching position; and Fig. 4 a schematic sectional view of the Fig. 1 shown embodiment of the switch according to the invention in a fourth switching position. In Fig. 1 In a schematic, sectional side view, a switch 10 is shown which is rotationally symmetrical in plan view and preferably has a circular shape.

[0068] The switch 10 has a housing 12 in which a temperature-dependent switching mechanism 14 is arranged. The housing 12 comprises a pot-shaped lower part 16 and an upper part 18, which is held to the lower part 16 by a bent or flanged edge 20.

[0069] In the Fig. 1 In the embodiment shown, both the lower part 16 and the upper part 18 are made of an electrically conductive material, preferably metal. The upper part 18 rests on a shoulder 24 extending around the interior of the lower part 16, with an insulating film 22 interposed therebetween.

[0070] The insulating film 22 provides electrical insulation of the upper part 18 from the lower part 16. In addition, the insulating film 22 also provides a mechanical seal that prevents liquids or contaminants from entering the housing interior from the outside.

[0071] Since the lower part 16 and the upper part 18 in this embodiment are each made of electrically conductive material, their outer surfaces can be used to establish thermal contact with an electrical device to be protected. The outer surfaces also serve as the external electrical connection of the switch 10.

[0072] On the outside of the upper part 18, as shown in Fig. 1 shown, a further insulation layer 26 may be applied.

[0073] The switching mechanism 14 has a temperature-independent spring part 28 designed as a spring washer and a temperature-dependent snap part 30 designed as a snap disc.

[0074] The spring part 28 is preferably designed as a bistable spring washer. The spring washer 28 therefore has two temperature-independent stable geometric configurations. Fig. 1 their first geometric configuration is shown.

[0075] The temperature-dependent snap-action part 30, which is referred to here as the first snap-action part 30, is designed, for example, as a bistable snap-action disk. The snap-action disk 30 has two temperature-dependent configurations: a geometric high-temperature configuration and a geometric low-temperature configuration. Fig. 1 In the first switching position of the switching mechanism 14 shown, the first snap disk 30 is in its low-temperature configuration.

[0076] The spring washer 28 rests with its edge 32 on an inner bottom surface 38 of the lower part 16. The inner bottom surface 34 is essentially concave and at the point where the edge 32 of the spring washer 28 rests in the Fig. 1 shown first switching position, slightly raised compared to the central area of ​​the inner bottom surface 34. The first snap disk 30 lies with its edge 36 in its Fig. 1 shown low temperature configuration on the spring washer 28.

[0077] The spring washer 28 is secured at its center 38 to a movable contact member 40 of the switching mechanism 14. The first snap-action disc 30 is also secured at its center 42 to this contact member 40. Thus, the temperature-dependent switching mechanism 14 is a captive unit comprising the contact member 40, the spring washer 28, and the first snap-action disc 30. When assembling the switch 10, the switching mechanism 14 can be inserted directly into the lower part 16 as a unit.

[0078] Above the first snap disk 30, in the Fig. 1 In the embodiment shown, a second snap-action part 44 is arranged. This second snap-action part 44, similar to the first snap-action part 30, is preferably designed as a temperature-dependent, bistable snap-action disk. This second snap-action disk 44 also preferably has two temperature-independent configurations, a geometric high-temperature configuration and a geometric low-temperature configuration. In the embodiment shown in Fig. 1 In the first switching position of the switching mechanism 14 shown, the second snap disk 44 is in its geometric low-temperature configuration.

[0079] The second snap disk 44 is located in the Fig. 1 shown embodiment preferably on the first snap disk 30. The second snap disk 44 is not firmly connected to the first snap disk 30. In the embodiment shown in Fig. 1 In the embodiment shown, the second snap disk 44 is also not firmly connected to the movable contact member 40. It is held by the switching mechanism 14 in its Fig. 1 The low-temperature configuration shown is therefore only carried or rests on top of it.

[0080] Since the second snap-action disc 44 significantly influences the switching behavior of the switch 10 just as much as the first snap-action disc 30, the second snap-action disc 44 can generally be considered part of the switching mechanism 14. Depending on the definition, however, the second snap-action disc 44 can also be considered a separate component.

[0081] On its upper side, the movable contact member 40 has a movable contact part 46. The movable contact part 46 cooperates with a fixed counter-contact 48, which is arranged inside the upper part 18. This counter-contact 48 is referred to here as the first stationary contact. The second stationary contact 50 serves in the Fig. 1 shown switch 10 the outside of the lower part 16.

[0082] In the Fig. 1 In the position shown, the switch 10 is in its low-temperature position (first switching position), in which the spring washer 28 is in its first configuration and the two snap discs 40, 44 are in their respective low-temperature configurations. The spring washer 28 presses the movable contact part 46 against the first stationary contact 48. In the low-temperature position of the switch 10 according to Fig. 1 Thus, an electrically conductive connection is established between the first stationary contact 48 and the second stationary contact 50 via the movable contact member 42 and the spring washer 30.

[0083] If the temperature of the device to be protected increases and thus the temperature of the switch 10 and the first snap-action disc arranged therein, the latter snaps from the Fig. 1 shown low-temperature configuration into its concave high-temperature configuration, which is shown in Fig. 2 is shown.

[0084] During this snapping action, the first snap-action disc 30 rests with its edge 36 on the second snap-action disc 44, whereby the second snap-action disc 44 is in turn clamped between the first snap-action disc 30 and the upper part 18 or the insulating film 22. With its center 42, the first snap-action disc 30 pulls the movable contact member 40 downwards and lifts the movable contact part 46 from the first stationary contact 48. At the same time, it bends the spring washer 28 downwards at its center 38, so that the spring washer 28 is released from its Fig. 1 shown first stable geometric configuration into its Fig. 2 The second geometrically stable configuration shown snaps over. The circuit is thus interrupted.

[0085] The switching process that moves the switch 10 from its Fig. 1 shown closed position into its Fig. 2 open position occurs when the switching temperature of the first snap disc 30 is reached or exceeded. This switching temperature is referred to here as the first switching temperature.

[0086] The second snap-action disc 44, on the other hand, is designed such that its switching temperature, at which it snaps from its geometric low-temperature configuration to its geometric high-temperature configuration, is slightly higher than the first switching temperature. The switching temperature of the second snap-action disc 44 is referred to herein as the second switching temperature.

[0087] Fig. 2 shows the switch 10 in its second switching position, in which the first switching temperature has been reached or exceeded, but the second switching temperature has not yet been reached.

[0088] The second snap disk 44 is located in the Fig. 2 shown, second switching position of the switch 10 is therefore still in its geometric low-temperature configuration, as it is also in Fig. 1 is shown. However, since the second snap-action disc 44 is not firmly connected to the movable contact member 40, the second snap-action disc 44 does not exert any force on the movable contact member 40 in this position that counteracts the force exerted on the movable contact member 40 by the spring disc 28 and the first snap-action disc 30. The switch 10 is therefore always opened when the first switching temperature is reached.

[0089] If the temperature of the switch 10 and thus also the temperature of the second snap disk 44 increases after reaching the Fig. 2 shown switching position even further beyond the second switching temperature, the second snap disk 44 also snaps from its Fig. 2 shown, convex low-temperature position into the Fig. 3 shown, concave high-temperature position. It then rests with its edge 52 on the upper part 18 or the insulating film 22 arranged underneath, and presses with its center 54 onto the first snap-action disc 30. As a result, the second snap-action disc 44 also exerts a force on the movable contact member 40, which keeps the movable contact part 46 spaced from the first stationary contact 48.

[0090] Such a further temperature increase despite switch 10 already being open is quite common in practice due to the residual heat generated by the electrical device to be protected. This is typically referred to as the overshoot temperature or the overshoot temperature range of switch 10.

[0091] The switching temperature of the second snap-action disc 44 is preferably located at this overswing temperature or in this overswing temperature range and is thus preferably only slightly higher than the first switching temperature of the first snap-action disc 30.

[0092] However, it is also fundamentally possible to design the second snap-action disk 44 in such a way that it snaps from its geometric low-temperature configuration to its geometric high-temperature configuration simultaneously with the first snap-action disk 30. In this case, the second switching temperature would therefore correspond to the first switching temperature. The function of the switch 10 would fundamentally remain the same, since it would also be opened upon reaching the first switching temperature. In this case, however, the Fig. 1 shown, first switching position to the one in Fig. 3 shown third switching position, in which both snap disks 30, 44 are snapped into their high-temperature configuration.

[0093] In principle, it would even be possible for the second switching temperature to be lower than the first switching temperature, so that when the switch 10 heats up, the second snap-action disc 44 snaps into its high-temperature configuration before the first snap-action disc and opens the switch. However, this would require that the force exerted by the second snap-action disc 44 in its high-temperature configuration on the movable contact member 40 be greater than the combined force exerted on the movable contact member 40 by the first snap-action disc 30 in its low-temperature configuration and the spring disc 28 in its first configuration.

[0094] In principle, however, it is preferred that the first snap disk 30 is responsible for opening the switch 10, i.e. that the first switching temperature is lower than the second switching temperature or at least equal to the second switching temperature.

[0095] Since the circuit of the electrical device to be protected is interrupted, the switch 10 now cools down again. As soon as the switch 10 has cooled down to or below the reset temperature of the first snap-action disc 30 (first reset temperature), the latter snaps out of its Fig. 3 shown high-temperature position to its low-temperature position, thereby pulling the spring washer 28 upwards again towards its first configuration. Since the reset temperature of the second snap-action disc 44 (second reset temperature) is lower than the first reset temperature, the second snap-action disc 44 remains in its high-temperature configuration when the first reset temperature is reached. This results in the Fig. 4 shown, fourth switching position, in which the movable contact part 46 remains spaced from the first stationary contact 48 and the switch 10 is thus still open.

[0096] In this case, the second snap-action disc 44 exerts a greater spring force on the movable contact member 40 than the first snap-action disc 30 and the spring washer 28 combined, which actually attempt to move the movable contact part 46 toward the first stationary contact 48. According to this embodiment of the switch 10, the second snap-action disc 44 has a higher spring constant than the first snap-action disc 30 and the spring washer 28 combined.

[0097] In this way, the second snap-action disc 44 provides the self-holding function, which keeps the switch 10 open even after the temperature falls below the first reset temperature. This self-holding function is only deactivated when the switch 10 cools down to or below the second reset temperature. Only then does the second snap-action disc 44 also snap back from its high-temperature configuration to its low-temperature configuration, so that the switch 10 is closed and the Fig. 1 shown first switching position.

[0098] Preferably, the second snap-action disk 44 is designed such that its second reset temperature is below room temperature. Thus, after opening, the switch 10 can only be reset by external cold treatment, for example, using a cold spray.

[0099] The switching temperature of the second snap-action disc 44 is preferably located at this overswing temperature or in this overswing temperature range and is thus preferably only slightly higher than the first switching temperature of the first snap-action disc 30.

[0100] However, it is also fundamentally possible to design the second snap-action disk 44 in such a way that it snaps from its geometric low-temperature configuration to its geometric high-temperature configuration simultaneously with the first snap-action disk 30. In this case, the second switching temperature would therefore correspond to the first switching temperature. The function of the switch 10 would fundamentally remain the same, since it would also be opened upon reaching the first switching temperature. In this case, however, the Fig. 1 shown, first switching position to the one in Fig. 3 shown third switching position, in which both snap disks 30, 44 are snapped into their high-temperature configuration.

[0101] In principle, it would even be possible for the second switching temperature to be lower than the first switching temperature, so that when the switch 10 heats up, the second snap-action disc 44 snaps into its high-temperature configuration before the first snap-action disc and opens the switch. However, this would require that the force exerted by the second snap-action disc 44 in its high-temperature configuration on the movable contact member 40 be greater than the combined force exerted on the movable contact member 40 by the first snap-action disc 30 in its low-temperature configuration and the spring disc 28 in its first configuration.

[0102] In principle, however, it is preferred that the first snap disk 30 is responsible for opening the switch 10, i.e. that the first switching temperature is lower than the second switching temperature or at least equal to the second switching temperature.

[0103] Since the circuit of the electrical device to be protected is interrupted, the switch 10 now cools down again. As soon as the switch 10 has cooled down to or below the reset temperature of the first snap-action disc 30 (first reset temperature), the latter snaps out of its Fig. 3 shown high-temperature position to its low-temperature position, thereby pulling the spring washer 28 upwards again towards its first configuration. Since the reset temperature of the second snap-action disc 44 (second reset temperature) is lower than the first reset temperature, the second snap-action disc 44 remains in its high-temperature configuration when the first reset temperature is reached. This results in the Fig. 4 shown, fourth switching position, in which the movable contact part 46 remains spaced from the first stationary contact 48 and the switch 10 is thus still open.

[0104] In this case, the second snap-action disc 44 exerts a greater spring force on the movable contact member 40 than the first snap-action disc 30 and the spring washer 28 combined, which actually attempt to move the movable contact part 46 toward the first stationary contact 48. According to this first embodiment of the switch 10, the second snap-action disc 44 has a higher spring constant than the first snap-action disc 30 and the spring washer 28 combined.

[0105] In this way, the second snap-action disc 44 provides the self-holding function, which keeps the switch 10 open even after the temperature falls below the first reset temperature. This self-holding function is only deactivated when the switch 10 cools down to or below the second reset temperature. Only then does the second snap-action disc 44 also snap back from its high-temperature configuration to its low-temperature configuration, so that the switch 10 is closed and the Fig. 1 shown first switching position.

[0106] Preferably, the second snap-action disk 44 is designed such that its second reset temperature is below room temperature. Thus, after opening, the switch 10 can only be reset by external cold treatment, for example, using a cold spray.

[0107] The switch 10 according to the second embodiment shown in Fig. 5 is basically based on the same operation as the switch 10 according to the second embodiment shown in Fig. 1-4 shown, first embodiment. This switch 10 also has, in addition to a spring part 28 designed as a temperature-independent spring washer, a first snap part 30 designed as a temperature-dependent snap disc, and a second snap part 44 also designed as a temperature-dependent snap disc. In this case, too, the second snap disc 44 effects the self-holding function of the switch 10, which is achieved in particular by the fact that the (second) reset temperature of the second snap disc 44 is lower than the (first) reset temperature of the first snap disc 30.

[0108] However, the structure of the switching mechanism 14' in the second embodiment of the switch 10 shown in Fig. 5 is somewhat different than in the first embodiment.

[0109] The movable contact part 46' of the movable contact member 40' has a slightly different shape here. Furthermore, the movable contact member 40' has a ring 56 surrounding the contact member 40'. This ring 56 is preferably pressed onto the movable contact part 46'.

[0110] The ring 56 has a circumferential shoulder 58 on which the first snap-action disc 30 rests with its center 42. According to this exemplary embodiment, in the low-temperature configuration of the first snap-action disc 30 shown in Fig. 5, the edge 36 of the first snap-action disc 30 is not supported on the housing 12. The edge 36 of the first snap-action disc 30 is freely suspended in the low-temperature configuration. In the closed state of the switch 10 shown in Fig. 5, the first snap-action disc 30 thus exerts no force on the movable contact member 40'.

[0111] The contact pressure between the movable contact part 46' of the movable contact member 40' and the first stationary contact 48 is at least partially effected by the spring washer 28 when the switch 10 is closed. The spring washer 28 is clamped with its center 38 between the ring 56 and the widened upper portion of the contact member 40'.

[0112] The edge 32 of the spring washer 28 rests on a spacer element 60. This spacer element 60 is preferably designed as a spacer ring that is inserted into the lower part 16 of the housing 12. A circumferential shoulder 62 is provided on this spacer element 60, which serves as a support for the edge 32 of the spring washer 28.

[0113] The spacer element 60 is clamped between two additional spacer rings 64, 66. The spacer ring 64 is arranged above the edge 32 of the spring washer 28 and is clamped between the spacer ring 60 and the upper part 18 with the insulating foil 22 interposed. The spacer ring 66 is arranged below the spacer ring 60 and is clamped between it and the lower part 16 of the housing 12.

[0114] In the embodiment shown in Fig. 5, the movable contact member 40' has, in addition to the ring 56, two separate components: a first component 68, which supports or forms the movable contact part 46', and a second component 70. The second component 70 is arranged on an underside of the first component 68 facing away from the first stationary contact 48. The two components 68, 70 of the movable contact member 40' are preferably connected to one another in a force-fitting, material-fitting, or form-fitting manner. For example, these two components 68, 70 can be welded, soldered, or crimped together. In principle, however, it would also be possible to form the two components 68, 70 of the movable contact member 40' as one piece or integrally connected to one another.

[0115] The second snap-action disc 44 engages the second component 70 of the movable contact member 40'. It rests with its center 54 on a circumferential shoulder 72 formed on the second component 70 and is attached or fixed to the movable contact member 40' at this point.

[0116] In the closed position of the switch 10 shown in Fig. 5, in which the second snap disc 30 is in its low-temperature configuration, the edge 52 of the second snap disc 44 rests on the inner bottom surface 34 of the base 16. In the closed position of the switch 10, the second snap disc 44 thus provides, in addition to the spring disc 28, the contact pressure between the movable contact part 46' and the first stationary contact 48.

[0117] Furthermore, a disc-, plate-, or ring-shaped support element 74 is arranged in the housing 12, more precisely in the lower part 16. This support element 74 projects laterally from the outside into the interior of the housing 12. At its edge 76, it is clamped between the spacer ring 66 and the spacer ring 60. In its center, the support element 74 has a hole 78 through which the movable contact member 40' projects.

[0118] The support element 74 divides the interior of the housing 12 into two regions: an upper region in which the spring washer 28 and the first snap-action disc 30 are arranged, and a lower region in which the second snap-action disc 44 is arranged. In other words, the spring washer 28 and the first snap-action disc 30 are arranged locally between the upper part 18 and the support element 74, whereas the second snap-action disc 44 is arranged locally between the support element 74 and the lower part 16.

[0119] The general functioning of the second embodiment of the switch 10 shown in Fig. 5-8 is basically similar to the functioning of the switch according to the Fig. 1-4 shown first embodiment.

[0120] The first snap-action disc 30 essentially serves to open the switch 10, i.e., to move it from its first closed switching position to its second open switching position. The second snap-action disc 44 essentially provides the self-holding function, which keeps the switch 10 open even when the first snap-action disc 30 snaps back from its high-temperature configuration to its low-temperature configuration after the switch 10 has been opened. Therefore, in this exemplary embodiment of the switch 10, it is also provided that the (second) switching temperature of the second snap-action disc 44 is the same as or higher than the (first) switching temperature of the first snap-action disc 30. Likewise, it is also provided here that the (second) reset temperature of the second snap-action disc 44 is lower than the (first) reset temperature of the first snap-action disc 30.

[0121] If the switch 10 and thus the first snap-action disk 30 heats up to a temperature above the first switching temperature, the first snap-action disk 30 snaps from its low-temperature configuration shown in Fig. 5 into its high-temperature configuration shown in Fig. 6. The first snap-action disk 30 rests with its edge 36 on the underside of the spring disk 28, thereby moving the spring disk 30 from its first geometric configuration shown in Fig. 5 into its second geometric configuration shown in Fig. 6.

[0122] Unlike in the first embodiment, the spring washer 28 and the first snap-action disc 30 exert a spring force on the movable contact member 40' that is greater than the spring force exerted by the second snap-action disc 44 on the movable contact member 40', which acts in the opposite direction. If the second switching temperature is higher than the first switching temperature and the second switching temperature has not yet been reached, the second snap-action disc remains in its low-temperature configuration, as shown in Fig. 6, in which it presses the movable contact member 40' toward the first stationary contact 48. However, due to the specified force ratios, the movable contact part 46' is nevertheless lifted off the first stationary contact 48 when the first switching temperature is reached (see Fig. 6).

[0123] In this exemplary embodiment of the switch 10, the spring washer 28 and the first snap-action disk 30 do not necessarily have to be designed such that the spring force they exert jointly on the movable contact member 40' is greater than the spring force exerted by the second snap-action disk 44 on the movable contact member 40'. If this is not the case, however, the (second) switching temperature of the second snap-action disk 44 must be the same as or even lower than the (first) switching temperature of the first snap-action disk 30. In this case, upon reaching the first switching temperature, the switching position of the switch 10 shown in Fig. 6 would not occur, but directly the switching position of the switch 10 shown in Fig. 7, in which both snap-action disks 30, 44 are in their high-temperature configuration.

[0124] In the first case described above, in which the first switching temperature is lower than the second switching temperature and the spring washer 28 together with the first snap-action disk 30 generates a greater force than the second snap-action disk 44, the switch 10 would first be brought into the switching position shown in Fig. 6 when the first switching temperature is reached and would only be brought into the switching position shown in Fig. 7 when the second switching temperature is reached.

[0125] In both cases, the switch 10 is opened as soon as the first switching temperature is reached and the circuit is interrupted.

[0126] In the switching position of the switch 10 shown in Fig. 7, the second snap-action disk 44 is in its high-temperature configuration. It rests with its edge 52 on the support element 74 and presses the movable contact member 40' downward with its center 54.

[0127] If the switch 10 subsequently cools down again, the first snap-action disc 30 snaps back from its high-temperature configuration shown in Fig. 7 to its low-temperature configuration shown in Fig. 8 upon reaching the first reset temperature. However, since the edge 36 of the first snap-action disc 30 cannot be supported on a part of the switch in its low-temperature configuration, but is freely suspended in the housing 12, the first snap-action disc 30 does not exert any force on the movable contact member 40' to move the movable contact part 46' toward the first stationary contact 48.

[0128] Since the second snap disk 44 remains in its high-temperature configuration shown in Fig. 8 when the first reset temperature is reached, it, together with the spring disk 28, which remains in its second geometric configuration, presses the movable contact member 40' downwards so that the movable contact part 46' remains spaced from the first stationary contact 48.

[0129] Fig. 9 shows a third embodiment of the switch 10 according to the invention in its closed position (first switching position). Since the interaction of the spring washer 28, the first snap-action disk 30, and the second snap-action disk 44 is based on a substantially identical or at least very similar functional principle as described with respect to the second embodiment shown in Figs. 5-8, the other switching positions of the switch 10 according to this third embodiment are not shown again here.

[0130] The switch 10 according to the third embodiment shown in Fig. 9 differs from the previous embodiments essentially in the construction of the housing 12". The lower part 16" is again made of electrically conductive material. The flat upper part 18", in contrast, is made of electrically insulating material. It is held to the lower part 16" by a bent edge 80.

[0131] A spacer ring 64" is also provided between the upper part 18" and the lower part 16", which keeps the upper part 18" spaced from the lower part 16". On its inner side, the upper part 18" has a first stationary contact 48" and a second stationary contact 50". The stationary contacts 48" and 50" are designed as rivets that extend through the upper part 18" and end externally in the heads 82, 84, which serve as the external connection of the switch 10.

[0132] The switching mechanism 14" is also designed differently here than before. The movable contact member 40" comprises a current transmission member 86, which in the embodiment shown in Fig. 9 is a contact plate whose upper side is coated with an electrically conductive material, so that when it is in contact with the contacts 48" and 50" as shown in Fig. 9, it ensures an electrically conductive connection between the two contacts 48" and 50".

[0133] The current transmission member 86 is connected to the spring washer 28 and the first snap-action disc 30 via a rivet 88, which is also to be regarded as part of the contact member 40". Similar to before, a second component 70" is arranged on the underside of this rivet 88, which has a circumferential shoulder 72" on which the second snap-action disc 44 rests with its center 54.

[0134] The key advantage of the switch assembly shown in Fig. 9 is that, in contrast to the first two embodiments of the switch 10 shown in Figs. 1-8, no current flows through the spring washer 28 or the two snap discs 30, 44 when the switch 10 is closed. This current flows only from the first external terminal 82 via the first stationary contact 48", the current transfer member 86, and the second stationary contact 50" to the second external terminal 84.

[0135] It is understood that the remaining structure of the switching mechanism 14", in particular the arrangement of the spring washer 28 and the two snap discs 30, 44, does not necessarily have to correspond to the arrangement shown in Fig. 9 in this switch structure either. The arrangement of the spring washer 28 and the two snap discs 30, 44 does not necessarily have to be the same or similar to the arrangement as described in the second embodiment shown in Figs. 5-8, but can in principle also correspond to the arrangement as shown in Fig. 1-4 shown, first embodiment was described.

Claims

1. A temperature-dependent switch (10), which comprises a first and a second stationary contact (48, 50) and at least one temperature-dependent switching mechanism (14) having a movable contact member (40), wherein the at least one switching mechanism (14), in its first switching position, presses the contact member (40) against the first contact (48) and thereby produces an electrically conductive connection between the two contacts (48, 50) via the contact member (40) and, in its second switching position, keeps the contact member (40) spaced apart from the first contact (48), wherein the at least one temperature-dependent switching mechanism (14) comprises a first temperature-dependent snap-action part (30) which switches from its geometric low-temperature configuration to its geometric high-temperature configuration when exceeding a first switching temperature, and switches back again from its geometric high-temperature configuration to its geometric low-temperature configuration when subsequently falling below a first reset temperature, wherein the switch (10) further comprises a second temperature-dependent snap-action part (44) which switches from its geometric low-temperature configuration to its geometric high-temperature configuration when exceeding a second switching temperature that is equal to or higher than the first switching temperature, and switches back again from its geometric high-temperature configuration to its geometric low-temperature configuration when subsequently falling below a second reset temperature that is lower than the first reset temperature, wherein switching the first snap-action part (30) from its geometric low-temperature configuration to its geometric high-temperature configuration and / or switching the second snap-action part (44) from its geometric low-temperature configuration to its geometric high-temperature configuration brings the at least one switching mechanism (14) from its first switching position to its second switching position, wherein the second snap-action part (44) is configured to keep the contact member (40) spaced apart from the first contact (48) even if the switch (10) has heated above the first and the second switching temperatures and has subsequently cooled down to a temperature between the first and the second reset temperatures, wherein the at least one switching mechanism (14) comprises a temperature-independent spring part (28) which is connected to the movable contact member (40), wherein the first snap-action part (30) acts on the spring part (28) when exceeding the first switching temperature and thereby lifts off the movable contact member (40) from the first contact (48), wherein the second snap-action part (44), in its high-temperature configuration, is configured to exert an opening force on the movable contact member (40), which opening force keeps the contact member (40) spaced apart from the first contact (48), and wherein the first snap-action part (30), in its low-temperature configuration, together with the spring part (28), exerts a closing force on the movable contact member (40), which closing force is oppositely arranged to the opening force and smaller in magnitude than the opening force.

2. The switch according to claim 1, wherein the second reset temperature is lower than room temperature, in particular lower than 15°C3. The switch according to claim 1 or 2, wherein the spring part (28) is a bistable spring part having two temperature-independent, stable geometric configurations.

4. The switch according to one of claims 1 to 3, wherein the first and / or the second snap-action part (30, 44) is a bi- or trimetal snap-action disc.

5. The switch according to one of claims 1 to 4, wherein the movable contact member (40) comprises a first component (68) and a second component (70) connected thereto by means of a non-positive, firmly bonded or positive connection, wherein the first snap-action part (30) engages on the first component (68) and the second snap-action part (44) engages on the second component (70).

6. The switch according to one of claims 1 to 5, wherein the switch (10) comprises a housing (12) on which the first and the second stationary contacts (48, 50) are provided and in which the at least one switching mechanism (14) is arranged.

7. The switch according to claim 6, wherein the housing (12) comprises a lower part (16) closed by an upper part (18), wherein the first stationary contact (48) or each of the two stationary contacts (48, 50) is arranged on an inner side of the upper part (18).

8. The switch according to one of claims 1 to 7, wherein the movable contact member (40) includes a movable contact part (46) that interacts with the first contact (48), and in that the spring part (28) interacts with the second contact (50).

9. The switch according to one of claims 1 to 8, wherein the first switching temperature is higher than the first reset temperature and the second reset temperature, and the second switching temperature is higher than the first reset temperature and the second reset temperature.