Temperature-dependent switch

Abstract

A temperature-dependent switch comprises first and second stationary contacts and a temperature-dependent switching mechanism having a movable contact member and a temperature-dependent snap-action part, which transitions between geometric low- and high-temperature configurations based on a temperature of the switch. Switching the snap-action part from its geometric low- to high-temperature configuration moves the switching mechanism from a first to a second switching position and thereby opens the switch. A closing lock prevents the switch once having opened from closing again by keeping it in its second switching position. The closing lock comprises a fusible medium which melts when a melting temperature of the medium is exceeded, contacts, in a molten state, a part of the switching mechanism when it is in its second switching position, and solidifies again and thereby locks it in its second switching position when the temperature of the switch falls below the melting temperature of the medium again.

Claims

1. A temperature-dependent switch, comprising: a first stationary contact, a second stationary contact, and a temperature-dependent switching mechanism having a movable contact member, wherein in a first switching position, the switching mechanism presses the movable contact member against the first stationary contact, thereby producing an electrically conductive connection between the first stationary contact and the second stationary contact via the movable contact member, and, in a second switching position, the switching mechanism keeps the movable contact member spaced at a distance from the first stationary contact, thereby disconnecting the electrically conductive connection, wherein the temperature-dependent switching mechanism comprises a temperature-dependent snap-action part, which is configured to switch from a geometric low-temperature configuration to a geometric high-temperature configuration upon reaching a switching temperature, and which is configured to switch back from the geometric high-temperature configuration to the geometric low-temperature configuration upon subsequently reaching a reset temperature that is lower than the switching temperature, wherein a switching of the temperature-dependent snap-action part from the geometric low-temperature configuration to the geometric high-temperature configuration moves the switching mechanism from the first switching position to the second switching position, thereby opening the switch, wherein a closing lock is provided that prevents the switch once having opened from closing again by keeping the switching mechanism in its second switching position, wherein the closing lock comprises a fusible medium which is configured to melt when a temperature of the switch exceeds a melting temperature of the medium, to contact, in a molten state, a part of the switching mechanism when the switching mechanism is in the second switching position, and to subsequently solidify again and thereby lock the switching mechanism in its second switching position when the temperature of the switch falls below the melting temperature of the medium again, wherein the melting temperature of the fusible medium is lower than the switching temperature of the temperature-dependent snap-action part.

2. The temperature-dependent switch according to claim 1, further comprising a housing, wherein the fusible medium is configured to produce an adhesive or firmly bonded connection between the part of the switching mechanism and a part of the housing, wherein the connection locks the switching mechanism in its second switching position.

3. The temperature-dependent switch according to claim 2, further comprising a reservoir that is arranged in the housing, wherein the fusible medium is stored in the reservoir.

4. The temperature-dependent switch according to claim 1, wherein the fusible medium is configured to contact, in the molten state, the movable contact member when the switching mechanism is in the second switching position.

5. The temperature-dependent switch according to claim 3, wherein the housing comprises a lower part and an upper part attached to the lower part, wherein the first stationary contact is arranged on an inner side of the upper part, and wherein the reservoir is arranged in the lower part in such a way that the movable contact member contacts the medium with a lower side that faces away from the upper part, when the temperature-dependent snap-action part switches from its geometric low-temperature configuration to its geometric high-temperature configuration.

6. The temperature-dependent switch according to claim 5, wherein the reservoir is arranged on an inner bottom surface of the lower part.

7. The temperature-dependent switch according to claim 6, wherein the reservoir comprises a container that is connected to the lower part by means of a non-positive, positive and/or firmly bonded connection.

8. The temperature-dependent switch according to claim 1, wherein the fusible medium comprises a solder.

9. The temperature-dependent switch according to claim 1, wherein the melting temperature of the medium is higher than the reset temperature of the temperature-dependent snap-action part.

10. The temperature-dependent switch according to claim 1, wherein the switching mechanism comprises a temperature-independent spring part which is connected to the movable contact member, wherein the temperature-dependent snap-action part is configured to act on the spring part upon reaching the switching temperature, thereby lifting off the movable contact member from the first stationary contact.

11. The temperature-dependent switch according to claim 10, wherein the spring part comprises a bistable spring disc having two temperature-independent, stable geometric configurations.

12. The temperature-dependent switch according to claim 10, wherein the movable contact member comprises a movable contact part that interacts with the first stationary contact, and wherein the spring part interacts with the second stationary contact.

13. The temperature-dependent switch according to claim 1, further comprising a housing, wherein the temperature-dependent snap-action part is fixed to the movable contact member, in its geometric low-temperature configuration the temperature-dependent snap-action part is freely suspended inside the housing without being directly supported by the housing.

14. The temperature-dependent switch according to claim 1, wherein the temperature-dependent snap-action part comprises a bimetal or trimetal snap-action disc.

15. The temperature-dependent switch according to claim 1, wherein the movable contact member comprises a current transfer member that is configured to interact with the first stationary contact.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a schematic sectional view of a first embodiment of the switch in its low-temperature position;

(2) FIG. 2 shows a schematic sectional view of the first embodiment of the switch shown in FIG. 1 in its high-temperature position;

(3) FIG. 3 shows a schematic sectional view of a second embodiment of the switch in its low-temperature position; and

(4) FIG. 4 shows a schematic sectional view of the second embodiment of the switch shown in FIG. 3 in its high-temperature position.

DESCRIPTION OF PREFERRED EMBODIMENTS

(5) FIG. 1 shows a schematic sectional view of a switch 10, which is rotationally symmetrical in top view and preferably has a circular shape.

(6) The switch 10 comprises 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.

(7) In the first embodiment shown in FIG. 1, both the lower part 16 and the upper part 18 are made of an electrically conductive material, preferably metal. A spacer ring 22, which supports the upper part 18 with an interposed insulating foil 24 and keeps the upper part 18 at a distance from the lower part 16, is arranged between the lower part 16 and the upper part 18.

(8) The insulating foil 24 provides electrical insulation of the upper part 18 against the lower part 16. The insulating foil 24 also provides a mechanical seal that prevents liquids or impurities from entering the interior of the housing from outside.

(9) Since the lower part 16 and the upper part 18 are in this embodiment each made of electrically conductive material, thermal contact to an electrical device to be protected can be produced via their outer surfaces. The outer surfaces are also used for the external electrical connection of the switch 10.

(10) Another insulating foil 26 can be applied to the outside of the upper part 18, as shown in FIG. 1.

(11) The switching mechanism 14 comprises a temperature-independent spring part 28 and a temperature-dependent snap-action disc 30. The spring part 28 is preferably designed as a bistable spring disc. Thus, this spring disc 28 has two temperature-independent stable geometric configurations. The first configuration is shown in FIG. 1. The temperature dependent snap-action disc 30 is preferably designed as a bimetal snap-action disc. The bimetal snap-action disc 30 has two temperature dependent configurations, a geometric high-temperature configuration and a geometric low-temperature configuration. In the first switching position of the switching mechanism 14 shown in FIG. 1, the bimetal snap-action disc 30 is in its geometric low-temperature configuration.

(12) The spring disc 28 rests with its edge 32 on a circumferential shoulder 34 formed in the lower part 16 and is clamped between this shoulder 34 and the spacer ring 22. In contrast, the bimetal snap-action disc 30 is freely suspended in its low-temperature configuration shown in FIG. 1. It is freely suspended with its edge 36 and is not supported by this edge on any part of the housing 12 or any other part of the switch 10.

(13) The spring disc 28 is with its center 40 fixed to a movable contact member 42 of the switching mechanism 14. The bimetal snap-action disc 30 is with its center 44 also fixed to the movable contact member 42. In the embodiment of the switch 10 shown in FIGS. 1 and 2, the movable contact member 42 comprises a ring 46 surrounding the movable contact member 42. This ring 46 is preferably pressed onto the movable contact member 42. It comprises a circumferential shoulder 47 on which the snap-action disc 30 rests with its center 44. The spring disc 28 is clamped between the ring 46 and the upper widened section of the contact member 42. In this way, the temperature-dependent switching mechanism 14 is a captive unit consisting of contact member 42, spring disc 28 and bimetal snap-action disc 30. When mounting the switch 10, the switching mechanism 14 can thus be inserted as a unit directly into the lower part 16.

(14) On its upper side, the movable contact member 42 comprises a movable contact part 38. The movable contact part 38 interacts with a fixed counter contact 48, which is located on an inner side of the upper part 18. This counter contact 48 is herein also referred to as the first stationary contact. The outside of the lower part 16 serves as the second stationary contact 50.

(15) In the position shown in FIG. 1, the switch 10 is in its low-temperature position, in which the temperature-independent spring disc 28 is in its first configuration and the temperature-dependent snap-action disc 30 is in its low-temperature configuration. The spring disc 28 presses the movable contact part 38 against the first stationary contact 48. In the closed, low-temperature position of the switch 10 as shown in FIG. 1, an electrically conductive connection is thus produced between the first stationary contact 48 and the second stationary contact 50 via the movable contact member 42 and the spring disc 28. The contact pressure between the movable contact part 38 and the first stationary contact 48 is generated by the temperature-independent spring disc 28. The temperature-dependent bimetal snap-action disc 30, on the other hand, is almost force-free in this state.

(16) If the temperature of the device to be protected, and thus the temperature of the switch 10 and the bimetal snap-action disc 30 located therein, increases to the switching temperature of the snap-action disc 30 or beyond this switching temperature, the snap-action disc will switch from its convex low-temperature configuration shown in FIG. 1 to its concave high-temperature configuration shown in FIG. 2. When this snap-action occurs, the edge 36 of the bimetal snap-action disc 30 is supported by a part of the switch 10, in this case by the edge 32 of the spring disc 28. Thereby, the bimetal snap-action disc 30 pulls with its center 44 the movable contact member 42 downwards and lifts off the movable contact part 38 from the first stationary contact 48. This simultaneously causes the spring disc 28 to bend downwards at its center 40 so that the spring disc 28 switches from its first stable geometric configuration shown in FIG. 1 to its second stable geometric configuration shown in FIG. 2. FIG. 2 shows the high-temperature position of the switch 10 in which it is open. The electric circuit is thus disconnected.

(17) When the device to be protected and thus the switch 10 including the bimetal snap-action disc 30 cool down again, the spring disc 28, upon reaching the reset temperature, switches back into its low-temperature position, as shown for example in FIG. 1. If the bimetal snap-action disc 30 cannot be supported by any part of the switch 10 in this low-temperature position, it switches so to say “in the empty space”. Due to the bi-stability of the temperature-independent spring disc 28, the switch 10 would then remain open anyway.

(18) However, this does not necessarily have to be the case, since the inner bottom of the lower part 16 may also be raised slightly at the sides, as shown in FIG. 1 by the dotted line 53. In this case, the bimetal snap-action disc 30 could rest with its edge 36 on this raised inner bottom 53. It is also possible that the bimetal snap-action disc 30 in its low-temperature position rests on a similar shoulder in the lower part 16 as the shoulder 34 on which the spring disc 28 rests. In these cases, switching back the bimetal snap-action disc 30 from its high-temperature position to its low-temperature position would cause the switch 10 to close again, in which case the bimetal snap-action disc 30 moves the movable contact member 42 upwards again and brings the movable contact part 38 into contact with the first stationary contact 48.

(19) Irrespective of whether the bimetal snap-action disc 30 in its low-temperature position is able to rest on a part of the switch 10 or not, the described switch-back process is prevented by a closing lock 51. This closing lock 51 is caused by a fusible medium 54, which is arranged on the inner bottom surface 56 of the lower part 16. This fusible medium is preferably a solder, especially preferably a soft solder. This solder 54 is preferably stored in a reservoir or container which is arranged on and/or integrated into the inner bottom surface 56.

(20) The fusible medium or solder 54 melts as soon as the temperature of the switch 10 reaches or exceeds a melting temperature of the medium or solder 54. If the solder 54 in this molten state then contacts a part of the switching mechanism 14 and solidifies afterwards again when the switch 10, and thus the solder 54, cools down again to a temperature below the melting temperature of the solder 54, the solder that has solidified at this point provides a firmly bonded or at least adhesive connection between the part of the switching mechanism 14 with which it comes into contact in the molten state and the lower part 16 of the switch 10.

(21) In the herein shown embodiment, the movable contact member 42 contacts the solder 54 as soon as the switch 10 is opened upon reaching the switching temperature and the switching mechanism 14 is moved to its second switching position by means of the bimetal snap-action disc 30, as shown in FIG. 2. In this situation, the lower side 55 of the movable contact member 42 contacts the solder 54. Preferably, upon reaching the second switching position of the switching mechanism 14, the movable contact member 42 dips at least partially with its lower side 55 into the reservoir 52 that is filled with the solder 54. The solder 54 should then already have melted. Accordingly, a solder 54 is preferably selected whose melting temperature is below or in the range of the switching temperature of the bimetal snap-action disc 30. In principle, however, the melting temperature of the solder 54 can also be slightly higher than the switching temperature of the bimetal snap-action disc 30, since the switch 10 typically heats up a little more even after it has been opened and the circuit has been disconnected. This is known as temperature overshoot.

(22) After reaching this so-called overshoot temperature, the device to be protected and thus also the switch 10 typically cools down again. As soon as the melting temperature of the solder 54 falls below the melting temperature during this cooling process, the solder solidifies. The lower side 55 of the movable contact member 42 then adheres firmly to the inner bottom surface 56 of the lower part 16. The closing lock 51 is thus activated.

(23) Even if the switch 10 cools down to the reset temperature of the bimetal snap-action disc 30, the latter will attempt to switch back to its low-temperature position, but this is prevented by the closing lock 51, which holds the movable contact member 42 in its position shown in FIG. 2. The closing lock 51 caused by the solidified solder 54 prevents the switch 10 from switching back even if the bimetal snap-action disc 30 can rest on the raised inner bottom 53 or any other part of the switch 10 when switching back to its low-temperature position. In this case, however, the melting temperature of the solder 54 should be selected higher than the reset temperature of the bimetal snap-action disc 30, since the closing lock must already be activated in such a case (i.e. the solder must already have cooled down) before the bimetal snap-action disc 30 switches back from its high-temperature position to its low-temperature position.

(24) The solder 54 used for the closing lock 51 can in principle also contact another part of the switching mechanism 14 when it is in its second switching position, for example, the bimetal snap-action disc 30. However, the advantage of creating a firmly bonded connection between the movable contact member 42 and the lower part 16 of the housing 12 using the solder 54 is that the movable contact member 42 is a relatively large and stable component that provides a large contact surface for such a firmly bonded connection. In addition, the inner bottom surface 56 of the lower part 16 provides anyhow sufficient space for mounting such a reservoir 52.

(25) The reservoir 52, in which the solder 54 is preferably stored, can be made in different ways. It can be a simple recess or hole in the inner bottom surface 56. Similarly, the reservoir 52 may, for example, be in the form of a circular bead arranged on top of or being integrated the inner bottom surface 56 and forming a closed contour within which the solder 54 is stored. In principle, however, it is also possible to insert a separate container or a surrounding wall (e.g. a ring) as a separate component into the housing 12 of the switch 10 and to connect it to the inner bottom surface 56 in a non-positive, positive or firmly bonded manner.

(26) The medium 54 does not necessarily have to be a solder. It can also be another fusible material or an adhesive that creates an adhesive connection between a part of the switching mechanism 14 and a part of the housing 12 in the second position of the switching mechanism 14.

(27) FIGS. 3 and 4 show a second embodiment of the switch 10′. FIG. 3 shows the closed position of the switch 10′, in which the switching mechanism 14′ is in its first switching position. FIG. 4 shows the open position of the switch 10′, in which the switching mechanism 14′ is in its second switching position.

(28) The second embodiment shown in FIGS. 3 and 4 differs from the first embodiment shown in FIGS. 1 and 2 mainly by the design of the housing 12′ and the design of the switching mechanism 14′. The closing lock 51 is, however, also in this case caused by a fusible medium 54, which is preferably arranged in a reservoir 52 on the inner bottom surface 56 of the lower part 16′ and which, in the second switching position of the switching mechanism 14′, ensures a firmly bonded or at least adhesive connection between the contact member 42′ and the lower part 16′ and thus prevents the switch 10′ from switching back.

(29) In the second embodiment shown in FIGS. 3 and 4, the lower part 16′ is again made of an electrically conductive material. The flat upper part 18′ is instead made of an electrically insulating material. It is held to the lower part 16′ by a bent edge 20′.

(30) Between the upper part 18′ and the lower part 16′, a spacer ring 22′ is provided here as well, which keeps the upper part 18′ at a distance from the lower part 16′. On its inner side 58, the upper part 18′ comprises a first stationary contact 48′ and a second stationary contact 50′. The contacts 48′ and 50′ are designed as rivets which extend through the upper part 18′ and end outside in the heads 60, 62, which serve for the external connection of the switch 10′.

(31) The movable contact member 42′ in this case comprises a current transfer member 64, which is in this case designed as a contact plate, the upper side of which is coated with an electrically conductive coating so that it provides an electrically conductive connection between the two contacts 48′ and 50′ in the contact position shown in FIG. 3. The current transfer member 64 is connected to the spring disc and the bimetal snap-action disc 30 via a rivet 66, which is also to be regarded as part of the contact member 42′. In the second switching position of the switching mechanism 14′, this rivet 66 contacts the fusible medium or solder with its lower side 55 (see FIG. 4), so that when the medium or solder 54 solidifies, a firmly bonded connection is produced between the movable contact member 42′ and the lower part 16′ of the switch 10′ as before, thus preventing the switch 10′ from closing again even upon reaching or undershooting the reset temperature.

(32) An advantage of the switch design shown in FIGS. 3 and 4 is that, in contrast to the embodiment of the switch shown in FIGS. 1 and 2, no current flows through either the spring disc 28 or the bimetal snap-action disc 30 when the switch is closed. This current flows only from the first external connection 60 via the first stationary contact 48′, the current transfer member 64 and the second stationary contact 50′ to the second external connection 62.

(33) It is to be understood that the foregoing is a description of one or more preferred exemplary embodiments of the invention. The invention is not limited to the particular embodiment(s) disclosed herein, but rather is defined solely by the claims below. Furthermore, the statements contained in the foregoing description relate to particular embodiments and are not to be construed as limitations on the scope of the invention or on the definition of terms used in the claims, except where a term or phrase is expressly defined above. Various other embodiments and various changes and modifications to the disclosed embodiment(s) will become apparent to those skilled in the art. All such other embodiments, changes, and modifications are intended to come within the scope of the appended claims.

(34) As used in this specification and claims, the terms “for example,” “e.g.,” “for instance,” “such as,” and “like,” and the verbs “comprising,” “having,” “including,” and their other verb forms, when used in conjunction with a listing of one or more components or other items, are each to be construed as open-ended, meaning that the listing is not to be considered as excluding other, additional components or items. Other terms are to be construed using their broadest reasonable meaning unless they are used in a context that requires a different interpretation.