Temperature-dependent switch

Abstract

A temperature-dependent switch has a temperature-dependent switching mechanism, a housing accommodating the switching mechanism, two first connections between which first connections the switching mechanism makes or interrupts an electrically conductive connection depending on the temperature of said switching mechanism, and a heating resistor that is arranged on an outside of the housing and is connected electrically in series with the two connections. The heating resistor is a sheet-like metal part that is welded to the housing and carries a further connection.

Claims

1. A temperature-dependent switch comprising: two first external connections for connecting said switch to an external circuit; a temperature-dependent switching mechanism that depending on its temperature makes or interrupts an electrically conductive connection between said two first external connections; a housing having an outside and accommodating said switching mechanism; and a heating resistor arranged on said outside of said housing and connected electrically in series with said two first external connections, said heating resistor being embodied as a sheet-metal part; said sheet-metal part being welded to the housing, and a further external connection of said switch being provided directly on the sheet-metal part.

2. The switch of claim 1, wherein the housing comprises an upper part and a lower part and wherein at least the lower part is electrically conductive and is electrically connected to one of said two first external connections, the sheet-metal part being welded to an exterior surface of the electrically conductive lower part.

3. The switch of claim 2, wherein the upper part and the lower part of the housing are electrically conductive.

4. The switch according of claim 1, wherein the sheet-metal part is welded to the housing by at least two welding spots.

5. The switch according to claim 1, wherein said further external connection comprises a connection piece that is welded to the sheet-metal part.

6. The switch according to claim 5, wherein the connection piece is welded to the sheet-metal part by at least two welding spots.

7. The switch according to claim 1, wherein the sheet-metal part comprises a connection section that protrudes beyond the housing, said further external connection being provided at said connection section.

8. The switch according to claim 1, wherein the further external connection is arranged centrally on the sheet-metal part.

9. The switch according to claim 1, wherein the sheet-metal part has an ohmic resistance value as measured between the further external connection and the housing, said ohmic resistance value being less than 100 m.

10. The switch according to claim 9, wherein the sheet-metal part has an ohmic resistance value as measured between the further external connection and the housing, said ohmic resistance value being between 2 and 50 m.

11. The switch according to claim 1, wherein the sheet-metal part has a thickness of at least 50 m.

12. The switch according to claim 2, comprising a stationary contact part fixedly connected to the upper part of said housing, wherein the switching mechanism comprises a movable contact part and a bimetallic snap-action disc that is mechanically connected to said movable contact part, when being at a temperature below its switching temperature, said bimetallic snap-action disc presses said movable contact part against said stationary contact part and, when being at a temperature above its switching temperature, said bimetallic snap-action disc lifts off said movable contact part from said stationary contact part, wherein the stationary contact part is connected to one of the two first external connections, and the switching mechanism is connected to the other of the two first external connections, at least when the movable contact part rest on the stationary contact part.

13. The switch according to claim 12, wherein the switching mechanism comprises a spring disc that preloads the movable contact part for resting on the stationary contact part, wherein the bimetallic snap-action disc lifts off the movable contact part from the stationary contact part when being at a temperature above its switching temperature.

14. The switch according to claim 1, comprising two stationary contact parts each being connected to one of the two first external connections, wherein the switching mechanism comprises a current transfer element that interacts with said two stationary contact parts.

15. The switch according to claim 14, wherein one of the two first external connections is electrically connected to the housing.

16. The switch according to claim 14, wherein the switching mechanism comprises a bimetallic snap-action disc that is mechanically connected to said current transfer element and presses said current transfer element against the two stationary contact parts when being at a temperature below its switching temperature, and lifts said current transfer element off from said stationary contact parts, when being at a temperature above its switching temperature.

17. The switch according to claim 16, wherein the switching mechanism comprises a spring disc that preloads said current transfer element for resting against said two stationary contact parts, wherein the bimetallic snap-action disc lifts off the current transfer element from the stationary contact parts when being at a temperature above its switching temperature.

18. The switch according to claim 1, which comprises an insulating base, said two first external connections being arranged on said insulating base, and the housing being plugged onto said insulating base.

19. The switch according to claim 18, wherein one of the two first external connections is electrically connected to the housing.

20. A temperature-dependent switch comprising two first external connections for connecting said switch to an external circuit, a temperature-dependent switching mechanism that depending on its temperature makes or interrupts an electrically conductive connection between said two first external connections, a housing having an electrically conductive section with an outside and accommodating said switching mechanism, and a heating resistor arranged at said housing and connected electrically in series with said two first external connections, said heating resistor comprising a sheet-metal part carrying a further external connection of said switch, said sheet-metal part being connected to said outside of said electrically conductive section of the housing by at least two welding spots.

21. A temperature-dependent switch comprising two first external connections for connecting said switch to an external circuit, a temperature-dependent switching mechanism that depending on its temperature makes or interrupts an electrically conductive connection between said two first external connections, a housing having an outside and accommodating said switching mechanism, and a heating resistor arranged on said outside of said housing and connected electrically in series with said two first external connections, said heating resistor being a sheet-metal part that is electrically and mechanically connected to said outside of the housing, said sheet-metal part having provided directly thereon a further external connection of said switch.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the invention are illustrated in the attached drawing and will be explained in more detail in the description below. In the drawing:

(2) FIG. 1 shows a schematic longitudinal section, which is not true to scale, through a temperature-dependent switch, in which a movable contact part interacts with a stationary contact part, and a heating resistor is welded on the outside of the housing of said switch;

(3) FIG. 2 shows a schematic view of the switch shown in FIG. 1 from below with a view of the heating resistor;

(4) FIG. 3 shows, in an illustration as shown in FIG. 1, a further temperature-dependent switch, in which two stationary contact parts interact with a current transfer element;

(5) FIG. 4 shows the switch provided with connection strands shown in FIG. 3 in plan view;

(6) FIG. 5 shows a schematic plan view of a further temperature-dependent switch with welded-on heating resistor; and

(7) FIG. 6 shows a schematic plan view of yet a further temperature-dependent switch with welded-on heating resistor.

DESCRIPTION OF PREFERRED EMBODIMENTS

(8) In FIG. 1, 10 denotes a temperature-dependent switch which comprises a pot-like lower part 11, which is closed by an upper part 12, which is held on the lower part 11with an insulation film 13 interposedby a flanged rim 14.

(9) A temperature-dependent switching mechanism 15 which comprises a spring snap-action disc 16, which centrally supports a movable contact part 17 on which a freely inserted bimetallic disc 18 rests, is arranged in the housing of the switch 10, which housing is formed by the lower part 11 and the upper part 12.

(10) The spring snap-action disc 16 is supported on an inner bottom 19 on the inside on the lower part 11, which is manufactured from electrically conductive material.

(11) The movable contact part 17 is in bearing contact with a stationary contact part 20, which is provided on an inner side 21 of the upper part 12, which in this embodiment is likewise manufactured from metal, although it is sufficient for the embodiment of the invention if the housing is electrically conductive at least in one section, i.e. if in the case of the switch 10 at least the lower part 11 is electrically conductive.

(12) In this way, the temperature-dependent switching mechanism 15 in the low temperature position shown in FIG. 1 produces an electrically conductive connection between the upper part 12 and the lower part 11, wherein the operating current flows via the stationary contact part 20, the movable contact part 17 and the spring snap-action disc 16.

(13) Alternatively, it is also possible to use instead of the spring snap-action disc 16 a bimetallic part that supports the movable contact part 17 and therefore conducts the operating current when the switch 10 is closed.

(14) If, in the case of the switch 10 shown in FIG. 1, the temperature of the bimetallic disc 18 increases beyond its response temperature, it snaps over from the convex position shown in FIG. 1 into its concave position, in which it lifts off the movable contact part 17 from the stationary contact part 20 counter to the force of the spring disc 16 and therefore opens the circuit.

(15) Such a temperature-dependent switch 10 is known, for example, from DE 196 23 570 A1, the content of which is hereby made the subject matter of the present disclosure.

(16) In the case of the switch shown in FIG. 1, a contact surface in a central region of the upper part 12 acts as a first connection 22. The lower part 11, with which contact can be made, for example, via the rim 14 or a bottom 26, acts as further first connection.

(17) The switch 10 is equipped with a heating resistor 24 in the form of a metal part, which is welded from outside onto the outer bottom 26 of the lower part 11 and is electrically in series with the first connections.

(18) In the embodiment shown, the metal part 25 is welded to the outer bottom 26 at four welding spots 27, which preferably takes place by means of resistance welding. Two of the four welding spots 27 are shown in FIG. 1.

(19) A contact surface that acts as further connection 28 for the switch 10 is provided centrally on the metal part 25.

(20) In a known manner, one connection lug can be soldered with its respective inner end onto each of the connections 22, 28, which connection lugs are then used for interconnection with an appliance to be protected. For this purpose, welding angles can be welded to the connections 22, 28.

(21) It is also possible to solder connection strands to the connections 22, 28.

(22) The metal part 25 has an ohmic resistance value in the milliohms range between the connection 28 andvia the welding spots 27the lower part 11.

(23) Any electrically conductive sheet-like metal part which has the corresponding resistance value given the dimensions possible here can be used as metal part, as will be explained in more detail below.

(24) Via the welding spots 27, the metal part 25 is connected both electrically and thermally to the lower part 11. During welding, the metal part 25, which in the embodiment shown has a thickness indicated at 29 of 50 m, becomes corrugated to such an extent that only the welding spots 27 contribute to the electrical and thermal contact to the lower part 11. The resultant corrugated nature is indicated at 31 in FIG. 1.

(25) The metal part 25 could also be welded laterally to the conductive lower part 11 if the bottom 26 is intended to be kept free as heat transfer surface.

(26) Alternatively, it would also be possible to weld the metal part 25 from outside onto the electrically conductive cover part 12, with the result that the connection 22 would be electrically in series with the connection 28 via the heating resistor 24. Then, for example, the rim 14 or the bottom 26 of the lower part 11 would be available as second connection.

(27) If necessary, an insulation layer can be arranged between the bottom 26 and the metal part 25. In the case of the switches 10 according to the invention produced and tested previously on the applicant's premises, this was not required, however.

(28) If desirable, the switch 10 can also be provided with a self-holding function, i.e. have a further resistor which is connected electrically in parallel with the first connections. For this, for example, the cover part 12 is manufactured from PTC thermistor material, in which case the insulation film 13 is dispensed with without being replaced, with the result that the PTC thermistor forming the cover part 12 is electrically connected to the two first connections 22 and 11/14. Such a switch is described in DE 195 17 310 A1.

(29) Alternatively, a self-holding resistor in the form of a thick-film resistor can also be arranged on the cover part, as is described by way of example in DE 195 14 853 A1. In the switch known from this document, the self-holding resistor is applied to the insulation film 13.

(30) FIG. 2 shows a view of the circular bottom 26 of the switch 10 shown in FIG. 1. It can be seen that the four welding spots 27 are fitted in the four corners 32 of the metal part 25.

(31) A welding angle 34 is fastened on the metal part 25 centrally with three welding spots 33, with a connection strand 35 being welded to said welding angle. Also shown is a second connection strand 36, which is electrically connected to one first connection 22.

(32) The square metal part 25 has edge lengths 37 of 10 mm, which, given a thickness 29 of 50 m, results in a resistance value of approximately 10 m between the connection strand 35 and, via the welding spots 27 and 33, the bottom 26 when a metal part consisting of spring steel strip of material no. 1.4310 is used.

(33) Long-time tests have confirmed that on a DC voltage drop of 14 volts such a switch 10 withstands an operating current of 25 A at a switch-off temperature of 160 C. for more than 3500 switching cycles without any impairment to the operation. For a short period of time, the switch 10 also withstands an operating current of 35 A at a switch-off temperature of 400 C.

(34) The metal part 25 can also have any other geometric shape, in particular the welding angle 34 can also be welded onto the metal part eccentrically. The metal part 25 can be rectangular, triangular, round, circular, oval or drop-shaped, for example, wherein the welding angle 34 or a connection piece formed as desired can be welded centrally or to the rim of the metal part 25, which can also protrude laterally beyond the base 26.

(35) It is merely important that the metal part, measured between the further connection 28 or in this case the welding angle 34 and the housing, has an ohmic resistance value of less than 100 ma preferably of approximately 10 m.

(36) In FIG. 3, 40 denotes a further temperature-dependent switch, which, in the same way as the switch 10 shown in FIG. 1, is provided with a heating resistor formed by a metal part.

(37) The switch 40 comprises a temperature-dependent switching mechanism 41, which is accommodated in a housing 42. The housing 42 has an upper part 43 that is manufactured from an insulation material and closes an electrically conductive lower part 44, whose rim 45 fixes the upper part 43 to the lower part 44.

(38) Within the meaning of the present invention, in this case it is the lower part 44 that forms the electrically conductive section of the housing 42, onto which the metal part 25 is welded.

(39) The switching mechanism 41 comprises a spring snap-action disc 46 and a bimetallic snap-action disc 47, with a pin-like rivet 48 passing centrally through said bimetallic snap-action disc 47 and said spring snap-action disc 46, by means of which rivet said discs are mechanically connected to a current transfer element 49 in the form of a contact plate.

(40) The spring snap-action disc 46 is clamped in with its rim 51 between a circumferential shoulder 52 internally in the lower part 44 and a spacer ring 53, on which the upper part 43 rests with its inner side 54.

(41) The bimetallic snap-action disc 47 is supported with its rim 55 on an inner bottom 56 of the lower part 44.

(42) The round, in the present case circular, current transfer element 49 has, in the direction of the upper part 43, an electrically conductive contact surface 57, which runs peripherally in the circumferential direction and interacts with two stationary contact parts 58, 59, which are arranged on the inner side 54 of the upper part 43.

(43) The stationary contact parts 58, 59 are in the form of inner heads of contact rivets 61, 62, which pass through the upper part 43 and end in outer sections 63, 64. An insulating web 65 is provided between the sections 63, 64.

(44) In each case one connection piece 67 or 68 with lugs 71 and 72, respectively, which each act as first connections of the switch 40, is arranged on the two outer sections 63, 64 of the contact rivets 61, 62.

(45) The lower part 44 has an outer bottom 69, to which the metal part 25 forming the heating resistor 24 is welded with four welding spots 27, as has been described above already for the switch 10.

(46) FIG. 3 again shows the corrugated nature 31 formed during welding and the connection 28.

(47) The metal part 25 could also in this case be welded laterally to the conductive lower part 44 when the bottom 69 is intended to be kept free as heat transfer surface.

(48) If appropriate, prior to welding of the metal part 25 to the bottom 69, the welding angle 34 is also welded to the connection 28, as has been described in FIG. 2. In the view from below, the switch 30 thus has the same appearance as the switch 10, with the result that reference is made in this regard to FIG. 2, so as to avoid repetition.

(49) In order to provide the switch 40 with connection strands, the upper, u-shaped lugs 71, 72 are bent back downwards onto the sections 63 and 64, respectively, and generally ends of the connection strands from which the insulation has been stripped are inserted into the tunnel thus formed and soldered.

(50) In the present case, however, a connection strand 73 is only soldered to the lug 71, as can be seen in the plan view in FIG. 4.

(51) The lug 72 assigned to the second stationary contact part 59 is electrically connected to a connecting part 74 in a comparable manner, which connecting part 74 is connected to the conductive lower part 44 over the rim 45 thereof. In the simplest case, the connecting part 74 is formed by soldering compound, which electrically and mechanically connects the rim 45 to the connection piece 68.

(52) In this way, the stationary contact part 59 is connected to the electrically conductive lower part 44, which is connected to the heating resistor 24 via the welding spots 27, to which heating resistor a second connection strand 75 is connected via the welding angle 34, as is indicated in the plan view shown in FIG. 4. The heating resistor 24 is thus connected electrically in series with the stationary contact part 59.

(53) If the current transfer element 49 in FIG. 3 is in bearing contact with the two stationary contact parts 58, 59, there is therefore a continuous electrically conductive connection from the first connection strand 73 via the connection piece 67 to the first stationary contact part 58, from there via the current transfer element 49, the second stationary contact part 59, the second connection piece 68 and the connecting part 74 to the rim 45 and from there to the lower part 44, which is connected to the second connection strand 75 via the heating resistor 24.

(54) If the cover part 43 is manufactured from PTC thermistor material, the PTC thermistor thus formed is in parallel with the first connections 71, 72 and provides a self-holding function, as is known from DE 198 27 113 A1.

(55) Alternatively, in accordance with DE 198 27 113 A1, the self-holding resistor can also be provided on the cover part 43 manufactured from insulating material on the inside or on the outside, for example formed as a thick-film resistor.

(56) FIG. 5 shows a plan view of a further embodiment of a switch 80, which is equipped with a heating resistor 24 in the form of a metal part 25.

(57) The switch 80 has an insulating base 81, out of which two connection electrodes 82, 83 protrude as connections. The base 81 is arranged in a metallic, electrically conductive housing 84, which has been pushed onto the base 81 as a cap. A temperature-dependent switching mechanismmasked by the housing 84 in the view of FIG. 5is held on the base 81, as is shown by way of example in DE 195 09 656 A1, DE 10 2004 036 117 A1, DE 10 2008 031 389 B3 or DE 10 2011 016 896 B3.

(58) The switching mechanism produces an electrically conductive connection between the two connection electrodes 82, 83 or opens the electrical connection depending on the temperature of said switching mechanism.

(59) In order to provide the switch 80 with a defined current dependence, the metal part 25 is welded onto the housing 84 at the welding spots 27, as has been described above for the switches 10 and 40. In this embodiment, a connection electrode 85 is welded to the soldering angle 34.

(60) The connection electrode 83 is electrically connected to the housing 84 via a connecting part 86; the connecting part 86 in this case performs the same function as the connecting part 74 in the case of the switch 40 from FIG. 4. The connecting part 86 is illustrated merely schematically in FIG. 5; any suitable configuration can be assumed.

(61) It goes without saying that, instead of the connection electrodes 82, 83, 85, connection strands can also be used. In this case, if appropriate, the connecting part 86 can be dispensed with and one of the two connection strands provided on the switch as first connections can be connected directly to the housing.

(62) The heating resistor 24 is thus connected electrically in series between the two first connections in the form of the connection electrodes 82 and 85 via the housing 84, the connecting part 86, the connecting electrode 83 and the temperature-dependent switching mechanism. It is used in a comparable manner to that of switch 40 for defined current-dependent switching.

(63) Irrespective of the nature and design of the temperature-dependent switching mechanism, temperature-dependent switches with two first connections, between which the switching mechanism produces an electrical connection in temperature-dependent fashion, and with a housing which is electrically conductive in at least one section, can be equipped in the described manner by means of the metal part used according to the invention with a current-dependent switching function.

(64) If the switch as such already switches in current-dependent fashion as well, this switching function can be configured in a more defined manner and improved by the metal part used in accordance with the invention.

(65) While, in the embodiments in FIGS. 1 to 5, the further connection 28 is arranged below the switch 10, 40, 80, i.e. within the contour thereof, FIG. 6 shows a plan view of an embodiment in which the metal part 25 protrudes laterally beyond the bottom 26 of the switch 10. A connection strand 91 is soldered to the first connection 22, and a further connection strand 92 is soldered to the further connection 28.

(66) The metal part 25 is also in this case welded from outside to the bottom 26 of the switch 10, as is shown in FIGS. 1 and 2.

(67) The metal part 25 in this case has a drop shape, and the further connection 28 in the embodiment shown in FIG. 6 is not centrally on the metal part 25 but is on a section 93 of the metal part 25 which, so to speak, forms the runout of the drop, i.e. where the metal part 25 protrudes laterally beyond the switch 10.