Temperature-dependent switching mechanism

Abstract

A temperature-dependent switching mechanism is equipped with a bimetal snap-action disc and a spring snap-action disc, which carries a movable contact part, the bimetal snap-action disc and the spring snap-action disc being captively held in an annular frame.

Claims

1. A temperature-dependent switching mechanism comprising a ring-shaped annular frame that does not have a closed bottom, a bimetal snap-action disc, a movable contact member and a spring snap-action disc carrying said movable contact member, said bimetal snap-action disc and said spring snap-action disc being captively held in said frame; and wherein the bimetal snap-action disc has a low-temperature position and a high-temperature position, a first peripheral shoulder being arranged internally in the frame, on which first peripheral shoulder a rim of the bimetal snap-action disc is supported during the transition from its high-temperature position into its low-temperature position.

2. The switching mechanism of claim 1, wherein the annular frame comprises an upper ring surface.

3. The switching mechanism of claim 1, wherein the annular frame comprises a lower ring surface.

4. The switching mechanism of claim 1, wherein the annular frame comprises an upper ring surface and a lower ring surface arranged parallel to one another and interconnected by a peripheral cylinder surface running transversely to the upper and lower ring surfaces.

5. The switching mechanism of claim 4, wherein a conical transition surface is arranged between the cylinder surface and the lower ring surface.

6. The switching mechanism of claim 1, wherein the movable contact member is a movable contact part, which is arranged between the bimetal snap-action disc and the spring snap-action disc.

7. The switching mechanism of claim 1, wherein the bimetal snap-action disc is fixed captively with play to the movable contact member.

8. The switching mechanism of claim 1, wherein the spring snap-action disc is fixed captively to the movable contact member.

9. The switching mechanism of claim 1, wherein a second peripheral shoulder is arranged inwardly in the frame, on which second peripheral shoulder a rim of said spring snap-action disc is supported.

10. The switching mechanism of claim 9, wherein the second peripheral shoulder is arranged in a groove running peripherally internally in the frame, in which groove said rim of said spring snap-action disc is arranged.

11. The switching mechanism of claim 10, wherein said rim of said spring snap-action disc is latched into said groove.

12. The switching mechanism of claim 9, wherein said rim of said spring snap-action disc is held in place by a protrusion extending over said rim of the spring snap-action disc, and formed only after said rim of said spring snap-action disc has been placed on the second peripheral shoulder.

13. The switching mechanism of claim 1, which comprises a current transfer member connected to the movable contact member.

14. The switching mechanism of claim 13, wherein the current transfer member is connected to the annular frame.

15. The switching mechanism of claim 13, wherein the annular frame comprises an upper ring surface and a lower ring surface, the current transfer member being arranged between the upper and lower ring surfaces.

16. The switching mechanism of claim 13, wherein the annular frame comprises an upper ring surface and a lower ring surface, the current transfer member being arranged with its rim above the upper ring surface.

17. The switching mechanism of claim 13, wherein the annular frame comprises an upper ring surface and a lower ring surface, the current transfer member being arranged with its rim below the lower ring surface.

18. The switching mechanism of claim 1, wherein the annular frame comprises electrically conductive material.

19. The switching mechanism of claim 1, wherein the annular frame comprises electrically insulating material.

20. The switching mechanism of claim 1, wherein the annular frame comprises electrical resistance material.

21. The switching mechanism of claim 1, wherein the annular frame comprises at least one resistive layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the invention are illustrated in the accompanying drawing and will be explained in greater detail in the following description. In the drawing:

(2) FIG. 1 shows a first embodiment of a switching mechanism with annular frame in a schematic, sectional illustration;

(3) FIG. 2 shows a further embodiment of the new switching mechanism in an illustration similar to FIG. 1;

(4) FIG. 3 shows a schematic sectional side view of a temperature-dependent switch equipped with the switching mechanism from FIG. 2;

(5) FIG. 4 shows a plan view of the switching mechanism from FIG. 1, but with additional current transfer member;

(6) FIG. 5 shows a schematic view of the current transfer member from FIG. 2;

(7) FIG. 6 shows a schematic sectional side view of a slip-in housing equipped with the switching mechanism from FIG. 1;

(8) FIG. 7 shows a schematic functional diagram of the switch from FIG. 3;

(9) FIG. 8 shows an illustration similar to FIG. 7, but with a self-holding resistor;

(10) FIG. 9 shows an illustration similar to FIG. 7, but with a series resistor for current-dependent switching;

(11) FIG. 10 shows an illustration similar to FIG. 8, but with series resistor for current-dependent switching and without current transfer member; and

(12) FIG. 11 shows an illustration similar to FIG. 10, without series resistor, but with self-holding resistor.

DESCRIPTION OF PREFERRED EMBODIMENTS

(13) In FIG. 1, a temperature-dependent switching mechanism is denoted by 10 and comprises a circular bimetal snap-action disc 11 and also a circular spring snap-action disc 12 arranged above the bimetal snap-action disc 11. The bimetal snap-action disc 11 and the spring snap-action disc 12 are arranged captively on a movable contact part 14.

(14) The bimetal snap-action disc 11 and the spring snap-action disc 12 are held captively in an annular frame 15, which is likewise circular and which comprises an upper ring surface 16 and also a lower ring surface 17 parallel thereto and arranged radially further inwardly than the upper ring surface 16. The upper ring surface 16 and the lower ring surface 17 are interconnected via a cylinder surface 18 running transversely to the ring surfaces 16, 17 and also via a conical transition surface 19, which runs at an incline between the cylinder surface 18 and the lower ring surface 17.

(15) Whereas the movable contact part 14 protrudes upwardly beyond the upper ring surface 16, the lower ring surface 17 protrudes downwardly beyond the movable contact part 14 and in particular beyond the bimetal snap-action disc 11 and also the spring snap-action disc 12, such that, when the switching mechanism 10 is opened, the movable contact part 14 does not protrude downwardly beyond the lower ring surface 17, such that no special measures have to be taken in order to prevent contact between the movable contact part 14 and an inner base of a switch equipped with the switching mechanism, when the switch is opened.

(16) The bimetal snap-action disc 11 rests loosely via the rim 21 thereof on an annular lower shoulder 22 running peripherally internally in the frame 15.

(17) The spring snap-action disc 12 rests via the rim 23 thereof on an upper shoulder 24 running peripherally in an annular manner internally in the frame 15 and formed in a groove 25, which is formed by the shoulder 24 and also a protrusion 26 extending over the rim 23.

(18) In this way, the spring snap-action disc 12 is held captively via the rim 23 thereof in the groove 25 and therefore in the frame 15.

(19) At its inner portion 27, the spring snap-action disc sits captively, but with play in a peripheral groove 28, which is arranged on the movable contact part 14.

(20) The bimetal snap-action disc 11 is held captively, but with play between the spring snap-action disc 12 and a peripheral shoulder 29 on the movable contact part.

(21) The switching mechanism 10 can be tested even before installation in a switch and can be stored in bulk form because the rims 21, 23 of the snap-action discs 11, 12 are protected by the frame 15 and the spring snap-action disc 12 can be contacted via the frame 15.

(22) As mentioned above, the switching mechanism 10 can alternatively comprise only one snap-action disc, in this case bimetallic snap-action disc 11, that is to be arranged within frame 15 the same way as shown in FIG. 1 for spring snap-action disc 12. Bimetallic snap-action disc 11 is in such case arranged with its rim within groove 25 and, thereby, held captively in frame 15. Further, bimetallic snap-action disc 11 in this case carries movable contact part 14 and is arranged with play via its inner portion in peripheral groove 28.

(23) The temperature-dependent switching mechanism 10 shown in FIG. 2 is in principle constructed similarly to the switching mechanism from FIG. 1, however it is additionally provided with a sheet-like current transfer member 31, which is welded at the centre 32 thereof to the movable contact part 14.

(24) The current transfer member 31 protrudes via the rim 33 thereof beyond the lower ring surface 17. The rim 33 can be fixedly connected to the ring surface 17 by spot welding. The switching mechanism 10 can thus also be tested prior to installation.

(25) A temperature-dependent switch 35 is shown in FIG. 3, said switch having a pot-like lower part 36, which is closed by a plate-like cover part 37.

(26) The switching mechanism 10 from FIG. 2 is placed in the lower part 36 such that the frame 15 bears internally via the cylinder surface 18 thereof against a peripheral wall 38 of the lower part 36, and the peripheral wall 38 is thus stabilized.

(27) Due to the placement of the switching mechanism 10 in the lower part 36, the current transfer member 31 is clamped via the rim 33 thereof between the lower ring surface 17 and an inner base 39 of the lower part 36.

(28) The lower part 36 is a deep-drawn part, such that the transition between wall 38 and base 39 is not formed exactly, in particular not at right angles. Because the frame 15 has the conical transition surface 19, it can nevertheless be positioned exactly in the lower part 36.

(29) An insulating foil 41 lies on the upper ring surface 16 of the frame 15 and extends upwardly laterally between the cover part 37 and the wall 38 and is then pressed from above onto the cover part 37, for which purpose the wall 38 has been flanged at the upper edge 42 thereof.

(30) In this way, the edge 42 presses onto the cover part 37, and said cover part presses via the insulating foil 41 onto the upper ring surface 16, whereby the frame 15 and therefore the switching mechanism 10 is fixedly assembled in the temperature-dependent switch 35 and at the same time the electrical contact between the inner base 39 of the lower part 36 and also the rim 33 of the current transfer member 31 is produced.

(31) The annular frame 15 can be manufactured here both from electrically conductive material and from electrically insulating material.

(32) A stationary counter contact 44 is arranged on an inner surface 43 of the cover part 37 and bears against the movable contact part 14 in the closed state of the switch 35 shown in FIG. 3.

(33) In the switching state shown in FIG. 3, the bimetal snap-action disc 11 is placed in a force-free manner in the switching mechanism 10, whereas the spring snap-action disc 12 is supported via the rim 23 thereof in the grove 25 and presses the movable contact part 14 against the stationary counter contact 44. In this way, the electrical circuit between the stationary counter contact 44 and the lower part 36 consisting here of electrically conductive material is closed, wherein the operating current of a device to be protected flows via the current transfer member 31 and, where applicable, also via the spring snap-action disc 12.

(34) The switch 35 has two outer connections, which are formed by the outer base 36 of the lower part 36 and the outer surface 44 of the stationary counter contact 44. When the switch 35 is closed, the two outer connections 36 and 44 are electrically conductively interconnected.

(35) When the temperature of the switch 35 rises above the transition temperature of the bimetal snap-action disc 11, said disc moves upwardly with its rim 21 in FIG. 3 and presses from beneath against the spring snap-action disc 12. Here, it draws the movable contact part 14 downwardly away from the stationary counter contact 44 until the spring snap-action disc 12 snaps over from one stable geometric configuration thereof as shown in FIG. 3 into the other stable geometric configuration thereof, in which it holds the movable contact part 14 at a distance from the stationary counter contact 44.

(36) When the temperature of the switch 35 decreases again, the bimetal snap-action disc first snaps back into the configuration thereof shown in FIG. 3. Because the movable contact part 14 is now positioned further below in the direction of the base 39, the bimetal snap-action disc 11 comes into contact here via the rim 21 thereof with the peripheral shoulder 22 and, with further shape change, presses the movable contact 14 toward the stationary counter contact 44 via the centre of the spring snap-action disc 12. Here, the spring snap-action disc 12 is also being curved upwardly in the middle thereof, until it snaps back into the stable geometric configuration thereof shown in FIG. 3, in which it presses the movable contact 14 against the stationary counter contact 44.

(37) The bimetal snap-action disc 11 is again supported in a force-free manner in this switching state.

(38) When the annular frame 15 consists of an electrically insulating material, it is possible to dispense with the insert of the insulating foil 41. The operating current then flows only through the current transfer member 31 when the switch 35 is closed, said current transfer member heating up during this process depending on the volume resistivity thereof.

(39) Because the current transfer member 31 is arranged on the side of the bimetal snap-action disc 11, the resistive heat developing leads to a rapid heating of the bimetal snap-action disc 11, which ensures an accurate response of the switch 35 to an excessively high operating current of a device to be protected.

(40) Because the spring snap-action disc 12 remains free of current flow in this embodiment, it has a long service life.

(41) If the annular frame 15 consists of an electrically conductive material or is covered by a layer of an electrically conductive material, it constitutes a parallel resistor, which is connected both to the electrically conductive cover part 37 and to the electrically conductive lower part 36, parallel to the switching mechanism 10. The insulating foil 41 is then dispensed with.

(42) Provided the switching mechanism is closed, the self-holding resistor thus formed is short-circuited by the current transfer member 31, which is a good electrical conductor. However, when the switch 35 opens, the self-holding resistor formed by the annular frame 15 is now in series between the stationary counter contact 44 and the lower part 36, such that a residual current flows through the switch 35 and holds the switching mechanism open until the voltage supply of the electrical device to be protected is switched off.

(43) Serving as heating resistor, the current transfer member 31 can additionally provide current-dependent switching.

(44) In a modification, the switching mechanism 10 from FIG. 1 can be used with the switch from FIG. 3, such that the current flow is then realized exclusively through the spring snap-action disc 12.

(45) In this case too, the annular frame 15 may consist of electrically conductive material or may have an electrically conductive layer, for example on the cylinder surface 18 or the lower ring surface 17.

(46) In this way, a series resistor would then be formed, which is connected in series with the spring snap-action disc 12 and provides current-dependent switching of the switch 35 in the manner discussed before.

(47) Furthermore, the frame 15 can be covered with resistance material such that it acts as a self-holding resistor.

(48) The height of the frame 15 between the upper and lower ring surface 16, 17 can be selected here such that the movable contact part 14 does not come into contact with the base 39 when the switch 35 is open.

(49) Whereas FIG. 2 shows a current transfer member 31 which protrudes downwardly beyond the lower ring surface 17, FIG. 4 shows a plan view of the switching mechanism 10 from FIG. 1, which is now provided with a current transfer member 45, which on the one hand is connected to the movable contact part 14 and on the other hand is connected to the upper ring surface 16, below which is extends.

(50) Alternatively, the current transfer member 45 could also extend over the upper ring surface 16, such that it would then be clamped in a switch 35 between the upper ring surface and inner surface 43 of the cover part 37.

(51) In the switching mechanism 10 from FIG. 4, the current transfer member 45 is permanently connected however both to the movable contact part 14 and to the frame 15, such that it not only serves for conducting the current, but also serves as an arc shield.

(52) The current transfer member 45 may also extend away from the movable contact part 14 only on one side, so as to thus leave free a large area of the upper side of the spring snap-action disc.

(53) An embodiment for the current transfer member 31 from FIG. 2 is shown in a schematic plan view in FIG. 5. The current transfer member 31 is formed as a circular disc, in which curved, helical slots 46, 47 running radially outwardly are located. These slots 46, 47 reduce the spring effect of the current transfer member 31, such that, during switching, said member does not counteract the spring force of the bimetal snap-action disc and the spring force of the sprig snap-action disc 12.

(54) In FIG. 6, a slip-in housing 50 with walls 51 made of electrically insulating material is shown, said walls delimiting an insertion opening 52. The switching mechanism 10 from FIG. 1 is inserted into the insertion opening 52. Here, the frame 15 comes into contact with a base electrode 53, and the movable contact part 14 comes into contact with a cover electrode 54.

(55) The base electrode 53 and cover electrode 54 are formed internally on the walls 51 and are connected to outer connections 55 and 56 respectively in a manner that is not shown.

(56) The slip-in housing 50 can thus be used as a temperature-dependent switch, in which the switching mechanism 10 makes or opens an electrical connection between the outer connections 56, 57 in a temperature-dependent manner.

(57) It is also possible for the slip-in housing 50 to be part of a device to be protected, in which a pocket forms the insertion opening 52. The outer connections may then lead to windings or components, between which the switching mechanism 10 makes or opens an electrical connection in a temperature-dependent manner.

(58) FIG. 7 shows a schematic functional diagram of the switch 35 from FIG. 3. The switch 35 is closed, such that the operating current of the electrical device to be protected flows through the cover part 35 and the movable contact part 14, from here through the spring snap-action disc 12 and in parallel through the current transfer member 31, and then through the frame 15 and the lower part 36.

(59) When the frame consists of electrically insulating material, the operating current consequently flows only through the cover part 35 and the movable contact part 14, from here through the current transfer member 31, and then through the lower part 36.

(60) It is then possible to dispense with the insulating foil 41.

(61) In the case of the switch 35 from FIG. 8, the insulating foil 41 is exchanged for a resistive layer 57 arranged between the cover part 37 and frame 15. The frame 15 consists of electrically conductive material. In the closed state, the current flows as with the switch 35 from FIG. 7. If the switch 35 is open, however, a residual current flows through the cover part 37, resistive layer 57, frame 15 and lower part 36. Here, a sufficient resistive heat develops in the resistive layer 57 and prevents a cooling of the bimetal snap-action disc 11 below the snap-back temperature thereof, such that the switch 35 remains open.

(62) Instead of a resistive layer 57, the frame 15 may also consist itself completely or in part of resistance material, in order to implement the self-holding function.

(63) In FIG. 9, the switch 35 from FIG. 7 is modified such that the current transfer member 31 is formed as a series resistor. The frame 15 is electrically insulating, such that it is possible to dispense with the insulting foil 41.

(64) In the closed state of the switch 35, the operating current flows through the cover part 37, movable contact part 14 and current transfer member 31 into the lower part 36. Here, the current transfer member 31 heats up as a result of the integrated series resistor in the event of an excessively high current flow, to such an extent that the developed resistive heat already opens the switch 35 before the heat developed by the device to be protected heats said switch to such an extent that the switch opens.

(65) The switch 35 from FIG. 7 is shown in FIG. 10, but without current transfer member 31. As a result, the frame 15 is made of resistance material, such that it acts as a series resistor for current-dependent switching.

(66) In the closed state of the switch 35, the operating current flows through the cover part 37, movable contact part 14, spring snap-action disc 12 and frame 15 into the lower part 36. Here, the frame 15 heats up due to the integrated series resistor in the event of excessively high current flow to such an extent that the developed resistive heat already opens the switch 35 before the heat developed by the device to be protected heats up said switch to such an extent that the switch opens.

(67) FIG. 11 shows the switch 35 from FIG. 10, wherein the frame 15 is electrically conductive here. Instead of the insulating foil 41, a resistive layer 57 is provided, as is the case with the switch 35 from FIG. 8.

(68) In the closed state of the switch 35.sup.IV, the operating current flows through the cover part 37, movable contact part 14, spring snap-action disc 12 and frame 15 into the lower part 36.

(69) When the switch 35.sup.IV opens, a residual current flows through the cover part 37, resistive layer 57, frame 15 and lower part 36. Here, a sufficient resistive heat develops in the resistive layer 57 and prevents the bimetal snap-action disc 11 from cooling below the snap-back temperature thereof, such that the switch 35 remains open.

(70) Instead of a resistive layer 57, the frame 15 here too may consist itself completely or partially of resistance material in order to implement the self-holding function.

(71) In addition, the switch 35.sup.IV may also comprise a resistive layer 58 between the frame 15 and lower part 36, said layer acting as a series resistor for current-dependent switching, because it is arranged in the circuit of the operating current when the switch 35.sup.IV is closed and heats the switch to such an extent in the event of an excessively high current flow that the switch 35.sup.IV opens.

(72) The resistance value of the resistive layer 57 is much greater here than that of the resistive layer 58.