EP0181573B1 - Temperature switch, particularly thermal release - Google Patents

Description

The invention relates to a thermal switch, in particular a temperature limiter, with the features of the preamble of claim 1.

An already proposed switch of this type (DE-U-8416805) has a bimetallic spring washer for thermal triggering, which is concave on one side in the idle state and convex on one side in the excited state. This spring washer is fastened flat on a flexible contact arm clamped on one side by means of retaining tabs which overlap the edge of the spring washer. In the excited state, the bimetallic spring washer, due to its convex curvature facing the contact arm, lifts the contact end of the contact arm from the base-fixed mating contact of the switch.

According to legal regulations, such thermal switches must be designed so that they do not switch on again automatically after thermal tripping. The consequence of this is that the temperature-dependent bending characteristic of such bimetallic spring washers must be designed in such a way that when the switch cools down to the region of the ambient temperature, there is no folding back from the convex to the concave position. In practice, the return point is in the order of magnitude of, for example, -20 ° C. for safety reasons. Bimetallic spring washers of this type are very complicated and expensive to manufacture because of their critical bending characteristics.

DE-U-7531355 shows a resettable temperature limiter which, between a curved bimetallic disc and a displaceably mounted transmission pin, has a curved metal disc which behaves independently of the temperature. Unlike the subject of the application, a manual reset process can only be carried out in the direction of the contact bridge.

The invention has for its object to meet the legal requirements regarding the reclosing of thermal switches with the help of simple bimetallic spring washers with normal, non-critical temperature-dependent bending characteristics.

This object is achieved by the characterizing feature of claim 1.

If a "steel spring washer" is mentioned in claim 1, it should be pointed out that spring washers made of a different type of material can also be used, provided they have the required bistable elastic properties. The centers of the two spring washers are coupled to one another in terms of movement, which can be done, for example, via a coupling pin passing through the washers.

A particularly advantageous embodiment of the invention is described by the characterizing features of claim 2. The flat contact of the spring washers ensures a particularly delay-free transmission and coupling of the triggering forces. Both disks are converted from their concave to the convex state of curvature almost simultaneously. The resetting device acting in the contact opening direction reduces the mechanical load on the steel spring washer when it is reset to the rest position.

A particularly simple mounting of both spring washers on the contact arm is described by the characterizing feature of claim 3. It is essential that the two disks are not rigidly connected to one another and to the contact arm, but are rather displaceably mounted relative to one another. As a result, no tensile stresses or shear forces are exerted on the panes during the triggering process, which increases the reliability of such thermal switches.

A particularly simple design of the retaining tabs is possible due to the characterizing feature of claim 4. In addition, the basic design of conventional thermal switches does not have to be changed due to the identical spring washers.

It is also important for the embodiment of the present invention that both circular and rectangular or other types of spring discs can be used for the spring discs.

Claims 5 ff. Describe particularly advantageous embodiments which reduce the mechanical load on the spring washers, in particular the bistable steel spring washer. This reduces the susceptibility to damage of such thermal switches.

According to the characterizing features of claim 5, the manual force is not exerted directly on the reset pin, but - indirectly via a sliding sloping surface - by a separately provided actuation button, the direction of displacement of the actuation button taking place in the plane spanned by the spring washers. This enables a very flat design (in relation to the spring washer surfaces) of the thermal switch. The force limitation, which can be achieved as a result of the deflection of force (pressure direction of the actuating button is perpendicular to the direction of displacement of the reset pin), has also proven to be particularly advantageous. It is only necessary to select the slope of the sloping surface accordingly and to form the parts of the actuating button which interact with one another from somewhat flexible material, so that the force limitation is achieved. In addition, it is advantageous that the manually applied pressure force is just introduced into the switch holder via the base or protruding contact strips is avoided so that bending forces, for example on the connection contacts (with which the switch is usually fastened in a plug-in holder).

A design of the switch according to claim 6 is particularly advantageous for the reproducibility of the resetting force, further advantages regarding the force limitation and the flat construction result from the overlapping construction of the mutually influencing parts according to claim 7.

Claim 8 enables a particularly soft power transmission from the actuating button to the steel spring washer.

Claims 9-12 teach a compact, robust and permanently reliably functioning construction of the mutual guide elements. Claim 9 largely protects the spring washers from the elements surrounding them, such as the actuating button and guide elements.

• Fig. 1 eine Seitenansicht des neuerungsgemäßen Schalters ;
• Fig. 2 eine weitere Ansicht in Pfeilrichtung II gemäß Fig. 1, teilweise im Schnitt ;
• Fig. 3 Funktionsschema : Schalter im Ruhezustand ;
• Fig._. 4 Funktionsschema : Schalter im thermischen Auslösezustand ;
• Fig. 5 Funktionsschema : Schalter im wiedereinschaltbereiten Zustand ;
• Fig. 6 Funktionsschema gemäß Fig. 3 eines Schalters mit modifizierter Kopplung der beiden Sprungscheiben.

The invention is explained in more detail using an exemplary embodiment shown in the figures and a detailed functional description. The advantages of the invention of the solution to the problem described in claim 1 become clear in particular from the functional diagrams according to FIGS. 3-6. Show it :

• Figure 1 is a side view of the switch according to the innovation.
• FIG. 2 shows a further view in the direction of arrow II according to FIG. 1, partly in section;
• Fig. 3 functional diagram: switch in the idle state;
• Fig _. 4 Functional diagram: switch in thermal tripping condition;
• Fig. 5 Functional diagram: switch in the state ready for restart;
• Fig. 6 functional diagram according to Fig. 3 of a switch with modified coupling of the two spring washers.

For thermal tripping in the idle state (the idle state is shown in FIGS. 2, 3 and 6), the switch 1 has concave discs (bimetal spring disc 2, bistable steel spring disc 2A) curved on one side in the excited state, which are attached to a contact arm 3 clamped in on one side essentially lie flat and are attached by the disc edges 4 overlapping retaining tabs 5. In the excited state, the bimetallic spring washer 2 lifts the contact end 6 from a mating contact 7 by bending the contact arm 3 as a result of its convex curvature, said contact end being fastened to a switch base 9 of the switch 1 via a contact carrier 8. At the same time, the bistable steel spring washer 2A is also transferred from its concave curvature to the convex curvature. The switch is now in its thermal tripping state analogous to the schematic illustration in FIG. 4. The circuit protected by the thermal switch is interrupted. When the bimetal spring washer 2 cools, it snaps back into its concave position according to FIG. 5 when a certain temperature is reached.

According to the legal regulations, however, the contact is not closed again, since the bistable steel spring washer 2A remains in its convex position and thus builds up a counterforce keeping the contact open. Remaining in this position is ensured by the fact that the two spring washers 2, 2A are not rigidly connected to one another and to the contact arm 3. This means that no bending moment can be exerted from the bimetal spring washer onto the bistable steel spring washer. The switch is manually reset to the closed position analogous to FIG. 3 by the reset pin 10, which is indirectly attached to the switch base 9 and is axially displaceable at right angles to the steel spring washer surface. It presses about the center 11 of the steel spring washer 2A in the contact opening direction by pressing an actuation button 16.

At the end 12 of the reset pin 10 facing away from the spring washers 2, 2A there is a sloping surface 13 which cooperates with a projection 14 on the inner end 15 of the actuating button 16, which is displaceably guided on the switch base 9 at right angles to the reset pin. The sliding inclined surface 13 is inclined towards the actuating end 17 of the actuating button 16 such that the reset pin 10 is displaced in the arrow direction 18 in the arrow direction 19 when the actuating button 16 is pressed in.

The reset pin 10 is held with its end 12 facing away from the spring washers on a resilient base projection 20 which carries the sloping surface 13 on its rear side 21 facing away from the steel spring washer 2A. The base projection 20 is designed as a rib extending in the direction of displacement 18 of the actuating button 16, the pivoting end 22 of which, provided with the sliding inclined surface 13, is overlapped by the likewise rib-shaped inner end 15 of the actuating button 16.

The rib-like inner end 15 of the actuating button 16 is also designed to be resilient at right angles to the direction of displacement 18, so that it can rebound in the direction of the arrow 23 when it slides onto the sloping surface.

The actuation button 16 is mounted on a U-shaped bracket 24 of the switch base 9, which engages around the base projection 20 carrying the reset pin 10 and is embodied essentially in the same manner. On the outer sides 25 of its U-legs 26, the bracket 24 is provided with longitudinal guides (grooves), in which guide elements (webs) are arranged displaceably by lateral longitudinal projections 27 arranged on the actuating button 16 and pointing in the direction of displacement parallel to the U-legs.

The bracket 24 is molded with a part of the switch base 9, the longitudinal projections 27 with the actuating button 16 in one piece from plastic.

The actuation button 16 is provided on its underside 29 with a peg-like guide projection 30 which is slotted transversely to the direction of displacement 18 and with its slot engages over a guide arm holder 31 lying flat in the direction of displacement or is guided thereon. In a blind hole recess 32 of the guide projection 30 a compression spring 33 is mounted, which is supported with its inner end on the edge 34 of the contact arm holder 31 facing the actuating button 16.

The central longitudinal axis 35 of the operating button 16 extends approximately in the plane of extent of the spring washers 2, 2A, which approximately forms the central longitudinal plane of the switch. The guide members (U-shaped bracket 24 and the longitudinal projections 27 of the operating button 16) are arranged offset from the central longitudinal plane, which results in particular from the view according to FIG. 2.

In Fig. 1 it can be seen particularly clearly that the longitudinal projections 27 are provided at their lower end facing away from the actuating button with inward-pointing claw-like extensions 36 which engage in side recesses 37 of the U-shaped bracket, the length of which approximately corresponds to the displacement path of the actuating button 16 corresponds. The U-shaped bracket 24 is provided with bevels 39 in the transition region of the U-legs into the crosshead 38.

FIG. 6 essentially corresponds to the representation according to FIG. 3, but the positions of the bimetal spring washer and the steel spring washer are interchanged. The movement coupling of the centers of the two spring washers takes place via a coupling element in the form of a rivet or pin 40, which, for example, passes through the two discs together. In contrast to the previously described embodiment of the switch according to FIGS the return temperature cannot jump into the concave position shown in FIG. 5, but remains in the convex position keeping the contact open due to the force of the steel spring washer. The bimetallic spring washer is reset to the concave position together with the steel spring washer by the reset pin 10.

Reference symbol list

• 1 switch
• 2 bimetal spring washer
• 2A bistable steel spring washer
• 3 contact arm
• 4 disc edge
• 5 retaining tabs
• 6 contact ends
• 7 counter contact
• 8 contact carriers
• 9 switch bases
• 10 reset pin
• 11 center of 2A
• 12 end of 10
• 13 sliding inclined surface
• 14 head start
• 15 end
• 16 operating button
• 17 end of actuation
• 18 arrow direction
• 19 arrow direction
• 20 base projection
• 21 back
• 22 swiveling end
• 23 direction of arrow
• 24 brackets
• 25 outsides
• 26 U-legs
• 27 longitudinal projection
• 28 bridges
• 29 underside
• 30 Leadership lead
• 31 contact arm holder
• 32 blind hole recess
• 33 compression spring
• 34 edge
• 35 central longitudinal axis
• 36 extensions
• 37 recesses
• 38 crosshead
• 39 bevel
• 40 rivet

Claims (16)

1. Thermal switch, particularly a temperature limiter, with the following features :

the switch (1) has a flexible contact arm (3) clamped at one end and which

as a thermal triggering means comprises a quick-break bimetallic plate (2) which is concavely curved onto itself when in the rest position and

of which the contact arm end, in the thermally triggered state, is by the reversal of the quick-break bimetallic plate (2) out of its concave and into its convex curvature lifted off a fixed contact (7) of the switch (1),

on a switch base (9) there is a reset device (reset stud (10) which acts substantially in a direction (19) for opening the contact, characterised by, bearing on the quick-break bimetallic plate (2) and/or the contact arm (3) and coupled to the triggering movement of the centre of the quick-break bimetallic plate (2), a bistable steel snap-action plate (2A) which, upon resetting, is pressed in the contact-opening direction (19).

2. A switch according to Claim 1, characterised by the following features :

when in the position of rest, the bistable steel snap-action plate (2A) incorporated between the quick-break bimetallic plate (2) and the contact arm (3) lies flat against the quick-break bimetallic plate (2),

when thermally triggered, the steel snap-action plate (2A) can likewise, by the application of force by the quick-break bimetallic plate (2) and the contact arm (3) likewise be moved out of its convex and into its concave state of curvature,

when in the thermally triggered state, the convexly curved surface of the steel snap-action plate (2A) can be moved directly or via that surface of the contact arm which extends parallel therewith indirectly in the contact opening direction (19) by the reset device (reset stud 10).

3. A switch according to Claim 1 or 3, characterised in that the bistable steel snap-action plate (2A) and the quick-break bimetallic plate (2) are jointly mounted by these two components in their marginal zone with retaining lugs (5) integrally moulded on the contact arm (3) and engaging over them with a clearance to allow movement.

4. A switch according to one of the preceding Claims, characterised in that the bistable steel snap-action plate (2A) is constructed so that its area coincides with that of the quick-break bimetallic plate (2).

5. A switch according to one of the preceding Claims, characterised by the following features :

the reset device is constructed as a reset stud (10) which is axially displaceable substantially at right-angles to the snap-action plates (2, 2A),

at the end (12) of the reset stud (10) which is remote from the snap-action plates (2, 2A) there is a slide-on ramp (13),

an actuating knob (16) for manually resetting the steel snap-action plate (2A) into the concave rest position is mounted on a switch base (9) for displacement at right-angles to the longitudinal axis of the reset stud (10), its inner end (15) which is towards the actuating end (17) being applied against the slide-on ramp (13) which is directed obliquely to the actuating end (17).

6. A switch according to Claim 5, characterised in that the end (12) of the reset stud (10) which is remote from the snap-action plates (2, 2A) is disposed on a flexurally resilient projection (20) on the base and which carries the slide-on ramp (13) on its rear surface (21) which is remote from the snap-action plates (2, 2A).

7. A switch according to Claim 5 or 6. characterised in that the projection (20) on the base _'s constructed as a rib extending in the direction of displacement (18) of the actuating knob (16) and of which the pivoting end (22) which is provided with the slide-on ramp (13) is overlapped by the likewise rib-like inner end (15) of the actuating knob (16).

8. A switch according to one of Claims 5 to 7-, characterised in that the inner rib-like end (15) of the actuating knob (16) is constructed to be resilient at right-angles to its direction (18) of displacement.

9. A switch according to one of Claims 5 to 8, characterised in that the actuating knob (16) is mounted on a U-shaped bracket (24) on the switch base (9) and which engages around the projection (20) on the base which carries the reset stud (10), extending substantially in the same plane as this latter and being provided on the outsides (25) of the arms (26) of the U-shape with longitudinal guides in which guide elements (webs 28) of lateral longitudinal projections (27) pointing in the direction (18) of displacement and disposed on the actuating knob (16) are displaceably mounted.

10. A switch according to one of Claims 5 to 9, characterised in that the bracket (24) is constructed from synthetic plastics material in one piece with a base part, as are the longitudinal projections (27) with the actuating knob (16).

11. A switch according to one of Claims 5 to 10, characterised in that the actuating knob (16) has disposed on its underside (29) and slotted crosswise to its direction of displacement (18) a stud-like guide projection (30) which engages over a plate-like contact arm holder (31) which extends substantially parallel with the snap-action plates (2, 2A).

12. A switch according to one of Claims 5 to 11, characterised in that in a blind recess (32) in the guide projection (30), there is a thrust spring (33) biased on that edge (34) of the contact arm holder (31) which-is towards the actuating knob (16).

13. A switch according to one of Claims 5 to 12, characterised in that the longitudinal median axis (35) of the actuating knob (16) lies substantially in the plane of extension (longitudinal median plane through the switch) of the snap-action plates, and in that the guide members (U-shaped bracket 24 with longitudinal guides, longitudinal projections 27 on the actuating knob (16) are laterally offset in relation to the longitudinal median plane.

14. A switch according to one of Claims 5 to 13, characterised in that the switch base (9) consists of two parallel and adjacently disposed insulating members, one of which merges in one piece into the U-shaped bracket (24) in the direction of the actuating knob (16).

15. A switch according to one of Claims 5 to 14, characterised in that the longitudinal projections (27), at their end remote from the actuating knob (16), are provided with inwardly pointing claw-like extensions (36) which engage lateral recesses (37) on the U-shaped bracket (24), their length corresponding substantially to the displacement path of the actuating knob (16).

16. A switch according to one of claims 5 to 15, characterised in that the U-shaped bracket (24) is provided with chamfers in the area where the arms (26) of the U merge into the cross-member (38).

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