EP0801408B1 - Overload switching device for electrical apparatus - Google Patents

Abstract

The thermal overload device has two switching stages each with fixed contacts [10,11] and a bridging contact [14] held by a spring element [15]. In line with the switching stages is a bimetallic element [12] that is heated by a unit [18] coupled into the electrical circuit. At a threshold temperature the bimetallic element inverts and displaces a plunger [16] to open the contacts. The device has a push button cap [26] inside of which is an indicator bulb [19] that has a electorial connections to one pair of contacts [10.11] that connect to the load. The switch may also be manually operated by pressing the push button.

Description

The invention relates to an overload switching device for electrical devices, in particular cable drums, with at least one pair of connection contact members arranged at an interruption distance and a bimetallic piece which, when heated from a cold position in which the interruption distance is bridged in an electrically conductive manner, when a switching temperature is exceeded in one of the Bridging overriding warm position deformed, the two connection contact members being electrically connected to one another via an electrical heating element and an electrical lighting element, of which the heating element in the area of the bimetal piece and the lighting element is covered by a cover cap made of translucent material, which in the installed state of the electrical device is visible and accessible from the outside.

Such an overload switching device is apparent from DE-OS 38 02 647. It serves to protect electrical consumers against overheating and can be used for different Most electrical devices are used. Special areas of application are in cable drums, electrical distributors and sometimes also in cables for the supply of electrical devices. The overload switching device lies with its connection contact members in the circuit of the at least one consumer to be monitored. If the overload and thus the temperature is too high and this exceeds a switching temperature, the bimetal piece responds so that it reaches its warm position and the connection contact elements in the power supply of the consumer are electrically separated from one another. As a result, the power supply to the consumer is interrupted.

In order to avoid the continuity of the current being established again by itself after a cooling time and thus the consumer being automatically switched on again, the heating element connected in parallel to the interruption distance is present in the known overload switching device. This heating element is ineffective when the bimetallic switch is closed, ie when the interruption distance between the connection contact members is bridged immediately, since it experiences no or minimal heating. However, if the bimetallic switch opens, so that the direct passage of current is interrupted, the current flow only takes place via the heating element, which is designed to be so high-impedance that the supply voltage drops to a large extent on it and the remaining low voltage drop at the consumer does not result in a malfunction of the latter can lead. The heating element heats up so strongly in a short time that the bimetal piece remains in its warm position and the direct power supply to the consumer is thus interrupted. Only when the consumer is disconnected from the mains, ie when the consumer is switched off or his mains plug or for example the mains plug of the cable drum is pulled out, does the heating element and thus the bimetal piece cool down.

In the known overload switching device is also a parallel to the interruption distance between the connection contact elements, there is a light element that is effective and lights up in accordance with the heating element in the event of a fault, which indicates that the direct connection between the connection contact elements is interrupted, so that the user who Illuminated element sees, knows that excessive current or overheating was the cause for switching off the electrical device. Without this light element, the user would be unclear as to why the electrical device has gone out, since the device may also be defective or another fuse may have triggered.

After the consumer has disconnected the heating element and with it the bimetal piece has cooled, the bimetallic piece in the known arrangement deforms itself into its cold position again, so that the direct power supply of the consumer is automatically restored. At the same time, the light element goes out.

To further increase security, however, it may be desirable to provide manual operation by the user instead of automatically resetting to direct power passage.

The present invention is therefore based on the object to provide an overload switching device of the type mentioned, in which, while maintaining the advantages of the known device after a fault, switching back to direct current passage requires manual operation. This should be achieved with as little effort as possible.

This object is achieved in that the bimetallic piece remains in its warm position regardless of the temperature and can be deformed by the action of a mechanical switching force from its warm position into the cold position when the switching temperature is undershot, and that the cover cap of the light element can be pressed in with a push button and with one in the area of the bimetallic piece actuating part is provided, which acts on the bimetallic piece when the cap is pressed in and exerts the switching force thereon, the heating element being arranged between the bimetallic piece and the cap and the bimetallic piece in the direction from the cap to the bimetallic piece viewed laterally over the heating element protrudes and that the actuating part located on the cover cap on the heating element protrudes past to the bimetal piece and its edge area is assigned.

The bimetallic piece is thus shaped and designed such that it remains in its warm position after its automatic deformation from the cold position to the warm position, even if the temperature drops again to a value below the switching temperature. It is therefore not only necessary to pull the power plug or the like to disconnect the consumer from the power supply, but also to operate it manually, namely by pushing in the cover cap, so that the bimetal piece is adjusted to its cold position by mechanical force. The cap to be pressed in is not a separate push button, but rather the part covering the lighting element, which thus has a double function, which reduces the manufacturing outlay and simplifies assembly on the electrical device.

From CH 244 173 A is known in the genus, with the exception of the electrical heating element which connects the two connecting contact elements electrically with one another, in which the bimetal piece remains in its warm position regardless of the temperature and when the switching temperature falls below it by the action of a mechanical switching force from it The hot position can be deformed snap into the cold position, the cover cap of the lighting element being able to be pressed in in the manner of a push button, so that the switching force is exerted on the cover cap when it is pressed in.

Appropriate embodiments of the invention are specified in the subclaims.

An embodiment of the invention will now be explained with reference to the single figure of the drawing, which shows an overload switch device according to the invention in a schematic longitudinal section.

The overload switching device shown in the drawing has a switch housing 1 which, in the exemplary embodiment, is divided into two in the sectional plane of the drawing, so that the surfaces of the switch housing lying in the plane of the drawing are unshaded. This housing 1 contains the for Function of the overload switching device required individual parts. The overload switching device is fixed to a wall 2 of an electrical device, for example a cable drum. It is provided in the exemplary embodiment that the device wall 2 has a through opening 3 through which a sleeve-like holding part 4 is inserted from the outside during assembly until an outer annular collar 5 of the holding part 4 comes into contact with the device wall 2. The holding part 4 has, on its area facing away from the ring collar 5, latching fingers 6 distributed over the circumference, which are inserted through the through-opening 3 and have latching projections 7 projecting radially outward at their end. The distance between the annular collar 5 and the locking projections 7 corresponds to the axial length of the through opening 3 or the housing part 8 surrounding it, plus the thickness of an end locking projection 9 of the switch housing 1. During assembly, the switch housing with its circumferential, radially inwardly projecting locking projection 9 held from the inside of the device against the housing part 8, after which the holding part 4 is inserted, the latching projections 7 initially elastically deflecting radially inwards until they come behind the locking projection 9 and spring there again radially outward, so that the locking projection 9 engages behind and the switch housing 1 is locked with the holding part 4. In this way, the switch housing is held on the device wall 2 at the same time, since the locking projection 9 is located between the latching projections 7 and the housing part 8.

The inside diameter of the locking projection 9 essentially corresponds to the inside diameter of the through opening 3.

With regard to the attachment of the switch housing to the device wall 2, however, the arrangement could also be made differently in detail. However, the option shown is very easy to assemble since it does not require any tools.

The switch housing 1 contains the various switch parts, which will be discussed below.

The switch housing 1 initially contains a pair of electrically conductive connection contact members 10, 11, which are inserted into suitable housing recesses and each form a connection part 10a, 11a protruding from the housing 1, which serve to connect the electrical supply line, which is to be secured with the overload switch device electrical consumers powered. In this case, the network-side part is connected to the one connection contact element and the consumer-side part of the supply line to the other connection contact element. The two connection contact members 10, 11 are arranged in the interior of the switch housing 1 at an interruption distance from one another and here form a contact point 10b or 11b.

Furthermore, a bimetal piece 12 is present in the housing 1, which in the drawing has its cold position assumed at room temperature, in which the interruption distance 13 between the connection contact members 10, 11 is bridged in an electrically conductive manner. In the exemplary embodiment, a bridge member 14 made of electrically conductive material is used for this purpose, which is arranged on the side of the terminal contact members 10, 11 facing away from the bimetal piece 12 and is spring-loaded towards the contact points 10b, 11b (leaf spring 15). In the exemplary embodiment, a plunger 16, which crosses the interruption distance 13, is also provided between the bimetal piece 12 and the bridge member 14, said plunger 16 being caught between the bridge member 14 and the bimetal piece 12 and, as it were, producing a movement coupling for these two parts. Since the bimetallic piece 12 is arched in the cold position shown in the direction away from the terminal contact members 10, 11, the plunger 16 lying against the central region of the bimetallic piece 12 assumes such a position that the bridge member 14 under the action of the leaf spring 15 on the Contact points 10b, 11b is present and an electrical current can flow through the connection contact members 10, 11 to supply the consumer.

The bimetal piece 12, the bridge member 14, the spring 15 and the plunger 16 are mounted and / or guided in the housing interior on correspondingly arranged housing walls. The connection contact members 10, 11 are also inserted into assigned housing recesses.

The details of how the bimetal piece 12 influences the electrical connection between the terminal contact members 10, 11 can in principle also be different. It is particularly important that the bimetal piece 12 at ambient temperature has such a shape (cold position) that the interruption distance 13 is bridged, and that the bimetallic piece 12 is deformed when a switching temperature is exceeded into a warm position that bridges the interruption distance 13. This warm position is indicated by dash-dotted lines at 17 in the drawing.

In the exemplary embodiment, the bimetal piece 12 bulges in the opposite direction when the switching temperature is reached, i.e. towards the connection contact members 10, 11, so that the plunger 16 is moved somewhat through the interruption distance 13 and the bridge member 14 is raised against the force of the spring 15 from the contact points 10b, 11b, so that the current passage through the connection contact members 10, 11 to the consumer is interrupted. In this way, the power supply to the consumer is interrupted when overheating occurs.

The two connection contact members 10, 11 are connected to one another via an electrical heating element 18 and an electrical lighting element 19. The heating element and the lighting element are connected in parallel to the bridging distance 13. This circuit is independent of the position of the bimetal piece 12, ie both the heating element 18 and the lighting element 19 are continuously connected to the terminal contact members 10, 11. For the mounting and electrical supply of the heating element 18, two spring clips 20, 21 are used in the exemplary embodiment, each of which is supported at one end on one of the connection contact members 10, 11 and at the other end on the heating element 18, so that it is simultaneously held against a housing surface , The electrical line sections 22, 23 leading to the luminous element 19 are connected to the spring clips 20, 21 in the exemplary embodiment. The lighting element 19 can be, for example, a glow lamp, an incandescent lamp or in principle also a light-emitting diode. An electrical resistor 24 is connected in series with the lighting element 19.

When the interruption distance 13 is closed by means of the bridge element 14, that is to say if the consumer is supplied via the connection contact elements 10, 11, the heating element 18 and the lighting element 19 have no effect. However, if the bimetal piece 12 switches to its warm position 17 so that the direct connection of the connecting contact members 10, 11 is disconnected, the lighting element 19 lights up and the heating element 18 heats up, so that the bimetal piece 12, in the area of which the heating element 18 is located, the temperature is kept above the switching temperature by the heat given off by the heating element 18. Only when the consumer or the device on which the overload switch is located is disconnected from the mains the bimetal piece 12 cool down. At the same time, the lighting element 19 goes out.

However, the bimetal piece 12 does not automatically return to its cold position corresponding to the direct passage of current through the connecting contact members 10, 11, but remains in its warm position 17 regardless of the temperature. The bimetal piece 12 is thus shaped such that it has no mechanical action remains in its warm position 17 from the outside once it has taken it. However, the bimetal piece 12 can be deformed from its warm position 17 into the cold position by the action of a mechanical switching force when the switching temperature is undershot, the deformation taking place snappingly over a dead center position. If this switching force is exerted too early when the temperature is still above the switching temperature, the bimetallic element 12 currently follows the force effect, but after the force effect ceases, it immediately deforms back into the warm position.

From the lighting of the lighting element 19 it can be seen that the malfunction is due to overheating.

The light-emitting element 19, which in the exemplary embodiment is held in an end-side, collar-like extension 25 of the switch housing 1, is covered by a cover cap 26 made of translucent material, which is also hereby encompassed transparently. The cap 26 is in the electrical Device installed condition visible and accessible from the outside, as can be seen from the drawing. This cover cap 26 performs a double function, since it serves not only to cover the lighting element 29 but also to apply the switching force to the bimetal piece 12. For this purpose, the cover cap 26 can be pressed in the manner of a push button towards the light-emitting element 19, it being provided with an actuating part 27 which extends into the area of the bimetallic piece 12 and which acts on the bimetallic piece 12 when the cover cap 26 is pressed in and on it, it is in the warm position 17 , exerts the switching force, so that the bimetal piece deforms into its cold position.

In the exemplary embodiment, the cover cap 26 is guided in the sleeve-like holding part 4, which is hollow for this purpose. In this case, the cover cap 26 has an essentially cylindrical jacket body 28, which is guided so that it can be pressed into the holding part 4. At the outer end of the casing body 28, the cover cap 26 is closed by a base 29 which forms the actual cover.

A so-called free release can also be integrated in the push-button-like cover cap 26 with the actuating section 27, which causes the actuating section 27 to only briefly press against the bimetal piece 12 when the cover cap 26 is depressed and then snaps away again, even when the cover cap 26 is pressed in remains. Such pressure switches are known per se, so that on the Representation of such a free release has been dispensed with.

The cap 26 is pressed in against the force of a spring 30 which is supported on the housing 1 on the other hand.

The heating element 18 is arranged between the bimetal piece 12 and the cap 26 in the practical embodiment. The bimetal piece 12 protrudes laterally over the heating element 18 in the direction from the cover cap 26 to the bimetal piece 12. Although this is not the case in the drawing plane, it is perpendicular to the drawing plane, i.e. below and above this. In this way, the bimetallic piece 12 is not covered over the entire area by the heating element 18, so that the actuating part 27 seated on the cover cap 26 can protrude past the heating element 18 to the bimetallic piece 12 and its edge region is assigned. The actuating part 27 visible in the drawing runs below the drawing plane past the heating element 18, so that it meets the edge region of the bimetal piece 12 there. The same conditions are present above the drawing level, i.e. a corresponding actuation section 27 also protrudes from the cover 26 toward the bimetal piece 12 above the drawing plane, so that the heating element 18 is overlapped on both sides.

In the warm position 17, the bimetal piece 12 bulges away in the direction away from the cover cap 26. Presses the actuating section 27 the edge region of the bimetallic piece 12 in the Drawing down, the bimetal piece 12, which is supported in the middle by the plunger 16 and the force of the spring 15, snaps into its cold position.

In the exemplary embodiment, the cover cap 26, the heating element 18, the bimetal piece 12 and the connecting contact members 10, 11 are thus arranged in succession in this order.

The bimetallic piece 12 expediently has the shape of a circular disk which is slightly conical or arched. This conical or curved shape can - in opposite directions - be present in both positions of the bimetal piece 12.

The heating element 18 is expediently designed like a plate and has an essentially rectangular shape. The long rectangular dimension of the heating element 18 is visible in the sectional illustration of the drawing.

The bimetallic piece 12, as already indicated, is arranged towards the cover cap 26 at a distance from the connection contact members 10, 11 and the interruption distance 13 present between them, the connection to the bridge member 14 arranged on the opposite side of the connection contact members being established by means of the plunger 16.

If you want to run not only one wire but two wires of the supply line via the overload switching device, this can contain a second pair of connection contact members 10 ', 11' for the second wire, to which the same bimetal piece 12 is assigned, so that in both pairs of Connection contact members 10, 11 and 10 ', 11' at the same time bridges the interruption distance 13 or the bridging is removed. The two further connection contact members 10 ', 11' are arranged in the same way as the connection contact members 10, 11 described to one another, again with a spring-loaded corresponding to the bridge member 14. lastetes bridge member 14 'is present. Because of the correspondence, the above description applies mutatis mutandis to this second pair of connection contact members with the associated details. This second pair of connection contacts 10 ', 11' is seen from the cover cap 26 behind the first pair of contacts 10,11. In this case, a second plunger 16 'extends between the bridge members 14, 14' of the two pairs of contact members in an extension of the plunger 16, via which the two bridge members 14, 14 'are coupled to one another in terms of movement.

Dash-dotted lines still indicate a third pair of connection contact members with associated spring-loaded bridge member, which is arranged in the same way as the second pair behind the first pair behind the second pair of contact members 10 ', 11', with a third plunger between the extends second bridge member 14 'to the bridge member of the third pair of terminal contact members. If the bimetal piece 12 switches over, all bridge members are actuated at the same time.

Claims (9)

1. Overload circuit breaker for electrical equipment, in particular cable drums, with at least one pair of terminal contact links (10, 11) arranged at a breaking distance (13) from one another, and a bimetal element (12) which, on heating from a cold position in which the breaking distance (13) is electrically conductively bridged, deforms on exceeding a switching temperature into a hot position which neutralises the bridging, wherein the two terminal contact links (10, 11) are connected electrically to one another via an electrical heating element (18) and an electrical luminous element (19), of which the heating element (18) in the area of the bimetal element (12) and the luminous element (19) are covered by a cover cap (26) of transparent material which, when installed in the electrical equipment, is visible and accessible from the outside, characterised in that the bimetal element (12) remains in its hot position irrespective of the temperature and, when it falls below the switching temperature, is deformable with a snap from its hot position (17) into the cold position through the action of a mechanical switching force, and that the cover cap (26) of the luminous element (19) may be pressed in like a push button and is provided with an actuating section (27) reaching into the area of the bimetal element (12) which, on pressing-in the cover cap (26), acts on and exerts the switching force on the bimetal element (12), wherein the heating element (18) is located between the bimetal element (12) and the cover cap (26), and the bimetal element (12) looking from the cover cap (26) towards the bimetal element (12) extends sideways over the heating element (18), and that the actuating section (27) resting on the cover cap (26) extends past the heating element (18) to the bimetal element (12) and the actuating section (27) is assigned to the edge area of the bimetal element (12).
2. Overload circuit breaker according to claim 1, characterised in that the cover cap (26), the heating element (18), the bimetal element (12) and the terminal contact links (10,11) are arranged consecutively in that order.
3. Overload circuit breaker according to claim 1 or 2, characterised in that the bimetal element (12) is a slightly conical or curved circular disc.
4. Overload circuit breaker according to any of claims 1 to 3, characterised in that the bimetal element (12) is arranged towards the cover cap (26) with clearance from the terminal contact links (10, 11) and the breaking distance (13) provided between the latter, that on the opposite side of the terminal contact links (10, 11) a bridge section (14) spring-loaded towards the terminal contact links (10, 11) is provided to bridge the breaking distance (13), and that a ram (16) passing through the breaking distance (13) is provided between the bimetal element (12) and the bridge section (14), wherein in its cold position the bimetal element (12) is curved away from the terminal contact links (10, 11) and in its hot position (17), with the bridge section (14) lifted from the terminal contact links (10, 11), it is curved towards the terminal contact links (10,11) by means of the ram (16).
5. Overload circuit breaker according to any of claims 1 to 4, characterised in that the heating element (18) has the shape of a substantially rectangular plate.
6. Overload circuit breaker according to any of claims 1 to 5, characterised in that the cover cap (26) may be pressed inwards against a spring force.
7. Overload circuit breaker according to any of claims 1 to 6, characterised in that the cover cap (26) is guided in a sleeve-like retaining part (4), which may be fixed in a through hole (3) of a wall (2) of the electrical equipment.
8. Overload circuit breaker according to claim 7, characterised in that it has located behind the wall (2) of the electrical equipment a switch housing (1) accommodating the switch components such as the terminal contact links (10, 11), bimetal element (12), heating element (18) and luminous element (19), which may be engaged by the retaining part (4) introduced from the outside into the through hole (3) and fitting up against the outside of the equipment wall (2) with a collar (5).
9. Overload circuit breaker according to any of claims 1 to 8, characterised in that it contains two or three pairs of terminal contact links arranged one behind the other and assigned a common bimetal element (12), so that the breaking distance is bridged or the bridging neutralised for all pairs simultaneously.