DE102015213375B4 - Thermal overload release device and protective switching device - Google Patents

Abstract

Thermal overload tripping device (10) for an electromechanical protective switching device (1), in particular for a circuit breaker or a circuit breaker,
- with a triggering element (11) which can be heated directly or indirectly by an electric current,
- in which the tripping element (11) has a fastening point at a first end (12), by means of which the tripping element (10) can be fastened in a housing (2) of the protective switching device (1),
- in which a second end (13) of the tripping element (11) is designed as a free end, which can be moved relative to the fastening point when it heats up due to the thermal expansion of the tripping element (11) in order, if a predefined threshold value is exceeded, to an unlatching point of the protective switching device (1st ) act, characterized in that the triggering element (11) is formed in one piece.

Description

The present invention relates to a thermal overload tripping device for an electromechanical protective switching device, in particular for a miniature circuit breaker or a circuit breaker. Furthermore, the present invention relates to an electromechanical protective switching device, in particular a circuit breaker or a circuit breaker, with such a thermal overload tripping device.

Thermal overload tripping devices are used in electromechanical protective switching devices - for example in a circuit breaker or in a circuit breaker - to interrupt a current flow when the electrical current exceeds a previously specified current for a specific, predefined period of time. Such protective switching devices are also referred to as overcurrent protection devices, which in the event of an overload or short circuit open the current path after a certain time and thus interrupt the flow of current. In this way, overcurrent protection devices protect electrical lines, themselves or electrical loads or consumers connected to the overcurrent protection devices from damage due to excessive heating, which would result from the overcurrent flowing over a longer period of time. An overcurrent can be caused by an overload or a short circuit.

Overcurrent protection devices can react differently depending on the requirement profile: for example, the response time for tripping the protective switching device depends on the current strength that occurs. In the event of an overload, the circuit is interrupted with a delay. The pre-defined tripping time for this is in the range of seconds, but can also be in the range of hours - in the event of a slight overload. On the other hand, in the event of a short circuit, in which a current of several thousand amperes can flow, the current flow must be interrupted within a few thousandths of a second.

Typical overcurrent protection devices are miniature circuit breakers or circuit breakers. Overcurrent protection devices are usually used in electrical installations. Since these protective switching devices are usually installed next to each other "in series" in an electrical installation distributor, which is also referred to as a distribution box, they are also referred to as modular installation devices.

A thermal overload tripping device is used in such an overcurrent protection device, for example, to unlatch a switching mechanism. A strip of thermobimetal is clamped in place at one end, ie connected in place to the housing of the overcurrent protection device. The strip of thermal bimetallic strip can bend out at the oppositely arranged end when heated accordingly and thereby unlatch an unlatching point of the switching mechanism, as a result of which an opening of a contact point of the overcurrent protection device is brought about. Such an overload tripping device is, for example, from the published application DE 10 2009 021 773 A1 previously known.

A thermal bimetal consists in principle of two firmly connected layers of different metals or metal alloys, which, however, have completely different temperature expansion behavior. When the temperature changes, this leads to one area of the thermal bimetal expanding more than the other area, so that the thermal bimetal is curved overall in the direction of the area with the lower temperature expansion behavior. The strip made of thermal bimetal is consequently a strip-shaped element which deforms in a predefined manner when there is a predefined temperature change. This temperature behavior is used in the design of the overload release device. However, thermobimetals are complex to produce and therefore comparatively expensive, which has a correspondingly negative effect on the production costs of the thermobimetal and thus of the overload tripping device or the electromechanical protective switching device. In order to obtain the desired tripping characteristics, it is also necessary to keep the mechanical play between the bimetal on the one hand and the housing and the switching mechanism of the protective switching device on the other hand as small as possible. This requires a high degree of precision when manufacturing the individual components and when assembling the overload tripping device and the protective switching device, which in turn is reflected in higher manufacturing costs.

It is therefore the object of the present invention to provide a thermal overload tripping device and an electromechanical protective switching device which are characterized by lower production costs while maintaining the same functionality and switching capacity.

This object is achieved by the thermal overload tripping device and the electromechanical protective switching device according to the independent claims. Advantageous configurations are the subject matter of the dependent claims.

The thermal overload tripping device according to the invention for an electromechanical protective switching device, in particular for a circuit breaker or a circuit breaker, has a tripping element which can be heated directly or indirectly by an electric current. The triggering element has a fastening point at a first end, by means of which the triggering element can be fastened in a housing of the protective switching device. Furthermore, a second end of the triggering element is designed as a free end, which can be moved relative to the attachment point when heated due to thermal expansion of the triggering element, in order to act on an unlatching point of the protective switching device when a predefined threshold value is exceeded. The triggering element is formed in one piece.

The trigger element is designed in one piece, i.e. it consists of a single material, and is therefore a cost-effective replacement for the thermal bimetal, which is made of two different materials. It can be heated directly or indirectly, so that a simple adaptation to existing constructions is possible. Direct heating is to be understood as meaning the direct flow of current through the tripping element, while indirect heating can be implemented, for example, by a heating element or also by the waste heat from components arranged adjacent to one another.

The triggering element can be attached at its first end to the housing of the protective switching device. If the temperature rises, the tripping element expands, whereby it is supported at another point of contact in the housing. Since free length expansion is now no longer possible between the point of contact and the attachment point, further expansion in length causes stresses in the release element, as a result of which it deforms in the area between the point of contact and the attachment point. This deformation leads to a movement of the second, free end of the tripping element, which is suitable for acting on the unlatching point of the protective switching device and thus tripping the protective switching device.

In an advantageous further development of the overload tripping device, the tripping element is formed from a material with a high coefficient of thermal expansion. The use of such a material with a high coefficient of thermal expansion makes it possible to set the tripping characteristics of the protective switching device more precisely.

In a further advantageous further development of the overload tripping device, the tripping element is made of a metallic material.

Since there is already a large number of metallic materials with material properties that are known in detail, the selection of a material suitable for this application is made easier. Among the materials suitable for this purpose, there are again a large number of metallic materials which have a high coefficient of thermal expansion and are also inexpensive to obtain and process. Furthermore, metallic materials are good electrical conductors and can therefore also be used as a directly heated release element.

In a further advantageous further connection of the overload tripping device, the free end is designed for direct action on the unlatching point of the protective switching device. A thermal bimetal usually acts on the unlatching point of the protective switching device with the aid of a bracket, for example a tension bracket. Since the triggering device acts directly on the unlatching point, the bracket as an additional coupling element can be dispensed with, which means that the production costs can be further reduced.

In a further advantageous further connection of the overload tripping device, the tripping element is U-shaped, with a first leg, a second leg and a connecting area connecting the two legs, with the first end at the end of the first leg and the second end at the end of the second leg is formed. Due to the U-shaped design, the tripping element can be installed in the housing of the protective switching device to save space, without having to make any compromises in terms of the required absolute linear expansion. This has a positive effect on the tripping characteristics of the overload tripping device and the protective switching device.

In a further advantageous development, the overload tripping device has an adjustment element, by means of which a position of the tripping element relative to the housing of the protective switching device can be adjusted without play.

Due to the backlash-free adjustment of the tripping element when it is installed in the housing of the protective switching device, it is ensured that the tripping element is already supported at the further point of contact in the housing at the beginning of the temperature increase. This precisely defines the zero point of the force acting on the housing - and thus the change in shape of the triggering element when the temperature rises. In this way, the movement of the free end of the triggering element can be determined exactly, ie without offset, as a function of the temperature change. The trigger Cha The characteristics of the overload tripping device, and thus of the protective switching device, can therefore be set precisely.

In a further advantageous further development of the overload tripping device, the tripping element has one or more pinch points, which are used to adjust the position of the tripping element relative to the housing of the protective switching device.

Due to the crushing points, which are attached between the fastening point and the further contact point during the assembly of the overload tripping device or the tripping element in the housing of the protective switching device, a lengthening of this section is achieved until the tripping element can be mounted without play in the housing of the protective switching device, despite possible manufacturing tolerances is. This type of backlash-free assembly represents a simple and extremely cost-effective way of setting the position of the tripping element relative to the housing, and thus in particular to the unlatching point of the protective switching device.

In a further advantageous further development of the overload tripping device, the play-free setting of the relative position of the tripping element relative to the housing can be implemented with the aid of an adhesive.

The use of an adhesive represents a further cost-effective alternative to the backlash-free installation of the overload tripping device or the tripping element in the housing of the protective switching device. Here, a region of the tripping element that is different from the fastening point, preferably the further contact point, is bonded with the aid of an adhesive - for example an adhesive or a potting compound, for example a synthetic resin - firmly connected to the housing. Due to the elongation, an increase in temperature leads immediately, i.e. without offset, to a force acting on the trigger element on the housing and vice versa, and as the temperature-related elongation progresses to the desired deformation of the trigger element. In this way, too, the tripping element can be installed without play, so that the tripping characteristic of the overload tripping device, and thus of the protective switching device, can be set in a predefined manner.

In a further advantageous further development of the overload tripping device, the play-free setting of the relative position of the tripping element with respect to the housing can be implemented with the aid of an adjusting screw.

The use of an adjusting screw is another alternative to installing the overload tripping device or the tripping element in the housing of the protective switching device without play. Here, the further point of contact is formed by the adjusting screw, which is screwed into the housing until the tripping element is installed without play in the housing is. In this case too, an increase in temperature (due to the associated elongation) leads directly, i.e. without offset, to a force acting on the triggering element on the housing and vice versa, and thus to the desired deformation of the triggering element. In this way, too, the triggering characteristic can be set in a predefined manner during assembly. If the adjusting screw is also accessible from the outside, readjustment is also possible when the housing is already fully assembled or closed.

In a further advantageous further connection of the overload tripping device, the adjustment element is arranged on the connection area of the tripping element. The arrangement of the adjustment element in the connection area of the release element represents a space-saving implementation option.

The electromechanical protective switching device according to the invention, in particular a circuit breaker or miniature circuit breaker, has a thermal overload tripping device of the type described above.

With regard to the advantages of the electromechanical protective switching device according to the invention, reference is made to the advantages of the overload tripping device according to the invention described above.

• 1 ein erstes Ausführungsbeispiel der Überlast-Auslösevorrichtung bzw. des Schutzschaltgerätes;
• 2A und 2B ein zweites Ausführungsbeispiel der Überlast-Auslösevorrichtung bzw. des Schutzschaltgerätes in verschiedenen Zuständen;
• 3 ein drittes Ausführungsbeispiel der Überlast-Auslösevorrichtung bzw. des Schutzschaltgerätes;

Several exemplary embodiments of the thermal overload tripping device or the electromechanical protective switching device are explained in more detail below with reference to the accompanying figures. In the figures are:

• 1 a first embodiment of the overload tripping device or the protective switching device;
• 2A and 2 B a second embodiment of the overload tripping device or the protective switching device in different states;
• 3 a third exemplary embodiment of the overload tripping device or of the protective switching device;

In the various figures of the drawing, the same parts are always provided with the same reference numbers. The description applies to all drawing figures in which the corresponding part can also be seen.

In 1 a first exemplary embodiment of the thermal overload tripping device 11 or of the electromechanical protective switching device 1 in the tripped state is shown schematically in a side view. The protective switching device 1 has a housing 2, the front housing shell being omitted from the drawing in order to allow a detailed insight into the structure of the protective switching device 1. An electrical connection terminal 8 is arranged in the left and right edge area of the housing 2, via which the protective switching device 1 can be contacted with external electrical connection lines (not shown). In the upper area, which corresponds to the front when the protective switching device 1 is installed, there is an actuating element 3 for manual operation—ie for switching on and off—of the protective switching device 1 . The actuating element 3 is mechanically coupled to a switching mechanism 4 of the protective switching device 1 . A switching contact 5 is arranged below the switching mechanism 4 and can be actuated, ie opened and closed, with the aid of the switching mechanism 4 . In the representation of 1 if the switching contact 5 is open, the actuating element 3 of the protective switching device 1 is accordingly in its OFF position. Furthermore, the protective switching device 1 has fastening means 9 which are arranged on the rear side of the housing 2 opposite the front side. The protective switching device can be fastened to a support element, for example a top-hat rail (not shown), with the aid of these fastening means 9 .

In the event of a short circuit, the protective switching device 1 has a so-called short-circuit tripping device 6 . A mechanical triggering signal is generated by the high short-circuit current and transmitted to the switching mechanism 4, as a result of which the switching mechanism 4 is triggered. As a result of this triggering, the switching contact 5 is finally opened. Accordingly, the actuating element 3 assumes its OFF position. An arc quenching device 7 is arranged below the short-circuit tripping device 6 . When the current-carrying switching contact 5 opens, an arc is first produced, which is driven in the direction of the arc quenching device 7 for quenching, where it is finally quenched.

In the event of an electrical overload, the protective switching device 1 has a thermal overload tripping device 10, which is 1 shown protective switching device 1 between the arc extinguishing device 7 and the right-hand terminal 8 is arranged. The thermal overload tripping device 10 has a tripping element 11 which in turn has a fastening point at its first end 12 with the aid of which the tripping element 11 can be fastened in the housing 2 of the protective switching device 1 . A second end 13 of the triggering element 11 is designed as a free end, which can be moved relative to the attachment point when heated due to thermal expansion of the triggering element 11 in order to act on an unlatching point of the switching mechanism 4 of the protective switching device 1 if a predefined threshold value is exceeded. In order to be able to mount the tripping element 11 without play in the housing 2 of the protective switching device 1 , it has several pinch points 17 which are arranged in an area between the fastening point and another point of contact between the tripping element 11 and the housing 2 . In the representation of 1 this further point of contact is formed on a middle section of the triggering element 11, which is arranged near the back of the housing in the assembled state. Due to the crushing points 17, which are attached during the assembly of the overload tripping device 10 or the tripping element 11 in the housing 2 of the protective switching device 1 between the fastening point and the further point of contact, a longitudinal expansion of this section is achieved until the tripping element 11 despite possible manufacturing tolerances is mounted without play in the housing 2 of the protective switching device 1. The number of pinch points 17 can vary and depends on the manufacturing tolerances of the components to be assembled, ie the housing 2 and the triggering element 11, from.

With the help of the pinch points 17, the relative position of the tripping element 11 relative to the housing 2 - and thus in particular relative to the unlatching point of the protective switching device 1 - can be adjusted without play. This ensures that the triggering element 11 is already supported at the further point of contact in the housing 2 at the start of its temperature-related elongation. A temperature increase due to the lengthening of the triggering element 11 thus leads directly, ie without an offset, to mechanical stress in the area between the fastening point and the further point of contact. As a result, the relevant section of the triggering element 11 is reversibly deformed, ie it is bent in order to at least partially reduce this stress. However, this deformation causes a movement of the free second end 13 of the triggering element 11, which acts on the unlatching point of the protective switching device 1. This structural design of the triggering element 11 ensures that the movement of the free end 13 of the triggering element 11 depends on the temperature change can be determined exactly, ie without an offset. The tripping characteristics of the overload tripping device 10 - and thus of the protective switching device 1 - can thus be adjusted exactly.

The term "offset" means that the temperature-related elongation of the triggering element 11 first compensates for the play between the triggering element 11 and the housing 2 caused by the assembly, before the triggering element 11 even touches the housing 2 in the further point of contact. Only from this point in time of contact can the triggering element 11 be supported at the further point of contact, so that a mechanical stress builds up in the event of further longitudinal expansion, which leads to the desired deformation of the triggering element 11 . This relationship can also be illustrated graphically: if the mechanical stress of the release element 11 is plotted as a function of its elongation, the resulting curve goes through the origin of the coordinate system in the case of a play-free assembly, while it goes through the origin of the coordinate system when there is mechanical play between the housing 2 and the release element 11 does not go through the origin, and thus has an "offset".

in the in 1 case shown, the triggering element 11 is U-shaped. It has a first leg 14, a second leg 15 and a connecting region 16 connecting the two legs. The first end 12 of the triggering element 11 is formed at the end of the first leg 14 , the second end 13 at the end of the second leg 15 . The connection area 16 forms the further point of contact of the tripping element 11 with the housing 2 of the protective switching device 1. Due to the U-shaped design, the tripping element 11 can be mounted in a space-saving manner in the housing 2 of the protective switching device 1, without compromising on the required absolute linear expansion - and thus the Release accuracy - to have to do.

In the 2A and 2 B a second exemplary embodiment of the thermal overload tripping device 10 or the electromechanical protective switching device 1 is shown schematically, the two figures showing the overload tripping device 10 or the electromechanical protective switching device 1 in various switching or operating states, each in a side view. Both figures show the electromechanical protective switching device 1 in a triggered state in which the actuating element 3 is in its OFF position and the switching contact 5 is open. However, while in 2A the thermal overload tripping device 10 is shown in a first switching or operating state, which corresponds to an operational state 2 B the overload tripping device 10 in a second, tripped switching or operating state, in which the tripping element 11 is correspondingly deformed due to thermal expansion. The temperature-related deformation of the triggering element 11 has the consequence that the second, free end 13 is bent in the direction of the first end 12, which is firmly fastened in the housing 2. This movement of the second end 13 is transmitted to the switching mechanism 4 by the bracket 20 coupled to the second end 13, whereupon the protective switching device 1 is triggered and the switching contact 5 is opened.

That in the 2A and 2 B illustrated second embodiment differs from that in 1 illustrated first embodiment essentially in that the backlash-free assembly of the triggering element 11 is realized in the housing 2 of the protective switching device 1 with the help of an adjusting screw 19. The adjusting screw 19 is screwed into the back of the housing 2 in the area of the fastening means 9 shown on the right until it touches the connection area 15 of the triggering element 11 . In this way, a play-free installation of the triggering element 11 in the housing 2 of the protective switching device 1 can also be implemented.

In 3 a third exemplary embodiment of the thermal overload tripping device 10 or of the electromechanical protective switching device 1 is shown schematically in a side view. Again, this representation is very similar to the representations in FIG 1 and 2 , but with the difference that the backlash-free assembly of the triggering element 11 in the housing 2 of the protective switching device 1 is realized in this third embodiment with the aid of an adhesive 18. This can be an adhesive or--to compensate for larger differences in length--a potting compound, for example a synthetic resin. Irrespective of which adhesive agent is used, a second fixation of the triggering element 11 in the housing 2 is hereby realized, on which the triggering element 11 can be supported directly, ie without offset, in the event of a temperature-induced lengthening. The mechanical stresses occurring between the triggering element 11 and the housing 2 subsequently lead to the predefined deformation of the first leg 14 of the triggering element 11, and thus to the predefined movement of the free second end 13 formed on the second leg 15. The use of the adhesive agent 18 thus represents a further cost-effective alternative to mounting the overload tripping device 10 or the tripping element 11 in the housing 2 of the protective switching device 1 without play.

In the representations of 1 until 3 the free second end 13 of the tripping element 11 is always coupled to the switching mechanism 4 of the protective switching device 1 via a bracket 20 . However, it is also possible to design the tripping element 11 in the area of its free second end 13 in such a way that it acts directly and immediately on the unlatching point of the switching mechanism 4 of the protective switching device 1 . In this case, the bracket 20 can be dispensed with.

Reference List

1

protective switching device

2

Housing

3

actuator

4

switching mechanism

5

switching contact

6

Short-circuit release device

7

arc extinguishing device

8th

terminal block

9

fasteners

10

Overload release device

11

release element

12

first end

13

second end / free end

14

first leg

15

second leg

16

connection area

17

pinch points

18

adhesive agent

19

adjustment screw

20

hanger

Claims (11)

Thermal overload tripping device (10) for an electromechanical protective switching device (1), in particular for a circuit breaker or a circuit breaker, - with a tripping element (11) which can be heated directly or indirectly by an electric current, - in which the tripping element (11) has a fastening point at a first end (12), by means of which the tripping element (10) can be fastened in a housing (2) of the protective switching device (1), - in which a second end (13) of the tripping element (11) is designed as a free end which can be moved relative to the fastening point when it heats up due to the thermal expansion of the triggering element (11) in order to act on a release point of the protective switching device (1) if a predefined threshold value is exceeded, characterized in that the triggering element (11) is formed in one piece. Overload release device (10) after claim 1 , characterized in that the triggering element (11) is formed from a material with a high coefficient of thermal expansion. Overload tripping device (10) according to one of the preceding claims, characterized in that the tripping element (11) is formed from a metallic material. Overload tripping device (10) according to one of the preceding claims, characterized in that the free end (13) is designed for direct action on the unlatching point of the protective switching device (1). Overload tripping device (10) according to one of the preceding claims, characterized in that the tripping element (11) is U-shaped with a first leg (14), a second leg (15) and one of the two legs (14, 15) connecting connection portion (16), wherein the first end (12) is formed at the end of the first leg (14), and the second end (13) is formed at the end of the second leg (15). Overload tripping device (10) according to one of the preceding claims, characterized in that the overload tripping device (11) has an adjustment element, by means of which a position of the tripping element (11) relative to the housing (2) of the protective switching device (1) can be adjusted without play is. Overload release device (10) after claim 6 , characterized in that the triggering element (11) has one or more pinch points (17) which are used for setting the relative position of the triggering element (11) relative to the housing (2) of the protective switching device (1) without play. Overload release device (10) after claim 6 , characterized in that the play-free setting of the relative position of the triggering element (11) relative to the housing (2) can be realized with the aid of an adhesive (18). Overload release device (10) after claim 6 , characterized in that the play-free adjustment of the relative position of the release seelements (11) relative to the housing (2) using an adjusting screw (19) can be realized. Overload tripping device (10) according to one of Claims 6 until 9 , characterized in that the adjustment element is arranged on the connection area of the triggering element (11). Electromechanical protective switching device (1), in particular circuit breakers or miniature circuit breakers, which has a thermal overload tripping device (10) according to one of Claims 1 until 10 having.

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