WO2018226165A1

WO2018226165A1 - Improved thermomagnetic actuator in a security electric switch

Info

Publication number: WO2018226165A1
Application number: PCT/SI2018/000008
Authority: WO
Inventors: Lucjan STREHAR; Domen Janc; Admir BAJRIC
Original assignee: Nela Razvojni Center Za Elektroindustrijo In Elektroniko, D.O.O.
Priority date: 2017-06-06
Filing date: 2018-05-10
Publication date: 2018-12-13
Also published as: RS61978B1; EP3635765A1; SI25460B; EP3635765B1; PL3635765T3; HRP20210886T1; SI25460A; RU2766444C2; RU2019144202A; RU2019144202A3

Abstract

The purpose of the invention is to improve reactiveness of a thermomagnetic actuator in a security electric switch, so that the time delay prior to interruption of the electric circuit through the switch due to electric overloading could be essentially reduced. The invention provides that a yoke (6) is along its complete circumference spaced apart from the internal surface of a casing (1) and is surrounded with an thermal insulating ring (10), which is uninterrupted along its complete circumference and is on the one hand rest on the internal surface of said casing (1) and on the other hand on said yoke (6). An anchor (2) is, at least on its side which is faced towards the closed end portion (1 ") of said casing (1), furnished with a centrally arranged throughout axial passage (2'), and on its opposite side, which is faced towards said yoke (6), with a centrally arranged cavity (2"), wherein said passage (2') within the anchor (2) is adapted to receive a thermal insulating guide (9), which is inserted between the anchor (2) and the casing (1), while said cavity (2") is adapted to receive a portion of said spring (3), which is faced towards the anchor (2), but not also that portion of the spring (3), which is faced towards the yoke (6). Moreover, a thermal insulating bush (11) is inserted between a bimetallic disc (7) and an actuating needle (5).

Description

Improved thermomagnetic actuator in a security electric switch

The invention refers to electricity, in particular to basic electric components, namely to switches and construction details related to switches, which are controlled by means of a suitable lever, and in particular to switches which are used in protection against electric overloads. Pursuant to the International Patent Classification IPC⁹) such inventions belong to at least one of classes H 01 H 71/52, H OI H 73/50 or H 01 H 71/40.

The aim of the invention is to create such thermomagnetic actuator in a security electric switch, which should upon integration thereof into each electric circuit be able to react much more accurate and quicker than known actuators in the state of the art switches, either to thermal overloads or also to a short circuit current occurred within said electric circuit.

As disclosed in DE 36 37 275 Al, interruption of an electric circuit, when a current overload occurs, can be achieved by means of a thermomagnetic actuator with a bimetallic disc, which is placed on an actuating needle, which is axially displaceable and inserted within a tubular casing, from which then said needle protrudes in a direction towards an interrupting assembly, which serves for interrupting of said circuit. On such basis, a thermomagnetic actuator has been created and used in protecting switches, which are as such disclosed in EP 2 545 576 Bl in v EP 2 837 014 Bl , to which a reference is made for the purposes of disclosure of this invention. In such protective switches the electric circuit extends through a coil, which is wound around said casing and is intended for intensifying of the magnetic field every time, when a sufficiently high current overload would occur. An anchor is firmly connected with said actuating needle and is exposed to said magnetic field. Said anchor is furnished with an one-side blinded axial passage, which is opened in a direction towards a yoke, which is also mounted within said casing on that side, which is faced towards said interrupting assembly, and said axially to and fro displaceable actuating needle is inserted therein. A spring is inserted within said blinded passage and protrudes from said passage towards the yoke. When a sufficiently intensive electric overload occurs, also the intensity of said magnetic field is increased up to the value, which leads to displacement of the anchor towards the yoke, by which simultaneously also the actuating needle is axially displaced towards said interrupting mechanism, by which the electric circuit should be interrupted promptly and without delay. As soon as said electric overload is eliminated, intensity of said magnetic field is decreased, and adhesion between the anchor and the yoke is reduced, upon which the spring is capable to depress the anchor apart from the yoke in order to to return the anchor together with the actuating needle back to their initial position.

In the case of some less intensive current overload, when the electromagnetic actuation is not yet achieved, the coil is heated and the heat from the coil is transferred towards the bimetallic disc within the casing, by which said disc is deformed and said actuating needle connected therewith is displaced towards said interrupting assembly for the purpose of interruption of the electric circuit. However, said heat transfer from the coil towards the bimetallic disc requires certain time, but in the meantime all surrounding components of the switch, among other also said yoke and said anchor, which are due to their essential weight capable to take-over i.e. to absorb an essential amount of heat energy. Due to such undesired heating of said neighboring components a correspondingly higher amount of heat energy is required for the purpose of deflecting said bimetallic disc, so that in such situation the required interruption of the electric circuit can be performed only with an essential time delay. In addition to that, said heating or overheating is in particular problematic, when certain components are made of plastics, which is usually quite useful due to its excellent electric insulating properties.

When bearing in mind the state of the art solutions, which are at present commercially available, such time delay prior to interruption of the electric circuit is often quite problematic and is extremely difficultly maintained within still acceptable limits. Said time delay by interrupting of the electric circuit could be generally reduced by intensifying of heat generating, e.g. by increasing the resistance in coil windings, which would however lead to permanently increasing of electric losses, which is quite inacceptable from the commercial point of view.

The present invention refers to an improved thermomagnetic actuator in a security electric switch. Such actuator is together with each belonging interrupting assembly mountable within the casing of a security electric switch, which comprises a tubular casing, which is closed on its one end portion and which is widened on its open end portion and is in the area of said open end portion adapted to receive a cover. Moreover, an actuating needle is inserted within said casing, which is centrally arranged and displaceable to and fro along said casing and which moreover in the area of said cover protrudes outside of said casing towards each disposable interrupting mechanism, which serves for establishing or interrupting of the electric circuit extending throughout said switch. Said needle is placed at certain distance apart from the closed end portion of said casing. An immovable yoke and a displaceable anchor are inserted within said casing, wherein that said yoke is located adjacent to said widened open end portion of the casing and the needle is extending through it with the possibility of its previously mentioned to and fro displacement, and wherein said anchor is arranged in the area of said closed end portion of the casing adjacent to said needle and can be displaced to and fro within said casing towards the yoke or away from it. Moreover, a compression spring is inserted within said casing between said yoke and said anchor and is intended to depress the anchor apart from the yoke. Still further, a bimetallic disc is inserted within said casing, through which said actuating needle is extending and is by means of said bimetallic disc axially displaceable in a direction towards said interrupting assembly of the switch. Besides, an electromagnetic coil is wound around said casing and is electrically connectable into each electric circuit, which is established throughout said security electric switch, in which said thermomagnetic actuator is integrated.

The present invention proposes that said yoke is along its complete circumference spaced apart from the internal surface of the casing and is surrounded with an thermal insulating sleeve, which is uninterrupted along its complete circumference and is on the one hand rest on the internal surface of the casing and on the other hand on said yoke. Moreover, said anchor is, at least on its side which is faced towards the closed end portion of the casing, furnished with a centrally arranged throughout axial passage, and on its opposite side, which is faced towards the yoke, with a centrally arranged cavity, wherein said passage in the anchor is adapted to receive a thermal insulating guide, which is inserted between the anchor and the casing, while said cavity is adapted to receive a portion of said spring, which is faced towards the anchor, but not also that portion of the spring, which is faced towards the yoke. Moreover, a thermal insulating sleeve is inserted between said bimetallic disc and said actuating needle and is displaceable arranged on said actuating needle and guided therewith, wherein its displacement is limited on the one hand by a thickened area on the actuating needle and on the other hand by said bimetallic disc.

The invention further provides that said thermal insulating guide of the anchor, said thermal insulating bush and said thermal insulating ring all consist of a non- ferromagnetic thermal insulating material, in particular of plastic.

The invention will be disclosed in more detail on the basis of an embodiment, the cross-section of which along its diametrical plane is schematically presented in Fig. 1.

The improved thermomagnetic actuator in a security electric switch according to Fig, 1 is together with each belonging interrupting assembly mountable within the casing of a security electric switch, which is as such disclosed in EP 2 545 576 Bl and EP 2 837 014 B l .

Such thermomagnetic actuator comprises a tubular casing 1, which preferably consists of aluminium and is closed on its one end portion 1 " and is moreover widened on its open end portion 1 ', and is in the area of said open end portion 1 ' adapted to receive a cover 8.

Said cover 8 consists of a non- ferromagnetic material, e.g. of plastics, and is in this shown embodiment mechanically pressed onto said casing 1 and furnished with a throughout passage, so that an actuating needle 5 extends there-through, which is centrally arranged within the casing 1 and protrudes outside of the casing 1.

Said actuating needle is axially displaceable to and fro along said casing 1 and protrudes outside of said casing 1 towards each disposable interrupting mechanism, which serves for establishing or interrupting of the electric circuit extending throughout said switch. Moreover, said needle 5 is placed at certain distance apart from the closed end portion 1 " of said casing 1.

Moreover, an immovable yoke 6 and a displaceable anchor 2 are inserted within said casing 1 , so that said yoke 6 is located adjacent to said widened open end portion of the casing 1 and the needle 5 is extending through it with the possibility of its previously mentioned to and fro displacement, while the anchor 2 is arranged in the area of said closed end portion 1 " of the casing 1 adjacent to said needle 5 and can be displaced to and fro within said casing 1 towards the yoke 6 or away from it.

A compression spring 3 is also inserted within said casing 1 between said yoke 6 and said anchor 2 and is intended to depress the anchor 2 apart from the yoke 6. Moreover, a bimetallic disc 7 is inserted within said casing 1 in the area of its widened end portion , through which said actuating needle 5 is extending, wherein by means of said bimetallic disc (7) said needle 5 is axially displaceable in a direction towards said interrupting assembly of the switch.

Furthermore, an electromagnetic coil 4 is wound around said casing 1 , which is electrically connectable into each electric circuit, which is established throughout said security electric switch, in which said thermomagnetic actuator is integrated. Said yoke 6 is along its complete circumference spaced apart from the internal surface of the casing 1 and is surrounded with an thermal insulating ring 10, which is uninterrupted along its complete circumference and is on the one hand rest on the internal surface of the casing 1 and on the other hand on said yoke 6. In the shown embodiment said thermal insulating ring 10 is made of a non-ferromagnetic thermal insulating material, optionally of plastics, and is tightly inserted between the yoke 6 and the casing 1. Besides, a thermal insulating bush 1 1 is inserted between said bimetallic disc 7 and said actuating needle 5, wherein said bush 1 1 is displaceable arranged on said actuating needle 5 and is guided therewith, wherein its displacement is limited on the one hand by a thickened area 5' on the actuating needle 5 and on the other hand by said bimetallic disc 7.

The anchor 2 is at least on its side, which is faced towards the closed end portion 1 " of the casing 1 , furnished with a centrally arranged throughout axial passage 2', and on its opposite side, which is faced towards the yoke 6, with a centrally arranged cavity 2", wherein said passage 2' within the anchor 2 is adapted to receive a thermal insulating guide 9, which is in this case made of plastics and is inserted between the anchor 2 and the casing 1 , while said cavity 2" is adapted to receive a portion of said spring 3, which is faced towards the anchor 2, but not also that portion of the spring 3, which is faced towards the yoke 6.

From the mechanical and electrical point of view, such thermomagnetic actuator according to the invention is functioning quite similar like the known actuator, which is disclosed in EP 2 545 576 B l and EP 2 837 014 B l . However, thanks to essentially amended concept of the anchor 2, which is now furnished with said passage 2' and the cavity 2", and thanks to introduction of said thermal insulating δ guide 9, said thermal insulating ring 10 and said thermal insulating bush 1 1 , the actuator according to the invention excels in essentially improved heat transfer from the source i.e. the coil 4 towards said bimetallic disc 7. Namely, as soon as the electric current occurs within said coil 4, heat energy is generated within the coil 4, which a portion of which is transferred to the surrounding air, and a portion is divided to partial heat flows j₂ through the casing 1 , as well as j i and thereafter ji_a through the bimetallic disc 7 and j_Jb through said actuating needle 5. Consequently, undesired heating of the other components of the actuator, in particularly of the yoke 6, the anchor 2 and the spring 3 there-between is herewith essentially eliminated, so that said bimetallic disc 7 is quickly supplied with a heat flow, which is necessary for achieving such temperature, which is required for change of the shape of the bimetallic disc 7, which then leads to displacement of said actuating needle 5 in a direction outside of the casing 1 and towards the interrupting assembly of the switch, in which said actuator is integrated. Thanks to such concept, reactiveness of the security electric switch according to the invention can be essentially improved, since the time delay prior to interruption of the electric circuit through the switch, when compared with the prior art solutions, can be essentially reduced.

Claims

PATENT CLAIMS

1. Improved thermomagnetic actuator in a security electric switch, which is together with each belonging interrupting assembly mountable within the casing of a security electric switch, and which comprises a tubular casing (1), which is closed on its one end portion (1 ") and which is widened on its open end portion (1 ') and is in the area of said open end portion (1 ') adapted to receive a cover (8), wherein an actuating needle (5) is inserted within said casing (1), which is centrally arranged and displaceable to and fro along said casing (1) and which moreover in the area of said cover (8) protrudes outside of said casing (1) towards each disposable interrupting mechanism, which serves for establishing or interrupting of the electric circuit extending throughout said switch, wherein said needle (5) is placed at certain distance apart from the closed end portion (1 ") of said casing (1), and wherein an immovable yoke (6) and a displaceable anchor (2) are inserted within said casing (1), so that said yoke (6) is located adjacent to said widened open end portion ( ) of the casing (1) and the needle (5) is extending through it with the possibility of its previously mentioned to and fro displacement, and that the anchor (2) is arranged in the area of said closed end portion (1 ") of the casing (1) adjacent to said needle (5) and can be displaced to and fro within said casing (1) towards the yoke (6) or away from it, and wherein a compression spring (3) is also inserted within said casing (1) between said yoke (6) and said anchor (2) and is intended to depress the anchor (2) apart from the yoke (6), and wherein moreover also a bimetallic disc (7) is inserted within said casing (1), through which said actuating needle (5) is extending and is by means of said bimetallic disc (7) axially displaceable in a direction towards said interrupting assembly of the switch, and wherein an electromagnetic coil (4) is wound around said casing (1), which is electrically connectable into each electric circuit, which is established throughout said security electric switch, in which said thermomagnetic actuator is integrated, characterized in that said yoke (6) is along its complete circumference spaced apart from the internal surface of the casing (1) and is surrounded with an thermal insulating ring (10), which is uninterrupted along its complete circumference and is on the one hand rest on the internal surface of the casing (1) and on the other hand on said yoke (6), and in that the anchor (2) is, at least on its side which is faced towards the closed end portion (1 ") of the casing (1), furnished with a centrally arranged throughout axial passage (2'), and on its opposite side, which is faced towards the yoke (6), with a centrally arranged cavity (2"), wherein said passage (2') within the anchor (2) is adapted to receive a thermal insulating guide (9), which is inserted between the anchor (2) and the casing (1), while said cavity (2") is adapted to receive a portion of said spring (3), which is faced towards the anchor (2), but not also that portion of the spring (3), which is faced towards the yoke (6), and in that a thermal insulating bush (1 1) is inserted between said bimetallic disc (7) and said actuating needle (5).

2. Actuator according to Claim 1 , characterized in that said thermal insulating bush (1 1) is displaceable arranged on said actuating needle (5) and is guided therewith, wherein its displacement is limited on the one hand by a thickened area (5') on the actuating needle (5) and on the other hand by said bimetallic disc (7).

3. Actuator according to Claim 1 or 2, characterized in that said thermal insulating guide (9) of the anchor (2) consists of an insulating material, which is not ferromagnetic.

4. Actuator according to Claim 3, characterized in that said thermal insulating guide (9) of the anchor (2) consists of plastics.

5. Actuator according to anyone of Claims 1 - 4, characterized in that a thermal insulating ring (10) consisting of a non-ferromagnetic thermal insulating material is tightly inserted between the yoke (6) and the casing (1).

6. Actuator according to Claim 5, characterized in that said thermal insulating ring (10), which is tightly inserted between the yoke (6) and the casing (1), consists of plastics.

7. Actuator according to anyone of Claims 1 - 6, characterized in that a thermal insulating bush (11), which is inserted between the bimetallic disc (7) and the actuating needle (5), consists of a non-ferromagnetic thermal insulating material.

8. Actuator according to Claim 7, characterized in that a thermal insulating bush (1 1), which is inserted between the bimetallic disc (7) and the actuating needle (5), consists of plastics.