CN101354980A - Heating elements for heating bimetals that can be applied to open protective switches - Google Patents

Abstract

The invention relates to a heating element (1) for heating a bimetal (7), which can be used in opening protective switches, in particular line protective switches or circuit breakers, the heating element has at least one heating An integrally formed fastening area (2) on the component (1) with at least one fastening plate (2', 2") deformed such that a conductor (8) can be fastened to the fastening area (2) middle.

Description

Heating elements for heating bimetals that can be applied to open protective switches

technical field

The invention relates to a heating element for heating a bimetal which can be used to open a protective switch, in particular a circuit breaker or a circuit breaker.

Background technique

For example, protective switches are used in building wiring technology to switch current-carrying lines to non-current in the event of excessive current. The protective switch is, for example, a line protective switch or a circuit breaker.

A bimetal is used for the thermal disconnection of the switch, through which the line current flows. The ohmic power transferred in the bimetal by the line current causes the bimetal to heat up. This heating causes bending of the bimetal due to the different thermal expansion coefficients of the two metal components. The bimetal part is arranged with reference to the connection of the locking mechanism in such a way that, due to its deformation which increases with increasing temperature, the connection is released at a predetermined opening temperature. In this case, the opening temperature corresponds to the rated current given by the device manufacturer, which is a measure of the opening sensitivity of the protective switching device.

At lower rated currents, it is practically impossible to heat the bimetal directly by means of only current flow in a confined installation space, since the electrical resistance necessary for the required heating cannot or cannot be realized with great difficulty. As a rule, in thermal disconnectors with a relatively low rated current, the bimetal is heated directly by means of a heating element which is thermally connected to the bimetal, for example by means of an externally mounted heating coil. In addition, the bimetal must be separated from the heating element by insulating material. Such directly heated bimetals are complicated to install and correspondingly expensive.

In order to electrically connect the heating element, the heating element is usually connected by means of soldering to a conductor (eg copper wire). Heating elements are constructed of materials with a high aluminum, chromium or manganese content and are therefore difficult to solder. Since, for example, aluminum can accumulate on the surface of the heating element and adversely affect the welding process, the firmness of the connection between the heating element and the conductor achieved during welding is very unstable.

Contents of the invention

The object of the present invention is to provide an advantageous heating element which can be connected to a conductor in such a way that the connection is less unstable than when soldering. In particular the heating element can be produced cost-effectively.

This object is achieved by a heating element according to claim 1 .

Advantageous refinements and developments of the invention are given by the subclaims.

According to the heating element for heating a bimetal of the present invention, the bimetal can be applied to a disconnecting protective switch, especially a circuit breaker or a circuit breaker, the heating element has at least one integrally formed on the heating element A fastening region having at least one fastening plate which is deformed in such a way that the conductor can be fastened in the fastening region.

The fixing area and the fixing plate form a crimped joint in which the conductor can be wrapped and fixed. The conductor can be crimped in the fastening region by deformation of at least one fastening plate. A stable, electrically conductive connection is formed between the heating element and the bimetal by crimping. The firmness of the connection has only minor instabilities through the pressure provided, for example, by the shape of the crimping tool. Furthermore, the one-piece forming of the crimping interface on the heating element results in a more cost-effective connection than, for example, a connection achieved by using loops rolled separately on the conductor and the heating element for crimping.

Preferably, the heating element is designed as a sheet metal punched and bent part. The heating element can be produced particularly easily and cost-effectively by punching out basic shapes from sheet metal and subsequently bending into intermediate shapes. The punched-out heating element can be bent, for example, in such a way that preferably the two fastening plates and the fastening region form an annular hole into which the conductor can be inserted and fixed by deformation of the fastening plates.

Preferably, the heating element has a further fastening plate outside the fastening region, by means of which the heating element can be fastened to the bimetal. The bimetal and the heating element can be thermally connected to one another by corresponding deformation of the other fastening plate.

By joining the heating element to the bimetal and crimping the conductor, the heating element transitions from the intermediate shape to the final shape.

It is advantageous to use a heating element in the protective switch.

A protective switch can be understood, for example, as a line protective switch, a circuit breaker, a telecommunications protective switch or a system protective switch. Of course, heating elements can also be used in FI/LS switches, that is to say in combinations of fault current and line protection switches.

A preferred embodiment of the protective switch has a heating element according to the invention, that is, the heating element is arranged along the bimetal and is electrically conductively connected to the first end of the bimetal only at the first end of the heating element, The electrically insulating material is arranged between the bimetal part and the heating element in such a way that the current flow between the bimetal part and the heating element takes place only via the two first ends.

The electrical insulating material ensures that the current flows completely through the heating element, so that the heating element is heated as a whole. In addition, a conductive connection between the heating element and the bimetal can be made so that the bimetal is at least partially passed through by an electric current and can thus also be heated additionally by this current flow. In this case, the current flow can not only flow from the bimetal into the heating element, but also in the opposite direction.

In order to achieve as rapid and uniform heating of the bimetal as possible especially at low rated currents, the advantage exists when the current-carrying parts of the protective switch are connected to one another in such a way that the current conveyed via the protective switch is initially drawn from the bimetal The second end is fed to the first end of the bimetal, the current is fed into the first end of the heating element via the conductive connection, and from there the current is only in the heating element at the second end of the bimetal It is conveyed in the direction of the central part and continues to be conveyed into the fixed area of the heating element, and finally conveyed out of the heating element through the conductor.

In this way, the bimetal is first flown by the current to be monitored almost over its entire length (i.e. from the second end to the first end), and then the heating element is passed by the current to be monitored over its entire length. Current flows through. The bimetal is thus heated over almost its entire length directly by the current flowing through the bimetal and also by the heating element. Preferably, the bimetal is thermally conductively connected to the heating element over a majority of its length (for example greater than 50%). As a result, the most efficient possible heating can be achieved even at low nominal currents, and thus the protective switch can be reliably opened.

An advantage is that the current flow in the circuit breaker can also be carried out in the opposite direction first through the heating element 1 and then through the bimetal 7 .

If the heating element and the conductor are connected to one another in another way, for example by means of separate collars by welding or crimping, the current flow can of course also advantageously be realized through the bimetal part and the heating element.

Description of drawings

The invention will subsequently be explained in detail on the basis of a number of exemplary embodiments shown in the drawings. show:

Figure 1 is a heating element punched from a plate,

Figure 2 is a side view of the heating element of Figure 1 after the bending process,

Figure 3 is a side view of the bent heating element turned by 90° relative to the side view of Figure 2,

Figure 4 is a schematic view viewed along the longitudinal axis of the curved heating element,

Figure 5 is a side view of a bent heating element secured to a bimetal and connected to a conductor.

Detailed ways

The same reference signs denote the same parts in the figures.

FIG. 1 shows a heating element 1 punched from a sheet metal. The plate is composed of a resistive material, such as a chrome-aluminum alloy, which can have a higher ohmic resistance at lower temperatures. The heating element 1 has a smooth basic shape after punching and has a first end 5 and a second end formed by a fastening region 2 with two fastening plates 2 ′, 2 ″. At the first end 5 Other fixing plates 4 are arranged below. In this embodiment, the heating element 1 has other fixing plates 4 arranged oppositely in pairs and perpendicular to the longitudinal axis of the heating element 1. Of course, other fixing plates can also have other shapes And not necessarily arranged in pairs opposite each other and/or perpendicularly to the longitudinal axis of the heating element.The fastening area 2 and the area with the other fastening plate 4 are connected to each other via the web 3 .

In order to be able to fasten the heating element 1 to the bimetal and to fasten the (electrical) conductor in the fastening region, the heating element 1 is bent from the basic shape into an intermediate shape after punching. Furthermore, the other fastening plates 4 are each bent by approximately 90° in the same direction, for example. This will be shown in Figures 2, 3 and 4. The schematic diagram of FIG. 1 corresponds to the schematic diagram of the bent heating element 1 in FIG. 3 . FIG. 2 shows a schematic view of a bent heating element turned by 90° relative to FIG. 3 , and FIG. 4 shows a schematic view from the direction of the first end 5 along the longitudinal axis of the heating element 1 . The fastening plates 2 ′, 2 ″ are bent in the process from the basic shape to the intermediate shape in such a way that they and the fastening region 2 form annular openings into which conductors can be inserted. By deforming the fastening plates 2 ′, 2 ″, the conductors can be crimped in the fastening region, for example with corresponding crimping pliers.

Figure 5 shows that the heating element 1 is fixed on a bimetal 7 having a first end 7' and a second end 7". Before the heating element 1 is fixed on the bimetal 7, the bimetal 7 first Wrapped with an electrically insulating material 6 (such as an electrically insulating film). Subsequently, the heating element 1 is arranged on the longitudinal axis of the bimetal 7 along its longitudinal axis, and the other fixing plates 4 are thus bent and pressed into the On the bimetal 7, that is to say, the bimetal 7 and the heating element 1 are fastened to each other and form a thermally conductive connection between the bimetal 7 and the heating element 1. In addition, the connecting piece 3 has a further fixing plate, for example at the end leading to the heating element 1. In the transition region of the part of 4, it is bent at about 180° in the direction of the first end 5 of the heating element 1, and the conductor 8 is inserted into the fixing region 2 and is fixed in the fixing region by deformation of the fixing plates 2', 2". 2 fixed. In order to ensure that no electrically conductive connection is formed between the bent connection piece 3 and the area with the other fastening plate 4, an electrically insulating material can be used, for example a shrink sleeve wrapped around the conductor 8, the fastening area 2 and the connection piece 3 (not shown in Figure 5). The connection between the conductor 8 and the fastening region 2 with the fastening plates 2 ′, 2 ″ takes place in such a way that there is an electrically conductive connection between the heating element 1 and the conductor 8 .

Preferably, the conductor 8 and the heating element 1 are cold welded by crimping. The first end 5 of the heating element 1 is electrically conductively connected to the first end 7 ′ of the bimetal 7 , for example by welding.

Preferably, the bimetal 7 with the heating element 1 affixed thereto is installed into a protective switch, such as a line protective switch or a circuit breaker, and is used to open the protective switch. The current flowing through the protective switch is firstly conveyed, for example via a corresponding conductive connection, to the second end 7" of the bimetal 7. From there the current will flow through the bimetal 7 to the first end 7' of the bimetal 7, It then flows into the first end 5 of the heating element 1. In the heating element 1, the current is conveyed in the direction of the first end 7' of the bimetal 7 and the heating of the heating element 1 causes the bimetal 7 to The point that is thermally connected to the heating element 1 is heated directly.

Claims (7)

1. A heating element (1) for heating a bimetal (7), which can be applied to disconnecting a protective switch, especially a line protective switch or a circuit breaker, characterized in that the heating element (1) having at least one fastening region (2) integrally formed on the heating element (1), said fastening region having at least one fastening plate (2', 2") deformed in such a way that A conductor (8) can be fixed in said fixing area (2). 2 . The heating element ( 1 ) according to claim 1 , characterized in that the heating element ( 1 ) is designed as a plate punched and bent part. 3 . 3. The heating element (1) according to claim 1 or 2, characterized in that the heating element (1) has a further fixing plate (4) in addition to the fixing region (2), by means of which According to the other fixing plates mentioned above, the heating element (1) can be fixed on the bimetallic piece (7). 4. A protective switch, in particular a line protective switch or circuit breaker, having a heating element (1) according to any one of claims 1 to 3. 5. The protection switch according to claim 4, characterized in that the heating element (1) is arranged along the bimetal (7), and the heating element is only at the edge of the heating element (1) The first end (5) is electrically conductively connected to the first end (7') of the bimetal (7) and between the bimetal (7) and the heating element (1) such that Electrically insulating material (6) is provided such that the current flow between said bimetal (7) and said heating element (1) is achieved only through the two said first ends (5, 7') . 6. The protective switch according to claim 5, characterized in that the current-carrying parts of the protective switch are connected to each other in such a way that the current conveyed by the protective switch first flows from the second side of the bimetal (7). The end (7") is fed to the first end (7') of the bimetal (7), the current is fed to the first end (5) of the heating element (1) via a conductive connection , and from there the current is conveyed only in the heating element (1) in the direction of the second end (7") of the bimetal and continues to the fixing area of the heating element (1) In (2), finally the current is delivered from the heating element (1) through the conductor (8). 7. The protective switch of claim 6, wherein the currents are delivered in opposite directions.

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