CUT-OFF ELEMENT AND OVERVOLTAGE PROTECTION ARRANGEMENT

Abstract

A cut-off element for electrical isolation of an electrical component or for opening of a circuit in overload has two terminal contacts, an insulating housing and a fuse element which is located within the insulating housing. In the normal state of the cut-off element, the two terminal contacts (2,3) are connected to one another in an electrically conductive manner via the fuse element. In the cut-off element, reliable isolation of an electrical component, in particular an overvoltage arrangement, is possible by the insulating housing being formed of two parts which are connected to one another and the first part of the housing, in case of overload, being isolated from the second part of the housing so that the connection of the two terminal contacts is broken via the fuse element.

Claims

1. A cut-off element for electrical isolation of an electrical component or for opening of a circuit in overload, comprising: two terminal contacts, an insulating housing and a fuse element which is located within the insulating housing, wherein, in a normal state of the cut-off element, the two terminal contacts are connected to one another in an electrically conductive manner via the fuse element, wherein the insulating housing is formed of two parts which are connected to one another, and wherein a first part of the housing is isolated from the second part of the housing in case of an overload so that the connection of the two terminal contacts via the fuse element is broken.

2. The cut-off element in accordance with claim 1, wherein the first part of the housing in the normal state is laminated or cemented to the second part of the housing.

3. The cut-off element in accordance with claim 1, wherein the first part of the housing and the second part of the housing are each made of a printed-circuit boards base material having at least one plated-through hole.

4. The cut-off element in accordance with claim 3, wherein the printed-circuit boards base material is FR-4.

5. The cut-off element in accordance with claim 3, wherein the parts of the housing are joined via flat surfaces, wherein said at least one plated-through hole of one of the first and second housing parts is arranged offset to the at least one plated-through hole of the other of the first and second housing parts, and wherein the fuse element connects the plated-through holes to one another, the fuse element being located between the first and second housing parts.

6. The cut-off element in accordance with claim 1, wherein an arc extinguishing medium surrounds the fuse element.

7. A overvoltage protection arrangement, comprising: at least one overvoltage-limiting component, two connecting elements for electrical connection of the overvoltage protection arrangement to a current or signal path to be protected, a thermally opening connection, and a cut-off element, wherein, in a normal state of the overvoltage protection arrangement, the overvoltage-limiting component being in electrically conductive contact with a connecting element via the thermally opening connection, wherein the thermally opening connection being constructed to open when the temperature of the overvoltage-limiting component exceeds a temperature limit, wherein the cut-off element comprises: two terminal contacts, an insulating housing and a fuse element which is located within the insulating housing, wherein, in a normal state of the cut-off element, the two terminal contacts are connected to one another in an electrically conductive manner via the fuse element, wherein the insulating housing is formed of two parts which are connected to one another by the fuse element, and wherein a first part of the housing is isolated from the second part of the housing in case of an overload so that the connection of the two terminal contacts via the fuse element is broken. wherein, in the normal state of the overvoltage protection arrangement, a first of the terminal contacts of the cut-off element is connected to one of the connecting elements in an electrically conductive manner, and a second of the terminal contacts of the cut-off element is connected in an electrically conductive manner to the overvoltage-limiting component via the thermally opening connection.

8. The overvoltage protection arrangement in accordance with claim 7, further comprising means for applying a force that acts on the cut-off element so that, in case of an overload, the cut-off element is separated from the overvoltage-limiting component or the first part of the housing is separated from the second part of the housing of the cut-off element.

9. The overvoltage protection arrangement in accordance with claim 8, wherein said means for applying a force is a spring element which applies a force to the first part of the housing.

10. The overvoltage protection arrangement in accordance with claim 7, wherein the overvoltage protection arrangement is located in a housing, and wherein the housing has an inspection port in a region of the cut-off element.

11. The overvoltage protection arrangement in accordance with claim 10, wherein a front end of the first part of the housing faces the inspection port and is visually distinguishable from a front end of the second part of the housing which faces the inspection port.

12. The overvoltage protection arrangement in accordance with claim 10, wherein the front ends are distinguishable by each of the ends having a differently colored marking from the other of the ends.

13. The overvoltage protection arrangement in accordance with claim 7, wherein the at least one overvoltage-limiting component comprises a varistor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG. 1 shows a simplified representation of one cut-off element in a sectional view, and

[0025] FIG. 2 shows a simplified representation of an overvoltage protection arrangement, with a cut-off element according to FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

[0026] FIG. 1 shows a cut-off element 1 with two terminal contacts 2, 3. The cut-off element 1 has an insulating housing 4 in which a fuse element 5 is embedded. The housing 4 is formed of a first part 6 and a second part 7, the two housing parts 6, 7 each comprise a base material of the type used for printed-circuit boards. The base material is a composite of an epoxy resin and a fiber glass fabric. The base material acts to insulate so that the current can only be transmitted via the terminal contacts 2, 3 and the fuse element 5. The two housing parts 6, 7 additionally each have a plated-through hole 8 so that the two terminal contacts 2, 3 in the normal state are connected to one another in an electrically conductive manner via the plated-through holes 8 and the fuse element 5.

[0027] The two parts 6, 7 are cemented to one another so that the cut-off element 1 is made as a type of printed-circuit board whose top (terminal contact 2) and bottom (terminal contact 3) are electrically connected to one another via the fuse element 5. When the fuse element 5 heats up due to a high flowing current, both the pressure and the temperature within the housing 4 rise. When the fuse element 5 has been heated up to such an extent that it vaporizes, the pressure and temperature in the housing 4 are so great that the adhesive action is no longer sufficient to keep the two housing parts 6, 7 together. In this way the housing 4 peels off and the printed-circuit board delaminates and the two parts 6, 7 of the housing 4 are separated from one another. This leads to the electrical connection between the two terminal contacts 2, 3 being interrupted via the fuse element 5. Moreover, by separating the two parts 6, 7 and thus also the two terminal contacts 2, 3, an arc which may arise when the electrical connection opens is also extinguished.

[0028] FIG. 2 shows an overvoltage protection arrangement 9 with a cut-off element 1 according to FIG. 1. The cut-off element 1 is connected in an electrically conductive manner to an overvoltage-limiting component 10, in this case, a varistor. The overvoltage protection arrangement 9 has two connecting elements 11, 12 with which the overvoltage protection arrangement 9 can be connected to the current path or signal path which is to be protected. The cut-off element 1 is connected to the varistor 10 via a thermally opening connection 13.

[0029] The thermally opening connection 13, which is made as a soldered connection, triggers when the varistor 10 is overly heated due to aging or small overvoltages. This opens the electrical connection between the cut-off element 1 and the varistor 10, as a result of which the overvoltage protection arrangement 9 is electrically isolated. In the case of a pulse-like surge current, the cut-off element 1 triggers by the fuse element 5 melting or vaporizing. In this way, the electrical connection between the connecting element 12 and the terminal contact 3, and thus, also between the connecting element 12 and the varistor 10, is interrupted so that the overvoltage protection arrangement 9 is likewise electrically isolated. In the case of a pulse-like surge current, the thermally opening connection 13 alone would be too slow to isolate the overvoltage protection arrangement 9 in time before the varistor 10, and thus, also the overvoltage protection arrangement 9, are altogether destroyed.

[0030] On the first terminal contact 2 of the cut-off element 1 and on the side of the cut-off element 1 facing away from the thermally opening connection 13 there is a spring element 14 which applies a force to the cut-off element 1 which is directed away from the thermally opening connection 13. At this point, if the cut-off element 1 or the thermally opening connection 13 triggers, the isolated part 6 of the cut-off element 1 or the entire cut-off element 1 is moved away from the overvoltage-limiting component 10 by the force of the spring element 14, as a result of which a relatively great distance arises between the two components which form the gap, the overvoltage-limiting component 10 and one part 7 of the housing 4 or the two parts 6, 7 of the housing 4 so that an arc which may form when the electrical connection is opened is extinguished.

[0031] Because the cut-off element 1 is made as a type of printed-circuit board material, it can have very small dimensions and can be easily connected to the varistor 10 via its terminal contact 3 and the soldered connection 13.

[0032] The amount of space which is required for the arrangement of the cut-off element 1 in the housing of the overvoltage protection arrangement 9 is thus very small.