GB2119575A

GB2119575A - Explosion-proof or flame-proof electrical switching device

Info

Publication number: GB2119575A
Application number: GB08311417A
Authority: GB
Inventors: Rudolf Dehm; Josef Ruck
Original assignee: Brown Boveri und Cie AG Germany; BBC Brown Boveri France SA
Current assignee: BBC Brown Boveri AG Germany; BBC Brown Boveri France SA
Priority date: 1982-04-29
Filing date: 1983-04-27
Publication date: 1983-11-16
Also published as: GB2160711A; GB2160711B; GB8517920D0; DE3215919C2; GB2119575B; DE3215919A1; FR2526217B1; GB8311417D0; FR2526217A1

Abstract

An explosion- or flame-proof switching device is formed by one or more poles, each comprising at least one contact point 16, 18. An arc extinguishing means e.g. a sheet pack 52, 54 is associated with each contact point. In order to reduce the size of, for example, a three-pole enclosed switching device, one or, according to the embodiment, two contact points, which are connected together by a contact bridge 24, are disposed with the arc extinguishing means in a pressure-resistant space. A guide pin 30 may be connected to the contact bridge so that the two movable contacts 26, 28 can be driven by means of a drive. Gas-evolving pins (81, 82, 77, 79, Figure 4) may be used instead of the sheet pack 52, 54. <IMAGE>

Description

SPECIFICATION Explosion-proof or flame-proof electrical switching device The invention relates to a switching device according to the classifying part of claim 1.

Explosion-proof switches with three poles were previously produced by inserting a non-explosionproof switch with its 3 poles, i.e. in its entirety, in a pressure-resistant space having a large volume, so that this large volume would prevent flashovers between the individual poles or restriking to the ionised quench gases. It was previously assumed that large volumes of this type within a pressure-resistant space were necessary to obtain adequate deionisation or mixing of the quench gases with non-ionised gas.

This resulted, particularly in the case of switches with a high switching capacity, in large-volume metal housing with corresponding lead-in wires for actuating the individual switch poles, which is why switching devices of this type with a high capacity were expensive and complicated.

Independently pressure-resistant pole chambers were previously only developed for switches having a low capacity.

The object of the invention is to provide an electrical switching device of the abovementioned type in which, in spite of a high switching capacity, the manufacturing cost is kept to a minimum and by means of which a clearly reduced pressure-resistant volume can be achieved.

This object is solved according to the invention by the characterising features of claim 1.

The subclaims contain further advantageous developments of the invention.

The solution according to the invention permits a three-pole switch to be produced in which the individual poles are in each case arranged in a pressure-resistant space. In comparison with known switches, switching devices of this type, i.e.

particularly contactors etc., require a very small pressure-resistant space, i.e. only the space for the direct accommodation of the contact points and the contact bridges together with the arc extinguishing means, which are either formed as pins of a gas-emitting material or as arc extinguishing sheet packs.

In the drawing: Figure 1 is a view of a switching device constructed according to the invention, Figure 2 is a sectional view along the section line AB in Fig. 1.

Figure 3 is a sectional view along the section line C-D of Figure 1, and Figure 4 is a view of a further embodiment of the invention similar to the view according to Figure 1.

An electrical switching device consists of a total of three switching poles which are constructed according to the invention, associated with one another and one of which is illustrated in Figure1 and indicated by the reference number 10. The switching pole comprises a housing 12 which, as can be seen from Figure 3, comprises a space 14 which is open at one side and in which the contact points 1 6 and 1 8 are disposed. Both contact points comprise a fixed contact 20 and 22, with which movable contacts 26 and 28, respectively, mounted on a contact bridge 24, cooperate in order to form the contact points 1 6 and 1 8, respectively.A guide pin 30, which is guided in the bore 32 of a guide sleeve 34, is secured to the contact bridge at the side at which the movable contact parts 26 and 28 are disposed, the said guide sleeve 34 being held in the housing 12 in a positive manner by means of an annular projection 36. The guide pin penetrates the housing 1 2 and extends on the opposite side into a semicircular recess 38 which can accommodate a cam wheel in a manner which is not shown in detail, which cam wheel can be turned by means of a drive shaft penetrating an opening 40, as a result of which the guide pin 30 and thus the contact bridge 24 can be moved in the direction of the arrow F.

It should also be added that the housing 12, or the switch pole 10, respectively, can be combined with an identically formed switch pole 10 by associating the two components in a mirrorinverted manner to form a two-pole switch. In order to form a three-pole switch, a third switching pole having the same orientation would have to be added to the upper surface, i.e. the upper surface shown in Figure 1, and a dummy switch or dummy housing to the side disposed symmetrically with respect to the central axis M-M. If two switch poles are disposed opposite one another, the two openings 40 of the two opposite switch poles form a circular opening and the two spaces 38 a circular cylindrical or ringlike space, in which spaces or openings the switch shafts and the cam discs are guided.

A recess 42, in which a helical coil compression spring 44 is inserted, is provided in the space 1 4 on the wall opposite the contact bridge, the spring 44 being supported at its other end guided by a pin 46 at the contact bridge 24.

This helical coil compresson spring 44 is used to apply the contact force between the two contact parts 26/20 and 28/22, respectively.

The two fixed contact parts are connected in a manner which is not shown in detail to bars (not shown) which extend inside the housing 12, are guided out of the housing and terminate in connecting parts 48 and 50, to which the input or output lines to (or from) the switch pole can be connected.

Arc extinguishing sheet packs 52 and 54 are arranged on both sides of the contact points 1 6 and 18, respectively, i.e. in the direction of movement of the arc, the direction of the arrow F1 and F2, respectively. These arc extinguishing sheet packs are formed in a conventional manner and, as can be seen from Figure 3, comprise arc extinguishing sheets 56, which are held at a distance from one another by holding plates 58 and 60. These holding plates consist, in a manner known per se, of a plastics material, for example an electropaper. The upper holding plate (figure 1) comprises two integrally formed protuberances 62 and 64 on both sides (this of course refers to the upper holding plates of both arc extinguising sheet packs), which are accommodated in corresponding recesses 66 and 68 in the housing.

The arc extinguishing sheet packs 52 and 54 are thus held in the housing.

Figures 2 and 3 show how the space 14 is enclosed in a pressure-resistant manner. It can be seen from Figures 2 and 3 that the space 14 widens towards the top, i.e. towards its open side (widened portion (70). A stepped structure 72 is thus formed which extends around the entire circumference of the opening or space 14. A cover plate 74 is placed in the stepped structure 72 and closes the space 14 at the top.

A metal plate 76 is placed on the cover plate 74, the circumference of which metal plate is greater than the circumference of the widened portion 70, as a result of which the plate 76 is resiliently deformed in the marginal region, i.e. at 78. The cover plate 74 is thus pressed in a frictional manner against the stepped structure 72. Casting resin 80 is then poured into the remaining space of the widened portion 70, so that the surface 0--0 closes flush with the remaining housing regions. The space 14 is closed in a pressure-resistant manner by means of the plate 74, the plate 76 and the casting resin 80.

A pole which is enclosed in a pressureresistant manner and comprises two contact points is thus obtained, with which contact points a respective arc extinguishing means, formed from an arc extinguishing sheet pack, is associated. The said pole can be switched by means of a drive by way of the pin 30 and can be combined with other identically formed poles to form a two-pole or multi-pole switch with a high switching capacity.

A further embodiment of the invention is illustrated in Figure 4, which shows, in an identical manner, the two contact points disposed in a space 74, which is in principle the same as the space 14, the only differences in the structure of the space being in the region of the arc extinguishing means. Instead of providing two arc extinguishing sheets, pins 77,79 and 81,82, respectively, which consist of a fibrous material, are rigidly inserted in the space 74 on both sides of the plane E-E containing the contact surfaces of the contact points 1 6 and 18. The pins 77 to 82 consist of a fibrous material, a material which emits gas under the effect of an arc. An arc produced between the two contact parts of the contact points 1 6 and 1 8 is thus easily extinguished in a manner simliar to that in the arrangement according to Figure 1.

The arrangement according to Figure 1 can be used for relatively high switching capacities, the one according to Figure 4 for lower switching capacities and both embodiments for switching capacities lying above those which are accepted in pressure-resistant housings formed in a manner known per se without arc extinguishing means.

For reasons relating to flow, the actual extinguishing chamber is then provided with two convex portions 84 and 86,88 and 90, which on one hand give the arc plasma a certain flow path and on the other effect an optimum guidance or conductance of the arc gases about the fibrous pins 77 to 82.

Claims

1. Explosion-proof or flame-proof switching device comprising at least one contact point with a fixed contact part and a movable contact part, characterised in that an arc extinguishing means is associated with the at least one contact point and that the at least one contact point is arranged with the arc extinguishing means in a common pressure-resistance space.

2. Switching device comprising two fixed contacts which can be connected by means of a contact bridge holding two movable contacts in order to form a switch pole or for protection in an explosion-proof embodiment characterised in that both contact points (16, 1 8), with each of which an arc extinguishing means is associated, are arranged in the pressure-resistant space.

3. Switching device according to claim 2, characterised in that a guide pin is secured to the contact bridge, extends out of the pressureresistant space, thus forming a gap, and can be actuated by means of a driving cam disc.

4. Switching device according to any of the preceding claims, characterised in that an arc extinguishing sheet pack is in each case provided as the arc extinguishing means.

5. Switching device according to any of claims 1 to 3, characterised in that at least one body of a gas-emitting material is associated with each contact point.

6. Switching device according to claim 5, characterised in that pins which consist of gasemitting material are secured in the pressureresistant space on both sides of the connecting plane (E-E) containing the contact surfaces of the two contact points and extend parallel to the connecting plane and at right angles to the direction of movement of the contact abridge.

7. Switching device according to claim 6, characterised in that the pins are formed of a fibrous material.

8. Switching device according to claim 7, characterised in that the pins are disposed in pocket-like integrally formed protuberances.

9. A switching device substantially as herein described with reference to Figures 1 to 3 or Figure 4 of the accompanying drawings.