GB2160711A

GB2160711A - Explosion-proof or flame-proof electrical switching device

Info

Publication number: GB2160711A
Application number: GB08517920A
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: 1985-07-16
Publication date: 1985-12-24
Also published as: DE3215919C2; GB8517920D0; GB2160711B; FR2526217B1; GB8311417D0; GB2119575A; DE3215919A1; FR2526217A1; GB2119575B

Abstract

An explosion-or flame-proof switching device is formed by one or more poles, each of which comprises two contact points (16, 18) for high switching capacities. Arc extinguishing sheets (52, 54) are associated with each contact point in order to reduce the size of, for example, a three-pole enclosed switching device. The two contact points include fixed (20,22) and movable (26/28) contacts, the latter being connected together by a contact bridge (24) having a guide pin (30) which extends out of the pressure-resistant chamber, so that the contact bridge and thus the two movable contact parts can be driven. <IMAGE>

Description

1

SPECIFICATION

Explosion-proof or flame-proof electrical switching device The invention relates to explosion-proof and flame-proof switching devices.

Explosion-proof switches with three poles were previously produced by inserting a non- explosion-proof switch with its 3 poles, ie, in its entirety, in an explosion-resistant chamber having a large volume, so that this large volume would prevent flashovers between the individual poles or restriking due to the ion- ised quench gases. It was previously assumed that large volumes of this type within a pressure-resistant chamber were necessary to obtain adequate deionisation or mixing of the quench gases with non-ionised gas. This re- sulted, particularly in the case of switches with a high switching capacity, in large-volume metal housings with corresponding leadin wires for actuating the individual switch poles, which is why switching devices of this type with a high capacity were expensive and compliated. Independently pressure-resistant pole chambers were previously only developed for switches having a low capacity.

The object of the invention is to provide an explosion-proof or flame-proof electrical switching device 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 chamber volume can be achieved.

The invention resides in an explosion-proof or flame-proof switching device comprising a pressure-resistant chamber in which are disposed two contacts points forming a double contact position and each comprising a fixed and a movable contact, movable contacts being provided on a contact bridge which bridges the two contact points, and the said bridge is provided with a quide pin which extends out of the pressure-resistant chamber while forming a gap, for actuation by means of a driving cam disc, an arc-extinguishing sheet pack being associated with each contact point as an arc extinguishing means.

The invention permits a three-pole switch to be produced in which the individual poles are in each case arranged in a pressure-resistant chamber. In comparison with known switches, switching devices of this type, ie, particularly contractors, etc, require a very small pressureresistant chamber, ie, only the space for the direct accommodation of the contact points and the contact bridges together with the 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 A-B in Fig. 1, and Figure 3 is a sectional view along the GB 2 160 71 1A 1 section line C-D of Fig. 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 Fig. 1 and indicated by the reference number 10. The switching pole comprises a housing 12 which, as can be seen from Figs 2 and 3, comprises a space 14 which is open at one side and in which the contact points 16 and 18 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, co- operate in order to form the contact points 16 and 18, 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 12 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, can be combined with an identically formed switch pole by associat- ing the two components in a mirror-inverted 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 Fig. 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 ring-like 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 14 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 compression spring 44 is used to apply the contact force between the two contact partsd 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.

2 GB 2 160711 A 2 Arc extinguishing sheet packs 52 and 54 are arranged on both sides of the contact points 16 and 18, respectively, ie, in the direction of movement of the arc, the direc- tion of arrow F1 and F2, respectively. These arc extinguishing sheet packs are formed in a conventional manner and, as can be seen from Fig. 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 know per se, of a plastics material, for example an electropaper. The upper holding plate (Fig. 1) comprises two integrally formed protuberances 62 and 64 on both sides (this of course refers to the upper holding plates of both arc extinguishing 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 housing.

Figs. 2 and 3 shows how the chamber 14 is closed in a pressure-resistant manner. It can be seen from Fig. 2 and 3 that the chamber 14 widens towards the top, ie, towards its open side (widened portion 70). A stepped structure 72 is thus formed which extends around the entire circumference of the chamber 14. A cover plate 74 is placed in the stepped structure 72 and closes the chamber 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, ie, 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 chamber 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 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.

The arrangement according to Fig. 1 can be used for relatively high switching capacities, for switching capacities lying above those which are accepted in pressure-resistant housings formed in a manner known per se with- out arc extinguishing means.

Claims

1. An explosion-proof or flame-proof switching device comprising a pressure-resis- tant chamber in which are disposed two con- tact points forming a double contact position and each comprising a fixed and a movable contact, movable contacts being provided on a contact bridge which bridges the two con- tact points, and the said bridge is provided with a guide pin which extends out of the pressure-resistant chamber while forming a gap, for actuation by means of a driving cam disc, an arc-extinguishing sheet pack being provided at each contact point.

2. A switching device substantially as herein described with reference to the accompanying drawings.

Printed in the United Kingdom for Her Majestys Stationery Office, Dd 8818935, 1985, 4235. Published at The Patent Office, 25 Southampton Buildings, London, WC2A lAY, from which copies may be obtained.