AU676934B2

AU676934B2 - Switch

Info

Publication number: AU676934B2
Application number: AU73771/94A
Authority: AU
Inventors: Paul Kadan
Original assignee: Felten and Guilleaume Austria AG
Current assignee: Felten and Guilleaume Austria AG
Priority date: 1993-11-02
Filing date: 1994-08-22
Publication date: 1997-03-27
Anticipated expiration: 2014-08-22
Also published as: ATA219993A; ES2106556T3; WO1995012888A1; PL314227A1; NO961789L; PL174603B1; EP0727088A1; AT410725B; EP0727088B1; HU215890B; NO307907B1; DE59403580D1; ATE156298T1; CZ127996A3; DK0727088T3; HUT75408A; HU9601165D0; AU7377194A; CZ285082B6; NO961789D0

Abstract

A switch has a fixed contact (5) secured to a contact strip (1) in the switch housing, a movable contact (2) pivoted in the switch housing and a conductor strip (3) which acts as a stop for the movable contact (2) in its OFF position. The space (8) between the contact strip (1) and the conductor strip (3) is bounded on both sides by plates (7). In the plates (7) there are three apertures (4) leading outwards from the space (8) bounded by the contact strip (1), the conductor strip (3) and the plates (7) into the spaces (11) between the plates (7) and the relevant walls (10) of the housing. Arc gases can flow out and back to the contact point through said apertures (4) in the plates (7) so that the movement of the arc gases to an arc quenching chamber is supported. In addition, owing to the local reduction in the area of the plates (7) by the apertures (4), a gas pressure difference is created between the front side and the rear side of the arc which supports the movement of the arc gases to the arc quenching chamber.

Description

SWITCH

The present invention relates to a switch, in particular an automatic safety switch having the features specified in the introductory section of independent Claim 1.

In known automatic safety switches the space between the fixed contact piece, arranged on a contact sthip and therefore supported thereby, and the movable contact which in the OFF position rests on a contact strip serving as a contact, is enclosed on both sides by plates made of ceramic or some other synthetic material. The ionised gases generated by the formed arc by the aperture of the contacts (raising of the movable contact from the fixed contact piece) leave this space and enter the arc quenching chamber, in which is disposed an arc quenching device made up of several de-ionising plates, and then exit therefrom through outlets out of the switch housing.

EP A 251 160 discloses an automatic safety switch having a quenching device with the features of the introductory section of independent Claim 1. In this known automatic safety switch open cutouts are provided in the plates to the very edge of these plates. These known cutouts serve to balance out the negative pressure which originates when the contact pieces in the fore-chamber are opened and with the assistance of the gas flow entering the fore-chamber through the apertures contribute to deionisation. This last feature can be reinforced by use of gas-emitting material for the plates.

It is essential for the effect of the arc steering that the contact point is fiully covered directly on the side so that the plasma column originating from ignition of the arc is deflected and thereby reaches the de-ionised plates with delay.

The aim of the present invention is to improve the deflection of the ionised gases to the de-ionised plates in the arc quenching chamber.

This is accomplished according to the present invention by the features of the characterising part of Claim I being put into practise with the switch.

Preferred and advantageous embodiments of the switch according to the present invention are the object of the sub-claims.

In the invention the space between the plates and bounded by the contact strips in connected to the spaces lying between the outer sides of the plates and the inner sides of the I adjoining walls of the housing by the apertures according to the present invention in the interior of the plates.

Due to the design according to the present invention of the plates which bound the space between the fixed contact piece and the movable contact in the OFF position, with at least one aperture gases originating from circuits, especially short-circuiting switches, flow back to the contact point in that they enter through at least the one aperture in the plates and flow back to the contact point between the plates and the housing walls. In the process the gas pressure hampering the arc course, thus the movement of the arc to the de-ionised plates in the arc quenching chamber, is reduced in the vicinity of the front of the arc.

Since the apertures according to the present invention, by comparison to the EP-A 251 160, where the apertures open out to the edge of thile plates or are formed by omission of edge components of the plates, are arranged inside the plates, the advantage arises whereby the advantageous effect of the apertures in the plates can be combined optimally with the actual function of the plates, which is protection of the housing. Moreover, the position of the apertures according to the present invention can match the conditions of the switch, for example the design of the contacts.

The gassing effect originating in all plates, which are used to bound the space between the fixed contact piece and the movable contact, during activation of the arc, which is particularly strong in plates made of synthetic material results in the following added effect in the vicinity of at least the one aperture in the plates the gassing effect through the diminished plate surface is less than in the remaining area of the plate. This results in a relatively strong gassing effect of the plates in the region at the contact point, such that the arc is further accelerated by the relatively increased gas pressure effective in the crest of the arc.

It is a particular advantage of the present invention if the one aperture in the plates is provided in the vicinity of a horn in the contact strip, which bears the fixed contact piece. The effect accelerating the arc (increased gas pressure in the arc crest) and resulting from the gas pressure difference on the basis of the gassing effect of the plates made of synthetic material is then especially beneficial.

Further details and features of the invention will emerge from the following description of an embodiment of the invention which is illustrated in the diagrams, in which: Figure 1 is a diagrammatic side elevation of the part of an automatic safety switch having a fixed contact piece, movable contact and a plate, and Figure 2 is a sectional view of the area of figure 1 with the associated housing components.

The present invention can be used in every switch which is configured for higher current strengths, especially for automatic safety switches such as circuit breakers which have to be switched off in the event of a short circuit.

As is known, the fixed contact piece is borne by a contact strip 1 which is formed into a horn 6 (U-shaped loop). Opposite contact piece 5 and horn 6 is a conductor strip 3 which serves as contact for movable contact 2, when this is in the OFF position illustrated in Figure 2.

Space 8 between contact strip 1 and conductor strip 3 is bounded on both sides by plates 7. Plates 7 are arranged in the housing, which accommodates the automatic safety switch, in is such a way that a space I 1 remains free between each of inwards directed surfaces 9 of housing walls 10 and outwards directed surfaces 12 of plates 7, as illustrated in Figure 2.

Provided in the vicinity of horn 6 in contact strip I, which supports fixed contact 5, in each of both plates 7 are apertures 4, for example in the form of boreholes, bounded on all sides by the material of plates 7. At least one aperture 4 is provided for each plate 7, whereby the arrangement shown in Figure 1 of three apertures located in the comers of an equilateral triangle is especially favourable on the side averted from contact piece 5 of horn 6 of contact strip 1 and is consequently advantageous according to the present invention.

When the switch is switched off, as in the event of a short circit (raising of movable contact 2 from fixed contact the following advantageous effect results from apertures 4 in plates 7: due to apertures 4 there is the possibility for the gases originating from (short circuit) switching off to flow back to contact point 5, as indicated symbolically by arrows in Figure 2.

Hereby the gas pressure hampering the arc course (deflecting of (short circuit) arc to the deionised plates of an arc quenching chamber, not illustrated here) is also reduced in the vicinity of the arc front (the front part of the arc).

Furthermore, the surface of plates 7 available for the gassing effect is reduced in the vicinity of horn 6 by apertures 4 in plates 7, wlhich are manufactured from a gassing synthetic material such as polynethylmethacrylate, because there is little material there due to apertures I- 4 4. The result thereof is a relatively stronger gassing effect of plates 7 in the vicinity of contact point 5, such that there is a relative gas pressure difference in the gases which have been formed by the gassing effect of plates 7, which is why the movement of the (short circuit) arc is accelerated by the increased gas pressure effective in the arc crest, which stems from tile gassing effect of plates 7.

The invention can be summarised as follows: A switch has a fixed contact 5 attached to a contact strip fixed in the housing of the switch, a movable contact 2 pivoted in the switch housing and a conductor strip 3 which acts as a stop for the movable contact 2 in its OFF position. Space 8 between contact strip 1 and conductor strip 3 is bounded on both sides by plates 7. In plates 7 there are three apertures 4 leading outwards from space 8 bounded by contact strip 1, conductor strip 3 and plates 7 into spaces 1 I between plates 7 and relevant walls 10 of the housing.

Arc gases can flow out and back to the contact point through apertures 4 in plates 7 so that the movement of the arc gases to an arc quenching chamber is supported. In addition, owing to the local reduction in the vicinity of plates 7 by apertures 4, a gas pressure difference is created between the front side and the rear side of the arc which supports the movement of the arc gases to the arc quenching chamber.

I 1

Claims

1. A switch, in particular an automatic safety switch, having a fixed contact attached to a contact strip fixed in a housing of the switch, with a movable contact pivoted in the switch housing and a conductor strip which acts as a stop for the movable contact in its OFF position, whereby space between the contact strip and conductor strip is bounded on both sides by plates and wherein the surfaces of the plates averted from the space exhibit a distance from the facing sides of the housing walls, characterised in that there is at least one aperture provided in each of the plates, which leads to the space bounded by the contact and conductor strips and the plates. ouooo

2. Switch as claimed in claim 1, characterised in that at least the one aperture of each plate is provided in the vicinity of the plates adjoining an arc quenching chamber.

3. Switch as claimed in claim 1 or 2, wherein a U-shaped bend is incorporated into the contact strip bearing the fixed contact piece, characterised in that the at least the one aperture is arranged in each plate in the vicinity of the bend of the contact strip.

4. Switch as claimed in any one of claims 1 to 3, characterised in that several apertures, preferably three apertures, are provided in each of the plates. Switch as claimed in claim 4, characterised in that in each plate there are two apertures adjoining the section of the contact strip forming the bend and a further aperture is arranged on both sides, said apertures arranged to form an essentially equilateral triangle.

MENSOMMEE-NIO

6. Switch as claimed in any one of claims 1 to 5, characterised in that the plates comprise a synthetic material, preferably polymethylmethacrylate, giving off gas under the effect of heat of an arc. DATED this 30th day of January, 1997. FELTEN GUILLEAUME AUSTRIA AG. WATERMARK PA, 1 NT TRADEMARK ATTORNEYS 290 BURWOOD ROAD HAWTHORN VICTORIA 3122 AUSTRALIA o -r r I