GB2070863A - Adjusting electrical contacts - Google Patents

Abstract

A method of adjustment of the relative positions of replacement fixed and movable contacts 2, 16 in an electrical switch wherein the movable contact 16 is adjustably mounted by a screw 17 on a spring biased movable support 13 consists in substituting, for a worn fixed contact 2, Fig. 1, a fixed pseudo-contact 26, Fig. 3a having a pseudo-contact surface 27 set back with respect to the contact surface P of a new fixed contact, replacing the worn movable contact 16 by a replacement movable contact 16% but leaving the screw 17 loose, moving the contact support 13 to the contact closed position to cause the new movable contact 16% to be displaced and to abut the pseudo contact surface 27 without spring pressure, fully tightening the screw 17 and finally replacing the fixed pseudo contact 26 by a new fixed contact. <IMAGE>

Description

SPECIFICATION Adjusting electrical contacts The invention relates to a method of adjustment of the position, in an electrical contact making and breaking apparatus, of a new movable contact, with respect to a new fixed contact, the movable contact being carried in adjustable manner, with the aid of fixing means, on a contact support on which a contact pressure is exerted by means of a spring, and the said fixed contact presenting, opposite to the movable contact, a contact surface situated in a first plane when the fixed contact is new, this surface being disposed in such a manner that when the contact surface is in a working position corresponding to the closure of the fixed and movable contacts, the said spring is compressed to a predetermined extent.

The invention likewise relates to an adjusting means permitting to carry out the adjustment of the position of the movable contact.

The methods used hitherto for carrying out, in the course of replacement, the adjustment of the position of a movable contact with respect to a fixed contact, consist generally in putting in the place of a pair of worn fixed and movable contacts a pairof new contacts the dimensions of which are exactly the same as those of the former. The placing in abutment of the two surfaces, respectively of the contact support and the movable contact must in this case take place between the new contacts in the state in which they are opened by a distance identical to that which is fixed by the constructor, in order that the value of the contact pressure shall be eventually maintained in the closed state.

However, this would only be totally adhered to if upon leaving the factory the apparatuses had perfectly identical dimensions, which is impossible to achieve by reason of the inevitable dispersion of the sides of the elements.

Furthermore, it is very costly to manufacture replacement contacts which are rigorously identical to those fitted on the apparatus in the factory. On the other hand, play appears in the course of use of an apparatus and it is extremely rare that the movable elements achieve for their working position, after a prolonged use, a position identical to that which they have in the new state, so that the results given by the known methods did not give entire satisfaction.

The adjustment of the movable contacts when the apparataus is in its closing position must permit the curing of the above-mentioned defects, but carrying it out is then complicated by the fact that it is necessary simultaneously to compress the pressure spring to a predetermined value, and to fix an adjustable movable contact on its support. This method of adjustment, which requires the use of very specialised tool means, is thus generally left aside in favour of others which only require less tool means.

The invention accordingly proposes to provide a method of adjustment which needs, for carrying it out, only a simple means, and which can be carried out in the closed position of the apparatus in order to give the movable contact an exact position, and which does not require the manufacture of two fixed and movable contacts having extremely precise dimensions.

According to the invention the method used provides that the contact support is placed in rest position and, after removal of the worn fixed and movable contacts, there is disposed in place of the fixed contact a fixed pseudo-contact having a pseudocontact surface situated in a second plane which is disposed beyond the first plane in the direction of closing of the movable contact and which is separated from the latter by a distance equal to the stroke which a new movable contact must carry out in order to impart to the pressure spring the said compression of predetermined value, a new movable contact being then placed on the support with the aid of lightly-tightened fixing means such that with the contact support being then placed in its working position, the movable contact can be displaced so as to become abutted without pressure on the pseudocontact surface, the fixing means being then locked, and the fixed pseudo-contact being replaced by a new fixed contact when the contact support is placed back in its rest position.

In a complementary feature intended to facilitate the carrying out of the method defined hereinabove, the invention provides a simple means, of fixed pseudo-contact, the cost of which is small and the use of which gives to the said method the whole of the advantages which should apply to it.

In accordance with a complementary object, the fixed pseudo-contact has a configuration analogous to that of a fixed contact and comprises a pseudosurface of contact situated in a second plane which is spaced from the first plane in which is placed the surface of contact of a new fixed contact, by a distance equal to the stroke which must be carried out by a new movable contact, in order to impart to the contact pressure spring a pressure of predetermined value.

Other features of the invention will be better understood from reading of the following description below with reference to the accompanying drawings, wherein: Fig. 1 is a side elevation and section of the contact elements, before closing, used in an electrical contact breaker apparatus to which the method can be applied; Figs. 2a and 2b illustrate the new contact elements respectively in positions of opening and of closing; Figs. 3a and 3b show a new movable contact and a fixed pseudo-contact respectively in positions of opening and in position of adjustment; Fig. 3c shows two new contacts placed in the apparatus; Fig. 4 shows a fixed pseudo-contact placed in the housing of a contact breaker apparatus for the carrying out of the method, and Fig. 5 shows an apparatus serving for carrying out the method when it is applied to a multi-polar apparatus.

An electrical contact breaker apparatus comprises the breaker elements visible in Fig. 1 wherein a housing 1 of the apparatus carries a fixed contact 2 and a movable assembly 3 intended to cause the closing and opening of a circuit.

The fixed contact 2 has a bearing surface 4 which is pressed against a barring surface 5 of the housing 1 contained in the plane Q and is fixed for example with the aid of a screw 6. One end 7 of the fixed contact projects at the exterior of the housing in order to permit the connection of an external con ductor.

At another end 8 of this contact there is placed a contact button 9 having a contact surface 10 placed in a plane P, for example parallel to plane Q and separated from the latter by a distance d when the contact button is new. This distance is provided for, in the course of manufacture, with certain toler ances.

The movable assembly 3 comprises an operating shaft 11 which can pivot about its axis through an angle a between two extreme positions I and II rep resenting a state of rest and a state of working. This shaft is fast with a lever 12 itself carrying a movable contact support 13 to which it is coupled by a pivot 14. The movable contact support carries at one end 15 a movable contact 16 which is fixed on this end by, for example, a screw 17; the position of this movable contact, which possesses a contact surface 18 directed towards the surface 10, can be modified in the direction of this latter surface 10, and then be fixed by tightening of the screw 17.

The pivoting support 13 is also subjected to the action of a contact pressure spring 19 which is, for example, passed through by a rod 20 a first end 21 of which is coupled at 22 to the lever 12, and the second end 23 of which carries an adjusting nut 24 which bears against the spring and permits the fixing of the initial compression of the spring when the support 13 is abutted against a stop 25 of the lever. In this state of initial compression the length of the spring is represented by "a". The position of the movable elements 3 shown in Fig. 1 corresponds to a state intermediate between the state of rest, or of open ing, and the state of working, or of closing, and thus represents an unstable state which has been chosen for clarity of the drawing.

Referring to Fig. 2a, wherein the contact breaker apparatus is in its state of rest, or of opening I, and is provided with new fixed contacts 2 and movable contacts 16, the surface 10 of the fixed contact is in the plane P.

When the lever 12 is directed towards a position II, seen in Fig. 2b, the surface 18 of the movable contact meets the surface 10 of the fixed contact before this lever has achieved that position, such that continua tion of the movement causes, on the one hand, a separation of the contact support 13 and the stop 14, and on the other hand a supplementary compres sion of the spring 19, the length of which becomes "b". This compression, of value "a-b" and which corresponds to a predetermined stroke of the mov able contact, must be determined and maintained in order to avoid phenomena such as welding and bouncing of the contacts, and irrespective of the degree of wear of the contacts compatible with good operation.

If the use of the apparatus was continued up to the point where the fixed and movable contacts were tota:;- worn, the su, rEce 10 of the fixed contact wouid then become placed in a plane T situated to the right of the plane P and towards the plane Q; the contact pressure would then be nil when the lever was in its position II, see Fig. 2b.

In the course of wearing, the resilient qualities of the spring generally do not change, so that the operation of changing and adjusting of the contacts seen in Figs. 3a, 3b and 3c commences from a state seen in Fig. 3a wherein the lever is placed in position I, and wherein the contact support has been provided with a new movable contact 16'; this movable contact has been mounted on the support with the aid of the screw 17 to which there has been imparted such a light degree of tightening that the contact 16' can move with respect to the support. In place of the worn fixed contact 2 there has been placed, and fixed by the screw 6, a fixed pseudo-contact 26 the general shape of which is analogous to that of the normal fixed contact 2.This fixed pseudo-contact has a fixed pseudo-contact surface 27 which is situated in a plane R parallel to the plane P and positioned to the right of the latter, this in the direction of closing of the movable contact.

This plane R is separated from the plane P by a distance "C" which is equal to the stroke which must be carried out by a new movable contact 16, fixed on its support, in order to communicate to the pressure spring 19 the necessary contact pressure, that is to say a supplementary compression which is represented by "a-b".

In the course of a subsequent stage, the lever 12 is placed in its working position II (see Fig. 3b) and preferably by the actuation of the control member of the apparatus, or by the energising of a control electro-magnet if the apparatus concerned is a contactor; in this position, wherein the contact support 13 must be pressed against the stop 14,the contact surface 18' of the movable contact 16' is brought to bear without pressure on the fixed pseudo-contact surface 27 and locking of the screw 17 is carried out to make fasttogetherthe new movable contact and the contact support; finally, the assembly 3 is brought back into position 1, the pseudo-contact 26 is taken off and is replaced by a new fixed contact 2' which is again supported by the screw 6, as shown in Fig. 3c.

It will thus be appreciated that the only difference which can exist between the geometrical positions of new contacts, mounted in the factory, and those of new exchange contacts will arise solely from manufacturing tolerances presented by the dimension "d' " of a replacement fixed contact, and not from the whole of the positioning tolerances which can detract from not only the movable assembly but also the bearing surface 5 of the fixed contact.

This feature assumes its full importance when one considers the quality of operation obtained in a multi-polar apparatus wherein there are used as many movable assemblies and as many bearing sur faces as there are phases comprised in the apparatus.

In this latter case, provision can be made for the use of an adjusting element 28 comprising a group of fixed pseudo-contacts, for example a group of three, in which the pseudo-contacts 29, 30, 31 would be coupled one to the other by deformable or resilient portions 32, 33 which would permit each of these pseudo-contacts to press itself perfectly on its own bearing surface, such as 5, see Fig. 5.

In order to avoid maintenance personnel inadvertently leaving a pseudo-contact in the apparatus, the pseudo-contact can comprise, as is shown in Figs. 4 and 5, an error-preventing element such as a wall 34 which will prevent the operation of the apparatus by placing itselt in, for example, the path to be traversed by a hood 4 during closing thereof.

It is evident that the same method applies to the adjustment of an electrical apparatus in which the contact pressure spring exerts its force on the movable contact by other direct or indirect means, the apparatus illustrated being shown only by way of example.

Claims (6)

1. A method for the adjustment of the position, in an electrical contact making and breaking apparatus, of a new movable contact with respect to a new fixed contact, the said movable contact being carried in adjustable manner by fixing means on a movable contact support on which a contact pressure is exerted by a spring, said fixed contact having opposite to the movable contact a contact surface which must be situated in a first plane when the fixed contact is new, this surface being placed in such a manner that when the contact support is in a working position corresponding to closure the spring is compressed to a predetermined extent, characterised in that:: (i) the movable contact support is placed in rest position, (ii) after removal of the worn fixed and movable contacts there is put in the place of the worn fixed contact a fixed pseudo-contact having a pseudocontact surface situated in a second plane which is placed beyond said first plane in the direction of closing of the movable contact and which is separated from the first plane by a distance equal to the stroke which a new movable contact must perform to communicate a predetermined value of pressure to the pressure spring, (iii) the new movable contact is mounted on the support with the aid of fixing elements which are left not fully tightened so that, with the contact support placed in its working position, the movable contact can be displaced until it is abutted without pressure on the pseudo-contact surface, (iv) the fixing means is then fully tightened, and (v) the fixed pseudo-contact is replaced by a new fixed contact when the contact support is again placed in its rest position.

2. Means, for carrying out the method claimed in claim 1, comprising a fixed pseudo-contact having a configuration analogous to that of a fixed contact and comprising a pseudo-contact surface to place in said second plane spaced from said first plane, in which is situated the contact surface of a new fixed contact, by a distance equal to the stroke that a new movable contact must carry out in order to impart a compression of predetermined value to a contact pressure spring.

3. Means, according to claim 2, wherein a plurality of pseudo-contacts are connected together by deformable couplings in such a manner that each pseudo-contact can be put in position without constraint in a same contact breaker apparatus.

4. Means, according to either of claims 2 and 3, wherein at least one pseudo-contact comprises a wall or extension the position of which prevents the operation of the contact breaker apparatus, or the placing in position of a hood of the apparatus, if the fixed pseudo-contact has not been replaced by a new fixed contact.

5. A method of adjustment, as claimed in claim 1, substantially as described herein with reference to the accompanying drawings.

6. Means, for carrying out the method claimed in claim 1, substantially as described herein with reference to the accompanying drawings.