GB2073622A

GB2073622A - Applying contacts to conductors

Info

Publication number: GB2073622A
Application number: GB8111679A
Authority: GB
Original assignee: Telemecanique Electrique SA
Current assignee: Telemecanique SA
Priority date: 1980-04-16
Filing date: 1981-04-13
Publication date: 1981-10-21
Also published as: NL8101880A; FR2484724B1; DE3115285C2; ES501349A0; GB2073622B; ES8203170A1; SE452532B; IT8121173A0; BE888440A; DE3115285A1; FR2484724A1; IT1168122B; SE8102437L

Abstract

In the provision of a contact surface on a bar of aluminium, machined ends 4, 5 of a bus bar 1 receive a housing in the form of a "U" formed by bending of a composite cut-out element 8 formed of copper and aluminium. The housing is then welded by its two arms 9, 10 to the bus bar at points 30-33 and the arms are then compressed to provide plane external surfaces. The housing has projecting edge portions 16-19 and a cross piece 11 which has an aperture 24 and stop surfaces 26, 27. <IMAGE>

Description

SPECIFICATION Process and means for providing a contact surface The invention relates to a process for the provision of a contact surface on a bus bar of aluminium, making use of a contact element, which is cut out in a sheet comprising a layer of copper and a layer of aluminium, which is bent and which is fixed on this region by electrical spot welds placing in contact the aluminium surfaces.

Such a process is in particular applicable to the provision of contact surfaces intended for the establishment of a removable electrical coupling between the first ends of bus bars disposed in a first section of protective sheath and second ends of bars of a second section analogous to the first, with the aid of appropriate coupling systems comprising for example a number of contact grippers.

The invention likewise concerns means for carrying out the process, in particular contact elements the constitutio.n and shape of which permit the provision of finished products of quality when they are used in the process mentioned above.

When it is desired to couple two ends of bus conductors of aluminium in a releasable manner, use is generally made of bolts which pass through two bar ends placed side by side, and perhaps with placing between the opposed surfaces of a layer of conductive grease.

Such processes cannot be recommended when repeated disconnections, although not very frequent, must be carried out, on the one hand by reason of permanent deformation which might be made to the ends and, on the other hand, by reason of ageing of the layer of grease; in such cases, it is desirable to use coupling devices adapted to cooperate with junction elements providing a connection by resilient pressure or by contact friction.

It has already been proposed to connect onto a bus bar of aluminium a conductive housing formed by bending of a composite copper-aluminium sheet, and fixed externally by electrical welding against a surface of the bar in such a manner that the internal space of the housing can be traversed by a removable coupling gripper of copper.

This contact device obtained by a known process is of interest when the housing is fixed in a region of the bar comprised between its ends but is nevertheless too bulky to be adapted to the situation where the ends of several bars housing in a sheath must be coupled electrically to the ends of corresponding bars housing in another sheath placed in extension thereof.

The invention accordingly proposes to provide firstly a process for the provision of contact surfaces on aluminium bars which does not present the defects of the prior art and which leads to the provision of products having small bulk and a remarkable regularity of behaviour due to a simple manner of construction and to a great ease of mounting.

According to the invention this result is obtained by carrying out the following operations: -The machining on a region of the end of the bar of two opposed parallel plane surfaces and at least one frontal bearing surface substantially parallel to a longitudinal axis of the bar; - The cutting out of an element, having a contour corresponding to that of a developed contact element, from a sheet comprising a layer of copper and a layer of aluminium; -The bending of this element in such a manner as to constitute a contact element forming a housing of generally "U" section which has two parallel arms, a common cross piece and two bending edge portions, the layer of aluminium being disposed at the interior of the housing; -The perforation of the cross piece, over a fraction of the height, with an elongated opening substantially parallel to a bending edge portion;; -The formation of bearing surfaces on at least one region of the housing placed outside of the external surfaces of the arms; -The introduction of the machined end of the bar into the internal space of the housing as far as a respective position at which the stop surfaces are applied against the bearing surfaces; - The application of two electrodes of an electrical spot welding machine on the external surfaces of the arms and the placing undervoltage of these electrodes until the moment when the internal surfaces of the arms are welded with the machined surfaces by the effect of passage of the current; - The compression of the external surfaces of the arms until there are obtained substantially parallel external plane surfaces;; - The operations of perforation and of formation being carried out in the course of the operation of cutting out or during the operation of bending.

The nature of the invention and of other complementary features concerning the means for carrying out the process will be better understood from reading of the description with reference to the accompanying drawings wherein: Fig. 1 is a view in perspective of a contact element and of one end of a bar before mounting; Fig. 2 is a view in half-section elevation of an end of a bar provided with its contact element; Fig. 3 is a view from above, sectioned along the plane PP' of Fig. 2, of a first manner of construction of the contact element; Fig. 4 is a view, analogous to that of Fig. 3, of a second manner of construction of the contact element; Fig. 5 is a section on PP' pf a portion of the contact element, on a larger scale.

A current distribution system can be constituted by the association end-to-end of sections of channel each constituted by a plurality of bus bars placed in a supporting sheath for protection of the bars.

Such a bar 1, of which an end 2 is shown in Fig. 1, without the adjacent bars and without the protecting sheath, comprises a front face 3 and two plane opposed parallel external faces 4 and 5 which have been provided by machining (for example by milling) on the width dof the bar, extending axially for a length a and set back by a dimension e with respect to the non-machined lateral external surfaces 6 and 7 of the rough bar, a thickness b separating the two surfaces 4 and 5.

A contact element 8 seen in Fig. 1, obtained by cutting out and bending of a composite sheet comprising a layer of copper and a layer of aluminium, see also Fig. 5, takes the form of a housing having principally the fdrm of a "U", having two parallel arms 9 and 10 joined by a cross piece 11, two parallel slightly rounded edges -12 and 13 being formed in the bending zones; the operation of bending has been carried out in such a manner that the layer of aluminium is placed at the interior of the housing, and such that the distance between two internal surfaces 14, 1 5 of the arms opposite to each other is substantially equal to the thickness b.

Projecting edge portions 16, 17 and 18, 19 opposed and directed one towards the other are disposed on the edges 20,21 and 22,23 respectively of the arms which are perpendicular to the edges, in such a manner that the housing can later be placed without a large play on the end 2 of the bar, as can be seen in Fig. 1.

In the cross piece 11 there has been formed an opening 24 substantially parallel to one edge, 12 or 13, the length C of which extends over a fraction of the height fof the cross piece which is itself close to the width d of the machined surfaces.

In two regions 26 and 26 of the cross piece, placed at one side and the other of the opening in the height direction, there are formed, for example by pressing, two bosses 27, 28 which project towards the interior 29 of the housing, see in particular Fig. 1, and create internal stop surfaces 27', 28' remote from the external surfaces of the arms.

The fixation of the contact element 8 is carried out by a series of operations comprising first of all the engagement of the end 2 into the internal space 29 of the housing until the moment when the stop surfaces 27', 28' of the bosses 27, 28 come into contact against the transverse bearing face 3, and finally the welding of the arms 9, 10 against the machined surfaces 4, 5 with the aid of an electric spot welding machine the two electrodes of which are applied on the opposed external faces 34, 35 of the arms, the positions of the welding points being indicated by the reference numerals 30, 32 and 31,33. -In the course of this welding operation, the electrodes of the machine, not shown, are applied in the directions F and G in such a manner as to grip between them the two arms and the end.

The presence of the edges 20,21,22,23 and that of the respective surfaces 28', 28' and 3 serve to impart to the housing a well defined position with respect to the end, whilst the presence of the opening 24 serves to avoid the passage, especially through the layer of copper of the housing, of parasitic currents whose existence would compromise the quality of the welding.

An operation of making parallel and plane the external faces 34 and 35 of the arms 9 and 10 is then carried out under pressure in order to cause the disappearance of slight depressions which may have appeared in the regions of the points 30,32 and 31,33.

The corresponding contact element, conforming to the construction and the manner of fixing which have been described, can advantageously be silvered on its external surface and cooperate with removable electrical coupling devices making use of frictional contacts and/or of localised tightening contacts making use for example of one or more resilient grippers.

In another manner of construction of a contact element 8' usable for the carrying out of the process for the provision of contact surfaces for bus bars 1' and seen in Fig. 4, the housing again comprises two- parallel arms 9', 10' and a cross piece 11' for engagement on an end 2' of the bar, but for example only having two projecting edge portions 16' and 19' placed towards the sides 36, 37 of the bar; further, the bearing and stop surfaces are here constituted by the parallel ends 3', 3" forming the coupling between the machined surfaces 5'; 4' and the non-machined surfaces 6', 7', and respectively by the end edges 27", 28" of the arms 9', 10' parallel to the cross piece 11', the internal length K comprised between the cross piece 11' and the ends 27", 28" being slightly greater than the length a; an opening 24' is provided as in the preceding case; here again the stop surfaces are placed remote from the external surfaces of the arms 34', 35'.

It is clear that the carrying out of the process described does not necessitate a sole and unique order of carrying out of all of the particular operations; thus, the formation of the opening and of the bosses or that of the ends 27", 28" can be carried out in the course of cutting out of the sheet during its bending or even after bending.

Such contact surfaces will advantageously be obtained with the aid of the process and means described in all cases where conditions of small bulk must be respected.

Claims

1. A process, for the provision of a contact surface on a bus bar of aluminium, making use of a contact element, cut out from a sheet comprising a layer of copper and a layer of aluminium, which is bent and which is fixed on this region by electrical spot welds, thereby placing the aluminium surfaces in contact, characterised by the carrying out of the following operations:: a) machining on an end region of a bar of two opposed parallel plane surfaces and at least one frontal bearing surface substantially perpendicular to a longitudinal axis of the bar, b) cutting out of an element having a contour corresponding to that of a developed contact element in a sheet comprising a layer of copper and a layer of aluminium, c) bending said element in such a manner as to constitute a contact element forming a housing of generally "U" section which has two parallel arms, a common cross piece and two bending edge portions, the layer of aluminium being placed at the interior of the housing, d) perforation of the cross piece, over a fraction of its height, to provide an elongated opening substantially parallel to a bending edge portion, e) formation of bearing surfaces on at least one region of the housing remote from the external surfaces of the arms, f) introduction of the machined end of the bar into the internal space of the housing as far as a respective position wherein the stop surfaces are applied against the bearing surfaces, g) application of two electrodes of an electric spot welding machine on the external surfaces of the arms, and placing of these electrodes under voltage until the internal surfaces of the arms are welded to the machined surfaces by the effect of the passage of current, h) compression of the external surfaces of the arms until there are obtained two plane external surfaces.

2. A process, as claimed in claim 1 F wherein the operations of perforation (d)) and of formation (e)) are carried dut in the course of the operation of cutting out or during the operation of bending.

3. A contact element, suitable for fixing by welding in accordance with the process claimed in claim 1 on an end of a bus bar of aluminium, having two opposed plane surfaces and at least one frontal bearing surface and characterised in that said element has the form of a housing having two parallel arms and a-common cross piece coupled to the two arms along two respective edges, the internal surfaces of said arms being covered with aluminium and the externa! body of the housing being of copper, the cross piece having over a fraction of the height of the cross piece a central opening substantially parallel to the edge portions, and respective stop surfaces being provided in said housing and disposed opposite to and in contact with respective bearing surfaces situated remote from the respective external surfaces of the arms, when the said end is introduced between the said arms.

4. A contact element, according to claim 3, for a bar end wherein the contact surface is constituted by a frontal surface of the end, wherein the stop surfaces are two internal surfaces of two bosses projecting towards the internal space of the arms and placed at each side of the opening in the direction of the height.

5. A contact element, according to claim 3, for a bar end wherein a stop surface is constituted by a coupling surface between a machined surface and a non-machined surface of the bar, wherein the stop means are constituted by at least one end edge of an arm parallel to the cross piece.

6. A contact element, according to any one of claims 3 to 5, wherein the opposed edges of the arms, placed perpendicularly to the edge portions, are bent in order to form respective parallel guide means adapted to cooperate with respective opposed surfaces of the end placed perpendicularly to the machined surfaces.

7. A process, as claimed in claim 1, substantially as described herein.

8. A contact element, as claimed in claim 3, substantially as described herein with reference to the accompanying. drawings.