Method of manufacturing an electrical contact

Abstract

 A slotted plate electrical contact is manufactured by a method involving cutting a metal plate (1) from an edge thereof and then forming one or more indentations (7) in the plate (1) thereby to space the edges (5, 6) formed by the cutting to provide a slot (8) of the required width.

Description

[0001] Method of manufacturing an electrical contact.

[0002] This invention relates to a method of manufacturing an electrical contact, and particularly an electrical contact of the type generally known as a slotted plate contact and comprising a metal plate having a slot open to one edge thereof into which slot an electrical conductor can be urged such that the slot walls grip the conductor and establish an electrical connection between the conductor and the contact. If the conductor is insulated then the slot walls also serve to cut through the insulation to establish the connection to the conductor.

[0003] Such electrical contacts are generally manufactured by stamping, and if necessary forming, operations carried out on sheet metal stock, but these generally used methods are not suitable when a contact having a very narrow width slot is- required, for example a contact to be manufactured from sheet metal stock of 0.5mm thickness and having a slot with a width less than 0.2mm to receive a conductor 0.2mm in diameter.

[0004] In U.S. Patent Specification No. 3234498 there is described a method of manufacturing a slotted plate contact in which a metal blank is sheared and punched, material on either side of a shear line then being deformed, by stamping, into engagement with material on the other side of the shear line, thereby to open the shear line into a slot to receive an electrical conductor.

[0005] This known method offers the advantage that the width of the slot formed from the initial substantially zero width shear line, can be controlled to a certain extent by control of the stamping operation whereby a slot of relatively narrow width can be formed-However, this known method has the disadvantage that since the stamping operation is carried out on what in effect are edges of the blank, the material is deformed into free space and thus the deformation cannot be controlled as precisely as is desirable. A further disadvantage is that since the stamping is effected intermediate the ends of the complete slot formed there is the possibility that the final connection portion of the slot will taper in width in an undesirable manner, this requiring a conductor to be inserted to an exact position in the slot for a reliable connection to be made. Another disadvantage of this known method is that it can be used only to open an initial shear line into a slot, and thus if plating of the contact is required the opening into a slot must initially be sufficient such that after plating the slot is of the correct width for the conductors with which it is to be used, this requiring very precise control of the stamping and plating operations.

[0006] According to this invention a method of manufacturing an electrical contact comprising a metal plate having a slot open to one edge thereof, into which slot an electrical conductor can be urged such that the slot walls grip the conductor and establish an electrical connection between the conductor and the contact, is characterised by the steps of cutting a metal plate along a line extending from an edge of the metal plate; and forming one or more indentations in the metal plate thereby to space the edges formed by the cutting operation to form a slot having the required width therebetween.

[0007] The cutting of the metal plate can be effected by a shearing operation, the edges formed by the shearing operation being maintained in substantially abutting relationship, the indentation or indentations being formed to separate the edges formed by the shearing operation.

[0008] Otherwise the cutting of the metal plate can be effected so as to form a relatively large slot between the edges thus formed, the indentation or indentations being formed to move the edges formed by the stamping operation towards each other.

[0009] Preferably a hole is formed in the metal plate prior to the cutting operation, the edges formed by the cutting operation extending from the edge of the metal plate to the hole.

[0010] The method of this invention has the advantage that the width and shape of the slot produced on forming of the indentation or indentations can be very accurately controlled, for example by appropriate choice of the position and/or the depth and/or the shape of the indentations, such that a slot of very narrow width can be produced.

[0011] The indentation or indentations can be formed by a stamping or pressing operation.

[0012] Further, with the method of this invention an initially too wide slot can be formed, plating then be effected, and the slot subsequently being closed up to the required width, very precise control of the plating operation thus being unnecessary.

[0013] This invention will now be described by way of example with reference to the drawing, in which Figures 1 to 4 illustrate various stages in the manufacture of a contact by a method according to this invention, and Figure 5 is a section on the line V - V in Figure 4.

[0014] Figure 1 shows a planar metal blank 1 stamped in known manner from sheet metal and carried by an integrally formed carrier strip 2 which in known manner would carry a plurality of similar blanks (not shown) in side-by-side relationship.

[0015] A hole 3, circular in this example, is formed in the blank 1, as shown in Figure 2, for example by a stamping operation.

[0016] The blank 1 is then sheared along a line 4 between the hole 3 and an edge of the blank 1, as shown in Figure 3, the edges 5 and 6 formed by the shearing operation being maintained in substantially abutting relationship.

[0017] Two indentations 7 are then formed in the blank 1 by a stamping or pressing operation, the indentations being formed at such positions that the edges 5 and 6 formed by the shearing operation are separated in the directions of the arrows A to form a slot 8 therebetween, as shown in Figure 4, the width of the slot 8 being dependent upon the shape and depth of the indentations 7 which, as shown in Figure 5, can be V-shaped in cross-section.

[0018] As can be seen from Figure 4 the positions of the indentations 7 are such that the edges 5 and 6 while being separated are retained in parallel relationship, although it will be appreciated that the indentations 7 can be positioned to give a slot 8 of tapering, that is increasing, width if required, such a slot being desirable since after initial insertion of a conductor, further movement of the conductor into the slot will not overstress the contact material. Further, while two indentations 7 are shown it will be appreciated that a similar slot-forming effect can be achieved by the use of only one appropriately positioned and dimensioned indentation 7.

[0019] As shown in the drawing, the edge of the plate 1 to which the slot 8 extends can be formed to provide an inwardly tapering mouth for the slot 8 thereby to facilitate insertion of a conductor (not shown) into the slot 8 on use of the contact.

[0020] Although in the method described above the indentations 7 are formed to separate the edges 5 and 6 forming the slot, the blank 1 can otherwise be initially stamped with a relatively large slot separating the edges 5 and 6, the indentations 7 then being formed so as to move the edges 5 and 6 towards each other to form a final slot 8 having the required width. To effect such closure of the initially formed slot the indentations 7 would need to extend from the hole 3 across the contact towards the free ends of the edges 5 and 6 rather than away from the free ends as described above with reference to the drawings.

[0021] Further, although in the methods described above a hole 3 is initially formed in the blank 1, such a hole is not essential, the shear or slot initially formed in the blank 1 merely extending from the edge of the blank 1 inwardly thereof.

Claims

1. A method of manufacturing an electrical contact comprising a metal plate (1) having a slot (8) open to one edge thereof, into which slot (8) an electrical conductor can be urged such that the slot walls (5, 6) grip the conductor and establish an electrical connection between the conductor and the contact, characterised by the steps of cutting a metal plate (1) along a line (4) extending from an edge of the metal plate (1); and forming one or more indentations (7) in the metal plate (1) thereby to space the edges (5, 6) formed by the cutting operation to form a slot (8) having the required width there between.

2. A method as claimed in Claim 1, characterised in that the cutting of the metal plate is effected by a shearing operation, the edges (5, 6) formed by the shearing operation being maintained in substantially abutting relationship, the indentation or indentations (7) being formed to separate the edges (5, 6) formed by the shearing operation.

3. A method as claimed in Claim 1, characterised in that the cutting of the metal plate is effected by a stamping operation to form a relatively large slot between the edges (5, 6) thus formed, the indentation or indentations (7) being formed to move the edges (5, 6) formed by the stamping operation towards each other.

4. A method as claimed in Claim 1, Claim 2 or Claim 3, characterised by the step of forming a hole (3) in the metal plate (1) prior to the cutting operation, the edges (5, 6) formed by the cutting operation extending from the edge of the metal plate (1) to the hole (3).

5. A method as claimed in any preceding claim, characterised in that the indentation or indentations (7) are formed such that the edges (5, 6) formed by the cutting operation are maintained parallel.

6. A method as claimed in any preceding claim, characterised in that the edge of the metal plate (1) to which the slot (8) extends is formed to provide an inwardly tapering mouth for the slot (8).

7. An electrical contact manufactured by a method as claimed in any preceding claim.

Drawing