GB2262195A - Component with silver contact insert - Google Patents

Abstract

An electrical component such as a copper terminal pin 2 for an electrical appliance such as a kettle, has a silver contact member 4 keyed into an edge thereof. In one embodiment the contact member is keyed into the end edge of the pin 2, although it may be keyed into a side [Fig. 7]. A slot (8, Fig. 6) is formed in the component, and the contact member 4 inserted in the slot. The area around the slot 8 is then deformed to retain the contact member. The contact member may be keyhole shaped. <IMAGE>

Description

Electrical Contacts The present invention relates to electrical contacts, for example, but not exclusively, electrical contacts as might be provided on a terminal pin in a cordless electrical appliance such as a kettle or hot water jug.

In a typical cordless appliance such as a hot water jug, a male pin connector extends downwardly from the jug body for engagement with a socket connector in the base. Typically the pin is made from brass, and in order to obtain a satisfactory electrical contact between the pin and the socket connector, a silver contact surface is formed on the end of the pin.

Such a contact surface may be formed by from so called "edge lay". This involves electron beam welding a thin strip of silver, of such a dimension as to give the desired depth of contact surface, onto the edge of a strip of brass, as so to obtain a composite strip. The pin is then stamped out of the strip to a desired shape, the silver edge portion of the pin forming the contact surface. This process is, however, an expensive one.

Another method involves the projection welding of a silver contact member onto the end of a pre-formed pin.

This is, however, a complicated, and therefore expensive method.

A silver plating may also be provided on a pin to provide a contact surface, but this is expensive since in practice it is difficult to plate selective areas of a pin, with the result that the whole pin is plated.

From a first aspect, therefore, the invention provides a method of providing an electrical contact on an electrical component comprising forming a slot in an edge of the component, forming a silver contact member having a keying portion, inserting the keying portion of the contact member into the slot, and deforming the component in the region of the slot around the contact member so as to retain the contact member in the slot.

Thus, a contact member is mechanically keyed into an edge of the component rather than welding or plating a contact to a component. This is simpler and more economical than existing procedures. This is particularly important in for example the manufacture of terminal pins for electrical appliances such as hot water jugs where savings of fractions of a-penny on an component are regarding as significant.

A high pressure is applied to the relevant region of the component so as to deform the component into intimate contact with the contact member. This ensures satisfactory thermal and electrical conduction between the contact member and the component.

In a preferred embodiment the component is a terminal pin, for example for a cordless appliance.

Conveniently therefore the slot may be formed in an end edge of the component, and the contact member arranged so as to project therefrom for engagement with a further contact. Thus a pair of lugs may be formed on the end of the pin which are pressed together firmly to locate the contact member therebetween. While this is a preferred arrangement, it would of course be possible to provide the slot in a side edge of the terminal pin if a contact were desired in such a position.

Preferably the component is a pressed component stamped from strip material, for example. Most conveniently the slot may be formed in the component as it is being stamped from the strip. Preferably the electrical component, at least in the region of the slot, is formed of copper. This material not only exhibits good electrical and thermal conductivity, but will also work harden when it deforms so that once the component is deformed around the contact member, it will not tend to relax, whereby the contact member will be retained firmly.

The contact member is preferably formed from a length of silver wire which has been cut to the appropriate length. A desired profile may be given to the contact member as it is cut from the wire, by, for example, using a guillotine blade with a suitably profiled cutting edge.

The keying portion of the contact member may be generally wedge shaped, and in one embodiment the contact member is preferably keyhole shaped, the rounded upper part of the keyhole profile forming a contact portion of the contact member and the outwardly tapering lower part being inserted in the slot for keying the contact member in the component.

The keying portion of the contact member may of course have other shapes, for example it may be T shaped.

The contact member may be press fitted into the slot, or merely loosely located in the slot prior to deforming the component around it. Deformation of the component may be performed in any suitable press.

The present invention also extends to an electrical component formed by a process in accordance with the first aspect of the invention and also provides, in a further aspect, an electrical component having a silver contact member mechanically keyed into an edge thereof.

Preferably the contact member extends above the surrounding material of the component to define a contact portion. Conveniently the contact member is generally keyhole shaped, the upper portion of the keyhole profile extending above the component surface to define the contact portion and the tapering portion being keyed into the component.

The component is preferably of copper so that upon being deformed to key the contact member in position, it work hardens to prevent relaxation and subsequent loosening of the contact member in use.

Preferably the component is a terminal pin for an electrical appliance, such as an electric water heating jug or kettle. The contact member may be keyed to on an end of the pin, for use, for example, in a cordless appliance, or on an side edge for use for example in a corded appliance.

Some preferred embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which: Fig. 1 is a side elevation of a terminal pin in accordance with the invention; Fig. 2 is a plan view of the terminal pin of Fig.

1; Fig. 3 is a side view of a contact member for use in the pin of Figs. 1 and 2; Fig. 4 is an end view of the contact member of Fig.

3; Figs. 5 and 6 are side and plan views of the terminal pin of Figs. 1 and 2 prior to insertion of the contact member; Figs. 7 and 8 are schematic side and end views respectively of further terminal pins in accordance with the invention arranged in a plug shroud.

Referring to Figs. 1 and 2, a copper terminal pin 2 has a silver contact member 4 mounted on one end thereof. The contact member 4 has a generally keyhole shape, with a tapering portion 4a keyed into the pin 2 and a rounded portion 4b standing proud from the surrounding surface of the pin. A small shoulder 4c is formed between the portions 4a, 4b.

The end portion of the pin 2 tapers both in the direction of its width and in the direction of its thickness. The tapering portion 4a of the contact member 4 is firmly held in position by the lugs 6 formed at the end of the pin.

The pin 2 is formed by stamping from a strip of copper as shown in Figs. 5 and 6. Lugs 6 formed at the end of the stamped pin together define a slot 8 in the end edge of the pin 2.

The contact member 4 (Figs. 3,4) is formed as a slug sheared from the end of a circular section silver wire of suitable diameter by a guillotine blade 10 (shown schematically) having a shape which is complementary to the desired upper profile of the contact member and which cooperates under pressure with a stop 12 to form the desired shape, as shown in Fig. 4.

If desired the guillotine profile may be such that the contact member is preformed with the keyhole profile as shown in Figure 1.

The contact member 4 is then inserted in the slot 8 in the pin 2, and the lugs 6 of the pin then bent over the edges of the contact member, as shown in Fig. 1, so as to retain the contact member in position. This is performed under considerable pressure in a suitable press so as to ensure that an intimate contact is obtained between the tapering section 4a of the contact member 4 and the surrounding faces of the slot 8, so that satisfactory electrical and thermal conduction will be obtained therebetween. The act of pressing the lugs 6 together preferably deforms the silver slightly to form a shoulder 4c, as shown although as stated the contact member may be. preformed with a keyhole shape already having a shoulder.Furthermore the end portion of the pin 2 is pressed so as to lengthen the taper in its thickness direction, which will further improve the contact between the contact member 4 and the pin 2.

In an automated process, the contact member 4 after it is cut from a wire may be retained by the guillotine blade 10, from where it may be pushed directly into the slot 8, the pin 2 then being pressed to deform its end region to retain the contact member 4.

Figs. 7 and 8 show a further embodiment of the invention.

In this embodiment, a contact member 14 is keyed into a side edge 16 of a line or neutral terminal pin 13 arranged in a plug shroud 22 of an electrical appliance.

A slot 18 is formed in the side edge 16 of the pin 13 between two lugs 20 which are pressed together so as to retain the contact member 14 therebetween. The upper portion 14a of contact 14 stands proud of the surrounding pin surface for cooperation with a further contact within a control for the appliance.

Claims (20)

Claims

1. A method of providing an electrical contact on an electrical component comprising forming a slot in an edge of the component, forming a silver contact member having a keying portion, inserting the keying portion of the contact member into the slot, and deforming the component in the region of the slot around the contact member so as to retain the contact member in the slot.

2. A method as claimed in claim 1 wherein the component is a terminal pin.

3. A method as claimed in claim 1 or 2 wherein the slot is formed in an end edge of the component.

4. A method as claimed in claim 1 or 2 wherein the slot is provided in a side edge of the component.

5. A method as claimed in any preceding claim wherein the component is a pressed component stamped from strip material.

6. A method as claimed in claim 5 wherein the slot is formed in the component as it is being stamped from the strip.

7. A method as claimed in any preceding claim wherein the electrical component, at least in the region of the slot, is formed of copper.

8. A method as claimed in any preceding claim wherein the contact member is formed from a length of silver wire which has been cut to the appropriate length.

9. A method as claimed in any preceding claim wherein the contact member is keyhole shaped, the rounded upper part of the keyhole profile forming a contact portion of the contact member and the outwardly tapering lower part being inserted in the slot for keying the contact member in the component.

10. A method as claimed in any preceding claim wherein the contact member is press fitted into the slot,

11. An electrical component produced by a method as claimed in any preceding claim.

12. An electrical component having a silver contact member mechanically keyed into an edge thereof.

13. An electrical component as claimed in claim 12 wherein the contact member extends above the surrounding material of the component to define a contact portion.

14. An electrical component as claimed in claim 12 or 13 wherein the contact member is generally keyhole shaped, the upper portion of the keyhole profile extending above the component surface to define the contact portion and the tapering portion being keyed into the component.

15. An electrical component as claimed in any of claims 12 to 14 wherein the component, at least in its contact mounting portion is of copper.

16. An electrical component as claimed in any of claims 12 to 15 wherein the component is a terminal pin.

17. An electrical component as claimed in any of claims 12 to 16 wherein said contact member is keyed into an end of said component.

18. An electrical component as claimed in any of claims 12 to 16 wherein said contact member is keyed into a side edge of the component.

19. A method substantially as hereinbefore described with reference to the accompanying drawings.

20. An electrical component substantially as hereinbefore described with reference to the accompanying drawings.