GB2093641A

GB2093641A - Improvements in or relating to electrical contacts

Info

Publication number: GB2093641A
Application number: GB8201977A
Authority: GB
Original assignee: Plessey Co Ltd
Current assignee: Plessey Co Ltd
Priority date: 1981-02-18
Filing date: 1982-01-25
Publication date: 1982-09-02
Also published as: GB2093641B

Abstract

An electrical contact for an electrical connector comprises an elongate electrically conductive strip consisting of two parts. The first part is resilient and is adapted to be used for making the contact, and this is joined (e.g. welded) to a rigid support part which holds the contact in the connector and is also used for making external electrical connections. Formed in the resilient part adjacent to the joint are two small, part-spherical projections and these are intended to tightly engage the material of the connector body and frictionally retain the contact in the connector body. The connector is preferably an edge connector for a printed circuit board. It has the advantage that it cannot be readily removed from a contact housing without damaging it. <IMAGE>

Description

SPECIFICATION Improvements in or relating to electrical contacts This invention relates to electrical contacts and more particularly to contacts for electrical connectors such as the type adapted to grip the edge of a printed circuit board and enable electrical contact to be readily made with the various parts of circuitry formed on the printed circuit board.

Such connectors usually consist of an insulating housing containing a plurality of electrical contacts arranged each side of a slot formed in the housing for the reception of the printed circuit board. The printed circuit board is provided with a plurality of electrical contact members along its edge which are adapted to engage the contacts in the edge connector. The connector is provided with suitable means for connecting electrical conductors to the contacts, the purpose of the arrangement being that if a fault develops in a printed circuit board then the board can simply be replaced without the necessity of disconnecting and reconnecting individual electrical conductors such as by soldering, removing screws or other similar operations.

One problem with edge connectors is that after a certain amount of use the electrical contacts may become worn or a fault may develop in the connector, such as a contact breaking or the connection between one of the electrical conductors and its contact being broken. In this case it is necessary to replace the contact or otherwise repair the damage and the contacts are therefore normally made removable to permit such faults to be remedied.

It is an object of the present invention therefore to provide an electrical contact which is a secure fit in a connector housing, but which can be readily removed therefrom without damaging the housing.

According to the present invention an electrical contact for an electrical connector comprises an elongate electrically conductive strip comprising two parts, the first part being a resilient contact making portion and the second part comprising a substantially rigid support portion for the connection thereto of one or more electrical conductors, the two parts being secured together, there being formed a projection on one of the parts adjacent to the joint between the two parts, which projection is adapted to tightly engage the material of the connector housing whereby to frictionally retain the contact in position in the connector housing.

Preferably the resilient contact making portion is formed with a bowed shape adjacent to one end and a channel section adjacent to the other end, the channel section being of a size to fit closely round the substantially rigid support portion.

The resilient contact making portion is preferably welded to the rigid support portion at the base of the channel section.

Preferably the at least one projection is formed in the base of the channel section and preferably there are two such projections spaced longitudinally along the base of the channel section.

Further projections may be formed in the sides of the channel section. These further projections may take the form of tabs cut and bent out of the sides of the channel section.

The invention also comprises an electrical connector having electrical contacts as set forth above.

An embodiment of the invention will now be described by way of example only with reference to the accompanying drawings in which Figure 1 is a three-dimensional view of an electrical contact constructed in accordance with the invention and Figure 2 is a cross-sectional view through an electrical edge connector showing two electrical contacts secured in position.

The electrical contact shown in Fig. 1 consists of an elongated resilient strip 10 of work hardened phosphor-bronze which is secured by a spot weld 1 2 to the end of a rigid square section phosphor bronze post 14. The upper end of the strip 10, as seen in Fig. 1, has a bowed portion 1 5 and the outermost surface of the bowed portion 1 5 has a coating of gold 1 6 to form a contact surface.The lower end of the strip 10 is formed into a U-shape or channel section 1 8 of such a size as to closely fit round the post 14, the upper end 20 of which is level with the upper end of the channel section 1 8. Formed in the strip 10 in the base portion of the channel section 1 8 are two part-spherical projecting portions 22 arranged longitudinally on the strip 10, which because of the resilience of the material of the strip 10 are themselves resilient. Each side 24 of the channel section 1 8 is provided with two cuts 26 and two lengths of the side are bent outwardly at an angle to produce projecting tabs 28.

The post 14 is accurately made with sharp corners 30 so that when un-insulated wire is wrapped tightly round the post gas tight electrical contact is made in well known manner.

The electrical edge connector shown in Fig.

2 has a body 32 of a polyester plastics material with a slot 34 for the reception of the edge of a printed circuit board (not shown).

The body 32 is formed with elongate grooves 36 arranged on each side of the slot 34, the grooves 36 extending into square holes 38 formed through turrets 40 formed on the base of the body. There may be only two such grooves, one each side of the slots 34, or there may be a number each side such as eight, sixteen or thirty-two. Each groove is narrower in width at its lower end 42 and a shoulder 44 is provided at the lower end of the narrower part between the slot 36 and the square hole 38.

Inside each groove is located an electrical contact with the bowed portion 1 5 extending into the slot 34 and the channel section 1 8 located in the narrower part of the groove 42 abutting the shoulder 44. The square section post 14 extends through the holes 1 8 and projects through the base of the connector body 32.

In this position the projecting portions 22 firmly engage with the material of the body 32 frictionally retaining each contact in postion. The tabs 28 also tightly engage the sides of the grooves thus increasing the retention forces.

The contacts are inserted and removed at the front (the upper end as seen in the drawings) of the body, 32 final insertion being achieved by using an elongate punch which engages the end 20 of each post 14 and forces it through the holes 38 until the channel section 1 8 engages the shoulder 44.

This method reduces to a minimum shear stresses on the weld joint 1 2 and avoids any damage or marking on the post 14. Removal of a contact uses an opposite method in which a punch or similar tool applies an impact to the rear (lower) end of the post 14 to release the channel section form the narrower part 42 of the groove 36. The contact can then simply be pulled out of the front of the body 32. The connector thus has front insertion and removal and a rear release facility of the contacts.

The elongated strips 10 are preferably shaped by partially cutting a continuous band of phosphor bronze and subsequent shaping of the bowed portion 15, the channel section 18, the projecting portions 22 and the tabs 22 is done whilst the strips 10 form part of the continuous band. The posts 14 are welded in position at this stage before the completed contacts are parted off from the band.

The use of the separate posts 14 enables posts of different lengths to be used when necessary for different applications.

Claims

1. An electrical contact for an electrical connector comprising an elongate electrically conductive strip comprising two parts, the first part being a resilient contact making portion and the second part comprising a substantially rigid support portion for the connection thereto of one or more electrical conductors, the two parts being secured together, there being formed a projection on one of the parts adjacent to the joint between the two parts which projection is adapted to tightly engage the material of the connector housing whereby to frictionally retain the contact in position in the connector housing.

2. An electrial contact as claimed in claim 1 in which the resilient contact making portion is formed with a bowed shape adjacent to one end and a channel section adjacent to the other end, the channel section being of a size to fit closely round the substantially rigid support portion.

3. An electrical contact as claimed in claim 1 or claim 2 in which the resilient contact making portion is welded to the rigid support portion at the base of the channel section.

4. An electrical contact as claimed in any preceding claim in which the at least one projection is formed in the base of the channel section.

5. An electrical contact as claimed in claim 4 in which there are two projections spaced longitudinally along the base of the channel section.

6. An electrical contact as claimed in any preceding claim in which further projections are formed in the sides of the channel section.

7. An electrical contact as claimed in claim 6 in which the further projections take the form of tabs cut and bent out of the sides of the channel section.

8. An electrical connector having an electrical contact as claimed in any preceding claim.

9. An electrical contact constructed substantially as hereinbefore described with reference to the accompanying drawings.

10. An electrical connector constructed and adapted to operate substantially as here it before described with reference to the accompanying drawings.