GB2028600A

GB2028600A - An insulation-piercing contact for an electric connector

Info

Publication number: GB2028600A
Application number: GB7829476A
Authority: GB
Original assignee: Ferranti PLC
Current assignee: Ferranti International PLC
Priority date: 1978-07-11
Filing date: 1978-07-11
Publication date: 1980-03-05
Also published as: FR2431201B1; DE2927468A1; FR2431201A1; GB2028600B

Abstract

An insulation-displacement contact (10) for an electric connector comprises a channel-shaped terminal element (11) having two side walls (13, 14) and a base (15), and a contact-making member (12). A number of tongues (16) extend into the channel from the side walls (13, 14), successive tongues extending from alternate side walls. The tongues (16) pierce the insulation (18) of a conductor forced by a tool (20) into the channel (11) to form a gas-tight joint between the tongues (16) and the core (19) of the conductor. The contacts (10) may be mounted in an insulating housing (30) by first hooking the end of the member (12) under a retainer 32 and then pressing the terminal element (11) past resilient retaining lugs (33), (34). <IMAGE>

Description

SPECIFICATION An insulation-displacement contact for an electric connector This invention relates to an insulationdisplacement contact for an electric connector, and to a connector including such contacts.

An insulation displacement contact is a contact in which electrical connection with an insulated flexible conductor is made, without stripping the insulation from a length of conductor by crushing and/or shearing of the insulation by suitablypositioned conducting surfaces.

The insulation immediately adjacent to these surfaces is thus displaced, and the surface cuts into or compresses the core of the conductor to form an effective electrical connection. The most common type of insulation displacement contact comprises a metal blade having a slot into which the conductor is forced, the width of the slot being less than the diameter of the core of the conductor. Care has to be taken to ensure that the core is not cut or compressed to an excessive extent which might lead to breakage of the core.

The type of connection formed may be referred to as a "gas-tight" joint since the conductor and the contact are in such close and firm mechanical contact that substance which would cause the formation of surface films or corrosion, and subsequent loss of electrical contact, cannot enter the joint. The joint thus has a perfect metal-tometal contact.

Insulation displacement have advantages over contacts requiring the removal of insulation from a length of conductor. In the first place there is a time saving due to the fact that removal of the insulation is not necessary. In addition, the surface of the core, being covered by the insulation until the instant of making the connection, will be clean and better able to form a satisfactory connection.

Many types of insulation displacement contact exist, as do connectors using this type of contact One of the problems is to ensure that a satisfactory connection is maintained for the life of the connector. In addition the dimensions of the slot must be accurate.

It is a object of the invention to provide an improved insulation -- displacement contact, and a connector using such contacts.

According to the present invention there is provided an insulation-displacement contact for an electric connector, which includes a terminal element for connection to an electric conductor, and a contact-making member, the terminal element comprising an elongated electricallyconducting channel member having two side walls and a base, and at least two projecting tongues each extending from one side wall towards the opposite side wall and located such that successive tongues extend from alternate ones of the two side walls and are spaced apart from one another along the length of the channel member, the distance between each projecting tongue and the spaced side wail being such that each tongue deforms the core of a conductor forced into the channel to produce a gas-tight joint.

Also according to the invention there is provided an electric connector which includes an electrically-insulating body member in which are located a plurality of contact members each as defined in the preceding paragraph.

The projecting tongues of each contact member may be stamped out of, and bent into the channel member from, either the side walls or the base of the channel member. Further projections may be formed to hold the tongues in position.

The invention will now be described with reference to the accompanying drawings, in which: Figure 1 is an isometric view of a contact member illustrating the insertion of a conductor; Figure 2 is a plan view of a contact with attached conductor; Figure'3 is a sectional view along the line Ill-Ill of Figure 2; Figure 4 is an isometric view of an alternatjve form of contact member; Figure 5 is a plan view of the contact member of Figure 4; and Figure 6 is a sectioned isometric view of part of a connector showing one contact member in position.

Referring now to Figure 1, this shows the contact member 10 having a terminal element 11 and a contact-making member 12. The terminal element 11 is a channel-shaped member having two parallel side walls 13 and 14 and a base 15.

Four tongues 1 6 project into the channel from the side walls, alternate ones of the tongues extending from opposite side walls. In the embodiment of Figure 1 the tongues are formed by shearing and bending parts of the side walls 13 and 14 into the channel as shown. The top edges of the tongues are chamfered to provide a sloping edge.

The contact-making member 12 of the contact member 10 isthin and resilient, and is formed into whatever shape is required. Figure 1 shows the contact-making member 12 formed at its free end into a hook-shaped contact. The portion 1 7 may be plated with a precious metal such as gold.

Figure 1 also shows a conductor having insulation 18 and a conducting core 19, and-an insertion tool 20.

A conductor is attached to the contact member 10 by placing the conductor on the top of the channel-shaped terminal element 11 and pressing it into position using the insertion tool 20. Figure 2 shows a conductor inserted in this way. As the conductor is pressed into position each of the four tongues 16 cuts into the insulation 18 of the conductor. This action compresses the conductor between each tongue and the opposite wall of the channel, the spacing being such that the tongue deforms the core sufficiently to produce a gastight joint without excessive weakening of the core. Figure 3 illustrates the actual connection so made. Since adjacent tongues are located on opposite sides of the channel, the core 1 9 of the conductor is in fact stretched slightly understress as the conductor is inserted.In addition the two walls and base of the channel are stressed due to the presence of the conductor core. These two stresses create strain energy resulting in a satisfactory electrical connection which does not deteriorate over a period of time. The relationship between the diameter of the conductor core and the spacing between a tongue and the opposite wall of the channel is difficult to specify, and under different circumstances the core diameter may be slightly greater than the spacing equal to it, or slightly less than the spacing.

The tongues 16 maybe formed in other ways than that described above. Figures 4 and 5 show an alternative form of contact member in which the tongues 16 are bent from the base 1 5 of the channel rather than from the side walls 1 3 and 14.

This avoids weakening the side walls. If it is necessary to prevent subsequent deformation of the tongues due, say, to tension on the conductor, small projections 21 may be punched in the side walls 13 and 14 on either side of each tongue 16.

Other ways of forming the tongues 1 6 may be used, though if the tongues are to close together the conductor may be weakened.

Figure 6 shows part of a connector using contact members of the type described above.

Part only of an insulating housing 30 is shown.

This housing is formed with a number of parallel recesses 31 each shaped to take a separate contact member, one of which is shown in position. The contact member is inserted by first engaging the hooked end of the contact-making member 12 under a retaining strip 32, and then pressing the termi l element into the recess 31 past a number of resilient retaining lugs 33 and 34. The lugs 33 prevent the terminal element from being lifted out of the recess 31 , whilst lugs 34 prevent movement which would disengage the hooked end of the contact-making member 12 from the retaining strip 32. Movement in the opposite direction is prevented by the hooked end itself and by shoulders 35 in the recess.

A connector of this type may carry a required number of contact members, and may be provided with some form of detachable cover if desired.

Other configurations of contact members are possible.

Claims

1. An insulation-displacement contact for an electric connector which includes a terminal element for connection to an electric conductor, and a contact-making member, the terminal element comprising an elongated electricallyconducting channel member having two side walls and a base, and at least two projecting tongues each extending from one side wall towards the opposite side wall and located such that successive tongues extend from alternate ones of the two side walls and are spaced from one another along the length of the channel member, the distance between each projecting tongue and the spaced side wall being such that each tongue deforms the core of a conductor forced into the channel to produce a gas-tight joint.

2. A contact as claimed in Claim 1 in which the outer edge of each projecting tongue is chamfered to form a cutting edge.

3. A contact as claimed in either of Claims 1 or 2 in which each projecting tongue is formed by shearing and bending a portion of the side wall of the terminal element.

4. A contact as claimed in either of Claims 1 or 2 in which each projecting tongue is formed by shearing and bending a portion of the base of the terminal element.

5. A contact as claimed in Claim 4 in which inwardly-directed projections are formed from the side walls to retain each projecting tongue in position.

6. An insulation-displacement contact substantially as herein described with reference to Figures 1 to 3 or Figures 4 and 5 of the accompanying drawings.

7. An electric connector which includes a body member of electrically-insulating material formed with a number of parallel recesses, each recess being arranged to receive a contact member as claimed in any one of Claims 1 to 6.

8. An electric connector substantially as herein described with reference to Figure 6 of the accompanying drawings.