AN ELECTRICAL CONNECTOR

Abstract: An electrical connector for forming an electrical connection with wires and particularly insulated wires. The connector comprises a connector element having first and second portions (2) with a slot for accepting a wire therebetween. In a preferred embodiment of the invention, the first and second portions are substantially perpendicular and present a stepped slot to a wire that is inserted. The angle between the wire and the first or second portions is in the range 5 DEG to 85 DEG and is typically 45 DEG . When an insulated wire is inserted into the slot, the insulation (8) is penetrated to enable the connector element to establish electrical contact with the conductor (6) of the wire.

Description: AN ELECTRICAL CONNECTOR The present invention relates to a connector for forming an electrical connection with wires, including those covered in insulation. Such connectors are commonly mounted in an array within a housing of insulating material. The present invention relates also to the design of connecting blocks for retaining the connector elements, and controlling their movements. A number of proposals and orientations for such insulation displacement connectors (IDCs) are known. All these proposals suffer from one or more of the disadvantages as described below. IDCs commonly comprise a caπtilevered split beam, whose narrow, slotted portion is dimensioned to be smaller than the diameter of the smallest wire to be terminated therein. At the upper end of the slot, there commonly exists a tapered section of slot which acts as a guide for an incoming wire. On insertion of a wire, any insulation is intended to be cut by the sides of this tapered section of the slot. Commonly, the narrow portion of the slot cuts into the wire forming an airtight joint between the wire conductor and both of the IDC slot sides. 1. Rat IDC at approximately 90° to the wire, movement of the two IDC forks forming the sides of the slot is restricted to one plane, tending to force the forks apart, widening the slot. However, it is noted that deflection is inversely proportional to the cube of the spring thickness. In this deflection mode, the thickness should be taken as the width of each IDC fork. The result is often an extremely stiff action with negligible widening of the slot when a wire is inserted. Such an arrangement is necessarily limited in the range of wire diameters which may be conveniently terminated if all diameters of wire are cut to essentially the same depth by the stiff slot sides. Also, since the slot impinges onto the wire in two places which are opposite to one another, and the profile of copper wire cut out by each IDC fork is rectangular in section, serious weakening of the wire in the IDC region is likely to be encountered, with an increased risk of wire shearing. 2. Rat IDC at approximately 45° to the wire. When a copper wire is inserted into the slot of a flat IDC held at 45° to the wire, movement of the two IDC forks forming the sides of the slot occurs in torsional mode, tending to force the forks apart and thus widening the slot. It is noted that the force exerted on the wire by such IDC forks is directly proportional to the angle of displacement. Such an arrangement would therefore be suitable for terminating a wide range of wire diameters, since the slot dimension would change to correspond with the gauge of wire inserted. This feature would depend for success on the presence of sharp edges on the IDC forks and it is noted that only one of the two corners of the IDC forks presented to the wire would have the sharp punching burr known to be beneficial for successful IDC connections. A risk of adverse consequences for contact reliability therefore exists. When shapes such as those required for IDC slot formation are punched from sheet metal, invariably the side from which the metal is punched is left with a blunt, rounded corner. Also, the opposite side of the sheet is left sharp where the punching tool emerged through the slot. For IDC applications it is highly desirable to make use of these sharp edges in order to produce an IDC of reduced insertion force and high reliability. When the connectors are mounted in an array the array usually consists of parallel pairs of forks. Consequently a capacitance exists between adjacent connectors in the array. This is known to cause problems, particularly at high operational frequencies of ti e order 100 MHz when capacitive effects are significant. 3. Bent IDC with each IDC fork at approximately 45° to the wire, movement of the two IDC forks forming the sides of the slot would tend to occur, forcing the forks apart and thus widening the slot. However, with this arrangement the two points of contact between the IDC forks and the wire are opposite one another, and not displaced along the length of the wire. There is therefore a significant risk of wire fracture at the IDC joint. The present invention alleviates all of these disadvantages of each of the foregoing. According to the invention there is provided an electrically conductive connector element having first and second portions with a slot for receiving a wire therebetween, the first portion lying in a plane at an angle to the plane of the second portion characterised in that at least a part of the first or second portion lies in the plane of the other portion. According to the invention there is further provided an electrical connector comprising an electrically insulated housing and a connector element of the invention. Preferably the planes of the first and second portions are at an angle of substantially 90°. One or more corners or edges of the first and second portions may be sharp so that when a wire is inserted into the slot the edges cut into the wire, and possibly also through any insulation on the wire, to form an airtight joint between the wire and the sharp edges of the slot. Preferably any such sharp edges or contact points provided on either portion lie in the plane of one of the first or second portions. Preferably two such contact points are provided, one on each of the first and second portions. When a wire is inserted into the slot the first and second portions of the connector element are forced apart, thus widening the slot. Consequently the connector element is capable of accepting wires with a wide range of diameters. Two or more connector elements may be provided to accept a wire whereby the connector elements are arranged in series with adjacent connector elements having progressively narrower slots. Preferably two connector elements are arranged in this way. This type of arrangement is capable of accepting a wider range of wire diameters than a single connector element. According to the invention there is further provided an electrical connector comprising a plurality of said connector elements . The electrical connector may receive a plurality of wires and establish electrical contact therewith. Preferably the connector elements of the said plurality are arranged in parallel whereby first and second portions of adjacent connector elements are substantially perpendicular. With this arrangement the capacitance and inductance between adjacent connector elements of the said plurality is kept to a minimum. This is particularly important for high frequency applications since capacitive and inductive effects and the associated problems increase with frequency. The invention will now be described further by way of example only and with reference to the accompanying drawings in which :- Rgure 1 is a schematic plan view of a connector element of the invention in use; Rgure 2 is a schematic plan view of two connector elements of the invention arranged for accepting a wide range of wire diameters; Rgure 3 is a schematic plan view of a prior art array of insulation displacement connectors; and Rgure 4 is a schematic plan view of an electrical connector comprising an array of connector elements in accordance with the invention. As shown in figure 1 the connector element comprises first and second portions 2 having a slot therebetween. A corner of each portion 2 is sharp so as to penetrate the insulation 8 and to form a point of contact 4 with the conductor 6 of a wire when the wire is inserted into the slot. As will be seen the contact points 4 are relatively spaced apart in the longitudinal direction of the wire. The connector portions 2 and the slot may have any suitable shape or dimension and are typically interconnected at a region below the slot (not shown). The element is typically housed in and braced by an insulating material such as a plastic moulding. Thus the described embodiment comprises a bent IDC with substantially perpendicular IDC forks held at typically 45° to the wire, though the angle between the wire and one of the IDC forks may be in the range 5° to 85° . The IDC includes a stepped slot arrangement which brings a number of benefits: i) On insertion of a wire, movement of the two IDC forks forming the sides of the slot occurs, tending to force the forks apart and this widening the slot. This arrangement is therefore suitable for terminating a wide range of wire diameters, since the slot dimension increases in response to insertion of a thicker wire. ii) The two points of contact between the IDC forks and wire are not opposite one another, but displaced along the length of the wire. The risk of wire fracture at the IDC joint is therefore significantly reduced. iii) The natural tendency of the wire to take the straightest possible route within the IDC is used to draw the wire across the piercing corners of the IDC. iv) Both of the two corners of the IDC forks presented to the wire has the sharp punching burr known to be beneficial for successful IDC connections. v) As the movements of each IDC fork in response to the insertion of a wire are in the same direction, the two piercing corners of the IDC forks are maintained substantially parallel to one another in the presence of a first inserted wire. This design is therefore suitable for the termination of a plurality of wires in each IDC slot. Rgure 2 shows an embodiment of the invention comprising two connector elements 10 and 12 arranged to accept a wide range of wire diameters. Typically the slot 14 of connector element 10 is approximately 0.3mm whereas the slot 16 of connector element 12 is of the order 0.6mm. In use a wire is pushed down between the two slots and depending on the diameter of the wire it will connect securely both mechanically and electrically to the connector element 10 and/or the connector element 12. When a small diameter wire is inserted into this two connector arrangement the wire will establish electrical contact with the connector element 10. The connector element 12 may make little or no contribution to the connection of the wire. Alternatively when a larger diameter wire is inserted, electrical contact is established with both connector elements 10 and 12. In this case the mechanical contact between the wire and connector element 12 is likely to be secure whereas there may be a risk of shearing in the region of the wire near connector element 10 due to the narrow slot weakening the wire. Rgure 3 shows the parallel arrangement of IDC connectors 18 in a known type of electrical connector. With this arrangement adjacent connector elements behave as capacitors which is undesirable, particularly in high frequency applications in which capacitive effects are increased. This problem is minimised by the arrangement of connector elements 20 in an electrical connector 22 in accordance with the invention as shown in Rgure 4. With this arrangement the forks of adjacent connector elements are substantially perpendicular which results in a lower capacitance than with the known arrangement of Figure 3. Thus, in a preferred embodiment of the invention an electrical connector comprises one or more electrical connector elements disposed in a housing of electrically insulating material. Each element is stamped from a piece of metal to form two arms arranged in respective planes to form a stepped slot therebetween, and having cantilever and torsional properties. The slot is sufficientiy long to accept a plurality of conductors terminated simultaneously, and is suitable for the termination of a wide range of wire gauges. When a wire, which may be insulated, is pushed into the slot along a plane which approximately bisects the angle between the planes of the arms, the sharp edges presented to the wire by each arm cut the insulation to make electrical contact with the conductor beneath. It will be appreciated that the present invention is not intended to be restricted to the details of the above embodiments which are described by way of example only.

Claims: Claims . An electrically conductive connector element having first and second portions with a slot for receiving a wire therebetween, the first portion lying in a plane at an angle to the plane of the second portion characterised in that at least a part of the first or second portion lies in the plane of the other portion. 2. An electrically conductive connector element according to claim 1 whereby the planes of the first and second portions are substantially perpendicular. 3. An electrically conductive connector element according to claims 1 or 2 whereby the first and second portions have sharp edges for establishing electrical contact with a wire when a wire is inserted into the slot. 4 An electrically conductive connector element according to any preceding claim whereby the first and second portions are resiliently movable so that when a wire is inserted into the slot the size of the slot increases. 5. An electrically conductive connector element according to any preceding claim whereby the slot is adapted to receive a plurality of conductors. 6. An electrical connector comprising an electrically insulated housing and a connector element of any preceding claim. 7. An electrical connector comprising two or more connector elements of any preceding claim whereby the connector elements are arranged in series and whereby the slot size of each connector element becomes narrower along the series. 8. An electrical connector comprising a plurality of connector elements according to any of claims 1 to 5 whereby the connector elements are arranged in parallel in such a way that the first and second portions of adjacent connector elements are substantially perpendicular.

Inventors: HEBENSTREIT MARTIN, ODLEY RICHARD AUSTIN, HEBENSTREIT, MARTIN, ODLEY, RICHARD, AUSTIN
Applicants: AUSTIN TAYLOR COMMUNICAT LTD, HEBENSTREIT MARTIN, ODLEY RICHARD AUSTIN, AUSTIN TAYLOR COMMUNICATIONS LIMITED, HEBENSTREIT, MARTIN, ODLEY, RICHARD, AUSTIN
Application year: 1995
Main classification: H01R4
IPC codes: H01R4