ELECTRICAL CONNECTOR

Abstract: An electrical connector has input and output terminals (12, 24, 26) which are interconnected by a transformer (16). The transformer provides electrical isolation and/or impedance matching between input and output terminals.

Description: ELECTRICAL CONNECTOR This invention relates to electrical connectors including an electrical connector which provides conductive isolation between input and output terminals and more particularly but not solely provides impedance transformation between input and output terminals and a connector which employs insulation displacement contacts and a method of connecting a cable to such a connector. The interconnection of equipment and/or supply lines in order to couple ac signals sometimes require d.c. isolation and often require impedance transformation in order to match the impedance of the coupled equipment or lines to provide maximum power transfer. It is often a requirement to provide interconnection between a coaxial line or connector and a two wire balanced or unbalanced line, or two terminal device, or between different impedance coaxial or two wire lines. One aspect of the present invention has been arrived at from a consideration of this requirement. According to one aspect of the invention there is provided an electrical connector having input and output terminals interconnected by a transformer. The connector may comprise a circuit board to which the transformer windings are connected and coupled to the input and output terminals. The transformer may be mounted on the circuit board. Preferably the transformer is formed on a torroidal core which torroidal core may be annular. At least one of the input or output terminals may comprise an elongate contact which extends through the void of the toroid and which may be secured to the printed circuit board. The circuit board preferably extends transversely of and is a snug fit within a hollow elongate body of the connector and may be a printed circuit board to which the transformer and input and output terminals are connected. Connectors are normally joined to the wires of cables by soldering or sometimes by wire wrapping. Terminals are often very close together and connectors are often required to be mounted close together on a panel. In such circumstances it is often difficult to terminate wires reliably and simply. The second and third aspect of this invention have been arrived at from a consideration of these requirements. According to a second aspect of the invention there is provided an electrical connector, comprising a body provided with a plurality of insulation displacement contacts extending substantially in parallel and each coupled directly or indirectly to a mateable contact of the connector, a housing locatable on the body over the insulation displacement contacts, a cable receiving element locatable in the housing and adapted to receive and position wire ends of the cable such that the wires each align with and are pierced by a different one of the insulation displacement contacts as the housing is located onto the body. According to a third aspect of the invention there is provided a method of connecting a cable to an electrical connector, comprising the steps of inserting the cable through a housing and through a cable receiving element, bending the wires around the end of the cable receiving element into predetermined relative dispositions, withdrawing the cable receiving element into the housing, introducing into the housing an electrical connector having parallely extending insulation displacement contacts which are disposed so as to align with said predetermined relative dispositions, effecting relative displacement between the housing and the connector to cause the connector to be forced into the housing such that the contacts pierce the insulation and make contact with the wires. In order that the invention and its various other preferred features may be understood more easily, some embodiments thereof will now be described, by way of example only, with reference to the drawings, in which:- Figure 1 is an axial cross sectional view of an electrical connector constructed in accordance with the invention, Figure 2 is a schematic circuit diagram showing the coupling provided by the connector of Figure 1 between coaxial and balanced or twisted pair lines, Figure 3 is a schematic circuit diagram showing an alternative coupling arrangement between a coaxial line and a pair of lines one of which forms an earth return line. Figure 4 is an axial cross sectional view of an electrical connector constructed in accordance with the invention for coupling coaxial lines of different impedance, Figure 5 is a schematic circuit diagram showing the coupling provided by the connector of Figure 4 between two coaxial lines, Figure 6 illustrates the individual components of a connector constructed in accordance with a second aspect of the invention, and Figures 7 to 13 illustrate steps in the assembly of the connector components of Figure 6 and the connection of a cable Referring now to Figures 1 δ. 2 there is shown an electrical- connector having an elongate tubular metal housing 10 the right hand extremity of which forms the outer terminal of a coaxial connector. The inner terminal 12, of the coaxial connector, in the form of an elongate pin 12 extends within the housing through an insulator 14 which is a sliding fit within the housing and which serves to support the terminal 12. This forms a typical coaxial connector interface. The terminal 12 extends through the void of a torroidal transformer 16 which can be a snug fit so that the toroid is effectively threaded onto the terminal. The terminal end extends through a hole in a printed circuit board 18 which is mounted transversely of the housing and which is a snug fit therein and may be secured and coupled thereto by soldering or swaging. The printed circuit board may be double sided. The terminal may be secured to a track on the printed circuit board by soldering or by swaging or riveting. The hole may be plated through to improve connection to the terminal. The transformer 16 has a winding 20 (Figure 2) which has one end coupled to a track on the board which is connected to the terminal 12 and another end connected to a track on the board which is electrically connected to the housing 10. A second winding 22 has its end connected via tracks on the printed circuit board to different ones of a pair of pcb socket connectors 24, 26 for connection to a balanced or twisted pair of lines 28. As will be seen from the circuit diagram of Figure 2 the connector provides d.c. isolation between the coaxial terminals and the two wire terminals and by appropriate choice of turns ratio of the windings also provides for impedance transformation to permit matching between lines of different impedance thereby to permit maximum signal power transfer. Such a transformer is sometimes known as a Balun transformer. The drawing of Figure 2 shows an optional earth return terminal 30 which is connected to the housing 10 and which can be used for connection to a screen of the balanced or twisted pair lines. It will be appreciated that although a balanced pair of lines is suggested in Figure 2, it is possible to couple to a pair of lines one of which is earthed by connecting one of the terminals 24 and one end of the second winding 22 to the housing. Such an arrangement is illustrated in the schematic circuit diagram of Figure 3. The drawings of Figure 4 shows a coaxial to coaxial connector having one coaxial interface identical with that of Figure l but having instead of a wire termination at the opposite end a socket type coaxial connector at the other end which has a central contact 32 which is connected to a track on the printed circuit board 18 and from there to one end of the second winding of the transformer the other end of which is connected to the housing 10 via a track on the printed circuit board. Alternatively, a second printed circuit board may be provided for receiving and securing the socket contact similar to the arrangement of board 18 and terminal 12. In such an arrangement wired connections between the two boards would be required. Figure 5 shows schematically the electrical connection of the construction of Figure 4. By appropriate choice of turns ratio different impedance lines can be coupled and matched e.g. 75 ohms to 120 ohms. It will be appreciated that a connector using the principles of this invention can be constructed to provide coupling between balanced two wire and balanced two wire lines, between balanced two wire and non balanced lines, between coaxial and balanced or non balanced two wire lines or between coaxial and coaxial lines. Although the construction of Figure 1 is shown to have a plug type coaxial portion a socket type portion could be provided instead. Although the construction of Figure 4 has a plug type coaxial portion and a socket type coaxial portion a plug to plug or socket to socket type connector could be provided. The transformer shown in the drawings is formed on a toroid which is preferably annular but may be of other form defining a closed magnetic loop e.g. rectangular. Such an arrangement is advantageous in terms of space saving in that it can be arranged transversely of the longitudinal axis of the connector and permit the terminal (s) to extend through its void to the circuit board. if space is of less significance then any other type of transformer can be employed. Although the schematic circuit diagrams show the first and second winding to be separate winding they can, if electrical isolation is not required, be part of a single winding auto transformer having appropriate taps connected to the terminals. The invention also includes a multi pin connector having a pin and/or socket contacts for signals or d.c. connection incorporating input and output terminals interconnected by a transformer as previously described. Advantages of using a printed circuit board in the end of the connector housing in the manner illustrated are: - (a) it provides a mounting for the transformer (b) it provides a simple means for terminating the inner terminal 12 and making connections to the transformer (c) it provides mechanical support for and positions the inner terminal 12 (d) it permits terminals to be provided in the form of standard PCB socket connectors, for example insulation displacement connectors, as illustrated in Figure 1. Alternatives are the provision of solder pads to permit connection to lines of a cable or the provision of contacts for mating with another connector. The connector could form an adaptor which accepts the conductors of a pair of cables or provides for interconnection between two cables which are terminated each by a plug or socket. (e) it facilitates electrical connection between the housing of the connector and the transformer winding. A particularly advantageous arrangement of connector which facilitates connection of the wires of a cable will now be described. These features can be employed with the connector which has been described in connection with Figures 1 to 5 or can be used with other typed of electrical connector. Figure 6 shows the individual components of a connector comprising a housing 40, a cable clamp 42, a locking ring 44 and a body 46. The body illustrated is a coaxial connector part, which may incorporate the features of Figures 1 to 5, having an axial pin 48, carried in an insulator, the body having a cylindrical metal casing 50 having portion 52 at one end surrounding the pin and coaxial therewith to form an end for coupling to a complementary connector. The portion 52 has an undercut 54 which circumvents the outer cylindrical surface and which serves to receive the locking ring 44 as will be hereinafter described. The other end of the body is substantially rectangular in cross section and has the corner edges of the casing inwardly tapered to facilitate insertion into the housing 40. The corners are each provided with a notch 56 between adjacent faces, which notches are disposed on a common cross sectional plane spaced from the end for cooperation with formations provided in the housing 40. The rear of the body is illustrated in Figure 7 from which it can be seen that an insulator 58, for example the insulator in which the pin is mounted or a circuit board such as 18 as shown in Figures 1 & 4, is provided with three insulation displacement contacts 60 which extending outwardly, are substantially mutually parallel, and are parallel to the axis of the body. The housing 40 is of rectangular open ended box like configuration at one end except that the internal peripheral surface does not have abrupt corners. A pair of rectangular cut outs 62 are provided one in each of two opposite walls of the box like end and thereby isolate corner webs 64 which serve to engage the notches 56 of the body when it is inserted into the housing the notches and webs thereby forming a latching arrangement for securing the body in the housing. The other end of the housing is formed by a cylindrical portion 66 which communicates with the interior of the rectangular part of the housing. The cable clamp 42 is moulded from an insulating material and at one end has a portion 68 of substantially circular cross section of diameter equal to the internal diameter of the cylindrical portion 66 of the body 40 and at the other end has a flange 70 of cross sectional dimensions conforming to the cross sectional dimensions of the interior of the rectangular part of the housing. The portion 68 has a longitudinal channel 72 which, as illustrated is an open channel forming a substantially "U" shaped slot, but could be a through bore, for receiving a cable end. The channel communicates with an aperture 74, which extends through the flange 70, and with three grooves 76, 78, 80 which extend outwardly along the end face of the flange and adjoin peripheral grooves 82, 84 & 86 respectively. The three grooves are also provided with a slot 88, 90, 92 which extends transversely of and to each side of the groove. The slots are mutually disposed so as to permit entry of one of the insulation displacement contacts 60. The assembly of the connector including attachment of a cable and termination to the wires of the cable will now be described with reference to Figures 8 to 13 of the drawings. Figure 8 shows a cable with its outer insulation jacket 90 trimmed back to expose two insulated wires 92, 94 and one none insulated wire 96 ready for termination to the connector. The prepared cable end is inserted through the cylindrical portion 66 of the housing 40 as shown in Figure 9. The cable end is then introduced from the rear of the cable clamp 42 into the channel 72 and the wires 92, 94, 96 are threaded through the aperture 74 in the flange 70 until the outer jacket touches a back face of the flange. This location is illustrated in Figure 10. The wires are then bent back over the flange end and down into one of the grooves 76, 78, 80 and back along an associated peripheral groove 82, 84, 86. In the drawing the wires are shown prior to pressing into the grooves. The grooves are sized such that the wires are a close fit and because of the tight bends they impose on the wires a "capstan effect" results in a high degree of retention. When the wires have been pressed into the grooves they are trimmed back as close as possible to the flange as is illustrated in Figure 11. The cable clamp is now pushed into the housing until it sits fully into the cavity as illustrated in Figure 12. The bore of the cylindrical portion 66 is inwardly tapered towards its extremity, or the portion 68 of circular cross section is inwardly tapered towards its extremity such that the "U" channel is compressed as the clamp 42 is inserted into the housing 40 and effects clamping onto the cable insulation jacket 90. The clamping is enhanced by notches 95 towards the extremity of the channel. The cable preparation is now complete. In order to terminate the cable to the body 46, the body is inserted into the box like open end in the direction of the arrow X shown in Figure 13 after first having ensured the correct orientation to permit alignment of the insulation displacement contacts with the slots 88, 90, 92 (Figure 6). The close fit automatically ensures that the contacts enter the slots as the connector is pressed into the housing and the contacts are caused to displace any insulation on the wires and to make secure contact with the wires themselves. The depth of penetration of wire into the slot is controlled by the depth of the wire retention grooves 76, 78, 80. The bare wire groove 80 is arranged to be relatively shallow. The slots provide support for the tines of the insulation displacement contacts which could otherwise become damaged if for example oversized wires were to be used in the assembly. At full insertion the extremity of the rectangular end of the housing 40, having been stretched by pushing up the tapered end of the body 46, results in snap engagement of the webs 64 each into a respective notch 56 in the connector body thereby providing a latching action. The clamping between the housing and the cable effected by cooperation with the cable clamp, and the latching between the housing and the body as the connection to the wires by the insulation displacement contacts is made results in mechanical integrity between cable and connector which provides strain relief such that the assembly resists breaking of the connection in the event of a pull on the cable. As all three insulation displacement connectors are mated simultaneously as the connector is pushed into the housing, the mating force could be quite high and it is envisaged that a mating tool for completing the insertion might be employed. When the termination is completed the locking ring 44 can be pressed onto the body and snapped into the undercut 54 this locking ring serves to locate the connector on a panel. The arrangement enables connectors to be mounted on panels with small distances between centres and it is possible to produce connectors which can be mounted with 10mm between centres with the connectors staying within a 10mm square available space. The terminating arrangement employing insulation displacement connectors enables simple termination with a minimum of tools and without soldering. The exemplary embodiment of electrical connector and terminating arrangement illustrated in Figures 6 to 13 employs a cable having 3 wires, however it will be appreciated that 2 or more than 3 wires may be employed and such constructions are intended are fall within the scope of this invention. Although a specific latching arrangement is described for securing the body 46 in the housing 40 other latching configurations can be employed as can any means for securing the body in the housing.

Claims: CLAIMS : 1. An electrical connector having input and output terminals interconnected by a transformer. 2. An electrical connector as claimed in claim 1, wherein the transformer is formed on a torroidal core. 3. An electrical connector as claimed in claim 2, wherein at least one of said input or output terminal comprises an elongate contact which extends through the void of the toroid. 4. An electrical connector as claimed in claim 3 , wherein the torroidal core is annular. 5. An electrical connector as claimed in any one of the preceding claims, comprising a circuit board to which the transformer windings are connected and coupled to the input and output terminals. 6. An electrical connector as claimed in claim 5, wherein the transformer is mounted on the circuit board. 7. An electrical connector as claimed in claim 5 or 6, wherein said at least one of the input and output terminals is secured to the circuit board. 8. An electrical connector as claimed in claim 7, wherein the printed circuit board has one or more holes through which a terminal extends. 9. An electrical connector as claimed in claim 8, wherein said one or more holes are plated through holes to which a terminal is connected by soldering. 10. An electrical connector as claimed in any one of the preceding claims, wherein one of the terminals forms part of a coaxial connector. 11. An electrical connector as claimed in any one of the preceding claims, wherein one of the terminals is a two wire or two pole connection. 12. An electrical connector as claimed in any one of the preceding claims, wherein one of the terminals is a balanced two wire or two pole connection. 13. An electrical connector as claimed in any one of claims 5 to 9, wherein one of the terminals is a coaxial termination and the connector has a hollow elongate body forming the outer contact of the coaxial termination and the circuit board is mounted transversely of the elongate body and has a terminal contact coupled thereto. 14. An electrical connector as claimed in claim 13, wherein the other of the terminals provides a two wire or two pole connection. 15. An electrical connector as claimed in claim 14, wherein the two wire or two pole connection forms a balanced output connection. 16. An electrical connector as claimed in claim 13, 14 or 15, wherein the circuit board extends transversely of and is a snug fit within the hollow elongate body. 17. An electrical connector as claimed in any one of claims 5 to 9 or 13 to 16, in which the circuit board is a printed circuit board to which the transformer and input and output terminals are connected. 18. An electrical connector as claimed in any one of claims 13 to 17, wherein the transformer has one winding which is coupled between the inner coaxial terminal contact and the body of the connector and another winding connected between the other terminals or poles of the connector to provide a balanced termination. 19. An electrical connector as claimed in any one of claims 13 to 17, wherein the transformer has one winding which is coupled between the inner coaxial terminal contact and the body of the connector and another winding which is connected between another terminal and the body of the connector. 20. An electrical connector substantially as described herein with reference to Figures 1 to 5 of the drawings. 21. An electrical connector, comprising a body provided with a plurality of insulation displacement contacts extending substantially in parallel and each coupled directly or indirectly to a mateable contact of the connector, a housing locatable on the body over the insulation displacement contacts, a cable receiving element locatable in the housing and adapted to receive and position wire ends of the cable such that the wires each align with and are pierced by a different one of the insulation displacement contacts as the housing is located onto the body. 22. An electrical connector as claimed in claim 21, wherein the cable receiving element is adapted to clamp the wire ends. 23. An electrical connector as claimed in claim 22, wherein the cable receiving element has an axial channel, through which the cable passes, and at one end a plurality of peripheral grooves are provided into which the wire ends can be clamped after bending backwardly. 24. An electrical connector as claimed in claim 23, wherein the axial channel is a "U" shaped slot extending along the cable receiving element. 25. An electrical connector as claimed in claim 23 or 24, wherein the cable receiving element has an outwardly directed flange at said one end in which the peripheral grooves are provided. 26. An electrical connector as claimed in claim 23, 24 or 25, wherein the peripheral grooves extend inwardly along the end of the cable receiving element to the axial channel. 27. An electrical connector as claimed in claim 26, wherein the end of the cable receiving element is provided with slots which extend transversely of and to the sides of the grooves and are positioned to receive the insulation displacement contacts. 28. An electrical connector as claimed in any one of claims 23 to 27, wherein the cable receiving element is resilient and the housing is inwardly tapered towards the rear and serves to compress the cable receiving element onto the cable outer sleeve to aid retention of the cable in the housing. 29. An electrical connector as claimed in any one of the preceding claims in which cooperating latching means is provided on the body and the housing whereby retention of the housing on the body is effected. 30. An electrical connector as claimed in claim 29, wherein the body and the inside of the housing are provided one with a projection and one with a cooperating peripheral groove together forming the latching means. 31. An electrical connector as claimed in claim 29, wherein the body, at the insulation displacement contact end, is substantially rectangular in cross section and is provided with notches between adjacent faces in a cross sectional plane spaced from the insulation displacement contact end and the housing has a complementary rectangular entry section for receiving the body and is provided with a pair of oppositely disposed wall apertures which isolate a leading section which latches into the notches. 32. An electrical connector substantially as described herein with reference to Figures 7 to 13 of the drawings. 33. An electrical connector as claimed in any one of claims 1 to 20 and incorporating the features of any one of claims 21 to 32. 34. An electrical connector as claimed in any one of claims 21 to 32 and incorporating the features of any one of claims 1 to 20. 35. A method of connecting a cable to an electrical connector, comprising the steps of inserting the cable through a housing and through a cable receiving element, bending the wires around the end of the cable receiving element into predetermined relative dispositions, withdrawing the cable receiving element into the housing, introducing into the housing an electrical connector having parallely extending insulation displacement contacts which are disposed so as to align with said predetermined relative dispositions, effecting relative displacement between the housing and the connector to cause the connector to be forced into the housing such that the contacts pierce the insulation and make contact with the wires. 36. A method of connecting a cable to an electrical connector substantially as described herein with reference to Figures 7 to 13 of the drawings.

Inventors: LAVERICK ROBERT CLEMENT, LAVERICK, ROBERT, CLEMENT
Applicants: ITT IND LTD, LAVERICK ROBERT CLEMENT, ITT INDUSTRIES LIMITED, LAVERICK, ROBERT, CLEMENT
Application year: 1996
Main classification: H01R13
IPC codes: H01R4, H01R9, H01R13