GB2300527A

GB2300527A - An electriccal connector a for coaxial cable

Info

Publication number: GB2300527A
Application number: GB9609098A
Authority: GB
Inventors: Vincent Shepherd
Original assignee: Caradon MK Electric Ltd
Current assignee: Caradon MK Electric Ltd
Priority date: 1995-05-01
Filing date: 1996-05-01
Publication date: 1996-11-06
Anticipated expiration: 2016-05-01
Also published as: GB9508839D0; GB9609098D0; GB2300527B

Abstract

A co-axial socket outlet (1) has improved connection between inner (108) and outer (104) conductors of a co-axial cable (100) and respective first (57) and second (6) connectors of the outlet (1), achieved by inserting the inner conductor (108) into the first connector (57) along a first longitudinal axis (X) and then bending the cable (100) at right angles to insert it laterally into a mouth (50) of the second connector (6) so that it is clamped into the mouth to be in the right angle direction (W) away from the first connector. This achieves a robust and compact result.

Description

Electrical connector The present invention relates to a means for making an electrical connection to a co-axial cable at an electrical wiring accessory providing a co-axial socket outlet.

Co-axial cable is frequently used for distributing electrical signals, for example television and radio signals, to an electrical wiring accessory providing a co-axial socket outlet. Co-axial cable is formed with a insulated centre or inner conductor surrounded by an outer conductive sheath the whole being protected by an external insulating sheath. Co-axial cables are known with more than one centre or inner conductor. The purpose of the conductive sheath is to minimise the interference picked up by the cable and to form an outer conductor. The purpose of the insulation around the centre or inner conductor is to both provide an electrically insulating spacer between the conductors, and to ensure that the cable has an impedance suitable for the transmission of the signals. Hence the insulating spacer is often formed of a cellular plastics material.Care ;-.as to be taken not to crush the insulating spacer as this alters the impedance of the cable and may interfere with the transmission of the signals. Electrical connections are made to the centre or inner conductor and the conductive sheath. To make a connection it is normal to remove a length of the external sheath and then to cut back the conductive sheath to expose the insulating spacer, and then to remove a short length of the insulating spacer from the centre or inner conductor to expose it. Electrical connection is commonly made to the outer conductive sheath by a clamp type terminal, and to the centre conductor by a tunnel type terminal.The clamp type terminal for the outer conductive sheath commonly comprises a metal strap with t screw passing through each end to enable the strap to be screwed down against a conductive plate.

The clamp onto the external sheath may also act as a strain relief, although where this is considered essential it is good practice to use a collet type of clamp on the outer-most insulation. Co-axial socket outlets are normally used to provide a termination for a co-axial cable at a convenient point in a room so that an occupant of the room may readily connect a television or radio or similar equipment to a said socket using a suitably terminated lead.

To connect a co-axial cable to an existing design of terminal connections it is necessary to either dismantle the clamp type terminal to enable the co-axial cable to be inserted after the centre or inner conductor has been secured in the appropriate terminal, or it is necessary to feed the co-axial cable axially through the clamp type terminal until the centre or inner conductor has entered its terminal a sufficient amount. Either method is both time consuming and inconvenient.

A terminal for co-axial cable is disclosed in EP 0 211 710, where the clamping member is formed as a resilient substantially U shaped clamp, which is fitted to a printed circuit board by soldering. The intention of the arrangement disclosed in EP 0 211 710 is to enable connection to the conductors of a co-axial cable which is positioned on the side of the printed circuit board away from the printed side which is formed with the conductors.

Hence the terminals disclosed have legs which fit through holes in the circuit board and are soldered on the printed side of the circuit board. For an electrical accessory providing a co-axial socket outlet such an arrangement would be impossible to use, since the co-axial socket must necessarily be positioned on a side of the printed circuit board facing to the front of the electrical accessory, and the connections are most conveniently made on an other side of the printed circuit board facing to the rear of the electrical accessory. Known arrangements for connecting to co-axial socket outlets have overcome this problem by the use of hand soldering. The disadvantage of hand soldering is cost and the need to avoid exposure of operators to solder fumes as much as possible.

It is an object of an embodiment of this invention to simplify the connection and to reduce the time required to connect an electrical conductor to an electrical terminal.

A co-axial cable termination according to this invention comprises a first electrical connector for making electrical connection to an inner cable conductor, the first electrical connector being arranged that connection is by the insertion of the inner conductor into the first electrical connector along a first longitudinal axis, and a second electrical connector arranged for making electrical connection to an outer cable conductor when the outer conductor is aligned with a second longitudinal axis, the first longitudinal axis being at right angles to the second longitudinal axis, wherein the second electrical connector has an open mouth which is arranged to accept the outer conductor being inserted laterally into the mouth and arranged to close around the outer conductor to make electrical contact.

The benefit of this is that a co-axial cable may be easily and quickly inserted into the open mouth by an installer, without any time wasted having to unscrew and remove clamping screws or terminal screws. This has the additional benefit of eliminating the risk of losing small parts such as the screws on installation. Further the alignment of the axes of the first electrical connector and the second electrical connector at right angles to each other reduces the risk of the inner conductor being pulled out of the first electrical connector. The avoidance of applying a pull out force is particularly beneficial where it is desired to use a screwless terminal for the first electrical connector. The use of a screwless terminal for the first electrical connector further simplifies the installation and saves the installer time.

Preferably the first electrical connector is a screwless terminal, where the electrical connection is made by simply inserting the inner conductor into the terminal along the first longitudinal axis.

According to a further aspect of the invention a co-axial cable termination has the open mouth formed between on one side an upstanding wall and on another side a movable clamping member.

The benefit of having the upstanding wall is that as the clamping member which forms part of the mouth closes about the outer conductor of the coaxial cable, an end of the clamping member shuts the mouth by passing in front of the wall. Hence it is impossible for the co-axial cable to be removed by a lateral force from the mouth once it is closed. The benefit of this is that the co-axial cable is positively located in the correct position when held by the clamping member, and good electrical contact with the co-axial cable is assured.

Electrical connection is preferably made to the co-axial cable conductors, by first making the electrical connection to the inner conductor with the cable positioned substantially in line with the first longitudinal axis, and then the cable is pivotally moved about the first electrical connector until it is substantially parallel to the second longitudinal axis, so as to enable the outer conductor to be inserted into the open mouth under the clamping member in a direction at right angles to the longitudinal axis of the conductor, the clamping member is then arranged to close about the outer conductor to make the electrical connection between the outer conductor and the second electrical connector.

Preferably the clamping member has an arctuate shape. The benefit of this is to permit an adequate clamping force without crushing a deformable support core within the electrical conductor. Co-axial cables are frequently provided with a cellular plastic annular insulator between an inner conductor and the external conductor. It is important not to crush this cellular plastic annular insulator as crushing it would affect the impedance of the cable and would cause attenuation of the signal.

A further disadvantage of the arrangement disclosed in EP 0 211 710 is that to provide an installer with alternative terminal locations the clamping members would have to be duplicated at each location.

Preferably the clamping member of the invention is moveable between at least two alternative terminal locations. The benefit of this is to increase the flexibility of the product providing alternatives that the installer may select to suit the particular requirements of a particular installation, while ensuring minimum product cost by only supplying one clamping member and clamping screw. A further advantage is that since the clamping member inevitably protrudes the rear of the electrical accessory there is a risk of accidental electrical contact with another conductor or the risk that the protruding clamping member would damage a cable trapped behind the accessory which would lead to signal interference.

in EP 0 211 710 the co-axial terminal shown is formed as a U shape where the U is orientated so that the arms are parallel with the longitudinal axis of the co-axial cable. However, to permit the screw to be inserted the arms are displaced to one side of the longitudinal axis. This is undesirable as it produces a torsional moment between the arms which has to be resisted by the hinge portion of the U shape.

According to an embodiment of the invention the clamping member is provided with a clamping screw arranged to close the mouth onto the outer conductor at a conductor location the clamping screw acting to one side of the conductor location so as to enable insertion of the outer conductor in a direction laterally to the second longitudinal axis into the mouth under the clamping member. Preferably the clamping member is formed so that the a screw receiving portion is formed in a lower arm of a single component formed in a U shape to receive the clamping screw, and the clamping member which is formed as the upper arm of the U shape has a hole for the clamping screw to pass through.To ensure the co-axial cable is secured firmly against the outer conductor without applying unnecessary stress to the printed circuit board, the lower arm is preferably positioned against the printed circuit board on the other side to the side bearing the conductor, and the clamping member is retained in the correct position by passing the clamping screw through the upper arm, then through a hole in the printed circuit board, and then into the screw receiving portion of the lower arm. To ensure the clamping force is applied optimally to Yhe co-axial cable it is preferable for the U shape to be orientated so that the arms are at right angles to a longitudinal axis of the co-axial cable.

Since it is preferable to solder the printed circuit board on the rear facing side, this is the side that must be formed with printed conductors, hence in clamping the outer conductor of the co-axial cable against this side the outer conductor preferably makes direct electrical contact with an enlarged pad area of one of the conductors. This ensures good electrical contact. A further advantage of soldering on the rear facing side is that other discrete electronic components such as capacitors that may be required may be fitted from the front facing side of the circuit board.The benefit of this is that the depth of a mounting box required for mounting the electrical accessory to a surface is determined by the protrusion of the rear of the electrical accessory behind a planar face of the mounting surface, and since by its nature the co-axial socket is the longest component, and hence an overall length of the co-axial socket determines a depth of the circuit board behind the planar face, and by mounting any other discrete electronic components on a front facing side a further increase in the overall depth of the electrical accessory is avoided.

In use a user will be concerned about the external protrusion of both a front surface of the electrical accessory, and the amount of space required to be allowed in front of the planar surface for the correct running of a flexible co-axial cable connected to a plug inserted in the socket. To ensure that this amount of space is minimised, the co-axial socket is preferably mounted downwardly inclined at an acute angle to the planar face. Hence not only is any bending of the flexible co-axial cable in order for it to hang against the planar surface reduced, but also depth of rearward protrusion of the electrical accessory may be further reduced. Preferably the rearward protrusion is such that the electrical accessory may be mounted to a standard 15 mm plaster depth mounting box.

According to another embodiment of the invention the clamping member is resilient and is arranged to exert a force to retain the electrical conductor under the clamping member without the use of a clamping screw.

An embodiment of the invention will be now described by reference to the following figures where: Figure 1 shows a rear perspective view of a co-axial socket outlet showing a frontplate for mounting the socket on the wall mounting, and a rear cover moulding which shrouds the electrical components of the socket apart from terminals for co-axial cable conductors; and Figure 2 shows a view of a cable clamping member as used in the socket outlet shown in Fig. 1; and Figure 3 shows another view of the cable clamping member shown in Fig. 2; and Figure 4 shows a sectioned side view of the co-axial socket outlet shown in Fig. 1.; and Figure 5 is a sectional view showing an alternative arrangement of the electrical termination for the outer conductor, taken on plane AA of Fig. 1.

Figure 1 shows an electrical accessory co-axial socket outlet 1, comprising a frontplate 2 for mounting the socket outlet on a surface with screws (not shown) passed through fixing holes 3 (only one visible) in the frontplate, and because the co-axial socket outlet shown in this Fig. 1 is a two gang socket outlet, a pair of rear covers 4 and 4' which each shrouds electrical components of its respective socket.

A co-axial cable 100 is shown fitted to the second socket in Fig. 1, and comprises an outer sheath or outer insulation 102, an outer conductive sheath or outer conductor 104, a cellular insulating spacer 106, and an inner conductor 108.

A first electrical connector 57 comprises a hole 5 in the rear cover 4 for access to a screwless terminal 56 (visible in Fig. 4) for making electrical connection to the inner conductor 108, and a second electrical connector 6 for making an electrical connection to the outer conductor 104 of the co-axial cable 100. The connector 6 comprises a cable clamping member 10 which is closed by means of a clamping screw 12 and a conductive pad 58 formed on a rear surface 52 of a printed circuit board 54. Alternative connector locations 14 and 14' are provided, which are primarily intended for use with a single gang socket outlet when they allow an installer the flexibility of changing the side from which the co-axial cable must enter the product.

Hence from Fig. 1 it may be seen that the cable may enter a single socket from either the direction of the Y arrow or the W arrow. On a two gang socket outlet such as that illustrated in Fig. 1 although it would be feasible to remove one cable clamping member 10 and the associated clamping screw 12 and reposition it to the alternative connector location 14, there would be a risk that a co-axial cable fitted in this location would foul the base 4' of the other socket.

Figs. 2 and 3 show perspective views of the clamping member 10. The clamping member comprises an upper arm 32 and a lower arm 34 joined together by a hinge portion 33. The upper arm has an arcuate end 30 under which the outer conductor 104 of the co-axial cable is clamped. The arcuate end 30 has a slight transverse curve 40 so that edges 42 and 44 bite into the outer conductor to obtain a good grip to resist axial movement. Two half shears 47 and 48 are provided at a join 49 between the upper arm 32 and the hinge portion 33. The upper arm 32 also has a hole 36 through which clamping screw 12 may pass, and the lower arm 34 has a screw receiving portion 38 formed to receive the clamping screw and engage with a threaded portion 13 of the clamping screw 12.The half shears permit the transverse curve 40 to extend down the arm towards the hinge portion to strengthen the arm particularly adjacent to the hole 36 and the half shears also reduce the strength of the joint between the upper arm and the hinge portion to encourage bending due to tightening of the clamping screw to take place at the join 49. At the free end of the lower arm 34 is a tang 46 which locates in a co-operating feature (not visible) of the frontplate 12 to resist the tuming moment when the clamping screw 12 is tightened.

In Fig. 4 a co-axial socket 90 is shown partly sectioned, which is electrically connected to a printed circuit board 54. The rear cover 4 is mounted to the frontplate 2 by snap fits 7 and 8, and the printed circuit board is located on pillars 64 and 66 and is retained by ledge 68 and an edge 17 of a curved wall 16 and the corresponding curved wall 18 at the alternative location.. A centre socket 92 of the co-axial socket 90 is soldered with solder 96 to a pad (not shown) surrounding a hole 60 in the circuit board 54. The centre socket 92 is electrically connected by the printed conductive tracks (not shown) on the rear surface 52 to the screwless terminal 56 and likewise an outer socket 94 of the co-axial socket 90 is electrically connected to the conductive pad 58 of the second connector 6. Arrow X indicates the direction of a first longitudinal axis which is shown by centre line 62, and passes through the centre of the hole 5 and the centre of the screwless terminal 56. Groove 20 is provided adjacent to hole 5 to receive the inner conductor 108.

An upstanding wall is formed by the curved wall 16 where the rear cover 4 meets the circuit board adjacent to conductive pad 58 and likewise by curved wall 18. The upstanding wall prevents the co-axial cable from being removed from under the closed clamping member 10 by force applied in the lateral direction along the line of arrow Z.

Fig. 5 shows an alternative clamping arrangement, where a resilient clamp 80 is provided, which is shown in a deflected state, held open by a force in the direction of arrow F so that a co-axial cable may be inserted into a mouth 82. Mouth 82 is formed on one side by an extension 84 and on the other side by a radius 15" formed where wall 16" meets the rear surface 9" of rear cover 4". In use this alternative arrangement works in the same way as that shown in Figs. 1 to 4, except that the clamping screw is not required as the necessary clamping force to retain an outer conductor under the arcuate end 86 is provided by the resilience of the clamping member 80.

For the embodiment of the invention described above by reference to Figs 1 to 4, an installer would first assess the best way to lay the cable in the mounting box to minimise cable bending. For a single gang co-axial socket outlet the co-axial cable may enter from the direction of either arrow W or arrow Y. The installer would then ensure that the cable clamping member 10 was fitted to the appropriate clamping location 14 or 14' of the circuit board of the co-axial socket outlet. If it is necessary to change the location of the cable clamping member 10, the installer simply has to remove the clamping screw 12 and withdraw the clamping member 10 from under the circuit board 54, and then slide it back under the circuit board 54 at the alternative connector location 14 on the other side of the co-axial socket outlet module.

Replacing the clamping screw 12 retains the clamping member to the printed circuit board in the alternative location as the screw passes through the hole The installer then strips the outer insulation 102 and part of the outer conductor 104 from the co-axial cable 100 in a conventional manner, to expose a short length of the inner conductor 108 and a short length of the cellular insulating spacer 106 as shown in Fig. 4. The cable is then held perpendicular to the rear of the co-axial socket outlet as shown in Fig. 4, and the exposed portion of the inner conductor 108 is inserted in the direction of arrow X into the rectangular hole 5 along the centre line 62 in the direction of the first longitudinal axis. The installer then is able to bend the inner cable conductor 108 adjacent to the hole 5 through 90 degrees so that it lies down in the groove 20.The installer then can slide the exposed outer conductor 104 laterally in the direction of arrow Z through the open mouth 50 under the adjacent cable clamping member 10, and tighten the clamping screw 12 to make the electrical connection between the conductive pad 58 and the outer co-axial cable conductor 104. In addition to making the electrical connection simply tightening the one clamping screw 12 also provides strain relief by means of the edges 42 and 44 biting into the outer conductor 104. The insulation provided by the groove 20 in the rear moulded cover 4 minimises the risk of a short circuit between the inner and outer conductors as it separates the conductive pad 58 from the screwless terminal 56. The shape of the cable clamping member ensures that as it is tightened the cable is securely retained without unduly deforming the inner insulation. Deformation of the inner layer of insulation is undesirable since it alters the impedance of the cable, which would reduce the signal strength supplied to a television or radio connected to the co-axial socket outlet. The facility to connect the coaxial cable from either side of the socket outlet is also important in avoiding bending the co-axial cable. Sharp bends in the co-axial cable are undesirable as they cause changes the impedance of the cable because the insulation between the inner and outer conductors collapses by creasing at the point of the bend.

Claims

1. A co-axial cable termination comprising a first electrical connector for making electrical connection to an inner cable conductor, the first electrical connector being arranged that connection is by the insertion of the inner conductor into the first electrical connector along a first longitudinal axis, and a second electrical connector arranged for making electrical connection to an outer cable conductor when the outer conductor is aligned with a second longitudinal axis, the first longitudinal axis being at right angles to the second longitudinal axis, wherein the second electrical connector has an open mouth which is arranged to accept the outer conductor being inserted laterally into the mouth and arranged to close around the outer conductor to make electrical contact.

2. A co-axial cable termination as claimed in claim 1 wherein the first electrical connector is a screwless terminal, and the electrical connection is made by inserting the inner conductor into the terminal along the first longitudinal axis.

3. A co-axial cable termination as claimed in claims 1 or 2, wherein the open mouth is formed between on one side an upstanding wall and on another side a movable clamping member.

4. A co-axial cable termination as claimed in claim 3, wherein the electrical connection means further comprises a clamping screw arranged to close the mouth onto the outer conductor at a conductor location, the clamping screw acting to one side of the conductor location so as to enable the insertion of the outer conductor laterally into the mouth under the clamping member.

5. A co-axial cable termination as claimed in either one of claims 3 or 4, wherein the clamping member has an arcuate shape.

6. A co-axial cable termination as claimed in any one of claims 3 to 5, wherein the clamping member is locatable at one of at least two alternative locations.

7. A co-axial cable termination as claimed in claim 4, wherein the clamping screw is arranged to retain the clamping member to a conductive part of the second connector.

8. A co-axial cable termination as claimed in claim 7, wherein the conductive part is a conductive surface of a printed circuit board.

9. A co-axial cable termination as claimed in claims 8, wherein the clamping member is formed as a U shape with an arcuate upper arm and a lower arm, such that when located the printed circuit board is positioned between the arms, and the clamping screw passes through a hole in the upper arm, and through a hole in the printed circuit board, and into a screw receiving portion formed in the lower arm.

10. A co-axial cable termination as claimed in any one of claims 4 to 9, wherein the clamping member when clamped about the outer conductor, provides means to restrain the co-axial cable against an axial force.

11. A co-axial cable termination as claimed in either one of claims 9 or 10, wherein a co-axial socket is mounted to the printed circuit board on an opposite side to the conductive part.

12. A co-axial cable termination as claimed in claim 11 wherein the coaxial socket is inclined at an acute or obtuse angle to the printed circuit board.

13. An electrical accessory being a co-axial socket outlet having a coaxial cable termination as claimed in any one of the above claims.

14. A co-axial cable termination substantially as described by reference to the Figures 1 to 4 contained herein.

15. A co-axial cable termination substantially as described by reference to Figure 5 contained herein.