ELECTRICAL CONNECTORS

Abstract: An electrical connector (1) comprising interengaging first and second parts (3, 5), each of which parts comprises a housing (7, 9) having co-operating locking means such that relative rotation of the first part in abutting engagement with the second part causes mechanical interlocking of the housings, each part further comprising at least one electrode (17, 19) rotatable about the axis of the part which forms a complementary pair with an electrode of the other part, the connector being arranged such that the electrodes of each complementary pair are brought into contact during relative rotation between the two parts to establish electrical communication simultaneously with mechanical engagement, in which the co-operating locking means comprises a multiple-threaded screw arrangement (11, 11a, 13, 13a, 15, 15a).

Description: ELECTRICAL CONNECTORS This invention relates to electrical connectors. Many types of electrical connectors are known and used to provide a disengagable coupling for the free ends of electrical conductors, such as electrical cables. For example, British patent No. 1084811 discloses a plug and socket type connector comprising a plug part and a socket part adapted to co-operate axially together, each part including a contact element rotatable about the axis of the part, the connector further comprising locking means in form of a bayonet-type coupling wherein a peg and socket provided on respective parts of the connector co¬ operate together when the plug is introduced into the socket to permit axial and rotational movement between the two parts and allowing for the contact element of the one part to make abutting contact with that of the other part. The contact element(s) of one part is provided with a spring-loaded terminal pin and the contact element of the other part with a kidney-shaped electrode recessed in a socket of complementary shape to that of the electrode. The connector is arranged such that, on relative rotation of the plug and socket parts, the kidney-shaped electrode wipes across and depresses the terminal pins of the corresponding electrode to establish electrical communication. The present invention seeks to provide improved electrical connectors offering significant advantages over known connectors. According to the present invention there is provided an electrical connector comprising inter- engaging first and second parts, each of which parts comprises a housing having co-operating locking means such that relative rotation of the first part in abutting engagement with the second part causes mechanical interlocking of their housings, each part further comprising at least one electrode rotatable about the axis of the part which forms a complementary pair with an electrode of the other part, the connector being arranged such that the electrodes of each complementary pair are brought into contact during relative rotation between the two parts to establish electrical communication simultaneously with mechanical engagement and wherein the co-operating locking means comprises a multiple-threaded screw arrangement. The electrical connectors of the invention may be used to join the free end of a cable to the corresponding end of a similar cable or to an electrical appliance in such a manner that the cable may be readily disconnected as and when required. The electrical connectors of the invention find particular utility in the coupling of two cables, e.g., power leads, communications cables etc., as the connector parts may readily be securely interconnected and separated without risk of mechanical damage to either cable. The electrical connectors of the invention offer the combination of: small size, simplicity of construction, stability of the join and the ease by which the two parts may be engaged and disengaged. The use of a multiple-threaded screw arrangement (sometimes referred to as a "multi-start screw-thread") , that is, a screw-thread of coarse pitch in which two or more separate thread segments are used to reduce the overall size of the thread provides a more secure method of coupling the two parts of a connector together than the bayonet-type coupling normally used in conventional electrical connectors. The multi-start thread is more robust, less susceptible to cross threading and more reliable than equivalent helical thread, the overall mechanism is fully engaged in a fraction of a turn, with no mechanical loading placed on the electrodes. Unlike many known connectors, there is no requirement for one of each pair of electrodes to be spring-loaded to ensure that electrical contact is made between the connector parts on coupling, thereby reducing the complexity and hence the unit cost of the connector. Moreover, the extra stability afforded by the use of a multiple- threaded screw allows the electrodes of each pair to be contacted in either a radial plane of the connector or a plane parallel to the radial plane of the connector, instead of the more common end-to-end arrangement seen in conventional electrical connectors, thereby allowing for a 'shallower' connection between the two parts and hence a reduction in the overall size of the connector. The multiple-threaded screw comprises at least two, preferably at least three and normally four or five such thread segments, to allow the extent of relative rotation between the two parts required to effect their mechanical interlocking to be reduced. Preferably the extent of rotation to complete the locking action is reduced to less than 90°, more preferably from 20 to 60° and most preferably from 20 to 45". The use of three or more thread segments allows an even pressure to be distributed about the housing of each connector part to produce a more stable join. In order to provide the operator with a positive indication that the parts of the connector are fully engaged the two parts are preferably provided with complementary projections configured to provide an increase in resistance to rotational coupling followed by a sudden decrease in resistance, preferably associated with an audible click. Such arrangements are known, for example, on storage containers for medicinal tablets, capsules etc. The projections may conveniently be provided towards the end of one or more of the multistart thread segments. Alternatively, the projections may be elsewhere on the housing of the two parts. This positive lock indication is particularly advantageous when the connector is used by blind or partially sighted users and when it is not visually obvious that a connector is not fully engaged. The two parts of the connector may be arranged such that they may be engaged in a single or plurality of orientations. For example, if there are three symmetrically disposed electrodes in each part of the connector and it is not essential for particular electrodes to mate, the use of a three-start thread arrangement will allow the parts to be engaged in three possible positions. However, if it is essential that particular electrodes from the two parts of the connector mate, e.g., in the case of a power lead having live, neutral and earth wires, the connector is constructed such that engagement may take place in only one orientation. This may readily be achieved by varying the depths or thickness of the complementary parts of the multistart thread to allow only one possible position for engagement. Each part of the connector comprises at least one electrode rotatable about the axis of the connector. The electrodes of each connector part form complementary pairs with those of the other part such that when the two parts are mechanically interlocked, an electrical path is established between each complementary pair. Normally, two electrodes are all that is required for a cable containing two wires, one live and one neutral, although three electrodes may be provided for a cable additionally comprising an earth wire. Ordinarily, the electrodes of each connector part are off-set from the longitudinal axis of the connector, although one electrode of each part may be positioned on the axis of the connector. The housing of each connector part preferably enshrouds its electrodes to minimise the risk of accidental electrocution. The electrodes of each part preferably contact each other in the radial plane of the connector, with each electrode comprising a surface complementary in shape to that of the other electrode. One electrode of each pair may advantageously be configured so as to releasably secure the other when mechanical engagement of the two connector parts is achieved. In one embodiment of the invention, each complementary pair of electrodes may comprise a terminal pin and socket, the socket being shaped to allow for movement of the pin during relative rotation of the connector parts. The socket preferably comprises a slot or channel following an arcuate path to allow for circumferential movement of the terminal pin. The slot may have, for example, a kidney or tear-shaped cross- sectional profile. Preferably, at least a portion of the walls of the socket comprise a conductive material with relative movement of the connector parts causing the terminal pins of the other part to abut the conductive socket wall(s) to make electrical contact therewith. Alternatively, the electrode may be recessed into the slot such that relative movement of the connector parts causes the terminal pin to wipe across the surface of the recessed electrode to make electrical contact. Each slot is advantageously configured so as to releasably secure the terminal pin in position when mechanical engagement of the two connector parts is achieved. Preferably the electrodes of both parts of the connector are recessed to protect the electrodes from percussion damage and to ensure live electrodes are not exposed. This feature is particularly important in connectors for cables of telecommunications and computer equipment which may have a large number of fragile electrodes. The feature is also desirable in connectors for power leads since there are no exposed sharp pins which can be stepped on and the connector parts may have a smooth outer surface which reduces the tendency of injury if a lead having a connector part was swung and contacts a person. According to accident statistics published by the Consumer Affairs Department of the Department of Trade and Industry, there are numerous injuries caused by stepping on the pins of a conventional plug and by children swinging power leads having a traditional plug attached to one end. In one embodiment of the invention one or both of the connector parts incorporates a shuttering mechanism which shields the electrodes. The shutter may conveniently comprise a disc positioned in front of the electrodes and mounted for rotation. The shutter has appropriate apertures which may be aligned with the electrodes when the two parts of the connector are engaged and solid portions which cover the electrodes when the parts are separated. The shutter may conveniently be rotated by engagement with a projection on the other part of the connector or by one of the electrodes, e.g., an earth electrode, which is positioned to engage the shutter to expose the other electrodes before the other electrodes mate. The presence of a shutter also reduces possible contamination of the electrodes by dirt, water etc. The electrical connectors of the invention may advantageously incorporate an anti-tamper mechanism similar to those used in the tops of bottles containing medicines, detergents and other cleansing fluids (commonly referred to as "child-proof" caps) which can only be separated by the successive application of axial and rotational force to the connector. Whilst the electrical connectors of the invention are applicable to a wide variety of situations where it is desired to provide a readily disengagable coupling for the free ends of two conductors, they find particular utility in power leads for electrical appliances and in light fittings and especially lu inaires comprising a series of interchangeable parts for assembly by the consumer. Electrical appliances, particularly domestic appliances, such as, kettles toasters, mixers, drills, jig saws, sanding machines, etc., may be manufactured with one part of the electrical connector of the invention integrally formed therein. Power leads having the other part of the connector fitted at one end, preferably with moulded connections, may be separately supplied. Thus a consumer would need only a limited number of power leads to service a large number of appliances. This arrangement would reduce the cost of supplying electrical appliances since they would not require individual power leads and plugs, it would be more convenient to the consumer as the appliances could be stored without wrapping the power lead around the item and it would enhance public safety as power leads of various lengths could be supplied having the connector part and plug ready fitted thereby avoiding the possibility of the public attempting to safely wire a plug. According to a further aspect of the present invention there is provided a modular assembly for a luminaire comprising at least three separate components including a support body, an arm and a lampholder, the support body comprising at least two electrodes adapted for connection to a power supply and mounting means for attachment to an arm, one end of the arm being adapted for attachment to said mounting means, the arm further comprising holding means to engage and support a lampholder, the lampholder being adapted for engagement with said holding means, and at least two conductors extending from said one end to said holding means, f d at least two conductors extending from said one end to said holding means such that the luminaire may be assembled by attaching the arm to the support body and the lampholder to the arm, during which assembly an electrical path is established between the electrodes of the support body and the lampholder via the conductors of the arm, wherein said mounting means comprises one part of electrical connector in accordance with the invention and said one end of the arm comprises the other part of the connector. Preferably, the holding means also comprises one part of an electrical connector in accordance with the present invention and the lampholder the complementary part of the connector. The luminaires of the invention generally comprise at least three individual components which may be readily packaged, either alone or in combination, e.g., using blister packaging etc., and optionally marketed as a range of interchangeable components. Thus, the consumer can design his own luminaire by selecting his own preferred combination of support body, arm(s) and lampholder(s) . The consumer on purchasing a conventional luminaire having an integral lampholder(s) is limited in his/her selection of available shades because of the type of shade fitting provided for the lampholder, i.e., he/she can only choose from shades having a complementary fitting to the selected lampholder/sconce. However, by forming the lampholder as a separate component of a modular luminaire assembly, the total number of design permutations may be further increased by the vendor offering not only various designs of lampholder but also the same design of lampholder provided with different shade fittings (there are about six types of shade fitting in common use) . A lampholder incorporating one part of the connector of the invention may additionally be provided with the starter and choke required by a low energy bulb. This would enable the starter and choke to be reused, as in a conventional strip light, and be conveniently housed within the lighting fitment allowing low energy bulbs to be manufactured and sold without an integral starter and choke. Luminaires comprising a number of disengagable component parts are more easily cleaned than their preassembled counterparts and breakage of one component does not necessitate scrapping of the complete luminaire. Furthermore, the storage requirements of individual components are reduced when compared with whole preassembled luminaires which results in less transport/delivery costs, less stock wastage and therefore greater economy for the vendor. Consequently, such modular luminaires may be sold through retail outlets such as supermarkets, D.I.Y. stores etc., which would not normally stock these articles. The manufacturer will save on labour costs by not having to assemble the luminaires and in addition, a range of interchangeable components is less likely to become redundant stock. The support body may be configured for use in pendant, pedestal or wall mounted formats. The support body for a pendant luminaire generally comprises a plurality of mounting means to support radiating arms and associated lampholders. Support bodies for pedestal or wall mounted luminaires may be associated with a single arm or a plurality of arms. Each arm may support a single lampholder or a plurality of lampholders. The same type of connector is desirably fitted to each arm and/or lampholder in the range of modular components offered by the manufacturer so that any one component is fully compatible with any other components chosen to make up the luminaire. The modular assemblies of the invention can be simply and readily assembled without the need for wiring, specialist tools or specialist knowledge on the part of the consumer. The principle of incorporating one part of a connector of the invention into a support body can readily be adopted for ceiling roses and junction boxes. Such a ceiling rose facilitates simple plug in pendant light fitting allowing the removal and replacement of any module without the need of tools or specialist knowledge. Furthermore, a number of junction boxes each having a connector part, can be connected in series to create a modular lighting system which can be recessed in a gridded ceiling and light fittings connected to one or more of the junction boxes using the other part of a connector of the invention. The lighting system can be readily altered if required without the need for specialist tools or knowledge simply by unplugging and moving lighting fitments thus providing a more flexible system than a track lighting system as it is composed of far fewer components, the system is more readily demountable to suite changing lighting requirements. Junction boxes for general wiring applications both for lighting and power supply may also be constructed having one or more parts of a connector of the invention formed therein. The connections to the electrodes can conveniently be colour coded to assist in wiring, not only with the conventional live, neutral, earth colour codes but optionally also to highlight the utility, e.g., connection to switch, connection to light fitting etc. The invention will now be described by way of example with reference to the accompanying drawings, in which: Figures 1 and 2 represent end views of the respective first and second parts of an electrical connector in accordance with the invention; Figures 3 and 4 represent side views of the respective first and second parts of the connector shown in Figures 1 and 2; Figure 5 represents a side view of the connector of Figures 1 and 2 when fully assembled. Figures 6 and 7 illustrate alternative embodiments of one part of an electrical connector in accordance with the invention; Figures 8a to 8i are simplified schematic representations of electrode arrangements suitable for use in the present invention; Figure 9 represents a simplified schematic representation of a modular luminaire assembly in accordance with the invention; Figure 10 is a partial section through the mounting assembly of the arm and support body of a modular luminaire assembly in accordance with the invention; Figure 11 is an exploded, partially-sectioned view of an electrical connector in accordance with the invention which is used in the mounting assembly shown in Figure 10, and Figure 12 is a perspective view of an electric bulb and lampholder incorporating an electrical connector in accordance with the invention, and Figure 13 illustrates a multiple-thread arrangement suitable for use in connectors of the invention. Figures 1 to 5 depict one embodiment of an electrical connector in accordance with the invention. The connector (indicated generally by (1)) comprises inter-engagable first and second parts (3 and 5 respectively) , each of which comprises a housing (7 and 9 respectively) , typically moulded from an insulating plastics material. One end (4) of each part (3 and 5) is adapted to be connected to the free ends of two conductors (not shown) which are to be joined together. The various means for coupling each part (3 and 5) to its respective conductor are well known to the skilled individual and will not be discussed herein. Ordinarily, the free end of each conductor is coupled to its respective connector part (3 and 5) prior to their mechanical engagement. The housing (7) of the first part (3) is provided with three thread segments (11, 13 and 15) which are engagable with complementary thread segments (11a, 13a and 15a) provided on the housing (9) of the second part (5) . In making the connection between the first and second parts (3 and 5) , the first part (3) in presented to the second part (5) in a position such that the three thread segments (11, 13 and 15) align with and enter the spaces between the thread segments (11a, 13a and 15a) of the second part (5) . Subsequent rotation of one connector part relative to the other causes the two parts to interlock (as shown in Figure 5) , thereby preventing them from being drawn apart by abstractive forces. The depth, size and/or spacing of the thread segments (11, 13, 15 and 11a, 13a, 15a) are selected such that the parts (3a and 5) may only be coupled in a single orientation. In a modified arrangement (not shown) the connector may have 3 symmetrically disposed electrodes and the three segments configured so that the parts may be coupled starting from three different positions, 120° apart. In the embodiment shown, each connector part (3 and 5) has two electrodes offset from the longitudinal axis of the connector (1) which form a complementary pair with those of the other connector part such that when the two parts (3 and 5) are interlocked, an electrical path is established between the complementary pairs of electrodes. The housing of each connector part (3 and 5) enshrouds the electrodes to minimise the risk of accidental electrocution by the user inadvertently contacting the live electrode(s) . In the embodiment shown, the electrodes of the first part (3) comprise terminal pins (17) . The electrodes of the second part (5) may be recessed in sockets (19) , the terminal pins (17) wiping across the surface of the electrodes on relative rotation of the connector parts (3 and 5) , to make electrical contact. Alternatively, or in addition thereto, the socket (19) itself may form part of the electrode with the walls of the socket (or at least a portion thereof) comprising a conductive material to allow the electrodes to be contacted in a radial plane of the connector (1) . Each socket (19) follows an arcuate path to allow for movement of the terminal pins (17) during relative rotation of the connector parts (3 and 5) . Referring to Figure 2 , each socket (19) comprises a slot having a tear-shaped cross- section oriented such that the terminal pin (17) enters at the widest point of the tear. On relative rotation of the connector parts (3 and 5) , each terminal pin (17) is caused to abut the walls of the socket (19) at its narrowest point to ensure good electrical connection between the two parts (3 and 5) . In an alternative embodiment (not shown) , one pair of electrodes may advantageously have a different shape or be slightly larger than the other pair to ensure that the connector can only be assembled in one orientation, thereby preventing the user from inadvertently confusing the polarity of the terminals and connecting live to neutral and vice-versa. Figure 6 illustrates one connector part (21) of an alternative embodiment of electrical connector in accordance with the invention. In this embodiment, the connector is provided with one axial socket (23) of circular cross-section and a second socket (25) offset from the longitudinal axis of the connector having a kidney-shaped cross-sectional profile to allow for movement of the terminal pin of the other part (not shown) . The other part of the connector is provided with one axial terminal pin and one positioned offset from the longitudinal axis to complement the part (21) shown. Figure 7 illustrates one connector part (27) of a further embodiment of electrical connector in accordance with the present invention. In this embodiment, the connector is provided with three sockets (29) offset from the longitudinal axis of the connector and having a tear- shaped cross-sectional profile. The other part of the connector (not shown) is provided with three terminal pins offset from the longitudinal axis to complement the part (27) shown. The connector part (27) may include a shutter (10) (shown in dashed outline) to protect the electrodes (29) . The shutter is positioned above the electrodes and is mounted for rotation about its centre. The shutter may be supported in any desired manner, e.g. , by a central support (not shown) or the periphery of the shutter may be held in a recess in the housing. The shutter has three apertures (12, 14, 16) dimensioned to accommodate the terminal pins of the other part. When the parts of the connector are separate the apertures (12, 14, 16) are not aligned with the terminals (29) . As the parts of the connectors are engaged and rotated the shutter (10) is rotated, e.g., by a projection or terminal pin engaging the shutter, thereby allowing the terminal pins to mate with the electrode sockets (29) . The final position of the apertures when the connector parts have been fully engaged is shown at (12a, 14a, 16a) . When the parts of the connector are rotated during separation the shutter is returned to its protective position. In the previously exemplified electrical connectors, the electrodes of the two connector parts have been formed as pairs of complementary pins and sockets. However, the electrical connectors of the invention are particularly advantageous in that, as a result of the strength and stability of a multiple- threaded screw coupling, the electrodes of each connector part may be contacted in a radial plane of the connector or in a plane parallel to the radial planes of the connector, thereby allowing for a reduction in the overall size of the connector. In this respect. Figures 8a to 8i illustrate a series of highly schematic drawings in which the movement of a single electrode from a first position (generally shown in dotted relief) , corresponding to the point at which the two connector parts would be in abutting engagement, but prior to relative rotation therebetween, to a second position in which it abuts the complementary electrode of the other part, corresponding to the point at which both mechanical and electrical union have been established. Only the positions of the electrodes are shown, all other details of the connector parts having been omitted. Referring to Figure 8a, one electrode (31) comprises a cylindrical pin and the other (33) a planar electrode. Referring to Figure 8b, the second electrode (35) has an arcuate cross-section to increase the area of contact between the electrodes (31 and 35) . Referring to Figure 8c, the second electrode (37) has a semi-cylindrical cross-section complementary to that of the other electrode (31) . Referring to Figure 8d, one electrode (39) is provided with a 'V shaped ' leading edge and the other electrode (41) has an arrow-shaped cross-section complementary thereto. Referring to Figure 8e, the second electrode (43) is provided with resiliently flexible flanges (45) which secure the first electrode (47) in position until such time as the user applies firm pressure to disengage the two connector parts. Referring to Figures 8f and 8g, each electrode (48 and 49) comprises one half of a cylindrical pin. Referring to Figure 8h, one electrode (50) comprises a split pin, the two halves of which are biased into the open position. The other electrode (51) has a semi-cylindrical cross-section complementary to that of the pin when in the closed position. On relative rotation of the two connector parts, the pin is forced into the closed position, the pressure exerted by the pin securing the electrode in position. Figure 8i illustrates a variation on the electrode arrangement shown in Figure 8g in which each electrode (48 and 49) is provided with a co-operating cam. surface (52 and 52a respectively) such that the application of firm pressure is required to both engage and disengage the two electrodes (48 and 49) . Figure 9 depicts a schematic representation of a modular luminaire assembly (53) in accordance with the present invention, which assembly comprises a support body (55) for a ceiling-mounted, pendant luminaire and a set of four radiating arms (57) , each associated with a single lampholder (59) . In alternative embodiments (not shown) , the support body could be configured for use as a pedestal or wall-mounted luminaire with a single arm or a plurality of such arms. In the embodiment shown, each arm, (57) supports a single lampholder (59) although the use of a plurality of such lampholders is equally permissible. The support body (55) houses a terminal block (61) which is wired into the lighting circuit of the domestic mains supply (not shown) . In the case of a pendant luminaire, the support body (55) is normally threaded onto a centre column extending from a ceiling rose which encloses the wiring from the mains supply. Each arm (57) is provided at either end with one part (63 and 65) of an electrical connector in accordance with the present invention. The terminal block (61) of the support body (55) is in turn, provided with a plurality of peripherally spaced sockets, each comprising the complementary connector part (67) to that of the arm connector part (63) . Similarly, each lampholder (59) is provided with a connector part (69) complementary to that of the arm connector part (65) . The lampholder connector part (69) and the arm connector part (63) are provided with electrodes (not shown) which engage electrodes in the connector part (65 and 67) of the arm (57) and terminal block (61) respectively. The electrodes of the arm connector parts (63 and 65) πre connected to conductors (71 and 73) extending along each arm (57) such that during assembly of the luminaire (53) , an electrical path is established between the terminal block (61) and each lampholder (59) via the conductors (71 and 73) of each arm (57) . The electrodes (not shown) of the arm connector part (65) and the terminal block connector part (67) are advantageously recessed in sockets (not shown) to minimise the risk of accidental electrocution during assembly of the luminaire (53) . The luminaire (53) is typically assembled by attaching each lampholder (59) to its supporting arm (57) and then attaching the assembled arms (57) to the support body (55) . Thus, each lampholder (59) is held in abutting engagement with its arm (57) and rotated so as to interlock the respective connector parts (65 and 69) , thereby securing the lampholder (59) in position. The arm (57) (with attached lampholder (59)) is then inserted into the support body (55) through an aperture (75) provided therein and rotated in abutting engagement with the terminal block (61) to interlock the respective connector parts (63 and 67) and secure the arm (57) in position. This procedure is repeated in turn for each arm (57) to complete the assembly of the luminaire (53) . Referring to Figures 10 and 11, another arrangement of electrical connector in accordance with the invention is shown for use in coupling the arm (57) of a luminaire to its support body (55) . Figure 10 depicts the connector in situ and Figure 11 is an exploded view of the connector. During the manufacture of the luminaire assembly, the wires (79) from the lampholder (not shown) extend along the hollow arm (57) of the luminaire and out of an aperture (81) . Each wire (79) is passed through an aperture (83) in the end wall of the first connector part (77) and connected to its respective terminal pin (17) , typically via a flat-ended screw (not shown) . Once wired to the lampholder, then the first connector part (77) is secured into a complementary recess (85) provided in the luminaire arm (57), e.g., by a screw thread arrangement, bayonet coupling, snap-fit etc., to complete the assembly of the luminaire arm (57) . The second connector part (87) comprises a central hub (89) having two sockets (19) of complementary shape to the terminal pins (17) of the first connector part (77) and a circumferential flange (91) . The external surface of the first part (77) is provided with four thread segments (93) (of which only two are shown) which are engagable with complementary thread segments (95) formed in the wall of the circumferential flange (91) . The central hub (89) of the second connector part (87) is dimensioned so as to be locatable in the outer sheath (97) of the first connector part (77) . Thus, by engaging the thread segments (93) of the outer sheath (97) with the complementary thread segments (95) of the second connector part (87) and rotating the arm (57) relative to the second connector part (87) , it is possible to interlock the two connector parts (77 and 87) to secure the arm (57) to the support body (55) . Each socket (19) follows an arcuate path to allow for movement of the terminal pins (17) during rotation of the two connector parts (77 and 87) . The electrodes (99) of the second connector part (87) are recessed in their respective sockets (19) such that the terminal pins (17) wipe across the electrodes (99) during relative rotation of each connector parts (77 and 87) to establish an electrical path therebetween. The electrical connectors of the invention find general utility in all aspects of light fittings. One application of the connectors is shown in Figure 12, in which an electric light bulb (101) is provided with one part of an electrical connector in accordance with the invention and the bulbholder (103) of a lamp (105) is provided with the complementary part of that connector, allowing the bulb (101) and bulbholder (103) to be coupled together. The bulb (101) generally comprises a glass 'bulb' (107) enclosing a filament (109) supported on conductors (111) and a base (113) having two electrodes in the form of terminal pins (17) , which electrodes are in electrical communication with the conductors (111) of the filament (109) . The base (113) further comprises a hood (115) which enshrouds the terminal pins (17) of the bulb (101) . The outer surface of the hood (115) is provided with three thread segments (93) which are engagable with three complementary thread segments (95) formed in the housing (117) of the bulbholder (103). To insert the bulb (101), the thread segments (93) of the hood (113) are aligned with those of the bulbholder (103) and the bulb (101) screwed into the bulbholder (103) . The central hub (119) of the bulbholder (103) is provided with two sockets (19) which receive the terminal pins (17) of the bulb (101) . Each socket (19) follows an arcuate path to allow for movement of terminal pins (17) during rotation of the bulb (101) . The walls of each socket (19) comprise a conductive material. Relative rotation of the bulb (101) and bulbholder (103) causes the terminal pins (17) of the bulb (101) to abut the walls of the socket (19) , thereby establishing an electrical path between the bulb (101) and bulbholder (103) . Figure 13 illustrates a multiple-thread arrangement suitable for use in the connector of the invention. One part of the connector is provided with recessed thread segments (131, 133, 135) which are engaged by corresponding raised thread segments (137, 139, 141) on the other part, when the connector is fastened. The complementary pairs of thread segments are dimensioned such that the parts may be assembled in only one configuration. The ends of the raised thread segments are provided with a projection (143) and the corresponding segments are provided with a recess (145) to provide a positive indication to the user when the connector is fully engaged. The projections (143) are dimensioned to touch the sides of the complementary thread segment as the parts are rotated to provided increased resistance to rotation. As the projections (143) are moved to the recess (145) there is a sudden decrease in resistance and an audible click indicating the connector is fully engaged.

Claims: CLAIMS : 1. An electrical connector comprising inter- engaging first and second parts, each of which parts comprises a housing having co-operating locking means such that relative rotation of the first part in abutting engagement with the second part causes mechanical interlocking of the housings, each part further comprising at least one electrode rotatable about the axis of the part which forms a complementary pair with an electrode of the other part, the connector being arranged such that the electrodes of each complementary pair are brought into contact during relative rotation between the two parts to establish electrical communication simultaneously with mechanical engagement, characterised in that said co-operating locking means comprises a multiple-threaded screw arrangement. 2. An electrical connector as claimed in Claim 1 in which the multiple-threaded screw comprises at least three thread segments. 3. An electrical connector as claimed in Claim 1 or Claim 2 in which the extent of relative rotation required to interlock the housings of the two connector parts is less than 90" 4. An electrical connector as claimed in any preceding Claim in which the housing of the first part comprises on an external surface thereof a multiple- threaded screw and the housing of the second part comprises on an internal surface thereof a multiple- threaded screw complementary to that of the first part and wherein at least a portion of the housing of the first part is dimensioned so as to be screwed into the housing of the second part. 5. An electrical connector as claimed in any preceding Claim in which each part comprises at least two electrodes rotatable about the axis of the connector. 6. An electrical connector as claimed in Claim 5 in which each part comprises three such electrodes. 7. An electrical connector as claimed in any preceding Claim in which one electrode of each complementary pair comprises a terminal pin and the other a socket complementary thereto. 8. An electrical connector as claimed in Claim 7 in which each socket comprises a slot following an arcuate path to allow for movement of the terminal pin therein during relative rotation of the two parts. 9. An electrical connector as claimed in any preceding Claim in which at least one part comprises a shutter which covers the electrodes when the parts are separated and moves to allow contact between pairs of electrodes when the parts are interengaged. 10. An electrical connector as claimed in any preceding Claim which comprises means to provide an indication to the user when the parts are rotated to fully engage the locking means. 11. An electrical connector as claimed in any preceding Claim further comprising an anti-tamper mechanism such that the two connector parts cannot be separated solely by the application of rotational force. 12. A modular assembly for a luminaire comprising at least three separate components including a support body, an arm and a lampholder, the support body comprising at least two electrodes adapted for connection to a power supply and mounting means for attachment to an arm, one end of the arm being adapted for attachment to said mounting means, the arm further comprising holding means to engage and support a lampholder, the lampholder being adapted for engagement with said holding means, and at least two conductors extending from said one end to said holding means such that the luminaire may be assembled by attaching the arm to the support body and the lampholder to the arm, during which assembly an electrical path is established between the electrodes of the support body and the lampholder via the conductors of the arm, characterised in that said mounting means comprises one part of an electrical connector as claimed in any preceding Claim and in which said one end of each arm comprises the other part of said electrical connector. 13. A modular assembly as claimed in Claim 12 in which said holding means comprises one part of an electrical connector as claimed in any one of Claims 1 to 11 and the lampholder comprises the other part of said electrical connector. 14. A modular assembly as claimed in Claim 13 comprising a support body , a plurality of arms, each arm having holding means for one or more lampholders, and a plurality of lampholders. 15. The combination of electrical appliance and a power lead in which the appliance comprises one part of an electrical connector as claimed in any one of Claims 1 to 11 and the power lead has the other part connected at one end thereof. 16. A junction box or ceiling rose for electrical wiring comprising at least one part of an electrical connector as claimed in any of Claims 1 to 11.

Inventors: BARNES CHARLES FREDERICK, BARNES, CHARLES, FREDERICK
Applicants: BARNES CHARLES F, SPIERS SANDRA MARIA, BARNES, CHARLES, FREDERICK, SPIERS, SANDRA-MARIA
Application year: 1992
Main classification: F21V23
IPC codes: F21V19, H01R13, H01R33