Low voltage distribution system with two-conductor track.

This invention relates to a low voltage distribution system with a two-conductor track.

By "low voltage" is meant fifty volts or less.

The invention has for its principal object the provision of a two-conductor track which will take an adaptor anywhere along the track for energising, for example, an electric lamp.

Another object is to provide an adaptor which will carry a lamp which can be rotated freely on the adaptor without twisting wires connecting the lamp to a rotatable contact assembly of the adaptor.

Another object is to make the track easily mountable to a support.

Another object is to provide a power supply connector which incorporates overload protection means.

The invention has various aspects.

According to a first aspect of the invention there is provided a low voltage distribution system comprising a two-conductor track and an adaptor which can be fitted thereto anywhere along the track, the adaptor comprising means for making electrical contact with the two conductors and means for interlocking mechanically with the track, including at least one movable member for positively displacing at least one interlocking member into interlocking engagement with the track, the interlocking member being resiliently biased out of said interlocking engagement.

According to a second aspect of the invention there is provided a low voltage two-conductor track comprising an outer metal casing forming at least part of one of the conductors, an inner metal conductor forming the other of the conductors and insulation supporting the inner metal conductor within the outer metal casing and insulating the two conductors electrically from each other, said outer metal casing, inner metal conductor and insulation all extending continuously along the whole length of the track, both conductors being exposed for electrical contact therewith by an adaptor applied to the track anywhere along the length of the track.

According to a third aspect of the invention there is provided a low voltage distribution system comprising a two-conductor track and an adaptor which can be fitted thereto anywhere along the track, the adaptor comprising a support which can be mechanically interlocked with the track, and an electrical contact assembly which is freely rotatably carried by the support, said contact assembly comprising an electrical centre contact and an electrical outer contact adapted and arranged for respectively contacting the two conductors of the track in any rotational position, two terminals connected electrically to the two contacts respectively and rotatable as one therewith, and insulating support means for the contact and terminals, said insulating support means also being rotatable as one therewith.

According to a fourth aspect of the invention there is provided a low voltage two-conductor track in combination with a fixing device for fixing the track to a support, the fixing device comprising a mounting member mounted or adapted to be mounted rotatably to the support and a connecting piece slidingly connected or adapted to be slidingly connected to the track by means of an undercut tongue and groove, the mounting member being adapted to receive the connecting piece in one rotational position and to interlock therewith in another rotational position.

The invention will be described by way of example with reference to the accompanying drawings, wherein:- <ul id="ul0001" list-style="none"><li>Fig. 1 illustrates a track and an adaptor;</li><li>Fig. 2 is an exploded view of the adaptor;</li><li>Fig. 3 is a section of the track and the adaptor;</li><li>Fig. 4 illustrates a modified track;</li><li>Fig. 5 illustrates the casing of the modified track and a fixing device, in plan view;</li><li>Figs. 6 and 7 are sections on lines VI-VI and VII-VII respectively of Fig. 5;</li><li>Fig. 8 is an underneath plan view corresponding to Fig. 5;</li><li>Fig. 9 is a cross-section through another modified track;</li><li>Fig. 10 is a section of a track with a modified adaptor;</li><li>Fig. 11 is a cross-section through the track and part of the adaptor of Fig. 10;</li><li>Fig. 12 is a cross-section through a double track;</li><li>Fig. 13 is a cross-section through a triple track;</li><li>Fig. 14 is a perspective view of a track power supply connector incorporating a thermal cut-out;</li><li>Figs. 15, 16 and 17 respectively are an end view, a plan view and a side view of a side contact in the connector of Fig. 14;</li><li>Figs. 18, 19 and 20 respectively are an end view, a plan view and a side view of a centre contact in the connector of Fig. 14, Fig. 20 being turned through a right angle to fit on the sheet; and</li><li>Figs. 21, 22, 23 and 24 respectively are a side view, a plan view, an underneath plan view and a section on line XXIV-XXIV of Fig. 21, of a rotary locking cam in the connector of Fig. 14.</li></ul>

Like references refer to like parts throughout.

Referring to Figs. 1 to 3, the illustrated track 10 is a two-conductor track of which one conductor is an outer conductor formed by an extruded aluminium casing 12 and the other conductor is an inner conductor formed by a copper strip 14 which is insulated by insulation 16, the strip 14 being held in place by lips 18 of insulation 16. The conductors 12 and 14 and insulation 16 all extend continuously (with uniform cross-sections) along the whole length of the track, the conductors 12 and 14 being exposed for electrical contact therewith by an adaptor 20 applied to the track 10 anywhere along the length of the track. The insulation 16 is of extruded plastic, having wings 17 which are held resiliently in place under lips 19 of casing 12.

The adaptor 20 comprises a plastic insulating body 22 which fits between two sides 24, 24 of the track 10, being somewhat narrower than an integral flat plastic top 25 which abuts the track sides 24, 24. Two pairs of resilient cantilever arms 26, 26, 26, 26 extend longitudinally of the body 22 in mutually opposite directions and are integral with the body 22. The tip of each arm 26 is formed with an outwardly projecting lip 28 which is interlockingly engageable with a respective one of the lips 19 of casing 12. The normal (i.e. unstressed) positions of arms 26 are inward, disengaging lips 28 from lips 19.

For biasing arms 26 outward to interlock lips 28 with lips 19, the adaptor 20 comprises two pivoted members 30 which can be selectively pivoted from the 'open' position of Fig. 2 (for disengagement) to the 'closed' position of Fig. 3 (in which they displace the two pairs of arms 26 apart into interlocking engagement with the track 10), about pivots 32. The two members 30 have flat tops 34 which lie flush with the top 25 of the body 22 in the closed position of Fig. 3. It will be appreciated that the space between each pair of arms 26, 26 is 'normally' (i.e. when unstressed) narrower than portion 36 of the respective member 30 which comes between them.

The adaptor 20 also comprises a rotatable contact assembly 40 which makes electrical contact with the track 10 in any rotational position. The contact assembly 40 comprises a sub-assembly 42 (Fig. 2) of an electrical centre contact 44 (to contact the strip 14) and a split sleeve outer electrical contact 46 (to contact the lips 19 of casing 12). An insulating plastic grommet (not shown) inside the sleeve contact 46 receives and positions the centre contact 44. The sub-assembIy 42 also includes two metal connector tags 48, 50 which are respectively integral with contacts 44, 46. Near where the centre contact 44 engages conductor 14, it is located by a bottom end wall 23 of body 22.

The contact assembly 40 also comprises, besides the sub-assembly 42, two semi-cylindrical half inner insulating sleeves 52a, 52b, an outer sleeve 54, a bracket 56, two electrical connector terminals 58a, b (respectively crimped to insulation-covered wires 60a, b) and a washer 62.

As assembled, the half sleeves 52a, 52b encase the sub-assembly 42; a flange 64 of an upstanding integral boss 66 of body 22 is rotatably received in a circular groove 52c of sleeves 52a, 52b to retain the contact assembly 40 on the body 22. The bracket 56 fits over the half sleeves 52a, 52b and has two tongues 56a which engage grooves 52d in half sleeves 52a, b to lock bracket 56 against relative rotation. The outer sleeve 54 also fits over half sleeves 52a, b and has tongues 54a engaging grooves 52d to prevent relative rotation. The terminals 58a, b fit onto the tags 48, 50, the wires 60a, b extending through the centre hole 54b in the top of the sleeve 54 and through the washer 62.

The bracket 56 is adapted to support a spot-lamp (not shown) or other illuminating device, to which the wires 60a, b are connected (not shown). Because the entire contact assembly 40 (that is, sub-assembly 42, half-sleeves 52a, b, outer sleeve 54, bracket 56, terminals 58a, b, wires 60a, b and washer 62) rotates as one unit. the wires 60a, b never get twisted either around themselves or around the bracket 56.

Furthermore, because the contacts 44 and 46 are respectively a centre contact and a sleeve contact of annular cross-section (both being co-axial with the axis of rotation) electrical contact is made with copper strip 14 and with the lips 19 of casing 12 respectively in all rotational positions of contact assembly 40.

The adaptor 20 can be fitted to the track 10 anywhere along its length with the members 30 initially 'open' as shown in Figs. 1 and 2, and locked in position by closing members 30 to the position of Fig. 3 in which arms 26 are displaced positively outwardly to interlock lips 28 with lips 19.

Fig. 4 illustrates a modified track 70 having a casing 72 of generally rounded, cylindrical configuration, in contrast to the rather angular configuration of casing 12 of track 10. In other respects the track 70 is similar to track 10.

For mounting the track 10 or the track 70 to a support, referring to Figs. 5 to 8 (which happen to show the modified track 70, with copper strip 14 and insulation 16 shown only in Fig. 6) a fixing device 74 is provided comprising a mounting member 76 mounted rotatably to the (not shown) support (e.g. by a screw 78), and a connecting piece 80 slidingly connected to the back of the casing 72 by means of engaging an undercut tongue 82 of the connecting piece 80 in an undercut groove 84 in casing 72. Laterally projecting wings 86 of connecting piece 80 are received through a rectangular opening 88 in the outside face of mounting member 76, which can then be rotated to retain the wings 86 in recesses 90 in mounting member 76. Since connecting piece 80 is slidable along the casing 72 of track 70, accurate positioning is less critical, making assembly easier.

The track 10 has an undercut groove (not shown) at the back of it, the same as groove 84 of track 70, and hence can be mounted in the same way.

The modified track 92 of Fig. 9 differs from the track 70 of Fig. 4 in having two circular cross-sectioned copper rods 94 partly embedded in and extending along the aluminium casing 96. The contact 46 of the adaptor 20 engages and makes electrical contact with exposed inner surfaces 98 of the two copper rods 96. In other respects the track 92 is identical to the track 70.

In the modification of Figs. 10 and 11, as compared with the arrangements described hereinabove, like references refer to like parts. However, the above-mentioned plastic grommet (not shown) of adaptor 20 is omitted from the adaptor 20ʹ of Fig. 10 Furthermore, the half inner sleeves 52aʹ, 52bʹ are provided with a cross-partition 100 just below the terminals 58a, 58b as seen in Fig. 10. A modified metal connector tag 48ʹ, integral with centre contact 44, carries a compression spring 102 which acts between the partition 100 and a bend at 104 in connector tag 48ʹ, to bias the contact 44 down onto the conductor strip 14ʹ of track 70 (compare Fig. 4).

The double track 100 of Fig 12 comprises two co-extensive, back-to-back tracks 102 and 104. Each of the tracks 102, 104 is similar to the above-described tracks of Figs. 1 to 11 apart from the casing shape. The two casings are integral, formed by a unitary casing member 106 which is generally H-shaped except that the sides 108, 108 are (,) - shaped, each being outwardly convex.

The triple track 110 of Fig. 13 comprises three co-extensive. side-by-side tracks 112, 114, 116 with integral casings formed by a unitary casing member 118.

Whereas the track 10 of Fig. 1 could be described as of generally triangular cross-section and the tracks of Figs. 4, 6, 9 and 11 as of generally cylindrical cross-section, the track of Fig. 13 is generally rectangular in cross-section and has a rear mounting groove 120.

The two tracks 102, 104 of the double track 100 of Fig. 12 can be separately switched, as can the three tracks 112, 114, 116 of triple track 110 of Fig. 13.

Referring to Figs. 14 to 24, a track power supply connector 122 incorporates a thermally-activated current-sensitive cut-out device 124 (hereinafter referred to as a thermal cut-out device 124) with a reset button 126 and is adapted to supply electrical power to the track 92 (see also Fig. 9) from a twin-conductor power lead 128.

More particularly, a side contact 130 (Figs. 14 to 17) of connector 122 connects conductor 132 of power lead 128 electrically to copper rods 94 of track 92. Side contact 130 has a metal ferrule 134 integral with two metal spring contacts 136, 138. The ferrule 134 is crimped in well-known manner to conductor 132, having an inner ear 140 to engage conductor 132 itself and an outer ear 142 to engage the insulation of power lead 128. The spring contacts 136, 138, which are separated by a slot 144, fit springily between conductor rods 94 and engage the side surfaces 98 (Fig. 9) thereof.

The other conductor 146 of power lead 128 is connected to the input of the thermal cut-out device 124 by a ferrule 148. The thermal cut-out device 124 incorporates a mechanism, not illustrated, of well-known type, including a bimetallic strip which carries all the current to the track 92 and which is effective upon excessive current, that is to say an overload, causing corresponding deflection of the strip, to open a pair of electrical contacts of the mechanism so as to cut off electrical power from the track 92. The mechanism is designed for this pair of electrical contacts to remain open until closed (after cooling of the bimetallic strip) upon operation of reset button 126.

A centre contact 150 (Figs. 14 and 18 to 20) connects the output of the thermal cut-out device 124 to the copper strip 14. The centre contact 150 has three spring contacts 152, 154, 156 which press down upon the copper strip 14. An insulating partition 158 (Fig. 14) separates ferrule 148 from centre contact 150.

To lock the connector 122 onto the track 92, the connector 122 is provided with a rotary locking cam 160 (Figs. 14 and 21 to 24) comprising a cam head 162 connected integrally to a cross-slotted operating head 164 by a shaft 166. The two "ears" of the cam head 162 engage undersides 168 (Fig. 9) of track 92.

The connector 122 comprises a housing 170 of insulating material that houses the cut-out device 124, contacts 130 and 150 and ferrule 148 and rotatably supports the locking cam 160.