WO2009115457A1

WO2009115457A1 - Electrical sockets

Info

Publication number: WO2009115457A1
Application number: PCT/EP2009/052964
Authority: WO
Inventors: Paul Trickett
Original assignee: Electrak International Limited
Priority date: 2008-03-19
Filing date: 2009-03-13
Publication date: 2009-09-24
Also published as: RU2010142262A; RU2496195C2; GB0805138D0; CN201319456Y; GB2458352A; GB2458352B

Abstract

An electrical socket box comprising: a base unit (1) comprising: a base housing; and two power rails (2) supported by the housing; a socket unit (6) comprising: a socket; and connectors (7) for connecting to each power rail; wherein the base unit and the socket unit are mutually configured so that the connectors of the socket unit are connectable to their respective power rails in a plurality of orientations of the socket unit with respect to the base unit and so that, when the socket unit is connected in each orientation, the base unit provides positive resistance to rotation of the socket unit relative to the base unit.

Description

Electrical Sockets

BACKGROUND OF THE INVENTION

This invention relates to an electrical socket box and particularly to an electrical socket box suitable for providing one or more connections to an electricity supply, such as a mains electricity supply available in a typical office or home. More particularly, the present invention relates to an electric socket box suitable for use in a modular distribution system.

Electrical socket boxes for providing one or more connections to an electrical power supply are well known. Designs differ around the worid and in dependence on the given application (for example, whether the socket box is for indoor or outdoor use), but socket boxes typically comprise a housing having one or more electrical socket units each adapted to receive an electrical plug. Electrical socket boxes can provide additional electrical connections in rooms having a limited number of wall-mounted electrical sockets, and are particularly suitable for providing a set of electrical sockets at a desk, cubicle or work area. Such electrical socket boxes may themselves be mounted in the floor, on a wall, at a desk or partition.

Electrical socket boxes allow each user in an office to be provided with an adequate number of sockets at their desk and facilitate the rapid reconfiguration of an office without requiring changes to the number and distribution of 'permanent' fittings such as wall-mounted sockets. Electrical socket boxes are now standard in a modern office having under-floor cabling.

Electrical socket box designs have been proposed that provide socket units which are rotatable within the socket box housing. Such designs are advantageous in situations in which the plugs of a number of different electrical appliances are to be inserted into the same electrical socket box but where the appliances are in different positions relative to the socket box. Such designs are also advantageous in situations in which one or more plugs to be inserted into the socket box are bulky and can only physically fit alongside other {possibly also bulky) plugs in the socket box in certain orientations. As electrical appliances requiring low voltage DC power supplies are becoming increasingly common, more and more plugs are incorporating transformers and switched mode power regulators. An increasing number of plugs are therefore bulky and connectable into a socket unit only if there is sufficient space about the socket.

By providing rotatable socket units, it is possible to rotate each socket unit so that the electrical cables leading from the plugs inserted into the respective socket units are allowed to follow a convenient path and so that one or more bulky plugs can be connected into a socket box without preventing other (possibly also bulky) plugs being connected into the same box.

UK Patent Application Number 9722460 describes an electrical socket box having rotatable socket inserts. Each socket insert is adapted to electrically connect each pin contact of the socket to a respective bus bar within a range of rotation of the socket insert. A slider contact maintains an electrical connection between the rotatable socket insert and the bus bar. This has the disadvantage that the contacts wear out over time through rotation of the sockets, particularly since, in order to ensure a good electrical connection, the slider contact is resiliently biased against the contacts of the socket insert and the bus bars. Furthermore, the design does not readily allow the exchange of socket inserts.

It is also generally the case that currently-available electrical socket boxes having rotatable sockets are considerably more expensive and complex than electrical socket boxes which do not have rotatable socket units.

There is therefore a need for a less complex, less expensive and more robust electrical socket box having the advantages of a socket box with rotatable sockets. SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided an electrical socket box comprising: a base unit comprising: a base housing; and two power rails supported by the housing; a socket unit comprising: a socket; and connectors for connecting to each power rail; wherein the base unit and the socket unit are mutually configured so that the connectors of the socket unit are connectable to their respective power rails in a plurality of orientations of the socket unit with respect to the base unit and so that, when the socket unit is connected in each orientation, the base unit provides positive resistance to rotation of the socket unit relative to the base unit.

Preferably the power raits are strips of conducting material suitable for carrying electric current.

The power rails may be held between a plurality of projections of the base housing or, along at least part of their length, the power rails may be at least partially sunk into one or more slots in the base housing.

Preferably the power rails are configured so as to define a mounting position for the socket unit at which the socket unit is connectable in a plurality of orientations with respect to the base unit. Preferably, in each of the plurality of orientations of the socket unit, the connectors of the socket unit are connectable to straight portions of the power rails.

In a preferred embodiment, at the mounting position, each power rail comprises a plurality of straight segments connected end-to-end and having constant angular variation between adjacent straight segments so as to define part of the boundary of a polygon. Preferably the part-polygons defined by the power rails have a common centre. In an alternative embodiment, at the mounting position, each power rail is arranged to lie in a circular arc. Preferably the circular arcs defined by the power rails have a common centre.

Preferably the base and socket units are mutually configured so as to define a direction of insertion of the socket unit into the base unit in which the connectors of the socket unit are connectable to their respective power rails. Preferably, at the mounting position, the power rails are elongate in a plane substantially parallel to the insertion direction.

Preferably the connectors of the socket unit are connectable to their respective power rails in a plurality of angular orientations of the socket unit about an axis substantially parallel to the insertion direction. Suitably the axis passes through a centre of symmetry of the socket unit.

The electrical socket box may further comprise one or more additional socket units, each socket unit having the same arrangement of connectors.

Preferably the connectors are adapted to releasably engage with the power rails. Preferably the connectors are adapted to make a push-fit engagement with the power rails. Preferably the connectors are spring loaded clips adapted so as to engage opposing sides of a power rail in a pinch-like grip. The connectors may be socket clips.

Preferably the socket unit comprises a socket housing bearing the connectors for connecting to each power rail. Suitably the housings of the socket and base units are mutually configured such that the base housing abuts part of the socket housing. Suitably the housings of the base and socket units are mutually configured such that one or more elements of the base housing are adapted to engage with one or more elements of the socket housing in each of the orientations of the socket unit. Preferably the abutment or engagement of the housings of the base and socket units prevents insertion of the socket unit at the mounting position other than in one of the plurality of orientations in which the connectors of the socket unit are connectable to their respective power rails. Preferably the abutment or engagement of the housings of the base and socket units prevents insertion of the socket at the mounting position other than in a direction substantially parallel to the insertion direction. Preferably the elements of the housings cooperate so as to prevent rotational motion of the socket unit in the base unit. Preferably the elements of the socket housing are located on the periphery of the socket housing,

The electrical socket box preferably further comprises an upper housing adapted to engage with the base unit so as to be operable to hold the socket unit in place in each of its orientations in the socket box while providing an opening through which the socket of the socket unit may be accessed. Preferably the upper housing is adapted to be releasably engaged with the base unit. Preferably, in the mounting position, the socket unit is held flush in the opening of the upper housing.

Suitably the upper and socket housings are mutually configured such that the upper housing abuts part of the socket housing. Suitably the upper and socket housings are mutually configured such that one or more elements of the upper housing are adapted to engage with one or more elements of the socket housing in each of the orientations of the socket unit. Preferably the elements or abutting surfaces of the upper and socket housings cooperate so as to prevent rotational motion of the socket unit in the socket box.

Preferably, at at least one end, each power rail is terminated at a connector adapted to allow connection of the socket box to a power supply. Further preferably the power rails are terminated at both ends at a connector arrangement, at one end the connector arrangement being a female connector arrangement and at the other end the connector arrangement being a male connector arrangement, the two being so adapted as to allow the female connector arrangement of one socket box to mate with the male connector arrangement of a second like socket box.

DESCRIPTION OF THE DRAWINGS

The present invention will now be described by way of example with reference to the accompanying drawings, in which:

Figure 1 shows an electrical socket box in accordance with the present invention, the top half of the socket box is not depicted so as to display the configuration of the internal bus bars;

Figure 2 shows a set of bus bars in accordance with the present invention;

Figure 3 illustrates the steps of connecting modular socket units into an electrical socket box in accordance with the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

The following description is presented to enable any person skilled in the art to make and use the invention, and is provided in the context of a particular application. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art.

The general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present invention. Thus, the present invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein.

The present invention provides an electrical socket box having a novel bus bar configuration that allows suitably adapted socket units to be mounted in a plurality of orientations. The present invention provides advantages of an electrical socket box having freeiy rotatable socket units without the increased complexity and cost of such socket box designs.

Figure 1 shows an electrical socket box in accordance with the present invention. Only a base part 1 of the housing is shown in the figure - the top part or cover 5 (which is illustrated in figure 3) is not shown. The base part supports two or more bus bars or power rails 2 on its inner surface. In a domestic/office scenario, there are three bus bars carrying the live, neutral and earth of a mains electrical supply system. However, there may be only two bus bars (for example, no earth) or more than three. The bus bars could carry any kind of AC system (for example, 3 phase supplies) which the socket box is adapted to handle. Alternatively, the bus bars could carry DC voltages.

Each bus bar is terminated at at least one end at a connector so as to allow connection of the bus bar to the power supply. A cable may provide a connection to each bus bar. The cable may be wired directly into the socket box such that the cable and socket box are provided as a single unit. The cable could be terminated at its free end by a connector adapted to be connected to the power supply system, or could be wired directly into the power supply system (for example, at a mains terminal block). Preferably the socket box is not provided with a cable wired directly to the bus bars and instead a set of connectors are provided in a set configuration so as to allow rapid connection and disconnection to the socket box by a suitably-adapted connector.

The bus bars are strips of conducting material for carrying electrical power within the socket box from the supply to which a socket box is connected. The bus bars are configured at various points along their length - at the mounting points - to receive the connectors of a socket unit. Fixing means may be provided on each bus bar at each mounting point adapted to fixedly engage with the corresponding connectors of a socket unit, but preferably the bus bars are shaped at the mounting points to allow snap-on connection to them by the corresponding connectors of a socket unit. The bus bars are preferably elongate in a plane substantially perpendicular to the plane of base part at the mounting points so as to facilitate such snap-on connection.

The bus bars are supported by the base part of the socket box housing. The bus bars may be fixed in place by any suitable means, such as: clips, grooves in the base part of the housing adapted to retain the bus bars in a plug fit, screws or other mechanical fixings. The one or more connectors terminating each bus bar may be adapted to at least partly affix the bus bar to the base unit. Alternatively, each bus bar may simply be supported on the base part between sets of projections located so as to prevent the bus bar moving laterally within the base unit. In such an arrangement, the bus bars and socket units may be held in place on the base unit by a cover or top part 5 of the housing adapted to engage with the base part.

It is further preferable that each end of the socket box is provided with a connection arrangement, with the bus bars extending between the connectors at each end of the socket box. This allows socket boxes to be chained together in series. Most preferably, the socket box is a modular socket box having at one end a female member 3 and at the other end a male member 4, the two being so adapted as to allow two socket boxes to be connected directly together: the female member of one socket box accepting the male member of a second socket box, This allows a compound socket box having the desired number and type of socket units to be formed from two or more such modular socket boxes.

Figure 2 shows a configuration of bus bars 2 in accordance with the present invention. A socket unit 6 is connectable to the bus bars at each of one or more mounting positions. Figure 2 shows four socket units connected to the bus bars at the four mounting positions. Each mounting position may be defined in a base unit of a socket box by one or more of: an arrangement of the bus bars; guide means of the base unit adapted to engage with a socket unit; and the position of an opening in the base unit. Each socket unit 6 has two or more electrically conducting connectors 7; one connector for each of the bus bars (in the figures there are three clips per socket unit for each of the three bus bars). In a preferred embodiment the connectors are resilient clips made of a conducting material such as metal. The clips are spring loaded so as to engage opposing sides of a bus bar in a pinch-like grip. A particularly suitable clip arrangement is a socket clip that provides two resilient arms biased so as to press against one another at a biting point. The free ends of the arms are bent away from one another so as to provide jaws into which a bus bar may be pushed, spreading apart the clip arms and allowing the bus bar to be held firmly between the clip arms.

Using sprung clips as connectors has the advantage that a particularly good electrical connection between the clip and bus bar is achieved. Furthermore, it prevents the clips moving relative to the bus bars, thus minimising wear and tear on the clips and bus bars and providing a mechanical connection between the socket unit and bus bars (and hence the base unit). So as to provide a convenient profile for the clips to engage with the bus bars are preferably elongate in a plane substantially perpendicular to the plane of base part.

Preferably connectors 7 provide a mechanical coupling to the bus bars such that the socket units are held in place at least partly by the connectors. It is advantageous if the connectors allow a push fit engagement with the bus bars such that a socket unit may be mated with a base unit by pushing the socket unit onto the bus bars. This is achieved by the use of the resilient socket clips shown in the figures.

To provide advantages of the present invention, the connectors 7 could be any kind of connector suitable for providing an electrical connection to the bus bars in at least two orientations of the socket unit, and in less preferred embodiments need not mechanically grip the bus bars. However, some aspect of the mutual configuration of the socket units and the socket box (whether it is through connection to the bus bars or mechanical coupling between base/top and socket housings) provides positive resistance to rotation of the socket units in the socket box in each of the defined orientations of the socket unit. The term "positive resistance" indicates that more than mere frictional resistance to motion is required: there is some degree of mechanical coupling between socket unit and socket box (base and/or top parts) which can be said to act to prevent rotation of a socket unit in its mounting position.

By providing only a finite number of orientations in which a socket unit is connectable to the bus bars, each connector can be sized to best fit the sections of bus bar available for connection. For example, in an embodiment in which the bus bars are polygonal, a connector can be sized to match the length of a side of the part-polygon defined by its corresponding bus bar. This optimises the electrical and mechanical connection made by a socket unit to the bus bars for a given configuration of bus bars.

The connectors 7 provide the electrical connections for the electrical socket of the socket unit. Each connector must therefore be configured to engage with the same bus bar in all possible orientations.

A socket box may be defined to consist of a base unit comprising base part 1 , top part 5 and power rails 2, and the socket units 6 which are mounted into the base unit.

In the figures, at each mounting position of a socket unit 6, the bus bars are configured so as to define part of the boundary of a polygon - in other words, the bus bars are made up of several straight segments joined end-to-end. Preferably there is a constant angle between adjacent segments of a bus bar and adjacent bus bars share the same angle between adjacent segments such that the symmetry is sufficient to allow straightforward connection to the bus bars by a socket unit in several orientations. Further preferably each segment of a bus bar is of the same length and there is a constant spacing between the straight segments of the bus bars. At each mounting position the bus bars could define part of any polygon, although at least two sides of the polygon must have sufficient length to accept the width of connector 7. The connectors of figure 2 are resilient metal socket clips, however, any connecting means suitable for providing an electrical connection to the bus bars may be used. It is advantageous if the connectors allow the socket units to be replaceably retained on the bus bars such that socket units can be removed and replaced in a different orientation at the same mounting position, or at a different mounting position, without requiring other means for holding the socket units in place.

The polygonal shape defined by the path traced by the bus bars need not be regular (i.e. have sides of equal length), however it is preferred since this allows the greatest number of orientations for a given polygon. The present invention allows each socket unit 6 may be mounted on the bus bars in at least two angular orientations about an axis substantially perpendicular to the plane defined by the base part (the "rotation axis"). Typically the bus bars define a common or adjacent plane to the plane defined by the base part. This is achieved by arranging the perpendicular distance from the rotation axis to at least two sides of a polygon defined by a particular bus bar to be equal to the distance from the rotation axis to the particular clip of the socket unit corresponding to that bus bar. For each clip to make a connection to its respective bus bar in at least two angular orientations of the socket unit this condition must be simultaneously true for each of the bus bars. If the shape defined by the bus bars at each mounting position is a regular polygon whose centre coincides with the rotation axis then all of the sides of the polygon defined by the bus bars generally fulfil this condition.

Alternatively, at each mounting position the bus bars could define part of the circumference of a circle. In this embodiment, the connecting means 7 is adapted to match the radius of curvature of the circle, or is sufficiently small in size with respect to the radius of curvature of the circle that a good electrical (and preferably mechanical) connection can be established. If the bus bars each define part of the circumference of a circle, the above-identified condition becomes: the centre of each circle must coincide with the rotation axis of the socket unit.

It will be appreciated that shapes other than partial polygons and partial circles may be defined by the bus bars provided that portions of the bus bars are located so as to allow connection by a socket unit in at least two orientations.

Between mounting positions, the bus bars may adopt any shape and need not maintain a constant spacing.

In order for a socket unit to be flush mountable in the base unit of a socket box in all orientations of the socket unit, the socket units and the base unit part into which the socket units are mounted should have a degree of rotational symmetry compatible with the polygonal shape defined by the bus bars. For example, in figure 3 the socket units have a circular shape, as do the openings in the top part 5 of the socket box. This allows the socket units to be flush mounted into the base unit (i.e. with no gaps between the socket units and the top part) in all orientations permitted by the bus bar arrangement. The socket units and the openings of top part 5 could share the same polygonal shape as that of the bus bars (an octagonal shape in the case of figure 3) such that the socket units have a flush fit in top part 5 in each orientation in which the socket units may be mounted on the bus bars.

In a preferred embodiment, the axis about which the socket unit may adopt at least two angular orientations passes through the centre of the socket unit when the socket unit is mounted on the bus bars. Such an embodiment is shown in the figures and described above. However, the axis about which the socket unit may adopt at least two angular orientations may be offset from the centre of the socket unit such that that the centre of the socket unit lies in different positions depending on the orientation of the socket. This is less advantageous since the opening in the top part for the socket unit must be larger than that part of the socket unit adjacent extending through the opening in order to allow the socket unit to adopt different orientations.

Instead of arranging for a socket unit to be flush mountable in the base unit, each socket unit could be provided with a flange having greater lateral extension than the main body of the sock unit such that the flange is sufficiently large to cover the opening in top part 5 in all orientations of the socket unit. The main body of the socket unit is sized so as to allow it to adopt each of the orientations in which the socket unit may be mounted on the bus bars. The flange could be arranged to extend within the base unit or over the outer surface of top part 5 so as to cover the opening in the top part. Providing a socket unit with a flange is particularly advantageous if the axis about which the socket unit may adopt at least two angular orientations is offset from the centre of the socket unit. Alternatively, blanking pieces could be employed to plug the openings in the top part of the socket box left when a socket unit is moved from one orientation into another.

In a preferred embodiment, the base unit and socket unit support elements which are adapted to engage with one another and provide a mechanical coupling between the base and socket units. Suitable elements include projections, ridges and slots. To give a particular example, one or more slots or walls provided in the base unit could be adapted to receive one or more splines of the socket unit. Alternatively, a mechanical coupling could be provided by simple abutment between one or more cooperating surfaces of suitably shaped base and socket units. The elements or abutting surfaces (the "guide means") are preferably arranged so as to only allow a socket unit to engage with the base unit in an orientation in which its connectors are appropriately located to mate with the bus bars. Furthermore, the guide means can be arranged to ensure that a socket unit may only be inserted into the base unit along a particular direction defined by the guide means. This can help to prevent damage to the connectors.

The provision of guide means and corresponding engaging parts on the socket units is advantageous in several ways. Firstly, it helps the user locate the socket unit in one of the possible orientations in which the connectors of the socket unit and the bus bars are properly aligned. Secondly, the guide means provide a mechanical mating of the socket unit with the base unit so as to strengthen the socket box and allow forces acting on the socket unit to be transferred to the base unit. The guide means positively resist the forces which can act on the socket unit when in use and prevent the connectors from bearing such forces alone. Preferably the guide means are located so as to engage with projections on the periphery of the socket unit since this provides better resistance to twisting forces acting on the socket units.

In an analogous fashion, guide means may be provided on the top part which are adapted to cooperate with elements or surfaces of the socket unit. In particular, the shape of the opening in the top part could be adapted to abut one or more surfaces of the socket unit so as to prevent rotation of the socket unit in the socket box and help align the socket unit in the box: for example, the socket unit and opening in the top part could share a polygonal shape such that the two may only mate together when the polygons are properly aligned.

It is particularly straightforward to provide guide means and corresponding engaging parts on the socket units if the base and socket units are made by injection moulding a suitable plastic.

Not all the connectors of a socket unit need be connected at corresponding points on adjacent bus bars. For example, the connectors of the socket units shown in figure 2 are staggered such that, in comparison with the other two connectors, one of the connectors is connected to a different "side" of the polygon defined by the bus bars when the socket unit is in a given angular orientation about its axis.

The connectors of a socket unit could be arranged to be connected at the comers of the polygon defined by the bus bars. Corner-shaped connectors are particularly effective at resisting lateral motion along the bus bars and provide a good mechanical coupling to the base unit. Figure 3 shows the steps involved in assembling a socket box in accordance with the present invention. From top to bottom the figure shows a set of socket units 6 being clipped onto the bus bars 2 in the desired orientations, A top part 5 of the socket box is then attached to the base part 1 of the socket box. The top part acts to hold the socket units in place and may include means for engaging with the socket units so as to prevent rotation of the socket units in the socket box and provide a strong mechanical connection between the component parts of the socket box. It is advantageous if the top part is releasably engaged with the base part such that the two parts of the socket box can be separated and reconnected as required. Preferably the top part snaps into the bottom part by means of sprung clips. Alternatively the two parts of the socket box may be connected by suitable fixing means, such as screws or nuts and bolts.

Conventionally, the housings of electrical socket boxes are moulded from plastic. In such an embodiment it is advantageous if the base part, top part and socket unit can each be formed in a single moulding step. It is well known for clips, guide means and the like to be formed during the moulding of a socket box housing such that each part is a single piece of moulded plastic.

Each socket unit is self-contained and has a common connector arrangement to allow attachment onto and removal from the bus bars as a single unit. It is particularly advantageous if the socket units are self-contained within a housing since this allows the socket units to be easily handled and protects the electrical components of the socket from the user and vice versa. The housing bears the connectors for connecting to the bus bars. By providing a socket unit with releasable connectors (such as metal socket clips or the like, as discussed above) the socket unit can be connected and disconnected from the bus bars without requiring wiring of the component parts of the socket unit into the socket box. By providing self-contained modular socket units having a common connector arrangement, socket units of one type may be readily exchange for socket units of another type. Socket units could optionally include fuses or surge protection circuitry. Socket units could having different current or voltage ratings. Importantly, socket units having the same common connector arrangement can be provided having different socket styles. For example, socket units having mains sockets appropriate to the US, continental Europe or the UK can be provided.

If necessary the base and socket units can be designed such that only certain socket units can be used in certain base units: for example, to prevent mixing of socket units complying with different electrical standards, or having different current/voltage ratings.

A further advantage of the present invention is that a only a single base unit design needs to be manufactured for most countries of the world, further reducing tooling costs. A socket box is tailored to the requirements of a particular country simply by mounting the appropriate type of socket unit in the socket box. It is also particularly straightforward to provide (where regulations allow) a socket box having a mix of different socket units. For example, a socket box could be provided having a mix of the different European socket types. This would be very useful for users wishing to connect several electrical appliances each having a different style plug. It is particularly advantageous if the user can select the set of socket units for a given socket box since this allows the socket box to be tailored to the particular requirements of the user.

The applicant hereby discloses in isolation each individual feature described herein and any combination of two or more such features, to the extent that such features or combinations are capable of being carried out based on the present specification as a whole in the light of the common general knowledge of a person skilled in the art, irrespective of whether such features or combinations of features solve any problems disclosed herein, and without limitation to the scope of the claims. The applicant indicates that aspects of the present invention may consist of any such individual feature or combination of features. In view of the foregoing description it will be evident to a person skilled in the art that various modifications may be made within the scope of the invention.

Claims

1. An electrical socket box comprising: a base unit comprising: a base housing; and two power rails supported by the housing; a socket unit comprising: a socket; and connectors for connecting to each power rail; wherein the base unit and the socket unit are mutuaily configured so that the connectors of the socket unit are connectable to their respective power rails in a plurality of orientations of the socket unit with respect to the base unit and so that, when the socket unit is connected in each orientation, the base unit provides positive resistance to rotation of the socket unit relative to the base unit.

2. An electrical socket box as claimed in claim 1, wherein the power rails are strips of conducting material suitable for carrying electric current.

3. An electrical socket box as claimed in any preceding claim, wherein the power rails are held between a plurality of projections of the base housing.

4. An electrical socket box as claimed in claim 1 or 2, wherein, along at least part of their length, the power rails are at least partially sunk into one or more slots in the base housing.

5. An electrical socket box as claimed in any preceding claim, wherein the power rails are configured so as to define a mounting position for the socket unit at which the socket unit is connectable in a plurality of orientations with respect to the base unit.

6. An electrical socket box as claimed in claim 5, wherein, in each of the plurality of orientations of the socket unit, the connectors of the socket unit are connectabie to straight portions of the power rails.

7. An electrical socket box as claimed in claim 5 or 6, wherein, at the mounting position, each power rail comprises a plurality of straight segments connected end-to-end and having constant angular variation between adjacent straight segments so as to define part of the boundary of a polygon.

8. An electrical socket box as claimed in claim 7, wherein the part-polygons defined by the power rails have a common centre.

9. An electrical socket box as claimed in claim 5, wherein, at the mounting position, each power rail is arranged to lie in a circular arc.

10. An electrical socket box as claimed in claim 9, wherein the circular arcs defined by the power rails have a common centre.

11. An electrical socket box as claimed in any of claims 5 to 10, wherein the base and socket units are mutually configured so as to define a direction of insertion of the socket unit into the base unit in which the connectors of the socket unit are connectabie to their respective power rails.

12. An electrical socket box as claimed in claim 1 1 , wherein, at the mounting position, the power rails are elongate in a plane substantially parallel to the insertion direction.

13. An electrical socket box as claimed in claim 11 or 12, wherein the connectors of the socket unit are connectabie to their respective power rails in a plurality of angular orientations of the socket unit about an axis substantially parallel to the insertion direction.

14. An electrical socket box as claimed in claim 13, wherein the axis passes through a centre of symmetry of the socket unit.

15. An electrical socket box as claimed in any preceding claim, further comprising one or more additional socket units, each socket unit having the same arrangement of connectors.

16. An electrical socket box as claimed in any preceding claim, wherein the connectors are adapted to releasably engage with the power rails.

17. An electrical socket box as claimed in any preceding claim, wherein the connectors are adapted to make a push-fit engagement with the power rails.

18. An electrical socket box as claimed in any preceding claim, wherein the connectors are spring loaded clips adapted so as to engage opposing sides of a power rail in a pinch-like grip.

19. An electrical socket box as claimed in any preceding claim, wherein the connectors are socket clips.

20. An electrical socket box as claimed in any preceding claim, wherein the socket unit comprises a socket housing bearing the connectors for connecting to each power rail.

21. An electrical socket box as claimed in claim 20, wherein the housings of the socket and base units are mutually configured such that the base housing abuts part of the socket housing.

22. An electrical socket box as claimed in claim 20 or 21 , wherein the housings of the base and socket units are mutually configured such that one or more elements of the base housing are adapted to engage with one or more elements of the socket housing in each of the orientations of the socket unit.

23. An electrical socket box as claimed in claim 20 or 21 , wherein the abutment or engagement of the housings of the base and socket units prevents insertion of the socket unit at the mounting position other than in one of the plurality of orientations in which the connectors of the socket unit are connectable to their respective power rails.

24. An electrical socket box as claimed in any of claims 21 to 23 as dependent on claim 11 , wherein the abutment or engagement of the housings of the base and socket units prevents insertion of the socket at the mounting position other than in a direction substantially parallel to the insertion direction.

25. An electrical socket box as claimed in claim 22, wherein the elements of the housings cooperate so as to prevent rotational motion of the socket unit in the base unit.

26. An electrical socket box as claimed in claim 25, wherein the elements of the socket housing are located on the periphery of the socket housing.

27. An electrical socket box as claimed in any preceding claim, further comprising an upper housing adapted to engage with the base unit so as to be operable to hold the socket unit in place in each of its orientations in the socket box while providing an opening through which the socket of the socket unit may be accessed.

28. An electrical socket box as claimed in claim 27, wherein the upper housing is adapted to be releasably engaged with the base unit.

29. An electrical socket box as claimed in claim 27 or 28, wherein, in the mounting position, the socket unit is held flush in the opening of the upper housing.

30. An electrical socket box as claimed in any of claims 27 to 29 as dependent on claim 20, wherein the upper and socket housings are mutually configured such that the upper housing abuts part of the socket housing.

31. An electrical socket box as claimed in any of claims 27 to 29 as dependent on ciaim 20, wherein the upper and socket housings are mutually configured such that one or more elements of the upper housing are adapted to engage with one or more elements of the socket housing in each of the orientations of the socket unit.

32. An electrical socket box as claimed in claim 30 or 31 , wherein the elements or abutting surfaces of the upper and socket housings cooperate so as to prevent rotational motion of the socket unit in the socket box.

33. An electrical socket box as claimed in any preceding claim, wherein, at at least one end, each power rail is terminated at a connector adapted to allow connection of the socket box to a power supply.

34. An electrical socket box as claimed in claim 33, wherein the power rails are terminated at both ends at a connector arrangement, at one end the connector arrangement being a female connector arrangement and at the other end the connector arrangement being a male connector arrangement, the two being so adapted as to allow the female connector arrangement of one socket box to mate with the male connector arrangement of a second like socket box.

35. An electrical socket box substantially as described herein with reference to any of figures 1 to 3.