GB2277201A - Rail-mountable enclosure for electrical device - Google Patents

Abstract

An enclosure for an electrical device such as a fuse module or a circuit breaker module, has an integral formation 26, 27 on one of its edges for removable mounting of the device on a mounting rail 300 or 400, the enclosure being formed exclusively of an electrically conductive material, preferably metal such as aluminium or an aluminium allow which has good electrically conductive properties and is readily workable. <IMAGE>

Description

Rail-Mountable Enclosure for Electrical Device This invention relates to an enclosure for an electrical device, such as a fuse module or a circuit breaker module, which is capable of being removably mounted on a standard mounting rail.

It is standard practice to provide modular electrical devices which can be readily mounted on an electrically conductive rail, and optionally slid along the rail to an operative position. Such devices stack neatly lengthwise along the rail, and abut face-to-face. Their identity is usually marked with a label on the exposed side edge remote from the rail, which may optionally project through an aperture in a partition wall, for example in a fusebox.

These rails are sometimes called DIN rails or TS-type rails, and they are easy to instal at low cost inside electrical equipment or on panels or walls.

The enclosures, sometimes known as terminal housings, are generally moulded for ready mounting and dismounting from such standard rails. By stacking or cascading them on a single rail, high density terminations and packaging are possible. Plastics mouldings are generally used for this purpose, since they can be made at low cost.

The problem with such rail-mountable enclosures for the electronics sector is that the more tightly the enclosures are packed together, the more likely there is that interference will occur between adjacent units, giving rise to electrical signals and data spilling over from one unit to the next. This is of especial concern today with the enforcement of EMC (Electro Magnetic Compatibility) directives. Manufacturers of such enclosures can often offer an electrically-screened version by spraying or filling the plastic with a metal, but this substantially increases the cost and is environmentally undesirable because the process uses volatile organic compounds.

A particular problem arises also with the hazardous applications of such devices, in filtering, screening and lightning protection for example. Not only is good screening essential, but also a good electrical earth bond is mandatory. So far, this has only been achieved with plastics or plastics/metal hybrid enclosures, at substantially greater expense and complexity.

The invention provides an enclosure for an electrical device, having an integral formation on one of its edges for removable mounting of the device on a mounting rail, characterised in that the enclosure is formed exclusively of an electically conductive material. This enables the entire enclosure to be screened to earth through the mounting rail, and prevents mutual interference between adjacent such devices. The enclosure may be manufactured simply, for example as a rectangular tubular extrusion cut to the appropriate length, and closed at its ends by metal panels.

The conductive material is preferably metallic, and preferably aluminium or an aluminium alloy which has good conductive properties and is readily workable.

The enclosure preferably has side walls which define a substantially invariant cross-sectional shape along an axis. Preferably, all the side walls are formed together as a unitary piece, for example as a generally rectangular tubular extrusion. The axis of invariance is preferably parallel to the mounting rail to which it would be mounted in use.

Conveniently, the enclosure is generally flat and box-shaped, with major front and rear walls and minor side walls. The integral formation would then be on one cf the minor side walls.

The invention also includes electrical devices incorporating such an enclosure, for example a fuse module, surge protection module or indeed any modulor electronic product suitable for rail mounting.

As indicated previously, the earth connection between the enclosure and the mounting rail can be important, particularly for electrical devices for hazardous applications. Accordingly, the invention also provides an enclosure for an electrical device, having an integral formation on one of its edges for mounting the device on an electrically conductive mounting rail, the formation comprising a jaws for gripping the rail inwardly or outwardly, and an integrally-formed member acting on the jaws for removably clamping the jaws shut.

The clamping member is preferably adjustably biased, in a transverse direction across the jaws, by a reaction force from the enclosure wall.

Preferably, the clamping member is a flexible beam which depends pivotally from the said one edge. This flexible beam may be a generally V-shaped member with two articulated flexible arms, preferably the articulation is positioned to engage the rail and to act as part of the jaws.

Preferably, the clamping member is adjustable by means of a separate adjusting element accessible from the exterior of the enclosure. This separate adjusting element may for example be a bolt, in threaded engagement with the enclosure wall. Where the clamping member is a V-shaped member, one arm is preferably pivotally dependent from the said one edge, and the other arm is engaged at its end by the adjusting element with which it is generally parallel.

In this case, the apex of the V-shaped member swings in an arc selectively to engage the rail in use, as the arms flex. The said other arm of the V-shaped member then preferably slides against an inclined surface of the enclosure wall which faces the rail, so that forcibly sliding that arm pushes the apex towards the rail.

A preferred example of the invention will now be described, by way of example only, with reference to the accompanying drawings, of which: Figure 1 is a section through the centre of an electrical device embodying the invention; Figure 2 is a perspective view, to a reduced scale, of the device of Figure 1, but with a slightly different configuration; and Figure 3 shows four examples of electrically conductive mounting rails of standard type, on which the device of Figure 1 or Figure 2 could be mounted.

The enclosure 10 of Figure 1 is intended to be universal, in that it can be mounted on, and locked to, a variety of standard mounting rails, including thcse shown in Figures 3(a) to 3(d). The U-shaped rail 400 of Figure 3(a) is 35 mm across and 7.5 mm high: the steel is 1 mm thick. The slotted rail 400' of Figure 3(b) has the same dimensions: the slots are 25 mm, spaced by 11 mm gaps.

The G-shaped rail 300 of Figure 3(c) is 32 mm across, 15 mm high at one side and about 8 mm high the other side; it may be made of steel or aluminium, in either case 1.5 mm thick. In the example of the G-shaped rail 300' of Figure 3(d), the base is slotted, with slots 25 mm long, spaced by 7 mm gaps. All four profiles are of the TS-type.

The enclosure 10 of Figure 1 consists of an aluminium extrusion 12 in the form of a generally rectangular "tube", cut normal to its axis in two parallel planes.

This tubular extrusion forms the minor sidewalls of the enclosure; the axis of extrusion is parallel with the rail 300 or 400 on which the enclosure is mounted in use.

The open ends of the extrusion 12 are closed by means of a pair of metal, preferably aluminium, panels 500, Figure 2, secured by screws or rivets 600 into keyhole-shaped channels 13a-13e in the side walls.

The enclosure 12 is provided with a bolt 100 in screw-threaded engagement in the upper side wall 12 of the enclosure. The head of this bolt is accessible from outside the enclosure, for vertical adjustment of its position within the enclosure. This is provided for clamping or releasing the enclosure from the rail, in a manner to be described in detail below.

A printed circuit board 200, on which is mounted terminal blocks 212 and various other components (not shown), is slotted within the enclosure, with its edges engaging in recesses 18a and 18b in the side walls 17a and 17b respectively. Corresponding recesses 19a and 19b are provided for other ancillary equipment (not shown).

External formations include channel recesses 14a and 14b, allowing the thinned wall to be punched or stamped through, for access to blocks 210, for example.

Correspondingly, channels 16a and 16b in the side walls 17a and 17b respectively would provide for access through the wall to the interior components, e.g. for plugs and other connectors.

Partly closed channels 15a and 15b are formed on an inclined corner at the top of each side wall, and would allow exterior components to be mounted thereon.

The upper wall 12 has a projecting central portion 120, which provides extra space for accommodating components within the enclosure, and also serves to provide a visible indication of the identity of the device. The projection 120 may for example be mounted through an aperture in a plate (not shown), for example a partition in a fusebox housing or other housing. An identification plate may be slotted into the shallow channel 11.

As shown in Figure 1, a second device 10 may be positioned on the other side of the rail 300 or 400, beneath the first such device. Alternatively, this part of the enclosure may be shaped to allow it to be clipped directly on to the opposite part of the adjacent device 10. Thus the devices may be configured to stack one on top of the other, for example with a removable snap fit.

The lower edge 20 of the enclosure 10 is formed so as to clamp on to a standard rail 300 or 400. The rail would normally be of steel or aluminium, and the aluminium of the enclosure would be sufficiently ductile to deform resiliently and to provide a reliable clamp against the rail.

The lower edge 20 has right-angled projections 21 and 22 which together define a channel for receiving one side of the rail. In the case of the U-shaped rail 400, the right-hand edge of the rail is received in a recess 23 in the projection 21. In the case of the G-shaped rail 300, the taller side of the rail includes a right-angled bend which fits against the inner walls of the channel.

Above the projection 22, the edge wall continues at an inclination of about 450 inwardly, defining an inclined wall 25 terminating at a hinge 29 surrounding the recess 13c for one of the screws or rivets 600. When assembled, the face closure plate 500 serves to anchor the pivot point 29, relative to the remainder of the enclosure.

A V-shaped clamping member 26,27 is formed integrally, and extends across a gap between the inclined wall 25 and a wall 32 connected to the left-hand side portion of the lower edge 20. The clamping member 26,27 tends to flex throughout the length of each of its arms 26,27, and also to bend at its articulation 28 (at its apex) and at its pivot 29. The right-hand arm 26 extends vertically between the pivot 29 and a clamping shoulder 31 which is intended to engage the left-hand side of the G-shaped rail 302. This in turn urges the end 302 of the rail into a recess 24 on the left-hand side of the projection 22. In the case that the enclosure is clamped to a U-shaped rail 400 instead, the left-hand side of the rail is engaged by a recess just above the clamping shoulder 31.

The left-hand arm 27 of the clamping member is a similar length to the right-hand arm, and extends parallel to the planar surface 32, at an angle of about 200 to the vertical. Sliding, generally vertical motion of the arm 27 along the surface 32 causes motion of the clamping shoulder 31 in an arc, selectively to clamp or to release the enclosure from the rail. The left-hand arm 27 terminates with an enlargement 30 whose upper surface is engageable by the adjustment bolt 100, with which the arm is generally parallel. The PCB 200 is formed with an aperture to allow the bolt to extend therethrough; optionally, those parts of the PCB which need to be earthed may be connected by a wire to the lever 27.

The device is assembled from the "tubular" extrusion 12, the closure face panels 500, the bolt 100 and screws or rivets 600, together with all the electrical or electronic components, terminals and so on. In use, it is connected to the rail simply by slotting it over the rail to the position as shown in Figure 1, and then adjusting the bolt 100 downwardly so as to bias the lever in the right-hand direction. Before final tightening of the clamp, the device can be slid along the rail to its appropriate position. Removal of the device is achieved by reversing this process. It will be appreciated that the lever and the projection 21 in effect form a jaws operated on by the lever 26,27. The projection 22 is necessary only for the G-shaped rail.

Claims (21)

1. An enclosure for an electrical device, having an integral formation on one of its edges for removable mounting of the device on a mounting rail, characterised in that the enclosure is formed exclusively of an electrically conductive material.

2. An enclosure according to Claim 1, comprising a rectangular tubular extrusion closed at its ends by panels of an electrically conductive material.

3. An enclosure according to Claim 1, in which the conductive material is metallic.

4. An enclosure according to Claim 3, in which the conductive material is of aluminium or aluminium alloy.

5. An enclosure according to Claim 1, having side walls which define a substantially invariant cross-sectional shape along an axis.

6. An enclosure according to Claim 5, in which all the side walls are formed together as a unitary piece.

7. An enclosure according to Claim 5, in which the axis of invariance is parallel to the mounting rail to which it is intended to be mounted in use.

8. An enclosure according to Claim 1, which is generally flat and box-shaped, with major front and rear walls and minor side walls, the integral formation being on one of the minor side walls.

9. An electrical device incorporating an enclosure according to any preceding claim.

10. An electrical device according to Claim 9, in the form of a fuse module, surge protection module or any modular electronic product suitable for rail mounting.

11. An enclosure for an electrical device, having an integral formation on one of its edges for mounting the device on an electrically conductive mounting rail, the formation comprising a jaws for gripping the rail inwardly or outwardly, and an integrally-formed member acting on the jaws for removably clamping the jaws shut.

12. An enclosure according to Claim 11, in which the clamping member is adjustably biased, in a transverse direction across the jaws, by a reaction force from the enclosure wall.

13. An enclosure according to Claim 11, in which the clamping member is a flexible beam which depends pivotally from the said one edge.

14. An enclosure according to Claim 13, in which the flexible beam is a generally V-shaped member with two articulated flexible arms.

15. An enclosure according to Claim 14, in which the articulation is positioned to engage the rail and to act as part of the jaws.

16. An enclosure according to Claim 11, in which the clamping member is adjustable by means of a separate adjusting element accessible from the exterior of the enclosure.

17. An enclosure according to Claim 16, in which the separate adjusting element is a bolt in threaded engagement with the enclosure wall.

18. An enclosure according to Claim 14, in which one arm of the V-shaped member is pivotally dependent from the said one edge and the other arm is engaged at its end by the adjusting element with which it is generally parallel.

19. An enclosure according to Claim 18, in which the apex of the V-shaped member is swingable in an arc selectively to engage the rail in use, as the arms flex.

20. An enclosure according to Claim 19, in which the said other arm of the V-shaped member slides against an inclined surface of the enclosure wall which faces the rail, so that forcibly sliding that arm pushes the apex towards the rail.

21. an enclosure substantially as described herein with reference to Figures 1 and 2 of the drawings.