GB2432264A

GB2432264A - Cable entry for electrical enclosure

Info

Publication number: GB2432264A
Application number: GB0522831A
Authority: GB
Inventors: Nicholas Smith; David Alfred Kelly
Original assignee: Hager Engineering Ltd
Current assignee: Hager Engineering Ltd
Priority date: 2005-11-09
Filing date: 2005-11-09
Publication date: 2007-05-16
Anticipated expiration: 2025-11-09
Also published as: GB2432264B; GB0522831D0

Abstract

A cable entry for an electrical enclosure comprises two elongate deformable elements 4, 5 which act across the cable and may be made of elastomeric polymer foam. Element 4 is supported by the back wall 1 of the box and element 5 has a rigid support 6.

Description

1 2432264 Apparatus The invention relates to an enclosure for

electrical, electronic or telecommunication equipment which is mounted on internal walls of buildings. In particular it relates to such an enclosure, particularly an electrical switchgear enclosure, also known as a consumer unit, with a cable entry point seal.

Where enclosures for electrical, electronic or telecommunication equipment, such as switches, fuse boxes, consumer switchgear units, telephone sockets, alarm systems, are mounted directly onto a wall without first forming a recess in the wall, it is :. : . necessary for the enclosure to be furnished with an entry point through which cables S...

* *** wires or trunking can enter and leave the enclosure.

S * S I * S.

:: 15 An adequate seal around the cable is required, commensurate with various *** standards, in order to prevent the ingress of parts of the human body, wires, screws, *.*.

S building debris, rubble, plaster or dust. International standard IEC 60529 classifies the level of protection provided against the intrusion of such solid objects. This invention is concerned with enclosures which have an ingress protection rating of IP4X, which means that the ingress of objects greater than 1mm in size is prevented.

Conventionally, in order to meet such standards, cables pass through apertures in the enclosure which may be individually fitted with grommets or mastic sealant used to form a seal between the cable and the edges of its respective aperture.

The sealing of the apertures is a time consuming process when fitting an enclosure.

Hence there is a need for an enclosure with a cable entry point that overcomes some

of these inconveniences of the prior art.

In a first aspect, the invention provides an enclosure for electrical, electronic or telecommunication equipment, adapted for mounting to a surface of a wall of a building, comprising a back plate, edge walls attached to the back plate and a cover removably attached to the edge walls, the enclosure comprising a cable entry point system, the entry point system comprising an elongate aperture in a edge wall, a first elongate deformable element provided on the back plate and adjacent to the aperture and a second elongate deformable element adjacent to the aperture and provided on . : : a first surface of a rigid support element which is removably attached to the back * ** plate or edge walls adjacent to the aperture whereby a surface of the second elongate deformable element is pressed towards a surface of the first elongate * * 15 deformable element for enveloping one or more cables passing though the aperture and between the surfaces of the first and second elongate deformable elements in * order to provide a seal sufficient to inhibit ingress of particulate matter through the elongate aperture or around the one or more cables into the enclosure.

Surprisingly, it has been found that by use of such a system, where cables are squeezed between two elongate deformable elements, which thus close off the aperture of the cable entry point, solid ingress protection ratings of IP4X or better can be achieved rapidly and conveniently without the need for fitting grommets or using a mastic sealant to or around the cable, or the need to provide a plurality of cable-specific apertures in an enclosure. --3

An enclosure for electrical, electronic or telecommunication equipment includes such enclosures as alarm boxes, consumer units, switchgear enclosures and other such electrical distribution enclosures, particularly but not exclusively where the enclosure is intended for fitment to the surface of a wall without first providing a recess in the wall to hold the enclosure. The invention is particularly appropriate for consumer units, where multiple cables enter and exit the unit.

Typically, the back plate and edge walls of the enclosure will be formed as a unitary piece, suitably as a plastic moulding. By edge walls is meant all the walls of the enclosure, including the sides, the top and the base. Suitably the enclosure will have the approximate form of a rectangular parallelepiped. * *5 * S I I.. I *.SS

* The cover is removably attached to the edge walls to complete the enclosure. This * * attachment may be by clips, screws bolts or any suitable attachment means. Where :: 15 the enclosure is a consumer unit, the back plate may hold various circuit breakers * : ::. which protrude through the aperture in the front cover, protected by a removable or * openable lid or cover enclosing the circuit breakers.

The elongate aperture in an edge wall of the enclosure may be formed entirely within the edge wall, or may be in the form of a cut-out in the edge wall, with the cover forming one of the long edges of the elongate aperture.

The elongate deformable elements may both be of the same material, or they may be of different materials. It is to be understood that in what follows, all pairings of suitable materials are included for the first and second elongate deformable elements.

A suitable material for the elongate deformable elements is an elastomeric polymer.

Suitably, the element will be in the form of a bar of substantially rectangular cross section when in its undeformed state. Alternatively, the element may be in the form of a flexible elastomeric fin. The material should be sufficiently deformable that the element can conform sufficiently to the contours of a cable, when the first and second elongate deformable elements of the invention are pressed together, around the cable in the enclosure of the invention, such that the passage of solid materials between the cable and the element is inhibited, preferably at least to a solid ingress protection rating of IP4X. The element may deform compressively (i.e. in a direction substantially at right angles to the surface of the cable) , for instance when the elongate element is a bar of rectangular cross section, or may be deformed laterally :.: * (i.e. along the surface of the cable) when the element is a flexible elastomeric fin. * .

The elongate deformable element may comprise or consist essentially of a solid : * : 15 elastomeric polymer, or may comprise or consist of a closed or open cell foam or *: :: * synthetic sponge, such as a polyurethane foam, polyester, expanded polyethelene, isoprene rubber, polyvinyl chloride (PVC), EPDM rubber (ethylene propylene diene monomer) or a gel type material. Such materials are commercially readily available and may have the additional advantage of fire redardancy. Such materials are particularly suitable when the elongate deformable element is in the form of a bar of substantially rectangular cross section.

When the elongate deformable element is an elastomeric fin, it is preferred that the material used is a synthetic rubber such as an isoprene rubber, nitrile (acrylonitrile) rubber or a silicone rubber, The fin has dimensions and flexibility such that is deformed laterally when pushed against a cable, i.e. it is deformed towards the outside or the inside of the enclosure along the surface of the cable.

When the elongate deformable element is an elastomeric fin, it is preferably provided with slits substantially normal (i.e. at right angles) to its long edge, the long edge adapted to contact cable, such that the elastomeric fin can more easily conform to the shape of the cable to prevent the ingress of solid materials. This allows for the prevention of ingress of solids without the need for excessive pressure forcing the first and second elongate deformable elements together.

The elongate deformable material may be in the form of a brush. In this case, the bristles of the brush deform laterally, passing to either side of cables or trunking, as the first and second elongate elements when the first and second elongate :.: . deformable elements of the invention are pressed together, around the cable or S'S.

trunking in the enclosure of the invention. The bristles may be natural bristle, or may * : be synthetic bristles. The use of a brush allows for the initial positioning or spacing of * 15 cables between the bristles as the enclosure is assembled. *.* e.**

: It is also to be understood that different materials may be used in suitable combination within one elongate deformable element. So, for example, an element may consist of a block of elastomeric polymer surmounted by a brush strip.

It is preferred if the elongate deformable elements are formed from a material which is flame or fire resistant or retardant.

The elongate deformable elements may by provided on the back plate and the rigid support element by any suitably means. They may be permanently attached or may be removably attached or held in place. For example the back plate and/or the rigid support means may be provided with a groove or slot into which its respective rigid support element will fit. This allows for convenient replacement or interchangeability of the elongate deformable means, to allow for the use of different elongate deformable means when different cable is used with the enclosure. The respective elongate deformable elements may be attached to the back plate and/or rigid support element by means of an adhesive or clips.

Preferably, the rigid support element is removably attached to the back plate or edge walls by attachment means located towards each end of the rigid support and adapted to engage with corresponding locating means provided on the edge walls or back plate. This simplifies the construction and casting of the back plate and edge wall assembly in that no locating means need to be provided in the central region of * I. :.: * the enclosure. * I

The attachment and locating means can be any suitable combination such as screw and tapped hole, but a preferred attachment means is a clip means adapted to *: : :.* engage with a locating means which is a recess means. ** ** * * *

Suitable clip means are resilient arms, where each arm is provided with a tooth to engage with a recess provided in the locating means. This arrangement allows for easy removal and reattachment of the rigid support means during the fitting of the enclosure, such that cables or trunking can be repositioned or spaced as needed.

In order that the enclosure is suitable for use with cables of different sizes, it is preferred that the locating means are provided with two or more spaced recess means such that the location of the second elongate deformable means relative to the first elongate deformable means may be selected to provide an adequate seal around the cable or trunking. This allows for the inhibition of the ingress of solid j,I -7 materials into the enclosure without the need for excessive stresses on the constructional materials of the enclosure.

The invention is particularly suited to enclosures for domestic electrical switchgear, also called consumer units. These typically have several cables entering or leaving the enclosure. The mains electrical supply is generally distributed to various circuit breakers contained within the enclosure by means of one or more bus bars (live and possibly neutral) and terminal bars for neutral and earth. Such domestic consumer units are often positioned in dwellings, garages or outhouses with a dusty environment, so the inhibition of the ingress of particulate matter into the consumer unit is a necessity. a S. * S S S.. I S...

It is advantageous to provide the terminal bars on a surface of the rigid support : element, opposite the first surface of the rigid support element which carries the * 15 second elongate deformable element. This multiple use of the rigid support element *: : : * saves the need for extra fittings in the enclosure, and allows for rapid and convenient assembly and fitting of the enclosure.

To speed the fitting and assembly, the entry point may also be provided with spacing means, such as arms, extending substantially normally from a longitudinal edge of the elongate aperture across the aperture whereby the cables entering the entry point may be mutually spaced. The spacing means loosely hold the cables in place as the enclosure is assembled, preventing the cables from bunching together and thus preventing such bunching from hindering the operation of the seal.

The invention will now be further described by way of example only with reference to the accompanying drawings, in which: Figure 1 shows a perspective exploded view of an enclosure according to the invention with the cover not shown.

Figure 1 shows an enclosure for domestic electrical switchgear for locating and holding circuit breakers through which the electrical mains supply is redistributed in a building. Such units are called consumer units or distribution boxes. The back plate 1 is provided with mounting holes 10 which can be used for fastening the back plate 1 to a wall with screws. The back plate is formed as a unitary moulding with the edge walls 2 and the upper edge wall 12 is provided with an entry point system 3 for cables formed between the back plate 1 and the top surface of a rigid support :.: . element 6. The entry point system 3 is furnished with spacers 11 projecting from the back plate 1. A first deformable elastomeric polymer foam block 4 is adhered to the back plate I adjacent to the upper edge wall 12.

* The rigid support element 6 has clips 7 at each end, each clip with a tooth 8. A second deformable elastomeric polymer foam block 5 is located in a groove formed in the rigid support element 6. At the opposite side of the rigid support element 6, terminal bars 9 are mounted on the support.

In use, cables are fed in over the first deformable elastomeric polymer foam block 4 and spaced with the assistance of the spacers 11. The rigid support element 6 is then pressed it place such that the cables are squeezed and held between the first deformable elastomeric polymer foam block 4 and the second deformable elastomeric polymer foam block 5. When in place, the clips 7 lock the support in place as the teeth 8 engage with latches (not shown) on the inside of the edge walls 2. Cable can be connected to the terminal bars 9 either before or after locking the rigid support element into place. The cover (not shown) is clipped into place to complete the enclosure. * .* * * * SI. S S... S... S. I * . a * *5

I..... * S S.. * S *.S. S. *. * a *

S

Claims

Claims 1. An enclosure for electrical, electronic or telecommunication

equipment, adapted for mounting to an internal wall of a building, comprising a back plate, edge walls attached to the back plate and a cover removably attached to the edge walls, the enclosure comprising a cable entry point system, the entry point system comprising an elongate aperture in a edge wall, a first elongate deformable element provided on the back plate and adjacent to the aperture and a second elongate deformable element adjacent to the aperture and provided on a first surface of a rigid support element which is removably attached to the back plate or edge walls adjacent to the aperture whereby a surface of the second elongate deformable :. :1:, element is pressed towards a surface of the first elongate deformable element for S...

* enveloping one or more cables passing though the aperture and between the S surfaces of the first and second elongate deformable elements in order to provide a S.... S * 15 seal sufficient to inhibit ingress of particulate matter through the elongate aperture or * around the one or more cables into the enclosure. * a. *I a a a * .

2. An enclosure according to claim 1 wherein the first and/or second elongate deformable element comprises an elastomeric polymer.

3. An enclosure according to claim 1 or 2 wherein the first and/or second elongate deformable element is a bar of substantially rectangular cross-section when undeformed.

4. An enclosure according to any preceding claim wherein the first and/or second elongate deformable element is a flexible elastomeric fin.

5. An enclosure according to claim 4 wherein the elastomeric fin is provided with slits substantially normal to its long edge to facilitate deformation.

6. An enclosure according to claim 1 wherein the first and/or second elongate deformable element is a brush.

7. An enclosure according to any preceding claim wherein the rigid support element is removably attached to the back plate or edge walls by attachment means located towards each end of the rigid support and adapted to engage with corresponding locating means provided on the edge walls or back plate. * .*

: 8. An enclosure according to claim 7 wherein the attachment means is a clip **SS means and the locating means is a recess means adapted to engage with the clip means.

S..... * 15

9. An enclosure according to claim 8 wherein the clip means are resilient arms * . each provided with a tooth to engage with a recess provided in the locating means.

10. An enclosure according to any one of claim 7 to 9 wherein the locating means are provided with 2 or more spaced recess means whereby location of the second elongate deformable means relative to the first elongate deformable means may be selected to provide an adequate seal around the one or more cables.

11. An enclosure according to any preceding claim wherein the enclosure is an electrical switchgear enclosure comprising one or more terminal bars.

12. An enclosure according to claim 11 wherein the terminal bars are provided on a surface of the rigid support element opposite the first surface of the rigid support element.

13. An enclosure according to any preceding claim wherein the cable entry point system is provided with spacing means extending substantially normally from a longitudinal edge of the elongate aperture across the aperture whereby cables entering the entry point may be mutually spaced.

14. An enclosure as hereinbefore described with reference to and as shown in the accompanying figures. * S. * S S Sea a *.* * * S... ** a a * . * *.

S..... * S S.. * . C... S. *S * * . * a

Amendments to the claims have been filed as follows 1. An electrical switchgear enclosure comprising one or more terminal bars adapted for mounting to an internal wall of a building, comprising a back plate, edge walls attached to the back plate and a cover removably attached to the edge walls, the enclosure comprising a cable entry point system, the entry point system comprising an elongate aperture in a edge wall, a first elongate deformable element provided on the back plate and adjacent to the aperture and a second elongate deformable element adjacent to the aperture and provided on a first surface of a rigid support element which is removably attached to the back plate or edge walls adjacent to the aperture whereby a surface of the second elongate deformable element is pressed towards a surface of the first elongate deformable element for enveloping one or more cables passing through the aperture and between the surfaces of the first and second elongate deformable elements in order to provide a seal sufficient to inhibit ingress of particulate matter through the elongate aperture or around the one or more cables into the enclosure, wherein the terminal bars are provided on a surface of the rigid support element opposite the first surface of the rigid support element.

2. An enclosure according to claim 1 wherein the first and/or second elongate deformable element comprises an elastomeric polymer.

3. An enclosure according to claim 1 or 2 wherein the first and/or second elongate deformable element is a bar of substantially rectangular cross-section when undeformed.

4. An enclosure according to any preceding claim wherein the first and/or second elongate deformable element is a flexible elastomeric fin.

5. An enclosure according to claim 4 wherein the elastomeric fin is provided with slits substantially normal to its long edge to facilitate deformation 6 An enclosure according to claim 1 wherein the first and/or second elongate deformable element is a brush.

7. An enclosure according to any preceding claim wherein the rigid support element is removably attached to the back plate or edge walls by attachment means located towards each end of the rigid support and adapted to engage with corresponding locating means provided on the edge walls or back plate.

8. An enclosure according to claim 7 wherein the attachment means is a clip means and the locating means is a recess means adapted to engage with the clip means.

9. An enclosure according to claim 8 wherein the clip means are resilient arms each provided with a tooth to engage with a recess provided in the locating means.

10. An enclosure according to any one of claims 7 to 9 wherein the locating means are provided with 2 or more spaced recess means whereby location of the second elongate deformable means relative to the first elongate deformable means may be selected to provide an adequate seal around the one or more cables.

11. An enclosure according to any preceding claim wherein the cable entry point S system is provided with spacing means extending substantially normally from a longitudinal edge of the elongate aperture across the aperture whereby cables entering the entry point may be mutually spaced.

12. An enclosure as hereinbefore described with reference to and as shown in the S accompanying figures.