WO2003056239A1

WO2003056239A1 - Covers for electric fittings

Info

Publication number: WO2003056239A1
Application number: PCT/GB2002/005599
Authority: WO
Inventors: Derek Alfred Ward
Original assignee: Environmental Seals Ltd
Current assignee: Environmental Seals Ltd
Priority date: 2001-12-21
Filing date: 2002-12-10
Publication date: 2003-07-10
Anticipated expiration: 2004-06-21
Also published as: GB0130519D0; AU2002350928A1; EP1476695A1

Abstract

A fire-resistant cover for an electrical fitting to be recessed into a supporting structure comprises a hood formed from wire mesh and shaped to include a top (4) and one or more upstanding side walls (3) each lined with a layer (2) of flexible cellular fire-retardant foam or sponge. The fire-retardant foam or sponge is coated with a primer solution including a sealant and with a flowable coating of fire-retardant material.

Description

COVERS FOR ELECTRICAL FITTINGS

This invention relates to covers for electrical fittings and more especially but not exclusively to a cover for a recessed- electrical fitting, such as a downlighter set in a plasterboard ceiling, which, in the event of a fire, isolates the fitting from the structure in which it is recessed to maintain the fire resistance thereof.

Light fittings recessed into ceilings are well known. Such light fittings are known as downlighters. The heat generated by such light fittings can be considerable and represents a fire hazard. Also the recess in which such a fitting is mounted can itself provide a path for fire and smoke to a room or area located above that ceiling.

For cosmetic reasons, the aperture which is cut into a plasterboard ceiling to receive a downlighter is kept to a minimum. This restricts the size of ventilated cover which can be employed, particularly where an existing downlighter is to be fire-proofed. Fire-resistant covers for downlighters have previously been proposed but are generally too large to pass through a downlighter recess formed in an existing ceiling. Also, where this is possible, the covers rely upon fixings into the exposed surface of the plasterboard ceiling for securement purposes. This is aesthetically unappealing.

Our European Patent 805903B discloses a fire-resistant cover for an electrical fitting to be recessed into a supporting structure. The cover comprises a fabric hood coated or impregnated with a liquid based intumescent material and includes an aperture through which a cable can pass. The cover is shaped to include a top supported by one or more upstanding side walls, and comprises an intumescent gasket including a card which overlies a fibrous sheet impregnated with carbon granules secured to the top of the cover. A plurality of ventilation apertures is provided in the cover through one of which electrical wiring can pass to an electrical fitting protected by the cover, and means for connecting the cover to adjoining surfaces of the structure in which the electrical fitting is recessed.

Whereas our earlier covers provide excellent fire resistance, they provide only limited soundproofing. An object of this invention is to provide an improved downlighter cover having fire resistance properties which match those achieved by covers in accordance with our earlier patent and which, additionally, exhibit good sound proofing properties.

According to the present invention in one aspect, there is provided a fire-resistant cover for an electrical fitting to be recessed into a supporting structure, the cover comprising a hood formed from wire mesh and shaped to include a top and one or more upstanding side walls each lined with a layer of flexible cellular fire-retardant foam or sponge coated with a primer solution including a sealant and with a flowable coating of fire-retardant material.

The wire mesh may be produced from steel wire and the lining may include one or more openings for the passage of electric cabling.

Means may be provided for connecting the cover to the supporting structure. These connecting means may comprise at least one fixing strap secured to the lower edge of the side wall(s) of the hood. The strap(s) may be deformable around an edge of the supporting structure to connect the hood to the supporting structure.

The primer solution may comprise an aqueous solution of an acrylic copolymer which includes ammonium polyphosphate.

The fire-retardant coating may comprise a chlorinated vinyl copolymer system which includes a quantity of ammonium polyphosphate, zinc borate and/or magnesium and/or calcium carbonates.

The foam or sponge may comprise polyurethane or alternatively a silicone coated with a silane primer.

The primer solution may be allowed to dry before the fire-retardant material is applied. One or both coatings may be applied by brushing, rolling or spraying.

The invention will now be described by way of example only with reference to the accompanying diagrammatic drawings in which :-

Figure 1 is a perspective view of a cover in accordance with the invention; and

Figure 2 is a side view in section of the cover shown in Figure 1.

The cover illustrated in Figures 1 and 2 is produced from a steel mesh cage lined with a layer 2 of flexible cellular fire-retardant foam or sponge. Typically, the thickness of the sponge lining is between 5 and 20mm; preferred thicknesses are 10 and 15mm. The cover is generally square or rectangular in cross-section and comprises upstanding side walls 3, a top 4 and fixing straps 5 which extend outwardly from the lower marge of two of the side walls and can be secured to the ceiling structure by pins, nails or the like. The foam or sponge lining is positioned in contact with the side walls and top wall of the cage. The lining may be secured to the cage by, for example, staples.

Typically the width of the cover is 289mm and the height of the cover is typically 145mm. In use, either the top or one of the side walls of the cover has secured to it a circular piece of card which overlies and is bonded to a similarly shaped piece of intumescent material to define an intumescent gasket. This material typically comprises a fibrous sheet impregnated with an intumescent material such as carbon granules. The gasket comprising the card and intumescent piece may simply be secured to a respective side wall by studs or rivets. The gasket may be formed with a central opening through which can pass electrical cabling for the light fitting and four ventilation apertures. Similar openings are formed in the top or side wall of the cover. Typically the outside diameter of the gasket is 60mm.

In a preferred embodiment, the fire-retardant lining for the wall and top of the cover comprises sheets of polyurethane form material of, say, 10mm thickness impregnated with an aqueous solution of a fire-retardant material is coated with a solution of an acrylic copolymer system which includes ammonium polyphosphate. At temperatures in excess of 250°C to 300°C the ammonium phosphate forms phosphoric acid which reacts with the fire-retardant coating for the polyurethane liner. This primer coating_. has a viscosity similar to that of water and acts to seal the open cells of the polyurethane foam. The primer coating therefore seals the exposed surfaces of the polyurethane liner whilst retaining the flexibility characteristics of the liner. The primer coating also provides a bond to which the subsequently applied fire-retardant coating can adhere.

The surfaces of the polyurethane liner are then coated with one or more coatings of a chlorinated vinyl copolymer system which includes a quantity of ammonium polyphosphate, zinc borate and/or magnesium and/or calcium carbonates. The viscosity of this fire-retardant coating is more akin to an emulsion or paste.

The coatings may be applied by means of a brush, roller or spray. The primer coating not only seals the open pores of the polyurethane block but also, as mentioned previously, provides a primed surface to which the fire- retardant coating can adhere. The coated liner retains its flexibility and the bond between the respective coatings is sufficient to prevent cracking or other damage to the surface during handling of the liner. In use, the heat generated by downlighters recessed into ceilings can represent fire hazards. In the event of such a fire, the intumescent content of the cover liner quickly expands to isolate the fitting entirely from the surrounding structure thereby confining the fire and maintaining the fire resistance of the structure.

It will be appreciated that the foregoing is merely exemplary of fire- proofed covers in accordance with the invention and that modifications can readily be made thereto without departing from the true scope of the invention.

Claims

1. A fire-resistant cover for an electrical fitting to be recessed into a supporting structure, the cover comprising a hood formed from wire mesh and shaped to include a top and one or more upstanding side walls each lined with layer of flexible cellular fire-retardant foam or sponge coated with a primer solution including a sealant and with a flowable coating of fire-retardant material.

2. A cover as claimed in claim 1 wherein the wire mesh is produced from steel wire.

3. A cover as claimed in claim 1 or claim 2 wherein the lining includes one or more openings for the passage of electric cabling.

4. A cover as claimed in any one of claims 1 to 3 wherein means are provided for connecting the cover to the supporting structure.

5. A cover as claimed in claim 4 wherein the connecting means comprise at least one fixing strap secured to the lower edge of the wide wall(s) of the hood.

6. A cover as claimed in claim 5 wherein the strap(s) are deformable around an edge of the supporting structure to connect the hood to the supporting structure.

7. A cover as claimed in any one of the preceding claims wherein the primer solution comprises an aqueous solution of an acrylic copolymer which includes ammonium polyphosphate.

8. A cover as claimed in any one of the preceding claims wherein the fire-retardant coating comprises a chlorinated vinyl copolymer system which includes a quantity of ammonium polyphosphate, zinc borate and/or magnesium and/or calcium carbonates.

9. A cover as claimed in any one of the preceding claims wherein the foam or sponge comprises polyurethane or alternatively a silicone coated with a silane primer.