EP1459008B1

EP1459008B1 - Covers for electrical fittings

Info

Publication number: EP1459008B1
Application number: EP02785640A
Authority: EP
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: 2006-07-12
Anticipated expiration: 2022-12-10
Also published as: DE60213130D1; EP1459008A1; WO2003056233A1; ATE333070T1; GB0130869D0; AU2002350927A1

Abstract

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

Description

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 down lighters. 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 down lighters 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 fabric hood shaped to include a top and one or more upstanding side walls each including a lining of 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 lining may be applied to the internal surfaces of the fabric top and side wall(s) of the hood. Alternatively, the lining may be sandwiched between two fabric sheets from which the top and side walls are made.
In a preferred arrangement, an intumescent gasket comprising a card which overlies a fibrous sheet impregnated with carbon granules is secured to the top or one of the walls of the cover. One or more ventilation apertures may be provided in the cover which also pass through the top or wall(s) of the cover to enable electrical wiring to pass to an electrical fitting protected by the cover.
The cover may also include a plurality of fabric pieces secured to the lower margin of the side wall of the cover for attachment to surrounding structure of the ceiling space.
These fabric pieces extend inwardly from the lower margin(s) of the side wall(s), the connecting means co-operating with the fabric pieces to secure the cover to the adjoining surfaces of the structure.
The connecting means may comprise at least one fixing strap secured to the interior fo the side wall(s) of the hood and deformable around an edge of the supporting structure to connect the hood to the supporting structure.
The fabric preferably is a fibrous cloth.
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;
Figure 2 is a section to an enlarged scale taken through one wall of the cover shown in Figure 1;
Figure 3 is a plan view from above of an alternative cover to that shown in Figure 1; and
Figure 4 schematically illustrates a fixing for securing the cover to an adjoining ceiling structure.

The cover illustrated in Figures 1 and 2 is produced from superimposed layers of a fibrous woven cloth 1 (e.g. a glass fibre woven cloth) between which are positioned one or more layers of flexible cellular fire-retardant foam or sponge 2. These foam or sponge layers therefore provide a lining for the cloth layers of the cover. Typically, the thickness of the foam or sponge lining is between 5 and 20mm; preferred thicknesses are between 10 and 15mm.
The cover is generally circular in cross-section and comprises an upstanding side wall 3, a top 4 and floor pieces 5 which extend inwardly from the lower margin of the side wall. The foam or sponge lining 2 is positioned between the superimposed fabric sheets of the side wall 3 and the top 4 of the cover.
Typically the side wall 3 is produced from lengths of sponge or foam lined glass fibre cloth which are sewn together at their ends, the top 4 then being secured to the upper margin of the side wall 3 again by sewing. The floor pieces 5 are simply sewn to the lower margin of the side wall and are cut to enable the pieces 5 to lie flat on the adjoining surface of the suspended ceiling.
In an alternative embodiment, the side wall 3 and the top 4 are formed from a single fabric sheet lined internally with a layer of flexible cellular fire-retardant foam or sponge.
Typically the outside diameter of the cover is 289mm and the height of the cover is typically 145mm. In use, the top or side wall of the cover has secured to it a circular piece of card 6 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 the top or side wall of the cover by studs or rivets. In Figure 1, the gasket 6 has no holes formed in it for the passage of electrical cabling for the light fitting to be encompassed by the cover. In this arrangement, any holes which may be required are produced on site simply by forming one or more holes as required. In the embodiment shown in Figure 3, the gasket is formed with openings 7 through which can pass electrical cabling for the light fitting and ventilation apertures 8. Typically the outside diameter of the gasket is 60mm.
As will be appreciated, on many occasions the ceiling opening through which the cover must pass when being fitted is relatively small. Because of the flexibility of the fabric material from which the cover and the gasket is formed, the cover can simply be squashed of folded to form a narrow tube which can readily pass through even the smallest ceiling opening for location about the margin of the opening. Before doing so, the electric cabling which carries current to the electrical fitting is passed through an opening formed or already present in the top 4 of the cover. Once sited, the floor pieces 5 of the cover are secured to the upper surface of the ceiling plasterboard using fixing pins 9 such as illustrated in Figure 4. Other simple forms of fixings may be employed. The fixing pins 9 have the advantage that they can be secured in place using finger pressure. Downlighting can then simply be connected to a source of electricity via the appropriate cabling and the opening formed in the plasterboard ceiling closed with a lens cover in the normal way.
In a preferred embodiment, the fire-retardant lining 2 for the wall and top of the cover comprises sheets of polyurethane foam material of, say, 10mm thickness impregnated with an aqueous solution of a fire-retardant material 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 of 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 and the gasket 6 quickly expands to isolate the fitting entirely from the surrounding structure thereby confining the fire and maintaining the fire resistance of the structure.

Claims

A fire-resistant cover for an electrical fitting to be recessed into a supporting structure, the cover comprising a fabric hood shaped to include a top (4) and one or more upstanding side walls (3) each including a lining of a layer (2) of flexible fire-retardant foam or sponge coated with a primer solution including a sealant and with a flowable coating of fire-retardant material.
A cover as claimed in claim 1 wherein the lining (2) is applied to the internal surface of the fabric top (4) and side wall(s) (3) of the hood.
A cover as claimed in claim 1 wherein the lining (2) is sandwiched between two fabric sheets (1) from which the top (4) and side walls (3) are made.
A cover as claimed in any one of the preceding claims wherein an intumescent gasket comprising a card (6) which overlies a fibrous sheet impregnated with carbon granules is secured to the top (4) or one of the walls (3) the cover.
A cover as claimed in claim 4 in which the gasket includes a plurality of ventilation apertures (8) which also pass through the top (4) or wall(s) (3) of the cover and through one (7) of which electrical cabling can pass to an electrical fitting protected by the cover.
A cover as claimed in any one of the preceding claims which also includes a plurality of fabric pieces (5) secured to the lower margin of the side wall (3) of the cover for attachment to surrounding structure of the ceiling space.
A cover as claimed in claim 6 wherein the fabric pieces (5) extend inwardly from the lower margin(s) of the side wall(s) (3) and wherein connecting means cooperate with the fabric pieces to secure the cover to the adjoining surfaces of the structure.
A cover as claimed in claim 7 wherein the connecting means comprises at least one fixing strap secured to the interior of the side wall(s) (3) of the cover and deformable around an edge of supporting structure to connect the hood to the supporting structure.
A cover as claimed in any one of the preceding claims wherein the fabric of the hood is a fibrous cloth.
A cover as claimed in any one of the preceding claims wherein the foam or sponge comprises polyurethane or a silicone coated with a silane primer.