This invention relates to fireproofed covers for conduit fittings for receiving electrical cabling.

Electrical services which pass through fire walls or ceilings present potential fire hazards should PVC sleeved electrical cables be subjected to excessive heat caused by, for example, a fire occurring in a room or ceiling area through which the electrical cables pass. Overheating of conduit fittings such as dry lining boxes through which electric cables pass and within which electrical connections are made, for example, for wall mounted sockets, can cause self ignition of the cables; also, conduit fittings subjected to excessive heat can rapidly deform thereby enabling high temperature gases and flames to reach the cables and cause fires to occur. Fire damage to conduit fittings also enables fire and smoke to pass from one room of a building to another thereby aiding the spread of fire within that building. These problems are of increased concern in the context of timber framed properties.

The use of fibrous pads coated with intumescent material adhered to one internal wall of a conduit fitting is known from our patent GB 2247977B. The presence of such pads within a conduit fitting inhibits the spread of fire and smoke by intumescing completely to fill the fitting interior when subjected to temperature increases occasioned by fire. For timber framed properties particularly, there is an additional need to provide acoustic sound-proofing properties for conduit fittings.

Flexible expandable seals are known which comprise a preformed flexible cellular foam or sponge which has been impregnated with fire- retardant material. When subjected to temperatures of the order of 300-

400 ⁰ C such seals lose integrity thereby allowing flames to pass between the walls or other members between which the seal is positioned. Expandable seals are also known which comprise layers of sponge and intumescent sheets. The sponge content of these seals deteriorates at temperatures around 200 ⁰ C while the sheets expand. Seal flexibility is therefore substantially lost.

Improved flexible preformed fire- retard ant seals are disclosed in our co-pending Application PCT/GBO 1/00323. These seals comprise preformed flexible cellular fire-retardant foam or sponge coated firstly with a primer solution including a sealant and secondly with a flowable coating of a fire-retardant material. These seals offer enhanced fire protection and acoustic properties.

Our patent application GB 2391716 discloses a cover for a conduit fitting which comprises sheets of preformed flexible cellular fire-retardant foam joined together by an intumescent adhesive to form a cover open on one of its sides.

The cover defines a snug fit about an open-sided conduit fitting. Whereas this cover has proved to be successful in providing protection for the conduit fitting and the electrical cabling present within the fitting interior, problems have occasioned in effectively securing the cover to the wall in which the conduit fitting is located. The present invention sets out to overcome this problem.

Patent US 4616104 discloses an electrical box designed to minimise the potential for sound, smoke or fire travelling therethrough when wall- mounted and has an interior rigid housing and a moulded non-combustible exterior casing. The casing is a unitary, single-piece sheathing, having openings only for attachment of line conduit.

Hitherto such seals have been employed in block form for use within, for example, wall cavities. It has now surprisingly been established that the fire-retardant and acoustic protection properties of the described preformed flexible cellular foam or sponge can be retained even when relatively thin sheets of this material are produced.

It has also been established that sheets of ceramic paper or felt coated with a fluid intumescent have good fire-proofing and sound- deadening properties.

Our International Application WO 2004/013528 discloses a cover for a conduit fitting which comprises sheets of preformed flexible cellular fire- retardant foam or sponge joined together by an intumescent adhesive to form a cover open on one of its sides and dimensioned to define a reasonably snug fit about the external walls of an open-sided conduit fitting. Each sheet is coated firstly with a primer solution including a sealant and secondly with a flowable coating of a fire-retardant material. The primer solution operates to close the open pores of the surface and provides a bond to which the fire-retardant coating can adhere.

Whereas these covers have proved to be extremely successful in providing security against the spread of fire with enhanced sound proofing qualities, it has been found that there is a need to ensure that movement between the cover and the protected conduit fitting is eliminated or, at least, minimised.

According to the present invention in one aspect, there is provided a cover for a conduit fitting for location within a wall recess which comprises sheets of preformed flexible cellular fire-retardant foam sponge joined together by an intumescent adhesive to form a cover open on one of its sides and dimensioned to define a reasonably snug fit about the external walls of an open-sided conduit fitting, and means for securing the cover to one or more of the walls which define the recess comprising

metallic fixing strips which extend from and generally normal to the base of the cover and protrude from the adjoining upstanding cover wall by a predetermined distance, the protruding end including an aperture through which a pin or screw can pass to secure the cover to the neighbouring edge of a wall in which the cover is positioned, each sheet of the cover being coated firstly with a primer solution including a sealant and secondly with a flowable coating of a fire-retardant material, the primer solution operating to close the open pores of the said at least one surface and to provide a bond to which the fire-retardant coating can adhere.

The securing means may comprise metallic fixing strips which extend from and generally normal to the base of the cover and protrude from the adjoining upstanding cover wall by a predetermined distance, the protruding end including an aperture through which a pin or screw can pass to secure the cover to the neighbouring edge of a wall in which the cover is positioned.

Preferably, the predetermined distance is equivalent to the thickness of a plasterboard sheet.

One object of this invention is to provide a fireproofed cover for conduit fittings such as dry lining boxes which can readily be positioned between and secured to adjoining plasterboard walls of timber framed properties.

All surfaces of the foam or sponge sheets may be coated.

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 plan view of a fireproofed cover in accordance with the invention; and

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

The cover illustrated in the drawings has walls 1 upstanding from a base 2 all cut from one or more sheets of polyurethane foam material impregnated with an aqueous solution of a fire-retardant material.

Extending upwardly from the base 2 are metallic fixing strips 3, the upper ends of which protrude beyond the upper margins of the walls by a predetermined distance, e.g. a distance generally equal to the thickness of a standard plasterboard sheet. Each strip end includes a hole 4 to enable the fixing strips to be secured to the adjoining edge surface of a plasterboard or other wall surface when the cover and conduit fitting is positioned within a wall recess. The ends of the fixing strip remote from the holes 4 are turned through 90° to lie between the adjoining surface of the walls and the base.

In one example of a cover in accordance with the invention, the walls 1 and base 2 are cut from sheets of polyurethane foam material impregnated with an aqueous solution of a fire-retardant material are coated with a solution of an acrylic copolymer system which includes ammonium polyphosphate. At temperatures in excess of 25O ⁰ C to 300 ⁰ C the ammonium polyphosphate forms phosphoric acid which reacts with the fire-retardant coating for the polyurethane sheets. 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 sheets whilst retaining the flexibility characteristics of the sheets. The primer coating also provides a bond to which the subsequently applied fire retardant coating can adhere.

The surfaces of the sheets 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 sheets retain their flexibility and the bond between the respective coatings is sufficient to prevent cracking or other damage to the surface during handling of the sheets.

In some instances it may be preferable to allow the primer coating to dry before the fire-retardant coating is applied.

Once dried, the sheets are cut to sizes which approximate to the dimensions of the walls of the conduit fitting to be covered. The edges of the sheets are then adhered together using an intumescent adhesive to

define an open-sided cover of a shape which matches the. fitting to be covered but dimensioned marginally larger to enable the fitting to fit snugly within the cover.

Following assembly, the cover is inserted through an opening in, say, a plasterboard cavity wall to which a wall socket or the like is to be mounted. If necessary, the cover can, because of its inherent flexibility, be folded or screwed up to pass through the opening. Before entry of the cover, the area of internal wall of the opposed plasterboard cavity wall opposite the opening is coated with a layer of intumescent adhesive to retain the cover in place between the opposed cavity wall surfaces. Openings or slots formed in the appropriate side of the cover enable electrical cabling to enter the cover interior. The required conduit fitting is then located within the cover and the cover is fixed in place by pins or screws passing through the holes 4 onto the adjoining side edges of the plasterboard.

Covers in accordance with the invention have enhanced sound- deadening properties which enable the covers to act as acoustic covers for conduit fittings.

In the event of fire, the intumescent contents of the cover, the adhesive and the pads located within the fitting expand to fill completely all spacings between the fitting and the adjoining wall surfaces and within the fitting itself to prevent the flow of fire or smoke between the adjoining rooms defined by the cavity wall.

It will be appreciated that the foregoing is merely exemplary of fire- retardant seals in accordance with the invention and that various modifications can readily be made thereto without departing from the true scope of the invention as set out in the appended claims.