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 services 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°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°C while the sheets expand. Seal flexibility is therefore substantially lost.

Improved flexible preformed fire-retardant seals are disclosed in our co-pending Application PCT/GB01/00323. 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.

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.

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 adjoining plasterboard walls of timber framed properties.

In one aspect, the invention provides a cover for encompassing the closed sides of a conduit fitting, the cover comprising sheets of a fire-retardant sound-proofed material joined together to define a cover open on one of its sides and dimensioned to fit snugly about the external walls of an open-sided conduit fitting.

According to the present invention in another aspect, there is provided 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 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.

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.

In use, the cover may be adhered to an internal surface of a wall of plasterboard or other material using an intumescent adhesive at a position opposite an opening made in an adjoining wall of plasterboard or other material which forms the other side of a wall cavity with cabling passing through one cover wall through suitably positioned openings; the required conduit fitting is then positioned snugly within the cover to enable a wall mounted plug, for example, to be wired into a ring main. Pads of intumescent containing material are positioned within the fitting before assembly within the cover.

As an alternative to sheets of preformed flexible cellular fire-retardant foam or sponge, covers in accordance with the invention may comprise sheets of ceramic paper or fireproofed felt coated with a fire-proofed material. Construction and installation of such covers is essentially as described above in relation to the cover produced from sheets of fire-retardant foam or sponge material.

In one example of a cover in accordance with the invention, 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 250°C to 300°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.

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.