Conventional fire doors are extremely heavy, difficult to instal, expensive and provide relatively limited protection as a barrier against smoke and flames. One reason for the weight and consequent installation problems is the use of heavy gauge metal sheets to inhibit the progress of smoke and flames. Because of the problems referred to above, fire doors are used sparingly and generally only at key access points.

One object of the present invention is to provide a relatively lightweight and easy to instal fire door capable of replicating the style and appearance of conventional interior and exterior doors and which, most importantly, offers full protection against the passage of smoke and flames for periods in excess of thirty minutes.

Fire protection periods in excess of sixty minutes have been achieved in fire testing of doors in accordance with the invention; this compares very favourably with fire protection periods offered by conventional fire doors.

In one aspect, the invention provides a fire door or fire panel which comprises a timber frame to which facing panels are secured and within which is retained a ceramic sheet coated on one or both sides with a cured solution of an aqueous polymer system containing one or more intumescent additives, the cloth being sized to fill substantially the entire space defined by the sides and cross members of the frame, and being positioned between and spaced from the facing panels of the door or panel.

The ceramic sheet may comprise a woven ceramic cloth, which may include a filament matrix to provide added integrity.

In a preferred embodiment, the coating solution comprises an aqueous acrylic vinyl acetate copolymer plasticised by a chlorinated paraffin, typically a coating marketed by the Applicant under the trade name"HWO1". This product is an emulsion paint designed to upgrade the fire rating of internal surfaces. It does not support combustion and when subject to heat intumesces to form an insulating barrier to fire and smoke. The fire retardancy and intumescence capability of the coating is created by the inclusion of, preferably, an ammonium polyphosphate, melamine and pentaerythritol system. The formulation may be stabilised for storage and ease of application by a surfactant and acrylic associative thickener.

Typically, the coating solution includes by weight % 8 to 17% of the polymer system, up to 0. 75 % of a defoamer, up to 0. 75 % of a biocide, up to 1.25% of a surfactant, up to 6.0 % of a plasticizer, up to 13.0% of melamine, up to 13% of pentaerythritol, up to 35. 0% of ammonium phosphate, less than 0.7% of an associative thickener, and up to 6.0% of a pigment, balance water.

In a preferred embodiment, the coating solution comprises 10 to 15% polymer system, up to 0.5% of a defoamer, up to 0.5% of a biocide, up to 1.0% of a surfactant, up to 5.0% of a plasticizer, up to 12% of melamine, up to 12% of pentaerythritol, up to 30% of ammonium phosphate, less than 0.5 % of an associative thickener and up to 5 % of a pigment.

The ceramic sheet is preferably coated on both of its sides, the coating being cured for a period typically of between four to eight hours. Typically, the coating is applied at a room temperature of between 5°C and 40°C. A typical service temperature range for the solution (i. e. the temperature range during which the solution is inactive) is-20°C and 70°C.

The inner peripheries of the sides and cross members of the frame may carry a continuous rail against one side of which the side edges of a unitary coated ceramic sheet abut and are attached, a second continuous rail then being secured to the inner peripheries of the sides and cross members of the frame in contact with the exposed side edges of the ceramic sheet to trap these edges between the rails and to hold the sheet firmly in place.

The facing panels may be of timber, ply, cardboard or other conventionally used material. The rails may be of timber or like material.

Once assembled, the fire door has the weight and appearance of a conventional interior or exterior door.

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 side view of a fire door in accordance with the invention with one facing panel removed; and Figure 2 illustrates to an enlarged scale a detail of the door shown in Figure 1.

The fire door illustrated in the drawings has a timber frame comprising sides 1 and upper and lower cross members 2,3. Typically, the external dimensions of the frame are 2135mm by 915mm and the cross sectional dimensions of the sides and cross members are 45mm by 20mm. The frame is closed by facing panels 4, only the rear panel being shown in Figure 1 for ease of clarity. Around the inner periphery of the frame is a pair of continuous rails 5,6. Typically, these are in section 20mm by 20mm and may be of timber or other suitable material. Cross members 7 extend between the door sides 1 on each side of the rails 5,6. Retained between the rails 5,6 is a sheet 8 of ceramic material coated with a cured solution of an aqueous polymer system containing one or more intumescent additives. In a preferred embodiment, the solution comprises acrylic vinyl acetate copolymer plasticised by a chlorinated paraffin. The sheet is typically a woven ceramic cloth which includes an internal matrix of metallic fibres to provide enhanced integrity. For ease of explanation, only sections of the sheet 8 are illustrated. It is to be understood, however, that the sheet 8 completely fills the space between the sides and upper and lower cross members of the frame. Whereas it is preferred that a unitary sheet is employed, two or more overlapping sheets may be used.

If required, a 150mm x 20mm block 9 is provided to receive a lock.

Typically, the coating solution included by weight % 8 to 17% of the polymer system, up to 0.75 % of a defoamer, up to 0.75 % of a biocide, up to 1.25 % of a surfactant, up to 6.0% of a plasticizer, up to 13.0% of melamine, up to 13 % of pentaerythritol, up to 35. 0% of ammonium phosphate, less than 0.7% of an associative thickener, and up to 6.0 % of a pigment, balance water.

In a preferred embodiment, the coating solution comprises 10 to 15% polymer system, up to 0.5 % of a defoamer, up to 0.5 % of a biocide, up to 1.0% of a surfactant, up to 5.0% of a plasticizer, up to 12 % of melamine, up to 12 % of pentaerythritol, up to 30% of ammonium phosphate, less than 0.5 % of an associative thickener and up to 5 % of a pigment.

For assembly purposes, the rail 5 is secured to the internal periphery of the sides and cross members of the frame by pins, adhesive or the like, and the cured ceramic sheet 8 is positioned within the frame with its side edges abutting against the rail 5. These edges may be attached to the rail 5 by adhesive or other conventional means. The rail 6 is then placed in position to trap the sheet edges between the opposed surfaces of the rails 5,6.

The cross members 7 are then secured to the frame providing additional support for the sheet 8 and, if appropriate, the block 9 for receiving a lock is positioned and secured to the frame. The cross members 7 on one side of the rails 5 and the block 9 may be installed before positioning of the sheet 8. Finally, the facing panels 4 are positioned onto the open sides of the frame and secured in place. As for the cross members, one facing panel may be secured in place before installation of the sheet 8.

The spacing between each side of the coated sheet 8 and the inner faces of each panel 4 is typically between 15 and 25mm, preferably 20mm.

In the event of a fire, once the temperature at the door surface rises to above the service temperature of the coating, the coating will intumesce to create an effective barrier to the passage of fire, heat and smoke. Fire tests conducted on doors in accordance with the invention have demonstrated protection against the passage of fire and smoke for periods in excess of thirty and sixty minutes.

Fire doors and panels in accordance with the invention are relatively lightweight and their appearance can match the appearance of conventional interior and exterior doors and panels. They offer the opportunity, therefore, of replacing all or a significant number of doors of a house or other building.

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