Flexible expandable seals are used, for example, within cavities between external and internal walls of buildings, between partitions and in roofing sections and concrete ceilings to provide inter alia fire-retardant properties.

Recent legislation imposes restrictions on impact and airborne sound transmissions in, inter alia, buildings and the present invention sets out to provide a flexible expandable fire-retardant seal which not only overcomes or alleviates many of the disadvantages to be found with existing fire-retardant seals but also has acoustic airborne and impact sound transmission properties to meet the requirements of all current legislation.

Our UK Patent Application 2234938 discloses an intumescent fire barrier of relatively light weight which comprises a layer of wire mesh sandwiched between sheets of ceramic fibre material each coated on at least one face with vermiculite. One or both sides of each sheet is coated with an intumescent paint which, on drying, provides a surface coating which can flex at least to a limited extent without cracking. The assembly of the wire mesh and coated fibre sheets is enveloped in one or more sheets of material having an external metallic foil surface.

Our International Patent Application WO 02/10525 Al discloses a fire-resistant spacer for separating tiled or slatted roof structures of adjoining buildings or building sections comprises at least one sheet of intumescent material and at least one sheet of deformable material sealed within an envelope of flexible material and a rib of flexible cellular fire- retardant foam or sponge in contact with an exposed surface of the envelope between opposed side edges thereof. The arrangement is such that in use the sides of the sealed envelope in which the intumescent material is present extend to positions at which they can be secured to neighbouring roof structure (preferably joists) of adjoining buildings or building sections with the rib extending between these neighbouring structures and to a height at least equal to the height of neighbouring tile battens of the roof structures, the sealed envelope and rib being subsequently covered by roof tiles.

UK Patent Application 2318594 discloses a concealed cavity fire stopping system which uses a preformed plastic sack which can be shaped to fill the voids or cavities common in the fabric of most buildings which unless fire stopped will allow fire spread through those cavities.

US Patent Application 2003/0049406 discloses a composite fire stopping article capable of fire stopping through-penetrations without the need for a secondary reinforcement structure which includes an interior insulating material, such as mineral wool, sandwiched between layers of an intumescent material. The insulating material and intumescent material may be enclosed in a bag formed of a polymeric material. The intumescent material is substantially free of graphite and consists essentially of filler material, binder material, and a hydrated alkali metal silicate intumescent component.

According to the present invention in one aspect, there is provided a flexible seal which comprises an elongate generally rectangular envelope of reinforced paper having an external metallic surface finish which encloses an elongate generally rectangular wire mesh and a similarly shaped elongate sheet of intumescent material, the seal being formed with a series of spaced airflow passageways extending from a lower surface to an upper surface of the seal.

The reinforced paper may comprise craft paper.

The seal may include two elongate sheets of intumescent material, one on either side of the wire mesh.

The intumescent sheet may comprise a ceramic fibrous material or a sheet or cloth of inorganic fibres coated or lined with intumescent material. Alternatively, the intumescent sheet may comprise ceramic fibres mixed with exfoliating graphite and/or sodium silicate in granular and/or powder and/or chip form.

Two or more rows of spaced airflow passageways may be provided, each row running lengthwise of the seal and generally parallel to the longitudinal axis of the seal. The airflow passageways of neighbouring rows may be out of register with one another. In cross-section, the passageways may be circular, rectangular, elongate, oval or otherwise.

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 from above of a seal in accordance with the invention; and Figure 2 is a section taken along line II-II of Figure 1.

The acoustic fire-retardant seal illustrated in the drawings is dimensioned for positioning within a wall cavity between the outer and inner walls of a building, for example a timber framed or brick walled building, at the transition between a lower and an upper storey of the building. The seal operates to prevent the movement of smoke and flames between the storeys in the event of a fire, to provide a ventilated acoustic barrier in normal circumstances and to inhibit the collection of moisture within the cavity to the detriment of, for example, the timber walls of a timber framed house.

The illustrated seal comprises an elongate envelope 1 of reinforced paper having an external metallic surface finish. The envelope is typically produced from craft paper. Positioned within the envelope 1 is a length of wire mesh 2 and a sheet of intumescent containing material 3. In Figure 2, the adjoining faces of the envelope 1, the mesh 2 and the sheet 3 are shown spaced apart. This spacing is for ease of illustration and understanding. In practice, the adjoining surfaces will be in contact with one another.

The intumescent strip or sheet may comprise a ceramic fibrous material or a sheet or cloth of inorganic fibres coated or lined with intumescent material. Alternatively, the intumescent strip or sheet may comprise ceramic fibres mixed with exfoliating graphite and/or sodium silicate in granular and/or powder and/or chip form.

A series of spaced ventilation passageways 4 extend through the seal. As shown, these passageways are generally oval in section.

Passageways having other cross-sections and a circular, elongate, rectangular or the like may however be employed. Typically, the width of the passageways, is around 5mm to 15mm and the length is typically around 20mm to 40mm. A preferred length is 2.5cm. As shown, three generally parallel rows of passageways 4 are provided. Typically, the spacing between neighbouring passageways of each row is between 25 and 40 mm; a preferred spacing is around 35mm. Other dimensions for the passageways and their spacings may however be employed. The width of the envelope is typically between 10cm and 30cm, preferably around 21cm, and its length is determined by the length of the cavity to be filled. A typical space is between 30cm and 40cm; a preferred length is 35.5cm. Typically, the seal is produced as a roll from which pieces of the required length can be cut.

In use, the seal is positioned lengthwise between the cavity walls of, for example, a brick built or timber framed house at the level of the transition between upper and lower storeys of the building. The seal is flexed across its width to fit the cavity and is retained in place by friction or by securing one or both sides of the seal to the adjoining walls. The seal is preferably positioned with its upper surface inclined towards the outer brick wall of the building and away from the inner wall or timber frame of the house. This prevents moisture collection on or close to the inner wall or timber frame. The passageways 4 enable air to circulate freely within the cavity.

In the event of a fire, the seal exfoliates completely to fill the cavity and prevent the flow of flames and smoke between the two storeys. In normal use, the seal acoustically insulates the upper floor of the building from airborne and impact sounds generated at the lower floor of the building and vice versa.

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. For example, a second sheet of intumescent containing material may be provided between the wire mesh 2 and the adjoining inner face of the envelope 1.