WO2017182818A1

WO2017182818A1 - Intumescent grille unit

Info

Publication number: WO2017182818A1
Application number: PCT/GB2017/051110
Authority: WO
Inventors: Robert Mann; Anthony Tapper; Colin Moss
Original assignee: Kilargo Pty Ltd
Priority date: 2016-04-22
Filing date: 2017-04-20
Publication date: 2017-10-26
Also published as: AU2017252595A1; AU2016100470A4; GB2549541B; GB2549541A; NZ748100A; AU2017252595B2

Abstract

Herein is provided an intumescent grille unit comprising: a plurality of slats, the slats being spaced apart to allow airflow between them, wherein each of the slats has opposing faces, and edges linking the opposing faces, the slats comprising: a core comprising an intumescent material; a non-intumescent outer shell, the shell having a static first portion, and a movable second portion connected to the first portion by a hinged or weakened section that extends along a direction substantially parallel to the edge of the slat, the second portion forming at least a portion of a face of the slat, wherein, on expansion of the intumescent material on exposure to heat, the second portion moves rotatably about the hinged or weakened section, to form a wall that extends toward an adjacent slat, reducing or preventing airflow between adjacent slats.

Description

Intumescent grille unit

Background Intumescent grille units are used in buildings, for example in doors and ventilation ducts, as passive fire barriers. The grille units are designed such that, in normal use, they allow air to flow through them, often between slats. However, when exposed to high temperatures, e.g. during a fire, intumescent materials within the grille units expand, decreasing the spacing between components (e.g. slats) of the units, such that airflow becomes restricted, and fire and/or smoke is prevented from spreading through the grille unit.

There are many different commercially available intumescent grille units, of different sizes and shapes, depending on the particular application. However, many units have some common features, such as a series of slats, typically about 44 mm wide, with a spacing of about 20 mm. Each slat includes a core of intumescent material, around which may be wrapped a thin aluminium foil, generously overlapped at the seam. When exposed to high temperatures, the intumescent material within the slats expands, together with the overlapping aluminium foil, and continues expanding until material from adjacent slats meets, thus closing the gap between the slats and preventing airflow and heat being able to pass through the grille.

While the prior art design of grille mentioned above has functioned reasonably well over a number of years, it is also associated with a number of problems. There has been a limit to the spacing between the slats, which can limit the airflow through the grille unit in everyday service. The slats are often rectangular in cross section, and, again, this can limit air flow past the slats, cause turbulence, and thus contribute to unacceptable noise as air flows through the unit. The intumescent material is often only available in sheets of fixed dimensions. This means that the sheets have to be cut to size (e.g. the 44 mm wide strips as mentioned above), before any other operations can commence, and this leads to considerable cut-offs and waste.

There is a desire to provide an alternative to, preferably an improvement upon, intumescent grille units of the prior art. In a first aspect, there is provided an intumescent grille unit comprising:

a plurality of slats, the slats being spaced apart to allow airflow between them, wherein each of the slats has opposing faces, and edges linking the opposing faces, the slats comprising:

a core comprising an intumescent material;

a non-intumescent outer shell, the shell having a static first portion, and a movable second portion connected to the first portion by a hinged or weakened section that extends along a direction substantially parallel to the edge of the slat, the second portion forming at least a portion of a face of the slat, wherein, on expansion of the intumescent material on exposure to heat, the second portion moves rotatably about the hinged or weakened section, to form a wall that extends toward an adjacent slat, reducing or preventing airflow between adjacent slats.

In a second aspect, there is also provided a method for making an intumescent grille unit according to the first aspect, the method comprising

providing the intumescent material, the non-intumescent outer shell, and associating them to form a plurality of slats.

Brief Description of the Figures

Figure 1A shows a cross-section of a plurality of slats from a prior art intumescent grille unit, before exposure to a fire.

Figure 1 B shows a cross-section of a plurality of slats from the prior art intumescent grille unit of Figure 1A, after exposure to a fire.

Figure 2A shows a cross-section of a plurality of slats from an embodiment of the intumescent grille unit according to the present invention, before exposure to a fire.

Figure 2B shows a cross-section of a plurality of slats from the intumescent grille unit of Figure 2A, after exposure to a fire. Figure 3A shows a cross-sectional view further embodiment of a slat for use in the grille unit of the present invention. Figure 3B shows a view of the end and one of the faces of the slat of Figure 3A.

Figure 3C shows a cross-sectional view further embodiment of a slat for use in the grille unit of the present invention.

Figure 4A shows an exploded view of an embodiment of the intumescent grille unit of the present invention. Figure 4B shows a further embodiment of a vertical frame for use in the intumescent grille unit of the present invention.

Figure 4C shows a further embodiment of a vertical frame for use in the intumescent grille unit of the present invention, connected to a slat, with a support in the form of a 'U'-shaped pin.

Figure 5 shows a further embodiment of an intumescent grille unit of the present invention. Detailed Description

Optional and preferred features of the present invention will be described below. Any optional or preferred feature may be combined with any other optional or preferred feature, and any aspect of the invention as described herein.

In an embodiment, each of the slats has the first portion and at least one second portion forming part of the shell on each of the opposing faces, and the second portions on adjacent slats, on expansion of the intumescent material on exposure to heat, move rotatably toward one another. In an embodiment, each of the slats has the first portion and at least two second portions forming part of the shell on each of the opposing faces, and the second portions on adjacent slats, on expansion of the intumescent material on exposure to heat, move rotatably toward one another. In an embodiment, each of the slats has the first portion and at least two second portions forming part of the shell on at least one of the opposing faces. In an embodiment, each of the slats has the first portion and second portions forming part of the shell on each the opposing faces, and the second portions on adjacent slats, on expansion of the intumescent material on exposure to heat, move rotatably toward one another, optionally such that they meet to form a wall. In some embodiments, the second movable portions may not meet on expansion of the intumescent material, but the movable portions nevertheless still act as a restriction to air flow and/or to heat, smoke and flames passing through the grille.

In an embodiment, each of the slats has two second portions forming part of the shell on each the opposing faces, which, on expansion of the intumescent material, move rotatably in opposite directions, with the second portions approximately opposite one another on adjacent slats, moving rotatably toward one another, preferably such that they meet to form a wall, such that two walls are formed on opposing sides of the grille unit.

In these embodiments, the movable second portions, on expansion of the intumescent material, can move toward one another, and, together, they can form a wall on at least one side of the grille unit, thus assisting in the restriction of airflow and acting as a barrier to heat, smoke and fire.

The shell may comprise a metal or a non-metal material. The shell preferably comprises a material, e.g. a metal, having a melting point of at least 400 °C, optionally a melting point of at least 500 °C, optionally a melting point of at least 600 °C. "Metal" includes elemental metals and alloys. The metal may be an extrudable metal. Extrudable metals include, but are not limited to, aluminium, alloys of aluminium, copper, brass, lead, tin, copper, titanium, molybdenum, vanadium, and zinc. The shell may comprise a non-metal fire-resistant material, e.g. a ceramic or a glass, e.g. a material such as a glass-fibre or ceramic-fibre reinforced material, such as glass or ceramic fibre-reinforced plastic.

In an embodiment, the shell comprises a layer, e.g. a metal layer (i.e. a layer comprising a metal), having first and second portions mentioned above, and the hinged or weakened section being formed by a section of the layer that is thinner than the sections of the first and second portions. The metal may be any suitable metal, e.g. a steel or aluminium. Aluminium is preferred, since it can be extruded and more easily formed into the shell than many other metals and is advantageously highly conductive of heat. In an embodiment, the shell comprises an aluminium layer, which may have been extruded, having first and second portions mentioned above, and the hinged or weakened section being formed by a section of the aluminium layer that is thinner than the sections of the first and second portions. The metal layer, e.g. aluminium layer, may be a metal extrusion, e.g. aluminium extrusion, which may be termed an extruded aluminium profile.

The shell, e.g. the metal layer, may have a thickness, in the first and second portions the same as or greater than in the thickness of the shell in the hinged or weakened section. The shell may have a thickness in the first and second portions of at least 0.1 mm, optionally at least 0.5 mm, optionally at least 0.6 mm, optionally at least 0.8 mm, optionally at least 0.9 mm, optionally at least 1 mm. The shell may have a thickness in the first and second portions of 5 mm or less, optionally 4 mm or less, optionally 3 mm or less, optionally 2 mm or less, optionally 1.5 mm or less. The shell may have a thickness in the first and second portions of from 0.1 mm to 5mm, optionally from 0.5 mm to 3 mm, optionally from 0.8 mm to 2 mm.

The shell may have a thickness, in the hinged or weakened section, of at least 0.05 mm, optionally at least 0.1 mm, optionally at least 0.2 mm, optionally at least 0.3 mm, optionally at least 0.4 mm, optionally at least 0.5 mm. The shell may have a thickness, in the hinged or weakened section, of 2 mm or less, optionally 1.5 mm or less, optionally 1 mm or less, optionally 0.8 mm or less, optionally 0.7 mm or less, optionally 0.6 mm or less. The shell may have a thickness, in the hinged or weakened section, of from 0.05 mm to 2 mm, optionally 0.1 mm to 0.9 mm, optionally 0.2 mm to 0.8 mm, optionally 0.4 mm to 0.9 mm, optionally 0.3 mm to 0.7 mm, optionally 0.4 mm to 0.6 mm.

In an embodiment, the shell comprises an aluminium layer, which may be an aluminium sheet or an aluminium extrusion, having first and second portions mentioned above, and the hinged or weakened section being formed by a section of the aluminium layer that is has been annealed to a greater extent than the first or second portions.

In an embodiment, the shell comprises a first portion, as defined herein, that is located along an edge of the slats, and optionally extends part way along each opposing face of the slat toward the other edge, and second portions of each section extends away from the first portion over each opposing face.

In an embodiment, the shell comprises two separate sections, each section comprising a first portion, as defined herein, that is located along each of the edges of the slats, and optionally extends part way along each opposing face of the slat toward the other edge, and second portions of each section extends away from the first portion over each opposing face, optionally such that a shell is formed around substantially the whole of the core comprising the intumescent material. The end of the second portions from each section on each face may meet or be spaced apart to a small extent (e.g. with the spacing being 2 mm or less, e.g. 1.5 mm or less, e.g. 1 mm or less, e.g. 0.5 mm or less).

In an embodiment, a support of a non-intumescent material extends through each of the slats, e.g. within the shell. "Extends through" indicates that the support extends through at least some of the length of the slat. The support may be located within the intumescent material or outside of the intumescent material. In an embodiment, a support of a non-intumescent material is provided proximal to one or both edges of each slat.

In an embodiment, the shell comprises two sections, each section comprising a first portion, as defined herein, that is located along each of the edges of the slats, and extends part way along each opposing face of the slat toward the other edge, and second portions of each section extends away from the first portion over each opposing face, optionally such that a shell is formed around substantially the whole of the core comprising the intumescent material, with each section comprising the first portion, as defined herein, and the support is located within the area of the core defined by the first portion of each section.

Preferably, the slats taper toward one or both of the edges. This has been found to assist airflow through the grille unit and reduce noise of the airflow as it does so. It has also been found that slats that taper toward one or both of their edges are easier to construct when using a mouldable, e.g. extrudable intumescent material, as described herein and/or the extrudable shell. Preferably, the spacing between adjacent slats is more than 20 mm, preferably 25 mm or more, preferably 30 mm or more, and preferably, the intumescent material in each adjacent slat is such that, when exposed to heat, is capable of expanding to close the gap between the slats. The spacing is measured before the grille unit has been exposed to heat to expand the intumescent grille materials. The use of certain intumescent materials as described herein, e.g. the extrudable and/or graphite-based materials, has allowed the spacing between slats to be widened compared to grille units of the prior art. The intumescent material preferably has an expansion volume of at least 75 cm³/g, optionally at least 100 cm³/g, optionally at least 150 cm³/g, optionally an expansion volume of at least 180 cm³/g, optionally an expansion volume of at least 200 cm³/g, optionally an expansion volume of at least 210 cm³/g, optionally an expansion volume of at least 220 cm³/g. The expansion volume is the maximum expansion volume displayed by the intumescent material.

The onset temperature, sometimes termed the intumescent temperature, is the temperature at which the intumescent material starts to expand. Preferably, the intumescent material has an onset temperature of 100 °C or more, optionally 1 10 °C or more, optionally 120 °C or more, optionally an onset temperature of 150 °C or more, optionally an onset temperature of 160 °C or more, optionally an onset temperature of 170 °C or more.

Preferably, the intumescent material comprises expandable graphite but other pressure-developing intumescent materials may be utilized, including, but not limited to, silicates, such as hydrated sodium silicate. Expandable graphite, sometimes termed expandable flake graphite or intumescent flake graphite, is a graphite that expands on exposure to heat, generating considerable pressure in the process, 10 Bar being typical within a closely confined space. The expandable graphite may be an intercalated graphite.

The expandable graphite may be graphite treated with a suitable intercalation agent. The intercalation agent may be an oxidising agent, which may be an oxidising acid such as sulphuric acid or nitric acid. The expandable graphite may be or comprise graphite bisulphate. Expandable graphite is available commercially, for example from Nano Technologies, Inc, in the form of Nyacol Nyagraph 249. Optionally, the intumescent material further comprises a thermoplastic material, and optionally alumina trihydrate or magnesium-based flame retardant compound or a mixture comprising antimony and a halogen. The thermoplastic material may comprise or be a thermoplastic polymer. The thermoplastic polymers may be selected from ethylene vinyl acetate (EVA), polyethylene (PE), polypropylene (PP), polystyrene (PS) or acrylonitrile butadiene styrene (ABS), polyvinyl chloride (PVC). For example, the thermoplastic polymer should be soft enough to allow the graphite to sufficiently expand when exposed to fire. In an embodiment, the intumescent material comprises a thermoplastic material comprising particles of an expandable material, such as expandable graphite, dispersed therein. In an embodiment, the intumescent material comprises (i) a thermoplastic material, (ii) an expandable graphite, (iii) alumina trihydrate or magnesium hydroxide, (iv) a flame retardant compound comprising antimony and a halogen or a flame retardant mixture comprising antimony and a halogen, and optionally the weight ratio of the alumina trihydrate or magnesium hydroxide to the flame retardant compound, such as halogenated antimony, or mixture comprising antimony and halogen is from about 1 : 10 to about 4:1. Alumina trihydrate and magnesium hydroxide are advantageous in that they decompose endothermically at high temperatures, and, in doing so, can absorb heat from their surroundings and produce a cooling effect. They have also been found to work synergistically with certain materials, particularly halogenated antimony or a mixture comprising antimony and a halogen (e.g. a non-halogenated antimony compound and a halogen-containing compound). Optionally, the intumescent material comprises about 30 wt% to about 60 wt% of a thermoplastic; about 5 wt% to about 55 wt% of expandable graphite; about 5 wt% to about 20 wt% alumina trihydrate or magnesium hydroxide; and a flame retardant compound or mixture comprising antimony and a halogen, the weight ratio of the alumina trihydrate or magnesium hydroxide to the flame retardant compound or mixture comprising antimony and halogen being from about 1 : 10 to about 4:1. The flame retardant compound may be brominated antimony. The halogen may be bromine. The flame retardant mixture may comprise antimony oxide, e.g. antimony trioxide, and a compound comprising bromine, such as ethane-1 ,2- bis(pentabromophenyl) (EBPBP).

An extrudable intumescent material comprising expandable graphite is available commercially, e.g. from Pyrophobic Systems, Ltd. The thermoplastic material allows moulding, e.g. extrusion of the intumescent material, and, once solidified after extrusion, is of sufficient consistency to be self-supporting but, when exposed to high temperatures, it softens and allows the intumescent material such as expandable graphite, to expand to move the shell as described herein.

The core comprising the intumescent material may have a maximum thickness, as measured, in a direction perpendicular from the edge-to-edge direction of at least 1 mm, preferably at least 2 mm, preferably from 1 mm to 10 mm, preferably 1 mm to 6 mm, preferably 2 mm to 6 mm, optionally about 3 mm or about 4 mm.

As mentioned, the intumescent material may be extrudable.

As described, herein is provided a method for making an intumescent grille unit as described herein, the method comprising

The method may comprise moulding the intumescent material to form the core, wherein during or after the moulding the intumescent material into the core, the shell is formed around the intumescent material. Preferably, the moulding comprises extruding the intumescent material. Optionally, during the moulding of the intumescent material to form the core, one or more apertures through the intumescent material are provided, which in the intumescent grille unit extend at least part way along the length of the slat, and one or more supports of a non-intumescent material are inserted into the apertures. In an embodiment, the shell is extruded from a non-intumescent material, such as aluminium, and the intumescent material is extruded to form the core, and the shell and core are brought into contact to form each slat, with supports, if present, then being inserted through slat. One or more frame members may be provided to engage with the slats, e.g. the support of the slats and/or the shell, to hold the supports in place relative to one another.

Figure 1A shows a cross-section of a plurality of slats (101) from a prior art intumescent grille unit (100), before exposure to a fire. Each slat includes a core (102) of intumescent material, which may be, for example, a silicate. An aluminium foil (103) is wrapped around each slat with a broad overlap at the seam. The foil acts as heat conductor to promote uniform expansion of the intumescent material and the overlapping seam allows expansion without breaking or tearing. A steel edge reinforcement (104) is present on each slat, to improve the mechanical stability and durability of the slat. Figure 1 B shows a cross-section of a plurality of slats from the prior art intumescent grille unit of Figure 1 A, after exposure to a fire. In this Figure, the direction of exposure to fire is indicated by triangles to the right hand side of the grille. On exposure to a fire, the intumescent material (102) of Figure 1A expands, stretching the overlapping aluminium foil, and continues expanding to close the gap between the slats. Airflow through the grille is thus prevented.

Non-limiting embodiments of the present invention will now be described with reference to the Figures, in which: Figure 2A shows a cross-section of a plurality of slats 201 from an embodiment of the intumescent grille unit (200) according to the present invention, before exposure to a fire. Each slat (201) has a core (202) comprising an intumescent material and a non- intumescent outer shell (203). The shell has two separate sections, each of which may be formed from a metal sheet or extrusion, e.g. an aluminium extrusion, and each section comprising a static first portion (203S) and a movable second portion (203M) connected to the first portion by a hinged or weakened section (203H) that extends along a direction substantially parallel to the edge (204) of the slat (not visible in this Figure, but shown in Figure 3B). The static first portion is located on an edge (204) of the slat and extends part way across each of the opposing faces 205 of the slat. The hinged or weakened section (203H) is formed by a section of the shell that is either thinner than the sections of the first and second portions and/or has been selectively annealed to maximise the likelihood of it acting as a hinge when the intumescent material expands. Two supports (206) of a non-intumescent material extend through each of the slats, in particular through apertures that extend through the intumescent core material (202). As can be seen, the slats taper toward both of their edges (204).

Figure 2B shows a cross-section of a plurality of slats from the intumescent grille unit of Figure 2A, after exposure to a fire. On expansion of the intumescent material in the grille of Figure 2A on exposure to heat, the second portion (203M) moves rotatably about the hinged or weakened section (203H), to form a wall (207) that extends toward an adjacent slat, reducing or preventing airflow between adjacent slats. In particular, each of the slats of Figure 2A has two second portions (203M) forming part of the shell on each the opposing faces, which, on expansion of the intumescent material, move rotatably in opposite directions, with the second portions approximately opposite one another on adjacent slats, moving rotatably toward one another, such that they meet to form a wall, such that two walls (207) are formed on opposing sides of the grille unit.

Figure 3A shows a cross-sectional view of a further embodiment of a slat for use in the grille unit of the present invention. In this embodiment, the shell comprises two separate sections, each section comprising the first, static portion (203S), that is located along each of the edges (204) of the slats, and extends part way along each opposing face (205) of the slat toward the other edge, and second, movable portions (203M) of each section extends away from the first portion over each opposing face, such that a shell is formed around substantially the whole of the core (202) comprising the intumescent material. In this embodiment, the support (206) is located within the area of the core defined by the first portion of each section.

Figure 3B shows a view of the end and one of the faces of the slat of Figure 3A. As can be seen, the hinged or weakened section (203H) of extends along a direction substantially parallel to the edge (204) of the slat.

Figure 3C shows a cross-sectional view of a further embodiment of a slat for use in the grille unit of the present invention. In this embodiment, a single support is located at the centre of the slat (approximately the same distance from each edge of the slat) in the core 202.

It was found that the embodiment shown in Figures 3A and 3B, i.e. with two supports extending through each slat, each of the supports located in the area defined by the first, static portion of the shell, was advantageous over the embodiment having a single support located centrally between the two edges of the shell, as shown in Figure 3C. It was found that having two supports prevented the slat rotating, which it may do with a single support in certain situations. Additionally, locating the supports in the static portion of the shell toward the edges of the slat reduces the chances of the slat coming away from the supports as the intumescent material expands. A further advantage of the embodiment shown in Figure 3A is that it has non-'handedness', i.e. so has identical properties no matter which side is placed 'up' or 'down' in the grille unit - this is achieved by locating the supports centrally with respect to the width of the slat (i.e. the width being in a direction perpendicular to the direction from edge to edge).

The movable second portion of the shell in Figure 3A also has gripping members (301), in the form of projections on the inner side of the shell that extend along the length of the shell in a direction parallel to the edges of the slat. The gripping members (301) have a triangular cross section, with the peak of the triangle extending into the intumescent material (202). The gripping members (301) serve to grip the intumescent material during normal use (i.e. before exposure to a fire) and thus maintain contact of the shell with the intumescent material. It has been found that locating the gripping members away from the ends of the movable second portion of the shell (as shown in Figure 3A) is advantageous over embodiments in which the gripping member is located at the end of the movable second portions (as shown in Figure 2A, for example), since it avoids creating a weakened spot in the intumescent material, and thus maintains the integrity of the intumescent core as the intumescent material expands on exposure to heat.

Figure 4A shows an exploded view of an embodiment of the intumescent grille unit of the present invention. In this Figure is shown two vertical frames (401) located at each of the ends of the slats (201 E). Two horizontal frames (402) are located above and below the end slats (201 E). Each of the slats has the construction shown in Figure 3C, although any of the other constructions mentioned herein may be used. Supports (206) in the form of pins are shown and, in constructing the grille unit, would be passed through apertures (401A) in the horizontal frames (402). The grille unit is intended for insertion into a square aperture in a suitable part of a building, e.g. a door or a ventilation duct. Both the vertical frames (401) and horizontal frames (402) have tabs (403) at their ends that interlock to hold the frames together to form a housing. The frame may be constructed using any suitable non-intumescent support material, such as a metal. Optionally, the frames each comprise a metal plate, e.g. steel plate, which may be galvanised. The metal plate may have a thickness of at least 0.1 mm, optionally at least 0.5 mm, optionally at least 0.8 mm, optionally from 0.5 to 5 mm, optionally from 0.5 to 2 mm, optionally from 0.5 to 1.5 mm, optionally about 1 mm.

The metal plate of the frame(s) may have apertures therethrough to insert the supports for the slats. The apertures should have diameter slightly larger (e.g. 0.05 mm to 0.3 mm larger) than the diameter of the supports to allow their insertion. Figure 4B shows a vertical frame (401) for use in certain embodiment of the intumescent grille unit that has two supports extending through the slats. It has two rows of apertures 401 A running along the length of the frame.

Figure 4C shows the vertical frame (401) of Figure 4B, connected to a slat (201) having the shell (203) and intumescent material (202), with a support (206) in the form of a Ί - shaped pin. The free end of the pin, once the pin is inserted into the slat and pin inserted into the apertures of both vertical frames, may be fastened by swaging, clenching, riveting or other suitable fastening means.

The support(s) in all embodiments may be of any suitable non-intumescent support material, which may, for example, be a metal or an alloy. The thickness of the supports can be determined on the basis of the weight of the slats they will bear. The thickness may, for example, be at least 1 mm, optionally at least 2 mm, optionally at least 2.5mm, optionally from 1 mm to 5 mm, optionally from 2 mm to 4 mm, optionally from 2.5 mm to 3.5 mm, optionally from 2.6 to 3.2mm, optionally about 2.8 mm. The supports may be in the form of pins. The pins may be a metal wire, which may, if desired be galvanised. The frames, if present, may also be in the form of plates of galvanised metal, e.g. galvanised steel. For example, the supports and/or frames may comprise galvanised steel, for example with a coating weight, as measured by the ASTM A653M, of at least 90 g/m² (also termed Z90) preferably at least 120 g/m² (also termed Z120), preferably at least 180 g/m² (also termed Z180), preferably at least 275 g/m² (also termed Z275). The galvanised coating for the support may be a zinc-based coating.

Figure 5 shows a further embodiment of an intumescent grille unit of the present invention. The grille unit is intended for insertion into a generally circular aperture in a suitable part of a building, e.g. a door or a ventilation duct. As can be seen the slats are not all of the same length, as they are in Figure 4A, with those toward the centre of the array of slats being longer than those toward each end of the array of slats. In this embodiment, the slats (201) have the construction shown in Figures 3A and 3B. In this embodiment approximately 'U'-shaped pins are used as the supports, such that each pin brackets adjacent slats. In constructing the intumescent grille as described herein, the intumescent material and the shell may both be extruded or otherwise fabricated separately, and then the shell pressed onto the extruded intumescent material to form the slat. If the shell has two separate sections, then each section can be extruded separately and pressed onto the intumescent material that has been formed into the shape of the core. The slats can be stored and then cut as desired into the appropriate lengths and then constructed into a grille unit. The extrusion of both the shell and the intumescent core material has been found to save on waste compared to processes of the prior art in which sheets of intumescent material needed to be cut to an appropriate size.

Claims

1. An intumescent grille unit comprising:

a core comprising an intumescent material;

2. The intumescent grille unit according to claim 1 , wherein each of the slats has the first portion and at least one second portion forming part of the shell on each of the opposing faces, and the second portions on adjacent slats, on expansion of the intumescent material on exposure to heat, move rotatably toward one another.

3. The intumescent grille unit according to claim 1 , wherein each of the slats has the first portion and second portions forming part of the shell on each of the opposing faces, and the second portions on adjacent slats, on expansion of the intumescent material on exposure to heat, move rotatably toward one another, such that they meet to form a wall.

4. The intumescent grille unit according to claim 1 , wherein each of the slats has two second portions forming part of the shell on each the opposing faces, which, on expansion of the intumescent material, move rotatably in opposite directions, with the second portions approximately opposite one another on adjacent slats, moving rotatably toward one another, such that they meet to form a wall, such that two walls are formed on opposing sides of the grille unit.

5. The intumescent grille unit according to any one of the preceding claims, wherein the shell comprises a metal layer having first and second portions mentioned above, and the hinged or weakened section being formed by a section of the metal layer that is thinner than the sections of the first and second portions.

6. The intumescent grille unit according to any one of the preceding claims, wherein the shell comprises a metal layer having first and second portions mentioned above, and the hinged or weakened section being formed by a section of the metal layer that has been annealed to a greater extent than the first or second portions.

7. The intumescent grille unit according to any one of the preceding units, wherein the shell comprises two sections, each section comprising a first portion, as defined in claim 1 , that is located along each of the edges of the slats, and optionally extends part way along each opposing face of the slat toward the other edge, and second portions of each section that extends away from the first portion over each opposing face, such that a shell is formed around substantially the whole of the core comprising the intumescent material.

8. The intumescent grille unit according to any one of the preceding claims, wherein a support of a non-intumescent material extends through each of the slats.

9. The intumescent grille unit according to claim 8, wherein a support of a non- intumescent material is provided proximal to one or both edges of each slat.

10. The intumescent grille unit according to claim 9, wherein the intumescent grille unit is as defined in claim 7, with each section comprising the first portion, as defined in claim 1 , that is located along each of the edges of the slats, and extends part way along each opposing face of the slat toward the other edge, and the support is located within the area of the core defined by the first portion of each section.

1 1. The intumescent grille unit according to any one of the preceding claims, wherein the slats taper toward one or both of the edges.

12. The intumescent grille unit according to any one of the preceding claims, wherein the spacing between adjacent slats is more than 20 mm, and the intumescent material is in each adjacent slat is such that, when exposed to heat, is capable of expanding to close the gap between the slats.

13. The intumescent grille unit according to any one of the preceding claims, wherein the spacing between adjacent slats is 25 mm or more.

14. The intumescent grille unit according to any one of the preceding claims, wherein the intumescent material has an expansion volume of at least 100 cm³/g.

15. The intumescent grille unit according to any one of the preceding claims, wherein the intumescent material has an expansion volume of at least 200 cm³/g.

16. The intumescent grille unit according to any one of the preceding claims, wherein the intumescent material comprises expandable graphite.

17. The intumescent grille unit according to any one of the preceding claims, wherein the intumescent material comprises expandable graphite, which is an intercalated graphite.

18. The intumescent grille unit according to any one of the preceding claims, wherein the intumescent material comprises graphite bisulphate.

19. The intumescent grille unit according to any one of claims 16 to 18, wherein the intumescent material further comprises a thermoplastic, and optionally alumina trihydrate or magnesium hydroxide, a flame retardant compound, such as halogenated antimony, or a mixture comprising antimony and a halogen.

20. The intumescent grille unit according to any one of the preceding claims, wherein the intumescent material is extrudable.

21. A method for making an intumescent grille unit according to claim 1 , the method comprising

22. The method according to claim 21 , the method comprising moulding the intumescent material to form the core, wherein during or after the moulding the intumescent material into the core, the shell is formed around the intumescent material.

23. The method according to claim 22, wherein the moulding comprises extruding the intumescent material.

24. The method according to any one of claims 21 to 23, wherein the shell is extruded from a non-intumescent material and the intumescent material is extruded to form the core, and the shell and core are brought into contact to form each slat.

25. The method according to any one of claims 22 to 24, wherein, during the moulding of the intumescent materials to form the core, one or more apertures through the intumescent material are provided, which in the intumescent grille unit extend at least part way along the length of the slat, and one or more supports of a non- intumescent material are inserted into the apertures.