Improvements relating to fire doors

Abstract

A door leaf 2 is defined with first 6 and second 8 metal panels or plates. There is a metal core 15 between them, which has a cellular or honey-comb structure, and it is bonded to the first and second

Description

Field of the Invention The present invention concerns fire doors. More particularly, but not exclusively, this invention concerns a fire-resistant door leaf, and a door leaf and frame assembly configured for use as a fire door. Background of the Invention Fire doors are provided in many buildings to help reduce the spread of smoke and flames in the event of a fire. A problem with known fire doors is that they can emit a significant amount of smoke when exposed to the temperatures associated with a typical building fire. A significant build-up of smoke on the non-fire-side of a fire door in the event of a building fire is undesirable because it can subject occupants of the building to smoke inhalation, or the smoke itself can ignite and cause the fire to spread further. Some prior art fire doors comprise a door leaf mounted in a three-part door frame which forms a seal with the top edge and vertical side edges of the door leaf when the door leaf is in a closed position. In this arrangement, the problem of smoke being emitted by the door leaf on the non-fire-side of the door can be mitigated by the negative pressure caused by the fire on the fire-side of the door leaf drawing smoke from the non-fire-side of the door leaf through the space between the bottom edge of the door leaf and the floor into the space on the fire-side of the door. Other prior art fire doors comprise a door leaf mounted in a four-piece door frame which additionally forms a seal with the bottom edge of the door leaf such that there is no gap at the bottom of the door leaf when the door leaf is in the closed position. In such arrangements a significant amount of smoke can build up on the non-fire-side of the door in the event of a fire. This may lead to the smoke igniting and creating a fire on the non-fire side of the door, or the building occupants being harmed by smoke inhalation. The present invention seeks to mitigate the above-mentioned problems. Alternatively or additionally, the present invention seeks to provide an improved door leaf and an improved door leaf and frame assembly. Summary of the Invention The present invention provides, according to a first aspect, a door leaf and frame assembly comprising a door leaf and a door frame, the door leaf being hingemounted to the door frame and moveable between an open position and a closed position. The door leaf comprises a first metal panel, a second metal panel, and a metal core disposed therebetween, wherein the metal core comprises a cellular structure bonded to the first metal panel and the second metal panel using an inorganic adhesive. The door frame comprises a first side member, a second side member, a crossbeam member, and a bottom member, the crossbeam member and bottom member extending between the first and second side members. When the door leaf is in a closed position the crossbeam member forms a seal with a top edge of the door leaf, the bottom member forms a seal with a bottom edge of the door leaf, the first side member forms a seal with a first vertical side edge of the door leaf, and the second side member forms a seal with a second vertical side edge of the door leaf. The present invention provides a door leaf comprising a sandwich structure formed by metal sheets bonded to a metal core with an inorganic adhesive. The metal core of the door leaf may be less likely to combust or chemically degrade in a way which releases a substantial amount of smoke when exposed to the temperatures associated with a building fire, relative to prior art doors formed from different materials. Similarly, the inorganic adhesive is also less likely to combust or release a substantial amount of smoke when the door leaf is exposed to the temperatures associated with a typical building fire in comparison to, for example, an organic adhesive. Therefore, when exposed to a fire within a building, the door leaf of the present invention may release significantly less smoke than prior art door leaves. Advantageously, the door leaf of the present invention may reduce the amount of smoke which escapes into the non-fire side of the door during a fire, relative to prior art door leaves. The first metal panel may define a first face of the door leaf. The second metal panel may define a second, opposite face of the door leaf. The outer surfaces of the first and second panels may be coated with, for example, a paint or other coating. The first metal panel and, alternatively or additionally, the second metal panel may form one or more side edges of the door, in addition to the faces of the door. The door leaf may have a vertical height of between approximately 320 centimetres and 60 centimetres. The door leaf may have a horizontal width of between approximately 140 centimetres and 50 centimetres. The door leaf may have a thickness of between approximately 3 centimetres and 6 centimetres. The metal core may have a thickness of between approximately 2.5 centimetres and 6 centimetres. The door leaf may comprise a window. The door leaf may comprise a handle and, alternatively or additionally, a lock. The first and / or second metal panels may comprise steel. The first and / or second panels may be formed from a sheet metal. The first and / or second panels may be formed from steel. Steel is a particularly suitable material owing to its relatively high durability and low cost. The cellular structure of the metal core may comprise an array of cells. Each cell may be formed by one or more cell walls. Each cell may extend along a cell length direction. The one or more cell walls may extend along a cell length direction. The one or more cell walls may also extend in the cell width direction. Each cell may be elongate, in other words, each cell may be longer than it is wide and / or high. The one or more cell walls may also extend in a cell height direction. The one or more cell walls may define a cell cross section in the plane that is a perpendicular to the cell length direction. The cell cross section may be polygonal. Each cell may be open at each end, in other words, there may not be a cell wall provided at opposing ends of the cell, in the plane of the cell cross section. In principle, any cellular metal material may be used which is able to provide the door leaf with rigidity, while also providing the advantage of having a significantly lower mass density than a solid metal core. Where the cells have a polygonal cell cross section, the cells may in principle have any number of cell walls, for example, the cells may have a triangular, square, pentagonal etc. cell cross section. In a preferred embodiment of the invention the cells have a hexagonal cell cross section. The cells may each be substantially identical in size and cross-section. The cells may be tessellated. The cellular structure may comprise a mixture of different types of cells with differently shaped cross sections. In some embodiments, the cells may have a circular cross section such that the cells are substantially cylindrical in shape. The walls of neighbouring circular cells may define further cells between the neighbouring circular cells. Each cell may have a cell wall thickness of between approximately 0.03 millimetres and 0.08 millimetres. In some embodiments, the cells may have a cell wall thickness of 0.04 millimetres, 0.05 millimetres, 0.06 millimetres, 0.07 millimetres, or 0.08 millimetres. The cells within the cellular structure may of course comprise differing wall thicknesses. Where the cells are hexagonal, the cells may have a cell width, measured between opposing parallel sides of the hexagon, of between approximately 6 millimetres to 26 millimetres. Each cell may have a length in the length direction of between 3 centimetres to 30 centimetres. The cellular structure may be oriented such that the cell width lies in a plane which is parallel with a plane defined by the length and width of the door. The cell structure may be oriented such that the cell height lies in a plane which is parallel with a plane defined by the length and width of the door. Each cell of the cellular structure may extend along the thickness direction of the door. The cell length may extend in a direction which is parallel with the thickness direction of the door. Alternatively or additionally, the cellular structure may be amorphous. For example, in some embodiments, the metal core may comprise a metal foam. The cells within the cellular structure will generally be hollow, in other words they may contain a gas or air. However, in some embodiments of the invention the cells may be filled with a filler material. The cellular structure of the metal core may comprise, or be formed from, aluminium. Aluminium provides a relatively light-weight and cost-effective core material in comparison with other metals such as steel, for example. Aluminium also has advantageous galvanic corrosion properties, relative to other potential core materials, and particularly when used in conjunction with steel. Therefore, a particularly advantageous embodiment of the invention may have a core comprising an aluminium cellular structure and first and second metal panels formed from steel. The inorganic adhesive may comprise a silicate adhesive. The adhesive may be a water based thixotropic inorganic adhesive. The adhesive may have a maximum continuous operating temperature of up to 1400 degrees centigrade. In some embodiments, the maximum continuous operating temperature may be even higher. For the avoidance of doubt, the inorganic adhesive may contain some organic material. For example, the inorganic adhesive may comprise up to 15 wt% organic material. In some embodiments of the invention, the inorganic adhesive may comprise up to 10 wt%, optionally up to 5 wt%, optionally up to 3 wt% organic material, optionally up to 1 wt% organic material, optionally up to 0.5 wt% organic material, optionally trace amounts of organic material and optionally substantially no organic material. In some embodiments of the invention, the first metal panel and the metal core may be bonded to one another over substantially all of the contact area between the metal core and the first metal panel. Alternatively, the first metal panel and the metal core may be bonded to one another over only part of the contact area between the metal core and the first metal panel. For example, inorganic adhesive may cover between 10% to 100% of the contact area of the first metal panel and the metal core. Similarly, the second metal panel and the metal core may be bonded to one another over substantially all of the contact area between the metal core and the second metal panel. The second metal panel and the metal core may be bonded to one another over only part of the contact area between the metal core and the second metal panel. For example, inorganic adhesive may cover between 10% to 100% of the contact area of the second metal panel and the metal core. The first and second side members may be oriented parallel to one another. The first and second side member may be oriented parallel to the vertical side edges of the door leaf when the door leaf is in the closed position. The first and second side members may be oriented at an angle to the vertical side edges of the door leaf when the door leaf is in the open position. The bottom member may be oriented parallel to the bottom edge of the door leaf when the door leaf is in the closed position. The bottom member may be oriented at an angle to the bottom edge of the door leaf when the door leaf is in the open position. The door leaf and frame assembly of the first aspect of the invention provides a fire door and frame arrangement in which all four edges of the door form a seal with the frame such that, in the event of a fire, a substantial amount of smoke cannot pass between the fire side of the door and the non-fire side of the door via the sealed bottom edge of the door. In this arrangement, any smoke which penetrates the non-fire side of the door in the event of a fire cannot be drawn to the fire-side of the door by the negative pressure on the fire-side of the door, as might happen where there is a gap underneath the door, for example. Prior art door leaves with a four-part frame may release smoke caused by combustion and / or chemical degradation of their constituent materials when exposed to a fire, which can result in a significant build-up of smoke on the non-fire side of the door. The door leaf in accordance with the first aspect of the invention, which is configured such that it may release substantially less smoke than prior art door leaves when exposed to a building fire, may therefore be particularly advantageous when used in this situation. According to a second aspect, the present invention provides a door and frame assembly comprising a first door leaf, a second door leaf, and a door frame, the first and second door leaves each being hinge-mounted to the door frame and moveable between an open position and a closed position, wherein the first and second door leaves each comprise a first metal panel, a second metal panel, and a metal core disposed therebetween; the metal core comprising a cellular structure and being bonded to the first metal panel and the second metal panel using an inorganic adhesive; the door frame comprises a first side member, a second side member, a crossbeam member, and a bottom member, the crossbeam member and bottom member extending between the first and second side members; and when the door leaf is in a closed position respective top edges of the first door leaf and second door leaf form a seal with the crossbeam member, respective bottom edges of the first door leaf and second door leaf form a seal with the bottom member, the first side member forms a seal with a first vertical side edge of the first door leaf, the second side member forms a seal with a first vertical side edge of the second door leaf, and respective second vertical side edges of the first and second door leaves form a seal with one another. It will of course be appreciated that features described in relation to one aspect of the present invention may be incorporated into other aspects of the present invention. Description of the Drawings ..................................................................*...............................................................................................................................................................................................w*.......... CM Embodiments of the present invention will now be described by way of example only with reference to the accompanying schematic drawings of which: Figure 1 shows a door leaf and frame assembly according to a first embodiment of the invention; 5 Figure 2 shows the door leaf of Figure 1 in isolation; Figure 3 shows a panel of the door leaf of Figure 2 in isolation; Figure 4 is a schematic cross sectional view of part of the core layer of the door leaf shown in Figure 2, as viewed along the thickness direction of the door; Figure 5 is a schematic partial cross sectional view of the door leaf shown in Figure 2, as viewed along the width direction of the door; and Figure 6 shows a door leaf and frame assembly in accordance with a second embodiment of the invention. Detailed Description A door leaf and frame assembly 10 according to an embodiment of the invention is shown in Figure 1. The door leaf and frame assembly comprises a door leaf 2 and a door frame 4, with the door leaf 2 being shown in a closed position relative to the door frame 4 in Figure 1. The door leaf 2, which is shown in isolation in Figure 2, is formed by an outer panel 6, an inner panel 8, a top edge 12, bottom edge 14, and two vertical side edges 13, 13’, which surround and enclose a core 15. In the presently described embodiment of the invention, the door leaf 2 has a thickness A of approximately 4.3 centimetres, a height H of approximately 200 centimetres and a width, W, of approximately 80 centimetres. It will be appreciated that in other embodiments of the invention the door leaf may have different dimensions, which may depend on the dimensions of the building opening that the door leaf is configured to be installed in. In the present embodiment, the door leaf 2 has a window 22, a door handle 18, and a lock. However, it will be appreciated that in other embodiments of the invention any one of these features may or may not be present. The outer panel 6, which defines a first side of the door leaf 2, is shown in isolation in Figure 3. The outer panel 6 is generally rectangular and has an outer surface 20’ and an inner surface 20”, with the outer surface 20’ forming an outer face 7 of the assembled door leaf 2. The outer panel 6 is formed from sheet metal, for example steel in this present embodiment, equal in length to the height of the door leaf 2 and equal in width to the width of the door leaf 2. The inner panel 8, which defines a second side of the door leaf 2 and is similarly constructed from sheet metal, has similar dimensions. The inner panel 8 and outer panel 6 are configured such that they fit together in a manner that will be understood by the skilled person to form the outer surface of the door leaf 2, which surrounds and encloses the core 15. The core 15 is formed from an aluminium honeycomb core structure, a cross section of which, as viewed along the thickness direction of the door leaf 2, is shown in Figure 4. As can be seen, the aluminium honeycomb core structure comprises an array of tessellated hexagonal cells 1 having cell walls formed from aluminium. An aluminium core provides the advantage that it does not bum or chemically degrade when exposed to the temperatures associated with a typical building fire, and therefore does not emit a significant amount of smoke when the door leaf is exposed to a building fire. Aluminium also provides a particularly advantageous core material because if its relatively high stiffness and relatively low mass density. However, it will be appreciated that in other embodiments of the invention, other suitable metals may be used for the cellular structure of the core 15. Furthermore, while the cellular structure forming the core 15 of the presently described embodiment of the invention is formed from a honeycomb structure, it will be appreciated that in other embodiments of the invention, other types of cell may be used, which may or may not be elongate and which may or may not have a polyhedral cross section. For example, each cell may comprise a single cell wall which defines a cell having a circular cross section. In some embodiments, an amorphous cellular structure may be used, which are not formed from a uniform repeating unit cell. Such structures may be provided by a foam, for example. Each hexagonal cell 1 of the core 15 is hollow and has six cell walls which define an elongate cavity extending along a length direction of each cell 1. In the presently described embodiment of the invention, the length direction of the cells 1 is oriented parallel to the thickness direction of the door leaf 2, such that each cell 1 extends from the inner panel 8 to the outer panel 6. Each hexagonal cell 1 has a cell width X of approximately 21 millimetres, the cell width being the distance between opposing parallel walls of the hexagon, as illustrated in Figure 4.The cells have a wall thickness t of approximately 0.06 millimetres. It will of course be appreciated that in other embodiments of the invention, the core may be formed by hexagonal cells having different dimensions. Figure 5 shows a cross section through the door leaf 2 viewed along the width of the door leaf 2, in a plane which is oriented perpendicularly to the view shown in Figure 4. It should be noted that, for the presently described embodiment of the invention, the corresponding view along the length of the door leaf 2 would also be similar. As can be seen in this embodiment, the core 15 has a thickness T extending from an inner surface of the inner panel 8 to an inner surface of the outer panel 6. In this case, because the length direction of the cells is aligned with the thickness direction of the core and door leaf 2, each elongate cell has a length equal to the thickness T of the core. However, in other embodiments of the invention, the length direction of the cells may not be aligned with the thickness of the core and door leaf. At the end of each hexagonal cell 1, where the hexagonal cells 1 meet the surface of the inner panel 8 and the outer panel 6, a layer of adhesive 24 is provided to bond the core 15 to the outer panel 6 and inner panel 8. The adhesive 24 used in this case is sold under the name “R&D 224 D” by John Winter &Co Ltd., and is a silicate based inorganic adhesive having an organic content of between 7 to 10 %. In other embodiments, the adhesive may be “Flamebond”, which is a water based thixotropic inorganic silicate adhesive sold by Fortafix Ltd. In other embodiments, other inorganic adhesives may of course be used. Inorganic adhesives provide the advantage that, while they can emit smoke when exposed to a fire, they emit significantly less smoke than adhesives containing more significant amounts of organic material. With reference to Figure 3, in order to construct the door leaf 2 an adhesive 24 is applied across the inner surfaces 20” of the outer and inner panels 6, 8, and the core 15 is then sandwiched between the inner and outer panels 6, 8. The adhesive is then left to cure. Because the door leaf 2 is constructed using metal panels and a metal core bonded together with an inorganic adhesive, the door leaf 2 does not emit a substantial amount of smoke when exposed to a fire within a building. As such, the door leaf 2 can reduce the amount of smoke present on the non-fire-side of the door leaf 2 in the event of a fire, relative to prior art door leaves. The door leaf 2 is mounted within the door frame 4 via hinges 16, as shown in Figure 1. The door frame 4 is formed by two vertical side members 25, 25’, and a crossbeam member 26 which spans the gap between the two vertical side members, at the top of the door. In the present embodiment, there is a bottom crossbeam member 28 which spans the gap between the two side members 25, 25’ at the bottom of the door leaf 2. The top edge 12, bottom edge 14, and two side edges 13, 13’ of the door leaf 2 are configured to form a seal with the crossbeam member 26, the bottom member 28, and the side members 25, 25’ of the door frame 4, respectively, when the door leaf 2 is in a closed position with respect to the door frame 4. In the event of a fire, the seal prevents smoke from moving between the fire-side and non-fire-side of the door leaf 2 through gaps between the door leaf 2 and the door frame 4, as will be well understood by the skilled person. Whilst the present invention has been described and illustrated with reference 5 to particular embodiments, it will be appreciated by those of ordinary skill in the art that the invention lends itself to many different variations not specifically illustrated herein. By way of example only, certain possible variations will now be described. Figure 6 shows another example embodiment of a door and frame assembly 100. The door and frame assembly comprises two door leaves 102, 103 and a door 10 frame 104 which surrounds the two door leaves 102, 103. Each of the door leaves 102, 103 has a substantially identical construction to the door leaf 2 of the first embodiment of the invention, shown in Figure 2, being formed by a metal outer panel 106, a metal inner panel 108, and a metal core comprising a metal cellular structure (not shown) which is bonded to the metal panels 106, 108 by an inorganic adhesive. 15 The structure of the second door leaf 103 is substantially same as the first door leaf 102 except that only the first door leaf 102 has a handle and a lock 118. The structure of the door frame 104 is substantially the same as the door frame 4 as described with reference to Figure 1, except that the door frame 104 of the present example embodiment has greater dimensions as it has to surround the side 20 edges of two door leaves 102, 103. The door frame 104 has hinges 116, 116’ on two side members 125, parallel to one of the side edges of each door leaf 102, 103, such that both door leaves can move from a closed position to an open position on their respective hinges 116, 116’. It will be appreciated by the reader that integers or features of the invention 25 that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, whilst of possible benefit in some embodiments of the invention, may not be desirable, and may therefore be absent, in other embodiments.

Claims

1. A door leaf and frame assembly comprising a door leaf and a door frame, the door leaf being hinge-mounted to the door frame and moveable between an open position and a closed position; whereinthe door leaf comprises a first metal panel, a second metal panel, and a metal core disposed therebetween;the metal core comprises a cellular structure and is bonded to the first metal panel and the second metal panel using an inorganic adhesive;the door frame comprises a first side member, a second side member, a crossbeam member, and a bottom member, the crossbeam member and bottom member extending between the first and second side members; andwhen the door leaf is in a closed position the crossbeam member forms a seal with a top edge of the door leaf, the bottom member forms a seal with a bottom edge of the door leaf, the first side member forms a seal with a first vertical side edge of the door leaf, and the second side member forms a seal with a second vertical side edge of the door leaf, the seals between the door leaf and the door frame being configured to prevent smoke passing between a fire-side and a non-fire-side of the door leaf and frame assembly via the seals.

2. A door leaf and frame assembly in accordance with claim 1, wherein the first or second metal panel of the door leaf comprise steel.

3. A door leaf and frame assembly in accordance with claims 1 or 2, wherein the cellular structure of the metal core of the door leaf comprises an array of elongate cells, each cell defined by one or more cell walls which extend along a length direction of the cell.

4. A door leaf and frame assembly in accordance with claim 3, wherein the cell walls define a cell cross section in a plane that is perpendicular to the cell length direction, and wherein the cell cross section is polygonal.

5. A door leaf and frame assembly in accordance with claim 4, wherein the cell cross section is hexagonal.

6. A door leaf and frame assembly in accordance with any of claims 3 to 5, wherein the cell length direction is oriented parallel to a thickness direction of the door leaf.

7. A door leaf and frame assembly in accordance with any preceding claim wherein the cellular structure of the metal core of the door leaf is formed from aluminium.

8. A door leaf and frame assembly in accordance with any preceding claim, wherein the inorganic adhesive comprises no more than 15 wt% of organic material.

9. A door leaf and frame assembly in accordance with any preceding claim, wherein the inorganic adhesive comprises a silicate adhesive.

10. A door leaf and frame assembly in accordance with any preceding claim wherein the door leaf further comprises a lock.

11. A door and frame assembly comprising a first door leaf, a second door leaf, and a door frame, the first and second door leaves each being hinge-mounted to the door frame and moveable between an open position and a closed position, wherein:the first and second door leaves each comprise a first metal panel, a second metal panel, and a metal core disposed therebetween; the metal core comprising a cellular structure and being bonded to the first metal panel and the second metal panel using an inorganic adhesive;the door frame comprises a first side member, a second side member, a crossbeam member, and a bottom member, the crossbeam member and bottom member extending between the first and second side members; andwhen the door leaf is in a closed position respective top edges of the first door leaf and second door leaf form a seal with the crossbeam member, respective bottom edges of the first door leaf and second door leaf form a seal with the bottom member, the first side member forms a seal with a first vertical side edge of the first door leaf, the second side member forms a sealwith a first vertical side edge of the second door leaf, and respective second vertical side edges of the first and second door leaves form a seal with one another, the seals between the door leaves and the door frame being configured to prevent smoke passing between a fire-side and a non-fire-side of the door leaf and frame assembly via the seals.

12. A door leaf and frame assembly in accordance with claim 11, wherein the first or second metal panel of the first or second door leaf comprises steel.

13. A door leaf and frame assembly in accordance with claims 11 or 12, wherein the cellular structure of the metal core of the first or second door leaf comprises an array of elongate cells, each cell defined by one or more cell walls which extend along a length direction of the cell.

14. A door leaf and frame assembly in accordance with claim 13, wherein the cell walls define a cell cross section in a plane that is perpendicular to the cell length direction, and wherein the cell cross section is polygonal.

15. A door leaf and frame assembly in accordance with claim 14, wherein the cell cross section is hexagonal.

16. A door leaf and frame assembly in accordance with any of claims 13 to 15, wherein the cell length direction is oriented parallel to a thickness direction of the first or second door leaf.

17. A door leaf and frame assembly in accordance with any of claims 11 to 16 wherein the cellular structure of the metal core of the first or second door leaf is formed from aluminium.

18. A door leaf and frame assembly in accordance with any of claims 11 to 17, wherein the inorganic adhesive comprises no more than 15 wt% of organic material.

19. A door leaf and frame assembly in accordance with any of claims 11 to 18, wherein the inorganic adhesive comprises a silicate adhesive.

20. A door leaf and frame assembly in accordance with any of claims 11 to 19, wherein the first or second door leaf further comprises a lock.09 12 24

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