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Patent Searching and Data


Title:
DOOR CONSTRUCTION
Document Type and Number:
WIPO Patent Application WO/2019/166814
Kind Code:
A1
Abstract:
A fire-resistant door system comprising: a door lining defining a door opening, and a door leaf configured to close the door opening with an edge surface of the door leaf confronting a face of the door lining across a gap extending around the rim of the door leaf, wherein: one of the door and the lining carries first and second intumescent seals exposed to and extending along the gap, the first and second seals being spaced apart by a spacing zone and being elongate along the gap; and the other of the door and the lining carries a third intumescent seal exposed to the gap and confronting the spacing zone.

Inventors:
BARRY, Matthew Adam (40 Portman Square, London Greater London W1H 6LT, W1H 6LT, GB)
Application Number:
GB2019/050566
Publication Date:
September 06, 2019
Filing Date:
February 28, 2019
Export Citation:
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Assignee:
HOWDEN JOINERY LIMITED (40 Portman Square, London W1H 6LT, W1H 6LT, GB)
International Classes:
E06B5/16
Domestic Patent References:
WO2008030087A12008-03-13
Foreign References:
EP1209314A22002-05-29
DE102008042874A12010-04-22
FR1180635A1959-06-08
US20030024184A12003-02-06
NL1003974C21998-03-09
Attorney, Agent or Firm:
SLINGSBY PARTNERS LLP (1 Kingsway, LondonGreater London, WC2B 6AN, WC2B 6AN, GB)
Download PDF:
Claims:
CLAIMS

1 . A fire-resistant door system comprising:

a door lining defining a door opening, and

a door leaf configured to close the door opening with an edge surface of the door leaf confronting a face of the door lining across a gap extending around the rim of the door leaf, wherein:

one of the door and the lining carries first and second intumescent seals exposed to and extending along the gap, the first and second seals being spaced apart by a spacing zone and being elongate along the gap; and

the other of the door and the lining carries a third intumescent seal exposed to the gap and confronting the spacing zone.

2. A fire-resistant door system as claimed in claim 1 , wherein the door lining comprises a door stop and the door lining carries a fourth intumescent seal located to confront a major face of the door when the door is closed.

3. A fire-resistant door system as claimed in claim 2, wherein the fourth intumescent seal is bonded by adhesive to a surface of the door stop that faces the door when the door is closed.

4. A fire-resistant door system as claimed in any preceding claim, wherein the first and second intumescent seals are located in recesses in one of the edge surface of the door leaf and the face of the door lining.

5. A fire-resistant door system as claimed in any preceding claim, wherein the third intumescent seal is located in a recess in one of the edge surface of the door leaf and the face of the door lining.

6. A fire-resistant door system as claimed in any preceding claim, wherein at least parts of the first and second intumescent seals are located on either side of the third intumescent seal.

7. A fire-resistant door system as claimed in any preceding claim, wherein the first, second and third intumescent strips are elongate along the length of the gap.

8. A fire-resistant door system as claimed in claim 7, wherein the first, second and third intumescent seals have major edges directed along the direction of elongation of the respective seal and towards the gap, and the major edges of the first and second intumescent seals that are closer to each other are aligned across the gap with respective major edges of the third intumescent seal.

9. A fire-resistant door system as claimed in any preceding claim, wherein the third intumescent seal and at least one of the first and second intumescent seals are configured to contact each other across the gap when expanded under the action of heat.

10. A fire-resistant door system as claimed in any preceding claim, wherein the said edge surface of the door leaf is the latch edge surface of the door leaf.

1 1 . A fire-resistant door system as claimed in any preceding claim, wherein the first, second and third intumescent seals extend along the latch edge surface and the upper edge surface of the door leaf and the faces of the door lining confronting those edge surfaces.

12. A fire-resistant door system as claimed in any preceding claim, wherein the first, second and third intumescent seals extend along the hinge edge surface of the door leaf and the face of the door lining confronting that edge surface.

13. A fire-resistant door leaf comprising:

first and second sheets of fire-resistant material sized to have at least 80% of the major area of the door leaf; a sheet of wood-based material sized to have at least 80% of the major area of the door leaf and located between the sheets of fire-resistant material;

the door having an edge surface comprising two spaced-apart strips of intumescent material.

14. A fire-resistant door leaf as claimed in claim 13, wherein the sheets of fire-resistant material are sheets of ceramic material.

15. A fire-resistant door leaf as claimed in claim 13 or 14, wherein the sheets of fire- resistant material occupy at least 50% of the thickness of the structure comprising the sheets of fire-resistant material and the sheet of wood-based material.

16. A fire-resistant door leaf as claimed in any of claims 13 to 15, wherein the door leaf comprises an edge portion of a wood-based material located along the edges of the sheets of fire-resistant material and the sheet of wood-based material, the edge portion forming an external edge of the door leaf and the intumescent strips being located in recesses in the external edge surface of the edge portion.

17. A fire-resistant door leaf as claimed in any of claims 13 to 16, comprising a latch mechanism, the latch mechanism being located in a recess in the sheet of wood-based material, the sheets of fire-resistant material being unimpinged by the recess.

18. A fire-resistant door leaf as claimed in claim 17, comprising a layer of insulating material located between the latch and the wall of the recess.

19. A fire-resistant door leaf as claimed in any of claims 13 to 18, wherein the intumescent strips extend around three edges of the door leaf.

20. A fire-resistant door system as claimed in any of claims 1 to 12, wherein the door leaf is a door leaf as claimed in any of claims 13 to 19.

21 . A method for increasing the fire protection of a building opening provided with a door lining and a door hingedly hung in the door lining, the door lining having a door stop comprising a face located so as to confront a major face of the door at the latch edge of the door when the door is closed and an intumescent seal located in a part of the lining that is located so as to confront the latch edge of the door when the door is closed, and the door having an absence of intumescent seals along its latch edge; the method comprising:

detaching the said door from the lining;

hingedly attaching a second door in the lining, the second door being provided with at an intumescent seal along its latch edge, and the second door being attached to the lining in a location such that when the second door is fully closed the action of heat can cause the intumescent seal of the second door to expand to contact the intumescent seal of the lining; and

adhering an intumescent seal to the said face of the door stop.

22. A method as claimed in claim 21 , wherein the second door is attached so when the second door is fully closed the intumescent seal of the second door partially overlaps the intumescent seal of the lining in a direction perpendicular to a major face of the second door.

23. A method as claimed in claim 21 or 22, wherein the intumescent seal of the second door and the intumescent seal of the lining are vertically elongate along at least 50% of the height of the second door.

24. A method as claimed in any of claims 21 to 23, wherein the intumescent seal adhered to the door stop is vertically elongate along at least 50% of the height of the second door.

25. A method as claimed in any of claims 21 to 24, wherein the second door is provided with two intumescent seals along its latch edge, and the second door is attached to the lining in a location such that when the second door is fully closed the action of heat can cause both intumescent seals of the second door to expand to contact the intumescent seal of the lining.

26. A method as claimed in claim 25, wherein the intumescent seals of the second door are spaced apart in a direction perpendicular to a major face of the second door.

27. A method as claimed in claim 26, wherein the second door comprises a latch, part of which extends out of the latch face of the second door between the intumescent seal of the second door for latching the second door closed in the lining.

Description:
DOOR CONSTRUCTION

[001 ] This invention relates to the construction of doors, for example fire-resistant doors.

[002] Fire-resistant (“FR”) doors are commonly fitted in buildings to inhibit the spread of fire and to improve occupants’ ability to escape in the event of a fire. Generally, in order to provide greater fire-resistance thicker and heavier door linings and door leaves are provided. Thicker door elements typically increase cost and make the elements harder for a builder to install.

[003] It would be desirable to have a design of door that provides substantial fire resistance but without excessive increase in the weight or thickness of the components.

[004] According to one aspect there is provided a fire-resistant door system comprising: a door lining defining a door opening, and a door leaf configured to close the door opening with an edge surface of the door leaf confronting a face of the door lining across a gap extending around the rim of the door leaf, wherein: one of the door and the lining carries first and second intumescent seals exposed to and extending along the gap, the first and second seals being spaced apart by a spacing zone and being elongate along the gap; and the other of the door and the lining carries a third intumescent seal exposed to the gap and confronting the spacing zone.

[005] In a direction across the width of the door, all of or just a part of the third intumescent seal may confront the spacing zone. The confrontation may be in a direction perpendicular to the plane of the surface in which the third intumescent seal is mounted.

[006] The door lining may comprise a door stop. The door stop may be elongate along the height of the door lining. The door stop may be located at least the latch side of the door lining. The door stop may be located so as to seat against the door when the door is closed. The door lining may carry a fourth intumescent seal located to confront a major face of the door when the door is closed.

[007] The fourth intumescent seal may be bonded by adhesive to a surface of the door stop that faces the door when the door is closed.

[008] The first and second intumescent seals may be located in recesses in one of the edge surface of the door leaf and the face of the door lining; for example the edge of the door leaf.

[009] The third intumescent seal may be located in a recess in one of the edge surface of the door leaf and the face of the door lining; for example, the face of the door lining.

[010] At least parts of the first and second intumescent seals may be located on either side of the third intumescent seal. The third intumescent seal may be located so that it substantially exclusively confronts material located between the first and second intumescent seals. The first and second intumescent seals may be located so that over the whole or substantially the whole of their lengths their closer edges confront either (i) the third intumescent seal or (ii) material of the surface in which the third intumescent seal is provided which is outboard of the third intumescent seal. The first, second and third intumescent seals may have major edges directed along the direction of elongation of the respective seal and towards the gap. The major edges of the first and second intumescent seals that are closer to each other may be aligned across the gap with respective major edges of the third intumescent seal.

[01 1 ] Each of the first, second and third intumescent seals may be elongate vertically on the or each edge face of the door leaf or the respective confronting face(s) of the lining. Each of the first, second and third intumescent seals may be elongate horizontally on the upper face of the door leaf or the confronting face of the lining. The first, second and third intumescent strips may be elongate along the length of the gap. [012] The third intumescent seal and at least one of the first and second intumescent seals may be configured to contact each other across the gap when expanded under the action of heat.

[013] The said edge surface of the door leaf may be the latch edge surface of the door leaf.

[014] The first, second and third intumescent seals may extend along the latch edge surface and the upper edge surface of the door leaf and the faces of the door lining confronting those edge surfaces.

[015] The first, second and third intumescent seals may extend along the hinge edge surface of the door leaf and the face of the door lining confronting that edge surface.

[016] Each of the intumescent seals may be in its unexpanded state. The intumescent seals may be intumescent strips.

[017] According to a second aspect there is provided a fire-resistant door leaf comprising: first and second sheets of fire-resistant material sized to have at least 80% of the major area of the door leaf; a sheet of wood-based material sized to have at least 80% of the major area of the door leaf and located between the sheets of fire- resistant material; the door having an edge surface comprising two spaced-apart strips of intumescent material.

[018] The sheets of fire-resistant material may be sheets of ceramic material.

[019] The sheets of fire-resistant material may occupy at least 50% of the thickness of the structure comprising the sheets of fire-resistant material and the sheet of wood- based material. [020] The door leaf may comprise an edge portion of a wood-based material located along the edges of the sheets of fire-resistant material and the sheet of wood-based material. The edge portion may form an external edge of the door leaf. The intumescent strips may be located in recesses in the external edge surface of the edge portion.

[021 ] The door leaf may comprise a latch mechanism. The latch mechanism may be located in a recess in the sheet of wood-based material. The sheets of fire-resistant material may be unimpinged by the recess.

[022] The door leaf may comprise a layer of insulating material located between the latch and the wall of the recess.

[023] The intumescent strips may extend around three edges of the door leaf.

[024] The fire-resistant door system described above may have a door leaf as described above.

[025] The first and second intumescent seals may be configured to extend at least across the gap at least partially on either side of the third intumescent strip under the action of heat. In that way the first and second intumescent seals may sandwich the third intumescent seal in the gap.

[026] According to a third aspect there is provided a method of installing a fire- resistant door system as set out above, the method comprising, at the installation location, adhering an intumescent seal to a door stop of the door lining.

[027] According to a fourth aspect there is provided a method for increasing the fire protection of a building opening provided with a door lining and a door hingedly hung in the door lining, the door lining having a door stop comprising a face located so as to confront a major face of the door at the latch edge of the door when the door is closed and an intumescent seal located in a part of the lining that is located so as to confront the latch edge of the door when the door is closed, and the door having an absence of intumescent seals along its latch edge; the method comprising: detaching the said door from the lining; hingedly attaching a second door in the lining, the second door being provided with at an intumescent seal along its latch edge, and the second door being attached to the lining in a location such that when the second door is fully closed the action of heat can cause the intumescent seal of the second door to expand to contact the intumescent seal of the lining; and adhering an intumescent seal to the said face of the door stop.

[028] The second door may be attached so that when the second door is fully closed the intumescent seal of the second door partially overlaps the intumescent seal of the lining in a direction perpendicular to a major face of the second door.

[029] The intumescent seal of the second door and the intumescent seal of the lining may be vertically elongate along at least 50% of the height of the second door.

[030] The intumescent seal adhered to the door stop may be vertically elongate along at least 50% of the height of the second door.

[031 ] The second door may be provided with two intumescent seals along its latch edge. The second door may be attached to the lining in a location such that when the second door is fully closed the action of heat can cause both intumescent seals of the second door to expand to contact the intumescent seal of the lining.

[032] The intumescent seals of the second door may be spaced apart in a direction perpendicular to a major face of the second door.

[033] The second door may comprise a latch, part of which extends out of the latch face of the second door between the intumescent seal of the second door for latching the second door closed in the lining. [034] Each intumescent seal may be of material such that it swells on heating. Preferably the intumescent activity of each seal commences not lower than 50°C or not lower than 80°C.

[035] The present invention will now be described by way of example with reference to the accompanying drawings.

[036] In the drawings:

Figure 1 is a general view of a door set.

Figure 2 is a cross-section through the latch edge of the door of figure 1 on line A-A of figure 1 .

Figure 3 is a cross-section through the latch edge of the door of figure 1 on line B-B of figure 1 .

Figure 4 is a cross-section through the latch edge of the door of figure 1 on line A-A showing intumescent seals in an expanded state.

Figure 5 is a cross-section through the latch edge of a door on a plane analogous to that of figure 2.

[037] Like parts are designated with like references in all the figures.

[038] Figure 1 shows a door set comprising a door frame, lining or casing 1 and a door leaf 2. The door lining comprises a pair of spaced-apart uprights 3, 4 which are connected at their upper ends by a header 5. The lining defines a door opening between the uprights and the header. The door leaf 2 is suspended from the lining by hinges 6. Each hinge is attached to the hinge edge 7 of the door leaf and to the hinge upright 3 of the door lining. At the latch edge 9 of the door leaf a latch mechanism (not visible in figure 1 ) is set into the door leaf. The latch is coupled to a handle 10. The handle can be operated to move the latch from an extended position in which it extends into the latch upright 4 and a retracted position in which it is free from the latch upright. In the extended position the latch blocks the door leaf from opening. When the latch is retracted the door leaf can be moved from the closed position as depicted in figure 1 to an open position by pivoting on the hinges 6. When pivoting on the hinges the door can swing through an arc as indicated by dashed lines in figure 1.

[039] The door set may be suitable for use as an internal or an external door. The door set may be suitable for use as a building door.

[040] Figure 2 is a cross-section through the latch side of the door set on line A-A of figure 1. The latch upright 4 comprises a door lining 20 and a door stop 21 . The door lining forms the side of the door lining. An inner face 22 of the door lining faces the latch edge 9 of the door leaf. When the lining is positioned in an opening in a wall, the outer face 23 of the door lining faces the wall. The door leaf is sized and positioned relative to the lining so that when the door is closed there is a small gap 24 between the latch edge of the door leaf and the inner face of the door lining. The gap permits the door leaf to be opened and closed without it fouling the lining. In practice, the gap 24 could, for example be between 1 mm and 5mm wide. The door stop extends inwardly with respect to the door opening from the inner face 22 of the door lining. The door stop has a stop face 25 which faces the door leaf when the door is closed. The door stop serves to prevent the door leaf from being moved excessively in the closing direction.

The door leaf is composed of a number of sheets 26, 27, 28, 29, 30 which are laminated together, and a lipping 31 which is attached along the latch edge of the sheets. Each of the sheets has a pair of major surfaces which are oriented so as to be parallel with the major faces of the door leaf. Each major surface of a sheet is substantially flat, although they could be shaped, e.g. corrugated.

[041 ] The core of the door leaf is provided by a sheet 28. Sheet 28 is formed of a structural board. Sheet 28 provides a substantial degree of the door leafs structural strength. Sheet 28 is preferably substantially rigid. Sheet 28 could be formed of a wood-based material such as wood or a composite wood material. Sheet 28 could be formed of a composite wood board, for example plywood or a particle board such as chipboard or fibreboard. Alternatively, it could be formed of a polymer material or a metal material. The thickness of the sheet 28 depends on the strength required of the door leaf, but in the case of a board formed of a particle board it may be between 10 and 40mm, more preferably between 15 and 25mm, more preferably between 17 and 19 mm.

[042] On either side of the core sheet 28, in the direction perpendicular to the main faces of the door leaf, are sheets 27, 29. Sheets 27, 29 are formed of a fire-resistant material. Sheets 27 and 29 provide a substantial degree of the door leafs resistance to fire. Each of sheets 27 and 29 preferably has any one or more of the following properties:

1 . it is of class A1 or A2 according to the latest version of EN ISO 1 182 and/or EN 13501 -1 adopted as at 1 February 2018;

2. it is of class REI 30 or REI 60 according to the latest version of EN 13501 -2 adopted as 1 February 2018;

3. it meets at least the integrity requirement of REI 30 or REI 60 according to the latest version of EN 13501 -2 adopted as at 1 February 2018;

4. it consists of or is more than 90% comprised of a ceramic material.

[043] Each of the sheets 27, 29 may be what is typically considered in the building industry to be a fire-resistant sheet. The thickness of each sheet 29, 27 may be between 5 and 20mm, more preferably between 7 and 14mm, more preferably between 8 and 10 mm. The sheets 27, 29 may be of the same or different thicknesses. The sheets 27, 29 may be of the same or different materials. Some examples of materials from which the sheets 27, 29 may be formed include calcium silicate, magnesium oxide, an intumescent material such as Palusol (TM), cement board and gypsum board. It has been found that calcium silicate boards are particularly suitable for the sheets 27, 29 because they can provide for integrity of the door leaf over a prolonged period during a fire. Calcium silicate boards consist of calcium silicate or substantially wholly comprise calcium silicate or comprise greater than 90% calcium silicate.

[044] On the outer faces of the fire-resistant sheets 27, 29 are facing sheets 26, 30. The facing sheets form the outer major surfaces of the door leaf. The facing sheets 26, 30 provide a cosmetic outer layer to the door leaf. The facing sheets could be made of any suitable material, for example wood veneer, engineered wood, plastics sheet, a foil (e.g. a self-adhesive foil) or metal sheet. The facing sheets could be constituted by a coating applied in liquid form, such as a paint or varnish, or could incorporate such a coating on their outer surface. It is preferable for the facing sheets to be made of the same material as the lipping 31 , so that the door leaf has a harmonious exterior appearance. The facing sheets could be, for example, between 0.5mm and 6mm in thickness. The facing sheets could be omitted.

[045] Each of the sheets 26-30 may be formed of a single element. Alternatively, each of the sheets may be formed of (i) two or more sub-sheets laminated in the thickness direction of the door leaf and/or (ii) two or more parts butted together in a direction across the thickness of the door leaf. Each of sheets 26-30 may be formed of a single material or of multiple materials. Sheets 26 and 30 may be formed of the same material(s) or of different materials to each other. Sheets 27 and 29 may be formed of the same material(s) or of different materials to each other. The outer face sheets 26, 30 may be omitted. The lipping 31 may be omitted. If the lipping is omitted, the intumescent seals 32, 33 to be discussed below may be inset into the fire-resistant panels 27, 29 and/or the core panel 28.

[046] The interface between the latch edge of the door leaf and the latch side of the lining is provided with several seals 32, 33, 34, 35. Each of these seals may be formed of an intumescent material: that is a material that expands when exposed to heat. In that way, the seals can close the gap between the door leaf and the latch side of the lining when the door is closed and a fire occurs. The seals on the door are configured so that under expansion at least part of each one lies on either side of the seal carried by the face of the frame, along substantially the whole length of the side of the door leaf at which they are installed.

[047] Seals 32 and 33 are carried by the door leaf. They have a surface exposed on the latch surface 9 of the door leaf. They are positioned so that they face the latch surface 22 of the door lining. As shown in figure 2, seals 32 and 33 may be located in respective rebates in the latch edge of the door leaf. This can mean that when they are in their unexpanded state the exterior surfaces of seals 32 and 33 are flush with the latch surface 9 as provided by the lipping 31. Alternatively, one or both of seals 32 and 33 may be adhered to the latch surface 9. Seals 32 and 33 are spaced apart in the transverse plane of the door. Material of the lipping is located between the seals.

[048] Seal 34 is carried by the door lining. It has a surface exposed on the latch surface 22 of the lining. It is positioned so that it faces the latch surface 9 of the door leaf. As shown in figure 2, seal 34 may be located in a rebate in the latch edge of the door lining. This can mean that when it is in its unexpanded state the exterior surface of seal 34 is flush with the latch surface 22 of the lining as provided by door lining 20. Alternatively, seal 34 may be adhered to the latch surface 22. Seal 34 faces the material of the lipping that spaces seals 32, 33 apart.

[049] Seal 35 is carried by the door lining. It has a surface exposed on the striking surface 25 of the lining. It is positioned so that it faces the striking surface 36 of the door leaf. As shown in figure 2, seal 34 may be adhered to the striking surface 25. This can make it easier to apply to the door stop, and can allow the door lining to be used for doors of a lower fire rating without the seal 34 being applied. Alternatively, seal 34 may be located in a rebate in the stop 21 of the lining 4.

[050] Each of the seals 32 to 35 is elongate and extends up substantially the full height of the door leaf. Each of the seals 32, 33 has an inner edge, which is the edge closest to the other of seals 32, 33 in the thickness direction of the door leaf. Seals 32 and 33 are preferably located in or on the door leaf so that when the door is fully closed (e.g. latched closed and/or with the striking face of the door leaf abutting the door stop and/or the seal 35 in its unexpanded state) they adopt a preferred and/or predetermined position with respect to seal 34. In one alternative, either or both of seals 32 and 33 may be positioned on the door leaf so that when the door is fully closed the inner edge of the respective seal(s) is/are aligned in the thickness direction with the closer one of the outer edges of seal 34. In this arrangement, the seals 32, 33, 34 are adjacent each other in the thickness direction, without overlapping in the thickness direction. In another arrangement, either or both of the seals 32, 33 may be positioned so that it is spaced from the seal 34 in the thickness direction. In another arrangement, either or both of the seals 32, 33 may be positioned so that it overlaps the seal 34 in the thickness direction. The seals 32, 33, 34 are positioned so that they interact when they expand under the action of heat. First, when the seals 32, 33, 34 are positioned close to each other in the thickness direction, seals 32 and 33 can make contact with seal 34 on expansion. This is illustrated in figure 4. This contact between the seals carried by the lining and by the door leaf can improve the closing of gap 24 and hence the fire resistance of the door. When seals 32, 33 are located at least partially on either side of seal 34 the three seals can interlock, improving fire resistance. Second, because the seals 32 and 33 extend from the opposite side of gap 24 from seal 34 the time taken to close the gap can be reduced. As shown in figure 4, the gap can be closed even when seals 33 and 34 have not met the opposing latch surface (22, 9 respectively) because they can make contact with a seal expanding from the opposing surface.

[051 ] The hinge side of the door leaf and the door lining, and the top of the door leaf and the door lining, may be constructed analogously to what is shown in figure 2. Thus, the seals 32-35 may extend continuously or substantially continuously around both sides and the top of the door leaf. Preferably each seal extends along substantially the whole of the length (e.g. greater than 90% of such length) of any edge of the door or any face of the door lining to which it is attached. At least the seals carried by the door may extend along just the latch edge and the top edge of the door. The hinge edge of the door (or more generally one longer edge of the door) may be free of intumescent seals. This configuration may make it easier for an installer to trim the width of the door to suit the size of a particular opening. The installer may attach one or more intumescent seals to the hinge edge of the door once the door has been cut to shape.

[052] The positions of the seals 32, 33 and 34 may be reversed, so that two seals are located on the inward-facing surface 25 of the lining and one on the outward-facing surface 9 of the door leaf.

[053] Figure 3 shows a cross-section through the door on line B-B of figure 1 , in the region of latch 10. The latch comprises a latch body 50, a striker 52, cover plates 53 and handles 54. The internal mechanism of the latch body (which may be conventional) is omitted from figure 4 for clarity. The interconnection between the handles and the latch mechanism may for example be a square or splined rod 51 . The latch body is located in a recess 55 in the door leaf. Conveniently the recess is defined entirely by the core 28 and the lipping 31. One reason why this can be advantageous is that the core 28 and the lipping 31 may be made of wood-based materials which are relatively easy to machine. Another reason why this may be advantageous is that it avoids disruption to the fire-resistant panels 27, 29. Thus, the latch may be located in a recess within the door leaf, which recess does not impinge on the fire-resistant panels 27, 29. Thus, providing a core 28 occupying the central part of the door leaf, with fire-resistant panels on either side of it can facilitate installing door furniture to be installed in the door leaf, and with a restricted impact on fire resistance. The striker 52 is attached to the door lining. When the latch is extended the striker receives a nib 56 of the latch to hold the door in its fully closed position. The cover plates 53 are attached to the major faces of the door leaf, and carry the handles 54.

[054] Intumescent material 57 lines the recess 55. The intumescent material 57 is located between the exterior walls of the recess and the latch body. The intumescent material helps to maintain the fire integrity of the door leaf despite the fact that it penetrated by the recess 55. Conveniently, the intumescent material 57 may take the form of a flexible sheet which is wrapped around the latch body before it is inserted into the recess. Then the latch body carrying the flexible sheet can be inserted into the recess.

[055] The latch is located generally centrally in the thickness of the door leaf. Preferably the latch body or mechanism is located so that it does not interrupt the seals 32, 33 carried by the door leaf. To this end, the seals 32, 33 may be located on either side of the latch mechanism in the thickness direction of the door leaf, as illustrated in figure 3. This allows for continuous sealing around the door latch in the event of a fire.

[056] Figure 5 shows a further cross-section through the latch edge of a door. In this example, the core 28 extends to the latch face of the door, and there is no separate lipping component. Cover sheets 26, 30 cover the major faces of the door. The latch edge of the door meets a door lining when the door is closed, which is the configuration shown in figure 5. The door lining comprises an upright 4 which adjoins the latch edge of the door when the door is closed, and a stop 21 which adjoins a face of the door when the door is closed. As in figure 2, in the region of the latch edge of the door the gap between the lining and the door is protected by four intumescent seals: 32, 33, 34, 35.

[057] Seals 32 and 33 are provided on the latch face of the door. They may be partially or fully recessed into the latch face of the door. Preferably, in their non- swollen state their exteriors are substantially flush with the remainder of the latch face of the door. Their outer surfaces may be exposed at the latch face of the door.

[058] Seal 34 is provided on the face of the upright 4 of the lining that confronts the latch face of the door. It may be partially or fully recessed into the upright. Preferably, in its non-swollen state its exterior is substantially flush with the remainder of the latch face of the door. Its outer surface may be exposed on the face of the upright 4 that confronts the latch face of the door. Preferably, in its non-swollen state its exterior is substantially flush with the remainder of the face of the upright that confronts the door. [059] Seal 35 is provided on the stop 21 . It is located so as to lie between the stop and the door when the door is closed. It may be fully or partially recessed into the stop. It may be provided on the surface of the stop. This may permit it to be more easily retro-fitted to the stop. Preferably, in its non-swollen state it does not contact the door when the door is fully closed.

[060] In the example of figure 5, the total depth of the door is 44mm. The depth of each of the door-carried seals 32, 33 in their non-activated state is 10mm. They are spaced apart by a depth of 14mm. The depth of seal 34 is 15mm. Thus the depth of seal 34 is less than the spacing between seals 32, 33. Each outer edge of seal 34 overlaps a respective one of the door-carried seals in a direction parallel to the faces of the door when the door is fully closed. This overlap can improve the level of sealing that occurs when the three seals expand and the door-carried seals make contact with the lining-carried seal. The overlap in the direction parallel to the face(s) of the door between each door-carried seal and the lining mounted seal when the door is fully closed may be less than 10mm, less than 5mm or less than 2mm. The depth in the direction parallel to the face(s) of the door of the lining-mounted seal that is not overlapped by the door-carried seals may constitute greater than 50%, or greater than 80% of the depth of the lining. Where the amount of overlap varies along the height of the door, the values given above may be mean values or may apply over greater than 50% or greater than 80% of the height of the door.

[061 ] Preferably each vertical seal (e.g. any one or more of seals 32, 33, 34) extends (continuously or discontinuously) over more than 80% or more than 90%.

[062] Examples of materials that may be used as intumescent seals include those comprising ammonium phosphate, hydrated sodium silicate and intercalated graphite.

[063] The door may be considered to be fully closed when, for example, the latch face of the door is parallel with the adjoining face of the door lining and/or the latch of the door is fully home in engagement with the door lining. [064] In the example of figure 5, the stop-carried seal 35 is adhered to the face of stop 21 rather than being recessed in to it. This can mean that the stop-carried seal can readily be attached to the stop even when the stop is already in situ in a building.

[065] One known design of fire door system involves a lining-mounted intumescent seal, perhaps similar to seal 34, a fire door hinged to the lining, the door carrying no intumescent seals - at least on its latch edge, and no seal on the door stop. Such a door system may have only a single intumescent sealing strip running on the door lining as it confronts the latch face of the door. This is typical for some types of 30 minute fire resistant doors (FR30). When such a door system has previously been installed at an opening it may be desired to improve the fire resistance at the opening. In such a context, it can be possible to increase the level of fire protection by (i) replacing the existing door with one that has door-carried intumescent seals, for example as shown in figure 2 or figure 5, by hanging the replacement door on hinges in the opening, and/or (ii) affixing an intumescent seal to the surface of the door stop. This may allow the protection at the opening to be increased to FR60, without replacing the door lining. Step (i) can be especially straightforward if the existing door is of standard dimensions, because a replacement door of similar dimensions can then be fixed in place relatively easily. Thus, a door system as described above can provides a relatively efficient way to increase the level of fire protection for openings that are already provided with doors.

[066] The door may be such as to meet the requirements for an FD60 door as at 1 February 2018. It may meet those requirements when installed in a suitably fire- resistant lining. The door may have a thickness of less than 50mm, more preferably less than 45mm. This is relatively thin for an FD60 door. The door set may comprise: (i) a door leaf as described herein, (ii) a pre-manufactured door lining having seal 34 but not seal 35 and (iii) seal 35, which may be adhered to the door lining at the time of installation.

[067] The applicant hereby discloses in isolation each individual feature described herein and any combination of two or more such features, to the extent that such features or combinations are capable of being carried out based on the present specification as a whole in the light of the common general knowledge of a person skilled in the art, irrespective of whether such features or combinations of features solve any problems disclosed herein, and without limitation to the scope of the claims. The applicant indicates that aspects of the present invention may consist of any such individual feature or combination of features. In view of the foregoing description it will be evident to a person skilled in the art that various modifications may be made within the scope of the invention.