GB2259932A - Access door assembly - Google Patents

Abstract

A shaftwall access door assembly comprises a door 10 and a door frame 14. The frame is constructed from metal edge strips 16 each having an out-turned front flange 20 for lapping over the outer face of the shaftwall and being concealed in use behind a skim of plaster; and an inturned rear flange defining a door seat and carrying in use a sealing gasket 28 for providing a hermetic seal with the door 10. The door 10 comprises a metal front panel 30 and a metal structural panel 36 spaced apart by a metal edge frame 32. with a heat-insulating material 37 such as mineral wool packed between the two panels. On the shaft side of the structural panel 36 is a heat-insulating panel 42 for example plasterboard. The door is self-closing by virtue of a door closing mechanism 52 acting between the door frame 14 and the door 10, and preferably an intumescent seal 48 is provided all around the periphery of the door 10 and door frame 14. The door assembly of the invention satisfies the legal requirements of fire resistance while at the same time providing good insulation performance and excellent aesthetic appeal. <IMAGE>

Description

TITLE Shaftwall access door assembly DESCRIPTION Field of the Invention The invention relates to access door assemblies for vertical service ducts that run through tall buildings.

These service ducts, which may be lift or elevator shafts or vertical shafts to accommodate electrical trunking, water and gas mains and air ducts, conventionally run vertically through tall multi-storey buildings, and service access has to be provided at each floor.

Prior Art A principal concern in the design of shaftwall access door assemblies is the need for fire resistance. If a multi-storey building catches fire, then the service shafts act as natural chimneys, spreading the fire from one floor to the next. For that reason it is very important to ensure that any fire outside the service shaft is prevented to the maximum extent possible from spreading into the shaft, and that any fire that commences in or does gain access to the interior of the service shaft is prevented as far as possible from spreading through the shaftwall to the floors above.

This requirement for fire resistance has led to a common design of shaftwall access door assemblies which are heavy in construction and highly visible from the inside of the building. Moreover, the known doors do not seal hermetically the inside of the service shaft from the interior of the building when closed, which means that even though the door itself might be fire resistant, hot gases could easily pass between the doors and door frames, assisting the spread of fire past the doors even though the prior proposed doors might themselves remain intact.

The use of metal has been proposed as a basis for the construction of shaftwall access doors with a long fire resistance, but such doors have without exception been found far from satisfactory because the metal is a good conductor of heat and on the occurrence of fire on one side of the door the opposite face of the door itself or of its frame rapidly becomes extremely hot which itself poses a threat to the safety of persons relying on that door to isolate them from the fire.

The Invention The invention provides a shaftwall access door assembly comprising: a door frame for fitting around an opening in a shaftwall, the frame being constructed from metal edge strips each having an out-turned front flange for lapping over the outer face of the shaftwall and an inturned rear flange defining a door seat, the front flange being provided with a keying surface to bond in place a skim of plaster over both the shaftwall and the front flange; a door comprising a metal edge frame supporting both a metal front panel and a metal structural panel towards the rear of the door, with a heat-insulating material between the front panel and the structural panel, and a heat-insulating panel mounted on the rear of the metal structural panel; one or more hinges mounting the door on the door frame, the hinge or hinges having a pivotal axis offset to a vertical alignment close to the plane of the front of the door, and the metal front panel extending closely around the hinge or hinges to conceal the hinge or hinges; a door closing mechanism acting between the door frame and the door to bias the door to its closed condition; and sealing means between the second heat-insulating door panel and the inturned rear flange of the door frame, to establish in use a hermetic seal across the door assembly when the door is closed.

A number of specific features of the door assembly of the invention combine to provide a construction which meets all of the criteria previously required in a door by the architects looking for a door with an attractive and non-intrusive aesthetic appearance, and the Fire Officer requiring both long fire resistance and good heat insulation. Many of these criteria were previously thought to be mutually self-exclusive.

From the aesthetic point of view, the concealment of the hinge or hinges of the door behind the metal front panel provides a significant advance in door design.

Preferably the metal front panel laps around the front and one side of each hinge in direct contact with the hinge itself, thereby placing the hinge as close as possible to the front vertical edge of the door.

By forming the out-turned front flange of the door frame with a keying surface to bond in place a skim of plaster over both the shaftwall and the front flange, the metal front face of the door frame which is starkly visible in all previous designs is concealed by the plaster skim.

Not only does this provide a neat and attractive appearance, concealing the front flange, but also the plaster skim in use provides an element of heat insulation between the front flange and the inside of the building. The insulation of the flange itself can be further increased by mounting, around the rearwardly facing face of the inturned flange of the door frame, a continuous cladding of a heat-insulating strip of plaster board. In that way the heat conduction from the inside of the shaft to the interior of the building, or vice versa, is interrupted by a heat insulating cladding on the inside of the shaft and the heat-insulating skim of plaster on the interior of the building side.

The door itself pays particular regard to both fire resistance and insulation performance. The door is formed from two metal panels, namely the metal front panel and the metal structural panel towards the rear of the door. Those two panels are supported in a mutually spaced relationship by means of the metal edge frame, optionally in conjunction with one or more lateral or vertical support members. A heat-insulating filler material such as mineral wool is packed between the front panel and the structural panel, but in addition the door carries a heat-insulating panel mounted on the rear of the metal structural panel. Preferably that heat-insulating panel covers the whole of the metal structural panel, to provide good heat insulation for that panel, preventing it from heating up rapidly in the case of a fire in the shaft itself.

Another important feature of the access door assembly of the invention is the self-closing characteristic. The door closing mechanism between the door frame and the door is preferably one that utilises a flexible wire or chain and a compression spring which lies between the door front panel and structural panel. Such a door closer is commerically available under the Trade Mark "PERKO".

Another very important characteristic of the access door assembly of the invention is the creation of a hermetic seal between the door and the frame when the door is closed. That hermetic seal is preferably provided by a sealing gasket mounted on the door seat provided by the inturned rear flange of the door frame, and extends all around the periphery of the frame. The hermetic seal ensures that no oxygen-containing air from one side of the door assembly can pass the door assembly to fuel a fire on the other side, and also ensures that flames cannot pass in the reverse direction. The fire resistance of the door assembly is, however, preferably substantially enhanced by forming an intumescent seal around the whole of the door and door frame, for sealing the space between the door and door frame in the case of fire.

The door is preferably fitted with a simple spring-loaded latch to retain it in its closed position, and that latch is preferably releasable by a removable key from the front of the door and by a non-removal finger knob from the rear. In the case of larger sized doors, two such latches might be necessary. The door sizes are typically anything in the range from 300 mm x 300 mm to 1800 mm high x 600 mm wide.

Drawings Figure 1 is a front elevation of a shaftwall access door assembly of the invention.

Figure 2 is a horizontal section taken in the plane A-A of Figure 1.

Figure 3 is a vertical section taken along the line of B-B of Figure 1 and Figure 4 is a vertical section taken along the line C-C of Figure 1.

Figures 2 to 4 are drawn to a larger scale than Figure 1, for clarity of detail.

Figure 1 shows an access door assembly with a full sized door 10, ofthelargest size that is likely to be specified in any design for shaftwall access. Typically the nominal dimensions of the door of Figure 1 are 1800 mm x 600 mm, and such a door 10 requires three horizontal metal strengthening channels 12 which are shown in phantom in Figure 1 and described below in greater detail with reference to Figure 4.

The construction of the door 10 and door frame 14 will be better understood with reference to Figures 2 and 3.

The door frame 14 comprises metal edge strips 16 around all four edges of the frame, each edge strip comprising a central web portion 18 with an out-turned front flange 20 for lapping over the outer face of the shaftwall 22, and an inturned rear flange 24. The four front flanges 20 are provided with a keying surface to bond in place a skim 26 of plaster over the shaftwall 22 and the front flange 20. The keying surface may be, for example, a series of perforations passing completely through each flange 20. By passing a plaster skim 26 over the shaftwall 22 and all four front flanges 20, the frame can be concealed by the internal decoration of the building, and is not at all visible to the casual observer.Furthermore, the plaster skim 26, although very thin, does act to some small degree as a heat insulating barrier between the door frame 14 and the interior of the building, should the frame itself become hot by reason of a fire on the inside of the shaft.

The four inturned rear flanges 24 together form a seat for the door 10 , and mount a rubber sealing gasket 28 which provides a hermetic seal between the door and the door frame when the door is closed.

The door itself comprises a metal framed panel 30 typically made of steel of thickness 1.0 mm and finished in a matt white stove enamel paint. Spot-welded around the edge of the front panel 30 is a metal edge frame 32 made from steel 1.6 mm thick, the edge frame 32 on the hinge edge being slightly offset from the door edge to accommodate the hinge 34, to be described below.

Spot-welded to the rear of the metal edge frame 32 is a metal structural panel 36 made of steel 1.2 mm thick, and between the two panels 30 and 36 is a heat-insulating filling of mineral wall 37 Figure 4 shows the detailed construction of one of three strengthening channels 12 providing reinforcement to the front and rear panels 30 and 36. Such strengthening channels are required only in the case of the larger doors constructed according to the invention. It will be observed that the channels 12 do not extend the full thickness from the front panel to the rear panel of the door, this being to provide good heat insulation across the whole of the height of the door.Each strengthening channel 12 is spot-welded to the door front panel 30 at intervals, and carries a rear heat-insulating packing of plasterboard spacing it from the door structural panel 36 to which it is secured by screws 40.

The structural panel 36 is itself completely clad on the shaft side by a heat-insulating panel 42, for example of plasterboard. It is against that panel 42 that the gasket 28 forms the hermetic seal when the door is closed.

A similar strip 44 of plasterboard is mounted on the shaft side of each inturned rear flange 24 of the frame 14, to provide additional heat insulation all around the edge of the frame on the shaft side. The plasterboard strips 44 are held in place by steel clips 46.

An intumescent seal 48 is provided around all sides of the door and door frame, so as completely to seal the small void between the door and door frame in the event of fire.

The hinge 34 is offset as close as possible to the front and one edge of the door 10, but is concealed by the door front panel 30 which passes across the front of the hinge and laps around its inside vertical edge at 50.

A door closer 52 is mounted internally of the door between the front panel 30 and the structural panel 36, and draws the door to its closed position by means of an anchorage 54 on the door frame 14.

A conventional spring-loaded latch 56 retains the door in its closed position, and is operable by a removable key 58 from the front, and by a finger release 60 at the rear.

The shaftwall access door assembly of the invention has been tested to a fire resistance of 2 hours, with good insulation performance throughout. It provides a hermetic seal between the interior of the building and the service shaft, is self-closing and has achieved all of those desirable characteristics while retaining maximum visual concealment, in that there is no visible flange around the aperture and no visible hinge. The door can very easily be mounted completely flush with the shaftwall access opening.

Claims (7)

1. A shaftwall access door assembly comprising: a door frame for fitting around an opening in a shaftwall, the frame being constructed from metal edge strips each having an out-turned front flange for lapping over the outer face of the shaftwall and an inturned rear flange defining a door seat, the front flange being provided with a keying surface to bond in place a skim of plaster over both the shaftwall and the front flange; a door comprising a metal edge frame supporting both a metal front panel and a metal structural panel towards the rear of the door, with a heat-insulating material between the front panel and the structural panel, and a heat-insulating panel mounted on the rear of the metal structural panel; one or more hinges mounting the door on the door frame, the hinge or hinges having a pivotal axis offset to a vertical alignment close to the plane of the front of the door, and the metal front panel extending closely around the hinge or hinges to conceal the hinge or hinges; a door closing mechanism acting between the door frame and the door to bias the door to its closed condition; and sealing means between the second heatinsulating door panel and the inturned rear flange of the door frame, to establish in use a hermetic seal across the door assembly when the door is closed.

2. A door assembly according to claim 1, wherein a latch mechanism carried by the door to retain the door in its closed condition is releasable by a removable key from the front of the door and by a finger-actuable release member from the rear of the door.

3. A door assembly according to claim 1 or claim 2, wherein an intumescent seal is provided around the whole of the door and door frame for sealing the space between the door and door frame in the case of fire.

4. A door assembly according to any preceding claim, wherein the heat-insulating material is mineral wool.

5. A door assembly according to any preceding claim, wherein the heat-insulating panel is a panel of plasterboard.

6. A door assembly according to any preceding claim, wherein the rear surface of the inturned rear flange of the door frame is clad with a heat-insulating strip of plasterboard.

7. A door assembly substantially as described herein with reference to the drawings.