GB2223677A - Trapdoors - Google Patents

Abstract

The trapdoor 17 is provided to optionally open and close an aperture in a horizontal plane at the upper end of a fixed stairway in a building, the horizontal plane being between a respective lower 11 and upper storey 12. The trapdoor 17 preferably has a smoke alarm 18 affixed to its underside face. <IMAGE>

Description

Trapdoors This invention relates to a trapdoor and is applicable particularly, but not exclusively to a trapdoor for the prevention of smoke and fumes passing up a stairway from a lower floor, to an upper floor of a building.

According to one aspect of the invention, there is provided a building including a fixed stairway between respective storeys of said building, the upper end of which stairway is located in a horizontal plane having an aperture therein above the stairway, and a trapdoor to optionally open and close said aperture.

The aperture is preferably in the plane of the floor of the upper storey and is conveniently of rectangular shape. In this embodiment, the trapdoor in its closed position may be flush with the floor of the upper storey. In some cases, such as where there is insufficient clearance between the staircase and an overhead beam or hall ceiling, it may be desirable to raise the level of the trapdoor when in its closed position, above the plane of the floor of the upper storey, thus forming a positive step up from the level of the upper floor, when the trapdoor is in its closed position.

In one embodiment of the invention, the trapdoor is opened by moving it upwardly from the aperture; in this embodiment, the trapdoor is generally hinged along one edge thereof, and, preferably, counterbalanced so as to facilitate raising thereof. Such counterbalancing may be effected by, for example, springs, counterweights or hydraulic operation.

In another embodiment of the invention, the trapdoor may be provided with runners such that it can be slid horizontally, substantially in or parallel to the plane of the floor of the upper storey.

In order to minimise the passage of air, smoke or fumes (in the case of a fire on the lower floor), a seal may be provided between the trapdoor and the aperture. The seal may be a rubber or plastics seal around the trapdoor edge, a brush seal, or a flexible metallic strip.

The trapdoor is preferably made of aluminium or plastics, or other suitable lightweight structural material; it preferably comprises at least one transparent area (such that a visible indication of flames etc. can be given through the trapdoor). This area may typically be of heavy duty, wire-reinforced glass.

According to another aspect of the invention, there is provided a trapdoor, for closing an aperture in a horizontal plane above a stairway, the trapdoor having a smoke alarm affixed to the underside face thereof. In one embodiment of the invention, the smoke alarm may be such that it sets off different audible tones depending on whether the trapdoor is open or closed. This would therefore give different types of warning depending on whether the door is open or closed.

The trapdoor may be opened and closed manually or electrically.

One embodiment of the invention is described, by way of example only, with reference to the accompanying drawing, which is a perspective view down part of a stairway, closable by a trapdoor, according to the invention.

In the drawing, a stairway 10, in a house or other building, rises from a lower floor 11 to an upper floor 12. The upper end of the stairway 10 is located in a horizontal plane having an aperture defined by walls 13,14 of the building, a landing 15 and the base of a guard rail 16.

A flat trapdoor 17, conveniently made of aluminium, wood, plastics or other suitable material is hinged at one edge thereof to an edge of the aperture. The trapdoor 17 can be swung to an upper, open position, or to a lower, horizontal, closed position, wherein it closes the aperture to prevent smoke, fumes or gases rising from the lower to the upper floor, up the stairway. For some situations the trapdoor 17 may be swung downwards from the closed position or may be lifted away for opening. Opening and closing may be manual or electrically operated.

In order to give maximum warning of smoke or heat in the building, below the level of the trapdoor 17, a smoke detector 18 is affixed to the underside face of the trapdoor 17.

Passage of smoke or the like past the closed trapdoor 17 is inhibited by a rubber or plastics seal around the edges of the trapdoor 17 or of the aperture which it closes.

Claims (9)

CLAIMS:

1. A building including a fixed stairway between a respective lower and upper storey of said building, the upper end of said stairway being located in a horizontal plane having an aperture therein above the stairway, a trapdoor being provided to optionally open and close said aperture.

2. A building according to claim 1, wherein said trapdoor is openable by moving it upwardly from said aperture.

3. A building according to claim 1 or 2, wherein said trapdoor in its closed position is in the plane of the floor of the upper storey.

4. A building according to any of claims 1 to 3, wherein said aperture is of rectangular shape and said trapdoor is hinged along one edge thereof.

5. A building according to any of claims 1 to 4, wherein a seal is provided between the trapdoor and the aperture.

6. A building according to claim 5, wherein said seal is a rubber or plastics seal, or a flexible metallic strip, around the trapdoor edge.

7. A building according to any of claims 1 to 6, wherein there is provided a smoke alarm affixed to the underside face of said trapdoor.

8. A building substantially as described herein with reference to the accompanying drawing.

9. A trapdoor, for closing an aperture in a horizontal plane above a stairway, the trapdoor having a smoke alarm affixed to the underside face thereof.