Viewing panels set in doors and like structures are used inter alia in hospitals and nursing homes to enable patients or residents in a ward or room to be seen by a nurse or attendant from outside without the need for entering the ward or room. Often these viewing panels include shutters which are moved within a frame to open and close the viewing panel.

Examples of a glazed fire door and a door panel with peep-holes can be seen from UK-A-2274480 and UK-A-2152566.

Presently available viewing panels present a fire risk to the extent that they provide ready access for smoke and flames in the event of a fire thereby significantly reducing the fire worthiness of the doors in which they are located.

The present invention sets out to provide a viewing panel which provides an effective barrier to the passage of smoke and flames in the event of a fire thereby maintaining the fire protection offered by a fire door.

According to the present invention in one aspect, there is provided a viewing panel for location within a door or like structure, the viewing panel comprising a frame within which are retained fixed and slidable apertured plates located between fixed sheets of transparent material, the slidable plate being movable by an arm secured to the plate which protrudes through an elongate slot formed in one of the transparent sheets between a first position in which the or each of its apertures is aligned with that or each of the apertures of the fixed metal plate and a second position in which the or each aperture is aligned with one or more land sections of the fixed plate, the land sections of one or both metal plates carrying strips of intumescent material which intumesce in the presence of excessive heat completely to fill the panel interior.

Beads of intumescent material may be positioned between the adjoining surfaces of the frame and the door or other structure in which the frame is located.

The transparent material may comprise glass or sheets of transparent polycarbonate or like material.

Each metal plate may include a single aperture or a plurality of such apertures.

In another aspect, the invention provides a viewing panel for location in a door or like structure, the viewing panel comprising a frame holding a fixed metal plate and a slidable metal plate each formed with one or more apertures of the same or similar size, strips of intumescent material secured to land surfaces of one or each metal plate and a sheet of transparent material fixed to one side of the frame, the slidable metal latebei-ngrnovableRetweeea first posìtion in which the o apertures are aligned and a second position in which the apertures of the slidable plate lie opposite land sections of the fixed plate.

The invention will now be described by way of example only with reference to the accompanying diagrammatic drawings in which: Figure 1 is a plan view of a viewing panel in accordance with the invention; Figure 2 is a side view in section of the viewing panel illustrated in Figure 1 ; and Figures 3 and 4 are plan views of a slidable apertured metal plate and a fixed plate which form parts of the illustrated viewing panel.

The viewing panel illustrated in the drawings is intended to be mounted within a suitably shaped opening of a door or like structure. The panel comprises a frame 1 in which a retained a fixed metal plate 2, a slidable metal plate 3, a front sheet of glass 4 and a rear sheet of glass 5.

All of these integers apart from the slidable plate 3 are fixed securely to the frame. The slidable metal plate 3 is supported within runners 6 which enable it to move sideways within the frame.

Both of the metal plates 2,3 are formed with apertures 7, 8 respectively through which the interior of a ward or room can be viewed from outside the respective door when the openings are aligned. For this purpose the slidable metal plate 3 is movable between a first position in which its aperture 8 aligns with the aperture 7 of the fixed metal plate 2 and a second position in which its aperture aligns with a land section 9 of the fixed metal plate. To facilitate movement of the slidable plate an arm carrying at its free end a handle 10 is provided which protrudes through a slot 11 formed in the front glass sheet 4.

In an unillustrated embodiment, each metal plate is formed with a plurality of apertures.

The fixed metal plate has secured to its land sections pieces of intumescent material, the extent of such material being such that in the event of excessive heat the material will intumesce to fill completely and close off the interior of the viewing panel. In this way the fire worthiness of the door is maintained. Alternatively, pieces of intumescent material may alternatively or additionally be secured to land sections of the movable plate 3.

In use, the illustrated viewing panel is located within a door of a ward or room with the front glass sheet 4 on the corridor side of the ward or room. A nurse or attendant passing the door can easily see into the room simply by sliding the handle 10 within the slot 11. If satisfied, the viewing panel can be closed simply by moving the handle to its original position. In the event of fire, the intumescent pieces exfoliate to protect the ward or room remote from the corridor from the ingress of smoke and fire.

It will be appreciated that the foregoing is merely exemplary of viewing panels in accordance with the invention and that various modifications can readily be made thereto without departing from the true scope of the invention.