GB2314922A - Apparatus for producing an air curtain - Google Patents

Abstract

Apparatus for producing an air curtain across an entrance to or exit from a room comprises a casing (2) into which air is drawn from above by a fan (3) and is propelled from the casing through an outlet (12) to be directed downwardly to form an air curtain across the entrance or exit of the room, at least one source (4 a , 4 b ) of ultraviolet radiation being provided within the casing so that air flowing between an entrance (5) for the air into the casing and the outlet (12) of the casing is sterilised by the ultraviolet radiation to produce a sterilised air curtain.

Description

APPARATUS FOR PRODUCING AN AIR CURTAIN This invention relates to apparatus for producing an air curtain across an entrance to, or exit from, a room.

Air curtains are used conventionally as air barriers between the interior and exterior of buildings. For example, large shops and department stores often have air curtains fitted to main entrance ways. The invention employs an air curtain in producing a sterile atmosphere.

It is important to maintain as sterile an atmosphere as possible in rooms which may be used for medical and/or biological purposes. For example, there is an obvious need to maintain a sterile atmosphere in an operating theatre.

Similarly, with some kinds of biological research, the atmosphere in a room or corridor may need to be kept sterile in order to avoid contamination. This may be the case where people are entering biological research rooms, from the outside, and may need to pass through a corridor leading to a research laboratory. This can introduce airborne bacteria and other microorganisms which may be prejudicial to the biological research. In the food industry, it is desirable to provide as germ-free an atmosphere as possible, especially in the catering and marketing fields, where many people may come and go in areas where food is handled and exposed. For example, in meat marketing carcasses are exposed to both handlers and purchasers who may enter and leave the area.

The present invention seeks to provide a relatively simple but efficient way of sterilising air in a room. The term "room" is intended to cover spaces within buildings, including corridors, or entrances, as well as rooms which are used for particular purposes.

The present invention provides apparatus for producing an air curtain across an entrance to, or exit from, a room, the apparatus comprising: a casing having an air inlet and an air outlet; a fan for causing a flow of air from the inlet to the outlet and for causing sufficient air flow from the outlet to form an air curtain across the entrance/exit of the room; the inlet and outlet being positioned on the casing so that the inlet is adapted for drawing air from the ceiling of the room into the casing, and the outlet is adapted for directing the air curtain downwardly across the entrance/exit; and means for producing ultraviolet electromagnetic radiation for the purpose of sterilising air, said means being located in the casing in the air flow between the inlet and the outlet, whereby sterilised air is supplied to the air curtain.

The apparatus may be installed over a doorway or other aperture into the room, and the air flow may be adjusted so as to provide an optimum resistance to air transfer, from the outside to the inside of the room, and vice versa when the doorway or aperture is open, whereby external air will be impeded from entering into the room.

In some cases, the room may be continuously open, such as may be the case with a corridor leading to the entrance to a laboratory. The air flow will be adjusted to ensure that the air curtain, which is directed towards the floor, will flow substantially along the floor of the room and then up a wall or walls, before crossing the ceiling and reentering the inlet of the casing. Air will therefore circulate within the room and through the apparatus, whereby the air is progressively sterilised. Thus, anyone entering through the air curtain, whose entry may cause airborne microorganisms, such as bacteria, to enter the room, will enter into a sterile atmosphere and the microorganisms will be induced to flow into the apparatus where they will eventually be eliminated by circulation through the ultraviolet radiation. Likewise, anyone leaving an area, such as a laboratory in which airborne microorganisms are present, will pass through a sterile atmosphere before passing through the sterile air curtain when leaving. If any of theses airborne microorganisms enter the room in which the sterile atmosphere is maintained, they will also eventually be eliminated.

In the case of a corridor open at each end, apparatus according to the invention may be located at each end of the corridor and arranged so that the air flows from the air curtains are directed so that they flow towards each other across the floor of the room, whereby they meet at some intermediate region and then rise up together to the ceiling where they diverge and flow in opposite directions to the respective air inlets. This arrangement provides protection at both ends of the corridor; it prevents air movement in either direction from unprotected areas; and it contains sterile air in the space between the air curtains.

In the case where a door is fitted to the entrancel exit and is opened, from time to time, to allow access to and from the room, the air curtain is still directed across the doorway, but preferably means are provided for reducing the fan speed when the door is closed. In these circumstances, the fan will operate at a relatively higher speed when the door is open, than when it is closed. When the door is closed the fan speed will automatically be reduced to: (a) reduce the noise level of the air curtain; (b) to reduce draughts caused by unnecessary air movement; and (c) to allow a higher effectiveness of disinfection of air passing through the air curtain. Suitably, the fan speed is maintained at a level sufficient to prevent immediate recycling of a localised portion of air within the controlled air space. This level can be determined by design, or by experiment, including any safety factor to ensure optimum performance. In general, a low proportion of bacteria passing through the air curtain will be eliminated, but continual recycling of air within the room ensures that a sufficient level of sterilisation is achieved and maintained. The change in fan speed may be controlled by, for example, a door switch triggered by either opening, or closing, the door.

Generally speaking, the fan speed can be regulated either manually, or automatically, so that it operates at various speeds. This may be either a graduated, or a continuous, form of control. Control of fan speed may also be effected with an open doorway by means for monitoring a temperature differential across the doorway, i.e. on opposite sides of the air curtain. This temperature differential is proportional to the pressure differential between the inside and outside of the room, hence providing an indication of the air flow required in the air curtain to provide acceptable fluidic resistance. Baffles may also be used as part of the design in achieving a good air curtain.

Preferably, the casing includes filter means for extracting dust from the air entering the casing and passing to the means for producing U/V radiation. The latter means may be, for example, ultraviolet tubes, whereby dust extraction helps to keep the tubes cleaner and thus more effective in sterilising air. Where ultraviolet tubes or lamps are used for sterilising the air, preferably a baffle is fitted to prevent any ultraviolet radiation from being seen directly inside the casing.

An embodiment of the invention will now be described with reference to the accompanying schematic drawings, in which: Fig. 1 represents a room in which an air steriliser is installed, and Fig. 2 is a section showing the interior of the air steriliser.

Referring to the drawings, an air steriliser 1 includes a casing 2 which houses a fan 3 and two ultraviolet tubes 4a,4b. The casing 2 has an air intake grille 5 adjacent a mesh filter 6, which is provided for removing dust and larger airborne particles from the inlet air. An ultraviolet radiation screen 7 is positioned above the lamps, so that anyone looking into the air intake grille would not directly view ultraviolet radiation. Internal baffles 8a,8b and a fan scroll 9 direct air towards the fan (which may be modular tangential fan). A pressure plate 10 also helps in directing the air flow. The casing 2 has an outlet 12 with adjustable outlet vanes 13 so as to assist in directing the outlet air flow in the correct direction to form an air curtain 14 across the entrance of the room 15.

The air flow within the room 15 is indicated by the arrows 16. As shown in the drawing, the air is directed downwardly as a barrier across the entrance/exit to the room and it then flows across the floor 17 and up the far wall 18, before passing the ceiling 19 towards the inlet of the casing 2. Arrows 20 represent some air, outside the entrance, which is drawn downwardly by the air curtain.

The number of tubes used will be depend on the size of the room and the size of the door aperture (taking into account whether the door is either open continuously, or from time to time to allow access).

Fan speed may be controlled by measuring a temperature differential between the interior and exterior of the room.

One technique that can be used is to assume a constant internal temperature (as controlled by the room's heating or air conditioning system) and to measure just the external temperature. Any change in this temperature difference can be compensated by a suitable change in the air curtain's air outlet velocity.

Temperature measuring probes (not shown) could also be located on the interior and the exterior of the room, for example for providing a temperature differential signal.

Where the room has a door (not shown) which is opened and closed, a door switch (not shown) may be fitted so that when the door is opened (or closed) the fan speed is adjusted accordingly. Preferably, the fan runs at a higher speed with the door open than with the door closed. This enables more microorganisms to be eliminated since they dwell for longer in the U/V radiation chamber. Also noise levels are reduced.

Claims (10)

1. Apparatus for producing an air curtain across an entrance to, or exit from, a room, the apparatus comprising: a casing having an air inlet and an air outlet; a fan for causing a flow of air from the inlet to the outlet and for causing sufficient air flow from the outlet to form an air curtain across the entrance/exit of the room; the inlet and outlet being positioned on the casing so that the inlet is adapted for drawing air from the ceiling of the room into the casing, and the outlet is adapted for directing the air curtain downwardly across the entrance/exit; and means for producing ultraviolet electromagnetic radiation for the purpose of sterilising air, said means being located in the casing in the air flow between the inlet and the outlet, whereby sterilised air is supplied to the air curtain.

2. Apparatus according to claim 1, wherein said means for sterilising air includes lamps which provide ultraviolet electromagnetic radiation

3. Apparatus according to claim 1 or 2 including filter means for extracting dust which has entered the air inlet whereby filtered air is supplied to the lamps.

4. Apparatus according to claim 1, 2 or 3 including adjustable baffles for directing the air flow from the air outlet to enable the air curtain to adjusted.

5. A room including the apparatus according to any preceding claim in which the apparatus is installed over a doorway or other aperture into the room, and the air flow is adjusted to provide a resistance to air transfer, from the outside to the inside of the room, and vice versa when the doorway or aperture is open, whereby external air will be impeded from entering into the room.

6. A room according to claim 5, which is continuously open and where the air flow is adjusted to ensure that the air curtain, which is directed towards the floor, will flow substantially along the floor of the room and then up a wall or walls, before crossing the ceiling and re-entering the inlet of the casing, so that air will circulate within the room and through the apparatus, whereby the air is progressively sterilised.

7. A room according to claim 5, which has more than one opening for access and wherein the apparatus is provided for each opening, the respective air curtains being directed so that air flows are caused to flow towards each other across the floor of the room, whereby they meet at some intermediate region and then rise up together to the ceiling where they diverge and flow in opposite directions to the respective air inlets.

8. A room according to claim 5, where a door is fitted to the entrance/ exit and is opened, from time to time, to allow access to and from the room, and further including means for reducing the fan speed when the door is closed and for causing the fan to operate at a relatively higher speed when the door is open.

9. A room according to claim 8, including means to maintain the fan speed at a level sufficient to prevent immediate recycling of a localised portion of air within the controlled air space.

10. A room according to any of claims 5-9, in which fan speed is controlled by switch means that responds either to door opening/ closing, or to means for detecting a change in the temperature difference between the inside and outside of the room.