Though the essentially closed space with which the present invention is concerned may be an inflatable storage chamber, the invention is applicable to other kinds of storage chamber or indeed other essentially closed spaces. In the following, the invention will be further described exclusively with reference to inflatable storage chambers though it is to be understood that the invention is not limited to this application of the fan assembly.

A known form of storage chamber for articles such as vintage cars and motor-cycles or other delicate machinery such as aero-engines comprises a flexible plastics material cover sheet connected to a base sheet thereby to define an essentially closed space within which the article to be stored may be positioned. One or more low-power fans are arranged to direct air into the chamber defined by the two sheets so as to inflate the space and so form the storage chamber. In order to prevent condensation within the chamber, which could damage for example paintwork on a vintage car, it is also known to treat the air entering the chamber, for example with a vapour-phase corrosion inhibitor and also to ensure that the air in the chamber is slowly replaced by fresh air from the external atmosphere.

A problem with inflatable storage chambers as described above is that in the event the relative humidity of the external atmosphere is high, condensation can still occur inside the storage chamber, especially should the external temperature fall. At times, it may be better to recirculate the air within the chamber rather than introduce fresh air having a relatively high humidity, particularly if the humidity of the air inside the chamber is lower than that outside the chamber. It would be possible to arrange manually openable and closable vents to allow control, but an aim of inflatable storage chambers as

described above is that products may be stored for long periods without the need for any manual intervention, for example, should the climatic conditions change.

In view of the above it is a principal aim of the present invention to provide a fan assembly suitable for use with an inflatable storage chamber. In a preferred form of this invention, a further aim is to provide a storage chamber together with such a fan assembly and which is able to perform better than the known chambers of this kind, with particular reference to reducing the likelihood of condensation within the chamber.

Accordingly, one aspect of the present invention provides a fan assembly for ventilating an essentially closed space, which assembly comprises a base plate adapted for mounting to an opening through a wall which encloses the space, the base plate defining an aperture therethrough, an electrically-driven fan arranged to draw air from a first plenum chamber on the upstream side of the fan and to drive that air into said space, the air flow passing through the aperture in the base plate, an air treatment unit disposed in or over an opening through the base plate between said space and the first plenum chamber and a first filter disposed in or over an opening between the first plenum chamber and the external atmosphere, whereby the air driven into said space is a mixture of air drawn from the external atmosphere through the first filter and air drawn from said space through the air treatment unit into the first plenum chamber to be recirculated into the space.

It will be appreciated that when the fan assembly of this invention is used to ventilate an essentially closed space such as an inflatable storage chamber of the kind described above, some of the air already within the chamber is recirculated by the fan but during that recirculation is mixed with fresh air drawn in from the external atmosphere. In this way, the replacement of air within the chamber by air from the external atmosphere is reduced. This will lead to a reduction in the wastage of any treatment agent which may be entrained in the air flow into the chamber. Moreover, the rate of change of the relative humidity of the air in the chamber can be significantly reduced, so

in turn minimising the likelihood of damaging condensation on articles stored within the chamber.

Depending upon the kind of storage chamber and the products to be stored therein, the air treatment unit may take a number of different forms.

For example, it could comprise a simple second filter, though perhaps of a different filtering capacity or pore size from those of the first filter. Alternatively the second filter could be of a different kind, such as an activated carbon filter.

The second filter may be provided within or sealed to the aperture in the base plate and may itself have an opening within which is mounted the fan. In the alternative, the fan may be mounted in an opening through a block of firm but resilient material, which resilient material is supported in or over the aperture through the base plate.

Another possibility for the air treatment unit is for it to include means to entrain a treatment liquid in the airflow from the closed space to the first plenum chamber. Such a treatment liquid could comprise a known form of a vapour-phase corrosion inhibitor to reduce the likelihood of corrosion of an article stored within the chamber, Another possibility is for the air treatment unit to include means to cool the airflow from the storage chamber to the first plenum chamber. Provided sufficient cooling of that airflow occurs, moisture in the airflow may condense out thereby reducing the moisture content of the airflow re-entering the chamber. In this case, a drain to the exterior of the storage chamber may be provided, to discharge any such condensate for instance into a container. Essentially the same effect may be achieved by including within the air treatment unit a suitable desiccant.

The fan assembly of this invention may have a second plenum chamber arranged between the second filter and the external atmosphere with a third filter disposed in relation to that second plenum chamber to filter air entering the second plenum chamber from the external atmosphere. Such a third filter may be secured to the base plate to overlie with clearance the first filter whereby the second plenum chamber is defined by the first and third filters and the base plate.

The third filter may comprise a multi-layer fibrous filter preferably constructed from weather-resistant and waterproof materials. By contrast, the first filter may comprise a porous open-cellular structure of a smaller pore size than that of the third filter.

According to a second aspect of the present invention there is provided a fan assembly as described above in combination with an inflatable storage chamber, with the fan assembly arranged to direct air into that chamber, the air so driven comprising a mixture of air drawn from the external atmosphere and also from the chamber and so being recirculated into the chamber.

By way of example only, certain specific embodiments of this invention will now be described in detail, reference being made to the accompanying drawings, in which:- Figure 1 is a diagrammatic perspective view, partially cut away, of an inflatable storage chamber including a pair of fan assemblies each of which is arranged in accordance with this invention ; Figure 2 is a vertical section through a first embodiment of a fan assembly, for use with the storage chamber of Figure 1; and Figures 3,4 and 5 are views similar to that of Figure 2, but respectively through second, third and fourth embodiments of a fan assembly.

Referring initially to Figure 1, there is shown an inflatable storage chamber of a generally known kind. This storage chamber comprises a plastics material base sheet 10 to which is releasably secured a cover sheet 11 preformed to have a generally rectangular shape, when viewed in cross- section both transversely and longitudinally. A two-part fastener 12 has a first part which extends around the lower edge of the cover sheet 11 and a second part which extends around the periphery of the base sheet 10, the two parts of the fastener being connectable together so as to secure the cover sheet 11 to the base sheet 10. For example, the fastener 12 may be a plastic clasp fastener (such as of the kind generally sold under the trade mark Zip) or may be a hook and loop fastener (such as of the kind generally sold under the trade mark Velcro). Whichever form of fastener is employed, the cover sheet 11 should relatively easily be releasable from the base sheet but when the

fastener connects the cover sheet to the base sheet, the two sheets should securely be held together.

Two circular holes are formed in an end wall 13 of the cover sheet 11 and in each of those holes is mounted a respective fan assembly 14. Those assemblies 14 are arranged to draw air from the external atmosphere and drive that air into the storage chamber. During an initial period of operation, the fan assemblies will inflate the chamber such that the air pressure within the chamber becomes super-atmospheric, whereafter the pressure within the storage chamber will be maintained. Any air leaking through the fastener 12 will be replaced by fresh air drawn from the external atmosphere, in addition to the leakage through the fastener vents (not shown) may be provided through the cover sheet 11, which vents may be adjusted in order to control the outflow of air from the storage chamber.

Referring now to Figure 2, there is shown a cross-section through one of the fan assemblies 14, mounted in the end wall 13. The fan assembly comprises a base plate 17 including a peripheral flange 18 by means of which the base plate is secured to the hole in the end wall 13 of the storage chamber. For this purpose, the material of the end wall may be reinforced for example with a second, relatively stiff annular piece 19 of plastics material bonded the material of the end wall so as to surround the hole, with the flange 18 sandwiched between the second piece 19 and the material of the end wall itself.

The base plate 17 defines a circular aperture 21 therethrough with a first filter 22 of a porous open cell structure mounted to the edges 23 of that aperture. The base plate also defines a recess 24 in the region of the aperture 21, within which recess is positioned an activated carbon filter 25. An orifice 26 extends through the carbon filter 25 and an electrically driven fan is fitted into that orifice 26. Though shown diagramatically in Figure 2, the fan comprises an impeller 28 mounted on the shaft of an electric motor (not shown) supported within a frame 29, which frame is positioned within the orifice 26. The motor typically is a low voltage dc motor and the overall fan may be similar to those widely employed in the computer industry, for cooling

power supplies and the like. The fan may additionally be supported by means of an insulator 30 connecting the fan frame 29 back to the base plate 17, to relieve loads on the activated carbon filter 25.

In the above manner, a first plenum chamber 31 is defined between the activated carbon filter 25, the base plate 17 and the first filter 22. Upon operation of the fan 27 to drive air into the storage chamber on which the fan assembly is mounted, air may enter the plenum chamber 31 either through the first filter 22 or through the activated carbon filter 25.

A second filter 33 of generally convex form has its periphery supported on lips 34 provided on the base plate 17, so as to extend over the first filter 22 but with clearance thereby to define a second plenum chamber 35. Thus, air passing through the first filter 22 to enter the first plenum chamber 31 must initially pass through the second filter 33 from the external atmosphere, to enter the second plenum chamber 35.

In normal operation, the air driven into the storage chamber will consist of a mixture of air drawn from that storage chamber to be recirculated and also a small quantity of air drawn from outside the storage chamber, to replace losses from the chamber. So long as the storage chamber remains inflated, the first plenum chamber 31 will be at a super-atmospheric pressure by virtue of the returning airflow from within the chamber, In this way the flow of air from outside the storage chamber through the second filter 33 will largely be restricted by the super-atmospheric pressure within the first plenum chamber 31. Only in the event that the leakage out of the storage chamber is such that the pressure will start to fall within the chamber will air flow into the first plenum chamber from the second plenum chamber, to make good the losses.

During initial inflation of the storage chamber, all of the air driven by the fan into the storage chamber will be used to inflate the chamber. Thus, there will be no return flow through the activated carbon filter 25 into the first plenum chamber 31 during this stage of the operation; rather, all of the air driven by the fan into the chamber will be derived from the second plenum chamber 35.

In order to achieve the above functionality it is important that the first filter 22 and the second filter 33 have appropriate characteristics, which may

easily be determined empirically. For example the first filter 22 may be of an open cellular form with a relatively small pore size and the second filter 33 may comprise a multi-layer fibrous filter with a greater pore size. The second filter 33 may be of weather resistant materials though as shown in Figure 1 the fan assembly may be protected by means of a louvre cover 36.

Figure 3 shows a second embodiment of the fan assembly generally similar to that of Figure 2 and like parts are given like reference characters; those parts will not be described again here.

In the arrangement of Figure 3 the activated carbon filter 25 of Figure 2 is replaced by an open cell polyurethane foam filter 38. A liquid storage vessel 39 is disposed over the filter 38 and has a nozzle 40 having an orifice to control the outflow of liquid from the vessel into the filter 38. In this way, the filter 38 will become impregnated with the liquid from the vessel 39 and the air flow through that filter will thus entrain the liquid, in vapour form. In turn, the air flow entering the chamber will carry the vapour, to treat whatever article might be positioned within the chamber. Typically, the liquid within the vessel 39 is a vapour-phase corrosion inhibitor, but could instead be some other chemical-for example a fumigant or insecticide.

Figure 3 shows a third fan assembly and again like parts with those of the previous embodiments are given like reference characters and will not be described again here. The fan 27 is carried on a firm but resilient foam mount 41 pressed into a recess in the base plate 42 similar to base plate 17. Base plate 42 also provides a cell 43, a further opening 44 through the base plate communicating with the interior of the cell. Mounted within that cell 43 is a Peltier element 45 having fins 46 whereby operation of the Peltier element will cool air flowing over that element. Provided the cooling is sufficiently great, moisture in the air flow from the storage chamber and passing over the element will condense out to fall into a water trap 47 at the bottom of the cell 43. A drainpipe 48 leads away from the water trap 47 to the exterior of the storage chamber.

In other respects, the arrangement of Figure 4 operates substantially as has been described above with reference Figure 2.

Figure 5 shows yet another embodiment of fan assembly. This assembly is similar to that of Figure 4; like parts are given like reference numbers and will not be described again here. In the arrangement of Figure 5 the Peltier element 45 is replaced by a desiccant 49 provided in a porous bag or provided on a card. The desiccant will draw moisture out of the air flow being recirculated by the fan. As with the previous embodiment, once the desiccant has become saturated the water will fall into a water trap 47 and so to a drain pipe 48 to be led away from the storage chamber.