TITLE TAN AIR FILTER SCREEN" This invention relates to an air filter screen for a fan, such as an oscillating fan or pedestal fan. In particular, it relates to a fan air filter screen that may be impregnated or coated with aromatherapy or pharmaceutical compounds to improve the quality of air moved by the fan. BACKGROUND TO THE INVENTION The use of axial flow fans for cooling is widely practiced. Many varieties of axial flow fan have been designed with the aim of producing a flow of air that is effective. These include ceiling fans, exhaust fans, pedestal fans, oscillating fans and fixed standard fans. The latter four of these are generally produced with guards to isolate the fan blades from external access. In particular, the guards are designed to prevent persons placing their fingers in the moving fan blades. An undesirable side effect of these fans is that they stir up dust by producing air movement. Oscillating fans are particularly aggressive in their operation and can produce a large amount of matter entrained in the moving air. This matter may comprise dust, fungi spores, mites, lint, pollen, etc. The matter can result in discomfort to persons in the vicinity of the fan due to the effects of hay fever, asthma, allergy or other reactions. Some means of minimising the amount of dust stirred up is desirable.

In this regard reference may be had to known exhaust fans, such as range hoods, that incorporate a filter to trap oil vapour. The use of filters is also known in air conditioning units that draw air from outside the air conditioned areas. None of the types of filters known for these applications are suitable for use with oscillating or pedestal fans or the like. The known filters are constructed within a planar frame to be fitted within a confining structure. Such a rigid construction cannot be fitted to the generally ovoid shape of the guards of the fans referred to above. Similar considerations apply to centrifugal flow fans although these fans are not used as extensively as axial flow fans. Nonetheless, suitable

filters for centrifugal flow fans are also desirable.

OBJECT OF THE INVENTION It is an object of the present invention to provide an air filter screen for a fan for improving the quality of air circulated by a fan. It is a further object of the invention to provide an air filter screen for a fan that reduces the quantity of dust or other airborne particles in the air. It is a still further object to provide an air filter screen for a fan that has an aromatherapeutic and/or pharmaceutical benefit.

Further objects will be evident from the following description. DISCLOSURE OF THE INVENTION in one form, although it need not be the only or indeed the broadest form, the invention resides in an air filter screen for a fan of the type having a guard surrounding blades of the fan, said air filter screen comprising : a non-woven, fibrous material sized and shaped to cover a rear ofthe guard and to extend partially over a front of the guard; said air filter screen having an inner circumference defining a hole; and an opening between the inner circumference and an outer circumference to facilitate fitting of the air filter screen to the guard; wherein air drawn through the air filter screen by the action of the fan is caused to follow a tortuous path through the material such that matter carried by the air contacts the material and is filtered from the air.

In preference the air filter screen further comprises a resilient band joined to the outer circumference to gather the material around the guard. Suitably the hole is in the center of the air filter screen and is of a size and shape to fit around a motor of the fan. There is preferably a resilient band joined to the inner circumference to gather the material around the motor.

The material is suitably a non-woven, expanded synthetic material having an open cellular structure. One suitable material is Rayon™.

To enhance the filtering effect the air filter screen may be coated or

impregnated with a light oil. A suitable light oil is tea tree oil.

In preference the air filter screen further comprises a colour additive that indicates the presence of the light oil. As the light oil evaporates the colour gradually disappears thereby indicating a time to replace the filter. Altematively, a chemical indicator may be incoφorated for indicating the time for replacing the air filter screen.

An aromatherapeutic effect can be obtained by incorporating one or more essential oils on or in the filter. Suitably, a blend of light oil and one or more essential oils are coated on or impregnated in the filter for providing the aromatherapeutic effect.

In another form, a wad treated with a one or more essential oils is retained in a wad retaining means joined to the air filter screen. The wad retaining means is preferably a loop or pocket joined to a rear part of the air filter screen. The wad is preferably formed from a non-woven, cellulose based fibre material.

In a still further form of the invention the air filter screen further comprises one or more therapeutic agents coated on or impregnated in the filter for providing a therapeutic effect. The therapeutic agent may be a pharmaceutical compound having a medicinal therapeutic effect. BRIEF DETAILS OF THE DRAWINGS

To assist in understanding the invention preferred embodiments will now be described with reference to the following figures in which : FIG 1 is a sketch of a conventional oscillating personal fan with a filter in place; FIG 2 is a sketch of the filter of FIG 1 ;

FIG 3 is a back view of the filter of FIG 2;

FIG 4 is a top view of the fan and filter of FIG 1 ; and

FIG 5 is a sectional view of the filter showing air flow paths.

DETAILED DESCRIPTION OF THE DRAWINGS In the drawings, like reference numerals refer to like parts.

Referring to FIG 1 , there is shown a filter 1 fitted to a conventional

oscillating fan 2. The fan 2 is of the type having a guard 3 fitted over the blades 4 to protect against injury. The filter 1 fits over the guard so as to fully cover the rear of the guard, as seen most clearly in FIG 4.

A resilient band is joined to the filter material along inner circumference 5 and outer circumference 6. The resilient bands serve to gather the filter material so as to fit neatly around the guard as seen in FIG'S

1 and 4. In the embodiment shown the resilient band is a strip of light elastic sown into the edge of the filter material.

The filter 1 has an opening 7 formed between edges 8 and 9 to facilitate fitting of the filter 1 to the fan 2.

In fitting the filter 1 to the guard 3 ofthe fan 2 the opening 7 allows the outer circumference 6 to pass around the fan motor 10. The outer circumference 6 extends over the front edge 11 of the fan 2, as seen most clearly in FIG 4. The inner circumference 5 fits closely around the fan motor 10. The edges 8 and 9 are overlapped to close the opening 7. In this manner the entire back of the fan guard 3 is covered by the filter 1 such that air drawn by the fan blades 4 must pass through the filter 1.

The non-woven, fibrous nature of the filter material is such that the overlapping edges remain in place due to catching of fibres between the respective edge regions 12, 13. The action of the air flow through the filter also assists in maintaining the filter 1 in place on the guard 3 of the fan 2.

Nonetheless, attachment means (not shown) such as hook and loop strips

(eg Velcro™) or clips may be used to ensure positive positioning of the filter

1 on the fan 2. The filter 1 is formed from a suitable non-woven, expanded synthetic material having an open cellular structure. The material allows air to flow through by following a tortuous path, as depicted in FIG 5. Arrows 14 represent the flow of air through the fan 1. The structure of the fan material is such that air cannot pass directly through the material but is deflected by contact with fibres of the material. If the air is laden with dust it will lose the dust to the filter during contact with the material.

In order to capture the benefit of the filtering effect it is important that the filter material is fluff and lint free. It is also preferable that the material is non-allergenic. Furthermore, the material should have suitable strength to withstand the degree of handling commonly associated with personal fans. The inventor has found that Rayon™ and polyester are suitable materials for the filter. Another suitable filter material is natural wool, although the cost of wool presently precludes it from being economically attractive.

Over a period of time the filter will become clogged with dust filtered from the air. To assist in determining the proper time to replace the filter a clear window can be provided in the filter. When the clear window is opaque from dust it is time to replace the filter. Although it may be possible to clean the filter, it is preferable to replace the filter if any of the preferred embodiments discussed below are employed.

To further enhance the filtering effect the filter 1 is impregnated or coated with a light oil, such as tea tree oil (melaleuca alternifolia). Tea tree oil has a double effect on the effectiveness of the filter. Firstly, it has an antimicrobial action to disinfect the air passing through the filter 1. Secondly, the oil aids in trapping dust from the air into the filter. The inventor has found that a light spraying of oil, say less than 1 ml per 100 cm ² is sufficient. Although Tea Tree oil is preferred it will be appreciated that other light oils such as eucalyptus oil, wheatgerm, jojoba, grapeseed or almond oil could be used.

Because the preferred light oils evaporate over time the filter has an effective life limited by the evaporation rate of the oil and the quantity of oil sprayed into the filter material. In one embodiment, this lifetime feature is enhanced by treating the light oil with a colour additive that indicates the presence of the oil. When the colour is gone from the filter it indicates that the oil has evaporated and the disinfectant value is negligible. This indicates to the user that it is time to replace the filter. Alternatively, a separate chemical indicated can be used to indicate the time to change the filter. The chemical indicator could be linked directly

to duration of use or to dust captured.

The inventors have found that the filter material provides a suitable matrix for carrying essential oils used in aromatherapy. Essential oils are volatile oils generally derived from the plants, leaves, stems, flowers or twigs of plants. Chemically, they are principally teφines (hydrocarbons), but many other types occur. The majority of essential oils have a low oral and dermal toxicity.

In a preferred embodiment the filter is sprayed with a light oil, such as Tea Tree oil and an aromatherapy blend of essential oils. The actual blend of essential oils is a matter of taste for the user but the inventor has found that the following blends have a pleasing effect. Relaxing blend : 8 parts geranium

3 parts clary sage

5 parts lemon

3 parts bergamot

Stimulating blend : 8 parts grapefruit

4 parts lavender 4 parts lime 2 parts basil

Bedroom blend : 8 parts palmarosa

1 part ylang-ylang

2 parts clary sage 2 parts nutmeg

4 parts lime

Persons having knowledge of aromatherapy will know that a large number of blends are possible from the thirty-six common essential oils.

They will also appreciate that the invention overcomes the common problem of getting the arometherapy compound into the air. A common method is by heating (eg in essential oil burners or vapourisers) however many essential

oils degrade at elevated tempertures. This embodiment of the invention gets the essential oils into the air without the need for elevated temperatures.

It is not necessary to spray the entire filter with the aromatherapy blend in order to achieve the desired effect. The aromatherapy blend can be absorbed into a wad which may then be positioned in a wad retaining means such as a pocket or loop on the filter. Such a loop is shown in FIG 3. The loop 15 is stitched to the filter 1 in a position that will be at the rear of the filter 1 when it is positioned on the fan 2. This location ensures that air flows past and through the wad during operation of the fan. The wad (not shown) is formed from a non-woven cellulose based fibre. The wad is placed in the loop or altematively the loop is simply sprayed with the aromatherapy mixture.

The wad approach is particulariy useful for personal use but treating the entire filter is preferred for industrial applications. A simple example is a filter treated with lavender for use in hospitals. If the entire filter is treated a larger volume of lavender can be supplied with a corresponding increase in life of the filter (assuming it does not get clogged up with dust).

In a further preferred embodiment the filter is impregnated or coated with a therapeutic agent rather than the aromotherapy compounds discussed above. In one further preferred embodiment the therapeutic agent is a pharmaceutical such as ventolin. This embodiment provides a method for the slow release of a therapeutic agent into a room were a person requiring the medication is working or resting. The inventor sees this embodiment as having particular application with young asthma sufferers at night. A filter impregnated or coated with ventolin and a light oil carrier could be operated in the room of a sleeping sufferer to provide a therapeutic effect throughout the night. Of course, the invention is not limited to ventolin but could be used with any medication that can be taken by slow release.

It may be necessary to employ a fixed oil or coating resin to facilitate treating of the filter with a therapeutic agent. Copolymers of polyvinylpyrrolidine/vinyl acetate, or vinyl acetate, butyl maleate and isobutyl

acrylate are examples of suitable agents for this purpose.

It will be appreciated that the filters described herein can be made in a variety of shapes and sizes to suit particular fans. The effect of the filter is accumulative over time while the fan to which the filter is fitted is operating. A small fan in a large room will take a considerable period of time to have full effect. Conversely, a large fan in a small room willl display a very rapid effect. The inventor has found that a 40cm oscillating fan fitted with a filter coated with a blend of essential oils has a noticeable effect in a moderate size room within a matter of minutes. Throughout the specification the aim has been to describe the preferred embodiments ofthe invention without limiting the invention to any one embodiment or specific collection of features.