FIELD OF THE INVENTION This invention relates to a device for use in filtering an air stream. More specifically the invention relates to filter elements for removing particulate matter in fan forced air streams such as in vacuum cleaners and air conditioning systems.

BACKGROUND OF THE INVENTION Air streams often include, intentionally or otherwise, entrained particulate matter which may, for a variety of reasons, be subject to removal by filtering.

In vacuum cleaners, for example, a filtering system may be used for the removal of dirt and debris from an air stream which is created by a motor and fan combination. It is known to use cloth filters which may be reused but which tend to clog with dirt and dust over time and then impede the flow of air through the system, reducing the efficiency of the vacuum cleaner and placing an increased load on the motor with the potential for consequent shorter operational life. Typically these cloth filters are formed from material such as wool or nylon.

A more recent development in the field of filters involves the use of disposable paper bags.

However, these bags, although air permeable, are also prone to clogging as their dust load increases with time. By and large the disposable paper bags also tend to be expensive and therefore relatively wasteful. They are also somewhat inconvenient as a user must ensure a supply of replacement bags at all times to avoid prolonged interruption to cleaning activities when a bag is full. In addition the bags may present a problem in disposal when their working life is finished, leading to potential waste pollution.

Commonly, a filter will be supported in a vacuum cleaner by a frame or similar structure, often in the form of a substantially cylindrical or rectilinear box-frame configuration.

Vacuum cleaners may sometimes include a secondary cloth filter element which remains in situ while a primary filter element is removed for emptying or disposal. Issues of convenience of use, longevity and cost are of particular importance in the context of commercial providers of cleaning services. Industrial use presents a significant challenge to a vacuum cleaner and the performance of the machine is of particular economic importance to an operator. The commercial use of a vacuum cleaner must ensure a client's premises are adequately cleaned while maintaining a profit margin that is not eroded by ongoing maintenance and replacement costs.

Filters are also commonly used in air conditioning units and circuits. Their use in these applications is associated with air quality and health issues. With accumulation of dust and other materials, such filters also tend to decrease efficiency of air flow. Regular cleaning and/or replacement is needed to maintain efficiency of the system.

It would be advantageous to provide a filter element that was durable and reusable while also maintaining efficient activity in use. It would be of further benefit if such a filter element were to be easily cleaned and, preferably, washable.

SUMMARY OF THE INVENTION Throughout this specification, unless the context requires otherwise, the word"comprise", or variations such as"comprises"or"comprising", will be understood to imply the inclusion of a stated element or integer or group of elements or integers but not the exclusion of any other element or integer or group of elements or integers.

In one form, although it may not be the only or indeed the broadest form, the invention resides in a filter element for filtering an air stream, the filter element formed from an air permeable synthetic chamois material.

In this specification, the expression"synthetic chamois"has the full scope of its meaning to a person skilled in the art. The expression includes commercially available material formed from Polyvinyl Alcohol ("PVA") fibres and a PVA binder crosslinked by a suitable

material, for example, formaldehyde. Other synthetic chamois are known to be made from nonwoven fibre and an originally hydrophobic acrylic latex binder which has functional groups to make the binder, and thus the article hydrophilic. These materials are described by way of non-limiting examples.

The filter element may be formed as a material sheet interchangeably configurable to form a shaped filter element for a vacuum cleaner, and releaseable holding means for maintaining the material sheet as the shaped filter element. "Filter element"includes a filter per se as well as a component or part of a filtering arrangement.

The filter element may be configurable in a bag-shape having an open top, continuous side walls and a bottom. The filter element may be configurable as a box-like shape. The box- like shape may be rectilinear with the filter element having at least one entrance aperture.

The filter element may be configurable as a shaped filter element which is, at least in part, conical.

The releaseable holding means may include one or more clips. Preferably, the releaseable holding means includes a zip. The zip may comprise two tracks and an interlocking slide wherein the tracks are separable and located on the material sheet. Preferably, in operation, the zip fixes side walls of the filter element in position. One track of the zip may be disposed towards a first edge of the material sheet and the second track may be disposed towards a second opposite edge of the sheet and on an opposite side of the sheet.

Preferably, the tracks are disposed to ensure that when they are interlocked the edges of the material sheet overlap. The fixing means may include at least one clip for securing a bottom section of the filter element.

Alternatively or additionally the releasable holding means may include a hook and pile fastener. The components of the hook and pile fastener may be disposed as described for the zip. The hook and pile fastener may be Velcro. Alternatively or additionally the holding means may include a button arrangement, a press stud, a slide and slot arrangement or any suitable means.

The material sheet may be preferably approximately in the form of a triangle. However, any suitable shape may be used.

Alternatively, the filter element may be permanently configured as a bag-like structure, or, indeed any shape suitably adapted for location in an air stream pathway.

In another aspect, the invention resides in a filter element for use with a vacuum cleaner wherein the filter element is formed from a hydrophilic material. Preferably, the hydrophilic material is a synthetic chamois. The synthetic chamois is most preferably a PVA synthetic chamois.

In another aspect, the invention resides in a method of filtering an air flow stream, said method comprising the steps of : filtering the air stream with a synthetic chamois material.

The method may further include the step of configuring an air filter element from the synthetic chamois material for location in an air stream pathway.

Configuring an air filter element may include the step of forming a bag-like structure reversibly configurable as a substantially planar sheet. Configuring the air filter element may include the steps of : adapting a sheet of material to the configuration of a filter element; applying releaseable holding means to maintain the sheet of material in said configuration; and locating the filter element in a vacuum cleaner or an air conditioning system.

The method may further include the step of : using the vacuum cleaner or air conditioning system; and cleaning the filter element by removing it from the vacuum cleaner or an air conditioning system, releasing the fastening means and removing collected debris from the sheet of material.

Removing the collected debris from the filter element may comprise the step of washing the debris from the material and, preferably, removing excess water.

The method may still further include the repetition of one or more of the above steps.

In still a further aspect, the invention resides in a vacuum cleaner including an air filter element formed from a synthetic chamois. The air filter element may be formed as a bag like structure. The air filter element may be formed with any shape suitable in a given situation.

The vacuum cleaner may include a secondary air filter formed from synthetic chamois material.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a top view of an air filter element of the present invention when configured as a sheet.

Figure 2 is a side view of the sheet of Figure 1 when configured as a shaped air filter element.

Figure 3 is a perspective view of an air filter element formed as a bag.

Figure 4 is a schematic, part cut away view of a vacuum cleaner including air filter elements of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to Figure 1, there is seen an air filter element 11 configured as a material sheet.

The air filter element 11 includes a top edge 12 a first side edge 13, second spaced side edge 14 and a bottom edge 15. The top edge 12 may be cut on a curve so that when configured to form a shaped filter element, a top edge of the filter element 11 is

substantially planar.

The air filter element 11 is formed from synthetic chamois. A form of material which particularly lends itself to this use is PVA synthetic chamois or Poly Vinyl Alcohol chamois. Synthetic devices for wiping surfaces have been known to be formed from a non-woven web made from polyvinyl alcohol (PVA) fibres and subsequently coated with covalently cross-linked PVA binder resins. Chemically cross-linked PVAs provide distinct advantages in the use of synthetic wiping devices. They increase and improve the elements of a dry wipe providing non-linting of a wipe surface, mechanical strength and hydrophilic properties.

Natural chamois is a highly absorbent material derived from a goat-like antelope and is commonly used to dry automobiles after washing. The absorbent properties of natural chamois have been emulated in several synthetic chamois. Synthetic chamois which is commercially available may be formed from PVA fibres and a PVA binder cross-linked by fornzaldehyde. Most synthetic chamois are known to be made of non-woven fibres and an originally hydrophobic acrylic latex binder which has functional groups to make the binder, and thus the material, hydrophilic.

These synthetic chamois lend themselves to great utility in application as a vacuum cleaner filter element. Dirt and dust particles may be simply hosed off the material which may then be wrung out as is routinely done during the process of drying a car or other surface.

After being wrung out, the material is substantially dry to the touch and may be relocated in a vacuum cleaner for continuing instant use even in the vicinity of the electric motor.

The inventor has surprisingly found that the synthetic chamois material has less tendency to clog during use and provides an effective and smooth flow-through membrane for air flow in the device. This ability is combined with the capacity for simple and efficient cleaning to provide a long term cheap, safe and effective vacuum cleaner filter element.

However, it is preferred if the synthetic chamois material is first substantially dried before relocation in a vacuum cleaner. The material dries quickly and may be washed repetitively without deterioration in its effectiveness. A series of filter elements may be carried by a

cleaner, facilitating the easy replacement of a full filter with an already dry substitute.

The present device has great advantages over prior art filter elements, which as noted above, often rely on disposal when full and have a tendency to clog and also at times allow dust to cross the filter membrane barrier and therefore provide a potential risk to the longevity of a driving motor of the vacuum cleaner.

The inventor has also surprisingly found that an advantage of a water absorbent cloth is that dust is effectively gathered by the cloth while in the vacuum cleaner but is easily removed subsequently when water is applied.

The air filter element 11 may be cut from a segment of a circle and in the present case it is cut with an angle 16 of approximately 81°. The angle 16 is shown subtended by outlined arms 17 which are co-linear with side edges 13 and 14. The arms are shown in outline as the apex of the section is removed to provide bottom edge 15, although this is not essential.

The sheet may be cut in the form of the shape outlined by the top 12, edges 13,14 and arms 17. The air filter element 11 supports a first zip track 18 and a second zip track 19 which is shown in outline as it is located on the opposite surface to that of the first zip track 18. The zip tracks 18,19 are shown in the vicinity of or towards the edges 13,14.

However, they are set back somewhat from the edges 13,14 which ensures there is a double overlap of the zip tracks when they are intermeshed. In use, the sheet member 11 is rolled to form a funnel shaped bag in such a way that the zip tracks 18, 19 are closely opposed. One of the zip tracks may support a locking slide which may receive an end of the other zip track. On sliding the locking slide the zip tracks are locked together by intermeshing of their respective teeth. This formation produces a funnel with open ends.

The bottom edge 15 may then be folded to obliterate the bottom opening and provide a blind sack configuration to the filter element. The closed bottom of the filter element may be fixed in place by a clip, hook and loop fastener, button or stud fixture.

In a preferred method of construction, the fabric is cut to a template, an open-ended heavy duty zip is stitched into place adjacent the edges for holding the sides in position and a removable reusable metal clip is used to clamp the folded end of the configured or shaped

bag.

It is clear to a skilled addressee that other means of fixing the edges in position relative to each other are available. For example, a hook and pile fastening means, button, press studs or a rail and slot arrangement may be used.

Figure 2 shows an air filter element similar to that, of Figure 1, but wherein the apex has not been truncated. The sheet is adapted to the shape of a filter element 20. In this view the element is shown as a cone with a substantially closed end at the apex. Fold lines 21 for the apex may be identified so that the apex 22 can be folded on itself to provide a closure to the bottom of the filter element. The bottom of the filter element may be fixed in place with clip 23. Other means of fixing the bottom in place are well known to a skilled addressee. For example, an elasticised loop may be used or a press stud or other appropriate means.

The present invention provides great utility as it may be removed from a vacuum and cleaned by releasing the releasable holding means to allow the filter element to adopt the configuration of a flat or soft sheet. At this stage, the collected material on the filter element may be removed by shaking, brushing or any suitable means. While the preferred embodiment includes a flat sheet, any suitable formation may be used. For example, the sheet may include one or more bracing battens or stiffening seams which serve to maintain the sheet in a 3 dimensional orientation to facilitate configuration of the filter element.

It is most preferred that the material forming the filter element 11 has characteristics which permit the application of water to remove dirt and dust particles. Most preferably the water may be applied through a hose nozzle so that the filter element may be simply unfolded, laid out and hosed off. A particular advantage in the use of water arises when used by sufferers of allergies and asthma. Water is best applied before dissembling the filter element. This minimises or eliminates airborne dust particles, thus preventing antigenic challenge to a user. This feature is also clearly of advantage to the health of a long term frequent user of a vacuum cleaner such as a commercial cleaner.

Suitable dimensions for a flattened sheet member may be a first edge of 41.5 cm, a second edge of 32.3 cm and an arc of approximately 81'to provide a top edge with a formed circumference of 71.5 cm and a zip of 29 cm length. A first track of the zip may be located 9 cm from and parallel to one edge. A second track may be located adjacent the other edge and angled to that edge so that when the zip is closed the angle of the second track compensates for the narrowing of the conical shape produced. For example, the second track may be 4.3 cm from the edge at its uppermost extreme and 2.7 cm from the edge of the other end. Although a conical type of device has been disclosed, it is clear that any suitable shape may be formed. For example, the filter element may be configured as a sock shape with a single zip line arranged to allow opening of the device. The filter element may also be configured in a rectangular box type shape or any other suitable shape when formed as a sock or bag like device, the air filter element may be permanently configured as such. Cleaning may be accomplished by everting the sack through an air entry aperture and dusting and/or washing the contents away from the air filter material. In its most basic form, the filter element may be located in operation as a substantially planar sheet of hydrophilic material.

The above described dimensions will result in a substantially conical filter element having an upper diameter of approximately 22 cm and side edges which will be reduced by folding.

Referring to Figure 3 there is seen an air filter element 24 of the present invention for location inside a vacuum chamber. The an air filter element 24 has a rubber reinforced top edge 25 which describes top opening 26 and which strengthens the top edge of the continuous side walls 27. The air filter element 24 also has a closed base 28. As described the air filter element 24 is supported in place when configured as shown. The air filter element 24 is formed of a hydrophilic material such as PVA synthetic chamois to provide the advantages already discussed. This element may be used in unison with another primary filter element or support element to provide a two tier protection. Both elements may be formed from synthetic chamois material. The air filter element 24 may be formed with a fastening line which permits it being dissembled so that it may be laid flat on a surface for cleaning. For example, zips may be located adjacent top and bottom edges with

a connecting zip line between those zips to provide a means for transforming the air filter element 24 to a flat sheet shape, although this is not essential.

The air filter element of the present invention removes most dust from the air and thereby maintains the cleanliness of the secondary filter and longevity of the motor. Further, exhaust air is much cleaner than in an inefficient, clogged system, leading to healthier environments especially for suffers of respiratory conditions such as asthma.

In cleaning the filter element, normal dust and debris may be washed out and preferably into a composting system. Application of water immediately eliminates the chance of dust inhalation by a user.

During trials, the inventor has established the filter element may easily be used at numerous different sites while maintaining its suction and is a considerable improvement over paper bag elements.

Referring to Figure 4, there is seen a schematic cut away vacuum cleaner system 30. The system comprises a cleaning head 31 fixed to a handle 32. The handle 32 is connected to a flexible hose 33 which provides an air stream pathway to a vacuum unit 34 which is preferably positioned on wheels 35.

Although a wheeled unit is shown, it is to be understood that the present invention is applicable in any suitable vacuum system and in particular in"backpack"type cleaners, which tend to be preferred by commercial cleaners.

The vacuum unit 34 has a lid 36 and side wall 37 which defines an internal chamber 38. A motor and fan unit 39 provides a forced air stream through the system in the direction shown by arrows.

Air is urged into the head 31 and flows up the handle 32 and hose 33 before entering the chamber 38 through inlet aperture 40. The air is forced through air filter element 41 which is formed of synthetic chamois material resulting in removal of particulate matter entrained

in the air stream. Air may then pass through secondary filter 42 before discharge into the local environment. Preferably, the secondary filter 42 also has a synthetic chamois element. The arrangement shown, with suitable amendments is also applicable to air conditioner units and systems.

While there are some advantages in drying the air filter element prior to location in a vacuum cleaner, the inventor has found the material may dry very effectively within an air stream and without damage to electrical and mechanical components.

The inventor has applied the present air filter element to a number of machines in commercial use. These machines undergo compulsory 6 monthly inspection and testing for safety purposes. The reports on these machines have indicated they are exceptionally clean around their motors. This indicates the air filtering elements are effectively and efficiently removing undesirable material from air, are not detrimental to the machines and are promoting longevity of the motors.

The air filter elements have been used in very adverse environments to assess their robustness. They have proven easy to clean and effective in maintaining their efficiency.

They have also proven to be highly resistant to damage in use. The inventor has also closely monitored the exhaust filters of these machines, which require weekly inspection.

No significant amounts of material were visually detectable on the exhaust filters, confirming the efficiency of the primary air filter elements.

Synthetic chamois material appears to create an environment that is unsuitable for microbial colonisation. As a result, filter elements formed from this material decrease the tendency for production of contaminated air streams.

Throughout the specification the aim has been to describe the preferred embodiments of the invention without limiting the invention to any one embodiment or specific collection of features. Those of skill in the art will therefore appreciate that, in light of the instant disclosure, various modifications and changes can be made in the particular embodiments exemplified without departing from the scope of the present invention. All such modifications and changes are intended to be included within the scope of the appendant claims.