FILTERS

[0001] This invention relates to filters. More particularly this invention relates to removably attachable filters for use on a computer electrical housing or other housing which uses fans for cooling of the electronic or electrical apparatus contained in the housing.

[0002] In this specification the term "housing" means an enclosure which comprises ferromagnetic material and in which circuit boards and other electrical and electronic consumer apparatus are stored such as computer boxes, amplifiers, network switches, patch panels or the like, the enclosure having an inlet through which air may be drawn into the enclosure and an outlet through which the air may be discharged. Computers are provided with fans for cooling the power supply as well as the electronic components inside the computer housing. Generally these fans are used to draw air out of the computer housing.

[0003] Generally dust particles are suspended in the air and as the cooling fans rotate in order to cool down the electrical components within the housing, the air together with suspended dust particles are caused to accelerate and when the accelerated air hits any surface they adhere to one another and adhere to the surfaces in the housing.

[0004] Dust particles have the known disadvantage of forming a layer or skin of dust on the housing forming an uneven surface on the collar of the fan housing and of forming an impediment to the required rotation. Further the dust often gets in to the motor and bearing of the motor reducing its efficacy and eventually causing the motor to seize.

[0005] Furthermore as the dust has been drawn in to the housing it has a tendency to collect and adhere on the vanes of other fans in the housing such as the central processing fan and in the fins and on the surface of the heat sink and thereby impeding heat exchange and consequently the cooling process. Furthermore the dust is forced in to optical drives such as CD ROMs and DVDs which has been known to cause problems with lasers and motors contained therein.

[0006] Various types of filters have been used to try and alleviate the abovementioned problems. Most have a significant drawback in that they require varying levels of mechanical intervention in order to install the filters and to remove and replace the filters as this proves necessary. Further in order to clean the filters after these have been in use requires varying degrees of mechanical disassembling and mechanical . reinstallation. The disassembly and installation generally relies on mechanical fasteners such as screws.

[0007] Furthermore known filters for solving the abovementioned problems often make use of linear low density foam filtering elements which has the further disadvantage of impeding airflow causing overheating problems.

[0008] Another known problem encountered with housings is the build up of water vapour within the housing. This has the disadvantage of leading to the build up of moisture ,pn electronic boards, components and or electrical components. Such build up may lead to oxidation causing short circuits and malfunction.

[0009] According to one aspect of the present invention there is provided a filter for a housing comprising a filtering means surrounded by a frame, preferably a rectangular frame, wherein the frame embodies magnetic means capable of being

magnetically attached to the housing so that the filter can be conveniently and easily attached to the housing in such a way as to be able to filter the air prior to it, the air, passing into the housing. The filtering means preferably comprises a woven mesh. The frame preferably comprises magnetic material. However it may comprise a main portion carrying a plurality of magnets.

[0010] - Preferably the filtering means is adhesively attached to the frame. It may be supported purely by the frame which extends around the periphery of the filtering means. However, it has been found to be convenient in addition to include a support for the filtering means, which support conveniently comprises at least two arms extending from the centre of the filtering means to the frame.

[0011] It is convenient for the frame to be formed of Cemdex (a mouldable plastic material that incorporates magnetic particles) or the like in an injection moulded process or to be made from a flexible magnetic material. By forming the magnetic body from a flexible magnetic substance, it, the magnetic body, will allow for rises and falls or different protrusions on the housing whilst still forming a moderately tight seal around the filter so that little or no air is allowed to pass in to the housing via the inlet port without having passed through the filter.

[0012] Preferably a cladding means is formed above the magnetic body, which cladding means is used to protect the edges of the filtering means and to improve the aesthetic appeal of the filter.

[0013] - Preferably the cladding means has the properties allowing printing or other application of decorative markings thereon to further enhance the aesthetic appeal thereof. The cladding means may be constructed of a plastics material which is rigid

or of flexible plastic or vinyl. The plastic or vinyl may have a resin coating or doming applied thereto to further enhance the aesthetic appeal thereof.

[0014] The filter may include at least two layers of filtering means enclosing a desiccant such as silica gel or other type of desiccant for reducing the moisture content of the air passing through the filtering means.

[0015] The filtering means preferably comprises a woven PET mesh network which conveniently allows particles of < 149 micron to pass therethrough. However, the apertures in the mesh may vary from 60 to 240 microns depending on particles which are to be filtered from the specific environment in which the housing is to be used.

[0016] It has been found to be advantageous for the filtering means to be held between the magnetic frame and the cladding body forming the top layer over the cladding.

[0017] Preferably the frame comprises a self adhesive magnetic frame having a self adhesive backing on to which the filtering means can be attached. Further it has been found to be convenient for the cladding means to comprise a self adhesive cladding body having a self adhesive backing on to which the filtering means can be attached so that the filtering means may be securely attached between the magnetic frame and the cladding body.

[0018] According to a further aspect of the present invention there is provided the combination of a housing with a filter comprising a filtering means surrounded by

a frame which embodies magnetic means, wherein the filter is removably connected to the housing by magnetic attraction with the filtering means covering the inlet.

[0019] Embodiments of the invention will now be described by way of example with reference to the accompanying drawings.

[0020] In the drawings :-

Figure 1 is a plan view of a filter of the invention;

Figure 2 is an exploded isometric view of parts of the filter;

Figure 3 is a detail cross-sectional view along line 3-3 of Figure 2;

Figure 4 is a exploded view of a further filter of the invention wherein a set of arms brace the magnetic body; Figure 5 shows a perspective view of the rear of a computer housing being fitted with the invention; and Figure 6 is an exploded view of a further filter of the invention incorporating desiccating means.

[0021] Referring now to Figures 1, 2 and 3, there is shown a filter 100 of the invention. The filter 100 comprises filtering means in the form of a square woven PET mesh 112 formed of polymeric threads 114. The apertures of the mesh 112 are 149 microns in size. The polymeric mesh 112 is consequently capable of filtering out particles of a size larger than 148 microns.

[0022] The polymeric mesh 112 is connected to a frame 116 extending around its periphery. The frame 116 comprises a magnetic body 118 formed from a flexible magnetic material which is capable of bending or moving without permanently affecting its shape. A self adhesive strip (not shown) is applied to the upper surface 120 of the

magnetic body 118. The mesh 112 is caused to be bonded to the magnetic body 118 when laid on to the exposed self adhesive surface 120.

[0023] The magnetic body 118 is 0.51 mm thick. The magnetism of the magnetic body 118 is between 200 to 300 Gauss.

[0024] A plastics cladding 124 is provided. It is cut to substantially the same shape as the magnetic body 118 and has a lower self adhesive surface 126. The self adhesive surface 126 is protected by a removable protective strip of air tight material (not shown). Once the strip is removed, the exposed adhesive surface 126 is then laid over the corresponding self adhesive surface 120 of the magnetic body 118 sandwiching the filter mesh 112 between the cladding 124 and the magnetic body 118 (as best shown in Figure 3) to form the flexible filter 100.

[0025] _ The magnetic body 118 is made from a flexible material which retains its flexibility throughout its useful lifespan allowing the filter 100 to be applied over uneven surfaces. As a result when the filter 100 is applied to a housing to cover the inlet aperture therein (as will be described more fully below) there will be very limited if any gaps are formed between the frame 116 of the filter 100 and the wall of the housing through which air can be drawn into the housing via the inlet without passing through the filter 100.

[0026] The magnetic body 118 and the cladding 124 are pre-cut using computer controlled cutting instruments (not shown). The cladding 124 is "kiss-cut" which ensures that the cladding 124 as well as the protective strip are not separated in the cutting process. This has the further advantage of facilitating neatness and precision in assembly.

[0027] The cladding 124 may have printed matter on the exposed side 128 thereof, being the side on the opposite surface of the self adhesive surface 126. This printed matter may comprise (i) details of the manufacturer, (ii) trade marks, (iii) logograms and (iv) other advertising material such as contact details of a company. Thus the filter 100 can be used as a promotional or advertising item. In addition this printed matter may be of any colour or may even be spray painted a metallic colour, or may take on any appearance.

[0028] .. The self adhesive cladding 124 is overlaid with a transparent, flexible resin coating 132. Such resin coating 132 may be in the form of dome in section which produces a raised domed surface over the pre-printed cladding 124 once the resin has dried. The cladding 124 and coating 132 serves to protect the edges of the filtering means and to improve the aesthetic appeal of the filter 100.

[0029] Reference is now made to Figure 4 wherein is shown a modified filter

134. The filter 134 is similar to the filter 100 (with the same parts having the same reference numbers but with the suffix ".1 ") save that it has cross members 136 running between th&.mid point of filter means to the midpoint of adjacent parallel sides of the dome section cladding 132.1 of the frame 116.1. The cross-members 136 serve to provide additional support to the mesh 112.1.

[0030] Referring now to Figure 5, there is shown a conventional computer housing 140 made of ferro magnetic sheet metal. An inlet port 142, made up of a number apertures 144, is formed in the rear face 146 of the housing 140. The port 142 defines the mouth through which air is be caused to be drawn by means of a fan (not shown) through the wall of housing to the interior of the housing 140. The form and configuration of the ventilation apertures 144 vary from housing to housing as provided

by the various manufacturers. The ventilation apertures 144 may be in the form of circular holes (as shown) provided in the housing and arranged in a circle. Alternative arrangements of ventilation apertures 144 are provided by different manufacturers. Thus for example the ventilation apertures 144 may take the form of a series of slots (not shown) provided in the housing 140.

[0031] The filter 134 is generally larger than the abovementioned inlet port 142.

The filter 134 is caused to adhere to the housing 140 by placing the magnetic material 118.1 on to the housing 140 surrounding the inlet port 142 so that the filter mesh 112.1 covers the port 142. As the housing 140 is made of ferro magnetic metal, the filter 134 is magnetically attached to the housing 140 and a magnetic seal is formed between the magnetic body 118.1 and the housing 140. The use of the magnet adhering to the rear wall will form a seal which ensures that little or no air will pass through the aperture without first having been filtered through the filtering means.

[0032] It will be appreciated that various configurations of ventilation apertures 144 are provided by different housing 140 manufacturers. The flexible filter 134 described above, will be capable of adapting to the form of the protrusions and/or apertures of the diverse arrangements and configuration of ventilation apertures 144 of various computer housing suppliers. It will be understood too that the filter 100 can be applied in similar manner to that described in relation to filter 134.

[0033] When the filter mesh 112 (or 112.1) shows signs of becoming dirty and or starts clogging with dust, the filter can be removed by simply pulling the filter away from the housing 140. The filter can then be washed and thereafter reattached about the aperture. It will be seen that these actions can be taken without making use of any tools or other mechanical or chemical fasteners.

[0034] Referring now to Figure 6 there is shown a further filter 150 of this invention. This filter 150 is adapted for use where the air has water entrained therein. The filter 150 comprises a pair of filter meshes, viz an inside mesh 152 and outside mesh 154. The outside mesh 154 may be of the same or of a smaller aperture size than the inside mesh layer 152. A desiccant 160 such as silica gel crystals are located between the inside mesh 152 and outside mesh 154. In use the desiccant will absorb the moisture passing through the filter and in turn reducing the moisture content of the air entering the computer.

[0035] The invention is not limited to the precise constructional details hereinbefore described and illustrated in the accompanying drawings. Thus for example the inside surface of the magnetic body may be coated with a bonding medium which remains tacky after use. Typically this may be adhesive polymers or thermoplastic rubbers. The bonding medium is covered by a protective strip. When it is intended to use the filter on a housing which does not comprise ferro magnetic material, the protective strip is removed and the filter is applied to the housing about the inlet port. When the mesh becomes dirty or clogged, the filter is removed and because the bonding medium remains tacky it can thereafter be attached to the housing. This can be repeated a number of times.

[0036] The shape and configuration of the magnetic computer dust filter may vary. It may be square, rectangular, oval or circular or any other geometric shape. The shape and configuration may take on the form of various caricatures or aesthetic designs of a size capable of covering the inlet port of the computer fan.

[0037] The frame may comprise a non-magnetic main body and a plurality of magnets secured thereto on its underside equi-spaced along the length of the frame.

[0038] Clearly various decorative printing and motives may be incorporated into the design of the magnet computer dust filter in order to enhance novelty and aesthetic appeal.

[0039] Any combination of features of the abovementioned embodiments may be used in combination.