GB2196874A - Filter element - Google Patents

Abstract

A filter element comprises two layers of glass filter paper folded to form pockets 2, 7 which are of tapered cross section, and filters downwardly flowing air 3. The pockets contain corrugated spacers of tapered form (Fig. 1), which are made by vacuum forming on to a mould (Figs. 3 to 7) made up of a row of spaced parallel bars. <IMAGE>

Description

SPECIFICATION Improvements in or relating to fluid filters BACKGROUND TO THE INVENTION This invention relates to fluid filters.

The invention is particularly concerned with high efficiency air filters, used for example, in the supply of air to "clean" rooms.

Such filters are traditionally made by folding filter paper over interleafing spacers of corrugated form. The spacers are usually made of thin (say 0.0015" or 0.0381mm) aluminium foil or Kraft paper, but such spacers cannot be stored without losing shape and, furthermore, have sharp edges which can puncture the filter paper.

SUMMARY OF THE INVENTION According to the present invention, a fluid filter comprises a plurality of juxtaposed pockets, each of elongate form for receiving fluid to be filtered, at least part of each pocket being of filter material, the pockets reducing in cross-sectional area from one end of a pocket to the opposite end thereof.

When fluid is caused to enter the larger end of a pocket, pressure forces are built up at the smaller end thereof which tend to divert incoming fluid so that it passes laterally through the filter material.

The pockets are preferably formed with a cross-section of triangular form, and are preferably tapered from end to end.

A plurality of further pockets may be provided, each of substantially the same form as the first-mentioned pockets, disposed so that one of the further pockets is positioned between an adjacent pair of the first-mentioned pockets, with its smaller end between the larger ends of said pair.

The pockets may be formed by non-filtering spacers disposed between sheets of filter material. The spacers may be of plastics material, formed by vacuum techniques.

The invention also comprises a spacer per se.

BRIEF DESCRIPTION OF THE DRAWINGS An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, wherein : Figure 1 is a view in perspective of an air filter, with parts removed, Figure 2 is a diagrammatic side view illustrating air flow through the filter, Figure 3 is a fragmentary plan view of a spacer moulding former, Figure 4 is a side view of a moulding bar, looked at in the direction of arrow IV of Fig.

3, Figures 5, 6 and 7 are, respectively, crosssectional views taken on lines V-Vr Vl-VI and VII of Fig. 4, and Figure 8 is a view in perspective of a filter housing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to Figs. 1 and 2, an air filter 1 for use in a "clean" room comprises a plurality of juxtaposed pockets 2, each of elongate form for receiving a downward flow of ventilating air 3 to be filtered. Parts of the pockets 2 are provided by folded sheets 4 of filter paper. The pockets 2 reduce in crosssectional area from the air-receiving end 5 of a pocket to the opposite, closed, end 6 thereof.

The pockets 2 are of triangular cross-section when viewed in plan, and are tapered from end to end.

The filter paper 4 comprises sub-micron glass fibres, formed into high density paper.

The filter 1 further comprises a plurality of further pockets 7, of substantially the same form as pockets 2. The pockets 7 are disposed so that each pocket 7 is positioned between an adjacent pair of pockets 2, but with its smaller (closed) end 8 between the larger ends 5 of said pair.

As shown in Fig. 2, when the down-flowing air 3 is caused to enter the larger end 5 of a pocket 2, pressure forces P are built up at the smaller end 6 thereof, which forces tend to divert the incoming air so that it passes laterally through the filter paper 4, as indicated by arrows 10.

The diverted air then enters the pockets 7 to enter the clean room 12 as indicated by arrows 13. As the air leaves the pockets 7, pressure is reduced therein which tends to assist the flow of air leaving the pockets 2.

(Arrows 10).

The air filter 1 is more efficient than a traditional filter. Thus it can be made smaller and less expensively.

The parts of the pockets 2 and 7 not formed by filter paper 4 comprise spacers 20 (Fig. 1) of plastics material. The favoured plastics material is P.V.C. (Polyvinyl chloride).

P.V.C. sheet of about 0.005 inch thickness (0.127 mm) is presently preferred.

A spacer 20 is preferably made by vacuum forming techniques. With reference to Figs. 3 to 7, a former 25 is provided, comprising a plurality of moulding bars 26 stacked side by side in parallel array, and clamped together.

Small gaps 27 between a pair of contiguous bars 26 form passageways for the extraction of air.

A one-piece former may be used as an alternative.

To assist assembly of the filter 1, a spacer 20 is formed with lugs 30 (Fig. 1) whereby the spacer may be handled more readily.

Fig. 1 is not a wholly accurate representation of the air filter 1 as it shows alternative depth spacers 20. In practice, the depth of spacers 20 would be uniform. Furthermore, the filter 1 would, in practice, be encased in a housing of box-like form.

With reference to Fig. 8, a housing 35 may be provided, comprising an open-ended moulding of plastics material formed with internal, oppositely-disposed rib-like locators 36 for the spacers 20. When the assembly of spacers 20 and paper 4 is fitted into the housing 35, the result is a tightly-packed structure. One end of the housing 35 is formed with an internal flange 37. The other end of the housing 35 is formed with flaps 38 which can be folded over (as shown at 38a) so as to form channels for receiving sealant material.

The spacers 20 do not have sharp edges and thus do not tend to puncture the filter paper, and, unlike spacers of thin metal foil, are stronger -than such spacers and do not lose their shape when stored. In addition, the spacers 20 are cheaper than spacers of aluminium foil.

Adhesive techniques may be employed to seal any slight gaps existing between the ends of a spacer 20 and the adjacent filter paper.

In a non-illustrated modification, an air filter is formed by a plurality of juxtaposed elements, each constructed entirely of filter material.

Claims (11)

1. A fluid filter comprising a plurality of juxtaposed pockets, each of elongate form for receiving fluid to be filtered, at least part of each pocket being of filter material, the pockets reducing in cross-sectionai area from one end of a pocket to the opposite end thereof.

2. A filter as claimed in Claim 1, wherein the pockets are formed with a cross-section of triangular form.

3. A filter as claimed in Claim 1 or 2, wherein the pockets are tapered from end to end.

4. A filter as claimed in Claim 1, 2 or 3, provided with further pockets, each of substantially the same form as the first-mentioned pockets, disposed so that one of the further pockets Is positioned between an adjacent pair of the first-mentioned pockets, with its smaller end between the larger ends of said pair.

5. A filter as claimed in any one of Claims 1 to 4, wherein the pockets are formed by non-filtering spacers disposed between sheets of filter material.

6. A filter as claimed in Claim 5, wherein the spacers are of plastics material.

7. A filter as claimed in Claim 6, wherein the spacers are formed by vacuum techniques.

8. A spacer for use with a filter according to Claim 5, 6 or 7.

9. A fluid filter, substantially as hereinbefore described with reference to Figs. 1 to 8 of the accompanying drawings.

10. A spacer, substantially as hereinbefore described with reference to Figs. 1 to 8 of the accompanying drawings.

11. Any novel subject matter or combination including novel subject matter herein disclosed.