GB2150461A

GB2150461A - Air filter

Info

Publication number: GB2150461A
Application number: GB08332093A
Authority: GB
Inventors: Dennis Albert George Marshall
Original assignee: Marshall D A G
Current assignee: Marshall D A G
Priority date: 1983-12-01
Filing date: 1983-12-01
Publication date: 1985-07-03
Also published as: GB8332093D0; GB2150461B

Abstract

The invention relates to an axial-flow air filter for insertion in a duct, which filter comprises an annular open-ended casing (10) containing pleated air-filtering sheet material (12) the marginal portions of which are embedded in the material of the casing so as to form a fluid-tight seal therewith, the casing being of spun-moulded construction to permit the said marginal portions of the pleated filtering material to be incorporated into the material of the casing while the latter is still in a liquid condition during the moulding process. <IMAGE>

Description

SPECIFICATION Air filter This invention relates to air filters, it being understood that filters in accordance with the invention can also be used to filter gaseous products other than air when so required.

In my U.K. specification No. 2,077,312A published on 16th December 1981, 1 have described pleated filtering material wherein the pleats are held in place by a hardened synthetic plastics material. The present invention is concerned with an air filter which makes use of pleated filtering material, preferably of the construction described and claimed in the said prior specification, and which is designed for "in-line" fitting within a duct through which air is passed.

Accordingly, the present invention is directed to an axial-flow air filter for insertion in a duct, which filter comprises an annular open-ended casing containing pleated air-filtering sheet material the marginal portions of which are embedded in the material of the casing so as to form a fluid-tight seal therewith, in which the casing is of spunmoulded construction to permit the said marginal portions of the pleated filtering material to be incorporated into the material of the casing while the latter is still in a liquid condition during the moulding process.

An example of an air filter in accordance with the invention is shown in the accompanying drawings, in which Figure 1 is a horizontal section through the air filter; Figure 2 is a half-section taken on the line Il-Il in Figure 1; Figure 3 is a perspective view of part of the pleated filter material incorporated in the filter; and Figure 4 is a diagrammatic view of the apparatus used to produce the pleated filtering paper shown in Figure 3.

The air filter shown in Figures 1 and 2 comprises an open-ended cylindrical casing 10 which contains pleated air filtering sheet material 12 extending over the entire internal cross-section of the casing so that any air passing through the latter must pass through the air filtering material. As indicated by the air flow arrows in Figure 1, air travels axially through the casing with a view fo the casing being inserted in a duct as an "in-line" fitting. In order that the casing may be properly sealed in such a duct without any possibility of air leaking around on the outside of the casing 10, flexible leaf seals 14 are embedded into the outer surface of the casing so that the leaf seals each make line contact over a complete circle with the inner surface of a circular-section duct in which the air filter is located.

In some instances, one end of the casing 10 may abut against an internal flange on the duct containing it. In that event, a ring seal 16 can be provided at one end of the casing in place of, or in addition to, one or other of the leaf seals 14.

As will be seen from Figure 1 and Figure 2, the marginal portions of the pleated filtering material are embedded to quite a considerable extent in the material of the casing 10 so as to form a fluid-tight seal therewith. Such a construction is made possible by cutting the pleated filtering material to a desired circular shape and then forming the casing 10 around it by a spun-moulding process using a mouldable synthetic plastics material for this purpose. In other words, the marginal portions of the pleated filtering material are incorporated into the material of the casing while the latter is still in a liquid condition during the moulding process.

The pleated filtering material can have pleats of varying depth, according to the conditions under which the filter will be used in practice. Usually the pleat depth will be between 20 and 100mm. The thickness of the casing 10 can likewise be varied, but will usually be between 10 and 15mm.

Preferably, the pleated filtering material has the construction described and claimed in my specification No. 2,077,312A wherein the pleats are held in place by spaced-apart lines, ribbons or blobs of a hardened synthetic plastics material. The particular filtering material shown in Figure 3 of the accompanying drawings shows lines 18 of such hardened plastics material, these lines being applied to the filtering material using the apparatus diagrammatically illustrated in Figure 4. In this apparatus, material is drawn off a roll 20 and is passed into initial folding means 22 which folds the material in zig-zag fashion, the material being filter paper, glass fibre paper, open-pore polyurethane foam or random fibre mat.After the material has left the folding means 22 it is opened out again to form a substantially flat surface as shown at 24, whereupon it passes under and above, respectively, two transverse lines of nozzles 26 and 28 which extend across the full width of the filtering material. Each nozzle is supplied with molten PVC or some other synthetic plastics material of low melting point from a pressure container (not shown) having heating means to melt the plastics material.

Immediately after the sheet material has moved past the nozzles 28, it is subjected to infra-red heating in infra-red heating apparatus 30. This heating hardens the PVC or other synthetic plastics material very rapidly. While this hardening is taking place, the material is refolded in zig-zag fashion to reform the pleats originally folded in it at the initial folding station 22. By the time the pleats are reformed the synthetic plastics material has already hardened to a tacky state. The lines 18 of PVC or other synthetic plastics material on adjacent pleats therefore adhere to each other as shown in Figure 3, and in this way the pleats are held in place very firmly once the PVC has thoroughly hardened.

It is to be understood that the invention is not restricted to the use of a cylindrical casing 10 - it could, for example, be of some other annular form.

It is also to be understood that other air filtering means or some kind of protective grille can be embedded in the material of the casing 10 in the same way as the pleated filtering material 12.

Claims

1. An axial-flow air filter for insertion in a duct through which air is passed, which filter comprises an annular open-ended casing containing pleated air-filtering sheet material the marginal portions of which are embedded in the material of the casing so as to form a fluid-tight seal therewith, the casing being of spun-moulded construction to permit the said marginal portions of the pleated filtering material to be incorporated into the material of the casing while the latter is still in a liquid condition during the moulding process.

2. An air filter according to claim 1, in which the pleated air-filtering sheet material extends over the entire internal cross-section of the casing so that any air passing through the latter must pass through the air-filtering material.

3. An air filter according to claim 1 or claim 2, in which the pleated filtering material is formed by being cut to a circular shape with the casing then being formed round it by a spun-moulding process using a mouldable synthetic plastics material.

4. An air filter according to any one of claims 13, in which the pleated filtering material has a pleat depth of between 20 and 100 mm.

5. An air filter according to any preceding claim, in which the thickness of the casing is between 10 and 15 mm.

6. An air filter according to any preceding claim, in which the pleats are held in place by spaced-apart lines, ribbons or blobs of a hardened synthetic plastics material such as PVC.

7. An air filter according to any preceding claim, in which the filtering material comprises filter paper, glass fibre paper, open-pore polyurethane foam or random fibre mat.

8. An air filter according to any preceding claim, in which other air-filtering means and/or a protective grille is embedded in the material of the casing in the same way as the pleated filtering material.

9. An air filter according to any preceding claim, in which flexible leaf seals are embedded in the outer surface of the casing so that the leaf seals each make line contact over a complete circle with the inner surface of a duct in which the air filter is located.

10. An air filter according to claim 9, in which one end of the casing is adapted to abut against an internal flange on a duct containing it, the casing being provided with a ring seal at that end in place of, or in addition to, one or other of the flexible leaf seals.

11. An air filter substantially as described herein with reference to the accompanying drawings.