FILTER APPARATUS

Abstract: A circular filter cartridge for air pollution control has a plurality of pleats (10) so arranged on fold lines as to define an inner end wall (20) for each pleat on the periphery of a circle (22) of a first diameter, and outer walls (24) extending between adjacent pleats lying on the periphery of a further circle (26) of increased diameter. By providing flat surfaces, dust or other pollution does not build up at any particular point on the filter and also wear on the cartridge is reduced, leading to a more efficient and cost effective filter cartridge. Lower pressures of compressed air or liquid can also be used for cleaning.

Description: Filter Apparatus This invention relates to filter apparatus and is parti¬ cularly concerned with circular filter cartridges for use in air pollution control. Such circular filter cartridges generally find use in industrial applications and can be, for example, one metre in length and some 300-400 millimetres in diameter. Heretofore the cartridges have been formed from a suitable filter mater¬ ial provided with pleats to enable the circular configuration to be achieved. The pleats are generally formed from folds in the material extending axially in use and in a zig-zag arrangement, thereby providing V-shaped grooves through which the polluted air passes. Such filter cartridges tend to cause acceleration of the foreign matter in the air into the point of the V causing a compacted build-up of the foreign matter as ell as the normal build-up of foreign matter on the side walls of the V . The filter material is normally cleaned by a reverse pulse of compressed air or backwash of liquid, but difficulties are then encountered in moving the foreign matter compacted at the root of the V. Because of this inefficient cleaning there is restriction in the depth of pleat which can be used and it has been found that approximately 20 % of the filter becomes inefficient after a short time. A further problem with such pleats is that the apex of the V facing towards the flow of the polluted air has a tend¬ ency to wear away quickly due to the abrasive action of the foreign matter being carried by the air. According to the present invention there is provided a filter comprising a filter material formed with pleats therein whereby to be capable of assuming a circular form, each pleat being formed by folds which provide side walls connected together by a base wall of predetermined width, and adjacent pleats being connected together by an outer wall of predeter¬ mined width. Preferably the filter is in the form of a circular cart¬ ridge wherein each base wall occupies part of the periphery of a circle having a first diameter, and each outer wall occupies part of the periphery of a circle with a larger diameter. The width of each base wall is of sufficient dimension as to prevent build-up of foreign matter at the inner end of the pleat. An embodiment of the present invention will now be described by way of example only with reference to the accompanying drawings, in which :- Fig. 1 is diagrammatic section through part of a circular filter cartridge, showing the cartridge in use; and Fig. 2 is a similar diagrammatic view to Fig. 1 but showing the cartridge during cleaning. Referring to the drawings, a circular filter cartridge for air pollution control, generally in an industrial environ¬ ment, is formed of a suitable filter medium, for example fabric or paper, extending between end plates. The cartridge is generally used with its axis extending vertically. The filter medium has a plurality of pleats 10, each of which has an inner end formed by a pair of spaced fold lines 12, 14, with the connection with adjacent pleats being defined by further fold lines 16,18. The fold lines 12,14 are so spaced apart as to define an inner end wall 20 for each pleat 10 lying on the periphery of a circle 22 of a first diameter. The fold lines 16,18 are spaced from the fold lines 12,14 respectively to define the lengths of radially extending side walls 21 of the respective pleat 10, and the fold lines 16,18 are spaced from the fold lines 18,16 respectively of adjacent pleats whereby to provide outer walls 24 extending between adjacent pleats and lying on the periphery of a further circle 26 of increased diameter, for example between 300 and 350 mm. In use, the dust or other pollution in the air passing through the filter in the direction of arrows 28 accumulates on the surfaces of the outer walls 24, the surfaces of the side walls 21, the surfaces of the end walls 20 and the base of the pleats 10, but is distributed thereover and does not build up at any particular point. Further, wear on the cartridge is reduced as the polluted air engages with flat surfaces. These surfaces enable the dust or dirt in the air to fall easily away from the surfaces, the lower end plate of the cartridge being preferably shaped to the same form as the pleats 10 to enable the released dust to fall and not build up against the lower end wall. When using a reverse pulse of compressed air or a backwash of liquid in the direction of arrows 30 for cleaning of the filter, the reverse pulse or backwash can penetrate through the end walls 20 as well as the side walls 21 and the outer walls 24 to give an overall cleaning action. Because substantially all of the dust or dirt on the filter surfaces is released during cleaning, pleats 10 of increased depth can be used, enabling a greater amount of filter area to be used for the same cross sectional area of filter. The filter cartridge becomes more efficient for its size and thus more cost effective. Lower pressures of compressed air or liquid can in fact be utilised during cleaning. The end plates are generally of greater diameter than the filter material to provide for endwise connecting together of cartridges where an increased length of filter is required. Various modifications may be made without departing from the invention. For example the shapes of the pleats can differ from that described and shown provided build-up of foreign matter is prevented in the pleats. Further, whilst this specification describes a filter cartridge for use in air pollution control this invention could be used in the filtration of liquids.

Claims: Claims : - 1. A filter comprising a filter material formed with pleats therein whereby to be capable of assuming a circular form, each pleat being formed by folds which provide side walls connected together by a base wall of predetermined width, and adjacent pleats being connected together by an outer wall of predetermined width. 2. A filter according to Claim 1, wherein the filter is in the form of a circular cartridge wherein each base wall occupies part of the periphery of a circle having a first diameter, and each outer wall occupies part of the periphery of a circle with a larger diameter. 3. A filter according to Claim 1 or 2, wherein the diameter of the circle of the outer wall is between 300 mm and 350 mm. 4. A filter according to any of Claims 1 to 3, wherein the width of each base wall is of sufficient dimension as to prevent build-up ' of foreign matter at the inner end of the pleat. 5. A filter according to any of the preceding Claims, wherein the filter material is fabric. 6. A filter according to any of Claims 1 to 4, wherein the filter material is paper. 7. A filter substantially as hereinbefore described with reference to the accompanying drawing.

Inventors: GIBSON GLENVILLE, GIBSON, GLENVILLE
Applicants: BRIND ENVIRONMENTAL LTD, BRIND ENVIRONMENTAL LIMITED
Application year: 1991
Main classification: B01D46
IPC codes: B01D46