Patent GB-1043528-A (GB)
Title: Improvements in or relating to air filters
Inventor: BARTLE JAMES WILLIAM
IPC: F02M35/024
Filed: 1962-09-18
Abstract: 1,043,528. Air filters. FRAM FILTERS Ltd. Dec. 18, 1963 [Sept. 18, 1962; Jan. 7, 1963], Nos. 35517/62 and 710/63. Heading B1T. An air filter for filtering the air supplied to internal combustion engines and the like comprises a casing, entry and exit means for air to be passed through the casing, and as plurality of filter elements in the form of annular cartridges consisting partly or wholly of pleated paper or other pleated filter material disposed coaxially one within another within the casing between the entry and exit means, adjacent cartridges being separated by a barrier of generally frusto-conical or cylindrical form having end flanges adapted to sealingly engage opposite ends of the cartridges so that the air is constrained to pass through all the cartridges in parallel. As shown in Fig. 3, two annular filter elements 1, 2 in the form of pleated paper filter cartridges are disposed coaxially within a two-part casing comprising a base 3 and a cover 4, there being an impermeable metal barrier 5 and generally frusto-conical form located between the two cartridges to completely separate them and constrain air to flow in parallel through them. At their ends, the cartridges are provided with impermeable, resilient caps, e.g. of polyvinyl chloride, which include integral moulded sealing gaskets 7, these aiding in securing perforated cylindrical strengthening members 8. The base 3 comprises an outer annular seating 9 for engagement with the lower end cap 6 and gasket 7 of the outer cartridge 2, and an inner dished portion 10 terminating at a central downwardly extending outlet 11. The cover 4 is removably secured to the base 3, so as to allow the cartridges 1, 2 to be removed from the casing and replaced after becoming clogged, by means of a stirrup 12 provided with a central bolt 13 adapted to protrude through an orifice in the centre of the cover 4. The stirrup 12 is attached to the dished portion 10 of the base 3 on opposite sides of the outlet 11 and, by turning a wing nut 14 against the cover 4 on the bolt 13, the cover is brought down towards the base 3, this movement being limited by abutment of the cover with the stirrup 12. The barrier 5 has top and bottom end flanges 15, 16 respectively adapted to sealingly engage top gasket 7 of outer cartridge 2 and bottom gasket 7 of inner cartridge 1. The cover 4 comprises a top laterally extending closure 17 whose periphery is brought down into a depending cylindrical skirt 18 encircling at its lower end the seating 9 of the base 3 and located with respect thereto by distance pieces 19 formed in the base. The annular gap between the skirt 18 and the outer cartridge 2 constitutes entry means 20 for the air to be filtered. Closure portion 17 of the cover 4 is inwardly dished at 21 to assist in locating inner cartridge 1, the upper end of this cartridge being engaged by the cover 4 and the lower end by flange 16 of barrier 5. The parallel flow arrangement leads to an increase in the available area of pleated paper of nearly 50% over a similar singlecartridge construction, and this gives rise to an even greater increase in dust-holding capacity. A heavy duty filter for use where dust loadings are high and having five cartridges formed with metal end caps which are integral with the barriers to provide a unitary cartridge construction is also described (Fig. 6, not shown). The air filter may utilize annular filter elements of material other than pleated paper, e.g. fibrous material, felt, wiregauze, fibreglass batt, fibreglass paper, asbestos paper, cotton, thin acetate fibre batt, and open pore expanded polyurethane or polyester foam. The latter three materials can readily be pre-shaped into annuli, while knitted or woven polypropylene can also be used in cylindrical wraps. It is possible to employ two dissimilar filter media arranged in series within a single filter cartridge. For example, in Fig. 8 (not shown) there is illustrated an arrangement identical with that of Fig. 3 except that the cartridges 1, 2 each comprise a first stage heavy duty outer wrap of acetate fibre batt or open pore expanded polyurethane wrapped around a second stage of pleated paper.