GB953418A - Filters for liquids - Google Patents

Abstract

953,418. Liquid filters. GENERAL MOTORS Ltd. Nov. 14, 1962 [No:. 14, 1961], No. 40622/61. Heading B1D. A filter unit 1 for a liquid filter comprises a pair of annular filter elements 2, 3 arranged end-to-end on a central support tube 4, one element 2 being formed by pleated synthetic resin-impregnated sheet filter material, such as filter paper, and the other element 3 being an annular mass of material the porosity of which is substantially greater than that of said sheet filter material. The other element 3 may be made of vegetable or other fibres, e.g. sisal grass fibres, or a mixture of sisal grass and other fibres especially cotton. Alternatively the filter element 3 may be made of cellular plastics material especially polyurethane foam. The element 2 may be made from a strip of synthetic resin-impregnated sheet filter material, especially paper, joined at its ends and folded about regularly spaced transverse fold lines to form an annular series of pleats 10, the ends of each pleat being individually sealed. Dimples 11 space each pleat 10 from an adjacent pleat and radial ribs 12 are impressed in the two parts of each pleat so as to provide drainage channels for filtered liquid. The element 3 may be placed directly against one end of the pleated paper element, or, as in Fig. 3, an annular disc 20 may be interposed between one end of the paper element 2 and the adjacent end of the other element 3 so as to seal the paper element 2 and provide a seat for the adjacent end of the other element 3. In operation, the two filter elements being in parallel and the rate of flow of liquid through 3 being substantially greater than through 2, the effect is to provide coarse filtration of a major portion of the liquid and fine filtration of a minor portion. When filter 2 becomes clogged a further period of full flow filtration through filter 3 can be obtained before it is necessary to change the filter element.