GB699168A - Improvements in liquid filters - Google Patents

Abstract

699,168. Filters. BOSCH GES., R. Feb. 14, 1952 [Feb. 15, 1951], No..3921/52. Class 46 In a filter eiement consisting of strips of filter material, e.g. filter paper, which are wound around a core to form a spiral with a certain clearance space between the strips, such spaces being so sealed at opposite ends of the element that liquid supplied at one end flows axially into certain of the intermediate spaces,. through the strips of filter material into the remaining spaces and then out at the opposite end, the clearance space between the strips of filter material and the seals at the end faces and at the edges of the strips are formed solely by shaping the strips of filter materials A strip 1 of filter paper, Fig. 1, has semi-spherical indentations 2 formed in its surface and tongues 7 along one edge which are folded over to provide between them outlet spaces 17. The opposite edge is folded over at 3 to prevent egress of liquid there. A second strip 8 has more pronounced indentations 9, one edge 11 formed with slots 12 and folded first inwards and then outwards, and the other edge 10 folded first inwards and then outwards. The outer part 13 of the edge 11 projects beyond the inner edge of the slot 12 after folding, .leaving inlet slots 16. The two strips are wound ..spirally about a metal tube 15 with sealed ends and the outermost windings 18 of the strips 1 and 8 are wider so as to project laterally beyond the coil, Fig. 2. The complete element is enclosed in a cylinder 19 to which the bottom part of the winding 18 is connected and to a disc 20 by a beading 21. At the outer end the windings 18 the cylinder 19 and a ring 22 are firmly connected by an annular groove 23. A further disc 24 is seamed to :the cylinder 19. An inlet 27.and outlet 28 are provided. Impurities deposited from the liquid being filtered, e.g. liquid fuel for Diesel engines, accumulate in the spaces 29 (between the outer surface of strip 1 and inner surface of strip 8) which are larger by reason of the larger indentations 9 than the outlet spaces 30; larger particles drop through the openings 16 on to a disc 20. The indentations may take the form of grooves set obliquely in the strip, the grooves of one strip intersecting -those of the other. Instead of indentations and folds, the strips may have areas of increased thickness at their edges and rib-like thickenings extending across them. The strength of the paper may be increased by addition of asbestos, or by impregnating with a lacquer so diluted as to glue the individual fibres without closing the pores of the paper. The tips of the indentations may also be separately laquered. Specification 693,495 is referred to.