GB726565A - Improvements in or relating to pressure filters - Google Patents

Abstract

726,565. Filters. BERLINE, R. Feb. 26, 1953, No. 5402/53. Class 46. [Also in Group XXXI] In a hollow-shafted rotary-disc filter each disc comprises a series of angular segments each delivering filtrate into a circular or partially-circular groove, and the groove or a series of homologous fractions of the circular grooves communicate with a discharge tube, located within the hollow shaft and provided with a controlling cock and a transparent portion at its outlet end, through which portion light rays are caused to pass to locate any tube delivering turbid liquid so that the cock controlling that tube may be turned off to by-pass the segments supplying the tube. The light may be received by a photo-electric cell controlling an alarm circuit. Filter discs A, Fig. 1, secured to a rotary shaft 10 in a cylinder 1, each comprise six sectors 35, Fig. 2, the filtrate from three adjacent sectors draining into a semi-circular groove 4 and thence to a discharge tube 51. The remaining three sectors drain into the other semi-circular groove 4 and thence into another discharge tube. Liquid to be filtered is supplied under pressure at 2 and filtrate is discharged into an endcasing 56 through portions 52 of heat-resisting glass at the ends of the discharge tubes 51. The tubes 51 form a cylindrical bundle and have at their axis a tubular infra-red or other electric lamp 54, the radiation from which may be received by a photo-electric cell controlling an alarm circuit 53, or may be observed visually, so that the cock 26 of any tube delivering turbid filtrate may be turned off. A device for giving warning when the filter cakes have attained maximum permissible thickness comprises a ball 13, Figs. 2 and 4, on a spring-loaded rod 14 pivoted in an oilfilled housing 16 closed by a membrane 18. The ball is located between adjacent filter discs so that when the cake surface reaches the ball the movement of the discs is communicated to it and tends to rotate the rod 14 about its pivot. The movement is transmitted through crank arm 19 and link 20 to the operating lever 21 of the switch 15 of a warning circuit. During drying of the cakes after washing, if necessary, compressed air is admitted at 25 and the cocks 26 are open to atmosphere. The discs are at the same time rotated. In a method of washing different from that normally adopted excess liquid is discharged at 31, washing liquid is introduced through nozzles 30 to remove the cakes, and the disc assembly is speeded up to stir the liquid with the asisstance of radial scraper blades then provided on the edges of the discs ; the apparatus is then again operated as a filter with washing liquid pumped in at 2, so that new cakes free of another liquor are formed. The cake material may be removed by admitting washing liquid at 30 and discharging the resulting sludge by screw conveyer 32 at 31. If the material is required dry the discs are rotated against scrapers 33, Fig. 2 (one on each side of each disc), moved into the position shown when necessary by rotation of a rod 34 to which they are secured. The bulk of the material is thus removed, the filter cloths on the discs being cleaned by other scrapers (not shown), or by metal or nylon brushes 39, Figs. 2 and 8 (see Group XXXI). These are mounted on a hollow shaft 43 which is rotated to bring the brushes into position between the discs and then moved longitudinally to bring them into contact with one or other set of disc faces. Then they are rotated by a handwheel 55 and chain 48, Figs. 8 and 9. Each disc segment comprises a sheet metal, wire netting or plastic material core member covered on each side with wire gauze which may in turn be covered by wire cloth, or the segment may be inserted into a bag the open edges of which are wedged at the periphery of the segment. Bolts Sa, Fig. 2, are provided to facilitate replacement of segments through an opening 38a, which also serves when scrapers 33 need replacing.