Patent GB-463419-A (GB)
Title: Improvements in or relating to filters
IPC: B01D35/18
Filed: 1935-09-26
Abstract: 463,419. Filters. GOODLASS WALL & LEAD INDUSTRIES, Ltd., and WARING, H. Sept. 26, 1935, Nos. 26631 and 30714. [Class 46] In filtering-apparatus comprising' a vertical hollow filtering-medium and a scraper to remove the cake formed on the medium, a shield or valve-member rotating with the scraper relatively to the medium is provided to prevent the passage of unfiltered liquid through the outlet for the cake. Material to be treated, for example a slurry of whiting and water, is supplied to the casing 11, Figs. 1 and 2, by a pipe 25 and directed therein over a cylindrical filter 30 by a shield 41 which is conical near its top and cylindrical below with an out-turned flange 42 at the bottom. The shield is attached to a rotating shaft 27. It has radially-extending ribs 43 .. 47 the vertical edges of which are separated from the filter 30 by a distance equal to the desired thickness of the cake. The rib 47 carries a scraper 48, which as it rotates, removes the cake forming on the filter and directs it through an aperture 49 in the wall of the shield to a lower section of the casing. A flange 50 on the shield closes the inlet from the pipe 25 periodically and prevents direct delivery of the material under treatment to the space between the ribs 43, 46. The next lower section has a two-armed rotor, one arm 53, Fig. 3, being bent backward so as to plaster the cake upon the filter and the other 54 carrying a scraper 55. There are lower sections 15, 16 each with four arms, two for plastering the cake on the filter and two carrying scrapers, and there is a final section with a rotor device as shown at the bottom of Fig. 4. This section is of greater diameter than the sections above it and the rotor comprises superposed hub castings 70 with wiper plastering blades 76 arranged spirally to overlap adjacent castings and radial arms carrying scrapers 80, which also overlap adjacent castings. Diaphragms 21, 22 which separate adjacent sections of the filter have apertures for the passage of the cake, these apertures being staggered relatively to each other. The shaft 27 may carry valve plates for closing these apertures during parts of each revolution. The filter cloth 30 of each section is supported from the inner wall of the casing by a framework which comprises brass rings 33, slotted to receive longitudinal brass bars 36, and wire rings 37 held in notches in the bars. The cloth is held in position and tensioned longitudinally by wedge-shaped rings 38 which also fit into notches in the bars 36 and project inwardly sufficiently to take wear of the scraper blades. The casing may be built up of longitudinal sections bolted together, the filter cloth being in sections to correspond. The annular spaces outside the filters have openings 31 for connection to vacuum and the discharge of filtrate and there are pipes which may pass through the central shaft for the supply of steam for cleansing the filter cloth. It is stated that the filtering-medium may be arranged to rotate. In the apparatus shown in the upper portion of Fig. 4, and in Fig. 5, there is an inner filter cloth 88 supported by a metal grating 87 over radial ribs 92 of a drum 86 mounted on the shaft 27. A scraper 91 is attached to this inner filter. The spaces between the ribs 92 are separately connected by pipes 93 and a distributing valve 95 at the end of the shaft 27 to sources of vacuum and of fluid under pressure. A valve plate 85 carried by the shaft 27 controls an aperture 84 in a diaphragm 83 which separates the upper section of the apparatus from the section below it. The inner filter may be stepped in tapered form to make the annular space outside it wider at the bottom than at the top. It is stated that there may be more than two coaxial filters one within the other. Specifications 16970/98, 264,011, [both in Class 46]; and 372,760 are referred to.