| 摘要 |
903,248. Filters; systems of filtration. BRITISH FILTERS Ltd. Jan. 11, 1961 [Jan. 29, 1960], No. 3332/60. Class 46. During periods when filtration is interrupted, compressed air is admitted at 34 to an annular space 28a and through apertures 31 to the region beneath a fixed piston 29 to force downwards a closure plate 17 and with it a cylinder 19 having a cover 20 which carries an annular scraper 22. Filter cake on the inside of a filter element 4 is thereby removed and drops on to a conveyer 25. A flexible pipe 38 serves for the supply and return of liquid to be filtered, for the supply of wash liquid and filter aid, and for connection to drain. A pipe 15 serves for discharge of filtrate, for supply of backwash liquid, and for connection to drain. A pipe 13 serves for admission of compressed air for drying the cake. Pipe 33 is complementary to pipe 34 for restoring the scraper to its upper position, each of these pipes being controlled by a three-way valve including a vent. All the valves governing the above-mentioned connections are fluid-pressure-operated and are controlled by pilot valves which are operated in timed sequence. Preferably the filter element 4 comprises inner and outer perforated drums between which is arranged a filter cloth coated on its inner face with filter aid held in place by tubular wire gauze. |
