Improvements in or relating to filters

摘要

755,243. Filters. INFILCO, Inc. Feb. 16, 1954 [Feb. 16, 1953], No. 4539/54. Class 46. Liquid to be filtered is introduced at 21, Fig. 1, through a valve 19 and filters through filter aid material deposited on the pervious lower portion 34 of each of a number of filter units 301, 302. Air is trapped in the top portion 12 of a casing 10 by introduction of the liquid, and the passage of filtrate into the units 301, 302. causes air to be trapped in an impervious, upper portion 33 of each unit. Filtrate from the outer units 302 passes by pipes 45 into a central unit 301, the lower end of which has an outlet port 37 and fits in a socket 35 on an outlet pipe 25. When backwashing of the units is necessary an air release valve 28 (preferably quickacting) is opened, the "release air " hitherto trapped under the top portion 12 thereby escaping, and the " operating air " trapped in the upper impervious portion of each filter unit thereupon expanding and driving filtrate back through the pervious portion at high velocity. The filter cake is thereby broken off and the unit.interstices cleaned. Compressed air is then admitted at 29 to maintain the solids in suspension during discharge of the dirty liquid through a drain valve 23. In Fig. 3 (not shown), the pervious and impervious parts of each filter unit are made separately but clamped together in use. Withdrawal of filtrate may be by means of an upper header 56, Fig. 4, which also supports the weight of the units and communicates with each by a conduit 55 extending through the " operating air " space. In this arrangement the filtrate may be withdrawn from the outer units downwards through the central unit instead of from all units through the conduit 25b as shown. Each unit may in every case comprise two or more sections 60, 61, Fig. 5, each section comprising an upper impervious portion 33c and a lower pervious portion 34c, each section except the uppermost communicating with the one above it for discharge of filtrate by a pipe 62, and the filtrate from the compound unit being withdrawn at 45c. In Fig. 8, each unit may comprise a cylindrical element 30f, Fig. 11, including an open-bottomed "release air" trap 762 extending substantially the length of the unit. This trap may be omitted, in which case the impervious portion 33e of the cylindrical wall extends nearly half-way down on each side of the vertical. Specification 524,385 is referred to.