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1. A backwash system for a fluid filter comprising:
(a) a fluid pressure vessel having an interior wall surface and an inlet and outlet communicating with the wall surface and adapted for connection respectively to a fluid supply and discharge line; (b) a removable filter cartridge having a plurality of tubular filter elements having oppositely disposed open ends disposed in an array with a pair of spaced tube sheets each disposed at one of opposite ends of the tubular filter elements with the tube sheets having a centrally disposed tube extending therebetween, wherein the cartridge is insertable in the pressure vessel; (c) a shaft received through the centrally disposed tube and journalled for rotation with respect thereto; (d) an outlet chamber formed, upon insertion of the cartridge in the pressure vessel, by sealing contact of the pair of tube sheets with the wall surface of the pressure vessel, wherein the outlet communicates exclusively with the outlet chamber and the opposite open ends of each of the tubular filter element are isolated from the outlet chamber and an outer peripheral surface of each tubular filter element intermediate the tube sheets is disposed in the outlet chamber; (e) an inlet chamber defined by one of the pair of tube sheets and portions of the wall surface of the pressure vessel and isolated from the outlet chamber wherein one common inlet end of each of the tubular filter elements communicates exclusively with the inlet chamber; (f) a drain chamber defined by the other of the pair of tube sheets and other portions of the pressure vessel interior wall and isolated from the outlet chamber, the drain chamber having a drain port provided therein wherein an opposite common open end of each of the tubular filter elements communicates exclusively with the drain chamber; (g) a disc-like valve member having at least one aperture therein, located for, upon rotation of the shaft, periodically blocking and opening respectively the common open end of each of the filter elements communicating with the drain chamber; (h) a paddle valve member disposed for rotation with the shaft in the inlet chamber and spaced closely adjacent the common inlet open end of the filter elements wherein the paddle member is configured and oriented such that upon rotation of the shaft in one direction the inlet open end of each filter element is sequentially blocked by the paddle member while the drain open end remains blocked, then subsequently the drain end of the filter element is opened at the opposite common end communicating the filter element with the drain chamber by the aperture in the disc-like member then subsequently the paddle valve opens the inlet common end communicating the filter element with the inlet chamber and the inlet fluid pressure causes fluid flow through the respective tubular filter element and flushing of filtered material to the drain; and, (i) motor means operative upon energization for rotating the shaft. |
