GB1075740A - Method and apparatus for filtering liquids - Google Patents

Abstract

1,075,740. Liquid filter. G. HIRS. June 17, 1966, No. 27206/66. Heading BID. In a liquid filter in which a pump 90 extracts filtered liquid from a chamber 46 separated by filter medium 84 from an inlet chamber 44, a switch 118 responds to decreasing pressure in chamber 46, resulting from clogging of the medium, to stop pump 90, reducing the pressure across the medium before initiating a filter cleaning/renewal mechanism. In Fig. 2 a web of paper filter medium is extended between endless chains 58 and members 42, 52 from supply roll 86 to medium discharge roll 110 and extends across a foraminous part 70..80 of ramp 42 through which filtered liquid passes. Actuation of switch 118 opens contacts 125, supplying pump motor 94, and closes contacts 123 causing motor 98 to drive chains 58. contaminated filter medium being discharged over rubber-coated roll 110 and fresh medium being unrolled from roll 86. Stoppage of pump 90 facilitates withdrawal of medium from foraminous wall 80. In an alternative embodiment, not shown, the filter medium is a fixed wedge-wire screen, and chains 58 carry scrapers which remove solids from the screen, once the pump has been stopped so that the solids are no longer held thereon. In Fig. 1 (not shown) the pump 90 returns filtered liquid by line 24 to a machine tool (22), the liquid being tool coolant. Switch 118 may operate in its two directions at different pressures so that the movement or scraping action proceeds for a short time once started. The pump stoppage permits liquid in line 24 to drain back causing reduction in pressure difference across the filter.