Filter

1,231,524. Filters. A.M.F. Inc. 5 Nov., 1969 [19 May, 1969], No. 54147/69. Heading B1D. In a filter comprising filtering material 59 arranged between a peripheral chamber and a central chamber in a housing 12 which has an inlet 13 for liquid-to-be-filtered and a liquidoutlet 15, the cover 23 of the housing is associated with a movable bar 25 which indicates when the filtering material is getting dirty and, in the upper part of the housing, there is a piston 43 which moves down and permits direct communication between the peripheral and central chambers when the filtering material is clogged. The bar 25 is connected to piston 43 via linkage 53, 51. The piston is actuated by spring 47 which operates when the differential-pressure overcomes the force of the spring. The piston first moves bar 25 to the warning zone of the cover 23, but as the differential-pressure builds up the piston is moved further downwards so that it reaches below the enlarged area of support 41 which permits communication between the peripheral and internal chambers of the filter. The bar 25 now enters the "by-pass" zone on cover 23. An electric alarm which may be incorporated into the system. This electric alarm switch can be correlated with the bar indicator or may operate independently. Vent valve 33 serves as an additional safety device, opening under sufficient pressure to allow gas or liquid to escape from the housing.