Self-cleaning filter

Claim 2

In a self-cleaning filter of the type comprising a plurality of vertical filter columns equidistantly arranged about a vertical axis and a rotatable pressure unit for forcing a cleaning fluid into each column sequentially and countercurrently, which unit comprises a cylinder having a horizontal axis and a piston mounted to reciprocate therewithin, said cylinder being mounted to rotate about said vertical axis to bring the space between said piston and one end of said cylinder into communication with each column successively, a spring biassing said piston toward said one end of said cyliNder, valve means connected to alternately subject the face of said piston remote from said one end alternately to the pressure prevailing within said filter and to atmospheric pressure, and means actuated by said cylinder at each end of its stroke for automatically reversing said valve means, the improvement according to which the other face of said piston is constantly subjected to the pressure within the filter, so that the pressure applied to produce counter-current cleaning is supplied solely by said spring, when both faces of the piston are subject to the pressure within the filter.

Claim 3

In a self-cleaning filter of the type comprising a plurality of vertical filter columns equidistantly arranged about a vertical axis and a rotatable pressure unit for forcing a cleaning fluid into each column sequentially and counter-currently, which unit comprises a cylinder having a horizontal axis and a piston mounted to reciprocate therewithin, said cylinder being mounted to rotate about said vertical axis to bring the space between said piston and one end of said cylinder into communication with each column successively, a spring biassing said piston toward said one end of said cyliNder, valve means connected to alternately subject the face of said piston remote from said one end alternately to the pressure prevailing within said filter and to atmospheric pressure, and means actuated by said cylinder at each end of its stroke for automatically reversing said valve means, the improvement according to which the other face of said piston is constantly subjected to the pressure within the filter, so that the pressure applied to produce counter-current cleaning is supplied solely by said spring, when both faces of the piston are subject to the pressure within the filter.

Claim 4

In a self-cleaning filter of the type comprising a plurality of vertical filter columns equidistantly arranged about a vertical axis and a rotatable pressure unit for forcing a cleaning fluid into each column sequentially and counter-currently, which unit comprises a cylinder having a horizontal axis and a piston mounted to reciprocate therewithin, said cylinder being mounted to rotate about said vertical axis to bring the space between said piston and one end of said cylinder into communication with each column successively, a spring biassing said piston toward said one end of said cyliNder, valve means connected to alternately subject the face of said piston remote from said one end alternately to the pressure prevailing within said filter and to atmospheric pressure, and means actuated by said cylinder at each end of its stroke for automatically reversing said valve means, the improvement according to which the other face of said piston is constantly subjected to the pressure within the filter, so that the pressure applied to produce counter-current cleaning is supplied solely by said spring, when both faces of the piston are subject to the pressure within the filter.

Claim 5

Filter as claimed in claim 1 which comprises a check valve for admitting fluid under the pressure prevailing within said filter to said one end of said cylinder, said check valve being spring biassed to a closed position, and positioned to be automatically closed when the pressure prevailing within said filter is applied to both faces of said piston.

Claim 6

Filter as claimed in claim 1 in which said valve means comprises a valve member which turns through an angle of substantially 60* between its two positions.

Claim 7

Filter as claimed in claim 3 comprising a leaf spring for actuating said valve member, said leaf spring having a first arm connected at its outer end to vertical means carried by said piston and a second arm connected at its outer end to a member mounted to pivot about a fixed axis, said member comprising a recess receiving a cam mounted to swing through an angle of substantially 150* about the same axis, and having an end projecting from said recess which contacts a roller mounted on said vertical piston-carried means so as to prevent said member from swinging until said piston is at one of the ends of its path of travel, at which time the ends of said spring arms are maximumly separated, and adjustable stop means limiting the swinging movement of said recess-comprising member.