Filtration apparatus

In a candle displacement filtration apparatus of the kind which comprises a cylindrical housing accommodating a hollow perforated cylindrical body or candle, and impermeable elastic sleeve disposed within the annular space defined by the inside of the housing and the outside of the cylindrical body and circumferentially attached at its ends to the housing of the cylindrical body, thereby dividing the annular space into an inner filtration compartment and an outer pressure applying compartment, a filter element disposed around and supported by the cylindrical body, outlet means for the discharge of filtrate which has passed through the filter element into the cylindrical body, an inlet into the inner compartment for liquid/solid mixtures, an inlet into the outer compartment for a hydraulic fluid under pressure, means for displacing the hollow perforated cylindrical body, or candle, axially relative to the cylindrical housing so that the cake adhering to the candle is exposed and can be discharged, and an inlet into the interior of the cylindrical body for compressed air, the improvement wherein the inlet to the inner compartment for liquid/solid mixtures comprises a substantially cylindrical chamber provided with circumferentially spaced apertures adapted to connect with the inner compartment, said chamber being located at one end of the cylindrical body in an extension thereof, an inlet line or lines into said chamber and a hollow cylindrical member coaxial with said extension and movably constructed and arranged to cover or expose said apertures and to form with said extension a cell the ends of which are defined by flanges extending from said hollow cylindrical member and slidably engaging with the walls of said extension, said cell being divided by a piston integral with said extension, means being provided on either side of said piston for supplying or venting air to or from either side of the cell.