Tube pressure filters

Claim 1

In a tube pressure filter which comprises (a) a pair of generally coaxial inner and outer tubular bodies arranged one within the other and adapted to be supported in a generally upright position; (b) an impermeable elastic sleeve disposed within and secured to the outer tubular body; (c) a filter element disposed around and supported by the inner tubular body; and (d) means for displacing the tubular bodies axially relative to one another between a first position and a second position, wherein the arrangement is such that in the first position of said tubular bodies they co-operate with each other to define a closed chamber of annular cross-section which is divided into generally coaxial and non-intercommunicating inNer and outer compartments by said impermeable elastic sleeve, the inner compartment including an inlet for a wet particulate solid material to be pressure filtered and the outer compartment including an inlet for hydraulic fluid under pressure, whereby a filter cake of a particulate solid material can be formed on the filter element, and in the second position of said tubular bodies said chamber is opened to enable a filter cake of particulate solid material to be discharged from the inner compartment, the improvement which comprises employing an impermeable elastic sleeve which elastic sleeve comprises a central portion for transmitting pressure to the wet particulate solid material in the inner compartment and flared end portions for securing the elastic sleeve to the outer tubular body and wherein the central cylindrical portion includes at least one annular thickened portion whereby at least one annular segment of the filter cake which is produced on the filter element is substantially thinner than the major part of said filter cake and is indented with reference to the outer surface of said major part of the filter cake, said at least one annular segment extending over a minor proportion of the length of said filter cake.