Device for filtering liquid of high viscosity supplied under pressure, in particular a device that can be connected to an extruder to filter thermoplastic melts of plastic composition

A device for filtering liquids of high viscosity supplied under pressure, in particular a device that can be connected to an extruder to filter thermoplastic melts of plastic composition, said device having at least two exchangeable filters attached in sealing relation to the end plane of a valve body, said filters being supplied with liquid through an annular passage in such a manner that the valve stems of the lift valves located at the branches of the annular passage remain surrounded by liquid also when said valves are closed, as a result of the clearance space surrounding the valve stems, characterised by the shaft of the valve stem being equal to the largest diameter of the valve seat and the shaft casing that surrounds the shaft in sealing relation extending up to the clearance space broadened with respect to the valve seat, the height of said space measured in the direction of draw being essentially equal to the diameter of the annular passage, whereby the front edge of said shaft when the respective valve is open approximately ends at the surface of the clearance space, and by having the valve stem in a closed position penetrate the wall of the valve body in a sealing relation up to the end plane of the valve body.