Filter unit for prolonged operation feeding extruders

摘要

A novel filter passes thermoplastics to extruders and pressure injection moulding machines. It includes replaceable filter elements (4, 5) in carriers (2, 3) located in two side channels (8a, 9a; 8b, 9b) in the filter casing (1). These channels connect in parallel between the main inlet- and outlet channels (6, 7). The filter carriers are inserted or removed through casing bores. Ahead of the carriers, in the main inlet channel (6), a block valve (10) is set to pass the thermoplastic to both filter elements. It has alternative positions preventing flow from the main channel into either one of the side channels. In these positions, the appropriate dirty sieve side (S) is connected to a take-off channel. In the novel design, the blocking unit (10) comprises a bolt or spool crossing the main inlet channel and adjustable transversely to the flow direction. The through-flow path from the main inlet into the side channels passes a necking (12) formed into the outer circumference of the bolt (11).