Filter for continuous thermoplastics extruder - has successive sieve chambers pushed progressively across outflowing stream without clogging risk

摘要

Filter assembly for plastics extruders and injection moulding machines is intended for continuous processing or extrusion of thermoplastics and has a sieve bolt slidable transversely to the extruder channel and containing a series of sieve chambers each containing a sieve. The sieve bolt is mounted sealed and under suction in the transverse passage across the extruder and there is a vent valve adjacent to the next sieve chamber to come into use. On both the upstream and the downstream sides of the sieve chambers (sieve bolts) there are tapered overflow ducts; the overflow duct on the upstream side is of such a form that it makes a communication between the extruder barrel and the next sieve chamber, which is just about to come into use, before the corresponding duct on the downstream side of this chamber. The sieve bolt operates on the known principle, i.e. it is moved transversely across the extruder as a fall in pressure on the downstream side of the sieve chamber at present in use indicates progressive clogging of this sieve.