Multi-zone screw for thermoplastic injection - has conventional feed, compression and metering zones and additional zone forming mixing and metering are with increasing channel depth

摘要

Injection screw for processing thermoplastics has a conventional three zone arrangement comprising constant depth feed, decreasing depth compression and constant depth metering zones. A fourth zone positioned after the metering zone forms a metering-mixing zone with an increasing channel depth. A fifth zone forming a second metering zone follows the metering-mixing zone and has the same channel depth as the first metering zone. The screw tip incorporates the second metering zone, which is formed by a constant depth part and followed by the conical pointed section. The screw tip is interchangeable and has a conical angle of 16-20 deg. pref. 17-19 deg. more pref. 18 deg. USE/ADVANTAGE - Injection of thermoplastics behind delicate materials (claimed) and processing sensitive melts. Gives optimum temp. control, eliminates a non-return valve and allows recycling of prodn. scrap from a back-injection process.