Oblique gates for injection moulding in cavities of varying thickness - for rapid mould filling without excessive melt temps.

摘要

Mouldings involving considerable variations in section thickness and aspect (length/thickness) are produced by injecting the moulding material through two or more gates and at an angle of 5-75 deg., pref. about 15 deg., relative to the moulding axis. Used esp. for making relatively deep, thin wall hollow mouldings with a thick base, e.g. casings for 'scaled' dry cell batteries, from thermoplastic melts of polyolefin, polyamide or plasticised polyacetal or PVC moulding materials. Esp. applicable to mouldings where greatest wall thickness/least wall thickness is over 3; length of thin section/length thick section over 4 and length of thin section/thickness of thin section over 30. Use of multiple injection points leads to more rapid filling, allowing the thinner cavity zones to be filled before the melt sets up, without having to use excessively high melt temps. and associated energy costs and moulding cycle extensions. Simpler and neater than alternative of moulding thick and thin wall zones separately and subsequently joining them together somehow. May allow the thickness of thin wall sections to be reduced to below 0.5 mm.