PURPOSE: To eliminate defect in production such as insufficient weight of the product by exerting hydraulic pressure at the back of a screw before injection for a specified time before injection to make a reverse flow prevention screw retreat to the screw side and completely close the resin channel.
CONSTITUTION: After a weighed amount of molten resin (a) is filled in a cavity 5 by rotating the screw 3 of an inline screw type injection molding machine, that is, after an electromagnetic change-over valve 11 has taken its middle position, an electromagnetic change-over valve 13 to control the pre-shut of a reverse flow preventing ring 1 is held at the position (a) for a specified time T, and the hydraulic pressure from a hydraulic pressure source 8 is made to work on an oil chamber 7 and a screw 3 is pressed against the side of a screw head 2 for time T. In this arrangement the ring 1 contacts closely the end face A of the screw 3 to close completely the resin channel, which makes the amount of injected resin always constant, and thereby the injection molded products have constant weight and shape.
SAKANISHI HIDEO
TASHIRO TAKEO
HIROZAWA MASAO
| JPS5031562A | 1975-03-28 | |||
| JPS541575A | 1979-01-08 |