Vent type injection molding machine.

摘要

In a vent type injection molding machine comprising a screw (1) contained in a heating cylinder, there are provided a plurality axially spaced apart vent openings (12,13) located at intermediate points of the heating cylinder for venting inside of the heating cylinder to the outside and control means for selectively opening and closing the vent openings in accordance with the position of the screw in the heating cylinder or the pressure of a thermoplastic resin injected by the injection molding machine. With this construction it is not only possible to prevent a vent-up phenomenon but also to decrease the length and weight of the injection molding machine.