Apparatus for injection molding of parts from foam plastics material

Abstract

The apparatus molds during each cycle homogeneous plastic material and foam plastic material. It includes a barrel member, a main passageway therein in which is located the screw member. A pair of injecting means for filling molds are provided, one having a homogeneous plastic injection chamber and the other having a foam plastic injection chamber. The first injection means is connected to the screw and barrel member upstream of the place where the inert fluid is introduced into the main passageway whereby homogeneous plastic material is discharged from the main passageway into the first injection means. The apparatus includes means for introducing an inert fluid into the main passageway whereby the rotating screw member mixes the gas with the molten plastic as it moves towards the discharge port which is connected to the second injection means whereby foam plastic material is injected into the foam plastic injection chamber. Each injection means has one or more nozzles connected to a mold located in a press. The molds for both the homogeneous and foam plastics material may be located in different presses or in the same press so that upon each cycle of the screw and barrel assembly and after both injection means have injected the plastic materials into the respective molds, the press or presses close and form the homogeneous plastic parts and the foam plastic parts. The several injection means or devices may be operated simultaneously or sequentially. Thus, it is possible to mold and form homogeneous and foam plastic parts during the same cycle using only one screw member.