Abstract: A backflow prevention device for a plasticizing and injection screw axially movable in a plasticizing cylinder of an injection molding machine, includes a base body having a leading head portion and a trailing neck portion and formed with a channel for passage of plastic melt by the screw to an anterior screw space, whereby a check valve is disposed in the channel. Bearing against an inner wall of the plasticizing cylinder and axially moving between open and closed positions is a locking ring so positioned behind the head portion in the area of the neck portion as to define a gap with the base body.

Abstract: A backflow prevention device for a plasticizing and injection screw axially movable in a plasticizing cylinder of an injection molding machine, includes a base body having a leading head portion and a trailing neck portion and formed with a channel for passage of plastic melt by the screw to an anterior screw space, whereby a check valve is disposed in the channel. Bearing against an inner wall of the plasticizing cylinder and axially moving between open and closed positions is a locking ring so positioned behind the head portion in the area of the neck portion as to define a gap with the base body.

Abstract: The invention relates to a plasticizing unit in injection-moulding machines, in particular for processing thermoplastics, with a plasticizing cylinder in which a rotatable and axially displaceable screw is arranged, at the head of which a non-return valve is provided, which has an axially displaceable barrier sleeve which encloses with radial play a tapered region which belongs to a basic body fixed in the screw head and is present between blades and a stop ring. The basic body has at least three blades, in that supporting elements provided on the surfaces of the blades facing the barrier sleeve, wherein at least the supporting surfaces of the supporting elements are made of a hard-wearing material.

Abstract: A method and an apparatus for applying afterpressure on injection molding compounds, particularly PET compounds in an injection molding machine including an injection mold and a screw connected to the injection mold through supply ducts. The injection molding material is conducted to the mold cavity by the screw in order to fill the injection mold. After the filling procedure has been concluded, the material flow is cutoff in the vicinity of the screw opening. During the phase of material shrinkage, the loss of volume is compensated by additionally conveying material present in the supply duct between the screw and the mold cavity. After cooling of the injection molding material, the continuous material flow of injection molding material into the mold cavity is separated from the material flow in the supply duct.