Nonreturn valve for the screw of a plasticising unit of an injection-moulding machine

A nonreturn valve for a screw of a plasticising unit of an injection-moulding machine, the nonreturn valve comprising:

• two half-shells configured to be arranged in a portion of the screw having a reduced screw diameter,
• each of the two half-shells comprising one or more channels for melt to flow through from the screw into the space in front of the screw,
• wherein each of the one or more channels lies substantially parallel to a longitudinal axis of the nonreturn valve or respectively to a longitudinal axis of the screw,
• a ball and a pin located within each of the one or more channels of the half-shells,
• wherein the pin is arranged after the ball relative to the direction of flow of the melt, and the pin is further arranged substantially transversely to the direction of flow of the melt,
• wherein each pin in its respective channel is arranged radially relative to the longitudinal axis of the screw, and a distal end of each pin extends to an exterior of its respective half-shell,
• each of the one or more channels of the half-shells having a first channel portion and a second channel portion, the first channel portion being positioned before the second channel portion relative to the direction of flow of the melt, and the ball and pin being arranged in the second channel portion,
• wherein the first channel portion has a channel diameter smaller than a diameter of the ball,
• wherein the second channel portion has a channel diameter greater than the diameter of the ball, and
• wherein a length of the pin is greater than the channel diameter of the second channel portion.