Abstract: An improved screw has a shaft having a surface and a central axis and at least one flight extending helically along the surface of the shaft in successive turns. A continuous groove is formed in the surface of the shaft and extends between successive, pushing and trailing, turns of the flight at a selected angle greater than zero. The groove defines at least one generally triangular land having a base aligned with a pushing turn of the flight and an apex between successive turns of the flight. The groove also defines another generally triangular land having a base aligned with a trailing turn of the flight. Barriers or dams may be provided on the lands and in the grooves. A second continuous groove may also be formed in the surface of the shaft.

Abstract: An improved screw has a shaft having a surface and a central axis and at least one flight extending helically along the surface of the shaft in successive turns. A continuous groove is formed in the surface of the shaft and extends between successive, pushing and trailing, turns of the flight at a selected angle greater than zero. The groove defines at least one generally triangular land having a base aligned with a pushing turn of the flight and an apex between successive turns of the flight. The groove also defines another generally triangular land having a base aligned with a trailing turn of the flight. Barriers or dams may be provided on the lands and in the grooves. A second continuous groove may also be formed in the surface of the shaft.

Abstract: A screw rotates in a containment barrel, and comprises a shaft having an upstream end and a downstream end At least one flight is secured to the surface of the shaft and extends helically in successive turns around the circumference of the shaft. An upstream barrier member extends radially from the surface of the shaft and generally transversely between successive turns of the flight. The upstream barrier is disposed proximal the upstream end of the shaft. A downstream barrier member extends radially from the surface of the shaft and generally transversely between successive turns of the flight. The downstream barrier is disposed proximal the downstream end of the shaft.

Abstract: An elongate projection or probe extends from the injection unit of an injection molding apparatus. A passage extends through the projection in fluid communication with the injection unit. A generally cylindrical receptacle is formed in a portion of the mold of the injection molding apparatus for receiving the projection in generally concentric sliding relation. The receptacle is in fluid communication with the mold cavity, wherein relative movement between the projection and the receptacle causes injection unit to be selectively in fluid communication with the mold.