We have developed "SK-control," a new check mechanism for controlling the reverse flow of molten resin to be injected into a metal mold. The reverse flow control is an important factor in the injection process to achieve precise molding in electric injection molding machines, which have become the main devices replacing hydraulic driven machines. "SK-control" has a different mechanism from the conventional one, and has the following features in combination with the good controllability of electric injection molding machines.

(1) The reverse flow of molten resin is prevented before injection, to reduce the variation of the reverse flow. Variation is a problem with conventional check mechanisms.

(2) The new mechanism has eliminated the axial movement of a check ring for metering resin to be injected. Instead, the check ring is rotated. The metering is made when a screw is rotated in the normal direction providing a path for resin flow, and after the metering the screw is rotated in the reverse direction to close the flow path.

(3) "SK-control" makes it possible to provide necessary compensation for changes in resin density.