An injection molding machine includes: a plunger provided inside a barrel and capable of moving forward and backward in an axial direction thereof and rotating about an axis thereof; a feed hole for feeding a molding material in liquid form into a front of the plunger; a packing provided on a backward side of the feed hole to prevent the molding material fed through the feed hole from flowing backward along the plunger; and a controller for controlling a retracting movement of the plunger based on pressure of the molding material fed from the feed hole to thereby perform metering. In this configuration, at least part of the feed hole is covered by a side surface of the plunger at least from start to end of the retracting movement.

A multi-mold block drive device includes a guide seat having a plurality of spaced-apart guide holes extending through inner and outer peripheral surfaces thereof, a plurality of speed reduction drive units each including a speed reducer driven by a servo motor and having an eccentric shaft, and a plurality of mold locking units each connected between one of the guide holes and a corresponding speed reduction drive unit. Each mold locking unit includes a pivot shaft, a linkage disposed between the pivot shaft and the corresponding guide hole, and a guide rod pivoted to the linkage. The linkage includes a crank driven by the eccentric shaft, a first link arm pivoted between the crank and the pivot shaft, and a second link arm pivoted between the crank and the guide rod. An injection molding machine having the multi-mold block drive device is also disclosed.

An injection molding machine includes: a plunger provided inside a barrel and capable of moving forward and backward in an axial direction thereof and rotating about an axis thereof; a feed hole for feeding a molding material in liquid form into a front of the plunger; a packing provided on a backward side of the feed hole to prevent the molding material fed through the feed hole from flowing backward along the plunger; and a controller for controlling a retracting movement of the plunger based on pressure of the molding material fed from the feed hole to thereby perform metering. In this configuration, at least part of the feed hole is covered by a side surface of the plunger at least from start to end of the retracting movement.

A multi-mold block drive device includes a guide seat having a plurality of spaced-apart guide holes extending through inner and outer peripheral surfaces thereof, a plurality of speed reduction drive units each including a speed reducer driven by a servo motor and having an eccentric shaft, and a plurality of mold locking units each connected between one of the guide holes and a corresponding speed reduction drive unit. Each mold locking unit includes a pivot shaft, a linkage disposed between the pivot shaft and the corresponding guide hole, and a guide rod pivoted to the linkage. The linkage includes a crank driven by the eccentric shaft, a first link arm pivoted between the crank and the pivot shaft, and a second link arm pivoted between the crank and the guide rod. An injection molding machine having the multi-mold block drive device is also disclosed.