Plastic injection molding machine safety mechanism

Claim 1

In combination with a plastic injection molding machine having two molds movable relative to each other for opening and closing the mold cavity formed therebetween, one of said molds being mounted on a movable platen supported on at least one guide bar having notches therein, and a safety gate movably mounted in selective blocking relationship between the molds and the operator of the machine, the improvement comprising: a pawl engageable with one of said notches in the guide bar for selectively preventing the advance of the movable platen; a mechanical linkage connected between the pawl and the safety gate for engaging the pawl with the bar whenever the gate is slightly opened, said linkage including; a torque shaft mounted for rotation between first and second angular positions; means for rotating the torque shaft between said first and second angular positions in response to movement of the gate out of blocking relationship; and means for engaging and disengaging said pawl when the torque shaft is respectively in said first and second angular positions comprising linkage means engaging said torque shaft at a point spaced apart from the axis thereof for transmitting rotational movement of said torque shaft to said pawl, said linkage means cooperating with said torque shaft and said pawl so that rotation of the torque shaft between said first angular position and said second angular position moves the pawl from said engaged position to said disengaged position.