Patent ID: 6843647

Claim:
An electrically-operated mold opening/closing device for an injection molding, comprising a fixed die plate for holding a fixed mold; a movable die plate for holding a movable mold; means for advancing and retreating said movable die plate toward and from said fixed die plate; a tie bar for connecting said movable die plate to said fixed die plate after said movable die plate approaches said fixed die plate and said fixed mold and said movable mold are closed; die plate connecting means; and mold clamping means used at the time of injection molding, characterized in that said means for advancing and retreating said movable die plate toward and from said fixed die plate comprises a moving base in which the upper surface thereof is connected integrally with said movable die plate and a slide unit is installed on the lower surface thereof; a pair of track rails which are provided on a base of said machine and form a linear guide by engaging with said slide unit; a ball screw shaft which is supported in parallel with said track rails by a bearing provided on the base of said machine and in which axial direction is restrained rotatably; a servomotor for driving said ball screw shaft; and a ball screw nut which is installed on the lower surface of said moving base so as to threadedly engage with said ball screw shaft, and said ball screw shaft and said ball screw nut are provided at a position between said paired track rails; further comprising means for relaxing a bending force due to a misalignment of the ball screw nut and the ball screw shaft.