Mold clamping apparatus and method of controlling operation of the apparatus

A mold clamping apparatus of an injection-molding machine for clamping a mold consisting of a stationary mold half and a movable mold half, said mold clamping apparatus comprising:

• a stationary platen fixedly disposed on a base of the injection-molding machine and being fixed with the stationary mold half;
• a rear platen fixedly disposed on the base of the injection-molding machine and being opposite to and spaced apart from said stationary platen and;
• a movable platen movably disposed between said stationary and rear platens and being fixed with the movable mold half;
• an electrically-operated movable-platen-driving device of ball-screw type, including a first ball-screw shaft supported by one of said movable and rear platens, a first ball-nut threaded-engaged with said first ball-screw shaft and supported by the other of said movable and rear platens, and a movable-platen-driving-electric motor adapted to rotate said first ball-screw shaft and nut relative to each other so as to generate a relative longitudinal motion of said first ball-screw shaft and nut so that said movable platen is moved toward and away from said stationary platen to close and open the mold;
• a pressure-generating cylinder device disposed on said rear platen and having a pressure-generating piston being moved by said relative longitudinal motion of said first ball-screw shaft and nut in order to generate a hydraulic pressure;
• a mold clamping cylinder device disposed on said rear platen and adapted to generate a mold clamping force based on said hydraulic pressure generated in and applied from said pressure-generating cylinder device, said mold clamping cylinder device having a mold clamping ram being connectable to said movable platen for applying said mold clamping force to said movable platen;
• and
• an engaging device having a first operating position for connecting said mold clamping ram with said movable platen, and a second operating position for disconnecting said mold clamping ram from said movable platen;
• said mold clamping apparatus clamping the mold such that said movable platen is moved toward said stationary platen to close the mold therebetween, and said pressure-generating cylinder is operated to generate said hydraulic pressure, based on said relative longitudinal motion of said first ball-screw shaft and nut, while said engaging device is placed in said first operating position in order to apply said mold clamping force generated in said mold clamping cylinder device to said movable platen.