Patent ID: 7401548
Filing Date: 2008-07-22
Classification: B30B

Abstract:
1. A drive device of a movable platen, comprising: an electric motor device includes an electric motor; a screw/nut mechanism which transfers output torque of the electric motor to the movable platen as thrust to move the movable platen; at least one hydraulic cylinder connected to a constant, high pressure source for generating working fluid of an almost constant pressure and a low pressure source via a valve; a thrust transfer device which transfers thrust of the at least one hydraulic cylinder to the movable platen and linking to allow the thrust to be transferred as required at an arbitrary stroke position of the screw/nut mechanism; a velocity detecting device which detects a velocity of the movable platen or an angular velocity of any rotation part disposed between a drive shaft of the electric motor device and the screw/nut mechanism; and a control device which controls the electric motor device and the at least one hydraulic cylinder, based on the velocity or the angular velocity detected by the velocity detecting device, wherein when the thrust generated by the electric motor is insufficient for the thrust to move the platen, the control device controls the electric motor and the hydraulic cylinder to secure the required thrust at the arbitrary stroke position by offset-driving the electric motor and turning on/off the at least one hydraulic cylinder depending on a magnitude of a shortage of the thrust to continuously change a composite thrust of the electric motor and the at least one hydraulic cylinder, the control device makes the at least one hydraulic cylinder serve as a pump during a predetermined period when load of the movable platen is small, and working fluid is charged from the low pressure source to the high pressure source by using thrust transferred from the electric motor device to the at least one hydraulic cylinder through the screw/nut mechanism, the movable platen and the thrust transfer device, and wherein the movable platen is a slide of a press machine.