| 摘要 |
PURPOSE:To accelerate the rise of die pressure by providing hydraulic pressure from two hydraulic fluid passages at both sides of a piston installed inside a die pressing cylinder and changing sequentially the clearance between the piston and the space inside the die pressing cylinder. CONSTITUTION:A pilot hydraulic pressure and main circuit hydraulic pressure are supplied into a hydraulic fluid passage C and hydraulic fluid passage A respectively when the die is operated at high speed. As a result, a piston 8 is caused to advance, opening a clearance F wide. Next, a pilot hydraulic pressure is supplied into hydraulic fluid passage G according to instructions for die operation at low speed and then a piston 11 is caused to advance by releasing a hydraulic fluid from the oil passage C. In this way, the piston 8 is caused to recede. At that time, the clearance F is narrow, little hydraulic fluid is required for the space E, and the pressure in space E would not be significantly reduced. If the same main circuit hydraulic pressure as for the passage A is applied to the passage H when pilot hydraulic pressure is released from the passages G, C at a signal for temperature rise and the clearance F is closed, space E begins to be pressurized immediately. |
