Patent ID: 6722270
Filing Date: 2004-04-20
Classification: B30B,F15B

Abstract:
A hydraulic press comprising:a multi-cylinder comprising a first cylinder chamber employed as a quick feed and pressurization cylinder having a small pressure receiving area and used for reciprocation, a second cylinder chamber employed as a quick return cylinder having an equal pressure receiving area to the pressure receiving area of the first cylinder chamber, a third cylinder chamber employed as a pressurization cylinder having a large pressure receiving area and used for reciprocation, and an integral piston member partitioning the respective cylinder chambers in said multi-cylinder; a constant volume, reversible hydraulic pump, and a servo motor driving the hydraulic pump to rotate in positive and counter directions; a closed hydraulic circuit connecting said first cylinder chamber to said second cylinder chamber through said hydraulic pump; an automatic supply hydraulic circuit connecting said third cylinder chamber to an oil tank through an automatic supply valve; a pressurization hydraulic circuit connecting one of discharge ports of said hydraulic pump to the third cylinder chamber through a check valve; a pressure sensor detecting oil pressure of said third cylinder chamber; and a controller controlling said servo motor based on a signal from said pressure sensor.