| 摘要 |
PURPOSE:To reduce the pressure oil piping system resistance by a method wherein a passage equipped with a valve member is provided so as to run from the front chamber to the rear chamber of a cylinder in order to apply pressure oil to a mold closing cylinder and, on the other hand, to flow the pressure oil in the front chamber of the cylinder to its rear chamber side through said passage. CONSTITUTION:When oil pressure is fed to the rear chamber 1b of a cylinder, differential pressure is generated due to the difference between the pressure receiving area of the front surface of a piston and that of its rear surface, resulting in moving the piston 2 at high speed toward the front chamber 1a of the cylinder and consequently performing mold closing. At this time, a part of pressure oil in the direction of movement flows through a running gap on the periphery of the piston 2 in the rear chamber 11b side of the cylinder, resulting in reducing the resistance of oil pressure. When the front end of the piston 2 reaches the front chamber 1a of the cylinder, the piston 2 fits to the front chamber 1a of the cylinder and said running gap is lost. However, at this time, an operating device 17 is hydraulically actuated so as to advance a rod 20 in order to retreat a valve member 12 against a spring member 13, resulting in opening a passage 11 and accordingly communicating the front chamber 1a of the cylinder with its rear chamber and preventing the oil pressure in the front chamber 11a of the cylinder from giving large resistance.
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