PURPOSE: To provide a booster device capable of automatically obtaining boosted oil pressure when necessary, without resetting the rated pressure of a hydraulic system.
CONSTITUTION: An operating valve 12 connected to a hydraulic pump 13 directional-controls pump-discharged pressure oil to control an opening and closing cylinder 4 for opening and closing a jaw of a breaker. A pilot type check valve 8 is interposed between expansion side oil passages 271, 272 between the operating valve 12 and the opening and closing cylinder 4. The checking action of the check valve 8 is released by pilot pressure guided from a contraction side oil passage 28 on the opposite side through a pilot oil passage 9. A sequence valve 7 is provided on an oil passage 26 branched from the expansion side oil passage 271 on the operating valve 12 side from the check valve 8. An electromagnetic change-over valve 6 is provided on a supply oil passage 29 supplied with pressure oil through the sequence valve 7. A double acting boosting cylinder 5 is connected to output oil passages 241, 242 of the electromagnetic change-over valve 6. The boosting cylinder 5 outputs boosted pressure oil to the expansion side oil passage 272 on the opening and closing cylinder 4 side from the check valve 8.
AWANO KATSUSUKE
KUBOTA YORIMICHI
TAMURA MANABU
