| 摘要 |
PROBLEM TO BE SOLVED: To provide a hoisting device of construction machinery, the operational feeling of which is improved. SOLUTION: When ladders 2 and 3 are developed, a hydraulic pump 101 is driven, and pressure oil is fed to a rod chamber 4b via a switching valve 112 until an arrival in a development-side speed-reduction starting position. The pressure oil is fed to the rod chamber 4b via an oil passage 405, into which a throttle 110 is inserted, without the medium of the switching valve 112, after the arrival in the development-side speed-reduction starting position, and a working fluid in a bottom chamber 4a is flowed into a working fluid tank 140 via a relief valve 108. When the ladders 2 and 3 are stored, the hydraulic pumps 101 and 102 are driven, and the pressure oil is fed to the bottom chamber 4a via the switching valve 112 until an arrival in a storage-side speed-reduction opening position. The working fluid is fed to the bottom chamber 4a via an oil passage 404, into which a throttle 106 is inserted, without the medium of the switching valve 112. The pressure oil is fed to the bottom chamber 4a via the oil passage 404, into which the throttle 106 is inserted, without the medium of the switching valve 112, after the arrival in the storage-side speed-reduction opening position, and the working fluid in the rod chamber 4b is flown into the tank 140 via a relief valve 109. COPYRIGHT: (C)2006,JPO&NCIPI
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