| 摘要 |
PURPOSE: A lifting apparatus for lower control arm of attachment device of tractor is provided to accomplish improvements enabling simplified design and accurate adjustment, and two lower control arms to be adjusted independently of each other for a compensation for a vertical slope. CONSTITUTION: An apparatus comprises position recording units(25, 25') for generating a position signal indicative of pivot position of lower control arms(2, 2', 3, 3'), respectively, hydraulic double-acting piston-cylinder units(11, 11', 12, 12') one ends of which are attached to a tractor(1) and the other ends of which are operating at the lower control arms(2, 2', 3, 3') via intermediate lever driving units(47, 48, 49, 50), the piston having at an end thereof cylinder chambers(23, 23') and the piston rod having at an end thereof cylinder chambers(24, 24'), and a switch circuit having directional valves(33, 33') switchable to at least three positions and which have four pairs of ports(31, 31', 32, 32', 34, 34', 36, 36'). A pairs of ports(31, 31') being connected to the cylinder chambers(23, 23'), ports(32, 32') being connected to cylinder chambers(24, 24'), ports(34, 34') being connected to a pressure medium supply source(P), and ports(36, 36') being connected to return lines(37, 37').
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