| CPC A01B 63/1006 (2013.01) | 15 Claims |
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1. A hydraulic circuit for an agricultural tractor, the hydraulic circuit comprising:
a hydraulic pump configured to supply hydraulic oil;
a horizontal control cylinder configured to control horizontality of a working machine for a work target surface by using a flow output from the hydraulic pump;
a horizontal control valve disposed between the hydraulic pump and the horizontal control cylinder, and configured to control operation of the horizontal control cylinder;
a lifting control valve configured to control operation of a lifting control cylinder that controls a height of the working machine for the work target surface by using the flow output from the hydraulic pump;
a lifting connection valve disposed between the hydraulic pump and the lifting control valve, and configured to selectively connect and block a flow path between the hydraulic pump and the lifting control valve; and
a basic hydraulic line forming flow paths between the hydraulic pump, the horizontal control cylinder, the horizontal control valve, the lifting control valve, and the lifting connection valve;
wherein the basic hydraulic line comprises:
a pump line connecting the hydraulic pump and the horizontal control valve; and
a branch line branching off from the pump line, and connected to the lifting connection valve,
wherein the lifting control valve controls whether to operate the lifting control cylinder by selectively connecting and blocking a flow path between the lifting connection valve and the lifting control cylinder,
wherein the lifting connection valve is provided such that, while the operation of the horizontal control cylinder is stopped, an overall flow output from the hydraulic pump is provided to the lifting control valve.
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