CONTROL DEVICE FOR QUICK DROP VALVE

PROBLEM TO BE SOLVED: To provide both the rapid dropping function and the floating function with a rapid drop valve by energizing a first or second solenoid valve to control the position of the quick drop valve when a direction control valve reaches the specified position. SOLUTION: When a control valve 17 is moved to the left, a cam 54 closes a switch 49 to energize a solenoid 43 and to move a solenoid valve 34 to the right. When a selector switch 52 is at the indicated position in a figure, a solenoid 38 is energized, a solenoid valve 32 is moved to the right, the low-pressure fluid from a cylinder lowering side 24 is communicated with a spring end 28 of the quick drop valve 11, the high-pressure fluid from the elevating side 23 communicates with a shift end 29, and the valve 11 is moved to the left. The fluid discharged from the elevating side 23 is merged with the fluid from a pump 14, and fills the expanding lowering side 24. The switch 52 is switched to achieve the connection to a solenoid 39, the valve 32 is moved to the left, and when the spring end 28 communicates with a tank, the valve 11 is moved to the left, and conduits 26, 27 are connected to each other to make a blade 13 in the floating condition.