Title:
BOOM HOISTING DRIVE CONTROL DEVICE FOR HIGH LIFT WORK VEHICLE
Document Type and Number:
Japanese Patent JP3392264
Kind Code:
B2
Abstract:
PROBLEM TO BE SOLVED: To eliminate boom hoisting when the first oil path is damaged, by applying an oil pressure in the second oil path to act as a pilot pressure in a counterbalanced valve with check valve, providing a solenoid switching valve in a pilot oil path, and providing a detector of detecting switching to a boom hoisting drive side of a direction switching valve in the direction switching valve.
SOLUTION: When a direction switching valve 8 is operated to a boom hoisting drive side, a solenoid switching valve 13 is switched to the first position A by a detecting result of a detector 14, and a pilot pressure from the second oil path 10 acts in a counterbalanced valve 12 with check valve, to drive a boom hoisted. In a condition that an oil chamber 7a of a leveling hydraulic cylinder 7 is on the load holding side, when stopped hoisting moving the boom with the direction control valve 8 neutral, an oil pressure is generated in the second oil path 10, but the solenoid switching valve 13 is placed in the second position B, consequently to bleed the pilot pressure of the counterbalanced valve 12 with check valve. In this condition, even when damaged the first oil path 9, the boom is prevented from its hoisting by the counterbalanced valve 12 with check valve.
Inventors:
Hiroshi Kawamoto
Hitoshi Okochi
Shuichi Masuda
Hitoshi Okochi
Shuichi Masuda
Application Number:
JP19431895A
Publication Date:
March 31, 2003
Filing Date:
July 05, 1995
Export Citation:
Assignee:
Tadano Co., Ltd.
International Classes:
B66F9/06; B66F9/22; B66F11/04; F15B11/20; (IPC1-7): B66F9/06; B66F9/22; B66F11/04; F15B11/20
Domestic Patent References:
| JP632485U | ||||
| JP532395U |
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