To surely prevent the breakage of an on-vehicle crane caused by over load with a structure of low cost.
In an on-vehicle crane comprising a support 13 attached to a loading space 12 of a vehicle, a crane arm 14 pivoted on an upper end of a column 17 of the support, a power unit 15 for oscillating the crane arm to move up and down the same, and a winch device for winding and unwinding a wire 68 comprising a hook at the pointed end of the same, a limit switch 78 installed between the column and the crane arm, is operated when the lowermost position of the crane arm is detected, to cut the power supply to a motor of the winch device, and an up blow valve and a thermal blow valve installed on the power unit are operated when the pressure of the hydraulic operating oil in the hydraulic cylinder device 34 is more than a specific value, to prevent the supply of the hydraulic operating oil to the hydraulic cylinder, and to make the exhaust of the hydraulic operating oil from the hydraulic cylinder device possible.
ISHIJIMA MASATOMO
SADAKATA KAZUHIKO
| JPH04292397A | 1992-10-16 | |||
| JPH01137999U | 1989-09-20 | |||
| JPS4824867B1 | 1973-07-24 | |||
| JPS4823110Y1 | 1973-07-05 |
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