| 摘要 |
PURPOSE:To prevent wrong operation and turning-over of a car by prohibiting the boom-related operation when a jack is not elongated. CONSTITUTION:An electrical contact LSI which is OFF-operated by a dog 24 when a boom 3 is in stored state is installed on the storing stay 23 of the boom 3, and the electrical contact LS2 which is OFF-operated when a jack cylinder 12 is elongated over a certain length is installed on a jack 11. If the boom 3 is operated erroneously and is departed from the stay 23, when the jack 11 is in no-elongation state by the operation of the cylinder 12, the electrical contact LSI is switched, and the electromagnetic part 22a is brought into conduction state. Through said conduction, the electromagnetic change-over valve 22 is switched to the lower position to allow the discharge oil from a pump 14 to circulate into an oil reservoir, and feeding of pressurized oil to the motor 7 for a turning base 2, the rising and falling cylinder 8 for boom 3, and the change-over valve group 15-17 of the expansion cylinder 9 for elongating and contracting boom is intercepted, and the boom-related operation can be prohibited. |
