DEVICE FOR PREVENTING EXPANSION OF OUTRIGGER OF SPECIAL VEHICLE

PURPOSE:To surely prevent the inadvertent expansion of an outrigger by feeding pressure oil from a steering pump to the contracting side oil passage of a double acting cylinder via a selector valve, a pressure reducing valve, and a check valve during the travel of a special vehicle. CONSTITUTION:During the travel of a special vehicle, if a PTO coupling 18 is separated, a changeover switch 42 is turned off to change over an electromagnetic selector valve 41 to an open side. Then, so long as the special vehicle is in a traveling posture, pressure oil from a normally-operated steering pump 21 is fed to a contracting side oil passage 10 via the branch passage 25B of a steering oil passage 25, an electromagnetic valve 41, a pressure reducing valve 40, and a check valve 39. The fed pressure oil acts on the contracting chambers 15B, 5B of a slide cylinder 15 and a jack cylinder 5 to keep the cylinder 15, 5 in a contracted condition. Hence, during the travel of the special vehicle, the inadvertent expansion of an outrigger can be prevented irrespective of the leakage or reduction in volume of the pressure oil, etc.