To attain the high efficiency of work and to reduce operator's fatigue and moreover to prevent misoperation by simplifying the operation of the clamping system of a body frame and a cutter support frame.
This excavation device for the underside of a pipe is provided with a clamp changeover main operating valve 73 provided at an intermediate part of an oil passage extending from a hydraulic pump 72 to a front clamp cylinder 26 and rear clamp cylinders 37, 38; an installation work changeover operating valve 84 provided at an intermediate part of a branch oil passage branched from the oil passage between the clamp changeover main operating valve 73 and the front clamp cylinder 26 and rear clamp cylinders 37, 38, to reach a middle clamp cylinder 53; and a clamp operation control valve 87 operated by a clamp opening/closing changeover switch 95 to change the direction of pilot pressure supplied to the clamp changeover main operating valve 73. The excavation device is further provided with an installation work changeover control valve 89 operated by an installation work changeover switch 96 to change the direction of pilot pressure supplied to the installation work changeover operating valve 84.
KIMOTO KENZO
MATSUDA MITSUNORI
