| 摘要 |
PURPOSE: To determine the disconnection of a power cable for a solenoid valve quickly, and to correspond to the disconnection at an early stage by arranging light-emitting elements in parallel with a wire and a capable for the electromagnetic solenoid of the solenoid valve supplying the pushing side of a hydraulic cylinder with a working fluid respectively and disposing the light-emitting elements on the front fo a target. CONSTITUTION: The rear end of a buried pipe 1 is pushed while excavating the ground by an excavating head placed in a cutting edge 3, and the cutting edge 3, a leader pipe 2 and the buried pipe 1 are pushed into the ground. The bending of course due to the properties of the ground is confirmed by monitoring a target 8 by a TV camera 9 at that time. When bending is confirmed, hydraulic cylinders 6 placed in the direction of curved propagation are operated, the direction of the cutting edge is corrected, and excavation is continued. Solenoids for solenoid valves corresponding to the hydraulic cylinders 6 are supplied with electricity through power cables by remote control and excited and opened, and pressure oil is fed and the hydraulic cylinders 6 are worked. Light-emitting diodes corresponding to the operated hydraulic cylinders 6 emit light at that time, and the normal operation of the hydraulic cylinders is displayed. When disconnection is generated in the power cable, the light-emitting diode does not emit light, thus instantaneously discriminating the working of the solenoid valve by viewing the light-emitting diode. |
