| 摘要 |
PROBLEM TO BE SOLVED: To provide a practical rotation detecting device which can endure a long period of use without the fear of damage due to contact with earth, stone, or water containing earth and sand. SOLUTION: This roller bit has a cutter part 9 and a fixed shaft part 10 passed through a through hole 9A in the cutter part 9 and by which the cutter part 9 is rotatably supported. The fixed shaft part 10 is provided with an oil supply passage 20 for supplying pressure oil and a n oil discharge passage 21 for discharging the pressure oil, and the cutter part 9 is provided with a communicating passage 22 for communicating the oil supply passage 20 to the oil discharge passage 21 so that the oil supply passage 20 and the oil discharge passage 21 are intermittently communicated to each other by the communicating passage 22 as the cutter part 9 rotates to guide the pressure oil in the oil supply passage 20 into the oil discharge passage 21. Further, a pressure sensor 26 which yields an electric signal on detecting the drop of the pressure oil and a relief valve 25 are provided, respectively, upstream and downstream of a supply duct 20a that guides the pressure oil to the oil supply passage 20, and when the oil supply passage 20 is communicated to the oil discharge passage 21 an indicator lamp 27 is blinked by the electric signal issued by the pressure sensor 26 to detect the rotation of the roller bit 4. |
