| 摘要 |
PROBLEM TO BE SOLVED: To detect easily surely an abrasion limit of a guide roller. SOLUTION: Air is supplied to an air passage 74A formed inside a guide roller from a compresser to keep an inside of the air passage 74A at a specific pressure. The air passage 74A, when a guide groove reaches an abrasion limit, is so formed as to be interconnected to the abraded guide groove 72A. Therefore, when the guide groove 72A is abraded to the abbrasion limit to be interconnected to the air passage 74A, air is leaked from the interconnected part to reduce air pressure in the air passage. By detecting drop of the air pressure in the air passage 74A with a pressure sensor 94, the guide groove 72A of the guide roller is detected to have reached the abrasion limit. |
