| 摘要 |
<p>PURPOSE:To detect drill breakage without fail even if each drill diameter differs, by installing plural optical fibers in group receiving reflected light from a drill, while providing an operational device, and finding drill breakage data from a combination of the reflected light quantities. CONSTITUTION:Both first and second fiber groups 10 and 11 consisting of a pair of bundles of a light emitting optical fiber and a light receiving optical fiber are installed, while the first threshold value conformed to a breakage quantity l1 of a drill 2a in a diameter R1 and the second threshold value conformed to a breakage quantity l2 of a drill 2b in a diameter R2 (R1>R2) are installed. And, the first threshold value is compared with a first electric signal of the first optical fiber group 10 at an operation part 16, and simultaneously it is compared with a second electric signal of the second optical fiber group 11. In consequence of the operation 16, if any of electric signals is lower than these first and second threshold values, it means that there is breakage and the breakage quantity is more than l1, and if it is dropped to only the second threshold value, it is so judged that there is breakage in the drill 2a and the breakage quantity l is l1>l>l2.</p> |
