| 摘要 |
PROBLEM TO BE SOLVED: To surely prevent buried metals such as reinforcing steel, a gas pipe, a water pipe, and a conduit for an electric cable from being cut when boring a concrete structure. SOLUTION: A controller 12 comprises a control part 13 controlling the on/off operation of a power source switch of a core drill 11, a detecting part 14 measuring a load current of a motor 5 for cutting, a computing part 15 computing a rate of a variation per unit time of the load current detected in the detecting part 14, and a comparing part 16 outputting a signal to the control part 13 when the rate of the variation of the current is found to exceed a threshold by comparing the rate of the variation of the load current computed by the computing part 15 with a preset threshold, wherein the control part 13 conducts the off-operation of the power source switch of the core drill 11 when the rate of the variation per unit time of the load current of the motor 5 for cutting which varies when a blade of the core drill 11 bites into metals such as the reinforcing steel. COPYRIGHT: (C)2009,JPO&INPIT
|
