| 摘要 |
PURPOSE:To detect any fault of a tool by the continuous rise of an armature current of a DC motor for driving a supply device, thereby to detect the fault in the tool accurately and with a high reliability without using any specific senser or jig. CONSTITUTION:In a case where a tool 5 is normal, the armature current of a DC motor 10 is small, and a voltage generated at a resistor 23 is also small. Hence, a high level signal is not generated from a comparator 25, and even when a signal is generated on some reason or other, a tool fault signal is not produced from a time limit circuit 27 because the time of the signal generated is extremely small. In a case where a fault, that is, a damage or an excessive wear occurs, a working resistance increases, and the feed resistance of a slide 6 increases, and hence the load of a motor 10 becomes large and the armature current becomes continuously large. For this reason, the output of the comparator 25 assumes continuously a high level, and a tool fault signal is produced as output from the time limit circuit 27, thus a fault alarm sender 28 being operated. |
