| 摘要 |
PURPOSE:To prevent a drill from breaking and a motor from burning and to save the consumption of electric power by detecting the amount of load of the electric drill motor that varies according to the change of cutting resistance. CONSTITUTION:A detecting section having several variable resistors 19, 19', 26, 26' and change-over switches 32, 32 is provided on the operating circuit of the electrical drill 3 and the feed motor 4 in order to detect the amount of load as change of voltage. When a signal voltage exceeding the control level has been detected, the electrical power circuit of the feed motor 4 only or of the electrical drill 3 also interrupted. When an overload is applied on the running drill 3, the motor stops automatically to prevent its breakage. |
