Patent ID: 7121773

Claim:
An electric drill apparatus having a low profile, comprising: an annular cutter for cutting at a high rotational speed, and having a plurality of cutting blades comprised of cemented carbide tips fixed on its lower end, a motor for rotating at a high speed suitable for a cutting operation of the annular cutter with the cemented carbide tips; a rotary shaft assembly for rotating the annular cutter attached to its leading end about an axis, the direction of which is different from that of an axis of a rotating shaft of the motor; a rotation reduction mechanism disposed between the motor and rotary shaft assembly for transmitting a driving force of the motor to the annular cutter through the rotary shaft assembly; a feed mechanism responsive to an operation of a manual handle, for moving the rotary shaft assembly along with a straight line to advance or retract the annular cutter attached to the rotary shaft assembly with respect to a work piece; an adhesion base disposed below a body of the electric drill apparatus for securing the electric drill apparatus to the work piece; and an automatic motor stopping/re-driving mechanism comprising: a main switching element connected in series between the motor and a power supply; a current detector for detecting a load current flowing through the motor; a determination unit for determining whether the load current detected by the current detector exceeds a first predetermined reference value; and a control unit for controlling the main switching element to turn on/off, wherein when the determination unit determines that the load current exceeds the first reference value, the control unit turns off the main switching element to shut off the current flowing through the motor, and subsequently when the determination unit determines that the load current decreases to be smaller than the first reference value, the control unit turns on the main switching element at a predetermined time after the determination, to supply the current from the power supply to the motor.