Electromagnetic base drill with intermittent feed

Abstract

The states of contact switches are switched when a mode switch is turned on. If the drilling operation is effected by means of a drill motor in this state, an oscillation signal which is repeatedly set to "H" and "L" in a preset period corresponding to an output of an oscillator is supplied to the control terminal of a firing pulse generator. The firing pulse generator interrupts supply of the control signal to the control terminal of a triac in the above preset period based on the oscillation signal supplied to the control terminal thereof to interrupt supply of an AC power source from a commercial AC power source to a bridge-type rectifier so as to intermittently drive a feed motor which is energized by an output of the rectifier in the above preset period. As a result, the drill motor can be intermittently fed towards a to-be-worked object by means of the feed motor, and, when the feeding operation is interrupted, a cutting operation can be instantaneously stopped and swarf can be cut apart.

Dependencies are inferred from the claim text.