GB1351387A - Machine tools - Google Patents

Abstract

1351387 Gauging GENERAL ELECTRIC CO 1 April 1971 8442/71 Heading B3B [Also in Division G1] A machine tool comprises a cutting tool 16, an induction motor 13 connected to a three-phase supply 21 for rotating the workpiece relative to the cutting tool 16, means for advancing the workpiece relative to the cutting tool to bring them into engagement for performing a machining operation, and apparatus for sensing the engagement of the tool with the workpiece comprising, means for sensing the no-load input to the motor 13 and storing a first electrical signal representative thereof, means for sensing the power input to the motor 13 in response to loading of said motor and producing a second signal representative thereof, means for combining said first and second signals to produce a third signal which varies according to the difference between the first and second signals, and means responsive to the third signal to provide an indication of the engagement of the tool with the workpiece. The said apparatus includes a transducer 20 connected to the power lines 21, an implifier 30 whose output passes through two channels, the first of which includes an amplifier 40 designed to retain a signal proportional to a no-load condition on the motor 13 and a resistor 52, the second of which includes a resistor 53. The difference between the signals in resistors 52, 53 is fed to a further amplifier 60 which may act through a control circuit 69 to produce a cutting path varied proportionally to a variable reference voltage, and/or a further amplifier 80 to operate, through a solenoid 81, a timer 82.