SPEED ADJUSTING SYSTEM FOR GRINDING WHEEL DRIVES AND THE LIKE

摘要

1380753 Grinding GENERAL ELECTRIC CO 28 Nov 1972 [22 Dec 1971] 54837/72 Heading B3D [Also in Division G3] The signal inputs to the control amplifier of the drive of a grinding wheel are modified so that the peripheral speed is kept constant as the diameter of the wheel is reduced by wear. The modifying effect is obtained by measuring the incremental current needed to accelerate the wheel and using this current to modify either the' desired speed signal or the fed back speed signal. In the embodiment shown the fed back speed signal 36SP1/SP is modified by the potentiometer 174 and is compared, as signal 114, with the fixed demand signal 24SP1/SP to produce a signal for controller 18SP1/SP. To effect an adjustment the drive is switched off by opening contacts 22SP1/SP so that wheel 10SP1/SP slows down and motor 160 runs coupled potentiometers 152, 174 to the position shown which corresponds to the speed needed for a full diameter wheel. When the motor has slowed, contacts 22SP1/SP are closed and the motor 14SP1/SP will accelerate following the ramp function output from demand signal 26SP1/SP. Motor current is detected by resistor 44SP1/SP and this voltage is compared with the voltage setting on potentiometer 49SP1/SP which again corresponds to unworn conditions. The output of incremental current signal generator 40SP1/SP charges capacitor 126 which is used to energize motor 160 and run potentiometers 154, 174 to a new position which corresponds to the worn wheel diameter. In the case where the desired speed signal is modified the current generator output is used to reduce a 'program' signal which is added to the actual speed signal and compared with the demand signal to produce the motor control signal, Fig. 1 (not shown). The adjustment takes place when the grinding wheel is out of contact with the workpiece and can occur automatically on operation of a normal start button.