GB726107A - Improvements relating to balancing machines - Google Patents

Abstract

726,107. Balancing machines. SMALL ELECTRIC MOTORS, Ltd. March 25, 1953, No. 8297/53. Class 40 (1) In a balancing machine in which the rotor is mounted in bearings provided with electrical tranducers the outputs of which are combined and operate, via a frequency-selective network, indicators of the magnitude and angular position of the necessary correcting masses in the two balancing planes, the tuning of the network is automatically maintained in correspondence with the frequency of the transducer signals if the speed of the rotor varies. This avoids errors which would otherwise arise from variations of the phase of the signal with respect to the position of the unbalance. In the system described, the position of the correcting masses is indicated stroboscopically, each pulse, resulting from the combination of the transducer signals, flashing a lamp to illuminate a scale on the rotor. Circuit arrangements. The combined signal from the transducers after amplification in tuned amplifiers 8, 14 passes to a circuit 26 for flashing the stroboscopic lamp and to a full wave rectifier 24 which supplies an indicator 25 of the extent of the unbalance. With the aid of a tapping to the rectifier cathode and a capacitor 29, a double frequency signal is passed to a control path comprising a tuned amplifier 30, clipper 33 and discriminator stage 34, whose tuned circuit is resonant at a frequency somewhat above twice the normal rotation frequecy, so that it operates on the substantially linear flank of its response curve giving across secondary 37 a voltage proportional to frequency. The secondary supplies a rectifier via frequency meter 38, and part of the rectified output is applied as bias, through smoothing inductance 40, to the first amplifier valve 8 to compensate for the loss of amplification as the dynamic impedance of the resonant circuit falls and to reactor valves 13, 19, 20 which adjust the frequency to which the amplifiers 8, 14 are tuned. The action is modified by a bias dependent on the strength of the signal through capacitor 29, which signal is rectified between grid and cathode of valve 30 and fed to the first amplifier valve and the reactor valves through 43, 42, to neutralize any strength-dependent component passing the valves 30, 33, 34. The phase of the voltage supplied to the stroboscope triggering circuit is thereby maintained constant with respect to the phase of the control box output.