GB922217A - Improvements in dynamic balancing machines and an improved method of empolying such machines - Google Patents

Abstract

922,217. Balancing rotors electrically. BIRFIELD ENGINEERING Ltd. June 18, 1959 [June 18, 1958], No. 19448/58. Class 40 (1). In a dynamic balancing machine comprising two vibration pickups whose outputs are combined in standard manner to determine the phase and magnitude of the unbalance in each of two predetermined balancing planes, the phase of each unbalance signal is used to position the rotor angularly so that the unbalance can be removed by spot welding a weight of appropriate magnitude, indicated by the amplitude of the unbalance signal. In one embodiment (Fig. 1) a shaft 4 is supported for rotation by a motor 19 between bearings 5 flexibly mounted on leaf springs 6 whose vibrations are sensed by pick-ups 11a, 11b. A welding gun 9a, 9b is located at each balancing plane to enable selected balancing weights W to be added to the shaft. To determine the phase and magnitude of the unbalance at the left-hand end 4a, signals from the pick-ups proportional to the velocity of vibration are combined at 12a in a ratio depending on the spacings, integrated at 13a to produce an output proportional to the amplitude of unbalance at 4a, and filtered at 22a to produce a D.C. voltage proportional to the fundamental component only. Unit 22a also contains a uniselector with several banks of contacts which, on one bank, hunts for the contact with a voltage equal to the unbalance signal, and, on another bank, lights the appropriate compartment of a rack 8a containing a series of different weights W. The signal from integrator 13a is also fed through a gain control unit 15a and a phase detector 16a where it is compared with the phase of the voltage from a reference generator 17 also driven by motor 19, to give a proportionate output signal which, after amplification at 20a, energizes a servomotor 21a to drive a selsyn transmitter 23a and indicator 25a. The motor 19 stops when lamps in both racks 8a, 8b are lit, and the selsyn units 23 are successively energized to rotate the shaft automatically to the correct angular position for the selected balancing weight to be welded to the shaft. In another embodiment (Fig. 2) the signals from the pickup heads 31a, 31b are amplified at 35a, 35b and recorded on two magnetic drums 34a, 34b driven synchronously with the test shaft. The output from amplifiers 35a, 35b are also rectified and fed to an indicator unit 36a, 36b comprising a moving coil galvanometer 37, 38 (Fig. 3) whose pointer 39 carries a flag 40 moving between lamps 41 and photo-cells 43, whereby an indicator lamp is energized to denote the magnitude of the required balancing weights. The driving motor is now de-energized and a centrifugal switch comes into operation when the shaft is almost stationary to feed the recorded signals on one of the drums 34a, 34b via a pick-up head 45a, 45b to a photo-electric galvanometer unit similar to the one above described, but containing a lamp 41 and photo-cell 43 in the zero position of pointer 39, and used to energize a brake 33 to locate the shaft in the correct angular position.