Patent GB-735657-A (GB)
Title: Improvements in dynamic balancing machines
IPC: G01M1/22
Filed: 1953-01-06
Abstract: 735,657. Electric indicating systems. AVERY, Ltd., W. & T. (Schenck Maschinenfabrik Ges., C.). Jan. 6, 1953, No. 352/53. Class 40 (1). In a device for facilitating calibration and compensation of a dynamic rotor balancing machine wherein a work-piece is rotated between two bearings synchronically with a generator developing two alternating voltages in quadrature, each bearing having an associated electromagnetic unbalance pick-up ; the pick - up voltages are initially compensated by voltages derived from the generator through transformer coupled variable potentiometers which are injected into the respective pick-up circuits so that the respective compensated pick-up circuits produce an artificial appearance of balance on a watt-meter measuring device whose quadrature coils are respectively energized thereby. An unbalanced work-piece 1 (Fig. 1) is rotatable by motor 8 and countershaft 5 on oscillatory bearings 2, 3 together with a quadrature voltage generator 7 and angularly graduated disc 6. Electromagnetic oscillation pick-ups 11, 12 develop voltages corresponding to the mechanical vibrations in amplitude and phase, which are respectively supplied together with the quadrature outputs of generator 7 to device 13 according to the invention which in turn supplies unbalance voltages to the balance analyzing apparatus 14 which may be of the kind described in Specification 715,627. Fig. 3 shows details of device 13 in which the quadrature outputs of generator 7 are connected over leads 20, 21 to energize four pairs of respective transformers 15, 19, the latter having variable resistances 27, 29, 31, 33 in the primary circuits for phase correction at the prevailing rotational speed. The secondaries of each pair are paralleled so that the resultant outputs of adjacent pairs of transformers 15, 19 are in quadrature and are applied to respectively energize potentiometers 26, 28 and 30, 32. The fixed centre tap of potentiometer 26 and the moving tap of potentiometer 28 are connected in the line 22 joining electromagnetic pick-up 11 to the input of balance analyzer 14 on opposite sides of a disabling switch 25, ganged to a similar switch 24 in the line 23 joining pick-up 12 to the balance analyzer, on opposite sides of which are connected the fixed centre tap of potentiometer 30 and the moving tap of potentiometer 32. Opening switches 24, 25 enables the quadrature components of the voltages generated by the oscillation pick-ups 11, 12 to be cancelled out by adjustment of potentiometers 26, 28 and 30, 32, for zero indication by analyzer 14, thus simulating a balanced work-piece. A tare weight of known magnitude is fixed to the work-piece in the left balancing plane positionally corresponding to the zero mark of disc 6 and another similar weight is fixed to the work-piece in the right balancing plane positionally corresponding to the 90 degree mark of disc 6. The oscillation voltages generated by pick-ups 11, 12 are due to the original unbalance + the balance due to the tare weights while the balance analyzer 14 indicates only that due to the tare weights, and may then be adjusted in known manner so that the left tare weight introduces no unbalance in the right balance plane and vice versa for the work-piece under test, and the analyzer may then be calibrated by the addition of tare weights of different magnitudes, after which the device 13 may be disabled by closing switches 24, 25 so that the calibrated and compensated analyzer 14 may be applied to measurement of unbalance in further workpieces. The quadrature generator outputs may alternatively energize their associated potentiometers direct, and the variable outputs between centre and variable taps may be transformer coupled into the appropriate analyzer input circuits. Specification 715,627 is referred to.