Patent GB-904834-A (GB)
Title: Apparatus for vectorial determination of the dynamic unbalance of rotors
IPC: G01M1/08
Filed: 1959-01-05
Abstract: 904,834. Measuring dynamic unbalances of rotors. AVERY Ltd., W. & T. Jan. 5, 1959 [Jan. 16, 1958], No. 318/59. Class 40 (1). [Also in Group XXXVI] Apparatus measuring magnitude and angle of unbalance of a rotor comprising a pick-up responsive to the unbalance vibrations thereof, a ganged pair of sine and cosine potentiometers having sliders producing two 90 degrees outphased sinusoidal voltages combined to a resultant voltage variable in phase according to the potentiometer slider settings, and a wattmeter instrument comparing the pick-up output with the resultant voltage for adjustment to phase difference of 0 degrees or 90 degrees. Fig. 1 shows apparatus for determining the magnitude and phase angle of a vector voltage derived from a moving coil transducer 21 responsive to the unbalance of a rotor and applied to energize the moving coil of a wattmeter 1 whose field coils are energized by a combination of two voltages in quadrature derived from 90 degrees spaced sliders 5, 6 of annular potentiometers having taps at 90 degrees intervals which are respectively interconnected over leads 7, 8 to the moving contacts 9, 10 of a relay 11 controlled by commutator 12 ganged for rotation with the potentiometer sliders by calibrated knob 14; the relay selecting alternative windings of phase generator 20 driven synchronously with the unbalanced rotor, which has 2 pairs of 90 degrees spaced windings staggered by 45 degrees. The potentiometer sliders are rotated by knob 14 to adjust the components in quadrature of the wattmeter field energization until the instrument reads maximum (Figs. 1a, 1b, not shown) and indicates the magnitude of the unbalance vector voltage; the phase angle of which is indicated by the calibrated scale 15 of the knob. The wattmeter is then adjusted for zero indication when the phase angle is again indicated by the knob setting, with 90 degrees error. In a modification (Fig. 2, not shown), there is provided a second wattmeter whose moving coil is energized from the unbalance vector voltage and whose field coils are energized from further sliders of the potentiometers displaced 90 degrees relatively to sliders 5, 6 so that the wattmeters are simultaneously adjustable for respective maximum and minimum readings. Vector diagrams of the variable potentiometric voltages are given (Figs. 2a, 2b, not shown). Fig. 3 shows a rotor balancing apparatus wherein a body 60 to be balanced is held by a receiver 61 rotatably carried in bearings of a spring-mounted sleeve 64 by vertical spindle 62 having a magnetic brake 65, operated by relay 66 in tandem with the windings of rotating field transmitter 68 driven with phase generator 20 and rotor 60, and receiver 69 driven with annular potentiometers as described above having 90 degrees spaced sliders adjustable by calibrated knob 14. A commutator reversing switch 20, also driven from knob 14, is connected in the excitation of the potentiometers from phase generator 20, and the sliders excite the fields of respective moving coil wattmeters 1, 40 whose moving coils are together energized by an unbalance vector voltage from vibration sensitive transducer 21 linked to sleeve 64, and the magnitude and phase angle of such voltage are determined as above; the relay 66 being operated to lock rotor 60 in an angular position corresponding to the unbalance phase angle adjustment of the potentiometer shaft for unbalance marking or correction. Fig. 4 shows an automatic rotor balancing apparatus wherein a body 60 is rotated with receiver 61 with a phase generator 20 to generate an unbalance vector voltage in transducer 21 which energizes the moving coils 23a, 23b of wattmeters 1, 40 whose field coils are energized respectively by sine and cosine voltages from annular potentiometers 5, 6, energized by the phase generator. The deflection of wattmeter 1 in accordance with the phase angle of the unbalance voltage makes contact 73 or 74 according to sense, which over contacts of switch 76 energizes servomotor 75 in the appropriate direction to adjust annular potentiometers 5, 6 to a position in which the deflection of wattmeter 1 is restored to zero while that of wattmeter 40 is at maximum, representing the unbalance amplitude. A rotary field transmitter 78 is driven by the motor (which is arrested after a rotation representing the degree of unbalance and thus the phase angle) so that on operation of switch 76 the signals from the transmitter are compared with those of a receiver 79 driven by motor 87 to operate relay 81 at coincidence to control the motor so that it drives a rotatary drill chuck 83 about an axis 84 through an angle corresponding to the phase angle, with reference to the body 60 when placed in a receiver 61 in correspondence to its position for rotatary unbalance testing. The drill is thus positioned at the point of the body from which material must be removed to achieve balance. Switch 76 also connects a second arrangement of motor 75<SP>1</SP>, transmitter 78<SP>1</SP>, and potentiometers 5<SP>1</SP>, 61 to replace 75, 78, 5, 6 so that the unbalance position of a second body may be determined and stored as a rotation of transmitter 78 while the drill assembly is being positioned to the unbalance point of a first body previously tested. The annular potentiometers may be replaced by phase variation rotary transformers having fixed sine and cosine windings energized from the phase generator and rotatable secondary windings, adjustable to vary the proportions of induced sine and cosine voltages.