Patent GB-585152-A (GB)
Title: Improved machine for balancing rotary bodies
IPC: G01M1/22
Filed: 1943-12-24
Abstract: 585,152. Balance of rotors; testing electrically. JACK & HEINTZ, Inc. Dec. 24, 1943, No. 21655: Convention date, Nov. 20, 1942. [Class 40 (i)] [Also in Group XIX] In a device for testing the balance of rotors, the rotor is mounted in a pair of bearing assemblies each of which is rigid axially of the rotor, but is free to move in any direction in a plane, perpendicular to the axis of rotation, and is connected to electrical means for generating voltage in response to, such movement, said voltage being amplified to indicate the degree of unbalance of the rotor, means also being provided for indicating the point of unbalance, e.g. a stroboscopic lamp. The rotor 4 is mounted between ball bearings carried in plates 9, 10. Each plate is supported by three cylinder assemblies 11 each comprising a central wire 13 (Fig. 6) fixed to the bearing plate 10 at one end and to the cylinder at the other end, and passing through a flexible diaphragm 15, so that the bearing plate can move in any direction in a plane perpendicular to the axis of rotation, but not otherwise. Movement is damped by threading a number of beads 18 on the wire 13 and filling the cylinder with a fluid. The cylinder assemblies 11 carrying jihe bearing plate 9 are mounted in a support 107 fixed to the base-plate 19, which is flexibly mounted at 20. Those carrying the bearing plate 10 are mounted in a support 108 fixed to a carriage 31 sliding between balls 37, 42 and urged towards the bearing plate 9 by a tension spring 32. This provides for the mounting of different size rotors. The sliding carriage 31 is clamped in position before the test. The rotor 4 is rotated by an air blast from nozzle 66. Air is supplied at 68 (Fig. 13) through filter 69, regulator 70, with pressure gauge valve 72 and adjustable needle valve 73 to nozzle 66. The valves 72, 73 can be byepassed by a foot-valve 72. Electrical connections.-The electrical pickups 28, 29 are preferably moving-coil type having bucking coils to cancel the effect of stray magnetic fields. The moving coils are connected by rods 26, 27 to the bearing plates 9, 10. Output from the pick-ups is fed through two parallel systems comprising input transformers 79, switches 80 for selecting the frequency range, mechanically interconnected at the push-button unit 81, amplifiers 82, bandpass filter 83 for filtering off voltages caused by extraneous noise such as ball bearing noise, to the mixer 84 where the two currents are mixed in correct amplitude and phase, thence to the selective amplifier 86 and meter 89 which indicates the amount of unbalance. The position of the unbalance is indicated stroboscopically by a lamp 93 which flashes once every-revolution of the rotor. Voltage from the amplifier 86 passes via the foot-actuated switch 109, phase corrector 111, flash amplifier 92 where the wave shape is changed to a very sharp wave front for flashing the lamp 93. By actuating the foot switch 109, the lamp is flashed from a time wave generator 110 for checking the speed of the rotor. Operation.-Hand valve 72 is opened and the foot valve 75 temporarily opened to raise the speed of the rotor rapidly to a predetermined speed, e.g. 12,000 r.p.m., which must be higher than the natural frequency of the bearing suspension, the speed being checked stroboscopically from the time wave generator 110 and maintained by adjustment of the needle valve 73. By, operating at a speed above such natural frequency, and by suitable adjustment of amplitude and phase of the two currents before mixing, a reading is obtained on the meter 89 proportional to the amount of material to be removed from the rotor at the point illuminated by the stroboscopic lamp 93. For identifying this point, the periphery of the rotor may be provided with indicia. The right and left hand sides of the rotor are separately tested-for balance by actuation of the switch R and L of the switch box 85.