Patent GB-570170-A (GB)
Title: Automatic balancing of rotating bodies
IPC: G01M1/34
Filed: 1943-01-26
Abstract: 570,170. Indicating unbalance of rotors electrically. BENDIX AVIATION CORPORATION. Jan. 26, 1943, No. 1332. Convention date, March 25, 1942. [Class 40 (i)] [Also in Groups XIX. XXII and XL] Apparatus for balancing an unbalanced rotatable body comprising means rotatably supporting the body to permit substantial vibration thereof under the action of unbalanced masses in the body, a vibration responsive device operatively associated with the body for generating periodic impulses timed in accordance with its vibrations means dependent on the timing of such impulses for producing a spark at the surface 6f the body at the point of location of the unbalanced masses and means operable with said spark-producing means for burning the sparked surface of the body to compensate for said unbalanced masses. As shown, an unbalanced gyroscopic rotor 10 is mounted on trunnions 11, 12 and rotated at speed, the vibrations of the trunnions being converted into electrical impulses by vibrationresponsive devices 15, 16 feeding transformers 19, 20. The secondaries of the transformers are connected by switches 23, 26 to an amplifier 35 through a network comprising two potentiometers 29, 32 which have been previously adjusted so that with a rotor deliberately unbalanced by a mass near the trunnion 11 or the trunnion 12, respectively, and the switches 23, 26 in upper or lower position, respectively, a voltmeter 36 gives a reading, while with the switches in reversed position, the voltmeter reads zero. In use the switches are set according to which position gives the greater reading on the voltmeter, an electrode 38 being moved into upper or lower position adjacent the rotor with movement of the switches. The amplifier 35 has a device 37 for adjusting the supply to the voltmeter according to whether the voltage is large or small, and a filter 39 compensates for vibrations of a frequency different from the fundamental rotor frequency. The amplifier feeds a transformer 41, the output of which is transformed into a fullwave pulsating direct current by a rectifier 43 before being impressed on the grid 45 of a tube 46. Another portion of the amplifier output is applied to a further grid 47 of the tube 46 and the output of the associated anode 49 is phaseshifted through 90 degrees by a condenser 50 and half-wave rectified in the right-hand half of tube 51, and then impressed on the grid 45 to suppress and boost alternate impulses from the tube 43 which is, however, further controlled by a transformer 59. The plate 53 associated with the grid 45 is connected to the control grid 55 of a gas-filled relay 56 controlled by a condenser 57, rectifier 57a and a transformer 58 supplied from the same source as the transformer 59, the secondary of which is half-wave rectified in the left-hand part of tube 51 to impress on the grid 45 a further voltage which reduces the total voltage on the grid to inoperative level except when the impulses from the transformer 59 and the amplifier 35 coincide, which occurs at the same time as the condenser 57 is fully charged. The impulse from the plate 53 then fires the gas-filled relay 56 and the secondary of the transformer 60 sends a high-voltage current to the electrode 38. This current is boosted by a low-voltage current of high amperage supplied by a transformer 66 through rectifiers 67, 68 controlled by a condenser 65. The electrode 38 which has previously been adjusted angularly by testing with a rotor of known characteristics burns away metal at the unbalanced part of the rotor. The operation continues until the voltmeter reads zero, when the switches 23, 26 are reversed and the operation repeated with the electrode 38 in lowermost position.