Patent GB-610705-A (GB)
Title: Improvements in apparatus for balancing rotary bodies
IPC: G01M1/22
Filed: 1944-03-29
Abstract: 610,705. Balancing rotary bodies. GENERAL ELECTRIC CO., Ltd., and WARD, L. G. March 29, 1944, No. 5824. [Class 40 (i)] [Also in Group XIX] In apparatus of the type having two electrical generators 13, Fig. 1, associated with the two bearings 11 of the rotary body 10 to produce alternating current due to unbalance forces, there are two phase - shifting and potential - dividing networks 18, 19, 20 and 21, 22, 24, respectively, Fig. 3, arranged to be fed with the outputs of the two generators, respectively, and each having output phase control means capable of being set to give alternatively two different and variable phase-shifts, output potential control means capable of being set to give alternatively two different and variable potential divisions, and a control switch 39 which applies the mixed outputs of the two networks alternatively to a meter and to a device for enabling the position of the unbalance to be determined. The resistor 20 in each phaseshifting circuit has two sliding contacts a, b and c, d, respectively, which can be alternatively connected by a switch 21 to one end 'of a potentiometer resistor 22, the other end of which is connected to a common return lead 23 to the generators 13. Each resistor 22 has two sliding contacts e, f and g, h, respectively, which can be alternatively connected by a switch 24 to an output socket 25. The four switches 21, 24 are ganged. Leads 29 from the socket 25 connect to a linear amplifier 27 which is connected to a meter 30 and to the cathode of a strobotron grid-controlled gasdischarge tube 32, through one of three leads 34 and one of three leads 37. The amplifier 27 is also connected by a lead 34 to a two-way switch 39 which, in the position shown, makes a connection to the meter 30 and the third lead 34, and in its other position connects the amplifier to a switch 40 which provides alternative tappings on a bias battery 41 for the grid 42 in the tube 32. Two pairs of pointers 43A, 43B and 44A, 44B are carried on brackets 45, 46 which are adjustable about the rotor axis, one pointer of each pair being adjustable in an arcuate slot in the bracket. Two pivoted pointers 48, 49 are disposed respectively in the two balancing planes to indicate more accurately the positions of balance points. The rotor 10 is driven through a belt 14 by a synchronous motor, means for lifting the belt clear of the rotor being provided. An electrically-operated means prevents the motor being switched on when the belt is raised, and to prevent the belt from being raised when the motor is switched on. Operation. A master rotor with a detachable unbalance weight in the left-hand plane is fixed in the apparatus, rotated, and sliding contacts a, c adjusted until the currents from the two generators 13 are in phase with each other as shown by the meter 30 indicating a minimum. The contacts e, f are then adjusted so that each rests nn a point of the same potential as shown when the meter 30 indicates nil. The output from one generator now eliminates that from the other. The unbalance weight is then removed and fixed in the other balancing plane, the ganged switches 21, 24 thrown over, and the remaining sliding contacts b, d, f, h adjusted so that the output from the second generator cancels that from the first. The switches 21, 24 are now reversed, whereby a reading is produced in the meter 30 which is proportional to the size of the unbalance in the right-hand plane. The weight is returned to the first position, the switches reversed, and an indication is given of the unbalance in the left-hand plane. With the master rotor still running, the switch 39 is moved to the strobotron position, and one of the main pointers 43A set opposite a mark on the rotor that appears stationary when the strobotron has been adjusted by the switch 40 to fire only at the maximum E.M.F. The rotor is stopped and turned by hand until the viewed mark is opposite the set pointer 43A. By manipulating the secondary pointer 43B relatively to the main pointer 43A, the position of the required balance weight is indicated. The master rotor is now replaced by a rotor to be tested, the two pointers 43A, 43B moved together as a unit until the pointer 43A is opposite a mark on the rotor which appears stationary, as before, the rotor stopped, moved until the mark is opposite the pointer 43B, when the position for the balance weight is then on top of the rotor. The last operation is repeated for the other plane, using the other pointer 44A, 44B. The apparatus can be used where a master motor is not available by driving two small alternators from the rotor to be tested and applying the voltage therefrom for bucking-out the voltages from the vibration generators 13, then adding known weights to the rotor so that the amplifying and mixing circuit can be adjusted as before. In a modification, the strobotron is replaced by a single phase alternator and cathode-ray oscillograph, the alternator being driven from the rotor and its output voltage applied to the deflecting plates of the oscillograph. The stator can be adjusted by hand to bring into phase the voltages of the alternator and amplified vibration generators, to give an indication of the position of the unbalance. Specification 585,152 is referred to.