GB632666A - Improvements in or relating to rotor balancing machines - Google Patents

Abstract

632,666. Testing balance of rotors. SPERRY GYROSCOPE CO., Inc. Oct. 30, 1946, No. 32298. Convention date, Oct. 30, 1945. [Class 106 (ii)] [Also in Group XXXVIII] Rotor - balancing apparatus comprises two adjustably-spaced resilient mountings each including a member supported by a group of resilient elements with freedom to vibrate in a plane normal to the axis of a rotor to be tested, the two members being so constructed as to receive the ends of a rotor adaptor in which the rotor is to be mounted, electrical means for measuring the vibrations of the rotor in two planes located in the vicinities of the ends thereof, means for generating an electrical signal varying with the angular position of the rotor and means for comparing the output of said measuring means with said signal to determine the location of unbalance of the rotor. The rotor 66, Fig. 2, is mounted in adjustable bearings in an adaptor 70 which rests in supports 20, each of which is symmetrically supported by three adjustable springs 22 (see also Fig. 4) connected at their opposite ends to arms 19 of a headstock slidable on a bedplate 11. The supports 20, which are arranged to be at a distance apart calculated for each type and size of rotor, each carry an armature 21 into which projects a central pole of a horseshoe magnet 27, a coil 29 being wound on the central pole so as to generate a varying voltage when the armature 21 vibrates due to rotor unbalance. The coils 29 are connected through slip-rings 39 and potentiometers 46, 47 to a switch 50 by means of which either coil is connected to a terminal EV of the electrical circuit, Fig. 8. This unbalance voltage is then attenuated by a potentiometer 191 and, with a switch 172 set to measure this voltage, the latter is applied to one grid of a double-triode valve 173, the output of which is amplified by a triode valve 174, filtered by a network 161 and further amplified and detected by a triode 175 and a double-diodetriode 176. The output of the latter is connected to a transformer 177, the secondary winding of which is connected to the diode anodes of the valve 176 where the unbalance signal is rectified and indicated by a meter 160. The reading of this meter, taken in conjunction with the settings of the potentiometers 191 and 46 or 47 is an indication of the amount of correction required by the rotor. The switch 172 is then positioned so that a reference voltage derived from an adjustably mounted photo-electric cell 146, Fig. 4, into which light from a lamp 144 is reflected from a partially darkened and partially polished portion of the rotor, is applied to the other grid of the double triode 173 and, after further amplification and rectification by the valves 174, 175 and 176, to the meter 160. Potentiometers 190, 200 are then adjusted until the meter indication corresponds to that given by the unbalance voltage after which the switch 172 is operated to apply both the unbalance and the reference voltages simultaneously to the double triode 173. The pick-up magnet 27 and coil 29 are then rotated by a calibrated disc 25 until the unbalance and reference voltages are in anti. phase as indicated by a zero reading on the meter 160. The dial 25, read against a pointer 31, then indicates the position of the unbalance. The switch 50 is then thrown over and the amount and position of unbalance is measured for the other end of the rotor in the same manner. The meter 160 is initially zeroized by a backing-off potential derived from a potentiometer 186 connected across one of two voltage regulator valves 181, 182 of the power supply circuit. If the rotor under test is of the bucket type, it is driven by an air jet from a nozzle 78, Figs. 2 and 4, a control valve lever 103 being initially set so that the air is led directly to the nozzle for starting purposes. When the desired speed has been attained, the lever 103 is thrown over so that the air is led by a needle valve 117 and through an adjustable pressure regulator 120 to the nozzle 78. If a smooth rotor is to be tested the nozzle 78 is replaced by a plug 111, Fig. 6, and a nozzle 131 having a hood 135 is inserted into an otherwise plugged duct 110 to which air is led, 'when the control lever 103 is in the running position, through a regulator-byepass valve 125 instead of through the pressure regulator. Specifications 498,899 and 511,320 are referred to.