Patent GB-420383-A (GB)
Title: Method of and apparatus for balancing rotatable bodies
IPC: G01M1/22
Filed: 1933-05-31
Abstract: 420,383. Testing balance of rotary bodies. TINIUS OLSEN TESTING MACHINE CO., 500, N. 12th Street, Philadelphia, U.S.A.-(Assignees of Ohlson, B. E. ; 500, N. 12th Street, Philadelphia, U.S.A.) May 31, 1933, No. 15749. Convention date, April 14. [Class 106 (ii)] Consists in translating the energy of the vibrations due to the unbalanced forces in the rotatable body into alternating electrical current, converting this current into direct current by mechanical means and measuring the direct current. Standards 5 longitudinally adjustable on a base 3, Fig. 2, are chambered to provide for the free vibration of rods 8 rotatably mounted in the base plates of the standards. The rods are arranged in pairs and carry worm gears 9, Fig. 4, of opposite hand gearing with right-and-left handed worms on a shaft 10 operated by a handle 11 by which the natural period of vibration of a set may be varied. A spring 12 bears on the gears and is secured at 13 to the standard. The rods are flat between the ends and have secured to their upper ends rods 15, more flexible than the rods 8, the rods 15 being rotatably secured to a vibrating cradle 16. In order to provide a right or left hand pivot for the cradle 16, each standard 5 has journalled in it a shaft 18, Fig. 5, carrying a pinion 19 gearing with a rack 20 carrying in turn a plunger 21 adapted to engage a ball bearing 22 in the frame 16. End standards 23 adjustably fixed to the base 3 carry solenoids 25, Fig. 12, with which co-operate magnetized armatures 26 fixed to the frame 16. The latter is provided with sets of rollers 27 mounted in adjustable brackets 28 to support the shaft of the rotor 29 to be tested. A top roller 32 fixed to a spring 30 prevents upward movement of the shaft. An electric motor 33 drives the rotor through a belt and universally jointed shaft 37, a coupling member 40 having pins 41 to engage holes in a flanged collar 42 friction tight on the rotor shaft. The member 40 has two tapped diametrically opposite holes equidistant from the centre into one of which a screw 46 of known weight is fixed, the disc being balanced with the screw in position. By removing the screw a definite unbalance is created. Commutator mechanism. The shaft 37 drives through gearing 46, 47 a commutator carrying insulated conducting rings 51, 52 engaged by brushes 55, 56 and connected with segments 180‹ apart. A holder 58 carries two sets of brush carriers 90‹ apart, each set comprising two brushes 180‹ apart. The holder 58 has spaced conducting rings 69, 70. One set of brushes are connected by leads to contacts 72, 74 and the other pair to contacts 76, 78. Spring contacts 79, 81 normally engage the contacts 76, 78 and are connected by leads 80, 82 to rings 69, 70. The switch thus formed is controlled by a push rod 83 of insulating material which has its free end slotted so that it can pass by the contacts 76, 78 and move the switch 79, 81 from contacts 76, 78 to contacts 72, 74 so that either pair of brushes bearing on the segments 63, 54 may be connected to the rings 69, 70. The rod 83 passes through an angle indicating disc 84 fixed to the holder 58 and working in conjunction with a fixed pointer 85. The drive shaft 37 has fixed to it an angle indicating disc 88. Electrical circuit. The solenoids 25 have a common lead 89 connected to the brush 55. The left hand solenoid 25 is connected by lead 90 to the contact 91 of a double throw switch 100 having contacts 101, 102 paired with contacts 91, 103, the latter being connected by the lead 104 with the right hand solenoids. The contacts 101, 102 are connected by the line 105 with the brush 56 connected in turn by lead 106 with one terminal of a direct current meter 107, the other terminal of which is connected by the line 108 with the brush 87. Operation. The rotor is placed on the bearings and coupled to the drive. One shaft 18 is now actuated to lock the support 16 at one end forming a pivot, and the other shaft 18 to unlock the other end. The vibration of the support and magnets generates an alternating current, the magnitude of which is proportional to the amplitude of the vibration and the phase relation to the angular location of the unbalance. By adjusting the commutator brushes until the commutator changes the direction of the current just when the E.M.F. is zero, the direct current meter indicates the maximum deflection. If the other pair of brushes displaced 90‹ from the first are connected by pushing in the rod 83, the meter should read zero as the commutator splits up the alternating current into two halves which counteract each other on the direct current meter. As this set of brushes will change the direction of current when the E.M.F. is a maximum, a slight change in position will result in a larger deflection of the meter. The angle of unbalance read on the disc 84 is referred to the body by means of disc 88 so that the body may be marked for correction.