Patent GB-409989-A (GB)
Title: Improved method of and means for testing and correcting want of balance of rotary bodies
IPC: G01M1/22
Filed: 1933-09-25
Abstract: 409,989. Testing balance of rotary bodies. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London.- (Assignees of Thearle, E. L. ; 1278, Dean Street, Schenectady, New York, U.S.A.) Sept. 25, 1933, No. 26393. Convention date, Sept. 23, 1932. [Class 106 (ii).] Comprises in combination, an elastically supported cradle, an instrument to indicate the amplitude of the vibration of the cradle, a pointer rotating in synchronism with the body, means for rotating the body, a source of light flashed by the vibration of the cradle, and a pair of pointers angularly spaced and mounted to move so that when one is aligned with an image of the pointer rotating with the body, the other when adjusted to coincide with the pointer driven by the body gives the position of the counterbalancing mass. The armature R to be balanced is mounted on a cradle F comprising side bars 13 and end bars 14 having half bearings for the rotor shaft. The cradle pivot comprises flexible metal strips 16 attached to blocks 17 and to a frame member 15 fastened to rails 11. The strips are in the same transverse plane as the plane of correction. The end of the frame furthest from the pivot is supported by a spring S. The rotor is driven by a belt 20. The amplitude of the cradle vibrations is indicated on a dial indicator 22 mounted on a pillar 21. A contact device is adjustably mounted on a part 25 longitudinally adjustable on the base of the machine. A screw 28 operated by a handle 35 and collar with pins engaging holes in a collar on the screw may be rotated in a nut in a part 26 to raise the latter and electric contacts on the pillar 25. A low voltage Neon lamp 40 is mounted in a closed casing 45 supported by wheels on the rails 11. At the one end the casing has an extension 47 on which are rotatably mounted a pair of rings 48, 49 of which the former carries a pointer H and the latter a longer pointer J and a scale. The rings are normally locked in their relative angular position by set screws. Inside the casing and in axial alignment with the armature F is a tube which projects through the casing. Located in the extension is an inclined mirror 53 and attached to the extension is a sight tube 54. On the end of the armature shaft is mounted a light weight disc D having a pointer G, though if the end of the shaft be large enough this may be omitted. An ordinary lamp 57 enables the pointers to be observed when the Neon lamp circuit is interrupted. The rotor R is speeded up until the critical speed is exceeded. The vibrations of the cradle lag behind the weight producing it by a definite angle O which is independent of the magnitude of the unbalanced force. The part 38 is gradually lowered until the Neon lamp flashes which is at the instant the cradle F is at its uppermost position. The lamp flashing once per revolution, the pointer G appears to be stationary. While the image is being viewed, the rings 48, 49 are turned by hand as a unit until the pointer H coincides with the image of pointer G. If the rotor be stopped in the position in which the light flashed at the top, the unbalanced weight W, Fig. 9, will be at an angle # equal to angle of lag down from the top position. If the rotor is now turned through an angle # equal to 180‹ # or until the pointers C. J. coincide, the unbalanced weight is at the bottom of the rotor. The pointers H. J. are adjusted in setting up the machine 80 that the angle between them is # which is found by trial. The amount of the weight to be added is proportional to the width of the blur of the needle of the indicator 22.