GB893197A - - Google Patents

Abstract

893,197. Measuring rotor unbalance electrically. SCHENCK MASCHINENFABRIK G.m.b.H., CARL. Sept. 15, 1958 [Sept. 14, 1957], No. 29419/58. Class 40 (1). Apparatus for balancing a disc-type rotor comprises a selsyn unit to determine the angular position of the unbalance and a watt-meter to indicate the magnitude of the unbalance, which also controls means for marking or removing the unbalance. As shown (Fig. 1), a tyre 1 to be balanced, is rotated by a vertical shaft 3 supported by leaf-springs 6, 7, the shaft also driving at one end a selsyn transmitter 11, and a reference phase generator 19 with adjustable stator. The other end of shaft 3 carries a differential gear 12 on whose casing is mounted a disc 13 which rotates synchronously with the tyre 1 and can be advanced or retarded by a motor 15 operating through a gear-wheel 16, also driving a selsyn receiver 18. The signal from a vibration pick-up 9 is fed to the rotor of a selsyn unit 22 whose stator windings are energized with synchronous 3-phase A.C. from transmitter 11, whereby the rotor is brought to an angular position indicative of the angular position of the unbalance of the tyre 1. This position is compared with that of the rotor of selsyn unit 18, and any difference is amplified at 34 and energizes motor 15 to drive the rotor of selsyn 18 and the casing of differential 12 and disc 13 until the rotors are in agreement, when two holes 37, 38 in the rotating disc are located opposite the unbalance position of the tyre. Marks may be made on the tyre by spray nozzles 39, 40 through the holes 37, 38 controlled by a watt-meter 27 indicating the magnitude of the unbalance by combining the signal from a further vibration pick-up 8 with the A.C. from generator 19, after its stator has been angularly adjusted by selsyn 22, via gears 20, 21, so that its output voltage is in phase with the unbalance signal obtained from pick-up 8. In another embodiment (Fig. 2) the 3-phase A.C. induced in the stator windings of selsyn transmitter 11 is fed to the field windings of a selsyn 53 whose rotor is fed with the signal from pick-up 9, whereby this rotor lines up with the phase position of the pick-up signal, and rotates the disc 33 and the stator of reference phase generator 66 accordingly. The 3-phase A.C. is now switched to selsyn 59, simultaneously locking the rotor of 53 by a magnetic clutch 58, and selsyn 59 drives the disc 13 and generator 66 at synchronous speed, with the holes 37, 38 in the correct phase position to allow the spray nozzles 39, 40 to indicate the position of the unbalance on the tyre 1. The spray nozzles, which are selectively operated in accordance with the magnitude of the unbalance as measured by wattmeter 27, may be replaced by tools for removing the tyre unbalance. Specifications 756,168 and 807,041 are referred to.