GB666898A - Improvements in or relating to means for measuring the eccentricity of rotary shafts - Google Patents

Abstract

666,898. Indicating axial displacement and eccentricity of a rotary shaft. GENERAL ELECTRIC CO., Ltd., BARUGH, J. K., and GARDINER, H. W. B. April 20, 1950. [April 20, 1949] No. 10498/49. Class 40 (i). To measure the radial, axial or oscillatory movement of a rotating shaft, the envelope of an a.c. whose frequency is independent of the speed of rotation of the shaft, is modulated by an electromagnetic means associated with the shaft, the mean amplitude being representative of the axial displacement and the oscillatory movement being represented by variations in the mean amplitude. As shown, the shaft under test 10, Fig. 2, carries a circular disc 14 cooperating with movement detectors 20 ... 23, and 30, 31, each comprising a core carrying an a.c. energized winding, so that the gap between the cores and the disc controls the inductance of the winding. Movement detectors 30, 31 detect axial movement of the shaft, while detectors 20, ... 23 detect vertical and horizontal movements. A motor 51, Fig. 3, drives a generator 50 supplying a.c. to the detectors 20, 22, 23, 21, 30, 31 which are connected in pairs as shown in bridge networks, each of which is normally unbalanced. The output from bridges 20, 22, and 21, 23 is rectified and applied over a smoothing circuit to a meter 69, 90 which thus indicates the average amplitude of the output of the bridges, i.e. the displacement of the shaft as a whole vertically or horizontally consequent upon rotation. The rectified output of the bridges is also applied to transformers 70 and rectified again and applied over amplifiers 72 to meters 73, 91 and recorders 74, 92 to indicate variations due to eccentricity of the shaft. The meters may be ratiometers fed with a.c. from generator 50 to compensate for any variation in the supply. A calibrating voltage may be obtained from an eccentric disc 54 driven by the motor 51 and co-operating with detectors 80, 81. whose output may be switched in place of the bridge outputs. Axial movement results in a variation in the out-of-balance of bridge 30, 31, 93, 94 which after rectification is registered on meter 97 and recorder 98.