Patent GB-688234-A (GB)
Title: Improvements in apparatus for measuring the disequilibrium of a rotating body
IPC: G01M1/22
Filed: 1951-02-20
Abstract: 688,234. Electric measuring systems. PISCHEL, W. Feb. 20, 1951 [Feb. 21, 1950; April 14, 1950], No. 4068/51. Class 40 (i). For measuring out-of balance forces of a rotating body R, Fig. 1, in two equalizing planes I, II i.e. the planes in which mass is to be added or removed from the rotor to effect balance, piezoelectric or other pick-offs GIII, GIV are arranged in the mounting planes III, IV of the rotor and their output voltages applied to similar potentiometers SIII, SIV disposed in the mounting planes, transversely of the rotor axis and also on opposite sides thereof with the zero points of the potentiometers on a line XX' parallel to the rotor axis. It is shown in the Specification that, to measure the out-of-balance force PII in the equalizing plane II, a lever 8 pivoted on the line XX' at a point K in the other equalizing plane I, will tap off from the two potentiometers SIII, SIV appropriate relative portions of the two pick-off voltages which, if added vectorially give a value UII proportional to PII. Similar considerations apply to PI the out-of-balance force in the equalizing plane I. To enable both PI and PII fo be measured simultaneously, the lever 8, Fig. 2, is pivoted in the respective mounting planes I. II at points 9, 9' a constant distance h apart and equispaced from the line XX'. The lever carries two wipers at each end 6<SP>1</SP>, 6", 7<SP>1</SP>. 7", the wipers of each pair being mounted a distance h apart. This arrangement corresponds to a duplication or that of Fig. 1, PI and PII being proportional to the voltages UI, UII respectively taken from the respective wiper pairs 61, 7' and 6", 7". These may be amplified at V and operate a meter J. calibrated in grams .weight, referred to a predetermined equalizing radius. In a practical embodiment the rotor 1, Fig. 3, driven by a synchronous motor 5 is mounted in V blocks 3 secured by blade springs 13 to carrier heads 11 movable relative to the machine bed 12 to adjust the distance between the bearings 3 (mounting planes). Each bearing is associated with a piezo-electric pick-up 15, connected across a potentiometer 6, 7 mounted on the corresponding head 11 in the mounting plane. Co-operating with each potentiometer is a slide 19, Fig. 5, having contacts 6<SP>1</SP>, 6" engaging the potentiometer at the distance h apart, the slides 19 of both potentiometers being rotatably mounted on slides 20 which slide on the lever 8 which is adjustable at 9, 9<SP>1</SP> by means of slides 22 movable along respective parallel guide rails 10, 10<SP>1</SP> disposed parallel to the rotor axis. The rails 10, 10' are a distance h apart and at a distance h/2 on opposite sides of the rotor axis. The guides 9, 9' are adjusted along the rails 10, 10<SP>1</SP> until they lie in the equalizing planes, and the potentiometers being disposed in the mounting planes, i.e. of the bearings, then as shown in the Specification, only one primary calibration of the apparatus is necessary in, respect of the dimension h after which any rotor may be tested, when, provided the guides 9, 9' are adjusted as above mentioned, the correct proportions are tapped off from the two potentiometers and added to compensate the out-ofbalance force measurement in one of the equalizing planes for errors (residual movements) introduced by out-of-balance forces in the other plane. A nomogramatic calculating device may be used in lieu of the Fig. 3 arrangement.