Patent GB-1507806-A (GB)
Title: Method and apparatus for testing the uniformity of a rotary body
IPC: G01H1/00
Filed: 1976-08-04
Abstract: 1507806 Testing the balance of a rotary body HOFMANN GmbH & CO KG MASCHINENFABRIK Gebr 4 Aug 1976 [14 Aug 1975] 32507/76 Heading G1N The invention relates to a method of and apparatus for testing the balance of a rotary body. The method comprises the steps of rotating the body e.g. a vehicle tyre 10, producing an electrical analysis signal whose amplitudes are proportional to the non-uniformities of the body, and obtaining a direct current voltage signal proportional to the speed of rotation of the body. The analysis signal and direct current voltage signal are then multiplied to form integrends which are integrated to provide the harmonic Fourier coefficients of the Fourier development series of the analysis signal, the magnitude and phase position of the non-uniformities being determined from the Fourier coefficient as from equations derived in the Specification. As shown the tyre 10 is rotated by a motor 12. The motor 12 is connected to a tachogenerator 14 which produces the D.C. voltage signal and to a rotary pulse transmitter 15 which emits a set of reference pulses and controls a trigger 16 and digital counter 17 such that the latter provides a command signal followed by a reset signal. The tyre 10 is loaded by a wheel 20 and the analysis signal appears at the output of a summing means 25 which is connected via scaling amplifiers 23, 24 to respective force-measuring transducers 21, 22. The tyre loading is indicated by a instrument 26. The portion of the analysis signal representing the static wheel loading is removed from the signal by a capacitor 27, the load variation only then  appearing at the output of an impedence converter 29. The modified analysis signal is then fed to a low pass filter 31 and thence to a maximum valve storage means 32 and the maximum value is displayed at 33. The maximum value is compared in a circuit 34 with a predetermined limit value set on an adjustment means 35 and depending upon the level of the maximum value relative to the limit value a lamp of good-bad display 36, 37 is actuated as also is a quality classification marker. The modified analysis signal is also fed to a plurality of parallel connected alternating means 39, 40, 41 each of which alternates the signal according to which harmonic of the signal is required to be measured. Each alternating means 39, 40, 41 is coupled to a respective coefficient calculator or computer 42, 43, 44 for the production of the Fourier coefficients. The D.C. voltage signal representing the rotational speed of the body is also multiplied by an integer in multipliers 45, 46, 47 before being applied to the computers 42, 43, 44 respectively. The direct current voltages produced by the computers 42, 43, 44 are fed to respective magnitude and angle calculators 48, 49, 50, the magnitude and angle being displayed on instruments 51 to 53 and 54 to 56 respectively. The last mentioned D.C. current voltages may be used to activate respective goodbad displays. Only one of the computors 42, 43, 44 may be provided in which case the outputs of the alternators 39, 40, 41 and multipliers 45, 46, 47 are fed successively in corresponding pairs to the computer. Each computer 42, 43, 44 comprises. two multipliers each connected to a respective integrator by a switch, the first multiplier being fed by an inverting summing means Fig. 1 (not shown).