Patent GB-1119044-A (GB)
Title: Improvements in or relating to integrators
IPC: F16C39/06
Filed: 1965-09-02
Abstract: 1,119,044. Differencing integrator. VYZKUMNY USTAV MATEMATICKYCH STROJU. 2 Sept., 1965 [3 Sept., 1964], No. 37534/65. Heading G4G. [Also in Divisions G1 and H1] An integrating device consists of an electric motor whose rotations are controlled by the parameter to be integrated, the motor being characterized by the absence of mechanical support or any frictional contact with the moving parts. The motor consists of a shaft 20 suspended by a magnetic levitation system including an electromagnet 30 and a ferromagnetic tip 23 on the otherwise nonmagnetic shaft. The shaft carries rotor discs 27, 21, 22 and 52 and the whole movement is mounted in an evacuated envelope 40. The envelope adjacent all but one, 27, of the rotor discs (which serves as an eddy current brake) has a bulbous enlargement 43, 44 or 45 which accommodates a means for producing electrically charged particles such as electrons. In each such means either an anode or a cathode electrode is constituted by the relevant rotor disc. In Fig. 1 the enlargements contain vacuum photo-cells in which the stationary electrodes 50, 51 and the rotor disc 52 are photo-cathodes; the peripheries 24, 25 of rotor discs 21, 22 and the annular fixed electrode 71 are the corresponding anodes. Rotor discs 21 and 22 are embraced by respective permanent magnets 11-12 and 13-14. In use of the Fig. 1 apparatus a light of constant intensity illuminates the cathode 52 and a light whose intensity varies in accordance with the quantity to be integrated illuminates one of the photo-cathodes 50 or 51. The electron flow in the photocells completes a circuit between the shaft and the external wiring and the interaction of the current across rotor disc 21 or 22 with its associated magnet produces rotation of the motor, whose revolutions are detected by means responsive to the movements of an index mark 26 on the shaft. To integrate the difference between two input signals both cathodes 50 and 51 are illuminated, each by light controlled by one of the input signals, and -the magnets 11-12, 13-14 being suitably poled-the torques produced by electron flow in the two photo-cells 43, 44 act in opposition on the shaft. Modifications to the Fig. 1 system.-Fig. 2 (not shown) depicts an arrangement in which sensitivity is increased by the incorporation of dynode electrodes in the photo-cells 43 and 44 of Fig. 1. Fig. 3 (not shown) depicts an arrangement in which the peripheries 24, 25 of the rotors 21, 22 are photo-cathodes and the envelopes of the corresponding photo-cells 43, 44 are of metal, constituting the cell anodes, but with transparent windows for admitting light to the photo-cathodes. In this arrangement the lower photo-cell 45 of Fig. 1 is replaced by one in which the rotor is anode and the cathode is fixed. Figs. 4 and 5 (not shown), depict alternative " ribbon light pipe " and mirror-lensprism systems for obtaining an appropriate distribution of light in a photo-cell of the kind used in the Fig. 3 embodiment. Fig. 8 (not shown) depicts a system for translating the movement of a meter, controlled by the quantity to be integrated, into the difference in intensity of two light beams which are applied as the two inputs to the Fig. 1 integrator. The meter incorporates a moving mirror which reflects light on to a so-called optical amplifier whose output is a pair of light beams one of which increases as the other decreases in intensity in dependence on the position of the input light beam. Alternative (non-photo-cell) systems.-Figs. 7 and 8 (not shown) depict arrangements in which the photo-cells 43 and 44 are replaced by a cathode-ray tube. The input signal to be integrated is converted into a current which controls electrostatically or electromagnetically the deflection of the cathode ray beam. This beam is wide enough to impinge on the peripheries 24, 25 of two rotor discs both of which are within the tube envelope, so that the sense and speed of rotation of the motor depends on the deflection of the cathode ray beam. Possible use with A.C. inputs.-Essentially the motor of the invention is a D.C. motor, but it can be used to integrate A.C. inputs by the expedient of replacing the permanent magnets 11-12, 13-14 by electromagnets energized by A.C. at a frequency which is an odd harmonic or sub-harmonic of the input signal frequency. In these circumstances the product of alternating magnetic field and the alternating current supplied to the rotor contains a D.C. component which can provide the necessary unidirectional torque. Damping.-The Fig. 1 apparatus has a conventional eddy current damping system 16, 17, 27. It is however possible to provide weak spring damping by the expedient of connecting a torsion fibre between the rotor and stator. Such a fibre does not support the rotor and is sufficiently weak to allow hundreds of full rotations of the integrating motor. It may be a conductive fibre, in which case it can replace the lower photo-cell 45 for Fig. 1 as the means for completing the external circuit. An electromagnetic equivalent of spring damping can be obtained by a system depicted in Fig. 9 (not shown) in which the rotor is provided with a supplementary disc acted on by an electromagnet controlled by a feedback system in which the current supply to the damping electromagnet is derived from a transducer . which senses the rotor's movement.