GB835020A - Improvements in or relating to apparatus for indicating the speed of rotation of rotating parts - Google Patents

Abstract

835,020. Speed indicating apparatus. SIEMENS-SCHUCKERTWERKE A.G. June 7, 1956 [June 8, 1955], No. 17695/56. Class 40 (1). [Also in Groups XXXV and XL (b)] In speed indicating apparatus the speed of a rotating test member determines the operating condition of a transistor which controls the current in an indicating circuit, and the distance travelled may additionally be indicated. As shown, Fig. 1, a plurality of permanent magnets 3, 4, mounted on the propeller shaft 1 of an automobile, induce a voltage which varies with the speed of rotation of the shaft 1 in a cored coil 5 whose ends are connected to the base and the earthed emitter respectively of a transistor 6 whose collector is connected through a resistor 7 and a moving-coil instrument 8, calibrated in terms of road speed, to one pole of a battery 12 whose other pole is earthed. A self-starting synchronous motor 10 in series with a capacitor 9 is connected in parallel with the instrument 8, and drives a counting mechanism 11 to register distance travelled. The coil 5 and the transistor 6 may be sealed by an oil-resisting insulating compound within a housing of, e.g. aluminium or zinc-plated sheet iron, which may be mounted in the gear-casing, and the teeth of a driven gear-wheel may provide or modify the requisite magnetic field. In a tachometer generator for mounting in the ball bearing of a shaft (Fig. 4) a coil 28, wound on laminated core 26, controls a transistor 29, and a central cylindrical permanent magnet 31 is driven via a rubber stud 33 by the shaft. Modifications for deriving speed indication from a front wheel or an automobile are described. A photo-transistor and a source of radiation which is periodically interrupted by a shutter mounted on a shaft may replace the tachometer generator, speed indication being given by a frequency-measuring device.