GB682908A - Improvements relating to surveying instruments - Google Patents

Abstract

682,908. Gyroscopic apparatus; surveying instruments. RUHR-FEINMECHANIK GES. Dec. 15, 1950, No. 30657/50. Classes 97 (ii) and 97 (iii). A surveying instrument particularly suitable for directional determination, e.g. in pits and mines, comprises in combination a gyroscope carried within an inner sphere or like body adapted to float freely within an outer sphere or like body, the inner sphere carrying an induction coil co-operating with an element in the outer sphere or with the outer sphere itself for centring the inner sphere within the outer sphere and a theodolite, whose axis of rotation is coaxial with the axis of rotation of both the spheres, coupled to the outer sphere and having a scale member connected to the outer sphere. As shown in Fig. 1 a gyro 1, electrically driven, is supported for rotation about a horizontal axis 22a in bearings 22 secured to casing 1a itself secured by plates 3a to a frame 3 firmly connected within an inner sphere 5 enclosed within an outer sphere 7 containing an electrically-conducting liquid 6 in which the sphere 5 floats. An induction coil 20 carried within the inner sphere 5 co-operates with a thin aluminium foil on the inner surface of the sphere 7 to produce a repellant action so as to float the sphere 5 centrally within the sphere 7. Theodolite 17 is supported on a stem 9 rotatable in the cover 10 and carries secured thereto the theodolite graduated scale member which is observed by microscope 19. The stem 9 is secured by spider arms 8 to the outer sphere 7, the main axis of the theodolite coinciding with the axis of rotation of the spheres. Lead ballast pieces 4 are firmly connected at the bottom of sphere 5 and to the frame 3 to locate the centre of gravity of sphere 5 considerably below the geometrical and displacement centres so that the floating of sphere 5 is stable and the gyro axis always horizontal. A brake-rod 12 is provided to engage frictionally the sphere 5 for regulating the amplitude of oscillation of the gyro. Hollow arms 8c contain wires passing through the stem 9 which carry current to the gyro 1 through corresponding opposing graphite portions on the spheres and the conducting liquid 6 therebetween, and wires included in a device for indicating the relative position of the inner and outer spheres. Cooling fluid to maintain the liquid 6 at a predetermined temperature is passed through cooling coils 21. The motor of gyro 1 is a three-phase asynchronous motor, the three windings 25a, Fig. 3, of which are connected to graphite sections 25, 26, 27 of sphere 5, the inductance 20 being connected between sections 25, 26. The current passes to sections 25, 26, 27 through the conducting liquid from corresponding graphite sections 29, 31, 30, Fig. 2, on the outer sphere 7 which has also two contacts 32, 33, Fig. 2, spaced 180 degrees apart and connected in circuit with two series resistances 34, 35, Fig. 2, so as to form a bridge network with the resistances of the liquid between the contacts 32, 33, and conducting strips 28, Fig. 3, on inner sphere 5. Symmetry of the strips 28 with respect to the contacts 32, 33, as indicated on the voltage meter V connected across resistances 34, 35 corresponds to the zero or operative position for the theodolite and is brought about by manual rotation of the sphere 7 about its vertical axis and provides the reference direction given by the gyro.