Patent GB-675553-A (GB)
Title: Elevation meter
IPC: G01C7/00
Filed: 1948-09-23
Abstract: 675,553. Recording clinometers. SUN OIL CO. Sept. 23, 1948, No. 24946/48. Class 97 (ii). [Also in Groups XIX, XXXVI and XXXVIII] When the movable element of a sensitive member is displaced relatively to a reference member by a variable force, signals are produced to control a generator which generates pulses representative of the variable force. In the particular application described the sensitive member is mounted on a vehicle and is used to measure the change of elevation of a route along which the vehicles is traversed. This measurement is effected by integrating over the course instantaneous velocity multiplied by the instantaneous size of the angle of inclination of the course with respect to time as shown in Fig. 1, and coil 2 mounted on a pendulum which measures the inclination of the vehicle and thus the size of the angle of inclination, co-operates with an electromagnetic coil 24 excited by a valve oscillator 32 to produce signals representative of inclination. ' These signals, which are a minimum when the pendulum occupies its normal mid-position corresponding to perpendicularity to the roadway, are fed via a tuned amplifier 52, 55 to a phase detector 66 which develops across feeds one or other of the resistors 86, 88 depending on the direction of deviation of the pendulum coil 2 a negative control bias on lead 96 or 98 to block one. or the other of gas-discharge tubes 104, 106 which are connected as R.C. relaxation oscillators to pulse automatically in the absence of the blocking bias. The output pulses trigger one or the other of valves 132, 134 which are connected flip-flop fashion and thus become respectively conductive as the pendulum swings through its null position. A pair of triodes 152, 154 with their respective grids connected to the flip-flop valves are energized from a stabilized H.T. supply comprising valves 153, 155, and the differential D.C. output from their anodes is fed back along lines 160, 162 to the pendulum coil which coacts with a permanent magnet system in the base to restore the pendulum towards its null position with overshoot. The pendulum is thus maintained in a state of continuous oscillation about the null position. For recording the change of elevation of the vehicle over a route, the flip-flop valves 132, 134 control the grid of gate valves 182, 184 in the cathodes of which are supplied with negative pulses which are derived from a photoelectric chopper device 193, 195 driven at the speed of the vehicle. In this manner one or other tube 182, 184 will pass pulses representative of the speed of the vehicle according to the amount and direction of swing of the pendulum. These pulses are frequency divided to a speed suitable to operate a mechanical counter and the differences between the two sets of pulses summed by a differential counter 230. Thus since the instantaneous output of tubes 182, 184 included two components, viz. (i) pulse frequency on the cathode dependent on the speed of the vehicle, and (ii) a component on the grid dependent on the pendulum swing, the integrated output represents elevation between the extreme points of the route taken by the vehicle. A correction for acceleration is introduced by a generator 25 as driven by the vehicle and feeding an impedance 302, the corrected integration being represented by a voltage derived from the resistors 313, 315 for operating the recorder 300. Pendulum apparatus, Fig. 4.-The coil 2 is supported by strips 4, 6 clamped to provide flexible fulcra on a casing 8 and surrounds an iron bar 12 associated with two E-shaped permanent magnet and providing a common polarity on the bar at the null position of the coil 2. A second laminated core 22, 28 carries a coil 24 which generates an A.C. flux in the core. The casing 8 is oil-filled to provide damping and adjustable steps limit the swing of the pendulum. Vehicle for pendulum apparatus, Fig. 7.- This vehicle comprises a trailer 233 having wheels 234, 235, 236, two of which viz. 235, 236 are interconnected by steering cables 242 so that where the towing bar 238 is moved angularly, the wheel 236 is tracked oppositely to the wheel 235 and good tracking is secured irrespective of the banking or other irregularities of the roadway. The photo-electric apparatus is mounted in the housing 247 and together with the generator 254 and recorder shaft is driven from the wheel 236 by a flexible shaft 193. Differential counter 230, Fig. 8.-The outputs from the frequency dividers 226, 228, Fig. 1, are fed to solenoids 346, 348 respectively which control the stepping of wheels 266, 268 continuously urged to rotate by friction discs 262, 264 driven by a motor 256. The stepping- wheel-shafts 274, 276 control the " sum " counter 286 and the " difference " counter 296 for the two sets of pulses through differential gears 278, 288. Modifcations.-(i) The oscillator 30 may be replaced by other forms of generator and the output of the coil 2 broken up into short pulses; (ii) The pendulum apparatus may be replaced by a gyroscope and the photo-cell apparatus 193, 195 by a variable frequency generator of other form; (iii) The output in the lines 96, 98 may be fed into an amplifier 350, Fig. 11 (not shown), which energizes a reversible motor driving a variable resistance to provide feed-back to the pendulum. Simultaneously this motor operates a modified form of differential mechanism the output of which represents the required integral; (iv) Instead of employing valves 104, 106 one or other of which is cut off while the other is pulsing, an arrangement of valves may be provided wherein two valves are pulsed continuously and the pulse rate is differentially varied when the pendulum swings, Fig. 12 (not shown), and the valves may be triggered by cathode injection of a signal from an oscillator, instead of selfoscillation as in Fig. 1. In this arrangement the narrow measuring pulses are converted into rectangular pulses of constant width.