GB926985A - Apparatus for determining the weight of railway vehicles - Google Patents

Abstract

926,985. Weighing-apparatus. SIEMENS & HALSKE A.G. May 5, 1960 [May 29, 1959], No. 15954/60. Class 40 (1). [Also in Group XXXVI] The weight of railway vehicles is measured in terms of the rail deflection caused by the pressure of the wheels, using two or more detectors spaced along the track and determining the difference between the measurement values given by the detectors. This method avoids errors due to yielding of the ballast under the sleepers (whether uniform or not) and the effect of an adjacent wheel. In Fig. 1, two strain-gauge detectors G1 and G2 are fixed to a rail between adjacent sleepers B2 and B3 and are sensitive to deflections produced by adjacent wheels R1 and R2 of a bogie. Two similar detectors g1 and g2 are attached to the opposite rail and each pair is included in an A.C. bridge (Fig. 7) with two fixed resistors, which may be dummy strain-gauges. The bridge outputs are joined in parallel so that the measured voltage represents the mean value of the wheel pressures and the indicated weight will not be incorrect due to asymmetric loading of the vehicle. The bridge is previously calibrated so that in use the output voltage never falls to zero, or alternatively a phase-sensitive demodulator is used. The fixed resistors may be arranged to compensate for temperature variations. Three detectors may be used (G10, G20, G30 in Fig. 1) disposed in two compound bridges (Fig. 8) whose outputs can be combined in any desired way. A fourth detector can be added so that the measured value is held for an appreciable time as the vehicle moves, without the use of storage circuit elements. Extra sensitivity can be obtained by replacing the fixed resistors of the bridges by further detectors arranged to be deflected in the opposite sense. The two pairs of detectors are then secured to a plate mounted on straps beneath the rail (Fig. 10, not shown) instead of to the rail itself. The output of the bridge (Fig. 9) is demodulated at DM and applied to a capacitor C1 through a diode 1, the contacts 11 and 12 being opened by the approach of the first wheel acting on a magnetic impulse generator or an optical system. When the output changes sign, the capacitor C1 discharges through the diode 2 into a smaller capacitor C2, so that the latter assumes a potential equal to the difference between the maximum and minimum peaks of the bridge output, this representing the weight of the vehicle. The contacts may alternatively be operated by a self-holding relay dependent on the output voltage of the demodulator, the relay being subsequently de-energized from the indicator circuit W. The system of Fig. 9 with detectors mounted on straps beneath the rail can be extended to the use of three or four detectors as described above (Figs. 11 and 12, not shown). Measurement may also be effected with a D.C. bridge or with an ohm-meter. The detectors may be piezo-electric or magneto-inductive impulse emitters. The measurements may be based on actual yielding of the rail or on its curvature.