Weighing device and method

摘要

918,895. Measuring weight electrically. RASKIN, S. H. Jan. 30, 1961 [Jan. 28, 1960], No. 3410/61. Class 40 (1). The weight of a moving load is determined by measuring the deflection or stress at a central portion of a beam rigidly supported at its ends, the configuration of the beam cross-section being such that the forces introduced by the load movement have no appreciable effect on the stress in the beam. Fig. 1 shows a side view of a railway truck wheel 16 rolling at a velocity T over a weighing section of a beam 12. This beam is rigidly supported at its ends 10, 11 on a base 4 and its centre section is located over a cavity in the base. The cross-section of the beam and of the truck wheel is shown in Fig. 2. The centre of gravity of the section coincides with the point at which the wheel contacts the rails and this point is precisely over the centre of the unsupported section of the rail. Vertically below the centre of gravity on the lower face of the beam is a strain gauge of known type. The maximum resistance of the gauge is the measure of the stress in the lower face of the beam when the wheel is directly over it. The Specification explains that when the centre of gravity of the section coincides with the point of application of the force the movement of the neutral axis produced by horizontal forces introduced by the rolling friction of the wheels has no appreciable effect either on the bending moment at the centre point or on the stress at the point of application of the strain gauge which stress will be due to the bending moment at the section only. A duplicate arrangement to enable the total weight on an axle to be measured may be used and by adding the weight from all wheels the total weight of the truck may be measured. Fig. 7 shows an arrangement used for measuring the weight of a road vehicle. The beam crosssection is different but again the centre of gravity of the cross-section coincides with the point of application of the load at the intersection of the vertical and transverse axes of the beam. The arrangement of Fig. 8 is used for measuring the weight of a metal ball 32 which rests at points 34, 35, the resulting force at these points passing through G. Figs. 9 and 10 show an arrangement for measuring the weight of granular material on a conveyer belt 40. This conveyer is provided with side belts 45 which prevent the material from contacting the side walls of the beam. The weight is measured by a strain gauge load cell 43 situated beneath the centre of the unsupported length of the beam which measures the deflection of the beam. Horizontal forces cause the point of application of the load cell to the beam to move horizontally a distance e but provided the distance is small compared with the distance L, L1 no appreciable error results.