METHOD FOR OBTAINING THE OPTIMUM UTILIZATION OF THE NATURAL GRAIN-SIZE OF SANDS AND GRAVELS FOR CONCRETE PRODUCTION

摘要

1,241,878. Weighing electrically. (B) WOHNUNGSBAUKOMBINAT VEB. March 31, 1969, No. 16809/69. Heading G1N. In a concrete-making apparatus the mean value weighted in accordance with mass of a parameter representing the coarseness (F-value) of each of three different grades of aggregate is derived from a bridge circuit arranged so that for a mean F-value below a required value supplementary grade-improving material is added to achieve the required value. Potentiometers 1, 2, 3 are coupled to weighing devices so that each develops a voltage proportional to the mass of a different one of three grades of aggregate, the mass representing voltages being summed at a bridge arm 5. Each of the voltages is multiplied at 4 by a factor representative of the F-value of its respective aggregate, the resulting products being summed at a bridge arm 6. The ratio of the voltages across these arms thus represents the mean F-value weighted in accordance with mass of the three grades of aggregate and is compared with the ratio of the parts of the variable resistance 7, representing the required mean F-value. Any unbalance voltage acts through a Schmitt trigger circuit 8 to imitate addition of a grade improving supplementary material of which the weight added is monitored by a potentiometer 9. When the bridge is balanced the circuit 8 terminates the addition of supplementary material and actuates a change-over switch 10 so that the ratio arms of the bridge are comprised by the parts of a variable resistor 11, instead of that 7, of which the setting corresponds to a desired ratio between the mass of a binding agent or water represented by a voltage 12, replacing that 6, and that 5, representing the sum of the masses of the aggregates and supplementary material. The three grades of aggregate (sand, gravel) are graded by a sieving plant before weighing. A common weighing scales may be used.