GB936693A - Improvements relating to the blending of materials - Google Patents

Abstract

936,693. Automatic control of volume. J. J. JISKOOT. June 5, 1962 [June 6, 1961], No. 20419/61. Class 38 (4). [Also in Group XIX] In a blending control system a pulse generator is driven at a reference flow rate and provides at a plurality of output channels pulse trains of different mean frequencies corresponding to different proportions of the reference flow rate and at least one flow controller is connected to one or a group of output channels to control the flow of a component to be blended by comparing the mean frequency of the pulses representing the actual flow with the selected pulses. As shown, a control panel has three controllers 10, 12 and 14 for component materials of a blend. Each controller receives pulses from a master pulser 16 which is a slave of a meter 18 in a line 20 leading to a blending manifold or of a manually adjustable blend-rate oscillator 24. The total flow of blend is derived from a counter 26. The master pulser comprises an electric motor driving a plurality of tone wheel generator, each of which is connected to an output channel, or alternatively the master pulser comprises cyclically-counting binary decade counters (see Group XIX), the output channel being connected to the appropriate sides of the flip-flops which form the counters. Each controller has a " set-percentage " switch 28 for selecting appropriate channels from the master pulser. The pulses in the selected channels are fed to a differential counter 30 which receives its other input from a flow-meter 32 in the corresponding component flow-line. The differential counter provides a control current, via a digital to analogue converter 34, which is fed to an electro-pneumatic transducer 36. The transducer 36 through an air-pressure control 38 determines the operation of a diaphragm motor 40 positioning a control valve 42 in the flow-line. Each controller provides automatic closed loop control of the flow rate in the associated flow-line in dependence on the setting of the switches 28. When the master pulser 16 is. controlled by the blend-rate oscillator 24 the percentage blend of component materials A, B, C is maintained constant and when the master pulser is controlled by the meter 18 the flows of component materials A, B, C are maintained as percentages of the flow in the line 20.