DRUCKSTEUEREINRICHTUNG

摘要

1303540 Automatic pressure control B H HADLEY 30 Dec 1970 [6 March 1970] 61822/70 Heading G3R [Also in Division F2] In a system in which high and low-pressure sources are coupled through electromagnetic valves to an output line, the pressure in the latter is compared with a reference pressure by a manometer, the error signal from which varies in opposite senses energization of the valves and hence the forces applied to the valve poppets, portions of which are of magnetic material. In Fig.1 fluid-pressure in a conduit 26 is applied to a fixed cistern 10 of a mercury manometer having a moving cistern 11 associated with a vacuum conduit 25 and elevated by a lead screw 28 to a position corresponding to a desired pressure to be maintained in conduit 26. Coarse, initial, errors between the pressure in conduit 26 and the desired pressure are detected by a differential pressure device 14 adjusting a capacitor 17 arranged in a bridge circuit 32 so that, with a switch 38 in a position opposite to that shown, the coarse error signal is applied through lead and normal operational amplifiers 41, 42 to a power amplifier 43 controlling valves 40 to adjust the flows in a high-pressure conduit 39 and a vacuum conduit 391 in opposite senses until the pressure in conduit 26 is more nearly correct. Then switch 38 is operated manually or automatically to the position shown and a valve 29 is opened so that in addition to applying the coarse error signal to amplifier 41, a fine error signal derived from capacitors 15 and 16, responsive to the mercury levels in cisterns 10 and 11 and arranged in a bridge circuit 35, is applied to amplifier 42. The output of amplifier 43, indicated at 61, 62 in Fig.2, is applied to moving coil-operated poppet valve 51, 50 to adjust the flows in high-pressure conduit 39 and vacuum conduit 391. To prevent sticking valve seatings 110 are non-magnetic but valves 55 are of magnetic material so that they are attracted to a permanent or electromagnet 117 attached to the moving coil 58. Diaphragm-operated ball valves 52 and 53 differentially responsive to the pressures on each side of valves 50, 51 control the flow to the latter so as to keep the pressure drop across them constant. The gains of amplifiers 41, 42, which have capacitive feedback, are automatically varied in a non-linear manner by photo-sensitive feedback resistors responsive to the magnitude of the pressure in conduit 26.