GB1380261A - Fluid flow control apparatus - Google Patents

Abstract

1380261 Respiratory appliances BRITISH OXYGEN CO Ltd 1 March 1972 [4 March 1971] 6022/71 Heading AST Apparatus (Fig. 1) for selectively providing constant, increasing or decreasing flow rates for each of two fluids, e.g. gases in a lung ventilator, which are subsequently to be mixed (Fig. 4) comprises a conduit 2, 4 for each fluid; a fluid-flow regulator 6 located in each conduit 2, 4; a chamber 14 communicating with both regulators 6; a first valve 20 for placing the chamber 14 selectively in communication with either the atmosphere or a source of pressurised fluid; a second valve 22 for venting the chamber to atmosphere through an adjustable impedance 24; and a pair of linked valves 26 for venting the conduits 2, 4 downstream of the regulators 6 to atmosphere. The source of pressurised fluid may be the source of one of the fluids to be mixed, in which case the chamber 14 is connected as shown to one of the conduits 2, 4 upstream of the regulator 6, via a regulator 16 and an adjustable throttle valve 18. The valves 20, 22, 26 are operated by solenoids S20, S22 and S26 respectively. Regulators 6 are designed to maintain a pressure in conduits 2, 4 substantially equal to that in the chamber 14. A constant flow rate of both fluids is thus obtained when all solenoids are deenergised, as shown, and the pressure in chamber 14 is at a constant high value. A reducing flow rate is obtained by energising solenoid S22 to vent chamber 14 to atmosphere. An increasing flow rate is obtained by initially energising solenoids S20 to S26, and then deenergising them. The above apparatus is connected in series with apparatus (Fig. 4) for mixing the two fluids in a preset ratio selected from a set of at least two possible preset ratios, and comprising at least one inlet conduit 40 for each fluid, and at least two outlet conduits 42 each connected to both or all inlet conduits 40 through separate preset flow impedances 52, and in which each outlet conduit 42 is connected through a separate outlet valve 56, 58, 60 to a common outlet manifold 48. When a plurality of inlet conduits 40 are provided for each fluid, each inlet conduit of each plurality is connected through a separate inlet valve 50, 51, 53 to a common inlet manifold 44. The apparatus shown supplies, through outlet valves 56, 58, 60, the two gases A, B mixed in three preset ratios, as well as supplying pure A or pure B through additional outlet valves 54 or 62 respectively. The flow rate is selected by operating a selected inlet valve. The inlet valves are solenoid operated. The ratio is selected by operating a selected outlet valve. Each flow impedance includes a non-return valve (64), Fig. 5 (not shown) in series with an adjustable throttle valve (66).