Patent GB-982821-A (GB)
Title: Improvements in and relating to fluid amplifiers
IPC: F15C1/08
Filed: 1961-05-16
Abstract: 982,821. Fluid amplifiers. B. M. HORTON. May 16,1961 [May 20, 1960], No. 17853/61. Heading G3H. A fluid amplifier has a negative feedback path extending from an output aperture. In the first example the amplifier comprises a power nozzle 16, opposed control nozzles 17, 18 and receiving apertures 19, 20 defined by a partition 26 and leading to capacity or stilling chambers 21, 22 connected respectively to output apertures 121, 122. The chamber 21 is connected to the feedback nozzle 17 by a passage 39 containing a porous plug 41 constituting a resistor. If an incompressible fluid is used the chambers 21, 22 may be defined by deformable material. If constant pressures are applied to the tubes 24, 25 leading to nozzles 17, 18 the device operates to maintain a substantially constant pressure in the chamber 21 since changes in the supply pressure to the nozzle 11 or changes in the flow from line 121 causes the feedback signal in nozzle 17 to change. The device may act as an amplifier with the feedback acting to linearise the relationship between the input and output signals and ensuring that the output signal is substantially independent of the viscosity and temperature of the fluid supply to the power nozzle 16. A biasing fluid pressure may be supplied to nozzle 17 via porous plug resistor 36 which fluid pressure and resistor determine the pressure which tends to be maintained in chamber 21. In another example, Fig. 2 (not shown) a reference pressure is fed to the nozzle 17 via a separate passage and the partition 26 is assymetrically disposed with respect to the nozzle 16 so that the greater part of the main fluid stream flows into chamber 21. In another example there are provided a pair of opposed feedback nozzles, a pair of opposed control nozzles and a central receiving passage. The feedback and control nozzle passages contain porous resistors. In another example, Fig. 4, the capacity chamber 61 interconnects the aperture 20 and the nozzle 17 but the curved surface 67 causes a wake in the fluid flow so that a low pressure region is developed at orifice 68 with the result that a negative feedback effect is still obtained. In another example, there is provided and amplifier employing four negative feedback paths two acting directly and two acting indirectly. In another example, Fig. 6, for use with an incompressible fluid the receiving apertures 19, 20 lead to capacity chambers 21, 22 connected directly to feedback nozzles 17, 17<SP>1</SP> below the control nozzles 18,18<SP>1</SP> respectively. Porous resistors 87, 87<SP>1</SP> are located before the nozzles 17, 17<SP>1</SP> and together with the fluid inertia they tend to smooth any fluctuation in fluid flow in the feedback paths and thus prevent oscillation. In another example four negative feedback paths are provided two crossconnected paths and two directly connected paths, the device having velocity feedback. In another example similar to that of Fig. 1 the connection between the capacity chamber 21 and the nozzle 17 has no porous resistor but the connection between the aperture 19 and the chamber 21 has a porous resistor. Specifications 970,985, 975,019 and 975,020 are referred to.