GB612054A - Improvements in and relating to flow metering mechanisms - Google Patents

Abstract

612,054. Fluid-pressure servo motor-control systems. NEGRETTI & ZAMBRA, Ltd., and IBBOTT, H. W: May 16, 1946, No. 14850. [Class 135] [Also in Group XXXVIII] A fluid-flow meter comprises a valve 1, Fig. 2, movable to vary the area of an orifice through which the fluid flows, the valve being actuated by a piston 9 in a cylinder through the spaces in which, on both sides of the piston, fluid can flow, a valve 5 controlling the fluid flow through the cylinder spaces, and a pressure responsive device 3 subjected to the differential pressure across the orifice adjusts valve 5 in response to said differential pressure so that the piston will be actuated to vary the area of the orifice to restore the differential pressure across it. The pressures on the two sides of the orifice are applied to the diaphragm 3 through passages A, B and the fluid acting on the outer side of the diaphragm also flows through a chamber 7, leaks round the edges of piston 9, and flows out past valve 5 to the inner side of the diaphragm and thence to the outlet side of valve 1. The fluid pressure acting on the front face of valve 1 is normally balanced by a spring 16 loading the piston. A stop 25 limits the movement of valve 1. The latter has a spring connection 12 with piston 9 to allow of relative movement between them should the valve jam or the pressure on the forward end thereof become excessive. A screw 17 allows of adjustment of the spring loading on the diaphragm, and a bimetallic strip 4 inserted between the screw and a spring 18 compensates for changes in the viscosity or density of the fluid due to changes in temperature. To give an indication of the position of valve 1, an extension 11 of the piston spindle carries either a pointer moving over an index or an iron core 27, Fig. 3, moving inside a coil 29 of which the two ends are connected to a further coil 31. Alternating current is supplied to the mid points of the coils, and when the position of core 27 changes, there will be a corresponding change in the position of an iron core slidable in coil 31. Core 32 carries a pointer moving over a scale. According to the Provisional Specification, separate pressure fluids are supplied to both sides of piston 9 and valve 5 is constituted by a a double-beat lift valve differentially controlling the leak of fluid from both sides of the piston.