Patent GB-698644-A (GB)
Title: Improvements in or relating to valves for controlling the flow of liquids
Inventor: FRASER JOHN
IPC: G05D9/04
Filed: 1951-08-02
Abstract: 698,644. Valves. AVERY-HARDOLL, Ltd. July 25, 1952 [Aug. 2, 1951], No. 18353/51. Class 135 A valve for controlling the flow of liquid into a vessel and of the kind in which the flow of liquid through the valve induces a suction of air through a passage, and when the inlet to the passage is closed by the rising level of the liquid in the vessel, the suction acts on a piston, diaphragm, &c. to close the valve is characterized in that the valve is closed in two stages, there being a reduced rate of flow of liquid after the first stage. In the figure, valve 57 is shown in the closed position in which the liquid from the inlet 13 can pass through a hole 58 to the back of the valve to balance the upward thrust of the liquid on the outer surface of the valve. The valve will then be held closed by its loading spring 72 which abuts at its upper end against a disc 69, upward movement of the latter being prevented by a spring ring 71. When a valve 66 closing an aperture in the bottom of valve 57 is raised by means of a handle 65, the liquid inside valve 57 escapes and the inlet pressure opens valve 57 to allow liquid to flow into the vessel 10 past a non-return valve 53. Valve 66 slides on a tube 59 which, at its lower end, is secured in a venturi tube 55, and as this venturi is in the path of the outflowing liquid, air will be drawn down the tube. The latter communicates at its upper end with the chamber underneath a piston 73, this chamber also communicating, according to the position of the piston, through a tube 77 or 78 with a further tube 35 or 36 depending into the vessel 10. Both tubes 35, 36 are open at the bottom, but tube 35 is longer than 36. With valve 57 fully open and piston 73 in its uppermost position, tube 36 will be cut off from, and tube 35 will be in communication with. the chamber under the piston, and as soon as the level of liquid in the vessel 10 reaches tube 35 and prevents air being drawn therethrough, the suction produced by the venturi 55 will act on piston 73 and pull it down to an intermediate position, and, thus, valve 57 will be partially closed and the flow of liquid into vessel 10 will be reduced. In this intermediate position, tube 35 will be cut off from, and tube 36 will be put into communication with, the chamber under the piston. As soon as the opening in tube 36 is closed off by the rising liquid, the suction induced by the venturi will act on the piston and pull it right down to close off both valves 66 and 57. A detent 84 holds the piston in its uppermost and intermediate positions. To allow various measured quantities of liquid to be fed into the vessel 10, a number of pairs of tubes 35, 36 are provided and the pair required for any particular quantity is selected by a rotary disc valve 31. The main valve unit is separable and is provided with a flange which engages at one side under an arcuate groove 22 on a base fitting and which, at the other side, is engaged by a detent 23. In a modification, the pairs of tubes 35, 36 are arranged in a circle in the casing surrounding valve 57 and the particular pair to be used is selected by rotating the casing. The tube up which air is drawn by the venturi is selected by a valve formed in the valve stem which carries piston 73. Valve 66 is actuated by a rotary movement of the operating handle.