GB613914A - Improvements in apparatus for maintaining a constant liquid level - Google Patents

Abstract

613,914. Float-actuated valves. MOORE, R. P. March 12, 1945, No. 6174. [Class 135] Apparatus for maintaining a constant liquid level in a tank provided with means for the inflow and outflow of liquid comprises valve means adjustable to vary the balance of inflow and outflow and operable by a servomotor in the form of a float, the level of which is controlled by the movements of a pilot float floating in the tank, such movements in either direction from a datum position operating to adjust the balance of inflow and outflow to restore the datum level in the tank. In Fig. 1, the level in a weir tank 11 is controlled by a valve 14 supplied from a filter chamber 10. The valve 14 is controlled by an open float 15 to which liquid is supplied or from which liquid is withdrawn by a flexible pipe 18 communicating by a pipe 19 with a source of supply 21 manually adjustable by a valve 22. Liquid drains from this system through a valve 23, operated through a lever 25 by the pilot float 28. The valve rod 24 is sheathed by a tube 27 extending above the maximum height of the liquid in the float 15. The datum level may be adjusted by movement of the fulcrum 26 of the lever 25 by a hand-wheel .30 co-operating with a scale 33. A diminishing level in the tank 11 tends to close the valve 23 and hence to sink the float 15 so that more liquid is admitted by the valve 14. The filter chamber 10 has an automatic inlet valve for maintaining a constant level therein. Liquid is discharged from the tank 11 over a weir 12 into a reservoir 13 and as the head over the weir is maintained substantially constant, the apparatus acts as a flow controller. The flow may be stopped at any time by opening a valve 34 which drains the float 15, causing the valve 14 to close. A float-operated valve 38 acts similarly when the reservoir 13 reaches a certain level. The latter valve opens suddenly against the pressure in the pipe 19 and consequently the level at which this happens may be adjusted by varying the area of the valve member 37 or the ratio of the length to the diameter of the float 35, or both. In a modification, the float which is not open at the top, floats in a separate tank supplied by the source 21 and drained through valves such as 23, 34, 38. As it takes time for the float 15 or the separate tank to fill, the flow is started up gradually.