GB1227351A - - Google Patents

Abstract

1,227,351. Automatic liquid level control. G.S.M. ELECTRICAL CONTROLS Ltd. April 2, 1968 [Jan. 4, 1967], No. 426/67. Heading G3R. The level of liquid in a container is maintained constant by controlling the supply of liquid to the container by a valve or pump the setting of which is determined by the state of a bridge circuit including resistances, capacitances or inductances varied by a float-operated magnet and the setting of the valve or pump respectively. In Fig. 1 a permanent magnet 24 is moved vertically by a float 20 with changes of water level in a boiler 10 so that another permanent magnet at 46 moves about its right-hand pivot to adjust a potentiometer (not shown). The potentiometer is associated with a relay circuit controlling a reversible electric motor which opens or closes a feed water valve as necessary to maintain the level constant. Follow-up is provided by a potentiometer, operated with the valve, which forms a bridge circuit with the magnetically operated potentiometer. A feed water pump may be controlled instead of a valve and the magnet may control an inductance or a capacity or a semi-conductor responsive to pressure or a magnetic field instead of a potentiometer. If the level falls unduly, another permanent magnet at 48 moves to a second stable position in which it influences a reed switch to operate a visual or audible alarm. A second float operated magnet 68 operates further reed switches 70, 72 to give alarm and shut down the boiler if water level gets outside still wider limits.