GB798212A - Improvements in or relating to means for controlling the level of a liquid in a container - Google Patents

Abstract

798,212. Automatic liquid level control systems. BROADWELL ENGINEERING CO., Ltd. Oct. 18, 1955 [Oct. 20, 1954], No. 302 19/54 Class 38 (4). In a floatless type of liquid level control system in which an electric motor-driven pump is automatically controlled through an electromagnetic relay and a motor starter when the liquid reaches a predetermined level and means associated with the motor starter maintain the condition of the relay and hence the pump until the level has changed to a predetermined extent, alternating current is passed through the liquid and the relay is energized from an A.C. supply through a bridge rectifier. As shown, when the level of liquid in a metal container C rises to make contact with an electrode 6 a circuit is completed between electrodes 3 and 6 to energize a relay 10 from an A.C. source 1 through a transformer 4 and a rectifier 5. The consequent closing of relay contacts 11 starts an electric motor driven pump (not shown) which extracts liquid from the container, and the closing of contacts 7 associated with the motor starter ensures that extraction continues until the level falls below the lower end of an electrode 8. Electrode 3 may be replaced by the metal stem of the pump or the metal container itself. A resistor may be included in series with the supply to rectifier 5, or the spacing or sizes of the electrodes may be varied, to suit the conductivity of the liquid. The electrodes may be telescopic to facilitate selection of levels.