GB810554A - Apparatus for controlling the level of a flowable material in a container - Google Patents

Abstract

810,554. Automatic level control systems. ROBERTSHAW-FULTON CONTROLS CO. June 27, 1955 [Oct. 15, 1954], No. 18551/55. Class 38 (4). , In a system for automatically controlling the level of fluent material in a container the supply of material to the container is cut off when the level reaches an upper limit by a relay hoving a winding in the anode circuit of an electron oscillator valve which is rendered oscillatory or not by the level of material in the container to operate the relay which also controls the connection of a reactance in the oscillator circuit to ensure that the relay operation is maintained until the material reaches a lower level. In Fig. 1, when fluent material supplied by a pump 18 to a container 16 reaches a level B the capacity between a vertical probe 14 and the container is sufficient to stop oscillation of a valve 22, thereby increasing the energization of a relay 12 so that it opens contacts 70 to stop pump 18. The closing of contacts 76 of relay 12 connect a variable capacitor 20 in the circuit so that extraction of the fluent material for use through a conduit 90 can reduce the material in the container to a level A, dependent on the setting of capacitor 20, before oscillation re-commences and pump 18 is re-started. In a modification a pair of horizontal probes connected together, and respectively situated at the upper and lower limits of level, replace probe 14. In another modification the increased capacity between the probe and the container starts oscillation at the upper limit of level and the consequent deenergization of relay 12 is arranged to stop the pump.