GB358579A - Improvements relating to level indicators, more particularly for blast furnaces - Google Patents

Abstract

358,579. Bins. TRIGGS, W. W., 57, Lincoln's Inn Fields, London. - (Freyn Engineering Co. ; 310, South Michigan Avenue, Chicago, U.S.A.) July 11, 1930, No. 21022. [Class 20 (i).] The level of material in a blast furnace or other receptacle is indicated by means of a weighted test member, which normally rests on the surface of the material and is controlled by a cable adapted to be wound up by an electric motor, the pull of the motor being limited to a value sufficient to keep the cable taut, but insufficient to lift the test member or to prevent it descending with the charge. The amount of cable paid out serves to indicate the level of the charge. The apparatus shown diagrammatically comprises a test rod 3 moving in a vertical sleeve 3a and suspended from a cable 4 connected to a winding drum 6 driven through gearing from an electric motor 7. The drum drives a recording-device 15 through a flexible shaft 12 and worm gearing 13. The test rod is raised before a fresh charge is fed to the furnace, and an arm 16 is arranged to open a normally closed limit switch 17a when the rod reaches its uppermost position. The bell 2 is operated by a movable cylinder 2a, to one end or other of which fluid under pressure is supplied by a four-way valve 2d operated by a reversible electric motor 30m. When the rod is resting on the charge, current is supplied to the motor 7 through a resistance which limits its torque to the desired amount. When it is desired to charge the furnace a complete cycle of operations is initiated by the momentary operation of a press button switch, which closes a maintaining circuit, and at the same time shorts the resistance. This allows the motor to develop its full torque, and the rod is raised until the operation of the limit switch 17a breaks the circuit and automatically applies a brake 10, which holds the rod in its raised position. At the same time, switches close to complete a circuit through the motor 30m, which operates the valve 2d and causes the opening of the bell 2. When the cylinder 2a reaches its uppermost position, limit switches 17c, 17d are operated to break the bellopening circuit, and to energize the motor 30m in the reverse direction. The bell now closes and the operation of the limit switch 17b completes the circuit through the motor 7 and its resistance, thus re-establishing the original conditions.