GB704511A - Improvements in or relating to liquid level indicators - Google Patents

Abstract

704,511. Electric follow-up systems. ASKANIA-WERKE AKT.-GES. May 23, 1952 [June 16, 1951], No. 13163/52. Class 40 (1). In a liquid level gauge wherein a float actuates a contact device to energise a reversible electric motor which drives the contact device to follow the float movements, the contact device comprises an enclosed mercury contact switch adapted to be closed by an external magnetic field the influence of which upon the contact tube is varied by relative movement of the float and tube. As shown, the mercury contact switch 10 is suspended within a shell 8 by electric cables 6 from a drum 2. The shell carries a lever 13 pivoted thereto by a blade spring 16, so that movements of the float 11 produce, through a further similarly pivoted lever 12, magnified movements of a magnetic screen 14 carried by the free end of the lever 13. Upward movement of the screen permits a permanent magnet 9 to close the electric contact 15 of the switch 10. A circuit is thereby closed to a moving coil relay 20, 21 which mechanically rocks a magnet 22 to close a mercury contact switch 24 to energise a motor 3 which drives the drum 2 to raise the shell 8. When this movement causes the screen 14 to be interposed between the magnet 9 and the switch 10, the contact 15 in the latter "breaks." The consequential de-energisation of relay 20, 21, rocks the magnet 22 in the reverse sense to open contact 24 and close contact 23 whereby the motor is driven in the reverse sense. The motor runs in this direction until the contact 15 again makes to reverse the motor. The motor thus hunts about a mean position indicative of the liquid level which may be registered directly by a counter 4 and also remotely through a transmitter 5. The magnet or the contact tube may move with the float, in alternative constructions.