Level sensing system with latching device

Abstract

A liquid level sensing means for use in a tank or the like, adapted to hold a liquid which is partially withdrawn and/or replenished from time-to-time. Disposed within the liquid is a buoyant, upright, hollow reed switch-like float element having a longitudinal axis parallel with the direction of movement of the liquid level within the tank. The switch element is adapted to float upon the surface of the liquid whose level is to be sensed. It is provided with an upper reed and a lower reed, each in alignment with the longitudinal axis of the float element. The upper reed is rigidly secured to the upper end of an envelope of the float element, while the lower reed thereof is spring biasly secured to the lower end of the float element envelope. At a location medially between the upper and lower ends of the float element envelope, there exists an area of overlap between the unsecured ends of the upper and lower reeds respectively. At the upper end of the reed switch envelope is provided a calibrating magnet which is a pole magnet having a magnetic axis substantially in alignment with the longitudinal axis of the envelope of the float element. It is secured proximally to the top of the envelope and within magnetic proximity to the upper reed. The calibrating magnet will induce in the upper reed a magnetic axis and field opposite to the magnetic axis and field of the calibrating magnet. This will in turn induce a magnetic axis and field in the lower reed opposite to that of the upper reed, but the same in direction to that of the calibrating magnet.