Level sensing system with latching device

Claim 1

A liquid level sensing system, comprising: (a) a tank or the like adapted to hold a liquid which is partially withdrawn or replenished from time to time; (b) a plurality of level sensing pole magnets secured in uniform relative vertical positions within said tank, each of said pole magnets having magnetic axes of like directional polarity; (c) within said tank, an elongate reed switch having a buoyant envelope thereabout and having a top and a bottom, said reed switch comprising an upper reed element, axially rigidly secured within said envelope from the top thereof, and a lower reed element axially secured by a radial spring of constant value from the bottom of said envelope, wherein opposite ends of said reed elements are unsecured, free ends defining an axial segment of radially-displaced, overlap, said radial displacement being smaller in dimension than said segment of axial overlap; (d) a compensating magnet secured in magnetic proximity to said upper reed element, said compensation magnet having a magnetic axis co-parallel and co-directional with the magnetic axis of said level sensing magnest, said compensating magnet inducing in said upper reed element a magnetic axis and polarity opposite that of said compensating magnet and of said upper reed element, thereby inducing into said lower reed element a magnetic axis and polarity opposite to that of said upper reed element and thereby the same as the polarity of said compensating magnet and of said level sensing magnets, whereby, when said envelope of said reed switch is beyond the magnetic proximity of any of said level sensing magnets, the radial component of said spring constant value, securing said lower reed element at its fixed end, will overcome the normal magnetic attraction between said free ends of said upper and lower reed elements to thereby maintain said reed elements in an open state and, further whereby, movement of said envelope into the proximity of one of said level sensing magnets will cause the mutual contacting of said free ends of said reed elements when said ends become magnetically proximal to that pole of the proximal level sensing magnet that is like in polarity to the free end of said upper reed element, and, conversely, will cause the opening of said free ends of said reed elements when said free ends are magnetically proximal to the pole of said proximal level sensing magnet that is opposite to polarity of the free end of said upper reed element, wherein the event, direction and velocity of said reed switch passing a particular level sensing magnet can be monitored from changes in the magnetic field geometry within the reed switch as well as from direct current flow monitoring within the elements of the reed switch.