Liquid level sensing means

Claim 1

A liquid level sensing means in a liquid reservoir, said reservoir having a container base with an open top, a cap for closing said base, said cap having means permitting communication between said reservoir and the atmosphere, and a flexible diaphragm sealingly disposed between said cap and said base separating liquid in said reservoir from the atmosphere, said diaphragm moving responsive to the level of said liquid, said sensing means comprising: a. a cylindrically-shaped extension integrally depending from said cap into a cylindrically-shaped cup formed in said diaphragm proximate its center, said extension and said cup having complementary dimensions; b. first magnet means disposed within said cylindrical extension with the opposed poles of said first magnet means oriented on a line corresponding to the direction of movement of said diaphram; c. galvano-magneto effect transducing means constituting a signal-generating electric circuit, said transducing means comprising a magneto-resistive element attached to each opposed magnetic pole face of said first magnet means; d. second magnet means carried by said diaphragm proximate its center and moveable with respect to said transducing means, said second magnet means being positioned in opposed relationship with said magneto-resistive element proximate said diaphragm even during movement of said diaphragm and influencing the magnetic flux density applied to said magneto-resistive element proximate said diaphragm for generating and electrical signal in said circuit when said second magnet means is lowered in accordance with change in the liquid level of fluid in said reservoir; and e. said magneto-resistive element remote from said second magnet means being subjected to a substantial constant level of magnetic flux density.