Liquid level sensing means

Claim 1

A liquid level sensing means in a liquid reservoir, said reservoir having a container base, a cap for enclosing 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 corresponding, cooperative dimensions; (b) a magnet means disposed within said cylindrical extension and a magneto-resistive element attached to each pole of said magnet means, said magneto-resistive elements being offset from each other and offset from the center line of said magnet means in a direction parallel to the movement of said diaphragm and being electrically in a circuit for effecting an electrical signal responsive to the magnetic flux applied to the magneto-resistive elements, each end of said magnet means including one said magneto-resistive element disposed in a respective vertical channel formed in the inside wall of said cylindrical extension; and (c) switching means including at least one switching member of magnetic material disposed on the inside wall of said cylindrical cup, said switching means being carried by said movable diaphragm such that said switching member passes proximate said magneto-resistive elements outside the wall of said cylindrical extension as the diaphragm moves in response to change in fluid level, thereby affecting the magnetic flux applied to said magneto-resistive elements.