Liquid-level sensing device

Claim 1

A device for sensing the level of a liquid, comprising: two dissimilar metal wires enclosed within and protruding from one end of an electrical insulating material, the protruding ends of said wires being joined together to form a thermocouple junction; a heating wire for maintaining said liquid-level sensing device at a temperature above that of the environment above the liquid, said heating wire being disposed with said electrical insulating material and electrically insulated from said dissimilar metal wires, said insulating material being in the form of a solid ceramic cylinder having a land surface and a recessed surface at one end thereof, there being two tubular ducts passing longitudinally through said cylinder to form apertures in said land surface and two tubular ducts passing longitudinally through said cylinder to form apertures in said recessed surface, the ducts forming apertures in said recessed surface being shorter than the ducts forming apertures in said land surface, said heating wire being disposed within the two shorter ducts and forming a U-shaped loop exterior to and between the apertures in said recessed surface, each of said dissimilar metal wires being disposed within one of the two longer ducts; a tubular metal sheath having an inside diameter larger than the outside diameter of said cylindrical insulating material thereby allowing said cylindrical insulating material to be slip fitted into said tubular sheath; a solid metal plug securely sealing one end of said tubular metal sheath and in contact with said thermocouple junction; electrical connections between said heating wire and a power source for activating said heating wire; and electrical connections between said dissimilar metal wires and a device for sensing the electrical potential across said thermocouple junction.

Claim 2

A device for sensing the level of a liquid, comprising: two dissimilar metal wires enclosed within and protruding from one end of an electrical insulating material, the protruding ends of said wires being joined together to form a thermocouple junction; a heating wire for maintaining said liquid-level sensing device at a temperature above that of the environment above the liquid, said heating wire being disposed with said electrical insulating material and electrically insulated from said dissimilar metal wires, said insulating material being in the form of a solid ceramic cylinder having a land surface and a recessed surface at one end thereof, there being two tubular ducts passing longitudinally through said cylinder to form apertures in said land surface and two tubular ducts passing longitudinally through said cylinder to form apertures in said recessed surface, the ducts forming apertures in said recessed surface being shorter than the ducts forming apertures in said land surface, said heating wire being disposed within the two shorter ducts and forming a U-shaped loop exterior to and between the apertures in said recessed surface, each of said dissimilar metal wires being disposed within one of the two longer ducts; a tubular metal sheath having an inside diameter larger than the outside diameter of said cylindrical insulating material thereby allowing said cylindrical insulating material to be slip fitted into said tubular sheath; a solid metal plug securely sealing one end of said tubular metal sheath and in contact with said thermocouple junction; electrical connections between said heating wire and a power source for activating said heating wire; and electrical connections between said dissimilar metal wires and a device for sensing the electrical potential across said thermocouple junction.