Diesel fuel tank having removable electric immersion heater assembly

Claim 1

In combination with a material holding tank having an opening in the top surface thereof, an immersion heater insertable through said opening for immersion in the material contained in said tank, said heater comprising an elongated heat conduction means in contact with the material to be heated and extending generally vertically across substantially the entire height of the tank from said top surface to the bottommost portion of the tank, an electric heating element positioned within the heat conduction means and serving as a source of heat to be transferred to the material to effect a heating thereof, said heat conduction means including an elongated outer tubular member of cylindrical configuration and having an open upper end and a closed lower end, the upper end of said outer tubular member being sealingly secured in said opening with the open end thereof opening outwardly of the tank, said heat conduction means further including an inner tubular member of cylindrical configuration coextensive in length with a major portion of the length of the outer tubular member and coaxially removably inserted within the outer tubular member through said open end thereof, said inner tubular member having an outer diameter slightly smaller than the inner diameter of said outer tubular member and a lower end spaced from the closed end of the outer tubular member, said heating element being fixedly secured to the lower end of said inner tubular member and extending into space between said lower end and said closed end, respectively, of said inner and outer tubular members, heat flow control means comprising an air filled, narrow, cylindrical space between the outer tubular member and the inner tubular member extending substantially throughout the entire length of the inner tubular member as well as around the entire circumference thereof adapted to receive therein by convective circulation heat generated by the heating element so conduction by a highly efficient heat transfer is afforded from said outer tubular member of the heat conduction means throughout essentially the entire length thereof to the material, an electric wire directed through an interior portion of the inner tubular member and connected at one end thereof to the heating element and extending outwardly through a circular plate flanged member secured to and closing the other end of said inner tubular member for connection with a source of electrical energy, the inner tubular member of said conduction means comprising an electrical return path for connection with the source of electrical energy connected to the heating element, and heat insulation material essentially filling the inner tubular member throughout and being of a low heat capacity thereby augmenting maximal heat transfer from the heat conduction means to the material to be heated.