Patent ID: 6892681

Claim:
A heat storage tank comprising a tank body for storing liquid while maintaining the warmth thereof and a housing having a fluid passage communicated with the interior of the tank body and allowing the liquid to pass therethrough, said tank body having an inner tank and an outer tank; said inner and outer tanks being welded together at a tank body port to define a sealed space between said inner tank and said outer tank; said sealed space being substantially a vacuum; and part of said housing being inserted and fitted into said tank body port, wherein a welded portion between said inner tank and said outer tank is not encircled with said housing but opens outward in the radial direction of the said tank body port, and a gap extended in the axial direction of said tank body port is defined between the welded portion of said inner tank with said outer tank and a welded portion-opposed part of said housing opposed to said welded portion in the axial direction of said tank body port; said gap having a size incapable of substantially retaining water drops.