PURPOSE: To improve the temperature retaining capacity of the titled tank by integrating all the constitutional elements of the tank by a method wherein a low pressure foaming hard urethane material is interposed between the ceiling plate of a cover surrounding the hot water storage tank having a semi-spherical bottom, and the side plate 8 of the cover, a spacer having a communication hole is interposed between the semi-spherical bottom of the tank and the bottom plate of the cover and a soft urethane material is filled into the space between the bottom of the tank and the bottom plate of the cover without leaving any gap.
CONSTITUTION: The spacer having the communication hole 11 is interposed between the hot water storage tank 6 having the semi-spherical bottom 7, and the bottom plate 12 of the cover surrounding the tank and an injection port 13 is provided at a part, and gas escape ports 14 and 15 at other parts, of the bottom plate 12. Then the low pressure foaming hard urethane material 17 is injected from the injection port 13 into the space defind by the tank 6, the ceiling plate 9 and the side plate 8 of the cover. The urethane material 17 may be in the form of a shaped frame of small thickness and light weight since the foaming pressure thereof is low and it is released immediately after foaming. Thus, upon completion of the filling of the urethane material 17 into the space up to a part near the bottom, the soft urethane resin material 18 is injected into the space through the port 13. The urethane resin material 18 thus injected passes the communication hole 11 and enters the space where it foams to thereby form a heat insulating layer. As a result, all the constitutional elements of the tank are made integral with one another by the urethane materials 17 and 18.
HIRATA KATSUMI
FUJISHIMA MICHIYUKI
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