Domestic electric appliance

Claim 1

A WATER HEATER TANK STRUCTURE HAVING GOOD STRUCTURAL STRENGTH AND GOOD CORROSION RESISTANT AND INSULATING QUALITIES CONSISTING OF A RELATIVELY THIN, FLEXIBLE, PREFORMED METAL SHEET, SAID SHEET FORMING WALL SURFACES NORMALLY MOVABLE RELATIVE TO EACH OTHER AND CAPABLE OF FORMING A STRONG BOND WITH POLYURETHANES, AND A HEAT INSULATING MATERIAL CONSISTING OF A SUBSTANTIALLY RIGID CLOSED CELL CLOSELY CROSS LINKED POLYUERTHANE FOAM OF IMPROVED STRENGTH HAVING THE CELLS THEREOF CONTAINING ESSENTIALLY ONLY A PREMANENTLY RETAINED FLUOROHALOGENATED SATURATED ALIPHATIC HYDROCARBON SUBSTANTIALLY INSOLUBLE IN THE FOAM, THE WALLS OF SAID CELLS HAVING AN IMPROVED SEAL FOR PERMANENTLY RETAINING SAID FLUOROHALOGENATED HYDROCARBON, SAID METAL SHEET AND POLYURETHANE FOAM FORMING A STRONG COEXTENSIVE PERMANENT BOND IN SITU THROUGHOUT THEIR AREAS OF CONTACT TO FORM A UNITARY STRUCTURE WHEREIN SAID FOAM PROVIDES SUBSTANTIAL RIGIDIFYING SUPPORT FOR THE SHEET, AND SAID POLYURETHANE FOAM ON THE SIDE THEREOF OPPOSITE SAID AREAS OF CONTACT WITH SAID METAL SHEET FORMING A BARRIER TO PREVENT THE PENETRATION OF WATER IN SAID TANK INTO CORRODING CONTACT WITH SAID METAL SHEET.