Patent ID: 7392766

Claim:
A liquid heating appliance comprising: a tank, having a burst pressure, for holding a liquid to be heated; a heating system operative to heat the liquid in the tank to a predetermined first heated temperature; and protective apparatus for preventing rupture of said tank caused by heated liquid-created overpressurization thereof, said protective apparatus including; a barrier structure comprising a hollow thermoplastic body portion forming a barrier to liquid outflow from said tank and having an interior exposed to the interior of said tank, said hollow thermoplastic body portion being heat-softenable, by pressurized tank liquid, at a second heated temperature greater than said first heated temperature, the heat-softened hollow thermoplastic body portion being burstable, at a heat-reduced burst pressure less than said burst pressure of said tank, to thereby create a pressure outlet passage through said hollow thermoplastic body portion that relieves internal tank liquid pressure before it reaches said burst pressure of said tank.