Patent ID: 7223457

Claim:
A composite element which has the following layer structure: (i) a thickness of from 2 to 20 mm of metal, (ii) a thickness of from 10 to 300 mm of plastic, and (iii) a thickness of from 2 to 20 mm of metal, where (i) and/or (iii) have an opening and wherein the opening has been closed and opens when the pressure difference between (ii) and the other, outward-facing side of (i) and/or (iii) is at least 10 bar, where the higher pressure is present in (ii) and the higher pressure results from an increase in temperature in (ii) and wherein the opening has been connected to one end of a pipe which extends into (ii) and whose other end is at a distance of 0.5 to 9.5 mm from the surface in contact with (ii) of the metal layer which does not have the opening connected to the pipe.