In Re Butler

BLAND, Associate Judge.

Appellant in 32 claims asked for a patent relating to an aluminum piston for automobiles and engines.

Appellant’s piston is claimed to overcome the difficulty in using aluminum pistons with east-iron or steel cylinders. The use of steel pistons in the ordinary cylinder was objectionable in so far as the piston was required to be too loose in order to avoid expansion and sticking. Aluminum pistons were found to be better, but, owing to the fact that aluminum and aluminum alloys are said to have a thermal coefficient of expansion approximately twice that of iron, the…