Appeal No. 98-2325
Application No. 08/546,116
exhaust air outlet pipe 16 to the inlet end of an exhaust air
muffler 18. Muffler 18 is described in the Belley
specification as being a “conventional known muffler” (column
1, line 63) for attenuating noise due to the exhaust air flow
from the central unit. Other than stating that the exhaust air
muffler is “conventional” the Belley specification does not
describe any of the internal noise-absorbing components in the
muffler. Appellants do not contest these findings.
Admittedly, Belley lacks an express teaching of a noise-
absorbing liner in the exhaust air muffler as argued by
appellants. The Sakaki reference, however, teaches a vacuum
cleaner muffler for reducing noise due to exhaust air flow
from the vacuum cleaner unit. According to Sakaki’s
specification, the exhaust air muffler is advantageously
provided with a liner 2 (described as a tube in the
accompanying translation) of suitable noise-absorbing
material, such a urethane foam, in an elongated muffler pipe
between the inlet and outlet ends of the muffler.
Based on the prior art evidence before us, foam liners,
particularly polyurethane foam liners, were well known in the
muffler art at the time of appellants’ invention as evidenced
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