Appeal No. 1996-1456
Application No. 08/059,840
Kato discloses a disk cartridge having a plastic shutter
instead of a conventional metal shutter. In order to provide
good moldability and high mechanical strength, heat resistance
and slidability, Kato makes the shutter of a thermoplastic
material, such as polyethylene or polypropylene, and a filler,
such as calcium carbonate, which is 5% to 30% by weight, and
preferably 10% to 20% by weight, of the plastic-filler composite
(see column 2, lines 14 through 41). Kato teaches that when the
filler is below 5% by weight, the shutter will have poor heat
resistance and mechanical strength, and that when the filler is
above 30% by weight, the plastic composite in molten form will
have poor flowability and moldability (see column 2, lines 51
through 57).
According to the examiner, it would have been obvious to one
of ordinary skill in the art at the time the invention was made
“to make the cartridge casing of Hitachi Maxell out of
polypropylene with a 10 to 20% by weight filler of calcium
carbonate as taught by Kato ... since it has high mechanical
strength and heat resistance” (main answer, page 5). The problem
here, however, is that this proposed reference combination runs
counter to the express teachings of Hitachi Maxell which mandate
that the percent by weight of filler to plastic not fall below 45
percent or rise above 65 percent. Given that Kato’s plastic-
filler composition is specifically designed for a disk cartridge
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