Appeal No. 2000-1917
Application 09/076,863
Johnson discloses “a heat exchanger in which corrosion-
resistant plastic components are used for surfaces which are
exposed to corrosive fluids and in which metal components are
used for rapid thermal transfer from the plastic components to
a thermal disposal or secondary fluid” (column 1, lines 14
through 19). Among the plastic components are “plastic tube
sheets 12, 13 to which thin-walled plastic tubes 14 are
secured in sealed relationship, as by providing exteriorly
protruding sleeves 15 on
the tube sheets and fusing the ends of the tubes to the
sleeves, as at 16" (column 2, lines 35 through 39). Johnson
teaches that
such components can be made of various plastics including
fluorocarbon polymers such as polytetrafluoroethylene (see
column 4, lines 14 through 47).
In proposing to combine the German reference and Johnson
to reject claim 1, the examiner concludes that it would have
been obvious at the time the invention was made to a person
having ordinary skill in the art “to employ in [the German
reference] components composed of polytetrafluoroethylene
(PTFE) for the purpose of improving corrosion resistance”
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