Appeal No. 1999-1083 Page 4
Application No. 08/759,394
ordinary skill in the art to have substituted it for an air-to-air heat exchange system, such as
is present in Bussjager’s first embodiment and in heat exchanger 7 of Des Champs.
With this as prelude, while we admit that the temperature differential between the
warm incoming air and the cooler exhaust air in Des Champs’ heat exchanger 4 if the
proposed modification were made might be less because the exhaust air had not
previously given up some of its heat, it is our view that one of ordinary skill in the art would
have recognized this to be a trade-off for achieving the improvements provided by the
Bussjager invention, such as better and more efficient cooling by the refrigerant coil and
the elimination of one heat exchanger pass for the exhaust air. In this regard, the
appellants have provided no evidence that the effect of Des Champs’ heat exchanger 4
would be impaired at all if the proposed modification were made, much less that it would
be “substantially” impaired, nor have they offered evidence that impairment of heat
exchanger 4 would have operated as a disincentive to one of ordinary skill in the art to
make the modification, It therefore is our view that the references are properly
combinable.
We also stand by our position that the modified Des Champs air conditioning
system meets the terms of the appellants’ claims 1 and 8. In this regard, Des Champs
discloses an air conditioning system which must have, although not shown, an outdoor coil,
a compressor and an expansion device, along with an indoor coil (5). A heat recovery
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