Appeal No. 1999-2775
Application No. 08/549,847
and maintaining tighter tolerances in milling, drilling and
grinding operations without part contamination (Vortec Catalog,
page 4). In this regard, it must be borne in mind that where two
known alternatives are interchangeable for their desired
function, an express suggestion of the desirability of the
substitution of one for the other is not needed to render such
substitution obvious. See In re Fout, 675 F.2d 297, 301,
213 USPQ 532, 536 (CCPA 1982); In re Siebentritt, 372 F.2d 566,
568, 152 USPQ 618, 619 (CCPA 1967).
We also again note the broad teaching in Lubbering '242
(col. 3, lines 11-13) that the cold gas supply may be "cold air
which has been cooled by suitable means to temperatures
substantially lower than minus 20° C" (emphasis added). As
conceded by appellants (brief, pages 5 and 7), vortex tube cold
air supply apparatus is well known and has been widely used in
industry, particularly for spot cooling and in enclosure cooling
systems since the 1960's. Thus, we consider that one of ordinary
skill in the art at the time of appellants' invention would have
recognized the vortex tube cold gas supply apparatus of Peter or
the Vortec Catalog as being "suitable means" within the context
of the broad disclosure in Lubbering '242.
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