Appeal No. 2004-0804
Application No. 09/757,886
resembling a frustum in cross-section.” (Page 5.) Further, EP
’262 teaches:
The aggregate area of the liquid discharge openings 6
in each downcomer duct 4 should be sufficient for
discharging all of the liquid flowing downwards
through the column interior at the intended liquid
loading and should be restricted with respect to the
horizontal cross-sectional areas of the lower parts of
the downcomer ducts so as to maintain in said
downcomer ducts a column of liquid which exerts at the
liquid discharge openings 6 a hydrostatic head
sufficient to prevent ascending gas from entering
these downcomer ducts 4.
This teaching would have reasonably suggested to one of ordinary
skill in the art that the cross-sectional area relationship
between the lower end and the upper end of the downcomer at tray
level is a result-effective variable.4
It is our judgment, therefore, that one of ordinary skill
in the art would have found it prima facie obvious based on the
prior art teachings as a whole to determine by routine
experimentation a workable or even optimum range of lower end
cross-sectional area to upper end cross-sectional area ratios,
thus arriving at an apparatus encompassed by appealed claim 3.
In re Peterson, 315 F.3d 1325, 1330, 65 USPQ2d 1379, 1382 (Fed.
Cir. 2003)(“The normal desire of scientists or artisans to
4 This is consistent with the appellants’ acknowledged
prior art (specification, pp. 1-2), which appreciated the cross-
sectional area relationship as a tray design consideration.
8
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