Page 7
Appeal No. 1998-1373
Application No. 08/377,473
Jelich teaches using pressure sensors for measuring pressure differential to detect this
condition. See column 2, line 35 et seq. It is our view that one of ordinary skill in the art
would have found it obvious, in view of the teachings of Jelich, to add pressure sensors to
the modified Heyl apparatus to measure the pressure differential across the filters to
detect a filter whose effectiveness has diminished due to being clogged. The rejection of
claim 4 therefore is sustained, along with the rejection of claims 5 and 6, which depend
from claim 4 and were grouped therewith.
Claims 22 and 25 have been found by the examiner to be unpatentable over the
combined teachings of Heyl, Clark and Hough, the latter being cited for its teaching of a
substantially vertically oriented first air plenum and first filter element. Of the three
references applied, Heyl discloses horizontally oriented elements, Hough discloses
vertically oriented elements, and Clark discloses both vertically and horizontally oriented
elements. In our opinion, this is evidence that vertical and horizontal orientations of filter
elements and the plenums in which they are installed were known alternatives in the art at
the time of the appellants’ invention, the selection of which would have been within the skill
of the artisan for the self evident advantages of each. In this regard, we observe that the
appellants have not argued in their Brief that the claimed vertical arrangement solves any
stated problem, provides an unexpected result, or is critical to the operation of the system.
The rejection of claims 22 and 25 is sustained.
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