Appeal No. 1999-1332
Application No. 08/591,857
appellants’ specification:
The present invention is based on the
realization that the dimensional stability
of conventional filter packs and the adhesive
layers required in any event for affixing
the filter pack to the case in a dust-tight
manner obviates the need to use a case which
itself is dimensionally stable. Consequently,
according to the present invention, the case
obtains dimensional stability only by being
cemented to the filter pack by means of
secondary adhesive layers. This, surprisingly,
provides good overall stability even though,
considered by themselves alone, neither the
filter pack nor the case is particularly
dimensionally stable. In this manner, the
cost of producing a cassette filter according
to the invention is considerably reduced.
Claim 1 is exemplary of the appealed subject matter and
reads as follows:
1. A cassette filter comprising:
a dimensionally stable filter pack; and
a cylindrical case that surrounds the filter pack in
a dust-tight manner, said case comprising flat sheets
that are cemented to one another and to the filter pack
via adhesive layers, said sheets alone not having enough
mechanical strength to provide a cassette that is
dimensionally stable, but having in combination with the
adhesive layers and filter pack sufficient strength for
this purpose;
wherein the sheets are fixed in position via their
connection to the filter pack.
2
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