Appeal No. 2003-1974
Application 09/317,409
What is “tied down” with a “tiedown ply” according to the written description in the
specification is the issue in the second ground of rejection. We find the following disclosure in
appellants’ specification:
. . . known methods utilized to reduce core crush during the autoclave process have
focused on preventing the differential movement by either mechanical/physical means
(i.e., using tie downs to keep the prepreg plies from differentially moving) . . .
. . . .
As discussed above, known prepreg plies have their differential movement
constrained to reduce core crush in honeycomb sandwich structures produced
therefrom. Known methods of constraining this differential movement have focused
on mechanical/physical constraining means (i.e., using tie downs) . . . . [pages 1-3.]
We further find that in addition to tiedown ply 150 in contact with honeycomb core 106,
Corbett discloses that
[t]raditionally, we use four complete cover sheet tiedown plies 175 in an effort to
anchor the layers and the core, and we show all these plies in FIG. 6, These traditional
plies 175 were commonly used in sandwich panel fabrication prior to introducing the
Hartz-type barrier film, and we commonly use them all, although we believe we can
now eliminate all but the outer plies and the peripheral, core contacting tiedown ply
150. That is, we would use three total plies rather than five, as FIG. 6 shows.
The tiedown plies 150 and 175 extend through the edgeband 160 beyond the net
trim line 165 to anchoring points that we tape to the layup mandrel. To further prevent
slippage of the tiedown plies, we have incorporated a low curing . . . film adhesive 180
between the tiedown plies just outside the net trim line of the part. The film adhesive
180 eliminates movement of one ply relative to the others when we apply pressure
during the autoclave curing cycle.
Thus, the tiedown method of the present invention can save material, reduce costs,
and save weight, if only the “picture frame” peripheral tiedown ply 150 is used (with
the traditional, internal sheets omitted). The normal tiedown procedure entails plys on
the outer surfaces of the skins and internally between the skin and underlying
adhesive. This tiedown system fails without the “picture frame” ply because the barrier
film 110 permits the core to slip. [Col. 6, lines 19-45.]
In comparing the disclosure that it was known to use “tie downs to keep the prepreg plies
from differentially moving” in appellants’ specification with the exclusionary phrase “in the
absence of a tiedown ply contacting the honeycomb core” in appealed claim 57, in light of the
disclosure in Corbett that different tiedowns are used for the honeycomb core, tiedown ply 150,
and for prepregs, tiedown ply 175, it seems to us that as a matter of fact, the “tiedown” for the
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