Appeal No. 2003-0387 Page 8
Application No. 09/772,275
26 may draw back from the side frame column 22, resulting in a rapid decrease in the
force Fc, which again reduces the warp moment, gFc.
Hawthorne states (column 4, line 51+) that a parametric study was made to
assess the effect of the variables in the equations (a), (b), (c) and (d) set forth in column
4, lines 22-33) and has led to the following conclusions:
(1) With regard to the coefficient of sliding friction :: Referring to FIG. 15,
although raising the value from 0.50 to 0.63 increases the ratio f for upward
motion, the point where the slip region is entered does not change appreciably.
By lowering the value to 0.10 the slip region is almost avoided. However, this is a
marginal level for practical application, i.e., it does not provide a comfortable
margin below the slip region. In the case of downward motion, lowering the value
causes higher values of negative ratio f. If these reach the region between -0.8
and -1.0, the wedge may slip downward relative to the bolster.
(2) With regard to wedge angle 2: Referring to FIG. 17, decreasing the
wedge angle lowers the ratio f for upward motion, but it does not have an
appreciable effect upon entry into the slip region. The ratio f for downward
movement of the bolster is well behaved.
(3) With regard to loaded car wedge spring force Fs : Referring to FIG. 18,
for upward motion of the bolster increasing the wedge spring force lowers the
maximum ratio f and changes entry into the slip region considerably. For
downward motion, the system is well behaved.
As a result of the parametric study it was concluded that merely varying a
single parameter probably would not result in a practical system to secure the
wedges against undesirable unloading during vertical motion, and that to achieve
one purpose of this invention it probably would be necessary to vary one or more
of the parameters studied. The study suggested reducing the wedge angle 2
from 35 to 30 degrees, reducing the column coefficient of friction from 0.50 to the
range of 0.25 to 0.30, and increasing the empty and loaded wedge spring force
substantially.
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