Appeal No. 2003-0387 Page 5
Application No. 09/772,275
Hawthorne then teaches in the SUMMARY OF THE INVENTION section that
The principal object of the present invention is to provide a wedge system
which is capable of achieving a warp stiffness high enough to elevate the critical
speed of truck hunting (the speed at which hunting will first occur) to a level
suitable for freight car operation.
Figures 1 and 2 show a typical freight car truck assembly having a pair of
laterally spaced side frames 10 carried by a pair of wheelsets 12 and spanned by a
bolster 14. Each side frame is provided with an opening 16 defined by a compression
member 18, a tension member 20, and a pair of side frame columns 22. The opposite
end portions of the bolster 14 extend respectively through the openings 16 and are
carried respectively by spring groups 24 acting against side frame spring seats. A
friction wedge 26 is carried by a spring 28 acting against the side frame spring seat to
urge the wedge upwardly between the bolster and the side frame column. As the
bolster moves vertically, the friction wedges slide against the side frame columns to
generate damping forces. Since the spring force loading a friction wedge is a function
of the spring group travel or vertical motion of the bolster, the spring force is greater
when the car is loaded than when the car is empty. Thus, the damping force varies with
the car weight.
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Last modified: November 3, 2007