Appeal No. 2005-0487
Application No. 09/961,821
during a retraction or compression stroke and a metered flow of
gas past the piston during an extension or expansion stroke. In
one embodiment (see Figures 5 through 9), the piston assembly
includes an O-ring 38 having on one side slots 190 defining free
flow bypass openings functional during a retraction stroke and on
the other side a single orifice groove 192 defining a metered
flow bypass opening functional during an expansion stroke. In a
second embodiment (see Figures 20 through 22), the piston
assembly includes an O-ring 226 which cooperates on one side with
free flow bypass apertures 228 in a facing wall of the piston
assembly and on the other side with a metering orifice slot 230
on an opposing facing wall of the piston assembly. Ludwig
teaches that these O-rings may be made of a flexible elastomeric
rubber or plastic to allow them to be stretched and snapped into
place on the piston assembly and to flex during use so as to shed
contaminants and prevent clogging of the bypass openings (see
column 2, lines 62 through 64; column 10, lines 8 through 16; and
column 11, lines 13 through 32).
As indicated above, independent claim 1 recites a piston-
cylinder assembly comprising, inter alia, an elastically
deformable valve ring which deforms into a flow-through pocket to
at least partially seal it off when the piston rod exceeds a
4
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Last modified: November 3, 2007