Patent ID: 7431135

Claim:
A two-stage shock absorber comprising: a pressure tube defining a working chamber; a piston body slidably disposed within said pressure tube, said piston body dividing said working chamber into an upper working chamber and a lower working chamber; a piston rod extending entirely through said upper working chamber and projecting out of said upper working chamber, said piston rod being connected to said piston body; a first and second valve assembly attached to said piston body, said first and second valve assemblies providing a first and a second passageway, respectively, through said piston body; a third fluid passageway defined through said piston rod; a sleeve slidably disposed on an inner surface of said pressure tube and on said piston rod within said upper working chamber, said sleeve being operable to progressively close said third passageway when movement of said piston body with respect to said pressure tube exceeds a specified distance; and said third passageway being comprised of a single bore and a groove extending from said bore in a downward helical spiral along an outer surface of said piston rod to a terminal end.