Patent ID: 7040468

Claim:
A shock absorber comprising: a cylindrical housing adapted to be filled with a damping fluid, said cylindrical housing having an interior; a piston slidably disposed within said cylindrical housing to divide the interior of said cylindrical housing into an upper working chamber and a lower working chamber; a passage extending between said upper and lower working chambers and adapted to selectively allow the damping fluid to flow therethrough during movement of said piston, said passage having an upstream end and a downstream end; a valve seat located adjacent to said downstream end of said passage; and a valve assembly operable to selectively open and close said passage during movement of said piston, said valve assembly including (i) a first valve disc held on and deflectable toward said piston, and separated from said valve seat, (ii) a second valve disc on said first valve disc and normally seated on said valve seat, said second valve disc including circular apertures arranged in a circumferentially spaced relationship and selectively openable and closable by said first valve disc, (iii) a third valve disc on said second valve disc and having notches arranged in a circumferentially spaced relationship, said notches each having an inner end and an outer end and cooperating with said circular apertures to form ports, said ports being constantly communicated with one of said upper and lower working chambers that is located downstream of said valve seat; and (iv) a fourth valve disc cooperating with said second valve disc to sandwich said third valve disc so that restrictive orifices are defined at the outer end of each of said notches, wherein said ports each have a cross sectional area greater than a cross sectional area of each of said restrictive orifices, regardless of a relative angular position between said second and third valve discs.