Patent ID: 6053831
Filing Date: 2000-04-25
Classification: F16H

Abstract:
A hydraulic tensioner comprising:a housing having a central bore with a central vertical axis, an inside surface and a base; said bore having a bore upper end, a bore middle portion and a bore lower end in the axial direction of said bore; said bore upper end having an upper end bore diameter, said bore middle portion having a middle bore diameter, said bore lower end having a lower end bore diameter, said bore diameters being defined as the distance across the inside surface of the bore in the radial direction at a specified point along the bore in the axial direction;a generally cylindrically shaped hollow piston having an inside portion and an outer surface, said piston slidably received within said bore, said piston having a piston upper end, a piston middle portion, and a piston lower end, said piston upper end having an upper end diameter, said piston middle portion having a middle portion diameter and said piston lower end having a lower end diameter, said piston diameters being defined as the distance across the outer surface of the piston in the radial direction at a specified point along the piston in the axial direction;said piston inside portion forming a fluid chamber with the base of said bore, said fluid chamber including a first fluid leakage passage from said fluid chamber, said first fluid leakage passage formed between the outside surface of said piston and the inside surface of said bore, said first fluid leakage passage having an upper end, a middle portion and a lower end corresponding axially to said piston and said bore upper end, middle portion and said lower end;said first fluid leakage passage having a first cross sectional area at said upper end between the outside surface of said piston at said piston upper end and said bore inside surface at said bore upper end; said first fluid leakage passage having a second cross sectional area located at said lower end between the outside surface of said piston lower end and said inside surface of said bore at said bore lower end; said first fluid leakage passage having a third cross sectional area at said middle portion between said outer surface of said middle portion of said piston and said inside surface of said middle portion of said bore;a piston spring located between the base of said bore and the inside of said piston, said piston spring biasing said piston in an outward axial direction from said bore;a second fluid passageway in the housing connecting the fluid chamber with a source of pressurized fluid; a check valve located in said second fluid passageway between said fluid chamber and said source of pressurized fluid, said check valve acting to permit fluid flow into the fluid chamber while blocking flow in the reverse direction; and,said first cross sectional area of said first fluid leakage passageway being smaller than said second cross sectional area of said first fluid leakage passageway.