Patent ID: 6945889

Claim:
A hydraulic tensioner for applying tension to a chain without external fluid pressure supply, comprising: a) a piston assembly comprising: i) a piston ( 31 ) with a hollow interior and an insert ( 42 ) surrounding the piston ( 31 ); ii) an inlet check valve ( 52 ) for controlling an entry of fluid into the piston, located such that when an end of the piston assembly is submerged in fluid, the inlet check valve permits fluid flow into the hollow interior; and iii) an outlet check valve ( 50 ) for preventing air entry when the piston extends and permitting controlled fluid outflow when the piston retracts, located at an opposite end of the piston assembly from the inlet check valve ( 52 ); b) a non-return mechanism coupled to the piston ( 31 ) such that the piston ( 31 ) extends but does not retract more than an included backlash ( 55 ) amount; and c) an inlet passageway ( 54 ) from the interior to the exterior of the piston ( 31 ), wherein the inlet passageway ( 54 ) is connected to the inlet check valve; wherein the tensioner is mounted such that the inlet passageway is located below the fluid level when the end of the piston assembly is submerged in fluid; and wherein the tensioner lifts fluid into the tensioner due to piston motion within the included backlash amount, action of the inlet check valve, and action of the outlet check valve, to fill an interior of the tensioner without an external fluid pressure supply.