Image Number 5 for United States Patent #5709625.
A hydraulic tensioner 10 includes a hollow housing 14 having formed therewith an intermediate partition wall 12, a circular hollow cylinder 16 disposed concentrically in the housing 14, and a piston rod 18 slidably received in the cylinder 16 with a small gap or clearance therebetween. The cylinder 16 and the piston rod 18 jointly define therebetween a high pressure oil chamber 20. The pressure in the high pressure oil chamber 20 counteracts the force tending to retract the piston rod 18. The piston rod 18 projects from an open end of the housing 14, and a seal 24 surrounds the piston rod 18 to seal or close the end of the housing 14. The piston rod 18 has secured thereto a rod guide 28 disposed within the low pressure oil chamber 26. A spring 36 is disposed in a compressed condition between the housing 14 and the rod guide 28 to urge the piston rod 18 in the advancing direction. The rod guide 28 has radially elongated oil holes or passages 38 formed in its surface which engages the spring 36. The oil passages 38 extend radially outwardly from an inner peripheral surface of the rod guide 28 press fitted with the piston rod 18 and also extends axially through the rod guide 28, and are positioned so that they are not closed by the end of the spring.