Hydraulic tensioner

A hydraulic tensioner for imparting tension to a chain comprising:

• a housing having an axially extending piston hole, the piston hole having at least one end open to atmosphere, a pawl spring hole extending inwards towards the piston hole from an outer surface of the housing, and a pawl hole extending laterally and communicating between the piston hole and the pawl spring hole;
• a piston having a first end for applying tension to the chain and a second end comprising rack teeth formed on at least a portion of an outer circumference thereof, the piston being axially slidable and forming a fluid chamber between the second end and the end of the piston hole of the housing;
• a piston spring in the fluid chamber of the housing for biasing the piston in a protruding direction;
• a pawl member having a front surface, a rear surface, an upper surface, a lower surface, joined by a pair of side surfaces, wherein teeth are formed on the lower surface thereof and engageable with the rack teeth of the piston, wherein the rack teeth of the piston and the teeth of the pawl member permit movement of the piston in a protruding direction but prevent movement of the piston in a retracting direction;
• and
• a pawl coil spring located in the pawl spring hole for biasing the teeth of the pawl member to engage the rack teeth of the piston and having an elliptical cross-sectional shape comprising:
• a pair of linear portions disposed opposite each other and a long axis, and a pair of semi-circular portions disposed at opposite ends of the linear portions;
• wherein the pawl hole is located relative to the pawl spring hole such that the linear portions of the pawl coil spring contact an upper surface of the pawl member.

A hydraulic tensioner for imparting tension to a chain comprising:

• a housing having an axially extending piston hole, the piston hole having at least one end open to atmosphere, a pawl spring hole extending inwards towards the piston hole from an outer surface of the housing, and a pawl hole extending laterally and communicating between the piston hole and the pawl spring hole;
• a piston having a first end for applying tension to the chain and a second end comprising rack teeth formed on at least a portion of an outer circumference thereof, the piston being axially slidable and forming a fluid chamber between the second end and the end of the piston hole of the housing;
• a piston spring in the fluid chamber of the housing for biasing the piston in a protruding direction;
• a pawl member having a front surface, a rear surface, an upper surface, a lower surface, joined by a pair of side surfaces wherein teeth are formed on the lower surface thereof and engageable with the rack teeth of the piston, wherein the teeth and the teeth of the pawl member permit movement of the piston in a protruding direction but prevent movement of the piston in a retracting direction;
• a pawl coil spring located in the pawl spring hole for biasing the teeth of the pawl member to engage the rack teeth of the piston and having an elliptical cross-sectional shape comprising:
• a pair of linear portions disposed opposite each other and a long axis, and a pair of semi-circular portions disposed at opposite ends of the linear portions;
• and
• a cover for covering the pawl spring hole in the housing having an upper surface connected to pair of supporting portions extending downward and inward towards the piston to support the pawl coil spring in a lateral direction and a pair of downwardly extending portion extending downward and inward towards the piston from the support portions to the piston hole to cover the pair of side surfaces of the pawl member;
• wherein the pawl hole is located relative to the pawl spring hole such that the linear portions of the pawl coil spring contact the upper surface of the pawl member.