Abstract: A ratchet tensioner includes a plunger locking and releasing mechanism for selectively locking and releasing a plunger relatively to a ratchet pawl pivotally mounted to a housing. The plunger locking and releasing mechanism has a lever-like pin contact portion formed integrally with a ratchet pawl body, a pin member-fitting hole formed in two opposed side walls of the housing in registry with the lever-like pin contact portion such that there being two pin-accommodating spaces defined between the lever-like pin contact portion and an inner peripheral surface of the pin member-fitting hole on opposite sides of the lever-like pin contact portion, and a pin member removably and selectively inserted in the pin-accommodating spaces.

Abstract: A ratchet-operated tensioner 1 is constituted by a principal plunger 4 slidably fitted into a cylinder chamber 3 formed in a tensioner body, an inner plunger 5 slidably fitted into the principal plunger, a compression spring 7 provided in an oil pressure chamber 6 and a ratchet mechanism 9. An O-ring 8 that slidably comes into contact with an inner wall of the principal plunger 4 is attached to an outer periphery of the inner plunger 5. In the ratchet-operated tensioner 1 with the pressure oil chamber according to the present invention the oil leak from the pressure oil chamber is prevented by preventing the oil leak from a gap between the principal plunger 4 and the inner plunger 7 during the engine's shutdown.

Abstract: A ratchet tensioner includes a plunger releasing mechanism for turning a ratchet pawl against the force of a plunger spring to disengage a locking prong of the ratchet pawl from a rack tooth of a plunger. The plunger releasing mechanism has a pin insertion hole formed in a plunger housing transversely across a recessed groove formed in the housing for mounting the ratchet pawl, and a sloped surface formed on the ratchet pawl and normally extending obliquely across the axis of the pin insertion hole. The sloped surface, upon abutment with the tip end of a pin which is inserted in the pin insertion hole, is capable of causing the ratchet pawl to turn against the force of the ratchet spring to thereby disengage the locking prong of the ratchet pawl from the rack tooth of the plunger for releasing the plunger.

Abstract: A ratchet tensioner includes a mechanism for selectively locking and releasing a plunger with respect to a ratchet pawl. The plunger locking and releasing mechanism has an actuator plate secured to the shaft of a ratchet pawl body for co-rotation therewith above the outside surface of a housing shaft in which a pin-accommodating hole is formed. The actuator plate has a pin-insertion hole smaller in diameter than the pin-accommodating hole and is manually movable about the axis of the shaft in opposite directions between a locking position in which the pin-insertion hole is in substantial alignment with the pin-accommodating hole and the engagement between a ratchet pawl and ratchet teeth on the plunger is maintained, and a releasing position in which the pin-insertion hole is out of alignment with the pin-accommodating hole, and the ratchet pawl is released from interlocking engagement with the ratchet teeth against the force of a ratchet pawl spring.

Abstract: A ratchet tensioner includes a plunger locking and releasing mechanism for selectively locking and releasing a plunger relatively to a ratchet pawl pivotally mounted to a housing. The plunger locking and releasing mechanism has a lever-like pin contact portion formed integrally with a ratchet pawl body, a pin member-fitting hole formed in two opposed side walls of the housing in registry with the lever-like pin contact portion such that there being two pin-accommodating spaces defined between the lever-like pin contact portion and an inner peripheral surface of the pin member-fitting hole on opposite sides of the lever-like pin contact portion, and a pin member removably and selectively inserted in the pin-accommodating spaces.

Abstract: A backlashless ratchet-type tensioner includes a tensioner housing, a plunger slidably fitted into a plunger accommodation bore formed in the tensioner housing and urged by a spring such that a tip portion of the plunger is projected to the exterior of the plunger accommodation bore, and a ratchet pivotally supported on a ratchet pin provided on the tensioner housing. At least one ratchet pawl formed on the ratchet is meshed with rack teeth formed on an outer surface of the plunger so as to prevent the plunger from receding into the plunger accommodation bore. A front face of the ratchet pawl is formed substantially perpendicular to a straight line which passes through a tip of the ratchet pawl and the center of the ratchet pin. The angle between a plane perpendicular to the axis of the plunger and the front face of the ratchet pawl meshed with a rack tooth is slightly smaller than the angle between the plane perpendicular to the axis of the plunger and a rear face of the rack tooth.