Patent ID: 7189174

Claim:
A chain tensioner comprising: a tubular housing having a bottom; a plunger installed in the housing so as to smoothly slide therein and having a hollow portion; a return spring inserted in the hollow portion of the plunger and providing the plunger with a force pushing outward; a plurality of latching grooves formed on an outer periphery of the plunger including an outer periphery of the hollow portion; a resister ring capable of locking in the latching grooves and sliding on the latching grooves back and forth along with the reciprocating movement of the plunger, the resister ring having a ring portion and a manipulation portion for radially expanding the ring portion, the manipulation portion being manipulable from outside of the tubular housing through a notch cut in the housing; a first stopper formed on an inner periphery of the housing and limiting backward movement of the plunger by mating the resister ring locked in the latching groove therewith; a second stopper capable of mating with the resister ring installed in front of the first stopper on the inner periphery of the housing; and an annular guide groove formed in the vicinity of an opening end of the inner periphery of the housing for setting the resister ring, and having the first and second stoppers on axially opposing walls at either end thereof.