A tensioner for a chain or belt

摘要

A chain or belt tensioner comprises a plunger (5) displaceable in a bore of a housing (1) between retracted and extended positions. A radially resilient stop ring (16) disposed in the bore between the plunger and housing is engaged in frictional contact with a smooth surface of the housing. A recess in the plunger (14) is defined opposite the smooth bore and has a tapered face (21) for engagement with a bevelled surface of the stop ring (16). The tapered face tapers radially inwardly in the direction towards the open end of the bore so that movement of the plunger relative to the housing towards the retracted position causes the tapered face to engage said surface of the stop ring and to force it to deform in a radial direction to a wedging position in which the stop ring is wedged between the tapered face and the bore surface so as to prevent further inward movement of the plunger. The recess has a second face that is engageable with the stop ring when the plunger is moved out of the housing towards the extended position so as to slide the member over the smooth bore surface. The invention provides for a stop mechanism that enables the inward retraction of the plunger to be prevented at an infinite number of positions. <IMAGE>