Abstract

A tensioner for a power transmission system includes two tensioning arms operatively engaged with a strand of either the chain or the belt of the power transmission system. The upper end of each tensioning arm is connected to a one way rotational clutch which is pivotally mounted between the upper ends of the tensioning arms. The one way clutch rotates in one direction in response to changing chain loads to adjust the tension substantially equally on both strands at the same time. In order to prevent over-tensioning, a damping means is included in the one-way clutch. When a pre-determined overload threshold is reached, the amount of torque required to overcome the coefficient of friction of a spring in the damper allows the one way clutch to slip in the direction opposite from its normal rotational direction, thereby relieving the overload condition on the chain.