Apparatus for maintaining tension of an endless drive member

An improved apparatus for tensioning endless drive members such as belts or chains, said apparatus comprising:

• a torque arm;
• means mounted on said arm for engaging an endless drive member to impart a tension maintaining force thereto;
• means pivotably supporting said torque arm at a location spaced from said means for engaging, for permitting rotation of said torque arm about an axis, said supporting means comprising:
• at least one elastomeric spring having a central bore surface, an outer circumferential surface and a first spring rate;
• means for securing one of said surfaces against rotation about said axis;
• means attached to said torque arm and the other of said surfaces for causing the other of said surfaces to rotate about said axis, whereby a countertorque is induced in or released from said elastomeric spring in response to changes in force applied to said torque arm by a drive member acting on said means for engaging;
• and
• means, operatively associated with said means for causing said other of said surfaces to rotate, for resisting rotation by providing an essentially elastic resistance at a second, substantially higher spring rate until a predetermined breakaway torque is applied and thereafter for allowing rotation while providing a rotational drag force to damp oscillations of said apparatus.