Tractor cable tensioner

Claim 1

IN AN ENDLESS TRACTION MEMBER ADAPTED FOR COACTION WITH AN OPPOSED PARALLEL REACH OF A SIMILAR ENDLESS TRACTION MEMBER TO MOVE AN ELONGATED MOVABLE MEMBER PARALLEL TO ITS AXIS, A TRACTION ASSEMBLY COMPRISING AN ENDLESS SPROCKET CHAIN HAVING SPACED PAIRS OF SUPPORTS EXTENDING OUTWARDLY FROM EACH SIDE, A SUBSTANTIALLY RIGID BLOCK MOUNTED ON EACH PAIR OF SUPPORTS AND TRANSVERSELY SURMOUNTING SAID SPROCKET CHAIN, EACH OF SAID BLOCKS HAVING RECESSES IN ITS UNDERSIDE AT EACH EXTREMITY AND IN SPACED RELATION FROM THE SPROCKET CHAIN, ROLLER MEANS ROTATABLY JOURNALED IN EACH RECESS ON AXES TRANSVERSE TO THE DIRECTION OF MOVEMENT OF THE CHAIN, AND EACH HAVING A PERIPHERAL PORTION EXTENDING BEYOND THE UNDERSIDE OF SAID BLOCK FOR ENGAGEMENT WITH A SUPPORTING TRACK, THE TOP SIDE OF EACH BLOCK HAVING A GROOVE WITH ITS SIDE WALLS EXTENDING PARALLEL TO THE SPROCKET CHAIN, AND A SURFACE LINER SECURED IN SAID GROOVE OF MATERIAL HAVING A HIGHER COEFFICIENT OF FRICTION THAN THE MATERIAL OF SAID BLOCKS.