Abstract: A rotational power-transmitting system which includes brake means automatlly operable to prevent transmission of "slip" forces from the driven member to the drive member when the drive member ceases delivering torque to the driven member. The system is preferably two-directional, i.e., the drive member is arranged to move the driven member either forwardly or rearwardly without interference from the brake means.

Abstract: A belt tensioner comprising a constant force spring trained between a stanary support means and a belt-engaged pulley. A slideway is provided to promote relatively frictionless movement of the pulley across the belt path.

Abstract: A chuck or coupling for connecting a rotary shaft to variable diameter work ieces; the work piece can be a pulley, shaft, bar stock or other mechanism required to be gripped by a chuck. The chuck structure comprises radially movable jaws slidably mounted on a rotary base or chuck body, together with a counter-balance for each jaw. Each counterbalance is located on a diametrical line passing through the associated jaw, whereby the jaw and counterbalance are subjected to oppositely directed radial forces during high speed rotation of the chuck structure. Centrifugal force is utilized to increase the gripping force of each jaw on the work piece.