Variable speed drive having speed limiting means

Claim 1

In a driving mechanism for a tractor having a frame, the mechanism having a variable-pitch sheave assembly operatively connected by belts to a driving pulley and a driven pulley for changing the speed ratio of said pulleys between to obtain a high-speed rate and a low-speed rate of the driven pulley upon swinging of said sheave assembly between a low-speed position and a high-speed position to vary the spacing of the axis of the sheave assembly relative to the axes of said pulleys, resiliently yieldable belt-tensioning means for urging said sheave assembly in a direction for maintaining the driving tension on said belts during movement of the sheave assembly between low-speed and high-speed positions, said belt-tensioning means exerting a first component of force tending to urge said sheave assembly away from high-speed position in maintaining the tension on said belts, the improvement of resilient biasing means anchored to said frame and operatively connected to said sheave assembly, said resilient biasing means being anchored to said frame and disposed to exert a second component of force tending to urge said sheave assembly toward high-speed position, said second component of force being substantially greater than said first component of force whereby the said sheave assembly is resiliently urged toward high-speed position, and adjustable limiting means carried by the frame and selectively adjustable to a plurality of limit positions to limit the maximum extent of the range of movement of the sheave assembly toward high-speed position and thus limiting the maximum speed of the driven pulley.