Speed change device

摘要

Complementary relatively stationary pulleys having axially oppositely stepped diameter portions form a variable speed drive between a motor coupled with one stepped pulley and a driven device coupled with the oppositely stepped pulley such as the spindle of a drill press on which the device is mounted. A transmission belt for the stepped pulleys is bodily shifted with an associated belt tensioning idler pulley, a belt shaper guide, and a compression belt former selectively to position the belt in alignment with chosen diameter portions of the two stepped pulleys to effect a desired speed change while the belt is in a deformed state out of contact with the stepped pulleys, following which the belt is retensioned to engage it with the chosen stepped portions of the complementary stepped pulleys.