Belt tensioner

Claim 1

A belt tensioning device comprising: a belt; a pulley in rolling contact with said belt; a stud bolt studded to a stationary member; a shaft of generally uniform round section, having an eccentric axis of rotation by being formed with an eccentric hole in which said stud bolt is fitted, said shaft being also formed with a circumferential groove; bearing means for concentrically and rotatably mounting said pulley on said shaft, having a plurality of balls and a ring attached to said pulley and formed with a circumferential groove which cooperates with the groove in said shaft to confine therein said balls; a coil spring disposed to encircle said shaft in an eccentric relation to said axis of rotation and having an end fixed to said shaft and the other end fixed to said stationary member so as to urge the shaft to rotate in the direction causing the pulley to move toward the belt; said stud bolt having a threaded free end portion protruded from said hole; and a nut screwed onto said threaded free end portion of the stud bolt to fixedly attach the shaft to the stationary member, whereby the degree of tension on said belt is readily adjustable by loosening said nut, rotating said shaft and tightening said nut.