US Patent 7422515 Wide belt sander

A wide belt sander has a base, a driving axle, a driving device, a driven axle bracket, a driven axle, a belt and an automatic adjustment device. The driving axle is rotatably mounted on the base and has a central axis. The driving device is mounted on the base and is connected to the driving axle. The driven axle bracket is rotatably mounted on the base along a longitudinal axis perpendicular to the central axis of the driving axle. The driven axle is rotatably mounted on the driven axle bracket along a rotating axis parallel with the central axis of the driving axle. The belt is endlessly mounted around the driving and driven axles. The automatic adjustment device is mounted between the base and the driven axle bracket to drive the driven axle bracket to swing relative to the base in a simple harmonic motion.