Abstract: A tennis ball throwing machine pneumatically expels tennis balls through a barrel having on one side of its inner wall a Velcro strip for spinning the ball. The barrel is rotated about its lengthwise axis so that the sense of the spin, topspin, backspin, or right or left hand spin, varies in dependence upon the angular disposition of the Velcro strip as of the moment the ball passes it. The output end of the barrel is bent at an angle to its lengthwise axis resulting in an orbital motion.

Abstract: Tennis balls are sequentially fed to an entranceway in the top of the plenum chamber of a pneumatic throwing machine by a flexible disk which rotates about a vertical axis. The balls roll by gravity down a chute onto the feed disk which has angularly spaced pocket holes. To prevent jamming of unpocketed balls between the top of the feed disk and the feed chute, the disk is sufficiently flexible as to be deflectable by an unpocketed ball and be discharged through an open escape path.