Abstract: A tennis ball retrieving and propelling device for placement on a surface having a ball delivery tube and a carrousel type ball retriever positioned below the ball delivery tube for receiving balls to be pneumatically transported to the ball delivery tube. The delivery tube is provided with a mechanism for constricting the effective cross sectional area thereof. The mechanism is provided with a releasing element for releasing the constriction to permit a ball to be pneumatically propelled through the tube. The mechanism includes a section of flexible tubing attached to the delivery tube, a cable surrounding the flexible tubing and a device attached to the cable for tensioning and releasing the cable to restrict and release a ball traveling through the flexible tube. The balls are pneumatically retrieved and propelled from the propelling device. The propelling device has elements for controlling the speed, azimuth and elevation of a ball delivered therefrom.

Abstract: A universal joint permitting relative angular deflection of two members, vided with transverse stiffness augmentation means which minimize rotational performance penalties. One member contemplates a receptacle adapted to receive in spaced-apart relation therefrom an annular plug formed on the other member. A rolling seal is positioned between the receptacle and plug. Tabs, segments or rings are placed on the annular plug and/or the confronting wall of said one member to increase the transverse stiffness under all load conditions, particularly at angle orientations of the aforesaid two members.