Abstract: A tennis ball server supplied by a motorized ball feeder comprised of a trough and rotating plate that feeds balls at one rate, and wherein the server is motorized to oscillate so as to vary elevation of trajectory at another rate and is also motorized to oscillate so as to vary the traverse at still another rate; the three dissimilar motorized rates providing unpredictably placed serves, with speed control over said serves.

Abstract: A device for ball games, sensing velocity and scoring against a damping screen comprised of areas simulating strategic plays against a player's opposition and comprised of electrical sensor means applied to the back side of the screen and of minimum mass and consisting of electrically conductive horizontal bars to be engaged by depending switch rods moved into engagement by displacement of the screen upon impact from a ball while completely absorbing impact energy, there being a plurality of bars and adjustably biased rods responsive to degrees of ball impact force, and scoring means with a display therefor.

Abstract: A tennis ball feeder and server characterized by a cooperating helical screw type ball feed and a rotating inertia wheel. The feed screw is positioned to revolve on a horizontal axis between a pair of spaced apart, upstanding rails which define an opening through which tennis balls pass to be advanced to the server by the feed screw. The feed screw is formed of a helical rod supported on radial spokes projecting from a horizontally disposed drive shaft. The inertia wheel is supported over a ball engaging rail in alignment with the longitudinal axis of the feed screw and adjacent one end thereof such that when a ball is advanced by the feed screw to an entrance end of the rail it will be wedged between the rail and inertia wheel to be propelled from the exit end of the rail.

Abstract: An apparatus for dispensing liquid additives wherein a solution of concentrate is displaced from a closed container thereof and discharged into a flow line of liquid moving under pressure, said displacement being effected by differential positive and negative upstream and downstream pressure ports in said flow line and controlled by means of a selected restrictor of porous material having a determinable density that functions according to said differential in pressure to fix the flow rate of displacement liquid, said concentrate being displaced and discharged thereby at a determinable rate through the negative pressure port.