| 摘要 |
<p>Balls such as table tennis balls or tennis balls are continuously fed to two pairs of adjacent flanged rollers of a ball-throwing head by a blower and two transfer ducts. Balls hit by the player are collected by a net and a trough, then fed back to the head. The rollers have separately variable speeds of rotation, a gap being provided between each pair of rollers and adapted to the diameter of the balls. The balls are directed alternately into each transfer duct, the opening of which is located opposite to each gap.</p> |
