| 摘要 |
A propulsion device, designed especially but not necessarily solely for propelling tennis balls for training purposes, has in common with earlier devices a rotary distributor or magazine, feeding balls in successively following order into a discharge conduit. The balls are discharged through a barrel which is mounted upon the housing of the equipment for adjustment about a transverse axis, thus to dispose the barrel at selected positions of inclination, to vary the trajectory of the ball when propelled, with the adjustment being preserved after selection by the user. An improved oscillatory motion is imparted to the entire device, hence to the barrel, following adjustment of the barrel to the selected position of inclination. The oscillatory travel is adapted to be programmed, that is to say, in oscillating the entire structure bodily, adjustments can be made that will permit pre-selection of the number of tennis balls to be propelled during each oscillatory cycle, other adjustments can be made with respect to the angle at which the discharge barrel is inclined, further adjustments can be made as to the width of the area within which the balls will drop, and still other adjustments can be made for pre-selection of a ball-drop pattern within a given width of training area. All of the adjustments can be effected singly or in any desired combination thereof, according to the training needs of the particular user.
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