GB315851A - Mechanical tennis ball server or projector for lawn tennis practice - Google Patents

Abstract

315,851. Jepson, P. July 21, 1928, [Convention date]. Projecting-appliances.-An apparatus for projecting tennis balls comprises a frame, a magazine to accommodate the balls, a ball-holder to receive the balls successively from the magazine, a rigid projector-arm co-acting with the ball holder, means for retracting the arm against the tension of a spring and means for releasing the arm to project a ball from the holder, the arm being mounted so as to swing beyond its normal position after the blow, and being returned thereto by spring influence. The framed casing 2, Fig. 1, has wheels 3 and sliding handles 4 to enable it to be pushed about. On the top of the casing is a magazine 6 comprising an outer cylindrical casing 7 and an inner drum 8 between which is a helical path 9 for the balls leading to a pivoted platform 10. This platform is oscillated to deliver the balls one at a time to a holder 12 in the path of a projector-arm 13 which operates in a slot 31 having guards 32. The platform 10 is oscillated by a bar 14, Fig. 4, pivoted to a lever 15, Fig. 5, which is rocked by a roller (not shown) eccentrically mounted on a sleeve 18 rotatably arranged on a shaft 19 and having a sprocket wheel 21 chain-geared to a wheel 23 driven by an electric motor 27 through reduction gearing 28 and a shaft 24. The projector arm 13 is secured to the shaft 19 and to it is pivoted a pawl 33 having two rollers 35, 36. One roller 35 bears against a cam plate 37 formed on the sleeve 18, the cam plate having a projection 38 which by its engagement with the roller 35 causes the projector-arm 13 to be retracted in a left-hand direction, Fig. 4. To the shaft 19 is secured a boss 44 having a camshaped periphery 48, Fig. 8, upon which a chain 45 is wound against the action of a spring 46 as the projector-arm is retracted. Upon the release of the projector-arm, a projection 49 on the boss 44 comes into contact with the chain when the arm reaches the limit of its stroke and thus reduces the shock. The other roller 36 on the pawl 33 pivoted to the projector-arm contacts with a member 39 which trips the roller 35 to project the ball from engagement with the cam plate 37. The trip member 39 is secured to a sleeve 40 which can be partly rotated around the shaft 19 by a handle 42 working in a slot 43 of the casing to vary the force of the blow. The ball holder 12 is rigidly mounted on a rod 50 which is slidably and rotatably mounted in bearings 51 at the top of the casing 2. One end of the rod is fitted with an arm 52 having a handle 53 which moves in a slotted guide plate 54 on the side of the casing 2. The inclination of the holder 12 is thus varied, and hence also the trajectory of the projected ball. The horizontal direction of the ball is varied by the lateral oscillation of the holder. The opposite end of the rod 50 is pressed by a spring 55 against a bell-crank lever 56 pivotally connected to a downwardly-extending link 59 which has a pin 60 engaging a fixed double-sided ramp 61. Below the pin, the link passes through a sliding frame 63 and is restrained by a bracket 64 from independent lateral movement but is free to move vertically. The frame 63 is moved by a handle 65 sliding in a slotted guide 66 in the casing 2. The link 59 terminates in a roller 67 which can be operated by either of two cams, 68, 69, provided, for different timing, on spur wheels 70, 71, driven by a pinion 72 from the motor-driven shaft 24. With the frame 63 in its middle position, the pin 60 is at the top of the ramp 61 and the ball holder 12 is stationary in its central position and a " straight " ball is delivered when the frame is moved to the left, the roller 67 engages the cam 68 and the holder is moved to and fro across the slot 31, the timing being such that balls are delivered alternatelv to each side of the machine. With the frame 63 in its righthand position, the ball-holder is moved in the slot 31, to deliver the successive balls irregularly. The striking end of the projector arm has a rounded striking end 74 and a concave portion 75, " spin " being imparted to the ball by the rounded end. Switchgear, etc., may be accommodated in a compartment 76 having a hinged door 79.