GB2031736A - Ball throwing machine - Google Patents

Abstract

Ball throwing machine for tennis balls, which are separately ejected from a tubular barrel 27 at the entrance of which the balls pass an elastically extendible choke 16 presenting an adjustable resistance by virtue of a collar 17, 18 and a tension spring fixed thereto, so that balls of different kinds are ejected with substantially uniform velocity. On their way to the choke the balls pass through a flexible tube 13, so that the barrel is movable in wide limits. <IMAGE>

Description

SPECIFICATION Ball throwing machine BACKGROUND OF THE INVENTION The present invention relates to a ball throwing machine for tennis balls and the like.

The machine has a ball magazine, means for generating air pressure, a conveying tube to which single balls are fed from the magazine and through which they are driven by air pressure, an elastic tubular choke at the output of said conveying tube which choke retains the ball until pressure has built up behind the ball sufficient to extend the choke and to drive the ball through it, and a tubular barrel from which the ball is ejected after having passed said choke.

Such a machine for throwing baseballs is known from US-patent 2,574,408. This machine hase a choke consisting of an elastic rubber ring, which in rest position is not under tension. A similar machine is known form the German patent application 2,361,147 (corresponding to the US patent application No 312 874). It has become apparent that these machines are not suited to throw balls of different sizes and qualities, in particular tennis balls of any make and wear, to the same distance. Small, worn out, and old balls pass these latter machines without building up sufficient pressure and are hardly ejected, while new, hard and not worn out balls pass the choke only with difficulty.

Therefore it is impossible to throw balls of different kinds, as normally used in throwing machines, to a uniform distance.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved ball throwing machine, which throws balls of different kinds with practically the same velocity and to the same distance.

In the machine according to the invention closing means are provided for holding said choke closed by applying a practically constant force to it from the outside apt to be overcome by the air pressure behind the ball, so that balls of different sizes and qualities are ejected with uniform speed. Because the force retaining the ball in the choke is constant independently of the ball diameter, all balls are thrown practically with the same velocity and to the same distance.

It is a further object of the invention not only to throw different kinds of balls uniformly but also to enable differend kinds of throws including sevice throws. For this reason the machine has a pressured vessel at its bottom and the conveying tube has a flexible part connecting the pressured vessel to the choke enabling the tubular barrel connected to said choke to be movable with respect to the pressured vessel up to a level corresponding to a service throw.

It is an important feature of the invention that the balls are slowly conveyed through the relatively long and flexible tube up to the choke; only then they are accelerated and ejected by the tubular barrel. The long, flexible tube enables the tubular barrel to be elevated up to the height of a service throw.

Further objects and advantages of the invention will become apparent from the following description and claims and from the accompanying drawing which show the machine in principle, that is the pressure generating part and the machine frame are omitted.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a side elevation of the ball throwing machine embodying the invention, Figure 2 is a more detailed view comprising the choke, Figure 3 shows schernatically a front view of automatic adjusting means for the tubular barrel and Figure 4 shows a partial, enlarged view of an impact plate for throwing twisted balls.

DETAILED DESCRIPTION OF THE DRAW INGS The ball throwing machine shown in Fig. 1 has a drum-shaped ball magazine 1, which can be rotated by a motor 2 via a driving belt 3. The magazine 1 is rotationally movable on rollers 4 in a fixed cylindrical casing 5, which has on top a funnel 6 and below it an opening.

Accessible through the opening of the casing the magazine 1 has an obturable opening, through which magazine 1 can be filled with balls. When the magazine is rotating, single balls are conveyed in a knwon manner into a tube 7. Single balls are thus conveyed from the discharge end of tube 7 to an input tube 8 fixed on a pressured vessel 9. During operation air is continuously blown into the vessel by means of a ventilator, which preferably is mounted in the vessel 9. Under the input tube 8 a non-return flap 10 and an input funnel 11 to a curved tube 12 are mounted in the vessel.The latter tube is connected to a flexible tube 13, whose upper end is connected to a support 1 5 by means of a collar 1 4. To the tube 1 3 foilows an elastic extensible tube 1 6 formed for instance by a rubber hose, the inner diameter of which, when not charged, is smaller than the diameter of any tennis ball used thus forming a choke for the ball. The flexible hose 1 6 passes between a collar formed by a semicircular lower part 1 7 fixed to the support 1 5 and an upper, also semicircular part 18, which is pivotally mounted by means of two side bars 1 9 on two trunnion studs 20.To a pin 21 is fixed on the collar part 1 8 a tension spring 22 is connected whose other end is fixed to a bar 23, which can be longitudinally displaced. Its position can be secured by means of a wing screw 24 in a lug 25 at the upper part 26 of a collar of which the lower part is connected to the the support 1 5. The collar with the upper part 26 serves for fixing one end of a tubular barrel 27, from which balls are ejected. The other end of the tubular barrel 27 rests on an appropriate support, e.g. the U-shaped fork 28.

Immediately after the choke formed by the elastic tube 1 6 the tubular barrel 27 is provided with a plurality of discharge openings 29, which can be partially or totally closed by means of a sleeve 30 rotatable around the tubular barrel 27.

Support 1 5 and fork 28 are fixed to rods 31 and 32 respectively (only partially shown) connected to the machine frame and adjustable in height. Thus it is possible to give to barrel 27 any desired position. The length of the flexible tube 1 3 can be chosen so that barrel 27 can be brought into such a height and tilted position that service balls may be thrown. Any other hight and inclination of barrel 27 may be chosen for throwing highspeed balls to any place of the court. The operation of the throwing machine essentially results from the description above. When the machine is put into service, no ball is neither in tube 7 nor in the input tube 8. The air delivered by the ventilator streams practically unimpeded through the conveying tube 1 3 and no pressure builds up in the vessel 9.By rotation of the magazine 1 a first ball comes through the tube 7 and its gate (not shown) to the input tube 8, through it and to the flap 10, which is open since no pressure exists in the vessel 9. The ball passes funnel 11, the curved tube 12, and the flexible tube 1 3 up to choke 16, where it is retained by the extendible tube of restricted diameter thereby blocking the air stream in the tube. Pressure builds up in vessel 9, closes flap 10 and thereby input tube 8. Thus no new ball can enter from input tube 8 to the vessel and the curved tube 1 2. As soon as a certain pressure has built up in vessel 9 and behind the ball retained in the choke, this ball enlarges the flexible tube by lifting the upper collar part 18, so that it can pass the choke and enter the tubular barrel 27.Driven by the pressure of the air coming from vessel 9 the ball is accelerated in the barrel 27 and projected from its discharging end. Depending on the desired speed the discharge openings 29 at the back end of barrel 27 are closed more or less, so more or less pressure is available for accelerating the ball during its course through the barrel.

By adjusting the position of the bar 23 in longitudinal direction the tension of spring 22 and thereby the force of collar part 18 on the elastic tube 1 6 can be adjusted. Whether worn out balls are used, which are relatively smooth and soft, or new balls which are usually of larger diameter, less smooth and more rigid, adjusting the force of spring 22 optimal adjustment and thus the desired velocity can be selected for any kind of balls.

The difference in speed and throwing distance are small and in any case tolerable for the training. When training beginners, balls of equal quality may be selected and thrown each to exactly the same place.

The force of spring 22 is practically constant because the spring is long compared to the difference of motion of the upper part 18 of the collar to the choke 1 6 caused by a big ball or a small ball.

The spring 22 may be replaced by a rod fixed to pin 21 and a weight adjustable on the rod and fixable my means of a screw, so that for any position of the weight a constant force acts on the choke independant of the size of the ball.

As soon as a ball has left the barrel 27, the pressure in vessel 9 breaks down and a further ball, already in the input tube 8 opens the flap 10 and follows the first ball through funnel 11, curved tube 12, flexible tube 13, choke 1 7 and is ejected from the tubular barrel 27 after the necessary pressure has been attained.

Fig. 3 shows additional means for ejecting the ball in various directions. The U-shaped fork 28 supporting the front end of the barrel 27 is either supported in a fixed position on the machine frame by a rod 32 or on a carriage 33, which is movable on rails 34 connected to the machine frame. On the pulley 35 rotating with the same speed as magazine 1 the lower part of a telescopic lever is pivotally fixed while its upper part 37 is connected to the carriage 33. The lower part 36 of the telescopic lever is pivotally connected to the machine frame by an axle 38.

The permanent rotation of magazine 1 during operation moves carriage 33 to and fro by means of the telescopic lever 36, 37, thereby displacing the discharging end of the barrel 27 so that succeeding balls are thrown out in different not predetermined directions. In Fig.

4 a further addition is shown, which gives new possibilities for throwing tennis balls. An impact plate 42 is fixed to the discharging end of barrel 27 in any desired rotational position. By means of a collar 40 clamped by a wing screw 39 to the barrel and a bracket 41 the impact plate is fixed at a small angle to the axis of the barrel. Balls ejected from the barrel hit this plate and are given a twist, whose direction depends on the position of the impact plate 42 and can be e.g. around a horizontal axis or around a vertical axis, the latter especially for a service throw. The impact plate may be adjustably fixed on the bracket 41, so that its angle to the axis of the barrel and thereby its effect can be varied.

This invention is not limited to the embodiment illustrated in the drawing and described above. Particularly, the ball magazine 1 for automatically dispensing single balls at its outlet 7 is desirable but not essential for this invention. This magazine may be omitted, and single balls may be manually charged into the inlet tube 8 as shown for instance in the USpatent No. 2,574,408 cited above.

Claims (9)

1. Ball throwing machine for tennis balls and the like comprising a ball magazine means for generating air pressure a conveying tube to which single balls are fed from the magazine and through which they are driven by air pressure, an elastic tubular choke at the output of said conveying tube which choke retains the ball until pressure has built up behind the ball sufficient to extend the choke and to drive the ball through it, and a tubular barrel from which the ball is ejected after having passed said choke, wherein closing means are provided for holding said choke closed by applying a practically constant force to it from the outside apt to be overcome by the air pressure behind the ball, so that balls of different sizes and qualities are ejected with uniform speed.

2. Ball throwing machine for tennis balls and the like comprising a ball magazine means for generating air pressure a conveying tube to which single balls are fed from the magazine and through which they are driven by air pressure, an elastic tubular choke at the output of said conveying tube which choke retains the ball until pressure has built up behind the ball sufficient to extend the choke and to drive the ball through it, and a tubular barrel from which the ball is ejected after having passed said choke, comprising a pressured vessel at the bottom of the machine, said conveying tube having a flexible part connecting said pressured vessel to said choke enabling said tubular barrel to be movable with respect to the pressured vessel up to a level corresponding to a service throw.

3. Ball throwing machine according to claims 1 or 2, wherein said choke is formed by a section of an elastic tube surrounded by an extendable collar forming said closing means.

4. Ball throwing machine according to claim 3, wherein said collar consists of two semicircular parts, one of which is fixedly attached to said conveying tube, the other one being forced towards the first one by spring means or by gravitational means.

5. Ball throwing machine according to claim 4, wherein said force is adjustable.

6. Ball throwing machine according to any claim 1 to 5, wherein said tubular barrel has adjustable pressure reducing openings.

7. Ball throwing machine according to any claim 1 to 8 having further an impact plate near the discharge end of said tubular barrel for rotating the ball before leaving the machine.

8. Ball throwing machine according to any claim 1 to 6 wherein said tubular barrel is fixed to at least one adjustable support.

9. Ball throwing machine according to claim 7 wherein said adjustable support is permanently moved sidewise by mechanical means.

1 0. A Ball throwing machine for tennis balls and the like, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.