GB2449079A

GB2449079A - Ball delivery machine

Info

Publication number: GB2449079A
Application number: GB0708848A
Authority: GB
Inventors: Peter J Eyre
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-05-08
Filing date: 2007-05-08
Publication date: 2008-11-12
Also published as: GB0708848D0

Abstract

A ball delivery apparatus 2 comprises a ball delivery head 32 having at least two counter-rotating wheels 48, 50 aligned in a plane. A gap is provided between the wheels such that a ball 52 may be pinched between them and thrown from the head. The apparatus includes means 6, 10, 8, 12 for respectively controlling a pitch angle a , a yaw angle q , a roll angle b and a height of the ball delivery head. The speed and spin speed of the delivered ball may be dependent upon the angular rotation of the wheels 48, 50. The apparatus may include means, e.g. wheels 16, which allow the apparatus to move horizontally. The apparatus may include a ball store 34. The ball store may be fixed to and move with the delivery head 32, or may be fixed, with the delivery head 32 moving relative to the ball store. The apparatus may include visible and/or audible warning means 26, 28 for indicating that a ball is to be delivered. The apparatus may include a controller 22 with data entry means 18 and/or programmable memory 24 for controlling the delivery of a ball. The apparatus may further include a receiver 30 for receiving signals from a remote control 114. The ball delivery machine is particularly suitable for use in tennis practice, teaching and coaching.

Description

BALL DELIVERY MACHINE

FIELD OF THE INVENTION

The invention relates to a ball delivery machine. The ball delivery machine is particularly suitable for use in tennis practise, teaching and coaching but its use is not exclusively limited to these applications.

BACKGROUND OF THE INVENTION

Ball delivery machines are useful as training aids for sports such as tennis. Such machines may be programmed to deliver balls in a manner which simulates different aspects of a game. For example, balls may be repeatedly delivered with the same trajectory and spin characteristics as part of a drill which is focused on one or more aspects of training. Alternatively, the ball delivery machine may be programmed to deliver balls with trajectory and spin characteristics which are not predictable but are varied randomly or pseudo-randomly in an attempt to mimic typical playing conditions.

Existing ball delivery machines which are capable of controlling the ball trajectory and spin characteristics are often complex and incorporate three or more spinning wheels.

Furthermore such machines typically are fixed in position such that the origin of the delivery remains static.

SUMMARY OF THE INVENTION

According to a first aspect of the invention there is provided a ball delivery machine comprising a ball delivery head comprising at least two rotating wheels, and means for controlling a pitch angle, a yaw angle, a roll angle and a height of the ball delivery head.

An orientation of an axis of spin of a ball is controlled by the roll angle of the ball delivery head. It is thus possible to provide a machine that can deliver a ball in a range of directions from a range of heights with variable spin and spin orientation.

Advantageously the height control means for the ball delivery head provides for the adjustment of the ball delivery head height between at least a serving height and a playing height. The serving height may correspond to a height of four metres or so, to represent the height of a player, plus outstretched arm and racket above the couft. A playing height may correspond to around one meter or less, representing a shot played from waist height or below. To enhance the accuracy of the conditions experienced by a player with respect to those conditions experienced during a real game of tennis, the ball delivery machine should be capable of delivering a first ball from a serving height typical of a serving height in a real game of tennis followed by a second ball from a playing height typical of a playing height in a real game of tennis. Such a transition should be quick, typically taking a second or so. During a game of professional tennis, bails can reach speeds of up to 100 mph (45 mIs) thus a ball can traverse the length of a tennis court in a time period of the order of 0.5 seconds. This is particularly true of a serve shot. Thus a player may be required to play a serve return shot followed by a subsequent stroke within a time period of around one second. Advantageously, a ball delivery machine should therefore be capable of playing a first serve shot from a serving height and a second playing shot from a playing height within a time period of around one second.

Advantageously the orientation of the delivery head is visible such that a player can anticipate, at least to some degree, the type of shot to be delivered by the ball delivery machine. This feature mimics the conditions faced by a player in a real game of tennis when the player can anticipate, at least to some degree, the likely trajectory of the shot to be played by an opponent from the orientation of the opponent's racket.

Preferably the ball delivery head comprises two counter-rotating wheels. This arrangement provides a simple means for controlling the ejection of the ball from the delivery head. The speed of a ball on delivery is a function of the angular velocities of the counter-rotating wheels. Also the spin speed of a ball on delivery is a function of a difference of the angular velocities of the counter-rotating wheels. Hence, both the ball speed and the ball spin speed may be controlled by independently controlling the angular velocities of the counter-rotating wheels. Thus the ball delivery head provides for the delivery of balls with top spin, back spin and, by virtue of being able to rotate the head to change its roll angle, both directions of side spin.

Optionally, the ball delivery machine may further comprise translation means for moving the ball delivery head horizontally. If the ball delivery machine rests on a playing surface such as a tennis court and faces along the length of the court, the ball delivery head is thus movable up and down, backwards and forwards and side-to-side with respect to the court. This confers the advantage that the ball delivery head may, for example, deliver balls from different points to a tennis court.

Preferably the ball delivery machine comprises a ball store which is fixed to and moves with the delivery head. Alternatively the ball store may be stationary and the ball delivery head moves relative to the ball store necessitating the connection of the ball store to the ball delivery head by a flexible pipe. When the ball store is attached to the ball delivery head, the movements of the ball delivery head are less restricted than is the case for the alternative arrangement where the flexible pipe may hamper the movement or even restrict the range of movement of the ball delivery head.

In one embodiment the ball delivery machine further comprises means for controlling the delay between the movement of the ball delivery head and a delivery of a ball and optionally the time to the next movement of the ball delivery head and/or ball delivery.

This feature is designed to replicate the delay experienced by a player during a game of tennis between consecutive shots being returned to the player and in training may be used to control the delivery rate to match the abilities of the person being trained.

Preferably the ball delivery machine further comprises a warning means for generating a warning signal before the ball delivery machine delivers a ball. For example, the warning means may comprise a light and/or a siren. The warning means therefore serves to recreate the conditions faced by a player during a real game of tennis when the player observes the movements of an opponent and can anticipate the timing of the opponent's shot.

Preferably the ball delivery machine further comprises a data entry means and/or programmable memory. Preferably the ball delivery machine also comprises a controller arranged to control the delivery of a ball in response to data provided via the data entry means and/or stored in the memory. The data may define the trajectory of a ball, a speed of a ball, a spin speed and spin orientation of a ball, a delay between the movement of the delivery head and a delivery of a ball, a delay between the delivery of a ball and a movement of the delivery head in preparation for a delivery of a further ball, and a delay between the generation of a warning signal and a delivery of a ball.

Provision of a programmable memory and a controller, facilitates the design, storage and execution of a shot. Different shots may then be combined to create a practice drill.

Such a drill may be designed to provide training which is focused on a single or several aspects of a player's game. Alternatively, the drill may be designed to simulate a real game as closely as possible where the ball machine delivers multiple balls in succession such that a player experiences playing conditions which resemble as closely as possible those conditions existing during a real game of tennis when the actions of an opponent are observable and, to some degree, predictable. A particularly important example of such a sequence of shots, is the delivery of a first ball from a serving height followed by the delivery of a second ball from a playing height. The ball delivery machine of the invention is capable of recreating either type of drill and is therefore likely to be invaluable for tennis training.

Optionally the ball delivery machine further comprises a receiver for receiving a signal from a remote control. Use of a remote control confers the advantage that a player may control the timing, sequence and nature of the drill during training without having to repeatedly return to the ball delivery machine located at an opposite side of a court to the player to initiate further drills or change the settings of the ball delivery machine.

According to a second aspect of the invention there is provided a method of delivering a ball using a delivery machine having a delivery head which has first and second rotating elements which engage with a ball to accelerate it, the method comprising controlling a position and an orientation of the delivery head and speeds of the rotating elements so as to control a ball direction and spin.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will be described further, by way of non-limiting example only, with reference to the accompanying figures, in which: Figure 1 is a schematic view of a ball delivery machine constituting an embodiment of the invention; Figure 2a shows the ball delivery machine of Figure 1 illustrating the mechanism for the adjustment of the ball delivery head height in side view and Figure 2b shows it from a front view; Figure 3 is a side view of the counter-rotating wheels of a ball delivery head in a default orientation; Figures 4a to 4c shows the counter-rotating wheels of a ball delivery head in a default orientation in side view, front view and plan view, respectively; Figure 5a to 5c show the counter-rotating wheels of a ball delivery head having a pitch angle a in side view, front view and plan view, respectively; Figure 6a to 6c show the counter-rotating wheels of a ball delivery head having a yaw angle y in side view, front view and plan view, respectively; Figure 7a to 7c show the counter-rotating wheels of a ball delivery head having a roll angle 13 in side view, front view and plan view, respectively; Figure 8 is a perspective view of an embodiment of a ball delivery head assembly; Figure 9 is a cross-section along the direction ZZ of the ball delivery head assembly of Figure 8; Figure 10 is a perspective view of an embodiment of a ball valve; Figure 11 is a perspective view of an embodiment of a ball transfer channel; Figure 12 is the same cross-section on ZZ of the ball delivery head assembly as that of Figure 9 after transfer of the ball in the ball transfer channel to the ball delivery head; Figure 13 is the same cross-section on ZZ of the ball delivery head assembly as that of Figure 12 after the ball magazine has rotated anti-clockwise such that the aperture in the ball magazine is directed downwards; Figure 14 is the same cross-section on ZZ of the ball delivery head assembly as that of Figure 13 after the ball magazine has rotated anti-clockwise such that the aperture in the ball magazine is directed upwards; and Figure 15 shows an embodiment of a carriage for the ball delivery head.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE PRESENT INVENTION

A ball delivery machine constituting an embodiment of the present invention is shown in Figure 1. The ball delivery machine is generally designated 2 and comprises a ball dehvery assembly generally designated 4, an actuator 6 for controlling the rotation of a ball delivery assembly 4 about an x axis, an actuator 8 for rotating the ball delivery assembly 4 about a y axis, an actuator 10 for rotating the ball delivery assembly 4 about a z axis, and an actuator 12 for controlling the height of the ball delivery assembly 4.

For clarity, large portions of the actuators 6, 8, 10 and 12 and their supporting structures have been omitted from Figure 1. The actuators provide rotation of the delivery assembly 4 about three orthogonal axes. Rotation about the z axis allows direction of delivery, i.e. to the left hand or right hand of the court to be controlled. Rotation about the x axis allows the pitch i.e. the up/down direction of the shot to be controlled.

Rotation about the y axis allows orientation of a spin applied to the ball to be controlled, and this gives it curvature in flight due to aerodynamic forces.

The machine further comprises an enclosure 14 having wheels 16, data entry means 18, a display 20, a controller 22, a programmable memory 24, a strobe light 26, a siren 28, and a receiver 30.

The ball delivery assembly 4 comprises the ball delivery head generally designated 32, a ball store 34, a ball valve 36 for controlling release of the balls from the ball store 34, a ball transfer channel 38 and a ball transfer device 40.

The ball delivery head 32 comprises an enclosure 42 having entrance and exit apertures 44 and 46 respectively, and two counter-rotating wheels 48 and 50 located between the apertures 44 and 46 and driven by respective motors (not shown). Also shown in Figure I are balls 52, 53, 54, 56 and 58.

The actuators 6, 8 and 10 are used for controlling the orientation of the ball delivery assembly 4 and the actuator 12 is used for controlling the height of the ball delivery assembly 4. The actuators 6, 8, 10 and 12 may, for example, comprise stepper motors.

The actuators 6, 8 and 10 are mechanically connected to the ball delivery assembly 4. In the interest of clarity, however, the connections have been omitted from Figure 1, but would be described in greater detail with reference to Figure 15.

The actuator 12 controls the height of the ball delivery assembly 4 as described with the aid of Figure 2. In this figure the same reference numerals are used to indicate like parts. Brackets 59 and 60 and the shaft 61 mechanically connect the ball delivery assembly 4 to an upright shaft 62 whilst still allowing its position to be varied by the orientation control actuators 6, 8 and 10. The shaft 62 is received by a tube 63 which is held in the enclosure 14. The tube 63 contains a compression spring (not shown) which urges the ball delivery assembly 4 towards a maximum height designated above a playing surface 64. The height control device 12 rotatably drives a shaft 66 which carries two toothed wheels 68. The vertical support shaft 62 has a cross bar 70 which also carries two toothed wheels 72. Chains 74 are anchored at a first end 76 and pass over toothed wheels 72 and toothed wheels 68. The height of the ball delivery head 4 is reduced when the device 12 rotates the shaft 66 and the toothed wheels 68 in a direction such that the length of the chain 74 extending from the anchor point 76 to the toothed wheel 68 is reduced and a downwards force is exerted on the spring contained within tube 63 causing it to compress.

When the ball delivery assembly 4 is at a height below its maximum, device 12 may rotate toothed wheel 68 such that the length of the chains 74 extending from the anchor points 76 to the toothed wheel 68 is increased or decreased and the height of the ball delivery assembly 4 is increased under a force exerted by the compression spring contained within tube 62 or further decreased, respectively. The ball delivery assembly 4 may also be lowered in height to a "pack-down" position wherein the ball delivery assembly 4 is substantially contained within enclosure 14 for storage or transport of the ball delivery machine 2.

In Figures 1 and 2 the ball store 34 is shown as being connected to ball delivery head 32 via the transfer channel 38. In this embodiment the ball transfer means 40 is designed to transfer balls from the ball store 34 to the ball delivery head 32 regardless of the orientation of the ball delivery assembly 4. It will be apparent that although the ball store 34 is depicted in Figures 1 and 2 at a height above the ball entrance aperture 44 of the ball delivery head 32, the ball store 34 may alternatively be located at a height substantially level or below the ball entrance aperture 44. The ball store 34 may alternatively remain fixed and be connected to the ball delivery head 32 via a flexible pipe. This flexible pipe allows for movement of the ball delivery head 32 with respect to the fixed ball store during operation of the ball delivery machine.

The operation of the ball delivery head 32 will be described with reference to Figure 3.

The counter-rotating wheels 48 and 50 rotate about parallel axes 78 and 80 respectively.

The wheels 48 and 50 are aligned so as to be adjacent to one another and are spaced apart so as to define a gap between the wheels that is less than the diameter of a ball.

For a tennis ball having a diameter of 67 mm for example, the gap between the wheels 48 and 50 is approximately equal to 38 mm. In Figure 3 a first tennis ball 82 is shown approaching the gap from the direction of the entrance aperture of the ball delivery head 44 in the direction of the linear velocity of the wheels 48 and 50 at the gap. The rotating wheels 48 and 50 have a surface roughness such that when a ball, such as ball 84 in Figure 3, comes into contact with the counter-rotating wheels 48 and 50, it is drawn into the gap in the direction of the linear velocities of the counter-rotating wheels 48 and 50 and compressed before being ejected towards the ball exit aperture 46 as shown for ball 86 in Figure 3. The wheels 48 and 50 may, for example, be covered with a neoprene rubber layer around their circumferences to enhance their frictional engagement with the balls. The speed at which the ball 86 is ejected from the ball delivery head 32 depends on the angular velocities of the counter-rotating wheels 48 and 50. More specifically, the speed of the ball 86 will be a function of the average of peripheral velocities of the counter-rotating wheels 48 and 50. The wheels 48 and 50 may also be rotated at different angular velocities to impart a spin on the ball 86 about an axis 88 parallel to the axes of rotation 78 and 80 of the wheels 48 and 50 respectively. Accordingly, the ball spin speed about the axis 88 is a function of the difference between the angular velocities 48 and 50.

The direction of a ball ejected from the ball delivery head 32 is determined by the orientation of the ball delivery head 32 as described with the aid of Figures 4a, 4b and 4c to 7a, 7b and 7c. Figures 4a to 4c show the counter-rotating wheels 48 and 50 in their default position. In Figures 5a to 5c, the ball delivery head is oriented by operating actuator 6 so as to have a pitch angle a which determines an initial elevation of a ball.

In Figures 6a to 6c the ball delivery head 32 is oriented by operating actuator 10 so as to have a yaw angle i* In Figures 7a to 7c the ball delivery head 32 is oriented by operating actuator 8 so as to have a roll angle 13. The axis about which a ball spins such as axis 88 of ball 86 in Figure 3, is parallel to the axes 78 and 80 of the counter-rotating wheels 48 and 50 respectively. Thus varying the roll angle f3 of the ball delivery head 32 as shown in Figure 7, changes the orientation of the ball spin axis in a plane perpendicular to the initial direction of travel of the ball. Thus the ball delivery machine 2 of Figure 1 is capable of delivering a ball having a top spin or back spin component and/or a side spin component.

The operation of the ball delivery assembly 4 will be described with reference to Figures 8 to 14. The ball valve generally designated 36 in Figure 8 comprises a cylindrical ball magazine 90 which is rotatable about an axis 92 and which has a circular aperture 94 formed in its surface. The ball valve 36 further comprises a pair of ball retention means 96 which extend vertically either side of the tubular magazine 90 so as to retain a ball 53 in the tubular magazine 90 when the aperture 94 is facing sideways. The ball valve 36 is shown in more detail in Figure 10. From Figure 10 it will be apparent that the ball valve 36 further comprises plates 98 and 100 which are substantially perpendicular to axis 92 and are located within the tubular magazine 90 in axial positions one either side of the aperture 94. The plates 98 and 100 serve to block any movement of the ball 53 in a direction parallel to axis 92 that might otherwise have occurred during movement of the ball delivery assembly 4.

As shown in Figure 8, the ball delivery assembly 4 further comprises the ball transfer channel 38. The ball transfer channel 38 comprises an enclosure 102 having a substantially square cross section and having a slot 104 formed in one side. The ball transfer channel 38 is shown in more detail in Figure Ii. The ball transfer channel 38 further comprises a plate 106, channel restriction plates 108 and 109, and an aperture 110. The plate 106 extends into the ball transfer channel so as to block the travel of a ball such as 52 in a direction away from the ball entrance aperture 44 of the ball delivery head 32. The channel restriction plates 108 and 109 serve to restrict the height of the ball transfer channel to a dimension "d". The region of the ball transfer channel 38 located axially between the plate 106 and the channel restriction plates 108 and 109 forms a ball retention region Ill. In use, a ball such as ball 52 is delivered from the ball value and enters the ball transfer channel 38 through the aperture 110 in a top surface of the ball transfer channel 38 and is temporarily held in the ball retention region 111.

Referring to Figure 8 once again, the slot 102 in the side of the enclosure 104 of the ball transfer channel 38 is sized to accommodate the passage of a rotating element such as a finger 112 which passes through the slot 104 and extends substantially across the enclosure 102 to the side of the enclosure opposite the slot. This is shown most clearly in the cross-section on ZZ shown in Figure 9. As the rotating finger 112 rotates, it urges a ball in the ball retention region Il 1, such as ball 52, towards the ball entrance aperture 44 until the ball 52 comes into contact with the channel restriction plates 108 and 109.

The restricted channel height "d" is chosen such that a ball such as the ball 52 cannot pass between the channel restriction plates 108 and 109 during normal movement of the ball delivery assembly 4, but is sufficiently large such that the force exerted by the moving finger 112 on the ball is sufficient to deform the ball or the channel restriction plates 108 or 109 to such a degree that the ball can move between the channel restriction plates 108 and 109 towards the ball entrance aperture 44.

The ball transfer cycle from the ball store 34 to the ball delivery head 32 will be described. During the ball transfer cycle, the ball magazine 90 and the rotating finger 112 are independently driven by motors (not shown). Figure 9 corresponds to the stage shown in Figure 8 prior to the ball 52 being transferred to the ball entrance aperture 44.

At this stage, the aperture 94 in the ball magazine 90 is positioned so as to retain a ball, such as the ball 53, within the ball magazine 90 and such that a ball in the ball store, 10.

such as the ball 54, rests upon the curved surface of the ball magazine 90. In Figure 9, for example, the aperture 94 is directed at an angle of substantially 300 downwards from horizontal and ball 56 rests on top of ball 54 and ball 58 rests on top of ball 56. Figure 12 shows the stage of the ball transfer cycle immediately following operation of the finger 112 to cause the transfer of a ball such as ball 52 to the ball delivery head 32.

The rotating finger 112 no longer extends through the slot 102 at this time while the direction of the aperture 94 is substantially similar to that shown in Figure 9. At the next stage of the ball transfer cycle shown in Figure 13, the magazine 90 has rotated such that the aperture 94 is directed substantially downwards while the rotating finger 112 has also rotated and is now directed out of the plane of the page. Accordingly, the ball 53 falls from the magazine 90 and enters the ball retention region 111 of the ball transfer channel 38 via the aperture 110. The ball magazine 90 and the rotating finger 112 continue to rotate until the stage shown in Figure 14 is reached. At this stage the aperture 94 in the ball magazine 90 is directed substantially upwards and admits a ball such as the ball 54 from the ball store 34. The rotating finger 112 and the ball magazine continue to rotate until the stage shown in Figures 8 and 9 is reached again but with a new ball such as the ball 53 in the ball transfer channel 38 at the beginning of the ball transfer cycle.

It should be understood that although the enclosure 102 of the ball transfer channel 38 has been described as having a substantially square cross section, the cross section of the ball transfer channel 38 could have any suitable shape and size to accommodate a ball.

The controller 22 of the ball delivery machine generally designated 2 in Figure 1, is in communication and controls the operation of the data entry means 18, the display 20, the programmable memory 24, the actuators 6, 8, 10 and 12, the strobe light 26, the siren 28, the receiver 30, the ball valve 36, the ball transfer means 40, and the motors driving the counter-rotating wheels 48 and 50. The controller 22 controls the orientation and the position of the ball delivery head 32 via the actuators 6, 8, 10 and 12, and further controls the speed of rotation of the wheels 48 and 50 in response to data entered via data entry means 18 andlor data stored in the memory 24. The data entered via the data entry means 18 or stored in the programmable memory 24 defines an initial direction and a height of delivery of the ball on ejection from the ball exit aperture 46. More specifically, the data defines the pitch angle, the yaw angle and the height of the ball delivery head 32. The data may also define the speed of rotation of the wheels 48 and thus controlling the speed and the spin speed of the ball. Furthermore the data defines the roll angle of the ball delivery head 32 and consequently the spin orientation of a ball in a plane perpendicular to the initial direction of the ball. In addition, the data defines the timing of the ball delivery. For example the data may define a delay between a movement of the delivery head and a delivery of a ball. The data may also define a delay between a delivery of a ball and a movement of the delivery head in preparation for a delivery of a further ball. For the purposes of alerting a player to the imminent delivery of a ball, the ball delivery machine 2 may also admit a warning signal in the form of a visible warning signal from the strobe light 26 and/or an audible warning signal from the siren 28. The data entered via the data entry means 18 and/or stored in the programmable memory 24 may also control a delay between the generation of such a warning signal and the delivery of a ball.

The initial direction of a ball on delivery, the ball speed, the spin orientation, and the ball spin speed, when taken together with the different aforementioned delays, define a shot. The programmable memory 24 may be programmed with the data corresponding to a plurality of shots to create a drill. For example, common training techniques may simply repeat the same shot many times thus providing a training capability for a particular type of shot. Alternatively, a serve shot may be followed by one or more different playing shots to form a drill which is designed to simulate the experience of a player during a real tennis rally. The controller 22 is also capable of communicating with an external computer 113 such as a laptop, for the purposes of downloading data which defines a shot or a drill as created on the external computer 113. This arrangement has the advantage that the shot and/or drill parameters may be defined in an environment remote from the ball delivery machine 2.

The ball delivery machine 2 may also be operated by a remote control 114. The remote control 114 is shown to be in wireless communication with the receiver 30 in Figure 1.

However, it should be apparent that the remote control 114 could alternatively be in wired communication with the receiver 30. The remote control 114 may be used to control any of the shot parameters or toinitiate a shot or a drill without having to approach the ball delivery machine 2.

The ball delivery machine 2 is mobile by virtue of the wheels 16. The ball delivery machine 2 may therefore be positioned at any location on a playing surface such as a tennis court with relative ease. The ball delivery machine 2 also comprises brakes (not shown) which serve to lock the wheels 16 thereby preventing further movement of the ball delivery machine during use or storage.

Figure 15 shows the support arrangement for the ball delivery head 32 in greater detail.

The actuator 10 comprises an electric motor 200 mounted on a support 202 which is rotatably fixed to the shaft 62. The motor 200 carries a gear 210 on a motor shaft which engages with a gear 212 fixed to the shaft 62 such that actuation of the motor 200 causes the support 202 to rotate around the shaft 62.

The support 202 has an upstanding portion 220 which houses a bearing 222 for engaging with a horizontal shaft 224. The shaft 224 carries a gear 226 which engages with a gear 228 carried by a motor 230 attached to the portion 220 so as to cause shaft 224 to rotate under the action of the motor 230. A similar arrangement designated 240 is formed at the end of shaft 224 with an axis of rotation perpendicular to shafts 224 and 62 to tilt the ball delivery head 32. Each of the motors are individually controllable.

As a result of the features described above, it is thus possible to provide an improved ball delivery machine.

Claims

1. A ball delivery machine comprising a ball delivery head comprising at least two rotating wheels, and means for controlling a pitch angle, a yaw angle, a roll angle and a height of the ball delivery head.

2. A ball delivery machine as claimed in claim I, wherein the height control means for the ball delivery head provides for the adjustment of the ball delivery head height between at least a serving height and a playing height.

3. A ball delivery machine as claimed in any of the preceding claims wherein the rotating wheels are two counter-rotating wheels.

4. A ball delivery machine as claimed in any of the preceding claims, wherein a speed of a ball on delivery is a function of the angular velocities of the rotating wheels.

5. A ball delivery machine as claimed in claim any of the preceding claims, wherein a spin speed of a ball on delivery is a function of the angular velocities of the rotating wheels.

6. A ball delivery machine as claimed in any of the preceding claims further comprising translation means for the translation of the ball delivery head in a plane perpendicular to a height axis of the ball delivery head.

7. A ball delivery machine as claimed in any of the preceding claims, further comprising a ball store wherein the ball store is fixed to and moves with the ball delivery head.

8. A ball delivery machine as claimed in any of claims I to 6, further comprising a ball store wherein the ball store is fixed arid the ball delivery head moves relative to the ball store.

9. A ball delivery machine as claimed in claim 7 or 8, further comprising a ball transfer system which transfers a ball from the ball store to the ball delivery head regardless of an orientation and a position of the ball delivery head.

10. A ball delivery machine as claimed in any of the preceding claims further comprising a warning means for generating a warning signal before the ball delivery machine delivers a ball.

11. A ball delivery machine as claimed in any of the preceding claims, further comprising a controller and a data entry means and/or a programmable memory wherein the controller controls the delivery of a ball in response to data entered using the data entry means and/or data stored in the programmable memory.

12. A ball delivery machine as claimed in claim 11, wherein the data defines a trajectory of a ball and/or a speed of a ball and/or a spin speed and/or a spin orientation of a ball and/or a delay between a movement of the delivery head and a delivery of a ball and/or a delay between the generation of a warning signal and the delivery of a ball.

13. A ball delivery machine as claimed in any of the preceding claims, wherein the ball delivery machine further comprises a receiver for receiving a signal from a remote control.

14. A method of delivering a ball using a delivery machine having a delivery head which has first and second rotating elements which engage with a ball to accelerate it, the method comprising controlling a position and an orientation of the delivery head and speeds of the rotating elements so as to control a ball direction and spin.