BALL-PROJECTION MACHINE

The present invention concerns a ball-projection machine, and is particularly but not exclusively concerned with a bowling machine for use in cricket practice, teaching and coaching .

Bowling machines are commercially available, one of the best known being the Merlyn bowling machine as disclosed in GB 2,294,979 B. This machine has four counter-rotating wheels which are spaced apart and disposed at 90° intervals with their axes lying in a common plane transverse to the axis of projection of the ball. One pair of opposed counter- rotating wheels can be used to impart a spin about one axis orthogonal to the axis of projection and the other pair of diametrically opposed counter-rotating wheels can be used to apply spin about the other axis orthogonal to the axis of projection, in each case by varying the relative speeds of the opposed wheels.

However since each of the four wheels requires its own electric motor, the weight of the individual motors, control mechanism, frame and lifting gear needed to raise the head of the machine to bowling height is quite considerable and the machine is somewhat heavy and cumbersome.

Furthermore it would be desirable to provide an improved ball feeding mechanism and to improve the control of the machine generally.

Accordingly, in one aspect the invention provides a bowling machine comprising a two-wheel ball-projecting machine wherein in use the rotating wheels cooperatively engage and project a ball and wherein the axes of rotation of the wheels are mutually angularly offset so as to impart a spin about the ball's axis of projection.

The angular offset of the axis of rotation of the wheels enables spin to be applied about the axis of projection of the balls and enables the machine to generate deliveries which emulate the deliveries (particularly leg break deliveries) of the best human bowlers (particularly spin bowlers) .

However it should be noted that the machine of the present invention is not limited to emulating bowling in cricket, but may also be arranged to deliver a baseball or a tennis ball for use in baseball or tennis respectively, for example .

Preferably the machine includes means for applying a differential thrust from the respective wheels to the projected ball thereby to impart a spin about an axis transverse to said axis of projection.

This embodiment can thereby emulate the known four wheel Merlyn spin bowling machine. Because the bowling machinery has two wheels and two drive motors rather than four, its weight is almost halved, making it more maneuverable, easier to raise to its operational height, less cumbersome and more easily transportable.

Conveniently the machine comprises electric motors coupled to the respective wheels and means for controlling the speeds of the electric motors . However other means for imparting a differential thrust may in principle be employed, e.g. involving a differential friction applied by the respective wheels.

Preferably the wheels are mounted on a subframe which is rotatable about an axis aligned with said axis of projection. This feature enables the spin axis transverse to

the axis of projection to be rotated in order to provide different cricket deliveries, for example.

In one embodiment the invention provides a machine which is programmable to bowl a ball with at least two of the following cricket deliveries:

a) straight b) inswing c) outswing d) backspin e) topspin f) off break g ⁾ leg break h) off cutter i) leg cutter

Preferably a sequence of deliveries each selectable from deliveries a) to g) is programmable by a user.

Preferably the machine is standardized to project the ball with at least one delivery whose parameters are specified by electronic data (e.g. stored on a memory card or other data carrier) readable by the machine (e.g. by means of a card reader) .

Further preferred features are defined in the dependent claims .

In another aspect the invention provides a ball- projecting machine comprising at least two opposed wheels spaced apart and arranged to cooperatively engage a ball introduced between them from a longitudinally-extending guide and to project the ball, the guide having a side opening communicating with a transversely-extending feed chute and the feed chute being inclined downwardly towards

the guide at an angle of 45° or less from the horizontal whereby in use, balls loaded in a row in the feed chute can be introduced successively and singly into the guide for projection along an axis aligned with said guide.

The above feature of the feed chute inclined at a relatively shallow inclination enables the balls to be fed gently by gravity into the guide and tends to prevent two balls being fed together into the guide and projected almost simultaneously. The ejection of two balls in very quick succession could present a safety hazard to the batter and is highly undesirable for that reason.

In a preferred embodiment the machine further comprises an actuator aligned with said guide and arranged to advance a ball in said guide into engagement with said wheels .

Preferably said actuator is a linear actuator having an advanced position in which it blocks said opening and a retracted position in which it uncovers said opening and is engageable with a ball fed through said opening into said guide. The above feature enables balls to be delivered from the machine in succession but with the assurance that only one ball will be fed into the guide at any given time, thereby virtually eliminating the risk of the nearly simultaneous two ball delivery noted above.

Furthermore a timer, a switch such as a "bowl" pushbutton or remote controller may be arranged to control said actuator so as to project a sequence of balls loaded in said feed chute. The actuator is preferably a solenoid actuator.

Preferably the machine includes programmable means for varying one or more operating parameters of the machine which determine the forces applied to the projected ball.

These forces determine the ball's trajectory through the air and its break off the ground.

Preferably the axes of rotation of the wheels are tiltable. This feature enables a spin to be imparted about the axis of projection of the ball.

Preferably the angle of inclination of the feed chute to the horizontal is 30° or less, more preferably 20° or less, e.g. about 15°.

Preferred embodiments of the invention are described below by way of example only with reference to Figures 1 to 8 of the accompanying drawings, wherein:

Figure 1 is a schematic rear elevation of a bowling machine in accordance with both aspects of the invention;

Figure IA is a magnified view of the pinion of motor 20 engaging the facing rack portions of the concentric frame members 5 and 6 in Figure 1;

Figure 2 is a schematic side ^' elevation of the bowling machine of Figure 1;

Figure 3 is a schematic perspective view of the bowling machine of Figures 1 and 2 showing a cover over the bowling head and also the supporting trolley;

Figure 4 is a diagrammatic front elevation of the wheels, guide and feed chute of the bowling machine of Figure 1 ;

Figure 5 is a similar diagrammatic front elevation showing a variant of the bowling machine of Figure 1 utilising four wheels;

Figures 6a) to i) show various diagrammatic rear elevations of the wheels and ball of the bowling machine of Figure 1 in the orientations required for various cricket deliveries;

Figure 7 is a diagrammatic view of the ball trajectories associated with the deliveries of Figures 6a) to i) ; and

Figure 8 is a perspective view of a variant of the bowling machine of Figures 1 to 4.

Referring to Figure 1, the machine comprises a control box 13 supporting a bearing 11a in which a main pivot 11 is mounted and carries the bowling head which is thus rotatable in azimuth. An instrument panel 12 of the control box will be described subsequently.

The bowling head comprises an upright semi-circular yoke 10 which carries lugs 9 at its opposite terminal portions on which is mounted an outer circular frame 5. A circular subframe 6 is mounted within frame 5 and, as shown in Figure IA, has teeth extending around its outer periphery. A motor 20 (not shown in Figure IA) is carried on the outer frame 5 and drives a pinion 12 (Figure IA) which engages the teeth formed on the outer periphery of subframe 6 and can thereby rotate subframe 6 by about 180 degrees about its axis. As will subsequently be explained, this enables the spin axis (lying in the plane of Figure 1) orthogonal to the axis of projection (extending perpendicularly out of the plane of Figure 1) to be varied.

To this end, the subframe 6 is provided with two oppositely disposed motor-driven wheel assemblies, each comprising a drive wheel 1 driven by an electric motor 2,

the motor 2 being mounted on a generally L-shaped frame 3 which is in turn rotatably supported on subframe 6 by a pivot mounting 4. The axes of the respective pivot mountings 4 are coincident with a diameter of subframe 6 and are also coincident with the diameters of the drive wheels 1 and with the radial mid-planes of the drive wheels .

As described below in more detail with reference to Figure 2, the actuator A includes a piston which projects into a delivery tube DT whose axis is aligned with the axis of projection of the balls (i.e. into the plane of the drawing of Figure 1) . A hopper H or feed chute communicates with a side opening in delivery tube DT and can be loaded with a row of balls B as shown. Finally, it should noted that the orientation of hopper H about the axis of projection of the balls i.e. the axis of delivery tube DT is fixed and is inclined at an angle of typically 15° to the horizontal to enable a gentle gravity feed of the balls.

Referring now to Figure 2, the ball feed arrangement is shown somewhat more clearly. The hopper H enables balls B to be fed by gravity into ^■ a recess R in the base of the delivery tube DT when the ball remains stationary holding back the next ball. An actuator A (which is suitably a solenoid actuator whose coil is connected to driver circuitry D on the control box 13) includes a piston P which is aligned with the axis of projection A ₅ of the balls and is shown in Figure 2 in a retracted position in which it uncovers an opening in tube DT which communicates with hopper H to allow a single ball B to be fed into tube DT.

When the 'bowling' cycle is started the piston P drives the balls out of the recess and into the nip of the opposed wheels while holding back the next ball. Once the first ball has been ^λ bowled' the piston P returns and the next ball rolls into the recess R. The wheels 1 are suitably 150mm to

220mm in diameter and are provided with polyurethane rims IA which are capable of gripping a ball fed between them. The wheels 1 are suitably 60mm thick i.e. somewhat less than the diameter of a cricket ball . The spacing between opposed peripheries of the wheels is suitably 54mm to grip a cricket ball. Each wheel is rotated by its associated electric drive motor 2 at a speed of 800 to 4000 rpm, typically 3,000 RPM, the upper wheel being rotated anticlockwise and the lower wheel being rotated clockwise so as to engage and eject the ball fed from tube DT. Tube DT thus acts as a guide and can either terminate immediately before the nip of the opposed wheels 1 or can include openings (not shown) to allow the peripheries of the polyurethane rims IA to extend into its bore and engage a ball therein.

In the advanced position (not shown) of the piston P, the side opening in tube DT is blocked and thus only one ball can be ejected at any one time from the machine. This is an important safety feature.

Leaf springs coupled to microswitches (not shown) sense the insertion of a ball into the delivery tube DT and provide signals to a column of indicator lights LP which light up successively as the instant of delivery from the machine approaches. These indicator lights are viewable by the batter and provide a visual cue for him.

The control box 13 includes a microprocessor for controlling the driver circuitry D which also includes outputs to the motors, including the drive motors 2 of the wheels 1 and motor 20 (Figure 1) which controls the orientation of subframe 6 as well as two further actuators TA (Figure 1) which are provided to vary the angle of tilt (i.e. the angular offset of the axes of rotation) of the drive wheels 1 about the pivot 4.

The control panel 12 (Figure 1) includes controls for switching on the machine, selecting the delivery, starting the motors and bowling (e.g. a ^Xλ bowl" pushbutton) . Controls for aiming the bowling head (via further actuators, not shown) are also provided.

The microprocessor is suitably coupled to a card reader R which can receive a solid state memory card MC containing electronic data defining various parameters such as wheel speed,, orientation of the subframe 6 and tilt of the drive wheels in order to mimic a desired delivery of a human bowler.

Alternatively or additionally, a delivery or a sequence of deliveries can be commanded from a remote controller RC (e.g. operated by the batsman) which transmits IR signals to an IR sensor S connected via suitable decoder circuitry DC to microprocessor μP.

The geometry of the ball delivery arrangement is shown in Figure 4. The axes of rotation A _x of the wheels 1 are tilted equally and oppositely out of the plane of Figure 1 by an angle phi _x and accordingly impart a spin about the axis of projection (not shown in Figure. 4) which projects perpendicularly from the plane of Figure 4. This spin is indicated by the curved arrows on ball B. Additionally, a differential deltaw can be applied to the rates of angular rotatation w of the wheels so that the upper wheel rotates at an angular velocity w + deltaw and the lower wheel rotates at an angular velocity w - deltaw. This differential imparts a spin about a spin axis SA lying in the plane of Figure 4 and intersecting the diameter of the ball passing through the central diameters of the drive wheels I and indicated by the chain dotted line. The orientation phi of this line is determined by the orientation of the subframe 6. Thus the orientation of spin axis SA can be controlled by

appropriately orienting the subframe 6 within frame 5 (Figure 1) .

Figure 5 shows a variant of the arrangement of Figures 1 to 4 drive wheels rotating as shown at angular velocities w + deltalw, w - deltalw, w + delta2w and w - delta2w impart an anticlockwise spin about the axis of projection as shown by the four curves arrowed in ball B. A delivery tube DT feeds the ball B into the nip of the drive wheels ^' and includes a side opening (not shown) defined by the intersection of this tube with a hopper H (or chute) which is inclined to the horizontal at an angle of e.g. 15°. The speed differentials deltalw and delta2w apply spins about respective axes in the plane of the drawings and these spins combine vectorially into a single spin in the plane of Figure 5 which is comparable to the spin about spin axis SA shown in Figure 4. By varying deltalw and delta2w the orientation and magnitude of this spin can be varied.

However the arrangement of Figure 5 is believed to be less practical than the arrangement of Figure 4 because of the tendency of the tilting drive wheels 1 to interfere with each other. Accordingly, the thickness of the wheels 1 is somewhat less than the diameter of ball B, e.g. 45mm. However, four drive wheels and four motors are required, resulting in a more . cumbersome and more complicated arrangement .

In each of the arrangements shown in Figures 6a) to i) , the ball is projected into the plane of the drawing away from the viewer.

Figure 6a) shows the two drive wheels 1 ejecting ball B along the axis of projection (not shown) into the plane of the drawing, with no spin, since the angular velocities w of the wheels 1 are equal and opposite. Accordingly, the wheels

can be rotated (by rotating subframe 6 of Figure 1) into any of the positions l' , l" or l'" for example without affecting the type of delivery but allow for greater control of direction and trajectory. In practice however the horizontal orientation will normally be used.

Figure 6b) shows a ball B having a spin Sl about a vertical axis as a result of a speed difference between the two horizontal drive wheels 1 (indicated by + and - signs on the respective drive wheels) . The resulting delivery is an inswing .

Figure 6c) shows the relative wheel speeds and hence the spin Sl reversed. This results in an outswing delivery.

The arrangement shown in Figure 6d) shows the axes of the drive wheels 1 horizontal with the lower drive wheel rotating faster than the upper drive wheel, resulting in a back spin as shown by arrow Sl. The resulting delivery is thus a backspin.

Figure 6e) shows the reverse arrangement in which the upper wheel rotates faster than the lower wheel, thereby reversing spin Sl. This results in a top spin delivery.

Figure 6f) shows an arrangement in which the drive wheels 1 are disposed with their centres aligned with the centre of ball B and disposed at 45° to the horizontal. The bottom left drive wheel rotates faster than the top right drive wheel whereby a spin Sl about an axis transverse to the axis of projection is generated and a clockwise spin S2 about the axis of projection is generated, resulting in an off break delivery.

Figure 6g) shows a similar arrangement rotated by 90° i.e. with the line of centres of the drive wheels and centre

of ball B again at 45°. This arrangement with angularly- offset axes of rotation of the drive wheels results in a backspin Sl about a 45° axis and an anticlockwise spin S2 about the axis of delivery, resulting in a leg break delivery.

Figure 6h) shows the wheel centres offset from the vertical clockwise, by about 15° with the upper wheel rotation axis tilted about the line joining the wheel centres and ball centre by about 30° to the left (i.e. anticlockwise in plan view) relative to the lower wheel rotation axis . The upper wheel rotates faster than the lower wheel, resulting in topspin Sl about an axis transverse the axis of projection and a clockwise spin Sl about the axis of projection. The resulting delivery is an off cutter.

Figure 61) shows a similar arrangement in which the wheel centres are offset anticlockwise from the vertical by about 15° with the upper wheel rotation axis tilted about the line joining the wheel centres and ball centres by about 30° to the right (i.e. clockwise in plan view) in relation to the lower wheel rotation axis. The resulting delivery is a leg cutter.

The resulting ball trajectories a) , b) , c) , d) , e) , f) and g) towards wicket w are shown in Figure 7. Deliveries d) and e) are shown in elevation and the other deliveries are shown in plan view.

In each case the angular offset (i.e. angle theta _x in Figure 4) is 30° but this is merely preferred and other offset angles could be employed. Furthermore the off break and leg break deliveries shown in Figure 6f) and g) employ a 45° disposition of the wheel centres (as shown in Figure 1) but this angle may. be varied in order to emulate the deliveries of any well known spin bowler, for example.

It will be therefore .be apparent that the delivery parameters, namely speed differential, disposition of the drive wheel centres and angular offset (about the line of centres) of the drive wheels as well as the basic parameter of speed of delivery (determined by the average speed of the drive wheels) as well as the aim of the bowling head can be varied and in principle programmed into the machine and/or read from solid state memory card MC (Figure 2) or entered from a remote controller or even a wireless connection to the Internet for example .

It will also be apparent that the spin S2 about the axis of projection of the ball is achievable when the axes of rotation of the drive wheels 1 are angularly offset about the line of centres of the wheels. This capability is a unique advantage .

Figure 8 shows a variant of the bowling machine with an improved frame 19' for supporting the bowling head 100. ^' The frame comprises a base portion having forwardly extending horizontal legs on which are mounted wheels 8' at the extremities thereof, a forwardly inclined yoke portion being pivotally mounted at the rear of the base portion and having an upper generally U-shaped yoke portion L2 pivotally mounted on the extremities of its two limbs. The limbs of the upper yoke portion L2 are inclined rearwardly and carry head 100 which is pivotally mounted on the extremities thereof. A feed hopper H for feeding balls into the assembly of rotating wheels (not shown) is provided and the bowling machine thus incorporates a ball feed and delivery mechanism which is similar to that shown in the upper portion of Figure 2.

The pivots P between the base and lower yoke portion Ll and the lower yoke portion Ll and upper yoke portion L2

enable the bowling machine to be collapsed vertically from a fully extended height of approximately 2.5m to a collapsed height of approximately 1.5m for transportation or storage. The pivot P at the extremities of the arms of upper yoke portion L2 enable the inclination of the bowling head 100 and hence the delivery axis A ₉ to be varied.

The electronic control arrangement and control panel are suitably similar to those shown in Figure 2.