BALL PROPELLING MACHINE

Abstract: A machine which can be used by a player practising a ball game such as tennis or badminton has an ejection mechanism comprising a pair of revolving discs (1a, 1b) spaced apart by a gap (2) through which can be drawn a ball (4) for ejection in a direction (3) which can be determined by appropriate adjustment of the vertical and horizontal positioning of the revolving discs by means of inclination drive (10) and sweep gear (12). Side spin or slice can be imparted to the ball by rotation of the revolving discs about an axis lying in the direction (3) of the ball ejection, whilst top spin or under spin can be imparted to the ball by varying the angular velocity of the discs (1a, 1b) by causing them to rotate at differing speeds. The ejection mechanism may be mounted on a height adjusting mechanism in order to vary the height at which the ball is ejected. The machine can be controlled by a microprocessor-based system which may be pre-programmed or operated by remote control.

Description: BALL PROPELLING MACHINE This invention relates to ball games, in particular but not exclusively racket games such as tennis and badminton, and is concerned with machines which can be used to assist players in practising for such games, e.g. the strokes employed in such racket games. Known tennis ball propelling machines use pressurised air current to force the ball under compression out of an elongate tube, or operate by squeezing a ball between a pair of high speed rotating wheels so that the ball is propelled out of the gap between the wheels. While all such machines have means of adjusting the inclination and direction of the ball ejection and the wheel type machines allow variation of the wheels' angular velocity to impart a degree of spinning to the ball in a vertical plane, resulting in pure top spin or under spin, there is no provision for controlling other characteristics of the ball subject to manipulation by the average tennis player, such as the height at which the ball is propelled, or characteristics mastered only by top grade tennis players, such as various side spins or "slice" at controllable angles. The term "programmable" when used in connection with existing propelling machines is misleading in the sense that no programming option is available in the prior art machines other than manual adjustment of one or more of a limited number of parameters. Other machines allow for a "random" mode, whereby the machine is set by means of a mechanical switch to deliver a series of balls with varying parameters at random. While several known machines claim to have programming capability, this is limited to a small number of pre- determined settings that are being performed repeatedly with no provision for adjustment to the ball trajectories by the user. It is a further disadvantage of the prior art machines that while known machines do have means for remote control operation, those do not provide complete control over the full range of ball characteristics, propelling heights and ball trajectory types. Tennis ball propelling machines thus suffer from the disadvantages of: (a) not providing for a ball service that is truly realistic; (b) not providing for variable imparting height; (c) propelling balls with only a restricted range of characteristics that is not satisfactory for efficient training; and (d) severely damaging the balls within a small number of shots. It is an object of the invention to provide a ball propelling machine which obviates the disadvantages of the known machines. Thus the present invention provides a mechanical and electronic apparatus and method for the control, adjustment, and manoeuvring of various types of propelling mechanism to be used for sport and recreational games such as tennis, badminton, volley-ball and the like. In accordance with the invention, there is provided a machine suitable for propelling a ball in the general direction of a player practising a game involving the use of such a ball, comprising in combination: a pair of substantially coplanar spaced revolvable discs having concave rims which are adjacent so as to form therebetween a gap; driving means capable of causing the discs to revolve in opposite directions when in use; feeding means capable of delivering a ball or the like into one end of said gap so that, in use, it is drawn through the gap by the adjacent rims of the revolving discs and ejected from the other end of the gap; and means for varying the horizontal and vertical positions of the discs and for rotating the discs about an axis which defines the direction of the ejected ball or the like; the arrangement being such that in use the player can obtain the desired ball characteristics by appropriate adjustment of the position of the pair of revolving discs in the vertical and horizontal planes respectively and by rotation of the discs about said axis. In a preferred embodiment of the invention, the operation of the machine is governed by a microprocessor-based system, which monitors and controls the operation either in accordance with the predetermined setup, or by responding to the player's requests. The microprocessor can be pre-programmed to control several mechanical motions, and utilize those motions to emulate a player in action. The microprocessor enables separate as well as combined actuation of any of said motions for adjustment of the machine to the required parameters for a single shot as well as to complete game patterns of varied shot and ball characteristics. The machine of the invention allows for retaining pre-programmed game patterns and customised characteristics and recording actual game patterns or shot characteristics. Thus full games be simulated in whole or in part. In a preferred embodiment, the player is equipped with a remote control, which allows for full operation of all machine features under real game conditions. The machine of the present invention is capable in a preferred embodiment, of providing the following ball characteristics: (a) Ball speed - controlled by adjustment of the speed of revolution of the discs; (b) Ball spin (top spin or under spin) - controlled by adjustment of the relative revolution speeds of the discs; (c) Side spin or "slice" (swivelling) - controlled by radially altering the orientation of the revolving discs relative to an axis lying in the direction of the ball ejection; (d) Imparting height - controlled by a height adjustment mechanism positioning the revolving discs at various heights above ground level; (e) Sweep (side angle) - controlled by adjustment of the horizontal position of the revolving discs; and (f) Inclination angle - controlled by adjustment of the vertical position of the revolving discs. It will be appreciated that by controlling the above enumerated characteristics, a control of the ball trajectory is achieved. Thus for instance a curved trajectory is obtained by combining speed and spin adjustment with side spin (swivel) , sweep, and height positioning. For a better understanding of the invention and to show how he same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a right side elevation of a ball propelling machine; Figure 2 is a rear view of the machine of Figure 1; Figure 3 is a vertical section through the machine of Figure 1; Figure 4 is a left side partial sectional view of the machine of Figure 1; Figure 5 is a left side elevation of a height adjustment mechanism for the machine showing different positions a, b and c; Figure 6 is a right side elevation of another height adjustment mechanism for the machine showing different positions a, b and c; Figure 7 is a schematic view of a part of a tennis court; and Figure 8 is a front view of the machine of Figure 1 showing different positions A and B. Referring now to the drawings, in Figures 1 and 2 there is shown a preferred ball propelling machine in accordance with the invention, which comprises a pair of revolvable discs la,lb having a gap 2 therebetween. Each disc has a concave rim 15a,15b (see Figure 2) . The discs la,1b are mounted on a V-shaped support 7 attached to a yoke 6 which surrounds a rotatable sleeve 8, into which is fitted a feeding tube 5 through which a ball 4 can be fed into the gap 2 and ejected therefrom in ball propelling direction 3. A side angle (sweep) drive mechanism 9 can operate a sweep gear 12 in conjunction with sweep bearing 14 so as to vary the horizontal position of the discs la,lb and an inclination drive mechanism 10 can operate so as to vary the vertical position of the discs la,lb. Likewise a swivel (spin angle) drive mechanism 11 can operate a swivel gear 13 so as to vary the orientation of the discs la,1b relative to direction 3. This assembly is mounted on a rotatable base 16 (see Figure 2) . Figure 3 shows the individual electric motors 20 which drive the revolvable discs la,lb and which can be operated at different speeds so as to control the ball spin of the ejected ball. Figure 4 shows a casing 17 and a hopper 18 having a ball feeding disc which is formed with grooves and revolves within the hopper 18 so as to feed a series of balls into the ball feeding tube 5. One form of height adjustment mechanism for the ball propelling machine is shown in Figure 5 and comprises a two segment arm which can be adjusted to various heights, examples of which are shown in a, b and c. The arm may optionally be fitted with a swivel joint 19 which can be used to vary the horizontal (side angle) position of the rotatable discs la,lb. An alternative form of height adjustment mechanism is shown in Figure 6 and comprises an extendible scissor- type mechanism which can be adjusted to various heights, examples of which are shown in a, b, and c. In Figure 7 there is shown a schematic representation of a tennis court showing an inclination angle oc between horizontal plane c, b and ball direction a, and side angle p between plane a,b and straight line c aimed directly across the court. In Figure 8 there is shown a front view of the two discs la,lb having concave rims with the gap 2 therebetween. the discs being mounted on the support 7 affixed to the rotatable base 16. In position A, no side spin would be imparted to the tennis ball, whereas in position B, the ball is ejected with a side spin. Ejecting Mechanism As shown in Figure 1, revolvable discs la,lb are disposed on double support 7 mounted in a rotating sleeve 8, with rotating sleeve 8 encircling the opening of a feeding tube 5 and they are rotatable in unison around axis 3 which defines the direction of ejected ball 4, while the position of the discs la,lb defines the degree of side spin or "slice" imparted to said ball. The relative angular velocity of discs la,1b may be varied to impart top or under spin to ball 4. Each of the discs la,lb has a rim presenting a concave surface to the ball, as shown in Figure 2 at 15a,15b. The concave surface radius and the size of gap 2 between the discs determine the ranges over which the characteristics of the ball can be varied. The discs la,lb may be made, for example, with a concave section of radius 50mm and a gap of 38mm between the deepest surface points of the rims of the two discs. In a preferred embodiment the revolvable discs are directly mounted on and driven by stationary shaft revolving case DC motors shown at 20 in Figure 3. In an alternative embodiment, the discs are driven by two standard high speed DC motors with either direct, gear, chain or belt drive. A variety of speed and spin amplitudes may be implemented by forming the concave sections 15a,15b of the discs with any radius in the range from 38 to 68mm, and any gap in the range from 28 to 48mm, while the' capability of emulating with precision the ball characteristics as produced by a human player is maintained throughout. Individual motor speeds are electronically controlled, allowing for speed and spin adjustment to either pre-set or programmable shots, or a combination of both. According to a further aspect of the invention motor speeds are remotely controllable for customised setting of ball characteristics. Ball Feeding Mechanism The ball feeding mechanism, shown in Figure 4, comprises a hopper 18 and a rotating disc (not shown) . Upon rotation of the disc, balls from the hopper are led to meet opening of the feeding channel one at a time. The feeding channel then diverts the ball through the external envelope of the ball container (hopper) 18, and into the feeding tube 5. The preferred embodiment, the rotating disc is driven by a stepping mechanism. The feeding tube 5 is positioned within the ball propelling head, to lead the ball in the direction of the gap 2 between the discs la,lb, where it is drawn into said gap 2 to be ejected therefrom in accordance with ejection data input. The rotating feeding disc is disposed in a vertical position within the hopper 18, collecting the balls and delivering them into the feeding channel as it rotates around its axis. In an alternative embodiment the rotating feeding disc is mounted horizontally at the base of the hopper. According to a further embodiment the rotating feeding disc comprises several engraved grooves for leading the balls and avoiding ball jamming. The ball is fed into the ejecting mechanism at the centre of the gap 2 between the rotating discs la,lb by the force of gravity or by a small propulsion device. Swivelling or Spin Angle Mechanism The swivelling mechanism provides means for continuous adjustment of the spin angle or "slice", said spin angle being the angle between the horizon and spin axis. Adjustment of the spin angle enables emulation of any mode of side spinning the ball, as may be produced by a left-handed or right-handed player playing fore-hand or back-hand at any height, direction, speed and degree of spinning. A 180 degree range of swivelling is provided (90 degrees to each side) to allow for any possible type of side spinning produced by an actual player. In the preferred embodiment, swivelling is performed by adjustment of the discs la,lb, said discs being rotatable around an axis 3 shown in Figure 1, which defines the direction of ejection of the ball 4 through the centre of the gap 2 between said rotating discs la,lb. Swivelling (spin angle) range is 90 degrees to each side. Adjustment of rotating discs la,lb is effected by them being mounted on double frame 7 which protrudes from rotating sleeve 8, said rotating sleeve 8 enclosing the feeding tube 5 while being held and rotated inside the yoke 6. Rotating is driven by swivel drive 11, utilizing a stepping mechanism and gear 13 to position rotating discs la,lb at an angle which may be pre-set, and is programmable and adjustable. The driving mechanism is a worm-wheel mechanism, the wheel being mounted on the rotating sleeve 8. Figure 8 shows by way example two different positions of the ejecting means. In the drawing generally designated A the discs are in a perpendicular position resulting in zero spin, whereas in the drawing generally designated B the discs have been rotated to assume a diagonal position whereby a side spin of controllable velocity is obtained. Side Spin Velocity Control Mechanism Either of the two rotating discs la,1b may be selected to rotate at a higher relative speed than the other whereby in combination with swivelling ati90° any kind of side spin may be emulated. Inclination Mechanism The inclination angle is defined as the angle OC between imparted ball direction a and the horizontal plane be as shown in Figure 7. The inclination mechanism provides means for continuous adjustment of the inclination angle, thereby enabling a variation of trajectories at a given speed and ejection height. It will be appreciated that the inclination angle may be positioned above the horizon as in Figure 7 creating a look up angle, or below it, creating a look down angle, not shown. Angles are fully adjustable and programmable, and may also be pre-set in the machine. Controlling the inclination angle allows for emulation of a full range of shots from service height down to ground level, including emulation of a player hitting down to ground level, as well as emulation of a player hitting a ball from various heights at different distances from the net. Range of inclination angle is from 15 degrees down and up to 45 degrees up. As shown in Figure 1, feeding tube 5 is mounted in a yoke 6 subject to inclination in a vertical plane, allowing modification of the inclination angle. Inclination is driven by inclination drive 10 utilizing a stepping mechanism comprising a gear 13 with a worm- wheel, mounted on the yoke 6. Sweeping or Side Angle Mechanism The sweeping mechanism provides means for continuous adjustment of the horizontal angle at which the ball is ejected from the propelling machine. The side angle p shown in Figure 7, is defined as the deviation of the direction a of the imparted ball from the vertical plane containing straight line c which is aimed directly across the court. It will be appreciated that deviation may be directed to the opposite side of line c. Controlling the said horizontal angle enables the production of varies trajectories aimed at diverse locations on the court, whereby emulation of a full range of shots targeted to any point between the base line and the net and across the width of the court is enabled. Due to the above described control mechanism the apparatus of the invention provides for serving more than one player by means of a simple machine. Range of sweeping (side) angle is from 45 degrees to the left to 45 degrees to the right. In the preferred embodiment, the propelling mechanism is supported on rotating base 16 which sweeps from right to left, driven by sweep drive 9 utilising a stepping mechanism and gear 12, as shown in Figure 1. In an alternative embodiment, the driving mechanism may be any type of motor, pneumatic or hydraulic device utilising gearing, and may also by applied at ground level or close to ground level as shown in Figure 5 at 19, allowing for sweeping the height control mechanism in toto with the ejecting mechanism on top. Elevation or Height Control Mechanism The height control mechanism provides means for continuous adjustment of the height at which the ball is ejected from the ejecting mechanism, whereby a variety or trajectories aimed at various heights are produced to emulate a player at varying distances from the net hitting the ball at varying heights. The range of elevation is from 0.3 metres up to 2.75 metres above ground level. In the preferred embodiment, the elevation mechanism consists of a scissor mechanism, shown in Figure 6. In an alternative embodiment, shown by way of example in Figure 5, a two, three or four segment arm may be used for lifting the ejecting mechanism. Springs or gas filled struts may be used for minimising the force required to raise the mechanism. Visual Indication of Ball Trajectory In accordance with a feature of the preferred embodiment, actual movements are visibly performed by the ejecting head of the apparatus whereby a visual indication to the player is enabled of the direction, inclination, height and side-spin at which the ball is to be ejected. This feature is extremely important while performing a complete training session or a full game. Ball Damage Prevention In accordance with a further aspect of the invention, the concave surface of the rims of the rotating discs as well as the surface material and texture are designed to provide a firm and stable grip of the tennis ball, accelerating it until ejection at the desired speed and spin with minimal damage to the ball, where damage is defined as loss of fiores on the ball surface, "shaving" or cutting of the ball. The present invention minimises the damage to the bail which is substantially less than effected by any other machine or professional player. In the preferred embodiment, the surface material is a synthetic plastics material, such as polyurethane, with smooth, minimally textured surface. In an alternative embodiment, the surface material may be any derivative of urethane or other material with similar characteristics, such as thermoplastics, thermosetting plastics, elastomers, or alloy-plastic material, any reactive plastic material or naturally occurring coating materials. Landing Point Control and Propelling Point Emulation The mechanical components, drives, and electronics of the apparatus of the invention provide means for very accurate control of ball characteristics, allowing a ball to be ejected and landed within 15cm of the desired location, provided the apparatus is positioned at a predetermined point on the court for calibration. Actual location of the apparatus notwithstanding, training with the ball coming from various locations may be emulated by adjusting the ball characteristics, trajectory and propelling height to produce a trajectory that simulates a shot coming from a desired location. In the preferred embodiment, two means are available to accurately design and adjust the trajectory and landing spot: (a) clear marks on the machine base for precise positioning at the centre of the base line, using the common lines marked on every tennis court, and (D) calibration and adjustment. Known shots can be used for calibration, the calibrating shots being straight shots from maximum service height aimed toward the opposite base-line at (1) the centre, and (2) to the right corner of the base-line. The machine can then be adjusted digitally to any location by specifying coordination of the desired new location. Independent Movement Around the Court In accordance with a further aspect of the present invention, the ball propelling apparatus is capable of independently moving around the court. This feature allows for perfect visual emulation of a complete game as well as training the player with various ball characteristics driven from different locations on the court. The machine is equipped with sensors which identify its location by means of infra-red or ultra-sonic transceivers or both on the machine and at the sides of the court. The same system provides the necessary means for adjusting the machine to face a predetermined direction such as straight facing the net. Power Source The apparatus of the invention may be connected to any mains power source and it may be made with an alternative power source such as a rechargeable sealed lead acid battery for backup. The battery may be charged utilising a solar charging system, with an alternative quick charging from the main power line. Microprocessor-based System Operation of the apparatus of the invention is wholly controlled by a microprocessor-based sub-system wherein the microprocessor is embedded in an electronic board. The said electronic board provides means for receiving instructions either by a wire connected personal computer or from a remote control apparatus allowing for individual determination of shot characteristics as well as customised adjustment of programs and training session design. Pre-programmed and customised parameters may be stored in the processor memory to (a) create a combination of desired ball characteristics, (b) create game patterns, (c) perform safety measures prior to ball ejection, (d) record, retrieve, display and/or print, ball characteristics, series of ball characteristics and evaluation of player responses to shots. It will be appreciated that various types of electronic circuits using different kinds of processors may be used to operate the apparatus of the invention. Thus for example the number of I/O lines may differ according to the features and capabilities of various models whereas external memory may be implemented by a variety of means utilising floppy discs or CMOS memory cards with the appropriate drives. Remote Control The remote control system of the apparatus is used as a remote console of the microprocessor, allowing the user a determination of shot characteristics as well as choice of customised programs and pre-designed training sessions. In the preferred embodiment a communication protocol is utilised in order to determine the said parameters. According to another aspect of the preferred embodiment the man-machine interface enables the use of menu driven options to simplify the determination process. In accordance with a further embodiment of the invention the remote control receives feedback information from the apparatus and is capable of displaying data on a remote display station, operating as a transceiver and a console in one. Training Sessions The electronic sub-system of the apparatus of the invention is capable of storing a large database of shots of varied characteristics. The said pre-stored shots can be used consecutively in any sequence or with repetitions, to form a training program. Shots may be ejected at a time upon player request, or successively, in accordance with a predetermined pattern. The time elapsed between each shot may be predetermined, adjusted by the player or randomly selected if the player so desires. The said electronic sub-system further enables recording new customised training sessions, and updating existing sessions. Sessions may be stored in the processor memory or in external memory for fast retrieval or future use. Game Simulation The said electronic sub-system is capable of storing a database of numerous games. Each game may simulate a real game or it may be designed to suit preferences of the player. The electronic sub-system allows for customising and recording new games, as well as utilising new update games provided by means of external memory device. Printing Games and Training Sessions The electronic sub-system of the apparatus further provides means for printing designed or actual games and training sessions via a printer. In the preferred embodiment the data is presented in the form of ball characteristics of each shot. Recording and printing may be used by coaches for assistance in training scnedule planning . Return-Shot Evaluation, Recording and Printing In accordance with a further aspect of the invention, coaches or players may record selected shots with an evaluation of the student's response to each shot. In the preferred embodiment, the coach selects his evaluation on a scale of "a" to "n", "a" being excellent and "n" being poor response, and records the ball characteristics with the student return evaluation. The coach and the student may then print the evaluated shots, analyse them and plan the student's next training session accordingly.

Claims: CLAIMSi A machine suitable for propelling a ball in the general direction of a player practising a game involving the use of such a ball, comprising in combination: a pair of substantially coplanar spaced revolvable discs having concave rims which are adjacent so as to form therebetween a gap; driving means capable of causing the discs to revolve in opposite directions in use; feeding means capable of delivering a ball or the like into one end of said gap so that, in use, it is drawn through the gap by the adjacent rims of the revolving discs and ejected from the other end of the gap; and means for varying the horizontal and vertical positions of the discs and for rotating the discs about an axis which defines the direction of the ejected ball or the like; the arrangement being such that in use the player can obtain the desired ball characteristics by appropriate adjustment of the position of the pair of revolving discs in the vertical and horizontal planes respectively and by rotation of the discs about said axis. A machine as claimed in Claim 1, wherein said driving means comprises individual separately controllable motors for the revolvable discs, whereby in use the speed and spin of the ejected ball can be controlled by appropriate adjustment of the motor of each disc. 3. A machine as claimed in Claim 1 or 2 , wherein said feeding means comprises a tube having one end positioned adjacent said one end of the gap and communicating at its other end with a storage hopper containing means for introducing balls or the like .stored in the hopper into said other end of the tube. 4. A machine as claimed in Claim 1, 2 or 3, wherein the concave rims of the revolvable discs are coated with a synthetic plastics material. 5. A machine as claimed in Claim 4, wherein the rims are coated with polyurethane. 6. A machine as claimed in Claim 1, 2, 3, 4 or 5, wherein the desired characteristics are obtained by means of electric motors which are capable of actuating the adjustment and/or rotation of the discs, and wherein means are provided to control the operation of the electric motors. 7. A machine as claimed in Claim 6, wherein said means for controlling the operation of said electric motors is a microprocessor. 8. A machine as claimed in Claim 7, wherein said microprocessor is programmed to receive signals emitted from a remote control device, enabling the player to determine shot characteristics or choose from a repertory of customised shots and training programs stored in the microprocessor memory or in any external memory. 9. A machine as claimed in Claim 8, wherein said microprocessor is adapted to communicate with a personal computer allowing for programming, retaining, recording and recalling of single shot or full game characteristics. 10. A machine as claimed in Claim 9, wherein means are provided for printing out single shot characteristics, games, training sessions and return shot evaluations. 11. A machine as claimed in Claim 10, wherein means are provided for recording game evaluation input. 12. A machine as claimed in Claim 8, 9, 10 or 11, wherein said remote control device receives feedback information from said machine. 13. A machine as claimed in any one of Claims 7 to 12 and further comprising sensors for the reception of signals from emitters positioned around the court which signals are processed by said microprocessor to define the location of said machine within the court. 14. A modification of the machine claimed in Claim 13, wherein the sensors are positioned around the court and the emitters are mounted on the machine. 15. A machine as claimed in Claim 13 or 14, wherein said sensors are receptors of infra-red radiation, or receptors of ultra-sonic signals. 16. A machine as claimed in Claim 13, 14 or 15, wherein the microprocessor is programmed to calculate the ball characteristics in accordance with said location of the machine.

Inventors: ELBAUM DANIEL, ELBAUM, DANIEL
Applicants: ELBAUM DANIEL, KOSM GERALD EMMANUEL, ROBO SPORTS TECH PTY LTD, ELBAUM, DANIEL, KOSMIN, GERALD, EMMANUEL, ROBO SPORTS TECHNOLOGIES PTY. LIMITED
Application year: 1992
Main classification: A63B69
IPC codes: A63B69