reference should be made at this time to fig1 , and 3 which illustrate perspective , plan view and longitudinal section drawings of an instant tennis game 10 according to the present invention . the game 10 comprises a partial court 12 less than 3 / 4 normal length and about 1 / 2 normal width for a tennis court . the court 12 may be approximately 70 feet long and 30 feet wide . a tennis net 14 is disposed about 20 feet from one end 16 of the court 12 . the game 10 is enclosed by a fence 18 . the fence 18 should be of normal height near the net 14 , but may be of less than normal height near the end 20 which is farthest from the net , since the purpose of the fence is to stop balls hit wildly . while the player may well hit the balls fairly high , it is very unlikely that the machine will hit balls toward the side 20 which will require a high fence . since some players will hit balls at the most amazing angles from the point of contact , the fence 18 in fig1 is illustrated as being of normal height all around the court 12 . a backboard 22 slanted so as to cause the tennis balls hit thereto to fall downward is placed near the end 16 . the backboard 22 may be acoustically responsive and may simulate a background similar to that of a normal tennis court . this inclined backboard 22 or backstop 22 may allow a scoring mechanism to record and display the player &# 39 ; s accuracy . this would be done by urging the player to hit for certain parts of the backstop 22 and keeping track of the number of times the player hits the selected segment ( not illustrated ) by means known to the prior art such as a pressure sensitive plate coupled electronically to an electronic counter and display . a ball delivery machine 24 , also referred to as a ball hurling machine 24 , hurls ball through a slot 26 by barrel means 28 . in order to simulate service , the ball machine 24 may be moved to either side 30 , 30 prime , of the backstop 22 . while fig1 and 2 illustrate lines 32 similar to those found on a tennis court , for the simulation of service , the center line would have to be moved toward one side or another . it would , of course , be very easy to draw multiple lines 32 , having different colors for the simulation of different playing experiences . the surface 34 of the court 12 is crowned , and is higher along the center line 40 , gradually sloping downward to side gutters 36 . the side gutters 36 join near the short end of the court 16 to form a ball return conduit 38 . the degree of crowning is such that tennis balls falling on the surface 34 roll to the nearest gutter 36 . each gutter slopes downward from the end 20 toward the end 16 at an angle of about 3 - 3 / 4 %. gravity causes the tennis balls to roll down the gutters 36 to the ball return conduit 38 . when the balls reach the lowest point in the ball return conduit 38 , air pressure means lifts them back to the ball machine 24 for return to the player . fig4 and 5 illustrate selected transverse sections of the court 12 . reference should be made at this time to fig6 which is a vertical section through the ball delivery machine 24 . fig6 may best be understood by viewing it in conjunction with fig7 a plan detail of the ball delivery machine 24 barrel elevation joint , with fig8 a vertical section detail of the ball spin control mechanism with fig9 a horizontal section detail of the barrel traverse joint , and with fig1 a vertical oblique section detail of the timing mechanism . tennis balls return via the gutters 36 to the conduit 38 . the balls form a line behind a ball delivery timing rotor 46 . the rotor 46 is set at a pre - determined rotation rate which determines the intervals between delivery of balls from the machine . the rotor 46 releases another tennis ball each one - third of a revolution . the rotor 46 continues to turn and picks up the next ball which is to be subsequently released . momentum imparted by the rotor 46 and gravity cause the ball to roll to the elbow 76 joining the return conduit 38 to the riser 44 . the velocity of the rotor is controlled by the timer 42 . the rotor is powered by the drive motor 48 . the rotor triggers the riser jets solenoid valve switch 50 subsequent to release of the ball . the switch 50 triggers the release of a blast of air of approximately 1 . 5 seconds in duration . the air is released through the air release hoses 99 beneath the rotor 46 and through the two additional air release hoses 99 which exit into the riser 44 . the air pressure from the hoses 99 forces the ball to rise up the riser 44 around the top elbow 54 into the exit barrel 28 from the ball machine . reference should be made at this time to fig1 , a single line circuit diagram for electrical power , control signals and compressed air . the ball trips a main propellant valve trigger 81 which throws a main propellant valve microswitch 82 . the switch 82 causes a main propellant valve 83 to permit the release of a sufficient blast of air through main propellant air line 99 prime to accelerate the ball so that it goes to the pre - selected point on the court . as the ball exits the barrel 28 , it may be given a preselected spin to simulate any of the shots of tennis . the elevation of the barrel 28 is controlled by a barrel elevation control 52 which is illustrated in detail in fig7 . a joint cover 56 couples the barrel 28 to the top elbow 54 . a polynoid 58 controls the barrel according to instructions received from the user of the machine . trunion arms jointed by shoulder bolts control the barrel through its vertical travel . the polynoid 58 is a linear motor which pushes or pulls the forward part of the barrel 28 up or down . pre - determined elevations of the barrel 28 and ball velocity permit precise control over the landing point and the angle of travel of the ball . the spin control mechanism 60 is best illustrated in fig8 . two spin control solenoids 62 are capable of generating spin in both directions . the depth of penetration of the solenoids 62 into the barrel 28 and the rotational velocity of spinning both control the amount of spin put on the ball . various combinations of spin from two perpendicular axes permit simulation of all possible types of spin which a tennis player can impart , whether the tennis player is left - handed or right - handed . a wheel 70 is spun by a motor 68 coupled to a motor mount 66 and a bell crank 64 . small dc motors which have very nearly instant start up capability are utilized to provide the power for spinning the balls . fig9 illustrates a traverse joint and actuator 72 which traverses the barrel from left to right in order to determine whether the ball is to be propelled at the player or to the player &# 39 ; s backhand or forehand . the traverse joint 72 rotates the upper elbow 54 in relation to the fixed position riser 44 . power for the rotation is supplied by a barrel traverse polynoid 88 . the traverse joint and actuator comprises a pair of torque arms hooked to a very simple slip joint . a linear motor pushes or pulls and thereby causes the barrel to go to either right or left . the timing mechanism 42 is best illustrated in fig1 . the motor 48 is a single direction rotation 110 volt instrument gear head motor or the equivalent . for most purposes , the motor turns the rotor at 4 or 5 rpm at the output shaft . there are three lobes on the rotor 46 so that three balls are released at equal intervals during every rotation of the motor . at 5 rpm rotational speed , 15 balls per minute would be released from the machine . the rotor 46 acts as a cam as it turns . as each lobe comes around past the microswitch 50 , it activates the microswitch 50 to trigger the blast of air moving the ball into position for delivery by a second blast of air . as best illustrated in fig1 , an air compressor 96 keeps a compressed air reservoir tank 97 filled to standards which are set by a pressure regulator 98 . the pressure regulator 98 may be manually controlled . air from the compressed air reservoir tank 97 flows to air lines 99 from which the air is dispensed to propel the ball . a low voltage dc transformer 95 or the equivalent such as a 110 vac source provides power for the machine 24 . a control panel and scoring read - out 92 provides two functions . it permits the player to set in a request for serve , spin , velocity , interval , direction , etc . in addition , it indicates how well the player is doing with his or her returns . various cards can be inserted into the control panel 92 to cause the machine 24 to deliver a pre - selected series of shots . in the alternative , a mini computer 93 can generate random numbers or can generate shots according to a program which can be set in by card , disc , tape , or other well - known means . a ball delivery light 79 can be set to warn the player a pre - selected period of time before each shot . a riser jet distribution manifold routes air to the selected line 99 , 99 prime , from the air tank 97 . a particular example of the invention has been described herein . other examples within the scope of the present invention will be obvious to those skilled in the art . the present invention is limited only by the following claims .
an instant tennis game simulating a real game of tennis is presented . a pneumatic tennis ball delivery machine replaces the normal opponent . the court is slightly crowned and has sloping gutters so that all balls are automatically , gravity - returned to the machine . solenoid controlled , motor - spun rollers permit simulation of various types of spins . ball trajectory from the machine is controlled by barrel angle , vertical and horizontal . the ball machine control system allows for repetition of one &# 34 ; shot condition &# 34 ; endlessly or a completely random variety of shots as directed by a programmed mini - computer or manually set &# 34 ; user controls ,&# 34 ; a program , or the equivalent .