Patent Publication Number: US-6220452-B1

Title: Table tennis ball-sorting device and table tennis apparatus

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a table tennis ball-sorting device and a table tennis apparatus including the same. 
     2. Description of the Related Art 
     Hitherto, a table tennis apparatus, for example, as disclosed in Japanese Utility Model Registration No. 3017687 has been proposed. Such a conventional table tennis apparatus includes a table having a net stretched on the center thereof, a ball projecting section that is disposed on the rearward of one playing surface (a playing surface on the side of a machine) and that projects, i.e. ejects, table tennis balls sequentially towards the other surface (a playing surface on the side of a player), wherein a plurality of optical sensors, each having a light emitting element and a light receiving element, are opposingly arranged on the left and right of the playing surface on the machine side along a longitudinal direction thereof. A drop position of the ball returned by the player on the machine-side playing surface is detected by the optical sensors, and a score corresponding to the position is given to the player. The result of a training thereby being displayed by a specific numeral value. 
     According to the conventional table tennis apparatus constructed as described above, balls returned or failing to be hit by the player are collected by an air flow formed along the floor to a collecting port, and returned by a negative pressure towards the ball projecting section through a hose. This enables the player to play continuously with a fixed number of balls. The construction of the ball projecting section of the table tennis apparatus is disclosed in, for example, Japanese Patent Publication No. 58-22229 and Japanese Utility Model Publication No. 63-7264. 
     According to the above conventional table tennis apparatus, however, faulty balls that are erroneously stamped on and deformed by the player&#39;s foot have been also collected and returned to the ball projecting section, and are projected from the ball projecting section after a lapse of a fixed period of time, so that normal proceeding of a game (training) may be prevented. In addition, since the player cannot continue the game when the number of faulty balls mixed into the ball projecting section increases, the faulty balls should be periodically manually sorted, and the maintenance of the apparatus becomes complicated. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a table tennis ball-sorting device which can be played in normal conditions at all times and which can simplify the maintenance of the device, and to provide a table tennis apparatus including the table tennis ball-sorting device. 
     According to a first aspect of the present invention, there is provided a table tennis ball-sorting device including a plurality of rails that are arranged side by side in substantially a horizontal direction at intervals that are capable of having passed therethrough only deformed balls. 
     With the described arrangement, dented and deformed balls on the rails drop from a spacing between adjacent rails, and non-dented normal balls roll on the rails downstream to be collected. 
     According to a second aspect of the present invention, there is provided a table tennis apparatus in which a ball projected from a ball projecting section disposed on a first playing surface of a table towards the other playing surface is returned towards the first playing surface, the table tennis apparatus, including a table tennis ball-sorting device including a plurality of rails that are arranged side by side in substantially a horizontal direction at intervals that are capable of having passed therethrough only deformed balls, wherein the rails arranged side by side constitute first and second ball sorting sections arranged from upstream upstream side of the device, and wherein the first and second ball sorting sections cross each other, and balls can be transferred from the downstream end of the first ball sorting section to an upstream part of the second ball sorting section. 
     With the described arrangements, dented and deformed balls on the rails of the table tennis ball-sorting device drop from the spacing between adjacent rails, and non-dented normal balls roll on the rails downstream to be collected, and are returned towards the ball projecting section. Consequently, since the dented balls that have been stamped on by the player&#39;s foot are not returned to the ball projecting section, it is possible to play under a normal condition at all times. In addition, since it is not necessary to manually sort the dented faulty balls, the maintenance of the apparatus is simplified. 
     The table tennis apparatus of the present invention may preferably include a ball returning unit for returning balls that have reached the downstream of the table tennis ball-sorting device towards the ball projecting section. 
     With the described arrangement, balls are automatically returned towards the ball projecting section. Consequently, normal balls are always projected from the ball projecting section, and normal play can be continuously performed. 
     The table tennis apparatus of the present invention preferably further includes a floor ball collecting section for collecting balls that have dropped on the front floor of the other playing surface towards the table; and a ball transfer unit for transferring the balls collected by the floor ball collecting section towards the upstream end of the table tennis-ball sorting device. 
     With the described arrangements, balls that have dropped by failing to be hit and the like on the front floor of the playing surface on the side of the player are collected towards the table by the floor ball collecting section and transferred towards the upstream end of the table tennis ball-sorting device by the ball transfer unit so as to be sorted. 
     In the table tennis apparatus of the present invention, a deformed ball carrying member consisting of a long receiver plate may preferably be arranged below the table tennis-ball sorting device. 
     With the described arrangement, dented balls that have dropped from the spacing of the rails are received by the deformed ball carrying member and carried downstream. 
     In the table tennis apparatus of the present invention, a ball collecting box may preferably be disposed at a lowermost position of the deformed ball carrying member. 
     With the described arrangement, the deformed balls are collected in the deformed ball collecting box, and it is possible to perform after-treatment, such as disposal. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an external perspective view which schematically illustrates a construction of a table tennis apparatus to which a table tennis ball-sorting device according to the present invention is applied; 
     FIG. 2 illustrates a construction of one playing surface of a table in the table tennis apparatus shown in FIG. 1; 
     FIG. 3 is a vertical sectional view showing a construction of a ball projecting section in the table tennis apparatus shown in FIG. 1; 
     FIG. 4 is a transverse sectional view showing a construction of the ball projecting section in the table tennis apparatus shown in FIG. 1; 
     FIG. 5 is a rear elevation showing a construction of a moving mechanism for the ball projecting section in the table tennis apparatus shown in FIG. 1; 
     FIG. 6 is a plan view showing a construction of a ball collecting section in the table tennis apparatus shown in FIG. 1; 
     FIG. 7 is a sectional view taken along line VII—VII of FIG. 6; 
     FIG. 8 is a sectional view taken along line VIII—VIII of FIG. 6; 
     FIG. 9 is a sectional view taken along line IX—IX of FIG. 6; 
     FIG. 10 is a plan view showing a construction of a ball scooping-up unit of the ball collecting section shown in FIG. 6; 
     FIG. 11 is a sectional view taken along line XI—XI of FIG. 10; 
     FIG. 12 illustrates a control block of the table tennis apparatus according to the present invention; 
     FIG. 13 is a flow chart of and initialization of the table tennis apparatus according to the present invention; 
     FIG. 14 is a flow chart of a game operation of the table tennis apparatus according to the present invention; 
     FIG. 15 is a flow chart of an operation of the ball scooping-up unit of the ball collecting section; 
     FIG. 16 is a flow chart of operation of a ball stirring unit of a ball supply section in the table tennis apparatus according to the present invention; 
     FIG. 17 is a flow chart of a light-up operation of a cold-cathode tube of a table in the table tennis apparatus according to the present invention; 
     FIG. 18 is a flow chart of a ball projecting operation of the ball projecting section; 
     FIG. 19 is a flow chart a detection operation of ball drop position and a score handling operation in the table tennis apparatus according to the present invention; 
     FIG. 20 is a flow chart of game-over handling; and 
     FIG. 21 is a schematic diagram of a ball scoring operation in the table tennis apparatus according to the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, a table tennis apparatus includes a table  10 , a ball projecting, i.e. ejecting section  20  for projecting balls towards a player&#39;s playing surface, a ball collecting section  30  for collecting balls dropped on a floor or the like, a display section  40  for displaying scores and a demonstration picture, a sound section  50  for outputting presentation music and sound effects, a box  60  for surrounding the table  10 , a control box  70  for setting various types of game (training) modes and the like, a control section  80  (FIG. 12) for controlling the overall operations of the apparatus, and a moving mechanism  90  for moving the ball projecting section  20  laterally. In this embodiment, the direction between both end lines of the table  10  is referred to as a longitudinal direction, while the direction between both side lines of the table  10  is referred to as a lateral direction from the point of view of the player. However, it is not necessary to actually provide the end lines and sidelines on the table  10  of the table tennis apparatus according to the present invention. 
     The table  10  includes a player&#39;s playing surface  12 , a playing surface  14  on a side of which the ball projecting section  20  is disposed, and a net  16  that is disposed between the playing surfaces  12  and  14  and stretched to have a predetermined height. As shown in detail in FIG. 2, the playing surface  14  includes a frame structure  141  and a plate body  142  formed by, for example, white semi-transparent resin for covering the top of the frame structure  141 . 
     The frame structure  141  is separated into a plurality of areas by lateral partition walls  148  and  149 , and a longitudinal partition wall  150 . That is, the frame structure  141  divides the playing surface  14  into almost three equal parts in the longitudinal direction to form a front area (a first area  143 ), a center area and a rear area. The center area is divided into two equal parts in the lateral direction to form a right-side second area  144  and a left-side third area  145 , and the rear area is divided into two equal parts to form a right-side fourth area  146  and a left-side fifth area  147 . 
     A plurality of green-luminary cold-cathode tubes  181  are disposed in the second area  141 , and a plurality of blue-luminary cold-cathode tubes  182  are disposed in the third area  145 . In addition, a plurality of red-luminary cold-cathode tubes  183  are disposed in the fourth area  146 , and a plurality of yellow-luminary cold-cathode tubes are disposed in the fifth area  147 . Color bulbs lit up by the passage of electric current through filaments may be used in place of the above cold-cathode tubes  181  to  184 . In the present invention, the cold-cathode tubes and bulbs are named generically as lamps. 
     The semi-transparent plate body  142  serves as a surface illuminant for each color light emitted from each cold-cathode tube, and as a diaphragm that is vibrated by a ball drop impact. The plate body  142  consists of a first plate  151 , a second plate  152 , a third plate  153 , a fourth plate  154  and a fifth plate  155  that correspond to the areas  143 ,  144 ,  145 ,  146  and  147 , respectively. The first to fifth plates  151  to  155  form first to fifth areas E 1  to E 5 , respectively, of the playing surface  14 . The plate body  142  has lateral grooves  156  and  157 , and a longitudinal groove  158  formed in the lower surfaces of the boundaries of the plates  151  to  155 , and uses the plates  151  to  155  as surface illuminants, thereby obtaining an illumination effect. 
     The first plate  151  has a pair of microphones  190  and  191  disposed on the lower surface thereof in the vicinity of diagonal positions, the second plate  152  has a pair of microphones  192  and  193  disposed on the lower surface thereof in the vicinity of diagonal positions, and the third plate  153  has a pair of microphones  194  and  195  disposed on the lower surface thereof in the vicinity of diagonal positions. In addition, the fourth plate  154  has a pair of microphones  196  and  197  disposed on the lower surface thereof in the vicinity of diagonal positions, and the fifth plate  155  has a pair of microphones  198  and  199  disposed on the lower surface thereof in the vicinity of diagonal positions. 
     Each of the microphones  190  to  199  serves as a vibration sensor, and detects onto which of the first to fifth plates  151  to  155  a ball has dropped. For example, when the ball drops onto the second plate  152 , a vibration radially propagates from the drop point to the periphery of the plate  152  while being damped, and the vibration is detected by the microphones  192  and  193 . While the vibration is also detected by the microphones of other plates, the plate onto which the ball has dropped can be defined from the difference in detection levels, a time lag of the propagation of the vibration, and so forth. In particular, since the grooves  156  to  158  are provided in the plate body  142 , the vibration is abruptly damped at the grooves, thereby preventing a wrong detection of the vibration. A detection signal output from each of the microphones  190  to  199  is input to a control section  30  and used for score handling or the like. 
     The grooves  156  to  158  are not necessary to detect the drop position of the ball, and the plate body  142  may have the plates  151  to  155  formed by individual members. When the plates  151  to  155  are formed by individual members, a member, such as one formed of rubber, for preventing the propagation of the vibration may preferably be provided in a gap formed between each of the adjacent members, and a member, such as one formed of rubber, for preventing the propagation of the vibration may preferably be disposed on a boundary of each of the plates so that each of the plates are provided on the member with a small gap formed therebetween. In addition, the plate body  142  and the microphones  190  to  199  constitutes a detection unit for detecting a drop position of the ball returned back from the player. In this embodiment, one or a plurality of areas E 2  to E 5  of the playing surface  14  is illuminated to recommend to the player that the ball be returned the illuminating areas so that the player can obtain a score higher than that obtained by the returning it to the non-illuminating areas when the return of the ball on the illuminating area is detected by the microphones. It should be appreciated that a score may be given to the player when returning the ball only to the illuminating areas. 
     The ball projecting section  20  is disposed at a rear of the playing surface  14  with almost an entirety thereof accommodated in a casing  200 . 
     Referring to FIGS. 3 and 4, the ball projecting section  20  includes a ball projecting cylinder  21  for projecting table tennis balls from one end thereof, a ball feeding cylinder  22  for feeding the balls to the ball projecting cylinder  21 , a ball supply section  23  for supplying the balls to the ball feeding cylinder, a ball dispensing unit  24  for dispensing balls one at a time from the ball feeding cylinder  22 , an urging force-imparting unit  25  for imparting an urging force in the direction of projection to the ball dispensed to the ball projecting cylinder  21 , a rotary unit  26  for rotating the ball projecting cylinder  21  around the axis thereof to change the type of projection of ball (such as curved ball, straight ball, etc.) an oscillating mechanism  27  for swinging the ball projecting cylinder  21  in the lateral direction of the table  10  to change the projecting direction of the ball, and an angle changing unit  28  for changing an angle of the ball in a direction of elevation. 
     The ball projecting cylinder  21  is disposed so as to be directed slightly diagonally upward with a projecting port  211  projected to the outside from an oblong window  201 , and projects the ball urged by the urging force-imparting unit  25  from the projecting port  211  towards the playing surface  12 . In addition, cutouts  212  and  213  into which a pair of rollers  251  and  252 , which are described later, partially enter are formed at opposite positions of an intermediate portion of the ball projecting cylinder  21 . 
     The ball feeding cylinder  22  is provided in the casing  200 , and has an L-shape consisting of a horizontal part  221  and a vertical part  222 , and the horizontal part  221  is fitted to the rear end outer periphery of the ball projecting cylinder  21  through a ball bearing  223 . This allows the ball projecting cylinder  21  to be rotated around the axis thereof. In addition, an opening  224  is formed at the rear of the lower end of the vertical part  222  into which a plate cam  241 , which is described later, of the ball dispensing unit  24  partially enters. 
     The ball supply section  23  is disposed above the ball projecting section  20 , which can be moved laterally by a moving mechanism  90  to be described later, and is fixed on the upper part in the casing  200 . The ball supply section  23  includes a ball hopper  231  for containing a plurality of balls, and a flexible tube  233  that is connected to a supply port  232  formed on the bottom of the hopper  231  and the vertical part of the ball feeding cylinder  22 . The hopper  231  includes a ball stirring unit  236  consisting of an external-mounted hopper-inside stirring motor  234 , and a stirring bar  235  having, for example, elasticity disposed inside thereof. The stirring bar  235  is rotationally driven by the motor  234 , whereby a jam of the ball BL at the supply port  232  is prevented. 
     The ball dispensing unit  24  consists of a plate cam  241 , and a plate cam motor  242  for rotationally driving the plate cam  241 . The plate cam  241  is integrally fixed to a perpendicular rotary shaft  242   a  of the plate cam motor  242  at the rear position of the ball feeding cylinder  22 . The plate cam  241  consists of a small diameter part M and a cam part N of which the diameter gradually increases in the direction of rotation. The small diameter part M has a diameter so as not to enter into the ball feeding cylinder  22 , and one side of the cam part N adjacent to the small diameter part M has a small diameter size and the other side has a large diameter size of at least one table tennis ball. The direction of the plate cam  241  is reversed in FIGS. 3 and 4 for reasons of explanation. 
     The plate cam motor  242  is fixed upward to a motor mounting plate  222   b  fitted on the bottom of the vertical part  222 . The plate cam motor  242  is rotated to rotate the plate cam  241  once in the direction shown by the arrow in FIG. 4, whereby the balls fed to the lower end of the vertical part  222  are dispensed one at a time towards the horizontal part  221 . That is, when the small diameter part M of the plate cam  241  starts to rotate at the position (initial position) opposite to the ball feeding cylinder  22 , the ball fed to the lower end of the vertical part  222  is abutted against the cam part N and dispensed to the horizontal part  221 . 
     A shielding plate  241   b  in an upright position is fixed on the plate cam  241  at a position apart from the rotary shaft  242   a.  On the other hand, a plate cam sensor  243  consisting of a photo-interrupter is fixed to a sensor mounting plate  222   c  provided above the plate cam  241 . In the plate cam sensor  243 , the positions of a light emitting element and a light receiving element are set so that the shielding plate  241   b  can pass through a gap formed therebetween. This allows the initial position of the plate cam  241  to be detected when the shielding plate  241   b  interrupts between the light emitting element and the light receiving element of the plate cam sensor  243 , so that the number of rotation of the plate cam  241  is counted each time the initial position is detected. 
     The urging force-imparting unit  25  includes a pair of rollers  251  and  252  disposed so that they are opposite to each other, and a pair of roller motors (DC motors)  253  and  254  for individually rotationally driving the rollers  251  and  252 . The rollers  251  and  252  are constructed by arranging rubber members  251   b  and  252   b  on the outer periphery of metallic members  251   a  and  251   a , and partially enter into the cutouts  212  and  213 . The roller motors  253  and  254  are fixed to motor mounting plates  214  and  215 , respectively. By the described arrangement, the rollers  251  and  252  are rotated in the directions shown by the arrows with sandwiching of the ball BL from both sides when the ball projecting cylinder  21  rotates around the axis thereof together with the roller motors  253  and  254 , thereby imparting an urging force in the projecting direction (forward direction) to the ball BL. The rollers  251  and  252  can impart a projecting speed to the ball corresponding to the peripheral speed thereof, and can apply a spin on the ball projected from the ball projecting cylinder  21  because of the impartment of a difference in the peripheral speed. 
     In other words, a top spin (drive) can be applied on the ball when the peripheral speed of the roller  251  is increased to relatively faster than the peripheral speed of the roller  252 . Conversely, a back spin can be applied on the ball when the peripheral speed of the roller  252  is increased to relatively faster than the peripheral speed of the roller  251 . In addition, when the peripheral speeds of the rollers  251  and  252  are substantially equalized, almost no rotating force is applied to the ball, and a so-called knuckle ball can be obtained. Furthermore, if a difference in peripheral speed is imparted to the rollers  251  and  252  in a state where the ball projecting cylinder  21  is rotated around the axis thereof, and the rollers  251  and  252  are tilted, it is possible to obtain a ball on which a side spin is applied. 
     The rotary unit  26  includes a follower gear  261  attached to the rear end outer periphery of the ball projecting cylinder  21 , a drive gear  262  meshed with the follower gear  261 , and a projecting cylinder motor  263  for rotationally driving the drive gear  262 . The motor  263  is fixed to a motor mounting plate  221   a  attached to the horizontal part  221  of the ball feeding cylinder  22 . The motor  263  rotates in both normal and reverse directions, whereby the ball projecting cylinder  21  is rotated around the axis thereof. 
     A radially extending shielding plate  262   a  is fixed to the side surface of the drive gear  262 . On the other hand, a sensor mounting plate  221   b  is attached to the motor mounting plate  221   a , and a rotation sensor  264  consisting of a photo-interrupter is fixed to the sensor mounting plate  221   b . In the rotation sensor  264 , the positions of a light emitting element and a light receiving element are set so that the shielding plate  262   a  can pass through a gap formed therebetween. This allows the initial position of the ball projecting cylinder  21  around the axis thereof to be detected when the shielding plate  262   a  interrupts between the light emitting element and the light receiving element of the rotation sensor  264 . A state where the rollers  251  and  252  are vertically positioned is regarded as the initial position of the ball projecting cylinder  21 . In this embodiment, the ball projecting cylinder  21  rotates both rightward and leftward based on the initial position within a range of 45°. 
     The oscillating mechanism  27  includes a cylindrical strut  271  fixed to a base  91  (see FIG.  5 ), a rotary shaft  273  which is fixed to the bottom of the horizontal part  221 , and is mounted in the strut  271  through a ball bearing  272 , a follower gear  274  fixed to the upper portion of the rotary shaft  273 , a drive gear  275  meshed with the follower gear  274 , and a projecting section oscillating motor  276  for rotationally driving the drive gear  275 . The motor  276  is fixed to a motor mounting plate  221   c  attached to the vertical part  222  of the ball feeding cylinder  22 . The motor  276  rotates in both normal and reverse directions, whereby the ball projecting section  20  is laterally rotated around the rotary shaft  273  to effect oscillating. By the described arrangement, a straight ball can be projected when the ball projecting section  20  is located laterally, and the ball can be projected aiming at both corners of the table  10  when the ball projecting section  20  is located in a slanting position. That is, the balls can be projected in a crosswise direction in addition to a straight direction by the oscillating mechanism  27 . 
     A shielding plate  273   a  of which one end is directed upward is attached to the lower end of the rotary shaft  273 . A sensor mounting plate  271   a  is attached to the front outer periphery of the lower end of the strut  271 , and a rotation sensor  277  consisting of a photo-interrupter is fixed to the sensor mounting plate  271   a . In the rotation sensor  277 , the positions of a light emitting element and a light receiving element are set so that the shielding plate  273   a  can pass through a gap formed therebetween. This allows the initial position of the ball projecting section  20  in the direction of rotation around the rotary shaft  273  to be detected when the shielding plate  273   a  interrupts between the light emitting element and the light receiving element of the rotation sensor  277 . A direction straight along the longitudinal direction of the table  10  is regarded as the initial position of the ball projecting section  20 . 
     A sensor mounting plate  271   b  is attached to the rear outer periphery of the lower end of the strut  271 , and an oscillating angle sensor  278  consisting of a variable resistor is attached to the sensor mounting plate  271   b . A rotary shaft element  277   a  of the oscillating angle sensor  278  is coaxially fixed to the rotary shaft  273  of the oscillating mechanism  27 . By the above arrangement, the oscillating angle of the ball projecting section  20  is detected by a voltage value output from the sensor  278  according to the amount of rotation of the rotary shaft  273 , so that the oscillating angle of the ball projecting section  20  is controlled based on the initial position thereof. 
     The angle changing unit  28  includes a guide plate  281  rotatably and forward-projectingly attached to the periphery of the projecting port  211 , and a guide plate motor  282  for rotating the guide plate  281  in a direction to interrupt the course of the ball projected from the projecting port  211  (i.e., a direction to cross the projecting direction). Both base ends of the guide plate  281  are journaled at opposite positions of the outer periphery of the proximal end of the projecting port  211  when the ball projecting cylinder  21  is in the initial position around the axis thereof. That is, one base end is journaled by a projection  211   a , and the other base end is journaled by a rotary shaft  282   a  of the guide plate motor  282  fixed to the motor mounting plate  211   b  which is fitted to a suitable position of the outer periphery of the projecting port  211 . 
     By the described arrangement, when the ball projecting cylinder  21  is in the initial position around the axis thereof, the guide plate motor  282  is rotated by a predetermined amount to rotate the guide plate  281 , whereby the projecting direction of the ball can be changed to be directed diagonally upward (i.e., the projection angle of the ball can be changed). That is, the ball at the projecting port  211  abuts against the guide plate  281  to be directed upward, so that it is possible to project the ball in a path describing a parabola. The shape of the parabola can be controlled by the amount of rotation (elevation angle) of the guide plate  281  and the ball-projecting speed. An angle control plate  283  is disposed on the opposite side of the guide plate  281  along the axial direction of the ball projecting cylinder  21 . By the described arrangement, when the projecting angle of a fast ball is greatly changed by the guide plate  281 , the ball comes into contact with the angle control plate so that the shape of the parabola can be controlled and it becomes difficult for the ball to go over the playing surface  12 . 
     A shielding plate  281   a  is attached on the base end of the guide plate  281  so as to extend rearward. On the other hand, a sensor mounting plate  211   c  is attached in the vicinity of the projecting port  211 , and a guide plate sensor  284  consisting of a photo-interrupter is fixed to the sensor mounting plate  211   c.  In the guide plate sensor  284 , the positions of a light emitting element and a light receiving element are set so that the shielding plate  281   a  can pass through a gap formed therebetween. This allows the initial position of the guide plate  281  to be detected when the shielding plate  281   a  interrupts between the light emitting element and the light receiving element of the guide plate sensor  284 . A direction along the axial direction of the ball projecting cylinder  21  is regarded as the initial position of the guide plate  281 . 
     A projecting angle sensor  285  consisting of a variable resistor is attached to the sensor mounting plate  211   c,  and a rotary shaft element  285   a  of the sensor  285  is fixed to a projection  281   b  of the guide plate  281  that is coaxially fixed to a projection  211   a . By the above arrangement, the amount of rotation of the guide plate  281  is detected by a voltage value output from the sensor  285 , so that the ball projecting angle is controlled based on the initial position thereof. 
     A description will now be given of the moving mechanism  90 . As shown in FIG. 5, the moving mechanism  90  includes a pair of guide members  92   a  and  92   b  fixed to the bottom of the base  91 , a guide rail  93  which is mounted on a table  202  fixed within the casing  200  (see FIG. 1) and which is disposed along the lateral direction in which the guide members  92   a  and  92   b  are slid, a pair of pulleys  94   a  and  94   b  disposed outside both the left and right ends of the guide rail  93 , a timing belt  95  which is looped over the pulleys  94   a  and  94   b  and to which the guide members  92   a  and  92   b  are attached, and a drive unit  96  for driving the pulley  94   a.  The drive unit  96  consists of a projecting section moving motor (AC servo motor)  96   a,  a pulley  96   c  fitted to a rotary shaft  96   b  of the motor  96   a,  and a timing belt  96   d  looped over the pulleys  96   c  and  94   a.    
     A shielding plate  91   a  is attached in the rear center of the base  91  so as to extend downward. On the other hand, a center base sensor  97  consisting of a photo-interrupter is fixed to a sensor mounting plate  93   a,  which projects rearward from the center of the guide rail  93 . In the center base sensor  97 , the positions of a light emitting element and a light receiving element are set so that the shielding plate  93   a  can pass through a gap formed therebetween. This allows the initial position of the base  91 , i.e., the initial position of the ball projecting section  20  in the lateral direction, to be detected when the shielding plate  91   a  interrupts between the light emitting element and the light receiving element of the sensor  97 . The center position of the table  202  in the lateral direction is regarded as the initial position of the ball projecting section  20 , and the lateral movement of the ball projecting section  20  is controlled based on the initial position. 
     A left base sensor  98  and a right base sensor  99  are fixed to sensor mounting plates  93   b  and  93   c,  respectively. The left base sensor  98  projects rearward from a left-of-center portion of the guide rail  93 , and the right base sensor  99  projects rearward from a right-of-center portion of the guide rail  93  (from the point of view of the player). Each of the left and right base sensors  98  and  99  consists of a photo-interrupter in which the positions of a light emitting element and a light receiving element are set so that the shielding plate  91   a  can pass through a gap formed therebetween. This allows a lateral movement range of the base  91 , i.e., a lateral movement limit position of the ball projecting section  20 , to be detected when the shielding plate  91   a  interrupts between the light emitting element and the light receiving element of the left base sensor  98  or the right base sensor  99 , so that the ball projecting section  20  does not overrun the limit position. 
     The ball collecting section  30  collects balls that have failed to be hit by the player, thus dropping on the floor, balls that have dropped on the floor from both side edges of the table  10  (so-called the sides of the side lines), and balls that have dropped from the rearward edge (so-called the side of the end line) towards the ball by an acceptable limit amount projecting section  20 , and sorts faulty balls that have been erroneously stamped on and deformed by the player&#39;s foot into a faulty ball collecting box  334 . The structure of the ball collecting section  30  is shown in FIGS. 6 to  9 . 
     Referring to these drawings, the ball collecting section  30  includes a floor collecting part  31 , left collecting part  32  disposed along the left side line of the table  10 , a rear collecting part  33  disposed along the end line of the table  10 , a right collecting part  34  disposed along the right side line of the table  10 , a longitudinal collecting part  35  longitudinally disposed in the casing  200 , a lateral collecting part  36  provided continuously at the end of the longitudinal collecting part  35  in the casing  200 , a ball scooping-up unit  37  for scooping up and transferring the balls collected by the floor collecting part  31  to the left collecting part  32 , and a ball by an acceptable limit amount scooping-up unit  38  for scooping up and transferring the balls transferred to the lateral collecting part  36  into a hopper  231 . 
     The floor collecting part  31  is formed to include the area where the player plays. The floor collecting part  31  includes a first floor part  311  disposed to be inclined downwardly towards the table  10  to an extent in which the part  311  does not affect play, a second floor part  312  provided continuously on the side of the table  10  of the first floor part  311 , and a ball gathering part  313  formed in the center of the second floor part  312 . The second floor part  312  is divided into a left floor part  312   a  and a right floor part  312   b  on either side of the ball gathering part  313 , and both floor parts  312   a  and  312   b  are disposed to be inclined downwardly towards the ball gathering part  313 . In addition, the ball gathering part  313  is disposed to be inclined downwardly towards the playing surface  14 . 
     By the described arrangement, balls drop on the first floor part  311  roll on the first and second floor parts  311  and  312 , and are collected in the ball gathering part  313 . In addition, the balls collected in the ball gathering part  313  are moved upward within a cylinder to be described later by the ball scooping-up unit  37 , and are transferred to the left collecting part  32 . In addition to normal spherical balls, partially dented faulty balls that have rolled into the ball gathering part  313  are transferred by the ball scooping-up unit  37  to the left collecting part  32 . 
     The left collecting part  32  includes a plurality of (five, in the drawings) rails  321  which are disposed side by side in substantially a horizontal direction with the height lower than that of the table  10 , and which are inclined downwardly towards the rear collecting part  33 , and a receiver plate  322  having substantially a C-shape in vertical cross section that is disposed below the rails  321  to be inclined downwardly towards the rear collecting part  33 . The rails  321  are disposed at intervals of slightly smaller than the diameter of the ball. Therefore, normal balls can be rolled between adjacent rails  321 , while partially dented faulty balls drop from the spacing between adjacent rails  321  onto the receiver plate  322  and are sorted. 
     By the described arrangement, normal balls roll on the adjacent rails  321  and are transferred towards the rear collecting part  33 , and dented faulty balls collected by the floor collecting part  31  drop from the spacing between the adjacent rails  321  onto the receiver plate  322 , roll on the receiver plate  322  (or the balls that do not roll are struck by subsequent dropped balls), and are transferred to a receiver plate  332  to be described below. The rails  321  and the receiver plate  322  are arranged so that the ends thereof intersect the rails  331  of the rear collecting part  33  and the receiver plate  332  in order to enable the balls to be transferred. 
     The rear collecting part  33  includes a plurality of (five, in the drawings) rails  331  which are disposed side by side in substantially a horizontal direction with the height lower than that of the table  10 , and which are inclined downwardly towards the right side of the playing surface  14 , and a receiver plate  332  which is disposed below the rails  331  inclined downwardly towards the right side thereof, a normal ball relay box  333  disposed below the right edges of the rails  331 , and a faulty ball collecting box  334  disposed below the right edge of the receiver plate  332 . 
     The rails  331 , similarly to the rails  321 , are disposed at intervals of slightly smaller than the diameter of the ball. Therefore, normal balls can be rolled between adjacent rails  331 , while partially dented faulty balls drop from the spacing between adjacent rails  331  onto the receiver plate  332 , and are sorted. The normal relay box  333  opens to the casing  200 , and is disposed to be inclined downwardly towards the casing  200 . 
     Since the dented faulty balls have been collected in the floor collecting part  31 , most of them drop from the spacing between the adjacent rails  321  of the left collecting part  32  onto the receiver plate  322 . However, since the balls on the rails  321  roll on the rails  321  using the same portions thereof as rolling axes, when the portions of the balls crossing the rolling shafts are dented, the balls do not drop from the spacing between the adjacent rails  321 . Thus, with respect to the faulty balls which have not dropped from the spacing between the adjacent rails  321 , the rear collecting part  33  is provided perpendicular to the left collecting part  32 , whereby the rolling axes are changed to be perpendicular to the rails  321  and the dented portions are opposed between the rails  321 , so that the faulty balls are dropped from the spacing between the rails  321 . 
     This allows the normal balls to be delivered to the normal ball relay box  333  via the rails  321  and  331 , and allows dented faulty balls to be dropped from the rails  321  or  331  onto the receiver plate  322  or  332 , and delivered to the faulty balls collecting box  334 . 
     The right collecting part  34  includes a plate  341  which has a height lower than that of the table  10  and which is disposed inclined downwardly towards the rear collecting part  33  and the table  10 . The rear edge part of the plate  341  projects on the normal ball relay box  333 . Since the normal balls returned by the player may probably be collected by the right collecting part  34 , the balls roll on the plate  341  and are delivered to the normal ball relay box  333  for a while. 
     The longitudinal collecting part  35  includes a plurality of (four, in the drawing) rails  351  disposed in substantially a horizontal direction to be inclined downwardly to the rear thereof, and a receiver plate  352  disposed below the rails  351  to be inclined downwardly to the front. The intervals of the rails  351  are set similarly to those of the rails  321  and  331 . The normal balls roll rearward on the rails  351 , while the dented faulty balls drop from the spacing between adjacent rails  35  onto the receiver plate  352 . 
     The front end of the receiver plate  352  is located above the faulty ball collecting box  334 . Since almost all of the dented faulty balls have been collected via the floor collecting part  31 , they should be collected in the faulty ball collecting box  334  when they pass through the rear collecting part  33 . However, because of influence of direction of the dented portions of the faulty balls on the rails  331 , the balls which have not dropped from the spacing between the adjacent rails  331  of the rear collecting part  33  will drop from the spacing between adjacent rails  351  by the change of the direction of the dented portions. 
     This allows the normal balls to roll on the adjacent rails  351  and are transferred toward the lateral collecting part  36 , and allows the dented balls to be dropped from the spacing between adjacent rails  351  and are collected in the faulty ball collecting box  334 . The rails  351  and the receiver plate  352  are arranged so that the ends thereof intersect the rails  361  and a receiver plate  362  of a lateral collecting part  36  in order to enable the balls to be transferred. 
     The lateral collecting part  36  includes a plurality of (four, in the drawing) rails  361  disposed in substantially a horizontal direction inclined downwardly to the left thereof, and a receiver plate  362  disposed below the rails  361  inclined downwardly to the right thereof. The intervals of the rails  361  are set similarly to those of the rails  351 , and the normal balls roll on the rails  361  to the left, while the dented faulty balls drop from the spacing between adjacent rails  361  onto the receiver plate  362 . This is similarly applied to a case where the balls are collected from the right collecting part  34  to be guided to the longitudinal collecting part  35  and to the lateral collecting part  36 . Since the collected balls from the right collecting part  34  have not passed through the left collecting part  32  and the rear collecting part  33 , the faulty balls from the right collecting part  34  are sorted in the longitudinal collecting part  35  and the lateral collecting part  36 . 
     The rails  321 ,  331 ,  351  and  361  constitute ball sorting sections, and the receiver plates  322 ,  332 ,  352  and  362  constitute deformed ball carrying sections. In addition, the rails  321  and  351  constitute a first ball sorting section, and the rails  331  and  361  constitutes a second ball sorting section. 
     Referring to FIGS. 10 and 11, the ball scooping-up unit  37  includes a flat first guide plate  372  fixed over a base plate  371  and provided continuously with the rear edge of the ball gathering section  313 , a curved second guide plate  373  provided continuously with the first guide plate  372 , a vertical transporting cylinder  374  provided vertically above the rear edge of the second guide plate  373 , a horizontal transporting cylinder  376  which is connected to the upper portion of the vertical transporting cylinder  374  by means of a connecting cylinder  375  and which is horizontally disposed, a ball stirring unit  377  for preventing a ball jam on the rear end of the first guide plate  372 , and a feeding unit  378  for feeding the balls fed to the second guide plate  373  to the vertical transporting cylinder  374 . 
     The first guide plate  372  is disposed to be inclined downwardly towards the second guide plate  373 , and has an oblong cutout  372   a  formed at the position opposite a shaft  377   e  to be described later for facilitating the passage of the balls below the shaft  377   e.  In addition, the first guide plate  372  has upright parts  372   c  and  372   d  formed at both sides of rear end thereof to form a narrow ball outlet  372   b  for passing therethrough balls one at a time. 
     The second guide plate  373  guides the balls rolled from the first guide plate  372  to the vertical transporting cylinder  374 . A cushion member  373   a,  such as a sponge, is attached to the top surface of the second guide plate  373  by bonding or the like. 
     The ball stirring unit  377  includes a shaft  377   e  which is rotatably supported by bearings  377   a  and  377   b  disposed at both sides thereof, and to which a plurality of flexible stirring rods  377   c  and  377   d  are attached alternatively in opposite phase positions at intervals of substantially one ball, and a drive unit  377   f  for rotationally driving the shaft  377   e.  The drive unit  377   f  consists of a gear  377   g  attached to one end of the shaft  377   e,  a gear  378   e  attached to one end of a shaft  378   c  to be described below, and a chain  377   h  looped over the gears  377   g  and  378   e , and is driven by a driving force of a stirring/feeding motor  379  to be described below. By the described arrangements, the shaft  377   e  is rotationally driven in the direction shown by the arrow in FIG. 11, and a plurality of balls that get trapped near the outlet  372   b  of the first guide plate  372  are stirred by the stirring rods  377   c  and  377   d  so as not to cause a ball jam near the outlet  372   b.    
     The feeding unit  378  includes a shaft  378   c  which is rotatably supported by the bearings  378   a  and  378   b  disposed on both sides thereof and which is disposed above the second guide plate  373  and in front of (left side in FIG. 11) the vertical transporting cylinder  374 , a feeding roller  378   d  mounted at the position opposite the vertical transporting cylinder  374 , and a stirring/feeding motor  379  for rotationally driving the shaft  378   c.  The motor  379  is fixed to a motor mounting plate  379   a.  The feeding roller  378   d  is formed of an elastic member, such as a sponge or rubber, and the diameter thereof is set to a size such that the distance between the roller  378   d  and the cushion member  373   a  bonded to the curved surface of the second guide plate  373  is slightly shorter than the diameter of the ball. 
     By the described arrangements, when the shaft  378   c  is rotationally driven in the direction shown by the arrow in FIG. 11 to rotate the roller  378   d,  a ball is fed to the vertical transporting cylinder  374  in a state of being elastically sandwiched between the feeding roller  378   d  and the cushion member  373   a . The ball fed into the vertical transporting cylinder  374  is pushed upward by the sequentially fed balls, and is delivered to the horizontal transferring cylinder  376 . The ball delivered to the horizontal transporting cylinder  376  is transferred to the left collecting part  32 . 
     A sensor mounting plate  370   a  is attached to the motor mounting plate  379   a,  and a first motor rotation sensor  370  consisting of a photo-interrupter having a light emitting element and a light receiving element is fixed to the sensor mounting plate  370   a.  A shielding plate  379   c  fitted to a rotary shaft  379   b  of the motor  379  passes through a gap formed between the light emitting element and the light receiving element of the sensor  370 , whereby the number of rotations of the motor  379  is counted. 
     Since the ball scooping-up unit  38  is of identical structure to the ball scooping-up unit  37 , a description thereof will be omitted. 
     The display section  40  is disposed on the front surface of the casing  200 , and includes a point display section  41  consisting of a 7-segment indicator, and an image display section  42  consisting of a dot-matrix indicator. The point display section  41  displays the number of remaining balls with respect to a predetermined number of balls, and displays each time a point obtained by the player by returning the ball from the ball projecting section  20  to the playing surface  14  is added. The image display section  42  displays a demonstration picture before starting the play, a presentation picture during the play, a demonstration picture when the play is over, a high score and the like. 
     The sound section  50  consists of amplifiers, speakers and so forth, and outputs a presentation music and sound effects during display of the demonstration picture and during the play, a ball projection sound each time the ball is projected from the ball projecting section  20 , and a sound effect when the ball returned by the player drops within the playing surface  14 . 
     The box  60  consists of a net or the like, and prevents the ball projected from the ball projecting section  20  and the ball returned by the player from flying far away. A door  61  for the player is provided on the right of the box  60 . 
     The control box  70  is mounted on the right of the playing surface  12  of the table  10 , and is placed across the inside and the outside of the box  60 . Inside the box  60 , there are provided a coin entrance CE in which a prescribed coin is inserted before starting play, a start button SW 1 , a game mode select button SS (a first course button SS 1 , a middle course button SS 2 , and an advanced course button SS 3 ) for use in selecting one of three types of game (training) modes of different degree of difficulty, and a coach mode select button CS for enabling the game to be played by two players. 
     Outside the box  60 , there are provided a start button SW 2 , and an area select button PS for use in selecting a drop area (drop position) of the ball in the playing surface  12  projected from the ball projecting section  20 . The area select button PS is used for dividing the playing surface  12  into two areas in the longitudinal direction, and for selecting one of the total six areas divided in the lateral direction. The button PS consists of six buttons PS 1 , PS 2 , PS 3 , PS 4 , PS 5  and PS 6  for individually selecting the areas. When one of the buttons is pushed, a spin-applied ball, for example, projected from the ball projecting section  20  drops on the selected area. 
     In the described arrangements, when the player plays alone, a coin is inserted in the coin entrance CE, a predetermined game mode is selected by the game mode selection button SS and then, the start button SW 1  is pushed, whereby the game is started. When the player plays the game with a competitor to imitate a coach, a coin is inserted in the coil entrance CE, the coach mode select button is pushed and then, the start button SW 2  is pushed by the competitor standing outside the box  60 , whereby the game is started. The competitor pushes a predetermined button to suitably select the drop area of the ball in accordance with the player&#39;s skill, before the ball is projected from the ball projecting section  20 , and then advances the play. Even if the coach mode select button CS is pushed, the ball is projected under a preset condition unless the area select button PS is pushed. 
     A type of projection of ball select button, a ball speed select button, a ball projecting position select button, a ball projecting angle select button, a ball projecting direction select button and the like may be provided so that, by pushing these select buttons when the coach mode is selected, the type of projection of ball, speed, projecting position and the like can be suitably selected each time the ball is projected. 
     Referring to FIG. 12, the control section  80  consists of a CPU for performing predetermined calculation and control processing, a ROM  82  in which a predetermined processing program is stored, and a RAM  83  for temporarily storing data. The entire operation of the table tennis apparatus is controlled in accordance with the above predetermined processing program. 
     The CPU  81  includes the following functional units: a game setting unit  811  for setting game contents in accordance with any one of the game modes selected from the three game modes of the first, medium, and advanced courses, a cold-cathode tube lighting unit  811  for selectively lighting the cold-cathode tubes  181  to  184  in accordance with a lighting command, a first discriminating unit  812  for discriminating whether or not a ball dropped onto the playing surface  14 , a second discriminating unit  813  for discriminating whether or not the ball dropped onto the cold-cathode tube lighting area, a cold-cathode tube winking unit  815  for selectively winking the cold-cathode tubes in accordance with a winking command, a score adding unit  816  for adding the present score to the score that is obtained immediately before the present score in accordance with the results of discrimination of the first and second discriminating units  813  and  814 , a point display section winking unit  817  for winking the point display section  41  when the score is added, a ball type setting unit for setting the type of projection of ball from the ball projecting section  20  in accordance with a setting command, a speed setting unit  819  for setting the speed of the ball projected from the ball projecting section  20 , a projecting position setting unit  820  for setting a projecting position of the ball from the ball projecting section  20 , a projecting angle setting unit  821  for setting a projecting angle of the ball from the ball projecting section  20 , a projecting direction setting unit  822  for setting a projecting direction of the ball from the ball projecting section  20 , a projecting condition setting unit  823  for setting a projecting condition of a ball so that the ball is projected towards the selected drop area in accordance with a pushing operation of the area selection button when the coach mode is selected, and a bounded ball addition disabling unit  824  for disabling a score addition with respect to the second drop of the ball bounded on the playing surface  14 . 
     A description will now be given of an example of the table tennis apparatus constructed as described above. 
     First, an initializing operation of each of the components will be described with reference to a flow chart shown in FIG.  13 . 
     When a power switch is turned on, a base plate is checked to determine whether or not the components such as the CPU and the like are functioning normally (step S 1 ), and then the components are initialized (step S 3 ). Then, the ball projecting section moving motor  296   a  is rotationally driven to move laterally the ball projecting section  20  (step S 5 ), and after a lapse of a fixed period of time, it is determined whether or not the ball projecting section  20  is located in the center of the table  10  (step S 7 ). If “yes”, the rotation of the motor  296   a  is stopped. If “no”, it is determined whether or not the ball projecting section  20  is located on the left end or the right end of the table  10  (step S 11 ). If “yes” in step S 11 , the ball projecting section  20  is moved to the center of the table  10  (step S 13 ) and thereafter, the procedure returns to step S 7 . If “no” in step S 13 , it is determined that the ball projecting section  20  is moving to the center of the table  10  and the procedure returns to step S 7  to execute subsequent operations. 
     Then, the oscillating angle of the ball projecting section  20  in the lateral direction is set (step S 15 ) and the ball projecting section  20  is laterally rotated. It is determined whether or not there is anything abnormal about the oscillating angle and the oscillating sensor  277  (step S 17 ), and a projecting angle of the projecting port  211  is set (step S 19 ) when “yes” in step S 17 . Thereafter, the guide plate  281  of the projecting port  211  is rotated by the angle corresponding to the set projecting angle, and it is determined whether or not there is anything abnormal about the guide plate sensor  283  and the projection angle sensor  285  (step S 21 ). If “yes” in step S 21 , the point display section  41 , the image display section  42  and the illumination lamp (not shown), and the like are initialized and the cold-cathode tubes  181  to  184  are subsequently initialized (step S 25 ). If “no” in step S 17  and step S 21 , error handling (for example, display of the abnormal section on the image display section  42 ) is performed (step S 27  and step S 29 ). 
     A game operation will now be described with reference to the flow chart shown in FIG.  14 . First, it is determined whether or not there is anything abnormal in the initializing operation of the components as described above (step S 31 ). If “yes”, a demonstration picture before starting the play is displayed on the image display section  42  (step S 33 ). Then, it is determined whether or not a coin has been slotted in the coin entrance CE (step S 35 ). If “yes”, game variables (the number of remaining ball, the projecting angle, and the like) are initialized (step S 37 ). 
     Then, it is determined whether or not a predetermined game course among the first course, the middle course and the advanced course is selected (step S 39 ). If “yes”, the game contents corresponding to the game course is set (step S 41 ). If “no” in step S 31 , error handling (such as the display of the abnormal section on the image display section  42 ) is performed (step S 43 ) to make it impossible to start the game. In addition, if “not” in step S 39 , the determination is repeatedly executed until the game course is selected. 
     When the game contents are set in step S 41 , the ball scooping-up units  37  and  38  of the ball collecting section  30  are actuated (step S 45 ), the ball stirring unit  236  of the ball supply section  236  is actuated (step S 47 ), and a predetermined color-luminary cold-cathode tube in the cold-cathode tubes  181  to  184  is lit up immediately before the projection of ball (step S 49 ). Then, a ball is projected from the ball projecting section  20  towards the playing surface  12  (step S 51 ), and the drop position of the ball returned by the player is detected to perform score handling (step S 53 ). Thereafter, it is determined by a count value of the plate cam sensor  243  whether or not the prescribed number of balls are projected from the ball projecting section  20  (step S 55 ). If “yes”, the procedure returns to step S 45 , and subsequent operations are repeatedly executed. 
     The operations in steps S 45 , S 47 , S 49 , S 51 , S 53  and S 57  shown in FIG. 14 will now be described in this order with reference to the flow charts of FIGS. 15 to  20 . While these operations are repeatedly executed in a predetermined cycle, for example, {fraction (1/60)} seconds, the flow charts of FIGS. 15 to  20  focus on the operations for reasons of explanation. 
     The operations of the ball scooping-up units  37  and  38  will be first described with reference to the flow chart of FIG.  15 . Since the operation of the ball scooping-up unit  37  is identical to that of the ball scooping-up unit  38 , a description will be given of the operation of the ball scooping-up unit  37 . 
     First, the stirring/feeding motor  379  is started to rotate in a normal direction (step S 71 ), and it is determined whether or not the motor has rotated once (step S 71 ). If “yes”, the number of rotations is counted up (step S 75 ), and a rotation timer is consecutively counted up (step S 77 ). 
     Thereafter, it is determined whether or not the count of the rotation timer has reached a prescribed number (step S 79 ). If “yes”, it is determined whether or not the number of rotations of the motor  379  has reached a prescribed number (step S 81 ). If “yes” in step S 81 , the error count is cleared (step S 83 ). That is, when a ball jam does not occur in the vicinity of the ball stirring section  377  and the motor  379  is normally operated, the operations of steps S 71  to S 83  are repeatedly executed during proceeding of the game. If “no” in step S 73 , the procedure advances to step S 77 . If “no” in step S 79 , the procedure returns to step S 73 , and subsequent operations are repeatedly executed until the count of the rotation timer reaches the prescribed number. 
     On the other hand, if “no” in step S 81 , i.e., the ball jam occurs in the vicinity of the ball stirring section  377  and the motor  379  is not rotated normally, the rotation of the motor  379  is stopped to clear the rotation timer (step S 85 ), and a stop timer is counted up (step S 87 ). Then, it is determined whether or not the count of the stop timer has reached a prescribed number (step S 89 ). If “yes”, the motor  379  is started to rotate in a reverse direction (step S 91 ). That is, the motor  379  is rotated in the reverse direction to eliminate the ball jam occurred in the vicinity of the ball stirring section  377 . If “no” in step S 89 , the procedure returns to step S 87 , and the determination is repeatedly executed until the count of the stop timer reaches the prescribed number. 
     When the motor  379  is rotated in the reverse direction in step S 91 , the stop timer is cleared, while the rotation timer is counted up (step S 93 ). Consecutively, it is determined whether or not the count of the rotation timer has reached a prescribed number (step S 95 ). If “yes”, the rotation of the motor  379  is stopped to clear the rotation timer (step S 97 ), and the stop timer is counted up (step S 99 ). Then, it is determined whether or not the count of the stop timer has reached the prescribed number (step S 101 ). If “yes”, an error is counted up (step S 103 ). If “no” in step S 101 , the procedure advances to step S 99  and the determination is repeatedly executed until the count of the stop timer reaches the prescribed number. 
     Consecutively, it is determined whether or not the error count reaches a prescribed number (for example, 3) (step S 105 ). If “no” the procedure returns to step S 71  and subsequent operations are repeatedly executed. That is, when the ball jam is eliminated by rotating the motor  379  in the reverse direction, steps S 71  to S 83  are repeatedly executed. When the ball jam is not eliminated by repeating the operations in steps S 85  to S 103  of prescribed times (for example, three times), the determination in step S 105  is “yes” and error handling (for example, display of the ball jam on the image display section  42 ). In this case, the balls are not projected from the ball projecting section  20  after a lapse of a fixed period of time. Thus, the proceeding of the game is stopped when the balls are not projected. 
     The operation of the ball stirring unit  236  of the ball supply section  23  shown in step  47  of FIG. 4 will now be described with reference to the flow chart shown in FIG.  16 . 
     First, the hopper-inside stirring motor  234  is stated to rotate (step S 121 ). Then, the rotation timer is counted up (step S 123 ) and thereafter, it is determined whether or not the count of the rotation timer has reached a prescribed number (step S 125 ). If “yes”, the rotation of the motor  234  is stopped, and the rotation timer is cleared (step S 127 ), and the stop timer is counted up (step S 129 ). Then, it is determined whether or not the count of the stop timer has reached a prescribed number (step S 131 ). If “yes”, the procedure returns to step S 121 , and subsequent operations are repeatedly operated. If “no” in step S 125 , the procedure returns to step S 123  to execute repeatedly the determination until the count reaches the prescribed number. In addition, if “no” in step S 131 , the procedure returns to step S 129  to execute repeatedly the determination until the count reaches the prescribed number. 
     The lighting operation of the cold-cathode tubes  181  to  184  in step S 49  shown in FIG. 14 will now be described with reference to the flow chart shown in FIG.  17 . 
     First, degree of difficulty handling according to the game course, score and the number of remaining balls is executed (step S 141 ). That is, when the game course of the low degree of difficulty (for example, the first course and the middle course) is selected, the degree of difficulty handling is performed so that the cold-cathode tubes in a plurality of areas of E 2  to E 5  of the playing surface  14  are lit up to make it easy to obtain scores. On the other hand, when the game course of the high degree of difficulty (for example, the advanced course) is selected, the degree of difficulty handling is performed so that the cold-cathode tube in one of the areas of E 2  to E 5  of the playing surface  14  are lit up to make it difficult to obtain scores. Even if the game course of the low degree of difficulty has been selected, when the score exceeds a predetermined value or the number of remaining balls decreases to less than a predetermined value, the degree of difficulty handling is performed so that the cold-cathode tubes in one of the areas of E 2  to E 5  of the playing surface  14  are lit up to make it difficult to obtain scores. 
     Then, before the projection of balls from the ball projecting section  20 , it is determined whether or not the degree of difficulty is low (step S 143 ). If “yes”, the cold-cathode tubes  182  and  184  (or  181  and  183 ) of the left-side (or right-side) two areas E 3  and E 5  (or E 2  and E 4 ) are lit up simultaneously. If “no” (i.e., when the degree of difficulty is high), the cold-cathode tube  181 ,  182 ,  183  or  184  in one of the four areas of E 2  to E 5  is lit up (step  147 ). 
     The ball projecting operation of the ball projecting section  20  in step S 51  shown in FIG. 14 will now be described with reference to the flow chart shown in FIG.  18 . 
     First, it is determined whether or not the projection of a prescribed number of balls has not been finished (step S 161 ). If “yes”, the type of projection and the speed of the next ball to be projected are decided (step S 163 ) according to the degree of difficulty of the game (that is decided by the selected game course, the present score and the present number of remaining balls). That is, when the degree of difficulty is high, the type of projection of ball, a manner of application of spin and the like are frequently changed, and the projecting speed is increased. When the degree of difficulty is low, the type of projection of ball, a manner of application of spin and the like are not changed so frequently, and the projecting speed is decreased. If “no” in step S 161 , the operation shifts to that of step S 53  shown in FIG.  14 . 
     Then, the projecting position of the next ball to be projected is decided according to the degree of difficulty of the game (step S 165 ). That is, when the degree of difficulty of the game is high, the ball projecting section  20  is moved laterally on the rear end of the playing surface  14  in accordance with the drop position of the ball returned by the player in the playing surface  14 . 
     That is, when the ball has dropped onto the right-side second area E 2  or the fourth area E 4  of the playing surface  14 , the drop of the ball onto the second area E 2  or the fourth area E 4  is discriminated by a detection signal output from a pair of the microphones  192  and  193  or  196  and  197 , and the ball projecting section  20  is moved to the center position or the right-end position on the right-half of the table  10 . In addition, when the ball has dropped onto the left-side third area E 3  or the fifth area E 5  of the playing surface  14 , the drop of the ball onto the third area E 3  or the fifth area E 5  is discriminated by a detection signal output from a pair of the microphones  194  and  195  or  198  and  199 , and the ball projecting section  20  is moved to the center position or the left-end position on the left-half of the table  10 . The movement of the ball projecting section  20  is controlled by the number of pulses supplied to the projecting section moving motor  96   a.    
     When the degree of difficulty of the game is low, the ball projecting section  20  is fixed to the center position, left-end position or the right-end position of the table  10  regardless of the drop position of the ball returned by the player on the playing surface  14 . 
     Then, the projecting angle of the next ball to be projected is decided according to the degree of difficulty of the game (step S 167 ). That is, when the degree of difficulty of the game is high, the projecting angle is frequently changed, or a ratio of the projection of the ball in a path describing a parabola is decreased, and a ratio of the projection of the low ball is increased. In addition, when the degree of difficulty of the game is low, the projecting angle is not frequently changed, or a ratio of the projection of the ball in a path describing a parabola is increased, and a ratio of the projection of the low ball is decreased. 
     Then, the projecting direction (straight direction or crosswise direction) of the next ball to be projected is decided according to the degree of difficulty of the game (step S 169 ). That is, when the degree of difficulty of the game is high, the projecting direction is frequently changed, while the projecting direction is not changed so frequently when the degree of difficulty of the game is low. 
     Then, the number of rotations of the roller motors  253  and  254  of the urging force-imparting unit  25  is quickly changed by a PWM control (pulse width modulation control), and the projecting cylinder rotating motor  263  of the rotary unit  26  is driven by the supplied voltage of a predetermined number of pulses, whereby the ball projecting section  20  is rotated in the normal direction or the reverse direction by a predetermined angle, and the type of projection of ball and the ball speed is set to be the type and the speed decided in step S 163  (step S 171 ). In addition, the projecting section moving motor  96   a  is driven by the supplied voltage of a predetermined number of pulses, whereby the ball projecting section  20  is moved to a predetermined leftward or rightward position, and the ball projecting position is set to the position decided in step S 163  (step S 173 ). The type of projection of ball in steps S 163  and S 171  refers to the type which is changed by the manner of application of spin by the urging force-imparting unit  25  and the rotary unit  26  on the ball. However, the ball speed changed by the urging force-imparting unit  25 , and the ball in a path describing a parabola produced by the angle changing unit  28  may be included in the type of projection of ball. 
     In addition, the guide plate motor  282  is driven until the voltage value output from the sensor  285  reaches a predetermined value, whereby the guide plate  281  is rotated by a predetermined angle, and the ball projecting angle is set to the angle decided in step S 167  (step S 175 ). Furthermore, the projecting section oscillating motor  276  is driven until the voltage value output from the oscillating angle sensor  278  reaches a predetermined value, whereby the ball projecting section  20  is rotated leftward or rightward by a predetermined angle, and the ball projecting direction is set to the direction decided in step S 169  (step S 177 ). 
     When the coach mode selection switch CS of the control box  70  is turned on, the operations of steps S 163  to S 169  are operated according to a signal that is output by turning on any one of the area select switches PS 1  to PS 6  provided in the control box  70 . In addition, even if the coach mode selection switch CS is turned on, the ball is projected under programmed conditions when no area selection switches are turned on. 
     Then, it is judged whether or not the ball projecting timing (for example, one projection per two seconds) has been provided (step S 179 ). If “yes”, the plate cam motor  242  is started to rotate, and the plate cam  241  is rotated in response thereto (step S 181 ). If “no” in step S 179 , the determination is repeatedly executed until the projection timing is provided. 
     Then, it is determined whether or not the plate cam  241  has rotated once (step S 183 ). If “yes”, a projection sound (for example, a sound effect generated when a ball is hit by a racket) is generated (step S 185 ). Thereafter, the rotation of the plate cam motor  242  is stopped and the rotation of the plate cam  241  is stopped in response thereto (step S 187 ). If “no” in step S 183 , it is determined whether or not a fixed period of time has elapsed since the plate cam  241  is started to rotate (step S 189 ). If “yes”, error handling (for example, display of the ball jam) is performed (step S 191 ). If “no” in step S 189 , the procedure returns to step S 183 , and subsequent operations are repeatedly executed. 
     The detection of the drop position of the ball, and score handling in step S 53  shown in FIG. 14 will now be described with reference to the flow chart shown in FIG.  19 . 
     First, it is determined whether or not the ball is projected from the ball projecting section  20  (step S 221 ). If “yes”, it is determined whether or not the last detection signals output from the microphones  190  to  199  are cleared (step S 223 ). If “yes”, it is determined whether or not the ball returned by the player has dropped onto the playing surface  14  (step S 225 ). If “no” in step S 223 , the determination is repeatedly executed until the above detection signals are cleared, and even if the next signals are output from the microphones  190  to  199  during the determination, the signals are ignored. 
     That is, when “yes” in step S 221 , a flag is set up, and while the flat is being set up, the detection signals from the microphones  190  to  199  that are output only when the ball drops on the playing surface  14  are incorporated into the score adding unit  816 . On the other hand, once the detection signals have been incorporated into the score adding unit  816 , the above flag falls, and even if the ball drops again on the playing surface  14  by bounding and the detection signals are output, the signals are ignored and are not incorporated into the score adding unit  816 . 
     However, when the previously projected ball is returned in a path describing a parabola to drop on the playing surface  14  immediately before the projection of the next ball, and bounds to drop on the playing surface  14  immediately after the projection of the next ball, a score is added doubly by the bound of the previously projected ball, and the score is not added by the next ball. Therefore, a detection signal output by the first bound is held for a fixed period of time (for example, 0.5 seconds), and even if the next detection signal is output during the holding time, the signal is ignored, thereby preventing the score from being added doubly. 
     A specific example will be described. As shown in FIG. 21A, it is assumed that the first ball {circle around ( 1 )} is projected from the ball projecting section  20  at the time t 1  and a flag F is set up, and the second ball {circle around ( 2 )} is projected and a flag F is set up at the time t 2 , for example, after two seconds. In this case, even if the first ball {circle around ( 1 )}that has been returned on the playing surface  14  continuously bounds on the playing surface  14  immediately before the projection of the second ball {circle around ( 2 )}, the flag F falls at the first bound time t 1a , so that no detection signals resulting from subsequent bounds are incorporated into the score adding unit  816 . 
     As shown in FIG. 21B, however, if the ball {circle around ( 1 )} bounds on the playing surface  14  at the time t 1b  immediately before the projection of the ball {circle around ( 2 )} and bounds again at the time t 1c  immediately after the projection of the ball {circle around ( 2 )}, the flag F is set up by the projection of the ball {circle around ( 1 )} immediately before the bound at the time t 1b , and the flag F is set up by the projection of the ball {circle around (2+L )} immediately before the second bound at the time t 1c . Thus, both detection signals are incorporated into the score adding unit  816 . 
     In this case, if the detection signal is held for, for example, 0.5 seconds after the first bound time t 1b  and a gate is provided so as not to receive new detection signal during this period, as shown in FIG. 21B, the detection signal resulting from the first bound of the ball {circle around ( 1 )} is incorporated into the score adding unit  816 , but the detection signal resulting from the second bound is not incorporated into the score adding unit  816  when the holding of the detection signal is cleared after the second bound time t 1c  of the first ball {circle around ( 1 )}. 
     The ball {circle around ( 2 )} usually bounds at the time t 2a  after the detection signal of the ball {circle around ( 1 )} is cleared, and the detection signal resulting from the bound is incorporated into the score adding unit  816 . The above 0.5 seconds is an example of the period of time for holding the detection signal. The time may be set to the time corresponding to the maximum value of the bound time, or slightly longer. 
     Returning to FIG. 19, if “no” in step S 225 , it is determined whether or not a fixed period of time has elapsed (step S 227 ). If “yes”, the procedure advances to step S 55  shown in FIG.  14 . If “no”, the procedure returns to step S 225  and the determination is repeatedly executed until the fixed period of time elapses. If “yes” in step S 225 , it is determined whether or not the ball returned by the player has dropped onto the areas E 2  to E 5  where the cold-cathode tubes  181  to  184  are being lit up (step S 229 ). If “yes”, a high score (for example, 2 points) is added to the previous score, and a sound effect, such as a music for honoring the score, is output for a fixed period of time (step S 231 ). In this embodiment, the drop of the ball on the boundary between the lighting area and the non-lighting area of the cold-cathode tubes is regarded as the drop onto the lighting area. 
     Then, in order to obtain the illumination effect, the cold-cathode tubes in the area onto which the ball has dropped are winked for a fixed period of time, while all the cold-cathode tubes in other areas are lit up only for a fixed period of time (step S 233 ). Consecutively, the added point is displayed on the point display section  41  and the display section  41  is winked for a fixed period of time, whereby scoring of the point is appealed (step S 235 ). 
     Game-over handling in step S 57  shown in FIG. 14 will now be described with reference to the flow chart of FIG.  20 . 
     First, the rotations of the motors in the ball projecting section  20 , i.e., the hopper-inside stirring motor  234 , the roller motors  253  and  254 , the projecting cylinder rotating motor  263 , the projecting cylinder oscillating motor  273 , the guide plate motor  282  and the projecting section moving motor  96   a  are stopped (step S 261 ), and a demonstration picture relating to game-over is displayed on the image display section  42  (step S 263 ). The demonstration picture includes a renewal of high score, display of final score, and the like. 
     Then, the motor  96   a  is rotationally driven and the ball projecting section  20  is returned to the initial position, in the center of the table  10  (step S 265 ), the motor  282  is rotationally driven and the guide plate  281  is returned to the initial position (step S 267 ), and further, the motor  276  is rotationally driven and the ball projecting section  20  is returned to the initial position in the oscillating direction (step S 269 ). 
     Thereafter, it is determined whether or not a fixed period of time has elapsed (step S 271 ). If “yes”, the rotations of the stirring/feeding motors  379  and  389  are stopped (step S 273 ). 
     While the present invention has been described with respect to what is presently considered to be the preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiment. To the contrary, the invention is intended to cover various modifications and equivalent arrangements included within the sprit and scope of the appended claims. 
     For example, it is possible to divide the playing surface  14  of the table  10  into total six areas by dividing the area near the net  16  into left-side and right-side areas. With this arrangement, even if a ball is hit into the area near the net  16 , the next ball can be projected according to the area into which the ball is hit. In addition, it is possible to divide laterally the playing surface  14  into three or more areas. If the three or more areas are formed laterally on the playing surface  14  and a microphone is installed on each of the areas, the ball projection section  20  can be moved to a position closer to the ball return position, so that a competitive play which is closer to the actual play can be performed. Furthermore, cold-cathode tubes may be provided in all areas, and cold-cathode tubes of the same color may be used in the areas. 
     In addition, the ball projecting section  20  may be disposed rearward of the playing surface  12  on the side of a player without providing the playing surface  14 . In this case, for example, it is possible to dispose a monitor rearward of the ball projecting section  20  for displaying a picture of a playing surface and a returned ball, to arrange laterally a number of optical sensors on the proximal side of the ball projecting section  20 , and to detect the ball return direction according to which optical sensor the ball returned by the player passes through to thereby move laterally the ball projecting section  20  according to the result of the detection. It is also possible to dispose longitudinally a board having a plurality of through holes formed therein in the form of a matrix in place of the playing surface  14 , to detect which through hole the returned ball passes through by optical sensors or mechanical switches so as to obtain the ball return direction thereby to move laterally the ball projecting section  20  according to the return direction. 
     Furthermore, a lamp such as a cold-cathode tube may be disposed in the first area E 1 . In addition, it is possible to use lamps of the same luminary color. A variation of a luminary color in each of the areas can be realized by using a white-luminary lamp and a colored plate body  142 . Furthermore, it is possible to constitute a surface illuminant by burying a plurality of light emitting diodes in the form of a matrix in the plate body  142  or the like. While the surface illuminant constitutes identifying means for identifying the areas of the playing surface, the identifying means can be constituted by other means such as lighting for illuminating the playing surface  14  from above. 
     Still furthermore, the ball sorting section may include only the rails  321  of the left collecting part  32  and the rails  331  of the rear collecting part  33 , or may include only the rails  351  of the longitudinal collecting part  35  and the rails  361  of the lateral collecting part  36 . 
     When the ball sorting section includes only the rails  321  and the rails  331 , balls that have rolled to the downstream of the rails  331  may be returned towards the ball projecting section  20  by the ball scooping-up unit  38 . When the ball sorting section includes only the rails  351  and the rails  361 , balls that have dropped around the table  10  may be collected, for example, to the rearward of the table  10  on the floor below the table  10 , and the collected balls may be transferred onto the rails  351 . 
     Yet furthermore, the ball sorting section may only include either of the rails  321  or the rails  331 , or either of the rails  351  or the rails  361 . In these cases, balls that have dropped around the table  10  may be collected by suitable means, and may be transferred onto the rails of the ball sorting section. In addition, the rails may be disposed horizontally so that the balls are rolled by wind pressure. 
     In addition, it is possible to construct the right collecting part  34  similar to the left collecting part  32 . It is also possible for the left collecting part  32  to include the same plate as that of the right collecting part  34 . In this case, balls that have rolled towards the downstream of the plate may be delivered to the rails  331  of the rear collecting part  33 . 
     Furthermore, the floor collecting part  31  may be extended to the rearward of the table  10 , and the balls that have been collected in the floor collecting part  31  may be transferred to the ball sorting section from the extended portion. In addition, the floor collecting part  31  may allows the balls to be rolled by window pressure or the like. 
     Still furthermore, in the described embodiment, the bounded ball addition disabling unit  824  prevents a signal detected by detection means from being incorporated into the score adding unit  816  when a ball bounds to drop again on the playing surface  14 . However, when addition resulting from the first drop of the ball is executed, the addition may be prevented from being executed by, for example, electrically shutting off a circuit of the detection means for a fixed period of time to disable the detecting operation.