EP0094267A1 - Ball throwing device - Google Patents

Abstract

Balls such as table tennis balls or tennis balls are continuously fed to two pairs of adjacent flanged rollers of a ball-throwing head by a blower and two transfer ducts. Balls hit by the player are collected by a net and a trough, then fed back to the head. The rollers have separately variable speeds of rotation, a gap being provided between each pair of rollers and adapted to the diameter of the balls. The balls are directed alternately into each transfer duct, the opening of which is located opposite to each gap.

Description

The present invention relates to a device for throwing balls on a playground and in particular on a ping-pong table.

Known ball-throwing devices for table tennis include a throwing head disposed at one end of the table, opposite the location of the player.

This throwing head successively sends the balls to the table, the player / receives with his racket and returns them to a screen or net for receiving the balls placed above the table, facing the throwing head.

This screen or net collects the balls which are then routed again to the launching head.

The launching head of known devices comprises one or two rotary rollers placed opposite a bale supply pipe. By turning, this or these rollers successively pick up the balls and project them towards the playing area. The balls are propelled in the aforementioned conduit generally by means of an air blower or by gravity from a tank.

The aforementioned devices are of great interest since they allow a single player to train without the need for a partner or an instructor and without having to constantly move to pick up the balls.

The conditions for launching the balls can be modified by varying the speed of rotation of the rollers of the launching head and by modifying the direction of launching of the balls.

In the case where the launching head has two rollers arranged one above the other, it is possible by rotating these rollers at speeds different from throwing the ball with "lifted" or "cut" effects comparable to the case where the ball is thrown by a player's racket.

In the most sophisticated known devices, efforts are therefore made to obtain conditions for launching balls almost as varied as in the case where two players play one opposite the other.

However, the known devices have a major drawback. In fact, given the inertia of the rotating rollers of the launching head, it is not possible to instantly modify the conditions for launching the balls. Thus, it is not possible to throw balls at a rate for example less than or equal to one ball per second whose projection speeds and effects would be different for each ball. Consequently, these devices do not in any way make it possible to restore the real conditions of the game of table tennis and ultimately, do not allow a player to be surprised by a ball thrown under conditions very different from those of the previous ball. As a result, players cannot be confronted with sudden and varied difficulties and thus it is difficult for students to progress as quickly as playing with an experienced instructor or player.

The object of the present invention is to remedy the aforementioned drawback by creating a device which makes it possible to reproduce in a perfect manner, the actual conditions for launching tennis balls, for example by allowing the instantaneous modification of the conditions of launch. of these bullets.

• - des moyens pour acheminer en continu les balles vers une tête de lancement qui comporte au moins un rouleau entraîné en rotation capable de prélever successivement les balles pour les projeter vers l'aire de jeu et des moyens pour récupérer les balles lancées par le joueur puis les acheminer à nouveau vers la tête de lancement.

The device for throwing balls aimed by the invention comprises:

• - means to continuously route the balls towards a throwing head which comprises at least one roller driven in rotation capable of successively taking the balls to project them towards the playing area and means for recovering the balls thrown by the player then forwarding them again towards the head of launch.

According to the invention, this device is characterized in that the launching head comprises two pairs of rotary rollers arranged side by side, in that means are provided for individually adjusting the speed of rotation of each roller, in that the rollers of each pair are separated by a space adapted to the diameter of the balls to allow the balls engaged in this space to engage simultaneously with the two rollers of each pair, in that a conduit for feeding the balls opens out opposite each of the aforementioned spaces and in that means are provided for conveying bales alternately in one or the other of the aforesaid conduits.

Thanks to this device, the balls can be conveyed alternately in one or other of the spaces between each pair of rollers.

During the time that a ball is routed to one pair of rollers, it is possible to change the rotation speed of the rollers of the other pair, so that the next ball taken by that other pair of rollers can be thrown in conditions different from those of the previous ball. It is thus possible to instantly modify the conditions for launching a ball, without being hindered by the inertia of the rotating rollers.

Therefore, the player can be faced with various difficulties, as in the case of the game played with an experienced player or an instructor. The game tennis is thus made much more attractive to the player.

According to an advantageous version of the invention, the launching head is pivotally mounted along a substantially vertical axis and is connected to means allowing the head to continuously scan a determined angular sector.

This scanning can be carried out at a more or less rapid speed, this speed and the scanning angle being modifiable according to the level of the player or the difficulties which it is wished to impose on him.

According to a preferred version of the invention, the means for conveying the bales alternately towards one or the other of the conduits emerging opposite the spaces comprised between the rotary rollers, comprise a main conduit connected at one of its ends to an air blower, and at its other end to a Y-connector / to the two aforementioned conduits, downstream of this Y-connector being arranged, opposite each conduit, a member which can engage alternately in the one or other of the conduits to prevent the passage of bullets.

The duration between the positions of engagement and withdrawal of this member can be modified according to the rate of launching of the balls that it is desired to obtain.

Other features and advantages of the invention will appear in the description below.

• - la figure 1 est une vue en perspective d'une table de tennis équipée d'un dispositif de lancement de balles conforme à l'invention;
• - la figure 2 est une vue en perspective de la tête de lancement et des moyens de propulsion des balles, logés dans un coffret;
• - la figure 3 est une vue en perspective du coffret et des moyens de réception et de collecte des balles;
• , la figure 4 est une vue en plan des moyens de commande du balayage angulaire de la tête de lancement;
• - la figure 5 est une vue latérale du dispositif conforme à l'invention placé en regard d'une table de tennis;
• - la figure 6 est une vue en coupe de deux rouleaux rotatifs superposés de la tête de lancement, perpendiculairement à l'axe de ces rouleaux et montrant en coupe partielle le conduit d'amenée des balles correspondant;
• - la figure 7 est une vue en coupe longitudinale des conduits d'amenée des balles dans la tête de lancement, avec leurs organes respectifs de répartition des balles vers la tête de lancement;
• - la figure 8 est une vue en coupe suivant le plan VIII-VIII de la figure 7;
• - la figure 9 est une vue en plan du tableau électrique de commande du dispositif;
• - la figure 10 est une vue du coffret renfermant le dispositif conforme à l'invention, en position de rangement.
• - la figure 11 est une vue schématique d'une variante des moyens de propulsion et de lancement des balles et
• - la figure 12 est une vue en coupe à échelle agrandie suivant le plan XII-XII de la figure 11.

In the appended drawings, given by way of nonlimiting examples:

• - Figure 1 is a perspective view of a tennis table equipped with a ball throwing device according to the invention;
• - Figure 2 is a perspective view of the launch head and propulsion means balls, housed in a box;
• - Figure 3 is a perspective view of the cabinet and means for receiving and collecting balls;
• FIG. 4 is a plan view of the means for controlling the angular scanning of the launching head;
• - Figure 5 is a side view of the device according to the invention placed opposite a tennis table;
• - Figure 6 is a sectional view of two superimposed rotary rollers of the launching head, perpendicular to the axis of these rollers and showing in partial section the corresponding ball supply duct;
• - Figure 7 is a longitudinal sectional view of the bales supply conduits in the launch head, with their respective bodies for distributing the balls to the launch head;
• - Figure 8 is a sectional view along the plane VIII-VIII of Figure 7;
• - Figure 9 is a plan view of the electrical control panel of the device;
• - Figure 10 is a view of the box containing the device according to the invention, in the storage position.
• FIG. 11 is a schematic view of a variant of the means for propelling and launching the balls, and
• FIG. 12 is a sectional view on an enlarged scale along the plane XII-XII of FIG. 11.

In the embodiment of FIGS. 1 to 5, the device for throwing balls, housed in a box 1 placed at one end of a tennis table 2, mainly comprises a throwing head 3, an air blower 4 (see FIG. 2) connected to lines 5, 6 for continuously conveying the balls 7 towards the throwing head 3, and means for recovering the balls 7 thrown by the player and then routing them again to the throwing head 3.

According to the invention (see Figures 2 and 6), the launching head 3 comprises two pairs of rollers 8, 9; 10, 11 arranged side by side substantially along two parallel and vertical planes. Each roller is rotated by a motor 12, 13; 14, 15 whose speeds are individually adjustable, for example by means of potentiometers or the like.

These rollers 8 to 11 and these motors 12 to 15 are carried by a yoke 16 fixed to the end of an arm 17 which is slidably mounted on a column 18.

The length of the arm 17 as well as the height of fixing of this arm on the column 18 are adjustable by acting on locking levers as designated by the reference 19. The yoke 16 carrying the rollers 8 to 11 is articulated relative to the arm 17 along a horizontal axis, so that the inclination of the launching head 3 relative to a horizontal plane can be adjusted. The locking lever 20 allows this head to be fixed in the desired angular position. The column 18 is pivotally mounted along a vertical axis XX ′ and it is connected to a connecting rod 21 (see FIGS. 2 and 4) articulated to a disc 22 rotated by a motor 23. This arrangement allows the head 3 to continuously scan a determined angular sector (see Figure 4).

This angular sector a can be modified by adjusting the position of the articulation point 21a of the connecting rod 21 on the disc 22.

The scanning speed of the launching head 3 can be modified by adjusting the speed of rotation of the motor 23.

In the embodiment shown (see FIGS. 2 and 6), the rollers 8 to 11 of each pair are separated by a space 24, 25 adapted to the diameter of the balls 7, to allow the ball engaged in this space 24 or 25 to be engaged simultaneously with the two rollers of each pair, as shown in Figure 6.

A pipe 26, 27 for supplying the bales 7 opens opposite each of the spaces 24, 25.

Furthermore, each roller 8 to 11 has two lateral flanges such as 8a, 8b made of flexible material defining on the periphery of each roller a U-shaped groove adapted to the diameter of the balls 7.

On the other hand, these rollers 8 to 11 comprise a tread 28 made of rubber or any other elastic material having a relatively high coefficient of friction with the balls 7.

Preferably, the height of the spaces such as 24 comprised between the treads 28 of two adjacent rollers 8, 9 or 10, 11 is slightly less than the diameter of the bales 7, which results in a slight crushing of the bands during the passage of the bales. bearing 28 which is favorable to the adhesion between the latter and the balls and increases the efficiency of the projection of these balls.

The conduits 26, 27 which bring these balls 7 alternately either between the rollers 8, 9, or between the rollers 10, 11 communicate with a main pipe 29 which is connected to a flexible pipe 6 which is itself connected to a vertical pipe 5 by means of a transverse pipe 30 made of transparent material (see FIG. 2).

The air blower 4 is connected to the vertical pipe 5 by an elbow 31 provided with an adjustable vent 32. Likewise, adjustable vents 33 are provided in the elbow 34 which connects the pipe 5 and the transparent pipe 30.

The internal diameter d of the supply lines ment of the balls 7 towards the launching head 3 is greater than the diameter of the balls, so that the latter are propelled by blowing and not by piston effect. On the other hand, the diameter of the conduits 26, 27 adjacent to the rollers 8 to 11 is at their free end substantially equal to the diameter of the balls 7 to increase the efficiency of their expulsion from these conduits 26, 27. In the embodiment shown (see in particular FIG. 7), the means for conveying the bales 7 alternately towards one or the other of the conduits 26, 27 which open opposite the spaces 24, 25 comprised between the rollers 8, 9; 10, 11 comprise a Y connector 35 communicating with the flexible pipe 29 and with the conduits 26, 27. Downstream of this Y connector is disposed opposite each conduit 26, 27, a finger 36, 37 biased by an electro - magnet 38, 39.

Each finger 36, 37 is movable between a position in which its end projects slightly inside the conduit 26 as indicated on the left part of FIG. 7 and in FIG. 8 or inside the conduit 27 and a position as shown on the right side of figure 7.

In the position shown in Figure 7, the passage of the balls 7 is prohibited in the conduit 26, while this passage is free in the conduit 27. Electromagnets 38, 39 are connected to means not shown but conventional for controlling the reciprocating movement of the fingers 36, 37 so as to allow successive passage at a frequency, for example between one and three bullets per second in the conduits 26, 27.

In FIG. 7, it can also be seen that the Y-connector 35 has at its entry a point 40 which avoids that a ball 7a (shown in dotted lines) occupies at the entry of the Y-connector a stable position capable of blocking the routing of the balls, so that this ball 7a is forced to engage either in the conduit 26, or in conduit 27.

Furthermore, the distance H between the fingers 36, 37 and the tip 40 of the Y connector is determined so that each branch of the Y connector cannot contain any ball capable of hindering the passage of a ball in the other branch of this Y-connector.

In FIGS. 1, 3 and 5, it can be seen that the means for collecting the balls 7 returned by the player comprise a net 41 stretched above the table 2 and in front of the throwing head 3. This net 41 is hooked to the end of two rods 42 fixed on the upper part 1a of the box 1. This net 41 includes a central window 43 (see FIG. 3) arranged opposite the launching head 3.

Under the lower edge 44 of the net 41, extends a chute 45 of cross section in an arc of a circle to collect the balls 7. This chute 45 has two slopes inclined towards its middle. The lowest point of this chute 45 corresponding to its middle, includes a bale 46 for collecting bales 7 which is connected by a flexible pipe 47 to the elbow 31 which connects the air blower 4 to the vertical pipe 5.

FIG. 9 represents the electrical control panel 48 for controlling the device according to the invention. This table 48 comprises four rotary knobs 49, 50, 51, 52 associated with potentiometers for individually adjusting the rotational speed of the motors 12 to 15 which drive the rollers 8 to 11. This speed can thus be set to a value between approximately 100 and 7,000 rpm.

A button 52a makes it possible to adjust the duration between the positions of engagement and withdrawal of the fingers 36, 37 solicited by the electromagnets 38, 39. Another button 53 makes it possible to adjust the rate of delivery of the balls alternately to the conduits 26, 27.

The button 54 makes it possible to adjust the speed of rotation of the motor 23 which controls the sweeping of the launching head 3.

The switches 55a and 55b control the reversal of the direction of rotation of two of the four drive motors of the rollers 8 to 11, which makes it possible to obtain the projection of the balls 7 with reinforced effects.

Other switches 56, 57 and 58 are respectively intended for starting the electrical supply of the switchboard 48, for starting the sweeping, and for starting the electrical supply for the control circuit of the electromagnets 38, 39.

Furthermore, the parallelepipedic box 1 containing the entire device according to the invention comprises (see FIG. 2) two parts 1b, the hinged together by means of hinges 59. These two parts 1b, 1c can be folded one on the other, as shown in Figure 10. The box 1 thus folded has a very small overall height which facilitates storage and transport of the device. The displacement of this box 1 can be facilitated by providing its base with rollers 60.

We will now describe the operation of the device that has just been described.

After placing the device in front of the table 2, as shown in Figures 1 and 5, the position of the launching head 3 is adjusted by acting on the levers 19 and 20.

The various switches of the electrical control panel 48 are placed in the operating position and a few balls 7 are introduced into the routing circuit of the latter towards the launching head. As soon as a ball 7 arrives in the elbow 31, it is propelled into the lines 5, 30 and 6 by means of the air blower 4.

The intensity of the blowing can be adjusted by adjusting the opening of the vents 32, 33. The transparent pipe 30 located at the top of the box 1 makes it possible to check the passage of the balls 7. The balls follow one after the other, nothing n 'existing on their trajectory which could hinder their passage.

The balls 7 then penetrate into the branches of the Y connector 35. Depending on the position of the fingers 36, .37 whose movement is controlled alternately by the electromagnets 38, 39, the balls are successively conveyed either, to the conduit 26, either towards conduit 27.

When they exit from these conduits 26, 27, the balls 7 are immediately taken up by the rotating rollers 8, 9 or 10, 11, then projected onto the tennis table 2.

The player placed at the opposite end of the table returns this ball to the other end of the table where it bounces-towards the net 41 which absorbs the latter and stops it. This ball falls into the chute 45 then rolls towards the drain 46. The cylindrical shape of the chute 45 prevents the balls from being returned to the outside and allows them to roll along the generatrices of the cylinder. This ball 7 is then sucked into the pipe 47 and is again conveyed to the launching head 3 by means of the blower 4.

The balls are thus expelled from the launch head at a rate of between one and three balls per second approximately, alternately between one or the other pair of rollers 8, 9; 10, 11.

During the game, you can modify the rotation speed of the drive motors of the rollers 8, 9, 10, 11 at any time to increase or decrease the force of projection of the balls or to give them "lifted" or " cut "analogous to the effects which can be given to a ball by means of a racket. We can thus obtain that the balls follow one another at a very high rate with projection forces and effects which differ from one ball to another.

The playing conditions can be modified instantly, as in the case of a real game where the player is in the presence of an opponent who naturally seeks to put him in difficulty.

Furthermore, during the course of the game, the scanning speed of the throwing head 3 can be continuously modified, so that the balls 7 are projected in variable directions, which makes it possible to restore the conditions of a real game and this makes the game particularly attractive.

FIG. 11 shows an alternative embodiment of the means of propulsion and launching of the balls 7. The main pipe 5 connected to the blower 4 is subdivided according to a Y-connector 65 into two horizontal pipes 5a, 5b which each open out opposite a launching head comprising the rollers 8, 9; 10, 11.

Each horizontal pipe 5a, 5b comprises a vent 61 whose dimensions are less than the diameter of a bale 7.

Upstream of the outlet 24, 25 of the conduits 5a, 5b, a roller 62 is arranged (see also FIG. 12) which is partially engaged inside the pipe 5a, 5b. This roller 62, when it is stopped, blocks the balls 7 and propels them one after the other when it is rotated. The roller 62 is advantageously made of elastic material, such as rubber, and defines, inside the pipe 5a, 5b, a passage section whose surface is slightly smaller than the section of a bale 7.

Furthermore, in the example shown, the launching heads are each mounted on a vertical support 63, 64 allowing the launching heads to be adjusted to different heights.

• Au départ, les rouleaux 62 étant à l'arrêt, les balles 7 soufflées par la soufflerie 4 sont dirigées indifféremment dans les conduites 5a, 5b. Lorsque les deux conduites 5a, 5b sont remplies de balles 7 jusqu'à l'évent 61 (comme dans le cas représenté par la conduite 5b), les balles 7 ne sont plus propulsées car aucun débit d'air n'est réalisé dans les conduites 5a, 5b puisque les évents 61 sont masqués par une balle 7. Tout le débit d'air est alors évacué par la dérivation 47.

The operation of this device is as follows:

• At the start, the rollers 62 being stopped, the balls 7 blown by the blower 4 are directed indifferently into the conduits 5a, 5b. When the two lines 5a, 5b are filled with balls 7 up to the vent 61 (as in the case represented by the line 5b), the balls 7 are no longer propelled because no air flow is produced in the lines 5a, 5b since the vents 61 are masked by a ball 7. All the air flow is then evacuated by the bypass 47.

It is then possible to control the simultaneous or successive rotation of the flexible rollers 62 which thus propel the balls 7 towards the launch rollers 8, 9; 10, 11. When the balls 7 are taken up by the rollers 62, these balls are rotated at the same speed as that of the rollers 62. By acting on the speed of rotation of the balls 7, it is obtained that the latter are sent with "lifted" or "cut" effects.

The fact that the launching heads are at different heights makes it possible to reproduce the real conditions of the game of tennis.

Of course, the invention is not limited to the embodiment which has just been described and many modifications can be made to it, without departing from the scope of the invention.

Thus, one can have opposite the launching head 3, as shown in Figure 6, a plate 61 whose inclination b relative to the horizontal can be adjusted at will, as well as its inclination relative to the vertical. This plate 61 thus cuts the trajectory of the balls 7 and deflects the latter, either upwards (lifted effect) or downwards (cut effect), either to the right or to the left. This plate 61 also makes it possible to modify the conditions for projecting the balls 7, thus imposing on the player additional difficulties liable to prove his skill.

It is also possible to place inside the box 1 facing the player, a lamp 62 (see FIG. 2) which lights up as soon as a ball is going to be thrown. The player is thus warned of the throwing of a ball, as in the case of a real game. We can also provide several lamps of different colors or intensities that warn the player that a ball will be thrown with or without lifted or cut effect or that it will be long or short.

The operation of the device can be fully automatic, according to a predetermined program using cards or pre-programmed perforated strips. Thus, we can design different operating programs imposing increasing difficulties on players adapted to their level of qualification.

Of course, the device according to the invention can also be applied to other ball games than table tennis such as the game of tennis on court.

Claims (17)

1. Device for throwing balls on a playing area (2) comprising means (4, 5, 6) for continuously feeding balls (7) to a throwing head (3) which comprises at least one roller driven in rotation capable of successively removing the balls (7) to project them towards the playing area and means (41, 45) for recovering the balls launched by the player then routing them again towards the launching head (3), characterized in that the launching head (3) comprises two pairs of rotating rollers (8, 9; 10, 11) arranged side by side, in that means (49, 50, 51, 52) are provided for individually adjusting the rotational speed of each roller, in that the rollers of each pair are separated by a space (24, 25) adapted to the diameter of the balls (7) to allow the balls engaged in this space to engage simultaneously with the two rollers of each pair, in that a pipe (26, 27) for supplying the balls opens out opposite each of th spaces (24, 25) and in that means (36, 37, 38, 39) are provided for conveying the balls alternately in one or other of the aforementioned conduits. 2. Device according to claim 1, characterized in that the launching head (3) is pivotally mounted along a substantially vertical axis and is connected to means (21, 22, 23) allowing the launching head (3) continuously scan a determined angular sector (a). 3. Device according to any one of claims 1 or 2, characterized in that means (21a) are provided for modifying the angular sector (a) swept by the launching head (3). 4. Device according to any one of Claims 1 to 3, characterized in that the rollers of each pair (8, 9; 10, 11) are arranged in the operating position, substantially in a vertical plane and have two lateral flanges (8a, 8b) defining with the surface of rolling of the rollers a substantially U-shaped groove adapted to the diameter of the balls (7). 5. Device according to claim 4, characterized in that the rollers (8,9, 10, 11) comprise a tread (28) made of an elastic material having a high coefficient of friction with the balls (7). 6. Device according to claim 5, characterized in that the height of the space (24, 25) between the rolling surface of the superimposed rollers is slightly less than the diameter of the balls. 7. Device according to any one of claims 1 to 6, characterized in that the means for conveying the bales alternately in one or the other of the conduits (26, 27) comprise a main conduit (6) connected to one of its ends to an air blower (4) and at its other end to a Y connector (35) connected to the two conduits (26, 27), in that downstream of the Y connector is disposed opposite each conduit (26, 27) a member (36, 37) which can engage alternately in one or the other of the conduits (26, 27) to prevent the passage of the balls (7). 8. Device according to claim 7, characterized in that said member is a finger (36, 37) biased by an electromagnet (38, 39), the end of this finger being able to project inside the conduits (26, 27). 9. Device according to any one of claims 7 or 8, characterized in that the distance H between the organs or fingers (36, 37) and the inlet (40) of the Y-connector (35) is determined so that each branch of the Y-connector (35) cannot contain any ball (7) capable of hindering the passage of a ball in the other branch of the fitting (35). 10. Device according to any one of claims 1 to 9, intended for throwing balls (7) on a tennis table (2), this device being intended to be placed opposite one of the ends of the table opposite the player, characterized in that the means for collecting the balls returned by the player comprise a net (41) stretched over the table (2) in front of the throwing head (3) and facing the player , this net comprising a central window (43) disposed opposite the launching head (3), in that under the lower edge (44) of the net (41) extends a chute (45) for receiving the balls which has two slopes inclined towards the middle of it, the lowest point of this chute (45) comprising a bale (46) for collecting bales which is connected by a pipe (47) to the main pipe (5) connected to the wind tunnel (4) for propelling the balls. 11. Device according to claim 10, characterized in that the section of the chute (45) is in an arc. 12. Device according to any one of claims 1 to 11, characterized in that the launching head (3) is connected to an electrical control panel (48) which comprises four buttons (49, 50, 51, 52) to adjust the speed of rotation of the rollers (8, 9, 10, 11), a button (52a) for adjusting the duration between the positions of engagement and withdrawal of the member (36, 37) which allows route the balls alternately in one or other of the conduits (26, 27) and a button (54) setting speed of the launch head (3). 13. Device according to claim 12, characterized in that it comprises buttons (55a, 55b) for reversing the direction of rotation of two of the four rollers (8, 9, 10, 11). 14. Device according to any one of claims 1 to 13, characterized in that opposite the launching head (3) is disposed a plate (61) associated with means for adjusting its inclination (b) relative to a horizontal and / or vertical plane, this plate intersecting the trajectory of the balls (7) in order to deflect them. 15. Device according to any one of claims 1 to 14, characterized in that the entire device is housed in a box (1) parallelepiped comprising two parts (1b, 1c) articulated together and foldable one on the 'other. 16. Device according to any one of claims 1 to 7, characterized in that the means for conveying the balls to the two launching heads comprise a main pipe (5) connected to an air blower (4) and connected by a Y-connector (65) with two pipes (5a, 5b) connected to each of the launching heads and each having a vent (61) which can be closed by the balls (7) and in that upstream of each head a roller (62) made of elastic material protruding inside the pipe (5a, 5b) is provided and capable of blocking the balls (7) when it is stopped and propelling them towards the launching head when controlling its rotation. 17. Device according to any one of claims 1 to 16, characterized in that the launching heads comprising the rollers (8, 9; 10, 11) are arranged on supports making it possible to adjust the height of each of the heads launch.

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