FR2624036A1 - METHOD AND DEVICE FOR PROJECTING A PRODUCT ON THE OPPOSITE FACES OF A PANEL - Google Patents

Abstract

The present invention relates to a method and a device for spraying a product, for example paint, on both sides of a panel 88 which may be curved. The latter moves horizontally between two paint spray guns 54, 56 mounted on a frame 34. The guns move vertically in translation while remaining vis-à-vis. The paint ejection nozzles 64 are mounted on sectors 60 movable in rotation relative to the bodies of the guns 54, 56. The paint jets can therefore have a constant orientation with respect to a plane tangent to a median surface of the panel at the bottom. point of impact. This device allows in particular the simultaneous painting of the two faces of a curved panel.

Description

l

  METHOD AND DEVICE FOR PROJECTING A PRODUCT ONTO THE FACES

OPPOSITE OF A PANEL

DESCRIPTION

  - The present invention relates to a method and a device for projecting a product, in particular paint, on the opposite faces of a panel which can be curved. In the aeronautical and space fields, it is necessary to paint or to protect with the aid of a product of protection of the panels whose shape is generally curved because it can be, for example, elements of a fuselage. At present, to paint these panels, we use the

  classical methods of industrial painting.

  Generally, the panel is brought to a loading station where it is hung under a beam running in an overhead rail. An overhead crane operates the assembly and positions the switches so that the panel can be brought manually into a paint booth. Inside the latter, the application of paint is carried out manually by an operator who uses a pneumatic gun. As the panels are generally large and can reach several meters in height and / or length, there are

  some difficulty painting the upper and lower parts.

  To paint the upper parts (which can be at a distance from the ground of the order of 2.5 meters), a walkable surface is used, while, for the lower parts (located at

  about 0.5 meters from the ground), The operator is forced to bend down.

  This succession of displacements in an unfavorable environment

makes this hard work.

  There are however automated painting systems. In a first system, an operator performs the application of paint or protective product to the first part by manually driving a robot. The movements of it are recorded as well as the instructions for the products, that is to say the nature of these depending on the location to be painted or protected, which constitutes the painting or protection program. for this type of parts. In a second system, the operator performs the application of the protective product or paint on the first part by training a puppet, Lighter than the robot, this puppet being called "syntaxer". It is the movements of the syntax that are recorded, as well as the instructions for the products, constituting the program for this type of part. This program is executed by the robot during processing

  subsequent series of pieces of this type.

  In a third system, the operator drives a puppet which represents the robot and the movements made by the puppet are reproduced by the robot which thus performs the first part. It is the movements of the robot that are recorded, as well as the product instructions, which constitutes the

  program for the type of parts envisaged.

  Finally, in other systems, a computer is used which determines the movements of the robot as a function of the coordinates of certain points of the part. For example, a programmer can give the calculator the coordinates of certain points linked to each other by speeds and accelerations, as well as the instructions for the products. The computer performs a calibration in order to calculate an average and correct any errors, this average constituting

  the program for the type of parts considered.

  Although these systems are automated, they have a number of disadvantages when it is necessary to paint both sides of a curved panel. In fact, all of these systems using robots execute only one side of the panel at a time. To paint or protect the two sides, you must either flip the panel, or pass the robot to the other side of it, or put two robots face to face. In all cases, the program for the first side is different from the program for the second side. A large memory capacity is therefore required and it must be checked that the face of the panel facing the robot corresponds to the program selected. In addition, you must ensure the correct positioning of the part in space, which requires

special hanging tools.

  The present invention aims to eliminate these drawbacks by proposing a method and a projection device which make it possible to simultaneously treat both sides of a panel by having a minimum number of controlled axes for controlling the devices for applying the product. and who does

  do not need to have a program for each type of room.

  According to the invention, the method consists: - of placing at least one pair of projection devices face to face in an arrangement such that a fictitious point of impact common to each pair of devices is placed on a median surface located equidistant from the opposite faces of the panel, each device having an orientation determined with respect to a plane tangent to this median surface and passing through said fictitious point of impact, and being located at a given distance from this plane; and - to generate a relative displacement between the panel and the projection apparatuses by maintaining the latter in

said provision.

  Using two facing projection devices

  opposite allows both sides to be treated simultaneously and to reduce the duration, and therefore the cost, of an operation. In addition, by permanently maintaining these devices in a determined orientation relative to the plane tangent to the median surface of the panel at the fictitious point of impact, and at a given distance from this plane, the two sides of a panel can be treated simultaneously. curve using a single program, having only two movements to control for projection devices, for example, as we will see later, a translation and a rotation of the supports on which the projection devices are mounted projection.

  In the present description, the word "jet" is taken

  in its most general sense and can designate a mist emitted by a sprayer as well as a jet of liquid ejected under pressure. Given that two projection devices emitting jets of product are used on each of the faces of a panel, it is understood that there are at least two points of impact, that is to say one on each side of the panel. In this

  description, the expression "real point of impact" can designate

  both a small spot corresponding to the place where the product is deposited on the panel at a given instant and the center of this spot if devices are used to cover a relatively large area, for example a sprayer. The expression "the fictitious point of impact" designates in all cases the middle of the segmeht joining

  the actual impact points of each face.

  According to another aspect of the process which is the subject of the invention, said relative displacement is generated between the panel and the projection apparatuses by scrolling the panel between the projection apparatuses in a first direction tangent to said median surface and by simultaneously animating the apparatuses for projecting a regular back-and-forth movement in a second direction perpendicular to the first and tangent to the median surface, the projection devices being maintained in said arrangement by simultaneously moving them in a third direction perpendicular to the first direction and the second direction and by orienting them simultaneously around a common axis parallel to the first direction and passing through the

fictitious point of impact.

  According to another aspect of the method of the invention, the panel is first scrolled in front of a learning system which determines the shape and the dimensions of the panel and a program is established on the basis of these characteristics which then generates the said panel. relative displacement between the panel and the

projection devices.

  An individual program is thus established for each panel to be treated, so that it is no longer necessary to have a program for each type of part, as in the prior art. This required a large memory capacity

  and therefore a more complex and costly device.

  The invention also relates to a device for

the implementation of this process.

  According to the main characteristic of this device, it comprises: at least one pair of projection devices arranged face to face and having a common fictitious point of impact, - means for generating a relative displacement between the panel and the devices projection by keeping the latter in an arrangement such that their common fictitious point of impact is placed on a median surface located equidistant from the opposite faces of the panel, and that their orientation relative to a plane tangent to this median and passing surface by said fictitious point of impact, as well as their

  distance to this plane, remain constant.

  Preferably, the means for generating a relative displacement between the panel and the projection apparatuses comprise: - first means for scrolling the panel between the projection apparatuses in a first direction contained in said median surface, - second means for animating simultaneously the projection apparatuses of a regular back-and-forth movement in a second direction perpendicular to the first direction and tangent to the median surface, - third means for simultaneously moving the projection apparatuses in a third direction perpendicular to the first direction and in the second direction, and - fourth means for simultaneously rotating the projection apparatus about a common axis parallel to the

  first direction and passing through The fictitious point of impact.

  Preferably, the projection devices are mounted on trolleys capable of moving simultaneously on two parallel uprights of a support frame, under the action of the second means, the support frame itself being able to move in its plane in said third direction, under the action of the third means, and each projection device being mounted on one of the carriages so as to be able to pivot

  around said common axis, under the action of the fourth means.

  In this case, the second means comprise a cable and pulley return system controlled by drive means and arranged on the frame so that an actuation of the drive means causes simultaneous movement, in the same direction and on the same length, carts. Preferably, the first means scroll the panel successively in front of a learning system, then between the projection devices, the learning system determining the shape and the dimensions of the panel and transmitting these characteristics to a computer which establishes a program of command of the second, third and fourth means when the

  panel scrolls between projection devices.

  The invention will appear better on reading the

  description which follows, given by way of example only

  illustrative and in no way limitative, with reference to the accompanying drawings in which: - Figure 1 is a schematic top view of a painting installation comprising a device according to the invention, and Figure 2 is a schematic elevational view of a device according to the invention, seen according to the arrow F of FIG. 1. If we refer to FIG. 1, we see that the painting installation firstly comprises a loading station 10 by where the panels arrive. to paint. The loading station 10 comprises one or more rectilinear rails 12 making it possible to move the panels or to leave them in the waiting position. The panels are hooked by their upper part to the rails 12. A transfer beam 14 maneuvered using a traveling crane (not shown in FIG. 1) can be moved between a first position 14a shown in solid lines and a second position 14b shown schematically in broken lines. In position 14a, the beam 14 is located substantially in the extension of the rail 12, while in position 14b, it is in the extension of a rail 16, similar to the rail 12, which allows the panel to pass through. first in front of a learning system 18, then in front of the painting device

26 object of the invention.

  The learning system 18 is a vision and telemetry device which can comprise, for example, two detectors 19 between which the panel passes. The system 18 determines the characteristics of the panel, such as its shape and dimensions. It is connected to a computer 20 which establishes a painting program as a function of these characteristics. This program fully automatically controls the

  painting device 26 which will be described in more detail below

  below with reference to Figure 2.

  A partition 22 shown in phantom in Figure 1 and having an opening 24 separates, in the painting installation illustrated in this figure, the area where the learning system 18 is located and the computer 20 of the area where is located the painting device 26. The opening 24

  comes in the form of a thin vertical slit (i.e.

  say perpendicular to the plane of Figure 1), its width being just sufficient to allow the passage of the panel. This partition 22 protects the rest of the installation against

  any paint splashes.

  We still see in Figure 1 a second transfer beam 28. This is movable between a first position 28a shown in solid lines and one or more positions 28b shown in broken lines. In position 28a, the beam 28 is located in the extension of the rail 16, but on the side opposite the beam 14 relative to the latter. The beam 28, which can be operated by an overhead crane, makes it possible to transfer the panels leaving the painting device 26 and to bring them inside an oven 30 where they are dried. A set of rails 32 located at the top of the oven allows the panels to be transferred from one end to the other of the latter. When the beam 28 occupies one of the positions 28b, it is in the extension of a rail 32. The rails 32

  can be made like rails 12 and 16.

  A painting operation in the installation illustrated in Figure 1 takes place as follows: The panels to be painted are hooked by their upper part to the rails 12, which allows them to be brought to

  the right end of these looking at the figure, that is

  say in the vicinity of the beam circulation zone 14.

  Thanks to the traveling crane, the latter is brought in front of the rail 12 where the panel to be painted is located and the latter is transferred from the rail 12 to the beam 14. This transfer can be carried out by any means known in the field of handling. . The beam 14 is at this time in position 14a then, when the panel is hung on it, it is moved to position 14b. By a reverse maneuver of the previous one, we detach the panel from the beam 14 and hang it on the rail 16. It then moves along it, from right to left looking at Figure 1. It passes first in front of the learning system 18, between the two detectors 19. As the panel scrolls between the detectors 19, the system 18 determines the exact shape and dimensions of the panel and these characteristics are communicated to the computer 20 which establishes the painting program according to the shape thus determined. The panel continues its way, 'passes through The slot 24 of The partition 22

  and arrives at the device 26.

  In the preferred embodiment illustrated here, and which will be described in more detail below with reference to FIG. 2, the device 26 essentially consists of a frame having two vertical uprights Along which the projection projectors move. paint or spray guns. The movements of the frame, of the guns relative to this frame and the sending of paint to the panel are determined, as the latter moves, by the established program

  beforehand by the computer 20.

  Once the operation is complete, that is to say once the panel is completely removed from the device 26, it is at the left end of the rail 16 looking at FIG. 1. The beam 28 is then brought in position 28a and the panel is transferred from rail 16 to this beam. This can be done in the same way as before. The traveling crane carrying the beam 28 is then maneuvered until the beam reaches one of the positions 28b. If necessary, the panel can be subjected, at this level, to a desolvation operation. The panel is then detached from the beam 28 and hung on the corresponding rail 32. It can therefore cross the oven at the appropriate speed so that the drying is completed during this crossing. When the panel arrives at the end of the rail 32 opposite to the beam 28, that is to say its straight end by looking at the figure, the beam 14 is brought into an intermediate position between positions 14a and 14b and in which it is in the extension of the rail 32. The panel is then detached from the latter and hung on the beam 14, then the traveling crane maneuvers the latter to take the panel

to an evacuation system.

  We will now describe The projection device of

  painting 26 object of the invention with reference to Figure 2.

  In the preferred embodiment, the device 26 essentially consists of a frame 34 comprising two parallel vertical uprights 36 and 38, substantially the same length and

262403'6

  the upper and lower ends of which are connected by horizontal crosspieces 40 and 42 respectively. This frame is located in a plane perpendicular to the direction of movement of the panel 88 and it is mounted on a fixed frame 43 so as to be able to move in its plane in a horizontal direction contained in this plane, that is to say from right to left and vice versa, looking at Figure 2. For this purpose, a screw-nut system is mounted between the upper part of the frame 34 and the fixed frame. The nut is constituted by a connecting piece 44 fixed in the middle of the upper crosspiece 40. This nut cooperates with a horizontal screw 46 supported by the frame and operated by a motor 48. Rollers 50 fixed on the lower crosspiece 42 of the frame 34 allow it to be guided by a rail 52

  integral with the frame, during this movement.

  The device further comprises two paint spraying devices, called "spray guns" in the remainder of this text for convenience, arranged face to face on

frame 34.

  The first of these pistols, bearing the reference 54, is mounted on the vertical upright 36 of the frame 34, while the second pistol 56 is mounted on the vertical upright 38. The

pistols 54 and 56 are identical.

  Each of the guns 54, 56 is mounted on a carriage, 58 movable in translation along the upright 36, 38, the carriages 55 and 58 being at the same height on the frame 34, as shown in FIG. 2. In its turned part towards the inside of the frame 34, each of the carriages 55, 58 supports a toothed sector 60 movable in rotation relative to this carriage and on which are mounted nozzles 64 used for the ejection of paint or any other product than the '' we wish to place on the panel. The two toothed sectors 60 have a common axis of rotation passing through a fictitious point of impact common to the two guns 54, 56 and perpendicular to the plane of the frame 34. A toothing. 61 formed on each of the toothed sectors 60 is meshed on a screw. endless 62, with an axis parallel to the uprights 36 and 38,

  rotatably supported by the corresponding carriage 55, 58.

  Consequently, the rotation of each screw 62, controlled by a motor 63, causes that of the toothed sector 60 around the axis

common above.

  In the particular case described here, there is a nozzle 64 at each end of the toothed sectors 60 and the incidence of the jet projected by each of the nozzles on the corresponding surface of the panel is approximately 45. However, it would not go beyond the scope of the invention to equip each projection device 54, 56 with a single nozzle placed, for example, in the center of the arc formed by it, or with a number of nozzles greater than 2. It would also not depart from the scope of the invention to use two projection devices equipped with a different number of nozzles, or with the same number of nozzles, but the incidence of which relative to the corresponding surface of the panel is not the same. The number and arrangement of the nozzles depends on each application

particular consideration.

  Finally, a flexible pipe 66 makes it possible to bring to each spray gun 54, 56 the paint as well as the electrical energy necessary for the control of the motors 63. The pipe 66 can be a pipe of large dimensions containing both the pipes more small diameter used to supply each nozzle 64 individually as well as the electrical wires supplying the motor 63. However, it would not go beyond the scope of the invention

  using a different layout.

  In the example described here, the hose 66 passes over a pulley 68 carried by the carriage 58, which makes it possible to maintain it without subjecting it to stresses which risk deforming it as the carriage 58 travels along the upright. 38. However, the presence of the pulley 68 is not compulsory, the main thing being that the hose 66 has a length and a

  sufficient flexibility to follow the movements of the carriage.

  The device illustrated in Figure 2 also includes a system. return allowing the two pistols 54 and 56 to be moved simultaneously and at the same speed along the uprights 36, 38. It can be seen that this return system consists first of all of a first target 70, one end of which is fixed to the upper part of the carriage 55 of the gun 54. From this point, the cable 70 has a first substantially vertical part and passes over a pulley 72 located at the junction between the upright 36 and the upper crosspiece 40 of the frame 34. The cable 70 then has a substantially horizontal part and passes over a pulley 74, arranged like the pulley 72, but which is located at the junction between the crosspiece 40 and the upright 38. The cable 70 then has a substantially vertical part parallel to the upright 38 and passes under another pulley 76 whose axis is fixed to the lower part of the upright 38. Finally, the target 70 has a last vertical part between the pulley 76 and the part

  lower of the carriage 58 of the gun 56 to which it is fixed.

  The return system comprises a second cable 78, one end of which is fixed to the upper part of the carriage 58. This cable 78 has a first substantially vertical part and passes over a pulley 80 disposed at a certain distance from the pulley 74 at the level of the junction between the upright 38 and the upper crosspiece 40. The cable 80 then runs along the upper crosspiece 40 of the frame 38 to a pulley 82 disposed in the vicinity of the pulley 72 in the same manner as the pulley 80 relative to the pulley 74. However, between the pulleys 80 and 82, the target 78 makes a dead turn around a drum controlled by a motor 84 carried by the connecting piece 44. The motor 84 drives this drum in rotation about an axis horizontal perpendicular to the plane of the frame 34. After having passed over the pulley 82, the cable 78 has a vertical part up to the lower part of the upright 36 which it runs along before passing under a pulley 86 disposed at the lower part d u upright 36, like the pulley 76 at the bottom of the upright 38. After having passed around the pulley 86, the cable 78 has a last vertical part between the latter and the part

  lower of the carriage 55 o it is fixed.

  Thus, when the motor 84 is set in motion so as to drive the drum in the direction of the arrow F1, this has the effect of moving the cable 78 from the pulley 82 towards the pulley 80. Consequently, the end of the cable 78 fixed to the lower part of the carriage 55 pulls it down. A given angle rotation of this drum therefore causes a displacement of given length x of the carriage 54 downwards. This has the effect of driving down, of a length x, the part of the cable 70 comprised between the pulley 72 and the carriage 55. The other end of the cable 70 therefore moves downwards by a distance x. Thus, the two carriages 55 and 58 are moved down by an equal distance. The motor 84 therefore makes it possible to simultaneously move the two carriages 55 and therefore the two pistols 54 and 56. These remain vis-à-vis during this movement if care has been taken to mount the carriages 55 and 58 at La same height

  on the uprights 36 and 38 of frame 34.

  We also see in Figure 2 the rail 16 on which is hung the panel 88 via a connecting system 90 shown schematically in phantom. The arrangement is such that the rail 16 is located in the vicinity of the upper cross member 40, but slightly below it, so that the rail 16, the panel 88 and the attachment system are located inside the space defined by the uprights 36 and 38 and the crosspieces 40 and 42. The rail 16 is oriented perpendicular to the plane of the frame 34 and the attachment system 90 is such that the direction of advance defined by the rail is parallel to a tangent to the middle surface of the panel. In FIG. 2, the frame 34 occupies its average position, that is to say that the rail 16 is located approximately in the middle of the crosspiece 40, but this position can vary thanks to the screw-nut system 44, 46 depending the curvature of the panel and the location of the panel that you want to paint. In any case, this movement is limited because the rail 16 must

14 2 2624036

  always be between the amounts 36 and 38.

  The operation of the device illustrated in FIG. 2 is as follows: At the start, the pistols 54 and 56 are located at the upper part of the frame 34 and occupy the positions 54a and 56a shown in solid lines. The painting program is established by the computer 20 as the panel passes in front of the learning system 18. According to this program, the frame 34 is moved by the screw-nut system 44, 46 so that the common fictitious point of impact of the guns 54 and 56 is on the median surface located equidistant from the opposite faces of the panel. Still according to this program, the toothed sectors 60 are oriented simultaneously by means of motors 63 actuating the screws 62, so that the guns 54 and 56 carrying the nozzles 64 have the desired orientation or incidence relative to a tangent plane at the middle surface

  above and passing through the fictitious point of impact of the pistols. The panel 88 then advances along the rail 16 in one direction

  perpendicular to the plane of the frame 34 until the front part of the frame is between the two pistols

54 and 56.

  The advance of the panel 88 is stopped and the engine 84 is started so that the two pistols 54 and 56 descend simultaneously along the uprights 36 and 38. During this movement, the frame 34 is moved. If necessary for the using the screw-nut system to maintain the fictitious point of impact on the middle surface of the panel. By construction, the distance separating each pistol from the plane tangent to this median surface,

  at the fictitious point of impact, remains constant during this displacement.

  On the other hand, we maneuver simultaneously and almost

  continues, depending on the curvature of the panel, the screws 62 in order to constantly orient the toothed sectors 60 so that the orientation of the spray guns, that is to say the incidence of the paint jets, relative to the tangent plane at the median surface of the panel at the point of fictitious impact, remains constant. Pistols

2624036

  54 and 56 thus arrive at the bottom of their stroke, in position 54b and 56b respectively, (these positions are shown in lines

mixed in Figure 2).

  A layer of paint was therefore deposited on each face of the panel on a vertical strip thereof having a certain width. The panel can be advanced (perpendicular to the plane of the figure) by a distance equal to the width of this strip and a paint application is repeated on a second strip during the upward movement of the guns, the motor 84 being actuated in reverse. We continue so on

  until the entire panel 88 is painted.

  It should be noted that, for safety reasons, the part of the pistols 54 and 56 comprising the endless screw 62 and the toothed sector 60 is protected by a skirt 92 which leaves no

  appear as the spray nozzles.

  Thus, the method and the device which are the subject of the invention have particularly advantageous advantages, the main one being that they make it possible to simultaneously treat the two faces of the panel with a minimum number of controlled axes. Indeed, the translation of the guns is simultaneous and the rotation of the toothed sectors 60 can be controlled with the same program. The only movements are therefore the displacement of the panel 88, the simultaneous displacement of the pistols in translation along the uprights 36 and 38, the simultaneous rotation of the toothed sectors 60 and the displacement of the

  frame 34 using the screw-nut system 44, 46.

  In addition, the use of the learning system 18 associated with the calculator 20 makes it possible to establish an individual program for each panel immediately before the actual painting operation. -It is no longer necessary to carry out learning operations as in the prior art, which takes time and makes the installation more complex, and therefore more expensive, by the need to have memory capacities important. Of course, all the movements described above are synchronized and function of each other; in any case, they are all controlled by the program established by the computer. This avoids all the prior operations which were necessary with the devices of the prior art, and in the first place the individual programming of parts by an operator, either on site or in a simulator. There is no longer any storage, management, communication or program loading operations, or program modification in the event of modification of the parts. In addition, it is no longer necessary to carry out an operation of recognizing a part or of a face thereof and it is possible to execute both faces simultaneously without the need to turn the part or use

  two guns with two different programs.

  In addition, the device which is the subject of the invention is light and simple to produce. Its movements are simple, which results in a simplified management of movements. Large panels can be treated as well as a series of smaller panels and it is easy to orient the nozzles to optimize the application of the product. This solution is inexpensive mechanically (simple construction) and its management is

very simple.

  Finally, the installation has good flexibility since the various movements make it possible to process panels of various shapes and sizes, and even panels having a significant curvature. Such a device makes it possible to treat flat or curved panels of thickness varying between 1

and 150 mm.

  If the above description has been made in the case

  particular of the projection of paint, such a device can be used to deposit on the panels any type of product, that is to say not only paints, whether it is a primer or a finishing layer, but also penetrant materials, chemical machining, rinsing, or even varnishes or wood treatment products, anti-scratch products to protect surfaces or finishing products from composite materials, etc. The device according to the invention can also be used to perform the simultaneous blasting of the two faces of a thin panel, in

  avoiding deformations of this panel in the impact zone.

  All materials receiving treatments or protections

  spray can be treated with this device.

  In the frequent case where the treated panels have a uniform curvature, there are simple connection functions between the movements of the carriages along the uprights and the angles of orientation of the projection devices around their common axis and the lateral displacements of the frame. . So he is

  possible to make these connections mechanically, without calling

  to an electromechanical system controlled by the computer.

  Finally, it is understood that the invention is not limited to the sole embodiments which have just been described, but that variants can be envisaged without thereby departing from the scope of the invention, in particular as regards the movements of the different parts and the control of these movements as well as the supply of guns with paint and / or electrical energy. Possibly, it would not go beyond the scope of the invention to keep the guns stationary and to move the panel relative thereto, or to use several pairs of projection devices simultaneously,

identical or different.

Claims (8)

  1. A method of projecting a product simultaneously on two opposite sides of a panel (88), this process being characterized by the fact that it consists: - in placing at least one pair of projection devices face to face ( 54, 56) in a provision such that a fictitious point of impact common to each pair of devices is placed on a median surface located equidistant from the opposite faces of the panel (88), each device having an orientation determined relative to to a plane tangent to this median surface and passing through said fictitious point of impact, and being located at a given distance from this plane; and - to generate a relative displacement between the panel (88) and the projection apparatuses (54, 56) while maintaining these last in said provision.   2. Method according to claim 1, characterized in that generates said relative displacement between the panel (88) and the projection devices (54, 56) by scrolling the panel between the projection devices in a first tangent direction at said median surface and simultaneously animating the projection apparatuses (54, 56) with a regular back-and-forth movement in a second direction perpendicular to the first and tangent to the median surface, the projection apparatuses being held in said arrangement by simultaneously moving them in a third direction perpendicular to the first direction and the second direction and by orienting them simultaneously around a common axis parallel to the first direction and passing through the point of fictitious impact.   3. Method according to any one of claims 1   and 2, characterized by the fact that the panel (88) is first made to pass in front of a learning system (18) which determines the shape and the dimensions of the panel and a program is established from these characteristics which then makes it possible to to generate said relative displacement between the panel (88) and the devices projection (54, 56).   4. Device for projecting a product simultaneously on two opposite faces of a panel (88), this device being characterized by the fact that it comprises: - at least one pair of projection devices (54, 56) arranged face to face and having a common fictitious point of impact, - means (16, 48, 63, 84) for generating a relative displacement between the panel and the projection apparatuses by maintaining the latter in an arrangement such as their point of the common fictitious impact is placed on a median surface located equidistant from the opposite faces of the panel, and that their orientation relative to a plane tangent to this median surface and passing through said fictitious impact point, as well as   their distance from this plane remains constant.   5. Device according to claim 4, characterized in that the means for generating a relative movement between the panel and the projection devices comprise: - first means (16) for scrolling the panel (88) between the projection devices (54, 56) in a first direction contained in said median surface, - second means (84) for simultaneously animating the projection apparatuses with a regular back-and-forth movement in a second direction perpendicular to the first direction and tangent to the median surface, - third means (48) for simultaneously moving the projection apparatuses in a third direction perpendicular to the first direction and the second direction, and - fourth means (63) for simultaneously rotating the projection apparatuses projection around a common axis parallel to La   first direction and passing through The fictitious point of impact.   6. Device according to claim 5, characterized in that the projection devices (54, 56) are mounted on carriages (55, 58) capable of moving simultaneously on two parallel uprights (36, 38) of a frame support (34), under the action of the second means (84), The support frame (34) being tui-m & me able to move in its plane in said third direction, under the action of the third means (48) , and each projection device (54, 56) being mounted on one of the carriages (55, 58) so as to be able to pivot around said axis   common, under the action of the fourth means (63).   7. Device according to claim 6, characterized in that said second means comprise a target and pulley return system (70 to 82, 86) controlled by drive means (84) and arranged on the frame (34) so that an actuation of the. drive means (84) generates a simultaneous movement, in the same direction and on the same length of the carriages (55, 58).   8. Device according to any one of claims   7, characterized in that the first means (16) make the panel (88) pass successively in front of a learning system (18), then between the projection devices (54, 56), the learning system determining the shape and dimensions of the panel and transmitting these characteristics to a computer (20) which establishes a control program for the second (84), third (48) and fourth (63) means when the   panel scrolls between projection devices.