FR2857901A1 - POST AND METHOD OF PRINTING BY SERIGRAPHY - Google Patents

Abstract

The invention relates to a printing station (12) by serigraphy of two objects of revolution arranged with object carriers (18A, 18B). The printing station comprises: - ink scraping means (32, 34) extending to the right of the object carriers (18A, 18B), - first drive means (30) of the screen in translation, - second drive means (38) adapted to modify the spacing between the scraping means (32, 34) and the object carriers, - control means (40) of the first (30) and second (38) drive means adapted to first ensure a temporary approximation of the scraping means (32, 34) of the first single holder (18A) and then a temporary approximation of the scraping means (32, 34) of the only second holder (18B) .The invention also relates to a printing process using this printing station.

Description

The invention relates to a silkscreen printing station and a

  printing method using such a printing station.

  Such a printing station is generally but not exclusively mounted in a screen printing machine for decorating conical or cylindrical containers.

  A printing machine of this type is described in particular in the French patent application published under the number FR 2 782 292. It comprises a turret which carries at its periphery a plurality of carrier objects and a plurality of fixed work stations which are distributed Circularly 10 around the turret to the right of the carriers objects. The turret is rotated to present the objects arranged on the object holders successively to different workstations.

  Generally, these workstations include a loading station objects to print, a tracking station, a dusting station, a flame station, a varnishing station, one or more printing stations, one or more positions drying and unloading station.

  A printing station consists of a squeegee, means for driving this squeegee, means for driving a screen having the pattern to be printed and means for controlling the squeegee drive means. of the screen.

  During a print phase of an object, the doctor blade is brought to bear on a surface of the mesh of the screen immediately below which the object to be printed is disposed. The screen thus clamped between the doctor blade and the object is moved parallel to its main plane. During this movement, the squeegee pushes the ink through the mesh on the object to be printed. In parallel, the object carriers are rotated in conjunction with the movement of the screen and at an identical peripheral speed so that the scene is printed on the periphery of the object.

  However, this type of machine can not operate at a rate greater than 100 strokes / minute.

  To increase this rate, it has been proposed in particular in the document EP 0 727 309, a dual production printing machine comprising a turret to which are fixed vertically-paired object holders parallel to the central axis of the machine. . Each pair of supports is pivotable about an axis parallel and median to the axes of rotation of the object carriers. After printing by a first printing station of an object fitted on a first support, the two supports pivot relative to each other to bring the second support to a second printing station arranged on around the frame next to the first printing station.

  This machine increases printing productivity by increasing the number of carriers for a fixed turret diameter.

  However, this machine is complex because of the additional mechanism of pivoting the pair of microscope carriers. In addition, this machine requires to double the number of printing stations for the same color. This makes its construction difficult in the case of printing in five or six colors.

  Furthermore, US Pat. No. 3,026,003 describes a machine capable of printing two objects simultaneously. The dual production machine includes a carrier conveyor belt from one processing station to another, a printing station, and a means for positioning a pair of microscope holders near a screen. the printing station.

  The printing station comprises two scrapers extending transversely on the screen, means for driving the screen and a drive means capable of bringing the two scrapers closer and further away from the screen. Two identical patterns are made side by side on the screen.

  At the beginning of the printing, the doctor blades are brought into contact with the screen and objects simultaneously and at the same end of each pattern. Then, the screen 25 is moved longitudinally in a defined direction. As the objects are arranged on bearings, the movement of the screen rotates the objects by friction. At the end of the screen, both objects were printed. The scrapers are lifted and the screen is moved in a reverse direction to return to its original position.

  To allow the simultaneous printing of the two objects, the axes of the supports thereof must be spaced at a distance at least equal to the length of the pattern to be printed, that is to say the perimeter of the receiving object. .

  The spacing between the two slides makes the machine cumbersome and in particular such object carriers can not be so implanted on a relative turret without this turret has a disproportionate diameter.

  An object of the invention is to provide a compact print station.

  For this purpose, the invention relates to a printing station of the aforementioned type, characterized in that it comprises the control means, adapted to ensure, during successive phases of movement of the screen, first a first temporary approximation of scraping means of only the first object-holder and a second temporary approximation of scraping means of the only second object-holder.

  The invention also relates to a screen printing process of a decoration on two objects of revolution each mounted on a first and a second movable mobile object holder, characterized in that it comprises the following successive steps a first step of bringing scraper means and the first object-holder closer together by enclosing between them a screen comprising the decor to be printed; a first step of translational movement of the screen with respect to the scraping means and first support-object, - a step of separation of the scraping means and the first object-holder, a second step of approaching the scraping means and the second object-holder sandwiching said screen, and-a second step of translational movement of the screen relative to the scraping means and the second object carrier.

  The invention will be better understood on reading the description which will follow, given solely by way of example with reference to the drawings, in which: FIG. 1 is an axial sectional view of a printing machine according to FIG. 'invention; - Fig 2 is a sectional view along the line 11-11 of Figure 1; FIG. 3 is a perspective diagram showing the elements of a printing station according to a first embodiment of the invention; FIGS. 4A to 4D are synoptic views illustrating different steps of the printing method according to the first embodiment of the invention; and FIGS. 5A and 5B are synoptic views of a second embodiment of the invention.

  The machine shown in Figure 1 is intended to print objects such as cylindrical tubes by a screen printing process.

  It comprises in known manner on the ground a circular frame 2 of central axis A1, a table 4, a rotating turret 6 and a fixed plate 8.

  The frame 2 carries radially at its periphery several work stations such as for example a drying station 10 and a printing station 12 for printing from a screen 13.

  The turret 6 comprises a circular plate rotatable about an axis corresponding to the central axis A1 of the frame. It is able to be driven in rotation 15 step by step by a standard motor 14 of the three-phase type associated with an indexer 16.

  The fixed plate 8 extends above the turret 6 and rests, by means of rolling means on a foot disposed axially above the table 4. It is coupled to the frame by lines.

  The turret 6, visible in FIG. 2, carries at its periphery several object carriers 18. The diameter of the turret 6 is such that the object carriers 18 arrive at the right of the workstations 10, 12 for the treatment objects loaded on the carriers 18.

  Since the objects to be printed are circular containers or flexible tubes, the object carriers 18 are cylindrical mandrels on which the objects are threaded.

  The supports 18 are distributed in pairs. The supports of the same pair extend parallel to each other in a horizontal plane in a generally radial direction of the turret 6.

  The distance between the screen and the axis of a microscope support is adjustable depending on the diameter of the microscope carriers and thus the objects to be printed.

  The maximum diameter of a printable object on a printing machine is defined as being equal to twice the distance separating the screen 13 from the axis of a microscope support.

  Advantageously, the minimum distance between the axes of a pair of microscope carriers is equal to the maximum diameter of a printable object on a printing machine.

  For example, if a machine can print objects with a diameter ranging from 15 millimeters to 60 millimeters, the maximum diameter of a printable object is 60 millimeters and the minimum distance between two microscope carriers is 60 millimeters. This distance does not take into account the thickness of the two objects to be printed and a minimum distance of non-friction between the two supports of the same pair.

  Preferably, the center distance between two object carriers of the same pair is less than one and a half times the maximum diameter of a printable object.

  The object carriers are rotatably mounted on themselves about axes A2 perpendicular to the central axis A1 of the frame. The object carriers 18 are adapted to be rotated by drive means 20 arranged on the fixed plate 8. For this purpose, the object carriers 18 comprise a drive finger engaging in a groove fixed plateau 8 well known in itself and will not be described in more detail here.

  The drive means 20 of the object carriers 18 comprise a numerically controlled motor and a belt looped around a plurality of pulleys. These means are adapted to ensure in one direction or in a reverse direction, the rotation of all the carrier objects arranged around the turret 6.

  Alternatively, these drive means could also individually drive each holder object of a pair.

  In a manner known per se, an incremental encoder is able to determine the instantaneous position of the objects mounted on the carriers 18.

  Fig. 3 schematically shows in perspective a printing station 12 equipped with the screen 13 as well as a pair of object carriers 18A, 18B.

  This printing station 12 is provided with a screen 13 and comprises means 30 for driving the screen 13, scraper means 32, 34 for the ink, driving means 38 for scraping means and control means 40 able to control the drive means 30 of the screen, the drive means 38 of the scraping means and the drive means 20 of the object carriers. It further comprises an ink injection nozzle not shown and optionally one or more counter-scrapers also not shown.

  The screen 13 is formed of a rectangular frame 42 supporting a mesh 44 stretched on which the decoration 46 to be printed has been made.

  Advantageously, a single decoration 46 has been made on the mesh 44 of the screen. When it extends over the entire periphery of the object, the decor has a length equal to the outer perimeter of the object to be printed.

  In addition, according to this embodiment of the invention, the minimum length of the screen is equal to the length of the development of the decor plus two distances called overflow distance D. We call overflow distance D, the distance according to the longitudinal axis of the screen 13 corresponding to a spreading surface of the surplus of ink after a first printing movement. Generally, the minimum overflow distance is about 20 millimeters.

  The drive means 30 of the screen comprise a brushless direct current motor with digital control independent of the rotary actuating motor of the object carriers. They are adapted to move the screen to a length at least equal to the length of the decor to be printed increased by the distance separating the two scrapers. In addition, the total displacement path of the screen 13 between its extreme position after a displacement in one direction and its extreme position after a displacement in the opposite direction is less than three times the length of the decoration to be printed on the objects.

  In a manner known per se, incremental encoders are fixed at each printing station 12 to determine the instantaneous position of each screen 13.

  The control means 40 are able to manage the control of the means 30 for driving the screen and the means 20 for driving the object carriers 18 to move the screen together with the rotary movement of the object carriers and at a linear velocity equal to the peripheral speed of the carriers.

  The scraping means comprise first and second scrapers 32, 34 movable vertically, that is to say in a plane transverse to the main plane of the screen 13. More specifically, the first scraper 32 is mounted to the right of the first support slide 18A. The second blade 34 is mounted to the right of the second object holder 18B.

  Advantageously, the distance between the two scrapers is equal to that separating the axes of the two carriers.

  Preferably, each scraper 32, 34 has at its end of support on the screen a chamfer whose tip is directed to the outside of the decor to facilitate the spreading of the ink.

  The means 38 for driving the doctor blades 32, 34 are capable of independently driving each doctor blade in vertical translation between a position resting on the mesh and a position at a distance from the latter.

  The driving means 38 of the doctor blades are made by either a pneumatic cylinder or a brushless DC motor and a displacement device, for example of the rack type, in printing cases requiring a high degree of precision.

  When a pneumatic cylinder is used to actuate the movement of the doctor blades, the control means 40 include a solenoid valve and a cam box.

  The printing station 12 also comprises non-represented means for adjusting the so-called off-contact distance. This distance d corresponds to the distance between the frame 12 of the screen 13 and the object carriers 18A, 18B. This distance d must not be zero to promote the cutting of the ink and its transfer from the mesh of the screen to the object to be printed.

  Advantageously, the printing station 12 of the invention makes it possible to obtain a non-zero angle α between a fictitious plane T tangent to the object-bearing support and the planes formed by the mesh on each side of the doctor blade when this latter is in support on the mesh. This non-zero angle avoids the phenomenon of orange peel on the object to be printed and guarantees a certain quality of printing.

  The control means 40 are programmed to control the means 38 for driving the doctor blades and the screen 13 so that on the one hand a single doctor blade 32, 34 is in contact with the mesh 44 of the screen 13. during the movement thereof, and that secondly the positions in support or remote squeegees are correlated with the direction of movement A, C of the screen.

  Figures 4A to 4D show several block diagrams illustrating different steps of the printing method according to the invention.

  In an initial step, illustrated in Figure 4A, the first doctor blade 32 is moved in vertical translation by the drive means 38 to come into contact with the mesh of the screen 44 and the first object holder 18A.

  Then, the control means actuate the driving of the screen in a direction A. At the same time, the first object-bearing support 18A is rotated in the direction indicated by the arrow B. The first doctor blade 32, arranged upstream of the A mass of ink and a first end of the decoration 46 push the ink through the mesh onto the object during the movement of the screen 13 and the first holder 18A.

  When the object pushed onto the first microscope carrier has been printed (Figure 4B), the first squeegee 32 is moved away from the screen. A mass of ink extends to the second end of the decoration over an overflow distance D. Then, in a next step, the screen 13 is moved in a translation movement in the opposite direction C and the second doctor blade 34 is lowered at the mesh level of the screen.

  Advantageously, the second squeegee 34 bears on the mesh 44 at the birth of the mass of ink so that it is not necessary to use a counter-squeegee to bring the ink to the decor.

  The second object-bearing support 18B is driven in a direction of rotation E that is opposite to the direction of rotation B of the first object-carrier 18A during the step of printing the object that it was carrying.

  Thus, the object fitted on the second support 18B is printed in opposite directions relative to the printing direction of the object fitted on the first support 18A.

  The control means 40 control the media drive means, the drive means 38 of the doctor blades and the drive means 30 of the screen so that the different steps are performed synchronously.

  The maximum deflection of the screen 13 between its two extreme positions during its race is substantially equal to the length of the development of the decor plus two times the overflow distance D and the distance between the two scrapers. The total travel distance of the screen 13 for the printing of said objects is between two and three times the length of the decoration to be printed on the objects. As a result, the encumbrance of the printing station 12 is reduced.

  Moreover, as an impression is made during each movement of the screen, the duration of a printing cycle of two objects is reduced compared to the duration of printing of two objects by a single production machine. Thus, the productivity of a printing machine having such a printing station is increased compared to a single production machine.

  FIGS. 5A and 5B schematically represent two printing steps in which a second embodiment of the invention is implemented. According to this second embodiment, the printing station 12 is equipped with a screen 124 having two decors 146, 147 to be printed made one next to the other in the longitudinal direction of the screen 13.

  The minimum distance between the two decors is defined by the longest length between the overflow distance D and the length of the spacing of the carriers 18A, 18B. This distance is advantageously less than the development of the decor.

  Furthermore, the printing station 12 advantageously comprises two counter-scrapers 132, 134 fixed between the two scrapers 32, 34. These counter-forces are arranged upstream of the scrapers relative to the direction of movement of the screen to repel the surplus of ink on the decor before the squeegees.

  Alternatively, a counter-squeegee having two scraping surfaces is used.

  In a variant, the printing station 12 comprises a single doctor blade.

  In this case, the driving means of this doctor blade are able to move the doctor blade in a transverse movement parallel to the screen between a position in line with the first object-bearing support 18A and a position in line with the second carrier-holder. object 18B.

  The printing method using this second embodiment includes a first step of printing a first object shown in Fig. 5A. This step is similar to the first step of the method described in connection with FIG. 4A and will therefore not be described here.

  When the step of printing the object on the first support 18A is completed, the first squeegee 32 is removed from the first 18A microscope support.

  The screen 124 continues its movement in the same direction A as during the step of printing the object fitted on the first support 18A.

  The second doctor blade 34 is brought into contact with the screen. The second slide holder 18B is rotated B in the same direction as the rotational movement used for printing the first object.

  When the second object has been printed, the second squeegee 34 is moved away from the screen 124. Then, the screen 124 is moved in a reverse direction E to return to its initial position.

  This last embodiment requires the use of two barriers 132, 134 to bring after each printing cycle ink on the decor and upstream of it.

  Unlike the first embodiment, this embodiment does not require to reverse the direction of rotation of the carriers after printing a first object.

  Advantageously, this second embodiment offers the possibility of printing a single decoration or two different decors 146, 147 on objects 20 fitted on one pair of microscope carriers.

Claims (15)

  1. Printing station (12) by serigraphy of at least two objects of revolution each arranged on a support (18A, 18B), the printing station being able to be equipped with a screen (13) carrying at least one decoration (46, 146, 147) to be printed and comprising: - means of scraping the screen (13) in line with at least one object-carrier (18A, 18B), - first drive means ( 30) of the screen (13) in translation along its main plane, - second drive means (38) adapted to modify the spacing between the scraping means (32, 34) and the object carriers (18A , 18B), - driving means (40) of the first (30) and second (38) drive means, characterized in that said control means (40) are adapted to ensure, during successive phases of displacement of the screen (13), firstly a first temporary approximation of the scraping means (32, 34) of the only first object-holder (18A) and then a second reconciliation temporarily removing the scraper means (32, 34) from the only second holder (18B).   2. Printing station according to claim 1, characterized in that the scraping means (32, 34) comprise a single doctor blade movable in translation along a plane parallel to the main plane of the screen (13), and in that the second drive means (38) is adapted to move the doctor blade from a position in line with the first object carrier (18A) to a position in line with the second carrier (18B).   3. Printing station according to claim 1, characterized in that the scraping means (32, 34) comprise a first (32) and a second scraper (34) extending respectively to the right of the first (18A) and the second (18B) microscope carrier, the first doctor blade (32) and the second doctor blade (34) being adapted to successively approach respectively the first (18A) and second (18B) microscope carriers.   4. Print station according to claim 3, characterized in that the first drive means (30) are adapted to ensure a movement of displacement of the screen (13) at least equal to the length of the decoration to be printed increased the distance between the two scrapers (32, 34).   5. Printing station according to any one of the preceding claims, characterized in that: - the first drive means (30) are adapted to move the screen (13) in one direction and in its opposite direction, and the control means (40) are adapted to control the movement of the screen (13) successively in one direction then in the other and to control the second (38) drive means so that only the distance between the doctoring means (32) arranged downstream relative to the direction of movement of the screen (13) and its associated object support (18A, 18B) is zero.   6. Printing station according to any one of the preceding claims, characterized in that it comprises a screen (13) on which is provided a single decoration (46) intended to be applied to the objects mounted on the first ( 18A) and the second (18B) object carriers.   7. Printing station according to any one of claims 4 to 6, characterized in that the total displacement of the displacement of the screen (13) for printing said objects is between two and three times the length of 20 decor (46) to print on objects.   8. Printing station according to any one of the preceding claims, characterized in that the second drive means (38) of the scraping means (32, 34) comprise a brushless DC motor.   9. Printing station according to any one of the preceding claims, characterized in that it comprises at least one counter-squeegee (132, 134) arranged upstream of the scraping means (32, 34) relative to the direction. moving the screen (13).   10. Printing machine comprising at least two object holders (18A, 18B), characterized in that it comprises at least one printing station (12) according to one of the preceding claims and in that the distance between the axis of the first and the axis of the second object carriers (18A, 18B) is less than one and a half times the maximum diameter of an object printable by said machine.   11. Printing machine according to claim 10, characterized in that it comprises: - a turret (6) carrying at its periphery a plurality of pairs of carrier-objects (18A, 18B) rotatably mounted, and - a frame circular (2) on which at least one printing station (12) is mounted to the right of the carriers (18A, 18B).   12. Printing machine according to claim 10 or 11, characterized in that it comprises: - third drive means (20) in rotation of the carriers 10 (18A, 18B) on themselves controlled by the control means (40), incremental coding means adapted to determine the instantaneous circular position of the objects mounted on the object carriers (18A, 18B), and in that the control means (40) are adapted to controlling the actuation of the first drive means (30) as a function of this circular position.   13. Printing machine according to claim 12, in combination with claim 3, characterized in that the control means (40) are able to control the third (20) drive means so that the 20 object holders (18A, 18B) rotate in opposite directions respectively at the first and second temporary approximations of the scraping means (32, 34) and the associated object holder (18A, 18B).   14. A method of screen printing a decor on two objects of revolution each mounted on a first (18A) and a second (18B) support 25 movable in rotation, characterized in that it comprises the successive steps following: a first step of approaching scraping means (32) and the first object-bearing support (18A) by enclosing between them a screen (13) comprising the decor (46) to be printed, a first translational movement step; of the screen (13) with respect to the doctoring means (32) and the first object-carrier (1 8A), - a step of spacing the doctoring means (32) and the first object-carrier (18A a second step of approaching the scraping means (34) and the second object-carrier (18B) sandwiching said screen (13) between them, and a second step of translational movement of the screen (13). ) relative to the doctoring means (34) and the second object support (18B).   Printing method according to claim 14, characterized in that the direction of movement of the screen (13) is reversed between the first and second screen moving steps (13), and that the An object mounted on the first (18A) and second (18B) carriers is printed on the first and second steps of moving the screen (13), respectively.