EP0379447A1 - Flexible pad-printing machine - Google Patents

Abstract

A flexible pad-printing machine comprises a movable magazine (2) of printing plates arranged in matrix form. A carriage (12) movable in a direction perpendicular to that of the magazine (2) carries, on the one hand, an ink-transfer pad (15) and, on the other hand, an inking device (17). The cleaning of the printing plates during the change of the type of product is carried out automatically by means of cleaning nozzles (18, 19). <IMAGE>

Description

The invention relates to a flexible pad printing device making it possible to carry out quickly and automatically the operations linked to a change in variant of the product to be marked, namely cleaning of the plate just used and of neighboring plates which may have been inked simultaneously, and presentation in the working position of the new plate, said device having a movable carriage carrying an ink device for inking the plates during movement of the carriage and an ink transfer pad support arranged for transferring the ink from the snapshot selected on the product.

Pad printing is a well-known marking process allowing automatic and repetitive transfer of a given graphic on the objects to be marked. A pad printing device essentially consists of:
- an ink tank,
- a plate, generally consisting of a metal plate in which the graphics to be produced are debossed,
- an ink transfer pad from the plate to the object to be marked,
- a handling device specific to the machine, ensuring the displacement of the stamp and the inking of the plate,
- a transitics device allowing the objects to be marked to be presented under the stamp, and to index them automatically and precisely.

A marking cycle comprises two phases, in this case a phase of inking the plate from the ink tank, so that the intaglio is completely filled with ink, the surface of the plate remaining dry and a transfer phase by the pad of this ink on the object to be marked. To this end, the stamp is animated by an inverted U kinematics allowing it to come to apply successively on the plate, where it absorbs the ink contained in the engraving, then on the object to be marked, where it deposits this ink.

Regarding inking, there are two techniques, that of the fixed and open reservoir, from which the ink is removed by a mobile pallet, spread over the plate, the excess being brought back into the reservoir by scraping, and that of the bottomless mobile tank moving horizontally so as to alternately cover the plate and uncover it to allow access to the pad, the lower edges of the tank being provided with sealing lips preventing leaks and ensuring scraping of the surface of the cliche.

In the following developments, the second device will be presented, it being understood that all of these developments could just as easily apply to the first.

This marking method has known advantages, in particular quality and speed.

On the other hand, in the currently known embodiments, it is handicapped by an insufficient flexibility. The passage from one variant of product to another indeed requires a change of plate, which implies a mechanical operation making it possible to remove the old plate and to replace it with a new one and ancillary cleaning operations, in particular cleaning. of the plate which has just been used to prevent the remainder of ink from drying in the engraving, and a cleaning of the stamp which, after the last marking of a series, retains a part of the ink which would pollute the first marking of the new series.

The problem is made worse when working on a product whose there are many variations, which results in the management and manipulation of an equivalent number of shots.

The currently known devices require significant manual intervention for the execution of these various operations. This results in a certain difficulty in using this technology within the framework of modern production systems, where one seeks on the one hand an integration of functions, requiring that the marking be put in line with the other functions of the process, without it it is necessary to call on large buffer stocks, and on the other hand the possibility of dividing production into small series, in order to closely monitor commercial needs.

The object of the present invention is to provide a set of devices making it possible to quickly and completely automatically carry out all of the operations linked to a change of variant, and this up to a very large number of variants.

The device according to the invention is characterized in that all of the pictures constitute a store with two coordinates, the first coordinate being given by a movement specific to the store itself, making it possible to bring a row of pictures into the working position. given, the second coordinate being given by the movement of the carriage carrying the stamp and the inking device, making it possible to choose in said row the plate to be used, these two movements being controlled by numerically controlled devices, themselves controlled by the system of automation fitted to the machine, in conjunction with a code reader allowing the identification of the products to be treated.

The system essentially consists of:
- a plate store placed on the machine itself, and organized so that any plate can be quickly and automatically put into the position of use;
- a digitally controlled manipulator ensuring the movement of the buffer, the ink tank, as well as the elements for cleaning the plates;
- transitics ensuring the conveying and indexing of the product to be marked.
- the pad cleaning device.

The magazine can be in the form of a flat or cylindrical matrix or possibly in the form of a noria.

• - la figure 1 est une vue schématique en plan d'un dispositif de tampographie selon l'invention, le chariot mobile n'étant pas représenté,
• - les figures 2, 2bis et 2ter sont des coupes suivant la ligne Y-Y de la figure 1 montrant le charriot en différentes positions,
• - la figure 2-IV est une vue analogue à celles des figures 2, illustrant une variante de réalisation,
• - la figure 3 est une vue en perspective d'une variante de réalisation du magasin de clichés;
• - les figures 4 et 4bis illustrent une autre variante de magasin.

Other advantages and characteristics will emerge more clearly from the description which follows, of an embodiment of the invention, given by way of nonlimiting example and shown in the appended drawings in which:

• FIG. 1 is a schematic plan view of a pad printing device according to the invention, the mobile carriage not being shown,
• FIGS. 2, 2bis and 2ter are sections along the line YY in FIG. 1 showing the carriage in different positions,
• FIG. 2-IV is a view similar to those of FIGS. 2, illustrating an alternative embodiment,
• - Figure 3 is a perspective view of an alternative embodiment of the plate store;
• - Figures 4 and 4bis illustrate another variant store.

According to the embodiment of the invention, represented by FIG. 1, the plates 1 are gathered in a rectangular matrix and carried by a magazine 2 which can move longitudinally in xx ′ according to the arrow F1, for example by being guided by two 3.3 ′ columns and by being actuated by a screw 4 driven by a stepping motor 5, any other guidance or motorization device is of course valid.

The axis yy ′ is the main axis of the machine perpendicular to the axis xx ′, and the motorization device of the magazine 2 makes it possible to bring any row of pictures opposite this axis, this in a time very short.

Also seen in Figure 1, the product to be marked 6 which moves along the arrow F2 on a conveyor 7, and can be indexed in the marking position, on the axis yy ′, by means known per se and not shown . It may be noted that each element of the product 6 or the pallet which supports it, is identified by a code, for example bar, giving the indication of the variant to which it belongs.

A sensor 8 capable of reading said code, and therefore of detecting changes in series is arranged at the edge of the conveyor 7. In the example presented, the reading is done on the product 6 ′, at the position which precedes the marking position. . At the edge of the conveyor 7 is also arranged a device 9 for cleaning the tampon, of a type known per se, for example with an absorbent strip which can move one notch after each cleaning. This device is driven by its own motor, not shown.

A release plate 10 is centered on the transverse axis y-y′ and achieves perfect geometric continuity with the plane of the plates 1. To improve this continuity, the plate 10 is kept in contact with the edge of the matrix of plates by 11.11 ′ springs. The role of this plate 10 will appear more clearly in the following description.

Referring to the following figures, we find the plate holder magazine 2 with its 3.3 ′ guide columns and its drive screw 4, the product to be marked 6 carried by the conveyor 7, the pad cleaning device 9 , and the plate of release 10 pushed by the spring 11. There is also the entire transverse manipulator carriage part which is not shown in FIG. 1.

This part consists of a carriage 12 with horizontal movement according to arrow F3. Like the plate holder magazine 2, this comprises a guide (not shown) and a digital motorization which can be produced for example by means of a toothed belt 13 stretched between two pulleys 14,14 ′, one of which is driven by a stepper motor (not shown).

The carriage 12 carries the following elements:
- The pad 15 and its support 16, the latter ensuring the guiding and the vertical displacement of the pad according to arrow F4;
- An ink tank 17 whose bottom is constituted by the plane of the plates 1, and which is provided with sealing lips and scraping said plane, as has been said above;
- A cleaning nozzle 18 which can on demand spray a solvent capable of ensuring the evacuation of the residual ink in the plates.
- A drying nozzle 19 working in cooperation with the previous one, and capable of sending a jet of compressed air.

For health reasons, the assembly can be placed under a hood fitted with a suction, so that the solvent vapors do not spread in the workshop.

On the other hand, to avoid the presence of too large a quantity of solvent on the plates, it is possible to provide for separating the rows of plates 1 by small discharge channels, the excess solvent being recovered either at the edges of magazine 2, either by holes drilled in the magazine, and possibly recycled.

In current operation, the carriage 12 is driven according to F3 in a regular reciprocating movement, at each end of which the buffer 15 performs a vertical return trip according to F4. The right end of the movement can be chosen between the axes uu ′ (figure 2bis) and vv ′ (figure 2ter) which correspond to the extreme positions of the pictures on the magazine 2. This possibility allows selection in "y", selection in "x" having been made at the start of the series by positioning the magazine 2. The left end of the movement of the carriage 12 is fixed, and corresponds to the axis zz ′ (FIG. 2) on which the product to be marked appears 6 .

The ink tank 17 is installed on the carriage 12 so that, at the end of the left stroke, it interests the shots located at the extreme left of the magazine 2. At the end of the right stroke, the position of the reservoir 17 is variable. For short strokes (Figure 2bis) it remains inside the matrix of pictures 1. For large strokes (Figure 2ter), it can come out clearly from this matrix. The reservoir then engages on the release plate 10 which constitutes, with the plane of the photographs, an almost continuous surface.

In all cases, it can be verified that the reservoir 17 is of interest, during its course, the photograph which is in use, and which will therefore be replenished each time with ink. A number of other shots in the row are also interested, or even all, which is not a problem as long as the machine does not stop, the ink being renewed at each cycle and therefore cannot dry in the engravings.

The risk of drying exists in the event of accidental or random shutdown. This problem will be analyzed later. In the case where the fixed tank technique is used, it is then provided on the plate 10, the carriage 12 then carrying the spreading pallet and scraping ink.

Note that, in this embodiment, we could replace the release plate 10 by simply enlarging the magazine 2 on the right. This solution has the drawback of making said magazine 2 heavy, and is moreover incompatible with the other principles of plate shops which will be described later.

When a change of series is to be carried out, the sequence of operations to be carried out is at most as follows:
- the sensor 8 having detected that the product 6 ′ is the first of a new series, the buffer 15 carries out the marking of the product 6, the last of the previous series, and the system switches to "change of series"mode;
- the carriage 12 moves back to the right until presenting the pad 15 above the cleaning device 9. The pad 15 then performs a vertical cycle at the bottom of which it strikes the strip of said device, on which it gets rid of its excess ink. Immediately after, the belt makes a small longitudinal movement, and is ready for the next change of series;
- The carriage 12 then resumes its course to the right, with actuation of the nozzles 18 and 19 which, appearing above the photographs immediately after the reservoir 17, eliminate the ink that the latter has just left in the engravings. This movement continues until the right end of travel, the operation of the nozzle 18 being interrupted a little before to avoid unnecessarily drowning the plate 10;
- depending on the identity of the new variant read by the sensor 8, the magazine 2 moves along F1 to bring into the working axis yy ′ the row to which the photograph 1 corresponding to this variant belongs;
- The carriage 12 moves to the left, until the end of the race. There is then inking of the new row of plates, and the system is in the initial situation from which the new work cycle will be able to start, namely:
. displacement and indexing of the product 6 ′ which is placed in the marking position.
. simultaneously, retraction of the carriage 12 until the buffer 15 is brought vertically to the new plate;
. inking the stamp;
. return of the carriage 12 at the left end of travel;
. product marking 6 ′;
- ... etc.

As described above, the sequence of change of series may present a defect, in the case where the new photograph is near the left edge of the magazine 2 (Figure 2bis). In these cases, the ink tank 17 will no longer cover the plates 1 located towards the opposite edge. However, these photos 1 will have been inked during the first movement to the left of the carriage 12. It can therefore be expected that the ink will dry in their engravings.

One can guard against this problem by one of the following means:
- provide the carriage 12 with a second pair of nozzles 18 ′, 19 ′ symmetrical with the nozzles 18,19 with respect to the reservoir 17. During the first stroke of the carriage 12, these nozzles are actuated when they pass over the photographs 1 concerned by the risk of drying. To improve the definition of the area intervention, it can be assumed that the carriage 12 marks slight downtime at the start and end of actuation of the nozzles 18 ′, 19 ′;
- during normal work, provide every "n" cycles for an additional stroke of the carriage 12 to the right, for the sole purpose of refreshing the inking of the photographs around the right edge of the magazine 2, which are not inked during the normal cycle;
- Increase the spacing between the buffer 15 and the reservoir 17, so that when the first is on the axis uu ′, the second is on the axis vv ′. In this way, the whole row of pictures is systematically interested during the work cycle, whatever it is;
- Provide the release position of the ink tank 17 to the left and not to the right of the plate matrix, as illustrated in Figure 2-IV. It is then necessary to provide a second release plate 10 ′ disposed symmetrically with the plate 10 and operating on the same principle. The series change sequence then consists of:
. a race to the right bringing the tank to the right of the axis vv ′,
. a stroke to the left during which the cleaning nozzles 18 ′, 19 ′ are actuated. The latter must of course for this be placed in positions 18 ′, 19 ′,
. the left limit switch leading the reservoir to the plate 10 ′ and the buffer above its cleaning device 9 (which has been placed to the left of the conveyor to illustrate an arrangement which limits the spacing between the working axis zz ′ and the pictures) we can then proceed to cleaning the stamp.
- bringing the new image into position;
- the return of the carriage 2 to the initialization position (buffer in the axis zz ′, reservoir in the axis uu ′).

A simplified series change sequence occurs when the new plate 1 belongs to the same row as the old one. The sequence is then limited to cleaning the stamp 15 on the device 9, plus possibly cleaning the plates 1 which were inked previously and which will no longer be.

According to a variant of the invention, the cleaning elements are no longer carried by the carriage 12, but arranged in fixed ramps along transverse axes parallel to y-y ′. We can thus have a spraying ramp, a drying ramp, and even a brushing line if necessary. We can then, before bringing a new image into position, use the movement of the magazine 2 to present the row to be cleaned successively opposite the transverse axes corresponding to these different functions.

This variant has the advantage of separating the functions well, and the disadvantage of having to increase the travel of the magazine 2.

It appears from Figure 1, that the device has a significant development along the axis x-x ′, that is to say a large longitudinal bulk of the machine. This drawback can be eliminated by giving the plate store a different geometric configuration.

According to one embodiment of the invention, illustrated by FIG. 3, the plates are arranged on a pseudo-cylindrical structure 20, the base 21 of which is a regular polygon with "n" sides. FIG. 3 represents a dodecagon, but any other value of "n" is of course possible. The selection of the row to be used is then made by rotation of the pseudo-cylinder 20, driven by the stepping motor 22, or any equivalent device. Compared to the plane matrix, this new principle, with equivalent capacity, leads to much more development weak in the longitudinal direction xx ′.

According to another embodiment of the invention, illustrated by FIGS. 4 and 4bis, bars 23 of plates are arranged in noria (FIG. 4) and secured by a couple of chains 24. FIG. 4bis shows in end view a number of bars 23, as well as one of the chains 24.24 ′ and one of the pulleys 25.25 ′ on which the chains come to mesh. The axis 26 on which the pulleys 25,25 ′ are keyed is itself actuated by a drive motor (not shown) exercising the same function as the motor 22 presented above.

This last principle is obviously the one which offers the maximum capacity in stereotypes for a reduced encombrmeent, because it uses the vertical dimension as much as possible. The noria of pictures can indeed descend without inconvenience to the ground level, or even lower if we agree to make an excavation.

Note that with the last two principles set out, the presence of the release plate 10 is essential, unlike, as we have seen, in the case of the plane matrix. With this detail, all that has been described previously in terms of inking-marking-cleaning devices fully applies to all the configurations presented. In the case where the variant in which the cleaning elements are arranged in separate ramps from the carriage 12 is used, the cylinder or noria structures are particularly advantageous, because they allow the row of plates to be cleaned to be presented naturally. opposite the successive positions corresponding to the different cleaning sequences and this without any increase in size. This possibility is illustrated very diagrammatically in FIG. 4. The magazine is rotated according to arrow F5, at least initially, and the row to be cleaned successively meets the spraying ramp (position 27), the drying ramp (position 28) and if necessary the brushing ramp (position 29). This being done, we bring then the new row in the working position using the direction of rotation which minimizes the distance to be covered. The principle would be the same with the cylindrical structure according to Figure 3.

We can further increase the capacity of the store by placing side by side, on a movable frame in "x", several cylinders or several norias. The selection operation then comprises, when necessary, a displacement of said chassis making it possible to bring in the axis y-y ′ the desired cylinder or noria. Note that this displacement does not generate additional dead time, insofar as it can be simultaneous with the rotation of the cylinders or the norias. Note also that all of the cylinders or norias can be rotated by a single motor. The capacity of the store then becomes almost unlimited, if not by notions of cost or size.

In some cases, rather than investing in a very large, dynamic plate store, it may be better to go for another solution. Indeed, depending on the number and the frequency of appearance of the variants of the treated product, a particular problem of cliché management may appear. In the case of a product where there are many variants whose frequency of appearance is very low, even unique, there is no need to clutter the dynamic store with such shots and, it may be more appropriate to store them at part, in the form of easily interchangeable bars 31.31 ′. This possibility is illustrated in FIG. 1, where we see the particular bars 31, 31 ′ fixed to the magazine 2 by an adequate mechanical means, of a type known per se, ensuring the necessary precision and maximum speed.

While a series is being executed, it is possible to proceed in masked time to the installation of the bar carrying the following image, in position 31 or 31 ′, preferably choosing the most accessible, namely 31 in the case of FIG. 1. It then suffices to declare the position in "x" and in "y" of the new photograph to the control system of the machine. It can then be treated like any other photo.

The same principle can be applied to stores with a cylindrical structure or in noria. It suffices that the rows of plates, or at least some of them, be made easily removable, which poses no particular problem.

A final problem to be dealt with is that of taking account of hazards. We have seen above that if the machine stops accidentally, there is a risk of ink drying in some shots. Since this problem must of course be addressed, two categories of cases can be distinguished. If the vagaries do not interest the carriage 12 or the cleaning device 18,19, a sequence of cleaning of the row of pictures is carried out before switching off the machine, namely complete stroke of the carriage 12 on the left right with solvent spraying and drying. The same operation is also to be performed when the machine is stopped during the series, for a voluntary cause.

In the case of other hazards making the carriage 12 or the cleaning device unavailable, the automatic cleaning sequence cannot take place. An alarm must then be triggered to ask the operating personnel to carry out a manual cleaning followed by an acknowledgment which will authorize the subsequent restart of the machine.

All of the information to be stored in memory as well as the execution of the sequences described above obviously requires an adequate performance management unit. Depending on the case, a large programmable controller can be used capacity, a microcomputer, or the combination of these two devices.

Claims (10)

1. Flexible pad printing device making it possible to quickly and automatically carry out the operations linked to a change of variant of the product (6) to be marked, namely cleaning of the plate (1) which has just been used as well as of neighboring plates which may have been to be inked simultaneously, and presentation in the working position of the new plate, said device having a movable carriage (12) carrying an ink device (17) for inking the plates (1) during movement of the carriage (12) and a support ( 16) of ink transfer pad (15) arranged to transfer the ink of the selected photograph onto the product (6), characterized in that all of the photographs (1) constitute a magazine (2) at two coordinates, the first coordinate being given by a movement specific to the store (2) itself, making it possible to bring into working position a given row of plates (1), the second coordinate being given by the movement of the carriage (12) carrying the The stamp and the ink device, making it possible to choose in the said row the plate to be used, these two movements being controlled by numerically controlled devices, themselves controlled by the automation system fitted to the machine, in connection with a reader. code (8) allowing the identification of the products (6) to be treated. 2. Device according to claim 1, characterized in that the store (2) of plates (1) is in the form of a planar matrix which can move in a given direction (x-x ′), the carriage (12 ) buffer holder (15) moving in a perpendicular direction (yy ′). 3. Device according to claim 1, characterized in that the store (2) of pictures (1) has a pseudo-cylindrical configuration, the selection of rows of pictures being done by rotation of the store around its axis. 4. Device according to claim 1, characterized in that the store (2) of plates (1) is in the form of a noria bars (23) connected by a pair of chains (24) meshing on notched pulleys (25), said pulleys being mounted on an axis whose rotation allows the selection of the bars constituting the rows of plates. 5. Device according to one of claims 1 to 4, characterized in that the same carriage (12) supports the stamp (15), the mobile inking device (17) as well as cleaning nozzles (18,19) allowing the spraying the row of plates (1) to be cleaned with a solvent, and drying with a jet of compressed air. 6. Device according to one of claims 1 to 4, characterized in that the cleaning nozzles (18,19) are arranged in fixed ramps parallel to the movement of the carriage (12), and optionally supplemented by a brushing device, the successive presentation of the row of plates to be cleaned in front of these various devices being ensured by the movement of the magazine (2). 7. Device according to one of the preceding claims, characterized by a clearance plate (10) ensuring geometric continuity with the plane of the plate (1) in service, and making it possible to accommodate the inking device (17) if it is of the mobile type and fixed to the carriage (12), when the latter reaches the end of the race, or carrying the inking device itself if the latter is of the fixed type. 8. Device according to claim 7, characterized by a second release plate (10 ′) placed symmetrically to the previous one, and capable of accommodating the inking device (17) during a sequence of change of plate (1). 9. Device according to one of the preceding claims, characterized by the presence of a cleaning device (9) for the tampon (15), a device in front of which the tampon is presented automatically during a sequence for changing the photograph (1), and can be placed either in the interval between the conveying of the products (6) and the plates (1), ie outside this interval. 10. Device according to one of the preceding claims, characterized in that one or more of the rows of plates (1) are in the form of easily removable bars (31), with a view to using plates stored in an external stock at the machine.

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