WO2007004053A2

WO2007004053A2 - Machine for lithographic printing of tin sheets

Info

Publication number: WO2007004053A2
Application number: PCT/IB2006/001955
Authority: WO
Inventors: Santiago Pedro Badran
Original assignee: Pakgoiz, Mario, Javier; Molina Castro, Hernando, Rafael
Priority date: 2005-07-06
Filing date: 2006-07-06
Publication date: 2007-01-11
Also published as: AR051361A1; WO2007004053A3

Abstract

A machine for lithographic printing of tin sheets using an offset system, characterized in comprising a central cylinder (3) having inside a series of electromagnets (15), around which a series of printing stations are arranged, each of them comprising a blanket or rubber cylinder (2) in contact with a printing cylinder (1) and with said central cylinder (3), a removable inking-damping device (4) and an eccentrics device (5) to move the blanket cylinder (2); wherein each removable inking-damping device (4) comprises two water and ink injecting porous cylinders (110) and a series of additional cylinders that distribute water and ink. The machine is completed with an exchange wheel (44) comprising lodgements (41) coinciding with the printer's lodgements on which lean the inking-damping devices (4). Said removable and exchangeable devices slide manually or automatically and are then located on the lodgements of the exchange wheel (44) to be removed, exchanged and washed by a washing station (48).

Description

A MACHINE FOR LITOGRAPHIC PRINTING OF HOJALATA

Technical field of the invention

The present invention relates to a machine for lithographic printing of tin by the offset system. This type of printers is used to decorate tin containers such as aerosols, canned cans, paint containers, etc. In a lithographic printer individual tin plates enter at one end and the printed tin with different colors comes out from the other, with which the containers are then assembled.

State of the art

All tin offset printers print the same with machines that print color by color in a linear fashion, that is, the tin travels a linear and horizontal path as it receives the different colors. As an example of these machines, those marketed by Crabtree firms can be cited; Bauer-Kunzi; Mailaender; Hoe and Planet.

Conventional printers that print 6 colors have six printing stations arranged in a straight and horizontal line. These printing stations are identical to each other and each of them is enabled to print a single color, so that with six of these stations, the machine can print six colors in a single pass of the tin. This linear arrangement means that a conventional printer that prints six colors has a total length of about 40 meters, which obviously takes up a lot of volume, so it would be desirable for the state of the art to provide a lithographic machine for printing tinplate in six colors that could circumvent the linear arrangement and solve its development in less space.

On the other hand, in conventional printers the inking-humidifying device is fixed to the machine, without the possibility of being removed. When it is desired to change the inks they contain, a manual cleaning process is carried out which consists in operating the printer (without printing, simply rotating all its cylinders) by pouring solvent with a container on the inking-humidifying cylinders.

After a few minutes of continuously pouring solvent, the cylinders "wash" until there are no traces of ink. It is only there where another ink of different color can be incorporated than the one that has just been washed.

This rudimentary cleaning process is done several times a day, as many times as inks have to be changed to make different prints.

The problem of this device is that the cleaning is carried out inside the machine, so that the mixture of ink and solvent that arises from the washing process, drains through all the other devices of the printer, splashing elements such as: gears; bearings, cams, etc. The latter damages the useful life of the machine and all its mechanical components, so it would be desirable for the state of the art to provide a lithographic machine for printing tinplate in which the inking-humidifying device could be removed from it and carried to a "washing station" outside the printer, so as not to compromise its mechanical parts at all. Another problem that arises from the state of the closest technique is that referred to the different color frequencies for different prints. In an offset printing process, the printing sequence of the different colors may change depending on the product to be printed. For example, in a certain product to be printed (aerosol containers), the printing sequence can be: RED-YELLOW-BLUE, while in another product that you want to print after the previous one (for example, food containers) it must be done with a different sequence and perhaps with some different color, such as: YELLOW-BLUE-BLACK.

In conventional printers it is necessary to wash each of the inking-humidifying devices to change the inks, since they do not allow to alter the preset sequence, which produces dead times, unproductive delays and accelerates the wear of the machine by continuous and successive washes of its parts, with the risks already mentioned above.

It is evident that these limitations of known printers could be solved, so it would be desirable for the state of the art to provide a lithographic machine for printing tinplate capable of making prints with different sequences and colors one after the other without having to stop the production to wash inking-humidifying devices.

On the other hand, it should be noted that the inking and humidifying device of conventional offset printers is bulky and complex, since it is composed of a device that provides ink (inker) and another device that provides water (humidifier). Its operation is based on taking ink from one pan and water from another Hit and transfer it from cylinder to cylinder to achieve a thin film, which forces you to have a device of no less than 20 or 2 cooperating rollers. This design of separate devices, on the one hand the inker and on the other the humidifier, does not allow any other arrangement that is not linear, since its large size is prevented, since it would take the printer impossible to operate because it is not ergonomic for the operator

Therefore, it is concluded that it would be desirable for the state of the art to provide a lithographic machine for printing tinplate with a unified inking-humidifying device that would adapt to a central (non-linear) arrangement, so that the complete machine has a size reduced compared to those known in the prior art.

According to all the arguments presented, a lithographic machine for printing tinplate in up to six colors is proposed by means of the present, with up to six printing stations arranged around a central cylinder equipped with a series of electromagnets that serve to attract the tin , each of said stations comprising a pair of cylinders mobilized by an eccentric device and a unified inking-humidifying device comprising a porous inkjet cylinder and a porous water injection cylinder. The whole set is completed with a feeder, a tin plate unloader, an ultraviolet light ink drying device and a removable unit exchange wheel, as well as an external washing unit for the inking-humidifying device that rotates the cylinders of it while it is being washed. Some of the constituent parts presented by the proposed invention have already been disclosed in isolation in other embodiments of the prior art, although with different configurations and applications. Such is the case of document DE2704527 that, although it has a porous cylinder that is loaded with ink, its application is restricted to copying machines for plastic identification cards or credit cards. Its configuration differs from the porous cylinder proposed here, which is intended exclusively for offset machines.

The patent EP 092279 B1 is also known, which reveals a cylinder with a porous membrane where the ink projects outwards, using a flexible porous membrane. In the type of offset machines where the proposed invention will be applied, the speed of rotation of the cylinders is so high that a flexible membrane would not withstand mechanical stresses. That is why in the porous cylinder proposed here, the element that has the pores is made of sintered metal tubes or porous hard plastic. In addition, the proposed porous cylinder is designed not only to inject ink, but also water, since the offset system requires the use of both water and ink.

Another known embodiment is the US patent 5,406,885 which also comprises porous cylinders of rigid material, although they, due to their structure, have no application in offset printing systems.

Finally, the US patent 6,389,967 discloses an arrangement that uses a porous cylinder, but the material that has the pores is only permeable to very low viscosity inks (viscosity close to that of water). The foregoing restricts its use in applications related to offset printing, since paste inks are used here, which has a very high viscosity.

None of the prior art documents that mention porous rollers solve the double ink-water application and that at the same time the inking-humidifying device containing said rollers was removed and interchangeable, which constitutes a real improvement in the problems to be solved. It raises the state of the art.

On the other hand, as will be explained in detail below, one of the advantages introduced by the machine for lithographic printing of tinplate by means of the offset system that is intended to be protected, is its circular arrangement around a central drum surrounded by six stations of Print. In this regard, the following documents are known that suggest non-linear provisions, such as US Patent 5,660,108 which also raises a circular arrangement, although it only has the capacity to print four colors. It is also a machine for the paper industry, where the central drum does not have any magnetic device nor does it have an ultraviolet drying system for the ink, nor does it include a removable and interchangeable "ink-humidifier" device.

The publication AU-A-89747/82 is also known, which discloses a machine that prints several colors in a single pass, but the layout of its printing stations are arranged in a linear and horizontal manner, so that it does not resemble Ia printer proposed here where the printing stations are distributed circumferentially around a single central cylinder. This printing machine does not have an ultraviolet drying system or an "inking device" removable and interchangeable humidifier. The same can be said of the English publication GB 2017003 A.

On the other hand, printing machines are known that use electromagnetic cylinders such as publication JP4072260, which comprises a cylinder that manages to attract and fix a tin on its periphery, which it does by means of the magnetic attraction generated by magnets fixed inside. This device differs from the proposed electromagnetic cylinder that is selective, while in that the magnets have no possibility to stop attracting the tinplate selectively, since they are permanent magnets.

Also known is the patent application JP 231015 comprising electromagnets, although they do not have the capacity to be demagnetized or magnetically selectively, since all electromagnets are activated or deactivated together. This differs from the cylinder proposed here, in which the electromagnets are selectively activated or deactivated and in portions as required.

Brief Description of the Figures

Figure 1 is a side view of the proposed printing machine without its side cover, so as to reveal its internal components.

Figure 2 is a more detailed perspective of the printer, this time without the outer cover of the central cylinder, which allows to see its interior.

Figure 3 schematizes the arrangement of the lithographic machines of the prior art, which are resolved in line, one station after the other. Figure 4 is a side view and a cross-section of the electromagnetic central cylinder, around which the inking stations are arranged.

Figure 5 shows a perspective view showing the inside of the central cylinder of Figure 4.

Figure 6 shows the arrangement of the central cylinder with its electromagnets and the six printing stations grouped around it.

Figures 7 to 12 show the printing sequence of the tin from the time it enters the printing circuit until it exits the same through the upper part of the central cylinder, enabling a new tin to enter said circuit.

Figure 13 presents a perspective of an isolated printing station, where the elements that constitute it are shown: printing cylinder, blanket or rubber cylinder and inking-humidifying device.

Figure 14 is a perspective of the printing cylinder of the printing station of Figure 13.

Figure 15 is a perspective of the blanket or rubber cylinder of the printing station of Figure 13. Figure 16 shows an exploded perspective detailing the device of eccentrics that have both the printing cylinder and the blanket or rubber cylinder, which allows them to move in a particular way.

In Figure 17 it can be seen in dotted lines the separation movement that the blanket cylinder has maintained with respect to the printing cylinder and the central cylinder, as a consequence of the work of the eccentrics of Figure 16.

Figure 18 shows a diagram of the arrangement of conventional printers of the prior art, which have two servo actuator devices, one for the printing cylinder and one for the blanket cylinder.

Figure 19 reveals the proposed arrangement with a single pneumatic piston, thanks to a new arrangement of the three cylinders involved.

Figure 20 shows a perspective of the proposed inking-humidifier device with only 9 cylinders.

Figure 21 is another perspective, but of the conventional inking and humidifying device possessed by offset printers of the known prior art, with an amount of 20 to 2 cylinders.

Figure 22 is a longitudinal section through the porous inkjet cylinder.

Figure 23 is an exploded perspective of the porous inkjet cylinder. Figure 24 shows the complete arrangement of the proposed lithographic machine, where the drying lamps located inside container modules, the tin plate feeder and the tin plate unloader are shown.

Figure 25 represents a perspective of the lithographic machine with the exchange wheel in position to be coupled.

Figure 26 shows the exchange wheel already attached to the printer.

Figures 27 to 31 are a series of perspectives that show the sequence of the exchange process of the removable units using the exchange wheel.

Figure 32 is a perspective showing the location of the washing station in the whole assembly.

Figures 33 to 35 are a series of perspectives that show the sequence of how a removable inking-humidifying device is transferred to the washing station using the exchange wheel.

Figure 36 shows in detail the washing unit and its components.

Figure 37 is a general perspective of the whole assembly of the invention. Detailed description of the invention

The machine described is a lithographic printer for printing tin. Its operation respects the basic guidelines of the offset printing method.

Usually, all tin containers are printed on conventional six-color machines, one after the other, the tin traveling a linear path between each color station until it is completely printed. The proposed printer prints those six colors in a single pass, but the tin no longer travels that path in a linear fashion but does so in a circular path. This last modification together with others that will be explained later make said printer have a smaller size and smaller amount of mechanical parts, all of which simplifies the printing process and reduces the costs of the machine.

As stated above, the claimed printer acts under the offset system, which uses a sheet of prestressed aluminum or steel on which a "photogravure" of the image to be printed is made. This sheet is wound on the printing cylinder (1).

A blanket or rubber cylinder (2) is in contact with the printing cylinder (1) and with the central cylinder (3). The central cylinder (3) has a series of electromagnets (15) inside which serve to attract the tin.

The inking-humidifying device (4) is responsible for depositing a thin layer of water and another thin layer of ink on the prestressed plate (100) that hugs the printing cylinder (1). The blanket cylinder (2) has the ability to move away from the printing cylinder (1) and the central cylinder (3) thanks to a device that has an eccentric part (5). These eccentric parts are holding the bearings (108) of the blanket cylinder (2). The eccentrics (5) are operated with a pneumatic cylinder (7). The incoming tin plate (9) adheres to the central cylinder (3) thanks to the magnetic effect generated by the electromagnets (15) that are inside said cylinder. The central cylinder (3) when turning with the tin (9) adhered to its periphery, forces it through the six printing stations (A, B, C, D, E and F). Once the six colors are printed, the tin must leave the central cylinder (3) for which the electromagnets are gradually deactivated as the tin advances. Finally, the tin leaves the machine (10).

For drying the ink, lamps in the form of tubes (8) that emit ultraviolet light are used. This type of light emits such radiation that reacts the photoinitiators of the printed ink and thus manages to dry it instantly.

As can be seen in Fig. 1 there are six sets called printing stations (A; B; C; D; E and F) and each of these stations is composed of: a printing cylinder (1), a cylinder of blanket or rubber (2), an inking-humidifying device (4) and an eccentric device (5) for the movement of the blanket cylinder (2).

A more complete image can be seen in Fig. 2, where each of the main parts can be seen and how they interrelate. These printing stations are identical to each other and each of them is enabled to print a single color, so that with six of these stations, the machine can print six colors in a single pass of the tin.

Conventional prior art printers that print 6 colors have six printing stations (G, H, I, J, K and L) arranged in a straight and horizontal line, as shown in Fig. 3, indicating at the beginning of the line the tin feeder (N) and at the end of it the tin unloader (M).

These known printers comprise a printing cylinder (11), a blanket cylinder (12) and a lower cylinder (13).

It will be appreciated that the six lower cylinders (13) of the conventional machine are replaced by a single central cylinder (3) in the machine that is here intended to be patented. This configuration is one of the distinguishing features of this design, where the offset printing system is also used, but with a completely different arrangement to existing printers, because the tin no longer travels a linear and horizontal path as it advances, but that it travels a circular path thanks to the fact that it adheres to the central magnetic cylinder (3) which, when turned, forces the tin to make its route through the six printing stations (A, B, C, D, E and F), which transfer the images to be printed. This arrangement allows the tin to leave the machine with the six colors already printed in one step. Said electromagnetic central cylinder (3) comprises a hollow metal cylinder (14) (see Fig. 4), which has a certain number of electromagnets (15) arranged on the inner periphery. These electromagnets (15) generate a magnetic force of attraction that will serve to fix the tin plates to be printed. In addition, this cylinder has two collinear shaft tips (16) with two bearings (17) at its ends, which gives the cylinder the ability to rotate.

On one side of the cylinder is connected by means of screws, a toothed crown (18), which may be straight, inclined, helical or bihelicoidal teeth, through which a gear force is transmitted that manages to exert the necessary torque to generate the rotating movement of the entire cylinder.

The electromagnets (15) are connected in groups arranged linearly forming rows. In Fig. 5, arrows (101) showing the direction of said rows can be seen.

The tin to be printed adheres to the periphery of the cylinder thanks to the magnetic force of the electromagnets (see Fig. 6). There you can see the bearings (19) of the rollers; the electromagnets (15); the central drum (3) and the incoming tin plate (22). In addition, the six print stations are identified with the letters A; B; C; D; E and F.

These rows of electromagnets are selectively energized. At the moment when the tin must adhere to the cylinder, all the electromagnets will be energized, but when the tin must be detached from the cylinder the successive rows of electromagnets will be de-energized in succession. That is to say, after the tin (22) made almost a full turn adhered to the cylinder, it is already fully printed because He crossed the different printing stations along the way. To remove said sheet, the circuit that energizes the row of electromagnets that is closest to the end thereof will be deactivated. Moments later, while the cylinder continues to rotate, the next row of electromagnets will be deactivated and so on. This process of de-energizing each row is carried out gradually until all the tin leaves the cylinder. The tin when leaving the cylinder falls on a conveyor belt (102) and is moved away from the machine to finally be stacked in the tin unloader (43).

The cylinder (3) throughout this process does not stop rotating at a continuous speed. Moments after the tin plate (22) is discharged, the electromagnets are re-energized sequentially in the same order as before they were de-energized. The latter is done so that the cylinder receives a new tinplate (21) to be printed.

In summary, it can be said that the drum is magnetized so that the tin can adhere to it and thus can pass through the printing stations. After all the colors were printed on the tin, it must be removed, for which the electromagnets are demagnetized sequentially, so that the tin leaves the cylinder following its path by means of a conveyor belt (102) until its final destination in the unloading device (43), which is where the already printed sheets are stacked.

The magnetization sequence of the electromagnets is detailed in an orderly manner in Figures 7 to 12. Next, it will be described step by step, as is the process of activation and deactivation of the electromagnets during the printing process: 1 ^or Step (Detailed in FIG . 7). Here the tin (22) approaches the machine to enter and be printed. In this instance all the electromagnets (15) are demagnetized, that is to say de-energized of the electric current.

2 ^or Step (Detailed in FIG . 8). The tinplate (22) makes contact with the central cylinder (3) and adheres to it by the magnetic force exerted by the electromagnets that are energized (23). Here it should be appreciated that the majority of the electromagnets (15) are demagnetized, while the electromagnets (23) are already connected and magnetized, attracting the tinplate (22).

3 ^or Step (Detailed in FIG . 9). The central cylinder (3) continues to rotate while the electromagnets are magnetized as the tin plate (22) enters. It will be seen that the magnetized electromagnets (23) are represented with striped rectangles, while those that are de-energized (15) are empty.

4 ^or Step: (Detailed in FIG . 10). Here is shown the tin (22) fully adhered to the central cylinder (3), which is rotating and forcing the tin (22) through the 6 AF print stations.

5 ^or Step: (Detailed in FIG . 11). The tinplate (22) begins to detach from the central cylinder (3) thanks to the successive rows of electromagnets (23) being disconnected (15) (demagnetized). 6 ^or Step: (Detailed in Fig.12 Ia). All electromagnets are disconnected and the tin (22) leaves the machine to go to the arrester (43). It is now where a new tin (21) is approaching from the bottom to repeat the entire process.

The six A-F printing stations, through which the tin receives the color printing, base its operation on the traditional offset system; However, this provision introduces novel variants that give the user greater freedom of action when considering the alternatives available to do their job. For example, each printing station has the ability to transfer a single color to the tin, so that if you wish to print four colors on a tin, four print stations will suffice, in the case of printing five five printing stations will be needed , etc.

In the claimed printer, six printing stations are arranged, so that this machine has the ability to print up to six colors on the same tin.

Said A-F printing stations are distributed around the periphery of the central cylinder (3) and each printing station comprises two cylinders (1 and 2) that rotate together with the central cylinder (3) thanks to a simple transmission of gears.

In Fig. 13 a complete printing station is shown where the elements that constitute it are: a printing cylinder (1), a blanket or rubber cylinder (2), the inking-humidifying device (4) and the device for eccentric (5). The printing cylinder (1) is a metal cylinder on whose periphery a prestressed plate (100) is held containing the engravings to be printed, such as drawings, letters or figures. This prestressed plate (100) can be made of aluminum or steel and its drawings or figures are obtained by photo-etching, exposing the plate to non-ionizing radiation and then with developing processes similar to the development of photographs. This type of plate is a commercial element and is commonly used in all types of offset printers.

This plate (100) has the particularity of fixing the ink only in the part where the engraving to be printed is located. The ink is deposited by means of rubber rollers belonging to the inking-humidifying device (4), which is in contact with the printing cylinder (1), as can be seen in the detail of Figure 13.

This printing cylinder (1) also has two shaft ends (103) with their respective bearings, this gives it the ability to rotate.

On both sides of the cylinder (1) there are two gears, one of them (104) can be straight, inclined, helical or bihelicoidal teeth and the other (105) is straight teeth. The first one (104) serves to grant the turning movement and the other (105) of straight teeth fulfills the function of transmitting said rotating movement to the inking-humidifying device (4). Here the primitive diameters of both gears (104) and (105) must coincide with the outer diameter of the associated cylinder when the presensitized plate (100) is placed. On the other hand, the blanket or rubber cylinder (2), comprises a metal cylinder similar to the printing cylinder (1) at whose periphery a blanket or rubberized shell (106) is hugged. This cylinder (2) is in contact with the printing cylinder (1) and fulfills the function of receiving the image from it and transmitting it to the tin during its rotation.

As can be seen in Figure 15, it comprises a gear (107) that can be made of straight, inclined, helical or bihelicoidal teeth, which receives the engagement force from the crown of the central cylinder (3). This rotating movement is also transmitted to the corresponding gear (104) of the printing cylinder (1) already described.

The primitive diameter of this gear (107) coincides with the outer diameter of the blanket cylinder (2) when the blanket (106) is in place.

Also, this cylinder (2) also has two shaft ends (108) with their respective bearings, which gives it the ability to rotate.

Both the printing cylinder (1) and the blanket cylinder (2) comprise eccentrics (5) at their ends.

This eccentric device (5) comprises metal parts (109) that serve as housing for the bearings (108). Said housing is arranged eccentrically with respect to its outer circumferential part. The eccentricity of this piece, allows the cylinder that rests there, to have a relative movement with respect to the surrounding cylinders. This can be seen in Fig. 17, which shows (in dotted lines) that the blanket cylinder (2) has been separated from the printing cylinder (1) and the central cylinder (3). The separation distance, in both cases, is indicated by the letter (Z).

This movement of the eccentric (5) is achieved by means of a mechanical servo actuator (7), which may be an electric actuator, a pneumatic or hydraulic piston, or a cam system. In this case, Fig. 17 shows a servo actuator (7) consisting of a pneumatic piston.

This eccentric device (5) is usually used in all types of offset printers to achieve the separation of the cylinders when the machine stops printing. Although it is a conceptually known system, a novel configuration is introduced in this, because to achieve that desired separation of the cylinders (1) and (2), a single servo actuator device (7) is used, while in all printers Conventional devices have two servo actuators, one for the printing cylinder and one for the blanket cylinder.

This can be seen in Fig. 18, where it has represented the known system used by conventional prior art machines, where two pneumatic pistons (31) appear for each cylinder (11), (12) and (13); while in Fig. 19 the novel configuration of this printer with a single pneumatic piston (7) is detailed. What is achieved is a technical simplification and lower costs, thanks to a new arrangement of the three cylinders involved. It will be seen that in the conventional printer the three cylinders are arranged "in line" vertically, while in the printer presented here the cylinders have an "angular" arrangement (the angle is represented with the Greek letter β). This new arrangement allows the machine to be built with a single servo actuator device (7), since when the piston is activated, the blanket cylinder (2) manages to separate simultaneously from the other two cylinders

(1) and (3).

Another of the essential components of each A-F printing station, in addition to the two cylinders (1) and (2) mentioned, is the inking-humidifying device (4). This device gathers in a single set two characteristic and inherent offset printing devices that are conventionally provided separately: the device that provides the ink (inker) and the device that provides the water (humidifier).

The proposed novel configuration, of compact design, replaces the two conventional systems of inking and humidifier that have all offset printers of the current state of the art.

It is at this point where one of the great advantages of the present technical innovation lies, since it replaces the individual inking and wetting systems of conventional printers with a single device less bulky and complex, using only 9 cylinders instead of 20 or 2 cylinders that have conventional printers.

In Fig. 20 it is proposed to establish this comparison, facing both devices: the proposed single inking-humidifier device (4) and the conventional device of offset printers (34). The prior art bases its operation on taking ink from one bat (35) and water from another bat (36) to transfer it from cylinder to cylinder until a thin film is achieved; while the printer proposed instead uses a hydraulic pump that injects the ink and water into two independent cylinders (110) of porous material (metal or plastic) that transfer the ink and water over the rest of the cylinders of rubber that are in contact with the prestressed plate (100) of the printing cylinder (1).

As the offset system needs to achieve a thin layer of ink and another layer of water that are transferred to the prestressed plate, the proposed configuration allows obtaining this result thanks to the porous cylinders (110) that rotate in contact with the rubber cylinders. This arrangement, so small in size and complexity, has allowed six printing stations to be distributed around a single central cylinder (3). The inking-humidifying devices of conventional printers cannot adapt to this arrangement of a single central cylinder, since their large size is prevented, since it would make the printer impossible to operate because it is not ergonomic for the operator. Therefore, this compact design of the inking-humidifying device (4) proposed here is what allowed the particular configuration of six AF printing stations arranged peripherally around a single central cylinder (3). This implies that the complete machine also has a very small size, which has an advantage directly proportional to the cost of the machine. To give an idea, a conventional printer that prints six colors has a total length of 40 meters, while this proposed design reaches a total length of only 8 meters. Another significant advantage is that these six inking-humidifier devices that have this new design, are removable equipment and simple to handle because they are light and small. This is important for two reasons: in conventional printers the inking-humidifying device is fixed to the machine, without the possibility of being removed. When it is desired to change the inks they contain, a manual cleaning process is carried out which consists in operating the printer (without printing, simply rotating all its cylinders) by pouring solvent with a container on the inking-humidifying cylinders. After a few minutes of continuously pouring solvent, the cylinders "wash" until there are no traces of ink. It is only there where another ink of different color can be incorporated than the one that has just been washed.

This rudimentary cleaning process is done several times a day, as many times as inks have to be changed to make different prints. The problem of this device is that the cleaning is carried out inside the machine, so that the mixture of ink and solvent that arises from the washing process, drains through all the other devices of the machine, splashing elements such as: gears; bearings, cams, etc. The latter damages the useful life of the machine and all its mechanical components.

On the contrary, in the proposed printer, the inking-humidifying device (4) is removed from the machine and taken to a washing station (48), which comprises airtight equipment that keeps the entire device confined, so that all solvent or ink splashes fall on a tray, without affecting the printer at all because it is far from it. Also inside the washing station (48) The solvent is automatically injected under pressure without the manual intervention of man.

In an offset printing process, the printing sequence of the different colors may change at the user's request, depending on the product to be printed.

For example: in a certain product to be printed, for example aerosol containers, the printing sequence is:

1) RED (located in the printing station (A)) 2) YELLOW (located in the printing station (B))

3) BLUE (located in the printing station (C))

But in the product that you want to print after the previous one, for example grocery containers, it must be made with a different sequence and perhaps with a different color, such as:

1) YELLOW (located in the printing station (B))

2) BLUE (located in the printing station (C))

3) BLACK (located in the printing station (F))

In conventional printers, it would be necessary to wash each of the inking-humidifying devices to change the inks. On the other hand, in the proposed printer, this is avoided since the inking-humidifying device of the printing stations (A) (red) and (B) (yellow) is removed from the machine and exchanged with each other, avoiding In this way having to wash the cylinders. Regarding the inking-humidifying device (C) that has blue ink and must be changed to black ink, the process is different. The inking-humidifying device (C) is removed, and it is placed inside the washing station (48) that is close to the printer and is an independent equipment. There it is washed automatically, without the intervention of the man and after washing, it is placed again in the machine to now inject black ink.

This entire procedure is performed more dynamically and quickly than in conventional printers and the most important thing is that the rest of the machine is not damaged by ink and solvent splashes.

The porous inkjet cylinder (110) is part of the inking-humidifying device and consists of several tubes of a porous material (37) (metallic or plastic) supported by a central steel tube (38) having clamping bolts ( 39) to keep the porous tubes positioned. The pressure ink from a hydraulic pump enters through the hole (40). This can be seen in detail in Figs. 22 and 23. The porous water injection cylinder (110) is identical to that of inkjet and is therefore mentioned with the same reference. The difference is that inside it water is injected instead of ink. Fig. 22 and Fig. 23 are also valid for this case, because constructively, both cylinders are equal.

Both the ink and water are injected into the porous cylinders by means of hydraulic pumps or another similar element that fulfills the same function. The effect achieved in these cylinders is that both the ink and the water injected, come out evenly and well distributed by the micropores of the porous tubes. This is fulfilled by the physical law that says that: "in a vessel that contains a fluid, the pressure is distributed uniformly at all points." The fastening bolts (39) that fulfill the functions of internal ribs or partitions that prevent the porous material covering the cylinder from undergoing deformation during use, since these cylinders (110) are rotating and permanently in contact with Some rubber cylinders. The latter are completely covered with ink or water, depending on the case and thus the desired effect is achieved, that is, two thin layers, one of ink and the other of water, necessary for a typical offset printing, both applied on the prestressed plate ( 100) of the printing cylinder (1).

Another of the innovations introduced in the present invention, consists of the ultraviolet drying device (8), which manages to dry the ink instantaneously, comprising lamps in the form of tubes that emit ultraviolet radiation.

The need for drying is that the tin passes from one station to another with the freshly printed ink, the same having to dry before entering, otherwise the printing could be ruined.

Although these ultraviolet instantaneous drying devices are well known and used in the graphic industry (both in paper and tin printing), in the present invention it has been arranged in a novel way around the central cylinder and inserted between the different stations of impression. This achieves that between one color and another color the complete drying of the ink is obtained. These lamps are located inside a container module (8) (See Figure 1), being able to observe that there are six container modules in the whole machine, each of them serves to dry a single color of ink.

The arrangement of all the elements that constitute the machine for the lithographic printing of tinplate by means of the offset system of the present invention, is completed with a plate feeder of tinplate (42), of the type commonly used in all types of offset machines and with a tin plate unloader (43), also commonly used in this technique, of a similar design as the tin plate feeder (see Figures 24 and 37)

One of the advantages already mentioned that were introduced in the particular configuration of the printer is precisely its circular arrangement around a central cylinder, which makes it less bulky. However, the highest printing stations are outside the operator's access radius and since they are removable and interchangeable, it is necessary to provide the operator or user with a means of reaching the farthest stations.

The solution provided by the inventor for this problem is verified through the exchange wheel (44) of inking-humidifying devices.

The inking-humidifying devices (4), as already explained, are removable and interchangeable units that facilitate color changes during the printing process. This exchange is carried out by means of the exchange wheel (44) (See Fig. 25), which is located next to the printer. For the purpose of better understanding of the invention, said wheel 25 is shown to said wheel separated from the printer, but in reality the same is next to the rest of the machine (this is seen in the following figures).

This wheel (44) comprises a central axis on which it rotates freely, either manually or automatically by means of an electric motor or other device that gives it movement.

The wheel (44) has housings (41) that coincide with the housings that the printer has in which the six inking-humidifying devices (4) rest. Said devices leave the printer sliding horizontally (manually or automatically) and move on to be placed in the housings of the exchange wheel (44).

Once the exchange wheel is "loaded" with the inking-humidifying devices (4) that are to be exchanged, said wheel is rotated to the corresponding position, so that the inking-humidifying device coincides with the destination housing. Once the wheel is stopped, the corresponding inking-humidifier device (4) is slid from the wheel (44) towards the printer. This is repeated until all the inking-humidifying devices that need to be replaced are relocated.

In Figures 26; 27; 28; 29 and 30 are shown step by step, the exchange of two inking-humidifying devices. What is intended is to place the inking-humidifier device (4F) where the (4D) is located and vice versa. • 1 ^or Step (Fig . 26) Here example arises where, six devices inking-dampening are desired exchange only two of them, for example the device (4) located within the housing of the printing device (F) and the device (4) of the housing of the printing device (D).

»2nd Step: (Fig. 27) Both devices (4F and 4D) are slid from the housings of the printer to the housings (41) of the exchange wheel (44).

• 3 ^or Step (Fig . 28) the wheel is rotated until the device (4D) coincides with the housing (F). The wheel stops. It is now when the device (4D) is slid (Fig. 29) horizontally until it fits into the housing of (F).

• 4 ^or Step (Fig . 30) wheel (44) is rotated in reverse to match the device (4F) with the position of the printing device (D). The device (4F) is now slid until it enters the printer (Fig. 31) in the printing device (D).

• 5 ^or Step: The wheel (44) and is "empty" and continues to rotate to return to original position Ia.

In this way the exchange of two inking-humidifying devices is achieved in a very simple way. If necessary, the same procedure can be performed with the 6 inking-humidifying devices, simultaneously.

However, there may be cases in which certain inking-humidifying devices must be "washed" in order to change the color of ink, as required by the printing process. As explained above, to perform this washing is used a device called "washing station", within which the device to be washed is located.

The washing station (48) consists of a metal capsule which inside comprises solvent injectors (52) connected to a hydraulic pump (50) that pumps said solvent from a tank. The solvent is sprayed at high pressure on the inking-humidifying device, managing to release all the ink that has adhered.

Within the washing station (48) there is a motorized device (51) that rotates the cylinders of the inking-humidifying device while it is being washed. After a few minutes, the effect produced by the solvent projected under pressure, makes the entire inking-humidifier device free of ink. Then, once the solvent flow has stopped, a stream of hot air begins to be injected into the equipment to dry the entire inking-humidifying device. Moments later, the device is already washed and dry, it is now when you can return to the printer for later use with another color of ink.

The process of movement and transfer of the inking-humidifying device from the printer to the washing station is also carried out by means of the exchange wheel (44).

The location of the washing station (48) is represented in Fig. 32.

This process is detailed below: • 1 ^or Step (Fig . 33) arises example where the device entintador- humidifier (4F) must be transported to Ia washing station. For this, the inking-humidifying device (4F) slides to the corresponding housing of the exchange wheel (44).

«2nd Step: (Fig. 34) Once the device (4F) rests on the exchange wheel, it is turned until said inking-humidifying device is taken to the lower position, where the station is located wash (48).

• 3 ^or Step (Fig . 35) Here the inking-dampening device is slid towards the washing station (48). Once located there, the automatic cleaning process with solvent and then with hot air will begin.

• 4 ^or Step: After washing the device will be placed in Ia printer using an inverse process to the newly described.

This process can be carried out in the same way to wash each of the six inking-humidifying devices, always using the exchange wheel as a link between the printer and the washing station.

In Fig. 36, the inking-humidifying device can be observed in isolation within the washing station. There, the injection unit (50) that supplies the washing solvent and the hot air for drying can be seen. Both the solvent and hot air come from the same equipment consisting of a hydraulic solvent pump and an air compressor. At the exit of this unit are the "injectors" (52) consisting of an inlet tube of greater section and six ducts that make up the injection nozzles. For those nozzles comes out sprayed the solvent while washing the inker-humidifier. After the washing is finished, drying continues, for which hot air is injected through the same nozzles that previously injected the solvent.

In addition the device has a built-in gear to generate the movement of the rollers of the inking-humidifier. This movement is carried out by an armored electric motor (51) that is activated during the entire washing and drying process.

It should be clarified that the upper cover (60) of the washing station remains closed during the washing operation.

Fig. 37 shows the complete printer where all the following devices appear:

• Tin plate feeder (42).

• Tin plate unloader (43).

• Printer (X).

• Exchange wheel (44).

• Washing station (48).

• Injection unit (50).

It emerges as a corollary of the above, that the present invention introduces visible improvements through its novel configuration, in relation to the problems posed by the prior art related to machine volume, costs, operability, useful life and flexibility of use of Ia same. By putting into practice the machine for the lithographic printing of exemplified and described tinplate, modifications and / or variants of embodiment may be introduced, all of which must be considered as included within the scope of protection of the present invention patent; scope that is determined fundamentally, by the text of the clauses claiming below.

Claims

1) A machine for lithographic printing of tinplate by means of the offset system, characterized in that it comprises a central cylinder (3) that has a series of electromagnets (15) inside, around which a series of printing stations (AF) are arranged. ), each comprising a blanket or rubber cylinder (2) that is in contact with a printing cylinder (1) and with said central cylinder (3), a removable inking-humidifying device (4) and a device for eccentric (5) for the movement of the blanket cylinder (2); wherein each inking device-removable humidifier (4) comprises two porous cylinders (110) for ink and water injection and a series of additional cylinders that distribute the water and the ink.

2) A machine for lithographic printing of tinplate, according to reiv. 1, characterized in that said porous cylinders (110) comprise several tubes of a porous material (37) supported by a central steel tube (38) having fastening bolts (39), and a hole (40) through which the ink enters under pressure from a hydraulic pump.

3) A machine for lithographic printing of tinplate, according to reiv. 1, characterized in that said printing cylinder (1) is a cylinder on whose periphery a prestressed plate (100) is held containing the engravings to be printed, said printing cylinder (1) also comprising two shaft ends (103) with their respective bearings and on both sides two gears (104) and (105). 4) A machine for lithographic printing of tinplate, according to reiv. 3, characterized in that one of the gears (104) can be straight, inclined, helical or bihelicoidal teeth and the other (105) is straight teeth.

5) A machine for lithographic printing of tinplate, according to reiv. 1, characterized in that the blanket or rubber cylinder (2), comprises a metal cylinder similar to the printing cylinder (1) on whose periphery a blanket or rubberized shell (106) is embraced, further comprising a gear (107) which may be of straight, inclined, helical or bihelicoidal teeth, and two shaft ends (108) with their respective bearings.

6) A machine for lithographic printing of tinplate, according to reiv. 1 to 5, characterized in that the eccentric device (5) comprises metal parts (109) that serve as housing for the bearings (108), said housings arranged eccentrically with respect to their outer circumferential part, achieving the movement of the eccentric (5 ) by means of a single mechanical servo actuator (7).

7) A machine for lithographic printing of tinplate, according to reiv. 1, characterized in that after each printing station (A-F) ultraviolet drying devices (8) are provided which comprise lamps in the form of tubes that emit ultraviolet light.

8) A machine for lithographic printing of tinplate, according to reiv. 1, characterized in that said electromagnetic central cylinder (3) comprises a hollow metal cylinder (14) having a certain number of internally arranged Electromagnets (15), also comprising two collinear shaft tips (16) with two bearings (17) at their ends, and a toothed crown (18), which may be straight, inclined, helical or bihelicoidal teeth, through Ia which transmits the gear force that manages to exert the necessary torque to generate the rotational movement of the entire cylinder.

9) A machine for lithographic printing of tinplate, according to reiv. 1, characterized in that the tin plate when leaving the central cylinder (3) falls on a conveyor belt (102) and is moved away from the machine to finally be stacked in a tin unloader (43).

10) A machine for lithographic printing of tinplate, according to reiv. 1, characterized in that it also comprises an exchange wheel (44) that is located next to the printer, said wheel (44) comprising a central axis on which it rotates freely, either manually or automatically, and a series of housings (41) that coincide with the housings that the printer has in which the six inking-humidifying devices (4) rest.

11) A machine for lithographic printing of tinplate, according to reiv. 1, characterized in that it also comprises a washing station (48) comprising a metal capsule which in its interior comprises solvent injectors (52) connected to a hydraulic pump (50) that pumps said solvent from a tank, in addition to a motorized device (51) which rotates the cylinders of the inking-humidifying device while it is being washed.