EP2550125A2

EP2550125A2 - Method and device for producing can bodies and can bodies

Info

Publication number: EP2550125A2
Application number: EP11711437A
Authority: EP
Inventors: Werner Boltshauser
Original assignee: COSMOCAN Tech AG
Current assignee: COSMOCAN Tech AG
Priority date: 2010-03-25
Filing date: 2011-03-22
Publication date: 2013-01-30
Also published as: WO2011116485A2; US20130048653A1; WO2011116485A3; AR080807A1; CH702885A2

Abstract

A metal strip should be directly printed for the production of cans. Another embodiment provides for the formation of an inner coating closed in the circumferential direction, after the formation of the laser seam on the tubularly shaped metal strip and before the separation of individual can shells. A further development relates to the use of at least one digital printing system. All solutions are based on the knowledge that slower and faster processing steps can be combined, wherein however linear inline production must then be dispensed with and, for example, fast processing steps are performed in a single line and slow processing steps are performed in parallel lines, or simultaneously at a plurality of processing stations. The metal web of a coil can also be divided into sub-webs by means of at least one longitudinal cut before further processing. By means of the novel solutions, various decoration and inner-coating desires can be fulfilled with little effort.

Description

Method and device for producing can bodies and can bodies

The invention relates to a method for producing cans according to the preambles of claims 1, 6, 12 on devices for producing cans according to the preambles of claims 18, 19, 20 and on can bodies according to the preambles of claims 16 and 17.

Can bodies are formed one or more parts. In one-piece aerosol aluminum cans, a cylindrical can body is provided by cold extrusion. Subsequently, a narrowed neck part is formed at the open end by upset necking. This manufacturing process is very complex due to the required for the many processing steps and the water and energy requirements for cleaning and drying. US Pat. No. 4,095,544 and EP 0 666 124 A1 describe the production of seam-free steel cans. In this case, the cylindrical can body is produced by means of stamping, pressing and ironing out of a tin or plastic-coated steel sheet. When forming a narrowed can neck enormous problems can occur because the material structure is changed by the stretching or hardened. In the known one-piece cans are located on the outside cans fat or oil residues. To form a decorative layer, cleaning (washing, drying), priming (drying), printing and overcoating are carried out directly on the outer surface of the vessel, which is very complicated.

DE 199 02 045 and US Pat. No. 6,773,217 B2 describe the coating of a tinplate belt from which punched blanks are punched and formed into can bodies for beverage cans, wherein large quantities of reject material and the problems mentioned above are created between the blanks result in an outer decorative layer. When printing molded aerosol cans, the printing costs can be of the order of magnitude of the raw can price. Disturbances on the printing press lead to interruptions in can production. Another disadvantage lies in the fact that in the execution of smaller can jobs on the printing press, the printing plates or printing cylinders must be replaced, resulting in the decommissioning of the entire cans. Production line leads. The printing press must be operated and monitored by a printing expert.

For the production of three-piece cans, sheet metal panels can be printed with grid-shaped decorations and then cut into individual frames, whereby the frames are further processed into can coats. In known printing, the handling of the metal sheets is expensive and the solvents used are disadvantageous and restrict the location for printing, which leads to undesirable transport routes. The cutting in two orthogonal directions corresponding to the respective desired nozzle height and the corresponding circumference of the can is complicated especially when changing over to cans with other masses. In addition, with the standard metal sheets used, there are always sheet metal sections in both directions that can not be used. From WO05 / 000498 a solution is known in which, starting from a metal strip with a forming and a welding step, a circumferentially closed tube is produced, are separated from the shell sections for cans. At each closed with a pushed laser longitudinal seam can jacket is attached to the lower end side of a can bottom with a laser seam. At the upper end a constriction is formed. Optionally, the upper end of the can jacket is necked by upset necking or spin-flow necking, which restriction can be performed until the valve seat is formed. A decorative layer on the outside of the can jacket is applied to the already formed tube in the form of a printed film on the outside. To ensure that the film holds well enough on the pipe, a complex precise application and connection is necessary. Optionally, the printed film is applied to the flat metal strip prior to forming and welding the tube. This creates the undesirable expense when forming the laser longitudinal seam, because the printed film must be kept away from the laser beam. WO05 / 068127 describes a similar production method wherein additionally the can jacket is pressed radially outwards against an inner mold. It is described a decorative film, which is optionally printed on its outside and on the inside of the can body facing with a primer and is applied after printing on the flat metal strip. A sealing layer is applied over the printing layer on the inside, which also passes through the printing layer between the film and the film Metal band ensures a tight seal connection. A pre-printed on the inside in a first printing and provided with the sealing layer film web is optionally printed in a further document on the front. This further printing step may be performed at the can manufacturer to apply specific decor information. This means, for example, that labels are applied to a basic décor in the further printing step, which are different for the respective sales markets. The provision and application of the decorative film is thus associated with several processing steps. According to EP 0 525 729, a decorative film is wound in the circumferential direction directly onto the can body and connected to the can body to form a closed film envelope. The separation and the application of a piece of film on the can body is very difficult, or associated with problems in thin films. From the documents US 4,199,851, DE 197 16 079 and EP 1 153 837 A1 solutions are known in which shrinkable plastic sheet material wound around a winding mandrel, formed into closed envelopes and as wrap-around labels in the axial direction on bottles or Cans are pushed and shrunk tightly. Moving the wrap-around labels over the bottles or cans is associated with a high risk of deformation and damage, especially for thin films. In addition to the actuation and friction forces, it is possible for electrostatic charges due to friction and associated variable electrostatic forces acting on the film to occur, so that rapid transfer of the cylindrically closed film is extremely prone to failure.

WO 2004/065273 A2 describes the joining of a piece of film to a closed film envelope on a concave inner surface against which at least a part of the film rests with the overlapping region. To achieve the sealing connection, the overlapping area is pressed from the outside of a pressure strip against the concave inner surface and connected via a sealing connection. The concave inner surface can be pushed together without jamming problems with the film envelope together over a Doing senkörper. In this situation, the film envelope is by a

Shrinking process transferred from the concave inner surface of the lateral surface of the can body. The shrinking process is carried out in an oven. For printing the film webs, a transfer method is described. In this case, at least one, but preferably get different colors, on a transfer surface and the transfer surface in one step on the film. The printed film Sheets must be printed in advance and stored until they are applied to cans. This creates planning and storage costs.

The printing and processing methods used for cans are very costly, both for direct printing of the cans and for printing and applying foils. If films are printed, more film sections must be produced than required cans, because yes, when applying the films on a metal strip or on the cans is expected to waste. If you print directly on the cans, the result is a donut shot until the correct color balance is achieved.

For printing on paper in relatively small numbers, digital printing techniques are popular. The digital methods do not require printing forms to be provided before printing. But they are slow compared to the printing methods with printing plates. Because the number of doses produced per time is very high for a cost-effective production of doses, only very fast printing process and therefore no digital printing processes are used for the can decor. US Pat. No. 5,207,153 describes a solution in which a marking is printed on the can jacket after application of the can decor with a digital inkjet printing process. From US 6,769,357 a solution is known in which the lateral surfaces of can bodies are digitally printed, wherein a transport device leads the can coats on spigot successively to the printheads with different colors and there rotates when printing by servomotors about the axes of the mounting bolts. When transporting from one print head to the next, the can coats must be kept in a defined orientation so that the different colors can be applied in a coordinated manner. The requirement for the mechanical transport device with respect to the exact alignment is very high, which leads to complex transport devices. If the alignment is not accurate enough, the picture quality will be poor. EP 521 606 B1 describes the production of a three-part can starting from a steel strip which comprises on one side a film strip printed by gravure printing and on the other side at least one thermosetting plastic layer or a thermoplastic resin layer. In order to ensure a good connection between the steel strip and the printed foil strip, heaters with a large expansion must be used because the high temperature is effective for a sufficiently long time got to. If the bond is insufficient, deformations such as the formation of a narrowed can neck can lead to undesirable deformations of the film relative to the sheet. Transverse to the longitudinal extent of the steel strip, the coatings have an extension which is slightly smaller than the can circumference. From the steel strip panels or frames for can coats are separated, which are then transformed and formed by means of resistance welding to closed can coats. The weld must be covered with cover coatings. The further processing of the panels and in particular the attachment of the cover coatings is expensive.

EP 646 428 A1 describes a similar solution, wherein only an inner coating and this is formed with an extrusion device directly on the flat sheet metal strip. Also in this solution, the further processing of the panels or frames and in particular the attachment of a seam cover is complex.

The common one-piece aluminum cans are sprayed with a solvent-containing varnish to provide an internal barrier inside after washing and drying, which is then dried in a drying oven to give off unwanted solvent vapors. Both the movable spray nozzle and the washing systems and / or the drying systems with the bearing shells for receiving the can bodies are elaborately constructed or undesirably large.

EP 426 258 B1 describes a solution in which can shells which are closed from sheet metal pieces about a device arm are formed, which are subsequently guided along the device arm by an inner coating apparatus. From the device arm, a synthetic resin powder is applied to the inside of the can coats, which is melted by the application of heat and enamelled and cured by cooling. Preferably, the synthetic resin powder is electrically charged and applied with a corona discharge. The handling of the individual pieces of sheet metal and the individual can coats is complex, in particular, synthetic resin powder passes between the can coats through to the outside, which leads to undesirable contamination. WO2005 / 000498 A1 describes an inner barrier in the form of a film, which is applied to the metal strip as a foil strip before tube forming. The metal strip is preheated with an induction heater. Subsequently, the foil strip is pressed onto the metal strip 1 via a deflection roller, so that a sealing layer of the foil strip connects the foil strip to the metal strip. A film strip with sealing layer is expensive to produce. To form a closed tube, a welding connection between the two lateral edges of the metal strip is necessary. Because the foil strip does not endure the temperature arising in the region of the weld seam, the foil strip will not laterally extend to the edges of the metal strip. In order to still be able to form a closed inner barrier, a seam covering tape is applied after seaming. The feeding and tight joining of the seam covering tape is complicated, because it must be spaced apart from this during the formation of the weld and only then is pressed by the compression of the tube formed at the seam area.

The present invention has for its object to find a solution with the cans can be easily and inexpensively manufactured, in particular, a high-quality decor and / or a dense inner coating to be achieved with the greatest possible flexibility with simple facilities.

In achieving this object, various inventions have been made which are particularly advantageous in combinations. A first invention relates to the direct printing of the metal strip. A second invention relates to the formation of a circumferentially closed inner coating after forming the laser seam on the tubular metal band formed before the separation of individual can coats. A third invention relates to the use of at least one digital printing system. All inventions is based on the finding that slower and faster processing steps can be combined, but then to dispense with a linear inline production and, for example, fast processing steps in a single line and slow in parallel lines, or simultaneously in several processing stations, performed , In addition, a fast printed metal web can also be wound into a coil, whereby such coils are further processed in parallel in slower processing. The metal web of a coil can also be divided into sub-webs prior to further processing with at least one longitudinal cut. In order to meet the versatile decor wishes with little effort, may be different Combined printing method and thereby used at various points of the can production or optionally a digital printing process only when filling the cans.

The object of the invention is solved by the features of claims 1, 6, 12, 16, 17, 18, 19 and 20. The dependent claims describe preferred or alternative embodiments.

In the context of the first invention, it has been recognized that essentially only two elaborate solutions are considered in can-making for printing according to the prior art, which points to a restrictive prejudice. For the printing of finished cans, very expensive and complex printing devices are used, which limit the can production to can manufacturing plants. On the other hand, printing on panels and film strips takes place in printing companies that are designed for special printing. Only with the knowledge that a metal strip must be printed directly, a solution has emerged that allows the printing of the decor and the manufacture of the can during filling operation.

In the inventive solution, the metal strip used for the production of can coats is printed in a printing step with decorative surfaces having in a first direction of the metal strip, preferably in the longitudinal direction, the extension in the direction of the can axis and transverse to the first direction, the expansion in the direction of the can circumference , wherein at least one longitudinal register mark is arranged in the region of each decorative surface, and the longitudinal register marks allow the control of separating steps so that the separated sections of the metal strip each comprise a complete decorative surface. The sections are used as can coats. Preferably, the metal strip is already closed before the separation step with a pushed laser longitudinal seam in the circumferential direction and then closed can coats are separated. With somewhat greater effort, it is also possible to reshape sections of the metal strip only after the separation step into the can shell shape and to close them with a pushed laser longitudinal seam in the circumferential direction. The many short laser longitudinal seams can always lead to problems at the end, because there the heat accumulated does not continue to flow and local overheating can occur. On one end of each can jacket a can bottom is attached. For printing, all known printing methods can be used, wherein preferably at least one offset or a flexo or a screen printing method is used. Because the curing or drying of the inks must take place very quickly during printing for the subsequent further processing or for the subsequent winding onto a coil, the ink is preferably cured by means of UV. About the colors can be applied or printed on a cover layer, which ensures about a smooth surface and a certain scratch resistance.

The at least one longitudinal register mark in the region of each decorative surface allows the desired control of the separating steps. If a small distance is formed between two successive decorations, an edge of the decoration can also be used as a longitudinal register mark. Preferably, however, a characteristic in the decor or optionally on the edge of the decor printed longitudinal register mark is used. Because the can coats or sections for can coats are separated after printing and because the decor preferably has to extend over the entire height of a can jacket, the distance between the decorations is chosen as small as possible. If necessary, even a distance is waived. Therefore, it is also very important that the dividing line be placed very precisely in the longitudinal direction of the metal strip, which can be achieved with printed longitudinal registration marks.

Because a laser connection to a can bottom is formed at least at one end face of the can jacket, it is advantageous if, at the end side, a narrow edge of the can jacket is free from the decoration. This free edge area is preferably ensured by the fact that the decor is not printed to the line at which the separation takes place. It would also be possible that when you separate or after separating the decor in the edge area is removed. It has been found that a laser connection is possibly also possible if the laser beam only after passing through the decor, or the associated removal of the decoration, the metallic layer of the nozzle senmantel with the metallic layer of the inside of the can jacket adjoining coffer floor connects.

If at least two decorations are printed side by side on the metal strip transversely to its longitudinal direction, the metal strip must be divided into the corresponding number of partial webs. Because the two long sides of each sub-orbit, or If necessary, the sections thereof, blended together and connected by means of laser welding, it is advantageous if the longitudinal sides of a narrow edge region of the can jacket is free from the decor. This free edge area is preferably ensured by the fact that the decor is not printed up to the long sides. It is expedient if a clean cut line is formed when splitting into partial webs or after splitting on both longitudinal sides. Optionally, the decor is removed in adjoining the cutting line or longitudinal side edge region.

So that different colors hold very well on the metal strip, a primer is preferably applied or printed before printing. The primer can be aligned on the one hand to the adhesion to the metallic surface and on the other hand to the provision of a printable surface. If these two tasks are not solved by the same paint, then a primer for the adhesion and then a top coat for the printable surface can be applied. Particularly advantageous is a primer which is applied as a sheet-metal coating or coil coating.

In coil coating, rolled metal strips are coated organically, whereby due to the simple geometry a high application efficiency can be achieved. The necessary steps are limited to painting and drying. If appropriate, cleaning, pretreatment and / or post-treatment are also carried out. If no fats and oils have been applied to the surface of the metal strip, cleaning can be dispensed with. It is possible, for example, to apply a first coating layer (primer) in a rolling process, to bake at about 240 ° C., then to apply a second coating layer (topcoat) in the rolling process and to bake it again at about 240 ° C. Subsequently, the metal strip can be rolled up into a coil or processed directly.

Because coil coating is best carried out directly during the production of the metal strip, metal strips primed with coil coating are special products. However, if such a special starting material is needed for can production, it can lead to undesirable bottlenecks or problems. It is useful to produce the cans starting from metal strips, which are readily available everywhere. The common steel belts are protected against oxidation with a tin or chrome coating and optionally with grease or oil. In order to be able to use common metal strips, the metal strip is cleaned and / or cleaned if necessary. brushes and then primed immediately before printing. The primer can be applied directly from a printing machine, especially only in the area of the decors to be printed. However, the primer must cure quickly, which is preferably achieved with a under UV radiation curing primer.

Solvent-containing coating systems are preferably used, in particular two-component systems (2K paints) with a binder of resin and hardener. But there are also solvent-free systems possible, for example under UV-curing primers. Common paint systems are based on polyester and polyurethane (and combinations), epoxy resin and polyvinylidene fluoride (PVDF). Polyurethane coatings come as 1- and 2-

Component systems for use. The curing is carried out at room temperature or elevated temperature. For 2-component systems, polyisocyanate and a polyhydric component can be used. Polyurethane coatings are particularly suitable for coil coating processes. The first paints suitable for metal were

Nitrocellulose lacquers with alkyd resins. Alkyd resins can be combined with many other film formers, such as phenolic resins and epoxy resins. Polyvinyl esters have good adhesion and adhere well to metallic surfaces. Acrylic resins can be used on metal in combination with other resins. The surface of the primer is chosen so that favorable printing process can be used with cheap inks. For example, it is possible to use a standard offset printing machine (film cylinder and blanket cylinder) with the versatile and, at the same time, economical oil-based inks. In addition to Haetset web offset printing inks, it is also possible to use water-dilutable or UV-curable inks and paints with solvents which dry at lower temperatures. In addition to offset printing, flexographic printing, packaging gravure printing and screen printing processes can also be advantageously used. In flexographic printing, low-viscosity ink (UV curable, solvent-based or water-based) is fed from a fountain roller to the applicator roll, and the applicator roller transfers the ink film to the raised printing plates of the forme cylinder. In gravure printing, the printing plate is inked with the wells by immersion in thin liquid paint and superfluous color with a steel knife (doctor blade) deducted.

In the packaging area is often worked with true colors and possibly also with primers. For this reason, the machines are usually equipped with a large number of inking units. In series multi-cylinder machines has each printing unit its own printing unit stand with impression cylinder and the metal band lays between the printing units a longer drying distance. When screen printing, the ink is printed with a rubber squeegee through a fine-mesh fabric on the printed metal strip or its lacquer layer. At those points of the fabric, where no color is to be printed according to the printed image, the mesh openings of the fabric are rendered opaque by a stencil. The speed is smaller compared to other printing methods. For screen printing, many colors are offered. They differ mainly in their adhesion properties, resistance on different materials and in their drying behavior. Due to the large color range, it is also possible to use, if appropriate, a color which can be applied directly to the metal and if appropriate has similar binders, such as the primer described above. In order to achieve rapid drying or hardening of the ink, it is preferred to use inks which can be cured with UV light or optionally with electron beams.

Offset printing is used primarily when the highest quality requirements in terms of screen printing and color fidelity are required. In combination with screen printing, hot foil stamping or cold foil printing special effects can be generated.

Favorable printing plates or printing rollers with flexible printing plates as well as the high degree of standardization in offset printing also make this process interesting for the printing of simpler decors at attractive prices. Wherever high coverage, detail accuracy and color strength are required to achieve brilliant, high-quality image effects, screen printing is ideally suited. Applying varnish allows special effects such as reliefs. Scented paints, thermochromatic paints and glittering paints are just a few examples of applications in screen printing. With the screen printing process, every decor can also be provided with braille braille.

For the production of round screen printing plates flexible screen printing plates are used which receive the desired color transparency by exposure and further processing steps. The processing is equivalent to other photopolymer printing plates used for letterpress and flexographic printing. All work steps can be carried out quickly with a few simple auxiliary devices. From the Reprofilm to the ready-to-use printing form you need less than 30 minutes. The screen printing plates can also be digitally imaged without analogue film. The printed metal strip may be processed into closed can jackets and further into cans according to any known method. However, it can be used particularly advantageously for further processing in which it is processed by at least one tube molding machine with a laser welding device into a blunt-ended tube from which sections are separated as can coats with a separating device. If at least two decorations are arranged laterally next to one another on the metal strip, then the metal strip is divided into a corresponding number of subbands which each have only the decoration for a can jacket in the transverse direction. A lateral trimming can also be performed to form clean and accurate lateral contact surfaces for welding. When cutting to the side, if required, the décor and the base can also be removed in a narrow edge area in order to expose the metallic layer from the outside for the laser seam.

In a preferred embodiment, slits are formed in the metal strip on the flat metal strip in normal planes to the longitudinal axis of the metal strip. These slots facilitate after the tube forming the separation of can coats or sections, because then only in the areas without slots a separation must be performed. However, the slots do not extend to the two lateral edge regions of the metal strip. In both lateral edge regions of the metal strip is dispensed with slots, because there yes, the laser longitudinal seam must be formed. Preferably, a slot is also omitted in the middle between the two lateral edge regions. After the tube has been welded, there are no slits in the laser seam and in the region opposite the central tube axis. At these contiguous areas, drive means, in particular drag caterpillars, can frictionally engage the pipe and achieve the feed desired for pipe production.

The slots are preferably formed directly on the printing press. They can be used as longitudinal register marks and then allow the desired control of the separation steps during later separation of the pipe sections. Optionally, the printing press also includes an embossing station, in which the metal strip is processed, for example, with embossing rollers. At the end of the printing machine, a longitudinal cutting device can be arranged, which divides the printed and slotted metal strip into sub-bands. The slots are formed so that the subbands at the edges and in the middle have no slots. The subbands can be rolled up and stored temporarily, or processed directly in parallel.

For printed cans with an inner coating, a circumferentially closed coating is applied to the inside of the resulting tube between the laser welding device and the separator. On at least one end face of each can jacket, a connection region is preferably formed, on which a terminating part can be fastened by means of a laser connection. Optionally, additional decor or information elements are printed on the can jacket with a digital printing system, this preferably taking place before or after the filling installation and allowing specific, in particular individualized, information to be applied to the cans.

In the context of the second invention, it was recognized that the inner coating after the laser welding of the resulting tube and before separating the can coats should be formed on the inside of the tube, because then the seam is covered and not every box must be coated individually.

For producing a can body with a can jacket and a can bottom, therefore, a metal strip is moved in its longitudinal direction, formed in a forming apparatus in a forming step continuously by blunt merging the lateral edge surfaces of the metal strip into a tube and a welding device in a welding step with a laser longitudinal seam closed at the butt-joined lateral edge surfaces in the circumferential direction. In a separating device, sections of the closed tube are separated by separation steps and provided as can shells with a laser longitudinal seam. Subsequently, connecting steps are carried out with which a can bottom is attached to one end face of each can jacket. In a processing area after the welding device and before the separating device, an inner coating step is performed with an inner coating device, in which a circumferentially closed inner coating is formed on the inside of the closed tube. Because it also covers the seam, can be dispensed with an additional seam covering step.

The thickness of the inner coating is usually smaller than the thickness of the metal strip. A good bond between the pipe wall and the inner coating is essential for many important because otherwise there is a risk during the separation step that the inner layering will detach somewhat from the pipe. In special applications, it may also be desirable to achieve only a slight adhesion between the inner coating and the metal body in order to be able to separate the components from one another with a defined peeling force. If the inside of the tube is circular in cross-section and without a step, ie butt welded, the extruded inner coating can be pressed well on the inside, which causes a good connection in a sufficiently adherent during extrusion plastic mass. In a preferred embodiment, in the inner coating step, the inner side is provided with an inner coating, preferably made of plastic, in particular polyethylene (PE) or low density polyethylene (LDPE), which is supplied by means of an extrusion die in the plasticized state. It goes without saying that the inner coating is selected in each case according to the specifications for the product to be filled into the can and thus, for example, PET or PP could also be used. The extrusion and on the inside applying a tubular plastic inner layer has the advantage that no drying or curing step must be carried out at a high temperature. If the plastic inner layer does not adhere to the inside of itself, the adhesion must be achieved if necessary with a previously applied to the flat metal band adhesive or sealing layer. Depending on the contact properties of the inside of the closed tube or the metal strip and the adhesive properties of the plastic inner layer, it may also be sufficient if the closed tube is heated before the plastic inner layer is applied. Optionally, an adhesion-promoting layer is applied between the inner side and the inner plastic layer, which is preferably supplied to the inner coating step by means of an extrusion die. The inner coating can be designed as a monolayer, or extruded as a multi-layer structure. In multilayer extrusion or coextrusion, this layer composite would consist of at least one adhesion promoter and at least one functional layer (two-layer coextrusion). If appropriate, the adhesion-promoting layer or a holding layer for the plastic inner layer is already applied to the metal strip before the inner coating step, with heat or optionally UV light being supplied for drying or curing. In a tube application from an annular extrusion die, a tubular plastic inner layer is extruded and preferably brought by means of a pressure difference for abutment against the tube inside. In a first group of solutions, a drag stopper is arranged in the interior of the tube after the extrusion nozzle, and the tube interior, which is surrounded by the extrusion die, the drag stopper and a section of the tubular plastic inner layer, is supplied with supporting air from the extrusion die. The resulting in this interior increased pressure presses the tubular plastic inner layer to the inside of the closed tube. Together with appropriate adhesion properties (adhesion promoter and / or heat) it is ensured that the plastic inner layer permanently adheres to the inside of the closed tube. Optionally, the tow plug leads to a pressing of the plastic inner layer to the inside of the closed tube.

In a second group of solutions, a negative pressure space is formed in the interior of the tube in front of the extrusion die, which provides a negative pressure radially outside the extrusion die, which draws the tubular plastic inner layer against the inside of the closed pipe.

Instead of the hose application, a print job could also be provided in which the coating material is pressed radially from the extrusion nozzle to the inside of the pipe. Since even small variations in the pipe diameter can lead to inaccuracies in the applied layer, the print job for this application seems less suitable than the hose application.

An extrusion device comprises, in addition to the extrusion die, the extrusion die, at least one melt line leading into the extrusion die, and at least one supply line and at least one extruder, which feeds the at least one line with the material to be extruded. Optionally, a melt pump is also connected between the extruder and the remainder. If at least two tubes are produced in parallel, then it is expedient to use the at least one extruder for feeding extruder tools used in parallel. An extrusion tool is associated with the interior of a resulting tube and is held from the side where the metal strip is still open, or the lateral edge surfaces of the metal strip not yet are merged. In the interior of the extrusion tool, connections are formed which lead at least the melt material for the plastic inner layer of at least one line to the extrusion nozzle in such a way that it can be removed in a tubular manner from an annular outlet opening. Optionally, compounds for a coupling agent are provided which is supplied so that it comes to rest between the plastic inner layer and the inside of the closed tube. The adhesion promoter is preferably discharged with the plastic material from a common nozzle opening. Optionally, the bonding agent is discharged separately from the plastic material from its own nozzle opening. Further connections in the extrusion tool can be provided for the support air supply and / or a vacuum connection.

The elements of the inner coating device are arranged so that the plastic inner layer is applied after the welding device to the inside of the tube. The extrusion die and the extrusion die may be arranged in a range from the molding apparatus to the welding apparatus.

For the tube forming, the laser welding of the tube longitudinal seam, the attachment of the circumferentially closed inner coating and the separation of can coats can be supplied to any metal strip, especially an uncoated and unprinted. Optionally, the metal strip used on the later inside comprises an adhesive coating for the circumferentially closed inner coating. Preferably, however, a metal strip already printed on the later outer side is used, wherein the decoration is preferably printed on a primer and optionally a cover layer is applied over the print. The closed can coats are further processed into cans according to a known method. If at least two decorations are arranged laterally next to one another on the metal strip, then the metal strip is divided into a corresponding number of subbands, which each have only the decoration for a can jacket in the transverse direction. Side trimming can also be performed to form clean and accurate lateral contact surfaces for welding. When cutting to the side, the décor and the primer can be removed, if required, even in a narrow edge area in order to expose the metallic layer from the outside for the laser seam. In embodiments which form slots in the metal strip on the flat metal strip in normal planes to the longitudinal axis of the metal strip, the separation of can coats or sections is facilitated after tube forming. It only has to be carried out in the areas without slots a separation. Preferably, the separation must be performed only in two with respect to the central tube axis opposite narrow portions of the tube circumference. Because the lateral surface of the tube deviates only slightly from a tangential plane in these subregions, two separating devices extending opposite each other and extending over the respective narrow region can be used for severing, each piercing the region to be separated from one side. Because the resulting tube is guided by a central mandrel and is continuously moving along the tube axis, the separator comprises cutting elements which are additionally moved with the tube during their cutting motion.

A simply constructed cutting device comprises a rotating drum with radially projecting cutting edges. The axis of rotation of the drum is arranged orthogonal to the tube axis. The drum diameter is selected so that the circumference corresponds to an integer multiple of the desired length of the pipe sections, wherein the cutting edges are arranged at corresponding circumferential intervals on the cylindrical outer surface of the drum and lie in planes parallel to the axis of rotation. For an efficient separation step, it is expedient for the cutting edge to cooperate with a support edge of the mandrel. Because the wall thickness of the tube is very small and the drum diameter is sufficiently large, the plane of the cutting edge during the cutting process is almost perpendicular to the tube axis and the resulting cutting line is then almost in a normal plane to the tube axis.

If a high demand is made that the cutting line lies in a normal plane to the tube axis, and / or if the cutting line extends over a large peripheral portion of the tube, then cutting edges can be used with guide means, such guiding means including the cutting edge the adjoining surfaces of the cutting device during the entire cutting process in a normal plane to the tube axis and at the same time moves this normal plane with the speed of the pipe feed. After the separation step, the cutting edge outside the tube is returned against the feed direction of the tube of the guide device. The guide device can move in a sectional plane along the tube axis, the cutting edge circular, wherein during cutting in Direction of the tube axis preferably a substantially constant coinciding with the feed rate of the tube speed should be ensured. The cutting edge moves not only radially with the cutting speed, but also in the direction of the pipe feed. When cutting, the cutting edge moves in the cutting plane preferably along a straight line, which should be understood as a small deviation from a circular line.

The support edge of the dome is preferably positioned so that the cutting edge is at the desired minimum distance from the support edge when hitting the pipe inside. This minimum distance is adapted to the wall thickness of the pipe. At the beginning of the cutting process, so when piercing the cutting edge in the pipe jacket, the inside of the pipe jacket is slightly pressed against the mandrel. So that no friction-induced braking of the tubular jacket takes place, the contact surface of the dome is formed by a material having the smallest possible coefficient of friction, for example of ceramic material. In order to keep the forces acting on the pipe when cutting from the cutting edge as small as possible, the cutting edge can be formed or optionally moved so that during piercing, only a portion of the cutting edge in contact with the tube and the other portions only then come into contact , Particularly suitable for this purpose is, for example, a tooth-shaped cutting edge, wherein the tooth tips lie substantially on a circle segment, so that at least a part of the teeth enter the tube substantially simultaneously during piercing. The feed and the recesses between the teeth are chosen so that at the end of the

Cutting the pipe is separated over the entire length of the cutting edge. It has now been found that cutting edges that extend over circular segments, not only advantageous for the separation of slotted tubes are used. Also independent of the claimed in the claims invention solutions are new and inventive, which provide for cutting continuously moving tubes along the tube circumference a plurality of cutting edges, which are movable substantially in normal planes to the tube axis radially to the tube axis, said at the end of the cutting movement the cutting edges lie radially inside the tube wall and have thereby complemented to form a closed line. Preferably, the cutting edges cooperate with a supporting edge of a dome inside the tube. After cutting, the cutting edges are again moved radially outward. The small radial movements of the cutting edges can be carried out in extremely short cycles. When separating with radial moving cutting edges produce no chips and it can be dispensed with the removal of chips.

For extremely thin-walled metal pipes may optionally be dispensed with a movement of the cutting edges in the direction of the tube axis, in which case the advanced during the cutting process extremely short pipe feed can be slightly deformed radially inwardly around the support edge. If the pipe feed is impaired by cutting edges which are fixedly positioned in the pipe longitudinal direction, the cutting edges are moved in the pipe longitudinal direction during cutting. For this purpose, the drum solution already described for achieving the slots or the solution can be used with guide means, such guide means keeping the cutting edges in a normal plane to the pipe axis during the cutting operation and at the same time moving this normal plane at the speed of the pipe feed. On at least one end face of each can jacket, a connection region is preferably formed, on which a terminating part can be fastened by means of a laser connection. Optionally, additional decorative or information elements are printed on the can jacket with a digital printing system, whereby this preferably takes place before or after the filling installation and allows specific, in particular individualized, information to be applied to the cans.

In the context of a third invention, which is also advantageous on its own, it has been recognized that in can production, digital printing systems can be used which are considered too slow and too expensive by those skilled in the can manufacturing field. In this case, prevailing in the field of can production prejudice was overcome, namely that due to the economy always very large quantities of a box must be made with a solid decor and thus only printing process with printing plates are suitable. In overcoming the prejudice, it had to be recognized that the manufacture of the can body and the provision of the decoration can be optimized separately. Even if the processing steps for producing the can body are very rapid, the pressure step can nevertheless be carried out more slowly if it is carried out, for example, for several doses in parallel or optionally only when filling the cans, or before or after filling. The cans can be made by any known method. It is particularly advantageous if the cans are made according to the first and / or second invention already described.

Printing is then performed during can production or filling with parallel printing systems using digital printing systems on substantially cylindrical can jackets. The widespread use of digital printing systems is geared to flat surfaces. It thus had to be overcome for the present invention, a prejudice of those skilled in the field of digital printing. This further prejudice consists in printing the product to be printed in the form of sheets or tapes in the flat form with the fastest possible digital printing, because this ensures rapid positioning and switching between the printing operations.

Digital printing of the can coats places the printheads of a digital press on a common print area, eliminating the need to move the can coats with controlled orientation from one printhead to the next. If the printheads are associated with a common print area, all different colors are applied during the same movement of the can jacket. The movement of the can jacket is either a rotational movement about the axis of the can jacket or a displacement of the can jacket in the direction of the axis of the can jacket. Because a can jacket does not have to be moved from one print area to the next, but is completely printed in a print area, the coordination of the printing of the various print heads does not depend on the accuracy of transporting the can jacket from one print area to the next.

Digital color printing enables accurate color reproduction of originals or certain normalized hues without creating a scrap when a new decor is printed. It can be made directly to each other cans with different decorations. In particular, the printed decor may also include a number or other decorative element that is different on each can, thus creating cans with an individualized decor. Changes to the print can be made in a few seconds by a mouse click.

In digital printing, there are various printing techniques such as inkjet printing, wax printing, thermal transfer printing, digital screen printing, laser printing, etc., each with appropriate properties. Further processing after printing also offers a wide selection of coating or protection options. Preference is given to digital printing with dry or liquid toners. Hot applied layers of paint are usually very resistant. Wax printing achieves a high luminosity and intensity due to a thick application of paint. Digital screen printing is very cheap and fast. Inkjet prints currently offer the best resolution and photo quality on a special primer. Color laser printers are cheap in price and cost per printed decor.

In order to be able to achieve all colors as well as possible, preferably digital prints with at least four colors are used. Preference is given to ink printers, for example an HP mPrinter 4000 ink printer with five colors. For very demanding applications, a 7 or 8 color inkjet print can be used with, for example, HP Vivera inks. The inks deliver a wide range of brilliant colors for true-to-life images and black-and-white presentations with neutral grays and rich blacks. With the white HP Indigo ink, a silky smooth surface can be printed. Even fluorescent colors can be used. A printhead management system with electrostatic control of the ink droplets reduces the need for cleaning and ensures a perfect condition of the printheads. If a suitable primer is placed on the can jacket prior to printing, the print quality and in particular the light resistance can be increased. The print is immediately water-repellent, smudge-proof and moisture-resistant. With a suitable primer the pressure is absolutely waterproof. Solvent-containing paint systems are preferably used for the primer, in particular two-component systems (2K paints) with a binder of resin and hardener. But there are also solvent-free systems possible. Common paint systems are based on polyester and polyurethane (and combinations), epoxy resin and polyvinylidene fluoride (PVDF). Due to the constant development of the colors, more and more surfaces can be printed without any problems and therefore an earlier surface treatment of the can is increasingly dispensed with.

There are digital printing systems in which the printheads are moved back and forth, with the can coats to be printed being moved in coordination with the movements of the printheads. The movement of the print heads is essentially orthogonal to the movement of the can coats. When the can coats are progressively wrapped around their longitudinal be rotated axis, the printheads are moved back and forth in the direction of the longitudinal axis, wherein the respective movement depends on whether the color of the print head in the corresponding region of the can jacket is needed. When the can coats are progressively shifted in printing in the direction of their longitudinal axis, the print heads are moved in the circumferential direction about the longitudinal axis, the respective movement depending on whether the color of the print head in the corresponding area of the can jacket is needed.

It goes without saying that moving printheads can preferably be arranged together on a common movement system. The movement of the printheads must be carried out in such a way that the printheads are led everywhere where at least one color has to be applied. If there is a separate motion system for each printhead, movement of individual printheads is restricted to areas where the corresponding color is needed. As soon as all print heads have printed on the assigned area of the can jacket, the can jacket can be moved a little further.

Movement of the printheads can be eliminated if the printheads span the entire pressure extent - the height or circumference of the can shells. Linear printheads can be longer than the can height to be printed, and then pressure control ensures that printing is limited to the desired height of the can jacket. For annular printheads, which are adapted to the circumference of the can jacket, corresponding printheads must be used for the different can diameters.

If linear printheads for different colors are circumferentially distributed (or slightly offset) around a rotation axis, printing of all colors may be performed simultaneously while rotating the can jacket, with the printheads each applying circumferentially offset image portions to their spacing. If the order of application is important, then one color after the other can be applied, in which case the can jacket must be rotated several times around its axis. For cylindrical can jackets, the linear printheads are straight. For rotationally symmetrical can shells, which deviate from the cylindrical shape, it would also be possible to use correspondingly shaped linear print heads, but then print heads would have to be provided for each sheath shape. If circular printheads are arranged centrally offset by a common feed axis in the axial direction, the printing of different colors corresponding image areas in the different printheads is slightly offset in time during the movement of the can jacket along the feed axis, wherein the time offset of the feed rate and the distance between the Depends on printheads.

The substantially simultaneous or parallel printing of multiple can coats can be performed on turntables, but this is relatively complex due to the synchronized transfers and tuned to the can diameter holding and transfer elements. In addition, a turntable on which many can coats are printed at substantially the same time has a large diameter and takes up a lot of space. The printing of the can coats is optionally carried out on can coats without bottom of the can and without upper end or without upper constriction. In particular, cylindrical can coats are printed. For this purpose, the system is arranged for printing between the system for producing the closed can coats and the system for attaching a can bottom. Preferably, however, ready-to-fill or already-filled cans are printed for filling.

The throughput required for printing is achieved with solutions in which several linear printing lines are provided in parallel. Dust areas are provided in front of the printing lines, from which the can coats to be printed are guided into the parallel printing lines. If the production of cans with a first one is changed over to cans with a second diameter, only a few elements have to be adapted to the changed diameter in the feeds to the parallel printing lines. In case of problems with a printing line, the can production does not have to be stopped, but only the storage area in front of the printing lines is filled a little more.

For printing on can coats this is preferably placed directly after production on pallets, with which they can be promoted from the area of the can jacket production by a dust area in front of the printing lines, by the printing lines and then to the next processing step of can making. to Promotion of can coats are preferably used pallets with magnetic material or with spontaneously non-magnetic but magnetizable material and magnetic conveyor. The pallets have areas which are formed for contact with steering surfaces of the conveyors and other guide elements. Preferably, the pallets are formed like a mandrel and thereby formed as an inner support structure for the can coats, which ensures the necessary stability for printing and the holding devices required by the printing lines.

The processing steps of the can parts can be carried out substantially independently of the pressure lines. Only when a large part of the printing lines has problems must the can production be stopped. It is expedient to provide more pressure lines than would be necessary for the throughput of can production. This can prevent unwanted backlog before printing. In the case of parallel printing lines, the individual lines can print different decors and feed the printed can coats separately for further processing. Preferably, however, the printed canned shells subsequently reach the printing lines in a common storage area from which they are fed to the next can production step.

Optionally, the printing is done directly before, during or after filling the cans, which optionally only a portion of the decor is printed at this point.

The drawings explain the solution according to the invention on the basis of exemplary embodiments. It shows

Fig. 1 is a schematic representation of the steps and apparatus used for the

Creating the decor to be used on cans,

FIG. 2 is a schematic representation of the steps and apparatus used to form an inner coating on can jackets. FIG.

3 is a schematic sectional view for forming the longitudinal seam, FIGS. 4 to 7 are schematic sectional views of Innenbeschichtungsein- directions 8 is a schematic representation of the steps and apparatuses used to create cans with décor and interior coating.

9a and 9b a front and side view of a drum with cutting edges for creating slots in the metal strip,

10a and 10b is a side or end view of two drums with cutting edges for the separation of pipe sections,

11 is a schematic representation of a printing device,

12a, 12b, 12c are schematic sectional views of a separating device with a guide device for moving the cutting edge in a normal plane with the tube moved to the tube axis

13a, 13b, 13c is an end view of the tube with the cutting axis radially movable to the tube axis,

14a, 14b, 14c is a side view of the tube with the tube axis radially bewegba ren cutting edges,

15a, 15b is an end view of the tube with cutting edges with teeth before and after cutting the tube.

Fig. 1 shows a device which allows an efficient and versatile creation of the decor of cans. Metal bands 1 are fed to the desired printing line. A printing device 2 with cylindrical printing forms imprints the metal strip with a desired number of colors. This results in decorative surfaces and longitudinal register marks, wherein the decorative surfaces in a first direction of the metal strip, preferably in the longitudinal direction, a height extent of the can decor in the direction of the can axis and transverse to the first direction, the circumferential extent of the can decor. The longitudinal register marks are arranged in the region of the decorative surfaces. Optionally, a primer is first applied with at least one printing form. For highly individualized prints or small series, digital printing systems 3 are used. Because they print slower, it may be useful to print multiple tapes in parallel. If necessary, a printed with the printing device 2 metal strip for applying small supplements to a digital printing system 3 is supplied.

A printed metal strip is fed to a forming device 4 with a first laser welding device and a separating device. Therein, the metal strip in its longitudinal moved direction and continuously formed in a molding step by blunt merging the lateral edge surfaces of the metal strip into a tube. In the case of the laser welding device, in a welding step, the shaped tube is closed in the peripheral direction with a laser longitudinal seam in the case of the butt-joined lateral edge surfaces. In a separator 5 sections of the closed tube are separated with separation steps. For cans with an internal coating, the metal strip is provided after the welding device and before the separator with an inner coating which adheres to the inside of the closed tube and is formed closed in the circumferential direction, thereby covering the seam.

In a connecting device 6, a can bottom is attached to one end face of each can jacket. Optionally, the upper can end is formed according to the desired can type. Another digital printing system 7 is designed to print a can jacket over a print height and the entire can circumference. For this purpose, within a common time interval and at a common time interval

Movement of the can jacket relative to the other digital printing system 7 applied all the colors of the at least one digital printing system with corresponding printheads in the required proportions on the can jacket, all printheads of the other digital printing system are assigned to a common pressure range, in whomh pressure range is the can jacket during the course of movement , The completely printed cans are filled in the filling plant 8 and sealed.

According to FIG. 2, the metal strip 1 is fed via a device 9 for trimming the lateral edges of the shaping device 4 with the first laser welding device 0 and the separating device 5. The metal strip 1 is moved with a dragline assembly 11 in its longitudinal direction. On the feed side of the laser welding device 10, the metal strip 1 is continuously formed in a molding step by blunt merging of the lateral edge surfaces into a tube. In the case of the laser welding device 10, in a welding step, the shaped tube is closed in the circumferential direction with a laser longitudinal seam at the buttomically brought together lateral edge surfaces.

For cans with an inner coating, the metal strip 1 is coated after the laser welding device 10 and before the separating device 5 with an inner coating device 12 on the inside. The resulting inner coating adheres to the inside of the closed tube, is formed closed in the circumferential direction and über- therefore covers the laser longitudinal seam. The coating material for the inner coating passes from a feed device 13 through the interior of the deformed metal strip to the inner coating device 12. For externally covering the laser longitudinal seam, an outer seam coating device 14 is arranged between the first laser welding device 10 and the separating device 5. Thus, the inner coating and possibly also the outer seam cover connects well with the metal strip, a heater 15 is used. On one end face of each inside coated and externally provided with a decor donated mantle 16 is fixed with a second laser welding a can bottom.

FIG. 3 shows a cross section in the case of the laser welding device 10. A mandrel 17, which leaves a free space in the region of the laser longitudinal seam 18, is located in the interior of the strip material 1a which is circularly shaped in the circumferential direction. So that the extremely thin strip material 1a in the laser longitudinal seam 18 coincides with the two lateral edges precisely dull, 18 pressing rollers 19 are provided on both sides of the laser longitudinal seam. The pressure rollers 19 may be occupied in the magnetizable band material 1a along the circumference with magnets 19a, so that the band material 1a can also be held precisely on the pressure rollers and thus can be dispensed with a friction-generating pressing on the mandrel 17. Feedthroughs (not shown) for the inner coating and optionally for the supply or removal of gas from the region of the laser welding device 10 lead through the mandrel.

FIG. 4 shows an internal coating device 12 for internal coating of the tube, which is produced from the metal strip 1. The metal strip 1 is formed with a shaping device 4 continuously by blunt merging the lateral edge surfaces of the metal strip 1 into a tube and closed with a laser welding device 10. In the illustrated embodiment, the internal coating device 12 is formed as an extrusion device and comprises an extrusion die 20, an extrusion die 21, at least one line 22 leading into the extrusion die 21 and at least one extruder, not shown, which feeds at least one line with the material to be extruded. The extrusion die 21 and the extrusion die are located inside the associated with standing pipe and are held from that side where the metal strip 1 is still open.

In the illustrated embodiment, the extrusion tool 21 cooperates with the molding device 4 in the region of the laser welding device 10 and assumes the function of the dome 17 according to FIG. 3, which leaves a free space in the region of the laser longitudinal seam 18.

In the interior of the extrusion die 21, connections 23 are formed, which lead material for the inner coating from a line 22 to the extrusion nozzle 20 so that the material is discharged as a tubular closed inner coating 24 from an annular outlet opening 20a. In the illustrated embodiment, a line for a bonding agent is shown radially outside the central conduit 22, which is arranged radially outwardly about the centrally supplied coating material via an annular connections 23. The components thus brought together pass through conical connections 23 to the extrusion nozzle 20. The adhesion promoter is located on the outside of the tubular inner coating 24 and ensures good adhesion of the inner coating 24 to the inner side 25 of the tube 26. The tubular inner coating 24 is preferably by means of a pressure difference brought to the concern to the inside 25 of the tube 26. To achieve the desired pressure difference is after the extrusion nozzle 20 in the tube inside

Tail plug 27 is arranged and the tube interior of the extrusion die 20, the tow plug 27 and a portion of the tubular inner coating 24 is supplied via a line 22, a connection 23 and a support air duct 28 through the extrusion die 20 through with supporting air. If necessary, the tube 26 in the region of the inner coating device 12 by a heater 29, in particular an induction heating, warmed to improve the adhesion of the inner coating 24 , The use of an adhesion promoter and / or the heating device 29 ensures that the inner coating 24 adheres permanently to the inner side 25 of the closed tube 26. The tow plug 27 is attached to the extrusion die 20 via a retaining connection 27a. Fig. 5 shows an embodiment with an extrusion die 21 which extends in the region with the not yet closed metal strip 1 from the tube interior radially outwards. In a compound 23, the coating material is fed centrally and directly around it, the bonding agent. The tubular inner coating 24 emerging from the extrusion die 20 is pressed by the drag stopper 27 against the inside 25 of the pipe 26. In this embodiment, the tool can also be located well in front of the closed metal strip 1, so that an extruded, in particular cooled, plastic hose is guided into the shaped metal strip 1. In the area after the metal strip welding the tubular closed inner coating 24 is attached to the tube inside 25 by supplying heat and by means of overpressure.

6 shows an embodiment in which the extrusion nozzle 20 has a first and a second annular outlet opening 20a, 20b, wherein the material of the inner coating exits through the first outlet opening 20a and the adhesion promoter through the second outlet opening 20b. The connections 23 are designed accordingly and connected to the lines 22.

FIG. 7 shows an embodiment in which a vacuum chamber 30 is formed in the interior of the tube in front of the extrusion die 20, which provides a negative pressure radially outside the extrusion die 20 and thus sucks the tubular inner coating 24 against the inside 25 of the closed pipe 26. The vacuum chamber 30 is closed on one side with a seal 31 and on the other with the tubular inner coating 24. The negative pressure is generated by a vacuum pump, which is connected via a connection 23 to the vacuum chamber 30. Two further connections 23 are used to supply the bonding agent and the coating material, which two components are brought together just before the extrusion die 20 so that the bonding agent after exiting the extrusion die 20, the inner side 25 of the tube 26 faces. The elements of the inner coating device 12 are arranged so that the inner coating 24 is applied to the inside 25 of the tube 26 after the laser welding device 10. Optionally, instead of the dome 17 according to FIG. 3, a sleeve 17a is arranged around the extrusion tool 21, which sleeve 17a has a free space in the region of the laser longitudinal seam 18. So that the extremely thin metal strip 1 in the laser longitudinal seam 18 coincides with the two lateral edges precisely dull, are For example, provided on both sides of the laser longitudinal seam 18 pressing rollers, not shown.

It is self-evident that in the embodiments of FIGS. 5 to 7 there is also provided a respective not-depicted shaping device (analogous to FIG. 4). In Figs. 5 and 6, the existing laser welding device was not drawn, wherein it would be positioned as in Fig. 4 or 7 in the region of the extrusion die 21 and a sleeve 17a. After the inner coating has been applied, sections 6 of the closed tube 26 are separated in a subsequent separating device 5 with separating steps (FIG. 2).

8 shows an embodiment with a printing machine 32 for printing decorative surfaces and a processing section with a forming device 4, a laser welding device 10, an inner coating device 12, a coating material feed device 13, a drag pack assembly 11 and a separating device 5. In the printing machine 32 is additionally to the printing steps 32b, optionally a priming step 32a performed.

Optionally, a cleaning station 51 is provided in which the surface of the cladding strip 1 to be printed is cleaned or treated in such a way that the first layer to be applied remains sufficiently stable on the metal surface. The treatment may include washing, brushing and / or further mechanical treatments. Optionally, a laser or plasma surface treatment is provided. After an optionally provided primary drying 52, a basecoat 32a can be carried out. According to the primer used, a hot air drying 54 and / or a UV drying 55 is provided. After the various printing steps 32b, a UV drying 55 is preferably carried out in each case. According to FIGS. 8 and 11, in a preferred embodiment, the printing press 32 comprises a slit device 33 which forms slits in the flat metal strip 1 in normal planes to the longitudinal axis of the metal strip 1. These slots facilitate after the tube forming the separation of can coats or sections, because then only in the areas without slots a separation must be performed. Slits are dispensed with in both lateral edge regions of the metal strip because there the laser longitudinal edges must be trained. Preferably, a slot is also dispensed with in the middle between the two lateral edge regions. The slots can be used as later register marks the later separation of the pipe sections 16. A part of a simply constructed slot device 33 is shown enlarged in FIGS. 9a and 9b. The slit device 33 comprises a rotating drum 34 with radially projecting cutting edges 35. The axis of rotation of the drum 34 is arranged orthogonal to the longitudinal axis of the metal strip 1. The drum diameter is selected so that the circumference corresponds to an integer multiple of the desired length of the pipe sections 6, wherein the cutting edges 35 are arranged at corresponding circumferential intervals on the cylindrical outer surface of the drum 34 and lie in planes parallel to the axis of rotation. For a good slot step, it is expedient if the cutting edge 35 cooperates with a support roller 36, in which case preferably the cutting edges 35 cooperate with supporting edges of the support roller 36. Because the wall thickness of the tube 26 is very small and the drum diameter is sufficiently large, the plane of the cutting edge is almost perpendicular to the metal strip 1 during the slotting operation.

Optionally, the printing press 32 also includes an embossing station 37, in which the metal strip is processed, for example, with embossing rollers. The embossing station 37 comprises a rotating drum with curved embossing surfaces, which are associated with the already printed decorative surfaces during embossing. The axis of rotation of the drum is arranged orthogonal to the longitudinal axis of the metal strip 1. The drum diameter is chosen such that the circumference corresponds to an integer multiple of the desired length of the pipe sections 6, wherein the embossing surfaces are arranged correspondingly on the cylindrical outer surface of the drum. For a good embossing step, it is expedient if the embossing surfaces cooperate with a somewhat elastic support roller 36 or a support roller with support surfaces adapted to the embossing surfaces.

At the end of the printing machine 32, a longitudinal cutting device 38 can be arranged, which divides the printed, slotted and optionally embossed metal strip 1 into sub-strips 41. The longitudinal cutting device 38 comprises at least one first cutting ring 39, which optionally cooperates with a second cutting ring or a support ring 40. The subbands 41 have no slits at the edges and in the middle. The subbands 41 can be rolled up and stored temporarily, or processed further directly in parallel. FIG. 8 also shows the further processing of the printed and slotted metal bands 41. With the molding device 4, the printed metal strip is closed rohrformig. With the laser welding device 10, the longitudinal seam is formed. The interior coating device 12 is used to apply the inner coating. There are no slots in the laser seam and in the area opposite the central tube axis. In these contiguous areas the drag caterpillars 11 frictionally engage the pipe 26 and achieve the desired feed rate for pipe production. A register mark reading device 42 recognizes the register marks or slots and controls the separating device 5, as well as optionally the drive of the drag caterpillars 1. The separator 5 separates after the tube forming can coats 16 and sections from.

FIGS. 10 a and 10 b show a simple separating device 5. Separation only has to be carried out in the regions without slots. Preferably, the separation must be performed only in two with respect to the central tube axis opposite narrow portions of the tube circumference. Because the lateral surface of the tube 26 differs only slightly from a tangential plane in these subregions, two opposing separating devices can be used for severing, each piercing the region to be separated from one side. Because the resulting tube 26 is guided by a central mandrel 42 continuously along the tube axis in motion, the separator comprises cutting edges 35, which are also moved in their cutting movement with the tube 26. The schematically (not to scale) illustrated separator comprises rotating

Drums 34 with radially projecting cutting edges 35. The axis of rotation of the drums is arranged orthogonal to the tube axis. The drum diameter is selected so that the circumference corresponds to an integer multiple of the desired length of the pipe sections 16, wherein the cutting edges 35 are arranged at corresponding circumferential intervals on the cylindrical outer surface of the drum 34 and lie in planes parallel to the axis of rotation. For a good separation step, it is expedient if the cutting edge 35 cooperates with a support edge 43 of the dome 42. Because the wall thickness of the tube 26 is very small and the drum diameter is sufficiently large, the plane of the cutting edge 35 is almost perpendicular to the tube axis during the cutting process and the resulting cutting line is then almost in a normal plane to the tube axis. Figures 12a, 12b and 2c show a separating device 5 in which the cutting edge 35 is moved via a guide device 44, such a guide device 44 holding the cutting edge 35 in a normal plane to the tube axis during the entire cutting process and this normal plane at the speed the pipe feed moves. After the separation step, the cutting edge 35 is returned outside the tube against the feed direction of the tube by the guide device 44. In a sectional plane along the tube axis, the guide device 44 can move the cutting edge in a circle-like manner, wherein during cutting in the direction of the tube axis preferably a substantially constant speed matching the feed rate of the tube is ensured.

In order to achieve this, in the illustrated embodiment, the cutting blade 35 'is connected to the cutting edge 35 at two spaced connection points 45, each with synchronously rotating discs 46. The distance of the two disk rotation centers 47 corresponds to the distance between the two connection points 45. To ensure that the speed component of the cutting edge 35 is constant in the direction of the pipe axis, straight guide lines 48 are provided for the connection points 45. In order for the connection points 45 to follow these guide lines 48 during the rotational movement of the disks 46, the connection points 45 on the disks 46 are held in radial guides 49, with spring elements 50 holding the connection points 45 in the possible outermost position.

In the enlarged view of the tube 26, the pressure layer 26a is shown on the outside, the inner coating 26b on the inside, and the metallic can wall 26c therebetween. The supporting edge 43 of the dome 42 is preferably positioned so that the cutting edge 35 still lies in the region of the dome 42 when hitting the tube 26 (FIG. 12 a). During the further penetration into the tube 26 (FIG. 2 b), the cutting edge 35 moves together with the tube 26 against the support edge 43, so that it reaches a desired minimum distance from the support edge 43 when the tube side is reached (FIG. 12 c) ). This minimum distance is adapted to the wall thickness of the tube 26. At the beginning of the cutting process, so when piercing the cutting edge 35 in the pipe jacket, the inside of the pipe jacket is slightly pressed against the mandrel 42. So that there is no friction-induced braking of the tubular jacket, the contact surface of the dome 42 of a material with the smallest possible coefficient of friction formed, for example of ceramic material.

In order to keep the forces acting on the pipe when cutting from the cutting edge as small as possible, the cutting edge 35 may be formed or optionally moved so that during piercing, only a portion of the cutting edge in contact with the tube and the other portions only then in contact to step. Particularly suitable for this purpose is, for example, a tooth-shaped cutting edge 35 shown at the beginning in FIG. 15a and at the end of a cutting process. The tooth tips lie substantially on a circular segment, so that at least a portion of the teeth engage substantially simultaneously in the recess Enter pipe. The feed and the recesses between the teeth are chosen so that at the end of the cutting process, the tube 26 is separated over the entire length of the cutting edge 35. 13a, 13b, 13c, 14a, 14b and 14c show the use of cutting edges 35 which extend over circular segments for cutting continuously moving tubes 26. In this case, a plurality of cutting edges 35 are provided along the pipe circumference, which are substantially in Normal planes to the tube axis from the outside of the tube are radially movable toward the tube axis, wherein at the end of the cutting movement, the cutting edges 35 are radially within the tube wall and have thereby complemented a closed line. Subsequently, the cutting edges are again moved radially outward. Preferably, the cutting edges 35 cooperate with a support edge 43 of a dome 42 inside the tube. In the case of extremely thin-walled metal tubes 26, movement of the cutting edges in the direction of the tube axis may possibly be dispensed with, in which case the extremely short tube advance advanced during the cutting process can be deformed somewhat radially inwards around the supporting edge 43. If the pipe feed is impaired by cutting edges which are fixedly positioned in the pipe longitudinal direction, the cutting edges are moved in the pipe longitudinal direction during cutting. For this purpose, the drum solution already described or the solution can be used with guide devices, such guide devices holding the cutting edges in a normal plane to the tube axis during the cutting process and at the same time moving this normal plane at the speed of the tube feed.

Claims

claims

A method of manufacturing a can body having a can jacket and a can bottom by which a metal strip is moved longitudinally against a separator, separating steps are performed by the separator to provide portions of the metal strip as can jackets with a longitudinal butted seam, at least one laser step is carried out to form the laser longitudinal seams of the can coats and connecting steps, with which a can bottom is fixed to one end of each can jacket, characterized in that the metal strip is printed in a printing step with decorative surfaces in a first direction of the metal strip, preferably in the longitudinal direction, a height extent of the can decor in the direction of the can axis and transversely to the first direction, the circumferential extent of the can decor, wherein arranged in the region of each decorative surface at least one longitudinal register mark i St, and the longitudinal register marks allows the control of the separation steps so that the separated can coats each comprise a complete decorative surface.

A method according to claim 1, characterized in that prior to the printing step for printing decorative surfaces a primer is applied to the metal strip, which preferably comprises at least one layer, optionally an adhesive layer and a printable upper layer, with a paint, in particular a two-component paint, wherein the Two-component paint preferably based on polyester and / or polyurethane and / or epoxy resin and / or polyvinylidene fluoride (PVDF) and / or nitrocellulose and / or alkyd resin.

A method according to claim 2, characterized in that the primer is applied with at least one printing form of a printing press, preferably only in the region of the decorative surfaces.

Method according to one of claims 1 to 3, characterized in that in the printing step at least one of the printing processes from the group of offset printing, screen printing and flexographic printing is used. Method according to one of claims 1 to 4, characterized in that in the printing step on the flat metal strip in normal planes to the longitudinal axis of the metal strip slits are formed in the metal strip, but which do not extend to the two lateral edge regions of the metal strip, the metal strip in a molding device in In a welding device in a welding step, the shaped tube is closed in the circumferential direction with a laser longitudinal seam at the butt-joined lateral edge surfaces and in a separating device with separating steps sections of the at least one cutting edge is moved from the outside against the tube axis and after cutting again away from the tube axis and in particular at least the at least a cutting edge is moved along with their cutting movement in addition to the pipe and then brought back into the position before the separation.

A method of manufacturing a can body having a can jacket and a can bottom by which a metal strip moves in the longitudinal direction thereof is continuously formed into a tube by blunting the lateral edge surfaces of the metal strip in a forming step in a forming step and forming the formed part by a welding device in a welding step Pipe is closed in the circumferential direction at the blunt merged lateral edge surfaces in a separating device with separation steps sections of the closed tube separated and provided as a can coats with a laser longitudinal seam and connecting steps are performed with those at one end each can jacket is attached to a bottom of the can, characterized in that in an operating region after the welding device and before the separating device with an inner coating device an inner coating layer Ritt is performed, in which on the inside of the closed tube, a circumferentially closed inner coating is formed.

A method according to claim 6, characterized in that the Innenbeschich- tion step, the inner side is provided with a plastic inner layer, which is supplied by means of an extrusion die. A method according to claim 6, characterized in that between the inside and the plastic inner layer, an adhesion-promoting layer is applied, which is preferably supplied in the inner coating step by means of an extrusion die.

Method according to one of claims 1 to 8, characterized in that the metal strip is divided along its longitudinal direction into at least two metal strips, each having only the decoration for a can jacket in the transverse direction and further processed separately in the further process steps.

Method according to one of claims 1 to 9, characterized in that at least two metal strips are processed in parallel lines to canned coats and the canned coats of parallel lines for performing the connecting steps, with which at one end of each can jacket a bottom of the can is attached, merges and be processed in a common device.

Method according to one of claims 1 to 10, characterized in that the metal strip at least one lateral trimming is performed to provide clean and accurate lateral contact surfaces for the welding of the laser longitudinal seam.

Method for producing a printed can body with a can jacket and a can bottom, in which method in a coat forming step the can jacket closed around a can axis is printed and in a digital printing step the can jacket is printed with at least one digital printing system over a print height and the entire can circumference, characterized that in the digital printing step within a common time interval and a common movement of the can jacket all, at least two colors of the at least one digital printing system with corresponding printheads are applied in appropriate proportions on the can jacket, all printheads of the at least one digital printing system are associated with a common pressure range in which pressure area the can jacket is located during the course of the movement.

13. The method according to claim 12, characterized in that the movement sequence of the can jacket for applying the colors of a digital printing system comprises at least one rotational movement about the axis of the can jacket, wherein the print heads extend in the direction of the can axis over the entire pressure level or the

Printheads are moved to print the entire printing height in the direction of the can axis.

A method according to claim 12, characterized in that the movement sequence of the can jacket when applying the colors of a digital printing system comprises at least a displacement of the can jacket in the direction of the axis of the can jacket, wherein the printheads extend around the can circumference or the printheads for printing the entire circumference in Direction of the can circumference are moved.

Method according to one of claims 12 to 14, characterized in that the digital printing step is optionally performed on both sides open can jacket or connected to a can bottom can jacket or on the finished box, in particular directly before or after filling the can, wherein the can jacket is conveyed via a conveyor with a storage area in one of at least two adjacent to the storage area digital printing systems and the can jacket is optionally placed on a pallet-shaped support. 16. can body with a can jacket and a can bottom, wherein the can jacket is formed of a metal sheet which has been separated from a metal band and closed with a pushed laser longitudinal seam, the can jacket on the outside a decorative surface and the can bottom at an end face of the can jacket is attached, characterized in that the decorative surface is formed as pressure on the flat metal strip and at least one longitudinal

Register mark comprises, which ensures the separation of a portion of the can jacket strip for the can jacket so that the can jacket comprises a complete decorative surface.

17 can body with a can jacket, which comprises an inner coating, and with a can bottom, wherein the can jacket is formed from a portion of a metal strip which continuously formed by blunt merging the lateral edge surfaces into a tube and with a laser longitudinal seam at the butt together - Menierten lateral edge surfaces is closed in the circumferential direction, and the

Can bottom is fixed to an end face of the can jacket, characterized in that the inner coating is an adhering to the inside of the closed tube, separated together with the metal strip and closed in the circumferential direction layer which covers the laser longitudinal seam.

18. A device for producing a can body with a can jacket and a can bottom, which device comprises a feed device, a separating device and a first and a second laser welding device, wherein the metal strip is moved by the feed device in the longitudinal direction of the metal strip against the separating device, of the separating device Separating steps are carried out to provide portions of the metal strip as can coats with a pushed longitudinal laser seam produced by the first laser welding device, and connecting steps are carried out by the second laser welding device, with which a can bottom is attached to one end face of each can jacket, characterized in that the device comprises a printing device with which the metal strip is printed in a printing step with decorative surfaces and longitudinal register marks, wherein the decorative surfaces in a first direction of the metal strip, preferably in the longitudinal direction, a height extent of the can decor in the direction of the can axis and transverse to the first direction, the circumferential extent of the can decor, the longitudinal register marks are arranged in the region of the decorative surfaces and the control of the separation steps so allow the separated can coats each include a complete decorative surface.

19. The device according to claim 18, characterized in that a slot device during the printing step on the flat metal strip in normal planes to the longitudinal axis of the

Metallbandes slits in the metal strip forms, but which do not extend to the two lateral edge regions of the metal strip, a forming device continuously forms the metal strip in a molding step by blunt merging the lateral edge surfaces of the metal strip to form a tube, a Schweisseinrich- device in a welding step the molded Tube with a laser longitudinal seam at the at least one cutting edge is moved from the outside against the tube axis and after cutting again away from the tube axis, and in particular at least the at least one cutting edge with separation steps sections separated closed tube a cutting edge is moved along with their cutting movement in addition to the pipe and then brought back into the position before the separation.

20. An apparatus for producing a can body with a can jacket and a can bottom, which apparatus comprises a feed device, a forming device, a first and a second laser welding device, a separating device and an inner coating device, wherein the metal strip from the feed device in the longitudinal direction of the metal strip against the forming device is moved, the shaping device transforms the metal strip into a closed mold, the first laser welding device connects the bluntly merged lateral edge surfaces of the metal strip with a laser longitudinal seam, separating the separating device with separating steps sections of the closed tube and the second laser welding device on a front side of each can jacket attached to a bottom of the can, characterized in that the internal coating device is arranged in a processing area after the welding device and in front of the separating device and an on formed inside the closed tube in the circumferential direction closed inner coating.

21. A device for producing a printed can body with a can jacket and a can bottom, which device comprises a jacket forming device and a digital digital printing system, wherein the digital digital printing system imprinted the can jacket on a printing height and the entire can circumference, characterized in that the digital digital printing system within a common Time interval and in a common movement of the can jacket applies all, at least two, colors of the at least one digital printing system with corresponding printheads in appropriately required proportions on the can jacket, all printheads of the at least one digital printing system are assigned to a common pressure range, in which pressure range, the can jacket during the movement sequence is located.