System and method for producing patterns on a roll of sheet metal using computer controlled printing heads

A system and method for printing a predetermined pattern on sheet metal wound in a roll is claimed. The sheet metal is placed in a processing line, wherein the roll of sheet metal is unwound from a first roll, processed and rewound into a second roll. During processing, the sheet metal is cleaned and painted. The painted sheet metal is then advanced under at least one computer controlled printing head that prints a predetermined pattern of ink onto the sheet metal. The printed pattern of ink is then coated with a protective coating.

DETAILED DESCRIPTION OF THE INVENTION Although the present invention system and method can be used to print a selected pattern on any rolled metal material, such as cold rolled steel, galvanized steel, stainless steel, aluminum, and the like, the present invention is particularly well suited for printing such patterns on rolled steel sheet metal. Accordingly, by way of example, the present invention system and method will be described in an application where it is used to print a selected pattern on steel sheet metal. Referring to FIG. 1 , there is shown a schematic of an exemplary embodiment of the present invention system 10 . The schematic illustrates the major processing steps performed on a roll of sheet metal as a selected pattern is printed onto the sheet metal. The processing begins with a roll 11 of raw sheet metal 12 , as it would be produced by a steel mill. The sheet metal 12 is unwound from its original roll 11 by an unwinding assembly 14 and is fed into a processing line. The processing line contains a plurality of processing stations, which will be described. At the opposite end of the processing line, the sheet metal 12 is again wound into a finished roll 16 . After the sheet metal 12 is unwound from its original roll 11 , the sheet metal 12 is advanced through a cleaning station 18 . At the cleaning station 18 , the sheet metal 12 is treated with degreasing solvents and rinsed. The cleaned sheet metal 12 may then be advanced through a chemical treatment station 20 , wherein the sheet metal 12 is chemically treated. The chemical treatment used on the sheet metal 12 depends upon the composition of the sheet metal 12 and can include, acid baths, alkaline baths, complex oxides, phosphate treatments or any other chemical treatment commonly used to treat the surface of different types of rolled metal alloys. After the sheet metal 12 is cleaned and optionally chemically treated, the sheet metal 12 is advanced through a primary paint applicator 22 . The sheet metal 12 is coated in a first color of primary paint 24 . The primary paint 24 is preferably applied by a roll coater that selectively applies a film of the primary paint 24 that is between one tenth of a millimeter and ten millimeters thick. As the sheet metal 12 exits the primary paint applicator 22 , the primary paint 24 is still wet. The painted sheet metal is then advanced through a curing chamber 26 that cures the primary paint. The painted surface of the sheet metal 12 is the substrate upon which a preselected design is to be printed. After the sheet metal 12 exits the curing chamber 26 , the sheet metal 12 advances through a printing station 28 . In the printing station 28 , there is at least one printing head 30 . Each printing head 30 is coupled to a programmable systems controller 32 and a source of ink 34 . There are many types of printing heads that are used in industry to print on paper and other traditional parchment substrates. However, such printing heads are designed to print ink onto paper or another traditional parchment substrate. For use with the present invention, the design of traditional ink jet printing heads is modified to the task of printing ink onto painted metal that is continuously moving through a processing line. Each ink jet printing head 30 is elongated to be at least as long as the width of the passing sheet metal 12 . As such, each ink jet printing head 30 is preferably made to be at least sixty inches long. Each ink jet printing head 30 is positioned over the sheet metal 12 at a perpendicular to the direction of travel associated with the sheet metal 12 . As such, the entire width of the sheet metal 12 will pass under a segment of each ink jet printing head 30 as the sheet metal moves through the printing station 28 . Another modification made to each ink jet printing head 30 is a dramatic increase in dispensing volume. In a sheet metal processing line, the sheet metal 12 advances through the line at a rate of between one hundred feet per minute and four hundred feet per minute. The dispensing output of each ink jet printing head 30 is designed with a maximum output that is capable of completely covering the moving sheet metal 12 with a layer of ink that is at least one tenth of a millimeter thick. The ink jet printing heads 30 preferably have the ability to print pixel points at a density of at least 600 ppi. However, printing heads with a resolution as low as 200 ppi can be used for certain patterns and rapid sheet metal velocities. Referring to FIG. 2 , it can be seen that the printing station may contain multiple ink jet printing heads 30 . Each of the ink jet printing heads 30 extends across the width of the sheet metal 12 . Each ink jet printing head 30 is fed by an ink supply 34 . The color of the different ink supplies 34 can be the same or can be different. If different color ink supplies 34 are used, the ink jet printing heads 30 can produce an image on the sheet metal 12 that contains multiple colors. All of the ink jet printing heads 30 are controlled by a single systems controller 32 . The systems controller 32 is a computer that contains the needed software to control the functions of the various ink jet printing heads 30 . In order for the systems controller 32 to coordinate the dispensing of ink from the various ink jet printing heads 30 to accurately create a needed design, certain variables must be known by the systems controller 32 . One of the variables that must be known is the exact speed of the sheet metal 12 passing under the ink jet printing heads 30 . The speed of the sheet metal 12 is needed to calculate the amount of ink to be dispensed from each of the ink jet printing heads 30 and when that ink is to be dispensed. To know the exact speed of the moving sheet metal 12 , a velocity sensor 38 is provided. The velocity sensor 38 can detect the actual speed of the sheet metal 12 moving through the printing station either mechanically or optically. The velocity sensor 38 is coupled to the systems controller 32 and informs the systems controller 32 of the exact speed of the moving sheet metal 12 . The information transferred to the systems controller 32 is continuously updated. As such, small variations in the speed of the moving sheet metal 12 can be instantly detected by the systems controller 32 . The second variable that must be known by the systems controller 32 is the image and/or pattern that is to be produced by the ink jet printing heads 30 . Such an image and/or pattern can be loaded into the systems controller 32 as a data file, either via a storage disc or as a data transfer through a computer network. Alternatively, the systems controller 32 may also include a data input interface, such as an optical scanner, keyboard and mouse, so that different images and patterns can be created directly within the systems controller 32 . Once the systems controller 32 knows what image and/or pattern is to be produced and the speed of the moving sheet metal, the systems controller 32 can control the various ink jet printing heads 30 so that the printing heads 30 reproduce that image and/or pattern onto the moving sheet metal 12 . Returning to FIG. 1 , it can be seen that once the ink jet printing heads 30 print the desired image and/or pattern onto the moving sheet metal 12 , the deposited ink can be allowed to air dry. Once the printed ink is cured, the sheet metal 12 advances through a coating applicator 42 . The coating applicator applies a protective top coat of transparent material over the ink. The protective top coat can be applied by spraying. Alternatively, the protective top coat can be applied by a roll coater that selectively applies a film of the protective top coat that is between one tenth of a millimeter and ten millimeters thick. After the application of the protective top coat, the sheet metal 12 is again advanced through a curing chamber 44 that cures the protective top coat. The top coat is water resistant when cured. As such, the protective top coat protects the underlying ink from the elements. This enables low cost inks to be used that otherwise would not be usable if left exposed to the elements. Referring to FIG. 3, a segment of a roll of sheet metal 12 is shown upon which has been printed an image. The image does not repeat. Rather, the image is unique from one end of the segment of sheet metal 12 to the other. The segment of sheet metal 12 can be used to create many consumer products, for instance a backyard pool. As such, the image on the product would be different from every different angle of viewing the product. Since the image and/or pattern printed on the sheet metal is controlled by the systems controller 32 ( FIG. 2 ), different segments of the same roll of sheet metal 12 can be printed with different images and/or patterns without having to change any physical aspect of the sheet metal processing line. In fact, different segments of the same roll of sheet metal can be printed with different images and/or patterns without even stopping the movement of the sheet metal in the processing line. Furthermore, since the image and/or pattern is programmed into the systems controller 32 ( FIG. 2 ) custom orders can be created for individual customers. These custom orders can be created in different sections of the same roll of sheet metal without stopping the movement of the sheet metal through the processing line. Accordingly, if a customer has a garden with yellow flowers in her backyard, that customer can order an above-ground pool, having sheet metal decorated as a garden with yellow flowers. Customers can therefore select the image and/or pattern on the sheet metal to match any color scheme or image they desire. In the embodiments described, the printed pattern of ink is applied to only one side of the sheet metal. It should be understood that by placing printing heads on either side of the sheet metal, the printed patterns can be created on both sides of the sheet metal. Although stationary ink jet printing heads 30 are shown in the embodiment of FIG. 2 , it will be understood that the ink jet printing heads 30 can either be stationary or can track back and forth across the width of the passing sheet metal 12 . Stationary ink jet printing heads 30 can be used if the length of the printing heads 30 is at least as long as the sheet metal 12 is wide. Moving ink jet printing heads can be used if the number and size of spray heads is insufficient to cover the passing sheet metal from a stationary point. It will be understood that the various figures described above illustrate only an exemplary embodiment of the present invention. A person skilled in the art can therefore make numerous alterations and modifications to the shown embodiments utilizing functionally equivalent components to those shown and described. All such modifications are intended to be included within the scope of the present invention as defined by the appended claims.