FIELD OF THE INVENTION

[0001] The invention relates to digital ink jet printers for printing graphics on cylindrical objects.

BACKGROUND OF THE INVENTION

[0002] The US promotional products industry generated over $ 18 billion in 2005 and continues to grow at a significant rate. However, current technology for decorating cylindrical promotional products includes much inefficiency. The predominant method of decorating products is by screen printing which has many associated problems. Preparing artwork requires separation of colours, manual colour matching, making screens, transferring the artwork onto the screens, and tedious set-up procedures to register the colours during printing. Screen printing also has its limitations in that it is incapable of printing process colours. The inks for glass and ceramics are severely limited by the Food and Drug Administration as there is concern regarding the carcinogenic properties of some of the ceramic inks. Furthermore, the cost of these various procedures tends to severely distort the selling price of the product that is being decorated. There is a need to eliminate the high energy used in curing the ink, for a much more productive method of decorating and for higher quality graphics.

SUMMARY OF THE INVENTION

[0003] Two new processes using digital graphics have been introduced recently to meet the needs discussed above. One process consists of digital offset printing on a film, wrapping the film around the product to be decorated, applying heat and pressure which transfers the ink to the product. The second process ink jet prints on a clear pressure sensitive film which is then cut to size and is applied, like a label, to the product for decoration. The digital ink jet printing process and the digital ink jet printer of the present invention greatly simplify the decorating process, reducing cost as it is printing directly onto the cylindrical product, and achieving superior quality graphics. The inks used are all organic, thereby eliminating health and environmental concerns.

[0004] The present invention provides a digital ink jet printer for printing directly onto a cylindrical object comprising: a printhead assembly comprising at least two printheads including ink operatively connected to said digital ink jet printer, at least a first one of the printheads having white ink; a carrier for supporting the object; positioning means for sequentially positioning the carrier relative to the printhead assembly for printing ink onto said object; a controller connected to the positioning means and to the printer for providing instructions for printing a pre-determined print pattern on said object and for sequentially moving said positioning means.

[0005] The present invention further provides a digital ink jet printer for printing and curing graphics directly onto on a cylindrical object comprising: (i) a printhead assembly comprising at least one printhead, wherein said at least one printhead contains ink and at least a first one of said at least one printhead having white ink; (ii) a UV lamp for curing ink, attached to the printhead assembly, wherein said UV lamp is aligned in a plane with said at least one printhead; and (iii) a carrier moveably attached to said printhead assembly, wherein said carrier is positioned such that the cylindrical object is below the printhead assembly.

[0006] The present invention further provides amethod of printing and curing graphics on a cylindrical object comprising the steps of: (a) placing a cylindrical object in a carrier; (b) moving the carrier under at least one printhead having white ink; (c) firing the white ink in the at least one printhead onto the cylindrical object; (d) optionally firing at least one other colour of ink onto the cylindrical object; and (e) curing the ink on the cylindrical object. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] In drawings which illustrate by way of example only a preferred embodiment of the invention,

[0008] Figure 1 is a perspective view of a preferred embodiment of the present invention in a first operating position

[0009] Figure 2 is a perspective view of a preferred embodiment of the present invention in a second operating position;

[0010] Figure 3 is a perspective view of a preferred embodiment of the present invention in a third operating position;

[0011] Figure 4 is a front view of an alternate embodiment of the present invention;

[0012] Figures 4A to 4G are enlarged views showing a movable substrate carrier in the embodiment of Figure 4 with the carrier in different positions; and

[0013] Figure 5 is a side view of the embodiment of the present invention shownb in Figure 4.

DETAILED DESCRIPTION OF THE INVENTION

[0014] As shown in the figures, digital ink printer system 1 includes a printhead assembly 2. The printhead assembly 2 has a printhead and preferably at least two printheads. Preferably, the printheads are the Xaar 318s for pens. There are other printhead designs for products such as glass tumblers or ceramic mugs. The printheads are preferably at least 50 mm wide. In the preferred embodiment shown in Figures 1 to 3, the printhead assembly operates as a shuttle, moving along the conveyor 31 loaded with pens 30, and has seven printheads, namely first printhead 4, second printhead 6, third printhead 8, fourth printhead 10, fifth printhead 12, sixth printhead 14 and seventh printhead 16. Each of the printheads receives ink from an ink container 26. [0015] In the preferred embodiment each of the printheads may contain ink of a different colour. These colours include at least white, cyan, magenta, yellow and black. Preferably the ink is HexiLok™ ink for glass and ceramics and metals. Other Hexion specialized inks are used on various other applications, such as pens.

[0016] A UV lamp 20 is attached to the printhead assembly 2. The UV lamp 20 is aligned in a plane with said at least one of the printheads. In the preferred embodiment, the printheads and the UV lamp 20 are all aligned on the same plane.

[0017] In the embodiment shown a cylindrical object such as a pen 30 is received in a chuck 28 of a carrier 36. The carrier 36 is moveably attached to the printhead assembly 2. The carrier 36 is positioned such that the cylindrical object 30 is below the printhead assembly 2. Preferably, the carrier 36 is capable of rotating the cylindrical object 30. The carrier 36 is adapted to move along an axis of movement along a plane that is parallel to the plane of the printheads. This is preferably accomplished by positioning means for sequentially positioning the carrier relative to the printhead assembly for printing ink onto said items 30. The rotation and positioning means is preferably in the form of a stepper motor 58 that is connected to either the carrier 30, the printhead assembly 2 or both. The stepper motor 58 is triggered by a sensor which gauges the diameter or the height of the object to be printed and moves the shuttle in a vertical direction so there is always a lmm clearance between the printhead and the object to be printed.

[0018] The cylindrical object 30 is preferably a promotional item and most preferably a pen. However the digital ink printer system 1 can be used to print on any type of cylindrical object.

[0019] The printhead assembly 2 can be attached to a moveable shuttle as shown, and the direction of the moveable shuttle can be perpendicular to an axis of movement of the carrier 30. Printheads are preferably spaced exactly 1 '/2" apart and are removable for maintenance. [0020] A controller is connected to the positioning means and to the printhead assembly 2 for providing instructions for printing a pre-determined print pattern on said items such as pens 30 and for sequentially moving the positioning means. The controller is preferably a computer 44, as shown in Figures 4 and 5. The computer 44 has a motion control panel 46 and a display screen 48. As shown in Figures 4 and 5, the digital ink printer 1 preferably includes a UV power supply 54 and a UV blower 52.

10021] The system includes stepper motors (not shown) that rotate the pen 30 and move the carrier 36 in four horizontal directions. The system also includes a final UV curing unit 20, shown in Figure 4.

[0022] In the operation of the preferred embodiment shown in Figures 1 to 3 wherein the cylindrical objects are pens 30, the pens 30 are fed to the printhead assembly 2 one at a time on the carrier 36. As the pen 30 approaches a printhead, the carrier 36 raises the pen where it is grasped by the chuck 28 and placed next to the printheads.

[0023] In the embodiment shown in Figures 1 to 3 the printheads and UV Lamp 20 travel horizontally on the shuttle with the pen 30 below them. The shuttle moves from right to left, sequentially bringing each print head 6, 8, 10, 12, 14 into printing position above the pen 30.

[0024] As the shuttle comes to a stop with the pen 30 under printhead 6, preferably first white ink is "fired" onto the rotating pen 30 as required in the graphics that have been pre-programmed. The white ink forms a suitable base for other colours to be applied to the pen 30. The shuttle then immediately moves so that the pen is disposed under each of printheads 8, 10, 12 and 14, stopping momentarily under each printhead required for the particular graphics programmed wherein one or more of cyan, magenta, yellow and black respectively are fired. At that point the entire graphics have been applied.

[0025] It is preferred that printing begins with white ink, even when the product being decorated is white. Digital ink jet inks are formulated to have the same surface tension so that they exactly lie in the same dot pattern each time (ink is jetted in small dots and they're applied between the dots of the previously applied colors). Unlike the cyan, magenta, yellow and black colors, white ink is jetted in larger dots which spread and flow into each other forming an almost continuous and opaque surface (blocking out light transmission) as the cyan, magenta, yellow and black colors are quite transparent. With a constant white background the cyan, magenta, yellow and black colors applied overtop produce the preplanned graphic effects and the desired color match. Printhead 4 is not necessarily used for printing in the preferred embodiment, but can be available in reserve for example if a second coat of white is required on a dark coloured pen 30.

[0026] In advance of the printing step, set up information is programmed into the computer regarding the specifications of the pen (i.e. barrel diameter and extension of the pen clip). On the first cycle of a new print job, after the pen is placed in to the chuck and mandrel, the printhead assembly 2 is positioned by a lead-screw, driven by a stepper motor, so that a set of limit sensors are exposed to the pen barrel by lowering the assembly until a signal is received from the barrel sensor. Also, the pen clip is positioned so that the printhead assembly 2 can sense the proper distance. Those distances are then recorded into the software and from there calculated to precisely position the printheads.

[0027] The printing step at each printhead is carried out with the pen barrel rotating in one direction as part of the image is deposited. Upon completion of a first ink deposit, the pen reverses back to the start of the image while the printhead is moved one pixel over. Due to the native nozzle spacing, the pen rotates forward to complete a first image of a first color. The first image is preferably the white. Furthermore, the first print is sometimes partially cured by a UV light, described below, to ensure that the rest of the colors have a solid base. The rest of the image is printed according to the same procedure at the other printheads. Upon completion of the printing the pen 30 is placed under the UV light 20 to completely cure the colors. The pen is then released into the carrier 36, and lowered into a conveyor (not shown in Figures 1 to 3), which moves over one position to load the next pen 30 to be printed. The chain conveyor may be extended so that products printed with HexiLok ink will enter an InfraRed or conventional curing oven (not shown) to fully cure the ink.

[0028] Glass, ceramic and metal products preferably are printed with the specially formulated HexiLok inks for adhesion and toughness and consist of two components. One of the components is UV cured as described above, the second component is cured by InfraRed or conventional heat in a conveyorized oven.

[0029] The machine mechanics function as follows: as the pen 30 is located under a printhead, a small stepper motor rotates the pen 20 chuck/mandrel 28 assembly forward and backwards at the precise positions to not let the pen clip touch the printhead nozzle surface. Also during this action the step or position of the pen 30 is fed back to the printing software for it to fire the nozzle at the right time. While the pen barrel shuttles forwards the first print is applied. As the pen reverses, the printhead assembly is moved over one pixel by a stepper motor with a canterlever cam. This cam has the capability to reposition the printhead assembly with accuracy of +/- .00025 inches, but also move the whole assembly 2" over to allow a full 4" wide (or high) print on the pen barrel. The printhead assembly is mounted on a linear zero clearance glider assembly (THK), and driven by a micro step controlled stepper motor to position the proper printhead over the pen in the exact location. Also this information is fed back to the printhead software to let it know what color to print. For color registration the printer can use the clip of the pen as reference or it can use the first print of the graphics. The basic graphics print quality of the DIJ Printer described herein is 300 - 360 dpi (dots per square inch), the usual magazine quality. The Xaar printheads make the DIJ printer capable of six or eight grey scales, up to a dpi range of 900 - 1200 which is described as 'near photo' quality.

[0030| The preferred ink for carrying out the present invention is HexiLok™ ink developed by Hexion Specialty Chemicals Inc., Cincinnati, Ohio. It has been found that HexiLok™ has exceptional adhesion qualities required for glass, ceramics and metal and eliminates both the silicone and the polyurethane, thereby reducing cost and shortening the printing process. DIJ Inks are drawn from ink bottles and pumped to the printheads by a specialized ink delivery system (not shown) which operates under negative pressure to eliminate bubbles in the printheads which would cause misprints.

[0031] HexiLok™ and other Hexion inks are available in white, cyan, magenta, yellow and black and are usually jetted in that sequence but the sequence will sometimes change for certain graphic effects. White is preferably used to create a sound and adhering base followed by the cyan, magenta, yellow and black colors. The cyan, magenta, yellow and black inks are adjusted to the same surface tension as the white ink.

[0032] HexiLok inks have two major components, one is cured by UV and the other component requires curing by either infrared or conventional heat.

[0033] In the embodiment of Figures 4 to 5, the printhead assembly 2 is fixed in a stationary position and the substrate (e.g. pen 30) is moved to the appropriate position for printing on a moving frame 32 . In this embodiment the motion of the pen 30 is controlled in a manner similar to that in the embodiment described above in respect of Figures 1 to 3 in which the pen 30 remains stationary while the printhead assembly 2 moves to the desired position.

[0034] Alternatively, the intermediate LED lamp 20 can be mounted to the shuttle 32, as shown in Figures 4 and 5, so that the pen 30 and the intermediate LED 20 travel together as they move under the five (or six) print heads, and the ink is partially cured as ink is deposited on the rotating pen 30, allowing partial curing at an intermediate stage while eliminating time consuming stops of the pen 30. Figures 4A to 4G show different positions of the shuttle 32 in the printing or 'pinning' portion 35 of the apparatus. In Figure 4A the pen 30 is loaded into the chuck 28. The loaded chuck 28 is thus shown in Figure 4B. The shuttle 32 moves (to the left in the drawings) so that ink from the white printhead 4 is applied to the pen 30 in Figure 4C. As the shuttle 32 continues to move ink is applied, as programmed, from the various printheads (not every printhead is used in every print cycle, depending on the colour being printed) so that in Figure 4D, 4E and 4F respectively show cyan, magenta and black being applied to the pen 30. Figure 4G shows the shuttle 32 in the final position, with the pen 30 being unloaded from the chuck 28.

[0035] The pen 30 with complete five color graphics is then picked from the printer by a conveyor and taken down the line for packaging to a UV curing tunnel. The pen preferably travels and rotates in a carefully designed shield 34 to prevent stray UV light to escape and accidentally cure the ink on the nozzles of the print head. Total time of the printing and UV curing for the finished product is preferably approximately 10 seconds.

[0036] In the operation of the preferred embodiment shown in Figures 1 to 3 wherein the cylindrical objects are pens 30, the pens 30 are fed to the printhead assembly 2 one at a time on the carrier 36. As the pen 30 approaches a printhead, the carrier 36 raises the pen where it is grasped by the chuck 28 and placed next to the printheads.

[0037] In the embodiment shown in Figures 4 and 5the printheads and UV Lamp 20 remain in a fixed position during printing and the pen 30 travels horizontally below them.

[0038] In this embodiment the pen 30, which is loaded into and held by the chuck or mandrel 28 in the manner described above, moves under printhead 6, as shown in Figure 2. As the pen 30 comes to a stop under printhead 6, preferably white ink is "fired" onto the rotating pen as required in the graphics. The pen 30 then immediately moves to printheads 8, 10, 12 and 14, stopping momentarily under each printhead where cyan, magenta, yellow and black respectively are fired. At that point the entire graphics have been applied.

[0039] In these embodiments the pen 30 may be associated with an intermediate LED UV light emitting unit comprising UV lamp curing unit 21, so that the graphics can be partially cured to prevent the ink droplets from spreading and assuring that the resolution of print remains unchanged. The intermediate UV curing unit 21, shown in Figures 4 to 5, is preferably largely or completely contained in a U-shaped housing, for example approximately 10 mm in length, 25 mm wide and 15 mm deep, and may contain a number of LEDs. The intermediate curing unit 21 is attached to theframe 32 and thus travels with the chuck 28 beneath the pen 30. However, the intermediate curing unit 21 is attached to the frame by a cylinder or solenoid 38, which retracts the intermediate curing unit 21 so that the pen 30 can be loaded into the frame 32 from below. Preferably a shield 34 shields that sides of the intermediate curing unit 21 to prevent light from scattering and curing ink on adjacent printheads when the unit is in operation. The pen 30 itself blocks the UV light from the intermediate curing unit 21 from striking the printhead that the pen 30 is disposed under for printing. A single LED 20 is sufficient for partial curing, thereby reducing the length that the pen 30 needs to travel to have all the ink colors applied and cured, because the print heads can be moved closer together, and reducing costs of the apparatus.

[0040] In the operation of this embodiment, the solenoid 38 retracts intermediate curing unit 21 and the carrier 36 pushes a pen 30 out of its nest 31a in conveyor 31 and loads the pen 30 into the chuck 28, as shown in Figure 4A. The solenoid 38 repositions the intermediate curing unit 21 under the pen 30, as shown in Figure 4B. In the embodiment of Figures 4 to 5 printheads 6, 8, 10, 12 and 14 are aligned in sequence from right to left, so the frame 32 moves from one printhead to the next, stopping briefly under each printhead so that ink can be applied and partly cured by intermediate curing unit 21 before the frame 32 moves to the next printhead, as shown in Figures 4C to 4F. After the ink has been applied as programmed, carrier 36 rises from the conveyor 31 , as shown in Figure 4G, unloads the pen 30 from the chuck 28 and returns the pen 30 to a nest 31 a in the conveyor 31.

[0041] Intermediate UV LED 21 may for example be actuated following each color print, to partially cure the ink drops as they are deposited on the pen 30 so that the drops hold their shape and produce a sharper print. This however requires the pen 30 to stop momentarily to achieve the partial cure after each color of print, thereby adding about four seconds to the time length of printing each pen 30.

[0042] Two computers are used in the graphics and order preparation and graphics printing. Artwork, color matching order details, model of pen, positioning of the graphics, etc. are entered in a first computer which sends the information to a PLC computer which drives the printhead assembly.

[0043] The digital ink printer system includes sensors for detecting the diameter of the pen so that the system automatically positions the printheads to the correct height with 1 mm clearance. If graphics are to be printed on the clip of the pen, the digital ink printer system senses the height and the printheads are automatically raised to the correct height.

[0044] If the pen has a clip attached the pen rotation and printing stop short of the clip and is UV cured as it rotates in the opposite direction and is ready for the next color to be applied.

[0045] The digital ink jet printer of the present invention has many capabilities. These include the ability to printing a 180° arc on a pen around a pen clip; printing on the pen clip; printing a 360° deg full wrap below the pen clip; printing a 4" full wrap on a pen with no clip; almost continuous printing where the computer counts the number of prints, pauses a few seconds at order completion, then begins a new order with different graphics. All functions are programmed into the system, are triggered by entering the graphics artwork and are automatically printed.

[0046] The present invention provides a printer that operates with complete automation. In the case of pens, they can be hand fed, or automatically located onto the printer's conveyor, then are picked off the conveyor, placed into the printer, printed, cured, deposited back on the conveyor and dropped into a shipping carton. Glass, ceramics and metal can be hand loaded and unloaded but ideally robots take the units from the shipping cartons, place them in the printer and later place them back in the shipping carton.

[0047] In an alternate embodiment of the invention, the printer is designed to print two products at the same time, thereby doubling the output.

[0048] Various embodiments of the present invention having been thus described in detail by way of example, it will be apparent to those skilled in the art that variations and modifications may be made without departing from the invention. The invention includes all such variations and modifications as fall within the scope of the appended claims.The invention can be applied to any digital printing process, the digital ink jet printer described herein being only one example of a printer in which the invention can be advantageously implemented.