Patent Description:
The present invention relates generally to the printing of images on articles of manufacture. In greater particularity, the present invention relates to printing images on the exterior of transparent and semi-transparent media, such as glass bottles. The invention also relates to the controlling of movement of media during a final curing process of ink applied to the exterior of transparent or semi-transparent media, such as <NUM>-dimensional objects like a bottle.

Documents <CIT>, <CIT> and <CIT> represent relevant prior art for the present invention. Several techniques are utilized to print images on manufactured goods, such as drink and cosmetics containers. These containers are made of various materials, such as plastics, glass, metals, and coated paper. The traditional method for placing images on these containers, sometimes called "imaging," is to print a label on a plastic or paper substrate and then affix the pre-printed label onto the container exterior with adhesive. During the last <NUM> years many manufactures have transitioned from label printing to direct printing onto the container surface, sometime referred to as "direct-to-shape" (DTS) printing. However, while a label is a flexible medium and may be printed using traditional flexible sheet printing using methods going back over <NUM> years, direct printing on containers poses many challenges. One challenge is that while paper readily absorbs and retains inks and is a well understood medium for imaging, the containers themselves are made of materials that are difficult to image. Inks of special chemical blends and additives must be used, sometimes in the presence of active drying or hardening processes such as catalyst exposure or fast-curing using ultra-violet (UV) radiation. Further, container shapes are fixed, and an imaging process must take into account the irregular and varied shapes of the containers that are to be imaged. Such challenging print surfaces comprise a good-many products, such as drink cans and bottles, home care products, cups, coffee tumblers, personal care items, automotive parts, sports equipment, medical products, and electronics containers to name just a few. Also, such products have varying optical properties, ranging from purely opaque to purely transparent. Hence, choosing the proper type of DTS printing equipment largely depends on the shape, size, number of colors, and type of substrate to be imaged, as well as the level of transparency of the product media and surface type onto which to transfer the image.

Various techniques have been developed to achieve DTS printing. One technique, "pad printing," allows the transfer of a two-dimensional image onto a three-dimensional surface through the use of a silicone pad, an ink cup, and an etched plate. Pad printing is ideal for difficult substrates such as products found in the medical field and promotional printing, but due to the expense of the process pad printing typically uses only <NUM> or <NUM> colors during a print job, thereby limiting the artistic expression available to three-dimensional surfaces.

Another technique screen printing utilizes a mesh or screen to transfer the ink to the substrate surface. The process requires creating a screen that selectively permits ink to flow through the screen using a blocking stencil. While a photographic process may be used to create the screen, and hence allows relatively good resolution of imaging, the process requires substantial set-up time and is less flexible because any update or small alteration to the image to be applied requires the creation of a new screen set which increases the time and expense for a screen process versus other DTS imaging processes. In addition, screen printing is typically restricted to only <NUM> or <NUM> colors because each color requires its own separate customized screen, thereby tending to limit artistic expression onto three-dimensional surfaces.

Due to the above limitations, inkjet printing has over time risen to be the preferred method for DTS printing, especially for package printing and printing on durable exterior surfaces, such as containers. Inkjet printing utilizes a digital printhead to print full color customized designs in one or multiple imaging passes and may be applied directly to the substrate surface of the object or medium. Developed in the <NUM>, inkjet printers were created to reproduce a digital image directly onto a printing surface which is achieved by propelling droplets of ink directly onto a substrate medium. The ink delivery mechanism used to propel the droplets of ink is called the "printhead," and is controlled by a connected computer system that sends signals to the printhead based upon a digital image held by the computer system. Since the digital image may be altered an infinite number of times, replication and refinement of an image applied through the printhead is easily achieved.

However, the design of printheads in an inkjet system varies greatly increasing the complexity of creating a DTS printer. Each head is uniquely designed for its application, and a variety of digital printer designs are available to be used to print on various substrates. Hence, various factors drive the selection of an inkjet printing system to be utilized for a DTS project, such as the type of product substrate to be printed, the volume of products to be printed, and the required manufacturing speed for the imaging of any product traversing through a manufacturing line.

Irrespective of the complexity of designing an inkjet printing system to meet a particular DTS target object, the benefits of inkjet printing in DTS applications have driven a preference to use inkjet systems in product manufacturing lines. The reasons for this are numerous. For example, inkjet printing requires less set-up time and allows for faster print and cure times. Inkjet printing also is configurable to allow printing on multiple items at once, whereas other printing methods are often restricted to a single print instance for each object being printed. Moreover, print jobs do not require fixed setup time and costs, such as the generation of screens or the installation of plates, and therefore digital images may be easily and inexpensively refined to meet the particular surface characteristics of a three-dimensional object, thereby maximizing the artistic expression capabilities of the printing system.

One great advantage of inkjet printing is the ability to change or refine graphic images quickly, sometimes almost in real-time, to adjust printing results or to reconfigure the printing system for a different three-dimensional object. Modern imaging software is template driven and allows for the importation of new or re-worked graphics instantly. Hence, the flexibility of image alteration on a job-by-job basis is a distinct advantage.

In addition, inkjet printers are flexible enough to be used for short and long printing production projects, thereby meeting various manufacturing demands. For example, a single machine may be used to prototype or provide a sample, low-volume job for a potential client, or that same machine may be used in the same facility to print thousands of articles in a day for high volume production run. Further, the same machine may use various types of inks to accommodate a myriad of three-dimensional object surface materials.

Finally, conveyor and assembly line capability allow the inkjet printing process to become highly automated which increases productivity and lowers labor costs. So-called "inline" printers can do such printing at incredibly fast production rates. Typically, the inkjet printhead remains stationary while the three-dimensional object surface is moved underneath the printhead to maximize material handling through-put rates. This type of inkjet system is ideal for barcoding and dating product packaging. Single-pass multi-color inkjet printers are similarly used to achieve higher quality imaging with more color options at slightly slower print speeds, but still at a high-rate of production.

One type of inkjet system is specialized to print on the surface of cylindrical containers and are called "digital cylindrical presses. " For example, The INX Group Ltd. (aka "Inx Digital" and "JetINX") a division of Sakata INX offers a cylindrical printing solution under its CP100 and CP800 line of direct-to-shape (i.e. DTS) inkjet printing systems. These systems allow for the creation of an inkjet production line to print directly onto axially symmetrical objects. Other companies offer similar systems, such as Inkcups Now Corporation which offers its Helix line of DTS printers. These printers use a rotatable mandrel to hold an object and rotate the object next to an inkjet printhead as the printhead jets ink onto the surface of the cylindrical object. An image is captured for transfer onto an object and a printing "recipe" created, either created by the printing machine itself or created separately on personal computer and then imported into the printing machine. The "recipe" includes information necessary for the printing of the image onto an object and the recipe parameters are specific to each type of printer utilized. In these types of DTS systems, the raw, undecorated three-dimensional object is usually referred to simply as "media.

The CP100 machine is a good example of an industry standard cylindrical DTS printing system. The system is a stand-alone machine that performs non-contact printing of images on generally cylindrical objects, and in particularly hollow cylindrical objects or hollow partially cylindrical objects, for example, single piece cans and bottles and two-piece cans and bottles. Each cylindrical object is hand-loaded onto the machine and secured by vacuum on a mandrel to prevent slippage, which is part of a carriage assembly that functions to linearly positioning the object beneath at least one digitally controlled inkjet printhead. The object is rotated in front of the printhead while ink is deposited onto the object to produce a desired printed design on its surface. The ink is either partially or fully cured immediately after printing by exposing the ink to an energy-emitting means, such as a UV light emitter, positioned directly beneath the object. A carriage assembly is fixedly mounted to a linear slide actuator, which is in turn fixedly mounted to a mounting frame, whereby the carriage assembly is free to traverse along the linear slide actuator. The carriage linearly advances the object in a position adjacent to the inkjet printhead such that a first portion of the object may be printed if the object length is longer than the length of the printhead. The object is rotated while the computer-controlled printheads deposit ink from a supply of ink located above the object being printed upon. Simultaneously the UV light emitter either partially or completely cures the ink. The carriage then continues to advance the object further such that the entire length of the object surface is printed upon. As may be understood, the continuous advancement of the object by the printhead may not be necessary if the printhead is longer than the image desired to be printed on the object, but this is typically not the case and the object must be advanced along a straight path underneath the printhead. The image itself comprises a digital image that is imported from a separate imaging application and loaded into a software application that is used to create the object recipe to accommodate the physical specifications of the object. A profile is loaded through an operating system present on the machine and utilized to control motion of the object held by the carriage assembly along the linear slide. A print engine running on the machine controls the delivery of ink onto the object via the inkjet printhead as the object is moved past the printhead in a digitally controlled manner. The precise deposition or expression of the ink via the inkjet heads is dependent upon the object recipe which includes the specific amount and color of ink applied to the object as it traverses the printhead. The structure and operation of standard cylindrical DTS printing systems are fairly well understood in the printing industry and disclosed in representative <CIT> and <CIT>.

One challenge facing such DTS printing systems is the application of images to the surfaces of clear media, such as transparent glass or plastic media, or even semi-transparent objects such as frosted or color tinted media. Typical DTS systems, such as the above referenced Helix line of DTS printers position UV pinning and curing lamps below a rotating object. However, for transparent or translucent media this poses a problem. Transparent and similarly optically transparent media tends to scatter UV light and often causes UV light to impinge upon the printheads of the inkjet system. The incident UV light often causes the instant hardening of the ink on the printhead nozzles. This can cause the total or partial fouling of the inkjet head requiring either removal and cleaning of the printhead, or more often the complete replacement of the printhead. This interferes with the production time of any print job causing significant delays as the inkjet head is replaced and then recalibrated. Moreover, partial fouling may cause the degradation of image quality applied to the surface of media which may not be discovered until much later in a production run of a high quantity of printed products, thereby causing the loss of time and costly ink required to reprint the media, or even causing the total loss of processed products which in most instances cannot be reprinted and must be discarded.

Some have tried to reposition inkjet printing heads or the curing lamps, such as horizontally positioned lamps relative to downwardly pointing inkjet printing heads, to avoid such fouling, but such designs limit the number of objects that may be printed simultaneously and also do not address the quality issue of printed images on clear media because such repositions do not provide a consistent and controlled dosage amount of UV light to be applied to images. This causes an uncertain and inconsistent application of UV light to the applied images and reduces the overall quality of the applied images resulting in a visually unattractive printing result for a consumer, or worse an inability of the image to adhere properly to the object once applied.

An additional problem with clear or transparent media is the inability to properly gauge the total amount of UV light that is being applied to the surface of each object during a printing process. Currently, 3D media or object printing is achieved by first applying a reduced amount of UV light to ink applied to the surface of an object, often referred to as "pinning" the ink to the surface, which causes a partial hardening of the ink so that it adheres to the object surface while the object is rotated. This also allows for different colors to be applied to the surface as successive layers of imaging colors are applied during rotation, thereby allowing for a full range of artistic expression onto the object surface. However, each ink and even each color of a particular ink is precisely formulated to harden when exposed to UV light, with each ink varying in the amount of hardening reaction responsive to the application of the UV light. In transparent object printing, UV light easily passes through and is reflected off the various curved surfaces in the object during the printing, pinning, and curing steps. The hardening of an image onto a surface resulting from UV light exposure is additive in nature, with each exposure step increasing the total amount of hardening of the ink during a printing process. If too little total UV light is applied to the surface of an object, an image may not exhibit acceptable visual quality or may not be retained once shipped to a consumer. If too much total UV light is applied, the printed image may also not be retained, and annoyingly exfoliates during use by a consumer. Hence, manufacturers have learned that a precise amount of UV light must be applied that varies with each printed design for each type of media being printed. In fact, the size and shape of each media must be accounted for in order for an acceptable and permanent image to be properly applied to the object.

Unfortunately, even if procedures are established to tailor the total amount of power that is necessary to optimally cure ink expressed onto the surface of three-dimensional objects, the reflective properties of clear media causes the final curing step to scatter UV radiation around the printing area, including the area where print heads are positioned during the application of ink to the media surface along with the partial curing or pinning of the image onto the exterior of the media. Hence, transparent media pose an acute problem during printing because a manufacture is unable to control the aberrant amount of UV light that impinges on the inkjet printing heads during a final cure process, thereby causing the above noted fouling of inkjet printing heads.

Therefore, what is needed is a method of controlling the movement of media through a final curing step to avoid the impingement of final cure UV radiation upon the adjacent inkjet printing heads, thereby avoiding costly delays in transparent media printing, while allowing the simultaneous processing of multiple media.

It is the object of the present invention to precisely control the movement of media during a final cure step in the printing of an expressed inkjet image on the surface of transparent media. The method controls a number of factors during final curing such as the lateral movement of media under a final cure lamp, the number of rotations that media undergoes during final curing, the timely modulation of UV lamp power during final curing, and the selection of UV emitter segments positioned away from a inkjet print head to reduce the amount of potential UV radiation from impinging upon one or more of the adjacent printing heads.

Other features and objects and advantages of the present invention will become apparent from a reading of the following description as well as a study of the appended drawings.

A method for reducing the scattering of UV light during final curing of printed images on transparent and semi-transparent media incorporating the features of the invention is depicted in the attached drawings which form a portion of the disclosure and wherein:.

Referring to the drawings for a better understanding of the function and structure of the invention, <FIG> and <FIG> show perspective views of the decorating machine <NUM> showing the primary external components of the system. Machine <NUM> includes a material handling or "feed" system portion <NUM> and a printer system portion <NUM> mated to one another in a "T" configuration. An operator is positioned adjacent to the feed system <NUM> at a convenient location <NUM> from which they may load undecorated media <NUM> onto a loading shuttle <NUM> positioned in a loading area <NUM> and adjust the operation of the system <NUM> through a human machine interface (HMI) via a display terminal (not shown) held by support <NUM>. The shuttle <NUM> is supported by a pair of rails <NUM> and includes media support brackets <NUM> that are sized to support a variety of sizes of media <NUM> in a horizontal orientation. For the purposes of the present system, the targeted type of undecorated media is a transparent (i.e. visually clear) or semi-transparent (e.g. translucent, frosted or colored glass containers) 3D object. Each portion (<NUM>,<NUM>) of the machine <NUM> includes suitable support frames <NUM>, external panels <NUM>, and support rollers <NUM> through which each subsystem is supported.

Once loaded with undecorated media <NUM>, shuttle <NUM> may be moved by the operator from the loading area <NUM> to a pickup area <NUM> along rails <NUM>. Pickup area <NUM> is positioned such that a pneumatic robot <NUM> may grip and raise each undecorated media piece above the shuttle <NUM> and deliver it onto a printing carriage <NUM> for conveyance into printing portion <NUM>, or for removal of decorated media <NUM> from printing carriage <NUM> and delivery into product removal area <NUM>. The removal area may include tilted supports <NUM> as shown to facilitate removal of decorated product from the machine <NUM> by an operator.

<FIG> shows a closer view of the media handling portion of the system <NUM> with the printer portion <NUM> removed. As may be seen, pneumatic robot <NUM> can move either left or right to deposit media from the loading pickup area <NUM> to the printer carriage <NUM> or from the printer carriage <NUM> to the product removal area <NUM>. Printer carriage <NUM> is supported by a portion of printer <NUM> that is positioned or mated with portion <NUM> within a vacant section <NUM> of material handler <NUM>. As more easily seen in <FIG>, pneumatic robot <NUM> includes a gantry subassembly <NUM> having a lower gripper assembly <NUM> depending downward via vertical supports as shown. Gripper assembly <NUM> includes at least two sets of gripping or grasping mandibles <NUM>(a,b) that are sized to open and close around 3D objects, such as a container like a wine bottle and the like, which are generally referred to herein as "media. " A pair of rails <NUM> are held by gantry <NUM> to allow for the slidable movement of gripper assembly <NUM> to slide along a media loading path 29a or along a media unloading path 29b. The arrangement allows for the rapid simultaneous movement of two sets of media to and from loading and unloading areas <NUM> and <NUM>.

Referring now to <FIG> and <FIG>, it may be seen that printer carriage <NUM> is supported by a pair of rails <NUM> on a lower enclosure <NUM> that is sized to fit into space <NUM> of material handler <NUM>. When enclosure is mated with handler <NUM>, the rails <NUM> permit printer carriage <NUM> to traverse from within the handler <NUM> and into a series of parallel printing tunnels <NUM> along path <NUM> and formed within printer section <NUM>. Printing occurs on each piece of undecorated media <NUM> within these tunnels <NUM>. The disclosed embodiment shows <NUM> tunnels, but the inventors foresee that the number of tunnels may be enlarged to increase material printing throughput to the extent that the material handling section is designed to move material across an increased number of tunnels using an enlarged gripping set.

Printer <NUM> includes a lower front enclosure section <NUM> that is connected to a taller section <NUM> that holds various printer support subsystems. Lower enclosure section <NUM> houses a standard personal computer or PC <NUM> that is connected through cables with display terminal (not shown) held by a display terminal support <NUM> for control of the system <NUM> via an HMI by an operator. A suitable PC for system <NUM> is a <NUM> Intel Core i7, with <NUM> GB RAM and an Intel UHD graphics processor <NUM>, and running Windows <NUM> (HP part No. 2X3K4UT#ABA). Section <NUM> includes an ink delivery subsystem <NUM> connected and controlled by the personal computer <NUM> for delivering ink to a series of inkjet printer heads within printer image deposition and curing area <NUM>. A suitable print engine and ink recirculation system for system <NUM> is the available from INX International Ink Co. under part Nos. <NUM>-<NUM> (Head Drive Mother Board) and <NUM>-<NUM> (Gen <NUM> Printhead Control Board) as part of their JetINX™ printhead drive electronics component and ink delivery system offerings. As will be further discussed, tunnels <NUM> are sized to allow the passage of media <NUM> underneath section <NUM> and include a plurality of inkjet heads and UV lamps that are positioned within close proximity to the surface of each piece of media <NUM> once positioned within each tunnel <NUM>. Suitable printheads for printer portion <NUM> are the Gen <NUM> Print Heads offered by Ricoh Company, Ltd. under part No. N220792N. Suitable UV lamps for both final curing and ink pinning are available from Phoseon Technology under its FireEdge FE400 LED curing line of products (Part No. FE400 80X10 8W).

<FIG> shows the tunnel area <NUM> above which a printhead and cure lamp support assembly <NUM>, including a support gantry <NUM>, are positioned to allow for adjustment of the relative positions of the printheads and cure lamps so that various sizes of media may be accommodated by the printer <NUM>.

Referring to <FIG> it may be seen the tiltable arrangement of the pinning UV lamps <NUM> in relation to the printheads <NUM> and final cure UV lamps <NUM>. Gantry <NUM> may be raised and lowed in response to operator inputs that set heights in relation to each media size, thereby raising and lowering the printheads <NUM> and final cure lamps <NUM> which are affixed and supported by support assembly <NUM>. Pinning lamps <NUM> are also supported by support assembly <NUM>, but are able to be tilted via connected motorized racks <NUM> as well as move laterally relative to the center of each media piece. An operator enters via a human machine interface (HMI) geometries for the media piece to be utilized in a printing job, such as for example the length, diameter, and conical slope (if any) of the surface of the media piece, and a PC actuates movement of the gantry <NUM> and motorized racks <NUM> to accommodate the media size. A suitable PC/HMI system for the herein described operator control may be found in U. No. <CIT>, at Col. <NUM>, line <NUM> through Col. <NUM>, line <NUM>, and <FIG> (commonly owned by the Applicant). Actual movement distances are self-generated via PC <NUM> and communicated electrically to a control board that issues movement commands to motors controlling the racks <NUM> and gantry height <NUM>. A suitable motion control board system for the above may be found in U. No. <CIT>, at Col. <NUM>, line <NUM> through Col. <NUM>, line <NUM>, and <FIG> (commonly owned by the Applicant). Printer support assembly <NUM> moves vertically (up and down) along path <NUM>, and UV pinning lamps <NUM> move laterally along path <NUM> and along angular path <NUM>. Motor <NUM> drives a primary lifting shaft <NUM> via gearing assembly <NUM> that in turn drives three passive vertical lifting drive shafts <NUM>. A quadrilateral gearing assembly <NUM> having a fixed support frame <NUM> fixed to gantry <NUM> and four corner gearing assemblies <NUM> connects and supports each drive shaft <NUM> so that when actuated rotational motor movement is converted into a coordinated level lifting motion of printing support frame <NUM>. Frame <NUM> includes a plurality of slots <NUM> to fixedly hold printheads above each tunnel <NUM> and a fixed rearward placed slot <NUM> for a UV curing lamp.

Movement of each pinning lamp <NUM> is achieved via a coordinated assembly of extendable plates and pivotal support bars and brackets <NUM>. Pinning UV lamps <NUM> are supported by a parallel series of transverse support bars <NUM> that adjustably hold lamps in pre-formed slots and held in place with retaining screws. Each support bar <NUM> is supported at its ends by brackets <NUM> and <NUM> which in turn are supported by connecting plates <NUM> so that pinning lamps <NUM> are slidably suspended above each piece of media across and above each tunnel <NUM>. End plates <NUM> are slidable held in slots formed in frame <NUM> so that as left most plates <NUM> are moved by gear <NUM> through gearing assembly <NUM>, the pair of brackets <NUM> and <NUM> are moved right or left, depending upon the rotational direction of drive shaft <NUM> driven by servo motor <NUM>. Brackets <NUM> and <NUM> are connected to support bars <NUM> via rotatable studs or fasteners <NUM> so that as the lateral position of brackets <NUM> and <NUM> are changed, bars <NUM> are correspondingly moved laterally. When actuated, servo motor <NUM> thereby precisely controls the lateral position of the UV lamps <NUM> relative to an underlying piece of media <NUM> positioned within tunnels <NUM>. The lateral position of brackets <NUM> and <NUM> are also adjustable relative to one another so that as bracket <NUM> is advanced to the right or left relative to lower bracket <NUM>, bars <NUM> are tilted about a rotational axis corresponding with the center of the lower positioned rotatable studs 46a. Therefore, changing the lateral relative positions of brackets <NUM> and <NUM> alters the angle <NUM> of each UV emitter <NUM> identically with every other UV emitter <NUM>. A spring-loaded set pin <NUM> locks the relative lateral position of each bracket <NUM> and <NUM> relative to one another, and upon pulling pin <NUM> out slightly the two brackets may be altered relative to one another to change angle <NUM> as desired. A series of pin indentations or holes within right most plate <NUM> allow for the selection and locking of one or more pre-set angles for emitters <NUM> by grasping and manipulating pin <NUM> and rotating the UV emitters to a desired angle. The lateral position is attained by actuating motor <NUM> by an operator and, in the present embodiment, the angle of the UV lamps <NUM> is adjusted by manipulating pin <NUM> to allow movement and locking of emitters <NUM> into a desired angle relative to the adjacent printheads <NUM> and underlying media <NUM>.

Importantly, the above described selectable positioning of UV lamps <NUM> in relation to the position of the media <NUM> and printheads <NUM> minimizes the potential for UV exposure to each printhead, either directly or via transparent media reflections, as will be further discussed. As may also be noticed, the final cure UV lamp <NUM> is positioned well behind each bank of inkjet printing heads <NUM>, but the UV pinning lamps <NUM> are positioned adj acent to each bank of printheads <NUM> and pointed downward and away from the bottom ink expression area (i.e. the printhead nozzle) of each printhead.

Referring again to <FIG>, printing carriage <NUM> is moved along path <NUM> and into tunnels <NUM>. As each piece of media moves into its own respective tunnel, the media is rotated, and the surface of the media is moved axially under each printhead <NUM> in a coordinated fashion. As a piece of media traverses under a print head the lateral position and rotation speed of the media is precisely controlled via spindles <NUM> and a drive motor causing movement of printing carriage <NUM> via a screw shaft <NUM> (not shown). In addition to being rotationally controllable, spindles <NUM> are self-stripping and are locked against each piece of media via air cylinders at one end, but having a spring-loaded configuration thereby clamping each piece of media within the print carriage <NUM> at the center of each individual media spindle.

As may be understood, the disclosed embodiment shows a material handling system <NUM> mated to printer <NUM> so that the disclosed configuration allows for the automation of material handling. However, printer portion <NUM> may be utilized separately without the automation system <NUM> in which case an operator would simply load each piece of media <NUM> directly onto printer carriage <NUM> by manually manipulating the spindle ends to insert a piece of media <NUM> for decorating within each spindle and removing a decorated piece of media <NUM> when complete.

For the purposes of discussions on the operation of the herein described printing and ink partial curing and final curing steps, a suitable ink delivery and print engine subsystem <NUM> may be found in U. No. <CIT>, at Col. <NUM>, lines <NUM>-<NUM>; Col. <NUM>, lines <NUM>-<NUM>; Col. <NUM>, line <NUM> through Col. <NUM>, line <NUM>; and <FIG> (commonly owned by the Applicant). Referring to <FIG> along with Table <NUM> below, a power scale factor formula is presented that allows for the calculation of the minimum amount of power such that a final acceptable UV cure dosage amount may be applied to the partially cured ink present on the surface of the (now) decorated media <NUM>. As an article having a partially cured or "pinned" image <NUM> traverses further within a respective tunnel <NUM> along path <NUM>, it enters into an illumination zone <NUM> concordant with the length (91a) of UV cure lamp <NUM> as the object <NUM> continues to rotate <NUM> at a known speed. Each lamp has a known width <NUM> and a known power density as set by its manufacture. Also, each type of ink deposited onto the surface of the object <NUM> also has a specified amount of UV energy necessary to optimally cure the ink, which is either supplied by the manufacture of the ink or can be obtained relatively easily by empirical testing.

The Power Scale Factor or "PSF" in Table <NUM> is a dimensionless value and often is simply a scaling factor or a percentage of the maximum power density. Given the amount of energy required to cure the deposited ink and given the known amount of UV energy emitted by lamp <NUM>, a power scale factor or PSF may be calculated using empirical UV dosage results so that the PSF may be utilized for future print jobs. This allows for the variation of various factors during printing to obtain optimal image quality on the exterior of the object <NUM>. For example, if <NUM>% of total dosage during pinning of an image <NUM> is applied, the lateral speed along path <NUM> and rotational speed <NUM> may be varied to accommodate a particular beam strength emitted from lamp <NUM> to achieve the remaining optimal dosage of <NUM>%. Lamp width <NUM> is typically small (e.g. <NUM>) relative to the circumference of an object <NUM> such that redundant image exposure may be ignored. Further, each lamp <NUM> may include a collimator to reduce the fanning or scattering of illumination zone <NUM> prior to impinging upon the surface of object <NUM>.

Another way to express the above PSF is with the following formula shown in Table 1A below:.

As may be understood, for non-3D objects, such as flat media, the Time of Exposure may be found by dividing the distance of travel of the media under a lamp with the linear velocity of the flat media. However, for 3D objects that require rotation such as media described herein, the time of exposure is the fraction of the time that the UV illumination zone <NUM> is incident with the expressed image applied to the surface of the media along the perimeter or circumference of the media.

Using the formula shown in Table <NUM>, an example PSF calculation is shown below.

Given a color ink curing dose density of 146mJ/cm<NUM> an example calculated PSF would be: <MAT>.

<FIG> shows an altered final cure step <NUM> to reduce the amount of UV radiation utilized in a final cure step. As object <NUM> moves under lamp <NUM>, the trailing edge of image <NUM> (i.e. the last part of an image that must be cured as the object moves from left to right and under the cure lamp within tunnel <NUM>) moves under lamp <NUM> and at some distance <NUM> becomes fully cured. The remaining distance under lamp <NUM> thereby becomes superfluous for the purpose of curing. Therefore, lamp intensity may be increased during a last portion of lateral travel <NUM> to finish full curing of the image <NUM> and then lateral movement stopped rather than moving the object the full length of the image underneath lamp <NUM>. This procedure thereby reduces the time of printing while also reducing the amount of duration of any potentially scattered light within tunnel <NUM>. As can be appreciated, a full number of turns under the emitter must be realized in order that all parts of image <NUM> receive the same minimum amount of UV radiation so that full curing is achieved. Table <NUM> below shows a formula for calculating the minimum number of turns required in order to achieve full curing.

An example calculation is shown below calculating the minimum number of turns required for the specified equation values per Table <NUM>. Given a 3D media having a circumference of <NUM> at the image location on the media, the following calculation leads to a minimum number of two (<NUM>) full turns to achieve full curing of image <NUM>.

<FIG> provides a further final cure option <NUM> for clear media. Lamp <NUM> includes left and right lighting segments <NUM>,<NUM>. For clear media, left segment <NUM> is deactivated and only right segment <NUM> utilized for curing of ink on image <NUM>, thereby removing the UV illumination field portion between location <NUM> and <NUM>. This re-positions the UV source of light in tunnel <NUM> to the right and moving a potential source of scattered stray UV light away from ink heads <NUM>. This option is selected through an operator inputted action via the HMI prior to the start of any print job.

Referring now to <FIG>, and <FIG>, it may be seen the positioning of pinning lamps relative to the printheads <NUM> within each tunnel <NUM>. The adjustment of the pinning lamp position <NUM> is accomplished as discussed above with respect to <FIG> and may be controlled through an HMI presented to an operator through a display held by display mounting <NUM>. The HMI displays the settings required for any selected piece of media and the operator makes whatever adjustments to the printer <NUM> that are required, including for example the lateral position of the pinning lamps, the tilt or angle of the pinning lamps in relation to the adjacent print heads, and the height of the frame member <NUM> over the media responsive to the diameter of the media. UV light emitted from lamp <NUM> is angled such that the right most edge <NUM> of illumination zone <NUM> preferably coincides with the tangential edge <NUM> of object <NUM> as it rotates <NUM> in a counterclockwise direction. The alignment of the right most zone edge <NUM> with the object edge <NUM> allows for the maximum emitted amount of UV light to be received on the rotating surface of the media <NUM> within the illumination zone <NUM>. Further, zone <NUM> is optionally refined to align the emitted UV light rays with a collimator placed on lamp <NUM> to further reduce scattering. As shown, wet ink <NUM> is jetted or expressed by printhead bank <NUM> onto the surface of object <NUM> as the object rotates counter-clockwise. The wet ink <NUM> is then exposed to UV light when it reaches illumination zone <NUM> and partially hardens into a gel <NUM> so that the applied ink does not shift on the surface of the media <NUM> during further printing. This arrangement allows for the wet ink to fully spread or "wet" the surface of object <NUM> prior to exposure to UV radiation in zone <NUM>. As the media rotates the slight rotational delay prior to exposure in zone <NUM> is important because it allows for a better artistic expression of the applied image. For example, the rotational delay allows for a more glossy, desirable image <NUM> to be applied to the object <NUM> when fully cured. Referring to <FIG>, clear media will expose ink to UV radiation below the potential tangency point <NUM> when the UV radiation passes through the clear media material, but given the rotational delay until exposure the point of UV impingement is sufficiently delayed to allow for full wetting of ink on the surface of a clear media object <NUM> to occur. Further, the downward UV light ray angle minimizes or even eliminates reflections on clear media so that printhead impingement does not occur. For translucent media, ink is exposed at the point of tangency <NUM> on the media with light scattering away from the ink heads <NUM> to avoid impingement. Critically, the downward angle of lamp <NUM> avoids UV light from impinging onto the nozzles of ink heads <NUM> on either type of media, thereby avoiding the fouling and deactivation of ink heads <NUM> during a print job when clear or semi-transparent media are being decorated. As shown, angle <NUM> of lamp <NUM> and the lateral position <NUM> along path <NUM> of lamp <NUM> may be adjusted in response to a geometry file associated with the dimensions of object <NUM> in order to optimize the positioning of lamp <NUM> so that the right most edge <NUM> of illumination zone <NUM> coincides with the tangency point <NUM>. This maximizes the amount of pinning UV radiation applied to the widest possible portion of media <NUM> without exposing ink heads <NUM> to UV light, even when clear media are being printed upon with the associated potential reflections of UV light.

Referring to <FIG>, it may be seen various positional embodiments <NUM> of UV lamp <NUM> and the effect of such positional changes on the UV illumination of rotating media <NUM>. Inkjet print heads <NUM> express ink onto the surface of media <NUM> in a wet condition <NUM> as media <NUM> rotates counterclockwise <NUM>. During rotation, the surface of media <NUM> rotates into various angular zones demarked by angles of <NUM> degrees <NUM>, <NUM> degrees <NUM>, <NUM> degrees <NUM>, and <NUM> degrees <NUM>, thereby creating four angular quadrants of <NUM> degrees each. A preferred illumination area <NUM> may also be seen consisting of plus or minus <NUM> degrees (<NUM>, <NUM>) from angular point <NUM> degrees <NUM>.

In relation to inkjet printing heads <NUM>, UV pinning lamp <NUM> may be moved into various lateral and angular positions <NUM> thereby altering the position of illumination field <NUM> issuing from lamp <NUM>. As previously described, inkjet heads <NUM> and UV lamps <NUM> are supported by frame member <NUM> but also extend just below the lower surface <NUM> of frame member <NUM> so as to interact with each piece of media <NUM> when inside tunnels <NUM> during a printing operation. Lamp <NUM> may be adjusted to move laterally away from printheads <NUM> along line <NUM> to various a user selected distances <NUM>(a-c) as measured from the edge of printheads <NUM> to a center pivot point <NUM> for lamp <NUM>. Pivot point <NUM> corresponds with retaining grommet 46a (see <FIG>) to allow lamp <NUM> to be rotated into various user selected angles <NUM>(a-c) as measured from a line bisecting lamp <NUM> and intersecting pivot point <NUM>, thereby forming an angle <NUM> with line <NUM>. Line <NUM> is parallel with lower surface <NUM> and also intersects pivot point <NUM> as shown. Angles thus formed may range preferably from approximately <NUM> degrees 206a, <NUM> degrees 206b, or <NUM> degrees 206c. As will be understood, by varying the lateral and angular position of lamp <NUM>, a UV illumination zone or field having various coverage areas <NUM>(a-c) relative to media <NUM> may be created. Each field has a right most illumination edge <NUM>(a-c) that varies with angle and lateral position such that intersection with ink layer <NUM> on the surface of media <NUM> creates a tangency point <NUM>(a-c) at the intersection location. Each tangency point varies in relation to the lamp position, but is preferably located within preferred angular zone <NUM> that maximizes the amount of power impinging upon the ink <NUM> during rotation while minimizing any potential for reflectivity of UV light to intersect the nozzles on printheads <NUM>. For example, for the media size depicted in <FIG>, a preferred position of lateral distance 204b is combined with an angular position of 206b to produce an illumination field of 91b. UV light will therefore partially harden ink <NUM> as is passes through field 91b, including tangency point 211b and keeping wet ink <NUM> within zones <NUM> and <NUM> until gelled. By adjusting the lateral and angular position of lamp <NUM>, a large range of media sizes and various types of inks may be accommodated within printer <NUM> without fouling the ink nozzles of the printheads <NUM> during printing.

<FIG> show the application of exposure control so as to minimize reflections of UV light during final cure by modulating different banks of emitters in lamp <NUM> or by modulating the power level of all emitters in lamp <NUM> (<FIG> shows the traditional method in which the entire 3D object is moved under a curing lamp for the entire length of the object resulting in the gross scattering of UV radiation <NUM>, likely in a direction toward a printhead <NUM>. The same traditional approach shown in <FIG> applies with a UV curing lamp emitter positioned underneath the object, which is the most common industry position standard for final curing of ink on 3D objects. <FIG> shows the improved, modulated approach. Two levels of intensity are used for lamp <NUM>. While an image is being printed and pinned onto the surface of object <NUM>, the entire object is moving into illumination zone <NUM>. As image leading edge <NUM> enters the start of the illumination zone <NUM>, intensity of lamp <NUM> is set at a value less than full value, for example <NUM>% of full illumination strength, but modulated to an intensity value responsive to a final UV exposure value calculated in accordance with the PSF value to achieve complete curing. Object <NUM> continues to move forward into the illumination zone <NUM> along path <NUM>. Once image <NUM> has been fully printed and pinned, the intensity of lamp <NUM> is increased to full power, or other second higher power depending about size and length of the image and lamp intensity, and again in accordance with the PSF value. The object continues through the illumination zone <NUM> until the left trailing edge <NUM> of image <NUM> attains a fully cured state. Since final cure lamp <NUM> does not use a full power level until after image <NUM> is fully printed, the total amount of UV light emitted by the cure lamp <NUM> is greatly reduced thereby reducing the amount of stray UV light at a high-power level being potentially scattered around the printing tunnel <NUM> during final curing of the media <NUM>. Since many types of transparent or translucent media include concave and convex surfaces, like for example a smooth, curved neck surface, this UV power reduction process minimizes the potential for a concentrated beam of UV light impinging upon a print head, or if it does it would do so at a reduced UV effect.

<FIG> shows a process <NUM> for using the PSF formula shown in Table <NUM> to control values in the printing process for the system <NUM>. The process starts <NUM> by calculating a PSF by using empirical observations <NUM>. Using the PSF value, an optimal pinning lamp dosage value is determined <NUM> for the transparent media <NUM> upon which an image is to be applied. The value calculated in step <NUM> is then subtracted from the total optimal UV dosage amount required to fully cure the image onto the surface of the media <NUM>. The PSF is further used to determine the final cure step parameters <NUM> which are then used to implement a final cure in the print job for a piece of media <NUM>, which ends the printing of a piece of media <NUM>. For example, an optimal media rotational speed for the printing of a piece of media in the printer can be calculated as follows: <MAT>.

<FIG> shows the process steps for adjusting the machine <NUM> for use on a particular 3D media shape in order to realize the reduced printhead fouling characteristics of the herein described system in a print job. Process <NUM> starts <NUM> by obtaining the 3D object geometries <NUM> by either taking manual measurements of the object and inputting those values into the system HMI or by reading into the system a geometry file that specifies the geometry values representing the object from a recipe file provided for the object and its assigned image to be applied. Responsive to the geometries for the object, the height of the printheads <NUM> held in slots <NUM> is adjusted <NUM> up or down along path <NUM> via commands issued to motor <NUM> to raise of lower printer support assembly <NUM>. The distance is adjusted <NUM> so that the printheads are optimally spaced <NUM> from the surface of the media to obtain the best image quality on the surface of the 3D object. Responsive to the diameter of the object, the lateral position <NUM> and angle <NUM> of the UV pinning lamp <NUM> is adjusted <NUM> relative to the central rotational axis of the media <NUM> in order to position the pinning lamp illumination zone edge to be coincident with the tangency <NUM> of the rotating 3D object surface (see <FIG>). Using the formulas for the PSF shown in Tables <NUM> and 1A, the required duration and illumination power for the pinning lamps <NUM> is calculated and set <NUM> to control the rotation rate of the media, the lateral advancement <NUM> and travel speed of printing carriage <NUM> in system <NUM>. The ink representing an image <NUM> is applied and rotates into the illumination zone <NUM> to become gelled or "pinned" onto the surface of the object <NUM>. This process of repeatedly applying and pinning an image onto an object surface is repeated until the print job is complete <NUM> and stopped <NUM>.

Claim 1:
A method for controlling the movement of transparent media during final curing of an image expressed onto the surface of said transparent media via an inkjet print head to minimize inkjet print head degradation, comprising the steps of:
a. applying an image to the exterior of said transparent media while said media is rotated;
b. using a UV lamp to partially cure said image into a gelled state such that said applied image is held in place on said exterior of said media during rotation thereof;
c. moving said media laterally along its rotational axis into proximity to a UV curing lamp and exposing said expressed image to UV light from said curing lamp to achieve final curing of said image on said media; and,
d. wherein UV radiation applied to the exterior of said media by said final curing lamp is modulated during said lateral movement step so that reflections of UV light from said media toward said inkjet print head are reduced to avoid causing fouling of said inkjet print head.