Card processing system with automatic drop-on-demand printhead maintenance routine

Abstract

The present invention provides a card processing system with an automatic maintenance routine for a drop-on-demand printhead, the card processing system comprising: a card input portion, the card input portion being configured to accommodate multiple plastic cards to be processed; a drop-on-demand card printer, the drop-on-demand card printer being located downstream of the card input portion and receiving plastic cards input from the card input portion, the drop-on-demand card printer comprising at least one drop-on-demand printhead; a controller, the controller being connected to the drop-on-demand card printer and automatically controlling its operation, the controller being programmed to automatically perform a purge routine on the at least one drop-on-demand printhead, wherein the purge routine comprises at least one step change in pressure to or from a maximum purge pressure.

Description

[0001] This application is a divisional application of a patent application with an application date of May 10, 2019, application number 201980031866.X (international application number PCT / US2019 / 031808), and invention name “Card processing system with automatic maintenance routine for drop-on-demand ink printhead”. Technical Field

[0002] The present disclosure relates to a card processing system for performing drop-on-demand printing on plastic cards, including but not limited to financial cards (e.g., credit cards, debit cards, etc.), driver's licenses, resident identification cards, business identification cards, gift cards, and other plastic cards. Background Art

[0003] In drop-on-demand (DOD) printing, ink is ejected from one or more nozzles of a printhead by electrically energizing selected ones of the nozzles of the printhead from which ink is to be ejected. If a nozzle is not used regularly, the nozzle may become completely or partially clogged with ink or other debris, thereby preventing its operation or causing the nozzle to erroneously eject ink.

[0004] In some DOD printing systems, a single item may be printed in what can be considered a production run, or, if multiple items are printed sequentially in a production run, the printing is typically the same from item to item, so the same set of nozzles are activated each time. Furthermore, in these DOD printing systems, item throughput (i.e., the number of items printed per unit time) is typically not a concern.

[0005] However, in card processing systems that employ DOD printing, card throughput (i.e., the number of cards printed per unit time) is an important factor, and efforts are made to minimize downtime of the card processing system for maintenance in order to maximize card throughput. Furthermore, in card processing systems that employ DOD printing, the printing performed on plastic cards, and the nozzles activated thereby, may vary from card to card in a batch print job, or may vary from one batch print job to another. Summary of the invention

[0006] A maintenance routine is described herein that can be used to maintain operability of one or more DOD printheads in a card processing system. The card processing system is used to print on plastic cards of the type that carry personalized data unique to the intended cardholder and / or other card information. Examples of plastic cards may include, but are not limited to, financial cards (e.g., credit cards, debit cards, etc.), driver's licenses, resident identification cards, business identification cards, gift cards, and other plastic cards.

[0007] The maintenance routines described herein are automated and can be used alone, together, or in any combination thereof to help maintain the operability of one or more DOD printheads in a card processing system. The card processing systems described herein can be any card processing systems that can process plastic cards by printing on plastic cards using a DOD printer having one or more DOD printheads (e.g., piezoelectric printheads) in conjunction with one or more of the following operations: reading data from and / or writing data to a magnetic stripe on a card, programming an integrated circuit chip on a card, embossing characters on a card, debossing characters on a card, laminating a card, using a laser to perform laser processing such as laser marking on a card, applying an outer coating to a portion or the entire surface of a card, inspecting the quality of personalization / processing applied to a card, applying security features such as a holographic foil to a card, and other card processing operations.

[0008] The DOD card printer used in the card processing system can have a single DOD printhead or multiple DOD printheads. The DOD printhead can be a piezoelectric printhead. The DOD printer can perform monochrome or multi-color printing. In an example of multi-color printing, five DOD printheads can be provided, each DOD printhead having multiple nozzles. Each printhead can be specified to print ink of a specific color such as cyan, magenta, yellow, black and white (CMYKW). The DOD printer can print using any suitable ink used in DOD printing, which is suitable for use on plastic cards of the type described in this article. For example, the ink can be an ultraviolet (UV) radiation curable ink.

[0009] The maintenance routines described herein may include, but are not limited to, the following routines: 1) a cover routine, in which a cover or cap is selectively and automatically placed over the printhead to protect the printhead; 2) a dither pulse routine, which energizes the nozzles of the printhead without causing the nozzles to eject ink; 3) a spit routine, in which the nozzles of the printhead are energized to eject one or more drops of ink; and 4) a purge routine, in which the nozzles are not electrically energized, but the vacuum pressure that holds the ink in the nozzles of the printhead is reversed to push the ink out of the nozzles.

[0010] The maintenance routine described herein is particularly beneficial when used with a DOD card printer in a card processing system. It is expected that the card processing system maintains a relatively high card throughput. In order to maintain such a high card throughput, it is important not to repeatedly shut down the card processing system for maintenance. In one example, the card processing system can process cards at a rate of at least about 500 cards per hour, or at least about 1000 cards per hour, or at least about 1500 cards per hour, or at least about 2000 cards per hour, or at least about 2500 cards per hour.

[0011] In addition, the card processing system prints on each card one by one in sequence. The printing on each individual card will be referred to as an individual card print job or similar job in this article. In addition, multiple cards can be printed in a continuous production run that will be referred to as a batch card print job or similar job in this article. In some embodiments, the printing performed during each individual card print job can and often does vary from card to card. For example, each card can be printed with the name and / or account number of the corresponding expected cardholder. Since the expected cardholder of each card is different and each card has a unique account number, the printing performed on each card will be different. In some embodiments, in a single batch print job, the printing on each plastic card can be the same. However, it may be necessary for the card processing system to perform multiple batch print jobs in a relatively short period of time (e.g., 1-2 hours), wherein each batch print job requires different printing on the cards in each batch print job. Alternatively, in other embodiments, the printing on some or all plastic cards in a single batch print job can be different.

[0012] Printing differs from card to card or from batch to batch means that some nozzles of the DOD print head of the DOD printer may not be used frequently or at all for a period of time, but these nozzles must be maintained in preparation for the next card or the next batch of printing without shutting down the card processing system (or shutting down the DOD printer), because shutting down for maintenance will reduce the throughput of the cards. In a non-limiting embodiment, some or all of the maintenance routines described herein are used for relatively small batches of printing jobs, such as less than 1500 cards, or less than 1000 cards, or less than 500 cards.

[0013] In one method described herein, a drop-on-demand printhead in a drop-on-demand printer in a card processing system is automatically maintained. The drop-on-demand printer is configured to print on plastic cards in the card processing system. The method includes automatically performing one or more of the following routines on the drop-on-demand printhead:

[0014] a) a jitter pulse routine performed at a first frequency;

[0015] b) a spitting routine performed at a second frequency less than the first frequency; and

[0016] c) Cleanup routine.

[0017] In another described embodiment, a method of printing on a plastic card in a drop-on-demand printer may be implemented, wherein the drop-on-demand printer has a drop-on-demand printhead. The method may include printing on a first plastic card using the drop-on-demand printhead, wherein the first plastic card includes at least one of a magnetic stripe and an integrated circuit chip. After printing on the first plastic card, a dithering pulse routine may be applied to the drop-on-demand printhead. After applying the dithering pulse routine, printing may be performed on a second plastic card using the drop-on-demand printhead, wherein the second plastic card includes at least one of a magnetic stripe and an integrated circuit chip. In some embodiments, printing on the first plastic card and the second plastic card may be part of the same production run or batch print job, wherein the first plastic card and the second plastic card are sequential and printing on the second plastic card occurs within a short time (e.g., less than 3-5 seconds) after printing on the first plastic card.

[0018] In yet another embodiment, a method of printing on a plastic card in a drop-on-demand printer in a card processing system may be implemented, wherein the drop-on-demand printer has a drop-on-demand printhead having a plurality of nozzles. The method may include inputting a first plastic card into the drop-on-demand printer and positioning the first plastic card relative to the drop-on-demand printhead for printing. Then, printing is performed on the first plastic card using a first subset of the plurality of nozzles of the drop-on-demand printhead. Within a short period of time (e.g., less than 5 seconds), after printing on the first plastic card is completed, a second plastic card is input into the drop-on-demand printer, the second plastic card is positioned relative to the drop-on-demand printhead for printing, and printing is performed on the second plastic card using a second subset of the plurality of nozzles of the drop-on-demand printhead. The second subset of nozzles used for printing on the second plastic card is different from the first subset of nozzles used for printing on the first plastic card.

[0019] A card processing system described herein may include: a card input configured to receive a plurality of plastic cards to be processed; and a drop-on-demand card printer located downstream of the card input and receiving the plastic cards input from the card input. The drop-on-demand card printer may include at least one drop-on-demand printhead. In addition, a controller is connected to the drop-on-demand card printer and automatically controls its operation. The controller is programmed to automatically perform one or more of the following routines on the at least one drop-on-demand printhead:

[0020] a) a jitter pulse routine performed at a first frequency;

[0021] b) a spitting routine performed at a second frequency less than the first frequency; and

[0022] c) Cleanup routine.

[0023] Another embodiment of the card processing system described herein may include: a card input portion configured to accommodate a plurality of plastic cards to be processed; and a drop-on-demand card printer located downstream of the card input portion and receiving the plastic card input from the card input portion. The drop-on-demand card printer may include at least one drop-on-demand printhead. In addition, an integrated circuit chip programming system may be disposed between the card input portion and the drop-on-demand card printer, wherein the integrated circuit chip programming system is configured to program the integrated circuit chip on the card. A controller is connected to the drop-on-demand card printer and automatically controls its operation. The controller is programmed to automatically perform one or more of the following routines on the at least one drop-on-demand printhead:

[0024] a) Jitter pulse routine;

[0025] b) spit routine; and

[0026] c) Cleanup routine.

[0027] In another embodiment described herein, a card processing system may include: a card input configured to accommodate a plurality of plastic cards to be processed; and a drop-on-demand card printer located downstream of the card input and receiving the plastic card input from the card input, the drop-on-demand card printer including at least one drop-on-demand printhead. A controller is connected to the drop-on-demand card printer and automatically controls its operation. The controller is programmed to automatically perform a purge routine on the at least one drop-on-demand printhead, wherein the purge routine includes at least one step change in pressure to or from a maximum purge pressure. In one non-limiting example, the at least one step change in pressure may occur in less than 1 second. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A card processing system as described herein is shown.

[0029] Figure 2 Shows Figure 1 The DOD card printer is a select component of your card processing system.

[0030] Figure 3 Movement of a cap of a DOD card printer toward a covering position over the DOD print head is shown.

[0031] Figure 4 Movement of a cap of a DOD card printer from a covering position toward a non-covering position is shown.

[0032] Figure 5 Various maintenance routines for the controller used on a DOD card printer are shown.

[0033] Figure 6Typical pressure variations across the ink in the nozzles of a printhead during normal operation and during a conventional purge routine using a pressure ramp are shown.

[0034] Figure 7 is a close-up view of a pair of nozzles of a printhead, illustrating the problem of free-flowing ink that can occur during a regular purge routine.

[0035] Figure 8 The pressure changes across the ink in the nozzles of a printhead are shown during normal operation and during a purge routine described herein using a step change in pressure. DETAILED DESCRIPTION

[0036] Figure 1 An example of a card processing system 10 described herein is shown. The system 10 is configured to process cards at least by printing on the cards using a DOD card printer 12 included in the system 10. In addition to printing by the DOD card printer 12, the system 10 may also include at least one other card processing capability. For example, additional card processing may include a magnetic stripe reading / writing system 14, which is configured to read data from and / or write data to a magnetic stripe on a card, and an integrated circuit chip programming system 16, which is configured to program an integrated circuit chip on the card. When the DOD card printer 12 prints using ultraviolet (UV) radiation curable ink, a UV curing station 18 may also be provided. The structure and operation of the systems 14, 16, 18 are well known in the art. Magnetic stripe read / write systems and integrated circuit chip programming systems are disclosed, for example, in U.S. Pat. No. 6,902,107 and U.S. Pat. No. 6,695,205, and can be found in the MX series central issuance system available from Entrust Datacard Corporation of Shakopee, Minnesota. An example of a UV radiation applicator in a card printing system is the Persomaster card personalization system available from Atlantic Zeiser GmbH of Emmingen, Germany.

[0037] Cards to be processed as described herein include, but are not limited to, plastic cards that carry personalized data unique to the intended cardholder and / or carry other card information. Examples of plastic cards may include, but are not limited to, financial cards (e.g., credit cards, debit cards, etc.), driver's licenses, resident identification cards, business identification cards, gift cards, and other plastic cards.

[0038] exist Figure 1In the illustrated system 10, a card input 20 is provided, which is configured to accommodate a plurality of cards to be processed. Cards are fed one by one from the card input 20 into the system 10 to process the rest of each card separately. The processed cards are conveyed to a card output 22, which is configured to accommodate a plurality of processed cards.

[0039] The operation of each system 12, 14, 16, 18, 20, 22 is controlled by one or more controllers 24. Alternatively, each of the systems 12, 14, 16, 18, 20, 22 or selected ones of the systems 12, 14, 16, 18, 20, 22 may have its own dedicated controller.

[0040] Any suitable mechanical card conveying mechanism known in the art may be used to convey cards through the card processing system 10. Examples of card conveying mechanisms that may be used are known in the art and include, but are not limited to, conveyor rollers, conveyor belts (with tabs and / or without tabs), vacuum conveying mechanisms, conveyor racks, and the like, and combinations thereof. Card conveying mechanisms are well known in the art and include those disclosed in U.S. Patents 6,902,107, 5,837,991, 6,131,817, and 4,995,501 and U.S. Published Application No. 2007 / 0187870, each of which is incorporated herein by reference in its entirety. One of ordinary skill in the art will readily appreciate the types of card conveying mechanisms that may be used and the structure and operation of these card conveying mechanisms.

[0041] Figure 1 The illustrated card processing system 10 is a type of system that may be referred to as a central issue card processing system. In a central issue card processing system, a card input 20 and a card output 22 are typically at opposite ends of the system 10, with a card processing mechanism such as a card reader between the card input 20 and the card output 22. Figure 1The systems 12, 14, 16, 18 in the central issuance card processing system are generally designed for high-volume processing of cards, and generally employ multiple processing stations or modules to process multiple cards simultaneously to reduce the overall per-card processing time. Examples of central issuance card processing systems include the MX series central issuance systems available from Entrust Datacard Corporation of Shakopee, Minnesota. Other examples of central issuance systems are disclosed in U.S. Patents 4,825,054, 5,266,781, 6,783,067, and 6,902,107, all of which are incorporated herein by reference in their entirety. In one example, the card processing system 10 (and the systems 12, 14, 16, 18 therein) can process cards at a rate of at least about 500 cards per hour, or at least about 1000 cards per hour, or at least about 1500 cards per hour, or at least about 2000 cards per hour, or at least about 2500 cards per hour.

[0042] exist Figure 1 In the embodiment, the systems 12, 14, 16, 18 are downstream of the card input 20 and between the card input 20 and the card output 22. The order or arrangement of the systems 12, 14, 16, 18 relative to each other and to the card input 20 may be different from Figure 1 The order shown is different.

[0043] System 10 may include Figure 1 Additional card processing systems, not shown, are well known in the art of card processing and may also be located between the card input 20 and the card output 22. For example, the system 10 may include: a card embossing system configured to emboss characters on a card; a debossing system configured to deboss characters on a card; a laminator system configured to apply a laminate to a card; a laser system that uses a laser to perform laser processing such as laser marking on a card; an overcoat station configured to apply an overcoat to a portion or the entire surface of a card; a quality control station configured to check the quality of the personalization / processing applied to the card; a security station configured to apply security features such as holographic foil to the card; and other card processing operations. Additional card processing systems may be located anywhere in the system 10, such as between the UV curing station 18 and the card output 22.

[0044] Figure 2 1 shows selected components of the DOD card printer 12. The DOD card printer 12 includes at least one DOD print head 26 and an automatic cover cap 28 configured to be in a covering position ( Figure 4 ) and non-covered locations ( Figure 2) The printing performed by the DOD card printer 12 may be monochrome or multi-color. Figure 2 Five DOD printheads 26a-e are shown, arranged side by side to sequentially print on the surface of the card 30 as the card 30 is transported past the printheads 26a-e (e.g., under the printheads 26a-e) in the direction of arrow 32. However, a smaller number of DOD printheads 26 (including one DOD printhead 26) or a greater number of DOD printheads 26 may be used.

[0045] The DOD print heads 26a-e can print using any suitable ink or coating used in DOD printing and suitable for use on cards of the type described herein. For example, the ink can be a UV radiation curable ink, a thermally curable ink that can be cured by applying heat to the thermally curable ink, or other inks or materials that can be deposited by the DOD print heads. In the case of five DOD print heads 26a-e, each DOD print head can print ink of a specific color. For example, DOD print head 26e can print cyan ink, DOD print head 26d can print magenta ink, DOD print head 26c can print yellow ink, DOD print head 26b can print black ink, and DOD print head 26a can print white ink. An example of a DOD printer that prints using UV radiation curable ink in a card printing system is the Persomaster card personalization system available from Atlantic Zeiser GmbH of Emmingen, Germany.

[0046] The DOD printheads 26a-e may be identical in structure to one another and are identical in structure to conventional DOD printheads known in the art. However, the structures of the printheads 26a-e may be different from one another, for example, the printhead 26a for white ink may be different from the printheads 26b-e for black, yellow, magenta, and cyan inks. Typically, each of the DOD printheads 26a-e includes a bottom surface that faces downward toward the card 30 to be printed. A nozzle plate is provided on a portion of the bottom surface through which ink is ejected. A plurality of openings are included in the nozzle plate, each of which is associated with a nozzle of the printhead that ejects ink. The printheads 26a-e may be piezoelectric printheads that require electrical energy to excite the printhead and distribute ink. The general mechanical construction and operation of a piezoelectric printhead are well known in the art.

[0047] Reference Figures 2 to 4 , the covering cap 28 may have a covering position ( Figure 4 ) and non-covered locations ( Figure 2) to perform the functions of the cover cap 28 described herein. The cap 28 can be selectively moved from Figure 2 The non-covered position is toward the bottom of the print head 26 Figure 4 The cap 28 is moved to a covering position. The cap 28 has multiple functions. One function is to protect the print head 26 from physical damage when the DOD card printer 12 is idle (i.e., not operating), so that the cap 28 is moved to the covering position. By keeping the print head 26 covered, inadvertent contact with the print head 26 when the DOD card printer 12 is idle is prevented. In addition, when UV radiation curable ink is used, the cap 28 also blocks UV light from reaching the print head 26, which can cause the ink on the surface of the nozzle plate to harden and negatively affect the operability of the nozzle. The cap 28 also provides a safe path for draining ink from the print head 26, making it easier to service the print head 26. Finally, the cap 28 provides a location for spitting and clearing ink during spitting and clearing routines (described further below) without endangering the mechanical structure of the DOD card printer 12 or the mechanical structure of the system 10.

[0048] exist Figure 2 In the example shown, the cap 28 can be moved back and forth under the DOD printhead 26 relative to the printhead in the direction of arrow 34 (generally perpendicular to the transport direction 32 of the card 30). Figure 2 The uncovered position is in the direction of arrow 34 toward and below the DOD print head 26. Figure 4 The cover position is actuated and then returns in the direction of arrow 34. Figure 2 The cap 28 defines a drip tray 36 that provides an area for ink and other debris to be collected as the ink is discharged and during the spitting and cleaning routines (described further below). The drip tray 36 has an area large enough to encompass at least the total area of ​​the nozzle plate of the printhead 26.

[0049] Reference Figure 5 , the controller 24 performs various automatic maintenance routines for the DOD card printer 12. The maintenance routines may include, but are not limited to, the following: a cover routine 40; a dither pulse routine 42; a spit routine 44; and a purge routine 46. The routines 40, 42, 44, 46 may be performed individually, collectively, or in any combination thereof to help maintain the operability of the DOD printhead 26, reduce downtime of the card processing system 10, and allow the DOD card printer 12 to adapt to printing variations from card to card or from batch print job to batch print job, thereby maintaining the card throughput of the card processing system 10.

[0050] The capping routine 40 selectively moves the cap 28 relative to the print head 26 from the Figure 2The non-covered position is positioned below the print head 26 Figure 4 For example, when the DOD card printer 12 is idle, the capping routine 40 moves the cap 28 to the covering position to protect the print head 26 from physical damage. By keeping the print head 26 covered, inadvertent contact with the print head 26 can be prevented when the DOD card printer 12 is idle. Additionally, when UV radiation curable ink is used, the capping routine 40 moves the cap 28 to the covering position so as to block UV light from reaching the print head 26, which could cause the ink on the surface of the nozzle plate to harden and negatively affect the operability of the nozzles. Additionally, the capping routine 40 moves the cap 28 so that the drip tray 36 is positioned below the print head 26 to collect ink expelled from the print head 26 during servicing of the print head 26. Furthermore, the capping routine 40 moves the cap 28 so that the drip tray 36 is positioned below the print head 26 to provide a location for spitting and purging ink during a spitting routine 44 and a purge routine 46 described further below. When the cap 28 is not needed, the capping routine 40 moves the cap 28 to the covering position. Figure 2 Non-covered position shown to allow printing.

[0051] The shaking pulse routine 42 sends electrical pulses to the nozzles of the print head 26 to electrically excite the nozzles without causing ink to be ejected. The nozzles may be almost (but not completely) excited to the point where ink drops are ejected. The electrical excitation of the nozzles caused by the shaking pulse routine 42 provides agitation of the ink in the nozzles of the print head 26 without ejecting the ink, thereby avoiding the cost of wasting ink. Since no ink is ejected, the shaking pulse routine 42 can be performed while the cap 28 is in the uncovered position. The electrical pulses of the shaking pulse routine 42 can be sent to the print head 26 at a desired frequency. For example, the electrical pulses of the shaking pulse routine 42 can be sent to the print head 26 at a rate of up to once per second or once per second. The electrical pulses can be sent to each print head 26 at the same time or concurrently, or the electrical pulses can be sent to the print head 26 at different times or non-concurrently.

[0052] The dither pulse routine 42 may be performed while the DOD card printer 12 is in operation. However, the dither pulse routine 42 is not performed during actual printing or use of the printhead 26 (in other words, the dither pulse routine 42 is not performed while any nozzle of the printhead is ejecting ink). For example, the dither pulse routine may be applied between printing on consecutive, adjacent cards (in other words, printing is performed on the first card, then the dither pulse routine is performed, then printing is performed on the second card that follows the first card in sequence, and so on). In another embodiment, the dither pulse routine may be performed after printing on a predetermined number (e.g., two, three, four, etc.) of cards (in other words, printing may be performed on two / three / four / etc. sequential cards, then the dither pulse routine is performed, then printing is performed on the next two / three / four / etc. sequential cards, and so on). In another embodiment, the dither pulse routine may be performed based on a specific, predetermined timing sequence during a batch print job, rather than based on the number of cards printed. For example, during a batch print job, at least one dither pulse routine may be performed approximately every 1 second, or approximately every 2 seconds, or approximately every 4 seconds, or approximately every 8 seconds, etc. In yet another embodiment, the dither pulse routine 42 may also be performed based on a specific, predetermined timing sequence, such as when the DOD card printer 12 is idle.

[0053] The ejection routine 44 sends electrical pulses to the print head 26 to electrically energize the nozzles of the print head to eject one or more drops of ink from the nozzles. The ejection routine 44 is similar to the physical operation that occurs during printing when a particular nozzle is energized to eject a single drop. The ejection routine 44 is particularly useful when using UV radiation curable ink, whereby the ejection routine 44 is used to eject ink that may have potentially begun the curing process out of the nozzle. This helps prevent nozzle clogging. The ejection routine 44 can be at any desired frequency. For example, the controller 24 can cause the DOD card printer 12 to execute the ejection routine 44 at the beginning of each batch print job to ensure that fresh ink is being used to print in the batch print job. In addition, when the DOD card printer 12 is idle, the controller 24 can cause the DOD card printer 12 to execute the ejection routine 44 at user-configurable intervals. In the ejection routine 44, as ink is ejected from the nozzle, the cap 28 is moved to the position before the ejection routine 44. Figure 4 The cap 28 is in the covering position so that the ejected ink is collected in the drip tray 36 of the cap 28.

[0054] During the purge routine 46, the nozzles of the printhead 26 are not electrically energized. Instead, the vacuum pressure that holds the ink in the nozzles of the printhead 26 is reversed to push the ink out of the nozzles. The purge routine 46 forcibly ejects ink that may have begun to clog the nozzles and ensures that an adequate supply of ink reaches each nozzle. The purge routine 46 also expels any air or particles that may have entered the nozzles. During the purge routine 46, as ink is ejected from the nozzles, the cap 28 is moved to the Figure 4 The cap 28 is placed in the covered position so that the ejected ink is collected in the drip tray 36 of the cap 28. The purge routine 46 is typically performed on the DOD card printer 12 on a longer time scale (e.g., at the beginning of the day before any printing operations begin, or once every predetermined number of hours (such as once every 12 hours), or once every 2 or 3 days, or once a week, etc.).

[0055] Reference Figure 6 , which shows the pressure variation acting on the ink within the nozzles of the print heads 26a-e under normal operating conditions and during a conventional purge routine. Figure 7 , which shows a small portion of one of the print heads 26a-e, under normal operating conditions of the DOD card printer 12, vacuum is selectively applied to each nozzle 50, which establishes an upward meniscus 52 of ink ( Figure 7 54). The nozzle plate 54 is considered clean when there is no ink on the surface of the nozzle plate or no ink below the level of the opening of the nozzle that can be applied to the card surface. During the purge routine, the vacuum is reversed to become a positive pressure large enough to force ink 56 out through the nozzle openings 58 of the nozzles 50 of the printheads 26a-e. Upon recovery from the purge routine, the vacuum is restored and all ink on the nozzle plate 54 that is in contact with the nozzle 50 and adjacent to the nozzle 50 is drawn back into the nozzle 50 through the nozzle openings 58 to restore the meniscus 52 in each nozzle 50.

[0056] However, in a conventional cleaning routine, ink 60 (see Figure 7 ) may be floating on the nozzle plate 54, wherein the floating ink 60 moves away from the nozzle opening 58 and may not be drawn back into the nozzle 50 when the vacuum is restored. Such floating or residual ink 60 that is not drawn back into the nozzle 50 is problematic because the ink 60 will be smeared on the first card that passes through the system after the cleaning routine is performed. Therefore, after the conventional cleaning routine, such as by performing a manual wipe or other cleaning routine of the nozzle plate 54, it is necessary to remove the floating ink 60 from the nozzle plate 54.

[0057] Back to Figure 6, shows a conventional purge routine 62, wherein at the beginning of the purge routine 62, the pressure acting on the nozzle 50 gradually ramps up from the normal operating pressure A until the pressure reaches the desired purge pressure Pmax. The purge pressure Pmax is maintained for a period of time Pmax-time to complete the purge, and then the pressure gradually ramps down to the normal operating pressure level A. The problem of floating ink 60 is most likely to occur at intermediate pressures (i.e., those pressures between the normal pressure level A and the purge pressure Pmax). However, in the conventional purge routine 62, there is a relatively slow ramp up to the purge pressure Pmax, and then a slow ramp down to the normal pressure, and a large amount of time is spent at the intermediate pressures, which increases the risk that the ink may float.

[0058] Reference Figure 8 By using a purge routine 70 that employs one or more step changes 72 in pressure, the problem of free-floating ink is minimized or eliminated. At the beginning of the purge routine 70, there is a rapid step change 72 or increase from the normal operating pressure to the purge pressure Pmax (rather than a step change as in Figure 6 In addition, there is a quick step change 72 or decrease / return from the purge pressure Pmax to the normal operating pressure. Using the step change 72 in pressure reduces the time spent at the intermediate pressure, which in turn reduces or eliminates free-floating ink. The end result is a nozzle plate 54 that is clean over a greater percentage of the purge routine.

[0059] In one embodiment, each step change 72 occurs in less than about 1 second. Aside from inherent delay times in sending and receiving signals, activating / deactivating pumps and valves, and other delays inherently associated with mechanical and electrical systems, the step changes 72 can be considered substantially instantaneous.

[0060] In one embodiment, the purge pressure Pmax of the purge routine 70 is greater than the purge pressure Pmax of the conventional purge routine 62. In one non-limiting example, the purge pressure Pmax of the purge routine 70 may be two or more times the purge pressure Pmax of the conventional purge routine 62. For example, if it is assumed that the Pmax of the conventional purge routine 62 is about 2 psi (or about 13789.5 Pa), the Pmax of the purge routine 70 may be about 4 psi (or about 55158 Pa) or more. In another non-limiting example, the purge pressure Pmax of the purge routine 70 may be about 1.5-2.5 times the purge pressure Pmax of the conventional purge routine 62. Therefore, if it is again assumed that the Pmax of the conventional purge routine 62 is about 2 psi (about 13789.5 Pa), the Pmax of the purge routine 70 may be about 3.0-5.0 psi (or about 20684.25 Pa to about 34473.75 Pa). Additionally, the purge time Pmax-time of the purge routine 70 may be less than the purge time Pmax-time of the normal purge routine 62 .

[0061] In one embodiment, the clearing routine 70 of the pressure step change 72 can be used on one or any combination of printheads that print cyan, magenta, yellow and black inks. In another embodiment, the clearing routine 70 of the pressure step change 72 can be used on a printhead that prints white ink.

[0062] Figure 8 The illustrated clearing routine 70 may be performed alone (ie, not in combination with the covering routine 40, the shaking pulse routine 42, or the spitting routine 44). Alternatively, Figure 8 The illustrated cleanup routine 70 may be executed in conjunction with one or more of the cover routine 40, the shake pulse routine 42, or the spit routine 44. The cleanup routine 46 described above may be Figure 8 The clearing routine 70 shown or such as Figure 6 The cleanup routine 62 shown is a conventional cleanup routine.

[0063] As described above, the shaking pulse routine can be described as being executed at a certain frequency (referred to as a first frequency) when the print head is not in use (i.e., when the nozzles of the print head are not ejecting ink). In addition, the ejection routine can be described as being executed at a frequency (referred to as a second frequency) that is less than the first frequency. Furthermore, the clearing routine can be described as being executed at a frequency (referred to as a third frequency) that is less than the second frequency.

[0064] The routines described herein provide a number of advantages, both individually and collectively. For example, the jitter pulse routines described herein allow sequential plastic cards to be printed using different nozzles of a drop-on-demand printhead. For example, a first plastic card may be input into a drop-on-demand printer, positioned relative to the drop-on-demand printhead for printing, and then printed on the first plastic card using a first subset of nozzles of the drop-on-demand printhead. A short period of time after the printing on the first plastic card is completed, a second plastic card is input into the drop-on-demand printer, positioned relative to the drop-on-demand printhead for printing, and then printed on the second plastic card using a second subset of nozzles of the drop-on-demand printhead. The second subset of nozzles used to print on the second plastic card is different from the first subset of nozzles used to print on the first plastic card. The short period of time may be any period of time between cards that is suitable for achieving the above-described card processing rate. For example, the period of time between the first sequential card and the second sequential card may be about 5 seconds or less; or about 3 seconds or less; or other period of time. Because all nozzles go through the dither pulse routine, any nozzles not used for the print job on the first plastic card are prepared by the dither pulse routine for the print job on the second plastic card. Thus, different print jobs using different subsets of nozzles can be performed on sequential plastic cards.

[0065] The card processing system described in this article can be configured as a system that can be referred to as a desktop card processing system. Such a desktop card processing system can include at least a card input and a card output (which can be at the opposite end of the system or at the same end of the system), a DOD card printer for printing on a card using UV curable ink, and a UV curing station for curing the UV curable ink applied to the card. Additional card processing systems such as those described above may also be included. Desktop card processing systems are generally designed for relatively small-scale single card processing. In a desktop processing system, a single card to be processed is input into the system, processed, and then output. These systems are generally referred to as desktop machines or desktop printers because their footprint is relatively small in order to allow the machine to reside on a desktop. Many examples of desktop machines are known, such as desktop card machines of the SD or CD series that can be obtained from Entrust Datacard Corporation of Shakopee, Minnesota. Other examples of desktop card machines are disclosed in US Pat. Nos. 7,434,728 and 7,398,972, each of which is incorporated herein by reference in its entirety.

[0066] The examples disclosed in this application are to be considered in all respects as illustrative and not restrictive. The scope of the invention is indicated by the appended claims rather than the preceding description; and all modifications within the meaning and range of equivalency of the claims are intended to be embraced herein.

Claims

1. A card processing system, the card processing system comprising: a card input portion configured to receive a plurality of cards to be processed; a drop-on-demand ink card printer located downstream of the card input and receiving a card input from the card input, the drop-on-demand ink card printer comprising at least one drop-on-demand ink printhead; A controller is connected to the drop-on-demand ink card printer and automatically controls its operation, the controller being programmed to automatically perform a purge routine on the at least one drop-on-demand ink printhead, wherein the purge routine includes at least one step change in pressure to a maximum purge positive pressure, the at least one step change in pressure causing a positive pressure to be applied within the nozzles of the at least one drop-on-demand ink printhead to force ink out of the at least one drop-on-demand ink printhead and purge free ink from the nozzle plate.

2. The card processing system of claim 1, wherein the controller is further programmed to automatically perform: a shaking pulse routine performed without causing ejection of the ultraviolet curable ink and performed at a first frequency; a jetting routine that causes ejection of ultraviolet curable ink and that is performed at a second frequency that is less than the first frequency; and The clean-up routine is performed at a third frequency that is less than the second frequency.

3. The card processing system according to claim 2, wherein: The drop-on-demand ink card printer includes a plurality of drop-on-demand ink card printer heads, and the controller is programmed to automatically perform each of the dither pulse routine, the spit routine, and the purge routine for each drop-on-demand ink print head.

4. The card processing system of claim 1 , further comprising at least one of the following systems located between the card input and the drop-on-demand card printer: a magnetic stripe reading / writing system configured to read data from and / or write data to a magnetic stripe on the card; and The integrated circuit chip programming system is configured to program the integrated circuit chip on the card.

5. The card processing system of claim 1 , further comprising a cap configured to be movable between a covering position and a non-covering position, wherein the cap covers the at least one drop-on-demand printhead and the non-covering position does not cover the at least one drop-on-demand printhead; and The controller is programmed to automatically execute a capping routine that automatically controls positioning of the cap relative to the at least one drop-on-demand printhead.

6. The card processing system according to claim 1, wherein: The at least one step change in pressure occurs in less than 1 second.

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