Patent Application
20150029259
Some printing systems form a printed image by ejecting ink from ink printheads. Thereby, ink is applied onto a print medium for printing a pattern of individual dots at particular locations. The printed pattern reproduces an image on the printing medium. At least some of these printing systems are commonly referred to as inkjet printers.
At least some printing systems provide means for applying a treatment fluid on the print area in order to treat the print area on which ink is printed. For example, the treatment fluid may be a fixer fluid to address coalescence, bleed, or similar effects characterized by ink migration across a printed surface. Another example of treatment fluid is a durability enhancer coating including polymers.
A printing system may include a treatment printhead to apply a treatment fluid by ejection over a particular location for ink placement. A treatment fluid may be applied to a particular print area before, after or, quasi-simultaneously to the application of the ink to that print area. However, though a treatment fluid may improve print quality, undesirable cross-contamination can occur by one of several mechanisms. For example, migration of aerosol droplets from a treatment fluid that is jetted from a treatment printhead can cross-contaminate other printheads.
The Figures depict examples, implementations, and configurations of the invention, and not the invention itself.
In the foregoing description, numerous details are set forth to provide an understanding of the examples disclosed herein. However, it will be understood by those skilled in the art that the examples may be practiced without these details. Further, in the following detailed description, reference is made to the accompanying figures, in which various examples are shown by way of illustration. In this regard, directional terminology, such as “top,” “bottom,” “front,” “back,” “left,” “right,” “vertical,”, etc., is used with reference to the orientation of the figures being described. Because disclosed components can be positioned in a number of different orientations, the directional terminology is used for purposes of illustration and is in no way limiting. Like numerals are used for like and corresponding parts of the various figures.
While a limited number of examples have been disclosed, those skilled in the art will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover such modifications and variations.
Printing system 10 includes a housing 12 enclosing a chassis (not shown) forming a print assembly 14. Print assembly 14 is supported by a leg assembly 16. It will be understood that print assembly 14 may be designed to be supported by a desktop during operation. A print media transport assembly 18 feeds a print medium 1 through a print zone 20 and advances print medium 1 in a media advance direction 54. Printing system 10 includes a user terminal 22 for receiving user inputs through, e.g., a keypad 24, and providing visual feedback to the user through, e.g., a display 25. It will be understood that user interaction may be implemented by other suitable means such as a personal computer operatively connected to printing system 10.
A carriage 28 is slidably mounted on a guide rod 30. Guide rod 30 defines a carriage transition axis 51 along which carriage 28 traverses over print zone 20 for performing printing. A carriage drive 32 (shown in
Carriage 28 includes positions for receiving respective printheads therein. As used herein, a printhead is a device including a nozzle or a group of nozzles (such as nozzle array 26 depicted in
In the example illustrated in
Treatment fluid ejected for treating printing ink on a print area may cause cross-contamination in an ink printhead. Cross-contamination may compromise performance of the ink printhead. For example, a treatment fluid including a fixer may cause that fixer reacts with ink at the nozzles of an ink printhead so that ink remains attached at the nozzle exits.
A mechanism for cross-contamination involves aerosol formation. Aerosol can form when ejected drops of treatment fluid divide into one or more primary droplets. (Satellite droplets may also result from the tail of ejected droplets becoming divided.) Aerosol generation may depend on a) the particularly used treatment fluid, b) the distance between the treatment printhead and the print medium (also referred to as printhead-media distance), c) carriage transition speed, and/or d) quantity of ejected treatment fluid. For example, the greater the printhead-media distance, the greater the quantity of aerosol that a treatment printhead may generate. In every case, even when the printhead-media is relatively small, a non-negligible risk exists that fluid ejected for treating printing ink on a print media generates aerosol. Even when aerosol generation is relatively low, cross-contamination may affect operation of an ink printhead, eventually, after a relatively long operational period of the printhead.
The present disclosure describes methods and systems for printing that facilitate prevention of cross-contamination caused by treatment fluid ejected for treating printing ink or the print area on which the printing ink is to be applied. Treatment fluid is ejected depending on the particular traversing direction of the carriage over a print area. As used herein, “printing ink” refers to ink ejected over a print area for reproducing an image portion thereon. Different examples of treatment fluid ejection depending on the particular traversing direction of the carriage are set forth below.
For example, printing may be performed such that the carriage traverses over a print area in a forward direction and a backward direction. During this transition, a specific amount of treatment fluid is to be ejected for treating the print area. In one of the forward direction or the backward direction, the treatment printhead trails behind the ink printhead. In the other direction, the treatment printhead leads before the ink printhead.
When the treatment printhead leads, the risk of cross-contamination is higher, since the ink printhead crosses the ejection area immediately after treatment fluid ejection. On the other hand, when the treatment printhead trails, the risk of cross-contamination is lower, since the ink printhead does not cross the ejection area immediately after aerosol generation by the preceding printhead. Therefore, in order to prevent cross-contamination, a portion of the treatment fluid for treating fluid on the print area may be ejected while the carriage traverses in the direction in which the treatment printhead trails behind the ink printhead. In some examples, most or all of the treatment fluid for treating fluid on the print area is ejected while a treatment printhead trails so as to further prevent cross-contamination. In the following, further examples are illustrated.
Treatment printheads 46, 48 are configured to eject a treatment fluid 58 through nozzle arrays 26 for treating ink in a print area of print medium 1. Application of the treatment fluid on a particular spot of a print area may be performed before, substantially simultaneously, or after application of the ink for reproducing a particular color on that spot. The block diagram shows that treatment printheads 46, 48 are fluidly connected to a treatment fluid reservoir 61. The printheads are separated from print medium 1 a printhead-media distance d.
Ink reservoir 60 and treatment fluid reservoir 61 may include disposable cartridges (not shown). The reservoirs may be mounted on carriage 28 in a position adjacent to the respective printhead. In other configurations (also referred to as off-axis systems), a small fluid supply (ink or treatment) is provided to cartridges (not shown) in carriage 28, each cartridge being associated to a respective printhead; main supplies for ink and fixer are then stored in the respective reservoirs. In an off-axis system, flexible conduits are used to convey the fluid from the off-axis main supplies to the corresponding printhead cartridge. Printheads and reservoirs may be combined into single units, which are commonly referred to as “pens”.
It will be appreciated that examples can be realized with any number of printheads depending on the design of the particular printing system. For example, printing system 10 may include at least one treatment printhead, such as two or more treatment printheads. Furthermore, printing system 10 may include at least one ink printhead, such as two to six ink printheads, or even more ink printheads. Further, a printhead of printing system 10 may be a disposable printhead or a fixed printhead, which is designed to last for the whole operating life of printing system 10. In the illustrated examples, ink printheads are disposed at one side of a treatment printhead. It will be understood that ink printheads may be disposed at both sides of a treatment printhead.
The carriage may include one treatment printhead. In the example illustrated in
In other examples herein, the carriage includes at least two treatment printheads disposed along a transition axis of the carriage (e.g., an axis parallel to guide rod 30). At least one ink printhead may be disposed between the treatment printheads. For example, as illustrated in
In the illustrated examples, unless a treatment printhead is completely offset from an ink printhead along an axis coincident with media advance direction 54, a treatment printhead trails or leads relative to the ink printheads during a carriage transition for printing. In the configuration illustrated in
The printheads may be arranged according to a linear configuration, in which the printheads are aligned along the direction of carriage transition (e.g., carriage transition axis 51). Such a linear configuration is illustrated in
A controller 62 based on an electronic processor unit is configured for being operatively connected to the above described elements of printing system 10 as well as a memory device 64 and a printjob source 66. Controller 62 is configured to execute methods according to the present disclosure.
Controller 62 may be implemented, for example, by one or more discrete modules (or data processing components) that are not limited to any particular hardware, firmware, or software (i.e., machine readable instructions) configuration. Controller 62 may be implemented in any computing or data processing environment, including in digital electronic circuitry, e.g., an application-specific integrated circuit, such as a digital signal processor (DSP) or in computer hardware, firmware, device driver, or software (i.e., machine readable instructions). In some implementations, the functionalities of the modules are combined into a single data processing component. In other versions, the respective functionalities of each of one or more of the modules are performed by a respective set of multiple data processing components.
Memory device 64 is accessible by controller 62. Memory device 64 stores process instructions (e.g., machine-readable code, such as computer software) for implementing methods executed by controller 62 as well as data that controller 62 generates or processes such as alignment correction data. Memory device 64 may include one or more tangible machine-readable storage media. Memory devices suitable for embodying these instructions and data include all forms of computer-readable memory, including, for example, semiconductor memory devices, such as EPROM, EEPROM, and flash memory devices, magnetic disks such as internal hard disks and removable hard disks, magneto-optical disks, and ROM/RAM devices.
Controller 62 receives printjob commands and data from printjob source 66, which may be a computer or any other source of printjobs, in order to print an image. In the example, controller 62 is configured to determine a print mask from the received data. The received data itself may already correspond to a print mask. A print mask refers to logic that includes control data determining which nozzles of the different printheads are fired at a given time to eject fluid in order to reproduce the printjob. Controller 62 is operatively connected to treatment printheads 46, 48, ink printheads 38-44, and the respective reservoirs to control, according to the print mask: a) ejection of ink 56 and treatment fluid 58, and b) motion of carriage 28 and print medium 1. The print mask may be stored in memory device 64.
The particular fluid ejection mechanism within the printhead may take on a variety of different forms such as those using piezo-electric or thermal printhead technology. For example, if the fluid ejection mechanism is based on a thermal printhead technology, the pulses forwarded to an IEE of IEE array 71 may be forwarded as a current pulse that is applied to a resistor within the particular IEE. The current pulse causes a fluid droplet (not shown), formed with fluid (i.e., ink or treatment fluid) from a fluid reservoir 76 (e.g., ink reservoir 60 or treatment fluid reservoir 61), to be emitted from the nozzle associated with the particular IEE.
The length of the rows of nozzles along the media advance direction defines a print swath 82. The width of this band along media advance direction 54 is commonly referred to as the “swath width,” which defines the maximum pattern of ink or fixer fluid which can be laid down in a single transition of carriage 28.
A printer such as printing system 10 can operate according to several different print modes. For example, in a single-pass print mode, after each printing pass the media is advanced a distance equal to the full span of a nozzle array (i.e., a swath width), such that each pass forms a complete strip of the image on the print medium. In a multi-pass print mode, the media only advances a fraction of the total length of a nozzle array after each printing pass of the printheads. For example, the media may be advanced a length corresponding to the length of a primitive 80. Thereby, each strip of the image to be printed is formed in successive passes of the printheads.
Ink may be applied when the carriage travels in one direction along the scan axis of carriage 28. Alternatively, printing may be bidirectional in that ink may be applied on a print area when the carriage travels in a “forward pass” and also when travelling in a “backward pass.” The print medium may be advanced after each pass or after both passes have been completed. Bidirectional printing is illustrated below with respect to
At step 410 an ink printhead and a treatment printhead are simultaneously displaced over a print area in a first direction and a second direction. For example, controller 62 may operate carriage drive 32 for displacing carriage 28 across print medium 1 so as to forth and back traverse over print area 84, i.e. in forward direction 50 and in backward direction 52. The forward transition is illustrated in
In which direction the treatment printhead trails or leads depends on the particular printhead arrangement. In
Step 410 may include a step 412 at which ink is applied to the print area for reproducing an image portion thereon. For example, at step 412 controller 62 may operate ink printheads 38, 40, 42, 44 to apply ink 56 for reproducing a portion of an image (e.g., printing pattern 36) as described above. It will be understood that during step 412 ink may be applied continuously or intermittently. Further, ink may be applied during the transition in one or both of the first and second direction.
Step 410 includes a step 414 at which treatment fluid for treating print area 84 is ejected from a treatment printhead depending on the direction in which the treatment printhead travels. Treatment fluid may be applied to the print area before, quasi-simultaneously to or after ink application as illustrated in the examples below. It will be understood that the treatment printhead may eject treatment fluid continuously or intermittently during its displacement at step 410.
As illustrated in
In some examples herein, and as illustrated by
In this example, controller 62 is configured to operate treatment printhead 46 for applying a first amount of treatment fluid (i.e., treatment fluid amount 96a) while leading and a second amount of treatment fluid (i.e., treatment fluid amount 96b) at trailing. Thereby, further to preventing cross-contamination, it is facilitated that some treatment fluid is applied to each print area quasi-simultaneously (i.e., at the same pass) to ink application in order to promote a more efficient treatment of deposited ink. Further, in a configuration in which a single treatment printhead leads relative to an ink printhead at a forward pass, as shown in
In a configuration with a single treatment printhead, the amount of treatment fluid ejected during a pass in which the single treatment printhead is at leading relative to the ink printhead(s) is chosen such that a) the amount is sufficiently low so as to prevent cross-contamination, and b) the amount is sufficiently high so as to sufficiently treat ink on the print medium before a still higher amount of treatment fluid is ejected in the following pass. This minimum amount may be chosen depending on the amount of ink already applied. In one example, the ejected treatment fluid at leading is 1/P of the total amount of ejected treatment fluid, where P is the number of passes; the ejected treatment fluid at trailing is (P−1)/P of the total amount of ejected treatment fluid. Thereby, it is facilitated an effective treatment of ink on the print medium while preventing cross-contamination.
The specific amount of treatment fluid to be applied to a particular print area may be completely ejected while the carriage traverses in the direction in which the treatment printhead trails behind the ink printhead. In other words, in such examples, treatment fluid is ejected from a particular treatment printhead only while the particular treatment fluid printhead is at trailing. Thereby, cross-contamination is further prevented since the risk of cross-contamination caused by a leading treatment printhead ejecting fluid is avoided. In the above example, such a printing process may be executed by ejecting only treatment fluid amount 96b. Such a printing process may be performed by alternatively ejecting treatment fluid from treatment printheads disposed at different sides of an ink printhead assembly. For example, processor 62 may be configured to operate treatment printheads 46, 48 for ejecting treatment fluid only while trailing behind ink printheads 38, 40, 42, 44. Such a double treatment printhead configuration, as further illustrated in
During the carriage transition across printing surface 90, each of the treatment printheads ejects a particular amount of treatment fluid over each print area. Further, each of the treatment printheads completely ejects the respective amount of treatment fluid for each print area while trailing behind ink printhead assembly 98. For example, as shown in
The examples particularly illustrate eight pass bidirectional print modes, i.e., four passes in a forward direction and four passes in a backward direction. In such print modes, the nozzles arrays in the printheads may be arranged with nozzle groups arranged extending along the media advance direction. Nozzles in a nozzle group are simultaneously fired. At each pass, a nozzle group ejects ink or treatment fluid over a particular print area corresponding to a fraction of the whole print swath. For example, each nozzle group may correspond to a pair of primitives illustrated in
The number in each box denotes at which pass a particular layer is deposited. A double number in a box corresponding to a treatment fluid layer indicates a layer deposited by single treatment printhead 46 at trailing (i.e., at odd passes). A single number in a box corresponding to a treatment fluid layer indicates a layer deposited by single treatment printhead 46 at leading (i.e., at odd passes). As illustrated in
In some examples performed with a single treatment printhead configuration, a treatment printhead leading in a particular pass does not eject treatment fluid over a particular area if the treatment printhead has already deposited a treatment fluid layer over the particular area. In the illustrated example of
Depositing layers corresponding to white boxes may unnecessarily increase the risk of contamination. For example, in the illustrated printing process, at the first pass ink printhead assembly 98 deposits ink layer 1, and single treatment printhead 46 deposits a treatment layer 11 at trailing. At the second pass ink printhead assembly 98 deposits ink layer 2, and single treatment printhead 46 does not eject treatment fluid at leading since treatment layer 11 is sufficient for suitably treating ink layer 2 (e.g., for promoting fixation of ink layer 2 to the print medium).
A print mode as illustrated in
Treatment fluid is ejected at the first four passes for depositing treatment fluid layers (depicted by dotted boxes in the Figure) according to a) the number of nozzle groups in the illustrated treatment fluid printheads, and b) the relative arrangement between the ink printheads and treatment fluid printheads. The number of each box denotes at which pass a particular layer is deposited. The subscript L in boxes corresponding to a treatment layer denotes a layer deposited by operation of left treatment printhead 46. As illustrated in
A print mode as illustrated in
The examples described above provide methods and systems for preventing cross-contamination. As discussed above, the examples may be successfully deployed in any printing system including a treatment printhead aligned, at least partially, with an ink printhead assembly in a traversing direction as described above. However, examples may be particularly used in industrial inkjet printers implementing ink treatment. Industrial printers are, generally, more prone to cross-contamination by generation of aerosol in view of the involved sizes and/or production rates. Further, examples may be particularly used in printers characterized by a relatively high printhead-to- medium distance since such systems may be more prone to cross-contamination caused by treatment fluid ejected for treating printing ink. Such relatively high printhead-to-medium distances may be of at least 2 mm or, more particularly, between 2 mm and 4 mm such as 2.3 mm.
Further, the examples may be successfully deployed for any treatment fluid. However, examples may be particularly used when the treatment fluid is a fixer fluid for preventing ink migration on a print medium. As used herein, “fixer fluid” refers to a solution composition that includes a liquid vehicle and a fixing agent for preventing ink migration on a print medium. The solution composition may be configured to be chemically stable and/or for ink-jet printing. The fixing agent may be a cationic polymer, a multivalent metal ion or ionic group and/or an acid. The fixing agent may precipitate with at least one compositional component of an associated ink. Some examples of fixer fluid are described in U.S. Pat. No. 6,585,364, U.S. Pat. No. 7,621,631, U.S. Pat. No. 6,821,329, or U.S. patent application with application number US2005/0231573. Cross-contamination caused by a fixer fluid may be particularly prejudicial since it may lead to fixation of ink at the nozzles exit thereby clogging a printhead.
In the foregoing description, numerous details are set forth to provide an understanding of the examples disclosed herein. However, it will be understood by those skilled in the art that the examples may be practiced without these details. While a limited number of examples have been disclosed, those skilled in the art will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover such modifications and variations as fall within the true spirit and scope of the disclosed examples.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2011/068450 | 10/21/2011 | WO | 00 | 4/16/2014 |
