WO2013162497A1

WO2013162497A1 - Flexure control to mitigate media curl

Info

Publication number: WO2013162497A1
Application number: PCT/US2012/034658
Authority: WO
Inventors: Alvin Marion Post; Wesley R. Schalk
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2012-04-23
Filing date: 2012-04-23
Publication date: 2013-10-31

Abstract

A system includes a controller to adjust the speed and feed direction in which media is guided through a printer. A flexure control module commands the controller to alter the speed and/or feed direction in which the media is guided though the printer during a printing process to mitigate curl in the media.

Description

FLEXURE CONTROL TO MITIGATE MEDIA CURL

BACKGROUND

[0001] Printers utilize many components to control how media such as paper is guided though the printers during a printing process. Such printing components can include a feed system having rollers to initially guide the media toward a print zone where a print head applies ink on to the media, or where an image is transferred to the media. As the media is fed through the printer and after printing, an output also having rollers can direct the media outside of the printer. For simplex operations, only one side of the media is printed and after respective printing in the print zone, the output rollers can guide the media to a finishing unit or a tray where it can be retrieved by the user. For duplex operations, both sides of the media can be printed in the print zone. Thus, after the first side of the media is printed, the media can be turned over and printed on the opposite side to complete the duplex operation. One feature of modern printers is to increase the size of the print head to allow larger swaths of ink to be printed and hence increase the speed at which printing can occur. When the size of the print head is increased in scanning printer designs, the distance between the feed and output rollers correspondingly increase. Although it is advantageous to increase printing speed utilizing larger print heads, increasing the distance between the rollers can make it more difficult to control the media and the shape of the media during printing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0002] FIG. 1 illustrates an example system that utilizes a controller and flexure control module to control the position of media in a print zone to mitigate curl in the media during a printing process.

[0003] FIG. 2 illustrates an example of feed and output systems that are employed to mitigate curl in media.

[0004] FIG. 3 illustrates an example diagram depicting the effects of print zone width on curl. [0005] FIG. 4 illustrates an example system for flattening media curl in printers.

[0006] FIG. 5 illustrates an example method for mitigating curl in media during a printing process.

[0007] FIG. 6 illustrates an example printer that employs a controller and retraction control module to mitigate curl in media during a printing process.

DETAILED DESCRIPTION

[0008] FIG. 1 illustrates an example system 100 that utilizes a controller 1 10 and flexure control module 120 to mitigate curl in media 130 during a printing process. The controller 1 10 can adjust the speed and feed direction in which the media 130 is guided through a printer 140, wherein the speed and direction can be altered according to commands issued by the flexure control module 120. The flexure control module 120 can command the controller 1 10 to move the media 130 during a printing process to a location where it is flexed opposite the direction of the curl, to mitigate curl in the media.

[0009] Curl refers to a bend or bow in the media 130 that typically occurs after ink has been applied to the media 130. Thus, when ink wets the top surface of the media 130, such as paper, for example, it causes the top surface of the paper to expand, whereas the dry underside of the paper does not similarly expand. The wetting in turn causes the media 130 to curl such that the top surface is convex, for example, although a contoured curl can also be flattened as described herein. Such curl can be mitigated by moving the media 130 to a location in the printer 140 where the media 130 is forced to bend in the opposite direction to the curl, such as near or between rollers that are typically employed to route the media through the printer. Such flattening to mitigate curl can occur as the result of single or multiple reversing and advancing operations though the rollers and/or by controlling how long the media is held near or between the rollers, for example.

[0010] The curl can be curved upwards or downwards from a platen 142 which acts as a guide for the media 130 and enables the media to pass though the printer 140. As used herein, the term printing process refers to substantially any operation of the printer 140 including simplex operations which are single-sided printings, duplex operations which are double-sided printings, partial printings, and form feed operations, for example. Also, although the controller 1 10 and flexure control module 120 are shown as separate components from the printer 140, such components can be integrated inside the printer, for example.

[0011 ] A print head 150 applies ink to the media 130 when the media enters a zone in the printer 140 referred to as the print zone which is where ink can be applied by the print head. As shown, a feed 160 and an output 170 can be employed to control the position and speed of the media 130 while in, entering, or exiting the printer 140. The feed 160 and output 170 can include rollers to guide the media 130. Rollers that pinch the media between them can be positioned relative to each other at an angle referred to as the pinch angle, and the pinch point can be at positions up or down, right or left. An example of a pinch angle is shown as a dotted arrow on the feed 160, wherein rollers that provide the feed are adjusted at an angle in the direction of the arrow. The output 170 can similarly have rollers adjusted with an independent pinch angle.

[0012] The rollers can be set to a pinch angle for the feed 160 and/or the output 170 between about 4 degrees and about 15 degrees although other pinch angle settings are possible. When the media 130 is held between pinch rollers 160 and extends into the print zone, resting on one of the platen ribs 142, it can be flexed such that the top surface is concave. This flexure is generally opposite to the flexure caused by curling of wetted media 130 and can be referred to as reverse bow. A portion of the media 130 that is curled can also be held near the feed 160 or the output 170 for a predetermined time delay period, either by stopping it or by feeding it through more slowly, and allowing the media to dwell in this location to mitigate the curl in the media and reduce further curl growth. Also, the flexure control

module 120 can advance and reverse the direction of the media 130 over multiple cycles to mitigate curl in the media, for example when ink is applied on the paper in several narrow swaths. [0013] In an example, narrow swaths of ink can be applied by the print head 150 via a subset of print nozzles rather than using all the print nozzles associated with the print head. For instance, if the print nozzles stretch for 20 mm along the direction of the print zone, potentially only 4 mm of the chain of nozzles are employed for printing a 4 mm wide swath of paper. In that case, the 4 mm wetted portion of the paper can be moved into a reverse flexure region near the rollers to mitigate the curl in that 4 mm section. The media 130 can then be moved back where it was to apply the next 4mm swath (or other dimension), and repeat as desired. Such process is illustrated below with respect to Fig 4.

[0014] Typically, the media 130 is held in a reverse flexure region which is typically near the roller pinch point about where the platen 142 begins or ends and illustrated at example reference location 180. This position can be held in the reverse flexure region at location 180 for a period of time (seconds). The number of seconds the position is held can depend on the media type, how much ink was used, and what the environmental conditions are, for example. Holding the position in the reverse bow region can be achieved either by stopping the curled media in that location, or by passing it through the region at a slow speed selected to provide a suitable residence time in the reverse bow region. The speed and feed direction can be monitored by an encoder (not shown) to provide feedback to the controller 1 10. The media 130 is typically paper but can be a synthetic material (e.g., plastic), or a mixture of the paper and the synthetic material, for example.

[0015] For purposes of simplification of explanation, in the present example, different components of the systems described herein are illustrated and described as performing different functions. However, one of ordinary skill in the art will understand and appreciate that the functions of the described components can be performed by different components, and the functionality of several components can be combined and executed on a single component or be further distributed across more components. The components can be implemented, for example, as an integrated circuit or as discrete components, or as a combination of both. In other examples, the components could be distributed among different printed circuit boards, for example. [0016] FIG. 2 illustrates an example of feed and output systems 210 and 220 that are employed to mitigate curl in media. When media such as paper, for example, is wetted with ink, it can curl in a print zone shown at 224 causing the paper to lift above a platen 230 and potentially leading to a printer jam and/or smearing of the image on the paper. This problem can become apparent when the top of form (TOF) or bottom of form (BOF) is passing though the print zone 224 and the paper is constrained by a single pinch point such as at feed pinch 240 and/or at output pinch 244. It is also possible for the curl to cause these problems in other parts of the printing system, after the media leaves the print zone, for example. The end of the paper near a curl 250 can be loose and when wetted, can be curled upward and away from the platen 230 and cause smears or jams in the printer.

Such curl 250 could also be in the opposite direction than shown (curled down toward the platen). For example, if the paper were reversed in a duplex operation, the curl 250 could be oriented in an opposite direction than shown. In such cases, the curl should be flattened before beginning the duplex printing operation.

[0017] As described above, the curl 250 can be mitigated by reversing and advancing the curl though the feed pinch at 240 and/or output pinch 244 in order to provide some flattening to the respective curl and arrest further curl growth later, after removal from the reverse bow region. This can include repeated

reverse/advance cycles for flattening the curl 250. This can also include introducing a delay while the point of substantially maximum curl at 250 is held in the region flexed concave up, near the feed pinch 240 or output pinch 244. The system 220 shows a bottom of form curl at 260 which can also be curled in the opposite direction depending on media orientation in which case, the curl should be flattened before beginning the duplex printing operation.

[0018] In one example, curl 250 or 260 can be referred to as cockle, wherein a distinction between curl and cockle is generally one of scale. The nature of curl is to cause media to become convex on the wetted side and not remain flat, and can be related to the width dimension of the print zone and related to the width dimension of the print head. This relationship between print zone width and curl is illustrated in FIG. 3 and is discussed below. As shown for reference only, an encoder 270 (or encoders) can be employed to monitor speed and direction of the feed and output of the printer.

[0019] FIG. 3 illustrates an example diagram 300 depicting the effects of print zone width on curl. As shown in the diagram 300, the height of the curl as depicted on the Y axis of line 310 begins to grow significantly as the distance of the paper is from the pinch point of the feed head as shown on the X axis in millimeters (this parameter would be the height of the curl 250 in FIG. 2). For example, after about 50 millimeters as shown at 320 of line 310, the curl can begin to increase

significantly. Thus, as print zones continue to grow wider to accommodate larger print heads, there is a need to mitigate increasing amounts of curl as described herein to maintain desired print quality and reliability. There can also be a time effect to consider as curl can grow over time, up to a minute or two, for example. Curl can grow slowly over a minute or two to large levels. In addition to mitigating the curl found early in this growth process, the systems and methods described herein can mitigate further curl growth after the media is taken out of the reverse bow region.

[0020] FIG. 4 illustrates an example system 400 for flattening media curl in printers. The system 400 includes feed rollers 410 that advance paper 420 over a platen 430 and under a print head 440 toward and output roller 450. Below the system 400, various example states of paper 420 are shown as it is advanced and retracted through the feed rollers 410 to mitigate curl in the paper. At 460, a curved paper is shown as the paper begins to curl after ink is applied by the print head 440. At 464, the paper 420 can be withdrawn toward the feed pinch in the roller 410 to flatten the paper. At 470, the paper 420 is advanced and a next pass printing occurs via the print head 440. At 474, the paper again begins to curl after the next pass of printing. At 480, the paper 420 is withdrawn toward the feed pinch in the roller 410 to again flatten the curl. At 484, the flattened paper is again advanced for a next pass at printing via the print head 440. The cycle depicted between states 460 and 484 can be repeated a number of times as desired. This can be for a

predetermined number of times (e.g., once or twice) or can be repeated based on feedback (e.g., curl height measured and cycle repeated until curl height measured outside of the reverse flexure region until flattened curl measured below predetermine threshold).

[0021] In one example, reverse bow relates to the flexure of the media via the pinch angle and pinch location as it enters or as it leaves the print zone. Thus, reverse bow can be designed into the feed pinch and the output system as a means of keeping paper down on the platen 430 and under the print head 440. It can have the side effect of biasing small scale cockle downward as well, but in wide print zones it may be ineffective by itself in controlling curl. That may be due to the unconstrained end of the paper being extended far from the constrained region near the remaining pinch point, making it easier for curl to lever the paper, for example.

[0022] Reverse bow can bend the media in a direction opposite to the curl and thus tends to counteract the curl. Wet media is somewhat plastic, and if curled, it can be bent back into a more straightened condition. A problem can occur in that the curled portion of the page may not be in the flexed region near the pinch points, at least not at the right time. When ink is deposited in a print swath on the top of a sheet, for example, it typically begins to curl. To mitigate this, after every swath (or a predetermined number of swaths), the paper can be reversed and backed up until the inked portion is brought back to the feed pinch point so that reverse bow can bend the wetted portion opposite to the curl to counteract it. The paper can then be advanced for the next swath in a flatter state as depicted in the state cycles at 460-484.

[0023] In view of the foregoing structural and functional features described above, an example method will be better appreciated with reference to FIG. 5.

While, for purposes of simplicity of explanation, the method is shown and described as executing serially, it is to be understood and appreciated that the method is not limited by the illustrated order, as parts of the method could occur in different orders and/or concurrently from that shown and described herein.

[0024] FIG. 5 illustrates an example method 500 for mitigating curl in media during a printing process. The method 500 includes directing media via rollers during a printing process at 510. As described above, input feed rollers,

intermediate rollers, or output rollers can be employed to guide the media. At 520, the method 500 includes applying ink to the media. In general, it is when the ink is applied to the media that curl begins to form near the top or bottom of the media such as paper, for example. At 530, the method 500 includes redirecting the media toward the rollers to flatten curl in the media. The media is typically directed to a region near the rollers (e.g., about where contact is made with the platen) where a reverse flexing force can be applied to the media to counteract the curl in the media. Thus, 530 of the method 500 can include redirecting the media to a location where the media is flexed opposite to the curl direction, to flatten the media. At 540, the method 500 includes holding the media for a time delay to allow curl in the media to further flatten. The holding can also include slowing of the media travel for the time delay. As noted above, such delay can be based on media type, the amount of ink utilized, or environmental conditions encountered during the printing process, for example. The method 500 can also include executing a flattening cycle that repeats the directing at 510, applying at 520, redirecting at 530, and holding at 540.

[0025] When duplexing, the simplex side bottom of form (BOF) may become the duplex side top of form (TOF) in some printers. The simplex BOF can curl when wetted. Thus, during duplex retraction or feeding of side two of the media, the corners of the duplex TOF can curl up enough to cause jams. By retracting the wetted simplex side BOF to or through the feed pinch slowly or with a time delay, the curl can be mitigated as described above. What differentiates this curl-mitigation operation from normal printer operation is that the paper speed at start of duplex retraction can be commanded slower than the rest of the duplex cycle. The reverse bow described above with respect to FIG. 4 can be utilized on the output side of the print zone, for example, to treat the BOF or TOF in a similar manner. This may be less effective as the reverse bow provided by output systems may be weaker than at the feed pinch (that is, the paper is not bent as tightly). Furthermore, media may be held less tightly against the output roll, and it may be more difficult to avoid dot placement errors after cycling the media position.

[0026] FIG. 6 illustrates an example printer 600 that employs a controller and flexure control module 610 to mitigate curl in media during a printing process. The printer 600 includes a print head 620 to dispense ink on a media 630. The controller 610 commands the print head 620 to dispense the ink on the media 630. A feed roller to receive the media and an output roller to eject the media is shown at 640, wherein the controller 610 controls the feed roller and the output roller to adjust the speed and direction of the media 630. The flexure control module in the controller 610 commands the controller to adjust the speed or direction of the media to direct the media toward the feed roller or the output roller to mitigate curl in the media A processor and memory module 650 can direct remote print commands to the controller 610. The flexure control module can command the controller 610 to perform multiple redirections of the media 630 through the feed roller or the output roller 640 to mitigate curl in the media. Also, the flexure control module in the controller 610 can adjust a delay so that the media remains in the feed roller or the output roller at 640 to mitigate curl in the media.

[0027] The printer 600 can also include a communications module 660 for receiving print commands and updating printer status. The communications module 660 can include local connections such as from a print cable and/or can include remote network connections such as can be received from a local network and/or over a public network such as the Internet, for example. The communications module 660 can be operated by the processor and memory module 660 which can include executable operating instructions to operate the printer 600. Such

instructions can operate the method 500 described above with respect to FIG. 5, for example. The processor and memory module 650 can also connect to an interface module 670 that performs interface operations to the controller 610 such as providing different print commands to the controller such as print, hold, retract, form feed, font commands, color commands, or other formatting commands, for example.

[0028] What have been described above are examples. It is, of course, not possible to describe every conceivable combination of components or

methodologies, but one of ordinary skill in the art will recognize that many further combinations and permutations are possible. Accordingly, the disclosure is intended to embrace all such alterations, modifications, and variations that fall within the scope of this application, including the appended claims. As used herein, the term "includes" means includes but not limited to, the term "including" means including but not limited to. The term "based on" means based at least in part on. Additionally, where the disclosure or claims recite "a," "an," "a first," or "another" element, or the equivalent thereof, it should be interpreted to include one or more than one such element, neither requiring nor excluding two or more such elements.

Claims

CLAIMS What is claimed is:

1 . A system comprising:

a controller to adjust the speed and feed direction in which media is guided through a printer; and

a flexure control module to command the controller to alter the speed or feed direction in which the media is guided though the printer during a printing process to mitigate curl in the media.

2. The system of claim 1 , wherein the printer further comprises a feed or an output to reverse the direction of the media during the printing process.

3. The system of claim 2, wherein the feed or the output include rollers that have a pinch angle setting to mitigate the curl in the media.

4. The system of claim 3, wherein the pinch angle setting is set to a pinch angle between about 4 degrees and about 15 degrees.

5. The system of claim 1 , wherein the media is held in a stationary position for a predetermined delay period or the media travel speed is reduced during the printing process to mitigate the curl in the media.

6. The system of claim 1 , wherein the flexure control module commands the controller to advance and reverse the direction of the media over multiple cycles to mitigate curl in the media.

7. The system of claim 1 , wherein the flexure control module adjusts a delay in the controller based on a media type, on the amount of ink utilized, or environmental conditions encountered during the printing process.

8. The system of claim 1 , wherein the speed and feed direction is monitored by an encoder to provide feedback to the controller.

9. The system of claim 1 , wherein the media is paper, a synthetic material, or a mixture of the paper and the synthetic material.

10. A printer, comprising:

a print head to dispense ink on a media;

a feed roller to receive the media and an output roller to eject the media; a controller to control the feed roller and the output roller to adjust the speed and direction of the media;

a flexure control module to command the controller to adjust the speed or direction of the media to direct the media toward the feed roller or the output roller to mitigate curl in the media; and

a processor and memory module to direct remote print commands to the controller.

1 1 . The printer of claim 10, wherein the flexure control module commands the controller to perform multiple redirections of the media toward the feed roller or the output roller to mitigate curl in the media.

12. The printer of claim 1 1 , wherein the flexure control module adjusts a delay that the media is held in a stationary position or the media travel speed is slowed during a printing process.

13. The printer of claim 13, wherein the delay is based on a media type, on the amount of ink utilized, or environmental conditions encountered during a printing process.

14. A method comprising:

directing media via rollers during a printing process;

applying ink to the media; and redirecting the media to a location where the media is flexed opposite a curl direction to flatten the media.

15. The method of claim 14, further comprising executing a flattening cycle that repeats the directing, applying, and redirecting.