Patent Application
20220363498
Printing devices can use a variety of different technologies to form images on media such as paper. Such technologies include fluid-ejection technologies such as inkjet-printing technologies. Printing devices deposit print material, such as colorant like ink, which can include other printing fluids or material as well. Some types of printing devices can print on just one side of media sheets, which is known as simplex printing, whereas other types can print on both sides of media sheets without requiring the user to manually reinsert the media sheets into the device after the first sides of the sheets have been printed, which is known as duplex printing.
As noted in the background, some types of printing devices, including fluid-ejection devices such as inkjet-printing devices, can print on both sides of media sheets without the user having to manually reinsert the sheets into the device after the first sides of the sheets have been printed. A printing device that is capable of such duplex printing prints on the first side of a media sheet, and then loads the sheet back into the device for printing on the second side of the sheet before ejecting it from the device. Duplex printing can be cost effective to end users by reducing the amount of media used by up to 50%.
A printing device can include various rollers, including a pick roller that loads media sheets from an input tray, drawer, or cassette, a feed roller and a turn roller that advance the sheets through the device for printing, and an ejection or output roller that ejects the sheets after printing. Some printing devices may have more than one motor that each control one or multiple rollers. For example, the pick roller may be controlled by a different motor than the motor controlling the feed, turn, and/or eject rollers.
When such a printing device performs duplex printing, the device can cause the pick roller to load the next media sheet at the earliest time possible while the feed and/or turn rollers are still advancing the current media sheet through the device for printing on the second side of the current sheet. For example, the loading of the next media sheet can be synchronized with advancement of the current media sheet so that the next sheet closely follows but does not come into contact with the current sheet in the device. Because the feed, turn, and eject rollers are controlled by a different motor than the pick roller, initiating rotation of the pick roller to load the next media sheet does not affect rotation of the feed, turn, and eject rollers.
However, for cost and other reasons, some printing devices have one motor that controls both the pick and feed rollers, and which may also control the turn and eject rollers. In the latter case, for instance, the printing device may have just one motor that controls every roller within the device. When such a printing device performs duplex printing, causing the pick roller to load the next media sheet while the feed and/or turn rollers are still advancing the current media sheet through the device for printing on the second side of the current sheet can result in degraded print or image quality.
Specifically, the pick roller may be linked to the motor via a pick transmission, such as a clutch, shift, switch, or other type of transmission. Engaging the pick transmission causes the motor to drive the pick roller, and disengaging the pick transmission causes the motor to cease driving the pick roller. Because the motor also drives other rollers, including the feed and/or turn rollers, engaging the pick transmission to initiate rotation of the pick roller can momentarily affect uniform rotation. For example, when the pick transmission is engaged, the additional load placed on the motor to overcome the initial resistance of the pick roller before the pick roller starts to rotate can result in the motor momentarily slowing the speed at which the feed and/or turn rollers are rotating.
Such an initial jolt to the feed and/or turn rollers when loading the next media sheet can affect print quality of the image being printed on the second side of the current media sheet. The current media sheet may skip forward a small amount, resulting in gaps in the image printed on the second side of the current sheet, or may skip backward a small amount, resulting in undesired overlap in adjacent portions of the image printed on the second side of the current sheet. If the second side of the current media sheet is actually being printed at the time of pick transmission engagement, the current portion of the image being printed may become distorted due to the shifting of the current sheet.
Furthermore, a printing device can include a print carriage that scans back and forth relative to a current swath of a media sheet along an axis perpendicular to the direction in which the sheet is advanced. The print carriage can include a fluid-ejection printhead, such as an inkjet printhead, which ejects print material like ink on the current swath of the media sheet as the carriage scans back and forth. Engagement and disengagement of the pick transmission can also momentarily affect print carriage movement, and therefore impair print or image quality if pick transmission engagement or disengagement occurs while the carriage is moving.
To avoid such potential impairment of print or image quality, a printing device that uses the same motor to drive the pick roller and the feed and/or turn roller may avoid engaging the pick transmission to load the next media sheet until the current media sheet has been ejected. Print or image quality degradation therefore cannot occur, because the current media sheet will have already had both sides printed and will have been ejected before the next media sheet is loaded. The print carriage will not be in motion since printing has been completed. However, waiting until the current sheet has been ejected before loading the next sheet results in a decrease of print speed, particularly as compared to a printing device having a separate motor to drive the pick roller such that loading of the next sheet can occur at the earliest time possible.
Techniques described herein ameliorate these and other issues. Subsequent to completion of printing on a current media sheet, a pick transmission of a printing device linking a motor of the device to a pick roller of the device is engaged to load a next media sheet via the motor driving the pick roller. While the next media sheet is being loaded, the current media sheet is ejected via the same motor driving an eject roller of the printing device. This motor can also drive a feed roller and/or a turn roller that advance media sheets through the device for printing.
Impairment of print or image quality is avoided, because printing on the current media sheet has been completed before the next media sheet is loaded. However, print speed is improved, because loading of the next media sheet occurs during, and not after, ejection of the current media sheet. In some printing devices, the resulting improvement in print speed can be on the order of one page-per-minute (PPM). More generally, the longer the time it takes to eject a media sheet from a printing device, which may be affected by how long the ejection path of the device is, the greater the improvement in print speed for the printing device in question.
The printing device 100 includes a motor 108. In the example, the motor 108 drives a feed roller 110, an eject roller 112, a pick roller 114 linked to the motor 108 by a pick transmission 116, and a turn roller 118 of the printing device 100. That is, the same motor 108 drives the feed roller 110, the eject roller 112, the pick roller 114, and the turn roller 118. The printing device 100 may include other rollers, in addition to the rollers 110, 112, 114, and 118 shown in
The feed roller 110 is driven by the motor 108 to rotate clockwise to advance a media sheet through a print zone directly under the nozzles 106 of the printhead 105. The eject roller 112 is driven by the motor 108 to rotate clockwise to partially or completely eject the media sheet from the printing device 100. The printing device 100 can include a passive eject roller 119 opposite the eject roller 112, and which is not driven by the motor 108. The passive eject roller 119 rotates in a direction opposite the direction of the eject roller 112 driven by the motor 108 when the eject roller 112 is rotating. The passive eject roller 119 can also be referred to as a pinch roller, and may be cylindrical or a wheel with protruding spikes (i.e., in the configuration of a star in cross-sectional profile). The passive eject roller 119 serves to engage the media sheet against the eject roller 112 that is being actively driven by the motor 108.
The eject roller 112 is driven by the motor 108 to rotate clockwise to completely eject the media sheet from the printing device 100 after the first side of the sheet has been printed when simplex printing, and after the second side of the sheet has been printed when duplex printing. By comparison, the eject roller 112 is driven by the motor 108 to rotate clockwise to partially eject the media sheet after the first side of the sheet has been printed when duplex printing. The eject roller 112 is then driven by the motor 108 to rotate in reverse (i.e., counter-clockwise) to load the media sheet back into the printing device 100 so that the second side of the sheet can be printed.
The printing device 100 includes a controller 120 that controls starting and stopping of the motor 108 driving the rollers 110, 112, 114, and 118, and also the polarity of the motor 108 and thus the direction of rotation of the rollers 110, 112, 114, and 118. The controller 120 further controls engagement and disengagement of the pick transmission 116 linking the motor 108 to the pick roller 114. When the pick transmission 116 is engaged, the motor 108 drives the pick roller 114 and causes the pick roller 114 to rotate clockwise, to pick and therefore load a top-most media sheet of a stack of media sheets placed on a bottom wall 122 of a drawer, cassette, or input tray of the device 100.
The controller 120 may be implemented as a processor and a non-transitory computer-readable data storage medium storing program code and executable by the processor. The processor and the medium may be integrated within an application-specific integrated circuit (ASIC) in the case in which the processor is a special-purpose processor. The processor may instead be a general-purpose processor, such as a central processing unit (CPU), in which case the medium may be a separate semiconductor or other type of volatile or non-volatile memory.
In the example, once loaded by the pick roller 114 from the bottom wall 122, a media sheet is advanced towards a separator wall 124 at which the sheet turns upwards towards the turn roller 118. The usage of a separator wall 124 is thus one way by which media sheet pick and separation occurs for loading of the media sheet. Pick and separation results in one media sheet being loaded: if the pick operation results in more than one sheet being picked, the subsequent separation operation ensures that just one sheet is ultimately loaded. In other implementations, a different pick-separation configuration may be employed, such as a pressure plate system as in laser printing devices and more sophisticated inkjet printing devices, a pick-singulation system as in automatic document feeders, and so on.
The turn roller 118 is driven by the motor 108 to rotate clockwise to turn the media sheet in the opposite direction from which it was loaded from the bottom wall 122, towards the feed roller 110. The feed roller 110 as noted advances the media sheet towards the print zone under the nozzles 106 of the printhead 105 within which the (first) side of the sheet incident to the nozzles 106 are printed, and then towards the eject roller 112. The eject roller 112 as also noted then partially or completely ejects the sheet.
In the case of duplex printing, the media sheet is partially ejected, and the eject roller 112 is reversed in rotation to load the media sheet back into the printing device 100, and to advance the sheet back towards the turn roller 118. The turn roller 118 again turns the media sheet towards the feed roller 110, which again advances the sheet towards the print zone under the nozzles 106. This time the other (second) side of the media sheet is incident to the nozzles 106 and is therefore printed before the sheet continues to be advanced by the feed roller 110 towards the eject roller 112. The eject roller 112 then completely ejects the media sheet onto an output tray 126, as also occurs in the case of simplex printing.
The printing device 100 therefore has two overlapping printing paths 128 and 130, denoted by solid-lined and dotted-lined arrows, respectively. The printing path 128 is the primary printing path. A media sheet follows the printing path 128 from loading from the bottom wall 122 to the separator wall 124 where the sheet turns upwards, through advancement through the print zone, and to complete ejection onto the output tray 126 or partial ejection from the printing device 100.
The print path 130 is the duplex printing path. Once a media sheet has been partially ejected from the printing device 100 at the end of the printing path 128, the media sheet can be loaded into the duplex printing path 130 at the eject roller 112, and towards the turn roller 118. At the turn roller 118, the duplex printing path 130 ends, and the media sheet again follows the printing path 128, and therefore advances a second time towards the print zone, before being completely ejected onto the output tray 126.
When the printing device 100 is to ready to duplex print a print job having multiple pages, the motor 108 is started (202), which can result in the rollers 110, 112, and/or 118 being driven. The pick transmission 116 is engaged (204) to cause the motor 108 to drive the pick roller 114. Therefore, a current media sheet is loaded (205) from the bottom wall 122, towards the separator wall 124 where the current sheet turns upwards, and to the turn roller 118, along the primary printing path 128. The pick transmission 116 can then be disengaged (206), causing the motor 108 to cease driving the pick roller 114. At this time, the current media sheet may also be subjected to deskewing so that it is properly orientated when continuing along the printing path 128.
The current media sheet is advanced by the turn roller 118 being driven by the motor 108 to the feed roller 110 that is also being driven by the motor 108, and which advances the current sheet towards and through the print zone and to the eject roller 112, still along the primary printing path 128 (208). The first side of the current media sheet is printed on while in the print zone (210). The current media sheet is then partially ejected by the eject roller 112 being driven by the motor 108 (212). Partial ejection means that the current media sheet remains positioned between the eject roller 112 and the passive eject roller 119 at or towards the trailing edge of the sheet, and the current sheet is not completely ejected onto the output tray 126.
The current media sheet is then loaded into the duplex printing path 130, via the motor 108 driving the eject roller 112 in the reverse (i.e., opposite) direction (214), and to the turn roller 118 at which the duplex printing path 130 rejoins the primary printing path 128. The current media sheet is again advanced by the turn roller 118 to the feed roller 110, which again advances the current sheet towards and through the print zone and to the eject roller 112 (216), along the primary printing path 128. The second side of the current media sheet is printed on while in the print zone (218).
Upon completion of printing on the second side of the current media sheet, if the current sheet is not the last media sheet to be printed to complete the print job (220), then the pick transmission 116 is engaged (222) to cause the motor 108 to again drive the pick roller 114. The pick transmission 116 should be engaged to load the next sheet at the start of ejection of the current sheet by the eject roller 112. The current media sheet is thus (completely) ejected by the eject roller 112 being driven by the motor 108 while the next media sheet is being loaded by the pick roller 114 being driven by the same motor 108 (224). The current media sheet is therefore ejected onto the output tray 126, and the method 200 continues with disengagement of the pick transmission at part 206, where the next media sheet is now considered the current media sheet.
In some cases, simultaneous ejection of the current media sheet and loading of the next media sheet occurs so long as the current sheet has been advanced by more than a threshold length past the feed roller 110. This ensures that media sheet overlap and therefore jamming of the printing device 100 does not occur due to insufficient separation between the current sheet and the next sheet. If the current sheet has not yet been advanced by more than this threshold length, the method 200 can deviate from
The method 200 is repeated in this manner until the current media sheet is the last media sheet that is to be printed to complete the print job. Once the second side of the last media sheet has been printed (220), this last sheet is completely ejected onto the output tray 126 via the eject roller 112 being driven by the motor 108 (226). The motor 108 can then be stopped (228), causing rollers 110, 112, and/or 118 that are still rotating to stop.
The method 200 thus overlaps ejection of the current media sheet with loading of the next media sheet, by engaging the pick transmission 116 upon completion of printing on the second side of the current sheet. In general, because the pick transmission 116 is not engaged until after the second side of the current media sheet has been printed, print or image quality is not affected by any slight motion of the current sheet resulting from pick transmission engagement. That is, pick transmission engagement can momentarily jolt the feed roller 110, causing the current media sheet to move slightly forwards or backwards.
Such pick transmission engagement should cause no more than a threshold amount of reverse motion of the current media sheet that corresponds to (e.g., is equal to) the distance between the feed roller 110 and the print zone under the nozzles 106. If more than this threshold amount of reverse motion occurs, then the portion of the current media sheet that has just been printed on may come into contact with the feed roller 110. As a result, any undried print material on this portion of the current media sheet may smudge.
The overlapping of the ejection of the current media sheet with the loading of the next media sheet in accordance with the method 200 improves overall print speed because loading of the next sheet does not have to wait for the current sheet to be completely ejected. However, pick transmission engagement may not be permitted until the print carriage 104 has remained stationary for a length of time, which is referred to as the hold time of the print carriage 104. Therefore, for overall print speed to actually be improved, the hold time should be less than a threshold length of time. This threshold is based on the print speed that would otherwise result during duplex printing if loading of the next media sheet did not occur until the current media sheet was completely ejected.
By comparison, if loading of the next media sheet occurs while the current media sheet is being ejected, per scenario 304, both ejection of the current sheet and loading of the next sheet are performed simultaneously during the length of time 310. The time savings realized by loading the next media sheet while ejecting the current media sheet is therefore equal to the length of time 312.
The time savings can increase with an increasing length of time that it takes to eject the current media sheet. For example, with respect to the printing device 100, if the eject roller 112 and the output tray 126 are located farther downstream from the feed roller 110 and the print zone, the current media sheet will have to travel farther before being completely ejected onto the tray 126, and therefore the length of time to eject the current sheet will increase. As another example, if the output tray 126 is positioned above the print carriage 104, such that the current media sheet has to travel upwards and reverse in direction before being ejected onto the tray 126, the current sheet will again have to travel farther before being completed ejected, and the time to eject the current sheet will also increase.
In
In the scenario 404, loading of the next media sheet is completed after the length of time 410 (equal to the length of time 408) occurs, whereas ejection of the current media sheet is not completely until after the length of time 412 also occurs. That is, although loading of the next media sheet occurs during ejection of the current media sheet, loading of the next sheet is finished before the current sheet is ejected. The time savings realized in this case is equal to the length of time 414, which is equal to the lengths of 406 and 408 minus the length of time 410.
The time savings realized in the scenario 404 is thus greater than the time savings realized in the scenario 304 of
The foregoing description pertains to duplex printing. By comparison, during simplex printing, ordinarily the pick transmission 116 of the printing device 100 may be engaged throughout the print job. The pick roller 114 may be continuously driven by the motor 108. Once the current media sheet has been picked and loaded by the pick roller 114, the next media sheet will then be picked and loaded. The next media sheet therefore follows the current media sheet through the primary printing path 128. That is, both the current media sheet and the next media sheet may be advancing through the primary printing path 128 at the same time.
However, during loading of the next media sheet, the leading edge of the next sheet may become momentarily stuck at the separator wall 124, which may result in the next sheet temporarily bulging upwards between the separator wall 124 and the pick roller 114. As the motor 108 continues to drive the pick roller 114, the leading edge of the next media sheet will soon dislodge and continue advancing upwards towards the turn roller 118. However, the force imparted by the motor 108 to do so can result in a brief jolt to the feed roller 110, similar to (but smaller than) the jolt experienced by the feed roller 110 during engagement of the pick transmission 116.
If at this time current media sheet is actually being printed, there can be an impact in print or image quality at the portion of the current sheet currently in the print zone. This degradation in quality is particularly pronounced when the media sheets have a thickness greater than the thickness of plain paper having a media weight of less than 90 grams per square meter. That is, the thicker the media sheets are, the more likely they are to become momentarily stuck at the separator wall 124 during loading. Further, such degradation in print or image quality may become more apparent (or more important to avoid) when printing in a higher than default quality mode, such as a high-quality or picture-quality mode. (In the default quality mode, print speed and image quality may be balanced, whereas in a draft mode, print speed may be favored at the expense of image quality, and in a high-quality or picture-quality mode, image quality may be favored at the expense of print speed.) In such cases, then, the techniques that have been described in relation to duplex printing can be employed to improve print or image quality during simplex printing.
When the printing device 100 is ready to simplex print a print job having multiple pages, the motor 108 is started (502) as in duplex printing, and the pick transmission 116 is engaged (504) to cause the motor 108 to drive the pick roller 114. Therefore, a current media sheet is loaded (506) from the bottom wall 122, towards the separator wall 124 where the current sheet turns upwards, and to the turn roller 118, along the primary printing path 128. The pick transmission 116 can then be disengaged (508), causing the motor 108 to cease driving the pick roller 114. The current media sheet at this time may also be subjected to deskewing.
The current media sheet is advanced by the turn roller 118 being driven by the motor 108 to the feed roller 110 that is also being driven by the motor 108, and which advances the current sheet towards and through the print zone and to the eject roller 112, still along the primary printing path 128 (510). The first side of the current media sheet is printed on while in the print zone (512). Upon completion of printing on the first side of the current media sheet, if the current sheet is not the last media sheet to be printed to complete the print job (514), then the pick transmission 116 is again engaged (516) to cause the motor 108 to drive the pick roller 114.
The current media sheet is thus (completely) ejected by the eject roller 112 being driven by the motor 108 while the next media sheet is being loaded by the pick roller 114 being driven by the same motor 108 (518). The current media sheet is therefore completely ejected onto the output tray 126. The method 500 continues with disengagement of the pick transmission at part 508, where the next media sheet is now considered the current media sheet.
The method 500 is repeated in this manner until the current media sheet is the last media sheet to be printed to complete the print job. Once the first side of the last media sheet has been printed (514), this last sheet is completely ejected onto the output tray 126 via the eject roller 112 being driven by the motor 108 (520). The motor 108 can then be stopped (522), causing rollers 110, 112, and/or 118 that are still rotating to stop.
The method 500 therefore overlaps ejection of the current media sheet with loading of the next media sheet during simplex printing, by engaging the pick transmission 116 upon completion of printing on the first side of the current sheet. Because the next media sheet is not loaded until after the current media sheet has been printed, print or image quality of the current sheet is not affected by the next sheet becoming momentarily stuck at the separator wall 124 or temporarily bulging between the wall 124 and the pick roller 114. Although print speed is reduced as compared to continuous media sheet loading during simplex printing, such a tradeoff may be nevertheless be worthwhile when print or image quality is paramount and/or when thick media sheets are being printed.
The printing device 100 includes a motor 108, and a feed roller 110 driven by the motor 108 to advance the current media sheet through the print zone. The printing device 100 can also include the turn roller 118 of
The printing device 100 includes a pick transmission 116 linking the motor 108 to the pick roller 114. Engagement of the pick transmission 116 causes the motor 108 to drive the pick roller 114, and disengagement of the transmission 116 causes the motor 108 to cease driving the pick roller 114. The printing device 100 includes a controller 120 to, subsequent to the completion of printing on the current media sheet, engage the pick transmission 116 to load the next media sheet while the current media sheet is being ejected (702).
Techniques have been described for loading a next media sheet while a current media sheet is being ejected within a printing device in which the same motor drives both a pick roller that loads the next sheet and an ejection roller that ejects the current sheet. This same motor may also drive a feed roller and a turn roller that advance the current media sheet towards and through a print zone. When used in conjunction with duplex printing, the described techniques increase print speed. By comparison, when used in conjunction with simplex printing, the described techniques can improve print or image quality.
