[0001] Media may have a tendency to curl. This may complicate a proper output or stacking of printed media.

BRIEF DESCRIPTION OF THE DRAWINGS

[0002] For the purpose of illustration, certain examples constructed in accordance with this disclosure will now be described with reference to the accompanying drawings, in which:

[0003] Fig. 1 illustrates an example of a diagram of a printer;

[0004] Fig. 2 illustrates an example of a diagram of a transverse cross section of a media output guide assembly and curved media;

[0005] Fig. 3 illustrates a portion of an example printer with an example media output guide assembly in perspective view;

[0006] Fig. 4 illustrates a portion of the example printer with example media output guide assembly of Fig. 3 in front view;

[0007] Fig. 5 illustrates a portion of the example printer with example media output guide assembly of Figs. 3 and 4, in side view;

[0008] Fig. 6 illustrates the individual example media output guide assembly of Figs. 3 - 5 in perspective view;

[0009] Fig. 7 illustrates a flow chart of an example method of printing and ejecting media; and

[0010] Fig. 8 illustrates a flow chart of another example method of printing and ejecting media.

DETAILED DESCRIPTION

[0011] In the following detailed description, reference is made to the accompanying drawings. The examples in the description and drawings should be considered illustrative and are not intended as limiting to the specific example or element described. Multiple examples of printers or media output guide assemblies can be derived from the following description and drawings through modification, combination or variation of the different elements. 83501 1 13

2

[0012] Fig. 1 illustrates an example of a printer 1 . The printer 1 includes a print zone 2. The print zone 2 can be defined as the region where advancing media 3 is printed upon. In one example a print platen is provided in the print zone 2. The printer 1 includes an imaging arrangement 4 to print onto the media 3 in the print zone 2. For example, the print zone is defined by the imaging arrangement 4.

[0013] The imaging arrangement 4 can be an electrophotographic or inkjet imaging arrangement. Examples of the imaging material are liquid or dry toner or ink. In one example the imaging arrangement 4 includes a receiving bay fixed to the printer 1 to receive an exchangeable cartridge that holds the imaging material. In other examples the imaging arrangement 4 includes a printhead assembly that is fixed to the printer 1 , wherein the printhead assembly can be a scanning or a page wide array printhead assembly.

[0014] In one example the printer 1 includes a media output tray 7. The media output tray 7 includes a media support surface 8 to support the media 3 or media stack.

[0015] The printer 1 includes a media output guide assembly 5 to curve the media 3 downstream of the print zone 2. A media output direction M runs from right to left in Fig. 1 . The media output guide assembly 5 is to curve a middle portion 3B of the media 3 by engaging the media 3 downstream of the print zone 2. In one example the middle portion 3C is curved so that it exhibits a U- shape. In one example the middle portion 3C is curved towards the media support surface 8. In the illustrated example the middle portion 3C is curved downwards so that media side portions 3C are above the middle portion 3B. In other, not illustrated examples the media 3 may be stacked in an inclined or approximately vertical orientation or directly on a desk or table top. In these examples the "belly" of the U-shaped media would be directed towards the media support surface, that is, the media tray or desk or table top.

[0016] In a further example explanation, just after the print zone 2 the recently deposited imaging material may be wet, cooling down, drying, curing, fusing or undergoing some kind of temperature or state change. As a result thereof the media 3 may tend to curl. In again further examples certain media types, such 83501 1 13

as for example relatively thin paper or short grained paper, are extra sensitive to curl, especially in combination with the imaging material being wet, cooling down, drying, curing, fusing or undergoing some kind of temperature or state change. Intentionally curving the media 3 at output may help in these and other example situations. For example, curving the media 3 after the print zone 2 can inhibit curling of the media 3 over a direction perpendicular to the media output direction M. For example, the curving of the media 3 after the print zone 2 may stiffen the media 3 at output.

[0017] Fig. 2 illustrates an example diagram of a media output guide assembly 105 and a transverse cross section of media 103 advancing through the media output guide assembly 105. The media 103 represents recently or currently printed media 103. For example the media 103 is output or ejected towards the viewer. The media output direction could be horizontal, upwards or inclined with respect to a horizontal. Different printer types may have different ways of ejecting and stacking media.

[0018] In the example of Fig. 2 the media output guide assembly 105 is provided with four example guides, of which two first guides 1 10 and two second guides 1 1 1 . As illustrated, the media output guide assembly 105 is to direct a middle portion 103B towards a media support surface 108 and side portions 103C away from the media support surface 108 so that the transverse cross section of the output media 103 includes a U-type shape. In one example the media support surface 108 is a support surface of a printer output tray that may be horizontal, inclined, or almost vertical. In another example the media support surface 108 is formed by a desk top surface on which a respective printer is placed, that is, the printer is to stack printed media onto the desktop on which it is placed.

[0019] In the example illustration, the first guide 1 10 contacts a first face of the printed media, while the second guide 1 1 1 contacts the opposite face of the printed media 103. The second guide 1 1 1 presses into the media 103 to bow the middle portion 103B towards the media support surface 108, while the first guides 1 10 hold the side portions 103C away from the media stack surface 108 so that the U-shaped cross section is formed. The point where the second 83501 1 13

4 guide 1 1 1 is to engage the media 3 is closer to the media support surface 108 than the point where the first guide 1 10 is to engage the media 3. As illustrated, in operation, the U-shape in the media 103 may span between the first guides

1 10 and its width Uw may span more than half of a width W of a print zone and/or media output tray support surface. In a further example the distance GD between the inner second guides 1 1 1 is more than half of the width W of the print zone and/or media output tray support surface. For example the formed "belly" of the U-shaped media is relatively wide.

[0020] In other examples the media output guide assembly 105 may include other numbers of guides 1 10, 1 1 1 , such as for example only one second guide

1 1 1 to push the middle portion 103C towards the media support surface 108.

[0021] Figs. 3 - 5 illustrate a portion of an example printer 201 including an example media output guide assembly 205 and Fig. 6 shows the individual media output guide assembly 205 of Figs. 3 - 5. In an example, the printer 201 includes output rollers 215. The output rollers 215 are disposed near the print zone for example downstream of the print zone, for example at the edge of the print zone. The output rollers 215 are to aid in advancing the media during printing. For example, the output rollers 215 are to eject the media from the printer 201 . In an example bottom output rollers 215 are disposed over the width of the printer to engage a face of the printed media that is not currently being printed. For example, the output rollers 215 are to eject the media towards the media stack through a short acceleration, allowing the media to be advanced over a certain distance and then fall down onto a media support surface by gravity. The media output guide assembly 205 is arranged downstream of the print zone and downstream of the media output rollers 215 to curve the printed media that is advanced by the output rollers 215. In certain examples the output rollers 215 are also arranged to return printed media for duplex printing.

[0022] The media output guide assembly 205 includes two top guides 21 1 to engage a top face of printed media. In an example the top face is the image face of the printed media. In case of duplex printing the image face is the face that is being printed, and/or the face with the most recently printed image. In one example the top guide 21 1 includes a low friction element to roll or slide 83501 1 13

5 over the image face during printing. For example the top guide 21 1 includes low friction wheel 216 such as a star wheel to roll over the image face during printing.

[0023] The media output guide assembly 205 includes two bottom guides 210 to engage a bottom face of printed media. The bottom guides 210 are arranged next to the top guides 21 1 on the outside of the top guides 21 1 . In an example the bottom face is the face of the media that is not being printed, or, in case of duplex printing, the face that was first printed. For example, in case of duplex printing the image on the bottom face may have already cooled down, cured, dried, fused, etc., so that there is less risk that the bottom guides 210 engage wetted imaging material. In one example the bottom guides 210 include a slide element such as a ski-like structure so that during media output the bottom face of the media slides over the bottom guide 210.

[0024] The guides 210, 21 1 are arranged in pairs 212 wherein each pair 212 contains a bottom guide 210 and a top guide 21 1 . The distance between a bottom guide 210 and a top guide 21 1 within a pair 212 is smaller than the distance between the pairs 212. The top guides 21 1 are disposed on the inside so that the distance between the top guides 21 1 is smaller than the distance between the bottom guides 212. Consequently, in this example, the distance between the pairs 212 is determined by the distance between the top guides 21 1 .

[0025] A point of the top guides 21 1 that is to engage the media is lower than a point of the bottom guides 210 that is to engage the media. This is perhaps best viewable in Fig. 5. The top guides 21 1 are arranged on the inside of the bottom guides 210 and by having the engagement point lower than the engagement point of the bottom guides 210 the top guides 21 1 press the middle portion of the media down, that is, in operation. In turn, the bottom guides 210 are to press side portions of the media, on both sides of the middle portion, upwards so that a U-shape is formed in the output media, as diagrammatically illustrated in Fig. 2.

[0026] In one example that is perhaps best understood with reference to Figs. 5 and 6 at least one of the guides 210, 21 1 is retractable. For example at least 83501 1 13

6 the bottom guides 210 are retractable. In the illustrated example, both the top and bottom guides 21 1 , 210 are retractable. In one example, the guides 210, 21 1 are to retract just before the output rollers 215 eject the printed media.

[0027] In an example the retractable top guide 21 1 includes a retractable arm 221 . In a further example, the arm 221 includes a rack 223 that is engaged by a pinion 225 or gear that in turn is drivable by a motor 227 (Fig. 6). For example, further transmission elements 229 are to transmit motor axle rotation to the pinion 225 and, finally, to the guide wheel 216. These further transmission elements 229 may include gears and axles. Both two top guides 21 1 may be drivable by the same motor 227 through said transmission elements 229.

[0028] For example, the arm 221 is retractable and extendable over a straight line L over its own longitudinal axis. For example the top guide 21 1 includes a pivoting arm 231 to support and guide the retractable arm 221 during retraction and extension of the top guide 21 1 . One end of the pivoting arm 231 pivots with respect to the retractable arm 221 and another end is mounted to a printer part in a pivoting manner and has a fixed location. In an example, the pivoting arm 231 is telescopic. For example the arm 221 is to retract substantially upwards and extend substantially downwards.

[0029] In an example the retractable bottom guide 210 also includes a retractable arm 222. In a further example, the bottom arm 222 includes a rack 224 that is engaged by a pinion 226 or gear that in turn is drivable by a motor 228. For example, further transmission elements 230 are to transmit motor axle rotation to the pinion 226 and, finally, to the bottom guide arm 222. The further transmission elements may include gears and axles. Both two bottom guides 222 may be drivable by the same motor 228 through said transmission elements 230.

[0030] For example, the bottom arm 222 is retractable and extendable over a straight line Lb over its own longitudinal axis. For example the bottom arm 22 is extendable away from the print zone and retractable towards and partly under the print zone.

[0031] The printer 201 includes a drive circuit 240 to instruct the drive of the bottom and top guide 210, 21 1 . In the discussed example such guide drive 83501 1 13

7 includes motors 227, 228. For example the guide drive includes open loop DC motors. For example, the drive circuit 240 is to instruct the guide drive to extend and retract the guides 210, 21 1 . For example the drive circuit 240 is to instruct the guide drive to extend and retract the guides 210, 21 1 before a trailing media edge passes and/or before the media is ejected. For example the drive circuit 240 is to instruct the media output rollers 215 to eject the media just after the guides 210, 21 1 are ejected.

[0032] Fig. 7 illustrates a flow chart of an example of a method of printing and ejecting media. For example the method includes advancing media over a print zone (block 300). For example the method includes printing on the advancing media (block 310). For example the method includes, during said printing, curving a middle portion of the media towards a media support surface so that a transverse cross section of the media includes a U shape (block 320). Such curving may occur downstream of the print zone.

[0033] Fig. 8 illustrates a flow chart of another example of a method of printing and ejecting media. For example the method includes advancing media over a print zone, wherein a general grain direction of grains in the media is perpendicular to the media advance direction (block 400). For example, the media is advanced in a landscape orientation or the media includes short grain paper. Here, the grain direction can be defined as a direction of the length of the grains. Here, short grained paper can be defined as paper wherein a length direction of the fibers in the paper is generally aligned with a short edge of the paper. For example the method includes printing on the advancing media (block 410), wherein the grain direction is perpendicular to the media advance direction.

[0034] In this example the media has a grain direction perpendicular to the media advance direction during printing. Therefore the fibers may offer relatively little resistance to curling and the short grained media may have a relatively strong tendency to curl at ejection, especially when the image has not fully dried, cured, fused or cooled down. In one example the method includes, while the image has not fully dried, cured, fused or cooled down, curving a middle portion of the media downwards so that a transverse cross section of the media 83501 1 13

includes a U shape (block 420). In one example this allows the short grain media to be stiffened and may prevent curling. The method includes a disengagement of the media by guides before a trailing edge has passed these guides (block 430). The method includes ejecting the media after the guides have disengaged the media (block 440).

[0035] While in this description directional indications including "bottom", "top", "downwards", and "upwards" are used, these can be interpreted as relative. For example the examples mentioned with respect to Figs. 3 - 6 could also be implemented in a printer that has an approximately vertical or inclined media output tray. In such assembly, similar media output guide assemblies can be applied.