[01 ] BACKGROUND

[02] Most printers have a print mechanism for forming images on paper or other print medium. For example, inkjet printers have a mechanism for depositing ink on the print medium. Such printers generally have a media-advance mechanism, i.e., sheet handler', that moves a print medium past the print mechanism so that ink can be deposited over a substantial area of the medium.

[03] Printers can have a media-feed mechanism for removing media from a tray and driving the medium toward the print mechanism. Depending on the implementation, the feed

mechanism may be part of the sheet handler or a separate

mechanism. Printers can have sheet-exit drive for driving a printed media away from the print mechanism and onto an output tray. An exiting medium may be deposited directly on the tray or, if the tray already is holding printed media, on media previously deposited on the tray.

BRIEF DESCRIPTION OF THE DRAWINGS

[04] The following figures represent examples and not the invention itself.

[05] FIGURE 1 is a schematic diagram of a sheet handler with a sheet-exit guide in accordance with an example.

[06] FIGURE 2 is a flow chart of a sheet-handling process in accordance with an example. [07] FIGURE 3 is a block diagram of an inkjet printer in accordance with an example.

[08] FIGURE 4 is a perspective view of a sheet handler of the inkjet printer of FIG. 3 in accordance with an example.

[09] FIGURE 5 is an elevational view of the sheet handler of FIG. 4.

[ 1 0] FIGURE 6 is a detail of a slotted wheel of the sheet handler of FIG. 4 after it has captured a leading edge of a sheet and rotated.

[ 1 1 ] FIGURE 7 is a perspective view of the sheet handler of FIG. 4 in a condition corresponding to FIG. 6.

[ 1 2] FIGURE 8 is a process implementable by the sheet handler of FIG. 4.

[ 1 3] FIGURES 9A-9I are a series of elevational views of the sheet handler of FIG. 4 corresponding to actions of the process of FIG. 8.

[ 1 4] FIGURES 10A and 10B are sequential depictions of a "catch" and "roll" problem addressed by the examples herein.

[ 1 5] DETAILED DESCRIPTION

[ 1 6] FIGS. 10A and 10B illustrate a problem with catching and rolling of a printed sheet as it exits a printer. In FIG. 10A, a sheet 1000 of print media is being driven out of a printer by an exit drive mechanism 1002. Due to gravity and curling, the leading edge 1004 of sheet 1000 contacts previously output media 1006 on an output tray 1008 of the printer. Curling may be caused by the nature of the medium, and/or the effect of the printing process on the medium. For example, some media types warp when wet with ink in an inkjet printer. Curling is most likely to occur when the grain direction of the media is transverse to a media-advance direction since stiffness and thus resistance to curl is less along the media-advance direction.

[ 1 7] Due to friction between the advancing sheet and previously printed media, leading edge 1004 fails to slide forward along previously output media 1006. This results in the sheet 1000 beginning to roll, as shown in FIG. 10B. Not only may this rolling damage the sheet, but following sheets may be affected, causing damage to the other sheets and perhaps jamming the printer.

[ 1 8] FIG. 1 is a schematic diagram of a sheet handler 100 with a rotatable slotted sheet-exit guide 102 installed. Sheet handler 100 may be a printer, scanner, copy machine, or other device that handles sheets of print media. Sheet handler 100 includes a sheet- exit drive 104 to drive a sheet 106 toward, past, and from rotatable slotted sheet-exit guide 102.

[ 1 9] Rotatable slotted sheet-exit guide 102 is part of sheet-handler 100. Sheet-exit guide 102 includes a slot 103 for receiving a leading edge 107 of sheet 106. Sheet handler 100 also includes an output tray 110. Once a sheet has been released by the sheet-handler 100, it may be deposited on output tray 110 or its contents, such as a stack 112 of one or more sheets previously processed by sheet handler 100.

[20] A process 200 implementable on sheet handler 100 is flow charted in FIG. 2. At 201 , a sheet is advanced from a sheet-exit drive. At 202, the advancing causes the leading edge of the sheet to engage a slot of a rotatable slotted sheet-exit guide. At 203 , the slot is rotated so as to apply a reverse (away from an output tray) curl to the sheet. At 204, the sheet is released to the output tray. [21 ] FIG. 3 is a schematic diagram of an inkjet printer 300 that employs a sheet handler such as sheet handler 100 of FIG. 1. Inkjet printer 300 includes an inkjet printhead drive 301, a sheet handler 308, and an output tray 310. A sheet stack 312 is shown already settled on tray 310. Sheet handler 308 includes a sheet-exit drive 304 to drive a sheet 306 toward, sheet-exit guide 302.

[22] Sheet-exit guide 302 includes a slot 303 for receiving a leading edge 307 of sheet 306. Sheet handler 308 also includes an output tray 310. Once a sheet has been released by the sheet handler 308, it may be deposited on output tray 310 or upon a stack 312 of one or more sheets previously processed by sheet handler 308.

[23] FIGS. 4 and 5 are perspective and elevational views,

respectively, of an output section 400 of a sheet handler such as sheet handler 100 of FIG. 1. Output section 400 includes a sheet- exit drive 402, a rotatable slotted sheet-exit guide 404, and base structure 406 that supports sheet-exit drive 402 and serves as an output tray 408. Sheet-exit drive 402 includes a support

structure 410 that supports a motor- driven-r oiler assembly 412 including a drive axle 414 and drive rollers 416. Sheet-exit drive 402 also includes a pinch roller assembly 420, supported from above, including an axle 422 and pinch rollers 424.

[24] Sheet-exit guide 404 includes a bracket 430 mounted from above. Bracket 430 supports axles 432 of wheels 434 with protruding features 436 extending generally tangentially from a wheel rim 438 so as to define slots 440; slots 440 can catch and guide a leading edge 442 of a sheet 444 as shown in FIG. 6 so that sheet 444, at least near leading edge 442, is curled upward away from output tray 408, as shown in FIG. 7. Although two wheels are shown, in alternative examples, the number may be one, two, three or more. Also, the widths and diameters of the wheels can vary according to the example and to any optimizations for a given sheet handler type and model. In the illustrated example, wheels 434 are about 2" in diameter. Wheels 434 may be made of smooth plastic, but other materials, including metals, are used in alternative examples. Although wheels 434 are mounted on separate axles, in other examples, one axle may support more than one wheel. In alternative examples, a conveyer belt or other support structure for slots can be used instead of wheels.

[25] A process 800, implementable on a sheet handler, is flow charted in FIG. 8. At 801, a sheet of print media is interacted with by an imaging, e.g., print or scan, operation. This interaction can apply to an entire surface of the sheet at once or can apply progressively, e.g., as the sheet is advanced by the sheet-exit drive. At 802, the leading edge of the sheet reaches an exit drive

mechanism, as indicated in FIG. 9A, which engages the sheet and urges it over the output tray.

[26] At 803, the leading edge is sufficiently past the exit drive mechanism that it reaches the sheet-exit guide, as indicated in FIG. 9B. Depending on the example, the slot may have been stationary or in rotational motion at the time the leading edge engages it. In either case, at 804, the slot, e.g., as part of its host wheel, rotates so that the engaged leading edge is led away from the sheet-exit drive and away from the output tray to induce a "reverse" curl, as shown in FIGS. 6, 7, and 9C. Note that, in the absence of the sheet-exit guide, the sheet could have a forward curl toward the output tray; in that case, the leading edge of the sheet would likely have contacted the output tray or its contents and either slid along or have caught, risked rolling into a cylindrical shape.

[27] At 805, the leading edge releases from the slot as indicated in FIGS. 9D, 9E, and 9F. This can be due at least in part to a spring force that builds up in the sheet as it is curled around the wheel. Otherwise a bracket or other structure may block the leading edge from following the wheel around at some point in the rotation.

[28] At 806, the sheet contacts the output tray or its contents. Depending on a number of factors, the leading edge may contact first, as indicated in FIG. 9H or another portion may contact first, as FIG. 9G seems to suggest might happen. In the latter case, the leading edge will not bind so that the chance of the sheet rolling is negligible. However, even if the leading edge contacts first, the angle at which it contacts is gentler and there is less distance to travel before the sheet settles in its final position in the output tray, which is reached at 807 as indicated at FIG. 91. Therefore, the opportunity for the sheet to roll is reduced (relative to the situation without a rotatable slotted exit guide in place), if not eliminated entirely.

[29] In alternative embodiments, the slots on the wheel or conveyor belt may differ in number or in manner of formation. The wheel, conveyor belt, or other underlying structure for the slots may be formed from a variety of plastics, metals, or other materials. Examples with conveyer belts can use a variety of pulley

arrangements respectively to provide for a respective variety of path shapes suited for different sheet handling applications. Smooth slot surfaces can facilitate entry of a leading edge into the slot.

Also, there can be one wheel, two wheels (as shown), three wheels or more, e.g., to accommodate different sheet widths. [30] The causes of the slot rotation can differ from example to example. In one example, wheels may be freely rotating. They may be stationary until urged to rotate by the force driving the sheet into the slot. Some friction may be applied against the rotation motion so that the wheel does not "bounce" away from the leading edge upon contact.

[31 ] In other examples, the wheels or other slot substrate may be motor driven, e.g., using the same motor that propels the sheet-exit drive. Gear ratios or other coupling can ensure suitable relative speeds for the sheet-exit drive and the slot rotation. For example, the linear speed of a slot can be slightly less than the linear speed of the leading edge to allow the latter to catch up with the former, assuming the former is rotating at a constant rate. In still other examples, the slot speed is varied or intelligently regulated to optimize capture, retention, and release of the leading edge.

[32] Herein, a "system" is a set of interacting non-transitory tangible elements, wherein the elements can be, by way of example and not of limitation, mechanical components, electrical elements, atoms, physical encodings of instructions, and process actions. Herein, "process" refers to a sequence of actions resulting in or involving a physical transformation.

[33] Herein, "device" refers to hardware. Herein, "medium" refers to a system including non-transitory tangible material in or on which information is or can be encoded with information including data and instructions. "Print medium" and "print media" refer to media bearing or suitable for bearing human-perceptible images (including text). "Computer-readable" refers to storage media in which information is encoded in computer-readable form. Herein, "processor" refers to hardware for executing instructions. A processor can be a monolithic device, e.g., integrated circuit, a portion of a device, e.g., core of a multi-core integrated circuit, or a distributed or collocated set of devices.

[34] Herein, a "sheet handler" is an at least partially mechanical system for handling sheets, e.g., of print media. Herein, "tray" refers to a physical structure suitable for supporting one or more sheets of media. "Output tray" refers to a tray on which a sheet handler deposits sheets after they have been processed (e.g., scanned or printed). Herein, a "drive" is a mechanism that propels something in a direction; an "exit drive" is a drive that propels something, e.g., a sheet of print media, out of something, e.g., a printer, a scanner, or other paper handler. Herein, a "guide" is a physical structure that causes something to follow a particular path; a guide may be a passive device or it may also positively drive something along the path.

[35] Herein, a "wheel" is a disc with a circular cross section that can rotate about an axle through the center of the circular cross section. A rim is a structure orsurface of a structure that follows the circumference of the circular cross section of a wheel. Herein, a "conveyor belt" is a closed loop material surface along with any drive and guide mechanisms that cause it to cycle around the closed loop. Herein, a "slot" is an empty (e.g., air-filled) space that is open to an exterior at one end or at two opposing ends. Herein,

"tangentially" means "more tangentially than radially".

[36] In this specification, related art is discussed for expository purposes. Related art labeled "prior art", if any, is admitted prior art. Related art not labeled "prior art" is not admitted prior art. In the claims, "said" introduces elements for which there is explicit verbatim antecedent basis; "the" introduces elements for which the antecedent basis may be implicit. The illustrated and other described embodiments, as well as modifications thereto and variations thereupon are within the scope of the following claims.

[37] What Is Claimed Is: