FIELD OF THE INVENTION The field of the invention is printers and copiers and particularly mechanisms and methods for flipping substrates on which images are printed.

BACKGROUND OF THE INVENTION When a printer or copier does two-sided copying, it generally prints one side of the paper first, then flips the paper over and prints the other side. A large number of patents and published patent applications exist for paper-flipping mechanisms, including GB 2 168 688 A to Xerox Corp. , US 4,969, 641 to Fukushima et al. , US 5,201, 517 to<BR> Stemmle, US 5,692, 740 to Holtje, US 5,692, 747 to Guerrero et al. , US 5,720, 478 to Carter<BR> et al. , US 6,199, 858 to Wyer, and PCT publication WO 02/060794 Al to Hallmark Cards Inc. These mechanisms typically work by moving the paper into an intermediate position, and then moving it back out along a different path, so that its orientation is changed. To prevent the paper from going back along the same path when its motion is reversed, something irreversible is done to it before moving it back. In some publications, the irreversible action is falling or sliding under the influence of gravity. Using gravity to move the paper reduces the need for active mechanisms such as motor-driven rollers or pneumatics, reducing cost and increasing reliability. However, the falling or sliding paper must be guided fairly closely to make sure it ends up in the right place without wrinkling or jamming. This leads to the possibility that the first printed side of the paper will be scratched or smudged as a result of rubbing against a surface that is guiding it.

WO 02/060794 Al discloses a mechanism for flipping card stock for two-sided printing, in which the surface is never rubbed. The card stock is held rigidly in a frame, and the whole frame is flipped over.

US 6,199, 858 to Wyer illustrates the difficulty of designing a flipping mechanism using rollers, that does not allow the paper to rub. The device disclosed in Wyer has the primary purpose of forming a shingled stack of paper, but it also flips the paper when forming the stack. In this device, the paper is fed through a first pair of rollers, and the lead end drops straight down to an intermediate position where it is caught between a

second pair of rollers. If the paper were very compliant and with no memory of its curvature, then there would be no need for guide walls, and the paper would drop directly between the second pair of rollers without rubbing against anything. But since paper is not completely compliant and does retain a curl, guide walls are needed to make sure the leading edge of the paper is fed into the gap between the second pair of rollers, and the paper can rub against the guide walls.

Other mechanisms for flipping print media, too numerous to mention, are also known in the art.

SUMMARY OF INVENTION An aspect of some embodiments of the invention concerns a mechanism which flips paper (or other media, herein referred to as"paper") over without allowing it to rub against any surface. A driver, for example a drive roller in contact with a pinch roller, draws in a piece of paper or other printing media, in such a way that the paper does not rub against any surface of the mechanism. This means that any surface that the paper is in contact with, or might be in contact with, such as the surface of the drive roller, is co- moving with the paper in the entire region of contact, or rolling along the paper. A leading portion of the paper then comes to rest against a stop, while a trailing portion of the paper continues to be drawn into the apparatus, pulled by the driver.

The difference in motion between the leading and trailing portions causes the paper to buckle, so that the paper is no longer in contact with any surface of the mechanism, except for the leading edge that is resting against the stop, and the part that is still being drawn in, which is held in contact with and moving with the driver. When the paper is completely drawn in, and loses contact with the driver, the paper falls, in a flipped over orientation, into output location, without rubbing against any surface. It is generally not necessary to guide the paper while it is falling, since its leading portion is still resting against the stop. Hence the paper ends up in a flipped orientation, without ever rubbing against any part of the mechanism.

Optionally, before the leading edge of the paper has reached the stop, the leading edge, or a portion of the paper close to the leading edge, is held against the drive roller by a holding mechanism such as a gripper, or a suction system. The holding mechanism releases the leading portion of the paper just before it reaches the stop, so that it will not rub against the drive roller.

Alternatively or additionally, the pinch roller travels with the leading portion of the paper around the drive roller, keeping the leading portion of the paper in contact with the drive roller, and guiding it to the location of the stop. Then, when the leading edge of the paper reaches the stop, the pinch roller rolls back along the drive roller to the trailing portion of the paper, in order to hold the trailing portion of the paper against the drive roller so the drive roller can draw the paper in without allowing it to rub. If the pinch roller moves back quickly enough, then the paper will not buckle too sharply even though the pinch roller stays in contact with the drive roller the whole time.

Optionally, instead of the holding mechanism, or the pinch roller, bringing the leading edge of the paper to rest against a stop, it brings the leading edge of the paper to a position where, once the holding mechanism releases the leading edge or the pinch roller rolls back, the leading edge is taken up by a nip between two rollers.

Optionally, instead of stopping the leading portion of the paper completely, its motion is only slowed down, or its motion is reversed. Optionally, it is not the leading portion of the paper that changes the rate or direction of its motion when it reaches a certain point, but the trailing portion starts to move faster, or both the leading and trailing portions change their motion. All of these options have equivalent effects. As long as the leading and trailing portions of the paper are moving toward each other, the paper will buckle. Having the paper come to rest against a stationary stop is simpler than the other options.

Optionally, when the leading edge of the paper comes to rest against the stop, it is held down, away from the drive roller, by clamp or a roller. This prevents the paper from sliding away from the stop when its trailing edge is released from the drive roller and pinch roller, and it falls down. It also prevents the leading edge of the paper from curling slightly upward and rubbing against the drive roller when the trailing edge of the paper is still held between the drive roller and the pinch roller, and the middle portion of the paper is buckling away from the drive roller. It also assures that the leading edge is at the stop, so that a series of pages are stacked on top of each other.

Optionally, instead of the paper falling directly into the output location when its trailing portion is released from the driver, it falls into a temporary position from which it is conveyed to the output location. The output location of the flipping mechanism is not necessarily the final destination of the paper. For example, the paper may be conveyed from the output location of the flipping mechanism to another location where the other

side of the paper is printed, for example, or where some other process takes place.

Alternatively, the output location is the final position of the paper in the printer.

Optionally, there is a bypass mechanism, which allows the paper to bypass the flipping mechanism.

There is thus provided, in accordance with an exemplary embodiment of the invention, a method for flipping over a printing media, comprising: a) capturing the printing media in a nip between a driver roller and a pinch roller; b) turning the driver roller while holding at least a leading portion of the printing media against the driver roller, so that the printing media moves forward around the driver roller; c) releasing the leading portion of the printing media from the driver roller; d) changing the forward velocity of the leading portion of the printing media, while the driver roller continues to move a trailing portion of the printing media caught in the nip forward, thereby causing the paper to buckle away from the driver roller; e) releasing the trailing portion of the printing media from the nip; and f) allowing the trailing portion of the printing media to fall so that it ends up in a flipped over orientation.

In an embodiment of the invention, holding at least a leading portion of the printing media against the driver roller comprises moving the pinch roller around the driver roller at substantially a same angular speed as the drive roller turns, thereby holding a leading portion of the printing media in the nip between the pinch roller and the driver roller. Optionally, releasing the leading portion of the printing media from the driver roller includes rolling the pinch roller back around the driver roller.

Optionally, changing the forward velocity comprises exerting a force on the leading portion. Optionally, exerting a force comprises guiding the leading edge of the printing media toward a stopping location which exerts said force as the driver roller continues to advance a trailing portion of the printing media.

Optionally, holding a leading portion of the printing media against the driver roller comprises using suction. Alternatively, holding a leading portion of the printing media against the driver roller comprises using a gripper.

In an embodiment of the invention, changing the forward velocity of the leading portion of the printing media comprises stopping the leading portion of the printing media by having the leading edge of the printing media hit a stop. Optionally, the method also

includes holding down the leading portion of the printing media with a leading edge clamp at said stop.

Optionally, changing the forward velocity of the leading portion of the printing media comprises capturing the leading portion between two stopping rollers, and slowing down the leading portion by slowing down the turning of the stopping rollers. Optionally, changing the forward velocity of the leading portion comprises stopping the leading portion by stopping the turning of the stopping rollers. Optionally, changing the forward velocity of the leading portion comprises reversing the direction of motion of the leading portion by reversing the direction of turning of the stopping rollers.

Optionally, allowing the trailing portion to fall comprises allowing the trailing portion to fall freely.

There is further provided, in accordance with an embodiment of the invention, a method of transporting a printing media from an input location to an output location selectively in an original orientation or in a flipped over orientation, comprising: if the printing media is to be transported in its original orientation: grabbing the printing media from the input location; selectively releasing the printing media to a transport conveyer; and transporting the printing media to the output location in its original orientation if it has been released to the transport conveyer; or if the printing media is to be transported in a flipped over orientation: performing the method of flipping over the printing media in accordance with the invention.

Optionally, allowing the trailing portion to fall comprises allowing the printing media to fall onto the transport conveyer.

Optionally, the transport conveyer is located in a position such that, when the trailing portion of at least some printing media falls, said trailing portion touches the transport conveyer, and said trailing portion is urged with the transport conveyer in such a direction and with sufficient force to help it fall into the flipped over orientation in a flat configuration. Optionally, said trailing portion touches a return portion of the transport conveyer.

In an embodiment of the invention, the transport conveyer is capable of running in either a forward or a reverse direction;

the transport conveyer runs in the forward direction if the printing media has been released to the transport conveyer; and otherwise the transport conveyer runs in the reverse direction, so that it will push said trailing portion in a proper direction to help it fall into the flipped over orientation in the flat configuration.

Optionally, the trailing portion is pushed on with a conveyer belt while the trailing portion is falling, in such a direction and with sufficient force to help it fall into the flipped over orientation in a flat configuration.

Alternatively or additionally, the trailing portion is blown on while it is falling, in such a direction and with sufficient force to help it fall into the flipped over orientation.

There is further provided, in accordance with an embodiment of the invention, apparatus for transporting a printing media from an input location and delivering it in a flipped over orientation to an output, comprising: a) a rotating driver roller; b) a pinch roller, juxtaposed with the driver roller, such that a leading portion of the printing media is captured in a nip between the pinch roller and the driver roller; c) a stopping element; and d) an angular driver, which rolls the pinch roller around the driver roller at substantially the speed at which the driver roller turns, thereby bringing the leading portion of the printing media around the driver roller toward the stopping element while the pinch roller holds the leading portion in the nip against the driver roller, and which starts to roll the pinch roller back around the driver roller to a trailing portion of the printing media as the leading portion nears the stopping element; wherein the stopping element, when the leading portion reaches it, causes the leading portion to move at a lower forward velocity than the forward velocity at which the trailing portion is moving, causing the printing media to buckle away from the driver roller such that the printing media does not contact the driver roller except at the nip, and the printing media falls into the output location after the trailing portion leaves the nip.

Optionally, the apparatus includes a leading edge guide associated with the pinch roller which guides the leading portion of the printing media to the stopping element.

Optionally, the apparatus includes a leading edge sensor which causes the angular driver to start rolling the pinch roller around the driver roller after the sensor detects that the leading edge of the printing media has reached the pinch roller.

There is further provided, in accordance with an embodiment of the invention, apparatus for transporting a printing media from an input location and delivering it in a flipped over orientation to an output location, comprising: a) a rotating driver roller; b) a pinch roller, juxtaposed with the driver roller, such that a leading portion of the printing media is captured in a nip between the pinch roller and the driver roller; c) a stopping element; and d) a holding mechanism which holds the leading portion against the driver roller after the leading portion is captured and when the leading portion reaches the stopping element, releases the leading portion from the driver roller, allowing the leading portion to engage the stopping element, such that the leading element moves at a lower forward velocity than a trailing portion of the printing media, caught in the nip, causing a portion of the printing media intermediate the nip and the leading to buckle away from the driver roller such that it does not contact the driver roller except at the nip.

Optionally, the holding mechanism comprises a suction system.

Optionally, the holding mechanism comprises at least one gripper.

Optionally, the apparatus includes a leading edge sensor, which activates the holding mechanism when the sensor detects that the printing media has been or is about to be captured.

Optionally, the stopping element is fixed in place and causes the leading portion of the printing media to stop moving when the printing media hits the stopping element.

Optionally, the stopping element comprises a pair of stopping rollers which captures the leading portion of the printing media in a stopping nip between the stopping rollers. Optionally, the stopping rollers cause the leading portion of the printing media to stop moving after they capture it. Optionally, the stopping rollers cause the leading portion of the printing media to slow down after they capture it. Optionally, the stopping rollers cause the leading portion of the printing media to reverse direction after they capture it.

Optionally, there is an air blower which blows air on the trailing portion of the printing media after it leaves the nip, in such a direction and with sufficient force to help it fall into the flipped over orientation.

In an embodiment of the invention, there is a bypass mechanism which, when activated, transports the printing media from the input location to the output location in an orientation that is not flipped over.

Optionally, the bypass mechanism comprises a bypass entrance, and the bypass mechanism is activated by moving the bypass entrance to a position such that the leading edge of the printing media enters the bypass entrance, instead of the leading portion of the printing media being held against the driver roller. Optionally, the leading edge of the printing media enters the bypass entrance after passing through the nip between the driver roller and the pinch roller Optionally, the bypass entrance comprises a bypass nip. Optionally, the bypass nip comprises a nip between a bypass pinch roller and a bypass conveyer belt, and the bypass mechanism comprises the bypass conveyer belt, which transports the printing media at least part of the way to the output location.

Optionally, the bypass conveyer is positioned so that the trailing portion of at least some of the printing media touches the bypass conveyer as said trailing portion falls, and the bypass conveyer belt pushes said trailing portion in such a direction and with sufficient force so as to help it fall into the flipped over orientation in a flat configuration.

Optionally, said trailing portion touches a return portion of the bypass conveyer as said trailing portion falls. Optionally, the bypass conveyer is operable to move in either a forward or a reverse direction, and the bypass conveyer moves in a forward direction when the bypass mechanism is activated, and in a reverse direction otherwise.

Alternatively, the bypass entrance comprises a bypass slot. Optionally, the printing media is drawn into the bypass slot by gravity. Alternatively or additionally, the printing media is drawn into the bypass slot pneumatically.

In an embodiment of the invention, there is an assisting conveyer belt which pushes against the trailing portion of at least some of the printing media after it leaves the nip, in such a direction and with sufficient force so as to help it fall into the flipped over orientation in a flat configuration.

In an embodiment of the invention, there is: a) a transfer rotor which grabs the printing media from the input location; and b) a transport conveyer which carries the printing media to the output location; and the transfer rotor selectively either transfers the printing media to the nip between the driver rotor and the pinch roller, or releases the printing media onto the transport conveyer before the printing media reaches said nip, thereby causing the printing media to reach the output location in an unflipped orientation.

BRIEF DESCRIPTION OF THE DRAWINGS Figs. 1 through 5 are schematic cross-sectional views of an exemplary embodiment of the invention, showing a time sequence of five stages in flipping a piece of paper or other printing media; Figs. 6 through 9 are schematic cross-sectional views of another exemplary embodiment of the invention, showing a time sequence of four stages in flipping a piece of paper or other printing media, corresponding respectively to Figs. 1,2, 3 and 4 in that embodiment of the invention; Fig. 10A is a schematic cross-sectional view of an exemplary embodiment of the invention, with a bypass mechanism disabled, and Fig. 10B shows the same embodiment with the bypass mechanism activated; and Figs. 11-13 are schematic cross-sectional views of different exemplary embodiments of the invention with bypass mechanisms.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS Fig. 1 is a cross-sectional view of a paper flipping mechanism 100, according to an exemplary embodiment of the invention. A piece of paper 102, or other printing media, goes through a pair of feeder rollers 104, which direct the paper so that its leading edge enters a nip 106 between a drive roller 108 and a pinch roller 110. Drive roller 108 is driven in a clockwise direction, optionally at a constant speed, by motor 112.

Optionally, one or both of drive roller 108 and pinch roller 110 do not have solid surfaces going all the way across the width of paper 102, but comprise one or more rims, covering only a portion of the width of the paper. As long as there is some overlap between the one or more rims of drive roller 108 and the one or more rims of pinch roller 110, then the drive roller and the pinch roller will form nip 106.

Optionally, feeder rollers 104 are an integral part of flipping mechanism 100.

Alternatively, feeder rollers 104 are the output of another mechanism which performs some process before the paper is flipped over, for example printing a first side of the paper. Optionally, at least one of feeder rollers 104 is motor driven, turning at the same surface speed as drive roller 108. Alternatively, feeder rollers 104 are passive, or their speed easily changes in response to any torque exerted on them by paper 102, so their speed adjusts to match the speed of drive roller 108 once paper 102 is taken up by drive roller 108. Alternatively, feeder rollers 104 are motor driven until paper 102 is taken up by drive roller 108, at which time feeder rollers 104 are decoupled from the motor driving

them and then move passively at the speed that paper 102 is moving. In some embodiments of the invention, there are no feeder rollers 104, and there is another mechanism for feeding the paper into flipping mechanism 100, for example, a pneumatic mechanism.

To avoid damaging a printed image on one side of the paper, feeder rollers 104, or an alternative mechanism, are optionally positioned close enough to nip 106, and at an orientation, such that the leading edge of paper 102 finds nip 106 and is taken up by drive roller 108 and pinch roller 110, without ever rubbing against drive roller 108 or pinch roller 110. Alternatively, paper 102 does not find the exact position of nip 106 every time, but paper 102 is moving at the same speed as the surface of drive roller 108 and pinch roller 110, due to feeder rollers 104, so even if drive roller 108 or pinch roller 110 has to deflect the leading edge of paper 102 to guide it into nip 106, the paper will not rub against drive roller 108 or pinch roller 110.

A sensor 114, located just past nip 106, senses when the lead edge of paper 102 has passed through nip 106. Optionally, there is a leading edge guide 116 attached to pinch roller 110, and sensor 114 is located just past the leading edge guide. Pinch roller 110 is attached to an angular driver 118, which is capable of moving pinch roller 110 back and forth around drive roller 108. Optionally, angular driver 118 is driven by its own motor, not shown in Fig. 1, separate from motor 112. Alternately, angular driver 118 is driven by motor 112, the same motor which drives drive roller 108, but there are gears and/or cams, not shown in Fig. 1, which allow angular driver 118 to disengage from motor 112, or to be driven in reverse by motor 112. Optionally, the gears also allow angular driver to be driven at different speeds, without changing the speed of drive roller 108.

In an exemplary embodiment of the invention, drive roller 108 rotates at a constant speed. When sensor 114 senses that the leading edge of paper 102 has passed nip 106 and/or leading edge guide 116, then sensor 114 sends a signal to a controller, not shown in Fig. 1, which causes angular driver 118 to start rotating at the same angular speed and direction as drive roller 108. Hence, pinch roller 110 and leading edge guide 116 (if leading edge guide 116 exists) stay close to the leading edge of paper 102, as drive roller 108 turns.

Alternatively, drive roller 108 starts to rotate only when the paper approaches the nip between the drive roller and the pinch roller. However, this alternative is less

advantageous than having the drive roller rotating continuously, since it requires control of and quick changes in the rotational velocity of the drive roller.

Eventually, as shown in Fig. 2, pinch roller 110 and the leading edge of paper 102 are near the bottom of drive roller 108. When the leading edge of paper 102 reaches a stop 202, optionally guided into the narrow space beneath drive roller 108 by leading edge guide 116, then the leading edge of paper 102 cannot go any further. At this time, an optional leading edge clamp 204 pushes paper 102 down, holding paper 102 at a point close to its leading edge, pulling paper 102 away from contact with drive roller 108, at least in the region between pinch roller 110 and the leading edge of paper 102. Leading edge clamp 204 holds this leading portion of paper 102 down against the bottom of an output tray 206, or against the top paper in a stack of papers that are already resting in output tray 206. This prevents paper 102 from rubbing against drive roller 108.

Alternatively, there is no leading edge clamp 204, and the leading portion of paper 102 simply falls away from drive roller 108, once the leading edge of paper 102 reaches stop 202. Having the leading portion of paper 102 fall away from drive roller 108 is optionally facilitated if, as explained below, pinch roller 110 starts to move back up drive roller 108 even before the leading edge of paper 102 has quite reached stop 202, but when the leading edge of paper 102 is close enough to stop 202 that pinch roller 110 and optionally leading edge guide 116 are no longer needed to guide the leading edge of paper 102 toward stop 202.

At the same time as the leading edge of paper 102 reaches stop 202, or optionally slightly before as discussed above, angular driver 118 reverses direction, bringing pinch roller 110 back up drive roller 108, as shown in Fig. 3. The motion of the pinch roller is preferably a rolling motion along paper 102 so that there is no rubbing of the paper on the pinch roller. Optionally, angular driver 118 goes back up drive roller 108 at a different angular speed than drive roller 108, for example it goes at a faster angular speed than drive roller 108. A trailing portion 302 of the paper, up to pinch roller 110, continues to move at the speed of drive roller 108, while a leading portion 304, between clamp 204 and the leading edge, is not moving. As a result, a middle portion 306 of the paper begins to buckle, separating from drive roller 108 between pinch roller 110 and clamp 204.

At first, shortly after the leading edge has stopped moving, middle portion 306 is very short, and cannot buckle very much without creasing. At this time, however, the paper has only been buckling for a short time, so the degree of buckling is small, and can

be accommodated within the short distance of middle portion 306 without bending too sharply and creasing. As the paper continues to buckle, it needs a greater length to accommodate the buckling, but a greater length is available in middle portion 306 because pinch roller 110 is moving away from the leading edge. Depending on the characteristics of the paper, creasing can be avoided if pinch roller 110 is moving back up drive roller 108 faster than some minimum speed, for example at least as fast as drive roller 108 is turning.

Optionally, leading edge guide 116, if it exists, moves back out of the way as pinch roller 110 moves back up drive roller 108, as seen in Fig. 3 and Fig. 4. In this way, leading edge guide 116 does not rub against the back of the paper as it buckles and moves further away from drive roller 108. For example, the angular guide rotates counterclockwise around the axis of pinch roller 110, so that it clears the stack of papers.

Alternatively, leading edge guide 116 is fixed in position relative to angular driver 118, at a position such that it effectively guides the leading edge of paper 102 to stop 202, but does not rub against middle portion 306 of the paper as it buckles.

When the trailing edge of paper 102 goes through nip 106 and is free of drive roller 108, the trailing portion of the paper falls down, as shown in Fig. 5. Optionally, instead of the trailing portion of the paper falling under the influence of gravity, it is forced downward by other means, for example by moving air. If gravity is not used, then the direction shown as down in the drawings need not be directly down. It should be understood that references herein to the paper falling may also refer to these other means of moving the paper.

Because the leading portion of the paper is resting against stop 202, there is no need to guide the paper into a correct position as it falls, so there is nothing for the trailing portion of the paper to rub against as it falls. If leading edge clamp 204 exists and is holding down the leading portion of paper 102, this prevents the leading edge of paper 102 from drifting even slightly away from stop 202 as it falls. After falling, the paper lies in output tray 206 in a flipped over orientation, relative to its orientation before feeding into the flipping mechanism. From output tray 206, paper 102 is optionally moved to a place where it is further processed, for example the other side of the paper is printed. Optionally, a plurality of papers are stacked in the output tray, with the bottom of the output tray moving down to accommodate the stack, before any papers are moved out of the output

tray. Alternatively, flipping the paper is the last process done to the paper, and paper 102, or a stack of flipped papers, remains in the output tray.

Figs. 6,7, 8 and 9 show a time sequence, corresponding to Figs. 1,2, 3 and 4, according to another exemplary embodiment of the invention. This embodiment of the invention differs from the embodiment described above, because pinch roller 110 may be fixed in position near the top of drive roller 108, and there is no angular driver 118 which moves pinch roller 110 around drive roller 108. Pinch driver 110 is, of course, free to rotate on its axis. Instead of using pinch roller 110 to hold the leading portion of paper 102 against drive roller 108 as drive roller 108 turns, there is a holder for the leading edge of paper 102, such as a suction system 616 inside drive roller 108, which holds the leading portion of paper 102 against drive roller 108.

Optionally, as in the embodiment shown in Figs. 1-4, drive roller 108 does not have a solid surface going all the way across the width of the paper, but has one or more rims which go across only a portion of the width of paper 102, and has one or more arms with suction cups, located, for example, to the side of the one or more rims, which hold the leading edge of paper 102, playing the same role as suction system 616.

In one embodiment of the invention, drive roller 108 rotates continuously and the feeding of the paper is synchronized with the arrival of the suction system at nip 106, between drive roller 108 and pinch roller 110.

In some embodiments of the invention, suction system 616 is activated when sensor 114 detects the leading edge of the paper passing through nip 106. Alternatively, suction system 616 is active even before the leading edge of paper 102 is picked up by nip 106, or suction system 616 is turned on at a time when the leading edge of paper 102 is expected to go past nip 106. In these cases, optionally there is no need for sensor 114.

Although Fig. 6 shows an opening in suction system 616 only at one azimuthal position at the surface of drive roller 108, optionally there are openings at the surface of drive roller 108 to provide suction at more than one azimuthal position around drive roller 108, since the leading edge of paper 102 optionally does not always contact drive roller 108 at the same azimuthal position. Just before the leading edge of paper 102 reaches stop 202, suction system 616 releases paper 102, and the leading portion of paper 102 falls away from drive roller 108, preventing paper 102 from rubbing against drive roller 108 after the leading edge of paper 102 comes to rest against stop 202.

Alternatively, instead of or in addition to suction system 616, there are grippers, not shown in the drawings, which hold the leading portion of paper 102 against drive roller 108. However, using a suction system instead of grippers has the advantage that it is not necessary to get the grippers out of the way of stop 202 as drive roller 108 continues to turn after the leading portion of paper 102 is released.

Fig. 7 shows the leading edge of paper 102 being released by suction system 616 from drive roller 108 as the leading edge of paper 102 reaches stop 202. Fig. 8 shows paper 102 beginning to buckle as drive roller 108 continues to turn, and Fig. 9 shows the paper buckling further as drive roller 108 continues to turn. The last step of the time sequence looks the same as Fig. 5, but without leading edge guide 116 or angular driver 118, showing the trailing edge of the paper released from nip 106, and the paper falling down.

Figs. 10A, 10B, 11, 12, and 13 show embodiments of the invention in which there is a bypass mechanism, which allows the paper to bypass the paper flipping mechanism.

Figs. 10A and 10B show one such embodiment, with the bypass mechanism disabled in Fig. 10A, and operating in Fig. 10B. Figs. 11,12, and 13 show other embodiments with alternative bypass mechanisms.

In Fig. 10A, an image is printed on the printing media at impression cylinder 1002.

A transfer rotor 1003, has an arm 1004 with a suction cup 1006 at one end, which picks up the printing media from impression cylinder 1002 after the image is printed. Suction cup 1006 follows a circular path 1008, carrying the printing media to drive roller 108. Fig.

10A shows arm 1004 extending also to the other side of rotor 1003, and another suction cup 1010 on the other end of arm 1004. Optionally, this allows one suction cup to bring one sheet of printing media to drive roller 108, while the other suction cup is picking up the next sheet of printing media from impression cylinder 1002. Alternatively, there is only one suction cup associated with transfer rotor 1003, or there are three or more suction cups associated with transfer rotor 1003. If there are two or more suction cups, they need not be in the same plane, parallel to the plane of the drawing. Optionally, each suction cup shown in Fig. 10A represents a plurality of suction cups, optionally each attached to its own arm, arranged one behind the other, which attach to different locations across the width of the paper, as is known in the art.

Optionally, drive roller 108 does not have a solid surface across the entire width of the printing media, but has at least one solid rim, and there is a suction cup 1012, mounted

on an arm 1014. Optionally, there are at least two rims, and arm 1014 and suction cup 1012 are located between two of the rims. Alternatively, whether or not there are at least two rims, arm 1014 and suction cup 1012 are located behind or in front of one of the at least one rims. Alternatively, drive roller 108 does have a solid surface across the entire width of the paper, and suction cup 1012 in Fig. 10A represents the opening of a suction system inside drive roller 108.

Suction cup 1012 picks up the printing media from suction cup 1010 (or from suction cup 1006 if suction cup 1006 is adjacent to drive roller 108 at the time). Suction cup 1012 then conveys the leading edge of the printing media so that it enters a nip 106 between drive roller 108 and a pinch roller 110. Optionally, pinch roller 110, like drive roller 108, does not have a solid surface all the way across the width of the printing media, but has one or more solid rims. If neither drive roller 108 nor pinch roller 110 have solid surfaces across their entire widths, then there is at least one region across the width of the printing media where drive roller 108 and pinch roller 110 both have rims, in order to form nip 106 between them.

The flipping mechanism in Fig. 10A works in the same way as the flipping mechanism described in Figs. 6-9, with suction cup 1012 in Fig. 10A playing the role of suction system 616 in Figs. 6-9. Suction cup 1012 carries the leading edge of the printing media down and around as drive roller 108 rotates. When the leading edge of the paper reaches leading edge stop 202, it is released from suction cup 1012, because the vacuum in suction cup 1012 is reduced, and/or because leading edge stop 202 prevents the leading edge from continuing around drive roller 108 with suction cup 1012. A trailing portion of the printing media continues to move through nip 106, driven by drive roller 108. As a result, the printing media buckles, and moves out from drive roller 108. The position of the printing media at successive times, after the leading edge reaches leading edge stop 202, is shown by dashed curves 1016,1018, 1020 and 1022. When the trailing edge of the printing media passes through nip 106, the printing media falls down to a transport belt 1024, in a flipped over orientation, and is carried away from drive roller 108..

Optionally, instead of transport belt 1024, the printing media falls to a fixed location, similar to output tray 206 in Figs. 6-9, for example. Optionally, there is a leading edge clamp, not shown in Fig. 10A, similar to leading edge clamp 204 in Figs. 6-9, which holds the leading edge of the printing media in place at leading edge stop 202. In this case, if the printing media is transported away on transport belt 1024 after being flipped, then

the leading edge clamp releases the leading edge of the printing media so that transport belt 1024 can transport the printing media away. Alternatively, the printing media is held against transport belt 1024 with sufficient strength, for example by a vacuum system or by another pinch roller, so as to pull the printing media out of the leading edge clamp.

Optionally, instead of suction cup 1012 holding the leading edge of the printing media to drive roller 108 as it continues past nip 106, pinch roller 110 moves around drive roller 108 and holds the leading edge of the printing media against drive roller 108, as in Figs. 1- 4.

Fig. 10A also shows a bypass mechanism 1026 which is inactivated, raised up and out of the way of the leading edge of the printing media as it emerges from nip 106. In Fig.

1 OB, bypass mechanism 1026 is activated by lowering it to a position such that the leading edge of the printing media enters bypass mechanism 1026, instead of continuing to travel around drive roller 108, after emerging from nip 106. Optionally, the entrance of the leading edge into bypass mechanism 1026 is assisted by having suction cup 1012 release the leading edge after it passes nip 106. Additionally or alternatively, bypass mechanism 1026 has its own vacuum system, which pulls in the leading edge of the printing media.

Once the leading edge is drawn into bypass mechanism 1026, the printing media follows path 1028, and lands on transport belt 1024, without flipping over. Optionally, bypass mechanism 1026 has its own drive roller and pinch roller, with a nip between them, which draws the leading edge of the printing media into bypass mechanism 1026, once the leading edge of the printing media is directed to it. Optionally, instead of being a slot as shown in Figs. 1 OA and 1 OB, bypass mechanism 1026 comprises a conveyer belt.

Fig. 11 shows a flipping mechanism similar to that shown in Figs. 10A and 10B, but with a different method of bypassing the flipping mechanism. In Fig. 11, transport belt 1024 extends under path 1008 of transport rotor 1003. When it is desired to bypass the flipping mechanism, suction cup 1006 or suction cup 1010 (whichever one has picked up the printing media from impression cylinder 1002) releases the printing media onto transport belt 1024, before the printing media reaches suction cup 1012 and drive rotor 108. Then the printing media follows path 1130, and ends up lying on transport belt 1024, without flipping over.

Fig. 12 shows another bypass mechanism, similar to that shown in Figs. 10A and 10B. Instead of transport rotor 1003 bringing the printing media directly to drive rotor 108, transport rotor 1003 (and suction cup 1006 or suction cup 1010) brings the printing

media to a conveyer 1202. From conveyer 1202, the leading edge of the printing media either falls down and is caught in nip 106, if the bypass mechanism is inactive, or continues on path 1204 if the bypass mechanism is inactive, eventually reaching a conveyer 1206 without flipping over. The flipped over printing media, on conveyer 1024, is also brought to conveyer 1206. Alternatively, conveyers 1024 and 1206 form a single long conveyer, and printing media from path 1204 is brought onto the single long conveyer. A potential advantage of using two separate conveyers 1024 and 1206 is that conveyer 1206 can be swung out of the way, for access to parts of the printer or copier that are underneath it for example, without affecting the flipping mechanism.

The bypass or flipping mechanism in Fig. 12 can be selected either by transferring the front end of the sheet to path 1204, or by diverting it to nip 106. In general, any method of diverting substrates to one or another path can be used, including movement of rollers (for example a downward movement of the first set of rollers in path 1204 will direct the sheet to nip 106), provision of a trap door, where closing the door causes the printing media to follow path 1204, while opening the trap door disables the bypass mechanism, causing the leading edge of the printing media to fall down and be caught by nip 106. Alternatively, the leading edge of the printing media is selectively directed to nip 106 or to path 1204 by a different method, for example pneumatically, or by an element which pushes against the printing media or by a diverting element which may be selectively placed in path 1204, when flipping is desired.

Fig. 13 shows a flipping mechanism with some additional features, together with a different bypass mechanism. As in Figs. 10A, 10B, 11 and 12, printing media is picked up from impression roller 1002 by suction cup 1006, which is attached to the end arm 1004 and swung around by transfer rotor 1003. Suction cup 1006 swings the printing media around clockwise, on circular path 1008. When the bypass mechanism is not active, suction cup 1006 transfers the printing media to suction cup 1012, which swings the printing media around counter-clockwise on circular path 1304. At about the time suction cup 1012 picks up the printing media from suction cup 1006, or optionally a little earlier, the leading edge of the printing media passes through nip 106 between rollers 110 and 1302. Although it looks as if rollers 110 and 1302 would interfere with the swinging motion of suction cups 1006 and 1012, in fact the suction cups and rollers are not in the same plane, so they do not interfere with each other. Optionally, each of rollers 110 and 1302 shown in Fig. 13 represents two rollers, one in back of the other, and the two side

edges of the printing media go through nip 106, while suction cups 1006 and 1012 are located in a plane between the rollers, somewhere in the center of the printing media.

Optionally, one or both of cups 1006 and 1012 shown in Fig. 13 represents two or more cups, one behind the other.

When the leading edge of the printing media reaches a stop 202, suction cup 1012 releases the printing media, and the leading edge of the printing media rests against stop 202. However, a trailing portion of the printing media, which is still caught in nip 106, continues moving forward, since one or both of roller 110 and roller 1302 is a drive roller, which continues to push the printing media through nip 106. As a result, the printing media buckles, and has a configuration similar to 1306. When the trailing edge of the printing media goes through nip 106, the printing media falls down to conveyer 1024 in a flipped over orientation, as shown by 1308 and 1310. Blower 1314 optionally blows a jet of air 1316 at the printing media, helping the media to fall down more quickly. Such an air jet may be particularly useful if the printing media is very light weight, and may prevent the printing media from folding over as it falls.

Conveyer belt 1318 optionally can turn in either direction, as desired. When the bypass mechanism is not activated, conveyer belt 1318 turns clockwise, so the lower portion moves to the left. As the printing media falls down, the upper edge may brush against the lower surface of conveyer belt 1318, which helps to unbend the printing medium and make it lie flat. Conveyer belt 1318 may be particularly useful for a heavy weight or stiff printing media, which does not lose its curl easily. Conveyer belt 1318 and air jets 1316 optionally work together to help make the printing media fall down.

Alternatively, only one of them is present, or only one of them is operative for some grades of printing media.

From conveyer belt 1024, the printing media is transported to a conveyer belt 1312. Alternatively, a portion of the printing media may fall directly onto conveyer belt 1312. Alternatively, there is only one long conveyer belt, instead of belts 1024 and 1312.

Optionally, conveyer belt 1024 and/or conveyer belt 1312 does not start moving until the printing media has fallen down completely, in order to prevent the printing media from folding over as it falls. Alternatively, one or both of belts 1024 and 1312 move continuously, particularly if the printing media falls down quickly enough so that folding is not a problem.

If the bypass mechanism is active, then instead of cup 1006 transferring the printing media to cup 1012 near nip 106, cup 1006 continues to hold the printing media, and releases the printing media only at position 1010. Although there appear to be two suction cups 1006 and 1010 going around transfer rotor 1003, the two cups 1006 and 1010 shown in Fig. 13 are intended to show two different positions of the same cup 1006 as it swings the printing media around. Optionally, however, there are two or even more than two suction cups and arms attached to transfer rotor 1003, so that one suction cup can be picking up one printing media while another suction cup is transferring another printing media.

When suction cup 1010 releases the printing media, a leading portion 1320 of it falls onto conveyer belt 1318. Optionally, suction cup 1010 holds the printing medium some distance away from the its leading edge, so that the leading portion flops over and is located directly above belt 1318 even before cup 1010 releases it. Alternatively or additionally, air jets 1316 help to push the printing media onto belt 1318. Alternatively or additionally, belt 1318 extends closer to suction cup 1010 than shown in Fig. 13, for example directly under it, but not in a position that would interfere with suction cup 1010.

Alternatively or additionally, a trailing portion of the printing media is still caught in nip 106 between rollers 110 and 1302 when the leading portion is released by suction cup 1010, and one or both of rollers 110 and 1302 is a drive roller, which continues to push the printing media to the left, causing leading portion 1320 to fall onto belt 1318.

When the bypass mechanism is active, belt 1318 moves counter-clockwise, so the top portion of the belt, where the printing media is resting, moves to the left. The printing media, which is not in a flipped over orientation, goes onto belt 1206 when it reaches the end of belt 1318. Printing media on belt 1312, which are in a flipped over orientation, also go onto belt 1206, when they reach the end of belt 1312. Alternatively, belt 1206 is not separate from belt 1312, but belts 1206 and 1312, and optionally belt 1024 as well, are replaced by one long belt, which printing media from belt 1318 falls onto. Dividing the belt into one than one belt, for example into three belts as shown, has the potential advantage of making it easier to gain access to the machine, since belt 1206, for example, can be swung up and out of the way, without affecting the other belts.

Although Fig. 13 shows both a bypass mechanism and new features of the flipping mechanism, including belt 1318 which participates both in the bypass mechanism and in the flipping mechanism, optionally only one or some of these features are present. For

example, optionally belt 1318 runs only in one direction, and is used only in the bypass mechanism, or only in the flipping mechanism. Optionally, some of the features of Fig.

13, such as blower 1314, can be utilized in the other embodiments.

Although this description and the claims refer sometimes to paper, the invention may also be used with any other printing media, and the claims cover the apparatus and the method when any printing media is used. The invention has been described in the context of the best mode for carrying it out. It should be understood that not all features shown in the drawings or described in the associated text may be present in an actual device, in accordance with some embodiments of the invention. Furthermore, variations on the method and apparatus shown are included within the scope of the invention, which is limited only by the claims. Also, features of one embodiment may be provided in conjunction with features of a different embodiment of the invention. As used herein, the <BR> <BR> terms"have", "include"and"comprise"or their conjugates mean"including but not limited to."