The field of the invention is printers and copiers, and particularly decurling mechanisms.
Handling of paper and other printing media in printers and copiers often involves having the paper travel with or around a roller. This generally occurs, for example, in printing an image on paper using an impression roller, especially for heated printing, as well as in some systems flipping paper over before printing a second side, or in flipping over a two-sided original page that is being copied, and in some systems conveying paper from an input tray to an output tray. Because paper tends to retain its curl to some extent after it is passed around a roller, printers and copiers use various methods of decurling paper, so that the final printed page, as well as the original paper being copied in a copier, is flat. U.S. Pat. No. 5,450,102, to Ishida et al, describes a decurling mechanism for a printer in which paper is decurled by bending it around a roller in the opposite direction from the direction in which it acquired its curl, but along the same axis.
Other printers decurl paper by bending it along an axis orthogonal to the original axis along which it was curled. For example, guides, mounted on walls to the sides of the paper, press against the paper from the sides, bending the paper as it falls into an output area. In some printers, the reaction force of the paper on the guides pushes the guides out of the way, thereby limiting the force that the guides exert on the paper. In some of these printers, there are counter-weights on the guides, so that the guides swing back up, to press against the next sheet of paper, after the paper falls into the output area. If the counter-weights nearly balance the weight of the guides, then the force required to push the guides out of the way is very small, and the guides exert only a very small force to bend the paper. Such an arrangement may be advantageous particularly when the paper is very light-weight and bends easily. However, the counter-weights take up room.
An aspect of an embodiment of the invention concerns a decurler with guides which push against the sides of a paper, bending it along an axis orthogonal to the axis along which it acquired its curl, thereby decurling it. In some embodiments of the invention, this decurling occurs as the paper is falling into an output area, for example an output tray, or an area from which the paper is conveyed to another location for further printing or processing. The guides are dynamic guides, pushed out of the way by the paper, and swinging back when the paper has passed, so that the guides are in position to decurl the next paper. Instead of using counter-weights as in some of the prior art, the dynamic guides are mounted on hinges which have an axis that is oriented at an angle slightly different from vertical. This arrangement takes up less space and has fewer parts than guides which use counter-weights. Because the hinges are nearly vertical, only a small force is needed to push the dynamic guides out of the way, so the guides exert only a small force on the paper when bending it. The guides can be pushed out of the way by a force that is approximately equal to the weight of each guide, times the angle that the hinge is oriented away from vertical. The low force of the dynamic guides is suitable for decurling light-weight paper. The best angle to use for the axis of the hinge depends on the length and shape of the guide and on the weight, dimensions and composition of the paper or other printing media, and is optionally determined experimentally.
An aspect of some embodiments of the invention concerns a strip which is attached at one end to a wall above the back of an output area where paper is dropped. The other end of the strip hangs down into the path of the paper. As the paper is brought from the back of the output area into a position above the output area, the paper lifts up the free end of the strip. As a trailing portion of the paper starts to fall down towards the output area, and especially when a leading portion of the paper is released, for example by releasing a suction system, the free end of the strip pushes down against the trailing portion of the paper, pushing the paper down to the output area. This prevents a problem, which can occur with light-weight paper, that the paper floats down too slowly and has time to become folded over as it falls, for example due to air currents.
Optionally, there are guides, and the hanging strip pushes the paper against the guides, to decurl the paper. Optionally, the guides are dynamic guides, optionally mounted on hinges at a small angle away from the vertical, so that the guides move out of the way easily. Then the hanging strip can push the paper down with more force, without the strip tearing the paper or bending it too sharply. In some embodiments of the invention and for some grades of paper, the extra force exerted on the paper by the strip, beyond the weight of the paper, is optimal for decurling the paper. The hanging strip and the off-vertical hinged dynamic guides thus work particularly well when used together, but they can also be used separately.
There is thus provided, in accordance with an embodiment of the invention, a decurler to decurl a curled printing media being transported into a release area, the decurler comprising:
a) at least one guide arm against which the printing media presses, positioned and adapted to bend the printing media along an axis substantially in a direction of transport thereof; and
b) a hinge on which the guide arm is mounted, the hinge being oriented at an angle of between 0.25 degrees and 20 degrees from vertical,
wherein a reaction force that the guide arm exerts on the printing media is suitable for decurling the printing media.
Optionally, the guide arm is mounted so that it remains in an equilibrium position to receive the printing media when there is no force on the guide arm, but the guide arm swings on the hinge away from the equilibrium position when the printing media presses vertically on the guide arm.
In an embodiment of the invention there is a second guide arm, and the two guide arms exert substantially equal forces on the printing media on opposite edges thereof, thereby bending it.
Optionally, the two guide arms are substantially mirror images of each other.
Optionally, the force that the guide arm exerts on the printing media is exerting on a trailing portion of the printing media.
Optionally, the guide arm includes a substantially flat contact surface, and the printing media presses against the contact surface when it presses against the guide arm.
In an embodiment of the invention, the guide arm is at least twice as long along a longest axis thereof as it is wide across any axis perpendicular to the longest axis.
Optionally, the guide arm is at least five times as long along the longest axis thereof as it is wide across any axis perpendicular to the longest axis.
Optionally, the longest axis is oriented at an angle to the vertical, for any position of the guide arm as it swings on the hinge.
Optionally, the angle of orientation of the long axis to the vertical is between 20 and 50 degrees, for any position of the guide arm as it swings on the hinge.
Optionally, the surface of the guide arm is smooth enough where the printing media presses against said surface so that the guide arm does not abrade the printing media.
Optionally, the guide arm has an L-shaped cross-section transverse to its longest axis.
In an embodiment of the invention, the hinge comprises an upper socket, an upper pin which fits into the upper socket, a lower socket, and a lower pin which fits into the lower socket, and the upper and lower pins are substantially collinear, and oriented at the angle from the vertical at which the hinge is oriented.
Alternatively, the hinge comprises an upper socket, an upper pin which fits into the upper socket, a lower socket, and a lower pin which fits into the lower socket, and the upper and lower pins are oriented substantially vertically, and displaced laterally from each other by a distance such that a line passing through both pins is oriented at the angle from the vertical at which the hinge in oriented.
Optionally, the angle from the vertical at which the hinge is oriented is less than or equal to 1 degree.
Alternatively, the angle from the vertical at which the hinge is oriented is between 1 and 2degrees.
Alternatively, the angle from the vertical at which the hinge is oriented is between 2 and 5 degrees.
Alternatively, the angle from the vertical at which the hinge is oriented is greater than 5 degrees.
Optionally, the guide arm is less than or equal to 40 mm long in its longest dimension.
Alternatively, the guide arm is between 40 mm and 80 mm long in its longest dimension.
Alternatively, the guide arm is between 80 and 120 mm long in its longest dimension.
Alternatively, the guide arm is greater than 120 mm long in its longest dimension.
Optionally, the guide arm has a mass less than or equal to 1 gram.
Alternatively, the guide arm has a mass between 1 and 2 grams.
Alternatively, the guide arm has a mass between 2 and 5 grams.
Alternatively, the guide arm has a mass between 5 and 10 grams.
Alternatively, the guide arm has a mass between 10 and 20 grams.
Alternatively, the guide arm has a mass greater than 20 grams.
Optionally, the guide arm can swing on its axis only over a limited range that does not include a position at which the guide arm has a local minimum in gravitational potential energy.
Optionally, there is a flexible strip which hangs down and pushes against a middle portion of the printing media as it moves in the feed direction, causing the printing media to bend along an axis substantially parallel to the direction of transport.
There is thus also provided, in accordance with an embodiment of the invention, a decurler to decurl a curled printing media as it moves in a direction of transport toward a release area in a printer or copier, comprising a flexible strip which hangs down and pushes against a middle portion of the printing media as it moves in the feed direction, causing the printing media to bend along an axis substantially parallel to the direction of transport.
Optionally, the strip pushes against a trailing portion of the printing media.
Optionally, there is at least one other strip which hangs down and pushes against the middle portion of the printing media as it moves in the direction of transport, causing the printing media to bend along an axis substantially parallel to the direction of transport.
Optionally, the strip has a thickness between 0.05mm and 0. 15mm.
Alternatively, the strip has a thickness between 0.1 5mm and 0.25mm.
Alternatively, the strip has a thickness between 0.25mm and 0.8mm.
Optionally, the strip has a width between 3 mm and 8 mm.
Alternatively, the strip has a width between 8 mm and 16 mm.
Alternatively, the strip has a width between 16 mm and 40 mm.
In an embodiment of the invention, the strip is made of steel.
Optionally, the strip is made of spring stainless steel.
Alternatively, the strip is made of tempered tool steel.
There is thus further provided, in accordance with an embodiment of the invention, a printer or copier for printing an image on a printing media, comprising:
Optionally, the transport mechanism comprises at least one suction arm with a suction cup at its end, which at least one suction arm picks up the printing media from a pick-up position above the release area, swings the paper to a release position above the release area, and releases the paper at the release position so that it falls into the release area.
Optionally, the at least one suction arms passes to one side of each of the at least one strips as the at least one suction arms swing around.
Exemplary embodiments of the invention are described in the following sections with reference to the drawings. The drawings are generally not to scale and the same or similar reference numbers are used for the same or related features on different drawings.
In addition to suction arm 106, there is also a second suction arm 110, which picks up the paper from suction arm 106, and which rotates counter-clockwise at the same angular rate as suction arm 106, and whose end follows a circular path 112. Finally, there is a third suction arm 114, which picks up the paper from suction arm 110, and which rotates clockwise at the same angular rate as suction arms 106 and 110, and whose end follows circular path 116. Suction arm 114 drops paper 102 into an output area 118. Optionally, output area 118 is an output tray. Alternatively, paper is conveyed from output area 118 to another location for further processing, for example for printing the other side of the paper.
Optionally, the three suction arms do not all rotate at the same angular rate. However, if their rotation rates at least have ratios that are the ratios of small integers, then the suction arms will periodically align at the proper points for transferring the paper from one suction arm to another. In a particular example of the invention, the ratios of the diameters of rollers 104, circle 108, circle 112 and circle 116 is 1:2:2:3.
Generally, each suction arm shown in the drawing represents a plurality of suction arms lined up in a direction normal to the plane of the drawing. Optionally, one or two of the suction arms shown in
Optionally, instead of one or more of the suction arms shown in
Although it looks in
Optionally, the paper hits a paper stop 121 and falls into tray 118, where it is pushed against alignment stop 119. The construction of a preferred embodiment of this part of the system is described in more detail in a concurrently filed PCT application entitled “Paper Stop”, the disclosure of which is incorporated by reference. Alternatively, a paper tray and stop according to the prior art can be used.
In an embodiment of the invention, dynamic guide 210 has a hinge 214, which is mounted on a bracket 216, which is attached to a wall 218 on one side of output area 118. Similarly, dynamic guide 212 has a hinge 220 which is mounted on bracket 222, attached to a wall 224 on the side of output area 118 opposite to wall 218. Hinges 214 and 220 both have axes that are displaced by a small angle from the vertical. The angle is exaggerated in
When paper 102 presses against dynamic guides 210 and 212, they swing on their hinges toward the walls they are mounted on, moving away from each other and allowing paper 102 to fall into output area 118. Because of the tilt of the axis of hinge 214 and hinge 220, dynamic guides 210 and 212 swing back away from walls 218 and 224, towards the center of output area 118, after paper 102 has fallen down and no longer presses against them, ready to receive the next paper. Because the hinge axes are tilted at only a small angle, little force is required to push dynamic guides 210 and 212 away. Thus, dynamic guides 210 and 212 exert only a small reaction force on paper 102. This small force is appropriate for decurling a very light-weight paper.
Optionally, there is only one dynamic guide, which presses against only one side of paper 102, bending it and decurling it. Optionally, in this case, an opposing force on the other side of paper 102 is provided by inertia, or friction, or by paper 102 leaning against the wall, or a fixed guide, on the other side. However, using two dynamic guides symmetrically arranged, as shown in
In the embodiment of
The horizontal force needed (in a direction normal to the wall) to push dynamic guide 210 toward the wall is approximately equal to the weight of dynamic guide 210 times the small angle that axis 316 makes to the vertical, and this force is approximately independent of the position of dynamic guide 210 as it swings around axis 316. Thus, there is an upper limit to how much horizontal force dynamic guides 210 and 212 exert on the paper, as the paper falls to the output area. For example, if each dynamic guide has a mass of about 5 grams, and hence a weight of about 0.05 newtons, and if each axis 316 is oriented at an angle of about 2 degrees (about 1/30 of a radian) from vertical, then the dynamic guides will not exert a force of more than about 0.0017 newtons from each side, about 1/30 of their weight. This calculation neglects the inertia of the dynamic guides, but if the dynamic guides are accelerating to the sides at much less than 0.3 m/s2, then the inertial force can be neglected. Alternatively, the mass of each of dynamic guides 210 and 212 is about 1 gram, or 2 grams, or 10 grams, or 20 grams, or 50 grams, or less than 1 gram, or more than 50 grams, or any intermediate mass. The optimum mass to use for a given weight of paper or other printing media is optionally determined experimentally. Although the two dynamic guides need not have the same mass, using mirror image guides of the same mass and shape will result in symmetric forces being exerted on the paper from both sides, which has the potential advantage of allowing the paper to stack more evenly, avoiding paper jams.
Optionally, instead of pins 308 and 310 being coaxial with axis 316 which is oriented obliquely, upper pin 308 and lower pin 310 are each oriented vertically, but they are displaced slightly from each other laterally, and the same is true of pin holders 312 and 314. This is shown in
Alternatively or additionally, a stop, not shown in
Optionally, a stop is also used to prevent dynamic guide 210 from reaching an angle where its gravitational potential energy is at a minimum. From such an angle, the dynamic guide will be unstable to a force pushing it toward axis 316, since it will swing quickly in one direction or the other with only a small change in the direction of the force. If the decurler operated with dynamic guide 210 at such an unstable angle, its behavior might be unpredictable.
As shown in
Optionally, dynamic guide 210 has an L-shaped cross-section, and the corner of the L is the first part of the dynamic guide to touch the paper as it falls. This configuration, with an edge that is not too sharp, has the potential advantage that the paper does get abraded as it falls. Optionally, other cross-sectional shapes without sharp edges are used. Another potential advantage of an L-shaped cross-section, or other shapes such as an I-beam cross-section, as opposed to a flat cross-section, is that it gives the dynamic guide additional stiffness, even if it is made very thin in order to keep its weight low. Alternatively, the dynamic guide has a flat cross-section, but has smooth enough edges so that they do not abrade, and is thick enough so that it is not too flexible.
After the leading portion of paper 102 is released by suction arm 114, and paper 102 starts to fall toward output area 118, as shown in
If strip 124 does not extend across the whole width of the paper, but only across a middle portion of the width of the paper, then strip 124 will tend to bend paper 102 in the same way as dynamic guides 210 and 212, helping to decurl it even before suction arm 114 releases paper 102. After suction arm 114 releases paper 102, strip 124 helps to push trailing portion 130 of paper 102 against dynamic guides 210 and 212. In the case where the paper is very light weight, this prevents the paper from floating down slowly, which might result in the paper folding over as it falls, or deflecting to the side, due to air currents for example, and causing the paper to crease after it reaches output area 118, for example from the weight of additional sheets of paper that fall on top of it, or causing the paper to be improperly aligned in output area 118. Strip 124 optionally serves this purpose even if there is no decurler present, or if the decurler is of a kind known in the prior art, fixed or dynamic, rather than the kind shown in
The length of strip 124 is preferably such that the strip is pushing against the paper when the paper is released and hits the stop. Optionally the end of the strip overlaps the trailing edge of the paper by about 2 cm at this time. The strip then pushes the trailing edge down, at the same time as the leading edge falls into the tray.
Optionally, the weight per length and the stiffness of strip 124, and the location of the bottom of strip 124 when it is hanging down, are chosen so that the force with which strip 124 pushes paper 102 against dynamic guides 210 and 212, and/or the force with which strip 124 pushes down paper 102 before suction arm 114 releases paper 102, is appropriate for decurling the paper used and for removing the paper from guide 125.
Optionally, strip 124 is light enough so that it is does not scratch, crease or tear the paper when it pushes against the paper, and it does not pull the paper off suction cups 114 or guide 125 before suction cups 114 are in position to release the paper. For example, strip 124 is 0.2 mm thick, 12 mm wide, and made of AISI 302 stainless spring steel, or tempered SAE 1070 tool steel. Alternatively, strip 124 is 0.1 mm thick, or 0.4 mm thick, or has another thickness, and/or strip 124 is 25 mm wide, or 6 mm wide, or has another width, and/or strip 124 is made of another kind of steel, or another metal, or plastic, or another material. Optionally, if strip 124 is made of a material of a different density or a different elastic modulus than spring steel or tool steel, then its thickness and/or width are adjusted from the values mentioned above so that strip 124 exerts approximately the same force on the paper. Alternatively, strip 124 exerts a greater force or a smaller force on the paper than it would with this composition and these dimensions, depending on the lightest paper for which it is designed.
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 terms “have”, “include” and “comprise” or their conjugates mean “including but not limited to.”
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/IL03/00351 | 4/30/2003 | WO | 00 | 4/8/2008 |