Paper transport system

0001The present disclosure broadly relates to printing systems and, more particularly, to paper sheet transport within printing systems. A gateless diverter consists of adjoining concave and convex elements to direct the leading edge of paper in transport away from potential stubbing points in a paper path.

0002Known printing systems are generally capable of marking sheets of media of a variety of types (e.g., plain paper, bond paper, recycled paper, card stock, and transparencies), sizes (e.g., letter, legal, A3, A4) and/or in different orientations (e.g., long-edge feed, short-edge feed). Typically, a known printing system will include at least one media tray capable of receiving a bulk quantity (e.g., stack, package, ream) of sheets of media and introducing the bulk quantity to a suitable sheet feeding system or mechanism to advance individual sheets in an known manner. Often, known printing systems will include numerous media trays with each tray receiving a different type, size and/or orientation of sheet media.

0003Many known printing systems are capable of determining which particular one of a number of pre-defined sizes and/or orientations of sheet media have been loaded into the storage tray. Unfortunately, these and other known printing systems and media tray arrangements suffer from problems and disadvantages that can, in certain applications, limit the use and/or effectiveness of the same. Similarly, the transport of paper sheets within a printing system can pose difficulties due to stubbing and/or jamming within a paper path.

0004<patcit id="pcit0001" dnum="US20060237899A1"><text>US 2006/0237899 A1</text></patcit> (Mandel) discloses a system for transporting paper within a printing machine, comprising a paper path with several entry points and nips, wherein the paper path can act as an inverter for sheets entering from a duplex path of an image marking machine of the printing machine.

0005In one example, paper is transported within the printing system via a path located within a door. In particular, the door paper path transports one or more sheets vertically from a tray module to an image marking engine (IME). These sheets can be introduced from both a multi-sheet inserter (MSI) and a paper feed platform (PFP) and can act as an inverter for sheets entering from a duplex path of the IME. The proximity of the MSI and PFP entry chutes, coupled with the offset of nips within the paper path, provide potential stubbing points when feeding sheets from the tray module. Actuated diverters have traditionally been employed in conventional print system designs. Diverters, however, add cost to print system designs since extra components are required. Moreover, actuated diverters wear down mechanically and are unreliable for long term use which is required of most printing systems. What are needed are systems and methods that overcome the above referenced difficulties associated with paper transport within a print system.

0006In one aspect, a system for transporting paper to prevent stubbing within a printing machine comprising: <ul id="ul0001" list-style="none" compact="compact"><li>a paper path that has a first end and a second end and a width defined by a first wall located in opposition to a second wall that facilitates transport of one or more sheets of paper from the first end to the second end;</li><li>a first entry point located between the first end and the second end that allows one or more sheets to enter the paper path in succession;</li><li>a first nip that is adjacent to the first entry point that directs the leading edge of the one or more sheets away from the first entry point;</li><li>a second entry point located a distance from the first entry point that allows one or more sheets to enter the paper path;</li><li>a second nip that is adjacent to the second entry point that directs the leading edge of the one or more sheets away from the second entry point;</li><li>and is characterized in that the paper path can act as an inverter for sheets entering at the second end from a duplex path of an image marking machine of the printing machine, and comprises</li><li>a gateless diverter that directs the one or more sheets of paper through the paper path, the gateless diverter including a convex section that is adjacent to a concave section to divert a leading edge of each of the one or more sheets fed from the second end away from the second entry point and the first entry point, wherein the one or more sheets of paper transported from the first end to the second end are advanced to the convex section via the first nip and advanced through the concave section to the second nip.</li></ul>

0007In another aspect, we provide method for transporting paper to avoid stubbing within a printing machine, the paper transporting being along a paper path that has a first end, a second end, a first, a second and a third transport nip, and a first and a second entry point, the method comprising: <ul id="ul0002" list-style="none" compact="compact"><li>receiving a sheet of paper into the first end of the paper path, the sheet of paper has a leading edge;</li><li>advancing the sheet through the paper path via the third nip to the first nip, wherein the third nip and the first nip each include at least one pair of rollers;</li><li>directing the leading edge of the sheet away from the first entry point via the first nip, the first entry point is located on the side of the paper path;</li><li>advancing the sheet past the first entry point through a convex section and a concave section of the paper path, wherein the convex section is located adjacent to the concave section; and</li><li>directing the leading edge of the sheet away from a second entry point via a third nip, the second entry point is located on the side of the paper path;</li><li>advancing the sheet past the second end to an image marking engine of the printing machine,</li></ul> characterized in that the method comprises further the steps of entering the sheet at the second end from a duplex path of the image marking engine of the printing machine, directing the leading edge of the sheet away from the second entry point and the first entry point via the concave section and the convex section, as the sheet passes the second and first entry points.

0008<figref idref="f0001">FIGURE 1</figref> illustrates a paper path, in accordance with an aspect of the subject embodiment;

0009<figref idref="f0002">FIGURE 2</figref> illustrates a nip adjacent to an entry point, in accordance with an aspect of the subject embodiment;

0010<figref idref="f0003">FIGURE 3</figref> illustrates a paper path employed with an upper and mid door of a printing machine, in accordance with an aspect of the subject embodiment;

0011<figref idref="f0004">FIGURE 4</figref> illustrates a paper path utilized with a vertical paper path baffle, in accordance with an aspect of the subject embodiment; and

0012<figref idref="f0005">FIGURE 5</figref> illustrates a dimensioned view of the paper path, in accordance with an aspect of the subject embodiment.

0013The embodiments described herein relate to an 'S' shaped gateless diverter for transport of paper sheets within a printing machine. A novel curved section of a paper path starts just prior to a first entry point (e.g., for a paper feed platform chute) and ends at just after a second entry point (e.g., for a multiple sheet inserter chute). The radii of the concave / convex sections and transition points are designed to ensure that curled sheets being fed from a multiple tray module avoid stubbing on exit chutes of one or more ancillary feeders. This ensures that the leading edge of a sheet is directed towards the right hand paper path away from the chutes. Both the proximity of the first and second entry points, coupled with the fact that they are offset, ensures that potential stubbing issues are produced if a straight paper path is employed. This avoids the requirement for actuated diverter gates.

0014With reference to <figref idref="f0001">FIG. 1</figref>, a paper path 100 is illustrated that allows sheets of paper to be fed from a number of trays in a print system without stubbing. In one example, the paper path 100 can transport paper sheets from an entry point (e.g., a multi-tray module) 104 to an entry/exit point (e.g., an image marking engine) 106. Entry points 108 and 110 allow paper sheets to be fed into the paper path 100 at additional locations to accommodate various desired operations. As illustrated, the entry points 108 and 110 inherently include one or more potential stubbing points (e.g., tips) based on an angle of entry into the paper path 100. Pages can also be stubbed if a paper path includes excessively acute angles and/or radii that are overly restrictive relative to the size of sheets that are fed through a paper path.

0015In conventional printing machines, there are a number of potential stubbing points associated with a paper path. First, all sheets fed from a multiple (e.g., three) tray module are transported vertically upwards through a section of a paper path towards the IME. As the sheet passes the entry points 108 and 110, it must avoid stubbing on the entry chutes associated therewith. Stubbing is potentially a problem for three different types of curl: down curled sheets in the process direction, cross process curled sheets, or bowl curled sheets (a combination of both process and cross process curl).

0016Secondly, sheets fed from entry points 108 and 110 must avoid stubbing on the right side of the paper path as illustrated in <figref idref="f0001">FIG. 1</figref>. The worst case for this problem is down-curled media stubbing on the right hand guide. Third, sheets fed from entry point 106 (e.g., a duplex path) must avoid stubbing with both the entry points 108 and 110 as the sheet is transported from the top (e.g., IME) of the paper path 100. The leading edge of sheets from the entry point 106 in the duplex path must pass both the entry points 108 and 110 in order to enable larger (e.g., A3) sheets to be inverted. In particular, out-curled sheets pose a significant problem in terms of stubbing. It is to be appreciated that although paper sheets are discussed herein, substantially any material can be employed for sheets including acetate, velum, etc.

0017In order to insure stub free travel in either direction along the paper path 100, a concave section 112 and a convex section 114 are positioned adjacent to each other to create an 'S' shaped gateless diverter 116. As a sheet passes entry points 108 and 110, the concave portion 112 and convex section 114 direct the leading edge of a sheet (not shown) away from potential stubbing points. In one aspect, the gateless diverter 116 reduces cross-process and bowl curl of pages that conventionally causes paper to stub on one or more obstacles within a paper path.

0018It is to be appreciated that substantially any number of concave sections and corresponding adjacent convex sections can be employed to eliminate stubbing within the paper path 100. Moreover, the radii and angle of direction of transport can vary to accommodate one or more metrics associated with printing such as paper size, paper thickness, print application, etc. The location of such adjacent concave and convex sections can be related to particular features of the paper path 100 such as one or more stubbing points, entry chutes, and path distance for example.

0019In an exemplary operation, a sheet enters the paper path 100 from one of four entry points 104, 106, 108, and 110. Sheets that enter the paper path 100 via 108 are illustrated as path 1; sheets that enter the paper path 100 via 110 are illustrated as path 2; sheets that enter the paper path 100 via 104 are illustrated as path 3; and sheets that enter the paper path 100 via 106 are illustrated as path 4. In addition, four nips, 126, 128, 130, and 132 are located throughout the paper path 100 to facilitate transport of paper sheets as they pass therethrough. In one example, each nip includes a pair of rollers (or equivalent) that rotate in an appropriate direction when in contact with a paper sheet.

0020In one example, the entry point 108 receives one or more sheets from a multiple sheet inserter (MSI). The one or more sheets are transported through a left hand door of a printing system to an image marking engine (IME) 122 via exit/entry point 106. In another example, one or more sheets are received by the paper path 100 via entry point 110 from a paper feed platform (PFP) that docks to the side of the printing machine. The one or more sheets are transported vertically through a door to the IME.

0021Alternatively or in addition, one or more sheets are fed to the paper path 100 via entry point 104 from a three tray module (3TM). The one or more sheets travel vertically through a door past the entry points 108 and 110 to the IME 122 via entry/exit point 106. Once the sheets are processed by the IME 122, they can reenter the paper path 100 (via a duplex path) again through entry point 106. In one example, the one or more sheets are longer than a standard (e.g., 8½" x 11 ", A4) size. Such an excessive length can cause sheets to become stubbed on one or more obstacles within the paper path 100.

0022For instance, for an A3 or 11"×17" sheet, the lead edge can travel down the paper path past entry point 108. In conventional systems, as a sheet passes an entry point on a paper path, the leading edge can become stubbed. This is especially true as the sheet passes between entry points (e.g., between entry points 108 and 110). In order to mitigate such stubbing, the concave section 112 and the convex section 114 are adjacently placed between the entry points to divert the leading edge of one or more sheets away from the entry points 108 and 110 as they pass. The nips 126 and 128 can be placed adjacent to the entry points 108 and 110 respectively to facilitate transport of one or more sheets through the paper path 100 and/or to prevent stubbing.

0023<figref idref="f0002">FIG. 2</figref> illustrates the nip 126 that is utilized adjacent to entry point 108 as shown in <figref idref="f0001">FIG. 1</figref> above. The nip 126 includes a roll 204 and a roll 206. Although a single roll pair 204 and 206 is illustrated, it is to be appreciated that a plurality of nips and associated roll pairs can be located across the width of the paper path 100. The rolls 204 and 206 can be comprised of substantially any material such as rubber, plastic, steel, etc. to facilitate optimum contact with the paper sheets that are passed therethrough.

0024In one example, a sheet is transported past the entry point 108 via the nip 126 and past the entry point 110 via the nip 128. Because the entry points 108 and 110 are located on the left hand side of the paper path 100, the nips 126 and 128 are rotated as the paper sheets enter to divert the sheet to the right hand side of the paper path. In this manner, the leading edge of the paper sheet is moved as far from possible from the entry points to minimize the possibility of the sheet stubbing and/or directed down an undesired path.

0025To direct the sheet in a desired direction, the rolls 204 and 206 can be positioned in particular location relative to each other or one or more features of the paper path 100. For example, the roll 204 can be placed such that the diameter of the roll 204 is lower relative to the diameter of the roll 206. In addition, the center line of the rolls (e.g., location wherein the rolls 204 and 206 are in the closest proximity to one another), can be offset from the center line of the paper path. For instance, center line of the rolls 204 and 206 can be located offset to the right relative to the center line of the paper path. In this manner, the leading edge of the sheet can be directed to the right based on the relative force of the rolls 204 and 206 on the sheet as it passes through the nip 126.

0026The tip 210 is the point of divergence between the paper path 100 and the entry point 108. In one embodiment, the tip 210 is recessed from the paper path 100 to avoid sheet (e.g., duplex) stubbing or travelling down the incorrect path. Such tip 210 location provides a greater clearance for the leading edge of a sheet to pass the entry point 210 unencumbered. To further enhance control of the leading edge location within the paper path, a ramp 216 is situated just past the entry point 108 within the paper path 100. The ramp 216 is a recessed portion of the side wall of the paper path that is shared with the entry point 108. The ramp 216 can have substantially any radius relative to a center point 220. This radius can be based at least in part upon the paper size, paper thickness and printing operation performed within the printing machine.

0027In many printing machines, actuated diverters are employed to ensure that paper sheets travel along an intended path (e.g., the paper path 100). The paper path 100 must be robust to all potential stubbing points by taking into account up-curl, down-curl and cross process curl of the paper sheets. <figref idref="f0003">FIG. 3</figref> illustrates an upper door 310 and a mid door 312 of a printing machine that utilize the paper path 100 to transport paper sheets therethrough. Similarly, <figref idref="f0004">FIG. 4</figref> illustrates a paper path baffle 410 employed with a printing machine that includes the paper path 100. It is to be appreciated that the gateless diverter 116 can be employed in substantially any location within substantially any printing machine.

0028In one example, the upper door 310, the mid door 312, and the paper path baffle 410 can be center registered wherein all the nip pairs through each component are double rolls located in the center of the paper path. As a result, the extreme edges of the sheet are not controlled by the roller pairs which creates a number of potential stubbing points caused by cross process curl. Conventionally, gateless diverters have been employed in printing machines to overcome such deficiencies. However, a gateless diverter has not been contemplated with these components in the areas of a printing machine illustrated in <figref idref="f0003">FIGS. 3</figref> and <figref idref="f0004">4</figref>. One reason is due to the proximity of entry points 108 and 110 (e.g., MSI and PFP chutes) and the fact that they are slightly offset.

0029<figref idref="f0005">FIG. 5</figref> illustrates a dimensioned view of the paper path 100. It is to be appreciated that the dimensions are for illustrative purposes only and one or more dimensions can be modified within the scope of the embodiments described herein. A three-dimensional model was employed to verify a design for cross process and bowl curl. In particular, a path taken by extremities of sheets that are not controlled by the central nips. In one approach, sheets are fed with these three different types of curl to a stress level of 100mm radius of curvature (e.g., 12mm flat curl for a 60gsm sheet). All stubbing points were eliminated.

0030Further analyses ensured that two other potential issues with the design were eliminated. First, the severity of the radii of the concave / convex sections (e.g., convex section 112 and 114) were minimized to ensure Nip G in the simplex direction and Nip E in the duplex direction have sufficient drive to feed heavyweight sheets through the paper path 100. Software was employed to predict the slip between the Nip G and Nip E. The slip levels that were predicted were not significant.

0031The contact forces between the sheet and guides were also predicted and checked against the image-marking limit for solid ink. The speed of the rolls of Nip E and Nip F were set to their worst case levels to either create a buckle between the nips or to stretch the sheet across the guides. The contact forces were checked against recommended guidelines for solid ink to PC-ABS, ABS and Steel to ensure that the image on the duplexed sheets was not damaged. The forces were well within the limits for all three materials.