Patent Publication Number: US-6209862-B1

Title: Print media pick and feed anti-wrap method and apparatus

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to print media feeding for hard copy printing and plotting apparatus and, more particularly, to a cut-sheet, print medium, pick and feed mechanisms. 
     2. Description of Related Art 
     Many office products such as computer printers and plotters, plain paper facsimile machines, and photocopiers use mechanisms that pick a sheet of paper from a stack of media in an input tray and feed a single sheet of pre-cut printing medium (for example, a sheet of paper of a particular size such as standard letter size, legal size, or A4 (metric), or transparencies, or envelopes) into the hard copy producing apparatus. These mechanisms are generically referred to as “sheet feeders.” 
     Sheet feeders usually are provided with an adjustable or replaceable media cartridge, tray, or other type of stacker in which a user can stack multiple cut-sheets of the media of choice. The use of media cartridges (essentially easily substituted paper trays) adapted to the various styles of media provide a mechanism for quick changes between any particular printing medium by the user. Upon receiving a media feed command (“FEED”) from the hard copy machine controller electronics, a sheet picking device is actuated to deliver the top sheet from the stack into the hard copy machine. Under proper operating conditions, a sheet picking mechanism associated with the stacker should deliver a single sheet of the print medium to the hard copy machine input mechanism, such as a set of pinch rollers used for registration and feed into the actual printing subsystem of the machine. 
     Misfeeds, multiple sheet feeds, paper jams, and the like are common problems associated with sheet feeders. FIGS. 1 and 1A depict a typical problem of a misfeed caused by a premature bending (“wrap” or “wrap-back”) of a picked sheet before its leading edge can be captured by an input mechanism (not shown; generally located close to the exit plane of the leading edge of a picked sheet) used to transport the sheet to a printing station. FIG. 1 shows a normal feed of a sheet  100  from a stack  101  of sheets in an input bin  102  by a pick mechanism  103  having a feed arm  104  and a motorized pick roller  105 . In FIG. 1 the sheet  100  is being properly fed up the input tray angled wall  106 . The details of a stack loader located below a hard copy apparatus&#39; printing mechanisms are shown in U.S. Pat. No. 5,507,478 by Nottingham et al. for PRINTING MEDIA STATUS SENSING, assigned to the common assignee herein and incorporated herein by reference. 
     FIG. 1A shows a misfeed in which the picked sheet  100  has wrapped around the pick mechanism  103  before properly exiting the bin and being received by the input feed mechanism. High humidity tends to exacerbate such a problem. Thin media or media that has any inherent curl in it is highly susceptible to the problem. 
     One solution to the problem is to flatten out the feed angle. U. S. Pat. No. 5,876,133 by Kleln et al. for a SHEET PRESENTER AND METHOD OF USING SAME has an elongated platform adapted to engage a printer. A pair of spaced walls extend upwardly from the platform to support pivotally an arm at one end thereof. A motor disposed at another end of the arm is operatively connected to a drive roller wherein the mass of the motor urges the corresponding end of the arm downwardly to engage a sheet. This however requires a much larger workspace footprint than a printer having a contained input tray located below the printing zone such as illustrated by FIGS. 1 and 1A and preferable in the marketplace. 
     Another solution is to provide a paper guide fixed to a pivotal feed arm  104 . However, such paper guides move with the arm. When the rollers of the feed arm are on a full stack, the paper guides protrude above the highest level of the feed arm, requiring extra height in the media bin to accommodate them. If the guides are made to be very short to minimize the amount that they protrude above the feed arm&#39;s highest position, they will not be effective when the paper stack is low and the feed arm pivoted into a more vertical than horizontal orientation. The picked sheet of a low stack will tend even more to wrap around the feed arm before reaching the top of the wall  106  where it can be captured by transport rollers. 
     Therefore, there is a need to facilitate the transfer of a sheet of print media from an internal input supply stack to a hard copy machine&#39;s printing zone. 
     SUMMARY OF THE INVENTION 
     In its basic aspects, the present invention provides guide device for a cut-sheet print media stack bin having a sheet egress guide wall associated with a pick mechanism, including: fixedly mounted substantially parallel to sheets stacked in said bin, a member having a reach such that a guiding end is substantially proximate an exit extremity of the guide wall; and a biased flexible guide attached to said member at a position distal of said guiding end, wrapped about said reach, and attached to said pick mechanism wherein moving said pick mechanism extends and retracts said flexible guide such that said flexible guide between said reach and said pick mechanism provides an anti-wrap barrier to the sheets during egress from said bin. 
     In another basic aspect, the present invention provides a method for preventing wrap of a picked cut-sheet of paper about a stack-following pick mechanism in an input bin, including the steps of: mounting a flexible member in fixed relationship to said bin and coupled to said pick mechanism; and moving a surface of the flexible member in coordination with said pick mechanism to form a closed exit path from said bin. 
     In another basic aspect, the present invention provides a print media anti-wrap device including: coupled to a pick device in a paper supply, a mechanism for maintaining a closed print media egress path configuration such that a leading edge of exiting paper is guided out of the supply and prevented from wrapping back onto the pick device. 
     Some of the advantages of the present invention are: 
     it provides a mechanism for preventing wrapping of a picked sheet of print media in an input bin; and 
     it does not increase the height of the input bin. 
     The foregoing summary and list of advantages is not intended by the inventor to be an inclusive list of all the aspects, objects, advantages and features of the present invention nor should any limitation on the scope of the invention be implied therefrom. This Summary is provided in accordance with the mandate of 37 C.F.R. 1.73 and M.P.E.P. 608.01(d) merely to apprise the public, and more especially those interested in the particular art to which the invention relates, of the nature of the invention in order to be of assistance in aiding ready understanding of the patent in future searches. Other objects, features and advantages of the present invention will become apparent upon consideration of the following explanation and the accompanying drawings, in which like reference designations represent like features throughout the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 (Prior Art) is a schematic illustration of a known manner print media bin and pick mechanism showing a normal sheet pick. 
     FIG. 1A (Prior Art) is a schematic illustration of a known manner print media bin and pick mechanism as in FIG. 1 but showing a wrap problem. 
     FIG. 2 is a first embodiment of the present invention. 
     FIG. 3 is an alternative embodiment of the present invention. 
     The drawings referred to in this specification should be understood as not being drawn to scale except if specifically annotated. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Reference is made now in detail to a specific embodiment of the present invention, which illustrates the best mode presently contemplated by the inventor for practicing the invention. Alternative embodiments are also briefly described as applicable. The term “paper” is used hereinafter to be synonymous with all forms of print media; no limitation on the scope of the invention is intended nor should any be implied. 
     FIG. 2 depicts in schematic form a first embodiment of the present invention. At least one paper guide  201  device is fixedly mounted by a stanchion  202  member to a chassis  203  of the hard copy apparatus or to a fixed frame member of the input bin  102 . An arm  204  member extends from one end  204 ′ attached to the stanchion  202  in a substantially parallel orientation to the stack  101 . The arm  204  has a second end  204 ″ reach which is proximate the upper reach of the angled wall  106  of the bin  102 . Mounted at the second end  204 ″ of the arm  204  is an idler roller  205 . In a low cost alternative, the idler roller  205  can be replace with a convex radius, smooth, surface member at the second end  204 ″ of the arm  204 . A flexible paper guide  206  is connected at a first end  206 ′ to the stanchion  202  by a substantially linear force biasing mechanism  207 , such as a spring. The flexible paper guide  206  in a preferred embodiment is a Mylar™ (a brand name for polyester film compounds) sheet because of its combined flexibility, strength, and low coefficient of friction. Other exemplary materials which may be employed are thin, flexible plastic, cloth, string or wire. A second end  206 ″ of the flexible paper guide  206  is affixed to the feed arm  104  at the pick roller  105  or to the pick roller axle. It will be recognized by those skilled in the art that this cantilevered arm  204  is one implementation and that any surface or mechanism that will support the roller-wrap point- 205  for the flexible guide  206  may be employed. 
     In operation, as the stack  101  of cut-sheet media is depleted, the pick mechanism  103  pivots and the pick roller  105  moves downwardly, away from the angled wall  106  and toward the center of the stack  101 . As it pivots, the pick mechanism  103  pull the flexible paper guide  206  against the bias  207  around the idler roller  205 . A picked sheet  100  is always guided between the angled wall  106  and the descending surface of the flexible paper guide  206 . Thus, acting together, the wall  106  and the surface of the flexible paper guide  206  form a substantially closed, relatively narrow, exit path for the picked sheet  100 . Any tendency of the sheet  100  of picked media to wrap is deflected back toward the angled wall  106  and toward the hard copy apparatus input paper transport mechanisms (not shown). 
     FIG. 3 is an alternative embodiment of an anti-wrap mechanism for a print media input bin. A small, solid, wrap deflector  301  is affixed to the feed arm  104 . A known manner mechanical or electromechanical, stack lift  303  is provided in the bin  102  below the stack  101 . If at all, the feed arm  104  swings only through a very small angle. The deflector  301  can be attached to the arm  104  adjacently to a modified, short angled wall  106 ′ of the bin  102 . Since the arm  104  is substantially in a fixed orientation, the deflector  301  can be small and does not increase the overall height of the bin  102 . 
     Thus, in accordance with the present invention there is a method and apparatus for preventing wrap-back of print media into a supply during a pick cycle provides a closed egress path regardless of orientation of a pick mechanism to the paper supply. In an exemplary embodiment, a biased, flexible member is mounted between a fixed position and a moving pick device such that the flexible member follows the pick device as the stack of print media depletes. 
     The foregoing description of the preferred embodiment of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form or to exemplary embodiments disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in this art. For example, the anti-wrap method and apparatus taught herein may be used in conjunction with rolled or fan-fold form of print media. While the primary paper path guide is shown as an angled wall of the bin itself, separate paper path guides are also known in the art. Similarly, any process steps described might be interchangeable with other steps in order to achieve the same result. The embodiment was chosen and described in order to best explain the principles of the invention and its best mode practical application, thereby to enable others skilled in the art to understand the invention for various embodiments and with various modifications as are suited to the particular use or implementation contemplated. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents. Reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather means “one or more.” Moreover, no element, component, nor method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the following claims. No claim element herein is to be construed under the provisions of 35 U.S.C. Sec. 112, sixth paragraph, unless the element is expressly recited using the phrase “means for. . ..”