Patent Publication Number: US-7717417-B2

Title: Devices for improving the reliability of feeding media sheets within an image forming device

Description:
BACKGROUND 
   The present application is directed to methods and devices for moving media sheets in an image forming device and, more specifically, to methods and devices for preventing and/or reducing transverse buckling of media sheets within the image forming device. 
   An image forming device, such as a color laser printer, facsimile machine, copier, all-in-one device, etc, includes a media feed system for introducing and using media sheets. The media feed system includes an input area where media sheets are initially placed prior to being introduced into a media path. A pick mechanism may also be located in the input area to contact and move a media sheet from the input area and into the media path. The proper functioning of the device requires that media sheets are fed reliably and consistently, as well as maintaining the proper timing between media sheets. 
   New image forming devices are trending towards lower cost, smaller height/footprint, and higher print quality. The smaller sizes have various advantages including that the devices fit within a smaller workspace and a reduction in shipping and packaging costs. In order to conserve space, a primary input tray and a multipurpose feeder may be located in the same general horizontal plane. 
   SUMMARY 
   The present application is directed to devices and methods for moving media sheets in an image forming device. In one embodiment, a contact member includes a contact roller that contacts a top-most media sheet in a stack of media sheets positioned on a support surface in an input area of the image forming device. A hub extends outward from an axial side of the contact roller. The hub includes a smaller diameter than the contact roller, forming a gap between the hub and the top-most media sheet when the contact roller is in contact with the top-most media sheet. The hub prevents or reduces transverse buckling of the top-most media sheet when it is moved from the stack of media sheets. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic view of an input mechanism according to one embodiment. 
       FIG. 2  is a schematic view of an image forming device according to one embodiment. 
       FIG. 3  is a perspective view of an input mechanism according to one embodiment. 
       FIG. 4  is a perspective view of a contact roller and hub according to one embodiment. 
       FIG. 5  is schematic end view of a contact roller and a hub according to one embodiment. 
       FIG. 6  is schematic end view of a contact roller and a hub according to one embodiment. 
       FIG. 7  is schematic end view of a contact roller and a hub according to one embodiment. 
       FIG. 8  is schematic end view of a contact roller and a hub according to one embodiment. 
       FIG. 9  is perspective view of a contact roller and hub according to one embodiment. 
       FIG. 10  is a perspective view of a contact roller and hub according to one embodiment. 
       FIG. 11  is a perspective view of an input mechanism according to one embodiment. 
   

   DETAILED DESCRIPTION 
   The contact member  15  includes a contact roller  14  that contacts a top-most media sheet in a stack of media sheets  12 . The stack of media sheets  12  is positioned on a support surface  101  in an input area  102  of the image forming device  100  ( FIG. 2 ). A hub  17  extends outward from an axial side of the contact roller  14 . The hub  17  includes a smaller diameter than the contact roller  14 . A gap  19  is formed between the hub  17  and the top-most media sheet  12  when the contact roller  14  is in contact with the top-most media sheet  12 . The hub  17  prevents or reduces transverse buckling of the top-most media sheet  12  when it is moved from the stack of media sheets  102 . 
   To understand the context of the present application,  FIG. 2  depicts a representative image forming device  100 . The input area  102  includes a support surface  101  to receive a stack of media sheets  12 . In this embodiment, the support surface  101  is formed by an input tray. The contact member  15  may include the contact roller  14  and the hub  17  and is positioned adjacent to the support surface  101  for the contact roller  14  to contact and introduce the media sheets  12  into a media path  104 . Input area  102  may also include a multipurpose feeder  103 . Multipurpose feeder  103  includes a support surface  101  to support one or more media sheets  12 , and a contact member  15  including a con tact roller  14  and a hub  17  to contact and move the media sheets  12  into the media path  104 . 
   Media sheets  12  are moved from the input area  102  and fed into a primary media path  104 . One or more registration rollers  105  align the media sheets  12  and precisely control its further movement along the media path  104 , A media transport belt  106 S forms a section of the media path  104  for moving the media sheets  12  past a plurality of image forming units  107 . Color printers typically include four image forming units  107  for printing with cyan, magenta, yellow, and black toner to produce a four-color image on the media sheet  12 . 
   An imaging device  108  forms an electrical charge on a photoconductive member within the image forming units  107  as part of the image formation process. The media sheet  12  with loose toner is then moved through a fuser  109  that adheres the toner to the media sheet  12 . An exit roll  10  forming a nip with a nip roll  110  is positioned at an output area. The exit roll  10  is driven by a motor  120  and rotates in a forward direction to expel the media sheet  12  from the device  100  and out to an output tray  112 . Alternatively, the exit roll  10  may rotate in a forward direction for a limited time until a trailing edge of the media sheet  12  passes an intersection point  113  along the media path  104 . The exit roll  10  is then rotated in a reverse direction to drive the media sheet  12  into a duplex path  114 . The duplex path  114  directs the inverted media sheet  12  back through the image formation process for forming an image on a second side of the media sheet  12 . 
   Examining the input area  102  now in more detail,  FIG. 3  illustrates one embodiment of an input mechanism  90  positioned at the support surface  101 . A dam  30  may be positioned at one end of the support surface  101  to direct the media sheets  12  from the input area  102  into the media path  104 . The darn  30  may be part of an input tray (as illustrated in  FIG. 3 ), or may be part of the body of the device  100 , as illustrated at the multipurpose feeder  103  of  FIG. 2 . As the input mechanism  90  moves a top-most media sheet  12  from the media stack, a normal buckle may be formed in the sheet  12  that is substantially perpendicular to the direction of feed. The normal buckle ensures that a single media sheet is moved from the stack and prevents or reduces simultaneously moving multiple sheets. The single sheet  12  moves from the stack, contacts the dam  30 , and is directed upward into the media path  104 . 
   The input mechanism  90  includes a pick arm  20  pivotally positioned or a shaft  24 . A drive shaft  16  extends outward from a distal end of the pick arm  20 . In one embodiment as illustrated in  FIG. 2 , a gear train  81  is positioned within the pick arm  20  and extends between a pick motor  80  and the drive shaft  16 . Activation of the pick motor  80  causes rotation of the drive shaft  16 . 
   One or more contact rollers  14  are attached to the drive shaft  16 . In the embodiment of  FIG. 3 , a pair of contact rollers  14  is attached to the shaft  16  with one on each side of the pick arm  20 . The pivoting orientation of the pick arm  20  maintains the contact rollers  14  in contact with a top-most media sheet  12  on the support surface  101 . The contact rollers  14  are typically constructed of a material with a high coefficient of friction to reduce slippage with the topmost media sheet  12  during rotation of the contact roller  14 . 
   A cantilevered hub  17  has one end connected to an axial side of contact roller  14  and has a free end extending outwardly from the axial side of the contact roller  14 . Hub  17  extends outwardly from the contact roller  14  in a direction away from the pick arm  20  (see  FIGS. 1 and 3 ). As illustrated in  FIG. 4 , hub  17  is positioned coaxially with the contact roller  14  and drive shaft  16  along a longitudinal axis A. The contact roller  14  has a width W 1  that extends along the axis A, and the hub  17  has a width W 2  along the axis A. The width W 1  is selected to provide adequate contact with the top-most media sheet to move the sheet  12  away from the support surface  101 . The width W 2  of the hub  17  is selected in one embodiment such that the hub  17  extends over at least a portion of the top-most media sheet  12 . In one embodiment, media sheets  12  are side justified against an edge  109  of the input area  102 . The input mechanism  90  is positioned and the width W 2  is selected such that the hub  17  extends over an edge of the media sheet  12 . In one embodiment, W 2  is greater than W 1 . 
   A schematic end view of the contact roller  14  and hub  17  is shown in  FIG. 5 . In one embodiment, a length L 1  of the contact roller  14  is greater than a length L 2  of the hub  17 . The difference between L 1  and L 2  defines the gap  19  between the hub  17  and the top-most media sheet  12  on the support surface  101 . In one embodiment, the gap  19  is about 0.5 mm. The hub  17  may be substantially solid as shown in  FIG. 5 , or may have a hollow interior as shown in  FIG. 3 . 
   The cross-sectional shape of the hub  17  may vary.  FIG. 5  illustrates one embodiment with both the contact roller  14  and the hub  17  having circular cross-sectional shapes.  FIG. 6  illustrates an embodiment with a rectangular cross-sectional shape, and  FIG. 8  illustrates a polygonal cross-sectional shape. Additionally, the hub  17  may not be symmetrical with respect to the cross sectional shape of the contact roller  14  as, illustrated in  FIG. 7 . In this embodiment, the gap  19  formed between the hub  17  and the top-most media sheet  12  varies depending upon the rotational position of the hub  17 . 
   As stated previously, the media sheets  12  are moved from the media stack to the media path  104 . The contact roller  14  is rotated and initiates movement of the top-most media sheet  12 . The contact roller  14  may form a normal buckle in the media sheet  12  that prevents more than one media sheet from being simultaneously moved from the media stack. The normal buckle is substantially perpendicular to the direction of feed. A leading edge of the media sheet  12  makes contact with the dam  30  such that the movement of the media sheet  12  changes from a substantially horizontal plane (i.e., essentially parallel to the support surface  101 ) to a plane at a vertical angle with the horizontal plane. The normal buckle in the media sheet  12  ideally forms a smooth bend in order to make this transition. During this movement, a transverse buckle may be formed in the media sheet  12 . The transverse buckle is substantially parallel to the direction of feed. The transverse buckle increases a beam strength of the media sheet  12  causing it to resist the creation of the normal buckle. The media sheet with the transverse buckle is more difficult to feed and may result in media jams and improper timing of the media sheet. 
   Transverse buckling is most prevalent in a media sheet with multiple layers, such as an envelope. Envelopes generally include multiple layers formed by front and back sides, and a flap that closes the envelope. As the envelope is moved from the support surface  101 , the contact roller  14  contacts a single layer. This may cause the other envelope layers that are not contacted to move from the support surface  101  at a different speed. This speed differential causes formation of the transverse buckle. 
   As the media sheet  12  begins to form a transverse buckle, the transverse buckle makes contact with the hub  17 . This contact operates to arrest further development of the transverse buckle and prevents the transverse buckle from exceeding a size of the gap  19 . The transverse buckle, then, is not allowed to reach the critical limit where a crimp forms thus allowing it to be fed more reliably. In one embodiment, the hub  17  rotates along with the contact roller  14 . In another embodiment, the hub  17  does not rotate. 
   In one embodiment, the hub  17  is constructed of a material with a coefficient of friction substantially lower than the coefficient of friction of the con-tact roller  14 . The lower coefficient of function may allow the hub  17  to contact the media sheet  12  without imparting a driving force. Thus, when the transverse buckle makes contact with the hub  17 , the hub  17  does not apply a significant additional driving force to the media sheet  12  as compared to the contact roller  14 . This reduces the possibility of skewing the media sheet  12  as a result of contact with the hub  17 . The contact roller  14  may be constructed from a variety of materials including but not limited to isoprene rubber and cork. The hub  17  may be constructed from a variety of materials including but not limited to thermoplastics such as acrylonitrile butadiene styrene, plastics and metals. 
   In one embodiment, the smaller the gap  19  the more efficiently the hub  17  breaks down the transverse buckle into smaller creases. However, the size of the gap  19  may be adjusted to account for particular characteristics of the media sheet  12  being fed. For example, a smaller gap  19  may be used with thinner and more flexible media sheets  12 . Such media sheets  12  may more easily form smaller creases that fit within the gap. Thicker and stiffer media sheets  12  may require a larger gap because transverse buckles in such media sheets  12  may not easily break down into smaller creases without permanently distorting the media or result in a misfeed. 
   In one embodiment, the hub  17  is removable from the contact roller  14 . Hubs  17  with different widths and lengths may be attached to the contact roller  14  to accommodate feeding of the particular media sheets  12 . For example, a hub  17  with a length only slightly smaller length than the contact roller  14  may be used when feeding sheets of 20 pound bond paper. However, a hub  17  with a greater difference in length than the contact roller  14  may be required to reliably feed envelopes constructed from 40 pound Bristol paper. In another embodiments the width W 2  of the hub  17  may also be varied to accommodate media sheets  12  of different overall dimensions. 
   The embodiment illustrated in  FIG. 4  shows the hub  17  with an essentially constant length along the axis A. In another embodiment as illustrated in  FIG. 9 , the hub  17  is tapered. In this embodiment, the length L 2  of the hub decreases in a direction along the axis A away from the contact roller  14 . The length L 2  may decrease essentially linearly as illustrated in  FIG. 9 . In another embodiment (not shown), the length L 2  decreases non-linearly.  FIG. 10  illustrates another embodiment of the hub  17  where the length L 2  initially decreases along the axis A in a direction away from the contact roller  14 , then the length L 2  increases. 
   The embodiment illustrated in  FIG. 3  illustrates a hub  17  connected to a first contact roller  14 . In the embodiment illustrated in  FIG. 11 , hubs  17  are connected to each of the contact rollers  14 . The second hub  17  may be essentially identical to the first hub  17 . In another embodiment, the width and/or length of the second hub  17  may vary from that of the first hub  17 . 
   The embodiment of  FIG. 2  illustrates one or more hubs  17  in use at an input section  102  of the image forming device  100 . Hubs  17  may be used in other areas within the image forming device  100 . In one embodiment, media sheets  12  are stacked during movement through the primary media path  104  or duplex path  114 . One or more hubs  17  may be attached to contact rollers  14  in these areas to arrest transverse buckles during feeding of the media sheets  12 . 
   The present assembly is applicable to preventing and/or reducing transverse buckling in media sheets with multiple layers, such as envelopes. The assembly may also be used with other multiple layer media sheets such as carbon-copy materials. Additionally, the assembly may also be used to prevent and/or reduce transverse buckling in various other types of media sheets such as but not limited to paper, transparencies, and card stock. 
   Terms such as “first”, “second”, and the like, are also used to describe various elements, regions, sections, etc and are also not intended to be limiting. Like terms refer to like elements throughout the description. 
   As used herein, the terms “having”, “containing”, “including”, “comprising” and the like are open ended terms that indicate the presence of stated elements or features, but do not preclude additional elements or features. The articles “a”, “an” and “the” are intended to include the plural as well as the singular, unless the context clearly indicates otherwise. 
   The present application may be carried out in other specific ways than those herein set forth without departing from the scope and essential characteristics of these embodiments. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.