Patent Publication Number: US-7584952-B2

Title: Sheet feeding assembly

Description:
BACKGROUND 
   Reproduction apparatuses typically include sheet feeding mechanisms to reliably feed individual sheets of media from a stack of media. For a given mechanism there is an optimum window, or vertical range, within which the top of the media stack must be presented to one or more feed rolls for reliable performance. This has been traditionally achieved using an elevating plate and associated elevating mechanism for raising and lowering the media stack to position the top of the media stack within the optimum window relative to the feed rolls. In the operating mode, a nudger roll, also commonly referred to as a pre-feed roll, is positioned above the media stack in contact with the top of the media stack. Rotation of the nudger roll engages the top sheet of the media stack, causing the sheet to begin moving from the media stack to a feed path. 
   In addition to the use of an elevating plate, conventional media feeder mechanisms also rely on the use of solenoid with the nudger roll. The solenoid operates to lower the nudger roll from an up position above the top of the media stack to a down position engaging the top of the media stack. The operations of an elevated plate mechanism and nudger roll solenoid are coordinated. With the elevated plate in a lowered position and the nudger roll in an up position, an operator can add media to the media stack. 
   To allow for increased media capacity, feeding mechanisms should accommodate reasonably large stack heights. Larger stack heights increase the complexity of both elevating plate mechanisms used to raise the media stacks and nudger roll solenoids. There are significant disadvantages associated with these mechanisms in the form of high manufacturing and maintenance costs. 
   SUMMARY 
   There is a need for feeding mechanisms that can reliably feed various types of media to marking devices or imaging devices without utilizing either a media stack raising mechanism and/or a solenoid operated mechanism for moving the nudger rolls. Eliminating the use of these mechanisms would eliminate the need for costly parts, such as solenoids, and thereby reduce manufacturing costs. Eliminating the use of a solenoid, which is inherently noisy, also provides the benefit of reduced operating noise. 
   Conventional feeding mechanisms employ motors to drive the feed and nudger rolls, and to operate the elevated plate mechanism. These motors are often reversible electric stepper motors, which in many cases are only operated in a single direction. There is a need for a feeding mechanism that better utilizes the capacity of reversible electric stepper motor by operating it in both of its available directions. 
   In embodiments, a sheet feeding assembly is provided that reliably feeds various types of media to a marking device or imaging device without requiring an elevated plate mechanism for raising and lowering a stack of media. 
   In embodiments, a sheet feeding assembly is provided that reliably feeds various types of media to marking devices or imaging devices without requiring a solenoid operated nudger roll. 
   In embodiments, a sheet feeding assembly is provided that is less expensive to manufacture and repair. 
   In embodiments, a sheet feeding assembly is provided that operates a reversible electric stepper motor in both directions. The assembly may include a frame with opposing sides connected by a cross member, a feed roll supported on the frame for rotation about a feed axis, a nudger support element pivotally mounted to the frame for rotational movement about a feed axis, and a nudger roll connected to the nudger support element for rotation about a nudger axis parallel to the feed axis. The assembly further includes a cam supported on the frame for rotation about a cam axis. The cam engages an extension member of the nudger support element extending outwardly from the feed axis, and is profiled to raise and lower the nudger roll as the cam rotates. The assembly further includes a reversible electric stepper motor to drive, without requiring the use of more than one motor, the feed roll, nudger roll and cam. 
   In embodiments, the feed roll and the nudger roll are driven in a forward direction when the motor is operated in a forward direction; and the cam is driven in a cam operating direction when the motor is operated in a reverse direction. This provides greater utilization of the capabilities of a reversible electric stepper motor than provided by feeder mechanisms that operate the stepper motor in only one direction. The sheet feeding assembly reliably feeds various types of media to marking devices or imaging devices without the need for an elevating plate mechanism or a solenoid operated nudger roll. 
   These and other objects, advantages and salient features are described in or apparent from the following detailed description of exemplary embodiments. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Exemplary embodiments will be described with reference to the drawings, wherein like numerals represent like parts, and wherein: 
       FIG. 1  is a perspective view of an exemplary embodiment of a sheet feeding assembly; 
       FIG. 2  is a left side view of the sheet feeding assembly of  FIG. 1 ; 
       FIG. 3  is a another left side view of the sheet feeding assembly of  FIG. 1 ; 
       FIG. 4  is a perspective view of an exemplary embodiment of a nudger support element and nudger roll in a down position; 
       FIG. 5  is a perspective view of an exemplary embodiment of a nudger support element and nudger roll in an up position; 
       FIG. 6  is a side sectional view of an exemplary embodiment of a nudger support element and nudger roll; 
       FIG. 7  is a side view of an exemplary embodiment of a cam and nudger support element extension member; 
       FIG. 8  is an exploded view of an exemplary embodiment of a cam and one-way clutched gear; 
       FIG. 9  is a schematic representation of an exemplary embodiment of a marking device having an exemplary embodiment of a sheet feeding assembly; 
       FIG. 10  is a functional block diagram illustrating an exemplary embodiment of a marking device; and 
       FIG. 11  is a flowchart illustrating an exemplary method of operating a sheet feeding assembly. 
   

   DETAILED DESCRIPTION OF EMBODIMENTS 
   The sheet feeding assembly described herein is discussed in the context of a marking device, for purposes of illustration. However, the feeding assembly could be implemented in any type of marking device or imaging device, such as a printer, facsimile machine, scanner, or a xerographic marking device or any other device that feeds sheet material through a feed path. 
     FIG. 1  illustrates an exemplary embodiment of a sheet feeding assembly  10  for feeding a sheet from the top of a stack of media to a feed path. The sheet feeding assembly  10  has a frame  12  comprising opposing sides  12   a  connected by a cross member  12   b . A feed roll  14  is supported on the frame  12  for rotation about a feed axis identified as A-A in  FIGS. 2 ,  3  and  7 . The sheet feeding assembly further comprises a nudger support element  16  is supported on the frame  12  for pivotal movement about the feed axis A-A. As shown in  FIGS. 4-5  and  7 - 8 , the nudger support element has an extension member  16   a  extending outwardly radially from the feed axis A-A. As shown in  FIGS. 4-5  and  7 , the extension member  16   a  of the nudger support element engages a rotary cam  22  at, for instance, a cam follower  16   b  protruding from the extension member  16   a.    
   A nudger roll  18  is connected to the support element  16  for rotation about a nudger axis, shown as B-B in  FIGS. 2 ,  3  and  6 , that is positioned parallel to the feed axis A-A. A rotary cam  22  supported on the frame  12  for rotation about a cam axis shown as C-C in  FIGS. 2 ,  3  and  7 . As shown in  FIG. 7 , the cam  22  is positioned and profiled for engagement with a portion of the support element extension member  16   a , such as the cam follower  16   b  protruding therefrom. In the depicted embodiment, a reversible electric stepper motor  24  drives the feed roll  14 , nudger roll  18  and cam  22 . 
   The sheet feeding assembly  10  may include a gear train assembly  20  intermediate the motor  24  and some or all of the feed roll  14 , nudger roll  18 , and rotary cam  22 . The motor  24  may directly drive one of these elements, making a gear train assembly unnecessary for that element. The feed roll  14  and nudger roll  18  each have a surface suitable for engaging the surface of a sheet of media, such as may be required to slidably remove a sheet of media from the stack of media. The feed roll  14  or nudger roll  18  may include single or multiple rollers or coaxially mounted wheels or conveying belts for moving single sheets of media. 
   As shown in  FIG. 3  by arrow F, the feed roll  14  is driven in a forward direction when the motor  24  is operated in a forward direction. The forward direction of the motor  24  is the direction of operation that provides for driving the feed roll  14  and nudger roll  22  in a direction that allows the feed roll  14  and nudger roll  22  to feed a sheet from the top of a stack to a feed path of a marking device or imaging device. In the exemplary embodiment shown on the left side views provided in  FIGS. 2 and 3 , with the motor  24  mounted to a gear plate  26  and attached to the left side of the frame  12 , a forward rotation of the motor  24  is represented by a clockwise rotation of the motor pinion  28 . This causes a clockwise rotation of the feed roll  14 , feed shaft  15 , nudger roll  18 , and nudger shaft  19  so that sheets are fed from the top of a stack of media from right to left under the nudger roll  18  and then under the feed roll  14 . 
   When the motor  24  is operated in a reverse direction as shown in  FIG. 2  by arrow R, the rotary cam  22  rotates. In the exemplary embodiment shown on the left side views provided in  FIGS. 2 and 3 , a reverse rotation of the motor  24  causes a clockwise rotation of the rotary cam  22  as viewed from the perspective of  FIGS. 2 and 3 . This is also shown from a right side view in  FIG. 7  as a clockwise rotation of the rotary cam  22 . 
   The gear train assembly may comprise a first one-way clutch connected to the nudger roll and a second one-way clutch connected to the feed roll. A third one-way clutched gear  33  may be connected to the camshaft  34  which is directly connected to the cam  22 . The camshaft  34  is also connected to a further one-way clutch housing  37 , which is shown in  FIG. 8 . Each of the one-way clutches restricts rotation of the respective feed roll  14 , nudger roll  18 , and cam  22  when the rotation of their respective drive shafts is opposite to the operational direction of the cam  22 . For the feed roll  14  and nudger roll  18 , the one-way clutch restricts rotation of the feed roll  14  and the nudger roll  18  in a reverse direction, i.e., opposite to the direction used to feed sheets, when the motor  24  is operated in a reverse direction. The one-way clutch housing  37  connected to the cam  22  via the camshaft  34  restricts rotation of the cam  22  in a direction opposite to the normal cam  22  operating direction when the motor  24  is operated in a forward direction, i.e., a direction that feeds sheets. 
   The cam  22  is profiled to move the nudger support element  16  and nudger roll  18  between an up position suitable for loading media onto the stack of media, shown in  FIG. 5 , and a down position suitable for operation of the nudger roll  18 , shown in  FIG. 4 . 
   An exemplary profile of the cam  22  is shown in  FIG. 7 . The cam  22  has a profile  22   a  that is slidingly engaged by the cam follower  16   b  of the nudger support element as the nudger roll  18  is lifted from and lowered to its down position. Cams having other profiles configured to provide for movement of a nudger roll  18  between a suitable up and down position upon rotation of the cam  22  may be used. In the exemplary embodiment, the nudger support element  16  is pivotally mounted to the frame  12  to provide for pivotal rotation about the feed axis A-A. The nudger roll  18  travels from its up and down positions along an arc D shown in  FIG. 6 . 
   An exemplary cam  22  and one-way clutched gear are illustrated in  FIG. 8 . These components comprise a bearing  32 , clutched gear  33 , cam shaft  34 , cam thrust washer  35 , cam thrust spring  36  and clutch housing  37  as well as the cam  22  itself. The spring loaded cam thrust washer  35  assists the other components of the clutched gear mechanism in keeping the cam  22  correctly in place such as by restricting over rotation, due to forces of inertia, and by restricting the cam from rotating in a forward direction due to machine vibration. 
   The sheet feeding assembly  10  may further comprise a biasing member (not shown) for biasing the nudger support element  16  and the nudger roll  18  toward the down position. The biasing may be of a form well-known in the art, such as but not limited to a spring. 
   The force applied by the biasing member may be tangential to the arc traveled by the nudger roll  18  as it travels between the up and down positions. The biasing force assists in maintaining contact between the nudger roll  18  and the top of the stack of media at a constant force, when the nudger roll  18  is in the down position. The cam  22  may be profiled to provide for the biasing force to assist in maintaining the cam in a stationary position when the nudger roll  18  is in the up position.  FIG. 7  provides a side view of the position of the cam  22  with the nudger roll  18  in the up position. The direction of operation of the cam  22  is clockwise. The biasing force is applied from the nudger support element  16  to the cam  22  in the direction shown as E in  FIG. 7 . This biasing force urges the cam  22  to rotate in a counterclockwise direction that is opposite to its direction of operation. The rotational movement of the cam  22  in this direction is restricted by operation of the one-way clutched gear, so the biasing force assists in keeping the cam  22  in a generally locked position. Thus, the depicted cam  22  is profiled so that when the nudger support element  16  is in the up position, the biasing member assists in maintaining the cam  22  in a stationary position by urging the cam  22  to rotate in a direction opposite to the cam  22  operating direction, which is restricted by the one-way clutched gear. 
   In this manner, it may be appreciated that during normal operation of the marking device or imaging device, the nudger roll  18  is in the down position on top of the media stack. The motor  24  operates in the forward direction to drive the nudger roll  18  to allow sheet feeding. The cam  22  is essentially disengaged and maintained in a stationary position. The cam  22  is rotated to the position shown in  FIG. 7  when there is a need to raise the nudger roll  18  above the top surface of the media stack for instance, to add media to the stack. In this raised position, the nudger roll  18  is essentially disengaged from the stack, and remain in a stationary position. To resume sheet feeding, the cam  22  rotates to reposition the nudger roll  18  in the down position, i.e., to drop the nudger roll  18  onto the top surface of the media stack. The raising and lowering of the nudger roll  18  is caused by the rotation of the cam  22 , which in turn results from the operation of the motor  24  in the reverse direction. The timing and duration of raising and lowering of the nudger roll  18  is controlled by the selective operation of the motor  24  in the reverse direction. 
   The sheet feeding assembly  10  may be part of a document handling assembly for use with a marking device or imaging device, including a photocopier of the xerographic type or other such type of printer, facsimile machine or scanner. For a general understanding of marking device, such as an electrophotographic printer, solid ink printer or copying machine, or an imaging device, such as a scanner, the exemplary embodiments according to this disclosure may be incorporated, reference is made to  FIG. 9 , which depicts schematically various components of a marking device. It should be apparent that this embodiment of a marking device is merely illustrative, and the sheet feeding assembly could be implemented in any type of marking device or imaging device. 
   The exemplary marking device  41  shown in  FIG. 9  comprises a cassette tray  42  for holding a stack of media  11 , a portion of which is positioned below a nudger roll  18  depicted in the up position. In the operating mode, the nudger roll  18  and feed roll  14  are driven in a clockwise rotation to transfer a sheet of media from the top of the stack of media  11  to a feed path  43 . 
   The exemplary marking device  41  provides for the transfer of four color toners (yellow, magenta, cyan and black) from a plurality of toner cartridges  44  onto a transfer belt  45 . The sheet of media is transferred along the feed path  43  by a plurality of transfer rolls  46  in turn between the transfer belt  45  and one of two primary transfer rolls  47  and further between a pair of fixing rolls  48  brought into abutting contact with each other, and then delivered out of the housing of the marking device  41 . The color toners are applied to the sheet of media upon contact of the sheet with the transfer belt  45 . The toners are subsequently fixed to the sheet upon contact with the fixing rolls  48 . 
   The exemplary marking device  41  further comprises an exposure unit such as a laser light source arranged within the housing of the marking device  41  at a specified position in the housing to irradiate surfaces of a plurality of rotating electrophotographic photoreceptors  49  after charging with laser light emitted from the laser light source. This performs the respective steps of charging, exposure, development, primary transfer and cleaning in turn in the rotation of the electrophotographic photoreceptors. Toner images of the respective colors are then transferred onto the transfer belt  45 , one over the other prior to application onto the sheet of media. 
   The exemplary document handling assembly has a sheet feed path extending from an input tray containing a stack of single sheet media to an output past a feed roll  14 . A nudger roll  18  is provided for selectively engaging a sheet at the top of the stack of media and driving the sheet into the paper path. Operatively connected to the nudger roll  18  is a rotary cam  22  for operating the nudger roll to the top of the stack of media. The document handling system is also provided with a reversible electric stepper motor  24  and a gear train assembly intermediate the motor  24  and each of the feed roll  14 , nudger roll  18 , and rotary cam  22 . The gear train transmits power from the motor  24  to rotate the feed roll  14  and the nudger roll  18  when the motor  24  is operated in a forward direction and to transmit power to rotate the rotary cam  22  when the motor  24  is operated in a reverse direction. 
     FIG. 10  is a functional block diagram illustrating an exemplary embodiment of a marking device or imaging device  41 , which includes a controller  51 , memory  52 , input signals  53 , an input/output interface  54 , and a motor  24 , which are interconnected by a data/control bus  55 . The controller  51  controls the operation of the nudger roll  14  via the motor  41  based on input signals  53  and/or other signals provided through an input/output interface  54 . The input/output interface  54  may provide information from a user input device  56  and/or a data sink  57 . The controller  51  performs any necessary calculations and executes any necessary programs for implementing the marking device or imaging device  41 , and its individual components including the motor  24 , and controls the flow of data between other components of the marking device  41  as needed. 
   The memory  52  may serve as a buffer for information coming into or going out of the marking device  41 , may store any necessary programs and/or data for implementing the functions of the marking system  41 , and/or may store data at various stages of processing. The memory  52 , while depicted as a single entity, may actually be distributed. Alterable portions of the memory  52  are, in various exemplary embodiments, implemented using static or dynamic RAM. However, the memory  52  can also be implemented using a floppy disk and disk drive, a writeable optical disk and disk drive, a hard drive, flash memory or the like. The links  58  may be any suitable wired, wireless or optical links. 
   The data sink  57  can be any device that is capable of outputting or storing processed data. The data source  59  can be a digital camera, a scanner, or a locally or remotely located computer, or any other known or later developed device that is capable of generating electronic image data. Similarly, the data source  59  can be any suitable device that stores and/or transmits electronic image data, such as a client or a server of a network. The image data source  59  can be integrated with the marking device or imaging device  41 , as in a digital copier having an integrated scanner. Alternatively, the data source  59  can be connected to the marking device or imaging device  41  over a connection device, such as a modem, a local area network, a wide area network, an intranet, the Internet, any other distributed processing network, or any other known or later developed connection device. 
   The controller  51  may base the operation of the motor  24  on one or more input signals  53  such as a signal from a position detector for the rotary cam  22 . The position detector may be of any type known in the art such as a photo-interrupt sensor. In embodiments, a photo-interrupt sensor detects the rising edge of the integral vane  22   a  of the cam as it is rotated by the motor  24 . 
   An additional input signal  53  may be provided in the form of a detector for the stack height of the stack of media. This detector may determine when there is a need to add media to the stack; at which point the controller  51  may place the nudger roll  18  in the up position by selectively operating the motor  24  in a reverse direction. 
   A one or more one-way clutched gear may also be provided to restrict rotation of the feed roll  14  and/or the nudger roll  18  when the motor  24  is operated in a reverse direction. An additional one-way clutched gear may be provided to restrict rotation of the cam  22  when the motor  24  is operated in a forward direction. The rotary cam  22  is profiled to allow the adjustment of the nudger roll  18  from a down position in which the nudger roll  18  contacts the top of the stack of media to an up position in which the distance between the nudger roll  18  and the top of the stack of media is suitable for loading media onto the stack of media. 
     FIG. 11  illustrates an exemplary method of operating a sheet feeding assembly for feeding a sheet from the top of a stack of media to a feed path. The method includes a first step S 110  of moving a nudger roll from a down position proximate the top of a stack of media to an up position. With the nudger roll in the up position, a user may add media to the stack of media to raise the height of the stack. At step S 120 , the method awaits a indication that media has been added. This may be done by, for example, receiving a manual input from the user indicating that media has been added, or by receiving a signal from a detector. The nudger roll is then moved from the up position to the down position in step S 130 . In step S 140 , the nudger roll is driven to urge a sheet from the stack of media to the feed path. Step S 140 , driving the nudger roll, may be accomplished by selectively operating a reversible electric stepper motor engaged with the nudger roll in a forward direction. Steps S 110  and S 130 , wherein the nudger roll is moved between its up and down positions, may be accomplished by selectively operating a reversible electric stepper motor engaged with the nudger roll in a reverse direction. This may be accomplished by rotation of a rotary cam operatively engaged to the nudger roll. 
   The method may provide that when the nudger roll is being driven, the nudger roll  18  is maintained in a stationary position, which may be accomplished by restricting the rotation of the rotary cam. A controller may further be provided for a step of controlling the operation of the motor based on one or more input signals such as from a rotary cam position detector. The rotary cam position detector assists in coordinating the operation of the sheet feeding system and may be provided in the form of a photo-interrupt sensor. 
   It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also, various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.