Abstract:
An automatic document feeder for moving a stack of individual sheets from a stack loaded position to a single sheet separator in a document processing apparatus uses a gate comprised of a rotatable stack stop having a finger movable between a stack blocking position and a stack transmitting position. The stack stop is driven through a drag clutch from a single source of rotary power which also drives the conventional single sheet separator and other movable parts of the document processing apparatus. Presentation of the stack to the single sheet separator is thus automated since the operator of the document processing apparatus loads the document stack against the gate comprised of the automated stack stop to avoid operator loading of a stack directly to the nip of the single sheet separator and resultant mispicks and multipicks of sheets from the stack.

Description:
BACKGROUND OF THE INVENTION AND PRIOR ART 
     The present invention relates to an apparatus for feeding a stack of individual cut sheets of flat flexible media such as paper, vellum, transparencies or the like to a single sheet separator roller of a document handling device such as a scanner, facsimile machine, printer or copier and combinations of such devices. The teachings of the invention are applicable generally to any office or business machine which uses a stack of flexible media sheets which are to be fed to the machine one at a time. 
     Inexpensive document processing apparatus typically requires the user to place a stack of documents to be processed into the apparatus for delivery to the nip of the single sheet separator. The skill (or carelessness) of the operator determines the frequency of improper placement of the stack into the document processing apparatus. If the stack is improperly placed, as by inadvertently skewing or fanning the leading edges of the individual document sheets or by pushing the stack too far into the nip, the single sheet separator more frequently may engage and pick the wrong sheet or it may pick multiple sheets simultaneously. Accordingly, it is an object of the present invention to provide an automatic document feeder for moving a stack of individual sheets from a stack loaded position to the single sheet separator so that the operator can load the stack against an automatic document feeder rather than directly against the single sheet separator mechanism where misfeeds due to improper stack loading may occur. 
     SUMMARY OF THE INVENTION 
     The present invention provides an automatic document feeder for moving a stack of individual sheets from a stack loaded position to a nip in a single sheet separator in a document processing apparatus comprising: 
     a) a pre-pick roller support shaft having spaced support bearings thereon; 
     b) a pre-pick roller rotatably supported on said shaft, said pre-pick roller having a sheet gripping surface thereon; 
     c) a pressure plate resiliently biased toward said sheet gripping surface to urge a stack of sheets against said sheet gripping surface of said pre-pick roller; 
     d) a stack stop rotatably mounted on said shaft, said stop having at least one finger moveable between a stack blocking position in which said finger contacts said pressure plate to move said pressure plate away from contact with said pre-pick roller and a stack transmitting position in which said finger no longer contacts said pressure plate; 
     e) a source of rotary power connected to said shaft for rotating said pre-pick roller support shaft in a reverse reset direction and in a forward sheet delivery direction; said pre-pick roller support shaft and said pre-pick roller having mutually engageable drive stops thereon positioned such that said pre-pick roller is: (1) freely rotatable on said shaft during loading of a stack in contact with said pre-pick roller into engagement with said finger and when said shaft is driven in said forward direction to move said finger from an initial stack blocking position to a stack passing position; and (2) rotated by said rotating shaft during shaft rotation in said forward direction until a leading edge of said stack has reached said nip. 
     The present invention further provides a document processing apparatus comprising a document processing section, a single sheet separator having a stack receiving nip and an automatic document feeder wherein said automatic document feeder comprises: 
     a) a pre-pick roller support shaft having spaced shaft support bearings thereon; 
     b) a pre-pick roller rotatably supported on said shaft, said pre-pick roller having a sheet gripping surface thereon; 
     c) a pressure plate resiliently biased toward said sheet gripping surface to urge a stack of sheets against said sheet gripping surface of said pre-pick roller; 
     d) a stack stop rotatably mounted on said shaft, said stop having at least one finger moveable between a stack blocking position in which said finger contacts said pressure plate to move said pressure plate away from contact with said pre-pick roller and a stack transmitting position in which said finger no longer contacts said pressure plate; 
     e) a source of rotary power connected to said shaft for rotating said pre-pick roller shaft in a reverse reset direction and in a forward sheet delivery direction; said pre-pick roller support shaft and said pre-pick roller having mutually engageable drive stops thereon positioned such that said pre-pick roller is: (1) freely rotatable on said shaft during loading of a stack in contact with said pre-pick roller into engagement with said finger and when said shaft is driven in said forward direction to move said finger from an initial stack blocking position to a stack passing position; and (2) rotated by said rotating shaft during shaft rotation in said forward direction until a leading edge of said stack has reached said nip. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic side elevation view of a first or stack receiving position of the operative parts of an automatic document feeder in a document handling device such as a facsimile machine having an outline shown in phantom. 
     FIG. 2 is a view like FIG. 1 showing the parts in a second position in which the stack stop has been moved out of stack blocking position and the stack has been moved by a pre-pick roller into engagement with a sheet separator. 
     FIG. 3 is an exploded perspective view of the pre-pick roller and paper stop mechanism. 
     FIG. 4 is a front view of a pre-pick roller support shaft. 
     FIG. 5 is a left end view of the support shaft of FIG.  4 . 
     FIG. 6 is a right end view of the support shaft of FIG.  4 . 
     FIG. 7 is a cross-sectional view of the pre-pick roller. 
     FIGS. 8 a  and  8   b  respectively comprise front and side elevation views of a pre-pick spring retainer hub. 
     FIG. 9 is a top plan view of a stack stop. 
     FIGS. 10 a  and  10   b  respectively comprise left side elevation and right side elevation views of the stack stop of FIG.  9 . 
     FIG. 11 is a top plan view showing the pre-pick mechanism and single sheet separator roller position on the sheet inlet platen of a document handling device. 
     FIG. 12 is a perspective view, partly broken away, of a document processing apparatus showing a power transmission for rotating both the separator roller and the prepick roller from a single reversible motor used to power the document handling device. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As seen in the schematic side elevation view of FIG.  1  and in FIG. 12, a typical document processing apparatus, such as a scanner, facsimile machine, printer or the like, is comprised of a chassis  10  including a base and a cover which may be pivotally attached to the base to enclose the operative parts and to provide access to the paper feed path which lies above a paper support platen  12 . Individual cut sheets from a stack of paper or other media to be scanned or upon which printing is to take place are delivered to a single sheet separator of conventional construction usually comprised of a separator roller  110  having a frictional surface which, in the illustrative apparatus shown, engages the lowermost sheet of paper in the stack, the stack being manually fed from the rear of the document processing apparatus. The single sheet separator also includes a resiliently biased separator pad  120  pivotally mounted on the chassis and resiliently urged against the separator roller  110  to separate a single sheet from the stack for delivery to the document processing portions of the document processing apparatus. 
     In the illustrated document processing apparatus comprising a combination facsimile machine/scanner, the paper delivery and support platen  12  is provided with a cutout or cutouts forming a recess or recesses  14 ,  16  in which the separator roller  110  and a pre-pick roller  30  and stack stop  50  pursuant to the invention are mounted. The pre-pick roller  30  and stack stop  50  as well as the separator roller  110  as shown are centrally located in the paper path although it will be appreciated that two or more axially aligned sheet separator rollers  110  preferably mounted on a common drive axle may be provided. 
     A transversely extending pre-pick roller support shaft  20  having spaced shaft support bearings  22 ,  24  thereon at or near the respective ends of the pre-pick roller support shaft  20  is provided, the bearings  22 ,  24  being received in suitable cradles in the recesses  14 ,  16  in the paper support platen  12  to support the shaft  20 . As best seen in FIG. 4, the left shaft support bearing  22  is of larger diameter than the diameter of the main portion of the shaft  20  and has a non-circular opening  23  of hexagonal or other suitable cross section for slidable reception of a similarly configured male end of a powered drive axle. The shaft  20  is also provided with a radially projecting and axially extending drive stop  26  thereon and with a flat  28  near the bearing  24  and an annular groove  108  for purposes to be described. 
     The pre-pick roller  30  as shown in FIG. 7 preferably comprises a spool shaped hub  32  which may be round or elliptical, having end flanges for confining the sides of an elastomeric tire  34  which has an annular sheet gripping surface thereon. Preferably hub  32  is made of a polytetrafluoroethylene or similar plastic and the tire  34 , which may comprise a single tire or a series of individual elastomer tires stretched over the hub  32 , has a peripheral sheet gripping surface thereon for engaging and moving a stack of paper forwardly to a sheet separating nip between the single sheet separator roller  110  and separator pad  120  at selected times. 
     The automatic document feeder also comprises a pressure plate  40  mounted in the cover of the document processing apparatus for pivotal movement about a pivot axis under the influence of a coil spring  42  which urges the pressure plate  40  downwardly toward the annular sheet gripping surface of the pre-pick roller  30 . 
     A gate or stack stop  50  configured generally as shown in the exploded perspective view of FIG. 3 is also rotatably mounted on the pre-pick roller support shaft  20 . The stack stop  50  includes at least one and preferably two spaced gate fingers  52 ,  54  thereon which are movable through an angle α between (1) a paper stack blocking position shown in FIG. 2 in which the finger or fingers  52 ,  54  are in contact with the pressure plate  40  to hold the pressure plate away from the surface of the pre-pick roller  30  and (2) a stack transmitting position shown in FIG. 1 in which the finger or fingers  52 ,  54  are lowered into the recess below the paper support platen  12  out of stack blocking position. 
     The stock stop  50  is rotatably supported on the pre-pick roller shaft  20  by axially spaced support bearings  56 ,  58 , one ( 58 ) of which has an axially extending spring support hub  60  integrally formed thereon. The stack stop support bearings  56 ,  58  are actually spaced a distance sufficient to receive the axial length of the pre-pick roller  30  therebetween. The detailed configuration of the presently preferred configuration of the stack stop  50  comprised of a single integrally formed piece is best seen in FIGS. 9 and 10; however, many other functionally equivalent single or multiple piece configurations can easily be designed by persons skilled in the art. A rotation limit stop  64  is also formed on the stack stop and is engageable with a fixed portion  66  of the chassis  10  of the document processing apparatus as the stack stop  50  is rotated on the shaft  20  to the position shown in FIG.  2 . An axially extending keyway  62  (FIG. 10) in the stack stop bearing  56  is also provided to permit the stack stop  50  to be slid onto the pre-pick roller shaft  20  past the radially extending drive stop  26  on the pre-pick roller shaft  20 . 
     A drag clutch  100  interconnects the pre-pick roller shaft  20  and the stack stop  50  in a manner to permit free rotation of the shaft  20  relative to the stack stop  50  as the shaft is driven in a forward paper delivery direction and for moving the stack stop finger or fingers  52 ,  54  into contact with the pressure plate  40  as the pre-pick roller shaft  20  is driven in a reverse or reset direction. 
     The drag clutch  100  is comprised of the axially extending spring support hub  60  on the stack stop support bearing  58  and a coil spring  102  which has a first end supported on and frictionally engaged with the spring support hub  60  and a second end which is frictionally engaged with and retained on a spring retainer hub  104  which in turn is non-rotatably mounted on the pre-pick roller shaft  20 . For this purpose, the roller shaft  20  is preferably configured with the flat  28  on its upper surface as seen in FIG.  4  and the spring retainer hub  104  is provided with a through bore having a flat  105  seen in FIG. 8B to ensure that the spring retainer hub, when assembled on the end of the pre-pick roller shaft  20 , does not rotate relative thereto. Shaft  20  is also preferably provided with the annular groove  108  which receives spring fingers  106  integrally formed with the spring retainer hub  104 . 
     The pre-pick roller shaft  20 , pre-pick roller  30 , the stack stop  50 , the drag clutch spring  102  and the drag clutch spring retainer hub  104  are assembled by positioning the pre-pick roller  30  between the support bearings  56 ,  58  of the stack stop  50  then sliding the stack stop  50  and pre-pick roller  30  onto the shaft  20 . It will be noted that the drive roller hub  32  has an internally projecting axially extending drive stop  36  therein which is engageable with the externally projecting drive stop  26  on the pre-pick roller shaft so that the parts must be relatively rotated when being assembled to ensure that the drive stop  26  on the pre-pick roller shaft passes through the keyway  62  of the stack stop  50 . The spring  102  may then be slid onto the end of the spring support hub  60  and the spring retainer hub  104  may then be slid onto the end of the pre-pick roller shaft  20  until the spring fingers  106  snap into the annular groove  108 . 
     A power source comprised of a reversible electric stepper motor  70  and a transmission  80  comprised of a plurality of gears is used to drive both the separator roller  110  and the pre-pick roller shaft  20  as well as other operative parts of the document processing apparatus. 
     Operation 
     The apparatus is first initialized or reset by energizing the motor  70  to rotate the pre-pick roller support shaft  20  in a reverse or reset direction (clockwise as seen in FIGS. 1 and 2) which causes the drag clutch  100  to rotate the stack stop  50  to bring the finger or fingers  52 ,  54  upwardly (clockwise) such that the fingers  52 ,  54  contact the pressure plate  40  to pivotally move it against the bias of the spring  42  to the FIG. 2 position where it is seen that the limit stop  64  has engaged the stationary portion  66  of the chassis. The drag clutch coil spring  102  is tightened as this takes place. Lifting of the pressure plate  40  away from the paper gripping surface of the pre-pick roller  30  provides a space into which the paper stack can be inserted without resistance. As the user inserts a new stack of paper into the document processing apparatus, the leading edge of the paper stack engages a gate provided by the upwardly positioned stack stop fingers  52 ,  54  such that the stack is now stationarily positioned over the pre-pick roller  30  and under the pressure plate  40  as seen in FIG.  2 . It should also be noted that, during loading of the stack into the document processing apparatus, the pre-pick roller  30  is freely rotatable when its traction surface is engaged by the stack during loading of the stack because the drive stops  26 ,  36  are not drivingly engaged with each other following reset and thus permit the leading edge of the stack to easily be moved into full contact with the fingers  52 ,  54 . Unrestricted rotation of the pre-pick roller during stack insertion prevents retarding of the bottom sheet of paper in the stack by the pre-pick roller tire  34  which could cause the stack to improperly fan forwardly which may cause an out-of-order pick and resultant incorrect order of scanning or printing which is to be avoided when scanning preprinted documents or when printing on both the front and back sides of individual sheets in a stack. 
     After stack loading at commencement of a scanning or printing operation, the motor  70  and transmission  80  are then caused to rotate forwardly to drive the pre-pick roller shaft  20  as well as the separator roller  10  forwardly (counterclockwise in FIGS.  1  and  2 ). The drag clutch spring  102  creates enough torque in its free direction to move the stack stop  50  downwardly through the angle α until it stops and remains stationary until reset. The drag clutch  100  thus causes the stack stop  50  to rotate from the position shown in FIG. 2 downwardly to the position shown in FIG. 1 allowing the pressure plate  40  to then urge the stack against the pre-pick roller tire  34  such that the stack is now automaticly moved forwardly until the leading edge of the stack reaches the nip of the single sheet separator. The force exerted on the stack stop  50  by pressure plate  40  also assists in lowering the stack stop  50 . Once the stack reaches the separator, the document sheets are individually fed to the scanning or printing section of the apparatus in conventional manner. After the last sheet is fed, the system automatically resets by driving the motor  70  and transmission  80  in the reverse direction to reverse the rotation of the separator roller  110  and pre-pick roller shaft to once again move the stack stop fingers  52 ,  54  from the FIG. 1 position to the FIG. 2 stack blocking position so that a new stack can be inserted into engagement with the gate fingers to ensure that the leading edge of the stack is not fanned before it reaches the nip of the single sheet separator. 
     Preferably, the pre-pick roller  30  is geared to rotate at a slower surface speed than the surface speed of the separator roller  110 . Because of this, lag begins to develop in the pre-pick roller system as soon as the motor  70  starts driving the system. When the bottom page has been pulled past the pre-pick roller  30  by the separator roller  110 , the annular surface of the pre-pick roller  30  now engages the next sheet in the stack. Because of the lag in the pre-pick roller  30 , the pre-pick roller  30  does not roll at this point so the second sheet is not forced past the separator system prematurely. The lag and gear ratios are designed in such a way that for all of the paper sizes supported, the pre-pick roller  30  will never apply paper moving force to the succeeding page in the stack until the previous page has cleared the separator roller  110 . 
     The gear ratios and other engineering details of the transmission for rotating pre-pick roller shaft and associated parts in the desired directions of rotation for the desired lengths of time are well within the skill of persons skilled in the art. Persons skilled in the art will also appreciate that various additional modifications can be made in the preferred embodiment shown and described above and that the scope of protection is limited only by the wording of the claims which follow.