Abstract:
A sheet feeding system has a pick roller, a first roller, and a second roller. The ends of the first and second rollers are coupled together. The pick roller acquires, or picks, a sheet from a stack of sheets and passes the sheet to the first and second rollers. One of the first and second rollers discourages unintended sheets passed with the sheet picked from the stack. The other of the first and second rollers advances the sheet. A logic processor evaluates interchange conditions and activates a drive mechanism when the evaluated interchange conditions reaches a threshold value. The drive mechanism interchanges the first and second rollers so that the second roller becomes the first roller and the first roller becomes the second roller.

Description:
FIELD OF THE INVENTION 
     This invention relates in general to sheet feeding technology and, more particularly, to interchanging separator rollers and feed rollers in a sheet feeder. 
     BACKGROUND OF THE INVENTION 
     A sheet feeder retrieves a single sheet from a stack of sheets and provides the single sheet to a device. Examples of devices that utilize sheet feeders include printers, copiers, scanners, facsimile machines, and multifunction devices. 
     One example of a conventional sheet feeder includes three rollers that cooperate to carry out the function of the sheet feeder. The three rollers are often referred to as pick, feed, and separator rollers. The pick roller contacts one of the sheets in a stack of sheets and rotates to urge the contacted sheet between the feed and separator rollers. Occasionally, the contacted sheet adheres to an adjacent sheet and both sheets move towards the feed and separator rollers. 
     The feed roller rotates to advance the contacted sheet. The separator roller rotates in a direction opposite the feed roller to help prevent an adhering sheet from being advanced with the contacted sheet. The contacted sheet advances against the rotation of the separator roller until the torque reaches a threshold. Then, the separator roller reverses direction. This action causes the separator roller to wear at a greater rate than the pick and feed rollers. Consequently, the separator roller must be replaced more frequently than the pick and feed rollers. 
     SUMMARY OF THE INVENTION 
     According to principles of the present invention, a sheet feeding system has a pick roller, a separator roller, and a feed roller. The ends of the separator and feed rollers are coupled together. The pick roller acquires, or picks, a sheet from a stack of sheets and passes the sheet to the separator and feeder roller. The separator roller discourages unintended sheets passed with the sheet picked from the stack. The feed roller advances the sheet. A logic processor evaluates interchange conditions and activates a drive mechanism when the interchange conditions meet interchange criteria. The drive mechanism interchanges the separator roller and the feed roller so that the separator roller becomes the feed roller and the feed roller becomes the separator roller. 
     According to further principles of the present invention, the drive mechanism includes either a rotatable shaft axially parallel to the first and second rollers and coupled to one of the first and second ends and a shaft driver configured to rotate the shaft or a toothed wheel gear coupled to one of the first and second ends and a gear driver configured to drive the gear, rotating the system. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is diagrammatical, partially cut away, front elevation representing one embodiment of the feed and separator rollers of the present invention. 
         FIG. 2  is diagrammatical side elevation representing one embodiment of a sheet feeding system of the present invention with the feed and separator rollers of FIG.  1 . 
         FIG. 3  is diagrammatical, front elevation representing one embodiment of the drive mechanism of FIG.  1 . 
         FIG. 4  is diagrammatical side elevation representing the drive mechanism of FIG.  3 . 
         FIG. 5  is diagrammatical, front elevation representing an alternate embodiment of the drive mechanism of FIG.  1 . 
         FIG. 6  is diagrammatical side elevation representing the drive mechanism of FIG.  5 . 
         FIG. 7  is diagrammatical, front elevation representing another alternate embodiment of the drive mechanism of FIG.  1 . 
         FIG. 8  is diagrammatical side elevation representing the drive mechanism of FIG.  7 . 
         FIG. 9  is a flow chart illustrating one embodiment of the method of the present invention for preserving a feed and separator roller combination. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Illustrated in  FIGS. 1 and 2  is one embodiment of a sheet feeding system  2  of the present invention. Sheet feeding system  2  includes combination  4  and pick roller  6 . Combination  4  includes feed roller  8 , separator roller  10 , roller driver  12 , coupling  16 , drive mechanism  18 , and optionally, coupling  14 , logic processor  20  and pivot shaft  22 . 
     Pick roller  6  is any one or more rotatable, generally cylindrically shaped rolling objects configured to frictionally contact one sheet  24  from a stack of sheets  26  and, by rolling, urge sheet  24  towards feed roller  8  and separator roller  10 . For clarity, contacting sheet  24  and urging sheet  24  towards feed roller  8  and separator roller  10  will be referred to as picking. In one embodiment, stack of sheets  26  reside in a sheet bin, cartridge, or tray  28  until picked by pick roller  6 . 
     Feed roller  8  is any one or more rotatable, generally cylindrically shaped, rolling objects configured to receive and frictionally contact sheet  24  and, by rolling, advance sheet  24  between feed roller  8  and separator roller  10  to a device or system (not shown). Examples of devices or systems to which feed roller  8  advances sheet  24  include printers, copiers, scanners, facsimile machines, and multifunction devices. 
     Feed roller  8  includes a rolling surface  30  and an inner core  32 . Rolling surface  30  may be of the same or a different material than inner core  32 . Rolling surface  30  and inner core  32  may be unitary or separate. 
     Separator roller  10  is any one or more rotatable, generally cylindrically shaped, rolling objects configured to receive and frictionally contact sheet  24  and, by rolling, discourage any of the sheets of stack  26  from advancing with sheet  24  to the device or system. Separator roller  10  is substantially parallel to feed roller  8 . Separator roller  10  rolls or rotates in a direction opposite feed roller  8 . 
     Separator roller  10  includes a rolling surface  34  and an inner core  36 . Rolling surface  34  may be of the same or a different material than inner core  36 . Rolling surface  34  and inner core  36  may be unitary or separate. Rolling surface  34  is adjacent rolling surface  30 . 
     In one embodiment, feed roller  8  and separator roller  10  extend only a portion of the way across a sheet pathway and are unsupported at one end. In this embodiment, coupling  14  and pivot shaft  22  are not present. In an alternate embodiment, feed roller  8  and separator roller  10  extend entirely across the sheet pathway and are supported at both ends. In this embodiment, coupling  14  and pivot shaft  22  are present. 
     Roller driver  12  is any apparatus or system for rotating feed roller  8  and separator roller  10 . In one embodiment, roller driver  12  includes two toothed wheel gears  38 . One gear  38  is affixed to feed roller  8  and the other gear  38  is affixed to separator roller  10 . 
     Couplings  14 ,  16  are any mechanism connecting an end of feed roller  8  to an end of separator roller  10 . Each coupling  14 ,  16  connects one set of ends of feed roller  8  and separator roller  10 . 
     Drive mechanism  18  is any apparatus or system configured to rotate combination  4  and interchange, in position, feed roller  8  and separator roller  10 . Once interchanged, feed roller  8  becomes separator roller  10  and separator roller  10  becomes feed roller  8 . In one embodiment, drive mechanism  18  is controlled by logic processor  20 . Drive mechanism  18  may be on the same ends of feed roller  8  and separator roller  10  as roller driver  12  or on opposite ends of feed roller  8  and separator roller  10  as roller driver  12 . 
     In one embodiment, drive mechanism  18  and couplings  14 ,  16  are sized and shaped so that feed roller  8  and separation roller  10  are centered within a sheet path. In alternate embodiments, drive mechanism  18  and couplings  14 ,  16  are sized and shaped so that feed roller  8  and separation roller  10  are located in any position across a sheet path. 
     Logic processor  20  is any apparatus or system configured to evaluate interchange conditions and to control drive mechanism  18 . Interchange conditions are any conditions useful for determining whether to interchange feed roller  8  and separator roller  10 . Examples of interchange conditions include number of sheets advanced by feed roller  8  and number of print jobs during which feed roller  8  advances sheets. In one embodiment, logic processor  20  is further configured to vary the interchange criteria that must be met by the interchange conditions before activating drive mechanism  18 . 
     Pivot shaft  22  extends from one of the couplings  14 ,  16  opposite drive mechanism  18 . Pivot shaft  22  is rotatably mounted in a position to provide a point of rotation for combination  4  to interchange feed roller  8  and separator roller  10 . 
     Illustrated in  FIGS. 3 and 4  are one embodiment of drive mechanism  18 . Drive mechanism  18  includes shaft  40  and shaft driver  44 . Shaft driver  44  extends from or is attached to one of couplings  14 ,  16 . Shaft driver  44  rotates shaft  40  that rotates combination  4  and interchanges, in position, feed roller  8  and separator roller  10 . 
     Illustrated in  FIGS. 5 and 6  are an alternate embodiment of drive mechanism  18 . Drive mechanism  18  includes toothed wheel gear  46  and gear driver  48 . Toothed wheel gear  46  extends from or is attached to one of couplings  14 ,  16 . Gear driver  48  rotates gear  46  that rotates combination  4  and interchanges, in position, feed roller  8  and separator roller  10 . 
     Illustrated in  FIGS. 7 and 8  are another alternate embodiment of drive mechanism  18 . Drive mechanism  18  includes pulley wheel  50 , belt  52 , and belt driver  54 . Pulley wheel  50  extends from or is attached to one of couplings  14 ,  16 . Belt  52  interconnects pulley wheel  50  and belt driver  54 . Belt driver  54  rotates pulley wheel  50  that rotates combination  4  and interchanges, in position, feed roller  8  and separator roller  10 . 
       FIG. 9  is a flow chart representing steps of one embodiment of the present invention. Although the steps represented in  FIG. 9  are presented in a specific order, the present invention encompasses variations in the order of steps. Furthermore, additional steps may be executed between the steps illustrated in  FIG. 9  without departing from the scope of the present invention. 
     Feed roller  8  and separator roller  10  are interchangeable. Since feed roller  8  and separator roller  10  are interchangeable, they are alternatively referred to as first roller and second roller. Either feed roller  8  or separator roller  10  may be referred to as first roller and either may be referred to as second roller. 
     Sheet  24  is picked  56  and urged  58  between first and second rollers. One of the first and second rollers rotates to advance  60  sheet  24  while the other of the first and second rollers rotates to discourage additional sheets from stack  26  from advancing with sheet  24 . 
     Criteria for interchanging first and second rollers are evaluated  62 . In one embodiment, evaluating  62  criteria for interchanging includes counting the pages advanced  60  by the first and second rollers. In an alternate embodiment, evaluating  62  criteria for interchanging includes measuring the sheet slippage of sheet  24  as sheet  24  is advanced  60  and comparing the sheet slippage to a slippage threshold. 
     If the evaluated criteria for interchanging indicate no interchange of first and second rollers is desirable, the process repeats until an interchange of first and second rollers is desirable. If the evaluated interchange conditions indicates an interchange of first and second rollers is desirable, second roller is interchanged  64  for first roller and first roller is interchanged  64  for second roller. An interchange of first and second rollers may be desirable upon any desired condition. Examples of desired conditions include after a desired number of print jobs, after a desired number of pages, and after an equal number of pages have been advance since a previous interchange. 
     In one embodiment, interchanging  64  the rollers includes activating shaft driver  44  to rotate shaft  42  and shaft  42  rotating combination  4  to interchange the first and second rollers. 
     In an alternate embodiment, interchanging  64  the rollers includes activating gear driver  48  to rotate gear  46  and gear  46  rotating combination  4  to interchange the first and second rollers. 
     In another alternate embodiment, interchanging  64  the rollers includes activating belt driver  54  to rotate pulley  50  and pulley  50  rotating combination  4  to interchange the first and second rollers. 
     The process may be repeated as many times as desired. In one embodiment, the process is repeated until rolling surface  30  or rolling surface  34  has worn so that it no longer functions properly. 
     The foregoing description is only illustrative of the invention. Various alternatives and modifications can be devised by those skilled in the art without departing from the invention. Accordingly, the present invention embraces all such alternatives, modifications, and variances that fall within the scope of the appended claims.