Patent Publication Number: US-7905480-B2

Title: Job separator and image recording apparatus having the same

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Japanese Patent Application No. 2007-021981, filed Jan. 31, 2007, the entire disclosure of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a job separator which may be configured to convey printed sheets by changing two conveyance positions back and forth, with respect to a sheet conveyance direction, onto an output tray of an image recording apparatus, and also relates to the image recording apparatus including the job separator. 
     2. Description of Related Art 
     Known image recording apparatuses such as printers, copiers, and facsimiles, include a device for ejecting printed sheets to a front or rear position with respect to a sheet conveyance direction, alternating between front and rear positions according to each document created on a computer or a word processor. In a known image recording apparatus, a plurality of pairs of drive rollers are positioned a predetermined distance away from one another, near a sheet ejection portion and in an upstream side with respect to a sheet conveyance direction. One pair of conveyance rollers, which is positioned nearest the sheet ejection portion, includes a drive roller positioned such that an upper surface of a sheet faces the drive roller, and an auxiliary roller positioned such that a lower surface of the sheet faces the auxiliary roller. The auxiliary roller is moved closer to or further away from the drive roller by a piston positioned on the side of the auxiliary roller, and the piston advances and retreats, thereby moving the auxiliary roller closer to or further away from the sheet to be fed. 
     In a known image recording apparatus, when the auxiliary roller faces the drive roller, the sheet is ejected onto an output tray, such that the leading end of the sheet is positioned downstream from a position between the rollers, with respect to the sheet conveyance direction. When the auxiliary roller moves away from the drive roller, such that the auxiliary roller stops at a position that is withdrawn from the upstream side in the sheet conveyance direction, the auxiliary roller does not contact or guide the lower surface of the sheet to be ejected. In this position, the sheet drops down when the sheet reaches an upstream side of the output tray, with respect to the sheet conveyance direction. In this manner, a known image recording apparatus can, for each document requested, change a position of a sheet to be ejected onto the output tray between an upstream-side position and a downstream-side position, alternately, with respect to the sheet conveyance direction. 
     Nevertheless, in a known image recording apparatus, the movable auxiliary roller moves back and forth in the sheet conveyance direction, on the side facing the lower surface of the sheet to be ejected. In addition, the piston configured to move the auxiliary roller is positioned also on the side facing the lower surface of the sheet to be ejected. In order to maintain the number of sheets accommodated by the output tray, space is provided in the output tray to allow the auxiliary roller to freely move. As a result, the height of the image recording apparatus increases, which increases the overall size of the image recording apparatus and may prevent the production of compact image recording apparatuses. 
     SUMMARY OF THE INVENTION 
     In an embodiment of the invention, a job separator comprises a first roller unit, comprising a first driven roller and a first drive roller, wherein the first driven roller and the first drive roller are configured to receive a sheet therebetween, and a second roller unit, positioned adjacent to and downstream of the first roller unit in a sheet conveyance direction. The second roller unit comprises a second driven roller and a second drive roller, wherein the second driven roller and the second drive roller are configured to receive a sheet therebetween. The second drive roller is configured to selectively move between a first position in which the second drive roller is positioned below the second driven roller, and a second position in which the second drive roller is positioned above the second driven roller. The first roller unit and the second roller unit are configured to convey a sheet in a substantially lateral direction. 
     According to another embodiment of the invention, an image recording apparatus comprises a recording unit configured to record an image on a sheet, a job separator positioned downstream of the recording unit in a sheet conveyance direction, the job separator comprising a first roller unit, comprising a first driven roller and a first drive roller, wherein the first driven roller and the first drive roller are configured to receive the sheet having the image thereon therebetween, and a second roller unit, positioned adjacent to and downstream of the first roller unit in the sheet conveyance direction. The second roller unit comprises a second driven roller, and a second drive roller, wherein the second driven roller and the second drive roller are configured to receive the sheet therebetween. The first roller unit and the second roller unit are configured to convey the sheet in a substantially lateral direction. The image forming apparatus further comprises an output tray positioned downstream of the job separator in the sheet conveyance direction, and a control unit configured to control a position of the sheet to be ejected on the output tray, wherein the control unit is configured to selectively move the second drive roller between a first position, in which the second drive roller is positioned below the second driven roller, and a second position, in which the second drive roller is positioned above the second driven roller. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present invention, and the needs satisfied thereby, reference now is made to the following descriptions taken in connection with the accompanying drawings. 
         FIG. 1A  is a schematic cross-sectional view of an image recording apparatus in which a printed sheet is conveyed toward an output tray on a downstream side of the image recording apparatus with respect to a sheet conveyance direction, according to an embodiment of the invention. 
         FIG. 1B  is a schematic cross-sectional view of an image recording apparatus in which a printed sheet is fed on a rotating second drive roller, and the sheet is conveyed and ejected to an output tray on a downstream side of the image recording apparatus with respect to a sheet conveyance direction, according to an embodiment of the invention. 
         FIG. 1C  is a schematic cross-sectional view of an image recording apparatus in which a second drive roller and a guide plate are withdrawn to a position higher than the second driven roller, and a printed sheet is ejected to the output tray on an upstream side with respect to a sheet conveyance direction, according to an embodiment of the invention. 
         FIG. 2A  is a left side view of a job separator when the image recording apparatus is in a state corresponding to the state shown in  FIG. 1C . 
         FIG. 2B  is a cross-sectional view of a job separator when the image recording apparatus is in a state corresponding to the state shown in  FIG. 1C . 
         FIG. 2C  is a left side view of a job separator corresponding when the image recording apparatus is in a state corresponding to the state shown in  FIG. 1A . 
         FIG. 2D  is a cross-sectional view of a job separator when the image recording apparatus is in a state corresponding to the state shown in  FIG. 1A . 
         FIG. 3  is a schematic plan view of a job separator according to an embodiment of the invention. 
         FIG. 4A  is a view of the height and the position of a second drive roller and a guide plate when the second drive roller is in the most upstream position, with respect to a sheet conveyance direction, according to an embodiment of the invention. 
         FIG. 4B  is a view of the height and the position of a second drive roller and a guide plate when the second drive roller begins moving downstream, with respect to a sheet conveyance direction. 
         FIG. 4C  is a view of the height and the position of a second drive roller and a guide plate when the second drive roller has moved further downstream than in  FIG. 4B , with respect to a sheet conveyance direction. 
         FIG. 4D  is a view of the height and the position of a second drive roller and a guide plate when the second drive roller has moved still further downstream than in  FIG. 4C , with respect to a sheet conveyance direction. 
         FIG. 4E  is a view of the height and the position of a second drive roller and a guide plate when the second drive roller and second driven rollers contact a recorded sheet and the second drive roller is in the furthest downstream position, with respect to a sheet conveyance direction. 
         FIG. 5A  is a view of the height and the position of a first and second control pin positioned within a guide groove when the second drive roller and the guide plate are in the position illustrated in  FIG. 4A . 
         FIG. 5B  is a view of the height and the position of a first and second control pin positioned within a guide groove when the second drive roller and the guide plate are in the position illustrated in  FIG. 4B . 
         FIG. 5C  is a view of the height and the position of a first and second control pin positioned within a guide groove when the second drive roller and the guide plate are in the position illustrated in  FIG. 4C . 
         FIG. 5D  is a view of the height and the position of a first and second control pin positioned within a guide groove when the second drive roller and the guide plate are in the position illustrated in  FIG. 4D . 
         FIG. 5E  is a view of the height and the position of a first and second control pin positioned within a guide groove when the second drive roller and the guide plate are in the position illustrated in  FIG. 4E . 
         FIG. 6  is a control block diagram of an image processing apparatus according to an embodiment of the invention. 
         FIG. 7  is a flowchart illustrating a main routine of a moving operation of a second drive roller according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Embodiments of the present invention and their features and technical advantages may be understood by referring to  FIGS. 1-7 , like numerals being used for like corresponding portions in the various drawings. 
     As shown in  FIG. 1 , in an embodiment of the invention, an image recording apparatus, e.g., a printer  1 , may be connectable with other machines, e.g., computers and facsimiles, and to telephone communication networks. Printer  1  may be configured to receive image data, e.g., photo data and text data, from connected machines and removable storage media, and may be configured to record images, e.g., photos and text, on a recording sheet P, based on the received image data. 
     As shown in  FIGS. 1A to 1C , printer  1  may include a recording part  4 , which may be housed in a main casing  2 . Main casing  2  may be made of a synthetic resin, and may have a slot (not shown) configured to removably receive a removable storage medium. When the storage medium, which may include image data or other data, is inserted into the slot of main casing  2 , printer  1  may display a list of images stored on the storage medium on a display part (not shown). A user may select a desired image from the listed images, and then may press a button, e.g., a digital camera print button, which may cause the desired image to be recorded or printed on sheet P. In this case, the image data may be directly sent from the storage medium to printer  1 , bypassing a computer connected to printer  1 , and may be recorded at a recording part  4 . 
     A sheet supply tray  3  may be positioned in a bottom of main casing  2 . Sheet supply tray  3  may be configured to be removably attached to an opening  2   a , which may be provided at the front of main casing  2 . Opening  2   a  may be generally aligned in a substantially horizontal alignment. Recording part  4  and an output tray portion  10  may be positioned above sheet supply tray  3 . An inclined separation plate  8  for separating sheets may be positioned at the rear side of sheet supply tray  3 . A sheet supply unit  6 , which may be mounted to main casing  2 , may include a sheet supply arm  6   a , a sheet supply roller  6   b , and a drive shaft  6   c . Sheet supply arm  6   a  may be configured to pivot on drive shaft  6   c  vertically. Sheet supply roller  6   b  may be positioned at a lower end of sheet supply arm  6   a , and may operate with an elastic separation pad, e.g., a leaf spring (not shown) of inclined separation plate  8 , such that sheets P of a stack in sheet supply tray  3  may be singly separated and fed. 
     A sheet P separated from the stack may be fed via a U-shaped sheet feed path  9 , to recording part  4 , which may be positioned above sheet supply tray  3 . Sheet P, which may be recorded at recording part  4 , may be ejected to output tray portion  10  in a position such that a recorded surface of sheet P faces upward. A job separator  14  may be configured to convey sheets P to a front position or a rear position on output tray  19 , alternately, with respect to sheet conveyance direction A. 
     Recording part  4  may include a carriage  7 , which may be configured to move reciprocally, and to have a recording head, e.g., an inkjet-type recording head  48 , positioned on a lower surface of carriage  7 . Carriage  7  may be configured to slide, and may be supported by two guide members, one on the upstream side, and one on the downstream side of carriage  7 , with respect to sheet conveyance direction A. Each guide member may extend in a y-axis direction, e.g., a main scanning direction, which may be perpendicular to a sheet conveyance direction with respect to  FIGS. 1A to 1C . 
     Recording part  4  further may include a carriage (CR) motor  44 , a platen  12 , and an encoder strip (not shown). CR motor  44  may be configured to drive a timing belt stretched around pulleys which are positioned in parallel with the upper surface of the downstream-side guide member, in order to move carriage  7  reciprocally. Platen  12  may be a plate-like member and may be configured to support sheet P, which may be fed under recording head  48 . The encoder strip may be positioned to extend in the main scanning direction. The encoder strip may be a part of an optical linear encoder, which may detect the position and the moving speed of carriage  7  in the main scanning direction. 
     As shown in  FIGS. 1A and 3 , a registration roller pair  13  may be positioned in an upstream direction from platen  12  in a sheet conveyance direction A. Registration roller pair  13  may combine a feeding function and a registration function. Registration roller pair  13  may include a drive roller  13   a  and a driven roller  13   b , which may feed sheet P into a space between a nozzle surface on the lower surface of carriage  7  and platen  12 . 
     Referring again to  FIG. 1A , job separator  14  may be positioned downstream from platen  12  in sheet conveyance direction A. Job separator  14  may include a first conveyance roller unit  15  and a second conveyance roller unit  16 . First conveyance roller unit  15  may be positioned adjacent to a downstream end of platen  12 . Second conveyance roller unit  16  may be positioned downstream from first conveyance roller unit  15 . Output tray portion  10  may include an output tray  19 , which may be removably attached to main casing  2  through opening  2   a.    
     First conveyance roller unit  15  may include a first drive roller  15   a  positioned such that a lower surface of sheet P may face first drive roller  15   a , and a first driven roller  15   b  may be positioned such that an upper surface of sheet P may face first driven roller  15   b . Sheet P may be contacted between first drive roller  15   a  and first driven roller  15   b.    
     Second conveyance roller unit  16  may include a second drive roller  16   a , a second driven roller  16   b , and a guide plate  17 . Second drive roller  16   a  may be positioned such that the lower surface of sheet P faces second drive roller  16   a . Second drive roller  16   a  also may be configured to move from a first position, substantially near first conveyance roller unit  15 , to a second position, further away from first conveyance roller unit  15  in sheet conveyance direction A. Second driven roller  16   b  may be positioned such that the upper surface of sheet P faces second driven roller  16   b . Guide plate  17  may extend toward first conveyance roller unit  15 , and may be configured to guide sheet P at the lower surface side of sheet P, while moving along with second drive roller  16   a.    
     Ink may be ejected downward from recording head  48 , which may be positioned on the lower surface of carriage  7 , onto an upper surface of sheet P, which may be supported on platen  12 . This ejected ink may cause an image to be recorded on the upper surface of sheet P. The upper surface of sheet P may contain partially wet immediately after the image has been recorded. As shown in  FIG. 3 , a plurality of first driven rollers  15   b  and second driven rollers  16   b  may be arranged at regular intervals on respective shafts in a width direction, e.g., a direction perpendicular to the sheet conveyance direction A, of sheet P, to reduce an area of the upper surface of sheet P which may contact portions of printer  1 . Each of first driven rollers  15   b  and second driven rollers  16   b  may be a spur roller, and may have teeth formed on an outside surface of each roller in a circumferential direction. Another spur roller  18  also may be positioned downstream from and above platen  12 , with respect to sheet conveyance direction A. 
     A pair of side plates  20  may support both ends of shafts of first drive roller  15   a  and first driven rollers  15   b  of first conveyance roller unit  15 , while allowing first drive roller  15   a  and first driven rollers  15   b  to rotate. A sheet feeding motor  45  and a transmission gear train may drive first drive roller  15   a . A pair of side frames  21  may support both ends of shafts of second drive roller  16   a  and second driven rollers  16   b  of second conveyance roller unit  16 , while allowing second drive roller  16   a  and second driven rollers  16   b  to rotate. Both ends of a shaft of second drive roller  16   a  may be slidably engaged in guide grooves  22  provided in side frames  21 . Guide grooves  22  may be inclined in a diagonally upward direction, toward a downstream side, with respect to sheet conveyance direction A in a side view. 
     As shown in  FIGS. 2B and 2D , guide groove  22  may extend horizontally at a low position on a side close to second driven roller  16   b , e.g., a beginning side, and may be inclined upward toward the downstream side with respect to sheet conveyance direction A, and may again extend horizontally at a high position on a side further away from second driven roller  16   b , e.g., an ending side. 
     As shown in  FIGS. 2B ,  2 D, and  5 A to  5 E, a first control guide groove  22   a  may be formed in communication with guide groove  22  at the beginning side. First control guide groove  22   a  may be configured to guide a first control pin  24  horizontally in sheet conveyance direction A, and may be configured to prevent first control pin  24  from moving vertically. Similarly, a second control guide groove  22   b  may be formed in communication with guide groove  22  at the ending side. Second control guide groove  22   b  may be configured to guide a second control pin  25  horizontally toward sheet conveyance direction A, and may be configured to prevent second control pin from moving vertically. 
     As shown in  FIGS. 2B and 2D , guide plate  17  may be bent slightly downward at the side that is closer to first conveyance roller unit  15 , e.g., the bending side. Both left and right sides of guide plate  17  may be attached to a pair of rotatable supporting plates  23 , which may be engaged with both ends of a shaft of second drive roller  16   a . Supporting plates  23  may be positioned in parallel with inner surfaces of side frames  21 . The center of gravity of an assembly of supporting plates  23  and guide plate  17  may be located upstream from a center of the shaft of second drive roller  16   a . First control pin  24  and second control pin  25  may protrude outward from corresponding supporting plates  23 , and may be inserted into guide grooves  22 . First control pin  24  may be positioned toward first control guide groove  22   a  from the end of a shaft of second drive roller  16   a , and second control pin  25  may be positioned toward second control guide groove  22   b , from the end of the shaft of second drive roller  16   a.    
     When second drive roller  16   a  and guide plate  17  move together, either upstream or downstream with respect to sheet conveyance direction A, between left and right side frames  21 , first control pin  24  and second control pin  25  may slide, and may be in contact with an upper end and lower end of each guide groove  22 , first control guide  22   a , and second guide control guide  22   b . This contact may change and control a position of guide plate  17 . 
     A rack member  26  may be configured to move second drive roller  16   a  from a first position closer to first conveyance roller means  15 , or to a second position, away from first conveyance roller means  15 , along sheet conveyance direction A. Rack member  26  may include a U-shaped bearing  26   a  and a rack portion  26   b . Bearing  26   a  may be formed on an upstream side of rack member  26  in sheet conveyance direction A, and may be designed to support each end of second drive roller  16   a , such that second drive roller  16   a  may move vertically. Rack portion  26   b  may be formed on a downstream side of rack member  26  in sheet conveyance direction A and has teeth on its upper surface. Rack member  26  may be positioned parallel to an outer surface of each side frame  21 . As shown in  FIGS. 2B and 2C , guide pins  29  may protrude from rack member  26 , and may be slidably engaged in a pair of guide portions  27  provided on upstream and downstream sides of each side frame  21 . Guide portions  27  may be formed linearly in a horizontal direction, so that rack member  26  may be guided linearly in the horizontal direction, along side frame  21 . 
     A rack drive motor  31  may be fixed to an outer frame  30 . Rack drive motor  31  may be capable of rotating in both clockwise and counterclockwise directions. A gear transmission mechanism  32  may be positioned between one side frame  21  and outer frame  30 . Gear transmission mechanism  32  may transmit a driving force from a pinion of rack drive motor  31  to rack portion  26   b  of rack member  26 . Gear transmission mechanism  32  may include one or more driven gears  32   a . Driven gears  32   a  may be fixed to both ends of a rotating shaft  33  and may be engaged with rack portions  26   b  of rack members  26 , on outer surfaces of side frames  21 . 
     Referring again to  FIGS. 1A and 2C , a first gear  34  may be fixed to an end of first drive roller  15   a , and an arm  35  may be rotatably supported by the end of first drive roller  15   a . An intermediate gear  36  may be supported at an end of arm  35 , and may be engaged with first gear  34 . Arm  35  may be urged upward by a spring (not shown). When second drive roller  16   a  approaches first conveyance roller unit  15 , intermediate gear  36  may engage a second gear  37  positioned at an end of the shaft of second drive roller  16   a . When second drive roller  16   a  is separated from first conveyance roller unit  15  on the downstream side in sheet conveyance direction A, intermediate gear  36  may disengage from second gear  37 . 
     When second conveyance roller unit  16  is located a distance L 1  away from first conveyance roller unit  15 , first drive roller  15   a  and second drive roller  16   a  may be positioned at roughly the same height, so that sheet P may be contacted between first drive roller  15   a  and first driven roller  15   b , and also between second drive roller  16   a  and second driven roller  16   b . Thus, sheet P, which may be positioned and contacted between second drive roller  16   a  and second driven roller  16   b , is conveyed, ejected, and placed on a downstream side of output tray  19  in sheet conveyance direction A. As shown in  FIG. 2C , in this state, power may be transmitted from first gear  34 , positioned at the end of the shaft of first drive roller  15   a , to second gear  37 , via intermediate gear  36 . First drive roller  15   a  and second drive roller  16   a  may rotate in the same direction, at the same circumferential velocity, e.g., a velocity of a point on the outer circumference of the roller. 
     Referring again to  FIG. 1B , when second conveyance roller unit  15  is located distance L 2 , e.g., L 1 +ΔL, away from first conveyance roller unit  15 , arm  35  may be urged upward by the spring, and may move upward. Intermediate gear  36  may maintain engagement with second gear  37  of second drive roller  16   a . Second drive roller  16   a  may be separated from second driven rollers  16   b  such that second driven roller  16   b  and sheet P may not be in contact, although first drive roller  15   a  and second drive roller  16   a  may rotate in the same direction at the same circumferential velocity. Sheet P may be received by guide plate  17 , and placed on second drive roller  16   a , which may be in operation. Thus, sheet P may be ejected on the downstream side of output tray  19 , in sheet conveyance direction A. 
     As shown in  FIG. 1C , when second conveyance roller unit  16  withdraws from first conveyance roller unit  15  toward the downstream side in sheet conveyance direction A, second drive roller  16   a  and guide plate  17  may withdraw to a position higher than or equal to second driven roller  16   b , and a rotational force may not reach second drive roller  16   a . In other words, printed sheet P, which may move to the downstream side in sheet conveyance direction A, may directly be ejected to an upstream side of output tray  19  in sheet conveyance direction A without being received by guide plate  17 . 
       FIGS. 4A to 4E  illustrate changes in height and position of second drive roller  16   a  and guide plate  17  when second drive roller  16   a  moves from the most upstream position, illustrated in  FIG. 4A  in sheet conveyance direction A, to a position in which second drive roller  16   a  and second driven rollers  16   b  may contact and urge a recorded sheet to the most downstream position, illustrated in  FIG. 4E , in sheet conveyance direction A. 
       FIGS. 5A to 5E  illustrate changes in positions of first control pin  24  and second control pin  25  in association with  FIGS. 4A to 4E . In a state shown in  FIGS. 4A and 5A , which also may be the state shown in  FIG. 1A , second drive roller  16   a  may be positioned in the first position, e.g., furthest upstream side in sheet conveyance direction A, and second drive roller  16   a  and second driven roller  16   b  may be capable of conveying sheet P therebetween. At this time, first control pin  24  may be fitted in first control guide groove portion  22   a , at the beginning side of guide groove  22 , such that first control pin  24  may move in a substantially horizontal direction. Guide plate  17  may be placed at a height such that guide plate  17  may receive and support sheet P, which may have been conveyed between first drive roller  15   a  and first driven roller  15   b , from below. The bending side of guide plate  17 , which may face first conveyance roller unit  15 , may be inclined slightly downward. Thus, sheet P may be ejected on the downstream side on the output tray  19  in sheet conveyance direction A. 
     In a state shown in  FIGS. 4B and 5B , second drive roller  16   a  may move slightly downstream from second driven roller  16   b , and may release contact of sheet P. At this time, first control pin  24  may move out of first control guide groove portion  22   a , and second control pin  25  may slide on a lower edge of guide groove  22 , that may be inclined upward. Second drive roller  16   a  may move slightly upward and, guide plate  17  may be inclined downward at the bending side at a height such that guide plate  17  receives sheet P, which may have been conveyed between first drive roller  15   a  and first driven rollers  15   b  from below. The state shown in  FIGS. 4B and 5B  also may be the same state shown in  FIG. 1B . 
     In the state shown in  FIGS. 1A and 1B , second drive roller  16   a  and the lowermost portion of guide plate  17  may be positioned higher than the maximum height of stack of sheets P in output tray  19 . In a state shown in  FIGS. 4C and 5C , second drive roller  16   a  may move further downstream in sheet conveyance direction A, along the upward inclined portion of guide groove  22 , and may be positioned higher compared to the state shown in  FIGS. 4B and 5B . At this time, first control pin  24  may slide on the lower edge of the inclined portion of guide groove  22 , second control pin  25  may slide on the upper edge of the inclined portion of guide groove  22 , and guide plate  17  may be maintained with a maximal downward incline at the bending side. 
     In a state shown in  FIGS. 4D and 5D , second drive roller  16   a  may be guided to an upper portion of the upward inclined portion of guide groove  22 , and may be positioned higher than all portions of second driven rollers  16   b . At this time, second control pin  25  may move in guide groove  22  from an upper edge of the upward inclined portion to a horizontal portion. The bending side of guide plate  17  may be raised upward, while its inclination angle may be restricted, such that guide plate  17  may not interfere with second driven rollers  16   b.    
     In a state shown in  FIGS. 4E and 5E , which also may be the state shown in  FIG. 1C , second drive roller  16   a  may be guided to the horizontal portion in the upper portion of guide groove  22 , and second drive roller  16   a  may be positioned at the second position, e.g., the highest position and the furthest position away from second driven rollers  16   b . At this time, second control pin  25  may slide in contact with an upper edge of second control guide portion  22   b , and guide plate  17  may be positioned with the bending side raised upward. Guide plate  17  and second drive roller  16   a  may be withdrawn, such that their lowest positions may be higher than a height of a path of sheet P ejected by first conveyance roller unit  15 . 
       FIG. 6  illustrates a control block diagram of printer  1 , including CPU  41 , ROM  42 , and RAM  43 . CPU  41  may perform various operations, e.g., image recording operations, and movement control operations of second drive roller  16   a . ROM  42  may store control programs and data required for operations, which may be retrieved and executed when CPU  41  performs each operation. A specified area of RAM  43  may be used as a work area and a buffer area for each operation. 
     In an embodiment of the invention, a user selects a document to be printed on sheet P. When a print operation starts, e.g., an image recording operation for the document is ordered, a conveyance position of sheet P on output tray  19  may be set to an upstream side or a downstream side, with respect to sheet conveyance direction A, by job separator  14 . When a plurality of image recording operations for corresponding documents are ordered, a conveyance position of each document may be alternated between the upstream side and downstream side, with respect to sheet conveyance direction A, on output tray  19 . 
       FIG. 7  shows a flowchart which illustrates the steps carried out by job separator  14  to convey sheet P at the downstream side on output tray  19  in sheet conveyance direction A, according to an embodiment of the invention. In step S 1 , second drive roller  16   a  may be withdrawn from an origin where rack member  26  may be located at the most upstream position in sheet conveyance direction A, to a position shown in  FIG. 1B , where second drive roller  16   a  may be released from a conveying position with second driven roller  16   b . Subsequently, in step S 2 , sheet feed motor  45  may activate, and sheet supply tray  3  may supply sheet P. Then, at step S 3 , a leading end of sheet P may be detected by sheet detection sensor  47 , which may be positioned in the vicinity of registration roller pair  13 . In step S 4 , the leading end of sheet P may be conveyed, and may contact registration roller pair  13  for registration. Sheet P may be conveyed between registration rollers  13 , and positioned between recording head  48  positioned on the lower surface of carriage  7 , and platen  12 , positioned on recording part  4 . When sheet P is in this position, a known printing operation, e.g., an image recording operation may be performed. 
     In step S 5 , a determination may be made regarding whether printing of the last line of sheet P that has been fed to recording part  4  is finished. If printing of the last line is not finished, sheet P, now recorded, may be placed on second drive roller  16   a  without being conveyed between second drive roller  16   a  and second driven roller  16   b . As sheet P is not conveyed, the upper surface or printed surface of sheet P is not brought into contact with second driven roller  16   b . This may prevent ink from peeling off and transferring to another part, which may decrease print quality, particularly in a high quality image, such as a photo image. 
     If printing of the last line is finished, then in step S 6 , second drive roller  16   a  may be advanced to a conveying position with second driven roller  16   b . In step S 7 , first conveyance roller unit  15  and second conveyance roller unit  16  then may be simultaneously driven. When sheet P is conveyed by second drive roller  16   a  and second driven roller  16   b  in second conveyance roller unit  16 , it remains in contact with second drive roller  16   a  and second driven roller  16   b  up to a trailing end thereof, and then may be reliably conveyed to the downstream side on output tray  19 , in sheet conveyance direction A. 
     In an embodiment of the invention, when the last line has been completely printed, sheet P may be conveyed to output tray  19  while being contacted by second conveyance roller unit  16  at the trailing end. Prior to being conveyed to output tray  19 , during image recording by recording head  48 , sheet P may be contacted by first conveyance roller unit  15 , which may be positioned upstream of second conveyance roller unit  16 , with respect to sheet conveyance direction A. Additionally, prior to being conveyed to output tray  19 , during image recording by recording head  48 , second conveyance roller unit  16  may be configured not to contact sheet P. Thus, a diameter of second drive roller  16   a  may be smaller than a diameter of first drive roller  15   a.    
     As shown in  FIGS. 1C and 2B , second drive roller  16   a  and guide plate  17  may be configured to be positioned higher than second driven roller  16   b , and may be configured to be withdrawn to a recessed portion of an intermediate cover  28  of printer  1 , when moving from first conveyance roller unit  15  toward the downstream side in sheet conveyance direction A. Thus, job separator  14  may be positioned without increasing the height of printer  1 . 
     Each rack member  26  may be an actuator, which may be configured to move second drive roller  16   a  and guide plate  17  back and forth in sheet conveyance direction A. While each rack member  26  may be moved horizontally, second drive roller  16   a  and guide plate  17  may be guided vertically along guide groove  22 . Thus, job separator  14  can be made compact without having to increase the height of job separator  14 . 
     First drive roller  15   a  may compose a material which may have a high coefficient of friction, e.g., Ethylene Propylene Diene monomer (EPDM). Second drive roller  16   a  may compose a material having a low coefficient of friction, e.g., polyacetal resin (POM). The invention may be applied to multifunction devices (“MFD”) which may have one or more of a printer function, copier function, scanner function, and facsimile function, as an example of the image recording device. 
     Although embodiments of the present invention have been described in detail herein, the scope of the invention is not limited thereto. It will be appreciated by those skilled in the art that various modifications may be made without departing from the scope of the invention. Accordingly, the embodiments disclosed herein are only exemplary. It is to be understood that the scope of the invention is not to be limited thereby, but is to be determined by the claims which follow.