Patent Publication Number: US-2011074082-A1

Title: Sheet feeder, image forming apparatus having the same, and method for sheet feeding

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 12/330,018, filed Dec. 8, 2008, which is based upon and claims the benefit of priority from U.S. provisional application 61/012768, filed on Dec. 10, 2007. The entire contents of U.S. patent application Ser. No. 12/330,018 are incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a sheet feeder, an image forming apparatus having the same and a method for sheet feeding, and particularly to a large capacity sheet feeder in which sheet bundles to be fed are horizontally arranged and can be stacked, an image forming apparatus having the same and a method for sheet feeding. 
     BACKGROUND 
     A certain image forming apparatus, such as a copier or an MFP (Multi-Function Peripheral), has a large capacity sheet feeder which can contain a large amount of sheets before printing. As one of such large capacity sheet feeders, there is a tandem large capacity feeder (hereinafter referred to as a tandem LCF). 
     The tandem LCF has two spaces in which sheet bundles can be horizontally arranged and contained. A sheet bundle stacking tray called a sheet feed tray is provided at a lower part of one of the spaces, and a sheet bundle stacking tray called a conveyance tray is provided at a lower part of the other space. A sheet bundle of, for example, about 1000 or more sheets can be stacked on each of the sheet feed tray and the sheet conveyance tray. 
     When a sheet is printed, the sheet is sequentially picked up one by one from the upper side of the sheet bundle stacked on the sheet feed tray. The picked up sheet is used for print processing through a conveyance path. 
     When a sensor detects that all sheets in the sheet bundle on the sheet feed tray are used, the conveyance tray on which a different sheet bundle is stacked is moved to the sheet feed tray side, and the conveyance tray is stopped at a position where the conveyance tray overlaps the sheet feed tray. Thereafter, the conveyance tray returns to the original position while leaving the sheet bundle stacked thereon on the sheet feed tray. As a result, the new sheet bundle is stacked on the sheet feed tray which became empty, and sheet feeding for a next print operation becomes possible. 
     Although the conveyance tray returned to the original position is empty, the conveyance tray is constructed to be capable of being pulled out to the outside independently of the sheet feed tray. Thus, even when sheets are being fed from the sheet feed tray, a sheet bundle to be next printed can be supplied on the conveyance tray. 
     It is desirable that ends of the sheet bundle stacked on the sheet feed tray are aligned in a longitudinal direction and a lateral direction (that is, alignment is performed in the longitudinal direction and the lateral direction). When printing is started in a state where the alignment is not performed in the longitudinal direction or the lateral direction, each sheet of the sheet bundle is picked up in such a state that the position of the sheet is shifted in the longitudinal direction or the lateral direction (or both directions), and there is a possibility that printing is performed at an unsuitable position. 
     In the tandem LCF of the related art, alignment in the movement direction of the conveyance tray (hereinafter, the movement direction of the conveyance tray is called a longitudinal direction, and the alignment in the longitudinal direction is called longitudinal alignment) can be relatively easily performed by pressing the sheet bundle to a side wall of the sheet feeder by the driving force of the conveyance tray. 
     However, alignment in a direction perpendicular to the movement direction of the conveyance tray (hereinafter, the direction perpendicular to the movement direction of the conveyance tray is called a lateral direction, and the alignment in the lateral direction is called lateral alignment) is insufficient. 
     SUMMARY 
     The present invention is made in view of the above circumstances, and it is an object to provide a sheet feeder in which both longitudinal alignment and lateral alignment can be well performed in a tandem large capacity sheet feeder, an image forming apparatus having the same and a method for sheet feeding. 
     In order to achieve the object, according to an aspect of the invention, a sheet feeder includes a sheet feed tray on which a first sheet bundle is stacked at a first position where sheet feeding to a conveyance path can be performed, and a conveyance tray on which a second sheet bundle is stacked at a second position adjacent to the sheet feed tray, and which conveys the second sheet bundle to the sheet feed tray and stacks the second sheet bundle on the sheet feed tray after the first sheet bundle is fed, presses the stacked second sheet bundle to a side plate provided in a direction perpendicular to a conveyance direction of the conveyance tray, and aligns an end of the second sheet bundle. 
     According to another aspect of the invention, an image forming apparatus includes a scanner to read an original document and to generate image data, an image forming section to print the image data on a sheet, and a sheet feeder to feed the sheet to the image forming section, in which the sheet feeder includes a sheet feed tray on which a first sheet bundle is stacked at a first position where sheet feeding to a conveyance path can be performed, and a conveyance tray on which a second sheet bundle is stacked at a second position adjacent to the sheet feed tray, and which conveys the second sheet bundle to the sheet feed tray and stacks the second sheet bundle on the sheet feed tray after the first sheet bundle is fed, presses the stacked second sheet bundle to a side plate provided in a direction perpendicular to a conveyance direction of the conveyance tray, and aligns an end of the second sheet bundle. 
     According to still another aspect of the invention, a method of sheet feeding includes stacking a first sheet bundle on a sheet feed tray disposed at a first position to feed a sheet to a conveyance path, stacking a second sheet bundle on a conveyance tray at a second position adjacent to the sheet feed tray, conveying the second sheet bundle to the sheet feed tray and stacking it on the sheet feed tray after the first sheet bundle is fed, and pressing the stacked second sheet bundle to a side plate provided in a direction perpendicular to a conveyance direction of the conveyance tray to align an end of the second sheet bundle. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings, 
         FIG. 1  is a perspective view showing an outer appearance example of an image forming apparatus of an embodiment; 
         FIG. 2  is a first perspective view showing a structural example of a sheet feeder of the embodiment; 
         FIG. 3  is a second perspective view showing the structural example of the sheet feeder of the embodiment; 
         FIG. 4  is a plan view showing the structural example of the sheet feeder of the embodiment; 
         FIG. 5  is a view showing a movable section of the sheet feeder; 
         FIG. 6  and  FIG. 7  are a perspective view and a plan view showing a state where a sheet bundle is not stacked in the sheet feeder, respectively; 
         FIG. 8  and  FIG. 9  are a perspective view and a plan view showing a state where a sheet bundle is stacked in the sheet feeder, respectively; 
         FIG. 10  and  FIG. 11  are a first perspective view and a first plan view showing the movement of the sheet bundle in the sheet feeder, respectively; 
         FIG. 12  to  FIG. 15  are views showing movements in which lateral alignment of the sheet bundle is performed; 
         FIG. 16  and  FIG. 17  are a second perspective view and a second plan view showing the movement of the sheet bundle in the sheet feeder, respectively; 
         FIG. 18  and  FIG. 19  are a third perspective view and a third plan view showing the movement of the sheet bundle in the sheet feeder, respectively; 
         FIG. 20  and  FIG. 21  are a fourth perspective view and a fourth plan view showing the movement of the sheet bundle in the sheet feeder, respectively; 
         FIG. 22  and  FIG. 23  are a fifth perspective view and a fifth plan view showing the movement of the sheet bundle in the sheet feeder, respectively; 
         FIG. 24  and  FIG. 25  are a sixth perspective view and a sixth plan view showing the movement of the sheet bundle in the sheet feeder, respectively; 
         FIG. 26  and  FIG. 27  are a seventh perspective view and a seventh plan view showing the movement of the sheet bundle in the sheet feeder, respectively; and 
         FIG. 28  and  FIG. 29  are an eighth perspective view and an eighth plan view showing the movement of the sheet bundle in the sheet feeder, respectively; 
     
    
    
     DETAILED DESCRIPTION 
     An embodiment of an image forming apparatus and a method of sheet feeding of the invention will be described with reference to the accompanying drawings. 
     (1) Structure 
       FIG. 1  is a view showing an outer appearance example of an image forming apparatus  1  of the embodiment. The image forming apparatus  1  includes an image forming section  10  to print image data on a sheet, a large tandem LCF  20  to feed a sheet to the image forming section  10 , a scanner  30  to read an original document, to convert it into image data and to output the image data to the image forming section  10 , and an auto document feeder  40  to automatically feed an original document to the scanner  30 . 
     Besides, the image forming apparatus  1  includes an operation display section  50  to give an instruction of printing in the image forming section  10  and an instruction of document reading in the scanner  30 . Further, a sheet tray  60  for discharging a sheet printed in the image forming section  10  and a foldable manual feed tray  70  are provided on the side of the image forming apparatus  1 . 
     The tandem LCF  20  is constructed to be capable of being pulled out in the front direction in  FIG. 1 . 
       FIG. 2  to  FIG. 4  are views showing a structure of the tandem LCF  20  in a state where the tandem LCF  20  is taken out to the outside. 
     The tandem LCF  20  includes a sheet containing section surrounded by front side plates  203  and  305 , two side panels  102  and  103 , and rear side plates  202  and  304 . The sheet containing section can contain a first sheet bundle P 1  and a second sheet bundle P 2  arranged side by side. 
     The first sheet bundle P 1  is stacked at the right position (first position) of the sheet containing section when viewed from the front side of a front panel  100 , and the second sheet bundle P 2  is stacked at the left position (second position) of the sheet containing section. 
     A sheet feed tray  101  on which the first sheet bundle P 1  is stacked is provided at the first position and on the bottom side. The rear side plate (side plate)  304  is provided to extend upward at the rear of the sheet feed tray  101  when viewed from the front side of the front panel  100 , and the front side plate (second side plate)  305  is provided to extend upward in front of the sheet feed tray  101 . 
     On the other hand, a conveyance tray  201  on which a second sheet bundle P 2  is stacked is provided at the second position and on the bottom side. The rear side plate (side plate)  202  is provided to extend upward at the rear of the conveyance tray  201  when viewed from the front side of the front panel  100 , and the front side plate (second side plate)  203  is provided to extend upward in front of the conveyance tray  101 . 
     Further, a sheet rear end guide  200  is provided to extend upward at the left of the conveyance tray  201  when viewed from the front side of the front panel  100 . 
     Besides, thin and long stoppers  302  and  303  extending in the up-and-down direction are respectively provided at a front position and a rear position between the sheet feed tray  101  and the conveyance tray  201 . 
       FIG. 5  is a view showing movable sections and their movement directions with arrows in the tandem LCF  20 . 
     An arrow A indicates a conveyance direction of the second sheet bundle P 2  by the conveyance tray  201 . As stated above, the first sheet bundle P 1  is stacked on the sheet feed tray  101 , and the second sheet bundle P 2  is stacked on the conveyance tray  201 . 
     A sheet is fed to the image forming section  10  from the first sheet bundle P 1  stacked on the sheet feed tray  101 . When all sheets in the first sheet bundle P 1  on the sheet feed tray  101  are fed, the conveyance tray  201  on which the second sheet bundle P 2  is stacked is moved in the arrow A direction from the second position, overlaps the sheet feed tray  101  at the first position and is stopped. At this time, the sheet rear end guide  200 , together with the conveyance tray  201 , is moved in the arrow A direction, and presses the end of the second sheet bundle P 2  in the conveyance direction (that is, the longitudinal direction) to the side panel  103  (see  FIG. 2  to  FIG. 4 , the illustration thereof is omitted in  FIG. 5 ). By this pressing, the longitudinal alignment of the second sheet bundle is performed. 
     Thereafter, the conveyance tray  201  moves in a direction opposite to the arrow A while leaving the second sheet bundle P 2  on the sheet feed tray  101 , and returns to the second position in an empty state. 
     An arrow B to an arrow G indicate movements relating to lateral alignment of the second sheet bundle P 2 . The lateral alignment may be performed when the conveyance tray  201  is at the second position, or may be performed at the position (first position) where it overlaps the sheet feed tray  101 . 
     When the lateral alignment is performed while the conveyance tray  201  is at the second position, the conveyance tray  201  moves the second sheet bundle P 2  in the direction perpendicular to the conveyance direction (that is, in the lateral direction). For example, the second sheet bundle P 2  is moved in an arrow C direction, and the end of the second sheet bundle P 2  in the lateral direction is pressed to the rear side plate  202 . Further, the front side plate  203  may be moved in an arrow E direction to press the end of the second sheet bundle P 2  at the opposite side in the lateral direction. By these pressing operations, the lateral alignment of the second sheet bundle P 2  is performed. Thereafter, the conveyance tray  201  and the front side plate  203  move in an arrow B direction and an arrow D direction and return to the original positions. 
     On the other hand, when the conveyance tray  201  performs the lateral alignment at the first position, after the conveyance tray  201  moves to the first position (that is, after the conveyance tray  201  overlaps the sheet feed tray  101 ), the second sheet bundle P 2  is moved in the arrow C direction, and the end of the second sheet bundle P 2  in the lateral direction is pressed to the rear side plate  304 . Further, the front side plate  305  may be moved in an arrow G direction to press the end of the second sheet bundle P 2  at the opposite side in the lateral direction. Also by these pressing operations, the lateral alignment of the second sheet bundle P 2  is performed. Thereafter, the conveyance tray  201  moves in the arrow B direction and returns to the original position, and similarly, the front side plate  305  moves in an arrow F direction and returns to the original position. 
     In  FIG. 5 , the arrows indicate the movements of the conveyance tray  201  and the front side plates  203  or  305  when the rear side end of the second sheet bundle P 2  in the lateral direction is pressed to the rear side plate  202  or  304  and the lateral alignment is performed. However, conversely, the lateral alignment may be performed in such a manner that the conveyance tray  201  and the rear side plate  202  or  304  press the front side end of the second sheet bundle P 2  to the front side plate  203  or  305 . 
     (2) Operation 
       FIG. 6  to  FIG. 29  are views for explaining a series of movements of the first and the second sheet bundles P 1  and P 2  in the tandem LCF  20 . 
       FIG. 6  is a perspective view showing the tandem LCF  20  in a state where the first and the second sheet bundles P 1  and P 2  are not stacked, and  FIG. 7  is a plan view showing the tandem LCF  20  in a state where the first and the second sheet bundles P 1  and P 2  are not stacked. In  FIG. 6  and  FIG. 7 , the structure necessary to describe the series of movements of the first and the second sheet bundles P 1  and P 2  is chosen and illustrated, and the illustration of the other structure is omitted. 
     Perspective views and plan views shown in  FIG. 8  and the following (except  FIG. 12  to  FIG. 15 ) are views when viewed from the same angle as the perspective view of  FIG. 6  and the plan view of  FIG. 7 . 
       FIG. 8  and  FIG. 9  are a perspective view and a plan view in a state where the tandem LCF  20  is pulled out from the image forming apparatus  1 , and the first sheet bundle P 1  is stacked on the sheet feed tray  101 , and the second sheet bundle P 2  is stacked on the conveyance tray  201 . 
     As shown in  FIG. 9 , the stoppers  302  and  303  provided between the first sheet bundle P 1  and the second sheet bundle P 2  are at closed positions, and facilitate positioning when the user stacks the first sheet bundle P 1  on the sheet feed tray  101 . 
     Besides, as shown in  FIG. 9 , a guide member  301  is provided adjacent to the stopper  302 , and when the tandem LCF  20  is pulled out from the image forming apparatus  1 , a tip of the guide member  301  is closed. Since the tip of the guide member  301  is closed, positioning is facilitated when the user stacks the second sheet bundle P 2  on the sheet feed tray  101 . 
       FIG. 10  and  FIG. 11  are a perspective view and a plan view in which after the first and the second sheet bundles P 1  and P 2  are stacked on the sheet feed tray  101  and the conveyance tray  201 , the tandem LCF  20  is pushed into the image forming apparatus  1 , and then, the second sheet bundle P 2  is laterally aligned at the second position. 
     When the tandem LCF  20  is pushed into the image forming apparatus  1 , as shown in  FIG. 11 , the tip of the guide member  301  is opened. 
     Besides, the conveyance tray  201  and the front side plate  203  move the second sheet bundle P 2  in an arrow direction of  FIG. 10  and  FIG. 11 , and performs the lateral alignment of the second sheet bundle P 2 . 
       FIG. 12  to  FIG. 15  are views showing a state where the second sheet bundle P 2  is laterally aligned by the movement of the conveyance tray  201  and the front side plate  203  in the lateral direction. 
     Immediately after a user stacks the second sheet bundle P 2  on the conveyance tray  201 , the ends of the second sheet bundle P 2  are not laterally aligned and are often irregular. 
     Then, when a not-shown sensor detects that the tandem LCF  20  in which the second sheet bundle P 2  is stacked on the conveyance tray  201  is pushed into the image forming apparatus  1 , the conveyance tray  201  moves in the arrow C direction, and presses the end of the second sheet bundle P 2  in the lateral direction to the rear side plate  202  to perform the lateral alignment, as shown in  FIG. 13 . 
     Further, as shown in  FIG. 14 , the front side plate  203  is moved in the arrow E direction to press the end of the second sheet bundle P 2  at the opposite side in the direction toward the rear side plate  202 , and the lateral alignment may be performed. Although the lateral alignment can be performed only by the pressing of the conveyance tray  201 , the lateral alignment can be more certainly performed by adding the pressing of the front side plate  203 . 
     Thereafter, as shown in  FIG. 15 , the conveyance tray  201  and the front side plate  203  move in the directions of the arrow B and the arrow D, respectively, and return to the original positions. At this time, the second sheet bundle P 2  in which the lateral alignment is completed is stacked on the conveyance tray  201 . 
     Meanwhile, sheets are sequentially fed from the first sheet bundle P 1  stacked on the sheet feed tray  101  to the image forming section  10  by a pickup roller  300  (see  FIG. 6 ), and as shown in  FIG. 16  and  FIG. 17 , all sheets in the first sheet bundle P 1  are fed to the image forming section  10  and the sheet feed tray  101  becomes empty. 
     When a not-shown sensor detects that the sheet feed tray  101  becomes empty, the stoppers  302  and  303  are moved to open positions, and a path in which the second sheet bundle P 2  moves to the first position is secured, as shown in  FIG. 18  and  FIG. 19 . 
     Thereafter, as shown in  FIG. 20  and  FIG. 21 , the conveyance tray  201  on which the second sheet bundle P 2  is stacked is moved toward the sheet feed tray  101 . 
     When the conveyance tray  201  moves to a position (first position) where it completely overlaps the sheet feed tray  101 , the sheet rear end guide  200  presses the end of the second sheet bundle P 2  in the longitudinal direction to the side panel  103 , and the longitudinal alignment is performed. 
     As described above, although the lateral alignment of the second sheet bundle P 2  may be performed when the conveyance tray  201  is at the second position, it may be performed after the conveyance tray  201  is moved to the first position. Arrows shown in  FIG. 22  and  FIG. 23  show movements when the lateral alignment is performed at the first position. When the lateral alignment is performed at the first position, the conveyance tray  201  presses the end of the second sheet bundle P 2  in the lateral direction to the rear side plate  304 . Further, the end of the second sheet bundle P 2  at the opposite side may be pressed by the front side plate  305  in the direction toward the rear side plate  304 . 
     When the longitudinal alignment and the lateral alignment are ended at the first position, the stoppers  302  and  303  are moved to the closed positions, as shown in  FIG. 24  and  FIG. 25 . For the case in which the lateral alignment is performed at the second position, only the longitudinal alignment is performed at the first position, and accordingly, immediately after the longitudinal alignment is ended, the stoppers  302  and  303  are moved to the closed positions. 
     Thereafter, as shown in  FIG. 26  and  FIG. 27 , the conveyance tray  201  is moved toward the second position. At this time, since the movement of the second sheet bundle P 2  is restrained by the stoppers  302  and  303 , the second sheet bundle P 2  is left on the sheet feed tray  101 . 
     Finally, as shown in  FIG. 28  and  FIG. 29 , the conveyance tray  201  is returned to the second position finally in an empty state. 
     While the second sheet bundle P 2  left on the sheet feed tray  101  is placed in a state where sheet feeding can be performed by the pickup roller  300  (see  FIG. 6 ), the conveyance tray  201  can be pulled out from the image forming apparatus  1  independently of the sheet feed tray  101 . Thus, even when the second sheet bundle P 2  is being fed from the sheet feed tray  101 , the empty conveyance tray  201  is pulled out and a different sheet bundle can be supplied. When the different sheet bundle is stacked on the conveyance tray  201  and the conveyance tray is pushed in, the state of  FIG. 10  and  FIG. 11  occurs, and hereinafter, the operation from  FIGS. 10 and 11  to  FIGS. 28 and 29  is repeated. 
     As described above, according to the tandem LCF  20  (sheet feeder) of the embodiment, the image forming apparatus  1  having the same and the method for sheet feeding, both the longitudinal alignment and the lateral alignment of the stacked sheet bundle can be well performed, and a large amount of sheets can be continuously fed. 
     The invention is not limited to the above embodiment, and at the practical stage, the components can be modified and embodied within the scope not departing from the gist. Besides, various embodiments of the invention can be formed by suitable combinations of the plural components disclosed in the embodiment. For example, some components may be deleted from all components described in the embodiment. Further, components of different embodiments may be suitably combined.