Abstract:
A sheet ejection device includes: a sheet ejection tray adapted to stack a sheet ejected thereon; an alignment member which aligns a position in a width direction and a direction perpendicular to a sheet ejection direction of the sheet on the sheet ejection tray; and a supporting unit which supports the alignment member so that the alignment member is displaced in a direction intersecting the sheet ejection direction when outer force is applied to the alignment member.

Description:
This application is based on Japanese Patent Application No. 2008-136364 filed on May 26, 2008, which is incorporated hereinto by reference. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a sheet ejection device that aligns a position of a sheet in its width direction on a sheet ejection tray, an image forming apparatus equipped with the sheet ejection device and a sheet finisher equipped with the sheet ejection device. 
     In a sheet ejection device that ejects a large quantity of sheets, the large quantity of sheets are ejected on a sheet ejection tray and are stacked, and after that, a bundle of sheets is given processing treatment. Therefore, the plenty of sheets are sometimes conveyed to another processor. In that case, a bundle of sheets prior to the processing treatment is required to have high compatibility. Accordingly, there is known a sheet ejection device equipped with an alignment member that aligns a bundle of sheets stacked on the sheet ejection tray. 
     Further, there is available a sheet ejection device by which a bundle of sheets is moved through shifting to a different position in the direction perpendicular to a sheet ejecting direction in a unit of one set of sheets so that dividing of sheets stacked on the sheet ejection tray in a unit of one set may become easy. In the sheet ejection device having the shifting function of this kind, high compatibility is required for each bundle of sheets at each shifting position. 
     Further, an image forming system that contains an image forming apparatus and is capable of processing at high speed is in a trend to be used as a shortrun printing apparatus, and when it is used as a shortrun printing apparatus, there is a growing trend wherein the image forming system is required to have capabilities to align a sheet on which an image has been formed with a sheet which has been processed by another apparatus to eject them. 
     In Unexamined Japanese Patent Application Publication No. 2002-211829, there is proposed to shift under the highly-aligned configuration and thereby to integrate by providing a shifting function on a sheet ejection tray. 
     In the case of a high-speed image forming apparatus and an image forming system composed of a high-speed image forming apparatus and a sheet finisher, a large quantity of sheets are integrated on a sheet ejection tray. 
     An integrated sheet is conveyed from a sheet ejection tray to another processing station, to be sent to the succeeding processing progress. 
     When conveying a sheet from a sheet ejection tray to the succeeding processing progress, the sheet is taken out of the sheet ejection tray manually in many cases. 
     However, handling of a sheet having a large volume and large mass is not easy, and there are sometimes generated accidents including destroyed alignments caused by contact between aligned sheets and surrounding mechanical parts, and injuries caused by contact between an operator&#39;s hand and mechanical parts. 
     In particular, when an alignment member is provided at the position near a sheet ejection tray, the number of chances to come in contact with the alignment member grows greater. 
     The alignment device disclosed in Unexamined Japanese Patent Application Publication No. 2002-211829 is not equipped with a safety device for the aforesaid accidents. 
     SUMMARY OF THE INVENTION 
     An aspect of the invention is as follows. 
     1. A sheet ejection device equipped with a sheet ejection tray on which ejected sheets are stacked and an alignment member that aligns positions of the ejected sheets in their width directions, which is characterized to have a supporting unit that supports the aforesaid alignment member so that the alignment member may be displaced in the direction for the alignment member to intersect the direction of ejection for sheets when an external force is applied on the alignment member. 
     2. An image forming apparatus is characterized to have a sheet ejection device described in the Item 1 above. 
     3. A sheet finisher is characterized to have a sheet ejection device described in the Item 1 above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram showing an overall structure of an image forming system equipped with a sheet ejection device relating to the embodiment of the invention. 
         FIG. 2  is a front sectional view of sheet ejection device  100 . 
         FIG. 3  is a diagram showing a mechanism to detect a height of an alignment member. 
         FIG. 4  is a block diagram of a controlling system that conducts shifting control. 
         FIG. 5  is a diagram showing a shifting process. 
         FIG. 6  is a diagram showing an alignment position, the first receding position and the second receding position. 
         FIG. 7  is a diagram showing a safety mechanism of a shifting section showing a safety mechanism of an alignment member. 
         FIG. 8  is a diagram showing a safety mechanism of a shifting section showing a safety mechanism of an alignment member. 
       Each of  FIGS. 9(   a )- 9 ( c ) is a diagram showing a safety mechanism of a shifting section showing a safety mechanism of an alignment member. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  is a diagram showing an overall structure of an image forming system composed of image forming apparatus A, automatic document feeder DF, sheet finisher FS and large capacity sheet feeding device LT. 
     The illustrated image forming apparatus A is equipped with image reading section  1 , image processing section  2 , image writing section  3 , image forming section  4 , a sheet conveying section and fixing device  6 . 
     The image forming section  4  is composed of photoreceptor drum  4 A, charging unit  4 B, developing unit  4 C, transfer unit  4 D, separation unit  4 E and cleaning unit  4 F. 
     The sheet conveying section is composed of sheet feed cassette  5 A, first sheet feed section  5 B, second sheet feed section  5 C, first conveyance section  5 D, second conveyance section (automatic two-sided copy conveyance section)  5 E and sheet ejection section  5 F. 
     Sheet finisher FS is connected to the sheet ejection section  5 F side on the illustrated left side of the image forming apparatus A. 
     Images on one side or both sides of document “d” placed on a document table of the automatic document feeder DF are read out by an optical system of the image reading section  1 , and are read in by CCD image sensor  1 A. 
     Analog signals converted photo-electrically by CCD image sensor  1 A are subjected to processing such as analog processing, A/D conversion, shading correction and image compression processing, in image processing section  2 , and are stored in an image memory (not shown). 
     In image writing section  3 , photoreceptor drum  4 A of the image forming section  4  is irradiated with light outputted from a semiconductor laser, and a latent image is formed. In the image forming section  4 , there are carried out treatments such as charging, exposure, developing, transfer, separation and cleaning. An image is transferred by transfer unit  4 D onto sheet S that is fed from the sheet feed cassette  5 A and from the large capacity sheet feeding device LT by the first sheet feed section  5 B. The sheet S carrying the image is subjected to fixing processing by the fixing device  6 , and is fed into sheet finisher FS from sheet ejection section  5 F. 
     The sheet S which has been subjected to the fixing processing is fed into second conveyance section  5 E by conveyance path switching plate  5 G, then, is fed again and in the image forming section  4 , and it is ejected from sheet ejection section  5 F after being subjected to image forming on the reverse side of the sheet S. 
     The large capacity sheet feeding device LT is composed of sheet stacking unit  11  and of first sheet feed unit  12 , and it stores a large number of sheets S stacked, and feeds sheet S into image forming apparatus A. 
     The sheet finisher FS is one that conducts folding processing and shifting processing for sheet S and addition sheet F to eject them to fixed sheet ejection tray  28  or to rising and falling sheet ejection tray  29 . 
     The sheet finisher FS is equipped with sheet carry-in section  21 , horizontal conveying section  22 , lower conveying section  23 , folding processing section  24 , addition sheet conveying section  25  and with upper conveying section  26 . 
     Sheet S ejected from the image forming apparatus A passes through the horizontal conveyance section  22  and the upper conveying section  26  to be ejected to fixed sheet ejection tray  28 , or passes through the horizontal conveyance section  22  to be ejected to the rising and falling sheet ejection tray  29 , or passes through the lower conveying section  23  to be ejected to the rising and falling sheet ejection tray  29  after being subjected to the folding processing in the folding processing section  24 . 
     Addition sheets F such as sheets for interleaf and sheets for a cover are stored in addition sheet feed section  27 , and addition sheets F are added to recording sheets coming from the image forming apparatus A, and they pass through the aforesaid conveyance section to be ejected to the rising and falling sheet ejection tray  29 . 
     Sheets S are ejected to the fixed sheet ejection tray  28 , in the mode to form a small number of images and in the image forming mode wherein neither folding processing nor shifting processing is carried out. 
     Under the modes including a folding mode, a mode of forming a large quantity of images for forming a large number of image sheets, and a shifting sheet ejection mode, sheets S and addition sheets F are ejected to the rising and falling sheet ejection tray  29 . 
     The folding processing section  24  is equipped with functions to conduct various types of folding processing such as twofold and various types of folding in three, as is widely known, whereby, folded sheets S and addition sheets F are conveyed upward, and then, are ejected in the rising and falling sheet ejection tray  29  by sheet ejection roller  30  provided on horizontal conveying section  22 . 
     Sheet ejection device  100  including the rising and falling sheet ejection tray  29  is equipped with shifting sheet ejection functions. 
     Next, the sheet ejection device  100  having shifting sheet ejection functions will be explained as follows. 
     Incidentally, in the following explanation, sheet S includes addition sheet F. 
       FIG. 2  is a front sectional view of sheet ejection device  100 . 
     The sheet ejection device  100  is structured to be a sheet ejection device of sheet finisher FS. However, it is also possible to make it to be a sheet ejection device of image forming apparatus A. 
     As stated above, sheet S and addition sheet F are ejected to rising and falling sheet ejection tray  29  representing a sheet ejection tray, and in the following explanation, a general name of sheet S is given to both of the sheet S and the rising and falling sheet ejection tray  29 . 
     Though the sheet S ejected by sheet ejection roller  30  is ejected to the rising and falling sheet ejection tray  29 , as stated above,  FIG. 2  shows sheet S stacked on the rising and falling sheet ejection tray  29 . 
     An upper surface of the sheet S is detected by sensor  105  that is composed of a photo-electronic sensor, and the rising and falling sheet ejection tray  29  is moved up and down so that the upper surface of the sheet S may be kept constantly at the fixed height. The up-and-down movement of the rising and falling sheet ejection tray  29  of this kind is carried out by a drive of a motor (not shown) controlled by a controller. 
     On the rising and falling sheet ejection tray  29 , there is formed concave portion  29 A that is positioned just beneath alignment members  101  and  102 . 
     When sheet S is stacked on the rising and falling sheet ejection tray  29 , there is formed a gap between the sheet S and the rising and falling sheet ejection tray  29 , by the concave portion  29 A as illustrated. 
     When an operator takes sheet S out of the rising and falling sheet ejection tray  29 , it is possible to take out sheet S by inserting a hand into the gap formed by the concave portion  29 A. 
     Above the rising and falling sheet ejection tray  29 , there are arranged side by side a pair of plate-like alignment members  101  and  102  which align sheet S in a horizontal direction (hereinafter referred to as width direction) that is perpendicular to the direction for conveyance and ejection of sheet S. 
     The paired alignment members  101  and  102  can swivel in the direction to recede from the rising and falling sheet ejection tray  29  around axis of gyration AX, and they are established at an alignment position shown with solid lines, a first receding position shown with dotted lines ( 101 A,  102 A) and a second receding position shown with dotted lines ( 101 B,  102 B). 
     The alignment members  101  and  102  are swiveled by a drive of motor  104  and are established at the aforesaid alignment position, first receding position and a second receding position. 
     At the alignment position shown with solid lines, the empty weight of the alignment member  101  or  102  makes it to be on sheet S. 
     The alignment members  101  and  102  reciprocate in the width direction of sheet S as will be explained later, and this reciprocating movement is conducted by a drive of motor (shift member)  103  in which the driving force of the motor  103  is transmitted to the alignment members  101  and  102  through a transmission mechanism employing a belt and a pulley. 
     Positions of rotation of the alignment members  101  and  102 , in particular, alignment positions, the first receding position and the second receding position are set based on signals outputted by sensor  106  (shown in  FIG. 3 ) composed of the photo-electronic sensor. 
       FIG. 3  shows a mechanism that constitutes a detecting device which detects a height of each of alignment members  101  and  102 . Encoder  107  is fixed on axis of gyration AX for alignment members  101  and  102 , and sensor  106  detects a position of rotation of the encoder  107 . 
       FIG. 4  is a block diagram of a control system that conducts shifting sheet ejection control in sheet ejection device  100 . In the drawing, the numerals  103  and  104  represent motors which drive respectively alignment members  101  and  102 , as explained earlier, and  106  represents a sensor that detects positions of rotations of alignment members  101  and  102 . 
     SE represents a sheet sensor provided at sheet carry-in section  21  in  FIG. 1 . 
     Controller  110  conducts shifting control based on detection signals of sensor  106  and of sheet sensor SE. 
     Next, shifting control will be explained, referring to  FIG. 5 . 
     In  FIG. 5 , directions shown by arrow V 1 , V 3  and V 5  represent a first direction that is perpendicular to the conveyance ejection direction for sheet S and is in parallel with sheet surface on the rising and falling sheet ejection tray  29  (hereinafter referred to as width direction). 
     Bundle of sheets SS 1  in quantity of sheets constituting one unit of an established shift is stacked on the rising and falling sheet ejection tray  29 , as shown in step SP 1 . 
     In the step SP  1 , alignment members  101  and  102  are set to the alignment height that is a lower position shown with solid lines in  FIG. 2 . This lower position is a position where a position of a lower end of alignment members  101  and  102  is slightly lower than a sheet supporting surface for the sheet of the rising and falling sheet ejection tray  29 . 
     Therefore, when the alignment member  101  or  102  is set to the lower position, the empty weight thereof makes it to be existent on the rising and falling sheet ejection tray  29 . 
     The alignment member  102  reciprocates in the width direction of sheet as shown with arrow V 1  to align sheet S. Sheet alignment is carried out in a way that the alignment member  102  moves each time a sheet of the sheet S is ejected. 
     At a step when bundle of sheets SS 1  arrives at the established number of sheets, which is notified by signals coming from sheet sensor SE, alignment members  101  and  102  move by about 2 mm outwards in step SP 2  to part from the side edge of bundle of sheets SS 1 , and then, the alignment members rise as shown with arrow V 2 . Incidentally, “outwards” means a direction toward an outside from the center of sheet S in terms of its width direction. 
     A distance of the movement shown with arrow V 2  is a distance by which a lower end of each of alignment members  101  and  102  parts from the upper surface of the bundle of sheets SS 1 . 
     In step SP 2 , alignment members  101  and  102  are set to a receding height at which the alignment members are away from the upper surface of the bundle of sheets SS 1 . 
     In the meantime, the receding height of the alignment members  101  and  102  shown in step SP 2  corresponds to the second receding position in  FIG. 2 . 
     The second receding position shown with  101 B and  102 B in  FIG. 2  is lower than the first receding position (shown with  1 - 1 A and  102 A) at which the alignment members  101  and  102  are positioned when sheet ejection device  100  is in the shutdown condition. 
     After rising, the alignment members  101  and  102  moves horizontally toward the right side (in the width direction) as shown with arrow V 3 . A distance of the movement shown with arrow V 3  is a distance corresponding to an amount of shifting. 
     Next, as shown in step SP 3 , the alignment members  101  and  102  fall as shown with arrow V 4 . 
     The alignment members  101  and  102  fall so that their lower edges may become lower slightly than the upper surface of the bundle of sheets SS 1 . As a result, the alignment member  102  mounts on the bundle of sheets SS 1 , and the lower edge of the alignment member  101  becomes to be slightly lower than the uppermost surface of sheet S. 
     In step SP 4 , the alignment member  101  reciprocates in the width direction as shown with arrow V 1 , to align a sheet. 
     Step SP 5  is a step identical to step SP 2  wherein alignment members  101  and  102  rise as shown with arrow V 2 , and then, move horizontally toward the left side as shown with arrow V 5 . 
     In step SP 6  following the step SP 5 , alignment members  101  and  102  fall as shown with arrow V 4 , to be set at shifted alignment positions. 
     In succeeding step SP 7 , alignment member  102  reciprocates as shown with arrow V 1 , to align sheet S. 
     Bundles of sheets SS 1 , SS 2  and SS 3  which have been subjected to shifting processing by aligning processes in steps SP 1 -SP 7  are formed. 
     In  FIG. 6 , alignment positions of alignment members  101  and  102 , the first receding position and the second receding position as positions in the width direction. 
     As illustrated, the first receding position is on the outside of the second receding position in terms of the width direction. 
     Namely, the first receding position is a position in the case when the alignment members  101  and  102  are in the standby state, and the first receding position is set to be outside of the operation range of the aforesaid position. 
     Further, the second receding position is a position wherein each of the alignment members  101  and  102  is shifted outward slightly (for example, 2 mm) from the alignment position, as stated earlier. 
     The alignment members  101  and  102  are set to the home position, namely, the first receding position, based on signals of sheet ejection completion. 
     In this case, each of the alignment members  101  and  102  is at the outside of an operation range parting greatly from the rising and falling sheet ejection tray  29  as shown in  FIG. 2 , and it is set to be high and to the position in the outside in the width direction as shown in  FIG. 6 . 
     Each of  FIGS. 7-9(   c ) shows a safety mechanism for the alignment member. 
       FIG. 7  is a front elevation of alignment member  101 ,  FIG. 8  is an exploded view of an installing structure for the alignment member and each of  FIGS. 9(   a )- 9 ( c ) is a plane view of the alignment member viewed from the upper part and it is a diagram showing operations of the safety mechanism. In the mean time, a safety mechanism shown in  FIGS. 7-9(   c ) and explained as follows is one for alignment member  101 , and a safety mechanism that is the same as the aforesaid safety mechanism is provided also on alignment member  102 . 
     The alignment member  101  has shaft  112  on the edge portion on the upstream side in the sheet ejection direction, and it is attached on intermediate supporting member  110  and on supporting member  111  by which the alignment member  101  is attached on a sheet finisher. Namely, the alignment member  101  is connected with the intermediate supporting member  110  and with the supporting member  111 , y getting the shaft  112  that forms a base portion of the alignment member  101  through a hole (not shown) of the intermediate supporting member  110  and through a hole provided on the supporting member  111 . 
     Coil springs  113  and  114  are wound around the shaft  112 . 
     A bottom end of the coil spring  113  is fixed on the alignment member  101 , and its top end is fixed on the intermediate supporting member  110 . 
     Further, a bottom end of the coil spring  114  is fixed on the supporting member  111 , and its top end is fixed on the intermediate supporting member  110 . 
     On the right side of the intermediate supporting member  110  in each of  FIGS. 9(   a )- 9 ( c ), there is formed projection  110 A, and on the left side thereof, there is formed projection  110 B. 
     The projection  110 A hits the supporting member  111 , while, the projection  110 B hits the alignment member  101 . 
     The alignment member  101  can swivel around the shaft  112 . The shaft  112  is in parallel with a sheet ejection direction in  FIG. 2 . 
     Namely, the alignment member  101  can swivel in the second direction around the shaft that is in parallel with a sheet ejection direction. 
       FIG. 9(   a ) shows a posture of the alignment member  101  on the occasion when no external force is applied,  FIG. 9(   b ) shows a posture of the alignment member  101  on the occasion when external force shown with F 1  is applied, and  FIG. 9(   c ) shows a posture of the alignment member  101  on the occasion when external force shown with F 2  is applied. 
     When external force F 1  is applied on the alignment member  101 , the alignment member  101  swivels clockwise as shown with W 1 . The direction W 1  is a direction toward the outside for the sheet stacking area (sheet width area) on rising and falling sheet ejection tray  29 , namely, it is a direction toward the outside from the center in the width direction. The relationship between sheet S on the rising and falling sheet ejection tray  29  and the alignment member  101  is as shown in  FIG. 9(   a ). As is illustrated, the direction W 1  is a direction to be displaced toward the outside while being pressed by an edge portion of sheet S in the width direction. 
     In the case of swiveling shown in  FIG. 9(   b ), an engagement action of projection  110 A prevents intermediate supporting member  110  from swiveling. Therefore, there is caused relative swiveling between the alignment member  101  and the intermediate supporting member  110 . 
     For this relative swiveling, stress of coil spring  113  acts upon the swiveling as resisting force. 
     Accordingly, if the external force F 1  is removed, the alignment member  101  returns to the state shown in  FIG. 9(   a ). 
     Namely, when sheet S or a hand of an operator comes in contact with alignment member  101  in the course of operation to take out sheet S from rising and falling sheet ejection tray  29 , the alignment member  101  swivels as shown with arrow W 1 , but it makes its comeback if contact is broken off. 
     When external force F 2  is applied on the alignment member  101 , the alignment member  101  swivels counterclockwise as shown with arrow W 2 . The direction W 2  is a direction toward the inside for the sheet stacking area (sheet width area) on rising and falling sheet ejection tray  29 . 
     In the case of swiveling shown in  FIG. 9(   c ), an engagement action of projection  110 B of the intermediate supporting member causes intermediate supporting member  110  and he alignment member  101  to swivel integrally, and the intermediate supporting member  110  swivels relatively to he supporting member  111 . 
     For this relative swiveling, stress of coil spring  114  acts upon the swiveling as resisting force. 
     Accordingly, if the external force F 2  is removed, the alignment member  101  returns to the state shown in  FIG. 9(   a ). 
     Namely, when sheet S or a hand of an operator comes in contact with alignment member  101  in the course of operation to take out sheet S from rising and falling sheet ejection tray  29 , the alignment member  101  swivels as shown with arrow W 1  and arrow W 2 , but it makes its comeback if contact is broken off. The meantime, after completion of ejection of sheets for series of jobs on rising and falling sheet ejection tray  29 , the alignment member recedes upward to part from the rising and falling sheet ejection tray after conducting the last aligning operations. Therefore, even when external force shown with F 2  is applied on the alignment member during operations to take out sheet S, and even when the alignment member swivels in the inner direction W 2  for a sheet stacking area on rising and falling sheet ejection tray  29 , it does not happen that the alignment member hits a bundle of sheets stacked on the rising and falling sheet ejection tray  29 , and the alignment is disturbed accordingly. 
     The supporting mechanism of the alignment member  101  explained above, namely, intermediate supporting member  110  that supports the alignment member  101  to be capable of being displaced in the second direction, supporting member  111 , and coil springs  113  and  114  constitute a supporting device that supports the alignment member. 
     As stated above, for alignment member  101 , a mechanism is one wherein the alignment member  101  always recedes independently of the direction for right and left for external force to be applied, thus, destruction of alignment of sheets can be prevented, and a safety mechanism that prevents injuries of an operator can be provided at a sheet ejection section. 
     Incidentally, it is preferable to use coil spring  113  having the spring constant wherein displacement resisting force in the case for alignment member  101  to be displaced in W 1  direction is greater than the stress from the sheet receiving in the case of alignment conducted when alignment member  101  is in contact with a sheet on rising and falling sheet ejection tray  29 . The alignment member  101  reciprocates in the width direction to align the sheets as shown in  FIG. 6 , and in the alignment operations, the alignment member  101  receives the force toward the outside in the width direction caused by the stress of the sheet, namely, the force F 1  shown in  FIG. 9(   b ). In the alignment operations, it is not desirable that the alignment member  101  is displaced by the force received from the sheet. By making displacement resisting force in the case when the alignment member  101  is displaced in the direction of W 1  to be greater than the stress received from sheets in the case of alignment, it is possible to secure safety while securing the sufficient alignment operations. 
     On the other hand, for the force toward the inside in the width direction, it is preferable that the alignment member  101  is displaced easily. To satisfy the conditions of that kind, it is also possible to establish the spring constant of the coil spring  113  to be higher than that of coil spring  114 , and thereby to make the displacement resisting force in the case of displacement in the direction of W 1  and the displacement resisting force in the case of displacement in the direction of W 2  to be different each other. Owing to this, it is possible to secure the structure that is easily displaced toward the inside and has high safety. 
     In the mean time, a supporting device of alignment member  102  is also the same as explained earlier, with respect to directions W 1  and W 2 , they are opposite to the occasion of the alignment member  101 . Namely, direction W 1  is a direction toward the inside, and direction W 2  is a direction toward the outside.