Patent Publication Number: US-6988729-B2

Title: Sheet conveying device and image forming apparatus including the same

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a sheet conveying device for conveying a sheet in an image forming apparatus or an image forming system including the same and more particularly to a sheet conveying device of the type using path selectors and a sheet finisher including the same. 
   2. Description of the Background Art 
   A sheet conveying devices of the type including a path that branches off in a plurality of directions is conventional. In this type of sheet conveying device, when the path branches off at two positions by way of example, two path selectors are serially arranged on the path for steering a sheet. However, the problem with this configuration is that the two path selectors positioned one after the other occupy substantial part of the path corresponding to the sum of their widths in the direction of conveyance. Stated another way, the path needs a width corresponding to the total width of the path selectors for steering the sheet. Consequently, a sheet finisher or similar apparatus, which includes the sheet conveying device, increases in width in the right-and-left direction, as seen from the operator&#39;s side, increasing the size of the casing of the sheet finisher in the direction parallel to the direction of sheet conveyance. 
   If the two path selectors are not serially arranged, but are arranged in parallel to each other, then the size of the sheet conveying device can be reduced by the width of one path selector. Parallel arrangement of two path selectors are taught in, e.g., Japanese Patent Laid-Open Publication Nos. 7-315668 and 2000-53302. 
   More specifically, in Laid-Open Publication No. 7-315668 mentioned above, two parallel path selectors are rotated simultaneously with each other, i.e., not independently of each other. This, however, gives rise to a problem that the path selectors occupy a wide area when rotated, and moreover a solenoid capable of outputting great power is required for driving the path selectors. 
   In Laid-Open Publication No. 2000-53302 also mentioned above, a first and a second path selector are located at a first and a second branching position, respectively, and interconnected by a first, a second and a third link member. A solenoid actuates the two path selectors via the link members. A third path selector is additionally located at the second branching position and driven about a fulcrum independent of the fulcrum of the second path selector. This configuration, however, has a problem that when the edge of upper one of the second and third path selectors, which are movable about the respective fulcrums, is brought into contact with the upper surface of the lower path selector, the distance between the edges of the two path selectors increases. It is therefore likely that a sheet cannot be accurately conveyed and jams the path. Although this problem may be solved if the edges of the upper and lower path selectors are configured as comb teeth, such comb-teeth edges are apt to catch, when a tab sheet is conveyed, the tab of the sheet. The arrangement taught in the above document will be described more specifically later with reference to the accompanying drawings. 
   Technologies relating to the present invention are also disclosed in, e.g., Japanese Patent Laid-Open Publication Nos. 5-286672, 7-252002 and 2002-154728. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide a sheet conveying device capable of surely dealing even with a tab sheet, obviating a sheet jam at path selectors, and saving space. 
   A sheet conveying device of the present invention includes a sheet conveying mechanism for conveying a sheet, path selectors each for steering the sheet being conveyed by the sheet conveying mechanism in a particular direction, and a drive mechanism for causing the path selectors to move independently of each other. The path selectors are rotatable about a single axis and positioned parallel to each other in such a manner as to sandwich a plane of sheet conveyance. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description taken with the accompanying drawings in which: 
       FIG. 1  is a view showing path selectors included in a conventional sheet conveying device and positioned to convey a sheet straightforward; 
       FIG. 2  is a view similar to  FIG. 1 , showing the path selectors positioned to steer a sheet upward; 
       FIG. 3  is a view also similar to  FIG. 1 , showing the path selectors positioned to steer a sheet downward; 
       FIG. 4  is a view showing another conventional sheet conveying device in which two path selectors are positioned parallel to each other and rotatable about respective fulcrums; 
       FIG. 5  is an external isometric view showing an image forming system made up of an image forming apparatus and a sheet conveying device embodying the present invention; 
       FIG. 6  is a view showing arrangements disposed in the image forming system; 
       FIG. 7  is a view showing path selectors included in the illustrative embodiment and positioned to convey a sheet straightforward; 
       FIG. 8  is a view similar to  FIG. 7 , showing the path selectors positioned to steer a sheet upward; 
       FIG. 9  is a view similar to  FIG. 7 , showing the path selectors positioned to steer a sheet downward; 
       FIGS. 10 and 11  are respectively an isometric view and a side elevation showing the path selectors of the illustrative embodiment together with a mechanism for driving them; 
       FIG. 12  is a fragmentary enlarged view showing a specific condition wherein one of the path selectors is switched; 
       FIG. 13  is a block diagram schematically showing a control system included in the illustrative embodiment; 
       FIG. 14  is a view showing guide plates and the path selectors arranged at a branching position; 
       FIG. 15  is a view showing one of shock absorbing members affixed to the path selectors; 
       FIG. 16  is a perspective view showing the positions of the shock absorbing members on the path selectors; and 
       FIG. 17  is a view showing stubs that constitute the axis of rotation of the path selectors. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   To better understand the present invention, brief reference will be made to a conventional sheet conveying device, shown in  FIGS. 1 through 3 . As shown, the sheet conveying device includes a path branching off such that a sheet, coming in in a direction X, is steered to any one of three different directions A, B and C. More specifically, two path selectors  31  and  30  are serially arranged on the above path and respectively assigned to the directions A and B and directions A and C. As shown in  FIG. 2 , the upstream path selector  31  in the direction X selectively steers the sheet to the direction A (straightforward) or the direction B (upward) while the downstream path selector  30  selectively steers the sheet steered to the direction A to the direction A or the direction C (downward). 
   However, the two path selectors  31  and  30  positioned one after the other occupy substantial part of the path corresponding to the sum of their widths in the direction of conveyance. Stated another way, the path needs a width corresponding to the total width of the path selectors  31  and  30  for steering the sheet. Consequently, a sheet finisher or similar apparatus, which includes the sheet conveying device, increases in width in the right-and-left direction, as seen from the operator&#39;s side), increasing the size of the casing of the apparatus in the direction parallel to the direction of sheet conveyance. 
   In light of the above, Laid-Open Publication Nos. 7-315668 and 2000-53302 each propose to arrange two path selectors in parallel for thereby reducing the size of the apparatus by the width of one path selector, as stated earlier. However, the parallel arrangement of path selectors taught in the above documents gives rise to other problems discussed previously. 
   Specifically,  FIG. 4  shows two parallel path selectors  27  and  28  taught in Laid-Open Publication No. 2000-53302. As shown, the path selectors  27  and  28  are respectively driven about fulcrums  39  and  40  independently of each other. Assume that the edge  27   b  of the upper path selector  27  is brought into contact with the upper surface of the lower path selector  28  in order to switch a path PS upward. Then, as the locus from the center of movement indicates, a distance L 1  between the edge  27   b  of the path selector  27  and the edge  28   b  of the path selector  28  increases. As a result, the leading edge Pa of a sheet P, coming in via the path PS, contacts the upper surface of the path selector  28  and is guided toward the downstream side thereby and then abuts against the edge  27   b  of the path selector  27 . Consequently, the sheet jams the path without being guided upward. 
   Referring to  FIG. 5 , an image forming system embodying the present invention is shown in an external view and made up of an image forming apparatus PR and a sheet finisher FR.  FIG. 6  shows various arrangements disposed in the image forming system. As shown, the image forming apparatus PR, having a copying function, is generally made up of an image reading section  31 , an image writing section  32 , a sheet feeding section  33 , and a document feeding section  34 . 
   The image reading section  31  reads a document with a scanner, not shown, in the main scanning direction while reading it in the subscanning direction by driving the scanner. The document feeding section  34  is implemented as an ADF (Automatic Document Feeder) and feeds the above document to a glass platen not shown. The image writing section  32  is implemented by conventional optics including a laser diode, a polygonal mirror and an F-θ lens, not shown, and optically writes an image on a photoconductive drum or image carrier in accordance with image data. The latent image is then developed by toner to thereby become a toner image. The toner image is transferred from the drum to a sheet. 
   Subsequently, the toner image is fixed on the sheet by a fixing unit. The sheet with the toner image thus fixed is handed over from the image forming apparatus PR to the sheet finisher FR via an outlet roller pair  35 . In the illustrative embodiment, the sheet feeding section  33  includes a stack of four sheet trays, as illustrated. A vertical path  36  extends at the right-hand side or outlet side of the trays. A sheet paid out from any one of the trays is conveyed to the image writing section  32  via the vertical path  36 . 
   The sheet with the toner image and driven out of the image forming apparatus PR enters the sheet finisher FR in a direction indicated by an arrow M. A punching unit  4  is positioned in the sheet finisher FR downstream of an inlet roller pair  1 , but upstream of a roller pair  6 , in the direction of sheet conveyance. A conveying unit  5  is positioned beneath the punching unit  4  and extends perpendicularly to the direction of sheet conveyance. After the punching unit  4  has punched the sheet entered the sheet finisher FR, the conveying unit  5  conveys the resulting scraps to a scrap hopper  3  adjoining the operating side OP,  FIG. 5 . The operator, standing at the operating side OP, inputs desired processing meant for the sheet finisher FR or the image forming apparatus PR on a control panel  37  or replaces toner or removes a jamming sheet, as the case may be. The scrap hopper  3  is mounted on the inside of a front cover  14 , which the operator is expected to open for replacing toner or removing a jamming sheet. 
   The sheet punched by the punching unit  4  is conveyed via path selectors  27  and  28  positioned downstream of the roller pair  6 , subject to sorting, stapling or similar processing, and then driven out to a shift tray  9 . Alternatively, the sheet may be simply driven out to a proof tray  29  via an upper path. 
   More specifically, in a sort mode, the path selector  27  unblocks a path on which a roller pair  7  is positioned while the path selector  28  blocks a path on which a roller pair  10  is positioned. In this condition, the sheet is driven out to the shift tray  9  via an outlet roller pair  8 . The shift tray  9  is shifted copy by copy in the direction perpendicular to the direction of sheet conveyance for thereby sorting the consecutive copies (sets of sheets). 
   In a staple mode, the path selector  7  unblocks the path including the roller pair  7  while the path selector  28  unblocks the path including the roller pair  10 , so that the sheet is stacked on a staple tray  12  via a staple discharge roller  11 . Every time a sheet is stacked on the staple tray  12 , a knock roller knocks it downward against a rear fence, and then jogger fences position the sheet in the direction perpendicular to the direction of sheet discharge. When a single copy or set of sheets is fully stacked on the staple tray  12 , a stapler  13  staples, e.g., the rear edge of the stack. Subsequently, a belt conveys the stapled stack upward toward the outlet roller pair  8 , so that the stapled stack is driven out to the shift tray  9 . 
   As stated above, the punching unit  4  and scrap hopper  3  are positioned most upstream of the various finishing steps and can basically deal with all sheets. It is therefore possible to directly deliver the punched sheet to either one of the proof tray  29  and shift tray  9  or to staple a punched sheet stack and deliver it to the shift tray  9 . 
   While the illustrative embodiment forms an image on the basis of a document optically read by the image reading unit  31 , an image may, of course, be formed in accordance with image data received from a data processing unit either directly or via a network. The punching timing of the punching unit  4  and the switching timing of the path selectors  27  and  28  are determined in accordance with the output of an inlet sensor  2  responsive to the leading edge of a sheet. 
   As shown in  FIGS. 7 through 9 , the sheet finisher FR includes an upper path PS 1 , a middle path PS 2  and a lower path PS 3  into which an inlet path PS merges. A sheet is conveyed along the inlet path PS in a direction X. The proof tray  29  is positioned at the downstream end of the path PS 1  while the shift tray  9  is positioned at the downstream end of the paths PS 2  and PS 3 . It is noteworthy that the path PS does not branch into the three paths PS 1  through PS 3  at two consecutive positions as in  FIGS. 1 through 3 , but branches at a single position. 
   The proof tray  29  receives sheets not finished at all. The shift tray  9  sorts consecutive copies one by one by shifting them in the direction perpendicular to the direction of sheet conveyance and moves upward or downward in accordance with the number of copies stacked thereon. For this purpose, a motor for shifting the shift tray  9 , a control mechanism and a motor for moving the shift tray  9  in the up-and-down direction are provided. 
   The roller pairs  7  and  8  positioned on the middle path PS 2  deliver a sheet conveyed via the middle path PS 2  to the shift tray  9 . A discharge roller pair  10 , the staple discharge roller pair  11  and the stapling unit  12  are arranged on the lower path PS 3 . 
   The first path selector  27  steers a sheet toward the proof tray  29  in a proof mode or steers it toward the shift tray  9  via the roller pair  7  in a shift mode. The second path selector  28  steers a sheet toward the shift tray  9  via the roller pair  7  or steers it toward the staple tray  12  via the roller pair  11 . 
   Reference will be made to  FIGS. 7 through 9  for describing the operations of the path selectors  27  and  28 . As shown in  FIG. 7 , when a sheet should be conveyed to the roller pair  7  straightforward, the path selectors  27  and  28  both are held in their initial positions, so that a sheet, coming in in the direction X, is driven out in a direction A. As shown in  FIG. 8 , to convey the sheet upward, the path selector  27  is rotated clockwise about a fulcrum or shaft O, so that the sheet conveyed in the direction X is delivered to the proof tray  29  in a direction B. Further, as shown in  FIG. 9 , to convey the sheet downward, the path selector  28  is rotated counterclockwise about the fulcrum O, so that the sheet is steered toward the staple tray  12  in a direction C. 
   The path selectors  27  and  28  will be described more specifically hereinafter together with a mechanism for driving them.  FIGS. 10 and 11  show the path selectors  27  and  28  and drive mechanism in an isometric view and a side elevation, respectively. As shown, the path selectors  27  and  28  are generally wedge-shaped in a section and rotatable about a single shaft O independently of each other. The shaft adjoins the bottoms of the wedge-shapes of the path selectors  27  and  28  between the path selectors  27  and  28 . The path selectors  27  and  28  are respectively connected to a first and a second spring  35  and  36 , which establish the initial or default positions, and respectively connected to a third and a fourth spring  37  and  38  that establish the switched positions. A first and a second solenoid  33  and  34  are respectively connected to the other ends of the third and fourth springs  37  and  38  so as to move the path selectors  27  and  28  via the springs  37  and  38 , respectively. 
   The first and second path selectors  27  and  28  are held at their initial positions shown in  FIG. 7  or  11  by the first and second springs  35  and  36 , respectively. More specifically, the springs  35  and  36  bias the path selectors  27  and  28  along the axis in the direction of sheet conveyance such that no moments act on the path selectors  27  and  28 . In this condition, the axes of the path selectors  27  and  28  are parallel to each other. When a sheet should be steered to the upper path PS 1  in the direction B, the first solenoid  33  is turned on to pull a hook  27   a  included in the path selector  27  via the third spring  37 , thereby rotating the path selector  27  to the position shown in  FIG. 8 . This condition is shown in  FIG. 12  in an enlarged view. 
   As shown in  FIG. 12 , the path selector  27  rotates about the shaft O, so that the distance L 2  between the edge  27   b  of the path selector  27  and the edge  28   b  of the path selector  28  is far smaller than the distance L 1 ,  FIG. 4 . Therefore, the leading edge Pa of a sheet P, coming in via the path PS, surely contacts an inclined surface  27   c  included in the path selector  27  even when bent downward. The sheet P is therefore steered upward along the inclined surface  27   c  toward the upper path PS 1 . 
   By contrast, as shown in  FIG. 4 , when the path selectors  27  and  28  parallel to each other rotate about the respective axes  39  and  40  and when the path selector  27 , for example, is switched, the distance L 1  between the edges  27   b  and  28   b  of the path selectors  27  and  28  is great. As a result, if the leading edge Pa of the sheet P is bent downward, then it does not to contact the surface  27   c  of the path selector  27 , but abuts against the leading edge  27   b  of the path selector  27 , jamming the path. 
   In the illustrative embodiment, the two path selectors  27  and  28  rotate about a single fulcrum or shaft O. Therefore, when the lower path PS 3  is selected in the condition of  FIG. 7  so as to convey the sheet P in the direction C, the second solenoid  34  is turned on to pull a hook  28   a  included in the second path selector  28  via the fourth spring  38  to thereby rotate the path selector  28  to the position shown in  FIG. 9 . In this condition, the relation between the paths selectors  27  and  28  shown in  FIG. 12  is inverted, i.e., the distance between the edge  27   b  of the path selector  27  and the edge  28   b  of the path selector  28  becomes L 2 . It follows that the sheet P can surely contact an inclined surface  28   c  included in the path selector  28  to be steered downward thereby along the inclined surface  28   c  toward the lower path PS 3 . 
   As stated above, the two path selectors  27  and  28  are rotatable about a single fulcrum or shaft, which is positioned between the path selectors  27  and  28 . This successfully reduces the distance between the edges  27   a  and  28   b  when either one of the path selectors  27  and  28  is rotated from the initial position. 
     FIG. 13  shows a control system  350  included in the illustrative embodiment. As shown, the control system  350  is implemented as a microcomputer including a CPU (Central Processing Unit)  360  and an I/O (Input/Output) interface  370 . The CPU  360  receives via the I/O interface  370  the outputs of various switches arranged on the control panel of the image forming apparatus PR and the outputs of various sensors including the inlet sensor  2 , a sensor responsive to the discharge of a sheet to the shift tray  9 , and a sensor responsive to the top of sheets stacked on the shift tray  9 . 
   The CPU  360  controls, in accordance with the outputs mentioned above, the up-down movement of a punch included in the punching unit  4 , the operation of the scrap conveying unit  5 , jogging effected on the staple tray  12  in the direction perpendicular to the direction of sheet conveyance, stapling effected by the stapling unit  13  the staple tray  12 , discharge of a stapled sheet stack from the staple tray  12 , up-down movement and shift of the shift tray  9 , operation of the knock roller, and so forth. More specifically, the CPU  360  controls the knock roller and jogging by counting pulses input to a motor assigned to the staple discharge roller  11 . 
   It is to be noted that the CPU  360  controls the sheet finisher FR in accordance with a program stored in a ROM (Read Only Memory), not shown, while using a RAM (Random Access Memory), not shown, as a work area. 
   In  FIGS. 7 through 9 , the edges of the path selectors  27  and  28  are shown as being protruding to the outside of guide plates, the path selectors  27  and  28  are, in practice, angularly movably accommodated in a branching portion PSO, as shown in  FIG. 14 . The branching portion PSO is made up of spaces PSO 1  and PSO 2  contiguous with each other. As shown in  FIG. 15 , to prevent the sheet P from jamming the spaces PSO 1  and PO 2 , the height H of each space PSO 1  or PSO 2  in the branching direction is made as small as possible for thereby preventing the leading edge Pa of the sheet P from contacting a guide plate PSa or PSb. It is therefore necessary to minimize the distance between the edges  27   b  and  28   b  of the path selectors  27  and  28  when the path selectors  27  and  28  are rotated. However, should the edges  27   b  and  28   b  contact each other, they would produce noise or would be damaged due to the resulting shock. 
   In light of the above, as shown in  FIG. 16 , shock absorbing members  27   d  and  28   d  are respectively positioned on one end of the edge  27   b  of the path selector  27  and one end of the path selector  28  opposite to the above end. The shock absorbing members  27   d  and  28   d  are positioned outside of the maximum sheet size in the direction perpendicular to the direction of sheet conveyance and therefore do not obstruct the sheet P even when the sheet P is conveyed between the surfaces of the path selectors  27  and  28  facing each other, as shown in  FIG. 7 . To minimize the height H mentioned earlier, the shock absorbing members  27   d  and  28   d  are provided with minimum necessary thickness for absorbing shocks. 
   As shown in  FIG. 17 , the shaft O is implemented as two stubs O extending axially outward from support members  28   e , which protrude from the second path selector  28 . Support members  27   e  protrude from the first path selector  27 , and each is formed with a hole receiving one of the stubs O. By suitably configuring the support members  28   e  and  27   e  as well as their engaging positions, it is possible to locate the stubs or shaft O at any desired position. While the stubs O should preferably be located symmetrically on an axis perpendicular to the direction of sheet conveyance, the above advantage is achievable only if the stubs O are positioned at the intermediate position of the conveyance path. Although the stubs O should preferably be positioned as far from the edges  27   a  and  27   b  of the path selectors  27  and  28  as possible, it suffices to locate the stubs O within the range of length of the path selectors  27  and  28 . 
   As stated above, a single fulcrum O about which the parallel path selectors  27  and  28  are rotatable is positioned between the path selectors  27  and  28 . This prevents the sheet P from abutting against the edge  27   b  or  28   b  for thereby further promoting stable conveyance. 
   Further, in the illustrative embodiment, the edges  27   b  and  28   b  of the path selectors  27  and  28  are not provided with a comb-teeth configuration, but are simply formed straight, allowing even a tab sheet to be surely conveyed without any jam. 
   While the illustrative embodiment has been shown and described as using the path selectors  27  and  28  to switch a path inside the sheet finisher FR, the present invention is similarly applicable to sheet processing to be effected at, e.g., the stage of the image forming apparatus PR preceding the image forming section or to sheet discharge (jam processing). 
   Because the path selectors  27  and  28  are parallel to each other, it is possible to save space by the length of at least one path selector in the direction of sheet conveyance. 
   In summary, it will be seen that the present invention provides a sheet conveying device capable of surely dealing even with a tab sheet by use of parallel path selectors, preventing a sheet from jamming a branching portion, and saving space. 
   Various modifications will become possible for those skilled in the art after receiving the teachings of the present disclosure without departing from the scope thereof.