Patent Publication Number: US-6698744-B2

Title: Sheet finisher for an image forming apparatus

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a copier, printer, facsimile apparatus or similar image forming apparatus and more particularly to a sheet finisher operatively connected to the image forming apparatus for executing preselected processing with sheets. 
     2. Description of the Background Art 
     A sheet finisher is proposed in various forms in the past and capable of stapling, punching or otherwise processing sheets sequentially driven out of an image forming apparatus. The prerequisite with a sheet finisher of the type jogging sheets one by one and then stapling them together is the accuracy of jogging. Various methods have heretofore been proposed for meeting such a prerequisite. 
     It is a common practice to jog sheets with a pair of jogger fences or similar jogging members. Many of conventional jogging members address to accurate jogging at or around the allowable limit of the number of sheets that can be dealt with by, e.g., a stapler. Many users, however, daily deal with a stack of ten sheets or less to be stapled together and rarely deals with a stack of fifty sheets or more, as known by experiment and proved by the results of various market researches. More specifically, accurate jogging of a small number of sheets impresses users favorably. 
     Generally, jogging of sheets becomes more difficult as the number of sheets to be stapled together increases. In light of this, the jogging members are moved toward each other to a distance slightly smaller than the width of sheets, thereby pressing the edges of a sheet stack. This kind of scheme is desirable when the number of sheets is small. However, as the number of sheets sequentially stacked increases, it becomes difficult for the sheets to move. This, coupled with an increase in the reaction of the sheets acting on the jogging members, causes not only the jogging members but also parts for driving them to bend, obstructing accurate jogging. 
     Another advantage achievable with the jogging members pressing a sheet stack, as stated above, is that they absorb irregularity in sheet width and loosens sheets being stacked for thereby enhancing accurate jogging. 
     Japanese Patent No. 2,960,770 teaches a sheet finisher of the type described. After the last sheet has been stacked and jogged, the sheet finisher taught in the above document causes jogging means to again move in order to press the sheet stack during stapling. With this configuration, the sheet finisher prevents the jogged sheets from moving during stapling. The sheet finisher, however, presses the sheet stack by the same amount during stapling as during jogging. This is because the sheet finisher addresses to accurate jogging at or around the allowable limit of the number of sheets, as stated above, and directed only toward the simplification of software. 
     When a large number of sheets are to be stapled, the jogging means taught in the above document again moves after the last jogging movement so as to press the sheets during stapling. This desirably maintains the sheets in the accurately jogged position even during stapling. However, when the number of sheets to be stapled together is small, the sheets are loosened and therefore bent. As a result, the sheets stacked together are apt to shift in the lengthwise direction, which is perpendicular to the direction in which the jogging means moves. 
     Technologies relating to the present invention are also disclosed in, e.g., Japanese Patent Laid-Open Publication No. 2000-191219. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a sheet finisher for an image forming apparatus capable of accurately jogging sheets without regard to the number of sheets. 
     In accordance with the present invention, a sheet finisher includes a stacking section for stacking sheets thereon, a jogging device for jogging the sheets sequentially stacked on the stacking section one by one, and a processing device for executing preselected processing with the sheets. The jogging device includes a pair of jogging members for jogging the sheets one by one, and a controller for controlling the jogging members. The controller moves, in accordance with the width of the sheets in a direction perpendicular to the direction of sheet conveyance, each jogging member to a first position remote from one edge of the sheets in the direction of width by a preselected amount, a second position closer to the edge than the first position by a preselected amount and slightly overlapping the edge, and a third position where, when the processing device executes the preselected processing, the jogging member substantially contacts the edge in accordance with the width. Assuming that the jogging members are spaced from each other by a distance of L 2  at the second position or by a distance of L 3  at the third position, the controller sets at least one of the distances L 2  and L 3  in accordance with the width or the number of the sheets. 
     An image forming system including the above sheet finisher and an image forming apparatus are also disclosed. 
    
    
     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. 1A shows a stack of sheets in a jogged state; 
     FIG. 1B demonstrates how the sheet stack bends when pressed by pressing members; 
     FIG. 2 shows a sheet finisher embodying the present invention; 
     FIG. 3 is an isometric view showing a jogging mechanism included in the illustrative embodiment; 
     FIG. 4 is a fragmentary view showing a return roller and members around it; 
     FIG. 5 is an isometric view showing a stapler also included in the illustrative embodiment; 
     FIG. 6 is a fragmentary isometric view showing a copy tray further included in the illustrative embodiment and arrangements around it; 
     FIG. 7 is a schematic block diagram showing a control system of the illustrative embodiment; 
     FIG. 8 is a flowchart demonstrating a procedure  1  available with the illustrative embodiment; 
     FIG. 9 shows a relation between a first to a third position and the amount of pressing; and 
     FIG. 10 is a flowchart showing a procedure  2  also available with the illustrative embodiment. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     To better understand the present invention, the problem with the sheet finisher taught in Japanese Patent No. 2,960,770 mentioned earlier will be described more specifically with reference to FIGS. 1A and 1B. In the event of stapling a large number of sheets, the jogging means included in the finisher again moves after the last jogging movement so as to press the sheets during stapling. This desirably enhances accurate jogging during stapling, as stated earlier. However, when the number of sheets to be stapled together is small, the sheets are loosened and therefore bent. As a result, the sheets stacked together are apt to shift in the lengthwise direction, which is perpendicular to the direction in which the jogging means moves. 
     More specifically, FIG. 1 shows a stack of sheets accurately jogged by pressing members included in the jogging means. As shown in FIG. 1B, when the pressing members are fed toward such a jogged sheet stack by an excessive amount, the sheet stack bends in a semicylindrical cross-section. Further, the sheets tend to move away from a staple stray (upward in FIG. 1B) because they are restricted by the pressing members at the side edges and restricted by a rear fence at the rear edge. Moreover, if the amount by which the pressing members press the sheet stack is constant, then the ratio of the amount to width varies in accordance with sheet size, effecting the influence on jogging accuracy. 
     Referring to FIG. 2, a finisher embodying the present invention is shown and operatively connected to a copier or similar image forming apparatus not shown. As shown, the finisher includes a sheet inlet for receiving sheets sequentially driven out of the copier. An inlet sensor  36  and an inlet roller  1  adjoin the sheet inlet. The inlet sensor  36  senses a sheet entering the finisher via the sheet inlet while the inlet roller  1  conveys the sheet into the finisher. A path selector  8  steers the sheet toward either one of a copy tray  12  and a stapler  11 . 
     Upper rollers  2  are positioned on the path extending from the path selector  8  toward the copy tray  12  so as to convey the sheet toward the tray  12 . An outlet sensor  38  is responsive to the sheet being conveyed by the upper rollers  2 . An outlet roller  3  drives the sheet out of the finisher to the copy tray  12 . A push roller  7  pushes the sheet driven out to the copy tray  12  to a preselected position. A lever  13  senses the sheet present on the copy tray  12 . A sheet level sensor  13  senses the angular position of the lever  13 . An elevation motor  51  (see FIG. 7) selectively moves the copy tray  12  upward or downward. Also, a shift motor  52  (see FIG. 7) moves the copy tray  12  in the direction perpendicular to the direction of sheet conveyance, as needed. 
     Lower rollers  4  are positioned on the path extending from the path selector  8  toward the stapler  11  so as to convey the sheet toward the stapler  11 . A sheet sensor  37  senses the sheet being conveyed by the lower rollers  4 . A brush roller or feed roller  6  conveys the sheet moved away from the sheet sensor  37  into the stapler  11 . A conveyance motor  54  (see FIG. 7) drives the lower rollers  4 . 
     The stapler  11  is positioned at the bottom of a stapling section  61  and driven by a staple motor  56  (see FIG.  7 ), which will be described later. The stapling section  61  additionally includes jogger fences  9  (only one is visible), a return roller or hit roller  5 , and a belt  10 . The jogger fences  9  cooperate to jog the sheet driven onto a staple tray included in the stapling section  61 . The belt  10  is positioned at the back of the jogger fences  9  for conveying a stapled sheet stack out of the stapling section  61 . A belt home position sensor  39  adjoins the belt  10  and is responsive to the home position of the belt  10 . A catch  10   a  (see FIG. 6) is positioned on the belt  10  for catching the sheet stack. The sheet sensor  37  is located at such a position that even when the return roller  5  is caused to act just after the sensor  37  has sensed the trailing edge of the sheet, the roller  5  can hit the trailing edge of the sheet. 
     More specifically, as shown in FIG. 3, a jogger motor  26  drives the jogger fences  9  via a belt  49 . A solenoid  30  supports the return roller  5  such that the roller  5  can swing in a pendulum fashion. A belt  47  transmits the rotation of the conveyance motor  54  to one of rollers constituting each lower rollers  4  and feed roller  6 . As shown in FIG. 4, a rear fence  19  is positioned below the jogger fences  9  such that the sheet abuts against the rear fence  19 . More specifically, as shown in FIG. 5, a pair of rear fences  19  are positioned side by side. 
     As shown in FIG. 5, a stapler motor  27  causes the stapler  11  to move via a belt  50  in a direction perpendicular to the direction of sheet conveyance, as indicated by a double-headed arrow. As shown in FIG. 6, belt motor  57  causes the belt  10  to turn in a direction indicated by an arrow. A stapler home position sensor  22  is responsive to the home position of the stapler  11 . 
     FIG. 7 shows a control system included in the illustrative embodiment. As shown, the control system includes a CPU (Central Processing Unit)  70  implemented by, e.g., a microcomputer. Various switches and sensors arranged in the finisher send their outputs to the CPU  70  via an I/O (Input/Output) interface  60 . The CPU  70  controls the conveyance motor  54  assigned to the inlet roller  1 , upper rollers  2 , lower rollers  4  and return roller  5 , a discharge motor  55  assigned to the outlet roller  3  and push roller  7 , the jogger motor  26  assigned to the jogger fences  9 , the stapler motor  27  assigned to the stapler  11 , and the belt motor  57  assigned to the belt  10  in accordance with the outputs of the switches and sensors. Such motors all are implemented as stepping motors. 
     Further, the CPU  70  controls, based on the outputs of the switches and sensors, a tray up-down motor  51  and a shift motor  52  that are assigned to the copy tray  12  as well as the staple motor  56 . The motors  51 ,  52  and  56  are not stepping motors. In addition, the CPU  70  sends a control signal to a solenoid  53  that actuates the path selector  8 . Counting pulses output from the conveyance motor  54 , the CPU  70  controls a solenoid  30  assigned to the return roller  5  in accordance with the number of input pulses. The CPU  70  constitutes positioning control means together with various operation programs for operating the CPU  70 . 
     The operation of the illustrative embodiment will be described hereinafter. First, assume that the operator of the copier selects a non-staple mode. Then, the solenoid  53  switches the position of the path selector  8  for steering sheets toward the upper rollers  2 . In this condition, the inlet roller  1  drives a sheet or copy driven out of the copier to the upper rollers  2  via the path selector  8 . The sheet is then sequentially driven by the upper rollers  2  and outlet roller  3  to the copy tray  12 . The push roller  7  positions the sheet to be stacked on the copy tray  12  in the direction of sheet conveyance. At this instant, as soon as the sheet sensor  38  senses the trailing edge of the sheet, the push roller  7  is decelerated in order to enhance accurate stacking. As sheets are sequentially stacked on the copy tray  12 , the top of the sheet stack raises one end of the lever  13 . When the sheet level sensor  33  senses the other end of the lever  13 , the tray up-down motor  51  is driven to lower the copy tray  12  by a preselected amount. As a result, the top of the sheet stack on the copy tray  12  is held at an adequate level at all times. 
     Assume that the operator selects a sort mode or a stack mode on a control panel mounted on the copier. Then, the shift motor  52  repeatedly shifts the copy tray  12  in the direction perpendicular to the direction of sheet conveyance, thereby sorting or stacking consecutive sheets until the job ends. At the end of the job, the copy tray  12  is lowered by about 30 mm. 
     A staple mode unique to the illustrative embodiment will be described with reference to FIGS. 3 and 9. As shown in FIG. 9, each jogger fence  9  is moved away from its home position to a first position 7 mm remote from one side of a sheet width and waits for a sheet there ([I]). The conveyance motor  54  drives the lower rollers  4  to thereby convey a sheet entered the finisher. As soon as the trailing edge of the sheet moves away from the sheet sensor  37 , the jogger fence  9  jogs 5 mm inward from the first position (stand-by position), as indicated by an arrow ([II]). On sensing the trailing edge of the sheet, the sheet sensor  37  sends its output to the CPU  70 . In response, the CPU  70  starts counting pulses output from the conveyance motor  54 . On counting a preselected number of pulses, the CPU  70  turns on the solenoid  30 . The return roller  5  swings in a pendulum fashion in accordance with the turn-on and turn-off of the solenoid  30 . More specifically, when the solenoid  30  is turned on, the return roller  5  hits the sheet to thereby return it downward until the sheet abuts against the rear fences  19 , thereby positioning the sheet in the longitudinal direction. Every time the inlet sensor  36  (or the sheet sensor  37 ) senses a sheet entered the finisher, the CPU  70  counts the sheet. 
     On the elapse of a preselected period of time since the turn-off of the solenoid  30 , the jogger motor  26  causes the jogger fence  9  to move 2.6 mm inward to a second position, as indicated by an arrow in FIG. 9, and stop there ([III]). As a result, the sheet is positioned in the lateral direction. Subsequently, the jogger fence  9  is returned from the second position to the first position by 7.6 mm so as to wait for the next sheet, as indicated by an arrow in FIG. 9 ([IV]). The jogger fence  9  repeats such a movement up to the last sheet. When the last sheet is introduced into the stapling section  61 , the jogger fence  9  moves 2.6 mm inward to the second position, as indicated by an arrow in FIG. 9, and stops there ([V]). Subsequently, the jogger fence  9  again moves 2.6 mm outward, as indicated by an arrow in FIG. 9 ([VI]), and then moves 2.2 mm inward to a third position, as indicated by an arrow in FIG. 9 ([VII]). Consequently, the jogger fences  9  press the opposite side edges of the sheet stack at the third position for thereby preparing the sheet stack for stapling. In FIG. 9, assume that the jogger fences  9  are spaced from each other by a distance of L 2  at the second position or by a distance of L 3  at the third position 
     FIG. 8 demonstrates a procedure  1  for determining the amount of pressing. As shown, the third position is set in accordance with the width of sheets, as measured in the direction perpendicular to the direction of sheet conveyance and the number of sheets to be stapled together. Also, a service person can change the third position on numeral keys arranged on the copier, as needed. After the jogging of the last sheet, the CPU  70  determines whether or not the width of the sheets is greater than B4T (B4 profile) (step  101 ). If the answer of the step  101  is YES, then the CPU  70  determines whether or not the number of sheets to be stapled together is greater than thirty (step  102 ). If the answer of the step  102  is YES, then the CPU  70  causes each jogger fence  9  to move 2.6 mm (7.6 mm inward from the first position), i.e., to press the edge of the sheet stack by 0.6 mm (step  103 ). On the other hand, if the answer of the step  101  or  102  is NO, then the CPU  70  causes the jogger fence  9  to move 2.2 mm (7.2 mm inward from the first position), i.e., to press the edge of the sheet stack by 0.2 mm (step  104 ). 
     It should be noted that the specific numerical values stated above are not theoretical values, but are simply typical values. While the illustrative embodiment varies the third position, the second position may be varied, in which case the third position will be varied relative to the second position. 
     On the elapse of a preselected period of time, the stapler  11  is driven to staple the stack of sheets. Assume that the operator selects a mode for stapling the sheet stack at a plurality of positions. Then, after stapling the sheet stack at one position, the stapler  11  is moved to another stapling position along the trailing edge of the sheet stack and again staples the sheet stack. After the stapling operation, the belt motor  57  is energized to drive the belt  10 . At the same time or on the elapse of a preselected period of time, the discharge motor  55  is energized in order to receive the sheet stack raised by the catch  10   a  of the belt  10 . 
     The jogger fences  9  are controlled in accordance with the sheet size and the number of sheets stapled together. For example, assume that the number of sheets is smaller than preselected one (thirty in the illustrative embodiment) or that the sheet size is smaller than preselected one (B4T in the illustrative embodiment). Then, the jogger fences  9  press the sheet stack whose trailing edge is raised by the catch  10   a . When a preselected number of pulses are output after the belt home position sensor  39  has sensed the home position of the belt  10 , the jogger fences  9  each are retracted by a preselected distance so as to release the sheet stack. The number of the above pulses corresponds to an interval between the time when the catch  10   a  abuts against the trailing edge of the sheet stack and the time when it moves away from the ends of the jogger fences  9 . When the number of sheets is greater than preselected one or when the sheet size is greater than preselected one, the jogger fences  9  are retracted by the preselected distance beforehand. 
     In any case, as soon as the sheet stack moves away from the jogger fences  9 , the jogger fences  9  are again moved to the first position or stand-by position to prepare for the next sheet. The procedure described above is repeated up to the last job. 
     In the illustrative embodiment, each jogger fence  9  presses the sheets by 0.6 mm up to the last sheet. It is sometimes preferable to control the amount of pressing before the last page also, depending on the sheet size and the number of sheets to be stapled together. FIG. 10 shows a procedure  2  for determining the amount of pressing. As shown, assume that the sheet width is smaller than B4T (NO, step  201 ) or that the sheet width is greater than B4T (YES, step  201 ), but the number of sheets to be stapled together is less than thirty (NO, step  202 ). Then, the jogger fences  9  press the sheets preceding the last sheet by 0.6 mm (step  204 ). If the answers of the steps  201  and  202  both are YES, then the jogger fences  9  press the sheet stack by an amount greater than 0.6 mm, e.g., 0.8 mm to 1.0 mm (step  203 ). In the illustrative embodiment, the jogger fences  9  have a generally L-shaped cross-section each. Therefore, even when the number of sheets is great and causes the sheet stack to bend relative to the staple tray, the jogger fences  9  prevent the sheet stack from dropping from the staple tray. 
     In summary, in accordance with the present invention, a sheet finisher allows the second and third positions to be adequately set in accordance with the sheet size and the number of sheets to be stapled together. The finisher can therefore accurately jog sheets without regard to the sheet size. Further, the finisher allows a sheet stack to be surely stapled while guaranteeing high-quality jogging. 
     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.