Exemplary embodiments of the present invention are explained in detail below with reference to the accompanying drawings.
The sheets that are not conveyed into the lower conveyance path 3 are conveyed past conveying rollers 21, sheet discharge sensor 22, discharge rollers 23, and collecting rollers 24 disposed along the upper conveying path 2, and ejected and stacked in the sheet discharge tray 4. A free-swinging filler 51, located above the discharge outlet hangs over the sheet P stacked in the sheet discharge tray 4, its tip touching the surface of the sheet P near the center. At the base of the filler 51 are disposed an upper top-surface detecting sensor 52 and a lower top-surface detecting sensor 53, which detect height of the stacked sheets P by detecting the tip of the filler 51. The upper top-surface detecting sensor 52 is disposed above the base of the filler 51 and the lower top-surface detecting sensor 53 is disposed below the base of the filler 51. The base of the filler 51 is midway between the two top-surface detecting sensors 52 and 53 (when both the upper top-surface detecting sensor 52 and the lower top-surface detecting sensor 53 are off), and is near the lower top-surface detecting sensor 53 (when the lower top-surface detecting sensor 53 switches off) at the home position thereof.
The lower top-surface detecting sensor 53 is turned on as the number of sheets, in other words, the height of the sheet bundle, loaded in the sheet discharge tray 4 increases. When the lower top-surface detecting sensor 53 is turned on, the control unit 72 controls a driving unit (not shown) that raises or lowers the sheet discharge tray 4 to lower the sheet discharge tray 4. The control unit 72 controls the driving unit to stop the descent of the sheet discharge tray 4 when the lower top-surface detecting sensor 53 is turned off after the sheet discharge tray 4 is lowered. This process of lowering the sheet discharge tray 4 is repeated until the height stipulated for the sheet discharge tray 4 is reached, upon which, the control unit 72 of the sheet processing device A outputs a stop signal to a control unit 71 of the image forming apparatus B, causing the image forming operation by the system to be stopped.
A prestack path 3a branches off from the lower conveyance path 3 at an angle that enables the sheet P to be carried in a direction opposite to a direction in which the sheet P is conveyed (conveyance direction). A switching pawl 9 disposed at the bifurcation serves as a guide during this reverse passage of the sheet P. Conveying rollers 30 (30a, 30b, and 30c), a sheet discharge sensor 31, and sheet discharge rollers 32 are disposed along the lower conveyance path 3. A stapling device 5 is disposed at the end of the lower conveyance path 3. The stapling device 5 includes the stapler 35, the stapling tray 34, a jogger fence 36, returning rollers 37, a releasing belt 38, a releasing pawl 38a, a rear-end fence 39, and a rear-end clamp 40. The stapler 35 moves in a direction perpendicular to the conveyance direction (i.e., sheet width direction) and staples the sheet bundle with a stapling pin by advancing in a direction perpendicular to the sheet surface. The stapling tray 34 stacks therein the sheet P ejected from the sheet discharge rollers 32. The jogger fence 36 aligns the sheet P in the stapling tray 34 by advancing or retreating in a direction perpendicular to the conveyance direction. The returning rollers 37 return the sheet P in the stapling tray 34 towards upstream of the conveyance direction. The releasing belt 38 releases the sheet P or the sheet bundle from the stapling tray 34 towards the sheet discharge tray 4. The releasing pawl 38a is affixed to the releasing belt 38 and pushes up the sheet P or the sheet bundle being released by the releasing belt 38. The rear-end fence 39 aligns the trailing edge of the sheet P returned by the returning rollers 37. The rear-end clamp 40 presses down on or releases the sheet bundle by advancing or retreating in the thickness direction of the sheet bundle.
How a sheet bundle of one lot is processed by the sheet processing device is described below. The sheet P, output from the image forming apparatus B and carried to the sheet processing device A, is detected by the inlet sensor 11 and is conveyed through the upper conveyance path 2. The control unit 72 determines the position of the path switching pawl 20 according to a sheet processing command issued by the control unit 71 of the image forming apparatus B. To carry the sheet P to the stapling tray 34, the path switching pawl 20 is turned counterclockwise in
Once released from a nip between the sheet discharge rollers 32 and deposited in the stapling tray 34, the sheet P drops onto the rear-end fence 39 by self-weight and by the returning rollers 37, where the trailing edge of the sheet P rests flush against the rear-end fence 39. After the lapse of time for alignment of the sheet P in the conveyance direction, the sheet P is aligned in the width direction by the jogger fence 36. This alignment process is repeated for every sheet P, whereby a plurality of sheets are aligned one by one.
How the sheet bundles of two or more lots are processed is described below. The sheets P are output from the image forming apparatus B at regular intervals and the interval between the lots is also constant. The first sheet P output from the image forming apparatus B is carried past the guiding rollers 10 and the conveying rollers 30a disposed in the upstream end in the conveyance direction, and past the switching pawl 9 up to a predetermined distance downstream such that the trailing edge of the sheet P gets past the tip end of the switching pawl 9 (but not past the conveying rollers 30b disposed in the mid-portion in the conveyance direction). If a signal is issued from the control unit 71 of the image forming apparatus B to carry the sheet P in the reverse direction, the conveying rollers 30b and 30c first stop turning and then start turning in the reverse direction. The switching pawl 9 then guides the sheet P to the prestack path 3a where it is pre-stacked. The switching pawl 9 is always elastically biased by force to give way to the prestack path 3a when the sheet P is carried in the reverse direction (i.e., a degree of force that allows the switching pawl 9 to rotate enough to let the sheet P pass through). The distance which the sheet P is carried in the prestack path 3a is calculated by taking a pulse count of a sensor (not shown) disposed immediately before the conveying rollers 30a in the conveying direction or by measuring time by a timer (not shown). Control timing is obtained based on the calculated pulse count or the measured time, and the sheet P is stopped when the trailing edge of the sheet P (the leading edge of the sheet P, when the sheet P is being carried in the reverse direction) is at the correct position. At this point, the sheet P is held by a nip between the conveying rollers 30b such that the sheet P sticks out a few millimeters from the nip. To reduce the distance that the sheet P sticks out from the nip, another sensor is placed as close as possible to the spot where the reverse movement of the sheet P begins. Thus, a conveyance error is reduced, and the sheet P is stopped at the precise spot. By stopping the sheet at the precise spot, the distance that the sheet P sticks out from the nip can be minimized. Consequently, the next sheet can be stacked on the current sheet P with a minimal gap, resulting in a reasonably well aligned stack in the stapling tray 34.
The second sheet is then conveyed by the conveying rollers 30a. When the sensor disposed immediately before the conveying rollers 30a in the upstream direction detects that the second sheet has been conveyed in the upstream direction up to a predetermined distance, e.g. 20 mm, from the conveying rollers 30b, the conveying rollers 30b and 30c begin to rotate in the reverse direction. Accordingly, conveyance of the first sheet P stacked on the lower conveyance path 3 and the prestack path 3a is restarted. Upon restart of conveyance, the first sheet P is held between a nip between the conveying rollers 30c on the downstream end, and the first sheet P and the second sheet are ejected into the stapling tray 34 together with the leading edge of the first sheet P slightly ahead of the leading edge of the second sheet.
If there are three sheets in a lot, the first sheet P and the second sheet are pre-stacked in the prestack path 3a and kept waiting until the third sheet comes along. The number of sheets kept waiting in the prestack path 3a is determined by a processing time of the previous lot of sheet bundle in the stapling tray 34.
A stapling process is described below. When an stapling mode signal is received from the image forming apparatus B, the stapler 35 moves in the width direction of sheets up to a predetermined point along the bottom edge of a sheet bundle and stands by at that point. A sheet carried via the lower conveyance path 3 is ejected into the stapling tray 34 by the sheet discharge rollers 32. The sheet comes up against the returning rollers 37 which drops the sheet downward so that the sheet comes to rest against the rear-end fence 39. The rear-end fence 39 aligns the sheet bundle in the conveyance direction (vertically). The jogger fence 36 aligns the sheet bundle in the width direction. When a sheet is dropped into the rear-end fence 39, the rear-end clamp 40 presses down on the sheet towards the stapling tray 34 so that the next sheet can be dropped into the rear-end fence 39.
When a predetermined number of sheets are aligned, the stapler 35 moves from the standby position to a stapling position, and staples the sheet bundle. With the lower edge (trailing edge) being supported by the releasing pawl 38a, the stapled sheet bundle is carried by the releasing belt 38 counterclockwise in
When the control unit 72 of the sheet processing device A receives an interior-edge stapling mode signal from the control unit 71 of the image forming apparatus B, the stapler 35 and the jogger fence 36 (36a and 36b) move to the positions shown in
As each sheet P is carried to the stapling tray 34, the returning rollers 37 align the position of the sheet P vertically while the jogger fence 36 aligns the position of the sheet P horizontally. Next, the buckling or the curl of the sheet in the stapling tray 34 is regulated so that the next sheet P can be ushered into the rear-end fence 39. This is accomplished by a motor 44 that moves a belt 44a, thereby causing a supporting member 41 of a clamping member 42 to approach the sheet P and leading the trailing edge of the sheet P towards the stapling tray 34. When the next sheet P is being conveyed into the stapling tray 34, the clamping member 42 retreats from the sheet P to return to the standby position (shown in
The control unit 72 determines counts the number of sheets in the stapling tray 34 and, as shown in
After the sheets are aligned, as shown in
In this mechanism where the stapler 35 and the rear-end clamps 40a to 40c are disposed in a range in which they come in the way of one another, the stapler 35 is kept retreated not to come in the way of the rear-end clamps 40a to 40c when sheets are being aligned and then moved to the stapling position after the aligning process is completed and just before the stapling process. However, when compared with the case where the stapler 35 is already at the stapling position, in this arrangement, the total time required for stapling process increases by the time that the stapler 35 takes to move from the standby position to the stapling position. This surplus time will not lead to reduced productivity if it can be absorbed before the first sheet of the next sheet bundle (next lot) is received. Otherwise, the productivity is bound to decline.
Accordingly, under a predetermined condition, the stapler 35 is moved to the stapling position before completion of alignment process of the last sheet of a sheet bundle. This control is explained below with reference to
When the sheet processing device A receives a start signal from the image forming apparatus B (step S101), the stapler 35 is moved to a position which is out of the way of the rear-end clamps 40a to 40c while being closest to the stapling position (step S102). For example, in the case of single-spot stapling, the stapler 35 is moved to the near-side stapling position for two-spot stapling (the position of the stapler 35 in
If the number of sheets for stapling is equal to or greater than the number of pre-stacked sheets (No at step S104), enough time is available for moving the stapler 35. Therefore, after the alignment process of the last sheet is completed (step S107), the stapler 35 is moved to the stapling position (step S108). In this case, as enough time is available for moving the stapler 35, the stapling process is performed while the sheet bundle is pressed down by all the three rear-end clamps 40a to 40c as shown in
Thus, in the control process shown in
Several factors such as a linear ejection speed, interval between sheets, sheet size, and the number of sheets for stapling affect the available time. For example, if the number of sheets for stapling is greater than the number of sheets that are pre-stacked, a larger number of sheets ejected from the image forming apparatus B are to be stacked, and hence plenty of time is available for processing. Even if the number of sheets for stapling is small, if the sheet size is large, such as A3, or the linear ejection speed of the sheet from the image forming apparatus B is low or the intervals between the sheets (inter-sheet intervals) are long due to the sheet-carrying specification of the image forming apparatus B, plenty of time is available for processing. Even if not enough time is available under individual conditions, combinations of these conditions may ensure plenty of time for processing. Thus, if more time than the total time required for the stapling process from alignment to ejection can be available before the first sheet of the next job or the pre-stacked sheet bundle of the next job is conveyed into the stapling tray 34, the sheet processing device acts to enhance stapling precision. Otherwise, the sheet processing device acts to enhance productivity.
If the number of sheets for stapling is equal to or greater than the number of pre-stacked sheets (Yes at step S201), the sheet processing device A determines to move the stapler 35 after completion of alignment process (step S202). If the number of sheets for stapling is less than the number of pre-stacked sheets (No at step S201), and the sheet size of the sheets for stapling is large, such as A3, the sheet processing device A determines to move the stapler 35 after completion of alignment process (step S202). If the sheet size is not large (No at step S203), the sheet processing device A determines whether the linear ejection speed is low or whether the inter-sheet intervals are long (step S204) based on the sheet-carrying specification of the image forming apparatus B. If the linear ejection speed is low or the inter-sheet intervals are long (Yes at step S204), the sheet processing device A determines to move the stapler 35 after completion of alignment process (step S202). If the linear ejection speed is high or the inter-sheet intervals are short (No at step S204), the sheet processing device A determines, based on predetermined conditions, whether more time can be taken for the first sheet of the next job or the pre-stacked sheet bundle of the next job to be conveyed into the stapling tray 34 than the total time required for the stapling process inclusive of all the processes from alignment to ejection (step S205). If more time is available (Yes at step S205), the sheet processing device A determines to move the stapler 35 after completion of alignment process (step S202). Otherwise (No at step S205), the sheet processing device A determines to move the stapler 35 before completion of alignment process (step S206), and proceeds to the stapling process.
Situations can be envisaged where stapling precision may take precedence over productivity. To address this requirement, it is selected whether to perform the control process for shifting the standby position of the stapler 35, rendering the sheet processing device A more flexible. For example, the sheet processing device A can be provided with a manual operation button to specify whether to perform the control process for shifting the standby position of the stapler 35. Alternatively, selection of whether to perform the control process for shifting the standby position of the stapler 35 can be made from an operation unit of the image forming apparatus B (for example, by setting in serviceman program (SP) mode). Such selection can also be made through a command issued over a network to the image forming apparatus B and subsequently passed on to the sheet processing device A. In any case, a user can directly or indirectly specify or change the settings, and thus, it can be determined whether to perform the control process for shifting the standby position of the stapler 35 for every job.
There are four standby positions at which the stapler 35 stands by, i.e., at the rear-end clamp 40b and 40c on both edges, as shown in
As set froth herein above, according to an embodiment of the present invention, productivity is enhanced by minimizing the distance a stapler has to move, and is maintained by moving the stapler to a stapling position before commencement of the stapling process. This process for enhancing productivity is performed according to sheet ejection condition. Thus, either enhanced stapling precision or enhanced productivity can be realized as desired.
Moreover, plenty of time can be made available for moving the stapler by increasing the number of sheets ejected in one lot into a stapling tray.
Although the invention has been described with respect to a specific embodiment for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art that fairly fall within the basic teaching herein set forth.
Number | Date | Country | Kind |
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2006-226796 | Aug 2006 | JP | national |