Title:
Multi-sheet buffer for compiling print sheets
Kind Code:
A1


Abstract:
In an apparatus where a printer module outputs print sheets into a finisher module, such as for stapling, a sheet buffer is used to withhold two or more sheets between the printer module and the finisher module so that the finisher module can complete a finishing operation. The withheld sheets are output from the buffer in overlapping fashion when the finisher is ready to accept them. The buffer can be under the control of the printer module or the finisher module.



Inventors:
Reeves, Douglas R. J. (Toronto, CA)
Application Number:
10/386803
Publication Date:
09/16/2004
Filing Date:
03/11/2003
Assignee:
Xerox Corporation
Primary Class:
Other Classes:
271/184, 271/902
International Classes:
B65H29/12; (IPC1-7): B65H29/00; B65H5/00
View Patent Images:
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Primary Examiner:
JOERGER, KAITLIN S
Attorney, Agent or Firm:
Xerox Corporation (Webster, NY, US)
Claims:
1. A method of operating a sheet buffer, the buffer comprising a sheet path and a diverter chute communicating with the sheet path, and means for moving each of a plurality of sheets through the sheet path, comprising: moving a first sheet through the sheet buffer in a process direction; moving the first sheet in a reverse direction into the diverter chute; moving a second sheet through the sheet buffer in the process direction; moving the second sheet in a reverse direction into the diverter chute; moving a third sheet through the sheet buffer in the process direction; and moving the first sheet and second sheet out of the diverter chute and along the process direction along a portion of the sheet path so that the first sheet, second sheet, and third sheet at least partially overlap as they exit the sheet path.

2. The method of claim 1, further comprising selectably changing a speed of the first sheet, second sheet, and third sheet as they exit the sheet path.

3. The method of claim 1, further comprising directing the first sheet, second sheet, and third sheet to a finisher.

4. The method of claim 1, further comprising outputting a signal permitting directing the first sheet, second sheet, and third sheet to the finisher.

5. The method of claim 4, wherein the signal is sent to a printer control system controlling a print engine.

6. The method of claim 1, further comprising moving the third sheet in a reverse direction into the diverter chute.

7. A method of operating a printer module and a finisher mechanism, comprising: the printer module outputting sheets at a substantially regular basic speed; and sending a signal, whereby at least a first sheet and a second sheet output from the printer module are temporarily withheld from the finisher mechanism and the first sheet and second sheet are output with a third sheet in an overlapping manner, as a result of the signal.

8. The method of claim 7, wherein the signal is sent as a result of an action of the finisher mechanism.

9. The method of claim 7, wherein the finisher mechanism is operated by a finisher control system.

10. The method of claim 9, wherein the signal is sent from the finisher control system to a printer control system operative of the printer module.

11. The method of claim 10, wherein the printer control system is operative of a buffer which physically withholds the first sheet and the second sheet.

12. The method of claim 9, wherein the signal is sent from a printer control system operative of the printer module to a finisher control system operative of the finisher mechanism.

13. The method of claim 9, wherein the finisher control system is further operative of a buffer which physically withholds the first sheet and the second sheet.

Description:

INCORPORATION BY REFERENCE

[0001] U.S. Pat. No. 5,303,017, assigned to the assignee hereof, is hereby incorporated by reference.

TECHNICAL FIELD

[0002] The present disclosure relates to a buffer for temporarily retaining sheets, as would be used in a printer or copier, especially in conjunction with a finisher, such as a stapler or folder, which accepts print sheets at high speed.

BACKGROUND AND DESCRIPTION OF THE PRIOR ART

[0003] In mid- to high-speed office equipment such as printers and copiers, the use of “finishers” is well-known. (As used herein, a “copier” will be considered a type of “printer.”) A typical finishing module, which may be separable from or integral with the main portion of the printer, includes devices for compiling print sheets, such as forming a single multi-page document to be printed, and optionally stapling the compiled sheets. Other known finisher features include folding, hole-punching, booklet making, etc.

[0004] Many types of actions performed by a finisher require an appreciable amount of time to carry out on a single sheet or on a compiled set of sheets. In the context of a digital printer, however, sheets are ejected from the print engine and accepted by the finisher at a generally regular frequency: in the case of a 60 ppm (page per minute) engine, a sheet is emitted every second; in a 120 ppm engine, a page is emitted every ½ second. A practical problem results when the finisher needs more time to perform an action than is permitted by the output of the engine. Thus, if a finisher requires ¾ of a second to perform a folding or stapling operation, an upstream engine operating at 120 ppm will emit a next sheet into the finisher while the finisher is performing the operation, probably resulting in a malfunction of the machine.

[0005] U.S. Pat. No. 5,303,017, incorporated by reference above, discloses a design of what can be called a “sheet buffer,” which is operatively disposed between a print engine and a finisher. The function of a sheet buffer is to temporarily withhold a sheet emitted by the print engine from the finisher for a brief period of time so that the finisher can perform an action (such as stapling or folding) on one or more previously-emitted print sheets. In the design shown in the '017 patent, a first sheet of interest, to be temporarily withheld, is passed through a nip formed by reversible exit rolls. Before the first sheet passes through the nips, the exit rolls are reversed and the first sheet is “backed up” into a diverter chute, where it is temporarily retained. A second sheet is then caused to move through the exit rolls simultaneously and at least partially overlapping with the first sheet. The output of the buffer is two sheets, which are at least partially overlapping, at once; the effect of the buffer is to temporarily withhold the sending of the first sheet to the finisher. The buffer in effect “buys time” for the downstream finisher to perform an action, such as stapling, on previous sheets.

[0006] In the current printing and reprographics industry, it is becoming common to want to hook up “legacy” finisher modules with newer, ever-faster print engines. In many cases, the print engine output speed is so much greater than the capability of the finisher to accept sheets that even withholding a sheet temporarily, as in the '017 patent, does not afford the legacy finisher enough time to perform an operation before further sheets are forced into it by the print engine.

SUMMARY OF THE INVENTION

[0007] According to one aspect of the present invention, there is provided method of operating a sheet buffer, the buffer comprising a sheet path and a diverter chute communicating with the sheet path, and means for moving each of a plurality of sheets through the sheet path. The method comprises moving a first sheet through the sheet buffer in a process direction; moving the first sheet in a reverse direction into the diverter chute; moving a second sheet through the sheet buffer in the process direction; moving the second sheet in a reverse direction into the diverter chute; and moving a third sheet through the sheet buffer in the process direction. The first sheet and second sheet are moved out of the diverter chute and along the process direction along a portion of the sheet path so that the first sheet, second sheet, and third sheet at least partially overlap as they exit the sheet path.

[0008] According to another aspect of the present invention, there is provided a so method of operating a printer module and a finisher mechanism. The printer module outputs sheets at a substantially regular basic speed. A signal is sent, whereby at least a first sheet and a second sheet output from the printer module are temporarily withheld from the finisher mechanism and the first sheet and second sheet are output with a third sheet in an overlapping manner, as a result of the signal.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] FIG. 1 is an elevational view of the basic hardware associated with a sheet buffer.

[0010] FIGS. 2-5 show a series of operations carried out by the basic hardware of FIG. 1.

[0011] FIGS. 6 and 7 are simplified elevational views of a high-speed printer with a finisher module.

DETAILED DESCRIPTION

[0012] FIG. 1 is an elevational view of the basic hardware associated with a sheet buffer, generally similar to that disclosed in the '017 patent. A main output path such as 12 is disposed, in one embodiment, between a print engine, outputting prints at a regular frequency, and a finisher or other module or mechanism intended to accept print sheets. The output path 12 is defined by upper and lower planar baffles 13 and 14. Exit rolls 16, which may be rotated in either direction by means not shown, form a nip at the downstream end of the output path 12, and feed rollers 22 are disposed at the upstream end. Between the exit rollers 16 and the upstream feed roller 22 is a diverter gate 24 for diverting a sheet being fed upstream by roller 16 into the entrance 32 of a sheet diverter chute 30 communicating with and branching off at an angle from the main output path 12. Within diverter chute 30 are reversible feed rollers 34. All of the rollers and diverters, along with any ancillary sheet position sensors of any type (not shown), can be controlled via any number of motors or actuators under the control of one or more processors (not shown), in manner generally familiar in the art of automated sheet handling.

[0013] FIGS. 2-6 show a series of operations carried out by the basic hardware of FIG. 1, according to one embodiment. In the figures, a series of sheets S1, S2, S3 arrive sequentially at the left of each Figure, such as if they were being output from a print engine operating at a basic speed, and then are emitted from the buffer effectively at once, with the various sheets at least partially overlapping. The overlapped multiple sheets can then be accepted by, for example, a stapler mechanism within a finisher to the right of the buffer in the Figures.

[0014] In FIG. 2, a first sheet to be emitted, S1, is drawn through the output path 12 through the nip of exit rollers 16, through what can be called a process direction, such as between a print engine and a finisher module. After the trail edge of S1 clears the chute 30, exit rollers 16 are reversed and diverter gate 24 is changed in position, causing S1 to be directed into chute 30 in a reverse direction opposite the process direction, as shown in FIG. 3. At approximately the same time, as also shown in FIG. 3, the second sheet to be emitted from the print engine, S2, is drawn by entrance feed rollers 22 through path 12, with the diverter gate 24 being readjusted at a precise time to clear the path 12 towards exit rollers 16.

[0015] In FIG. 4, exit rollers 16 are reversed and thus direct S2 toward chute 30, where S1 has remained. At approximately the same time, the third sheet to be emitted from the print engine, S3, is drawn by entrance feed rollers 22 through path 12, with the diverter gate 24 being readjusted at a precise time to clear the path 12 towards exit rollers 16.

[0016] In FIG. 5, exit rollers 16 are rotated (along with rollers 34) to extract sheets S1 and S2, each to some extent overlapping the other, from chute 30 and directing them, along with third sheet S3, together through exit rollers 16 to a finishing module to the right of the buffer in the Figures. As sheets S1, S2, and S3, pass through exit rolls 16, each sheet to some extent overlaps the others.

[0017] Although the above sequence of operations show a method which results in three overlapping sheets being emitted from the buffer, the above steps can readily be modified, such as by repeating the steps shown in FIGS. 3 and 4, to cause the buffer to emit four or more sheets at once.

[0018] For further control of the precise timing of the outputting of the sheets S1, S2, and S3 to a finisher, the motion of the exit rollers 16 can be finely controlled, such as to momentarily stop (or, more broadly, momentarily change the speed of) the final output of the sheets so that the output occurs in a narrowly-defined time window. The precise timing can be mandated by a control system associated with either a print engine or a finisher module, as will be described below.

[0019] FIGS. 6 and 7 are simplified elevational views of a high-speed printer with a finisher module, showing two possible embodiments. In either case, a buffer such as shown as sheet path 12 above is operatively interposed between a printer module 100 and a finisher module 110. The printer module 100 is controlled by a control system (such as including a microprocessor) 101 and the finisher module 110 is controlled by control system 111; the control systems are capable of communicating with each other, so that different finisher modules can be paired with different printer modules. The printer module 100 typically includes, for example, a paper stack 102 from which blank sheets are drawn and a print engine such as including a photoreceptor 104 for placing images on the sheets. The finisher module 110 may include a stapler mechanism 112 and an output tray 114, as well as any other mechanism such as for folding, hole punching, booklet making, etc.

[0020] In the FIG. 6 embodiment, the buffer is effectively a part of (that is, is physically disposed in and is controlled by) the printer module 100. In this way, if a printer module 100 of a predetermined basic output speed is linked with a finisher module 110 which is to some extent incapable of accepting sheets at that speed, the control system 101 within printer module 100 can be used to operate the hardware such as shown in FIG. 1 above to temporarily withhold one sheet, or two sheets as in the operations of FIGS. 2-5 above, as needed for the finisher module 110 to perform a particular action, such as stapling, at a particular time. Depending on the design of the finisher module 110, the overall system can be designed so that control system 101 accepts some sort of ready signal from control system 111; or if the finisher module 110 does not have a suitably addressable control system 111, the temporary withholding of sheets in the buffer can be initiated by the control system 101, such as to follow any stapling command.

[0021] In the FIG. 7 embodiment, the buffer such as including sheet path 12 is effectively a part of (that is, is physically disposed in and is controlled by) the control system 111 of finisher module 110. In this case, when sheets from the printer module 100 are sent into finisher module 110 at too high a frequency for the finisher module to perform a desired action at a particular time, control system 111 can cause two or more of the incoming sheets to be temporarily withheld from, for instance, the stapler mechanism 112, such as when previously-accepted sheets are being stapled. This temporary withholding of sheets can be initiated, for example, by an actuation of the stapler or other mechanism 112, and/or by signals received by physical sensors (not shown) indicating the positions of sheets within the module 110.

[0022] The withholding of two or more sheets, within either module 100 or 110, enables the print engine within print module 100 to operate at a constant high speed without having to slow itself down to accommodate the limitation of a mechanism within finisher module 110. When the mechanism such as 112 of finisher module 110 is performing a time-consuming operation, a signal can be sent from finisher control system 111 or printer control system 101, to cause whichever control system is operative of the buffer to initiate the withholding actions described above, and indeed cause the withholding of more than two sheets as needed until the finisher module is able to accept further sheets. At the architectural level, the signal to initiate the withholding of sheets can be designed to originate with the printer control system 101 if it is known or suspected that the output speed of the printer module 100 is significantly higher than the capability of a finisher module 110 likely to be coupled therewith; conversely, the finisher control system 111 can originate the signal (even to printer control system 101) when it detects or is otherwise instructed that sheets are being output from printer module 100 faster than is consistent with an action of the finisher module.

[0023] In another possible embodiment, the printer control system 101 can accept a “not ready” signal from the control system 111 of finisher module 110, and withhold any number of sheets in the buffer accordingly until the finisher module is able to accept further sheets. This use of “ready” or “not ready” signals can be employed even if it is known that a certain finisher action will take a certain amount of time, or in response to detected jams or other malfunctions associated with the finisher module, where it is unknown when the finisher module will be ready to accept further sheets.