Sheet feeding or delivering – Delivering – With transfer means between conveyor and receiver
Reexamination Certificate
2000-12-05
2003-04-22
Ellis, Christopher P. (Department: 3651)
Sheet feeding or delivering
Delivering
With transfer means between conveyor and receiver
C399S364000
Reexamination Certificate
active
06550762
ABSTRACT:
Disclosed in the embodiments herein is an improvement in high speed printing utilizing a combination of two cooperative sheet inverters to improve the overall productivity of the printing system. As is well known, sheet inversion properly coordinated and/or collated with the printing sequence is important for duplexing (both sides sheet printing), sheet output collation, finishing, and the like. The system disclosed herein avoids the typical conventional approach of using a much higher paper path (sheet feeding) velocity in a single inverter (which can be as much as twice the normal paper path or process speed of the printer) yet can maintain collation, maintain a proper inter-sheet gap in the sheet path and insure that successively printed sheets do not impact or interfere with one another, even with high speed printing with rapidly successive sheets moving in the paper paths.
With the disclosed embodiments, sequential sheets in the paper path may be alternatingly inverted by the two inverters. Directly sequential sheets need not be inverted in the same inverter. Thus, a much lower speed inverter operation can be employed, providing numerous advantages. For example, with lower speed inverters, less power may be required, acoustic noise may be lower, and system reliability, including reduced sheet jam rates, may be improved. Also, a subsequent sheet need not be delayed for the inversion of a preceding sheet in order to avoid sheet impact or collision, or sheets becoming out of sequential page order in pre-collated printing. Thus, the disclosed dual inverter system embodiments provide opportunities for improved high speed pre-collated printing productivity without increasing the operating speeds and sheet reversal rates of sheets in the inverter and without requiring an increase in the inter-sheet or inter-pitch gaps between sheets.
By way of background, various types of sheet inverters are known in the art. The following patent disclosures are noted merely by way of a few examples. In particular, there is art on copiers or printers having two sheet inverters in a printer/finisher system where one inverter is in the duplex loop path and the other inverter is in the finisher input or the output path of the copier or printer. Noted, for example, is FIG. 3 of Xerox Corporation U.S. Pat. No. 5,697,040, issued Dec. 9, 1997 to Douglas T. Rabjohns and James S. Stoll. It shows a xerographic printer with both a duplex path sheet inverter and an output path sheet inverter 176. Also, it is known for example from U.S. Pat. No. 5,568,246, issued Oct. 22, 1996 to Paul D. Keller et al, to combine in series two different printing systems into a so-called dual engine printing system. In doing so, the single inverters of each of these print engines provide two inverters, but they are in two separate print engines. Details of other sheet inverters for other reproduction apparatus include, for example, Xerox Corp. U.S. Pat. Nos. 4,986,529 and 5,131,649, and other references cited therein. However, as will be appreciated from the disclosures herein, those systems do not provide the function, result or advantages of the presently disclosed embodiments.
Further by way of technical background, because of the location of the interfaces between the inverter/duplex loop and the rest of the paper path in many printers, the sheet inverter speed, the duplex loop speed, and the exit speed of the printer, often need to be much higher than the process speed. This also imposes difficulties and constraints on the sheet drives, the registration subsystems, etc.
As will be understood by those skilled in the art, the term “process speed” in some contexts can refers to the sheet velocity related to the printing rate of the system. For example, in xerographic systems the process speed may be the velocity at which the image substrate sheet is fed to, and image-transferred at, the transfer station engagement with the photoreceptor belt or drum, which is running at the process speed. In general, it is desirable to be able run most of the rest of the paper paths of the reproduction apparatus at substantially the same process speed. Otherwise, sheet acceleration or deceleration is required at the sheet velocity transition zones of the paper paths, and spacing problems between sequential sheets may arise. Sheet acceleration in particular can cause slippage, or other problems, with the frictional drive wheel or belt systems typically used for sheet feeding in reproduction apparatus (printers or copiers). As is also well known in the art, there is a “handoff” problem in going between a sheet transport or feeder operating at one velocity and the next, or downstream, sheet transport. Other sheet control or registration issues besides slippage can occur, such as rapid nip release of the upstream feed system, or other loss of accurate sheet position control transitioning problems. However, the term “process speed” as used herein, unless specified otherwise, may more broadly encompass the velocity of the sheets moving in the particular paper path to which the dual inverters are operatively connected. Especially since, for example, it is known to run printer output paths and/or duplex paths at a higher sheet transport velocity than the sheet velocity at image transfer.
In many high volume printer architectures being used at the present day, the sheet inversion system requires that all sheets being inverted be rapidly accelerated from the process speed to a much higher inverter speed as they enter the inverter. That is, to be accelerated in a very short distance from a process or other speed to approximately twice the process speed for movement into the inverter. That is typically followed by rapid deceleration of the sheet in the inverter from that higher speed, and then re-acceleration to that higher speed for exiting from the inverter. In addition to the above-described difficulties, this also imposes more critical sheet timing and registration problems. With the disclosed embodiments, the much slower velocity of the sheet in the inverters greatly reduces these problems.
There is an additional potential advantage in providing two inverters capable of alternatively providing the same function in the same basic sheet path location, with each inverter capable of running independently. If one inverter system fails, or becomes temporarily unusable, the overall reproduction system can still operate at a reduced processing speed, without a total shutdown. For example, if there is a paper jam in one inverter, the machine controller can sense this and automatically slow down the printing rate to approximately half speed, and exclusively utilize the other available inverter until the jam is cleared from the jammed inverter.
The disclosed dual alternate inverter embodiments have additional potential advantages. For example, they may utilize, and even duplicate, otherwise conventional or existing inverters or inverter components. That is, this system may use two of any of various well-known or other types of sheet inverters. It may be incorporated into various types of high-speed reproduction apparatus, or finishers therefor, with little modification. For example, an existing high volume Xerox Corporation DocuTech® 5090 or DocuTech® 5390 printer, and their existing high volume finishing systems, such as the Xerox Corporation Model Nos. 4135 or 5090 DocuTech® finishing systems.
The entrance and exit paths and locations of the dual inverters will, of course, vary depending on the desired application of the system and the reproduction apparatus, as will be explained further herein. For example, the location and configuration of the dual inverters and their input and output paths may be different for application in a sheet output or finisher system, as opposed to utilizing the dual inverter system in a duplex loop return path for second side printing. In either case the dual inverters may optionally be in a separate connecting modular unit from the reproduction apparatus.
The functions of both of those two sheet handling and inversion applicat
Deuble Mark A.
Ellis Christopher P.
Xerox Corporation
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