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(11) | EP 0 810 485 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Copy sheet timing method |
| (57) A setup procedure to compensate for paper path timing variations due to mechanical
machine to machine variations and includes the steps of: running a predetermined number
of copy sheets from a given tray (112, 114); calculating the mean arrival time of
the copy sheets to a sensor (19); and using the calculation to adjust the nominal
feed and jam check timing for that feeder. |
[0001] This invention relates generally to an electrographic printing machine, and more particularly, concerns an improved copy sheet timing method for such a machine.
[0002] High speed xerographic reproduction machines and printers, such as, the Xerox DocuTech® 135 and Xerox® 5090 produce copies at a rate in excess of several thousand copies per hour, and therefore, the need for precise registration and transport of copy sheets is essential. Presently, some copiers and printers use a servo driven registration system that can compensate for and successfully register copy sheets that arrive at a particular sensor point over a large variation in time (approximately ± 50 ms). A conventional modified feed algorithm will then adjust the feed times of copy sheets to center them in the operating window. It has been found that at speeds beyond 135 copies per minute this window shrinks down to a point where sheets may not register under all tolerance conditions, that is, there is no guarantee that the first sheet of a run will fall within the operating window, so that modified feed can then start to adjust feed times. Many of these tolerances are such that they do not vary much over time. For example, those tolerance conditions caused by drive roll and belt diameter changes due to wear. These small variations can be compensated for by the machine's present modified feed algorithms. However, this can only happen if the first sheets of a job falls within the servo operating window. Analysis shows this may not always happen with high speed feeding and jams will probably occur.
[0003] The machine disclosed in US-A-5,313,253 discloses a monitoring system tnat constantly monitors sheet path velocity and comprises the velocity profile gained thereby to a baseline velocity signature established at the factory. If the constantly monitored velocity profile is not within the preestablished operating parameters as set forth at the factory, automatic machine adjustment procedures are initiated and/or automatic service alerts are initiated.
[0004] Registration systems, such as, in US-A-4,826,148 are adaptable to handle a wide variety of copy sheet sizes at high speeds, however, there still exists the need to compensate for paper path timing variations.
[0005] The present invention contemplates a new and improved system and method that compensates for paper timing variations due to mechanical machine to machine variations.
[0006] According to the present invention, a printing machine that transports copy sheets at a high rate of speed incorporates a registration timing setup procedure that includes: running a predetermined number of copy sheets from a feeder; calculating the mean times; and using the information to adjust the nominal feed and jam check timing for that feeder.
[0007] According to a more limited aspect of the invention, a customer service engineer utilizes a setup diagnostic screen to measure the actual time taken for a sheet to travel through a given portion of a paper path. This time may be used as a nominal value for timing purposes for the particular machine involved.
[0008] The present invention will be described further, by way of examples, with reference to the accompanying drawings, in which:-
[0009] FIG. 1 is a schematic side view of a copier/printer that incorporates the registration timing setup procedure of the present invention.
[0010] Reference is now made to the drawing where the showings are for the purpose of illustrating a preferred embodiment of the invention and not for limiting same, the various processing stations employed in the printing machine illustrated in Figure 1 will be briefly described.
[0011] Referring now to FIG. 1, printer section 8 comprises a laser type printer and for purposes of explanation is separated into a Raster Output Scanner (ROS) section 87, Print Module Section 95, Paper Supply section 107, and Finisher 120. ROS 87 has a laser, the beam of which is split into two imaging beams 94. Each beam 94 is modulated in accordance with the content of an image signal input by acousto-optic modulator 92 to provide dual imaging beams 94. Beams 94 are scanned across a moving photoreceptor 98 of Print Module 95 by the mirrored facets of a rotating polygon 100 to expose two image lines on photoreceptor 98 with each scan and create the latent electrostatic images represented by the image signal input to modulator 92. Photoreceptor 98 is uniformly charged by corotrons 102 at a charging station preparatory to exposure by imaging beams 94. The latent electrostatic images are developed by developer 104 and transferred at a transfer station 106 to a print media 108 delivered by Paper Supply section 107. Media 108, as will appear, may compromise any of a variety of sheet sizes, types and colors. For transfer, the print media is brought forward by servo controlled rolls in timed registration with the developed image on photoreceptor 98 from either a main paper tray or from auxiliary paper trays 112, or 114. The developed image transferred to the print media 108 is permanently fixed or fused by fuser 116 and the resulting prints discharged to either output tray 118, or to output collating trays in finisher 120. Finisher 120 includes a stitcher 122 for stitching (stapling) the prints together to form books, and a thermal binder 124 for adhesively binding the prints into books and a stacker 125.
[0012] The control of all machine functions, including all sheet feeding, is, conventionally, by the machine controller 10. Controller 10 is preferably a known programmable microprocessor, exemplified by the microprocessor disclosed in US-A-4,166,558. The controller 10 conventionally controls all of the machine steps and functions described herein, and others, including the operation of the document feeder 20, all of the document and copy sheet deflectors or gates, the sheet feeder drives, the finisher, etc. The controller also conventionally provides for storage and comparison of the counts of the copy sheets, the number of documents recirculated in a document set, the desired number of copy sets and other selections and controls by the operator through the console or other panel of switches connected to the controller, etc. The controller is also programmed for time delays from correction control, etc. Conventional path sensors or switches may be utilized to help keep track of the position of the documents and the copy sheets and the moving components of the apparatus by connection to the controller. In addition, the controller variably regulates the various positions of the gates depending upon which mode of operation is selected.
[0013] Referring now to a particular aspect of the present invention, the copier/printer of FIG. 1 is configured to eliminate or "null out" variations in copy sheet velocity due to mechanical machine to machine variations, such as, different machine lengths, baffle tolerances, and roll sizes as opposed to wear items and another tolerances due to manufacturer build variations. This is accomplished by use of a simple setup procedure by a technician, such as, a customer service engineer (CSE) who monitors a diagnostic screen on the console of the printer. The CSE uses the console to trigger the running of about 10 to 20 copy sheets from a particular feed tray. The controller 10 calculates the mean time of travel of copy sheets from the tray to a sensor 19 that comprises an emitter 24 and a receiver 25. This mean time data represents the nominal feed time for this tray on this machine and is used to adjust the feed and jam check timing for the feeder in order to ensure that the copy sheet from this tray will arrive at the predetermined downstream sensor within the servo operating window. The conventional modified feed system used, for example, in the Xerox Docutech® 135 or Xerox® 5090 can fine tune the feed times.
[0014] Alternatively, a CSE uses the diagnostic screen on the console of the printer to trigger the feeding of a copy sheet from a predetermined feeder. The time it takes the copy sheet to travel from the feeder to sensor 19 is measured by controller 10 and this time represents a nominal value that is used to set a jam check timing window for this particular feeder.
[0015] It should be understood that this copy sheet initialization procedure could be part of the install setup by the CSE and be applied to all trays for accurate timing. The scheme or procedure could also be run periodically in the event of timing problems or if paper path components are changed. In addition, the procedure may be useful if the customer uses different paper stock having different sheet transport times due to thickness or friction. Safeguards are built into the system to establish worst case boundaries for feed times so that real paper path hardware problems are not compensated for in error by timing changes.
1. A method for compensating for paper path timing variations of copy sheets in a copier/printer,
comprising the steps of:
providing a paper tray (112, 114) with copy sheets therein;
providing a feeder for feeding a predetermined number of the copy sheets from said paper tray (112, 114);
providing a sensor (19) at a predetermined location downstream from said paper tray (112, 114);
calculating the mean time of arrival of the predetermined number of copy sheets at said sensor (19); and
using said calculated mean time to adjust said feeder to feed copy sheet to reach said sensor (19) within a nominal feed time.
2. A method as claimed in claim 1, including the step of using said calculated mean times
to adjust copy sheet jam check timing.
3. A method as claimed in claim 1 or claim 2, wherein said predetermined number of copy
sheets include from about 10 to about 20.
4. A machine setup method including a procedure adapted to minimize variations in sheet
velocity due to mechanical machine to machine variations, comprising the steps of:
providing a paper tray (112, 114) with copy sheets therein;
feeding a predetermined number of copy sheets from said paper tray (112, 114);
providing a copy sheet sensor (19) downstream of said paper tray for sensing the passage of said copy sheets thereover and giving off a signal indicating the passage of each copy sheet thereover;
providing a controller (10) for receiving said signals from said sensor and calculating the elapse of time from the feeding of each copy sheet to its arrival at said sensor; and
using said calculated time to adjust said feeding from said feed tray to a nominal feed time between said feed tray and said sensor.
5. A method as claimed in claim 4, including the step of using said calculated time to
set jam check timing for the machine.