Printer dynamic job recovery in an electronic reprographic printing system

A printer dynamic job recovery operation in an electronic reprographic system includes automatic detection of a printed sheet having an image thereon with a relative loss of integrity. Specified sheets are automatically purged to a specified location in response to such detection. The purging can begin at the first detected sheet or up to three sheets in advance of the detected sheet. Job recovery for job completion can be initiated immediately without cycling down the printer.

CROSS REFERENCE TO RELATED APPLICATION 
This application is related to U.S. patent application No. 07/589,544, 
entitled "Method and Apparatus for Operating an Electronic Reprographic 
System Upon Detection of a Fault," filed Sep. 28, 1990, the disclosure of 
which is herein incorporated by references. 
BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a system of electronic reprographics and, 
more particularly, to a system of electronic reprographics which performs 
printer dynamic job recovery without any loss in job integrity. 
2. Description of the Related Art 
In light lens printing systems, a lamp or flashing unit flashes light on a 
document and has an image created synchronously on a photoreceptor belt. 
The photoreceptor belt picks up toner from which a copy is made. 
In electronic reprographic printing systems, a document or series of 
documents comprising at least one print job are successively scanned. Upon 
scanning of the documents, image signals are obtained and electronically 
stored. The signals are then read out successively and transferred to a 
printer for formation of the images on paper. Once a document is scanned, 
it can be printed any number of times or processed in any number of ways 
(e.g., words deleted or added, image magnified or reduced, etc.). If a 
plurality of documents comprise a job which is scanned, the processing or 
manipulation of the scanned documents can include deletion of one or more 
documents, reordering of the documents into a desired order, or addition 
of a previously or subsequently scanned document or documents. The 
printing or processing can be relatively synchronous with scanning, or 
asynchronous after scanning. If asynchronous, a time interval exists 
between scanning and printing or processing. The system can then 
accumulate a number of scanned jobs in the system memory for subsequent 
processing or printing. The order of the jobs to be printed may be 
different from the order of jobs as scanned depending on the priority of 
the jobs and the desires of the operator for increasing productivity or 
through-put and decreasing printer or scanner down-time. 
For a variety of reasons, the printed job may include sheets having images 
of questionable integrity. This can be the result of a system fault, a 
Raster Output scanner fault causing a failure to image properly, paper 
misfeed or misregistration, lack of communication between the Raster, 
Output scanner and control system, etc. 
The related art has disclosed printing systems which include job recovery 
including sheet purging. 
U.S. Pat. No. 4,327,993 to Gauronski et al discloses a method and apparatus 
for performing job recovery in a reproduction machine wherein purge sheets 
are sent to a tray not currently in use or to a tray which contains the 
rest of a copy job. When the purged sheets are sent to the tray which 
contains the copy job, they must be separated from the copy job once 
copying is complete. 
U.S. Pat. No. 4,206,996 to Clark et al discloses a job recovery method and 
apparatus wherein duplex job recovery is accomplished by purging all 
sheets, optionally flagging missing copies by inserting blank sheets into 
the copy job and then rerunning the copy job as necessary. 
There have thus been attempts to remedy the presence of such sheets by 
providing the systems with the capability to initially purge themselves 
well prior to the required sheet and initiate job recovery prior to the 
required sheet after the control system waits for all possible purge 
sheets in the paper path to be delivered. Operator attention is required, 
and there is a loss of job integrity caused by the inability to recover to 
the correct sheet. 
OBJECTS AND SUMMARY OF THE INVENTION 
Accordingly, one object of the present invention is to provide an 
electronic reprographic system which provides job recovery without 
requiring cycling down of the system. 
Another object of the present invention is to provide an electronic 
reprographic system which performs job recover without requiring operator 
attention. 
Another object of the present invention is to provide an electronic 
reprographic system which performs job recovery without risk of loss of 
job integrity. 
A further object of the present invention is to provide an electronic 
reprographic system which automatically remedies the presence of sheets 
having images of questionable integrity. 
To achieve the foregoing and other objects and advantages, and to overcome 
the shortcomings discussed above, an electronic reprographic system having 
printer dynamic job recovery is provided which detects the presence of 
sheets having images of questionable integrity. The system operates to 
remedy the presence of such sheets by redirecting all sheets of 
questionable integrity to a purge destination and recovering to the 
correct sheet in the job without requiring any operator attention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A. The System 
Referring now to the drawings, and particularly to FIGS. 1 and 2 thereof, 
there is shown an exemplary laser based printing system 2 for processing 
print jobs in accordance with the teachings of the present invention. 
Printing system 2, for purposes of explanation, is divided into a scanner 
section 6, controller section 7, and printer section 8. While a specific 
printing system is shown and described, the present invention may be used 
with other types of printing systems such as ink jet, ionographic, etc. 
Referring particularly to FIGS. 2-4, scanner section 6 incorporates a 
transparent platen 20 on which the document 22 to be scanned is located. 
One or more linear arrays 24 are supported for reciprocating scanning 
movement below platen 20. Lens 26 and mirrors 28, 29, 30 cooperate to 
focus array 24 on a line-like segment of platen 20 and the document being 
scanned thereon. Array 24 provides image signals or pixels representative 
of the image scanned which, after suitable processing by processor 25, are 
output to controller section 7. 
Processor 25 converts the analog image signals output by array 24 to 
digital and processes the image signals as required to enable system 2 to 
store and handle the image data in the form required to carry out the job 
programmed. Processor 25 also provides enhancements and changes to the 
image signals such as filtering, thresholding, screening, cropping, 
reduction/enlarging, etc. Following any changes and adjustments in the job 
program, the document must be rescanned. 
Documents 22 to be scanned may be located on platen 20 for scanning by 
automatic document handler (ADF) 35 operable in either a Recirculating 
Document Handling (RDH) mode or a Semi-Automatic Document Handling (SADH) 
mode. A manual mode including a Book mode and a Computer Forms Feeder 
(CFF) mode are also provided, the latter to accommodate documents in the 
form of computer fanfold. For RDH mode operation, document handler 35 has 
a document tray 37 in which documents 22 are arranged in stacks or 
batches. The documents 22 in tray 37 are advanced by vacuum feed belt 40, 
document feed rolls 41 and document feed belt 42 onto platen 20 where the 
document is scanned by array 24. Following scanning, the document is 
removed from platen 20 by belt 42 and returned to tray 37 by document feed 
rolls 44. 
For operation in the SADH mode, a document entry slot 46 provides access to 
the document feed belt 42 between tray 37 and platen 20 through which 
individual documents may be inserted manually for transport to platen 20. 
Feed rolls 49 behind slot 46 form a nip for engaging and feeding the 
document to feed belt 42 and onto platen 20. Following scanning, the 
document is removed from platen 20 and discharged into catch tray 48. 
For operation in the CFF mode, computer forms material is fed through slot 
46 and advanced by feed rolls 49 to document feed belt 42 which in turn 
advances a page of the fanfold material into position on platen 20. 
Referring to FIGS. 2 and 3, 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 90, 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 transfer station 106 to a print media 108 delivered by Paper Supply 
section 107. Media 108 as will appear may comprise any of a variety of 
sheet sizes, types, and colors. For transfer, the print media is brought 
forward in timed registration with the developed image on photoreceptor 98 
from either a main Paper tray 110 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 finisher 120. Finisher 120 includes a stitcher 122 
for stitching Or stapling the prints together to form books and a thermal 
binder 124 for adhesively binding the prints into books. 
Referring to FIGS. 1, 2 and 5, controller section 7 is, for explanation 
purposes, divided into an image input controller 50, User Interface (UI) 
52, system controller 54, main memory 56, image manipulation section 58, 
and image output controller 60. 
Referring particularly to FIGS. 5A-5C, control section 7 includes a 
plurality of Printed Wiring Boards (PWB's) 70, PWB's 70 being coupled with 
one another and with System Memory 61 by a pair of memory buses 72,74. 
Memory controller 76 couples System Memory 61 with buses 72, 74. PWB's 70 
include system processor PWB 70-1 having plural system processors 78; low 
speed I/0 processor PWB 70-2 having UI communication controller 80 for 
transmitting data to and from UI 52; PWB's 70-3, 70-4 and 70-5 having disk 
drive controller/processors 82 for transmitting data to and from disks 
90-1, 90-2 and 90-3, respectively, of main memory 56 (image 
compressor/processor 51 for compressing the image data is on PWB 70-3); 
image manipulation PWB 70-6 with image manipulation processors of image 
manipulation section 58; image generation processor PWB's 70-7 and 70-8 
with image generation processor 86 for processing the image data for 
printing by printer section 8; dispatch processor PWB 70-9 having dispatch 
processors 88 and 89 for controlling transmission of data to and from 
printer section 8; and boot control-arbitration-scheduler PWB 70-10. 
The scanned image data input from processor 25 of scanner section 6 to 
controller section 7 is compressed by image compressor/processor 51 of 
image input controller 50 on PWB 70-3. As the image data passes through 
compressor/processor 51, it is segmented into slices N scanlines wide, 
each slice having a slice pointer. The compressed image data together with 
slice printers and any related image descriptors providing image specific 
information (such as height and width of the document in pixels, the 
compression method used, pointers to the compressed image data, and 
pointers to the image slice pointers) are placed in an image file. The 
image files, which represent different print jobs, are temporarily stored 
in system memory 61 which comprises a Random Access Memory or RAM pending 
transfer to main memory 56 where the data is held pending use. 
As best seen in FIG. 1, UI 52 includes a combined operator controller/CRT 
display consisting of an interactive touchscreen 62, keyboard 64, and 
mouse 66. UI 52 interfaces the operator with printing system 2, enabling 
the operator to program print jobs and other instructions, to obtain 
system operating information, instructions, programming information, 
diagnostic information, etc. Items displayed on touchscreen 62 such as 
files and icons are actuated by either touching the displayed item on 
screen 62 with a finger or by using mouse 66 to point cursor 67 to the 
item selected and keying the mouse. 
Main memory 56 has plural hard disks 90-1, 90-2, 90-3 for storing machine 
Operating System software, machine operating data, and the scanned image 
data currently being processed. 
When the compressed image data in main memory 56 requires further 
processing, or is required for display on touchscreen 62 of UI 52, or is 
required by printer section 8, the data is accessed in main memory 56. 
Where further processing other than that provided by processor 25 is 
required, the data is transferred to image manipulation section 58 on PWB 
70-6 where the additional processing steps such as collation, make ready, 
decomposition, etc., are carried out. Following processing, the data may 
be returned to main memory 56, sent to UI 52 for display on touchscreen 
62, or sent to image output controller 60. 
Image data output to image output controller 60 is decompressed and readied 
for printing by image generating processors 86 of PWB's 70-7, 70-8 (seen 
in FIG. 5A). Following this, the data is output by dispatch processors 88, 
89 on PWB 70-9 to printer section 8. Image data sent to printer section 8 
for printing is normally purged from memory 56 to make room for new image 
data. 
Referring particularly to FIG. 6, system control signals are distributed 
via a plurality of printed wiring boards (PWB's). These include EDN core 
PWB 130, Marking Imaging core PWB 132, Paper Handling core PWB 134, and 
Finisher Binder core PWB 136 together with various Input/Output (I/0) 
PWB's 138. A system bus 140 couples the core PWB's 130, 132, 134 and 136 
with each other and with controller section 7 while local buses 142 serve 
to couple the I/0 PWB's 138 with each other and with their associated core 
PWB. 
On machine power up, the Operating System software is loaded from memory 56 
to EDN core PWB 130 and from there to the remaining core PWB's 132, 134 
and 136 via bus 140, each core PWB 130, 132, 134, 136 having a boot ROM 
(not shown) for controlling downloading of Operating System software to 
the PWB, fault detection, etc. Boot ROMs also enable transmission of 
Operating System software and control data to and from PWB's 130, 132, 134 
and 136 via bus 140 and control data to and from I/0 PWB's 138 via local 
buses 142. Additional ROM, RAM, and NVM memory types are resident at 
various locations within system 2. 
Referring to FIG. 7, jobs are programmed in a Job Program mode in which 
there is displayed on touchscreen 62 a Job Ticket 150 and a Job Scorecard 
152 for the job being programmed. Job Ticket 150 displays various job 
selections programmed while Job Scorecard 152 displays the basic 
instructions to the system for printing the job. 
B. Fault Recovery 
System 2 has the capability to detect and correct for various faults. Upon 
detection of a fault, system 2 will take the appropriate actions defined 
for each individual fault or simply take the worst case action for cases 
where multiple faults are detected. 
Dynamic recovery is defined as printer 8 job recovery without cycle down 
and is used only in conjunction with the video loss purge which is 
described below. Dynamic recovery requires the printer 8 to assess the job 
completion progress of all partially completed jobs and start recovery job 
scheduling without specific direction. 
When system 2 is in a full execution mode (i.e., the photoreceptor is being 
charged and discharged) but a sheet of paper is not being imaged, a pitch 
skip occurs. A single pitch skip occurs during the printing of a job when 
controller 7 cannot provide the required print image to the printer 8 at 
the specified print time for that particular image. Each pitch skip 
encountered represents a period of time when the printer 8, although in 
operation, is not producing any hard copy output. The percentage of pitch 
skips is calculated as the total number of pitch skips divided by the 
total number of impressions made plus the total number of pitch skips. 
Printer 8 can be thought of as requiring an image file at every print 
pitch, the images being provided to printer 8 by controller 7. If the 
controller 7 cannot provide the required image before printer 8 is ready 
to print it, the printer 8 waits, thus incurring pitch skips. The pitch 
skip is thus due to the controller 7 not being able to provide the 
required image fast enough. 
The printer 8 may skip pitches when performing dynamic recovery after a 
video loss purge. The printer 8 may skip pitches between the last video 
loss purge sheet and the next good sheet. The actual number o skip pitches 
will be decreased by the number of side one sheets committed to a duplex 
loop at the time that the video loss purge started. 
C. Video Loss Purge 
When the printer 8 detects, or is informed, that the video data for a sheet 
in the paper path has lost integrity, a video loss purge is performed. The 
video loss purge is performed, for example, when there is detected a 
failure to image properly or when printer 8 detects sheet misregistration. 
Detection of such a fault automatically results in the application of the 
video loss purge. 
FIGS. 8A-8C depict exemplary operation of system 2 upon performance of 
dynamic job recovery according to the present invention. 
Referring now to FIG. 8A, there is shown a flow chart depicting a basic 
operation of system 2 upon performance of dynamic job recovery. Printer 8 
is informed of or detects a fault indicating the presence of a sheet in 
the paper path having a video image with a loss of integrity (step 200). 
Upon such detection, printer 8 redirects the specified sheet and all 
trailing sheets in the paper path to a specified purge location (step 
202). Additionally, all scheduling of additional sheets is momentarily 
interrupted. According to the present invention, up to three sheets in 
advance of the specified sheet may be purged. Printer 8 waits for delivery 
of all purge sheets (step 204). Dynamic job recovery can then be performed 
as soon as the last purge sheet is delivered (step 206). 
FIG. 8B shows a flowchart depicting an optimized operation of system 2 upon 
performance of dynamic job recovery. As in FIG. 8A, printer 8 is informed 
of or detects a fault indicating the presence of a sheet in the paper path 
having a video image with a loss of integrity (step 208). Upon such 
detection, printer 8 redirects the specified sheet and all following 
sheets to a specified purge location (step 210). All scheduling of 
additional sheets is momentarily interrupted. Printer 8 waits for delivery 
of the first purge sheet (step 212). From the first purge sheet delivery, 
the printer 8 determines the last good sheet (i.e., sheet whose image has 
no loss of integrity) which has been successfully delivered (step 214). 
Optimized dynamic job recovery can then be performed as soon as the first 
purge sheet is delivered (step 216). Job recovery includes rescheduling of 
the job based on the delivery of the last good sheet. 
FIG. 8C shows a flowchart depicting an advanced operation of system 2 upon 
performance of dynamic job recovery. Printer 8, as in the previous 
operations, is informed of or detects a fault indicating the presence of a 
sheet in the paper path having a video image with a loss of integrity 
(step 218). Upon such detection, printer 8 redirects the specified sheet 
and all following sheets to a specified purge location (step 220). Using 
information on the last sheet scheduled stored in the printer controller 
memory, the printer 8 immediately determines the last good sheet scheduled 
prior to the fault occurrence (step 222). Recovery to the correct sheet 
begins immediately without being based upon the delivery of purge sheets 
(step 224). FIG. 9 is a chart providing an overall comparison of the 
exemplary operations described above. 
By limiting the number of sheets purged by the system, dynamic job recovery 
can thus be initiated significantly sooner since the system is not 
required to await delivery of a large number of purge sheets. Only a 
minimum number of sheets need be purged. Job scheduling is resumed with 
the next sheet, thereby improving printer productivity while reducing the 
operator perceived malfunction rate. A foundation is provided for a retry 
strategy for all malfunctions that do not require immediately turning off 
paper path drives. As the dynamic job recovery is performed automatically, 
no operator attention is required. Job integrity is maintained by job 
rescheduling to replace all sheets purged to the purged destination. 
While this invention has been described in conjunction with specific 
embodiments thereof, it is evident that many alternatives, modifications 
and variations will be apparent to those skilled in the art. Accordingly, 
the preferred embodiments of the invention as set forth herein are 
intended to be illustrative, not limiting. Various changes may be made 
without departing from the spirit and scope of the invention as defined in 
the following claims.