Electrophotography – Machine operation – Job mode
Reexamination Certificate
2002-07-24
2004-05-25
Braun, Fred L. (Department: 2852)
Electrophotography
Machine operation
Job mode
Reexamination Certificate
active
06741819
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of Korean Application No. 2001-79716, filed Dec. 15, 2001, in the Korean Industrial Property Office, the disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a duplex printing method of a printing apparatus such as a printer or a copier, and more particularly, to a duplex printing method in which a sequence of pages to be printed is determined using a page backup algorithm in a state of a printer engine error, such as paper jam or paper empty, in order to print print data on both sides of a print sheet.
2. Description of the Related Art
A block diagram of a typical printing apparatus having a duplex printing function is shown in FIG.
1
. The printing apparatus shown in
FIG. 1
includes an interface unit
10
, a controller
12
, a memory
14
, an image forming unit
16
, and a sheet handler
18
.
The controller
12
converts print data received from an external source through the interface unit
10
into images, stores the images in the memory
14
, and transmits the images corresponding to respective pages to be printed to the image forming unit
16
in a predetermined printing sequence. The image forming unit
16
prints a received image on a sheet picked up by the sheet handler
18
. The image forming unit
16
and the sheet handler
18
are parts that actually perform a printing function and are collectively referred to as a printer engine.
The controller
12
includes a scheduler (not shown) determining the printing sequence of the respective pages to be printed, an interpreter (not shown) processing the received print data, and a video controller (not shown). The image forming unit
16
forms an image on a corresponding sheet. The sheet handler
18
handles sheets and includes a duplex loop (not shown) for a duplex printing function.
Generally, the printing apparatus having the duplex printing function is provided with the duplex loop so that the duplex printing function can be implemented under the control of the controller
12
. The duplex loop is an apparatus handling (processing) sheets for the duplex printing function.
The duplex loop is denoted by a reference numeral 28 shown in FIG. 1 of U.S. Pat. No. 6,069,704 and is also shown in FIG. 1 of U.S. Pat. No. 5,488,458 as a duplex loop path denoted by a reference numeral 13. Thus, a description about structure and operations of the duplex loop will be omitted.
Scheduling methods of determining the printing sequence of the pages to be printed for the duplex printing function in the printing apparatus such as a printer are different from each other depending on the number of sheets handled by the printer. That is, the scheduling methods are different from each other depending on the number of sheets which can be accommodated (disposed) in the duplex loop of the printer at a time, i.e., the number of sheets accommodated in the duplex loop during a period from the picking-up of the sheets to the printing out of the sheets. The number of sheets accommodated and handled in the duplex loop at a time indicates the number of sheets which can be processed in accordance with the duplex printing function in bulk and is hereinafter simply referred to as a duplex loop capacity.
The duplex loop capacity varies with a length of the duplex loop and the size of a sheet. As an example, it is assumed that sheets of the same size are accommodated and handled in the duplex loop. However, the present invention is not limited to the sheets of the same size.
If the duplex loop capacity of the printer is N, the video controller of the printer must be provided with 2N pages. For example, in a case where the duplex loop capacity is 5, when 10 pages are to be printed, the pages to be printed would be scheduled in order of second page→fourth page→sixth page→eighth page→tenth page→first page→third page→fifth page→seventh page→ninth page. Here, if there are only nine pages to be printed, the position of the tenth page should be skipped and processed as a null page. If there is a continuous printing job following the above printing job, the skipped part should be minimized to minimize a duplex cycle and the like. The method of scheduling the printing sequence of the pages to minimize a duplex cycle is disclosed in a U.S. Pat. No. 6,069,704.
However, the continuous printing job is sometimes interrupted or abruptly terminated. There may occur a processing error, such as paper jam or toner empty, in terms of mechanical characteristics of the printer or copier or a physical error such as paper empty in terms of a capacitive limit of a paper cassette.
In the above case, the printer can operate at a full speed only after the controller
12
generates image data corresponding to respective ones of the pages in the form of a bitmap or a similar form such as a display list or a compressed bitmap throughout the ten pages.
If the processing on the fifth page is delayed after completing the processing on first through fourth pages, or if a memory overflow occurs, it is needed to print just four pages in advance. As described above, the page scheduling needs to be changed depending on circumstances due to a capacity limit of the controller itself and a physical limit of the printing apparatus.
All cases which the errors can occur while the duplex printing function is performed in the printer will be reviewed. As an example, it is assumed that the duplex loop capacity is 2 in all of the following cases.
1. Continuous Duplex Printing or Fast Duplex Printing Mode
For example, when 8 pages are printed on both sides of 4 sheets, the printing sequence may be 2→4→1→6→3→8→5→7. Here, the numerals, such as 1 and 2, indicate page numbers. That is, numeral 2 indicates a second page.
In the fast duplex printing mode, at the moment that a next page to be printed is determined immediately after printing of the second page is completed, the fourth page should be prepared in the form of the bitmap or the similar form such as the display list or the compressed bitmap.
This mode allows a maximum engine efficiency in the printer having the duplex loop capacity of 2 to be accomplished.
2. Normal Duplex Printing or Normal Duplex Printing Mode
When 8 pages are printed, the printing sequence may be 2→1→4→3→6→5→8→7. This printing mode can occur in the following state.
First, it occurs when the third and fourth pages are not prepared at the moment of printing of a next page after the second page is completely printed, due to very complicated data or an insufficient capacity of a memory.
Second, it occurs when sheets are used in the printer engine having the duplex loop capacity of 2. In other words, long sheets may not be allowed by the duplex loop having the duplex loop capacity of 2 in terms of characteristics of the printing apparatus.
3. Continuous and Normal Duplex Printing Mode
When 10 pages are printed, the printing sequence may be 2→1→4→6→3→8→5→7→10→9.
This mode occurs when processing of the third and fourth pages and processing of the ninth and tenth pages are delayed or when the size of the sheets is large. In other words, this occurs when only the normal duplex printing mode is performed in the printing apparatus.
4. Duplex Printing Mode after Instant Engine Stop
For example, there may be three cases of the printing sequence.
Case 1: 2→engine error and stop→2→4→1→6→3→8→5→7
Case 2: 2→4→engine error and stop→2→4→1→6→3→8→5→7
Case 3: 2→4→1→engine error and stop→4→6→3→8→5→7
In the case 1 where the printer engine stops due to an engine error after the second page is printed, only the second page of a pair of the first and second pages has been printed, so the printing function restarts from the second page.
In the case 2 wh
Braun Fred L.
Samsung Electronics Co,. Ltd.
Staas & Halsey , LLP
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