Patent Publication Number: US-2009225355-A1

Title: Printing apparatus and printing control method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to and incorporates by reference the entire contents of Japanese priority document 2008-057683 filed in Japan on Mar. 7, 2008. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a printing apparatus and a printing control method. 
     2. Description of the Related Art 
     An Internet printing system that performs printing via the Internet network has been recently developed (Japanese Patent Application Laid-open No. 2003-271347). 
     Recently, as shown in  FIG. 20 , an extranet that interconnects intranets  200  and  300  in companies or offices via an Internet network  400  has been used. According to a network environment shown in  FIG. 20 , a printing process can be performed from a host computer such as a server on the intranet  200  on one side to a printer on the intranet  300  on the other side. 
     However, in the Internet printing system disclosed in Japanese Patent Application Laid-open No. 2003-271347 or the network environment shown in  FIG. 20 , even if the printing is held due to a print-disabled state (paper out, paper jam, toner out, or other failures) of the printer requiring an operator&#39;s operation in the middle of printing, the host computer cannot check the status of the printer, and the printer can be left in a printing hold state. 
     In addition, in the network environment, because there is no means for sending information such as an output destination/output number of pages on the printer side to the server, after the server executes printing, it cannot check the status of the printer. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to at least partially solve the problems in the conventional technology. 
     According to one aspect of the present invention, there is provided a printing apparatus including a connecting unit that makes a network connection to other printing apparatus that performs a printing process of printing data transmitted from a host apparatus on a printing medium on a downstream side in a data transmission direction; a first transmitting unit that transmits print hold information for holding the printing process to the other printing apparatus; a second transmitting unit that transmits the printing data to the other printing apparatus; a third transmitting unit that transmits page deletion information for deleting data corresponding to a printed page to the other printing apparatus every time a page is printed on the printing medium; and a fourth transmitting unit that transmits, when a function of the printing apparatus cannot satisfy a condition specified by the host apparatus at a time of printing, print-disable information to the other printing apparatus, and releases a hold of the printing process in the other printing apparatus according to the print-disable information. 
     Furthermore, according to another aspect of the present invention, there is provided a printing control method for a printing apparatus that performs a printing process of printing data transmitted from a host apparatus on a printing medium. The printing control method includes making a network connection to other printing apparatus on a downstream side in a data transmission direction; first transmitting including transmitting print hold information for holding the printing process to the other printing apparatus; second transmitting including transmitting the printing data to the other printing apparatus; third transmitting including transmitting page deletion information for deleting data corresponding to a printed page to the other printing apparatus every time a page is printed on the printing medium; and fourth transmitting including transmitting, when a function of the printing apparatus cannot satisfy a condition specified by the host apparatus at a time of printing, print-disable information to the other printing apparatus, and releasing a hold of the printing process in the other printing apparatus according to the print-disable information. 
     The above and other objects, features, advantages and technical and industrial significance of this invention will be better understood by reading the following detailed description of presently preferred embodiments of the invention, when considered in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of a system configuration example of a network print system according to an embodiment of the present invention; 
         FIG. 2  is a schematic diagram of a system configuration example of the network print system; 
         FIG. 3  is a block diagram of one example of a configuration of a print server; 
         FIG. 4  is a block diagram of one example of a configuration of a printer; 
         FIG. 5  is a schematic diagram of a functional configuration of a printer substituting process; 
         FIG. 6  is a sequence diagram of a network printing process procedure including the printer substituting process; 
         FIG. 7  is a schematic diagram of a table of printer information; 
         FIG. 8  is a schematic diagram of updating of the table; 
         FIG. 9  is a schematic diagram of a method of sequentially merging and transmitting response information; 
         FIG. 10  is a schematic diagram of a functional configuration relating to a job synchronizing process in the printer substituting process; 
         FIG. 11  is a sequence diagram of a printing process procedure at a normal time; 
         FIG. 12  is a schematic diagram of a merging process of response information; 
         FIG. 13  is a schematic diagram of a page information table; 
         FIG. 14  is a schematic diagram of a failure information table; 
         FIG. 15  is a sequence diagram of a printing process procedure when a print-disabled state occurs during a printing process; 
         FIG. 16  is a schematic diagram of an alternative printing function; 
         FIG. 17  is a schematic diagram of one example of alternative printing; 
         FIG. 18  is a schematic diagram of a printing process of a printing result report; 
         FIG. 19  is one example of the printing result report; and 
         FIG. 20  is a schematic diagram of a system configuration example in a conventional network environment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Exemplary embodiments of the present invention will be explained below in detail with reference to accompanying drawings. In the embodiments, a laser printer or a multi-function peripheral (MFP) is applied as a printing apparatus. 
       FIG. 1  is a schematic diagram of a system configuration example of a network print system  100  according to an embodiment of the present invention. As shown in  FIG. 1 , for the network print system  100  according to the present embodiment, a network environment is assumed in which an intranet A and an intranet B in plural companies or offices, which are corporate networks based on the Internet technique, are interconnected with each other via an Internet network  150 . 
     As shown in  FIG. 1 , for example, as the intranet A in a head office of a convenience store chain, there is assumed a server client system in which a plurality of clients  3  such as a computer and a printer is connected to various server computers (hereinafter, “server”)  1  via a network  2  such as a local area network (LAN). In the intranet A, a firewall  6  is provided at a boundary between the Internet network  150  and a corporate network  5  excluding a public server  4  such as World Wide Web (WWW). The firewall  6  monitors a packet that comes in and out between the corporate network  5  and the Internet network  150 , to allow the passage of the packet or discard the packet according to a predetermined rule, thereby ensuring security in the corporate network  5 . 
     On the other hand, for example, as the intranet B in a franchise store, there is assumed a server client system in which the clients  3  such as the computer and the printer are connected to the various servers  1  via the network  2  such as the LAN. Also in the intranet B, the firewall  6  is provided at the boundary between the Internet network  150  and the corporate network  5  excluding the public server  4 . 
     The network connection between the intranets A and B is not limited to the Internet network  150 , and the intranets A and B can be connected by using a dedicated communication line. 
     The network  2  is not limited for wire communication, and can be for wireless communication (infrared, radiowave, or the like). The network  2  can use optical fibers as well. 
     As shown in  FIG. 2 , the network print system  100  can directly perform the printing process, for example, for a promotional material or the like from a print server  11 , which is one of the servers  1  provided in the intranet A in, for example, the head office of the convenience store with respect to a printer  31 , which is one of the clients  3  provided in the intranet B of the franchise store. As shown in  FIG. 2 , a plurality of printers  31  having the same function are provided in the intranet B. 
     The print server  11  (the server  1 ) provided in the intranet A is explained next.  FIG. 3  is a block diagram of one example of a configuration of the print server  11 . As shown in  FIG. 3 , the print server  11  includes a central processing unit (CPU)  41  that performs operation control of the print server  11 . A read only memory (ROM)  42  for storing a program executed by the CPU  41  at the time of start-up or required data, and a random access memory (RAM)  43  for configuring a work area and the like of the CPU  41  are connected to the CPU  41  via an internal bus  56 . 
     Further, a character generator  44 , a clock circuit  45 , a network-transmission control unit  47 , a magnetic disk device  48 , a compact disk read only memory (CD-ROM) device  49 , a display control unit  52 , and an input control unit  55  are connected to the CPU  41  via the internal bus  56 , and data is transferred between the respective components mainly via the internal bus  56 . 
     The character generator  44  generates display data in graphic characters. The clock circuit  45  outputs information of current date and time. 
     A network interface (I/F) circuit  46  connects the print server  11  to the network  2 , which is the LAN, and the network-transmission control unit  47  performs a communication control process with respect to various predetermined protocol suites for transferring various pieces of data with other servers  1  and the clients  3  via the network  2 . For example, the network I/F circuit  46  connects the printer  31 , which is one of the clients  3  provided in another intranet (the intranet B) via the network  2  and the Internet network  150 , and performs operations such as transmitting print data or the like to the printer  31 , or receiving printing status or the like from the printer  31 . 
     The magnetic disk device  48  stores an operating system (OS) and various data such as various application programs running on the OS, work data, file data, and image information data. According to the present embodiment, a print data transmission program and the like are stored as the application program. The CD-ROM device  49  reads data (various types of data such as various application programs, work data, file data, and image information data) stored in a CD-ROM  50 , which is a replaceable recording medium. 
     In the print server  11 , when a user turns on power, the CPU  41  starts up a program referred to as a loader in the ROM  42 , and reads the OS from the magnetic disk device  48  into the RAM  43  to start up the OS. The OS starts up the application program, reads information, or stores the information in response to user&#39;s operation. The recording medium is not limited to the CD-ROM  50 , and can be a computer readable recording medium such as a flexible disk (FD), a CD-recordable (CD-R), a CD-rewritable (CD-RW), a digital versatile disk (DVD), and a semiconductor memory. In this case, the CD-ROM device  49  can be of course changed to the one capable of reading the data on the recording medium. Further, the application program is not limited to the one operating on the predetermined OS, and can be the one that allows the OS to take over execution of a part of various types of processing described later, or the one included as a part of predetermined application software or a group of program files constituting the OS. 
     Generally, the application program installed in the magnetic disk device  48  of the print server  11  is recorded on the recording medium such as the CD-ROM  50 , and the application program recorded on the recording medium is installed in the magnetic disk device  48 . Accordingly, a portable recording medium such as the CD-ROM  50  can be the recording medium that stores the application program. Further, the application program can be taken in from outside via, for example, the network I/F circuit  46  and installed in the magnetic disk device  48 . 
     A display device  51  such as a cathode ray tube (CRT) and a liquid crystal display (LCD) displays a screen for operating the print server  11 , and the display control unit  52  controls a display content of the display device  51 . 
     A keyboard device  53  issues various instructions to the print server  11  by various key operations, and a screen display device  54  is for performing an operation such as indicating an arbitrary point on the display device  51  (for example, a pointing device such as a mouse), and the input control unit  55  obtains input information of the keyboard device  53  and the screen display device  54 . 
     An appropriate application program is started up by the print server  11 , and printed document information is generated by the application program and stored in the magnetic disk device  48 , or printed document information stored on the CD-ROM  50  is read by the CD-ROM device  49  and taken into the print server  11 , or the printed document information is reconstructed from information received by an e-mail via the network  2  and the Internet network  150  and taken into the print server  11 , and stored in the print server  11 . 
     The printer  31  (the client  3 ), which is the printing apparatus provided in the intranet B, is explained next.  FIG. 4  is a block diagram of one example of a configuration of the printer  31 . As shown in  FIG. 4 , the printer  31  includes a printer controller (a motherboard)  61  that performs various types of control processing such as control processing of respective units in the printer  31  and image forming processing. An operation panel  62 , a printer engine  63 , and a magnetic disk device  64  are connected to the printer controller  61 . 
     The printer controller  61  is a general term of a control mechanism that converts print data from the various servers  1  in the respective intranets A and B (for example, the print server  11  in the intranet A) to drawing data according to a control mode set at that time and a control code from the various servers  1  in the respective intranets A and B (for example, the print server  11  in the intranet A), and outputs the drawing data to the printer engine  63 , and is configured by a module described below. That is, the printer controller  61  includes a CPU  81  as a control subject, a RAM  82 , a ROM  83  for storing various pieces of information unique to the printer  31 , a non-volatile RAM (NV-RAM)  84  as a nonvolatile memory capable of holding data regardless of power ON/OFF, a font ROM  85  as a memory for holding several types of typefaces used at the time of printing, an engine I/F  86 , a panel I/F  87  that connects the operation panel  62 , a disk I/F  88  that connects the magnetic disk device  64 , and a network I/F  89 . 
     The RAM  82  is used as a work area of the CPU  81 , a buffer for receiving data from various servers  1  in the respective intranets A and B, and an image expansion area after processing. 
     The engine I/F  86  transfers a control signal from the printer controller  61  to the printer engine  63  and a status signal from the printer engine  63  to the printer controller  61 . 
     The network I/F  89  transfers a control signal and data from the various servers  1  in the respective intranets A and B (for example, the print server  11 ) to the printer  31  and a status signal from the printer  31  via the network  2 . 
     The operation panel  62  is a switch capable of changing status display, mode, and printing condition of the printer  31 . 
     The printer engine  63  forms an image according to an electrophotographic process and records and outputs the image on recording paper. More specifically, the printer engine  63  electrostatically forms an image on a photoconductor based on the drawing data and control information from the printer controller  61 , and feeds transfer paper from a paper feeder to form an image. 
     The magnetic disk device  64  stores various types of printed document information, and stores appropriate information files other than the printed document information. In addition, the magnetic disk device  64  stores the OS and various application programs running on the OS. According to the present embodiment, a printing program and the like are stored as the application program. 
     The printer  31  with such a configuration reads the OS from the magnetic disk device  64  to the RAM  82  when the user turns on the power, as in the server  1 , to start up the OS. The OS started up in this manner starts up the application program, reads information, or stores the information in response to the user&#39;s operation. The application program is not limited to the one operating on the predetermined OS, and can be the one that allows the OS to take over execution of a part of various types of processing described later, or the one included as a part of the predetermined application program or a group of program files constituting the OS. 
     Generally, the application program installed in the magnetic disk device  64  of the printer  31  is recorded on the recording medium such as the CD-ROM (not shown), and the application program recorded on the recording medium is installed in the magnetic disk device  64 . Accordingly, the portable recording medium such as the CD-ROM can be the recording medium that stores the application program. Further, the application program can be taken in from outside via, for example, the network I/F  89  and installed in the magnetic disk device  64 . 
     The printer  31  according to the present embodiment includes the magnetic disk device  64 . However, the printer  31  is not limited thereto, and the application program and the OS can be stored on a computer readable recording medium such as a semiconductor memory. 
     Among various types of arithmetic processing performed by the CPU  41  in the print server  11  and the CPU  81  in the printer  31 , a printer substituting process, which is a characteristic process of the network print system  100  according to the present embodiment, is explained next. 
     In the network print system  100 , when print data is input from the print server  11  as a host apparatus of the intranet A to the printer  31  in the intranet B via the Internet network  150 , drawing data is generated for the input print data on the printer  31  in the intranet B based on the control information of the printer controller  61 , the generated drawing data is transmitted from the printer controller  61  to the printer engine  63 , and a print start command is issued to start printing. In the printer  31  performing the printing process in the intranet B, a print-disabled state (paper out, paper jam, toner out, or other failures) requiring an operator&#39;s operation may occur even in the middle of printing. In the network print system  100 , therefore, when the print-disabled state requiring the operator&#39;s operation occurs in the printer  31 , which is performing the printing process, the printer substituting process is performed such that an object to be printed is switched to another printer  31 , thereby enabling to continue printing, so that the print-disabled state does not occur in the intranet B. 
     The print server  11  stores the print data transmission program in the magnetic disk device  48  as the application program. That is, in the print server  11 , when the print data transmission program operating on the OS is started up, the CPU  41  controls respective units according to the print data transmission program, to perform a print data transmission process, which is a part of the printer substituting process. 
     The printer  31  stores the printing program in the magnetic disk device  64  as the application program. That is, in the printer  31 , when the printing program operating on the OS is started up, the CPU  81  controls respective units according to the printing program, to perform the printing process, which is a part of the printer substituting process. 
       FIG. 5  is a schematic diagram of a functional configuration of the printer substituting process of the printer  31 . As shown in  FIG. 5 , the printer  31  includes a connecting unit  101  that connects to another printer  31  via a network on a downstream side in a data transmission direction, a hold-information transmitting unit  102  that transmits print hold information for holding the printing process to the other printer  31  located on the downstream side, a data transmitting unit  103  that transmits the transmitted data to the other printer  31  located on the downstream side, a delete-information transmitting unit  104  that transmits page delete information to the other printer  31  located on the downstream side, every time one page is printed on the printing medium, for deleting data corresponding to a printed page stored by the other printer  31  according to the page delete information, and a print-disable-information transmitting unit  105  that transmits print-disable information indicating that a condition specified by the print server  11  at the time of printing does not match a function of the printer  31  to the other printer  31  located on the downstream side, and releases the hold of the printing process in the other printer  31  according to the print-disable information. As shown in  FIG. 5 , the printer  31  further includes a storage unit  106  that stores a function specifiable at the time of printing, and an update unit  107  that updates the function stored in the storage unit  106 . 
     Main processes of the printer substituting process are specifically explained for each scene. 
       FIG. 6  is a sequence diagram of a network printing process procedure including the printer substituting process. In  FIG. 6 , as the intranet B, there is assumed a system in which three printers, that is, a printer  31   a  as a “main printer”, a printer  31   b  as a “sub printer  1 ”, and a printer  31   c  as a “sub printer  2 ” are connected via the network by the connecting unit  101 , respectively. 
     The “main printer” is uniquely determined by the host apparatus. However, the “sub printer  1 ” and the “sub printer  2 ” can be determined fixedly or the sequence thereof can be changed for each process. For example, the sequence of the “sub printer  1 ” and the “sub printer  2 ” can be realized by storing an IP address of the printer, to which the data is transmitted next, in the storage unit (the ROM  83 , the NV-RAM  84 , or the magnetic disk device  64 ) of the printer, and referring to the stored IP address at the time of data transfer. 
     An apparatus acquiring process is performed first in the network printing process. 
     (1) Upon reception of an “Acquire apparatus” command from the print server  11 , the main printer performs a printer occupying process and transmits the “Acquire apparatus” command to the sub printer (the sub printer  1  in  FIG. 6 ). At this time, the hold-information transmitting unit  102  in the main printer specifies a hold of a paper ejection as information. The information is the print hold information for holding the printing process. 
     In addition, the storage unit  106  in the main printer holds the function specifiable at the time of printing as a table of printer information in the NV-RAM  84 , and the update unit  107  in the main printer updates the table of the printer information held in the NV-RAM  84 .  FIG. 7  depicts the table. As shown in  FIG. 7 , the table holds information unique to each model, which is held in the ROM  83  and cannot be changed (color/monochrome, multi feed detection, and the like), and information held in the NV-RAM  84  and changeable for each model (information of a finisher or the like optionally incorporated). Such a table is generally created at the time of startup. In the present embodiment, however, the latest table is created by update, every time the “Acquire apparatus” command is received from the print server  11 . Therefore, when the finisher is incorporated after startup and before reception of the “Acquire apparatus” command, the table is updated as shown in  FIG. 8 . 
     (2) The sub printer (the sub printer  1  in  FIG. 6 ) performs the printer occupying process. Further, because a hold of paper ejection is specified in the information, the sub printer holds the paper ejection from the printer. In addition, the update unit  107  in the main printer updates the table of the printer information held in the NV-RAM  84 . When there is a lower-level sub printer (on the downstream side in the data transmission direction) (the sub printer  2  in  FIG. 6 ), the sub printer transmits the “Acquire apparatus” command received from an upper-level printer (an upstream side in the data transmission direction) to the lower-level sub printer. When there is no lower-level sub printer, the sub printer transmits an “Apparatus acquisition response” command to an upper-level printer. Further, the lower-level printer transmits the “Apparatus acquisition response” command to the upper-level printer. The apparatus acquisition response includes an IP address of the printer, and as shown in  FIG. 9 , the upper-level printer sequentially merges the response information (the IP address of the printer) from the lower-level printers and transmits the merged information. The main printer waits for the response from the sub printer and transmits the “Apparatus acquisition response” command to the print server  11 . 
     Accordingly, the print server  11  receives the information as a result of merge of pieces of information of all printers. 
     An information transmission from the printer to the print server  11  is performed via the Internet network  150  and the firewall  6 . Therefore, the passage thereof is permitted by ruling or the information is attached to an e-mail and transmitted. The same applies to information transmission from the printer to the print server  11  described below. 
     The print server  11  manages the printer information obtained by merging the pieces of information of respective sub printers and the main printer as a log. 
     (3) Upon reception of a “Start JOB” command from the print server  11 , the main printer performs a “JOB start” process, and transmits the “Start JOB” command to the sub printer (the sub printer  1  in  FIG. 6 ). At this time, the main printer adds an obtained JOB ID to the information. 
     (4) The sub printer (the sub printer  1  in  FIG. 6 ) performs a JOB start process, but does not create the JOB ID. The sub printer achieves synchronization of job management between the printers by using the JOB ID notified from the main printer. When there is a lower-level sub printer (the sub printer  2  in  FIG. 6 ), the sub printer transmits the “Start JOB” command received from an upper-level printer to the lower-level sub printer. When there is no lower-level sub printer, the sub printer transmits a “Job start response” command to an upper-level printer. Further, the lower-level printer transmits the “Job start response” command to the upper-level printer. The main printer waits for the response from the sub printer, and transmits the “Job start response” command to the print server  11 . 
     Upon completion of the apparatus acquiring process in the network printing process, the printing process is performed. 
       FIG. 10  is a schematic diagram of a functional configuration relating to a job synchronizing process in the printer substituting process of the printer  31 . As shown in  FIG. 10 , the printer  31  includes a paper-ejection-notification receiving unit  311 , a job management table  312  formed in the NV-RAM  84 , and a command receiving unit  313 , as the functional configuration relating to the job synchronizing process. 
     The paper-ejection-notification receiving unit  311  receives a printing completion notification from the printer engine  63 . The paper-ejection-notification receiving unit  311  then reads the job management table  312 , counts up the number of printed pages for each JOB ID, and stores the number of printed pages in the job management table  312 . In addition, upon reception of a failure notification from the printer engine  63 , the paper-ejection-notification receiving unit  311  stores an error code relating to the failure notification in the job management table  312 . 
     The command receiving unit  313  receives a command (Transmit data/Monitor status) transmitted from the print server  11  (the server  1 ) or the upper-level printer  31  located on the upstream side in the data transmission direction, and transmits the received command to the lower-level printer (sub printer)  31  located on the downstream side in the data transmission direction. Further, upon reception of the response information corresponding to the Monitor status command from the lower-level printer (sub printer)  31 , the command receiving unit  313  reads the job management table  312  to merge page information (including the number of printed pages) included in the response information. When the error code or failure information is included in the response information corresponding to the Monitor status command received from the lower-level printer (sub printer)  31 , the command receiving unit  313  merges the failure information. The command receiving unit  313  returns the response information in the job management table  312  to the print server  11  (the server  1 ) or the upper-level printer  31 . 
     In such a functional configuration, a printing process procedure at a normal time is explained with reference to a sequence diagram shown in  FIG. 11 . 
     (11) Upon reception of the “Transmit data” command from the print server  11 , the data transmitting unit  103  in the main printer transmits the “Transmit data” command to the sub printer (the sub printer  1  in  FIG. 6 ). 
     (12) When there is a lower-level sub printer (the sub printer  2  in  FIG. 6 ), the data transmitting unit  103  in the sub printer (the sub printer  1  in  FIG. 6 ) transmits the “Transmit data” command received from the upper-level printer to the lower-level sub printer. When there is no lower-level sub printer, the sub printer transmits a “Data transmit response” command to the upper-level printer. The lower-level sub printer then performs the printing process. The main printer waits for the response from the sub printer, transmits the “Data transmit response” command to the print server  11 , and performs the printing process. 
     (13) The delete-information transmitting unit  104  in the main printer transmits a “Delete page” command to the sub printer every time paper is ejected. The delete-information transmitting unit  104  in the sub printer receives the “Delete page” command, and when there is a lower-level sub printer, transmits the “Delete page” command received from the upper-level printer thereto. The sub printer having received the “Delete page” command achieves synchronization of the number of printed pages, and deletes the printed pages. 
     (14) Upon reception of the “Monitor status” command from the print server  11 , the main printer transmits the “Monitor status” command to the sub printer (the sub printer  1  in  FIG. 6 ). 
     (15) When there is a lower-level sub printer (the sub printer  2  in  FIG. 6 ), the sub printer (the sub printer  1  in  FIG. 6 ) transmits the “Monitor status” command received from the upper-level main printer to the lower-level sub printer (the sub printer  2  in  FIG. 6 ). When there is no lower-level sub printer, the sub printer transmits a “Monitor status response” command to the upper-level printer. In the present embodiment, as shown in  FIG. 12 , the upper-level printer merges the response information from the lower-level printers, and transmits the merged information to the upper-level printer (the main printer as the highest-order printer transmits the information to the print server). 
     As shown in  FIG. 12 , the upper-level printer generates page information including the number of printed pages obtained by adding the number of printed pages by all the lower-level printers which have responded and the number of printed pages by the upper-level printer, the number of printers, which is the total number of all the lower-level printers which have responded and the main printer, and the printer information (IP address of each of the lower-level printers which have responded and the main printer, JOB ID, and the number of printed pages) as a part of the response information, for each JOB ID. 
     Further, in the present embodiment, the main printer also generates the failure information as a part of the response information. The failure refers to a state in which a print-disabled state (paper out, paper jam, toner out, or other failures) requiring an operator&#39;s operation occurs in the printer. As shown in  FIG. 12 , the main printer generates failure information including an error code relating to a failure content, the number of failed printers, printer information (IP address of each of the lower-level printers that have notified an error and the upper-level printer having an error, error code, and failed JOB ID) as a part of the response information, for each failed JOB ID.  FIG. 12  depicts a case that there is no failure information in the lower-level printer. 
     As described above, main printer waits for the response from the sub printer to merge the response information, and transmits a “Monitor status response” command to the print server  11 . If any print-disabled state (paper out, paper jam, toner out, or other failures) requiring an operator&#39;s operation does not occur in the main printer, the printing process is complete. 
     On the other hand, the print server  11  having received the “Monitor status response” from the main printer receives the response information as a printing result in which the pieces of information of all the printers are merged. The Monitor status response includes the printing status, and therefore the print server  11  can detect the number of printed pages and completion of printing. In this case, because printing is performed only by the main printer, only the number of printed pages by the main printer is returned back to the print server  11 . The print server  11  manages the response information as the printing result in which the pieces of response information of all the printers are merged as a log. 
       FIG. 13  is a schematic diagram of a page information table T 1 . As shown in  FIG. 13 , page information, which is a part of the response information transmitted from the main printer in the Intranet B, is stored in the page information table T 1  formed in the RAM  43  of the print server  11 . The page information table T 1  includes a basic part a, the number of printers b, which is the total number of printers which have responded, and a detailed part c. The JOB ID and the number of printed pages by all the printers are stored in the basic part a as a log. The IP address of each printer, the JOB ID of each printer (full match), and the number of printed pages by each printer are stored in the detailed part c as a log. 
       FIG. 14  is a schematic diagram of a failure information table T 2 . As shown in  FIG. 14 , failure information, which is a part of the response information transmitted from the main printer in the Intranet B, is stored in the failure information table T 2  formed in the RAM  43  of the print server  11 . The failure information table T 2  includes a basic part d, the number of printers e, which is the total number of printers having a failure, and a detailed part f. The error code relating to the failure content and the JOB ID having the failure are stored in the basic part d as a log. The IP address of each printer having the failure, the error code of each printer having the failure, and the JOB ID of each printer (full match) having the failure are stored in the detailed part f as a log. 
     An alternative printing function when a print-disabled state (paper out, paper jam, toner out, or other failures) requiring an operator&#39;s operation occurs in the printer during the printing process is explained next. The alternative printing-function performs printing with a printer group formed by chaining plural printers via the LAN. The connection method of the printers is not limited to the chain type, and various connection methods such as a star type, a bus type, and a ring type can be also employed.  FIG. 15  is a sequence diagram of a printing process procedure when the print-disabled state occurs during the printing process. 
     (16) When a print-disabled state (for example, paper out) requiring the operator&#39;s operation occurs in the main printer, the print-disable-information transmitting unit  105  in the main printer transmits a “Release hold of paper ejection” command to the sub printer (the sub printer  1  in  FIG. 6 ). The main printer holds a paper ejection function and does not perform paper ejection thereafter. 
     The print-disabled state includes a case that a condition specified by the print server  11  at the time of printing does not match the function of the main printer. For example, the state includes a case such that the main printer is a monochrome printer, although the condition specified by the print server  11  at the time of printing is color print. Determination whether printing is possible is performed by comparing the condition specified by the print server  11  with the table relating to the printer information stored in each printer. 
     (17) The sub printer (the sub printer  1  in  FIG. 6 ) having received the “Release hold of paper ejection” command compares the condition specified by the print server  11  with the table relating to the printer information. When determining that printing is possible, the sub printer releases the hold of the paper ejection to start continuous printing. When determining that printing is not possible because the condition specified by the print server  11  does not match the function of the printer, and when there is a lower-level sub printer (the sub printer  2  in  FIG. 6 ), the sub printer transmits the “Release hold of paper ejection” command to the lower-level sub printer. 
     (18) The sub printer (the sub printer  1  in  FIG. 6 ) transmits a “Delete page” command to the main printer every time the paper is ejected. When there is a lower-level sub printer (the sub printer  2  in  FIG. 6 ), the sub printer transmits the “Delete page” command to the lower-level sub printer. Upon reception of the “Delete page” command, the main printer and the lower-level printer achieve synchronization of the number of printed pages and delete the printed page. 
     (19) Upon reception of the “Monitor status” command from the print server  11 , the main printer transmits the “Monitor status” command to the sub printer (the sub printer  1  in  FIG. 6 ). 
     (20) When there is a lower-level sub printer (the sub printer  2  in  FIG. 6 ), the sub printer (the sub printer  1  in  FIG. 6 ) transmits the “Monitor status” command received from the upper-level main printer to the lower-level sub printer (the sub printer  2  in  FIG. 6 ). When there is no lower-level sub printer, the sub printer transmits the “Monitor status response” command to the upper-level printer. The main printer waits for the response from the sub printer, and transmits the “Monitor status response” command to the print server  11 . Accordingly, the print server  11  receives the information of a printing result in which the pieces of information of all the printers are merged. The Monitor status response includes the printing status, and therefore the print server  11  can detect the number of printed pages and completion of printing. In this case, because printing is performed by the main printer and the sub printer  1 , the numbers of printed pages by the main printer and the sub printer  1  are merged and returned as a response. 
     In the present embodiment, as shown in  FIG. 16 , when a failure in the print-disabled state (for example, paper out) requiring the operator&#39;s operation occurs in the main printer, or when a condition specified by the print server  11  does not match the function of the printer and it is determined that printing is not possible, printing is continued by the sub printer  1  without informing the print server  11  of the failure. Further, when a failure of the print-disabled state (for example, paper out) requiring the operator&#39;s operation occurs in the sub printer, or when the condition specified by the print server  11  does not match the function of the sub printer  1  and it is determined that printing is not possible, because there are two sub printers  2 , printing is continued by the sub printer  2  without informing the print server  11  of the failure. 
     Because the main printer has a failure, the failure information is set as a part of the response information. However, because the sub printer  1  is in operation, the failure information as the printer is not set, and the failure information of the main printer is set as a breakdown. This is because the print destination is regarded as a printer “group” according to the alternative printing function. 
       FIG. 17  is one example of alternative printing.  FIG. 17  depicts a case of using  10  pieces of print data, in which after paper out occurs after five sheets are printed by the main printer, the printing process is shifted to the sub printer  1 , and the paper jam occurs after three sheets are printed by the sub printer  1 . Thereafter, the printing process is shifted to the sub printer  2 , and two sheets are printed by the sub printer  2 . As shown in  FIG. 17 , when a failure occurs, the failure information is added as a part of the response information. 
     On the other hand, the print server  11  having received the “Monitor status response” command from the main printer receives the response information of the printing result in which the pieces of information of all the printers are merged. The Monitor status response includes the printing status, and the print server  11  can detect the number of printed pages and completion of printing. In this case, because printing is performed by the main printer, the sub printer  1 , and the sub printer  2 , the total number of printed pages by the main printer, the sub printer  1 , and the sub printer  2  is returned to the print server  11  as a response. As shown in  FIGS. 13 and 14 , the print server  11  manages the response information of the printing result obtained by merging all pieces of response information of all the printers as a log. 
     Upon completion of the printing process in the network printing process, an apparatus releasing process as shown in  FIG. 6  is performed. 
     (5) Upon reception of a “Finish JOB” command from the print server  11 , the main printer performs a JOB finishing process and transmits the “Finish JOB” command to the sub printer (the sub printer  1  in  FIG. 6 ). 
     (6) The sub printer (the sub printer  1 ) in  FIG. 6  having received the “Finish JOB” command from the main printer performs the JOB finishing process. When there is a lower-level sub printer (the sub printer  2  in  FIG. 6 ), the sub printer (the sub printer  1  in  FIG. 6 ) transmits the “Finish JOB” command received from the upper-level main printer to the lower-level sub printer (the sub printer  2  in  FIG. 6 ). When there is no lower-level sub printer, the sub printer transmits a “Finish JOB response” command to the upper-level printer. The main printer waits for the response from the sub printer, and transmits the “Finish JOB response” command to the print server  11 . 
     (7) Upon reception of a “Disengage apparatus” command from the print server  11 , the main printer performs a disengaging process of the printer, and transmits the “Disengage apparatus” command to the sub printer (the sub printer  1  in  FIG. 6 ). 
     (8) The sub printer (the sub printer  1  in  FIG. 6 ) having received the “Disengage apparatus” command from the main printer performs the disengaging process of the printer. When there is a lower-level sub printer (the sub printer  2  in  FIG. 6 ), the sub printer (the sub printer  1  in  FIG. 6 ) transmits the “Disengage apparatus” command received from the upper-level main printer to the lower-level sub printer (the sub printer  2  in  FIG. 6 ). When there is no lower-level sub printer, the sub printer transmits an “Apparatus disengage response” command to the upper-level printer. The main printer waits for the response from the sub printer, and transmits the “Apparatus disengage response” command to the print server  11 . 
     The printing process of a printing result report is explained next. As shown in  FIG. 18 , the print server  11  generates an output data of the printing result report based on the printer information managed by the print server  11  as a log and the information of the printing result (see  FIGS. 13 and 14 ) in which the pieces of information of all the printers are merged, and transmits the output data to the main printer. A function of a report generating unit and a function of a report transmitting unit are executed here. 
     The printing result report is printed by the printer having performed the printing process lastly according to the printing process. 
       FIG. 19  is one example of the printing result report. The printer information (IP address), the start page, the last page, and the number of pages printed are printed for each printer in the printing result report shown in  FIG. 19 , together with the JOB ID, a document name, and the total number of printed pages. For the printer having a failure, the content thereof is also printed. Because both of a transmission side and a reception side confirm the printing result report, alternative printing can be confirmed, and due to an alternatively printed history of the printer, forgetting to pick up a printed sheet or picking up a wrong sheet can be prevented. 
     As described above, according to the present embodiment, even if a print-disabled state (paper out, paper jam, toner out, or other failures) requiring the operator&#39;s operation occurs in the printer in the printing operation, an alternative printer takes over the printing job continuously. Therefore, the printing is not held even if the failure occurs, and printing can be reliably performed, thereby enabling to increase printing reliability. Further, even if the printer does not match with the condition specified by the print server and it is determined that printing is not possible, an alternative printer matching with the condition specified by the print server takes over the printing job continuously, thereby enabling to perform printing reliably and increase the printing reliability. 
     The information of the lower-level printer and the information of the high-order printer are merged and returned to the upper-level printer (or a host apparatus), thereby enabling to check various pieces of information reliably by the host apparatus. For example, by merging the pieces of information including the printing status (output destination, the number of output pages, and the like) of respective printing apparatuses and responding to the upper-level printer (or the print server), the transmission side (the print server) can check the printing result by each printing apparatus reliably. 
     Because the report is printed based on the information including the printing status (the output destination, the number of output pages, and the like) of the respective printing apparatus obtained by the host apparatus, consolidated data can be printed as the printing result report. Accordingly, because both of the transmission side and the reception side confirm the printing result report, alternative printing can be confirmed, and due to an alternatively printed history of the printer, forgetting to pick up a printed sheet or picking up a wrong sheet can be prevented. 
     Because the printer group connected via the network includes plural printers having the same function, even if the printer is switched, the same printing result can be obtained. 
     With regard to the print server, suspension of printing due to a failure can be prevented by incorporating the alternative printing function on the printer. Accordingly, it is possible to reduce the number of development steps of recovery processing at the time of a failure in the printer. 
     With regard to the printer, by configuring the main printer and the sub printer with a common application, the printer can be provided at a reasonable price. 
     Although the invention has been described with respect to specific embodiments for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art that fairly fall within the basic teaching herein set forth.