Patent ID: 12204802

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

1. First Embodiment

<1.1 Configuration of Printing Device>

FIG.1is a schematic diagram showing an overall configuration of an inkjet printing device100according to a first embodiment of the present invention. As shown inFIG.1, the inkjet printing device100includes a printer body110and a control unit120. The printer body110includes a paper feeding unit80configured to hold a long belt-shaped printing medium consisting of continuous paper rotatably around a horizontal axis and supply the same, a printing mechanism70configured to print an image by ejecting ink such as, for example, aqueous ink on the printing medium supplied from the paper feeding unit80and to inspect the image after the printing medium is dried, and a winding unit90configured to wind up the outputted continuous paper on which printing is completed. The control unit120controls operation of the printer body110so that the image is printed on the printing medium on the basis of job data given from outside.

The printing mechanism70includes a first driving roller41configured to convey the printing medium supplied from the paper feeding unit80to an inside of the printing mechanism a plurality of conveying rollers (also simply referred to as “rollers”)43for conveying the printing medium inside the printing mechanism70, a printing unit10configured to perform printing by ejecting ink (e.g., aqueous ink) on the continuous paper, a drying unit20configured to dry the printing medium by applying hot air to the printed printing medium, an inspection unit30configured to inspect the printed image by collating the image printed on the printing medium with image data, and a second driving roller42for outputting the printing medium from the printing mechanism70. The first driving roller41and the second driving roller42are driven in conjunction with each other by a motor (not shown). By switching a rotation direction of the motor, regarding the printing medium, conveyance to an upstream side in a conveyance direction and conveyance to a downstream side in the conveyance direction are switched. The first driving roller41, the second driving roller42, and the conveying rollers43configure a conveyance unit40.

The printing mechanism70is provided with a reading unit50configured to read a position mark printed on a printing resumption page when printing is resumed after interruption. The reading unit50is disposed in the vicinity of the printing unit10and on the upstream side in the conveyance direction with respect to the printing unit10and on the downstream side in the conveyance direction with respect to a position of the position mark after the printing medium is rewound. A reason why the reading unit50is disposed on the downstream side in the conveyance direction with respect to the position of the position mark after the printing medium is rewound is that the position of the position mark printed on the printing started page can be surely recognized when the printing is resumed after the printing medium is rewound to the upstream side. After the printing resumption, when the position mark printed on the printing resumption page passes through the reading unit50, the reading unit50notifies the control unit120that the printing resumption page has passed. As a result, the control unit120can control the printing unit10so that the printing is resumed from the printing resumption page (page to be printed first after printing resumption).

In addition, a rotary encoder60is disposed on the further upstream side in the conveyance direction with respect to the printing unit10. The rotary encoder60can measure a moving distance of the printing medium by counting a number of rotations of the first driving roller41. Location of the rotary encoder60is not limited to the vicinity of an entrance of the printing mechanism70, and the rotary encoder60may be disposed in the vicinity of the second driving roller42.

Although the configuration of the inkjet printing device100that performs color printing is shown inFIG.1as the configuration of the printing device100, an inkjet printing device configured to perform monochrome printing or a printing device configured to perform printing by another printing method can also be adopted.

FIG.2is a plan view showing one configuration example of the printing unit10included in the printing device100shown inFIG.1. As shown inFIG.2, the printing unit10is configured of inkjet head arrays15K,15C,15M, and15Y for a K color (black), a C color (cyan color), an M color (magenta color), and a Y color (yellow color) arranged in line in the conveyance direction of the printing medium. Each of the inkjet head arrays is configured of a plurality of inkjet heads16arranged in zigzag. Each of the inkjet heads16includes a large number of nozzles configured to eject ink. Each of the nozzles of the inkjet heads16included in the inkjet head array15K for the K color ejects ink of the K color, each of the nozzles of the inkjet heads16included in the inkjet head array15C for the C color ejects ink of the C color, each of the nozzles of the inkjet heads16included in the inkjet head array15M for the M color ejects ink of the M color, and each of the nozzles of the inkjet heads16included in the inkjet head array15Y for the Y color ejects ink of the Y color.

In the above description, a case where printing is performed by ejecting aqueous ink is exemplified. However, the present invention is not limited thereto, and the present invention can also be applied to a case where an image is printed using UV ink (ultraviolet curing ink). Note that, in the case of using the UV ink, it is necessary to cure the UV ink by ultraviolet irradiation in order to fix the printed image on the printing medium. Since the present invention can be applied to the case of performing printing using either of the aqueous ink and the UV ink as described above, a term “fixing unit” may be used instead of the “drying unit”. In addition, while drying treatment is performed in the case where the aqueous ink is used, curing treatment is performed in the case where the UV ink is used, and thus a term “fixing treatment” may be used as a term including the drying treatment and the curing treatment.

The inspection unit30captures an image after drying by the drying unit20by an imaging element, and performs inspection by comparing the captured image with the image data sent from outside. However, the present invention is not limited thereto, and the configuration may be such that an image and a barcode representing the image are printed by the image the printing unit10and the inspection unit30performs inspection by reading the barcode and collating whether or not the image represented by the barcode matches the printed image. Since the barcode can be read even if the printed barcode is not dried, it is also possible that the barcode is read immediately after printing and the collation is performed using the barcode. In the case where the collation using the barcode is performed before the printed image is dried, a positional relationship between the drying unit20and the inspection unit30is opposite to the positional relationship shown inFIG.1.

<1.2 Hardware Configuration of Control Unit>

FIG.3is a block diagram showing a hardware configuration of the control unit120included in the printing device shown inFIG.1. As shown inFIG.3, the control unit120includes a body130, an auxiliary storage device121, an optical disk drive122, a display unit123, a keyboard124, a mouse125, and the like. The body130includes a CPU111, a memory112, a first disk interface unit113, a second disk interface unit114, a display control unit115, an input interface unit116, an output interface unit117, and a network interface unit118. The CPU111, the memory112, the first disk interface unit113, the second disk interface unit114, the display control unit115, the input interface unit116, the output interface unit117, and the network interface unit118are connected to one another via a system bus. The auxiliary storage device121is connected to the first disk interface unit113. The optical disk drive122is connected to the second disk interface unit114. The display unit (display device)123is connected to the display control unit115. The keyboard124and the mouse125are connected to the input interface unit116. The printer body110is connected to the output interface unit117via a communication cable. A communication line5is connected to the network interface unit118. The auxiliary storage device121is a magnetic disk device or the like. An optical disk6as a computer-readable recording medium such as a CD-ROM or a DVD-ROM is inserted into the optical disk drive122. The display unit123is a liquid crystal display or the like. The display unit123is used to display information desired by an operator. The keyboard124and the mouse125are used by a worker to input an instruction to this control unit120.

The auxiliary storage device121stores a printing control program (program for controlling execution of printing processing by the printer body110) P. The CPU111implements various functions of the control unit120by reading the printing control program P stored in the auxiliary storage device121into the memory112and executing the program. The memory112includes a RAM and a ROM. The memory112functions as a work area for the CPU111to execute the printing control program P stored in the auxiliary storage device121. The printing control program P is provided by being stored in the computer-readable recording medium (non-transitory recording medium). That is, for example, the user purchases the optical disk6as a recording medium of the printing control program P, inserts the optical disk6into the optical disk drive122, reads the printing control program P from the optical disk6, and installs the printing control program P in the auxiliary storage device121. Alternatively, the printing control program P transmitted via the communication line5may be received by the network interface unit118and installed in the auxiliary storage device121.

FIG.4is a block diagram showing a schematic functional configuration of the control unit120implemented by executing the printing control program P. As shown inFIG.4, the control unit120includes a printing control unit160configured to control operation of the printing unit10, a conveyance control unit170configured to control operation of the conveyance unit40, and a communication unit180for communicating a printing control status for the printing medium and a conveyance control status of the printing medium with a communication unit of a second printing device100bdescribed later, the communication being performed by using the communication line. While the control unit120further includes an inspection control unit configured to control operation of the inspection unit30and a drying control unit configured to control operation of the drying unit20, these are omitted inFIG.4.

The printing control unit160includes a printing interruption control unit161. When a printing interruption cause occurs, the printing interruption control unit161controls the printing unit10to interrupt printing operation after completing printing up to a printing-interruption-time last page, which is the last page among pages that are being printed on the printing medium, and further printing a position mark indicating a printing resumption position on a printing resumption page (page to be printed first after the printing resumption), which is the next page of the printing-interruption-time last page. Other operations of the printing unit10are directly controlled by the printing control unit160.

The conveyance control unit170includes a conveyance speed control unit171and a rewinding control unit172. When a printing interruption cause occurs, after the printing up to the printing-interruption-time last page is performed and printing operation of the printing unit10is interrupted, the conveyance speed control unit171controls the conveyance unit to start decelerating a conveyance speed of the printing medium, and further to stop the conveyance of the printing medium after the printing-interruption-time last page is conveyed to the drying unit20. Thereby, the pages printed in a period from the time of the occurrence of the printing interruption cause to the time of the printing interruption are dried.

The rewinding control unit172controls the conveyance unit40so that the printing medium is rewound until a distance from a position (printing resumption position) of the position mark printed on the printing resumption page to the printing unit10becomes equal to or longer than an acceleration distance required to obtain a conveyance speed that allows the printing resumption page to be printed, before the conveyance of the printing medium is resumed for printing resumption after printing operation is interrupted. Specifically, a rewinding distance of the printing medium is a total distance of a deceleration distance from start of deceleration of the printing medium to stop of the conveyance of the printing medium, a length of the printing unit10in the conveyance direction, and the acceleration distance required to accelerate the printing medium to a printable speed after printing resumption. The rewinding distance of the printing medium is measured by the rotary encoder60counting a number of rotations of the first driving roller41. Other operations of the conveyance unit40are directly controlled by the conveyance control unit170.

<1.3 Procedure from Printing Interruption to Resumption>

<1.3.1 Outline>

FIG.5is a flowchart showing a procedure of the printing device100shown inFIG.1from occurrence of a printing interruption cause to printing resumption. An outline of a procedure from the occurrence of the printing interruption cause to the resumption of printing will be described with reference to the flowchart shown inFIG.5.

In the printing device100, when an image is being printed on the printing medium, whether or not a printing interruption cause has occurred is monitored (step S100). When the printing interruption cause does not occur, whether or not a printing interruption cause occurs is further monitored while continuing printing. When a printing interruption cause occurs, processing proceeds to step S110, and the printing unit10completes printing of all the pages being printed.

After completion of printing of all the pages being printed at the time of occurrence of the printing interruption cause, the printing unit10prints the position mark on a page (printing resumption page) next to the printing-interruption-time last page, the position mark indicating that the page is the first page at the time of printing resumption (step S120). When the printing of the position mark is completed, the printing unit10stops printing operation (step S130). Next, the conveyance unit40starts to decelerate the conveyance speed, conveys all the pages for which printing is completed after the occurrence of the printing interruption cause to the drying unit20, and stops the conveyance of the printing medium after the completion of the drying of all the pages for which printing is completed after the occurrence of the printing interruption cause (step S140). The inspection by the inspection unit30is then stopped (step S150). Thereafter, the conveyance unit40rewinds the printing medium so that the printing resumption page is positioned at the printing resumption position on the upstream side (step S160).

In step S170, the printing device100stops the operation of the printing mechanism70and waits until there is a printing resumption instruction. When the printing resumption instruction is given, the conveyance unit40conveys the printing medium to the downstream side in the conveyance direction while accelerating the printing medium (step S180). As a result, the conveyance speed is accelerated to the printable speed before the printing resumption page reaches the printing unit10, and the printing unit10is enabled to normally perform printing in step S200described later.

Thereafter, the position mark printed on the printing resumption page of the printing medium is read by the reading unit50disposed in the vicinity of the printing unit10, and the printing unit10is notified that the printing resumption page has passed through the reading unit50(step S190). Then, the printing unit10receives the notification from the reading unit50and resumes printing from the printing resumption page (step S200).

<1.3.2 Details of Procedure>

FIG.6is a diagram showing changes in the printing medium in the printing device100shown inFIG.1from the time of the occurrence of the printing interruption cause to the time of printing resumption. With reference toFIG.6, a process from the time of the printing interruption to the time of printing resumption will be divided into four stages of a first stage to a fourth stage, and operation of the printing mechanism70and a printing state of the printing medium in each of the stages will be described.

RegardingFIG.6, a numeral attached to a top of each page represents a page number of each of the pages. In the printing unit10, the inkjet head arrays15K,15C,15M, and for the K color, the C color, the M color, and the Y color are disposed in this order from the upstream side in the conveyance direction toward the downstream side in the conveyance direction, and thus the printing of each of the pages is also performed in this order. The position mark is printed with the K color ink ejected from the inkjet head array for the K color. First, the position mark is printed, and then images of the K color, the C color, the M color, and the Y color are printed in this order. InFIG.6, a progress status of printing can be grasped by the printing mark for each of the colors drawn in each of the pages.

Regarding the first stage, the printing medium when the printing interruption cause occurs during printing is shown. In this example, in each of pages1to16, the position mark, and images of the K color, the C color, the M color, and the Y color are printed. That is, printing of the pages1to16is completed. As for the pages1to6, the drying by the drying unit20is completed, and the inspection by the inspection unit30is being performed. As for the page7, although the drying is completed, it has not yet been conveyed to the inspection unit30. As for the pages8to14, the drying by the drying unit20is being performed. As for the pages15and16, printing is completed, and it will be conveyed to the drying unit20.

Pages17to20are being printed in the printing unit10. Specifically, as for the page17, printing of the position mark and printing of the images of the three colors of K, C, and M are finished. As for the page18, printing of the position mark and printing of the images of the two colors of K and C are finished. As for the page19, printing of the position mark and printing of the image of K color are finished. As for the page20, only the position mark is printed.

Regarding the second stage, the printing medium on which printing to be executed before interrupting the printing when the printing interruption cause occurs is completed is shown. Since the printing interruption cause occurred during printing of the position mark on the page20, the images of the colors that have not yet been printed are sequentially printed for each of the pages17to20being printed. As a result, the images are printed on each of the pages up to the page20, which is the printing-interruption-time last page. Furthermore, after only the position mark is printed on a page21, which is the printing resumption page to be printed first at the time of printing resumption, the printing unit10stops printing operation. Next, deceleration of the conveyance speed of the printing medium is started, and each of the pages17to20, on which printing is completed, is conveyed into the drying unit20while decelerating.

In the example shown inFIG.6, the position marks are printed not only on the page21, which is the printing resumption page, but also on the pages1to20on which the images are printed. However, the present invention is not limited thereto, and the configuration may be such that no position mark is printed on the pages on which the images are printed and the position mark is printed only on the printing resumption page. Furthermore, regarding the case where the position mark is printed also on each of the pages on which the images are printed, the position mark to be printed on the page21, which is the printing resumption page, may be a mark having a shape different from that of the position mark printed on the other pages on which the images are printed.

Regarding the third stage, the printing medium in a rewound state to resume printing is shown. A position of the page21, which is the printing resumption page, is a position at which a distance to the inkjet head array15K for the K color on the most upstream side of the printing unit10is equal to or longer than a distance at which a speed that allows the printing resumption page to be printed by acceleration of the conveyance speed can be obtained, and is a position on the upstream side of the reading unit50.

Regarding the fourth stage, the printing medium when printing of the page21, which is the printing resumption page, is resumed is shown. The conveyance speed of the printing medium is accelerated to a printable state before the printing of the K color is started on the page21by the inkjet head array15K for the K color of the printing unit10. Upon reading the position mark printed on the page21, the reading unit50notifies the printing unit10that the page21has passed. As a result, printing is resumed when the page21reaches the position of the inkjet head array15K for the K color. Thereafter, similarly, by sequentially controlling the respective inkjet head arrays15C,15M, and15Y for the C color, the M color, and the Y color while conveying the printing medium to the downstream side in the conveyance direction, the images of these colors are sequentially printed, and printing of the page21is completed. Similarly, images of the four colors are printed on a page22and subsequent pages.

Note that the inspection performed before the printing interruption is continued until the conveyance unit40is stopped even after the printing is interrupted. Therefore, after the printing resumption, the inspection does not need to be performed again for the page for which the inspection has already been completed, and the inspection may be performed only for the page for which the inspection is not completed when the conveyance unit40is stopped. However, the inspection may be performed again for the page for which the inspection has already been completed.

With respect to the example shown inFIG.6, by performing printing as described above when the printing interruption cause occurs, a blank portion does not appear between the page on which the image is printed last after the occurrence of the printing interruption cause and the page21on which the image is printed first after the printing resumption. Therefore, the occurrence of damaged paper is prevented.

<1.4 Effect>

According to the present embodiment, when the printing interruption cause (a matter that should interrupt printing) occurs during printing of the image on the printing medium using the printing device100, the printing unit10completes printing of the page being printed when the printing interruption cause occurred, and the printing medium is rewound after the printing medium is dried. After the printing interruption cause is resolved, the printing medium is accelerated to a printable speed, and printing is resumed from the printing resumption page on which the position mark is printed. Therefore, a blank portion does not appear between the printing-interruption-time last page, which is the page printed last before the printing interruption, and the printing resumption page, which is the page to be printed first after printing resumption. This prevents the occurrence of damaged paper.

2. Second Embodiment

<2.1 Configuration of Printing System>

In the present embodiment, a printing system200in which two printing devices (a first printing device100aand a second printing device100b) are connected via a reversing unit150will be described. The two printing devices (the first printing device100aand the second printing device100b) configuring the printing system200both have the same configuration as the printing device100in the first embodiment. InFIGS.7and8described later, components of the first printing device100acorresponding to the components of the printing device100in the first embodiment are denoted by adding “a” to ends of the reference numerals, and components of the second printing device100bcorresponding to the components of the printing device100in the first embodiment are denoted by adding “b” to ends of the reference numerals. This printing system200, unlike the printing device100in the first embodiment, the paper feeding unit80is provided only in the first printing device100a, and the winding unit is provided only in the second printing device100b.

FIG.7is a schematic diagram showing an overall configuration of the printing system200according to the second embodiment of the present invention. As shown inFIG.7, in the printing system200according to the present embodiment, the first printing device100aconfigured to print an image on a front surface (a first surface) of a printing medium and the second printing device100bconfigured to print an image on a back surface (a second surface) of the printing medium are connected in series via the reversing unit150. Each of the first printing device100aand the second printing device100bis an inkjet printing device having the same configuration as the printing device100in the first embodiment. In the printing system200, first, the image is printed on the first surface that is the front surface of the printing medium by the first printing device100a, then the front surface and the back surface of the printing medium are reversed by the reversing unit150, and then the image is printed on the second surface that is the back surface of the printing medium by the second printing device100b.

The first printing device100aincludes a first control unit120a, and a first printing mechanism70aincluding a first printing unit10a, a first drying unit20a, and a first inspection unit30a. The second printing device100bincludes a second control unit120b, and a second printing mechanism including a second printing unit10b, a second drying unit and a second inspection unit30b.

FIG.8is a block diagram showing a part of the configurations of the first control unit120aand the second control unit120bincluded in the printing system200shown inFIG.7. The first control unit120aand the second control unit120bare configured to be communicable via the communication unit180so as to be able to indicate operation statuses and control statuses of the devices to each other. As a result, the first control unit120aand the second control unit120bcan cooperatively control the conveyance operation and the like of the printing medium between the first printing device100aand the second printing device100b. As shown inFIG.8, the first control unit120aincludes a first printing control unit160aconfigured to control the first printing unit10aand a first conveyance control unit170aconfigured to control the first conveyance unit40a. The first printing control unit160aincludes a first printing interruption control unit161a, and the first conveyance control unit170aincludes a first conveyance speed control unit171aand a first rewinding control unit172a. Similarly, the second control unit120bincludes a second printing control unit160band a second conveyance control unit170b. The second printing control unit160bincludes a second printing interruption control unit161b, and the second conveyance control unit170bincludes a second conveyance speed control unit171band a second rewinding control unit172b. Hereinafter, a function of each of the components will be described.

When a printing interruption cause occurs, the first printing interruption control unit161acontrols the first printing unit10ato interrupt printing operation after completing printing up to a first printing-interruption-time last page, which is a last page among pages that are being printed on the first surface of the printing medium, and further printing a first position mark indicating a printing resumption position on a first printing resumption page, which is a next page of the first printing-interruption-time last page. Similarly, the second printing interruption control unit161bcontrols the second printing unit10bto interrupt printing operation after completing printing up to a second printing-interruption-time last page and further printing a second position mark on a second printing resumption page. Thus, the first printing interruption control unit161aand the second printing interruption control unit161bindependently control the first printing unit10aand the second printing unit10b, respectively.

No buffer part is provided in the first conveyance unit and the second conveyance unit40bin the printing system200. Therefore, when conveying the printing medium in the printing system200, the first conveyance unit40aand the second conveyance unit40bneed to simultaneously convey the printing medium in a same direction at a same speed. Therefore, the first conveyance control unit170aand the second conveyance control unit170bneed to cooperatively control the first conveyance unit40aand the second conveyance unit40b, respectively, so that the printing medium is conveyed in the same direction at the same conveyance speed by the first conveyance unit40aand the second conveyance unit40b.

After the printing of the first position mark is completed, the first conveyance speed control unit171acontrols the first conveyance unit40ato start to decelerate the conveyance speed of the printing medium and to convey the first printing-interruption-time last page to the first drying unit20a. The second conveyance speed control unit171bsimilarly controls the second conveyance unit40b. In this regard, the first conveyance speed control unit171aand the second conveyance speed control unit171bcooperatively control the first conveyance unit40aand the second conveyance unit40b, respectively, until the first printing-interruption-time last page is conveyed to the first drying unit20aand the second printing-interruption-time last page is conveyed to the second drying unit20b.

The first rewinding control unit172aand the second rewinding control unit172bcooperatively control the first conveyance unit40aand the second conveyance unit40b, respectively, so that the printing medium is rewound after the drying of the first printing-interruption-time last page is completed in the first drying unit20aand the drying of the second printing-interruption-time last page is completed in the second drying unit20b. This allows the first conveyance unit40aand the second conveyance unit40bto cooperatively convey the printing medium. The first rewinding control unit172acontrols the first conveyance unit40aso that the printing medium is rewound until a distance from the printing resumption position of the first printing resumption page to the first printing unit10abecomes equal to or longer than an acceleration distance required to obtain the conveyance speed that allows the first printing resumption page to be printed when the printing is resumed, and the second rewinding control unit172bcontrols the second conveyance unit40bso that the printing medium is rewound until a distance from the printing resumption position of the second printing resumption page to the second printing unit10bbecomes equal to or longer than an acceleration distance required to obtain the conveyance speed that allows the second printing resumption page to be printed when printing is resumed.

Although not shown inFIG.8, the first control unit120aincludes a first inspection control unit configured to control the inspection by the first inspection unit30a, and the second control unit120bincludes a second inspection control unit configured to control the inspection by the second inspection unit30b. The first inspection control unit and the second inspection control unit control the first inspection unit30aand the second inspection unit30b, respectively, to inspect all the pages for which the inspection of the images printed on the printing medium is not completed, after the conveyance of the printing medium is resumed.

A first reading unit50aconfigured to read the first position mark is disposed in the vicinity of the first printing unit10aof the first printing device100a, and on an upstream side in a conveyance direction with respect to the first printing unit10aand on a downstream side in the conveyance direction with respect to a position of the first position mark after the printing medium is rewound. Similarly, a second reading unit50bconfigured to read the second position mark is disposed in the vicinity of the second printing unit10bof the second printing device100b, and on an upstream side in a conveyance direction with respect to the second printing unit10band on a downstream side in the conveyance direction with respect to a position of the second position mark after the printing medium is rewound. After the conveyance resumption of the printing medium, the first reading unit50areads the first position mark printed on the printing medium, and notifies the first printing unit10avia the first printing control unit160athat the first printing resumption page from which printing is to be resumed has passed. Similarly, the second reading unit50bnotifies the second printing unit10bvia the second printing control unit160bthat the second printing resumption page from which printing is to be resumed has passed.

In addition, the first printing device100aand the second printing device100binclude a first rotary encoder60aand a second rotary encoder60b, respectively. The first rotary encoder60afinds a conveyance distance of the printing medium by counting a number of rotations of the first driving roller41a. Similarly, the second rotary encoder60balso finds a conveyance distance of the printing medium. A total distance of a deceleration distance, a rewinding distance, and an acceleration distance required in each of the first printing device100aand the second printing device100bis found by each of the first rotary encoder60aand the second rotary encoder60b.

<2.2 Outline of Procedure from Printing Interruption to Resumption>

FIG.9is a flowchart showing a procedure of the first printing device100aand the second printing device100bfrom occurrence of a printing interruption cause to printing resumption. An outline of the procedure from the occurrence of the printing interruption cause to the printing resumption will be described with reference to the flowchart shown inFIG.9.

In the printing system200including the first printing device100aand the second printing device100b, when images are being printed on a printing medium, whether or not a printing interruption cause has occurred is monitored (step S300). When the printing interruption cause does not occur, whether or not a printing interruption cause occurs is further monitored while continuing printing. When a printing interruption cause occurs, processing proceeds to step S310, and each of the first printing unit10aand the second printing unit10bcompletes printing of all the pages being printed.

After completion of printing up to the first printing-interruption-time last page, the first position mark is printed on the first printing resumption page in the first printing device100a, and after completion of printing up to the second printing-interruption-time last page, the second position mark is printed on the second printing resumption page in the second printing device100b(S320). After completion of printing of the first position mark, the first printing unit10astops printing operation, and after completion of printing of the second position mark, the second printing unit10bstops printing operation (step S330). Next, the first conveyance unit40aand the second conveyance unit40bcooperatively start to decelerate the conveyance speed of the printing medium, performs conveyance of the first printing-interruption-time last page to the first drying unit20aand conveyance of the second printing-interruption-time last page to the second drying unit20b, respectively, and stop the conveyance of the printing medium after completion of drying (step S340). Then, the image inspection by the first inspection unit30aand the image inspection by the second inspection unit30bare stopped (step S350).

Thereafter, the first conveyance unit40aand the second conveyance unit40bcooperatively rewind the printing medium so that the printing resumption pages(the first printing resumption page and the second printing resumption page) are positioned at the printing resumption positions on the upstream side (step S360). In step S370, the first printing device100aand the second printing device100bstop the operation of the first printing mechanism70aand the second printing mechanism70b, respectively, and wait until there is a printing resumption instruction. When the printing resumption instruction is given, the first conveyance unit40aand the second conveyance unit40bcooperatively convey the printing medium to the downstream side in the conveyance direction while accelerating the printing medium (step S380). As a result, the conveyance speed is accelerated to the printable speed before the first printing resumption page reaches the first printing unit10aand the second printing resumption page reaches the second printing unit10b, and the first printing unit10aand the second printing unit10bare enabled to normally perform printing in step S400described later.

Thereafter, the first position mark printed on a front surface side is read by the first reading unit50a, the first printing unit10ais notified that the first printing resumption page has passed through the first reading unit50a, the second position mark printed on a back surface side is read by the second reading unit50breads, and the second printing unit10bis notified that the second printing resumption page has passed through the second reading unit50b(step S390). Then, the first printing unit10aand the second printing unit10bresume printing from the first printing resumption page and the second printing resumption page, respectively (step S400).

<2.3 Effect>

According to the present embodiment, in the case where printing is performed on the front surface and the back surface of the printing medium by connecting the first printing device100aand the second printing device100b, for neither of the front surface nor the back surface of the printing medium, a blank portion appears between the page printed last before printing interruption and the page printed first after printing resumption. This prevents the occurrence of damaged paper.

3. Others

While the present invention has been described in detail above, the above description is illustrative in all aspects and is not restrictive. It is understood that numerous other modifications and variations can be devised without departing from the scope of the invention.