Patent Description:
If a printing interruption cause (a matter that should interrupt printing) occurs while printing is performed on a printing medium by using a printing device, the printing is interrupted, and the printing is resumed after the printing interruption cause is eliminated. However, there may be a blank portion between a page printed last before the printing is interrupted and a page printed first after the printing is resumed. For example, <CIT> discloses that, in order to overcome a problem that a printing position on the front surface and a printing position on the back surface deviate from each other because the printing medium expands and contracts when back surface printing is performed after printing on a front surface of a printing medium is performed and then the printing medium is dried, printing is performed in consideration of expansion and contraction of the printing medium in a width direction occurring during drying after the front surface printing. In addition, <CIT> describes that in a case where a thick portion is formed on a long belt-shaped printing medium at a predetermined cycle, printing is stopped before the thick portion reaches a printing region, and a relative position between a printing head and a recording region is switched to a retraction position, and the relative position between the printing head and the recording region is switched to the printing position after the thick portion passes through the printing region, by which a periodic shift of the printing position before and after the interruption of a printing process can be suppressed.

However, the printing method described in <CIT> is a method of correcting a positional shift between an image printed on the front surface of the printing medium and an image printed on the back surface of the printing medium. Therefore, in a case where after the printing resumption, the printing is performed on the same surface as the surface on which the printing has been performed before the interruption, a blank portion appears between the page printed before the interruption and the page printed after the interruption. In addition, the printing method described in <CIT> can be applied to the case where the printing medium has a thick portion periodically. However, even if the printing method is applied in a case where continuous paper without a thick portion is used and printing is resumed after printing interruption, it is not possible to prevent the blank portion from appearing between the page printed before interruption and the page printed after interruption.

A further prior art document is <CIT>. According to this prior art document, a recording device continuously records a recording mark in a blank area between the image of one page and the image of the next page. In case an error occurrence is detected, sheet conveyance is immediately stopped, the printing operation is interrupted and an invalid section end mark is recorded immediately after the printed image. After the error has been resolved, a restart page is identified and an invalid section start mark is printed. Further prior art documents are <CIT> and <CIT>.

In view of the above circumstances, an object of the present invention is to provide a printing device and a printing system capable of resuming printing so that a blank portion does not appear between a page printed before interruption and a page printed after interruption when printing is interrupted due to occurrence of a printing interruption cause. This object is achieved by the subject-matters of the independent claims. Further advantageous embodiments of the invention are the subject-matters of the dependent claims.

One aspect of the present invention is directed to a printing device (<NUM>) configured to print an image over a plurality of pages on a first surface of a printing medium having a long belt shape, the printing device comprising:.

According to the above-described configuration, when a printing interruption cause (a matter that should interrupt printing) occurs while an image is being printed on the printing medium, the printing unit completes printing of all the pages being printed, and further, stops printing operation after printing only the position mark indicating the page to be printed first when the printing is resumed. Thereafter, the conveyance control unit controls the conveyance unit to decelerate and stop the printing medium. Therefore, the printing is resumed from the page with the position mark printed, and no blank portion appear between the page printed last before printing interruption and the page printed first after printing resumption. As a result, the occurrence of damaged paper is prevented.

Another aspect of the present invention is directed to a printing system (<NUM>) comprising: a first printing device (100a) configured to print a first image on a first surface of a printing medium including the first surface and a second surface that is a back surface of the first surface; a second printing device (100b) configured to print a second image on the second surface; and a reversing unit (<NUM>) provided between the first printing device (100a) and the second printing device (100b) and configured to reverse the first surface and the second surface,.

According to the above-described configuration, when a printing interruption cause (a matter that should interrupt printing) occurs while an image is being printed on the printing medium, the first printing unit and the second printing unit complete printing of all the pages being printed, and further, stop printing operation after printing only the position marks (the first position mark and the second position mark) indicating the pages to be printed first when the printing is resumed. Thereafter, the first conveyance control unit and the second conveyance control unit respectively control the first conveyance unit and the second conveyance unit to decelerate and stop the printing medium. Thereby, the printing is resumed from the pages on which the position marks (the first position mark and the second position mark) are printed, and no blank portion appear between the pages printed last before printing interruption and the pages printed first after printing resumption. As a result, the occurrence of damaged paper is prevented.

These and other objects, features, modes, and advantageous effects of the present invention will become more apparent from the following detailed description of the present invention with reference to the accompanying drawings.

<FIG> is a schematic diagram showing an overall configuration of an inkjet printing device <NUM> according to a first embodiment of the present invention. As shown in <FIG>, the inkjet printing device <NUM> includes a printer body <NUM> and a control unit <NUM>. The printer body <NUM> includes a paper feeding unit <NUM> configured to hold a long belt-shaped printing medium consisting of continuous paper rotatably around a horizontal axis and supply the same, a printing mechanism <NUM> configured to print an image by ejecting ink such as, for example, aqueous ink on the printing medium supplied from the paper feeding unit <NUM> and to inspect the image after the printing medium is dried, and a winding unit <NUM> configured to wind up the outputted continuous paper on which printing is completed. The control unit <NUM> controls operation of the printer body <NUM> so that the image is printed on the printing medium on the basis of job data given from outside.

The printing mechanism <NUM> includes a first driving roller <NUM> configured to convey the printing medium supplied from the paper feeding unit <NUM> to an inside of the printing mechanism <NUM>, a plurality of conveying rollers (also simply referred to as "rollers") <NUM> for conveying the printing medium inside the printing mechanism <NUM>, a printing unit <NUM> configured to perform printing by ejecting ink (e.g., aqueous ink) on the continuous paper, a drying unit <NUM> configured to dry the printing medium by applying hot air to the printed printing medium, an inspection unit <NUM> configured to inspect the printed image by collating the image printed on the printing medium with image data, and a second driving roller <NUM> for outputting the printing medium from the printing mechanism <NUM>. The first driving roller <NUM> and the second driving roller <NUM> are 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 roller <NUM>, the second driving roller <NUM>, and the conveying rollers <NUM> configure a conveyance unit <NUM>.

The printing mechanism <NUM> is provided with a reading unit <NUM> configured to read a position mark printed on a printing resumption page when printing is resumed after interruption. The reading unit <NUM> is disposed in the vicinity of the printing unit <NUM> and on the upstream side in the conveyance direction with respect to the printing unit <NUM> and 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 unit <NUM> is 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 unit <NUM>, the reading unit <NUM> notifies the control unit <NUM> that the printing resumption page has passed. As a result, the control unit <NUM> can control the printing unit <NUM> so that the printing is resumed from the printing resumption page (page to be printed first after printing resumption).

In addition, a rotary encoder <NUM> is disposed on the further upstream side in the conveyance direction with respect to the printing unit <NUM>. The rotary encoder <NUM> can measure a moving distance of the printing medium by counting a number of rotations of the first driving roller <NUM>. Location of the rotary encoder <NUM> is not limited to the vicinity of an entrance of the printing mechanism <NUM>, and the rotary encoder <NUM> may be disposed in the vicinity of the second driving roller <NUM>.

Although the configuration of the inkjet printing device <NUM> that performs color printing is shown in <FIG> as the configuration of the printing device <NUM>, 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> is a plan view showing one configuration example of the printing unit <NUM> included in the printing device <NUM> shown in <FIG>. As shown in <FIG>, the printing unit <NUM> is configured of inkjet head arrays <NUM>, 15C, <NUM>, and 15Y 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 heads <NUM> arranged in zigzag. Each of the inkjet heads <NUM> includes a large number of nozzles configured to eject ink. Each of the nozzles of the inkjet heads <NUM> included in the inkjet head array <NUM> for the K color ejects ink of the K color, each of the nozzles of the inkjet heads <NUM> included in the inkjet head array 15C for the C color ejects ink of the C color, each of the nozzles of the inkjet heads <NUM> included in the inkjet head array <NUM> for the M color ejects ink of the M color, and each of the nozzles of the inkjet heads <NUM> included in the inkjet head array 15Y 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 unit <NUM> captures an image after drying by the drying unit <NUM> by 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 unit <NUM> and the inspection unit <NUM> performs 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 unit <NUM> and the inspection unit <NUM> is opposite to the positional relationship shown in <FIG>.

<FIG> is a block diagram showing a hardware configuration of the control unit <NUM> included in the printing device shown in <FIG>. As shown in <FIG>, the control unit <NUM> includes a body <NUM>, an auxiliary storage device <NUM>, an optical disk drive <NUM>, a display unit <NUM>, a keyboard <NUM>, a mouse <NUM>, and the like. The body <NUM> includes a CPU <NUM>, a memory <NUM>, a first disk interface unit <NUM>, a second disk interface unit <NUM>, a display control unit <NUM>, an input interface unit <NUM>, an output interface unit <NUM>, and a network interface unit <NUM>. The CPU <NUM>, the memory <NUM>, the first disk interface unit <NUM>, the second disk interface unit <NUM>, the display control unit <NUM>, the input interface unit <NUM>, the output interface unit <NUM>, and the network interface unit <NUM> are connected to one another via a system bus. The auxiliary storage device <NUM> is connected to the first disk interface unit <NUM>. The optical disk drive <NUM> is connected to the second disk interface unit <NUM>. The display unit (display device) <NUM> is connected to the display control unit <NUM>. The keyboard <NUM> and the mouse <NUM> are connected to the input interface unit <NUM>. The printer body <NUM> is connected to the output interface unit <NUM> via a communication cable. A communication line <NUM> is connected to the network interface unit <NUM>. The auxiliary storage device <NUM> is a magnetic disk device or the like. An optical disk <NUM> as a computer-readable recording medium such as a CD-ROM or a DVD-ROM is inserted into the optical disk drive <NUM>. The display unit <NUM> is a liquid crystal display or the like. The display unit <NUM> is used to display information desired by an operator. The keyboard <NUM> and the mouse <NUM> are used by a worker to input an instruction to this control unit <NUM>.

The auxiliary storage device <NUM> stores a printing control program (program for controlling execution of printing processing by the printer body <NUM>) P. The CPU <NUM> implements various functions of the control unit <NUM> by reading the printing control program P stored in the auxiliary storage device <NUM> into the memory <NUM> and executing the program. The memory <NUM> includes a RAM and a ROM. The memory <NUM> functions as a work area for the CPU <NUM> to execute the printing control program P stored in the auxiliary storage device <NUM>. 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 disk <NUM> as a recording medium of the printing control program P, inserts the optical disk <NUM> into the optical disk drive <NUM>, reads the printing control program P from the optical disk <NUM>, and installs the printing control program P in the auxiliary storage device <NUM>. Alternatively, the printing control program P transmitted via the communication line <NUM> may be received by the network interface unit <NUM> and installed in the auxiliary storage device <NUM>.

<FIG> is a block diagram showing a schematic functional configuration of the control unit <NUM> implemented by executing the printing control program P. As shown in <FIG>, the control unit <NUM> includes a printing control unit <NUM> configured to control operation of the printing unit <NUM>, a conveyance control unit <NUM> configured to control operation of the conveyance unit <NUM>, and a communication unit <NUM> for 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 device 100b described later, the communication being performed by using the communication line. While the control unit <NUM> further includes an inspection control unit configured to control operation of the inspection unit <NUM> and a drying control unit configured to control operation of the drying unit <NUM>, these are omitted in <FIG>.

The printing control unit <NUM> includes a printing interruption control unit <NUM>. When a printing interruption cause occurs, the printing interruption control unit <NUM> controls the printing unit <NUM> to 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 unit <NUM> are directly controlled by the printing control unit <NUM>.

The conveyance control unit <NUM> includes a conveyance speed control unit <NUM> and a rewinding control unit <NUM>. 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 unit <NUM> is interrupted, the conveyance speed control unit <NUM> controls the conveyance unit <NUM> 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 unit <NUM>. 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 unit <NUM> controls the conveyance unit <NUM> so 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 unit <NUM> becomes 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 unit <NUM> in 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 encoder <NUM> counting a number of rotations of the first driving roller <NUM>. Other operations of the conveyance unit <NUM> are directly controlled by the conveyance control unit <NUM>.

<FIG> is a flowchart showing a procedure of the printing device <NUM> shown in <FIG> from 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 in <FIG>.

In the printing device <NUM>, 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 unit <NUM> completes 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 unit <NUM> prints 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 unit <NUM> stops printing operation (step S130). Next, the conveyance unit <NUM> starts 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 unit <NUM>, 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 unit <NUM> is then stopped (step S150). Thereafter, the conveyance unit <NUM> rewinds 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 device <NUM> stops the operation of the printing mechanism <NUM> and waits until there is a printing resumption instruction. When the printing resumption instruction is given, the conveyance unit <NUM> conveys 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 unit <NUM>, and the printing unit <NUM> is enabled to normally perform printing in step S200 described later.

Thereafter, the position mark printed on the printing resumption page of the printing medium is read by the reading unit <NUM> disposed in the vicinity of the printing unit <NUM>, and the printing unit <NUM> is notified that the printing resumption page has passed through the reading unit <NUM> (step S190). Then, the printing unit <NUM> receives the notification from the reading unit <NUM> and resumes printing from the printing resumption page (step S200).

<FIG> is a diagram showing changes in the printing medium in the printing device <NUM> shown in <FIG> from the time of the occurrence of the printing interruption cause to the time of printing resumption. With reference to <FIG>, 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 mechanism <NUM> and a printing state of the printing medium in each of the stages will be described.

Regarding <FIG>, a numeral attached to a top of each page represents a page number of each of the pages. In the printing unit <NUM>, the inkjet head arrays <NUM>, 15C, <NUM>, and 15Y 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 <NUM> 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. In <FIG>, 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 pages <NUM> to <NUM>, 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 pages <NUM> to <NUM> is completed. As for the pages <NUM> to <NUM>, the drying by the drying unit <NUM> is completed, and the inspection by the inspection unit <NUM> is being performed. As for the page <NUM>, although the drying is completed, it has not yet been conveyed to the inspection unit <NUM>. As for the pages <NUM> to <NUM>, the drying by the drying unit <NUM> is being performed. As for the pages <NUM> and <NUM>, printing is completed, and it will be conveyed to the drying unit <NUM>.

Pages <NUM> to <NUM> are being printed in the printing unit <NUM>. Specifically, as for the page <NUM>, printing of the position mark and printing of the images of the three colors of K, C, and M are finished. As for the page <NUM>, printing of the position mark and printing of the images of the two colors of K and C are finished. As for the page <NUM>, printing of the position mark and printing of the image of K color are finished. As for the page <NUM>, 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 page <NUM>, the images of the colors that have not yet been printed are sequentially printed for each of the pages <NUM> to <NUM> being printed. As a result, the images are printed on each of the pages up to the page <NUM>, which is the printing-interruption-time last page. Furthermore, after only the position mark is printed on a page <NUM>, which is the printing resumption page to be printed first at the time of printing resumption, the printing unit <NUM> stops printing operation. Next, deceleration of the conveyance speed of the printing medium is started, and each of the pages <NUM> to <NUM>, on which printing is completed, is conveyed into the drying unit <NUM> while decelerating.

In the example shown in <FIG>, the position marks are printed not only on the page <NUM>, which is the printing resumption page, but also on the pages <NUM> to <NUM> on 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 page <NUM>, 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 page <NUM>, which is the printing resumption page, is a position at which a distance to the inkjet head array <NUM> for the K color on the most upstream side of the printing unit <NUM> is 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 unit <NUM>.

Regarding the fourth stage, the printing medium when printing of the page <NUM>, 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 page <NUM> by the inkjet head array <NUM> for the K color of the printing unit <NUM>. Upon reading the position mark printed on the page <NUM>, the reading unit <NUM> notifies the printing unit <NUM> that the page <NUM> has passed. As a result, printing is resumed when the page <NUM> reaches the position of the inkjet head array <NUM> for the K color. Thereafter, similarly, by sequentially controlling the respective inkjet head arrays 15C, <NUM>, and 15Y 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 page <NUM> is completed. Similarly, images of the four colors are printed on a page <NUM> and subsequent pages.

Note that the inspection performed before the printing interruption is continued until the conveyance unit <NUM> is 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 unit <NUM> is 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 in <FIG>, by performing printing as described above when the printing interruption cause occurs, a blank portion does not appear between the page <NUM> on which the image is printed last after the occurrence of the printing interruption cause and the page <NUM> on which the image is printed first after the printing resumption. Therefore, the occurrence of damaged paper is prevented.

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 device <NUM>, the printing unit <NUM> completes 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.

In the present embodiment, a printing system <NUM> in which two printing devices (a first printing device 100a and a second printing device 100b) are connected via a reversing unit <NUM> will be described. The two printing devices (the first printing device 100a and the second printing device 100b) configuring the printing system <NUM> both have the same configuration as the printing device <NUM> in the first embodiment. In <FIG> and <FIG> described later, components of the first printing device 100a corresponding to the components of the printing device <NUM> in the first embodiment are denoted by adding "a" to ends of the reference numerals, and components of the second printing device 100b corresponding to the components of the printing device <NUM> in the first embodiment are denoted by adding "b" to ends of the reference numerals. This printing system <NUM>, unlike the printing device <NUM> in the first embodiment, the paper feeding unit <NUM> is provided only in the first printing device 100a, and the winding unit <NUM> is provided only in the second printing device 100b.

<FIG> is a schematic diagram showing an overall configuration of the printing system <NUM> according to the second embodiment of the present invention. As shown in <FIG>, in the printing system <NUM> according to the present embodiment, the first printing device 100a configured to print an image on a front surface (a first surface) of a printing medium and the second printing device 100b configured to print an image on a back surface (a second surface) of the printing medium are connected in series via the reversing unit <NUM>. Each of the first printing device 100a and the second printing device 100b is an inkjet printing device having the same configuration as the printing device <NUM> in the first embodiment. In the printing system <NUM>, first, the image is printed on the first surface that is the front surface of the printing medium by the first printing device 100a, then the front surface and the back surface of the printing medium are reversed by the reversing unit <NUM>, and then the image is printed on the second surface that is the back surface of the printing medium by the second printing device 100b.

The first printing device 100a includes a first control unit 120a, and a first printing mechanism 70a including a first printing unit 10a, a first drying unit 20a, and a first inspection unit 30a. The second printing device 100b includes a second control unit 120b, and a second printing mechanism 70b including a second printing unit 10b, a second drying unit 20b, and a second inspection unit 30b.

<FIG> is a block diagram showing a part of the configurations of the first control unit 120a and the second control unit 120b included in the printing system <NUM> shown in <FIG>. The first control unit 120a and the second control unit 120b are configured to be communicable via the communication unit <NUM> so as to be able to indicate operation statuses and control statuses of the devices to each other. As a result, the first control unit 120a and the second control unit 120b can cooperatively control the conveyance operation and the like of the printing medium between the first printing device 100a and the second printing device 100b. As shown in <FIG>, the first control unit 120a includes a first printing control unit 160a configured to control the first printing unit 10a and a first conveyance control unit 170a configured to control the first conveyance unit 40a. The first printing control unit 160a includes a first printing interruption control unit 161a, and the first conveyance control unit 170a includes a first conveyance speed control unit 171a and a first rewinding control unit 172a. Similarly, the second control unit 120b includes a second printing control unit 160b and a second conveyance control unit 170b. The second printing control unit 160b includes a second printing interruption control unit 161b, and the second conveyance control unit 170b includes a second conveyance speed control unit 171b and a second rewinding control unit 172b. Hereinafter, a function of each of the components will be described.

When a printing interruption cause occurs, the first printing interruption control unit 161a controls the first printing unit 10a to 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 unit 161b controls the second printing unit 10b to 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 unit 161a and the second printing interruption control unit 161b independently control the first printing unit 10a and the second printing unit 10b, respectively.

No buffer part is provided in the first conveyance unit 40a and the second conveyance unit 40b in the printing system <NUM>. Therefore, when conveying the printing medium in the printing system <NUM>, the first conveyance unit 40a and the second conveyance unit 40b need to simultaneously convey the printing medium in a same direction at a same speed. Therefore, the first conveyance control unit 170a and the second conveyance control unit 170b need to cooperatively control the first conveyance unit 40a and the second conveyance unit 40b, respectively, so that the printing medium is conveyed in the same direction at the same conveyance speed by the first conveyance unit 40a and the second conveyance unit 40b.

After the printing of the first position mark is completed, the first conveyance speed control unit 171a controls the first conveyance unit 40a to start to decelerate the conveyance speed of the printing medium and to convey the first printing-interruption-time last page to the first drying unit 20a. The second conveyance speed control unit 171b similarly controls the second conveyance unit 40b. In this regard, the first conveyance speed control unit 171a and the second conveyance speed control unit 171b cooperatively control the first conveyance unit 40a and the second conveyance unit 40b, respectively, until the first printing-interruption-time last page is conveyed to the first drying unit 20a and the second printing-interruption-time last page is conveyed to the second drying unit 20b.

The first rewinding control unit 172a and the second rewinding control unit 172b cooperatively control the first conveyance unit 40a and the second conveyance unit 40b, 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 unit 20a and the drying of the second printing-interruption-time last page is completed in the second drying unit 20b. This allows the first conveyance unit 40a and the second conveyance unit 40b to cooperatively convey the printing medium. The first rewinding control unit 172a controls the first conveyance unit 40a so that the printing medium is rewound until a distance from the printing resumption position of the first printing resumption page to the first printing unit 10a becomes 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 unit 172b controls the second conveyance unit 40b so that the printing medium is rewound until a distance from the printing resumption position of the second printing resumption page to the second printing unit 10b becomes 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 in <FIG>, the first control unit 120a includes a first inspection control unit configured to control the inspection by the first inspection unit 30a, and the second control unit 120b includes a second inspection control unit configured to control the inspection by the second inspection unit 30b. The first inspection control unit and the second inspection control unit control the first inspection unit 30a and the second inspection unit 30b, 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 unit 50a configured to read the first position mark is disposed in the vicinity of the first printing unit 10a of the first printing device 100a, and on an upstream side in a conveyance direction with respect to the first printing unit 10a and 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 unit 50b configured to read the second position mark is disposed in the vicinity of the second printing unit 10b of the second printing device 100b, and on an upstream side in a conveyance direction with respect to the second printing unit 10b and 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 unit 50a reads the first position mark printed on the printing medium, and notifies the first printing unit 10a via the first printing control unit 160a that the first printing resumption page from which printing is to be resumed has passed. Similarly, the second reading unit 50b notifies the second printing unit 10b via the second printing control unit 160b that the second printing resumption page from which printing is to be resumed has passed.

In addition, the first printing device 100a and the second printing device 100b include a first rotary encoder 60a and a second rotary encoder 60b, respectively. The first rotary encoder 60a finds a conveyance distance of the printing medium by counting a number of rotations of the first driving roller 41a. Similarly, the second rotary encoder 60b also 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 device 100a and the second printing device 100b is found by each of the first rotary encoder 60a and the second rotary encoder 60b.

<FIG> is a flowchart showing a procedure of the first printing device 100a and the second printing device 100b from 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 in <FIG>.

In the printing system <NUM> including the first printing device 100a and the second printing device 100b, 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 unit 10a and the second printing unit 10b completes 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 device 100a, 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 device 100b (S320). After completion of printing of the first position mark, the first printing unit 10a stops printing operation, and after completion of printing of the second position mark, the second printing unit 10b stops printing operation (step S330). Next, the first conveyance unit 40a and the second conveyance unit 40b cooperatively start to decelerate the conveyance speed of the printing medium, performs conveyance of the first printing-interruption-time last page to the first drying unit 20a and conveyance of the second printing-interruption-time last page to the second drying unit 20b, respectively, and stop the conveyance of the printing medium after completion of drying (step S340). Then, the image inspection by the first inspection unit 30a and the image inspection by the second inspection unit 30b are stopped (step S350).

Thereafter, the first conveyance unit 40a and the second conveyance unit 40b cooperatively 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 device 100a and the second printing device 100b stop the operation of the first printing mechanism 70a and the second printing mechanism 70b, respectively, and wait until there is a printing resumption instruction. When the printing resumption instruction is given, the first conveyance unit 40a and the second conveyance unit 40b cooperatively 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 unit 10a and the second printing resumption page reaches the second printing unit 10b, and the first printing unit 10a and the second printing unit 10b are enabled to normally perform printing in step S400 described later.

Thereafter, the first position mark printed on a front surface side is read by the first reading unit 50a, the first printing unit 10a is notified that the first printing resumption page has passed through the first reading unit 50a, the second position mark printed on a back surface side is read by the second reading unit 50b reads, and the second printing unit 10b is notified that the second printing resumption page has passed through the second reading unit 50b (step S390). Then, the first printing unit 10a and the second printing unit 10b resume printing from the first printing resumption page and the second printing resumption page, respectively (step S400).

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 device 100a and the second printing device 100b, 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.

Claim 1:
A printing device (<NUM>) configured to print an image over a plurality of pages on a first surface of a printing medium having a long belt shape, the printing device comprising:
a conveyance unit (<NUM>) configured to convey the printing medium;
a printing unit (<NUM>) configured to print an image by ejecting ink on the first surface of the printing medium conveyed by the conveyance unit (<NUM>); and
a control unit (<NUM>),
wherein the control unit (<NUM>) includes:
a printing control unit (<NUM>) configured to control operation of the printing unit (<NUM>); and
a conveyance control unit (<NUM>) configured to control operation of the conveyance unit (<NUM>),
the printing control unit (<NUM>) includes a printing interruption control unit (<NUM>),
characterized in that the control unit is configured to control, when a printing interruption cause occurs, the printing unit (<NUM>) to interrupt printing operation after completing printing of a printing-interruption-time last page being printed on the first surface of the printing medium, and further printing a position mark indicating a printing resumption position on a printing resumption page that is a next page of the printing-interruption-time last page, and
the conveyance control unit (<NUM>) includes a conveyance speed control unit (<NUM>) configured to control, after interruption of printing operation, the conveyance unit (<NUM>) to start deceleration of a conveyance speed of the printing medium and stop a conveyance of the printing medium.