NL2034907B1

NL2034907B1 - Inkjet printing system having external drying device

Info

Publication number: NL2034907B1
Application number: NL2034907A
Authority: NL
Inventors: Tang Zhenhua
Original assignee: Guangzhou Kingtau Machinery&Electronics Equipment Co Ltd
Priority date: 2022-08-02
Filing date: 2023-05-24
Publication date: 2023-11-21
Also published as: NL2034907A; WO2024027091A1; DE202023102224U1; BE1030192B1; CN115384187A; BE1030192A1; CN115384187B

Abstract

The present disclosure relates to the ﬁeld of inkjet printing, and discloses an inkjet printing system having an external drying device. The system includes an unwinding device, a roller printing device, a ﬁrst drying device, and a winding device. A printing medium is unfolded by the unwinding device, and is subjected to inkjet printing by the roller printing device, the printing medium printed then is dried by the ﬁrst drying device, and is wound by 10 the winding device finally. The printing medium enters and exits from the same side of the roller printing device, and the ﬁrst drying device is extemally arranged on the same side that the printing medium enters and exits from the roller printing device.

Description

INKJET PRINTING SYSTEM HAVING EXTERNAL DRYING DEVICE

FIELD OF TECHNOLOGY

[0001] The present disclosure relates to the field of inkjet printing, in particular to an inkjet printing system having an external drying device.

BACKGROUND

[0002] Inkjet printing is a kind of printing without contact, pressure, and printing plates.

The principle of inkjet printing is as follows: firstly, picture and text information to be processed is input into an electronic computer and is edited by an electronic color separation system, and then the stored picture and text information is input into an inkjet printer; under the control of the electronic computer, nozzles of inkjet printheads jet tiny and atomized ink drops to the surface of a printing medium, and the ink drops directly form pictures on the surface of the printing medium under the charge effect, thereby realizing picture and text printing. Printers generally include flat-plate type printers and roller type printers according to driving mechanisms for the printing media. The roller type printers are gradually applied to large-batch commercial printing due to many advantages, such as high printing speed and good color registration.

[0003] The roller type printer typically includes a roller, a linear movement platform, and an inkjet printhead assembly. The roller is located below the linear movement platform and the inkjet printhead assembly, and the surface of the roller is configured to wind and deliver the printing medium. The linear movement platform drives the corresponding inkjet printhead assembly to adjust the distance between the inkjet printhead assembly and the printing medium. The inkjet printhead assembly usually includes an inkjet printhead array composed of a plurality of inkjet printheads and an inkjet printhead carrier for mounting the inkjet printhead array. When the printing medium passes below the inkjet printhead assembly, the fixed inkjet printhead assembly jet ink continuously to complete picture and text printing.

[0004] Generally, the ink used in inkjet printing includes oily ink, water-based ink, and UV ink. The oily ink uses non-water-soluble solvents as dissolution color bases, while the water- based ink uses water and water-soluble solvents as dissolution color bases. The oily ink and the water-based ink are both solvent inks, such ink attaches pigments or dyes to the printing media through solvent penetration and evaporation on the printing media during printing.

With regard to the UV ink, under ultraviolet radiation, the ink drops form films and are dried by means of UV light having different wavelengths and different energy. For the solvent ink, particularly the water-based ink, after picture and text printing is completed on the printing media, the ink can only be sufficiently attached to the surface of the printing media with long-time drying. However, in the prior art, only small drying device can be generally internally provided in the roller type printers using the water-based ink due to the structure limitations thereof, so that the drying process of the water-based ink can be accelerated by means of the drying devices to match with the printing speed of the roller type printers.

Usually, the operation speed of the rollers and the inkjet speed of the inkjet printhead assembly of the roller type printers are much higher, the printing media with picture and text printing completed thus will pass the drying devices quickly. Therefore, the effective drying time for the water-based ink on the printing media is generally very short, which will cause that the printing media are immediately delivered to the next process with the water-based ink not sufficiently dried. Further, in such configuration, part of the water-based ink on the printing surface of the printing media will be deviated and dispersed under the action of rubbing by the external force, resulting in blurry pictures and texts, which seriously affects the inkjet printing quality. Moreover, with the increase of the printing speed of the roller type printers, the increase of the printing width, the increase of the picture and text coverage, and the deepening of picture and text colors, the total amount of the water-based ink per unit length of the printing media will be increased, accordingly, the drying degree of the water- based ink will be lower, and the blurriness of the picture and text will be in turn higher.

SUMMARY

[0005] It is therefore an object of the present disclosure to provide an inkjet printing system having an external drying device, which is free from the problem of blurry pictures and texts caused by that undried ink on a surface of a printing medium is lightly rubbed, thereby achieving the effect of improving the inkjet printing quality of the pictures and the texts.

[0006] According to the present disclosure, the inkjet printing system having an external drying device includes an unwinding device, a roller printing device, a first drying device, and a winding device. A printing medium to be printed is unfolded by the unwinding device, and is subjected to inkjet printing by means of the roller printing device, the printing medium printed then is dried by the first drying device, and is wound by the winding device finally.

The printing medium enters and exits from the same side of the roller printing device, and the first drying device is externally arranged on the same side that the printing medium enters and exits from the roller printing device.

[0007] It should be noted that, in the present disclosure, taking the roller printing device as a datum, the axial direction of a roller thereof defines a front-and-back direction, the horizontal direction of the roller defines a left-and-right direction, and the vertical direction of the roller defines an upper-and-lower direction.

[0008] According to the present disclosure, the printing medium is wound on the roller of the roller printing device, enters and exits from the same side of the roller, and is tensioned and reversed by means of the roller, so that the printing medium can enter the first drying device, arranged on the same side, for drying, without being reversed or supported by any other devices. Therefore, in the process that a printing surface of the printing medium is delivered to the first drying device after being subjected to inkjet printing, undried ink on the surface thereof can be effectively prevented from being rubbed by an external force.

Besides, the first drying device is independent of the roller printing device, and thus the first drying device will be not limited by the structure of the roller printing device. The drying temperature and the effective length to be dried can be calculated by the first drying device according to the drying speed of the ink and the printing speed, and the printing width of the roller printing device. The unlimited external first drying device thus can ensure sufficient drying of the ink on the surface of the printing medium passing through the inside of the first drying device. It should be noted that the first drying device can refer to relevant standard products in the prior art. The internal structure thereof is not in contact with the printing surface of the printing medium according to the present disclosure. Therefore, in the process that the printing surface of the printing medium passes through the first drying device, the undried ink on the surface thereof can be gradually and sufficiently dried under the non- contact condition. Accordingly, with the configuration that the printing medium in the present disclosure enters and exits from the same side of the roller printing device and is directly output to the first drying device, externally arranged on the same side, for sufficient drying after inkjet printing, the problem of blurry pictures and texts caused by the fact that the undried ink on the surface of the printing medium is lightly rubbed can be solved, thereby achieving the effect of improving the inkjet printing quality of the pictures and the texts.

[0009] The printing medium in the present disclosure is stored in the form of a roll material.

Such printing medium can only be input into the roller printing device for inkjet printing after being unfolded by the unwinding device, and should be wound by the winding device after picture and text printing is completed. The unwinding device and the winding device can refer to any standard products in the prior art. Automatic input and output of the printing medium of the inkjet printing system thus can be realized by means of the unwinding device and the winding device. Besides, the external drying device can be in form of a modular design, so that the length thereof can be adjusted flexibly according to the drying time required by the ink.

[0010] According to the present disclosure, each of the unwinding device and the winding device includes a first sensor and/or a second sensor. The first sensor is configured to obtain the thickness of the roll material by measuring a rolling surface position of the printing medium, and the second sensor is configured to obtain the deviation of the roll material by measuring an edge position of the printing medium.

[0011] In such configuration, the printing medium in the form of the roll material is placed on a rotating shaft of the unwinding device or a rotating shaft of the winding device, and the first sensor is fixed to a certain position away from the respective rotating shaft. The first sensor can obtain the thickness of the roll material by measuring a rolling surface position of the printing medium, namely, measuring the distance between an outer surface of the roll material and the first sensor, and then calculating the difference value. Therefore, the system can obtain the remaining amount of the unprinted printing medium by the first sensor of the 5 unwinding device, so that the roll material can be fed and supplemented timely, and the system can also obtain the stock of the printed printing medium by the first sensor of the winding device, so that the oriented printing medium on the winding device can be timely discharged and packaged. In the other hand, after the printing medium exits from the unwinding device, or before the printing medium enters the winding device, the printing medium during delivery may deviate relative to the roll material on the rotating shaft. The second sensor provided in the present disclosure can obtain the offset of the printing medium and in turn obtain the offset, required to be adjusted, of the roll material on the rotating shaft, by measuring the position deviation of two side edges of the printing medium on delivery, thereby achieving the deviation correction of the system. Consequently, the second sensor of the unwinding device makes the unprinted printing medium being centrally input into the roller printing device, and the second sensor of the winding device makes the printed printing medium being rolled aligned.

[0012] Specifically, the first drying device in the present disclosure can include a box body, and heaters, cross flow fans, and transmission rollers which are arranged in an inner cavity of the box body. The cross flow fans and the transmission rollers are vertically opposite to each other, and the several transmission rollers and the several cross flow fans are arranged at intervals in a lengthwise direction of the box body. In such configuration, the printing medium passes through gaps between the several transmission rollers and the several cross flow fans in sequence.

[0013] The box body in the present disclosure can sequentially include a horizontal section and an inclined section in a delivery direction of the printing medium, the ratio of the length of the inclined section to the length of the horizontal section is greater than or equal to 2, and the inclined section has an inclination angle of 25° to 30°.

[0014] According to the present disclosure, the heaters are configured to heat air in a closed space of the box body. The cross flow fans and the transmission rollers are oppositely arranged each other, and the printing medium passes through gaps between the cross flow fans and the transmission rollers. The number of transmission rollers may be larger than or equal to that of the cross flow fans. In such configuration, when the printing surface of the printing medium faces downwards, each of the cross flow fans is located below the respective transmission rollers, and each of the transmission rollers is located above the respective the cross flow fans; and when the printing surface of the printing medium faces upwards, each of the cross flow fans is located above the respective transmission rollers, and each of the transmission rollers is located below the respective the cross flow fans. The cross flow fans continuously blow the hot air in the box body to the printing surface of the printing medium to dry the ink on the surface thereof, and the transmission rollers support the back of the printing medium to prevent the printing medium from being deformed. Given that after being blown to the printing medium, the hot air will rise to be gathered at the upper portion of the box body, the design of the inclined section of the box body can make the hot air at a low position being reused and blown to the printing medium at a high position, thereby increasing the utilization efficiency of heat energy in the box body and reducing the power of the first drying device.

[0015] The box body may further include a heat exchange channel and a heat exchanger.

The heat exchanger is in communication with the inner cavity of the box body by means of the heat exchange channel, and the heat exchanger is configured to adjust the temperature of the inner cavity of the box body to keep the temperature within the optimal ink drying temperature range.

[0016] According to the present disclosure, the winding device may further include a guide belt, the first drying device may correspondingly include a traction mechanism arranged in the inner cavity of the box body thereof. The guide belt is unfolded by the winding device, is clamped by the traction mechanism, and is delivered to the other side of the box body in an opposite direction of the delivery direction of the printing medium. The guide belt passes through the gaps between the several transmission rollers and the several cross flow fans in sequence.

[0017] During first printing, the printing medium is unfolded from the unwinding device and is wound in the winding device after passing through the roller printing device and the first drying device. In order to match the high-speed printing of the roller printing device, the first drying device is usually designed very long, causing that a long section of the printing medium will be wasted and cannot be subjected to inkjet printing. When in a case without traction, the box body of the first drying device is required to be opened, making the printing medium being manually passed through the internal structure of the first drying device, such process thus is tedious. However, the above-mentioned problems can be effectively solved by the configuration of the cheap guide belt and the traction mechanism.

The guide belt is arranged on the winding device, and the traction mechanism is arranged in the box body of the first drying device. After being unfolded, the guide belt is clamped and driven by the traction mechanism to move in the opposite direction of the delivery direction of the printing medium, passing through the several transmission rollers and the several cross flow fans in sequence, and finally reaching an input end of the first drying device.

Subsequently, after being further reversely wound on the roller printing device, the guide belt can be connected to the unfolded printing medium at one end of the unwinding device.

[0018] Additionally, a preheating device may be further arranged between the unwinding device and the roller printing device, which is configured to preheat the passing printing medium. During high-speed printing, the printing medium quickly passes through a first heating roller and a second heating roller of the roller printing device, the effective heating time of the printing medium thus is too short, so that it is difficult to heat the printing medium sufficiently. The configuration of the preheating device in the present disclosure can effectively make up for the defect. It makes the printing medium being heated by stages to reach the ideal working temperature by the combination of the preheating device, the first heating roller, and the second heating roller.

[0019] According to the present disclosure, the roller printing device preferably includes a roller, a linear movement assembly, and an inkjet printhead assembly. The roller is configured to wind and deliver the printing medium, the linear movement assembly is configured to drive the inkjet printhead assembly to adjust the distances between the inkjet printhead assembly and a surface of the roller, and the inkjet printhead assembly is configured to perform inkjet printing on the printing medium. A plurality of the inkjet printhead assemblies and a plurality of the linear movement assemblies will be provided.

Each inkjet printhead assembly includes an inkjet printhead carrier and a plurality of inkjet printheads mounted on the inkjet printhead carrier. The inkjet printheads are distributed in several rows in parallel on the inkjet printhead carrier, and the inkjet printheads in the two adjacent rows are in staggered and overlapped arrangement. The inkjet printheads are mounted obliquely relative to the inkjet printhead carrier, and the several rows of inkjet printheads are arranged around the surface of the roller, lower surfaces of the several rows of inkjet printheads are combined to form a recessed inkjet surface, and each surface of the recessed inkjet surface is tangential with the surface of the roller.

[0020] The specific numerical values of the inclination angles can be obtained by the simplified relationship of the inkjet printhead carrier and the inkjet printheads. The inkjet printhead carrier has a first reference line which points to the circle center of the surface of the roller, nozzle orifices of each of the inkjet printheads have a second reference line which points to an inkjet direction of the nozzle orifices, and the included angle between the first reference line and the second reference line defines a deflection angle 9. The inkjet printheads are mounted obliquely at the deflection angle ¢ relative to the first reference line.

[0021] A calculation formula for the deflection angle ¢ is as follows: ¢ = tan"? cali wherein L refers to the distance between the nozzle orifices and the first reference line; H refers to the height from the inkjet printhead carrier to the surface of the roller; a refers to the included angle between a movement direction of the nozzle orifices and the first reference line; and R refers to the radius of the surface of the roller.

[0022] Preferably, the roller printing device may further include a first heating roller, or a first heating roller and a second heating roller. The first heating roller is configured to heat the printing surface of the printing medium, and the second heating roller is configured to heat the back of the printing medium. The printing medium is wound on the first heating roller and the roller in sequence, or the printing medium is wound on the second heating roller, the first heating roller and the roller in sequence. In such configuration, prior to inkjet printing, the printing medium is heated. It is beneficial to attachment of the ink and drying of a solvent on the heated printing medium, thereby improving the color quality of the pictures and the texts, and reducing subsequent drying requirements for the first drying device. With the double sides of the printing medium heated, folding deformation of the printing medium due to heating can be further avoided.

[0023] Optionally, the roller printing device may further include a first UV curing assembly and a second UV curing assembly, which are configured to cure the ink, attached to the surface of the printing medium, by stages. A plurality of the first UV curing assembly may be provided according to the plurality of the inkjet printhead assemblies. Each first UV curing assembly is arranged on one side of the inkjet printhead carrier of each inkjet printhead assembly. The second UV curing assembly is arranged away from the inkjet printhead assembly. The printing medium passes through the plurality of the inkjet printhead assembly and the first UV curing assembly, and the second UV curing assembly in sequence.

[0024] For UV ink, UV curing assemblies are required to cure the ink. Color-separated repeated printing is used for inkjet printing, so that a plurality of inkjet printhead assemblies are usually provided, and each inkjet printhead assembly is configured for inkjet printing of one color. With the configuration of the first UV curing assembly and the second UV curing assembly, when the printing medium passes through the plurality of inkjet printhead assemblies in sequence, every time inkjet printing of one color is completed, the UV ink is pre-cured by the respective first UV curing assemblies to avoid unclearness of pictures and texts caused by the mutual interference of the undried UV ink having different colors. After inkjet printing of all colors is completed on the printing medium, the UV ink of all colors is cured finally and completely by the second UV curing assembly.

[0025] Preferably, the roller printing device may further include an air ionizing bar which is configured to remove static electricity on the surface of the printing medium. In such configuration, the printing medium passes through the air ionizing bar and the inkjet printhead assemblies in sequence.

[0026] Preferably, the roller printing device may further include a tensioning roller assembly which is configured to adjust the tension of the printing medium entering the roller printing device. With such configuration, the printing medium wound around the tensioning roller thus can be tighten or loosen with the vertical movement of the tensioning roller.

[0027] Additionally or optionally, the roller printing device may further include a second drying device which is configured to pre-dry the printing medium subjected to inkjet printing.

[0028] According to the present disclosure, the printing medium is configured to enter and exit from the same side of the roller printing device and is directly output to the first drying device, externally arranged on the same side, for sufficient drying after inkjet printing. With such configuration, the problem of the blurry pictures and texts caused by the fact that the undried ink on the surface of the printing medium 1s lightly rubbed thus can be effectively solved, thereby achieving the effect of improving the inkjet printing quality of the pictures and the texts.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG. 1 is a view showing an inkjet printing system having an external drying device according to an embodiment of the present disclosure.

[0030] FIG. 2 is a schematic diagram of inkjet printheads in staggered and overlapped distribution according to an embodiment of the present disclosure.

[0031] FIG. 3 is a section view of an inkjet printhead assembly according to an embodiment, in which two rows of inkjet printheads are provided.

[0032] FIG. 4 1s a section view of an inkjet printhead assembly according to an embodiment, in which three rows of inkjet printheads are provided.

[0033] FIG. 5 is a schematic diagram of calculation of a deflection angle ¢ (0¢=0) of an inkjet printhead having a single row of nozzle orifices according to an embodiment of the present disclosure.

[0034] FIG. 6 is a schematic diagram of calculation of a deflection angle ¢ (00) of the inkjet printhead having the single row of nozzle orifices according to an embodiment of the present disclosure.

[0035] FIG. 7 is a schematic diagram of calculation of a deflection angle ¢ (00) of the inkjet printhead having multiple rows of nozzle orifices according to an embodiment of the present disclosure.

[0036] FIG. 8 is a section view of an inkjet printhead carrier according to an embodiment of the present disclosure.

[0037] FIG. 9 is a side view of an inkjet printhead assembly according to an embodiment of the present disclosure.

[0038] FIG. 10 is a structure diagram of an inkjet printhead assembly according to an embodiment of the present disclosure.

[0039] FIG. 11 is a structure diagram of the inkjet printhead assembly in FIG. 10, from another perspective.

[0040] FIG. 12 is a section view of a printing device according to an embodiment of the present disclosure.

[0041] FIG. 13 is a schematic diagram of an inkjet printing system according to one embodiment of the present disclosure, showing connection of a printing medium and a guide belt

[0042] Reference signs: 100 roller printing device, 200 unwinding device, 210 first sensor, 220 second sensor, 300 first drying device, 310 box body, 311 horizontal section, 312 inclined section, 320 cross flow fan, 330 transmission roller, 340 heat exchanger, 350 traction mechanism, 400 second drying device, 500 winding device, 600 preheating device; 110 inkjet printhead assembly, 111 inkjet printhead carrier, 112 inkjet printhead, 113 nozzle orifice, 114 first mounting groove, 115 second mounting groove, 121 first reference line, 122 second reference line, 123 third reference line, 124 fourth reference line, 130 roller, 140 linear movement assembly, 141 servo motor, 142 lead screw nut, 143 sliding block, 144 guide rail, 145 connecting plate, 150 nozzle cleaning assembly, 151 negative-pressure suction nozzle, 152 reciprocating driving mechanism, 161 first heating roller, 162 second heating roller, 171 first UV curing assembly, 172 second UV curing assembly, 180 air ionizing bar, 190 tensioning roller assembly.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0043] The drawings of the present disclosure are only used for illustrative description and cannot be understood as limitations on the present disclosure. In order to better describe the following embodiments, some components in the drawings may be omitted, enlarged or reduced, which does not represent the sizes of actual products; and for those skilled in the art, it is understandable that some well-known structures in the drawings and descriptions thereof may be omitted.

[0044] FIG. 1 shows an inkjet printing system having an external drying device according to one embodiment of the present disclosure. It should be noted that some structures, which are not contributing to describe the invention, are omitted to facilitate the clear identification of the main structural features. The inkjet printing system according to the invention includes an unwinding device 200, a roller printing device 100, a first drying device 300, and a winding device 500. In this embodiment, a printing medium to be printed is unfolded by the unwinding device 200 and is subjected to inkjet printing by means of the roller printing device 100, the medium printed is then dried by the first drying device 300, and is wound by the winding device 500 finally. The printing medium is configured to enter and exit from the same side of the roller printing device 100, and the first drying device 300 is externally arranged on the same side that the printing medium enters and exits from the roller printing device 100.

[0045] It should be noted that, in this embodiment, taking the roller printing device 100 as a reference, the axial direction of a roller thereof defines a front-and-back direction, the horizontal direction of the roller defines a left-and-right direction, and the vertical direction of the roller defines an upper-and-lower direction.

[0046] According to the present embodiment, the printing medium is wound on the roller of the roller printing device 100, enters and exits from the same side of the roller, and is tensioned and reversed by the roller, so that the printing medium can enter the first drying device 300 arranged on the same side for drying, without being reversed or supported by any other devices. Therefore, in the process that a printing surface of the printing medium is delivered to the first drying device 300 after being subjected to inkjet printing, undried ink on the surface thereof can be effectively prevented from being rubbed by an external force.

Besides, the first drying device 300 is independent of the roller printing device 100, and thus the first drying device 300 is not limited by the structure of the roller printing device 100.

The drying temperature and the effective length to be dried can be calculated by the first drying device 300 according to the drying speed of the ink, the printing speed, and the printing width of the roller printing device 100. The unlimited external first drying device 300 in the present embodiment thus can ensure sufficient drying of the ink on the surface of the printing medium passing through the inside of the first drying device. It should be noted that the first drying device 300 can refer to relevant standard products in the prior art. The internal structure of the first drying device 300 is not in contact with the printing surface of the printing medium according to the present embodiment. Therefore, in the process that the printing surface of the printing medium passes through the first drying device 300, the undried ink on the surface thereof can be gradually and sufficiently dried under the non- contact condition. Accordingly, with the configuration that the printing medium in this embodiment enters and exits from the same side of the roller printing device and is directly output to the first drying device, externally arranged on the same side, for sufficient drying after inkjet printing, the problem of blurry pictures and texts caused by that the undried ink on the surface of the printing medium is lightly rubbed thus can be solved, thereby improving the inkjet printing quality of the pictures and the texts.

[0047] Furthermore, the printing medium is stored in the form of a roll material. Such printing medium can only be input into the roller printing device 100 for inkjet printing after being unfolded by the unwinding device 200, and should be wound by the winding device 500 after picture and text printing is completed. It should be noted that the unwinding device 200 and the winding device 500 can refer to any standard products in the prior art. Automatic input and output of the printing medium of the inkjet printing system thus can be realized by means of the unwinding device 200 and the winding device 500. Besides, the external drying device 300 can be in form of a modular design, so that the length thereof can be adjusted flexibly according to the drying time required by the ink.

[0048] In this embodiment, as shown in FIG. 1, the winding device 500, the first drying device 300, and the unwinding device 200 are located on the left side of the roller printing device 100 from left to right in sequence. The printing medium enters from the left side of the roller printing device 100, returns after picture and text printing is completed, and still exits from the left side of the roller printing device 100. The unwinding device 200 and the winding device 500 are driven by AC servo motors so as to match rotation of the roller 130 to prevent the printing medium from being pulled.

[0049] According to the present embodiment, each of the unwinding device 200 and the winding device 500 has a first sensor 210 and/or a second sensor 220. The first sensor 210 is configured to obtain the thickness of the roll material by measuring a rolling surface position of the printing medium, and the second sensor 220 is configured to obtain the deviation of the roll material by measuring an edge position of the printing medium.

[0050] In such configuration, the printing medium in the form the roll material is placed on a rotating shaft of the unwinding device 200 or a rotating shaft of the winding device 500, and the first sensor 210 is fixed to a certain position away from the respective rotating shaft.

The first sensor 210 can obtain the thickness of the roll material by measuring a rolling surface position of the printing medium, namely, measuring the distance between an outer surface of the roll material and the first sensor, and then calculating the difference value.

Therefore, the system can obtain the remaining amount of the unprinted printing medium by the first sensor 210 of the unwinding device 200, so that the roll material can be fed and supplemented timely. The system can also obtain the stock of the printed printing medium by the first sensor 210 of the winding device 500, so that the printed printing medium on the winding device 500 can be discharged and packaged timely. In the other hand, after the printing medium exits from the unwinding device 200, or before the printing medium enters the winding device 500, the printing medium during delivery may deviate relative to the roll material on the rotating shaft. With such configuration, the second sensor 220 can obtain the offset of the printing medium and in turn obtain the offset, required to be adjusted, of the roll material on the rotating shaft, by measuring the position deviation of two side edges of the printing medium on delivery, thereby achieving the deviation correction of the system.

Consequently, according to the present embodiment, the second sensor 220 of the unwinding device 200 makes the unprinted printing medium being centrally input into the roller printing device 100; and the second sensor 220 of the winding device 500 makes the printed printing medium being rolled aligned.

[0051] Specifically, the first sensor 210 of the unwinding device 200 and the first sensor 210 of the winding device 500 can be Keyence range sensors and are mounted below the unwinding device 200 and the winding device 500 respectively. The second sensor 220 of the unwinding device 200 is mounted at the input end of the roller printing device 100, and the second sensor 220 of the winding device 500 is mounted at the input end of the winding device 500.

[0052] According to the present embodiment, the first drying device 300 includes a box body 310, and heaters, cross flow fans 320, and transmission rollers 330 which are arranged in an inner cavity of the box body 310. The cross flow fans 320 and the transmission rollers 330 are arranged vertically oppositely, and the several transmission rollers 330 and the several cross flow fans 320 are arranged at intervals in a lengthwise direction of the box body 310, In such configuration, the printing medium passes through gaps between the several transmission rollers 330 and the several cross flow fans 320 in sequence.

[0053] Further, the box body 310 sequentially includes a horizontal section 311 and an inclined section 312 in a delivery direction of the printing medium, the ratio of the length of the inclined section 312 to the length of the horizontal section 311 is greater than or equal to

2, and the inclined section 312 has an inclination angle of 25° to 30°.

[0054] The heaters are configured to heat air in a closed space of the box body 310. The cross flow fans 320 and the transmission rollers 330 are oppositely arranged, and the printing medium passes through gaps between the cross flow fans 320 and the transmission rollers 330. The number of transmission rollers 330 may be larger than or equal to that of the cross flow fans 320. When the printing surface of the printing medium faces downwards, each of the cross flow fans 320 is located below the respective transmission rollers 330, and the transmission rollers 330 are located above the respective cross flow fans 320; and when the printing surface of the printing medium faces upwards, each of the cross flow fans 320 is located above the respective transmission rollers 330, and each of the transmission rollers 330 are located below the respective cross flow fans 320. The cross flow fans 320 continuously blow the hot air in the box body 310 to the printing surface of the printing medium to dry the ink on the surface thereof, and the transmission rollers 330 support the back of the printing medium to prevent the printing medium from being deformed.

Considering that after being blown to the printing medium, the hot air will rise to be gathered at the upper portion of the box body 310, the design of the inclined section 312 of the box body 310 in the present embodiment can make the hot air at a low position reused and blown to the printing medium at a high position, thereby increasing the utilization efficiency of heat energy in the box body 310 and reducing the power of the first drying device 300.

[0055] In this embodiment, the box body 310 further includes a heat exchange channel and a heat exchanger 340. The heat exchanger 340 is in communication with the inner cavity of the box body 310 by means of the heat exchange channel, and the heat exchanger 340 is configured to adjust the temperature of the inner cavity of the box body 310 to keep the temperature within the optimal ink drying temperature range.

[0056] Referring to FIG. 1, in this embodiment, the cross flow fans 320 are in one-to-one correspondence with the transmission rollers 330, the numbers are equal, the cross flow fans 320 are located below the transmission rollers 330, and the transmission rollers 330 are located above the cross flow fans 320. The heaters are integrated on the cross flow fans 320.

The several cross flow fans 320 and the several transmission rollers 330 are arranged at the intervals of 800-1000 mm. The cross flow fans 320 and/or the transmission rollers 330 can be dismounted and taken out from front and rear sides of the box body 310 for routine maintenance. In such configuration, the printing medium enters from an input end on the right side of the box body 310, passes through the gaps between the several transmission rollers 330 and the several cross flow fans 320 in sequence, then is dried, and finally exits from an output end on the left side of the box body 310.

[0057] As shown in FIG. 13 where also some structures, not necessary for describing the invention, are omitted to facilitate the clear identification of the main structural features, additionally or alternatively, the winding device 500 includes a guide belt, the first drying device 300 correspondingly includes a traction mechanism 350 arranged in the inner cavity of the box body 310 thereof. The guide belt in this embodiment is unfolded by the winding device 500, is clamped by the traction mechanism 350, and is further delivered to the other side of the box body 310 in an opposite direction of the delivery direction of the printing medium. The guide belt passes through the gaps between the several transmission rollers 330 and the several cross flow fans 320 in sequence.

[0058] During first printing, the printing medium is unfolded from the unwinding device 200 and is wound in the winding device 500 after passing through the roller printing device 100 and the first drying device 300. In order to match the high-speed printing of the roller printing device 100, the first drying device 300 is usually designed very long, causing that a long section of the printing medium will be wasted and cannot be subjected to inkjet printing.

In addition, when in a case without traction, the box body 310 of the first drying device 300 is required to be opened, making the printing medium being manually passed through the internal structure of the first drying device 300, such process is tedious. However, the above- mentioned problems can be effectively solved by the configuration of the cheap guide belt and the traction mechanism 350. The guide belt is arranged on the winding device 500, and the traction mechanism 350 is arranged in the box body 310 of the first drying device 300.

After being unfolded, the guide belt is clamped and driven by the traction mechanism 350 to move in the opposite direction of the delivery direction of the printing medium, then passing through the several transmission rollers 330 and the several cross flow fans 320 in sequence, and finally reaching an input end of the first drying device 300. Subsequently, after being further reversely wound on the roller printing device 100, the guide belt can be connected to the unfolded printing medium at one end of the unwinding device 200.

[0059] In this embodiment, the guide belt can be wound on the rotating shaft of the winding device 500 in advance, or be separately rolled and arranged on one side of the rotating shaft.

There may be one guide belt which has the same width as the printing medium, and there may also be two or more guide belts. When in use, one end of the guide belt is fixed to the rotating shaft of the winding device 500, and the other end is connected to the printing medium. The traction mechanism 350 may be manipulators mounted on the front and rear sides of the box body 310, and the manipulators can clamp the guide belt to move along a delivery track of the printing medium. The guide belt is connected to the printing medium on the right side of the first drying device 300 according to the present embodiment.

[0060] Preferably, a preheating device 600 is further arranged between the unwinding device 200 and the roller printing device, which is configured to preheat the passing printing medium. During high-speed printing, the printing medium quickly passes through a first heating roller and a second heating roller of the roller printing device, the effective heating time of the printing medium thus is too short, so that it is difficult to heat the printing medium sufficiently. The configuration of the preheating device 600 can effectively make up for the defect. It makes the printing medium being heated by stages to reach the ideal working temperature by combination of the preheating device 600, the first heating roller, and the second heating roller.

[0061] Preferably, the roller printing device 100 is further provided with a second drying device 400, which is configured to pre-dry the printing medium after inkjet printing.

[0062] As shown in FIGS. 2, 3 and 4, an inkjet printhead assembly having a deflection angle is provided according to one embodiment of the present disclosure. The inkjet printhead assembly includes an inkjet printhead carrier 111 and a plurality of inkjet printheads 112 mounted on the inkjet printhead carrier. The inkjet printheads 112 are distributed in several rows in parallel on the inkjet printhead carrier 111, and the inkjet printheads 112 in the two adjacent rows are staggered and overlapped. The inkjet printheads 112 are mounted obliquely relative to the inkjet printhead carrier 111, and the several rows of inkjet printheads 112 are arranged around the surface of the roller, lower surfaces of the several rows of inkjet printheads 112 are combined to form a recessed inkjet surface, and each surface of the recessed inkjet surface is tangential with the surface of the roller.

[0063] The lengthwise direction of the inkjet printhead carrier 111 defines a front-and-back direction, the widthwise direction thereof defines a left-and-right direction, and the height direction thereof defines an upper-and-lower direction. A normal direction at the center of the lower surface of the inkjet printhead 112 is generally taken as the inkjet direction of each inkjet printhead 112. The inkjet printheads 112 in each row are mounted obliquely relative to the inkjet printhead carrier 111, thus the inkjet directions of the inkjet printheads 112 in each row are inclined relative to a certain datum line of the inkjet printhead carrier 111, and the inkjet directions of the inkjet printheads 112 in each row have different inclination angles.

The several rows of inkjet printheads 112 are arranged above the surface of the roller in a surrounding manner. The lower surfaces of the several rows of inkjet printheads 112 thus are no longer in a common plane, and are combined into the recessed inkjet surface. When the inkjet printhead carrier 111 drives the inkjet printheads 112 to get close to the surface of the roller and the distance between the lower surfaces of the inkjet printheads 112 and the surface of the roller is zero, each surface of the inkjet surface is tangential with the surface of the roller. The inkjet surface is thus equivalent to a part of a circumscribed polygon of the surface of the roller. According to the present embodiment, the inkjet printheads in each row are mounted at different inclination angles relative to the inkjet printhead carrier, thus the inkjet directions of the inkjet printheads can point to the circle center of the surface of the roller, and then the problem that the multiple rows of staggered and overlapped inkjet printheads cannot be perpendicular to the surface of the roller simultaneously can be solved, thereby achieving the effect of improving the overall printing quality of the inkjet printhead assembly.

[0064] FIGS. 5-7 show how to define the deflection angle of each inkjet printhead. The specific numerical values of the inclination angles can be obtained by the simplified relationship of the inkjet printhead carrier 111 and the inkjet printheads 112. The inkjet printhead carrier 111 has a first reference line 121 which points to the circle center of the surface of the roller, nozzle orifices 113 of each of the inkjet printheads 112 have a second reference line 122 which points to an inkjet direction of the nozzle orifices 113, and the included angle between the first reference line 121 and the second reference line 122 defines a deflection angle 9. The inkjet printheads 112 are mounted obliquely at the deflection angle ¢ relative to the first reference line 121.

[0065] A calculation formula for the deflection angle 9 is as follows: ¢ = tan™?! es wherein L refers to the distance between the nozzle orifices and the first reference line; H refers to the height from the inkjet printhead carrier to the surface of the roller; a refers to the included angle between a movement direction of the nozzle orifices and the first reference line; and R refers to the radius of the surface of the roller.

[0066] In such configuration, the first reference line 121 of the inkjet printhead carrier 111 is used as the datum line, which can be the center line of the inkjet printhead carrier 111.

When the inkjet printheads 112 are mounted obliquely at the deflection angle ¢ relative to the first reference line 121 of the inkjet printhead carrier 111, all that is required to ensure that the inkjet directions of the inkjet printheads 112 in each row point to the circle center of the surface of the roller is to make the first reference line 121 point to the circle center of the surface of the roller, in such way the inkjet printheads 112 in each row are perpendicular to the surface of the roller simultaneously. The second reference line 122 starts from the center of the nozzle orifices 113 of each inkjet printhead 112 and points to the inkjet direction of the nozzle orifices 113. When the single inkjet printhead 112 has a single row of nozzle onfices 113, the second reference line 122 is the inkjet direction of the inkjet printheads 112 in the row, and the deflection angle 9 is the inclination angle at which the inkjet printheads 112 in the row are mounted relative to the inkjet printhead carrier 111. When the single inkjet printhead 112 has multiple rows of nozzle orifices 113, each row of the nozzle orifices 113 has one second reference line 122, and thus a plurality of deflection angles ¢ can be calculated. Since the distances of the multiple rows of nozzle orifices 113 are short, the average value of the deflection angles ¢ of the multiple rows of nozzle orifices 113 or the deflection angle ¢ of the middle of the multiple rows of nozzle orifices 113 can be calculated as the inclination angle at which the inkjet printheads 112 in the row are mounted relative to the inkjet printhead carrier 111. Therefore, within the allowable range of errors, the inkjet directions of the multiple rows of nozzle orifices 113 of the inkjet printheads 112 in the row are nearly perpendicular to the surface of the roller.

[0067] In the other hand, as the height H from the inkjet printhead carrier to the surface of the roller changes in a certain range, and for the inkjet printheads 112 in each row, a plurality of deflection angles ¢ can be calculated. However, the height H and the radius R of the arc- shaped printing surface differ by several orders of magnitude, the deflection angles ¢ change slightly, accordingly, within the allowable range of errors, the average value thereof can be taken as the inclination angle at which the inkjet printheads 112 in the row are mounted relative to the inkjet printhead carrier 111. When the height H from the inkjet printhead carrier and the surface of the roller is zero, a lower surface of the inkjet printhead carrier 111 and an imaginary extension surface thereof are tangential with the surface of the roller. The height H from the inkjet printhead carrier and the surface of the roller is equivalent to the working height of the inkjet printheads 112. Therefore, the distance L between the nozzle orifices and the first reference line should be the numerical value when the height H from the inkjet printhead carrier and the surface of the roller is zero. Besides, when the height H of the inkjet printhead carrier 111 is adjusted, the inkjet printhead carrier 111 will not move along the first reference line 121 thereof. According to the present embodiment, when the included angle a between the movement direction of the nozzle orifices and the first reference line is formed on the outer side of the surface of the roller, the included angle o is a negative value; and when the included angle a between the movement direction of the nozzle orifices and the first reference line is formed on the inner side of the surface of the roller, the included angle a is a positive value.

[0068] Preferably, the ratio of the radius R of the surface of the roller to the distance L between the nozzle orifices 113 and the first reference line 121 is as follows: R/L = 10. For the inkjet printheads 112 having multiple rows of nozzle orifices 113, the distances L between the nozzle orifices and the first reference line include the minimum value Laan and the maximum value Lmax. When the ratio of R to L is calculated, the distance L should be

Lmax; and further, the following should be met: R/(Lyax — Lyn) = 20. On one hand, when the ratio of R to L differs by one order of magnitude, the difference of the numerical value of the calculated deflection angle ¢ of each row of the nozzle orifices 113 of the single inkjet printhead 112 is small, and thus the average value of the deflection angles ¢ of the multiple rows of nozzle orifices 113 or the deflection angle ¢ of the middle of the multiple rows of nozzle orifices 113 can be calculated as the inclination angle at which the inkjet printheads 112 in the row are mounted relative to the inkjet printhead carrier 111. Then, within the allowable range of errors, the inkjet directions of the multiple rows of nozzle orifices 113 of the inkjet printheads 112 in the row are nearly perpendicular to the surface of the roller. On the other hand, when the ratio of R to L differs by one order of magnitude, the distance of each row of nozzle orifices 113 of the single inkjet printhead 112 is also correspondingly small, thus the height of each row of nozzle orifices 113 relative to the surface of the roller can be nearly equal, and thus the influence of the curvature of the surface of the roller on the inkjet quality of the inkjet printheads 112 can be reduced.

[0069] Preferably, the numerical value of the included angle between the movement direction of the inkjet printhead carrier 111 and the first reference line 121 is as follows: la} < 20° When the inkjet printhead carrier 111 is located at different heights H, the included angle a will affect the actual distance between the nozzle orifices 113 of the inkjet printheads 112 and the first reference line 121. When the included angle a is the positive value, the included angle a will increase the actual distance between the nozzle orifices 113 and the first reference line 121; and when the included angle a is the negative value, the included angle a will shorten the actual distance between the nozzle orifices 113 and the first reference line 121. Such influence will be increased with increase of the numerical value of the included angle a. Therefore, in the actual application, the numerical value of the included angle a should not exceed 20°, and the value range of the included angle a should be [-20°, 20°].

[0070] Preferably, the deflection angle ¢ is in a range of 1° to 5° According to the calculation formula of the deflection angle 9, the deflection angle 9 is comprehensively affected by the distance L, the height H, the included angle a and the radius R. When the deflection angle ¢ of the nozzle orifices 113 of the inkjet printheads 112 relative to the first reference line 121 is in the range of 1° to 5°, the influence on the inclination angles of the inkjet printheads 112 can be reduced that caused by the working height of the inkjet printhead carrier 111 and the distribution condition of the nozzle orifices 113 of the inkjet printheads 112. For example, for the inkjet printheads 112 having the multiple rows of nozzle orifices 113, when the inkjet printheads 112 are mounted obliquely at 3° relative to the inkjet printhead carrier 111, within the error range of 2°, any row of the nozzle orifices 113 of the inkjet printheads 112 can be deemed as perpendicular to the surface of the roller at any working height, and the inkjet directions thereof point to the circle center of the surface of the roller.

[0071] The inkjet printheads 112 can be mounted obliquely relative to the inkjet printhead carrier 111 in a way that the inclination angles therebetween are changing, that is, the inclination angles of the inkjet printheads 112 relative to the inkjet printhead carrier 111 can change with the deflection angle in different situations, and the inkjet printheads 112 are connected to the inkjet printhead carrier 111 by an automatic inclination angle adjustment device. Alternatively, the inclination angles may be fixed, and the inkjet printheads 112 are connected to the inkjet printhead carrier 111 by a manual inclination angle adjustment device (for example, adjusting sheets, adjusting fasteners, etc.).

[0072] As shown in FIGS. 8-11, the inclination angles are fixed. In such configuration, the inkjet printhead carrier 111 is provided with several mounting grooves which are configured to fix the inkjet printheads 112, and the center line of each mounting groove defines a third reference line 123 which is inclined at the deflection angle ¢ relative to the first reference line 121. The mounting grooves inclined at the deflection angle ¢ are machined on the inkjet printhead carrier 111 in advance, the inkjet printheads 112 are directly placed into the mounting grooves to achieve that the inkjet printheads 112 can be mounted obliquely at the deflection angle @ relative to the first reference line 121. Compared with the manner of connecting the inkjet printheads 112 to the inkjet printhead carrier one by one by means of the adjusting sheets or the adjusting fasteners, such manner greatly improves the oblique mounting efficiency and precision of the inkjet printheads 112.

[0073] Specifically, the mounting grooves include first mounting grooves 114 and second mounting grooves 115, which are arranged symmetrically each other along the first reference line 121, the crossing included angle between lower surfaces of the first mounting grooves 114 and lower surfaces of the second mounting grooves 115 is the mounting included angle 8, and the mounting included angle is as follows: 8 = 180 °— 20. The two rows of inkjet printheads 112 can be assembled into an inkjet printhead 112 array by staggering and overlapping, and thus the two rows of mounting grooves distributed in parallel are correspondingly arranged. The manner of symmetrically arranging the first mounting grooves 114 and the second mounting grooves 115 along the first reference line 121 is beneficial to simplifying of machining and manufacturing of the inkjet printhead carrier 111.

Further, the lower surfaces of the first mounting grooves 114 and the second mounting grooves 115 are flush with the lower surfaces of the two rows of inkjet printheads 112 respectively so as to avoid the interference influence on the inkjet process of the inkjet printheads 112, and thus the lower surfaces of the first mounting grooves 114 and the second mounting grooves 115 are also combined into a recessed surface which is overlapped with the inkjet surface of the inkjet printheads 112.

[0074] In this embodiment, there are two rows of inkjet printheads 112 and two rows of mounting grooves, which are arranged symmetrically relative to the first reference line 121 of the inkjet printhead carrier 111. The single inkjet printhead 112 has four rows of nozzle orifices 113, and the specific model is XAAR2001-GS12C. The inkjet printheads 112 are mounted obliquely at the deflection angle p=2.56° relative to the first reference line 121 of the inkjet printhead carrier 111. Correspondingly, the radius of the corresponding arc-shaped printing surface is S70 mm, the width of the inkjet printheads 112 is 50 mm, and the mounting included angle 8 between the first mounting grooves 114, and the second mounting grooves 115 is 174.88°. The plurality of inkjet printheads 112 are mounted one by one in the first mounting grooves 114 and the second mounting grooves 115 by means of the fasteners.

Additionally, in other embodiments, three rows of inkjet printheads 112 may be arranged in parallel, and the center line of the inkjet printheads 112 in the middle row is overlapped with the first reference line 121.

[0075] As shown in FIGS. 9-11, additionally or alternatively, the inkjet printhead assembly further includes a nozzle cleaning assembly 150 which is mounted on the inkjet printhead carrier 111. The nozzle cleaning assembly 150 has a negative-pressure suction nozzle 151 and a reciprocating driving mechanism 152. The negative-pressure suction nozzle 151 abuts against the lower surfaces of the inkjet printheads 112; and the reciprocating driving mechanism 152 drives the negative-pressure suction nozzle 151 to reciprocate in the lengthwise direction of the inkjet printhead carrier 111.

[0076] In this embodiment, the negative-pressure suction nozzle 151 1s located below the inkjet printhead carrier 111, and the upper surface of the negative-pressure suction nozzle 151 is identical with and is in contact with the inkjet surface of the inkjet printheads 112.

The inside of the negative-pressure suction nozzle 151 is in communication with an external negative pressure device, and when the negative pressure device works, the upper surface of the negative-pressure suction nozzle 151 has a suction force. The reciprocating driving mechanism 152 is mounted on the inkjet printhead carrier 111 and drives the negative- pressure suction nozzle 151 to reciprocate in the lengthwise direction of the inkjet printhead carrier 111. During normal printing, the negative-pressure suction nozzle 151 stays at one end of the inkjet printhead carrier 111 in the lengthwise direction and does not affect normal working of the inkjet printheads 112; and during cleaning, the reciprocating driving mechanism 152 pushes the negative-pressure suction nozzle 151 to go through all the inkjet printheads 112 in sequence, and the negative-pressure suction nozzle 151 dredges and cleans the nozzle orifices 113 of the inkjet printheads 112 by means of the suction force of the upper surface. With the arrangement of the nozzle cleaning assembly 150, during cleaning of the inkjet printheads 112, the inkjet printhead assembly is not required to be dismounted, and the whole cleaning process is automatic, thus greatly improving the working efficiency.

[0077] FIG. 12 shows a roller printing device 100 having a deflection angle according to one embodiment of the present disclosure. The printing device includes a roller 130, a linear movement assembly 140, and the above-mentioned inkjet printhead assembly 110 having the deflection angles. The roller 130 is configured to wind and deliver a printing medium, and the linear movement assembly 140 is configured to drive the inkjet printhead assembly 110 to adjust the distance between the inkjet printhead assembly 110 and a surface of the roller 130, and the inkjet printhead assembly 110 is configured to perform inkjet printing on the printing medium.

[0078] Preferably, the roller 130 is located below the linear movement assembly 140 and the inkjet printhead assembly 110. The vertical center line of the roller 130 defines a fourth reference line 124. In this embodiment, four inkjet printhead assemblies 110 and three linear movement assemblies 140 are included. The four inkjet printhead assemblies 110 surround the roller 130 in sequence from left to right at intervals and are arranged symmetrically relative to the fourth reference line 124; the three linear movement assemblies 140 surround the roller 130 in sequence from left to right at intervals and are arranged symmetrically relative to the fourth reference line 124. Specifically, the inkjet printhead assembly 110 on the left side (leftmost) is fixedly connected to the linear movement assembly 140 on the left side (leftmost), the inkjet printhead assembly 110 on the right side (rightmost) is fixedly connected to the linear movement assembly 140 on the right side (rightmost), and the two inkjet printhead assemblies 110 in the middle are simultaneously and fixedly connected to the linear movement assembly 140 in the middle. Each linear movement assembly 140 drives the corresponding inkjet printhead assembly 110 independently to adjust the distance between the inkjet printhead assembly 110 and the surface of the roller 130.

[0079] In this embodiment, the four inkjet printhead assemblies 110 correspond to CMYK (cyan, magenta, yellow and black) of color printing respectively, that is, each inkjet printhead assembly 110 is only responsible for inkjet of one color, so that small number of the inkjet printheads 112 on the inkjet printhead carrier 111 thereof is provided(two rows at least), and thus the machining and manufacturing difficulty of the inkjet printhead carrier 111 is reduced.

In addition, the inkjet printhead assemblies 110 on the left side (leftmost) and the right side (rightmost) are separately driven by the linear movement assemblies 140 on the left side (leftmost) and the right side (rightmost) respectively, so that the movement directions of the inkjet printhead assemblies 110 can be overlapped with the first reference lines 121 thereof, that is, the included angles a are zero, and then the included angles a can be prevented from affecting the operation that the inkjet printheads 112 are perpendicular to the surface of the roller 130 for printing. Secondly, the two inkjet printhead assemblies 110 in the middle are simultaneously driven by the linear movement assembly 140 in the middle, so that the number of the linear movement assemblies 140 can be reduced, and the overall size of the printing device thus can be reduced. Of course, in order to ensure the inkjet quality of the two inkjet printhead assemblies 110 in the middle, the included angles a between the movement directions of the nozzle orifices thereof and the first reference lines should be as small as possible. Accordingly, the three linear movement assemblies 140 drive the inkjet printhead assemblies 110 to move to adjust the working heights of the inkjet printhead assemblies 110 during inkjet so as to meet the requirements of printing media of different thicknesses and different inkjet.

[0080] In this embodiment, each of the inkjet printhead assemblies 110 is of the structure as shown above, and the radius of the corresponding roller 130 is 570 mm. The inkjet printhead assemblies 110 surround the roller 130 in sequence at intervals of 30°. The included angles between each of the first reference lines 121 of the two inkjet printhead assemblies 110 in the middle and the fourth reference line 124 of the roller 130 are 15°.

[0081] In this embodiment, each of the linear movement assemblies 140 further includes a servo motor 141, a lead screw nut 142, etc. for providing power, and sliding blocks 143, guide rails 144, a connecting plate 145, etc. for providing supporting. The axe of each lead screw nut, namely, the center line of each linear movement assembly 140 points to the circle center of the roller 130. The three linear movement assemblies 140 surround the roller 130 in sequence at intervals of 45°, and the center line of the linear movement assembly 140 in the middle is overlapped with the fourth reference line 124 of the roller 130. In addition, each of the inkjet printhead assemblies 110 on the left side and the right side is mounted centrally at the lower portion of the connecting plates 145 of the respective linear movement assembly 140 on the left side and the right side by means of fasteners, and the first reference lines 121 of the inkjet printhead carriers 111 thereof are overlapped with the center lines of the linear movement assemblies 140. The two inkjet printhead assemblies 110 in the middle are simultaneously mounted at a lower portion of the connecting plate 145 of the linear movement assembly 140 in the middle by means of fasteners, and included angles of 15° are formed between the first reference lines 121 of the inkjet printhead carriers 111 thereof and the center line of the linear movement assembly 140.

[0082] In this embodiment, an outer surface of the roller 130 is provided with a plurality of air holes, the inside of the roller 130 is in communication with the external negative pressure device, and the printing medium is adsorbed onto the outer surface of the roller 130 by means of the air holes under the negative pressure. The axial end of the roller 130 is connected to a driving device (for example, an electric motor). After the roller 130 delivers the printing medium to enter a printing area for printing, the air holes in the roller 130 are connected to the negative pressure, and then the printing medium is adsorbed onto the outer surface of the roller; and after the roller 130 delivers the printing medium to exit from the printing area and the air holes in the roller 130 lose the negative pressure, the printing medium is wound around the surface of the roller by means of the tension of the printing medium. Refer to a printer roller having a negative pressure adsorption function in Chinese patent No. 202110615060.4 for the specific structure of the roller 130.

[0083] Preferably, the roller printing device 100 further includes a first heating roller 161, or a first heating roller 161 and a second heating roller 162. The first heating roller 161 is configured to heat the printing surface of the printing medium, and the second heating roller 162 is configured to heat the back of the printing medium. In such configuration, the printing medium is wound on the first heating roller 161 and the roller 130 in sequence, or the printing medium is wound on the second heating roller 162, the first heating roller 161 and the roller 130 in sequence. Prior to inkjet printing, the printing medium thus is heated. It is beneficial to attachment of the ink and drying of a solvent on the heated printing medium, thereby improving the color quality of the pictures and the texts, and reducing subsequent drying requirements for the first drying device 300. With the double sides of the printing medium heated, folding deformation of the printing medium due to heating can be further avoided.

[0084] Optionally, the roller printing device 100 further includes a plurality of first UV curing assemblies 171 and a second UV curing assembly 172, which are configured to cure the ink, attached to the surface of the printing medium, by stages. Each of the several first

UV curing assemblies 171 is arranged on one side of the inkjet printhead carrier 111 of each of the several inkjet printhead assemblies 110. The second UV curing assembly 172 is arranged away from the inkjet printhead assemblies 110. The printing medium passes through the several inkjet printhead assemblies 110, the several first UV curing assemblies 171, and the second UV curing assembly 172 in sequence.

[0085] For UV ink, UV curing assemblies are required to cure the ink. Color-separated repeated printing is used for inkjet printing, so that a plurality of inkjet printhead assemblies 110 are usually provided, and each inkjet printhead assembly 110 is configured for inkjet printing of one color. When the printing medium passes through the plurality of inkjet printhead assemblies 110 in sequence, every time inkjet printing of one color is completed, the UV ink is pre-cured by the respective first UV curing assemblies 171 to avoid unclearness of pictures and texts caused by the mutual interference of the undried UV ink having different colors. After inkjet printing of all colors is completed on the printing medium, the UV ink of all colors is cured finally and completely by the second UV curing assembly 172.

[0086] Preferably, the roller printing device 100 further includes an air ionizing bar 180 which is configured to remove static electricity on the surface of the printing medium. The printing medium in this embodiment passes through the air ionizing bar 180 and the inkjet printhead assemblies 110 in sequence.

[0087] Preferably, the roller printing device 100 further includes a tensioning roller assembly 190 which is configured to adjust the tension of the printing medium entering the roller printing device 100. The printing medium in this embodiment wounds around the tensioning roller thus can be tighten or loosen with the vertical movement of the tensioning roller.

[0088] In this embodiment, the input end and the output end of the roller printing device 100 are located on the left side, and the printing medium enters from the lower left side with the printing surface facing upwards and exits from the lower left side with the printing surface facing downwards. The tensioning roller assembly 190 is located on the left-most side of the roller 130. The first heating roller 161 and the second heating roller 162 are located on the left side of the roller 130 and on the right side of the tensioning roller, and the first heating roller 161 is located below the second heating roller 162. The air ionizing bar 180 1s located on the left side of the roller 130 and above the second heating roller 162. The four first UV curing assemblies 171 are individually mounted on the right sides of the inkjet printhead carriers 111 of the four inkjet printhead assemblies 110, and the first UV curing assemblies 171 are all located above the roller 130. The second UV curing assembly 172 is mounted on the right side of the roller 130. The second drying device 400 is mounted on the lower right side of the roller 130.

[0089] In this embodiment, the delivery track of the printing medium is as follows: the printing medium enters from the left side of the roller 130, is wound around the tensioning roller, the second heating roller 162, and the first heating roller 161 in sequence, and then is wound on the roller 130. The printing medium passes through the air ionizing bar 180, the four inkjet printhead assemblies 110 and the corresponding four first UV curing assemblies 171, the second UV curing assembly 172, and the second drying device 400 in sequence.

Finally, the printing medium exits from the lower side of the left side of the roller 130 after being reversed around the roller 130.

[0090] Obviously, the above-mentioned embodiments of the present disclosure are only examples to clearly describe the technical solutions of the present disclosure, and are not intended to limit the particular embodiments of the present disclosure. Any modification, equivalent replacement and improvement made within the spirit and principles of the claims of the present disclosure should fall within the scope of protection of the claims of the present disclosure.

Claims

CONCLUSIONS

1. Inkjet printing system with an external drying device, comprising an unwinding device, a roller printing device, a first drying device and a winding device, wherein a printing medium to be printed can be unfolded by the unwinding device and can be subjected to inkjet printing by the roller printing device, after which the printed printing medium can be dried can be wound up by the first drying device and ultimately by the winding device; and wherein the print medium is configured to enter and exit on the same side of the roll printer and the first dryer is externally located on the same side.

The ink-jet printing system of claim 1, wherein each of the unwinding devices and the winding device includes a first sensor and/or a second sensor, the printing medium being in the form of a roll material, the first sensor being configured to measure a thickness of the roll material obtainable by measuring a rolling surface position of the printing medium; and the second sensor is configured to obtain an offset of the roll material by measuring an edge position of the print medium.

3. The ink-jet printing system of claim 1, wherein the first dryer includes a box housing and heaters, cross-flow fans and transmission rollers disposed in an interior cavity of the box housing, the cross-flow fans and transmission rollers being vertically opposed and spaced at intervals in the longitudinal direction of the bucket body are placed; and the print medium can be passed successively through openings between the transmission rollers and the cross-flow fans.

4. The ink-jet printing system according to claim 3, wherein the box housing successively contains a horizontal section and an inclined section in a delivery direction of the printing medium, a ratio of a length of the inclined section to a length of the horizontal section is greater than or equal 1s to 2, and the inclined section has a slope angle of 25° to 30°.

The ink-jet printing system of claim 3, wherein the winding device further comprises a guide belt, the first drying device correspondingly further comprising a traction mechanism disposed in the inner cavity of the carton housing thereof; wherein the guide belt can be unfolded by the winding device, can be clamped by the traction mechanism and can be delivered to the other side of the loading container in an opposite direction to the delivery direction of the printing medium; and the guide belt can pass successively through the openings between the transmission rollers and the cross-flow fans.

The ink-jet printing system of any one of claims 1 to 5, wherein the roller printing device includes a roller configured to wind and deliver the printing medium; an inkjet printhead assembly configured to perform inkjet printing on the printing medium; and a linear movement configured to drive the ink-jet printhead assembly to adjust a distance between the ink-jet printhead assembly and a surface of the roller; wherein the ink-jet printhead assembly includes an ink-jet printhead carrier and a plurality of ink-jet printheads mounted on the ink-jet printhead carrier, the plurality of ink-jet printheads are distributed in a plurality of rows parallel to the ink-jet printhead carrier and the ink-jet print heads in the two adjacent rows are in a staggered and overlapping distribution; and the plurality of ink-jet printheads are mounted obliquely to the ink-jet printhead carrier and disposed about the surface of the roller, lower surfaces of the plurality of ink-jet printheads are combined into a recessed inkjet surface and each surface of the recessed inkjet surface is tangential to the surface of the roller.

The ink-jet printing system of claim 6, wherein the ink-jet printhead carrier has a first reference line pointing toward a circular center of the roller surface, nozzle openings of each of the ink-jet printheads have a second reference line pointing toward an inkjet direction of the nozzle openings, and an included angle between the first reference line and the second reference line defining a deflection angle ¢, wherein the inkjet print heads are mounted obliquely with respect to the deflection angle ¢ with respect to the first reference line, and a calculation formula for the deflection angle ¢ is ¢ = tan? =e L refers to a distance between the nozzle openings and the first reference line; H refers to a height from the ink-jet printhead carrier to the surface of the roller; a refers to an included angle between a direction of movement of the nozzle openings and the first reference line; and R refers to a radius of the surface of the roller.

8. The ink jet printing system of claim 6, wherein the roller printing apparatus further includes a first heating roller, or a first heating roller and a second heating roller, and wherein the first heating roller is configured to heat a printing surface of the printing medium, the second heating roller is configured to heat a back side of the printing medium and the printing medium is wound on the first heating roller and the roller in sequence, or the printing medium is wound on the second heating roller; the first heating roller and the roller in order.

9. The ink-jet printing system of claim 6, wherein the roller printing apparatus further includes a first UV curing assembly and a second UV curing assembly configured to cure ink attached to the surface of the printing medium in stages, and wherein the first UV curing assembly is positioned on one side of the ink-jet printhead carrier of the ink-jet printhead assembly, the second UV curing assembly is positioned away from the ink-jet printhead assembly, and the printing medium is the ink-jet printhead assembly, the first UV curing assembly and can traverse the second UV curing assembly in sequence.

10. The ink-jet printing system of claim 6, wherein the roller printing device further includes an air ionization bar configured to remove static electricity on the surface of the printing medium, and is capable of traversing the printing medium in sequence through the air ionization bar and the ink-jet printhead assembly.