Printing device and method

Abstract

To provide a printing device which further improves a printing speed of roller digital printing.SOLUTION: The printing device includes: n printheads which communicate with at least two different inks, and are arranged along a first direction; a printing medium which is rotated around a rotary shaft, and is so located as to face the printhead; a movement control device which controls movement of the printhead and movement of the printing medium; and a printing drive mechanism which controls printhead printing. The printing medium is divided into s printing regions along the first direction, each printing region is printed by one printhead, and herein, s and n is a positive integer equal to or greater than 1. By dividing the printing region into a plurality of printing regions, a relative movement distance between the printhead and the printing medium in a printing end process is shortened, and further, the overall printing completion time is reduced.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to the field of inkjet printing, and more particularly to printing devices and methods. [Background technology]

[0002] Inkjet printing technology requires that an inkjet printhead and a printing medium are displaced relative to each other, and ink is ejected from the nozzles of the inkjet printhead according to an image to form ink droplets, which pass through the space between the printhead and the printing medium and are ejected at predetermined positions on the printing medium, and the formation of each ink droplet is controlled to achieve the formation of a printed image. Summary of the Invention [Problem to be solved by the invention]

[0003] In conventional roller digital printing, printing media such as clothing and paper are placed on rollers to achieve continuous printing and effectively improve printing efficiency. However, existing roller digital printing devices, such as the technical solution disclosed in JP2019123960, include multiple printheads, each arranged in a line and ejecting only one color of ink. Printing is completed when the entire print medium passes through all printheads equipped with various colors of ink. The distance the print medium passes in a straight line through the printheads is equal to the linear length of the print medium plus the linear length of all printheads. Therefore, the printing speed is determined by the linear movement speed and the distance. Furthermore, JP2019123960 only includes one roller, which requires replacement of parts after each printing job, resulting in delays in continuing production. To address the delays caused by part replacement, CN106427169A discloses a method for printing multiple rollers using a single printhead. This method prints with one roller while the other roller loads the print medium, reducing delays due to part replacement and improving printing efficiency. However, single-roller printing does not improve printing speed. Accordingly, CN110481157A discloses a roller printing device in which the printing direction of the print head (i.e., the direction of print head movement) forms a certain angle with the direction of the roller axis, allowing the print head and roller to move synchronously to print, thereby improving printing speed. However, due to the existence of the angle, once the print head moves a certain distance, there is no print medium below it. This printing method limits the length of the print medium, and cannot meet printing requirements for long print media. Therefore, how to further improve the printing speed of roller printing devices and meet the requirements for print media of various lengths remains a problem to be solved by those skilled in the art. [Means for solving the problem]

[0004] A printing device according to a first aspect of the present application includes n print heads that communicate with at least two different inks and are aligned along a first direction, a print medium that rotates around a rotation axis and is positioned opposite the print heads, a movement control device that controls movement of the print heads and the print medium, and a print drive device that controls printing by the print heads. The print medium is divided into s print areas along the first direction, and each print area is printed by a print head, where s and n are positive integers greater than or equal to 1.

[0005] Correspondingly, a printing method using the above-mentioned printing device is provided in a second aspect of the present application, comprising arranging n print heads along a first direction, connecting the print heads and the printing medium to a movement control device, dividing the printing medium into s printing areas along the first direction, the movement control device driving the printing medium to rotate around the rotation axis and driving the print heads and the printing medium to move relatively along the first direction, the print drive device controlling the print heads to print a pattern on the printing medium, and one printing area being printed by one print head.

[0006] A printing device and a printing method are provided in a third aspect of the present application, in which a printing medium is divided into multiple printing areas, and printing is performed using multiple print heads containing multiple different inks, thereby shortening the relative travel distance between the print heads and the printing medium during the printing process, thereby reducing the overall printing completion time and improving printing speed.

[0007] The fastest printing speed can be achieved by setting the print heads at approximately the same intervals along the first direction, the same lengths of the printing areas, and the same print head intervals and print area lengths. Furthermore, if the number of print heads does not match the number of printing areas, the print heads can be used alternately to balance the frequency of use of each print head and avoid various problems caused by overuse or underuse of the print heads. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic structural diagram illustrating a printing device according to an embodiment; [Figure 2] FIG. 2 is a schematic structural diagram showing a printing unit. [Figure 3] FIG. 2 is a schematic diagram showing an arrangement of nozzles. [Figure 4] FIG. 1 is a top view illustrating a printing device according to an embodiment. [Figure 5] 1 is a schematic structural diagram illustrating a printing device according to an embodiment; [Figure 6] 1 is a schematic cross-sectional view showing a print medium and a printhead. [Figure 7] FIG. 2 is a schematic diagram illustrating a printing process of a printing device according to an embodiment. [Figure 8] FIG. 10 is a schematic diagram illustrating the end of printing in a printing device according to an embodiment. [Figure 9-1] FIG. 2 is a schematic diagram illustrating a printing process of a printing device according to an embodiment. [Figure 9-2] FIG. 2 is a schematic diagram illustrating a printing process of a printing device according to an embodiment. [Figure 9-3] FIG. 2 is a schematic diagram illustrating a printing process of a printing device according to an embodiment. [Figure 9-4] FIG. 2 is a schematic diagram illustrating a printing process of a printing device according to an embodiment. [Figure 9-5] FIG. 2 is a schematic diagram illustrating a printing process of a printing device according to an embodiment. [Figure 9-6] FIG. 2 is a schematic diagram illustrating a printing process of a printing device according to an embodiment. [Figure 10-1] FIG. 2 is a schematic diagram illustrating a printing process of a printing device according to an embodiment. [Figure 10-2] FIG. 2 is a schematic diagram illustrating a printing process of a printing device according to an embodiment. [Figure 10-3] FIG. 2 is a schematic diagram illustrating a printing process of a printing device according to an embodiment. [Figure 10-4] FIG. 2 is a schematic diagram illustrating a printing process of a printing device according to an embodiment. [Figure 10-5] FIG. 2 is a schematic diagram illustrating a printing process of a printing device according to an embodiment. [Figure 10-6] FIG. 2 is a schematic diagram illustrating a printing process of a printing device according to an embodiment. [Figure 11-1] FIG. 2 is a schematic diagram illustrating a printing process of a printing device according to an embodiment. [Figure 11-2] FIG. 2 is a schematic diagram illustrating a printing process of a printing device according to an embodiment. [Figure 11-3] FIG. 2 is a schematic diagram illustrating a printing process of a printing device according to an embodiment. [Figure 12] 1 is a schematic structural diagram illustrating a printing device according to an embodiment; [Figure 13-1] FIG. 2 is a schematic diagram illustrating a printing process of a printing device according to an embodiment. [Figure 13-2] FIG. 2 is a schematic diagram illustrating a printing process of a printing device according to an embodiment. [Figure 14] 1 is a schematic structural diagram of a printing device according to an embodiment; [Figure 15-1] FIG. 2 is a schematic diagram illustrating a printing process of a printing device according to an embodiment. [Figure 15-2] FIG. 2 is a schematic diagram illustrating a printing process of a printing device according to an embodiment. [Figure 15-3] FIG. 2 is a schematic diagram illustrating a printing process of a printing device according to an embodiment. [Figure 16] 1 is a schematic structural diagram illustrating a printing device according to an embodiment; [Figure 17] 1 is a schematic structural diagram illustrating a printing device according to an embodiment; [Figure 18] 1 is a schematic structural diagram illustrating a printing device according to an embodiment; [Figure 19] 1 is a schematic structural diagram illustrating a printing device according to an embodiment; [Figure 20] 1 is a schematic structural diagram illustrating a printing device according to an embodiment; [Figure 21] 1 is a schematic structural diagram illustrating a printing device according to an embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0009] It should be noted that in the description herein, descriptive orientations or positional relationships, such as "center," "top," "bottom," "left," "right," "vertical," "horizontal," "inside," and "outside," are based on the orientations or positional relationships shown in the drawings and are intended solely to simplify the description of the present invention. They do not indicate or imply that the devices or elements referred to have a specific orientation or a structure or operation in a specific orientation, and therefore should not be understood as limiting the present invention. The terms "first," "second," and "third" are used for descriptive purposes only and should not be understood as indicating or implying relative importance. Furthermore, unless otherwise expressly specified and limited, the terms "attached," "coupled," and "connected" should be understood broadly, and may refer to, for example, a fixed connection, a detachable connection, or an integral connection; a mechanical connection, an electrical connection; a direct connection, an indirect connection via an intermediate medium, or internal communication between two elements. Those skilled in the art will understand the specific meanings of the above terms in this application under specific circumstances.

[0010] As shown in FIG. 1a, the printing device includes a motion controller 52 and a print driver 51. The motion controller 52 controls the movement of the print heads 56 and the print medium 30 via a transmission 57, and the print driver 51 controls the printing of the print heads 56. The motion controller 52 and transmission 57 can provide rotational and linear motion and control. An image data source 53 provides image material data that is converted into printing commands by an image processor 54. The term "image" herein includes any dot pattern specified by the image material. This may include graphic or text images. It may also include various 2D or 3D dot patterns used to print functional devices or three-dimensional structures. Such printing requires the use of appropriate inks. The motion controller 52 provides real-time feedback of the position of each print head 56 and the position of the print medium 30 to the print driver 51 and the image processor 54. The image processor can adjust the image data based on the relative positions of the print heads 56 and the print medium 30. The print driver 51 sends an output signal to an electric pulse source 55 based on image data converted by an image processor 54, and the electric pulse source 55 sends an electric pulse waveform to a print head 56. The print head 56 can also provide real-time feedback to the print driver 51 on information such as the print head temperature, which is used to adjust printing parameters (e.g., ink ejection voltage waveforms). The printing device includes at least one print head. The print driver 51 further instructs the print head 56 when to start and stop printing based on the position of the print head 56 and the position information of the print medium 30, and controls each print head, each printing unit, and each nozzle in the print head 56 throughout the process based on the pattern to be printed.

[0011] As shown in FIG. 1b, the printing device includes three identical printheads, a first printhead 1, a second printhead 2, and a third printhead 3, aligned along a direction 11. The printing device further includes a roller 20, a guide rail 40, an actuator 50, a transmission rod 60, and a motor 70, which form part of the transmission device in FIG. 1a. For clarity, the figure omits the connection and fixing structures between the drive and transmission device. The guide rail 40 extends longitudinally along the direction 11, and the printheads are distributed along the direction 11 and fixed to the guide rail 40. The axis of the roller 20 is G (dotted line in the figure) and can be driven to rotate about the axis G. The printing medium 30 may be embedded on the surface of the roller 20. A movement control device 52 issues a command, and the motor 70 drives the rotation of the transmission rod 60, which in turn drives the rotation of the roller 20. The rotation of the printing medium 30 mounted thereon can be controlled via the control roller 20. The roller 20 rotates along a rotation axis G, and drives the print medium 30 attached to its surface to rotate about the G axis. The movement control device 52 also controls the linear movement of the print heads on the guide rails 40 via actuators 50, which may be connected to the first print head 1, the second print head 2, and the third print head 3, respectively, and the three print heads may be connected to a common fixed and movable mechanical structure that moves linearly back and forth on the guide rails along the direction 11.

[0012] In an embodiment of the present invention, each printhead includes at least two printing units. FIG. 2 shows an arrangement of four printing units, using a first printhead 1 as an example. As shown in FIG. 2a, the first printhead 1 includes three printing units 10 arranged along a direction 11. The first printhead 1 communicates with three colors of ink, c1, c2, and c3, and each printing unit 10 communicates with one color of ink. c1, c2, and c3 may be any color, e.g., c1 is magenta ink, c2 is cyan ink, and c3 is yellow ink. FIG. 2b shows an arrangement of four printing units, with the four printing units 10 arranged along a direction 11. The first printhead 1 communicates with four colors of ink, c1, c2, c3, and c4, and each printing unit 10 communicates with one color of ink. c1, c2, c3, and c4 may be any colors, e.g., c1 is magenta ink, c2 is cyan ink, c3 is yellow ink, and c4 is black ink. As shown in FIG. 2c, the first printhead 1 includes four printing units 10, which are aligned along a direction 13 and have an angle between the direction 13 and a direction 11, the angle being between 0 and 90 degrees. The first printhead 1 communicates with four colors of ink, c1, c2, c3, and c4, and each printing unit 10 communicates with one color of ink. c1, c2, c3, and c4 may be any colors, e.g., c1 is cyan ink, c2 is yellow ink, c3 is magenta ink, and c4 is black ink. 2d, the first print head 1 includes four printing units 10, which are aligned along a direction 12, perpendicular to a direction 11, and communicate with four colors of ink c1, c2, c3, and c4, and each printing unit 10 communicates with one color of ink. c1, c2, c3, and c4 may be any colors, for example, c1 is yellow ink, c2 is magenta ink, c3 is cyan ink, and c4 is black ink.In another embodiment shown in Figure 2, the first print head 1 may also be connected to inks of different functions, for example, three printing units are connected to magenta ink, cyan ink, and yellow ink, respectively, and one printing unit is connected to a color fixing agent. The above is an example of four printing units, but other arrangements of printing units are also included.

[0013] Corresponding printing units in each printhead communicate with the same ink. For example, the printing units in the first printhead 1, second printhead 2, and third printhead 3 are all arranged as shown in Figure 2b, with printing unit c1 in the first printhead 1 communicating with cyan ink, and printing units c1 in the second printhead 2 and third printhead 3 also communicating with cyan ink. Printing unit c2 in the first printhead 1 communicating with magenta ink, and printing units c2 in the second printhead 2 and third printhead 3 also communicating with magenta ink. Printing unit c3 in the first printhead 1 communicating with yellow ink, and printing units c3 in the second printhead 2 and third printhead 3 also communicating with yellow ink.

[0014] Each printing unit in the printhead includes multiple nozzles. FIG. 3 shows the arrangement of four nozzles. As shown in FIG. 3a, the printing unit 10 includes six nozzles 100, marked 1, 2, 3, 4, 5, and 6, aligned in a row along direction 11. The six nozzles are aligned according to the mark numbers. As shown in FIG. 3b, the nozzles are aligned in a row along direction 13, with an angle between direction 13 and direction 11. As shown in FIG. 3c, the printing unit 10 includes two rows of nozzles 100 aligned in direction 11. The two rows of nozzles are spaced apart from each other along direction 12 and intersect with each other at a distance of 1 / 2 the center of each adjacent nozzle along direction 11. Each row includes four nozzles, with the nozzles in the first row marked 11, 12, 13, and 14, respectively, and the nozzles in the second row marked 21, 22, 23, and 24, respectively. 3d, the printing unit 10 includes a plurality of nozzles 100 arranged along a two-dimensional region (shown by the dotted line in the figure), with the length L of the two-dimensional region along direction 11 being greater than the width W of the two-dimensional region along direction 12, which is perpendicular to direction 11. The nozzles are arranged in four rows along direction 11, with each row including three nozzles. The nozzles in the first row are marked 11, 12, and 13, respectively; the nozzles in the second row are marked 21, 22, and 23, respectively; the nozzles in the third row are marked 31, 32, and 33, respectively; and the nozzles in the fourth row are marked 41, 42, and 43, respectively. Nozzles marked with the same mantissa are arranged in a single column, and the direction of the column forms an angle with respect to direction 12. The above shows four types of nozzle arrangement methods, and those skilled in the art will recognize that other types of nozzle arrangement methods can also be applied to the technical solution of the present application, and the number of nozzles is not limited to the technical solution shown in the figures, and may be any other number.

[0015] Furthermore, as shown in FIG. 1b, the printing device may include a printing medium 30 arranged opposite the print head, with the print head on top and the printing medium 30 on the bottom, with the nozzles of the print head facing the printing medium 30. The printing medium 30 is attached to a roller 20 and rotates around a rotation axis G. The cross section of the printing medium 30 in a plane perpendicular to the rotation axis G is circular, with the rotation axis G passing through the center of the circle (FIG. 5), and the rotation axis G is parallel to the direction 11. The print heads are aligned along the direction 11, and the centers of the nozzle arrays in the printing units (FIGS. 2 and 3) form a straight line along the direction 11 and are arranged in the same plane as the rotation axis G, which intersects with the curved surface of the cylindrical surface that constitutes the printing medium 30. The intersection line Q and the rotation axis G are parallel to the direction 11 and also parallel to the nozzle plate in each unit. The vertical distance between the intersection line Q and the nozzle plate of the print head, also referred to as the printing distance, may be controlled and adjusted via a mechanical structure (not shown) in which the actuator 50 and guide rail 40 are connected to the transmission rod 60. In the embodiment of FIG. 1b, the printing distance along direction 11 is constant. A constant printing distance ensures uniformity in print quality. For a particular print head, the closer the printing distance, the higher the print quality. The print medium 30 is divided into three printing areas along direction 11, named H area, J area, and K area, respectively, depending on the number of print heads.

[0016] The print medium 30 is inserted from the first end 21 to the second end 22 of the roller 20; that is, the print medium 30 is inserted from the first end 21 to the second end 22 until it is completely inserted onto the surface of the roller 20. The print medium 30 may be a cylindrical body (e.g., a wine bottle, a metal tube, a plastic tube, a cardboard tube, etc.), or a flexible material such as knitted fabric, cloth, plastic film, paper, or leather, such as socks, pants, or underwear, that can be fitted flat onto or covered by the cylindrical surface of the roller 20 in its normal shape. The size of the roller 20 is determined by the size of the print medium. It may be combined with the cylindrical body without slipping, or a flexible material may be required to have a sufficient surface area so that it can be flatly covered by the cylindrical body without overlapping or irreversible deformation. In the case of a rigid cylindrical body, it may be fitted onto an appropriate roller 20, or it may be directly connected to another rotation mechanism without using a roller. The axis of the other rotating mechanism or the axis of roller 20 overlaps with rotation axis G. The length of the printing medium 30 along direction 11 of roller 20 is m, and generally, the length along the axial direction of roller 20 is greater than m. When printing begins, the distance between the nozzle of the first print head 1 closest to the first end (e.g., hole 1 in FIG. 3a) and the first end 21 along direction 11 is a. The printing medium 30 equally divides the area according to the print head; that is, the length along the first direction of the H area, J area, and K area is c. The print heads are identical and are arranged at equal intervals b, which is also the distance between corresponding nozzles in adjacent print heads; that is, the relative positions of the nozzles in each print head are the same. Referring to FIGS. 2c and 3d, each print head has four printing units, and each printing unit has a two-dimensional nozzle array. The spacing between the first print head 1 and the second print head 2 is the distance along the first direction (direction 11) between the nozzle 21 in the printing unit c1 of the first print head 1 and the nozzle 21 in the printing unit c1 of the second print head 2.It also refers to the distance along the first direction between the nozzle 32 in the c2 unit of the first printhead 1 and the nozzle 32 in the printing unit c2 of the second printhead 2. Similarly, the spacing between the second printhead 2 and the third printhead 3 also refers to the distance between corresponding nozzles of adjacent printheads, and all spacings between adjacent printheads described below refer to the distance between corresponding nozzles of adjacent printheads. In the embodiment shown in Figure 1, m = a and b = c. When the length m of the intervening space changes, the spacing between the printheads is adjusted to make m = a and b = c = m / n.

[0017] Figure 4 is a top view of the printing device, omitting the actuators, connecting wires between the actuators and the printheads, brackets, and other components to more intuitively illustrate the positional relationship between the printheads and the printing medium. As shown in Figure 4a, the first printhead 1, the second printhead 2, and the third printhead 3 are aligned along direction 11, the printing units 10 in each printhead are aligned along direction 13, and the printing medium 30 is divided into three printing regions H, J, and K along direction 11 (the direction in which the rotation axis G is located). As shown in Figure 4b, the first printhead 1, the second printhead 2, and the third printhead 3 are aligned along direction 11, the printing units 10 in each printhead are aligned along direction 11, and the printing medium 30 is divided into three printing regions H, J, and K along direction 11. 4c, the first print head 1, the second print head 2, and the third print head 3 are aligned along a direction 11, the printing units 10 in each print head are aligned along a direction 12, and the printing medium 30 is divided into three printing areas H, J, and K along the direction 11. The above shows three patterns of the positional relationship between the print heads and the printing medium, and those skilled in the art will understand that the printing units may be aligned in other ways as long as the alignment direction of the print heads is parallel to the printing medium.

[0018] When the printing device is printing, the printing medium 30 continuously rotates around the rotation axis G at a constant angular velocity, and simultaneously, each print head synchronously advances at a constant speed along direction 11 to print. The movement direction of the print head coincides with the direction of the rotation axis G, ensuring that the print head always corresponds to the printing medium during the movement process and does not deviate from the printing medium. In multi-color printing, each printing unit corresponds to one color, and each time the printing medium rotates once, the print head advances in direction 11 a distance equal to the length of one printing unit of the print head along direction 11. The first print head 1 is responsible for printing area K, the second print head 2 is responsible for printing area J, and the third print head 3 is responsible for printing area H, and each printing area is printed by one print head. In the embodiment where m = a and b = c = m / n, the distance from each printhead to its respective printing area is equal, and therefore the required printing range is also equal. Each printhead starts printing simultaneously, finishes printing simultaneously, and completes the entire printing process. The relative movement distance between the printhead and the print medium is equal to the length of a single printhead along direction 11 plus the length of the printing area, i.e., c = b. Therefore, the larger the number of printheads (n), the smaller the spacing b between adjacent printheads, the smaller the corresponding printing area length c = b, and the faster the printing speed. The length of a printhead refers to the distance along direction 11 between the two furthest nozzles on a single printhead. For example, see Figures 2c and 3c for the first printhead. The length of the printhead may be the distance along first direction 11 between nozzle 11 in printing unit c1 on the first printhead 1 and nozzle 24 in printing unit c4 on the first printhead 1. The length of any printhead must be shorter than the length of , preferably less than half the length of the printing area. Furthermore, the length of the printing unit means the distance along the direction 11 between the two nozzles that are farthest apart in one printing unit. Taking printing unit c1 as an example, referring to Figure 3c, the length of the printing unit is the distance along the first direction between nozzle 11 and nozzle 24.The length of the printing unit is less than m / n and the length of the printhead is less than or equal to the number divided by the printing unit.

[0019] In another embodiment, the spacing between adjacent printheads may be unequal. The spacing difference between any two adjacent pairs of printheads can be designed to be no more than 50% of the spacing between any other adjacent pair of printheads. For example, the spacing difference between the first printhead 1 and the second printhead 2 and the second printhead 2 and the third printhead 3 does not exceed 50% of the spacing between the first printhead 1 and the second printhead 2 or the spacing between the second printhead 2 and the third printhead 3. The spacing difference between any two of the lengths of the print zones H, J, and K does not exceed 50% of the length of any print zone. If the spacing between the first printhead 1 and the second printhead 2 is equal to the length of the print area K, and the spacing between the second printhead 2 and the third printhead 3 is equal to the length of the print area J, then the distance along the direction 11 from the start of printing to the first end 21 of the third printhead 3 is equal to the length of the print area H, where K ≠ J ≠ H. In this case, it is possible for all three printheads to start printing simultaneously, but they will not finish printing simultaneously. The printing time is determined by the maximum spacing between adjacent printheads, which is also the length of the corresponding maximum print area. When printing on similar media, arranging printheads at uneven intervals takes longer and results in uneven printing losses for each printhead.

[0020] As shown in FIG. 5, when the printing medium 30 is a truncated cone, it can be a truncated cone of a normal shape, such as a paper cup, or a flexible material such as knitted fabric, cloth, plastic film, paper, or leather, such as socks, pants, or underwear. It can also be a flexible material with the surface size of a truncated cone, which forms a flat surface after being fitted or covered onto the surface of the truncated cone. The axis of the truncated cone is G (dotted line in the figure). When the truncated cone rotates around the axis, the printing medium 30 is driven to rotate around the rotation axis G. The cross section of the printing medium 30 in a plane perpendicular to the rotation axis G is circular, and the rotation axis G passes through the center of the circle. Although all of these cross sections of the truncated cone are circular, the diameters of the cross sections at different axis points are different. When using the cylinder / roller method of FIG. 1, the axis G is parallel to a line in the same plane, direction 11, and the intersection line Q between the surface of the truncated cone and the plane is inclined relative to direction 11. That is, the distance between the printing medium and the print head varies along the direction 11 (one end is closer to the print head and the other end is farther from the print head), i.e., the printing distance varies along the direction 11. This causes the printing position of the ink droplets to vary along the direction 11, resulting in uneven print quality and gradual deformation of the image. To solve this problem, in FIG. 4, the rotation axis G is tilted with respect to the direction 11 on the same plane, with the tilt angle equal to 90°-α, where α is the angle between the base of the larger diameter of the truncated cone and the line Q. After the rotation axis G is tilted, the line Q is parallel to the direction 11, so the printing distance is almost constant along the direction 11. The printing medium 30 is similarly divided into three printing areas along the direction 11, and each print head prints one printing area. An actuator 50 is connected to the first print head 1, the second print head 2, and the third print head 3, respectively, and controls the linear movement of the print heads along the guide rail 40. The motor 70 drives the rotation of the transmission rod 60, which drives the rotation of the roller 20, and controls the rotation of the print medium 30 about the G axis through the rotation of the roller 20. All other functions in Figure 5 are consistent with the descriptions in Figures 1 to 4.

[0021] The above embodiment solves the problem of varying distances between the print medium and the printhead along direction 11. As shown in FIG. 6 , in the direction perpendicular to the plane defined by axis G and direction 11, i.e., along the width of the printhead (direction 12 in FIG. 3 ), these printheads (e.g., printheads with nozzles arranged in a two-dimensional area) have a certain width. Because the surface of the print medium is an arc-shaped surface in this direction, the distances from the nozzles in the printhead to the print medium are not equal along the printhead width direction (direction 12). Taking the first printhead 1 as an example, the distances at which ink droplets ejected from nozzles at different positions along direction 12 fall on the print medium at relative positions are different. The distance between the nozzles in the middle position is closest, and the distance between the nozzles on both sides is farthest. If the roller radius is not significantly larger than the printhead width (r / d≫1), the difference in distance between the printhead nozzles and the print medium cannot be ignored. Therefore, the narrower the printhead width (the distance between the nozzles at both ends of the printhead along direction 12), the better, as r / d≫1 is satisfied. However, if the printhead width is too narrow, it will seriously affect the printing speed and resolution, so it is necessary to find the maximum printhead width that will achieve acceptable print quality. Let i be the distance from the most distal nozzle of the first printhead to the printing medium 30. Exceeding this distance will affect the printed effect. Let f be the distance from the middle nozzle of the first printhead to the printing medium, and r be the radius of the printing medium 30. Then, cosβ = (f + ri) / r, and the value of β can be obtained. The width of the first printhead is d = 2r * sinβ. If the width of the first printhead 1 is less than or equal to d, the required print quality can be achieved.

[0022] When the printing device shown in FIG. 1b prints, all printheads move synchronously and begin printing after entering their respective printing areas. FIG. 7 shows the printing process in progress, with the first printhead 1 entering area K and printing, while the second printhead 2 entering area J and printing, and the third printhead 3 entering area H. FIG. 8 shows the printing process completed, with each printhead printing its assigned area and then leaving the corresponding area, completing one printing pass. To print at a higher resolution and / or with a higher ink coverage, a similar printing device simply returns the printheads to their initial printing positions and repeats the printing process shown in FIGS. 1, 7, and 8. This printing process can be repeated multiple times, also known as multiple-pass printing. In the case of multi-color printing (one print head prints two or more colors), the distance the print head and the print medium move along the first direction each time the print medium rotates around is equal to e / k, where e is the length of one printing unit along the first direction, k is a pass, and k is a positive integer greater than or equal to 1. In the case of single-color printing, the relative distance the print head and the print medium move along the first direction each time the print medium rotates around is equal to e / k, the length of one print head along the first direction, and k is a positive integer equal to 1 (i.e., the number of passes). For clarity, actuators, connecting wires between the actuators and print heads, and motors are omitted from Figures 7 and 8, and the content of these parts will also be omitted from subsequent figures. This does not affect the understanding of those skilled in the art.

[0023] In an actual application process, the spacing b between the print heads and the length m of the printing medium 30 may not be the optimal match shown in Figures 1b and 7-8. Figures 9-1 to 9-6 show the printing process when the spacing b between adjacent print heads is greater than the length c of the printing area.

[0024] Specifically, as shown in Figure 9-1, the lengths of the print areas are equal (c = m / n), and the print heads are spaced apart at equal intervals b. Since b > c, and each print head is responsible for printing a corresponding area, the third print head 3 should be closest to the start of area H at the start of printing. The distance b between adjacent print heads and the length c of the print area determine that the distance from the second print head 2 to area J is greater, and the distance from the first print head 1 to area K is greatest. The result is a > m. When printing, the third print head 3 enters area H first and begins printing, while the other print heads proceed to their respective printing areas but do not print. As the print heads move forward, the second print head 2 enters area J and begins printing, as shown in Figure 9-2. At this time, the third print head 3 has already printed a portion of it, and the first print head 1 has not yet entered area K. The printheads continue to move along direction 11, and as shown in FIG. 9-3, the first printhead 1 enters region K and starts printing, while the second printhead 2 and third printhead 3 are both in the process of printing. The printheads continue to move forward, and as shown in FIG. 9-4, the third printhead 3 finishes printing, while the second printhead 2 and first printhead 1 are both in the process of printing. The printheads continue to move forward, and as shown in FIG. 9-5, the second printhead 2 finishes printing, while only the first printhead 1 prints region K. The printheads continue to move forward, and as shown in FIG. 9-6, the first printhead 1 finishes printing, while the second printhead 2 and third printhead 3 both finish printing, completing the print job on the print medium. 9-1 to 9-6, the first one to start printing finishes printing first, and the second one to start printing finishes printing later, so each print head starts printing at a different time and finishes printing at a different time. Compared with adjusting the print head positions so that b=c and m=a (as shown in FIG. 1), this method takes longer to print.

[0025] Similarly, FIGS. 10-1 to 10-6 show the printing process when b < c.

[0026] Specifically, as shown in FIG. 10-1, the lengths of the printing areas are equal (c = m / n), and the print heads are arranged at equal distances with an interval b between them. At the start position of the printing, the first print head 1 should be the closest to the start end of the K area, the second print head 2 should be farther from the J area, and the third print head 3 should be the farthest from the H area. When printing, the first print head 1 first enters the H area and starts printing, while the other print heads move to their respective printing areas but do not print. The print heads then continue to move forward. As shown in FIG. 10-2, the second print head 2 enters the J area and starts printing. At this time, the first print head 1 has already printed a part in the K area and continues printing, and the third print head 3 has not yet entered the H area. The print heads then continue to move along direction 11. As shown in FIG. 10-3, the third print head 3 enters the H area and starts printing. At this time, both the second print head 2 and the first print head 1 are in the printing process. The print heads then continue to move forward. As shown in FIG. 10-4, the first print head 1 completes the printing in the K area. At this time, both the second print head 2 and the third print head 3 are in the printing process. The print heads then continue to move forward. As shown in FIG. 10-5, the second print head 2 finishes printing. At this time, only the third print head 3 is printing the H area. The print heads then continue to move forward. As shown in FIG. 10-6, the third print head 3 finishes printing. At this time, both the second print head 2 and the first print head 1 have finished printing, and the printing work on the printing medium is completed. In the states shown in FIGS. 10-1 to 10-6, the one that starts printing first finishes printing first, and the one that starts printing later finishes printing later. The printing start times of each print head are different, and the completion times are also different. The printing time is longer than that in FIGS. 1, 7, and 8.

[0027] In the printing process of the above embodiment shown in Figures 9-10, the spacing between the print heads may not be equal, but the difference should not exceed 50%, and preferably the spacing is equal. The lengths of the print areas may also not be equal, but the difference should not exceed 50%, and preferably the lengths are equal. With the combination of different print spacings and different print area lengths, the order in which the print heads start and finish printing may differ from that shown in Figures 9-10, but the process is similar. Each print head starts printing at a different time and completes printing at a different time. This results in a longer printing time than the optimized layout shown in Figures 1, 6, and 7.

[0028] As shown in Figures 11-1 to 11-3, the printing device includes two print heads, the distance between the first print head and the second print head is b, and the printing medium is divided into three regions, of which the lengths of region J and region K are both c, and the length of region H can be less than c, and c and b are approximately equal.

[0029] When printing begins, the first print head 1 and the second print head 2 start printing at the same time as they move synchronously in the direction 11, as shown in FIG. 11-1. After the first print head 1 completes printing in the K region and the second print head 2 also completes printing in the J region (as shown in FIG. 11-2), the first print head 1 and the second print head 2 still move along the direction 11, but the first print head does not print until the second print head completes printing in the print region H and the second print head 2 completes printing on the print medium 3 (FIG. 11-3).

[0030] After the above printing is completed, the print head can move in the reverse direction to print, that is, the print head moves in the reverse direction along the direction 11, and when starting to print, the first print head 1 and the second print head 2 are positioned as shown in Figure 12, the first print head 1 prints the printing area J and the printing area K, and the second print head 2 prints the printing area H, and the printing process is similar to the method shown in Figures 11-1 to 11-3, but in the reverse direction.

[0031] As shown in Figures 13-1 to 13-2, when the length m of the printing medium is smaller than n*b, the printing device includes three print heads, the distance between the second print head 2 and the third print head 3 is b, the printing medium 30 is divided into two printing areas, and the lengths of the printing area H and the printing area J are both c, where c=b.

[0032] When starting printing, as shown in Fig. 13-1, all print heads move synchronously in the direction 11, the second print head 2 and the third print head 3 start printing at the same time, the third print head prints the printing area H, the second print head prints the printing area J, and the first print head 1 does not print. As shown in Fig. 13-2, the third print head 3 and the second print head 2 complete printing for the printing areas H and J respectively, and the first print head 1 does not print in this printing process.

[0033] Since long-term disuse of print head 1 will affect inkjet performance and maintenance will be wasteful, after printing multiple times, printing begins in the manner shown in Figure 14, where the distance between the first print head 1 and the second print head 2 is b, and b = c. The print heads move in the opposite direction of direction 11, with the first print head 1 printing in printing area J, the second print head 2 printing in printing area H, and the third print head 3 not printing.

[0034] As shown in Figures 15-1 to 15-3, the print heads can move synchronously or independently. In Figure 15-1, the first print head 1 is aligned with the edge of the printing area K, the second print head 2 is away from the printing area J, and part of the third print head 3 is in the printing area H. During printing, the third print head 3 can be moved first from the position shown in Figure 15-1 to the position shown in Figure 15-2, and the second print head 2 can be moved from the position shown in Figure 15-1 to the position shown in Figure 15-3, resulting in the embodiment shown in Figure 1. Alternatively, the print heads can be moved according to the length m of the printing medium, with the spacing between the print heads set to b = m / n and the length of each printing area set to c = b, similarly forming the embodiment shown in Figure 1. The speed at which the print head moves may also be different, for example, if different areas of the print medium require different resolution or some print areas need to be blank, and in areas where the resolution requirement is low or where the print head needs to be blank, the print head may scan over faster, and in areas where higher resolution is needed, the print head may print slower.

[0035] As shown in FIG. 16 , the printing areas may overlap, with an overlapping area I between printing area H and printing area J, where the length of area I is d, and d does not exceed 20% of the length of any of the printing areas H, J, and K. The overlapping area I is printed by both the first print head 1 and the second print head 2, with some of the dots in the overlapping area I being printed by the first print head 1 and the remaining dots being printed by the second print head 2. The provision of the overlapping area I facilitates feathering, making the connection between printing area H and printing area J more natural and improving print quality. In other printing cases involving overlapping areas, the same printing method as above may be used, and a description thereof will be omitted here.

[0036] While the embodiment of Figures 1-16 includes only one row of printheads, Figure 17 shows an embodiment including multiple rows of printheads along a cross section perpendicular to the G axis. In the multiple row printheads, each printhead corresponds to the printhead in the previous embodiment, with the printheads 41 in each row aligned along direction 11 and each row extending along direction 11. The printheads 41 in each row are parallel to each other and are positioned along a tangent to the cylindrical surface 42 whose distance to the roller 20 surface is the same as the shortest vertical distance h to the roller 20 surface. To improve printing resolution or speed, the printheads in each row may print interleaved with each other.

[0037] FIG. 18 shows a printing device in which a roller 20 rotates in the direction indicated by the arrow, and a printing medium 30 is coated on the surface of the roller 20. Three printheads 1, 2, and 3 are arranged along the direction 11. Each printhead includes four printing units 10, which are arranged along the direction 11. The nozzles in each printing unit 10 are arranged in four rows along the direction 11. The four printing units 10 eject black (K), cyan (C), magenta (M), and yellow (Y) inks, respectively, from left to right (the order of the ink positions may be interchanged). In the same printing unit, the first row of nozzles is symmetrically distributed with the fourth row of nozzles, and the second row of nozzles is symmetrically distributed with the third row of nozzles, with the distances from the corresponding two nozzles to the surface of the printing medium 30 being the same. Each color printing unit employs a multi-row nozzle design, which improves printing speed, increases nozzle redundancy, and extends printhead life. The figure shows only the structure of the first printhead 1, and the second printhead 2 and the third printhead 3 shown may have the same structure and are not marked in the figure for the sake of simplicity, which does not affect the understanding of those skilled in the art.

[0038] Figure 19 shows another printing device, which differs from Figure 18 in that the printheads are arranged in two rows along direction 11, with printheads 1, 2, and 3 in one row and printheads 4, 5, and 6 in the other row. The printheads in the two rows are arranged symmetrically, i.e., the first printhead 1 and the fourth printhead 4 are identical and symmetrical, the second printhead 2 and the fifth printhead 5 are identical and symmetrical, and the third printhead 3 and the sixth printhead 6 are identical and symmetrical. All of the printheads may have a structure similar to that shown in the first printhead 1. In each printhead, the first row of nozzles is mirrored to the fourth row of nozzles of the opposing printhead, the second row of nozzles is mirrored to the third row of nozzles of the opposing printhead, the third row of nozzles is mirrored to the second row of nozzles of the opposing printhead, and the fourth row of nozzles is mirrored to the first row of nozzles of the opposing printhead, with the distances from any two corresponding nozzles to the surface of the print medium 30 being the same. Using printheads with multiple rows can improve printing resolution and speed. The figure shows only the structures of the first printhead 1 and the fourth printhead 4; the other printheads may have identical structures and are not marked in the figure for simplicity's sake. This does not affect the understanding of those skilled in the art.

[0039] Figure 20 shows a printing device. It differs from Figure 19 in that the printheads are arranged in two rows along the direction 11, with printheads 1, 2, and 3 in one row and printheads 4, 5, and 6 in the other row, and the printheads in the two rows are interleaved. The gap between the first printhead 1 and the second printhead 2 is nearly aligned with the fourth printhead 4, and the gap between the second printhead 2 and the third printhead 3 is nearly aligned with the fifth printhead 5. Similarly, the gap between the fourth printhead 4 and the fifth printhead 5 is nearly aligned with the second printhead 2, and the gap between the fifth printhead 5 and the sixth printhead 6 is nearly aligned with the third printhead 3. The term "almost aligned" refers to the fact that the length of a printhead along the direction 11 is nearly equal to the length of the corresponding gap, and the printheads may be larger or smaller than the gap. The internal structure of each printhead may be any of the above-described structures. When printing, roller 20 rotates and each print head moves back and forth along direction 11, and the gaps between print heads in the same row are aligned with print heads in other rows, so that each print head only needs to move a distance equal to the width of one print head, rather than the print head width plus the distance between print heads, greatly improving printing efficiency.

[0040] Figure 21 shows another printing device, which differs from Figure 20 in that the printheads are arranged in four rows along direction 11, with printheads 1, 2, and 3 in the first row, printheads 4, 5, and 6 in the second row, printheads 7 and 8 in the third row, and printheads 9 and 17 in the fourth row, with the first and second rows positioned in the middle and the third and fourth rows positioned on either side. The printheads in the first and second rows are aligned, and the printheads in the third and fourth rows are aligned. The printheads in the first and third rows are staggered, and the printheads in the second and fourth rows are staggered. Specifically, the gap between the first printhead 1 and the second printhead 2 nearly corresponds to the seventh printhead 7, the gap between the second printhead 2 and the third printhead 3 nearly corresponds to the eighth printhead 8, and the gap between the seventh printhead 7 and the eighth printhead 8 nearly corresponds to the second printhead 2. The gap between the fourth printhead 4 and the fifth printhead 5 nearly aligns with the ninth printhead 9, the gap between the fifth printhead 5 and the sixth printhead 6 nearly aligns with the tenth printhead 17, and the gap between the ninth printhead 9 and the tenth printhead 10 nearly aligns with the fifth printhead 5. The structure within each printhead may be any of those described above. When printing, roller 20 rotates and each print head moves back and forth along direction 11, with the print heads in the two rows aligned and the gaps between print heads in the same row aligned with the print heads in the other row, so each print head only needs to move half the distance of the print head width and does not need to move the distance of the print head width plus the spacing between the print heads, making it more efficient than printing in Figure 20.

[0041] In other embodiments, the print head may not move, and the print medium may rotate and move along the first direction, which should be understood by those skilled in the art and can also achieve the technical effect of the present application.

[0042] The technical features of the above embodiments may be combined in any manner, and for the sake of brevity, not all possible combinations of the various technical features in the above embodiments are described; however, unless there is a contradiction, all combinations of these technical features should be considered within the scope of the present specification.

[0043] The above examples only show some embodiments of the present invention, and the descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent of the present invention. However, for those skilled in the art, without departing from the spirit of the present invention, all of these fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent of the present invention should be governed by the appended claims.

Claims

1. 1. A printing device, comprising: n printheads arranged along a first direction, each printhead communicating with at least two different inks and including at least two printing units, each printing unit communicating with one ink, and corresponding printing units in different printheads communicating with the same ink; a printing medium that rotates around a rotation axis and is arranged opposite the print head; a movement control device that controls the movement of the print head and the movement of the printing medium; a print driver for controlling printing of the print head; The printing medium is divided into s printing areas along the first direction, and each printing area is printed by one print head, where s and n are positive integers greater than or equal to 1; A printing device, characterized in that the line on which the rotation axis is located is on the same plane as the line on which the first direction is located.

2. A printing device as described in claim 1, characterized in that the printing units are arranged along the first direction, or the printing units are arranged along a second direction and have an angle between the second direction and the first direction.

3. 3. The printing device of claim 2, wherein the printing unit includes at least one row of nozzles, the nozzles in each row aligned along a first direction, or the nozzles in the at least one row aligned along a direction that is angled with the first direction.

4. 3. The printing device according to claim 2, wherein the printing unit includes at least two rows of nozzles, the nozzles in each row being aligned along a first direction and separated along a direction perpendicular to the first direction, and the nozzles in two adjacent rows being staggered along the first direction; or the printing unit includes a plurality of nozzles aligned along a two-dimensional area, the length of the two-dimensional area along the first direction being greater than the width of the two-dimensional area along a second direction perpendicular to the first direction.

5. 3. The printing device of claim 2, wherein any one of the printing units has a length e along the first direction, the printing medium has a length m along the first direction, and e is smaller than m / n.

6. 2. The printing device according to claim 1, wherein the printing medium is a cylinder or a truncated cone, the cross section of the printing surface of the printing medium perpendicular to the rotation axis is circular, and the rotation axis passes through the center of the circle.

7. A printing device as described in claim 1, characterized in that the intersection line between the plane and the surface of the printing medium closest to the print head is parallel to the first direction.

8. 2. The printing device according to claim 1, wherein the printing device includes a roller on which the print medium is fitted.

9. 2. The printing device according to claim 1, wherein all of the printing areas have the same length along the first direction, and the distance between two adjacent print heads is equal to the length of the printing area.

10. The adjacent printing areas partially overlap each other, and the length of the overlapping area along the first direction is less than 50% of the length of any of the printing areas including the overlapping area.

2. The printing device according to claim 1.

11. 2. The printing device according to claim 1, wherein the printheads are arranged in at least two rows along the first direction.

12. 1. A printing method comprising: arranging n print heads along a first direction; connecting the printhead and the print medium to the motion control device; Dividing the print medium into s print areas along the first direction; a motion control device that drives the print medium to rotate about the rotation axis and drives the print head and the print medium to move relative to each other along the first direction; A printing method using a printing device described in any one of claims 1 to 11, characterized in that the print drive device controls the print head to print a pattern on the printing medium, and one printing area is printed by one print head printing.

13. 13. The printing method of claim 12, wherein the relative movement distance between the print head and the printing medium along the first direction each time the printing medium rotates once is equal to e / k, where e is the length of one printing unit in the print head along the first direction, and k is a positive integer greater than or equal to 1.

14. 13. The printing method of claim 12, wherein, in a one-time printing process, when s<n, n-s print heads do not print; when s>n, at least one print head is responsible for printing two print areas; when s=n, lengths of all the print areas along the first direction are equal, the intervals between all two adjacent print heads are equal, the lengths of the print areas along the first direction are equal to the interval between the two adjacent print heads, and all the print heads start printing at the same time; or, when the lengths of the print areas along the first direction are not equal to the interval between the two adjacent print heads, the n print heads start printing in order according to their arranged order.

15. 13. The printing method of claim 12, wherein the spacing between adjacent print heads is adjustable, and the spacing between adjacent print heads is adjusted to b = m / n according to the length m of the printing medium along the first direction, and each printing area has a length c = b along the first direction.

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