Tablet printer and tablet printing method

Abstract

To provide a tablet printer and a tablet printing method which can stably print tablets while preventing lowering of productivity.SOLUTION: A tablet printer 1 includes a supply device 10 for storing a plurality of tablets T, and subsequently supplying the stored tablets T, a conveyance device 20 for conveying the tablets T supplied from the supply device 10, an inkjet type printing head 51 for discharging an ink droplet onto the tablets T conveyed by the conveyance device 20, and printing the tablets T, a maintenance device 80 for performing maintenance of the printing head 51, and a control device 90 for controlling the printing head 51, and the maintenance device 80, wherein the control device 90 allows the maintenance device 80 to execute the maintenance at timing set on the basis of the kinds of the tablets T supplied from the supply device 10, when printing the tablets T.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] An embodiment of the present invention relates to a tablet printing apparatus and a tablet printing method. [Background technology]

[0002] A technology is known that uses an inkjet print head to print identification information such as letters and symbols on tablets. A tablet printing device that uses this technology transports multiple tablets in a line on a conveyor, and ejects ink (e.g., edible ink) from the nozzles of an inkjet print head arranged above the conveyor toward the tablets that pass under the print head, thereby printing the identification information on the tablets on the conveyor.

[0003] Inkjet print heads are periodically maintained to maintain their ejection performance. More specifically, maintenance includes wiping to remove ink and other substances adhering to the surface (nozzle surface) where the nozzles of the print head are located, and dummy ejection to discharge a fixed amount of ink from the nozzles to maintain stable ejection from the nozzles. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-58220 A Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, among tablets, there are tablets (hereinafter simply referred to as plain tablets) that are not coated on the surface, such as plain tablets and OD (orally disintegrating) tablets (oral disintegrating tablets). In such tablets, the fine powder that constitutes the tablet is easily separated from the tablet. If the fine powder separated from the tablet adheres to the nozzle surface of the print head, it will cause ejection defects. Therefore, when printing on plain tablets, it is necessary to set the timing of maintenance according to the characteristics of the above-mentioned plain tablets. However, since printing on tablets cannot be performed during maintenance, frequent maintenance will lead to a decrease in productivity.

[0006] An object of the present invention is to provide a tablet printing device and a tablet printing method that can stably print on tablets while preventing a decrease in productivity. [Means for solving the problem]

[0007] The tablet printing device of the embodiment comprises a supplying device that stores a plurality of tablets and sequentially supplies the stored tablets, a transporting device that transports the tablets supplied from the supplying device, an inkjet type print head that prints by ejecting ink droplets onto the tablets transported by the transporting device, a maintenance device that performs maintenance on the print head, and a control device that controls the print head and the maintenance device, and when printing on the tablets, the control device causes the maintenance device to perform maintenance at a timing set based on the type of tablet supplied from the supplying device.

[0008] The tablet printing method of the embodiment comprises a supplying process for sequentially supplying tablets, a transporting process for sequentially transporting the supplied tablets, a printing process for printing by ejecting ink droplets from an inkjet print head onto the tablets being transported, and a maintenance process for performing maintenance on the print head at a predetermined timing, and the maintenance process, which is performed while the printing process is being performed, is performed at a timing set based on the type of tablets being supplied.

[0009] The tablet printing device of the embodiment comprises a supply device that stores a plurality of tablets and sequentially supplies the stored tablets, a transport device that transports the tablets supplied from the supply device, an inkjet type print head that prints by ejecting ink droplets onto the tablets transported by the transport device, a maintenance device that performs maintenance on the print head, and a wiper maintenance device that performs maintenance on a wiper provided in the maintenance device, wherein the wiper includes a wiper that wipes the nozzle surface of the print head and absorbs liquid adhering to the nozzle surface, and the wiper maintenance device comprises a suction nozzle that sucks up the liquid held by the wiper.

[0010] The tablet printing method according to the embodiment includes a supplying step of sequentially supplying tablets, a transporting step of sequentially transporting the supplied tablets, a printing step of printing by ejecting ink droplets from an inkjet print head onto the tablets being transported, a print head maintenance step of performing maintenance using a maintenance device having a suction section that suctions the nozzle face of the print head and a wiper that wipes the nozzle face of the print head, and a wiper maintenance step of suctioning liquid held by the wiper using a suction nozzle, and is characterized in that a suction source that applies suction force to the suction nozzle and a suction source that applies suction force to the suction section are common. Effect of the Invention

[0011] According to an embodiment of the present invention, printing can be stably performed on tablets while preventing a decrease in productivity. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a front view showing a schematic configuration of a tablet printing apparatus according to a first embodiment. [Diagram 2] FIG. 1 is a plan view showing a schematic configuration of a tablet printing apparatus according to a first embodiment. [Diagram 3] 1 is a diagram illustrating an example of a schematic configuration of a maintenance device according to a first embodiment. [Figure 4] FIG. 2 is a diagram illustrating an example of a schematic configuration of a control device according to the first embodiment. [Diagram 5] FIG. 2 is an operation state diagram of the maintenance device according to the first embodiment. [Figure 6] FIG. 13 is a diagram illustrating an example of a schematic configuration of a maintenance device according to a second embodiment. [Figure 7] 10 is a flowchart showing a maintenance process according to a second embodiment. [Figure 8] FIG. 11 is a diagram illustrating an example of a portion of a maintenance device according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] <First embodiment> The first embodiment will be described with reference to FIGS.

[0014] (Example of tablet printing device configuration) As shown in Figures 1 and 2, the tablet printing apparatus 1 of the first embodiment includes a supply device 10, a conveying device 20, a detection device 30, a first imaging device 40, a printing device 50, a second imaging device 60, a collection device 70, a maintenance device 80 (see Figure 2), and a control device 90.

[0015] The supply device 10 has a hopper 11 and a chute 12. The supply device 10 is positioned at one end side of the conveying device 20, and is configured to be able to supply tablets T, which are printing objects, to the conveying device 20. The hopper 11 stores a large number of tablets T, and sequentially supplies the stored tablets T to the chute 12. The chute 12 aligns the tablets T supplied from the hopper 11 in a line and supplies them to the conveying device 20. The supply device 10 is electrically connected to a control device 90, and its drive is controlled by the control device 90.

[0016] The conveying device 20 has a conveying belt 21, a driving pulley 22, a plurality of driven pulleys 23, a motor 24, a position detector 25, and a suction chamber 26. The conveying belt 21 is an endless belt and is stretched over the driving pulley 22 and each driven pulley 23. The driving pulley 22 and each driven pulley 23 are rotatably provided on the device body (not shown), and the driving pulley 22 is connected to the motor 24. The motor 24 is electrically connected to the control device 90, and its driving is controlled by the control device 90. The position detector 25 is a device such as an encoder and is attached to the motor 24. This position detector 25 is electrically connected to the control device 90 and transmits a detection signal to the control device 90. The conveying device 20 rotates the conveying belt 21 together with each driven pulley 23 by the rotation of the driving pulley 22 by the motor 24, and conveys the tablets T on the conveying belt 21 in the rotation direction of the arrow H1 in FIG. 1, i.e., in the conveying direction H1.

[0017] A plurality of circular suction holes 21a (see FIG. 2) are formed in the conveyor belt 21. These suction holes 21a are through holes that suck the tablets T, and are arranged in two parallel rows along the conveying direction H1 to form two conveying paths. Each suction hole 21a is connected to the inside of the suction chamber 26 (see FIG. 1) through a suction path (not shown) formed in the suction chamber 26, and it is possible to obtain suction force from the suction chamber 26. A pump is connected to the suction chamber 26 through a suction pipe (not shown), and the inside of the suction chamber 26 is depressurized by the operation of the pump. The suction pipe is connected to approximately the center of the side surface (plane parallel to the conveying direction H1) of the suction chamber 26. In addition, the pump is electrically connected to the control device 90, and its drive is controlled by the control device 90. When the inside of the suction chamber 26 is depressurized, the tablets T placed on each suction hole 21a of the conveyor belt 21 are sucked by the suction hole 21a and held on the conveyor belt 21.

[0018] The detection device 30 includes a plurality of detection units 31 (two in this embodiment). The detection units 31 are positioned downstream in the conveying direction H1 from the position where the supply device 10 is provided, and are provided above the conveyor belt 21. The detection units 31 detect the position of the tablet T on the conveyor belt 21 in the X direction (see FIG. 2) by projecting and receiving laser light. For example, a displacement sensor or a proximity sensor is used as the detection unit 31. For example, various laser sensors such as a reflective laser sensor are used as the displacement sensor. The detection device 30 is electrically connected to the control device 90, and transmits a detection signal to the control device 90.

[0019] The first imaging device 40 includes a plurality of first imaging units 41 (two in this embodiment). The first imaging unit 41 is positioned downstream in the conveying direction H1 from the position where the detection device 30 is provided, and is provided above the conveyor belt 21. Based on the position information of the tablet T in the X direction detected by the detection device 30, the first imaging unit 41 performs imaging at the timing when the tablet T reaches the imaging position directly below the first imaging unit 41, acquires a first image (image for tablet position detection) including the upper surface of the tablet T, and transmits the acquired first image to the control device 90. The first image is used to detect the positions of the tablet T in the X direction, Y direction, and θ direction. As the first imaging unit 41, various cameras having imaging elements such as a CCD (charge-coupled device) or a CMOS (complementary metal oxide semiconductor) are used. The first imaging device 40 is electrically connected to the control device 90, and its drive is controlled by the control device 90. In addition, illumination for imaging is also provided as necessary.

[0020] Here, the positions of the tablet T in the X and Y directions are, for example, positions in the XY coordinate system relative to the center (reference position) of the imaging area of ​​the first imaging unit 41. The position in the θ direction is, for example, a position indicating the degree of rotation of the tablet T relative to the center line in the Y direction of the imaging area of ​​the first imaging unit 41. This position in the θ direction is detected when the tablet T has a shape having a directional property, such as when a score line is provided on the tablet T or when the tablet T is molded into an ellipse, an oval, a rectangle, or the like.

[0021] The printing device 50 has a print head 51 and an elevation mechanism 52. The print head 51 is positioned downstream in the transport direction H1 from the position where the first imaging device 40 is provided, and is provided above the transport belt 21. The print head 51 has a plurality of nozzles 51a (for example, several hundred to several thousand) (see FIG. 2), and is provided so that the direction in which the nozzles 51a are arranged in a row (nozzle row) is perpendicular (one example of intersection) to the transport direction H1 in a horizontal plane. Note that in FIG. 2, for the sake of simplicity, four nozzles 51a are shown. The print head 51 ejects ink from each nozzle 51a individually by the operation of a drive element for each nozzle 51a. As the print head 51, various inkjet type print heads having drive elements such as piezoelectric elements, heat elements, or magnetostrictive elements are used. The print head 51 can be raised and lowered by the elevation mechanism 52 (see FIG. 1) so as to approach or move away from the transport belt 21. The print head 51 is raised and lowered during maintenance of the print head 51. Maintenance of the print head 51 will be described later. The printing device 50 is electrically connected to a control device 90, and its drive is controlled by the control device 90.

[0022] The second imaging device 60 includes a plurality of second imaging units 61 (two in this embodiment). The second imaging unit 61 is positioned downstream in the conveying direction H1 from the position where the printing device 50 is provided, and is provided above the conveyor belt 21. The second imaging unit 61 performs imaging at the timing when the tablet T reaches the imaging position directly below the second imaging unit 61 based on the position information of the tablet T in the X direction detected by the first imaging unit 41 and the detection unit 31, acquires a second image including the upper surface of the tablet T, and transmits the acquired second image to the control device 90. The second image is used to inspect the print pattern printed on the tablet T. As the second imaging unit 61, various cameras having imaging elements such as CCD and CMOS are used, as in the first imaging unit 41 described above. The second imaging device 60 is electrically connected to the control device 90, and its drive is controlled by the control device 90. In addition, illumination for imaging is also provided as necessary.

[0023] The recovery device 70 is positioned downstream in the conveying direction H1 from the position where the second imaging device 60 is provided, and is provided at the end of the conveying device 20 on the downstream side in the conveying direction H1. The conveying device 20 releases the tablet T when the tablet T on the conveying belt 21 reaches a predetermined position, for example, the end of the conveying device 20 on the downstream side in the conveying direction H1. The recovery device 70 is configured to collect the tablets T that are released from the conveying device 20 and fall, separating them into defective and non-defective. For example, by blowing gas onto the tablets T in the middle of falling, and changing the falling direction of the tablets T for defective and non-defective, or by changing the falling path by a member such as a plate, it is possible to collect the tablets T that fall into defective and non-defective. For example, the defective tablets are tablets that fail printing, and the non-defective tablets are tablets that pass printing. The recovery device 70 is electrically connected to the control device 90, and its drive is controlled by the control device 90.

[0024] 2 and 3, the maintenance device 80 includes a liquid receiving unit 81, a suction unit 82, a wiper 83, and a movement mechanism 84. The maintenance device 80 is provided so as to be aligned with the print head 51 in the direction in which the nozzles 51a of the print head 51 are aligned in a plan view (Y direction in FIG. 2). Note that the movement mechanism 84 is omitted in FIG. 2 to simplify the illustration. Details of the maintenance device 80 will be described later.

[0025] During maintenance of the print head 51, the maintenance device 80 moves between the conveyor belt 21 and the print head 51 and cleans the underside (nozzle surface) of the print head 51. The maintenance device 80 is electrically connected to the control device 90, and its drive is controlled by the control device 90.

[0026] The control device 90 controls each part of the tablet printing device 1, such as the supply device 10, the transport device 20, the detection device 30, the first imaging device 40, the printing device 50, the second imaging device 60, the recovery device 70, and the maintenance device 80, based on various information and various programs. The control device 90 also receives detection information (e.g., detection signals) transmitted from the position detector 25 and the detection device 30, and also receives image information transmitted from the first imaging unit 41 and the second imaging unit 61. The control device 90 is realized, for example, by an electronic circuit such as an integrated circuit or a computer.

[0027] Next, a configuration example of the control device 90 will be described with reference to FIG.

[0028] 4, the control device 90 has an image processing unit 91, a storage unit 92, and a control unit 93. An input device 90a and an output device 90b are connected to the control device 90. The input device 90a is realized by, for example, a switch, a touch panel, a keyboard, a mouse, etc. The output device 90b is realized by, for example, a display, a lamp, a meter, etc.

[0029] The image processing unit 91 captures the first image captured by the first imaging device 40 and the second image captured by the second imaging device 60, and processes the images using a known image processing technique. For example, the image processing unit 91 processes the first image obtained from the first imaging device 40, acquires the presence or absence of cracks, chips, and dirt on the tablet T, and further acquires the positions of the tablet T in the X direction, Y direction, and θ direction. The image processing unit 91 also processes the second image obtained from the second imaging device 60, and acquires the printing position, shape, and size of the printing pattern (e.g., letters and marks) printed on the tablet T. The image processing unit 91 transmits to the control unit 93 the acquired information on the presence or absence of cracks, chips, and dirt on the tablet T, the acquired position information on the X direction, Y direction, and θ direction of each tablet T, and further the printing position information, shape information, and size information of the printing pattern on each tablet T.

[0030] The storage unit 92 stores processing information, various programs, and the like. For example, it is realized by a semiconductor memory element such as a RAM (Random Access Memory) or a flash memory, or a storage device such as a hard disk or an optical disk. The storage unit 92 stores data on the type of tablet T to be printed, data on the ink used for printing, print data related to printing, data on the movement speed of the conveyor belt 21, and the like. The print data includes information on print patterns such as characters and marks.

[0031] The control unit 93 is, for example, a computer such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit), and controls each unit. For example, the control unit 93 controls the supply device 10, the transport device 20, the detection device 30, the first imaging device 40, the printing device 50, the second imaging device 60, the collection device 70, the maintenance device 80, the image processing unit 91, the storage unit 92, and the like, based on various information and various programs stored in the storage unit 92. The control unit 93 also receives detection signals transmitted from the detection device 30 and the position detector 25, and the like. The control unit 93 is realized, for example, by one or both of hardware and software.

[0032] For example, the control unit 93 acquires the position of the tablet T in the X direction on the conveyor belt 21 based on the detection information transmitted from the detection device 30, i.e., the timing at which the tablet T on the conveyor belt 21 was detected, and sets the imaging timing of the first imaging device 40, the print start timing of the print head 51 of the printing device 50, and the imaging timing of the second imaging device 60 based on the position information indicating the position of the tablet T in the X direction, generates timing information indicating these timings, and stores it in the storage unit 92. The print start timing is the timing at which printing is started on the tablet T that has reached the printing position directly below the print head 51. The control unit 93 can acquire information such as the movement amount (rotation amount) and speed of the conveyor belt 21 based on the detection information transmitted from the position detector 25.

[0033] Further, the control unit 93 sets whether or not printing is possible for the tablet T for which the presence / absence information has been obtained based on the presence / absence information of cracks, chips, and dirt on the tablet T transmitted from the image processing unit 91. Then, the control unit 93 sets printing conditions for the tablet T for which the presence / absence information has been obtained based on the position information of the tablet T in the X direction, Y direction, and θ direction transmitted from the image processing unit 91. For example, the control unit 93 determines the range of the nozzle 51a used for printing the target tablet T in the print head 51, that is, the nozzle range to be used, based on the position information of the tablet T in the Y direction and the printing data, and sets printing conditions including the nozzle range to be used and the timing of starting printing. In addition, when the tablet T has a shape having a directionality, the control unit 93 sets printing conditions corresponding to the position of the tablet T in the θ direction based on the position information of the tablet T in the θ direction. As an example, the control unit 93 registers 180 different printing patterns in the memory unit 92, in which the orientation of the printing pattern is rotated by 1 degree in a range from 0 degrees to 179 degrees, and selects from among these printing patterns a printing pattern with an angle that matches the position of the tablet T in the θ direction, and sets the printing conditions.

[0034] Furthermore, the control unit 93 judges whether or not the printed pattern has been printed in a predetermined shape and a predetermined size at a predetermined position on the tablet T, i.e., whether or not the printed pattern has been normally printed on the tablet T, based on the printing position information, shape information, and size information of the printed pattern printed on the tablet T transmitted from the image processing unit 91 (printing state inspection). For example, in judging the shape and size of the printed pattern, the control unit 93 registers a printing pattern for inspection in the memory unit 92, and compares the printing pattern for inspection with the printed pattern on the tablet T after actual printing (the printing pattern printed on the tablet T).

[0035] The control unit 93 appropriately stores various information (for example, information on the presence or absence of cracks, chips, and dirt on the tablet T, position information, timing information, printing conditions, print quality information, etc.) in the storage unit 92. When the target tablet T is collected by the collection device 70, for example, when the tablet T falls from the downstream end of the conveying device 20 in the conveying direction H1 and a predetermined time (for example, several seconds) has elapsed, the various information is deleted from the storage unit 92. However, if such information is required in a later process, it is possible to leave the various information for each tablet T without deleting it, or to store it in a storage medium outside the device. When storing the various information for each tablet T, this information may be linked to the manufacturing date and time, lot number, etc. and stored, so that when a defective product occurs after shipping for the printed tablet T, the cause can be traced back.

[0036] (Example of maintenance device configuration) Next, the configuration of the maintenance device 80 will be described with reference to Fig. 3. Fig. 3 is a diagram of the print head 51 and maintenance device 80 as viewed from the upstream side in the transport direction H1. As described above, the maintenance device 80 comprises the liquid receiving unit 81, the suction unit 82, the wiper 83, and the movement mechanism 84. When maintenance is not being performed, these are positioned so that, from the print head 51 side, the wiper 83, the suction unit 82, and the liquid receiving unit 81 are lined up in this order, and are provided so as to be movable as a unit by the movement mechanism 84.

[0037] The liquid receiving portion 81 is formed, for example, in a box shape that is open at the top. This liquid receiving portion 81 receives ink ejected from each nozzle 51a of the opposing print head 51 during maintenance of the print head 51. The length of the liquid receiving portion 81 in a direction perpendicular to the transport direction H1 is provided to be at least longer than the nozzle row in which the nozzles 51a are lined up. In the first embodiment, the length of the liquid receiving portion 81 in a direction perpendicular to the transport direction H1 is longer than two print heads 51 lined up (longer than the length of two print heads).

[0038] The suction unit 82 is a vacuum wiper having a slit-shaped suction port at its upper portion that extends in the transport direction H1. The length of the slit-shaped suction port is approximately the same as the length of the print head 51 in the transport direction H1. The suction unit 82 is connected to a suction pump (not shown). While the suction pump is operated, the suction unit 82 moves in a manner that scans the nozzle surface while in close proximity to the nozzle surface of the print head 51, thereby sucking up and removing ink adhering to the nozzle surface.

[0039] The wiper 83 wipes away and removes powder and ink adhering to the nozzle face by sliding in contact with the nozzle face of the print head 51. The wiper 83 has a first wiper 83a and a second wiper 83b.

[0040] The first wiper 83a has a liquid-absorbent fiber material, such as nonwoven fabric, on the upper part. The first wiper 83a is soaked with wiping liquid (e.g., an aqueous solution containing ethanol). In other words, the first wiper 83a is a wet wiper. The supply of wiping liquid to the first wiper 83a may be performed by an operator or may be automatically performed. By supplying the wiping liquid, the first wiper 83a is soaked with the wiping liquid.

[0041] The second wiper 83b has a liquid-absorbent fibrous material such as nonwoven fabric on its upper portion, similar to the first wiper 83a. The second wiper 83b is a dry wiper (no wiping liquid is supplied).

[0042] The movement mechanism 84 has a ball screw 84a, a slider 84b, and a motor 84c. The liquid receiving portion 81, the suction portion 82, and the wiper 83 are fixed to the slider 84b, and the ball screw 84a is rotated by the motor 84c, so that the movement mechanism 84 can be moved between a maintenance position and a standby position. Here, the maintenance position is the position of the maintenance device 80 when maintenance is being performed on the print head 51, and is a position between the conveyor belt 21 and the print head 51. The standby position is the position of the maintenance device 80 when maintenance is not being performed, and is a position shifted from above the conveyor belt 21 (a position toward the back of the paper in FIG. 1).

[0043] (Printing process) Next, the printing process performed by the tablet printing device 1 will be described with reference to Figs. 1 and 2. This printing process also includes an inspection process. Here, the printing process refers to continuously printing on a plurality of tablets T supplied from the supply device 10 and transported by the transport device 20. Various information such as data required for printing is stored in advance in the storage unit 92.

[0044] When the printing process of the tablet printing device 1 is started under the control of the control unit 93, the motor 24 is driven and the conveyor belt 21 rotates in the conveying direction H1 with the rotation of the drive pulley 22 by the motor 24. With the conveyor belt 21 rotating in the conveying direction H1, the tablets T are sequentially supplied from the hopper 11 to the chute 12, and are arranged in two rows by the chute 12 and supplied onto the conveyor belt 21. The tablets T supplied onto the conveyor belt 21 are arranged in two rows on the conveyor belt 21 and conveyed at a predetermined moving speed.

[0045] The tablet T on the conveyor belt 21 is detected by the detection device 30. More specifically, when the tablet T on the conveyor belt 21 reaches the laser light irradiation position of the detection unit 31 of the detection device 30, the arrival of the tablet T is detected by the detection unit 31 from a change in the received light output. Based on the timing at which the tablet T is detected, the position of the tablet T in the X direction on the conveyor belt 21 is recognized by the control unit 93. Then, position information indicating the position of the tablet T in the X direction is generated by the control unit 93 and stored in the memory unit 92.

[0046] Next, the tablet T on the conveyor belt 21 is imaged by the first imaging device 40. In detail, the tablet T on the conveyor belt 21 is imaged by the first imaging device 40 at the timing when it reaches the imaging position directly below the first imaging device 40, and the first image obtained by imaging by the first imaging device 40 is transmitted to the control device 90. Based on this first image, information on the presence or absence of cracks, chips, and dirt on the tablet T, as well as position information on the tablet T in the X direction, Y direction, and θ direction are generated by the image processing unit 91 and stored in the memory unit 92. Whether or not printing is possible on the target tablet T is set based on the information on the presence or absence of cracks, chips, and dirt on the tablet T, and based on information such as the position information in the X direction, Y direction, and θ direction of the tablet T and the printing pattern, printing conditions including the nozzle range to be used and the printing start timing for the tablet T set to printable (printable tablet T) are set in the memory unit 92. In addition, the ejection timing for the tablet T (the timing for ejecting ink onto the tablet T) is determined based on the above-mentioned printing start timing (the timing for starting printing on the tablet T).

[0047] Printing is performed by the printing device 50 based on these printing conditions. That is, the control unit 93 controls the printing head 51 of the printing device 50 to print a predetermined printing pattern on the printable tablets T on the conveyor belt 21. In detail, the printable tablets T on the conveyor belt 21 that have passed under the first imaging device 40 are printed by the printing head 51 based on the above-mentioned printing conditions at the print start timing when the tablets T reach the printing position directly below the printing head 51. In the printing head 51, ink is appropriately ejected from each nozzle 51a, and a printing pattern (for example, a number, an alphabet, a katakana character, a symbol, a figure) is printed on the printing surface, which is the upper surface of the tablet T. The ink applied to the tablet T dries during transportation. In addition, a drying unit (not shown) that dries by gas or heat may be provided, and the ink may be dried by the drying unit.

[0048] Thereafter, the printed tablets T on the conveyor belt 21 are imaged by the second imaging device 60. In detail, the printed tablets T on the conveyor belt 21 are imaged by the second imaging device 60 at the timing when the tablets T on the conveyor belt 21 reach an imaging position directly below the second imaging device 60, and the second image obtained by imaging by the second imaging device 60 is transmitted to the control device 90.

[0049] This second image is analyzed by the image processing unit 91 of the control device 90. In detail, information regarding the printed pattern printed on the tablet T, i.e., the printing position, shape, and size of the printed pattern, is acquired by the image processing unit 91. The second image transmitted from the second imaging device 60 is analyzed by the image processing unit 91, and inspection information indicating the printing position, shape, and size of the printed pattern printed on the tablet T is generated and stored in the memory unit 92.

[0050] Based on this inspection information, the control unit 93 executes a print status inspection. In detail, based on the inspection information related to the printing position, shape, and size stored in the memory unit 92, the control unit 93 judges whether the printing pattern has been normally printed on the tablet T, and print quality information indicating whether the tablet T is printed properly is generated and stored in the memory unit 92. For example, in the print status inspection, the printing pattern used for printing is stored in the memory unit 92 as a printing pattern for inspection, and non-defective product information related to the predetermined printing position, shape, and size of the printing pattern for inspection is compared with inspection information related to the printing position, shape, and size of the actually printed printing pattern stored in the memory unit 92, and it is judged whether the printing pattern has been normally printed on the tablet T (pass or fail).

[0051] Finally, the tablets T on the conveyor belt 21 are collected by the collection device 70. More specifically, when the inspected tablets T are positioned at the downstream end of the conveyor belt 21 as the conveyor belt 21 moves, they are released from the state held by the conveyor belt 21, drop from the conveyor belt 21, and are collected by the collection device 70. At this time, the tablets T that passed the inspection drop as they are and are collected by the collection device 70 as non-defective products, but the tablets T that were rejected or non-printed are separated from the non-defective products by blowing air on them as they fall from the conveyor belt 21, and are collected by the collection device 70 as defective products.

[0052] (Maintenance process) In a printing operation that performs such a printing process, the maintenance of the print head 51 is performed at a predetermined timing. Examples of the maintenance method include purging, wiping, and dummy ejection. Purging is an operation in which ink is pumped from the print head 51 toward the liquid receiving portion 81 while the liquid receiving portion 81 is facing the print head 51, thereby ejecting the ink from the print head 51 toward the liquid receiving portion 81. By performing the purging operation, air bubbles and ink that has dried, thickened, or solidified can be removed from inside the nozzles 51a, thereby preventing ejection defects. Wiping is an operation to remove ink and the like that has adhered to the nozzle surface of the print head 51. Wiping is performed by suction using the suction portion 82 or wiping using the wiper 83. By performing wiping, powder and ink that has adhered to the nozzle surface can be removed, thereby preventing ejection defects. Dummy ejection is an operation (preliminary ejection operation) in which, while the liquid receiving portion 81 is facing the print head 51, the inkjet drive element is driven to eject a small amount of ink. The dummy ejection can also remove the thickened ink from inside the nozzle 51a. Note that the printing operation means that the tablet printing device 1 is in an operating state, that is, in a state in which printing can be performed, including the printing process and the maintenance process.

[0053] Incidentally, there are various types of tablets T, such as plain tablets, OD tablets (orally disintegrating tablets), and coated tablets (sugar-coated tablets, film-coated tablets, etc.). The amount of fine powder that may be generated by separating from the tablets T differs depending on the type of tablets T. Therefore, the amount of fine powder of the tablets T that may adhere to the nozzle surface of the print head 51 differs depending on the type of tablets T. In other words, even if printing is performed on tablets T for the same time or the same number of tablets, the amount of fine powder that adheres to the nozzle surface of the print head 51 differs. In other words, the degree of contamination of the nozzle surface by fine powder differs.

[0054] Therefore, in this embodiment, the timing of maintenance performed by the maintenance device 80 during the printing process is set based on the type of tablet T. More specifically, the timing of maintenance is set so that the interval between maintenance by the maintenance device 80 is longer during the printing process in which printing is performed on tablets T that are less likely to generate fine powder than during the printing process in which printing is performed on tablets T that are more likely to generate fine powder. For example, when the tablets T supplied from the supply device 10 are any of coated tablets, plain tablets, and orally disintegrating tablets, the timing is set so that the interval between maintenance by the maintenance device 80 is longer for plain tablets than for orally disintegrating tablets, and longer for coated tablets than for plain tablets.

[0055] Details of such a maintenance process will be described. First, the storage unit 92 of the control device 90 prestores information regarding the type of tablet T and the timing of maintenance performed during the printing process of the tablet T of that type. For example, if the types of tablets T are three types, coated tablets, plain tablets, and orally disintegrating tablets, the timing S1 of maintenance for the coated tablets, the timing S2 of maintenance for the plain tablets, and the timing S3 of maintenance for the orally disintegrating tablets are stored. The timings S1, S2, and S3 are the time between the execution of this maintenance and the execution of the next maintenance, and the relationship between them is S1>S2>S3. These timings S1, S2, and S3 can be obtained by performing a printing process for each tablet T and observing the degree of dirt due to the adhesion of fine powder to the nozzle surface of the print head 51.

[0056] When executing the printing process, the type of tablets T to be printed in the current printing process is input in advance and stored in the memory unit 92 of the control device 90. During the printing process, the control device 90 causes maintenance to be performed at a timing corresponding to the type of tablets T stored in the memory unit 92 based on the type of tablets T stored in the memory unit 92. For example, when the type of tablets T stored in the memory unit 92 is plain tablets, the control device 90 causes the maintenance device 80 to perform maintenance at a timing S2 corresponding to the plain tablets.

[0057] The maintenance operation is as follows: During the maintenance process, the supply of the tablets T by the supply device 10 is temporarily stopped.

[0058] When it is time to perform maintenance on the print head 51, the control device 90 controls the lifting mechanism 52 to lift the print head 51. More specifically, the print head 51 is lifted to a height position where the lower surface of the print head 51 does not come into contact with the suction unit 82 and the wiper 83 even when the suction unit 82 and the wiper 83 of the maintenance device 80 are moved. This forms a space between the conveyor belt 21 and the print head 51 into which the maintenance device 80 can enter.

[0059] Next, the control device 90 controls the movement mechanism 84 to position the liquid receiving part 81 so as to face the nozzle face of the print head 51. Furthermore, the control device 90 controls the lifting mechanism 52 to lower the print head 51 to a height where the nozzle face of the print head 51 does not come into contact with the suction part 82 but comes into contact with the wiper 83 when wiped, as shown in FIG.

[0060] In this state, the control device 90 pressure-feeds the ink in the print head 51 to perform a purging operation.

[0061] Next, the control device 90 controls the movement mechanism 84 to move the suction unit 82 and the wiper 83 to the left in Fig. 5. During this movement, the print head 51 is subjected to vacuum wiping by the suction unit 82, wet wiping by the first wiper 83a, and dry wiping by the second wiper 83b, in that order.

[0062] When these wiping operations are completed, the control device 90 controls the lifting mechanism 52 to raise the print head 51 to a height position where it will not come into contact with the suction unit 82 or the wiper 83. When the lifting of the print head 51 is complete, the control device 90 controls the movement mechanism 84 to position the liquid receiving unit 81 so that it faces the nozzle face of the print head 51. Then, with the liquid receiving unit 81 and the nozzle face of the print head 51 facing each other, the control device 90 causes the print head 51 to perform dummy ejection.

[0063] When the dummy discharge is completed, the control device 90 controls the moving mechanism 84 to move the maintenance device 80 (the suction unit 82 and the wiper 83) to a standby position. Next, the lifting mechanism 52 is controlled to lower the print head 51 to a height position where printing is performed on the tablets T. When the print head 51 is lowered, the maintenance process ends. When the maintenance process ends, the supply of tablets T by the supply device 10 is resumed, and a printing process is performed to print on the tablets T. Note that, although an example of performing purging, vacuum wiping, wet wiping, dry wiping, and dummy discharge has been described as the maintenance operation, it is not necessary to perform all of these, and the order of performing them may be set arbitrarily. For example, the process and order to be performed as the maintenance operation may be set for each type of tablet T.

[0064] The maintenance process performed during the printing process has been described. However, even during printing operation, a situation may occur in which the printing process is not performed for several hours due to some cause. For example, during unmanned operation for a long period of time, such as during nighttime operation, if a part becomes clogged in the supply device 10, it may become impossible to supply tablets T for several hours until an operator performs recovery work. In such a case, the print head 51 is in a standby state so that printing can be performed when the supply of tablets T is resumed.

[0065] In this embodiment, in response to such a case, the timing S4 of maintenance during the time when the supply of the tablets T from the supply device 10 is stopped during printing operation is stored in the memory unit 92. While the supply of the tablets T is stopped, no fine powder is generated from the tablets T. Therefore, there is almost no adhesion of fine powder to the nozzle surface of the print head 51 compared to during the printing process. Therefore, the timing of maintenance does not need to consider the dirt on the nozzle surface due to the adhesion of fine powder, and it is sufficient to mainly consider the thickening of the ink due to the drying of the ink in the nozzle 51a. For this reason, the timing S4 is set to a value larger than any of the timings S1, S2, and S3 set in the printing process. In other words, it is set so that the interval between maintenance is longer.

[0066] As a result, when the supply of tablets T from the supply device 10 is stopped during printing operation, the control device 90 performs maintenance on the print head 51 at a timing S4 that is set longer than the interval between maintenance operations performed during the printing process.

[0067] In addition, when the supply of the tablets T is stopped for a long time, the driving of the conveying device 20 may be stopped. More specifically, the rotation of the conveying belt 21 may be stopped, and the decompression in the suction chamber 26 may be stopped. In such a case, in addition to the fact that there is almost no adhesion of fine powder to the nozzle surface as described above, the airflow around the nozzle surface of the print head 51 is also weakened. That is, the airflow caused by the rotation of the conveying belt 21 is no longer generated, and the suction from the suction holes 21a of the conveying belt 21 is no longer generated, so that the airflow generated around the nozzle surface due to these factors is no longer generated. If the airflow around the nozzle surface is weakened, the replacement of air near the opening of the nozzle 51a becomes slow, so that the solvent atmosphere of the ink near the opening of the nozzle 51a is easily maintained, the drying of the ink in the nozzle 51a is suppressed, and the thickening of the ink due to drying is suppressed. Therefore, in such a case, the maintenance timing S4 is set so that the maintenance interval is longer than when the supply of the tablets T from the supply device 10 is simply stopped. For example, if the timing for maintenance when the supply of tablets T from the supply device 10 is simply stopped is set to S4a, the timing for maintenance when the supply of tablets T from the supply device 10 is stopped and the operation of the conveying device 20 is stopped is set to timing S4b, which is less frequent than timing S4a (i.e., the interval between maintenance is longer).

[0068] As a result, when the supply of tablets T from the supply device 10 is stopped and the drive of the conveying device 20 is stopped while printing is in progress, the control device 90 performs maintenance of the print head 51 at a timing S4b that is set so that the maintenance interval is longer than the maintenance interval when the supply of tablets T from the supply device 10 is simply stopped.

[0069] The fact that the supply of tablets T from the supply device 10 has stopped can be known, for example, by the presence or absence of a detection signal from the detection device 30. That is, when the amount of tablets T supplied from the supply device 10 is less than the planned production number of tablets T (the amount that should be supplied from the supply device 10) but the detection signal for tablets T is not output from the detection device 30 for a predetermined period of time, it can be determined that the supply of tablets T from the supply device 10 has stopped.

[0070] As described above, according to the first embodiment, the tablet printing device 1 includes a supply device 10 that stores a plurality of tablets T and sequentially supplies the stored tablets T, a conveying device 20 that conveys the tablets T supplied from the supply device 10, an inkjet type print head 51 that prints by ejecting ink droplets onto the tablets T conveyed by the conveying device 20, a maintenance device 80 that performs maintenance on the print head 51, and a control device 90 that controls the print head 51 and the maintenance device 80. When printing on the tablets T, the control device 90 causes the maintenance device 80 to perform maintenance at a timing set based on the type of tablets T supplied from the supply device 10. This makes it possible to stably print on the tablets T while preventing a decrease in productivity. That is, according to the tablet printing device 1 of the first embodiment, when printing is performed on a type of tablet T that requires a high frequency of maintenance of the print head 51, the maintenance timing can be set so that the maintenance interval is shorter than when printing is performed on a type of tablet T that does not require a high frequency of maintenance of the print head 51. For this reason, when printing is performed on a type of tablets T that does not require frequent maintenance of the print head 51, it is possible to prevent maintenance from being performed more frequently than necessary, and even when printing is performed on a type of tablets T that requires frequent maintenance, it is possible to perform maintenance of the print head 51 at an appropriate timing. As a result, it is possible to stably print on the tablets T while preventing a decrease in productivity.

[0071] In the first embodiment, the timing of maintenance is set so that the interval of maintenance by the maintenance device 80 is longer for tablets T that are less likely to generate fine powder than tablets T that are more likely to generate fine powder. As a result, for example, the timing of maintenance can be set so that the interval of maintenance is shorter for tablets T that are more likely to generate fine powder (the interval of maintenance is longer for tablets T that are less likely to generate fine powder). Therefore, when printing is performed on tablets T that are less likely to generate fine powder and for which fine powder is less likely to adhere to the nozzle surface of the print head 51, the timing of maintenance can be set so that the interval of maintenance is longer than when printing is performed on tablets T that are more likely to generate fine powder and for which fine powder is more likely to adhere to the nozzle surface of the print head 51. As a result, when printing is performed on tablets T that are less likely to adhere to fine powder on the print head 51, it is possible to prevent maintenance from being performed more frequently than necessary, and when printing is performed on tablets T that are more likely to generate fine powder and tablets T that are less likely to generate fine powder, maintenance of the print head 51 can be performed at an appropriate timing. This makes it possible to stably print on the tablets T while preventing a decrease in productivity.

[0072] In the first embodiment, when any one of coated tablets, plain tablets, and orally disintegrating tablets T is supplied from the supply device 10, the timing of maintenance by the maintenance device 80 is set so that the interval between maintenance is longer for plain tablets than for orally disintegrating tablets, and longer for coated tablets than for plain tablets. In general, fine powder is more likely to be generated from tablets T than uncoated tablets and orally disintegrating tablets than uncoated tablets. Therefore, by setting the timing of maintenance as described above, the more easily fine powder is generated from tablets T, the more frequent the maintenance of the print head 51 is, and the less easily fine powder is generated from tablets T, the less frequently the maintenance of the print head 51 is. As a result, when printing is performed on tablets T on which fine powder is less likely to adhere to the nozzle surface of the print head 51, it is possible to prevent maintenance of the print head 51 from being performed more frequently than necessary, and when printing is performed on tablets T on which fine powder is more likely to adhere to the nozzle surface of the print head 51, it is possible to perform maintenance of the print head 51 at an appropriate timing. This allows stable printing on tablets T while preventing a decrease in productivity.

[0073] Furthermore, in the first embodiment, while the supply of tablets T from the supply device 10 is stopped, the timing of maintenance by the maintenance device 80 is set so that the interval between maintenance is longer than when printing is performed on the tablets T. This makes it possible to prevent maintenance from being performed more frequently than necessary on the print head 51 in a standby state when the print head 51 is in a standby state without tablets T being supplied from the supply device 10. As a result, in addition to the above-mentioned effects, it is possible to reduce the consumption of ink involved in maintenance while maintaining stable ejection from the nozzles 51a of the print head 51.

[0074] In the first embodiment, the conveying device 20 includes a conveying belt 21 having a plurality of suction holes 21a and a suction unit that applies negative pressure to the suction holes 21a to suction and hold the tablets T in the suction holes 21a. The control device 90 sets the timing of maintenance so that the interval between maintenance by the maintenance device 80 is the longest while the supply of the tablets T from the supply device 10 is stopped and the suction unit is stopped. As a result, when the print head 51 is in a standby state without the tablets T being supplied from the supply device 10 and the ink in the nozzles 51a of the print head 51 is in a state where thickening of the ink is unlikely to occur, the timing of maintenance can be set so that the interval between maintenance is longer than that described above. As a result, it is possible to further reduce the consumption of ink associated with maintenance.

[0075] <Second embodiment> In this embodiment, components common to the first embodiment will be described using the same reference numerals.

[0076] Incidentally, when printing on tablets that are prone to generating powder, such as plain tablets, powder may be generated and the generated powder may adhere to the nozzle surface. Normally, in the nozzle 51a of the inkjet print head 51, the ink filled in the nozzle 51a is adjusted to form a concave surface by a meniscus at the discharge port due to the head difference with the ink container connected to the print head 51. Therefore, when purging is performed, a part of the ink pushed out from the nozzle 51a is drawn into the nozzle 51a together with the powder adhering to the discharge port and the periphery of the discharge port of the nozzle 51a in order to form the meniscus again. This may cause the nozzle 51a to become clogged, resulting in poor discharge.

[0077] Therefore, when the tablet T to be printed is a tablet that is prone to generating powder, such as an uncoated tablet, in the maintenance of the print head 51, wiping is performed before purging (before the ejection operation is performed) to remove the powder adhering to the nozzle surface. In other words, after wiping, purging is performed, and then wiping is performed again. Below, the maintenance process of the print head 51 when the tablet T to be printed is an uncoated tablet will be described.

[0078] As shown in FIG. 6, the second wiper 83b in this embodiment has a liquid-absorbent fiber material such as nonwoven fabric on the upper part, similar to the first wiper 83a. The second wiper 83b is a dry wiper (no wiping liquid is supplied). The suction nozzle 82a is connected to the suction pump 82c described above via a pipe 82b. The second wiper 83b is provided with a suction nozzle 82a so that a suction force can be applied to its surface. The pipe 82b branches midway and is connected to the suction unit 82. The pipe 82b is provided with a switching valve 82d and a switching valve 82e, and by switching these, it is possible to switch between applying and not applying the suction force from the suction pump 82c to the suction unit 82 and also to switch between applying and not applying the suction force from the suction pump 82c to the suction nozzle 82a.

[0079] The maintenance process for the print head 51 is shown in Fig. 7. The process shown in Fig. 7 is executed by each unit under the control of the control device 90. The type of tablet T to be printed is input in advance by the operator via the input device 90a when starting the printing operation, and is stored in the memory unit 92. While the maintenance process is being carried out, the supply of tablets T by the supply device 10 is temporarily stopped.

[0080] When it is time to perform maintenance on the print head 51, the lifting mechanism 52 is controlled to lift the print head 51 (step S101). This increases the distance between the conveyor belt 21 and the print head 51. At this time, the print head 51 is lifted to a height position where the lower surface of the print head 51 does not come into contact with the suction unit 82 and the wiper 83 even if the suction unit 82 and the wiper 83 are moved as described below.

[0081] Next, the movement mechanism 84 is controlled to position the liquid receiving portion 81 so that it faces the nozzle face of the print head 51. Furthermore, the lifting mechanism 52 is controlled to lower the print head 51 to a height where the nozzle face of the print head 51 does not come into contact with the suction portion 82 but comes into contact with the wiper 83 when wiped, as shown in Fig. 5 (step S102).

[0082] The movement mechanism 84 is controlled to move the suction unit 82 and the wiper 83 to the left in Fig. 5. As a result, the print head 51 is subjected to vacuum wiping by the suction unit 82, wet wiping by the first wiper 83a, and dry wiping by the second wiper 83b in this order (step S103). This wiping removes powder adhering to the nozzle surface of the print head 51.

[0083] At this time, in order to apply the suction force from the suction pump 82c only to the suction portion 82, the switching valve 82d is in a closed state and the switching valve 82e is in an open state.

[0084] When the first wiping is completed, the lifting mechanism 52 is controlled to lift the print head 51 (step S104). When the print head 51 has lifted, the movement mechanism 84 is controlled to position the liquid receiving portion 81 so as to face the nozzle face of the print head 51. Furthermore, the lifting mechanism 52 is controlled to lower the print head 51 to a height at which the wiper 83 comes into contact with the nozzle face of the print head 51 when wiping, as shown in FIG. 5 (step S105).

[0085] Thereafter, the ink in the print head 51 is pumped out to perform a purging operation (step S106).

[0086] Next, a second wiping is performed. The movement mechanism 84 is controlled to move the suction unit 82 and the wiper 83 to the left in FIG. 5. As a result, the print head 51 is subjected to vacuum wiping by the suction unit 82, wet wiping by the first wiper 83a, and dry wiping by the second wiper 83b in this order (step S107). The second wiping is the same operation as the first wiping in step S103 described above.

[0087] When the second wiping is completed, the lifting mechanism 52 is controlled to lift the print head 51 (step S108). When the print head 51 has lifted, the movement mechanism 84 is controlled to position the liquid receiving portion 81 so as to face the nozzle face of the print head 51 (step S109). With the liquid receiving portion 81 and the nozzle face of the print head 51 facing each other, the inkjet driving elements of the print head 51 are driven to perform dummy ejection (step S110).

[0088] When the dummy discharge is completed, the movement mechanism 84 is controlled to move the maintenance device 80 (the suction unit 82 and the wiper 83) to the standby position (step S111), and the lifting mechanism 52 is controlled to lower the print head 51 to a height position for performing the printing operation (step S112). When the print head 51 is lowered, the maintenance process is completed. When the maintenance process is completed, the supply of tablets T by the supply device 10 is resumed, and the printing operation is performed.

[0089] (Wiper maintenance process) In this way, when the tablet T to be printed is a tablet that generates a lot of powder, such as an uncoated tablet, when performing regular maintenance of the print head 51, first, a first wiping is performed to remove the powder, and then a second wiping is performed after purging. In this way, with each repetition of wiping, the first wiper 83a gradually dries out and its moisturizing power decreases, and the second wiper 83b gradually gets wet and its liquid absorption efficiency deteriorates. Therefore, maintenance of the wiper 83 is performed.

[0090] Here, a mechanism for maintaining the wiper 83 is referred to as a wiper maintenance mechanism, and the wiper maintenance mechanism includes a suction nozzle 82a, a pipe 82b, a suction pump 82c, switching valves 82d and 82e, a tank S described below, and a tongue portion 83a1 (all of which are shown in FIG. 8).

[0091] The control unit 93 judges whether the number of maintenance operations has reached a predetermined number, and when it judges that the predetermined number has been reached, it issues a warning, such as by displaying a message on a display device (not shown) to request the first wiper 83a to supply wiping liquid. This causes the operator to additionally supply wiping liquid to the first wiper 83a. When the supply is completed, the operator presses a button on the display device, and the control unit 93 judges that the maintenance of the first wiper 83a has been completed.

[0092] Furthermore, when the control unit 93 determines that the number of maintenance operations has reached a predetermined number, the control unit 93 opens the switching valve 82d and closes the switching valve 82e so that the suction force from the suction pump 82c acts on the suction nozzle 82a. In this way, the suction nozzle 82a sucks up and dries the excess liquid that has soaked into the second wiper 83b. The position at which the suction nozzle 82a is provided may be a position facing the second wiper 83b, and may be a position at which the suction force from the suction pump 82c can suck up the liquid held by the second wiper 83b. However, since the suction nozzle 82a moves together with the second wiper 83b, it is desirable to provide the suction nozzle 82a at a position lower than the nozzle surface of the print head 51 so as not to contact the nozzle surface. The maintenance of the second wiper 83b is performed in parallel with the maintenance of the first wiper 83a. When the suction of the second wiper 83b is performed for a predetermined time, the control unit 93 determines that the maintenance of the second wiper 83b is completed.

[0093] The predetermined number of maintenance operations can be determined and set in advance by experiments or the like, either when the first wiper 83a dries and is no longer able to wipe off the powder or ink adhering to the nozzle surface of the print head 51, or when the liquid absorption efficiency of the second wiper 83b decreases and it is no longer able to absorb the liquid (ink or wiping liquid) adhering to the nozzle surface of the print head 51. The ink used varies depending on the type of tablet T, and when the percentage of volatile solvents such as ethanol contained in the ink is low, the time until the liquid absorption efficiency of the second wiper 83b decreases tends to be shorter. Therefore, it is desirable to determine the predetermined number of operations by experiments or the like for each type of ink used for the tablet T. In addition, the timing of maintenance of the first wiper 83a and the second wiper 83b does not have to be simultaneous. In this case, the specified number of times for maintenance is determined by determining the time until maintenance is required for each of the first wiper 83a and the second wiper 83b (as described above, the time until the first wiper 83a dries out and is no longer able to wipe off powder and ink adhering to the nozzle face of the print head 51, and the time until the liquid absorption efficiency of the second wiper 83b decreases and it is no longer able to absorb liquid adhering to the nozzle face of the print head 51), and setting each as the specified number of times for maintenance.

[0094] When the control unit 93 determines that the maintenance of the first wiper 83a and the second wiper 83b is completed, the control unit 93 starts the printing process again.

[0095] By carrying out such a maintenance process for the wiper 83, the wiper 83 can be continuously used without needing to be replaced, thereby reducing costs.

[0096] A roll-shaped wiper having an axis in a direction perpendicular to the direction in which the nozzles 51a are arranged may be used as the wiper 83. In this case, when maintenance of the wiper 83 is completed, the wiper 83 may be rotated so that the portion of the first wiper 83a with the most wiping liquid attached and the portion of the second wiper 83b that is the driest are positioned opposite the nozzle surface.

[0097] Further, in the above embodiment, the supply of wiping liquid to the first wiper 83a is performed by an operator, but a predetermined amount of wiping liquid may be automatically supplied by a supply nozzle (not shown).

[0098] As shown in FIG. 8, the first wiper 83a may be configured to be constantly supplied with wiping liquid. That is, a tongue portion 83a1, which is a part of the first wiper 83a, is dripped and immersed in a tank S in which wiping liquid is stored. Since the material of the first wiper 83a is a fiber material having a liquid-absorbent property such as a nonwoven fabric, the wiping liquid in the tank S is supplied to the first wiper 83a by the capillary phenomenon through the tongue portion 83a1. When such a configuration is used, the maintenance process of the wiper 83 described above may include only the maintenance of the second wiper 83b. Alternatively, the maintenance process of the wiper 83 may include refilling the tank S with wiping liquid or changing the length of the tongue portion 83a1. The lower part of the main body of the first wiper 83a may be immersed in the wiping liquid in the tank S.

[0099] In addition, the maintenance of the wiper 83 is performed when the maintenance process of the print head 51 reaches a predetermined number of times, but it is not limited to this and may be performed constantly in parallel with the printing process and the maintenance of the print head 51. That is, the first wiper 83a is always supplied with wiping liquid by a method using a tank S shown in FIG. 8. In addition, the switching valve 82d of the second wiper 83b is always open, and the suction nozzle 82a is always sucking the surface of the second wiper 83b. During the maintenance of the print head 51, the switching valve 82e is also open, but the suction nozzle 82a may be used to perform suction at the same time in parallel without closing the switching valve 82d.

[0100] As described above, according to the first embodiment, the maintenance of the wiper 83 can be appropriately performed, so that the life of the wiper 83 can be extended and the frequency of replacement of the wiper 83 can be reduced. This can reduce costs. In addition, the suction pump 82c used for the suction unit 82 and the suction pump 82c that applies suction force to the suction nozzle 82a used to dry the second wiper 83b are the same, so that the limited space of the tablet printing device 1 can be used effectively.

[0101] Furthermore, when replacing the wiper 83, it is necessary to perform a highly accurate height adjustment in order to wipe the nozzle surface of the print head 51 by contacting it with an appropriate pressure, which takes time. During the time required to replace the wiper 83 and adjust the height, the tablet printing device 1 must be stopped. According to this embodiment, the frequency of replacing the wiper 83 can be reduced, so that the stoppage of the tablet printing device 1 due to the replacement of the wiper 83 can be minimized, and production efficiency can be improved.

[0102] <Other embodiments> In the above description, two print heads 51 are provided, but one or three or more may be provided. Also, one maintenance device 80 may be provided for one print head 51, or one maintenance device 80 may be shared by multiple print heads 51.

[0103] Further, although the liquid receiving portion 81, the suction portion 82, and the wiper 83 are shown as being moved integrally in the above embodiment, the present invention is not limited to this and each of them may be provided so as to be movable independently.

[0104] Also, although an example has been given in which the wiper 83, the suction unit 82, and the liquid receiving unit 81 are moved by the moving mechanism 84 so as to face the print head 51, this is not limiting. For example, the print head 51 may be moved, or both the print head 51 and the maintenance device 80 may be moved. In other words, it is sufficient to configure the print head 51 and the maintenance device 80 to move relative to each other.

[0105] Moreover, the second wiper 83b may be, for example, a blade, as long as it can remove the wiping liquid (cleaning liquid) adhering to the nozzle surface.

[0106] In addition, although the information on the ink used for printing is input to the control device 90 by the operator via the input device 90a, this is not limiting. For example, the tablet printing device 1 may be equipped with an RF tag reading unit, and when an ink container (bottle or cartridge) is attached to the tablet printing device 1, the RF tag attached to the ink container may be read to obtain the ink information. Also, a barcode or two-dimensional code may be attached to the ink container, and the ink information may be input to the tablet printing device 1 by reading this.

[0107] In addition, the above-mentioned maintenance process is exemplified as being performed periodically during printing operation, but is not limited to this, and may also be performed when a discharge defect in the nozzle 51a or a printing defect is detected based on the second image.

[0108] In the first embodiment, the timing of maintenance is set based on the type of tablet T, but the present invention is not limited to this and may be set based on the type of ink used to print on the tablet T. For example, ink thickens as it dries. When the ink in the nozzle 51a thickens, it may not be possible to eject the ink from the nozzle 51a. Therefore, when the ink in the nozzle 51a thickens, it is necessary to perform maintenance such as discharging the ink in the nozzle 51a. On the other hand, the ink varies in ease of drying depending on its composition (type). Therefore, the timing of maintenance to discharge the thickened ink differs depending on the type of ink. Therefore, it is necessary to set the timing of maintenance based on the type of ink.

[0109] In addition, even if the ink is easy to dry, if the ink ejection frequency from the nozzle 51a is relatively high, the ink in the nozzle 51a does not stay in the nozzle 51a for a long time, and thickening is unlikely to occur. Conversely, the ink in the nozzle 51a with a relatively low ejection frequency is likely to thicken because it stays in the nozzle 51a for a long time. Therefore, the timing of maintenance based on the type of ink should be set based on the nozzle 51a with the low ejection frequency in the print head 51. At this time, it is preferable to compare the timing of maintenance set based on the type of tablet T and set the timing of maintenance with a shorter maintenance interval.

[0110] In addition, in the above-mentioned maintenance process, the speed of wiping by the first wiper 83a and the second wiper 83b was not specifically mentioned, but the moving speed of the first wiper 83a and the second wiper 83b (the speed at which the wiper 83 slides on the nozzle surface of the print head 51) may be controlled by controlling the moving mechanism 84. For example, the control unit 93 may count the number of times the print head 51 is wiped, and when the number of times exceeds a predetermined number, the moving speed of the moving mechanism 84 may be reduced to reduce the moving speed of the first wiper 83a and the second wiper 83b. Alternatively, the control unit 93 may measure the time from the start of operation of the tablet printing device 1, and determine that the number of times of wiping by the wiper 83 has exceeded the predetermined number due to the passage of a predetermined time, thereby reducing the moving speed of the moving mechanism 84 to reduce the moving speed of the first wiper 83a and the second wiper 83b. As the operation time of the print head 51 increases, ink may also adhere to the nozzle surface of the print head 51 and accumulate. However, by reducing the movement speed of the moving mechanism 84 by the control unit 93, the wiping liquid held in the first wiper 83a in particular is sufficiently supplied to the nozzle surface of the print head 51, and the ink adhered to the nozzle surface can be suitably removed. The speed may be gradually reduced from the start of operation of the tablet printing device 1, not only when the wiping exceeds a predetermined number of times or when a predetermined time has elapsed. The wiping speed may be reduced only for either the first wiper 83a or the second wiper 83b, and the wiping liquid may be sufficiently supplied to the nozzle surface of the print head 51 by reducing the movement speed of only the first wiper 83a, and the adhered ink may be removed. In this case, it is preferable to configure the first wiper 83a and the second wiper 83b to be able to move independently. For example, one of the first wiper 83a and the second wiper 83b may be moved by the moving mechanism 84, and the other may be moved by a moving mechanism different from the moving mechanism 84 (in the same direction as the moving mechanism 84).

[0111] In the second embodiment, when the supply of wiping liquid to the first wiper 83a is to be performed automatically, a wiping liquid supply unit may be provided to the first wiper 83a. By providing the wiping liquid supply unit, the amount of wiping liquid supplied to the first wiper 83a can be changed by controlling the wiping liquid supply unit depending on whether the ink contains a fixing agent (e.g., a substance classified as a paste, gum base, or thickening stabilizer) or does not contain a fixing agent.

[0112] Also, a wet state detection sensor may be provided that detects the amount of wiping liquid contained in the first wiper 83a (the wet state of the first wiper 83a). The wet state detection sensor transmits a detection value to the control device 90. The control device 90 can determine the wet state of the first wiper 83a based on the detection value transmitted from the wet state detection sensor. The control device 90 may start a maintenance process for the wiper 83 based on the determination result.

[0113] The amount of wiping liquid supplied to the first wiper 83a may be adjusted according to the composition of the ink, for example, the type and content of the fixing agent.

[0114] In addition, in the above-mentioned maintenance process of the print head 51, the speed of wiping by the first wiper 83a and the second wiper 83b was not specifically mentioned, but the moving speed of the first wiper 83a and the second wiper 83b (the speed at which the wiper 83 slides on the nozzle surface of the print head 51) may be controlled by controlling the moving mechanism 84. For example, the control unit 93 may count the number of times the print head 51 has been wiped, and when the number of times exceeds a predetermined number, the moving speed of the moving mechanism 84 may be reduced to reduce the moving speed of the first wiper 83a and the second wiper 83b. Alternatively, the control unit 93 may measure the time from the start of operation of the tablet printing device 1, and determine that the number of times of wiping by the wiper 83 has exceeded the predetermined number due to the passage of a predetermined time, thereby reducing the moving speed of the moving mechanism 84 to reduce the moving speed of the first wiper 83a and the second wiper 83b. As the operation time of the print head 51 increases, ink may also adhere to the nozzle surface of the print head 51 and accumulate. However, by reducing the movement speed of the moving mechanism 84 by the control unit 93, the wiping liquid held in the first wiper 83a in particular is sufficiently supplied to the nozzle surface of the print head 51, and the ink adhered to the nozzle surface can be suitably removed. The speed may be gradually reduced from the start of operation of the tablet printing device 1, not only when the wiping exceeds a predetermined number of times or when a predetermined time has elapsed. The wiping speed may be reduced only for either the first wiper 83a or the second wiper 83b, and the wiping liquid may be sufficiently supplied to the nozzle surface of the print head 51 by reducing the movement speed of only the first wiper 83a, and the adhered ink may be removed. In this case, it is preferable to configure the first wiper 83a and the second wiper 83b to be able to move independently. For example, one of the first wiper 83a and the second wiper 83b may be moved by the moving mechanism 84, and the other may be moved by a moving mechanism different from the moving mechanism 84 (in the same direction as the moving mechanism 84). In addition, maintenance of the wiper 83 may be performed at this timing.

[0115] Also, for the maintenance of the second wiper 83b, it is possible to dry the surface of the second wiper 83b by ejecting drying gas onto it. However, the sprayed drying gas may dry out the nozzle surface of the print head 51, causing the ink in the nozzles 51a to harden, leading to printing defects. For this reason, drying by the suction nozzle 82a described above is most suitable. Drying gas may be sprayed in parallel with drying by the suction nozzle 82a, but in this case, it is preferable to spray the drying gas in a direction away from the nozzle surface of the print head 51 to prevent the nozzles 51a from drying out.

[0116] Here, the above-mentioned tablet T can include tablets used for medicine, food, cleaning, industrial or aromatic purposes. In addition, the tablet T can be a plain tablet (plain tablet), a sugar-coated tablet, a film-coated tablet, an enteric-coated tablet, a gelatin-coated tablet, a multi-layered tablet, a dry-coated tablet, etc., and various capsule tablets such as hard capsules and soft capsules can also be included in the tablet T. Furthermore, the shape of the tablet T can be a disk shape, a lens shape, a triangle shape, an oval shape, etc. In addition, when the tablet T to be printed is for medicine or food, an edible ink is preferably used as the ink to be used. As the edible ink, any of a synthetic pigment ink, a natural pigment ink, a dye ink, and a pigment ink can be used.

[0117] Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, modifications, and combinations can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0118] 1 Tablet printing equipment 10 Feeding device 20. Conveyor 21 Conveyor belt 30 Detection Device 40 First imaging device 50 Printing device 51 Print Head 60 Second imaging device 70 Recovery Device 80 Maintenance Equipment 81 Liquid receiving part 82 Suction part 83 Wiper 83a First Wiper 83b Second Wiper 84 Moving mechanism 90 Control device T Tablet

Claims

1. A supply device that stores a plurality of tablets and sequentially supplies the stored tablets; a conveying device that conveys the tablets supplied from the supplying device; An inkjet print head that ejects ink droplets onto the tablets transported by the transport device to perform printing; a maintenance device for performing maintenance on the print head; A control device that controls the print head and the maintenance device; Equipped with The control device, when performing printing on the tablets, causes the maintenance device to perform maintenance at a timing set based on the type of the tablets supplied from the supply device.

2. The tablet printing device according to claim 1 , wherein the control device sets the timing so that the interval between maintenance by the maintenance device is longer for the tablets that are less likely to produce fine powder than for the tablets that are more likely to produce fine powder.

3. The tablet printing device described in claim 2, wherein the control device sets the timing so that, when the tablets supplied from the supply device are coated tablets, uncoated tablets, or orally disintegrating tablets, the interval between maintenance by the maintenance device is longer for the uncoated tablets than for the orally disintegrating tablets, and longer for the coated tablets than for the uncoated tablets.

4. The tablet printing device according to any one of claims 1 to 3, wherein the control device sets the timing so that the interval between maintenance by the maintenance device is longer while the supply of the tablets from the supply device is stopped than when printing is performed on the tablets.

5. The conveying device includes a conveying belt having a plurality of suction holes, and a suction unit that applies negative pressure to the suction holes to suck and hold the tablet in the suction holes, The tablet printing device of claim 4, wherein the control device sets the timing so that the interval between maintenance by the maintenance device is the longest while the control device stops the supply of the tablets from the supply device and stops the suction unit.

6. The maintenance device includes a wiper that wipes a nozzle surface of the print head, a liquid receiving portion that receives ink ejected from the print head, and The tablet printing apparatus according to claim 4 , further comprising:

7. a supply step of sequentially supplying tablets; a conveying step of sequentially conveying the supplied tablets; a printing step of printing by ejecting ink droplets from an inkjet print head onto the tablets being conveyed; a maintenance step of performing maintenance on the print head at a predetermined timing, A tablet printing method, wherein the maintenance process, which is performed while the printing process is being carried out, is performed at a timing set based on the type of tablet to be supplied.

8. A supply device that stores a plurality of tablets and sequentially supplies the stored tablets; a conveying device that conveys the tablets supplied from the supplying device; An inkjet print head that ejects ink droplets onto the tablets transported by the transport device to perform printing; a maintenance device for performing maintenance on the print head; a wiper maintenance device for performing maintenance on a wiper provided in the maintenance device; Equipped with the wiper includes a wiper that wipes a nozzle face of the print head and absorbs liquid adhering to the nozzle face, The wiper maintenance device of the tablet printing apparatus is provided with a suction nozzle that suctions the liquid held by the wiper.

9. the maintenance device further includes a suction unit that sucks the nozzle surface, The tablet printing apparatus according to claim 8 , further comprising a common suction source that applies suction force to the suction nozzle and the suction portion.

10. a control device that controls the print head and the maintenance device, 10. The tablet printing apparatus according to claim 8, wherein the control device issues a warning to perform maintenance by the wiper maintenance device when a number of times that the maintenance device has performed maintenance on the print head reaches a predetermined number.

11. a supply step of sequentially supplying tablets; a conveying step of sequentially conveying the supplied tablets; a printing step of printing by ejecting ink droplets from an inkjet print head onto the tablets being conveyed; a print head maintenance process in which maintenance is performed using a maintenance device having a suction unit that sucks the nozzle face of the print head and a wiper that wipes the nozzle face of the print head; a wiper maintenance step of sucking the liquid held by the wiper by a suction nozzle, A tablet printing method, wherein a suction source that imparts suction force to the suction nozzle and a suction source that imparts suction force to the suction portion are common.

12. The tablet printing method of claim 11 , wherein the print head maintenance step and the wiper maintenance step are performed simultaneously.

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