Tablet printing machine

Abstract

To provide a tablet printing device capable of suppressing reduction in printing quality.SOLUTION: A tablet printing device 1 according to an embodiment includes: a transportation device 20 that transports a tablet T; an inkjet-type print head 51 that performs printing on a tablet T transported by the transportation device; a maintenance device 80 that performs maintenance of the print head 51; and a control device 90 that controls the print head 51 and the maintenance device 80. The control device 90 changes operation of the maintenance according to either one or both of a type of the tablet T to be transported and a type of an ink.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Embodiments of the present invention relate to a tablet printing device.

Background Art

[0002] To print identification information such as characters and symbols on tablets, a technique of performing printing using an inkjet printing head is known. A tablet printing device using this technique conveys a plurality of tablets in a row by a conveyor, and ejects ink (for example, edible ink) from the nozzles of an inkjet printing head disposed above the conveyor toward the tablets passing below the printing head, and prints identification information on the tablets on the conveyor.

[0003] In an inkjet printing head, maintenance of the printing head is periodically performed to maintain its ejection performance. Also, when ejection failure occurs, maintenance of the printing head is performed to restore the ejection performance.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Tablets without coating on their surfaces, such as plain tablets and OD (Orally Disintegrating) tablets (hereinafter simply referred to as plain tablets), may generate powder when the powder adhering to their surfaces falls off or the surfaces are scraped during conveyance. The generated powder may adhere to the nozzle surface of the printing head. If the nozzles are blocked by the powder adhering to the nozzle surface, it may cause ejection failure. The occurrence of ejection failure leads to a deterioration in print quality.

[0006] Therefore, efficient printhead maintenance is required depending on the type of tablet.

[0007] The present invention aims to provide a tablet printing apparatus that can prevent a decrease in print quality. [Means for solving the problem]

[0008] The tablet printing apparatus according to this embodiment comprises a conveying device for conveying tablets, an inkjet type print head for ejecting ink onto the tablets conveyed by the conveying device to perform printing, a maintenance device for maintaining the print head, the print head, and a control device for controlling the maintenance device. The maintenance device includes a wiper for wiping the nozzle surface of the print head and a liquid receiving section for receiving ink ejected from the print head. The control device determines the type of tablet being transported. If the tablets being transported are uncoated tablets, the maintenance device is controlled to perform the wiping and then purge from the print head. If the tablets being transported are coated tablets, the maintenance device is controlled not to perform the wiping before purging. do 。 [Brief explanation of the drawing]

[0009] [Figure 1] This is a front view showing a schematic configuration of a tablet printing apparatus according to the first embodiment. [Figure 2] This is a plan view showing a schematic configuration of a tablet printing apparatus according to the first embodiment. [Figure 3] This figure shows an example of a schematic configuration of a maintenance device according to the first embodiment. [Figure 4] This figure shows an example of a schematic configuration of the control device according to the first embodiment. [Figure 5] This is a flowchart showing the maintenance process according to the first embodiment. [Figure 6] This is an operating state diagram of the maintenance device according to the first embodiment. [Figure 7] This figure illustrates an overview of the maintenance process according to the second embodiment. [Modes for carrying out the invention]

[0010] <First Embodiment> The first embodiment will be described with reference to Figures 1 to 6.

[0011] (Example of tablet printing machine configuration) As shown in Figures 1 and 2, the tablet printing apparatus 1 according to the first embodiment includes a supply device 10, a transport device 20, a detection device 30, a first imaging device 40, a printing device 50, a second imaging device 60, a recovery device 70, a maintenance device 80 (see Figure 2), and a control device 90.

[0012] The supply device 10 has a hopper 11 and a chute 12. This supply device 10 is located at one end of the conveying device 20 and is configured to supply tablets T, which are the objects to be printed, to the conveying device 20. The hopper 11 holds 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 single 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.

[0013] The conveying device 20 includes a conveying belt 21, a drive 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 between the drive pulley 22 and each driven pulley 23. The drive pulley 22 and each driven pulley 23 are rotatably mounted on the device body (not shown), and the drive pulley 22 is connected to the motor 24. The motor 24 is electrically connected to a control device 90, and its drive 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 drive pulley 22 by the motor 24, and conveys the tablets T on the conveying belt 21 in the rotational direction of arrow H1 in Figure 1, i.e., the conveying direction H1.

[0014] Multiple circular suction holes 21a (see Figure 2) are formed in the conveyor belt 21. Each of these suction holes 21a is a through-hole that attracts a tablet T, and they are arranged in two parallel rows along the conveying direction H1 to form two conveying paths. Each suction hole 21a is connected to the suction chamber 26 (see Figure 1) via a suction path (not shown) formed in the suction chamber 26, and suction force can be obtained from the suction chamber 26. A pump is connected to the suction chamber 26 via a suction tube (neither shown), and the inside of the suction chamber 26 is depressurized by the operation of the pump. The suction tube is connected to approximately the center of the side surface of the suction chamber 26 (the surface parallel to the conveying direction H1). The pump is also electrically connected to a control device 90, and its drive is controlled by the control device 90. When the inside of the suction chamber 26 is depressurized, tablets T placed on each suction hole 21a of the conveyor belt 21 are attracted by the suction holes 21a and held on the conveyor belt 21.

[0015] The detection device 30 comprises a plurality of detection units 31 (two in this embodiment). The detection units 31 are positioned downstream in the transport direction H1 from the location where the supply device 10 is installed, and are located above the transport belt 21. These detection units 31 detect the position of the tablet T on the transport belt 21 in the X direction (see Figure 2) by transmitting and receiving laser light. For example, a displacement sensor or a proximity sensor can be used as the detection unit 31. As a displacement sensor, various types of laser sensors, such as a reflective laser sensor, can be used. The detection device 30 is electrically connected to the control device 90 and transmits a detection signal to the control device 90.

[0016] The first imaging device 40 includes a plurality of first imaging units 41 (in this embodiment, two). The first imaging unit 41 is positioned on the downstream side in the conveying direction H1 from the position where the detection device 30 is provided, and is provided above the conveying belt 21. Based on the position information in the X direction of the tablet T detected by the detection device 30, this 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 (an image for detecting the tablet position) 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 CCD (Charge Coupled Device) and 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 provided as necessary.

[0017] Here, the positions of the tablet T in the X direction and Y direction are, for example, the positions in the XY coordinate system with respect to the center (reference position) of the imaging region of the first imaging unit 41. Also, the position in the θ direction is, for example, the position indicating the degree of rotation of the tablet T with respect to the center line in the Y direction of the imaging region of the first imaging unit 41. This position in the θ direction is detected when the tablet T has a shape with a directionality, such as when the tablet T has a score line, or when the tablet T is molded into an elliptical, oval, or rectangular shape.

[0018] The printing device 50 includes a print head 51 and a lifting mechanism 52. The print head 51 is positioned downstream of the position where the first imaging device 40 is provided in the conveyance direction H1, and is provided above the conveyance belt 21. The print head 51 has a plurality (for example, several hundred to several thousand) of nozzles 51a (see FIG. 2), and is provided such that the direction in which the nozzles 51a are arranged in a row (nozzle row) is orthogonal (an example of intersection) to the conveyance direction H1 within a horizontal plane. In FIG. 2, for simplicity of the drawing, the nozzles 51a are shown as four. The print head 51 individually discharges ink from each nozzle 51a by the operation of a drive element for each nozzle 51a. As this print head 51, various inkjet printing heads having drive elements such as piezoelectric elements, heating elements, or magnetostrictive elements are used. The print head 51 can move up and down so as to approach or separate from the conveyance belt 21 by a lifting mechanism 52 (see FIG. 1). The up and down movement of the print head 51 is performed during maintenance of the print head 51. The 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.

[0019] 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 of the position where the printing device 50 is provided in the conveyance direction H1, and is provided above the conveyance belt 21. The second imaging unit 61 is The first imaging unit 41 and Based on the position information in the X direction of the tablet T detected by the detection unit 31, imaging is performed at the timing when the tablet T reaches the imaging position directly below the second imaging unit 61, a second image including the upper surface of the tablet T is acquired, and the acquired second image is transmitted 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, similar to the aforementioned first imaging unit 41, for example, various cameras having imaging elements such as CCDs or CMOSs are used. The second imaging device 60 is electrically connected to the control device 90, and its drive is controlled by the control device 90. Note that illumination for imaging is provided as necessary.

[0020] The recovery device 70 is positioned downstream in the transport direction H1 from the position where the second imaging device 60 is installed, and is located at the downstream end of the transport device 20 in the transport direction H1. The transport device 20 releases the tablet T when it reaches a predetermined position, for example, the downstream end of the transport device 20 in the transport direction H1. The recovery device 70 is configured to separate and recover the tablets T that fall after being released from the transport device 20 into defective and good tablets. For example, it is possible to separate and recover the falling tablets T into defective and good tablets by blowing gas onto the tablets T in the process of falling to change the direction of fall for defective and good tablets, or by changing the fall path with a plate or other material. For example, defective tablets are those that did not pass printing, and good tablets are those that passed printing. The recovery device 70 is electrically connected to the control device 90, and its drive is controlled by the control device 90.

[0021] As shown in Figures 2 and 3, the maintenance device 80 comprises a liquid receiving section 81, a suction section 82, a wiper 83, and a moving mechanism 84. The maintenance device 80 is installed so as to be aligned with the print head 51 and in the direction in which the nozzles 51a of the print head 51 are aligned in a plan view (the Y direction in Figure 2). Note that in Figure 2, the moving mechanism 84 is omitted for the sake of simplification. Details of the maintenance device 80 will be described later.

[0022] The maintenance device 80 moves between the transport belt 21 and the print head 51 during maintenance of the print head 51 and cleans the underside (nozzle surface) of the print head 51. The maintenance device is electrically connected to the control device 90, and its drive is controlled by the control device 90.

[0023] The control device 90 controls various parts of the tablet printing apparatus 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 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 receives image information transmitted from the first imaging unit 41 and the second imaging unit 61. The control device 90 is implemented, for example, by an electronic circuit such as an integrated circuit or a computer.

[0024] Next, an example of the configuration of the control device 90 will be described with reference to Figure 4.

[0025] As shown in Figure 4, the control device 90 includes 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 this control device 90. The input device 90a can be implemented by, for example, a switch, a touch panel, a keyboard, or a mouse. The output device 90b can be implemented by, for example, a display, a lamp, or a meter.

[0026] The image processing unit 91 takes in 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 known image processing techniques. For example, the image processing unit 91 processes the first image obtained from the first imaging device 40 to obtain whether or not there are cracks, chips, or stains on the tablet T, and further obtains the position of the tablet T in the X, Y, and θ directions. The image processing unit 91 also processes the second image obtained from the second imaging device 60 to obtain the printing position, shape, and size of the printed pattern (e.g., characters or marks) printed on the tablet T. The image processing unit 91 transmits the acquired information on whether or not there are cracks, chips, or stains on the tablet T, the acquired position information in the X, Y, and θ directions of each tablet T, and the printing position information, shape information, and size information of the printed pattern on each tablet T to the control unit 93.

[0027] The memory unit 92 stores processing information and various programs. For example, it is implemented by semiconductor memory elements such as RAM (Random Access Memory) and flash memory, or by storage devices such as hard disks and optical discs. The memory unit 92 stores data on the type of tablet to be printed, data on the ink used for printing, printing data related to printing, and data on the movement speed of the conveyor belt 21. The printing data includes information on printing patterns such as characters and marks.

[0028] The control unit 93 is a computer, such as a CPU (Central Processing Unit) or MPU (Micro Processing Unit), and controls each part. For example, the control unit 93 controls the supply device 10, transport device 20, detection device 30, first imaging device 40, printing device 50, second imaging device 60, retrieval device 70, maintenance device 80, image processing unit 91, and storage unit 92 based on various information and programs stored in the storage unit 92. The control unit 93 also receives detection signals transmitted from the detection device 30 and position detector 25. The control unit 93 can be implemented using either hardware and / or software.

[0029] 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 is detected. Based on this position information indicating the position of the tablet T in the X direction, the control unit 93 sets the imaging timing of the first imaging device 40, the printing start timing of the print head 51 of the printing device 50, and the imaging timing of the second imaging device 60. It then generates timing information indicating these timings and stores it in the storage unit 92. The printing start timing is the timing at which printing begins for the tablet T that has reached the printing position directly below the print head 51. The control unit 93 can also acquire information such as the amount of movement (amount of rotation) and speed of the conveyor belt 21 based on the detection information transmitted from the position detector 25.

[0030] Furthermore, the control unit 93 sets whether or not to print on the tablet T based on the information transmitted from the image processing unit 91 regarding the presence or absence of cracks, chips, or dirt on the tablet T. Then, the control unit 93 sets printing conditions for the tablet T that has been set to printable. At this time, the control unit 93 sets printing conditions for the tablet T based on the position information of the tablet T in the X, Y, and θ directions transmitted from the image processing unit 91. For example, the control unit 93 determines the range of nozzles 51a to be used to print the target tablet T in the print head 51, i.e., the nozzle range to be used, based on the position information of the tablet T in the Y direction and the print data, and sets printing conditions including the nozzle range to be used and the printing start timing. If the tablet T has a directional shape, 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 stores 180 different print patterns in the storage unit 92, each obtained by rotating the orientation of the print pattern by 1 degree in the range of 0 to 179 degrees. From these print patterns, it selects a print pattern with an angle that matches the position of the tablet T in the θ direction and sets the print conditions.

[0031] Furthermore, the control unit 93 determines whether the print pattern has been printed in a predetermined shape and size at a predetermined location on the tablet T, based on the print position information, shape information, and size information of the print pattern printed on the tablet T transmitted from the image processing unit 91, that is, whether the print pattern has been successfully printed on the tablet T (print status inspection). For example, in determining the shape and size of the print pattern, the control unit 93 registers an inspection print pattern in the storage unit 92 and compares that inspection print pattern with the actual print pattern on the tablet T after printing (the print pattern printed on the tablet T).

[0032] The control unit 93 stores various information (for example, information on the presence or absence of cracks, chips, or dirt on the tablet T, location information, timing information, printing conditions, printing quality information, etc.) in the storage unit 92 as appropriate. However, when the target tablet T is recovered by the recovery device 70, the various information is deleted from the storage unit 92 after a predetermined time (for example, a few seconds) has elapsed since it fell from the downstream end of the transport direction H1 in the transport device 20. However, if this information is needed in subsequent processes, it is possible to leave the various information for each tablet T without deleting it, or to save it on storage media outside the device. When storing the various information for each tablet T, this information may be linked to the manufacturing date and lot number, etc., so that if defective tablets T are found after shipment, the cause can be traced back to investigate.

[0033] (Example of maintenance device configuration) Next, the configuration of the maintenance device 80 will be described with reference to Figure 3. Figure 3 is a view of the print head 51 and the maintenance device 80 from the upstream side in the transport direction H1. As mentioned above, the maintenance device 80 includes a liquid receiving section 81, a suction section 82, a wiper 83, and a moving mechanism 84. When maintenance is not being performed, these are positioned in the order of wiper 83, suction section 82, and liquid receiving section 81 from the print head 51 side, and are provided to be movable as a single unit by the moving mechanism 84.

[0034] The liquid receiving section 81 is formed, for example, in the shape of a box with an open top. This liquid receiving section 81 receives ink ejected from each nozzle 51a of the opposing print heads 51 during maintenance of the print heads 51. The length of the liquid receiving section 81 in the direction perpendicular to the transport direction H1 is provided to be at least longer than the nozzle row in which the nozzles 51a are arranged. In the first embodiment, the length of the liquid receiving section 81 in the direction perpendicular to the transport direction H1 is longer than two print heads 51 placed side by side (longer than the length of two print heads).

[0035] The suction unit 82 is a vacuum wiper having a slit-shaped suction port at its top 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 operating the suction pump, the suction unit 82 moves in close proximity to the nozzle surface of the print head 51 and scans the nozzle surface, thereby sucking up and removing ink adhering to the nozzle surface.

[0036] The wiper 83 slides in contact with the nozzle surface of the print head 51, thereby wiping away and removing powder and ink adhering to the nozzle surface. The wiper 83 has a first wiper 83a and a second wiper 83b.

[0037] The first wiper 83a has an absorbent fibrous material, such as a nonwoven fabric, on its upper part. The first wiper 83a is impregnated with a wiping liquid (for example, an aqueous solution containing ethanol). In other words, the first wiper 83a is a wet wiper. The supply of the wiping liquid to the first wiper 83a may be performed by an operator or may be supplied automatically. When the wiping liquid is supplied, the first wiper 83a becomes impregnated with the wiping liquid.

[0038] The second wiper 83b, like the first wiper 83a, has an absorbent fibrous material, such as nonwoven fabric, on top. The second wiper 83b is a dry wiper (no wiping liquid is supplied).

[0039] The moving mechanism 84 has a ball screw 84a, a slider 84b, and a motor 84c. The liquid receiving section 81, the suction section 82, and the wiper 83 are fixed to the slider 84b, and the ball screw 84 aThe device is rotated by motor 84c, allowing it to move between a maintenance position and a standby position. Here, the maintenance position is the position of the maintenance device 80 when the print head 51 is being maintained, and is located between the transport 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 located offset from above the transport belt 21 (the position towards the back of the paper in Figure 1).

[0040] (Printing process) Next, the printing process performed by the aforementioned tablet printing apparatus 1 will be explained with reference to Figures 1 and 2. This printing process also includes an inspection process. Various information, such as data required for printing, is pre-stored in the storage unit 92.

[0041] When the tablet printing device 1 starts the printing process, the motor 24 is driven, and the conveyor belt 21 rotates in the conveying direction H1 as the drive pulley 22 and driven pulley 23 are rotated by the motor 24. With the conveyor belt 21 rotating in the conveying direction H1, tablets T are sequentially supplied from the hopper 11 to the chute 12, and the chute 12 arranges them in a line and supplies them onto the conveyor belt 21 randomly, not at regular intervals. The tablets T supplied onto the conveyor belt 21 are transported in two lines on the conveyor belt 21 at a predetermined speed.

[0042] The tablets T on the conveyor belt 21 are detected by the detection device 30. Specifically, when a tablet T on the conveyor belt 21 reaches a detection position directly below the detection unit 31 of the detection device 30 (for example, the laser beam irradiation position), the detection unit 31 detects it, and based on the timing of the detection of the tablet T, 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 storage unit 92.

[0043] Next, the tablets T on the conveyor belt 21 are imaged by the first imaging device 40. Specifically, the tablets T on the conveyor belt 21 are imaged by the first imaging device 40 when they reach the imaging position directly below the first imaging device 40, and the first image obtained by the imaging by the first imaging device 40 is transmitted to the control device 90. Based on this first image, the image processing unit 91 generates information on whether or not the tablets T are cracked, chipped, or dirty, as well as the position information of the tablets T in the X, Y, and θ directions, and stores this information in the storage unit 92. Based on the information on whether or not the tablets T are cracked, chipped, or dirty, the printability of the target tablets T is set, and based on the position information of the tablets T in the X, Y, and θ directions and information such as the print pattern, the storage unit 92 sets printing conditions, including the nozzle range to be used and the printing start timing, for tablets T set to printable (printable tablets T). Based on the aforementioned printing start timing (the timing at which printing begins on the tablets T), the ejection timing for the tablets T (the timing at which ink is ejected from the tablets T) is determined.

[0044] Printing is performed by the printing device 50 based on these printing conditions. In other words, the control unit 93 controls the print head 51 of the printing device 50 to print a predetermined printing pattern on the printable tablets T on the conveyor belt 21. Specifically, the printable tablets T on the conveyor belt 21 that have passed below the first imaging device 40 are printed by the print head 51 at the printing start timing when they reach the printing position directly below the print head 51, based on the aforementioned printing conditions. The print head 51 appropriately ejects ink from each nozzle 51a, and a printing pattern (for example, numbers, alphabets, katakana, symbols, figures) is printed on the printable surface, which is the upper surface of the tablet T. The ink applied to the tablet T dries during conveyance. Alternatively, a drying unit (not shown) that dries by gas or heat may be provided, and the ink may be dried by this drying unit.

[0045] Subsequently, the printed tablets T on the conveyor belt 21 are imaged by the second imaging device 60. More specifically, the printed tablets T on the conveyor belt 21 are imaged by the second imaging device 60 when they reach the imaging position directly below the second imaging device 60, and the second image obtained by the imaging by the second imaging device 60 is transmitted to the control device 90.

[0046] This second image is analyzed by the image processing unit 91 of the control device 90. Specifically, the image processing unit 91 acquires information about the printed pattern printed on the tablet T, namely the printing position, shape, and size of the printed pattern. 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 on the tablet T is generated and stored in the storage unit 92.

[0047] Based on this inspection information, the control unit 93 performs a print condition inspection. Specifically, based on the aforementioned inspection information regarding the print position, shape, and size stored in the storage unit 92, the control unit 93 determines whether or not the print pattern was successfully printed on the tablet T, and print quality information indicating the print quality of the tablet T is generated and stored in the storage unit 92. For example, in a print condition inspection, the print pattern used for printing is stored in the storage unit 92 as an inspection print pattern, and good product information regarding the predetermined print position, shape, and size of the inspection print pattern is compared with the inspection information regarding the print position, shape, and size of the actual printed print pattern stored in the storage unit 92 to determine whether or not the print pattern was successfully printed on the tablet T (pass or fail).

[0048] Finally, the tablets T on the conveyor belt 21 are collected by the collection device 70. More specifically, when the inspected tablets T are located at the downstream end of the conveyor belt 21 as it moves, they are released from being held by the conveyor belt 21 and fall from the conveyor belt 21 to be collected by the collection device 70. At this time, the tablets T that pass the inspection fall as they are and are collected as good products by the collection device 70, but the tablets that fail the inspection or are not printed tablets are separated from the good products by air blowing on them as they fall from the conveyor belt 21 and are collected as defective products by the collection device 70.

[0049] (Maintenance process) In a printing operation that performs such a printing process, maintenance of the print head 51 is performed periodically (for example, every 10-20 minutes). Maintenance methods include purging, wiping, and dummy ejection. Purge is an operation in which ink is pumped under pressure with the liquid receiving unit 81 facing the print head 51, causing ink to be ejected from the print head 51 towards the liquid receiving unit 81. By performing the purging operation, air bubbles in the nozzle and dried and solidified ink can be removed, preventing ejection failures. Wiping is an operation in which the nozzle surface of the print head 51 is suctioned by the suction unit 82 or wiped with the wiper 83. By performing the wiping operation, powder and ink adhering to the nozzle surface can be removed, preventing ejection failures. Dummy ejection is an operation (preliminary ejection operation) in which the inkjet drive element is driven with the liquid receiving unit 81 facing the print head 51 to eject a small amount of ink.

[0050] Incidentally, as mentioned above, when printing on uncoated tablets, powder is generated, and this powder can adhere to the nozzle surface. Normally, within the nozzle of an inkjet print head, the ink filled in the nozzle is adjusted to form a concave surface at the discharge port by a meniscus, due to factors such as the difference in water head between the ink container connected to the print head. Therefore, when purging is performed, some of the ink pushed out from the nozzle is drawn back into the nozzle along with the powder adhering to the discharge port and its surroundings in order to reform the meniscus. This can cause the nozzle to clog and lead to poor discharge.

[0051] Therefore, if the tablet T to be printed is an uncoated tablet, the maintenance of the print head 51 involves wiping before purging (before ejection) to remove any powder adhering to the nozzle surface. On the other hand, if the tablet T to be printed is a coated tablet (such as a sugar-coated tablet or a film-coated tablet) that does not generate (or generates little) powder, wiping before purging is not necessary. Details of this maintenance process will be explained below.

[0052] Figure 5 shows the maintenance process for the print head 51. The processes shown in Figure 5 are executed by each part under the control of the control device 90. The type of tablet T to be printed is entered in advance by the operator via the input device 90a when the printing operation is started and stored in the storage unit 92. During the maintenance process, the supply of tablets T by the supply device 10 is temporarily stopped.

[0053] First, let's explain the case where the tablet T to be printed is a coated tablet. When it is time for maintenance of the print head 51, the lifting mechanism 52 is controlled to raise 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 raised to a height position where the lower surface of the print head 51 does not come into contact with the suction unit 82 and wiper 83, even when the suction unit 82 and wiper 83 are moved as described later.

[0054] Next, the moving mechanism 84 is controlled to position the liquid receiving section 81 so that it faces the nozzle surface of the print head 51. Furthermore, the lifting mechanism 52 is controlled to lower the print head 51 to a height where, as shown in Figure 6, the nozzle surface of the print head 51 does not come into contact with the suction section 82 but does come into contact with the wiper 83 (step S102).

[0055] Based on the information about the type of tablet T to be printed, which has been previously input by the operator via the input device 90a and stored in the memory unit 92, the control device 90 determines that the tablet T is a coated tablet (step S103: No), and then pumps the ink in the print head 51 and performs a purge operation (step S104).

[0056] Next, the moving mechanism 84 is controlled to move the suction unit 82 and the wiper 83 toward the left in Figure 6. As a result, the print head 51 sequentially receives vacuum wiping by the suction unit 82 (step S105), wet wiping by the first wiper 83a (step S106), and dry wiping by the second wiper 83b (step S107).

[0057] Once wiping is complete, the lifting mechanism 52 is controlled to raise the print head 51 (step S108). When the print head 51 is raised, the moving mechanism 84 is controlled to position the liquid receiving section 81 so that it faces the nozzle surface of the print head 51 (step S109). With the liquid receiving section 81 and the nozzle surface of the print head 51 facing each other, the inkjet drive element of the print head 51 is driven to perform dummy ejection (step S110).

[0058] Once the dummy dispensing is complete, the moving mechanism 84 is controlled to move the maintenance device 80 (suction unit 82 and wiper 83) to the standby position (step S111), and the lifting mechanism 52 is controlled to lower the print head 51 to the height position for printing (step S112). Once the print head 51 has lowered, the maintenance process is complete. After the maintenance process is complete, the supply of tablets T by the supply device 10 is resumed, and printing is performed.

[0059] Next, we will explain the case where the tablet T to be printed is an uncoated tablet. When it is time for maintenance of the print head 51, the print head 51 rises (step S101), as in the case of the coated tablet described above, and once the liquid receiving section 81 is positioned opposite the nozzle surface of the print head 51, the print head 51 lowers (step S102). Then, in step S103, based on the information of the type of tablet T to be printed that has been previously input by the operator via the input device 90a and stored in the storage unit 92, if the control device 90 determines that the tablet T is an uncoated tablet (step S103: Yes), the process proceeds to step S113 and wiping is performed.

[0060] Specifically, the moving mechanism 84 is controlled to move the suction unit 82 and the wiper 83 toward the left in Figure 6. As a result, the print head 51 sequentially undergoes vacuum wiping by the suction unit 82 (step S113), wet wiping by the first wiper 83a (step S114), and dry wiping by the second wiper 83b (step S115). This wiping process removes powder adhering to the nozzle surface of the print head 51.

[0061] Once wiping is complete, the lifting mechanism 52 is controlled to raise the print head 51 (step S116). When the print head 51 is raised, the moving mechanism 84 is controlled to position the liquid receiving section 81 so that it faces the nozzle surface of the print head 51. Furthermore, the lifting mechanism 52 is controlled to lower the print head 51 to a height where the wiper 83 contacts the nozzle surface of the print head 51 when wiping is performed, as shown in Figure 6 (step S117).

[0062] Once the print head 51 descends, the steps from step S104 onward are executed, just as in the case where the tablet T is a coated tablet.

[0063] As described above, according to the first embodiment, the tablet printing apparatus 1 comprises a transport device 20 for transporting tablets T, an inkjet type print head 51 for printing on the tablets T transported by the transport device 20, a maintenance device 80 for maintaining the print head 51, and a control device 90 for controlling the print head 51 and the maintenance device 80. The control device 90 changes the maintenance operation according to the type of tablets T being transported. This allows for efficient maintenance. Therefore, it is possible to prevent ejection failures and a decrease in print quality.

[0064] Furthermore, in the first embodiment, if the printing target is a plain tablet, wiping is performed before purging (before the ejection operation). Wiping removes powder adhering to the nozzle surface. This prevents powder from being drawn in along with some of the ink that has been pushed out from the nozzle during purging, when the ink is drawn back into the nozzle to re-form the meniscus. Therefore, it is possible to prevent ejection failures and a decrease in print quality.

[0065] Furthermore, in the first embodiment, vacuum wiping by the suction unit 82 is performed before wet wiping by the first wiper 83a. During printing, powder adheres to the nozzle surface, and powder may also adhere to and mix with the ink adhering to the nozzle surface. By performing vacuum wiping before wet wiping, powder mixed with the ink can also be removed. Any ink that could not be removed by vacuum wiping can be removed by wet wiping. In addition, after wet wiping by the first wiper 83a, dry wiping is performed by the second wiper 83b. The wipe liquid adhering to the nozzle surface by wet wiping can be removed by dry wiping. This type of wiping allows for efficient cleaning of the print head 51.

[0066] On the other hand, when printing on coated tablets, there is little to no powder residue on the nozzle surface, so wiping before purging is not necessary. Therefore, by performing print head maintenance, it is possible to prevent ejection problems while shortening maintenance time.

[0067] <Second Embodiment> Next, a second embodiment will be described. In the second embodiment, only the differences from the first embodiment will be described, and the same points will not be explained.

[0068] Inks used for printing on tablets may contain a fixing agent, depending on their composition and the physical properties of the tablet being printed on.

[0069] Fixatives include substances classified as gelling agents, gum bases, and thickening stabilizers. Specifically, these include acetylated adipate cross-linked starch, acetylated oxidized starch, acetylated phosphate cross-linked starch, acetate starch, oxidized starch, hydroxypropyl starch, phosphate cross-linked starch, phosphorylated starch, and phosphate monoesterified phosphate cross-linked starch. Other examples include okra extract, seaweed cellulose, brown algae extract, gluten, gluten hydrolysates, konjac extract, sweet potato cellulose, nata de coco, mannan, and rennet casein. Also, Aureobasidium culture solution, Agrobacterium succinoglycan, Amaseed gum, gum arabic, arabinogalactan, alginic acid, Welan gum, Elemi resin, Ozokerite, Cassia gum, Gati gum, Curdlan, Carrageenan (processed Eukema algae, refined carrageenan, Eukema algae powder), Karaya gum, Carob bean gum, Xanthan gum, Chitin, Chitosan, Guar gum, Guar gum enzyme hydrolysate, Guaiac resin, Gutta hankan, Gutta percha, Glucosamine, Yeast cell wall, Psyllium seed gum, Desert Artemisia seed gum, Sheraton Examples include shellac (white shellac, refined shellac), gellan gum, jeltong, sorba, sorbin, tamarind seed gum, tara gum, chicle, chrylte, tunu, low molecular weight rubber, dextran, tragacanth gum, okra, natto bacteria gum, nigagutta, paraffin wax, microcrystalline cellulose, fercerelan, seaweed extract, pullulan, rice husk powder, pectin, venezuelan chicle, macrophopsis gum, mastic, massarandobaba batata, myrrh, peach resin, ramsang gum, letchudevaka, levan, rosidingha, rosin, etc.

[0070] Inks containing fixatives can prevent the ink from peeling or fading after printing. However, the presence of fixatives can increase the viscosity of the ink, and when it dries and solidifies, it can become more adhesive to the nozzle surface, making it difficult to completely remove the ink even with wiping.

[0071] Therefore, in the second embodiment, the amount of wipe liquid supplied to the first wiper 83a (wet wiper) and the number of dots during dummy ejection are changed depending on whether or not the ink supplied to the print head 51 contains a fixing agent (type of ink). A summary of the second embodiment is shown in Figure 7.

[0072] Information about the ink to be used for printing is input in advance by the operator to the control device 90 via the input device 90a. Before starting the printing operation of the tablet printing device 1 or before starting the maintenance process, the first wiper 83a is supplied with wiping fluid. At this time, if the ink contains a fixative, the amount of wiping fluid supplied is increased compared to when the ink does not contain a fixative. Also, in the dummy ejection during the maintenance process (step S110 in Figure 5), if the ink contains a fixative, the number of dummy ejections (number of dots) is increased compared to when the ink does not contain a fixative.

[0073] Furthermore, the support member for the first wiper 83a may be a box-shaped container with an open top, in which the wiping liquid is stored. In this case, by immersing a portion of the lower side of the first wiper 83a (the side opposite to the side that contacts the nozzle surface) in the wiping liquid stored in the container, the first wiper 83a can be kept wet for a longer period of time. In addition to the amount of wiping liquid supplied to the first wiper 83a, the amount of wiping liquid contained in the first wiper 83a can also be increased by increasing the capacity of the container (the support member for the first wiper 83a). Moreover, the amount of wiping liquid contained in the first wiper 83a can be changed by changing the volume of the portion of the first wiper 83a that is immersed in the wiping liquid.

[0074] As described above, the second embodiment provides the same effects as the first embodiment. Furthermore, in the second embodiment, the amount of wiping liquid supplied to the first wiper 83a is changed depending on whether or not the ink contains a fixative. More specifically, if the ink contains a fixative, the amount of wiping liquid supplied to the first wiper 83a is increased. This results in the first wiper 83a containing a larger amount of wiping liquid being used for wiping. Therefore, even if the ink contains a fixative, it becomes easier to remove the ink adhering to the nozzle surface by dissolving the ink.

[0075] Furthermore, when wet wiping is performed, the pressure created when the nozzle surface and the first wiper 83a come into contact causes the wiping liquid to seep out from the first wiper 83a. Some of the seeped-out wiping liquid may enter the nozzle. If the wiping liquid enters the nozzle, the ink inside the nozzle will be diluted. If the amount of wiping liquid contained in the first wiper 83a is large, the amount of wiping liquid that seeps out will also be large, and the amount of wiping liquid that enters the nozzle may increase. Therefore, when wiping is performed with the first wiper 83a containing a large amount of wiping liquid, the number of ejections (number of dots) in dummy ejection is increased. Dummy ejection allows the wiping liquid that has entered the nozzle to be discharged. This prevents the ink from becoming diluted and the visibility of printed identification information from deteriorating when the printing operation is resumed afterward.

[0076] <Other Embodiments> In the above description, it was stated that two print heads 51 are provided, but there may be one, or three or more. Also, one maintenance device 80 may be provided for each print head 51, or multiple print heads 51 may share one maintenance device 80.

[0077] Furthermore, although the example shows the liquid receiving section 81, suction section 82, and wiper 83 moving as a single unit, the system is not limited to this, and each may be provided to be independently movable.

[0078] Furthermore, while it has been illustrated that the wiper 83, suction unit 82, and liquid receiving unit 81 are moved by the moving mechanism 84 to face the print head 51, the invention is not limited to this. For example, the print head 51 may be moved, or both the print head 51 and the maintenance device 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.

[0079] Furthermore, if the supply of wiping fluid to the first wiper 83a is to be automated, a wiping fluid supply unit can be provided on the first wiper 83a. By providing a wiping fluid supply unit, the amount of wiping fluid supplied to the first wiper 83a can be changed depending on whether the ink contains a fixative or not, by controlling the wiping fluid supply unit.

[0080] In addition, a wipe fluid supply unit (not shown) may be provided separately from the first wiper 83a to periodically supply wipe fluid to the first wiper 83a. The amount of wipe fluid supplied periodically may be changed depending on the type of ink. For example, when using ink containing a fixative, the amount of wipe fluid supplied to the first wiper 83a may be increased. Alternatively, the frequency of supplying wipe fluid to the first wiper 83a may be increased.

[0081] Furthermore, a wetness detection sensor can be provided to detect the amount of wiping liquid contained in the first wiper 83a (the wetness state of the first wiper 83a). The wetness detection sensor transmits the detected value to the control device 90. The control device 90 can determine the wetness state of the first wiper 83a based on the detected value transmitted from the wetness detection sensor. Based on the determination result, the control device 90 may control the number of dummy dispensing cycles. Alternatively, the relationship between the elapsed time since supplying wiping liquid to the first wiper 83a, the number of wiping cycles, and the wetness state may be determined in advance through experiments, and based on this, the wetness state of the first wiper 83a at the timing of wiping may be determined, and the number of dummy dispensing cycles may be controlled accordingly.

[0082] Furthermore, while we have exemplified the removal of powder by wiping before purging when the tablet T to be printed is an uncoated tablet, the method of removing powder is not limited to this. For example, cleaning solution may be supplied directly to the nozzle surface of the print head 51. In other words, any method that can remove powder adhering to the nozzle surface is acceptable.

[0083] Furthermore, the second wiper 83b only needs to be able to remove the wiping liquid (cleaning liquid) adhering to the nozzle surface, and may be, for example, a blade.

[0084] Furthermore, while it has been illustrated that information about the ink used for printing is input to the control device 90 by the operator via the input device 90a, this is not the only example. For instance, the tablet printing device 1 may be equipped with an RF tag reader, and when the 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 information about the ink. Alternatively, 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 code.

[0085] Furthermore, the amount of wipe fluid supplied to the first wiper 83a may be adjusted according to the composition of the ink. For example, it may be adjusted according to the type and content of the fixative. Also, the number of dummy ejections may be changed according to the amount of wipe fluid supplied to the first wiper 83a. In other words, the number of dummy ejections may be increased as the amount of wipe fluid increases.

[0086] Furthermore, while the example given for dummy ejection involved changing the number of ejections depending on whether or not the ink contains a fixative, this is not the only example. For instance, the amount ejected per ejection in dummy ejection could be changed. Alternatively, both the number of ejections and the amount ejected could be changed.

[0087] Furthermore, although the aforementioned maintenance process was exemplified as being performed periodically during printing operations, it is not limited to this; it may also be performed when nozzle 51a ejection failure occurs or when a printing failure is detected based on the second image. Performing the maintenance process can restore the ejection performance of the print head 51.

[0088] Furthermore, although the aforementioned maintenance process did not specifically mention the wiping speed of the first wiper 83a and the second wiper 83b, the moving speed of the first wiper 83a and the second wiper 83b (the speed at which the wipers 83 slide along 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 a predetermined number is exceeded, it may reduce the moving speed of the moving mechanism 84 to reduce the moving speed of the first wiper 83a and the second wiper 83b. Alternatively, the control unit 93 may measure the time elapsed since the start of operation of the tablet printing apparatus 1, determine that the number of times the wipers 83 have wiped has exceeded a predetermined number after a predetermined time has elapsed, and reduce 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 operating time increases, ink may solidify and accumulate on the nozzle surface of the print head 51. However, by reducing the movement speed of the moving mechanism 84 using the control unit 93, the wiping liquid, especially that held in the first wiper 83a, is sufficiently supplied to the nozzle surface of the print head 51, and the ink that has solidified on the nozzle surface can be effectively removed. The speed may be controlled to gradually decrease from the start of operation of the tablet printing device 1, not only when the number of wipes exceeds a predetermined number or when a predetermined time has elapsed. Note that the wiping speed may be reduced by reducing only one of the first wiper 83a and the second wiper 83b, and the wiping liquid may be sufficiently supplied to the nozzle surface of the print head 51 and the solidified ink removed by reducing the movement speed of only the first wiper 83a. In this case, it is preferable to configure the first wiper 83a and the second wiper 83b to move independently. For example, one of the first wiper 83a and the second wiper 83b is moved by the moving mechanism 84, and the other of moving mechanism 84 Alternatively, the movement may be performed using a different movement mechanism (in the same direction as movement mechanism 84).

[0089] Furthermore, the second wiper 83b is a dry wiper, but as the operating time increases, the print head... D5 The second wiper 83b gradually becomes wet as it absorbs ink adhering to the nozzle surface of the first wiper 83a and the wiping liquid supplied from the first wiper 83a. Therefore, a drying unit (not shown) for drying the second wiper 83b may be provided, and the control unit 93 may, for example, when the number of wiping cycles by the wiper 83 exceeds a predetermined number, or when the operating time of the tablet printing device 1 has elapsed a predetermined time, use the drying unit to dry the second wiper 83b. Preferably, the drying unit dries the second wiper 83b by discharging a drying gas away from the nozzle surface of the print head 51. This is to prevent the nozzle surface of the print head 51 from drying out due to the drying gas, which would cause the ink on the nozzle 51a to harden and lead to printing defects. The drying unit may, for example, supply the drying gas from a drying section that dries the ink applied to the tablet T via piping (not shown). The flow rate of the drying gas supplied from the drying unit to the second wiper 83b may be gradually increased. In other words, as the number of wiping cycles by the second wiper 83b increases, the amount of drying gas supplied by the drying unit may be increased to ensure that the second wiper 83b dries more reliably.

[0090] Here, the aforementioned tablet T can include tablets used for pharmaceutical, edible, cleaning, industrial, or fragrance purposes. Furthermore, tablet T can include uncoated tablets, sugar-coated tablets, film-coated tablets, enteric-coated tablets, gelatin-coated tablets, multilayer tablets, and core tablets, and various types of capsule tablets such as hard capsules and soft capsules can also be included in tablet T. In addition, tablet T can take various shapes such as disc-shaped, lens-shaped, triangular, and oval. Moreover, if the tablet T to be printed is for pharmaceutical or edible purposes, edible ink is preferable as the ink used. This edible ink can be any of synthetic dye ink, natural dye ink, dye ink, or pigment ink.

[0091] Although several embodiments of the present invention have been described above, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be implemented in a variety of other forms, and various omissions, substitutions, modifications, and combinations are possible without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of Symbols]

[0092] 1. Tablet printing device 10 Feeding device 20 Conveying device 21 Conveyor belt 30 Detection device 40 First imaging device 50 Printing device 51 Printhead 60 Second imaging device 70 Recovery device 80 Maintenance equipment 81 Liquid receiving section 82 Suction part 83 Wiper 83a First wiper 83b Second wiper 84 Moving mechanism 90 Control device T Tablets

Claims

1. A conveying device for transporting tablets, An inkjet type print head that ejects ink to print on the tablets being transported by the transport device, A maintenance device for performing maintenance on the print head, The print head and the control device for controlling the maintenance device, Equipped with, The maintenance device includes a wiper for wiping the nozzle surface of the print head, It has a liquid receiving section that receives ink ejected from the print head, The control device controls the maintenance device to perform the wiping and then purge from the print head when the type of tablet being transported is an uncoated tablet, and controls the maintenance device to not perform the wiping before purging when the type of tablet being transported is a coated tablet.

2. The aforementioned wiper, A first wiper, which is a wet wiper supplied with wiping fluid, The second wiper is a dry wiper, A tablet printing apparatus according to claim 1, having the following features.

3. The tablet printing apparatus according to claim 2, wherein the control device controls the number of dummy ejections by the print head, or the amount of ejection, or both, according to the amount of wipe liquid supplied to the first wiper.

4. The maintenance device further comprises a suction unit for sucking the nozzle surface, The tablet printing apparatus according to claim 2, wherein in the wiping process, the print head is subjected to the following processes in order: suction by the suction unit, wiping by the first wiper, and wiping by the second wiper.

5. The tablet printing apparatus according to claim 2, characterized in that the control device reduces the wiping speed of at least one of the first wiper and the second wiper when the number of wiping cycles by the first wiper and the second wiper exceeds a predetermined number of cycles.

6. The system further comprises a drying unit for drying the second wiper, The tablet printing apparatus according to claim 2, characterized in that the control device dries the second wiper with the drying unit when the number of wiping cycles by the second wiper exceeds a predetermined number of cycles.

7. The system further includes a wipe liquid supply unit that supplies the wipe liquid to the first wiper, The tablet printing apparatus according to claim 2, characterized in that the control device supplies the wipe liquid from the wipe liquid supply unit to the first wiper at predetermined intervals.

8. The tablet printing apparatus according to claim 7, characterized in that the control device changes the amount of wipe liquid supplied from the wipe liquid supply unit to the first wiper or the frequency of supplying the wipe liquid according to the type of ink.

Images