Tablet printing apparatus and tablet printing method

Abstract

The objective is to provide a tablet printing apparatus and tablet printing method that can prevent a decline in print quality. [Solution] Tablets are supplied sequentially, the supplied tablets are transported sequentially, ink droplets are ejected from the print head onto the transported tablets to perform printing, the print head is maintained by a maintenance device having a first wiper and a second wiper that wipe the nozzle surface of the print head, and when the print head maintenance process is performed a predetermined number of times, the first wiper and the second wiper are maintained. Wiper maintenance involves applying a first suction force to one of the first and second wipers, which is used as a wet wiper after wiper maintenance, and applying a second suction force stronger than the first suction force to the other wiper, which is used as a dry wiper.

Description

Technical Field

[0001] Embodiments of the present invention relate to a tablet printing apparatus and a tablet printing method.

Background Art

[0002] In order 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 apparatus using this technique conveys a plurality of tablets in a row by a conveyor, and discharges ink (for example, edible ink) from 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. More specifically, wiping to remove ink and the like adhering to the surface (nozzle surface) where the nozzles of the printing head are provided, and dummy ejection to discharge a certain amount of ink from the nozzles to maintain stable ejection from the nozzles are performed as maintenance.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Wiping methods include wet wiping, which involves wiping with a hygroscopic material soaked in a wiping solution; dry wiping, which involves wiping without a wiping solution; and vacuum wiping, which involves using a wiper connected to a suction source to suck the nozzle surface. In particular, ink used for printing on tablets needs to dry quickly on the tablet surface because printing is performed on tablets during transport, and after printing, multiple tablets are collected on the same conveyor or in a collection box, or placed in PTP (press-through-pack) packaging sheets. For this reason, inks often contain a large amount of highly volatile solution. Ink that adheres to wipers used to wipe inkjet heads that eject such ink tends to harden upon drying. If wiping is performed again with hardened ink attached to the wiper, it may damage the nozzle surface, requiring frequent wiper replacement, which incurs extra costs and effort. Furthermore, continued use without replacing the wiper will result in a decrease in print quality.

[0006] The present invention aims to provide a tablet printing apparatus and a tablet printing method that can prevent a decrease in print quality. [Means for solving the problem]

[0007] The tablet printing apparatus according to the embodiment includes a supply device for storing a plurality of tablets and sequentially supplying the stored tablets, a transport device for transporting the tablets supplied from the supply device, an inkjet type print head for printing by ejecting ink droplets onto the tablets transported by the transport device, a maintenance device for maintaining the print head, a moving mechanism for moving the print head and the maintenance device relative to each other, a first wiper and a second wiper provided on the maintenance device for sequentially contacting and wiping the nozzle surface of the print head, a wiper maintenance device for maintaining the first wiper and the second wiper, and the print head, the maintenance device, the moving mechanism, and the wiper The system comprises a control device for controlling a wiper maintenance device, wherein the control device causes the wiper maintenance device to perform wiper maintenance when the number of times the print head has been maintained by the maintenance device exceeds a predetermined number of times, and the wiper maintenance by the wiper maintenance device is performed by supplying and suctioning cleaning fluid to the first wiper and the second wiper, and in the suction, a first suction force is applied to one of the first and second wipers which will be used as a wet wiper containing wiping fluid after the wiper maintenance is completed, and a second suction force stronger than the first suction force is applied to the other wiper which will be used as a dry wiper.

[0008] The tablet printing apparatus according to the embodiment includes a supply device for storing a plurality of tablets and sequentially supplying the stored tablets, a transport device for transporting the tablets supplied from the supply device, an inkjet type print head for printing by ejecting ink droplets onto the tablets transported by the transport device, a maintenance device for maintaining the print head, a moving mechanism for moving the print head and the maintenance device relative to each other, a first wiper and a second wiper provided on the maintenance device for sequentially contacting and wiping the nozzle surface of the print head, a wiper maintenance device for maintaining the first wiper and the second wiper, and a control system for the print head, the maintenance device, the moving mechanism, and the wiper maintenance device. The system comprises a control device, the control device, when the number of times the print head has been maintained by the maintenance device exceeds a predetermined number of times, causes the wiper maintenance device to perform wiper maintenance, the wiper maintenance by the wiper maintenance device is performed by supplying and suctioning cleaning fluid to the first wiper and the second wiper, and in the suction, the suction force to be applied to the wiper that will be used as a dry wiper after the wiper maintenance is completed is applied to both the first wiper and the second wiper, and then wipe fluid is supplied only to the wiper that will be used as a wet wiper after the wiper maintenance is completed.

[0009] The tablet printing method according to the embodiment comprises: a supply step of sequentially supplying tablets; a transport step of sequentially transporting the supplied tablets; a printing step of printing by ejecting ink droplets from an inkjet print head onto the transported tablets; a print head maintenance step of maintaining the print head using a maintenance device having a first wiper and a second wiper for wiping the nozzle surface of the print head; and a wiper maintenance step of maintaining the first wiper and the second wiper when the print head maintenance step has been performed a predetermined number of times, wherein the wiper maintenance step is performed by supplying and suctioning a cleaning solution to the first wiper and the second wiper, and is characterized in that a first suction force is applied to one of the first and second wipers which is used as a wet wiper after the wiper maintenance step is completed and suction is performed, and a second suction force stronger than the first suction force is applied to the other wiper which is used as a dry wiper and suction is performed. [Effects of the Invention]

[0010] According to embodiments of the present invention, it is possible to provide a tablet printing apparatus and a tablet printing method that can prevent a decrease in print quality. [Brief explanation of the drawing]

[0011] [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 side view showing an example of a schematic configuration of a wiper according to the first embodiment. [Figure 6] This is a plan view showing an example of the schematic configuration of the first wiper according to the first embodiment. [Figure 7] It is a figure which shows an example of the schematic structure of the maintenance device which concerns on a 1st Embodiment. [Figure 8] It is a figure which shows an example of the schematic structure of the maintenance device which concerns on a 2nd Embodiment. [Figure 9] It is a figure which shows a time when the maintenance device which concerns on a 2nd Embodiment is located in a maintenance position. [Figure 10] It is a figure which shows a time when the maintenance device which concerns on a 2nd Embodiment is located in a 2nd standby position. [Figure 11] It is a figure which shows a time when the maintenance device which concerns on a 2nd Embodiment is located in a maintenance position.

MODE FOR CARRYING OUT THE INVENTION

[0012] <First Embodiment> A 1st Embodiment is demonstrated referring FIGS. 1-6.

[0013] (Configuration example of tablet printing device) As shown in FIGS. 1 and 2, the tablet printing device 1 which concerns on a 1st Embodiment includes a supply device 10, a conveyance device 20, a detection device 30, a 1st imaging device 40, a printing device 50, a 2nd imaging device 60, a collection device 70, a maintenance device 80 (refer to FIG. 2), and a control device 90.

[0014] The supply device 10 has a hopper 11 and a shooter 12. This supply device 10 is positioned on one end side of the conveyance device 20, and is comprised so that the tablet T which is a printing object may be supplied to the conveyance device 20. The hopper 11 accommodates a large number of tablets T, and sequentially supplies the accommodated tablets T to the shooter 12. The shooter 12 aligns the tablets T supplied from the hopper 11 in a line and supplies them to the conveyance device 20. The supply device 10 is electrically connected to the control device 90, and its drive is controlled by the control device 90.

[0015] 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.

[0016] 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.

[0017] The detection device 30 includes a plurality of detection units 31 (two in this embodiment). The detection unit 31 is positioned downstream of the position where the supply device 10 is provided in the conveying direction H1 and is provided above the conveying belt 21. This detection unit 31 detects the position of the tablet T on the conveying belt 21 in the X direction (see FIG. 2) by transmitting and receiving laser light. As the detection unit 31, for example, a displacement sensor, a proximity sensor, or the like is used. Further, as the displacement sensor, for example, various laser sensors such as a reflection type laser sensor are used. The detection device 30 is electrically connected to the control device 90 and transmits a detection signal to the control device 90.

[0018] 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 of the position where the detection device 30 is provided in the conveying direction H1 and is provided above the conveying belt 21. Based on the position information of the tablet T in the X direction 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 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 driving is controlled by the control device 90. In addition, illumination for imaging is provided as necessary.

[0019] 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. Further, 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 directional shape, such as when a scoring line is provided on the tablet T or when the tablet T is molded into an elliptical, oval, rectangular, or other shape.

[0020] The printing device 50 includes a print head 51 and a lifting mechanism 52. The print head 51 is positioned downstream in the transport direction H1 from the position where the first imaging device 40 is installed, and is located above the transport belt 21. The print head 51 has multiple (for example, several hundred to several thousand) nozzles 51a (see Figure 2), and the direction in which the nozzles 51a are arranged in a row (nozzle row) is perpendicular to the transport direction H1 in the horizontal plane (an example of intersection). In Figure 2, for the sake of simplification, four nozzles 51a are shown. The print head 51 ejects ink individually from each nozzle 51a by the operation of a drive element for each nozzle 51a. Various inkjet type print heads having drive elements such as piezoelectric elements, heating elements, or magnetostrictive elements are used as the print head 51. The print head 51 can be raised and lowered to approach or move away from the transport belt 21 by the lifting mechanism 52 (see Figure 1). The printing head 51 is raised and lowered during maintenance of the printing head 51. Maintenance of the printing head 51 will be described later. The printing device 50 is electrically connected to the control device 90, and its drive is controlled by the control device 90.

[0021] The second imaging device 60 comprises a plurality of second imaging units 61 (two in this embodiment). The second imaging units 61 are positioned downstream in the transport direction H1 from the position where the printing device 50 is installed, and are located above the transport belt 21. 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, the second imaging unit 61 takes an image when the tablet T reaches the imaging position directly below the second imaging unit 61, acquires a second image including the top surface of the tablet T, and transmits the acquired second image to the control device 90. The second image is used to inspect the printing pattern printed on the tablet T. As with the first imaging unit 41 described above, various cameras having image sensors such as CCD or CMOS are used as the second imaging unit 61. The second imaging device 60 is electrically connected to the control device 90, and its drive is controlled by the control device 90. Illumination for imaging is also provided as needed.

[0022] 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.

[0023] 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.

[0024] 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 80 is electrically connected to the control device 90, and its drive is controlled by the control device 90.

[0025] 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.

[0026] Next, an example of the configuration of the control device 90 will be described with reference to Figure 4.

[0027] 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.

[0028] 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.

[0029] 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 T 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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).

[0034] 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.

[0035] (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 liquid receiving section 81, suction section 82, and wiper 83 from the print head 51 side, and are provided to be movable as a single unit by the moving mechanism 84.

[0036] 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).

[0037] 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 and tablet powder adhering to the nozzle surface.

[0038] 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.

[0039] The first wiper 83a and the second wiper 83b are both roll-shaped wipers made of an absorbent fibrous material, such as nonwoven fabric. When used as a wet wiper, the first wiper 83a and the second wiper 83b are impregnated with a wiping liquid (for example, an aqueous solution containing ethanol) on their surface, and when used as a dry wiper, they are in a dry state (a state in which they do not contain wiping liquid, or contain at least less wiping liquid than a wet wiper, or at least a state in which they can absorb liquids such as ink and wiping liquid that adhere to the nozzle surface of the print head 51 during the maintenance process of the print head 51 described later).

[0040] The moving mechanism 84 has a drive unit (not shown), and the liquid receiving unit 81, the suction unit 82, and the wiper 83 can be moved by the drive unit to 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 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 located offset from above the conveyor belt 21 (details will be described later).

[0041] (Wiper maintenance device) As shown in Figures 5 and 6, the first wiper 83a and the second wiper 83b are each equipped with maintenance devices. Figure 5 is a side view of the first wiper 83a and the second wiper 83b, and Figure 6 is a top view of the first wiper 83a. Note that the illustration of this maintenance device is omitted in Figure 3, which was explained earlier.

[0042] The first wiper 83a is housed inside the case 831. A cleaning fluid supply pipe 831a for supplying wipe fluid (an example of a cleaning fluid) and a suction pipe 831b for drawing water from inside the case 831 are connected to the bottom of the case 831 via corresponding openings. The cleaning fluid supply pipe 831a is connected to a cleaning fluid supply tank (not shown), and the suction pipe 831b is connected to a recovery tank (not shown). As mentioned above, the first wiper 83a is a roll-shaped wiper and is rotatable, but as will be described later, when it slides in contact with the nozzle surface of the print head 51, it is fixed in place by a stopper (not shown) to prevent it from rotating.

[0043] Similarly, the second wiper 83b is housed inside the case 832, and the cleaning fluid supply pipe 832a and the suction pipe 832b are connected to the bottom of the case 832 via corresponding openings. The cleaning fluid supply pipe 832a is connected to a cleaning fluid supply tank (not shown), and the suction pipe 832b is connected to a recovery tank (not shown). Like the first wiper 83a, the second wiper 83b is a roll-shaped wiper and is rotatable, but is fixed in place by a stopper (not shown) to prevent rotation when it is in contact with and sliding against the nozzle surface of the print head 51.

[0044] Here, we illustrate the case where the first wiper 83a functions as a wet wiper. The wiping fluid is supplied into the case 831 by opening a valve 831c located between the cleaning fluid supply pipe 831a and the cleaning fluid supply tank, so that the surface of the first wiper 83a housed in the case 831 becomes saturated with the wiping fluid. The wiping fluid supplied into the case 831 initially soaks into a portion of the first wiper 83a and gradually spreads over the entire surface. When it is necessary to remove the wiping fluid from the surface of the first wiper 83a, a negative pressure is generated inside the case 831 by opening a valve 831d located between the suction pipe 831b and the recovery tank, thereby removing the excess wiping fluid from the surface of the first wiper 83a.

[0045] Next, we will illustrate the case where the second wiper 83b functions as a dry wiper. That is, the second wiper 83b is kept dry when wiping the print head 51, and wiping fluid is supplied when maintenance is performed on the second wiper 83b. The wiper maintenance process for supplying wiping fluid to the second wiper 83b from the cleaning fluid supply pipe 832b will be described later.

[0046] The first wiper 83a and the second wiper 83b are held in a state where a portion of each is in contact with the inner wall of the cases 831 and 832. Alternatively, they are held in a state where there is a small gap between the inner wall of the cases 831 and 832 and the first wiper 83a and the second wiper 83b. This allows suction to be applied to the opening on the bottom surface of the cases 831 and 832 that is connected to the suction pipe 831b, creating negative pressure inside the cases 831 and 832, which in turn removes excess wipe liquid.

[0047] Case 831, cleaning fluid supply piping 831a, suction piping 831b, valves 831c and 831d are examples of a first wiper maintenance device (wiper maintenance device), and case 832, cleaning fluid supply piping 832a, suction piping 832b, valves 832c and 832d are examples of a second wiper maintenance device (wiper maintenance device).

[0048] (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. Here, the printing process refers to the continuous printing of multiple 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.

[0049] Under the control of the control unit 93, when the printing process of the tablet printing device 1 is started, the motor 24 is driven, and the conveyor belt 21 rotates in the conveying direction H1 as the drive pulley 22 is 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 two rows and supplies them onto the conveyor belt 21. The tablets T supplied onto the conveyor belt 21 are conveyed in two rows on the conveyor belt 21 at a predetermined moving speed.

[0050] 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 the irradiation position of the laser beam of the detection unit 31 of the detection device 30, the detection unit 31 detects the arrival of the tablet T from the change in the received light output. Based on the timing of this 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.

[0051] 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.

[0052] 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 transport belt 21. Specifically, the printable tablets T on the transport 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 tablets T is dried during transport. This can be done by natural drying, or a drying unit (not shown) that uses gas or heat to dry the ink may be provided and the ink may be dried by the drying unit.

[0053] 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.

[0054] 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.

[0055] 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).

[0056] 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.

[0057] (Maintenance process) In a printing operation that performs such a printing process, maintenance of the print head 51 is performed at predetermined timings. Maintenance methods include purging, wiping, and dummy ejection. Purge is an operation in which ink is pumped under pressure with the ink receiving unit 81 facing the print head 51, causing ink to be ejected from the print head 51 towards the ink receiving unit 81. By performing the purging operation, air bubbles and ink that has dried, thickened, or solidified can be removed from inside the nozzle 51a, preventing ejection failures. Wiping is the removal of ink and other substances adhering to the nozzle surface of the print head 51. Wiping is performed by suction by the suction unit 82 or wiping by the wiper 83. By performing wiping, 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 ink receiving unit 81 facing the print head 51 to eject a small amount of ink. The thickened ink can also be removed from the nozzle 51a by dummy ejection. Note that "printing operation" refers to the state in which the tablet printing apparatus 1 is operational, that is, in a state where printing can be performed, including the printing process and maintenance process.

[0058] The maintenance procedure is as follows. During the maintenance process, the supply of tablets T by the supply device 10 will be temporarily stopped.

[0059] When it is time for maintenance of the print head 51, the control device 90 controls the lifting mechanism 52 to raise the print head 51. More specifically, the print head 51 is raised to a height where the lower surface of the print head 51 does not come into contact with the suction unit 82 and wiper 83 of the maintenance device 80, even when the suction unit 82 and wiper 83 are moved. This creates a space between the conveyor belt 21 and the print head 51 that the maintenance device 80 can enter.

[0060] Next, the control device 90 controls the moving mechanism 84 to position the liquid receiving section 81 facing the nozzle surface of the print head 51. Furthermore, it controls the lifting mechanism 52 to lower the print head 51 to a height where, as shown in Figure 7, when wiping, 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.

[0061] In this state, the control device 90 pressurizes the ink in the print head 51 and performs a purging operation.

[0062] Next, the control device 90 controls the moving mechanism 84 to move the suction unit 82 and the wiper 83 to the right in Figure 7. During this movement, the print head 51 receives 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. Here, the first wiper 83a and the second wiper 83b are wipers made of nonwoven fabric in a roll shape, but they do not rotate when wiping the nozzle surface of the print head 51, and wipe the nozzle surface while remaining fixed.

[0063] Once these wiping operations are complete, the control device 90 controls the lifting mechanism 52 to raise the print head 51 to a height where it does not come into contact with the suction unit 82 or the wiper 83. Once the print head 51 has finished rising, the control device 90 controls the moving mechanism 84 to position the liquid receiving unit 81 so that it faces the nozzle surface of the print head 51. Then, with the liquid receiving unit 81 and the nozzle surface of the print head 51 facing each other, the print head 51 is made to perform dummy ejection.

[0064] When the dummy dispensing is complete, the control device 90 controls the moving mechanism 84 to move the maintenance device 80 (suction unit 82 and wiper 83) to the standby position. That is, it moves it to the left as shown in Figure 7. Next, it controls the lifting mechanism 52 to lower the print head 51 to the height position for printing on the tablet T. When the print head 51 is lowered, the maintenance process is complete. After the maintenance process is complete, the supply of tablet T by the supply device 10 is resumed, and the printing process is performed to print on the tablet T.

[0065] (Wiper maintenance process) Next, the maintenance process for the wiper 83 will be explained using Figure 5 (and Figure 6). As mentioned above, maintenance of the print head 51 is performed in the following order: vacuum wiping by the suction unit 82, wet wiping by the first wiper 83a, and dry wiping by the second wiper 83b. As mentioned above, the suction unit 82 performs vacuum wiping without contacting the nozzle surface of the print head 51. That is, in the maintenance device 80, the first wiper 83a, which is a wet wiper, first contacts and wipes the nozzle surface of the print head 51, and then the second wiper 83b, which is a dry wiper, contacts and wipes the nozzle surface of the print head 51. As wiping by the wiper 83 is repeated, the wiping liquid that has soaked into the first wiper 83a gradually dries, and ink, tablet powder, etc. adhere to the surface of the first wiper 83a and solidify. Furthermore, with the second wiper 83b, the wiping liquid supplied to the nozzle surface and the ink that was attached to the nozzle surface adhere to it more than with the wiping by the first wiper 83a, and the dry state is no longer maintained.

[0066] Therefore, maintenance of the wiper 83 is performed when maintenance of the print head 51 by the wiper 83 has been performed a predetermined number of times (or when a predetermined time has elapsed since the start of operation of the device). The optimal timing for performing maintenance on the wiper 83 varies depending on the type of ink used in the print head 51 and the type of tablet being printed. Specifically, in printing using ink that contains many highly volatile components, the ink tends to dry out quickly. Also, in the case of tablets that generate a lot of tablet powder (for example, OD (Orally Disintegrating) tablets), a large amount of tablet powder tends to adhere to the nozzle surface of the print head 51 in a short time. In such cases, the wiper 83 tends to become dirty or dry out quickly when the print head 51 is maintained by the maintenance device 80, so it is desirable to take this into consideration and determine the timing of wiper 83 maintenance in advance through experiments, etc.

[0067] First, the maintenance of the first wiper 83a will be described. Open the valve 831c and supply new wipe fluid to the case 831 of the first wiper 83a. The wipe fluid is supplied so that, for example, an area greater than or equal to the radius of the circular cross-section of the first wiper 83a is submerged. Alternatively, the wipe fluid level in the case 831 is supplied so that it reaches more than half the height of the case 831. When the wipe fluid is supplied to the case 831, it penetrates the entire surface of the first wiper 83a, and the ink that had adhered to and solidified on the surface of the first wiper 83a liquefies again and floats to the surface. At this time, the first wiper 83a may be rotated by a rotating mechanism (not shown) so that the surface that was in contact with the print head 51 is on the bottom side of the case 831 when the wipe fluid is supplied. Once the first wiper 83a is sufficiently saturated with wiping fluid (the time required for the wiping fluid to saturate may be determined in advance through experiments, and this can be judged based on the elapsed time), valve 831c is closed. Next, valve 831d is opened to suction out the dirty wiping fluid, and valve 831d is closed. Then, valve 831c is opened to supply the wiping fluid, valve 831c is closed, valve 831d is opened to suction out, and valve 831d is closed. This operation is repeated a predetermined number of times (for example, 4 times, for a total of 5 times). After maintenance of the first wiper 83a, it is necessary to retain enough wiping fluid in the first wiper 83a to use it as a wet wiper again. Therefore, the suction force (first suction force) by the suction pipe 831b during the final suction by the suction pipe 831b is set taking this into consideration.

[0068] Next, the maintenance of the second wiper 83b will be described. Valve 832c is opened to supply new wiping fluid to the case 832 of the second wiper 83b. The wiping fluid penetrates the entire surface of the second wiper 83b, and the ink that had adhered to the surface of the second wiper 83b and solidified becomes liquefied again. After a predetermined time has elapsed, valve 832c is closed and valve 832d is opened to suction the inside of the case 832 and collect the soiled wiping fluid. This operation is repeated a predetermined number of times (for example, 4 times, for a total of 5 times). After the maintenance of the second wiper 83b, it is necessary to allow the second wiper 83b to dry sufficiently to be used as a dry wiper again, so the suction force by the suction pipe 832b during the final suction by the suction pipe 832b (second suction force) is determined taking this into consideration.

[0069] The second suction force is stronger than the first suction force described above. Alternatively, if the suction force per unit time applied by suction pipe 831b to case 831 and suction pipe 832b to case 832 is the same, the second suction force may be increased by making the time spent being sucked by suction pipe 832b longer than the time spent being sucked by suction pipe 831b. In other words, the second suction force is a suction force that allows the amount of wiping liquid contained in the wiper used as a dry wiper (second wiper 83b in this embodiment) to be less than the amount of wiping liquid contained in the wiper used as a wet wiper (first wiper 83a in this embodiment) after it has been sucked by the first suction force.

[0070] Furthermore, maintenance of the wiper 83 is performed when the maintenance device 80 is not in use and is in a standby position. This allows printing on the tablets T by the print head 51 to continue while maintenance of the wiper 83 is being performed, thus enabling maintenance of the wiper 83 without reducing productivity.

[0071] As explained above, according to the first embodiment, maintenance of the wiper 83 of the maintenance device 80 is performed at a time when the print head 51 is not being maintained by the maintenance device 80. This prevents the wiping liquid that has soaked into the surface of the first wiper 83a, which functions as a wet wiper, from gradually drying out, and prevents the ink that has been wiped from the nozzle surface by the first wiper 83a from solidifying on the surface of the first wiper 83a. Alternatively, it prevents the wiping liquid from adhering to the second wiper 83b, which functions as a dry wiper, and preventing it from remaining dry. This prevents damage to the print head 51 caused by continued use without maintenance of the wiper 83, and prevents a decrease in print quality caused by printing being performed without sufficient maintenance of the nozzle surface of the print head 51 due to continued use without maintenance of the wiper 83. In addition, since the wiper 83 can be used again after maintenance without replacing the wiper 83 itself, it is possible to avoid unnecessary costs and effort.

[0072] <Second Embodiment> In this embodiment, components common to the first embodiment will be described using the same reference numerals.

[0073] As shown in Figure 8, the maintenance device 800 in this embodiment is provided with a liquid receiving section 81, a suction section 82, and a wiper 83, as well as a liquid receiving section 810 and a suction section 820.

[0074] The liquid receiving section 810 is identical to the liquid receiving section 81, and the suction section 820 is identical to the suction section 82. The liquid receiving section 810 and the suction section 820, and the liquid receiving section 81 and the suction section 82 are arranged symmetrically with respect to the wiper 83. Maintenance of the print head 51 using this maintenance device 800 will now be described.

[0075] The maintenance device 800 is capable of moving between the maintenance position, a first standby position, and a second standby position by a moving mechanism 84 (not shown in Figure 8). The maintenance position is the position of the maintenance device 800 during maintenance of the print head 51, and is located between the transport belt 21 and the print head 51. As shown in Figure 8, the first standby position is the position to the left of the print head 51 when viewed from the upstream side in the transport direction H1, and the second standby position is the position to the right. Before maintenance by the maintenance device 800 begins, the maintenance device 800 is initially positioned in the first standby position, as shown in Figure 8.

[0076] (First maintenance procedure) When it is time to perform maintenance on the print head 51, the control unit 90 controls the lifting mechanism 52 to raise the print head 51, controls the moving mechanism 84 to position the liquid receiving section 81 facing the nozzle surface of the print head 51 (see Figure 9), and pumps the ink from inside the print head 51 to perform a purging operation. Next, the control device 90 controls the moving mechanism 84 to move the maintenance device 800 to the right as shown in Figure 9, and performs wiping by facing the nozzle surface in the order of the suction section 82, the first wiper 83a which functions as a wet wiper, and the second wiper 83b which functions as a dry wiper. After wiping is complete, the control device 90 continues to move the maintenance device 800 to the right, controlling it so that the liquid receiving section 810 is directly below the nozzle surface of the print head 51, and causes the print head 51 to perform dummy ejection with the liquid receiving section 810 and the nozzle surface of the print head 51 facing each other. Here, the maintenance device 90 is in the maintenance position when at least one of the liquid receiving section 81, suction section 82, wiper 83, suction section 820, or liquid receiving section 810 of the maintenance device 800 is in a position facing the nozzle surface. Once dummy dispensing is complete, the control device 90 controls the lifting mechanism 52 to raise the print head 51 and move the maintenance device 800 to the right to the second standby position shown in Figure 10. Next, the lifting mechanism 52 is controlled to lower the print head 51 to the height at which printing will be performed on the tablet T. Once the print head 51 has lowered, the maintenance process is complete.

[0077] (Wiper maintenance process) In this embodiment, the maintenance device 800 is moved from the first standby position to perform maintenance on the print head 51 using the maintenance device 800, and then the wiper 83 is maintained at the second standby position. The maintenance process for the wiper 83 is the same as the method described in the first embodiment, and only the differences will be explained.

[0078] In this embodiment, maintenance of the wiper 83 involves, after completing maintenance of the first wiper 83a and the second wiper 83b, preparing the first wiper 83a, which was being used as a wet wiper, for use as a dry wiper, and the second wiper 83b, which was being used as a dry wiper, for use as a wet wiper. Specifically, after supplying wiping fluid to the case 831 of the first wiper 83a and repeating the operation of sucking the case 831 a predetermined number of times (for example, 4 times), the suction force during the final (5th) suction by the suction pipe 831b is set to the second suction force described in the first embodiment. On the other hand, in the second wiper 83b, after supplying wiping fluid to the case 832 and repeating the operation of sucking the case 832 a predetermined number of times, the suction force during the final suction by the suction pipe 832b is set to the first suction force described in the first embodiment. This allows the first wiper 83a to be in a state where it is dry enough to be used as a dry wiper, while the second wiper 83b has enough wipe liquid on its surface to be used as a wet wiper.

[0079] (Second maintenance procedure) After a predetermined time has elapsed and it is time to perform maintenance on the print head 51 again, the control device 90 controls the lifting mechanism 52 to raise the print head 51 and move the maintenance device 800 to the left as shown in Figure 11, so that it is positioned from the second standby position to the maintenance position. The liquid receiving section 810 is positioned to face the nozzle surface of the print head 51 (see Figure 11), and the ink in the print head 51 is pumped out to perform a purging operation. After that, the control device 90 controls the moving mechanism 84 to move the maintenance device 800 to the left as shown in Figure 11, and wipes the nozzle surface in the order of suction section 820, second wiper 83b, and first wiper 83a. After wiping is complete, the control device 90 continues to move the maintenance device 800 to the left, controlling it so that the liquid receiving section 81 is directly below the nozzle surface of the print head 51, and with the liquid receiving section 81 and the nozzle surface of the print head 51 facing each other, the print head 51 is made to perform dummy ejection.

[0080] When the dummy ejection is complete, the control device 90 controls the moving mechanism 84 to move the maintenance device 800 to the first standby position. Next, it controls the lifting mechanism 52 to lower the print head 51 to the height position for printing on the tablets T. When the print head 51 is 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.

[0081] As explained above, the second embodiment provides the same effects as the first embodiment. In addition, in the first maintenance process for the print head 51, the first wiper 83a is used as a wet wiper and the second wiper 83b is used as a dry wiper, followed by a maintenance process for the wiper 83, and in the second maintenance process for the print head 51, the first wiper 83a is used as a dry wiper and the second wiper 83b is used as a wet wiper. Of the wet wiper and the dry wiper, the wet wiper that first contacts the print head 51 is used to wipe away ink adhering to the nozzle surface of the print head 51. The wet wiper is more prone to getting dirty and wears out faster than the dry wiper that comes into contact later. However, according to this embodiment, the wet wiper that wipes the print head 51 first is alternated. Since the wiper that wipes the nozzle surface of the print head 51 in the dirtiest state is alternated between the first wiper 83a and the second wiper 83b, the wear of the wiper 83 can be slowed down compared to when it is used without alternation.

[0082] <Other Embodiments> In the above explanation, it was stated that two print heads 51 are provided, but there may be one, or three or more.

[0083] In the embodiments described above, the tablet printing device 1 is shown to print only on one side of the tablet T on the conveyor belt 21, but it is not limited to this. For example, a conveying mechanism that inverts the tablet T may be employed to print on the other side of the tablet T as well.

[0084] 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.

[0085] Furthermore, in the above embodiment, it was illustrated that a suction unit 82 is provided in front of the wiper 83 in the direction of movement of the maintenance device 80, and a suction unit 82 or 820 is provided in front of the wiper 83 in the direction of movement of the maintenance device 800. However, the invention is not limited to this, and the suction units 82 and 820 are not necessarily required to be provided.

[0086] 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 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.

[0087] Furthermore, while 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 defect is detected based on the second image.

[0088] Furthermore, in the second embodiment described above, the wiper that first wipes the nozzle surface of the print head 51 is swapped between the first wiper 83a and the second wiper 83b by changing the direction of movement of the maintenance device 800, but the embodiment is not limited to this. For example, a rotating mechanism that can swap the positions of the first wiper 83a and the second wiper 83b may be provided between maintenance of the print head 51, and the swapping may be performed in between maintenance.

[0089] Furthermore, in the second embodiment described above, the movement direction of the maintenance device 800 by the moving mechanism 84 is changed each time maintenance of the print head 51 is performed, but the embodiment is not limited to this. For example, maintenance of the print head 51 may be performed a predetermined number of times (e.g., 5 times) by moving back and forth between the first standby position and the maintenance position shown in Figure 8, then the maintenance device 800 may be moved to the second standby position to perform maintenance on the wiper 83, and then the maintenance of the print head 51 may be performed a predetermined number of times by moving back and forth between the second standby position and the maintenance position. The same effects as in the second embodiment can be obtained even if this is done.

[0090] 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 wiper 83 slides along the nozzle surface of the print head 51) may be controlled by controlling the moving mechanism 84.

[0091] Furthermore, a wetness detection sensor can be provided to detect the amount of wiping fluid 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. Based on the detected value transmitted from the wetness detection sensor, the control device 90 can determine the wetness state of the first wiper 83a. Based on the determination result, the control device 90 may initiate a maintenance process for the wiper 83.

[0092] Furthermore, in the above-described embodiment, the first suction force applied to the wet wiper during the wiper maintenance process is set considering how to hold enough wipe liquid in the wiper 83 (first wiper 83a or second wiper 83b) to be used as a wet wiper. Here, if the tablet T is a coated tablet such as a sugar-coated tablet, it may be necessary to include a large amount of fixing agent (e.g., resin) in the ink used for printing. In such cases, the viscosity of the ink increases, and a large amount of wipe liquid may be required to wipe away the ink adhering to the nozzle surface of the print head 51. The first suction force may also be set considering the type of tablet T and the type of ink used.

[0093] Furthermore, while the above-described embodiment illustrates the use of a wiping liquid as an example of a cleaning liquid, it is not limited to this. For example, maintenance of the wiper 83 may be performed by supplying a cleaning liquid other than the wiping liquid through cleaning liquid supply pipes 831a and 832a, and at the end of the maintenance, the wiping liquid may be supplied to the wiper to be used as the next wet wiper.

[0094] Furthermore, in the above-described embodiment, the suction force of the wipe liquid at the end of the maintenance process for the first wiper 83a and the second wiper 83b was exemplified as being set to the first suction force for those to be used as wet wipers and to the second suction force for those to be used as dry wipers, but the invention is not limited to this. For example, both may be suctioned with the second suction force, and the wipe liquid may be supplied only to the wiper to be used as a wet wiper.

[0095] Furthermore, while the above-described embodiment illustrates the connection of cleaning fluid supply pipes 831a, 832a and suction pipes 831b, 832b to the bottom surfaces of cases 831 and 832, the embodiment is not limited to this. For example, supply and suction may be performed from the side walls and top surfaces of cases 831 and 832.

[0096] 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.

[0097] 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]

[0098] 1. Tablet printing machine 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, 800 Maintenance equipment 81, 810 Liquid receiving section 82, 820 Suction part 83 Wiper 83a First wiper 83b Second wiper 831 cases 831a Cleaning fluid supply piping 831b Suction piping 831c valve 831d valve 832 cases 832a Cleaning fluid supply piping 832b Suction piping 832c valve 832d valve 84 Moving mechanism 90 Control device T Tablets

Claims

1. A supply device that holds multiple tablets and sequentially supplies the held tablets, A conveying device for conveying the tablets supplied from the supplying device, An inkjet type print head that ejects ink droplets to print on the tablets being transported by the transport device, A maintenance device for performing maintenance on the print head, A moving mechanism for moving the print head and the maintenance device relative to each other, The maintenance device is provided with a first wiper and a second wiper that sequentially contact and wipe the nozzle surface of the print head, A wiper maintenance device for performing maintenance on the first wiper and the second wiper, A control device that controls the print head, the maintenance device, the moving mechanism, and the wiper maintenance device, Equipped with, The control device, when the number of times the print head has been maintained by the maintenance device exceeds a predetermined number of times, causes the wiper maintenance device to perform wiper maintenance. The wiper maintenance by the wiper maintenance device is performed by supplying and suctioning a cleaning solution to the first wiper and the second wiper, and in the suction, a first suction force is applied to one of the first and second wipers which will be used as a wet wiper containing the cleaning solution after the wiper maintenance is completed, and a second suction force stronger than the first suction force is applied to the other wiper which will be used as a dry wiper.

2. The tablet printing apparatus according to claim 1, characterized in that the cleaning solution is the same as the wiping solution.

3. The control device causes the wiper maintenance by the wiper maintenance device to be performed during the maintenance of the print head. The tablet printing apparatus according to claim 1 or 2, characterized in that, before and after the wiper maintenance, the wiper that contacts the print head first among the first wiper and the second wiper is changed.

4. Maintenance of the print head by the maintenance device is performed by moving the print head and the maintenance device relative to each other using the moving mechanism. The tablet printing apparatus according to claim 1 or 3, characterized in that, due to movement by the moving mechanism, the wiper that first contacts the print head among the first wiper and the second wiper is a wet wiper.

5. The tablet printing apparatus according to claim 3, wherein the change of the wiper that first contacts the print head is performed by changing the direction of movement of the moving mechanism.

6. A supply device that holds multiple tablets and sequentially supplies the held tablets, A conveying device for conveying the tablets supplied from the supplying device, An inkjet type print head that ejects ink droplets to print on the tablets being transported by the transport device, A maintenance device for performing maintenance on the print head, A moving mechanism for moving the print head and the maintenance device relative to each other, The maintenance device is provided with a first wiper and a second wiper that sequentially contact and wipe the nozzle surface of the print head, A wiper maintenance device for performing maintenance on the first wiper and the second wiper, A control device that controls the print head, the maintenance device, the moving mechanism, and the wiper maintenance device, Equipped with, The control device, when the number of times the print head has been maintained by the maintenance device exceeds a predetermined number of times, causes the wiper maintenance device to perform wiper maintenance. The wiper maintenance by the wiper maintenance device is performed by supplying and suctioning cleaning fluid to the first wiper and the second wiper, and in the suction, the suction force to be applied to the wiper that will be used as a dry wiper after the wiper maintenance is completed is applied to both the first wiper and the second wiper, and then the wiper fluid is supplied only to the wiper that will be used as a wet wiper after the wiper maintenance is completed.

7. A supply process that sequentially supplies tablets, A conveying step for sequentially transporting the supplied tablets, A printing process in which ink droplets are ejected from an inkjet print head onto the transported tablets, A print head maintenance process, which involves maintaining the print head using a maintenance device having a first wiper and a second wiper for wiping the nozzle surface of the print head, When the print head maintenance process has been performed a predetermined number of times, a wiper maintenance process is performed to maintain the first wiper and the second wiper, Equipped with, The wiper maintenance step is performed by supplying and suctioning a cleaning solution to the first wiper and the second wiper, and is characterized in that, after the wiper maintenance step is completed, a first suction force is applied to one of the first and second wipers which is used as a wet wiper and suction is performed, and a second suction force stronger than the first suction force is applied to the other wiper which is used as a dry wiper and suction is performed.

Images