TWI761036B - Tablet printing apparatus and maintenance method of tablet printing apparatus - Google Patents

Abstract

The present invention provides a technique for efficiently eliminating ink clogging while suppressing ink consumption in a tablet printing apparatus. The tablet printing apparatus includes an ink jet head having a plurality of nozzles capable of ejecting ink, a pressure adjustment unit capable of adjusting the pressure in the head, and a heater capable of raising the temperature of the ink to a first temperature and a second temperature inside the head device, and a control unit that controls each unit. The control unit can perform a printing step of ejecting ink of the first temperature from some nozzles to the surface of the tablet, and a recovery step of increasing the pressure in the head to eject ink of the second temperature from all the nozzles. The second temperature is a higher temperature than the first temperature. In this way, in the recovery step, by reducing the viscosity of the ink, the pressure loss in the nozzle is reduced, so that the amount of ink ejected in the recovery step can be suppressed.

Description

Tablet printing device and maintenance method of tablet printing device

The present invention relates to a tablet printing device that prints on the surface of a tablet and a maintenance method of the tablet printing device.

A character or code for identifying the product is printed on the surface of the tablet, which is a form of medicine. Such characters and codes are sometimes printed by engraving, but the engraving has a problem of low visibility. In particular, in recent years, the variety of tablets has been diversified due to the spread of general-purpose pharmaceuticals. Therefore, in order to easily identify the tablet, attention has been paid to a technique of clearly printing the surface of the tablet by an inkjet method.

In Patent Document 1, an example of a conventional apparatus for printing on the surface of a tablet by an ink jet method is described. [Prior Art Literature] [Patent Literature]

[Patent Document 1] International Publication No. 2016/159096

[The problem to be solved by the invention] In an ink jet type tablet printing apparatus, ink droplets are ejected onto the tablet from a plurality of nozzles provided on the ejection surface of the ejection head while the tablet is being conveyed. Hereinafter, this "droplet of ink" is simply referred to as "droplet of ink". In such an ink jet printing apparatus, the liquid level of the ink is arranged inside each nozzle. Therefore, in a nozzle that is used less frequently, the solvent of the ink evaporates from the liquid surface, and the rise of the meniscus, the aggregation of the ink components, the concentration of the ink components, and the like occur in the nozzle. As a result, the fluidity of the ink is lowered, and the problem of ink clogging occurs.

In order to solve such a problem, in a general inkjet printing apparatus, a maintenance method called a purge process is used in which the ink in the head is pressurized and the ink is ejected from all the nozzles at the same time. The ink is ejected by applying pressure by the cleaning process, and the generated agglomerated ink components or concentrated ink are ejected out of the nozzles.

On the other hand, the printing rate of the tablet printing apparatus is about 8%, which is lower than that of other printing apparatuses. Therefore, in many nozzles, the period during which ink is not ejected is long. That is, in the tablet printing apparatus, the fluidity of the ink tends to decrease compared with the case of other printing apparatuses, and the number of nozzles which are clogged with ink also increases.

Therefore, in the tablet printing apparatus, in order to eliminate the ink clogging by the conventional cleaning process, it is necessary to increase the cleaning time or the number of cleanings. That is, more ink is consumed than other printing devices.

However, edible inks used in tablet printing apparatuses are very expensive compared to inks used in ordinary media such as paper and film.

The present invention has been made in view of such a situation, and an object of the present invention is to provide a technique capable of efficiently eliminating ink clogging while suppressing the consumption of ink. [Means of Solving Problems]

In order to solve the above-mentioned problems, the first invention of the present application is an inkjet-type tablet printing apparatus for printing the surface of a tablet, comprising: an inkjet-type head including a plurality of nozzles capable of ejecting ink; a pressure adjustment unit , which can adjust the pressure in the nozzle; a heater can heat the ink ejected from the nozzle to a first temperature and a second temperature inside the nozzle; and a control unit controls the nozzle, the pressure adjustment unit and the heater, and the control unit can perform: a printing step of ejecting the ink of the first temperature from a part of the nozzles on the surface of the tablet; and a recovery step, The pressure in the head is increased by the pressure adjustment unit, and the ink of the second temperature is ejected from all the nozzles as ejection objects, and the second temperature is higher than the first temperature temperature.

A second invention of the present application is a maintenance method for a head having a plurality of the nozzles for ejecting ink in an ink jet tablet printing apparatus that prints on the surface of a tablet, comprising: A) placing the head The step of raising the temperature of the ink inside to the second temperature; B) after the step A), the pressure in the nozzle is increased, and the ink is ejected from all the nozzles as ejection objects, The second temperature is higher than the first temperature, which is the temperature of the ink in the head when printing the tablet. [Effect of invention]

According to the first and second inventions of the present application, in the recovery step, the temperature of the ink is set to the second temperature higher than the first temperature in the printing step. Thereby, the viscosity of the ink is reduced, and the pressure loss in the nozzle is reduced. As a result, the amount of ink ejected in the recovery step can be suppressed.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the direction in which a plurality of tablets are conveyed is referred to as a "conveyance direction", and a direction perpendicular and horizontal to the conveyance direction is referred to as a "width direction".

<1. Overall configuration of tablet printing device> FIG. 1 is a diagram showing the configuration of a tablet printing apparatus 1 according to an embodiment of the present invention. The tablet printing device 1 is a device that prints images such as a product name, a product code, a company name, and a brand logo on the surface of each tablet 9 while conveying a plurality of tablets 9 as pharmaceuticals. As shown in FIG. 1 , the tablet printing apparatus 1 of the present embodiment includes a tablet conveying mechanism 10 , a printing unit 20 , a drying mechanism 30 , and a control unit 100 .

The tablet conveyance mechanism 10 is a mechanism for conveying a plurality of tablets 9 as printing objects while holding them. The tablet conveyance mechanism 10 includes a pair of pulleys 11 and an endless conveyance belt 12 spanned between the pair of pulleys 11 . The plurality of tablets 9 put into the tablet printing apparatus 1 are arranged at equal intervals by a carrying mechanism 51 including a vibrating feeder, a conveying drum, or the like, and are supplied to the outer peripheral surface of the conveying belt 12 . One of the pair of pulleys 11 is rotated by the power obtained from the conveyance motor 13 . Thereby, the conveyance belt 12 is rotated in the direction of the arrow in FIG. 1 . At this time, the other of the pair of pulleys 11 is driven to rotate in accordance with the rotation of the conveyance belt 12 .

FIG. 2 is a partial perspective view of the tablet conveyance mechanism 10 . As shown in FIG. 2 , the conveyor belt 12 is provided with a plurality of suction holes 14 . The plurality of suction holes 14 are arranged at equal intervals in the conveyance direction and the width direction. In addition, as shown in FIG. 1 , the tablet conveyance mechanism 10 includes a suction mechanism 15 that sucks gas from the space inside the conveyance belt 12 . When the suction mechanism 15 is operated, the space inside the conveyor belt 12 becomes a negative pressure lower than the atmospheric pressure. The plurality of tablets 9 are adsorbed and held in the adsorption holes 14 by the negative pressure.

In this way, the tablet conveyance mechanism 10 conveys the plurality of tablets 9 by the rotation of the conveyance belt 12 while holding the plurality of tablets 9 in the plurality of suction holes 14 at regular intervals. A plurality of tablets 9 are conveyed in the horizontal direction below the four heads 21 to be described later.

In addition, as shown in FIG. 1 , the tablet conveying mechanism 10 has an air blowing mechanism 16 inside the conveying belt 12 . When the blower mechanism 16 is operated, among the plurality of suction holes 14 of the conveying belt 12, only the suction hole 14 facing the unloading mechanism 52 becomes a high positive pressure with a relatively large air pressure. As a result, the suction of the tablets 9 in the suction holes 14 is released, and the tablets 9 are transferred from the conveying belt 12 to the unloading mechanism 52 . The unloading mechanism 52 unloads the tablets 9 delivered from the conveying belt 12 to the outside of the tablet printing apparatus 1 by, for example, another conveying belt.

The printing part 20 is a part which records an image on the surface of the tablet 9 conveyed by the conveyance belt 12 by an inkjet method. As shown in FIG. 1 , the printing unit 20 of the present embodiment has four heads 21 . The four heads 21 are located above the conveying belt 12 and are arranged in a line along the conveying direction of the tablets 9 . The four ejection heads 21 eject ink droplets of different colors from each other toward the surface of the tablet 9 . The four heads 21 eject, for example, ink droplets of various colors of cyan, magenta, yellow, and black. Then, a multi-color image is recorded on the surface of the tablet 9 by superimposing the monochrome images formed by the respective colors. In addition, edible ink produced from a raw material approved by the Japanese Pharmacopoeia, the Food Sanitation Law, and the like is used for the ink ejected from each head 21 .

FIG. 3 is a bottom view of a spray head 21 . In FIG. 3 , the conveying belt 12 and the plurality of tablets 9 held by the conveying belt 12 are indicated by two-dot chain lines. As shown on an enlarged scale in FIG. 3 , a plurality of nozzles 211 capable of ejecting ink droplets are provided on the lower surface of the ejection head 21 . In the present embodiment, a plurality of nozzles 211 are two-dimensionally arranged in the conveyance direction and the width direction on the lower surface of the shower head 21 . The nozzles 211 are arranged in a shifted position in the width direction. In this way, when the plurality of nozzles 211 are arranged two-dimensionally, the positions of the nozzles 211 in the width direction can be brought close to each other. However, the plurality of nozzles 211 may be arranged in a line in the width direction.

As a method of ejecting ink droplets from the nozzles 211 , for example, a so-called piezoelectric method is used, which applies a voltage to a piezoelectric element to deform it, thereby pressurizing and ejecting the ink in the nozzle 211 . However, the ejection method of the ink droplets may be a so-called thermal method in which the ink in the nozzles 211 is heated and expanded by energizing the heater and ejected.

The drying mechanism 30 is a mechanism for drying the ink adhering to the surface of the tablet 9 . The drying mechanism 30 is provided on the downstream side in the conveyance direction rather than the printing unit 20 around the conveyance belt 12 . The drying mechanism 30 uses, for example, a hot air supply mechanism that blows heated gas (hot air) toward the tablets 9 conveyed by the conveying belt 12 . The ink adhering to the surface of the tablet 9 is dried by hot air and fixed on the surface of the tablet 9 .

The control unit 100 controls the operation of each unit in the tablet printing apparatus 1 . FIG. 4 is a block diagram showing the connection between the control unit 100 and each unit in the tablet printing apparatus 1 . As conceptually shown in FIG. 4 , the control unit 100 includes a processor 101 such as a central processing unit (CPU), a memory 102 such as a random access memory (RAM), and a hard magnetic The computer of the storage part 103, such as a disc drive, is comprised. A computer program P for executing the printing process is installed in the storage unit 103 .

In addition, as shown in FIG. 4 , the control unit 100 is communicable with the aforementioned conveyance motor 13 , the suction mechanism 15 , the blower mechanism 16 , the four heads 21 , the drying mechanism 30 , the carry-in mechanism 51 , and the carry-out mechanism 52 , respectively. connect. In addition, the control unit 100 is also communicably connected to the head moving mechanism 22 , the cleaning unit 24 , the erasing unit 25 , and the ink supply mechanism 70 , which will be described later. The control unit 100 temporarily reads the computer program P and data stored in the storage unit 103 into the memory 102 , and based on the computer program P, the processor 101 performs arithmetic processing to control the operation of the various units. Thereby, the printing process with respect to the several tablets 9, or the maintenance process mentioned later is performed.

<2. About the nozzle moving mechanism and cap>

Next, the head moving mechanism 22 and the cap 23 will be described with reference to FIGS. 5 and 6 . FIG. 5 is a partial side view of the printing unit 20 viewed from the position of the hollow arrow in FIG. 1 . FIG. 6 is a longitudinal cross-sectional view of the cap 23 .

As shown in FIG. 5 , the internal space of the tablet printing apparatus 1 is divided into a printing area A1 and a retreat area A2. The printing area A1 is a printing space in which the tablet 9 is printed while the tablet 9 is conveyed by the tablet conveying mechanism 10 described above. The evacuation area A2 is an evacuation space in which the head 21 is retracted and standby before or after printing, and a device that does not need to be in the same space as the tablet 9 is accommodated.

Between the printing area A1 and the retreat area A2, a partition wall 60 is provided that separates the two areas. The partition wall 60 has an opening 61 through which the shower head 21 passes. The opening 61 can be opened all the time, or a baffle mechanism that opens when the spray head 21 passes through can also be installed.

As described above, the printing unit 20 has the four heads 21 . In addition, as shown in FIG. 5 , the printing unit 20 includes a head moving mechanism 22 and a cap 23 for each head 21 . That is, the printing unit 20 of the present embodiment includes four heads 21 , four head moving mechanisms 22 corresponding to each head 21 , and four caps 23 corresponding to each head 21 .

The head moving mechanism 22 is a mechanism for moving the head 21 between the printing position P1 and the standby position P2. The head moving mechanism 22 of the present embodiment includes an arm 221 and an arm moving mechanism 222 .

The arm 221 is a member extending in the width direction. The shower head 21 is fixed to the front end of the arm 221 on one side in the width direction. The arm moving mechanism 222 moves the arm 221 in the up-down direction and the width direction in accordance with an instruction from the control unit 100 . Thereby, the arm 221 and the head 21 move integrally in the vertical direction and the width direction.

The arm moving mechanism 222 is realized by, for example, combining a horizontal direction (width direction) moving mechanism and a vertical direction moving mechanism. These moving mechanisms are realized by, for example, a mechanism that converts the rotational motion of a motor into linear motion via a ball screw, or a mechanism such as a linear motor or an air cylinder.

As shown in FIG. 5 , the head moving mechanism 22 moves the head 21 in the vertical direction and the width direction between the printing position P1 and the standby position P2. The head 21 prints the tablet 9 at the printing position P1. When the head 21 is arranged at the printing position P1 , the plurality of nozzles 211 face the tablets 9 held by the conveyor belt 12 . In the standby position P2 , the plurality of nozzles 211 of the shower head 21 are covered with the caps 23 .

The standby position P2 is a position lower than the printing position P1. Therefore, when the head 21 is moved from the printing position P1 to the standby position P2, the head moving mechanism 22 moves the head 21 in the width direction from the printing position P1 to the retreat area A2, arranges it in the intermediate position P3, and then descends to Standby position P2.

When moving the head 21 from the standby position P2 to the printing position P1, the head moving mechanism 22 moves the head 21 in the reverse order. That is, the head moving mechanism 22 moves the head 21 to the printing position P1 in the width direction within the printing area A1 after raising the head 21 from the standby position P2 to the intermediate position P3.

Furthermore, the intermediate position P3 may be higher than the printing position P1. In this case, the head moving mechanism 22 raises the head 21 from the printing position P1 to the same height as the intermediate position P3, and then, at this height, moves to the intermediate position P3 in the retraction area A2 in the width direction. And, then, it can be lowered to the standby position P2.

In this case, when moving the head 21 from the standby position P2 to the printing position P1, the head moving mechanism 22 moves the head 21 in the width direction to the printing position after raising the head 21 from the standby position P2 to the intermediate position P3 In the area A1, the head 21 is then lowered and arranged at the printing position P1.

The cap 23 is a substantially rectangular parallelepiped frame body whose upper surface is opened. The cap 23 is fixed to a predetermined position in the retraction area A2. The cap 23 covers the plurality of nozzles 211 of the head 21 arranged at the standby position P2. In this way, when the nozzle head 21 is not in use, by covering the nozzle 211 with the cap 23, the ink in the nozzle 211 can be prevented from drying.

In this embodiment, the cap 23 includes a cleaning unit 24 and an erasing unit 25 .

The cleaning unit 24 is a unit for cleaning the plurality of nozzles 211 of the shower head 21 . As shown in FIGS. 5 and 6 , the cleaning unit 24 includes a cleaning nozzle 241 and a cleaning liquid supply unit 242 .

The cleaning nozzle 241 sprays the cleaning liquid supplied from the cleaning liquid supply part 242 to the plurality of nozzles 211 inside the cap 23 . Specifically, as shown in FIG. 6 , the cleaning nozzle 241 includes a plurality of ejection ports 240 that eject the cleaning liquid upward. By cleaning the plurality of nozzles 211 of the head 21 with the cleaning unit 24, fine powder and the like adhering to the nozzles 211 in the printing area A1 can be removed. Furthermore, the cap 23 may not include the cleaning unit 24 .

The erasing unit 25 is a unit for erasing the ejection surface (lower surface) of the ejection head 21 including the plurality of nozzles 211 . The erasing unit 25 includes a blade 251 and a blade moving mechanism 252 .

The blade 251 is a member for wiping off ink droplets or cleaning liquid adhering to the lower surface of the head 21 . As the blade 251, a plate-shaped member formed of, for example, flexible rubber or the like is used. In addition, among the blades 251, only the front end portion 250 that is in contact with the shower head 21 may be formed of a flexible member.

The blade moving mechanism 252 is a mechanism for rotationally moving the blade 251 . The blade moving mechanism 252 includes, for example, a drive source such as a motor, and a power transmission mechanism that transmits the rotational motion of the motor to the blade 251 . When the blade moving mechanism 252 is operated, the blade 251 is rotationally moved between the storage position Q1 shown by the solid line in FIG. 6 and the erasing position Q2 shown by the two-dot chain line in FIG. 6 .

When the head 21 is arranged at the standby position P2 and the plurality of nozzles 211 are covered with the caps 23, the blade 251 is arranged at the storage position Q1. At the storage position Q1 , the entire blade 251 is stored inside the cap 23 .

On the other hand, when the ink droplets or cleaning liquid on the lower surface of the ejection head 21 are erased by the blade 251, the ejection head moving mechanism 22 raises the ejection head 21 to the erasing position P4 higher than the standby position P2, so that the lower surface of the ejection head 21 leaves the Cap 23. Then, the blade 251 is rotated from the storage position Q1 to the erasing position Q2. At the erasing position Q2 , the front end portion 250 of the blade 251 is in contact with the lower surface of the head 21 . Then, the head moving mechanism 22 horizontally moves the head 21 in the width direction. Thereby, the plurality of nozzles 211 on the lower surface of the ejection head 21 and the ink droplets, cleaning liquid, etc. adhered to and around the nozzles 21 are wiped off by the front end portion 250 of the blade 251 .

In addition, the erasing position P4 for erasing the lower surface of the nozzle head 21 may be the same as the intermediate position P3, or may be different from the intermediate position P3.

<3. About the configuration of the ink supply mechanism and the head> Next, the configuration of the ink supply mechanism 70 for supplying ink to the head 21 and the head 21 will be described with reference to FIG. 7 . FIG. 7 is a schematic diagram showing the configuration of the head 21 and the ink supply mechanism 70 . As described above, the printing unit 20 has the four heads 21 . The printing unit 20 includes an ink supply mechanism 70 for supplying ink to the head 21 for each head 21 . That is, the printing unit 20 of the present embodiment further includes four ink supply mechanisms 70 .

As shown in FIG. 7 , the ink supply mechanism 70 includes an ink storage unit 71 , a pressure adjustment mechanism 72 , and a pipe 73 , respectively.

The ink storage unit 71 is a container for storing ink to be supplied to the head 21 . The ink storage portion 71 includes a pressure sensor 711 for detecting the pressure in the ink storage portion 71 .

The pressure adjustment mechanism 72 is a mechanism for adjusting the pressure inside the ink storage unit 71 . The pressure in the ink storage portion 71 is adjusted by the pressure adjustment mechanism 72 , and the pressure adjustment mechanism 72 can indirectly adjust the pressure in the ejection head 21 when the ink storage portion 71 communicates with the ejection head 21 . That is, the pressure adjustment mechanism 72 constitutes a pressure adjustment portion capable of adjusting the pressure in the head 21 .

In the present embodiment, the ink storage unit 71 is a tank with a fixed capacity. Furthermore, the pressure adjustment mechanism 72 adjusts the pressure in the ink storage portion 71 by adjusting the gas pressure of the gas layer above the ink storage portion 71 . However, the ink storage portion 71 may be a so-called ink bag filled with ink in a flexible container. In this case, the pressure adjustment mechanism 72 can adjust the pressure in the ink storage portion 71 by, for example, adjusting the pressure applied from the outside through the ink storage portion 71 serving as an ink bag.

The piping 73 communicates and connects the lower end portion of the ink storage portion 71 and an ink supply port 81 of the head 21 to be described later. For example, a solenoid valve 731 for controlling the communication of the piping 73 is inserted into the piping 73 . In the state where the solenoid valve 731 is open, when the pressure in the ink storage portion 71 is higher than the pressure in the head 21 , ink is supplied from the ink storage portion 71 to the head 21 . In addition, a check valve may be inserted into the piping 73 together with the solenoid valve 731 or instead of the solenoid valve 731 . In addition, a filter for removing solid content, foreign matter, or the like in the ink may be inserted into the piping 73 .

The heads 21 respectively include a casing 80 , an ink supply port 81 provided on the casing 80 , an ink storage chamber 82 , a plurality of independent flow paths 83 , a plurality of independent ink chambers 84 , and a plurality of nozzles 211 . In addition, in FIG. 7 , for convenience, six independent flow paths 83 , independent ink chambers 84 , and nozzles 211 are shown, but in the actual head 21 , a plurality of nozzles 211 and the same number of independent flow paths are provided. Road 83 and independent ink chamber 84.

The ink supply port 81 is a communication port that communicates the ink storage chamber 82 with the outside. The downstream end portion of the piping 73 of the ink supply mechanism 70 is connected to the ink supply port 81 . Thereby, the ink supplied from the ink storage unit 71 through the piping 73 is first stored in the ink storage chamber 82 through the ink supply port 81 .

The ink storage chamber 82 temporarily stores ink to be supplied to the individual ink chambers 84 . Inside the ink storage chamber 82, a heater 821 for heating the ink and a temperature sensor 822 for detecting the temperature of the ink are included.

The heater 821 is a heating mechanism for raising the temperature of the ink in the head 21 . The control unit 100 controls the heater 821 based on the temperature of the ink detected by the temperature sensor 822 . Thereby, the heater 821 can raise the temperature of the ink in the head 21 to a temperature such as a first temperature and a second temperature which will be described later. That is, the heater 821 can raise the temperature of the ink ejected from the plurality of nozzles 211 to the first temperature and the second temperature.

The independent flow path 83 is an ink flow path connecting the ink storage chamber 82 and each of the independent ink chambers 84 . When the pressure in the independent ink chamber 84 is lower than the pressure in the ink storage chamber 82 , ink is supplied from the ink storage chamber 82 to the independent ink chamber 84 via the independent flow path 83 .

The independent ink chamber 84 is a storage part of the ink provided for each nozzle 211 . The independent ink chamber 84 is refilled with the ink supplied into the head 21 . The lower ends of the independent ink chambers 84 communicate with the nozzles 211, respectively.

The nozzles 211 communicate the independent ink chamber 84 with the external space. When the ink is not ejected, the liquid surface of the ink forms a meniscus inside the nozzle 211 . In addition, the lower end portion of the nozzle 211 is arranged to be exposed from the lower surface of the casing 80 .

Pressure generating elements 841 are respectively arranged on the wall surfaces of the independent ink chambers 84 . The pressure generating element 841 is an actuator that increases the pressure inside the independent ink chamber 84 . The head 21 of the present embodiment is a so-called piezoelectric discharge head. Therefore, a piezoelectric element is used for the pressure generating element 841 of the present embodiment. When a discharge signal as an electrical signal is sent from the control unit 100 to the pressure generating element 841, the pressure generating element 841 is deformed, and the ink filled in the independent ink chamber 84 is pressurized. Then, as the pressure in the independent ink chamber 84 increases, the ink in the independent ink chamber 84 is ejected in the form of droplets from the nozzles 211 . Furthermore, the ejection head 21 is not limited to the piezoelectric type, and may be an ejection head of other types.

<4. About the temperature management in the print head in the printing step and the recovery step> Next, the temperature management in the head 21 before the start of the printing step and during the recovery step in the tablet printing apparatus 1 will be described with reference to FIGS. 8 and 9 . FIG. 8 is a flowchart showing the flow of temperature management in the head 21 before the start of the printing step. FIG. 9 is a flowchart showing the flow of the recovery procedure.

The control unit 100 can cause the tablet printing apparatus 1 to execute at least the printing step and the restoring step. In the printing step, the control unit 100 ejects ink of the first temperature from some of the nozzles 211 to the surface of the tablet 9 while the tablet conveying mechanism 10 conveys the tablet 9 . Thereby, printing processing is performed on the surface of the tablet 9 . On the other hand, in the recovery step, the control unit 100 increases the pressure in the head 21 to discharge the ink of the second temperature using all the nozzles 211 as discharge targets. That is, in the recovery step, the control unit 100 executes a maintenance method called a so-called clearing process. In addition to the printing step and the recovery step, the control unit 100 can also perform other steps such as a cleaning step of cleaning the lower surface of the head 21 .

First, the flow of temperature management in the head 21 before the start of the printing step will be described with reference to FIG. 8 . As shown in FIG. 8 , at the start of the printing step, first, the pre-printing heating step including steps S111 , S112 and S113 , and the pre-printing moving step including steps S121 and S122 are performed in parallel.

In the pre-printing temperature rise step (step S111 to step S113 ), first, the control unit 100 drives the heater 821 to start the temperature rise of the ink in the head 21 to the first temperature (step S111 ). Then, when the temperature rise is started, the control unit 100 monitors whether or not the temperature of the ink detected by the temperature sensor 822 has reached the first temperature (step S112 ).

In step S112 , when the control unit 100 determines that the temperature of the ink has not reached the first temperature (step S112 /No (No)), the process returns to step S112 and waits. In step S112, when it is determined that the temperature of the ink has reached the first temperature (step S112/Yes), the control unit 100 starts feedback control of the heater 821 to maintain the temperature of the ink in the head 21 at the first temperature temperature (step S113).

On the other hand, in the pre-printing moving step (step S121 to step S122 ), first, the control unit 100 operates the head moving mechanism 22 to move the head 21 to the printing position P1 (step S121 ). Then, after the movement is started, the control unit 100 monitors whether or not the head 21 has reached the printing position P1 (step S122 ). In step S122, when the control unit 100 determines that the head 21 has not reached the printing position P1 (step S122/NO), the process returns to step S122.

When the control unit 100 starts the feedback control in step S113 and determines in step S122 that the head 21 has reached the printing position P1 (step S122/Yes), the process proceeds to step S13 to start the printing step (step S13).

Here, the first temperature is the temperature of the ink in the head 21 in the printing step. During the printing step, the temperature of the ink in the nozzle 21 is maintained at the first temperature by feedback control. Therefore, in the printing step, the control unit 100 ejects the ink of the first temperature on the surface of the tablet 9 from a part of the nozzles 211 of the ejection head 21 .

Next, the flow of the recovery procedure will be described with reference to FIG. 9 . As shown in FIG. 9 , when the recovery step is started, first, the pre-clearing heating step including steps S211 and S212 and the pre-clearing moving step including steps S221 and S222 are performed in parallel.

In the pre-cleaning temperature raising step (step S211 to step S212 ), the ink in the print head 21 is heated to a second temperature higher than the first temperature by the heater 821 . First, the control unit 100 drives the heater 821 to start raising the temperature of the ink in the head 21 to the second temperature (step S211 ). Then, when the temperature rise is started, the control unit 100 monitors whether or not the temperature of the ink detected by the temperature sensor 822 reaches the second temperature (step S212 ).

In step S212 , when the control unit 100 determines that the temperature of the ink has not reached the second temperature (step S212 /No (No)), the process returns to step S212 and waits.

On the other hand, in the moving step before erasing (step S221 to step S222 ), first, the control unit 100 operates the head moving mechanism 22 to move the head 21 to the standby position P2 (step S221 ). Then, after the movement is started, the control unit 100 monitors whether or not the head 21 has reached the standby position P2 (step S222 ). In step S222 , when the control unit 100 determines that the head 21 has not reached the standby position P2 (step S222 /No (No)), the process returns to step S222 .

When the control unit 100 determines in step S212 that the temperature of the ink has reached the second temperature (step S212/Yes), and determines in step S222 that the head 21 has reached the standby position P2 (step S222/Yes), the process proceeds to step S23. Then, the control unit 100 stops the temperature increase of the ink in the head 21 by the heater 821 (step S23 ). That is, the control unit 100 confirms that the temperature of the ink in the head 21 has reached the second temperature, and stops the temperature increase of the ink.

Furthermore, when it is determined in step S212 that the temperature of the ink has reached the second temperature (step S212/Yes), and if it is not determined in step S222 that the head 21 has reached the standby position P2, the control unit 100 may perform heating. The feedback control of the device 821 is used to maintain the temperature of the ink in the print head 21 at the second temperature.

After the temperature increase of the ink by the heater 821 is stopped, the control unit 100 increases the pressure in the head 21 and discharges the ink for all the nozzles 211 (step S24 ).

As a specific procedure performed by the control unit 100 in step S24 , for example, first, the solenoid valve 731 is closed to cut off the communication between the ink storage unit 71 and the head 21 . Then, the pressure in the ink storage portion 71 is increased by the pressure adjustment mechanism 72 . After that, the solenoid valve 731 is opened, whereby the pressure in the shower head 21 is rapidly increased.

In step S24 , the ink of the second temperature is ejected from the nozzles 211 by increasing the pressure in the ejection head 21 . At this time, the amount of ink ejected in step S24 is smaller than the amount of ink ejected in a general cleaning process. Therefore, the ink ejected in step S24 stays on the lower surface of the head 21 .

In this manner, in step S24, the clearing process is performed at the standby position P2. That is, the standby position P2 is a maintenance position where the cleaning step is performed. In addition, by performing steps S211 to S212 and steps S221 to S222 in parallel, before the cleaning step, the ink in the head 21 is moved from the printing position P1 to the standby position P2, which is a maintenance position, while the ink in the head 21 is moved. The step of raising the temperature to the second temperature.

After step S24, the control section 100 erases the lower surface of the head 21 by the erasing unit 25 (step S25). Specifically, after the head 21 is moved to the erasing position P4 by the head moving mechanism 22 , the blade 251 is arranged at the erasing position Q2 by the blade moving mechanism 252 . Then, the head 21 is moved in the width direction by the head moving mechanism 22 , and the blade 251 comes into contact with the lower surface of the head 21 to wipe off the ink accumulated on the lower surface of the head 21 .

Furthermore, in step S24, the head 21 may be arranged at the erasing position P4. In this case, in the pre-erasing movement step (step S221 to step S222 ), the head 21 is arranged at the erasing position P4 instead of the standby position P2. That is, the maintenance position where the erasing step is performed is the erasing position P4.

After the erasing step of step S25 is completed, the restoring step of the spray head 21 is completed. After that, when the printing step is performed, the head 21 is arranged at the printing position P1. In addition, when the printing step is not performed thereafter, the head 21 is arranged at the standby position P2.

As described above, in the tablet printing apparatus 1, the temperature (second temperature) of the ink ejected from the nozzles 211 in the recovery step is higher than the temperature (first temperature) of the ink ejected from the nozzles 211 in the printing step temperature.

In the nozzles 211 that are used less frequently, the solvent evaporates from the ink surface and the ink in the nozzles 211 does not flow, resulting in the rise of the meniscus, the aggregation of ink components, and the concentration of ink components. The pressure loss in 211 increases.

Therefore, in the recovery step, the temperature of the ink in the head 21 is set to a second temperature higher than the first temperature, which is the temperature of the ink in the printing step. The ink of the second temperature has a lower viscosity than the ink of the first temperature. Therefore, during the cleaning process, the viscosity of the ink can be reduced, the fluidity of the ink can be improved, and the pressure loss in the nozzle 211 can be reduced. This makes it possible to eliminate ink clogging in the nozzles 211 even when the amount of ink ejected in the purge process is smaller than that in the normal purge process.

That is, in the recovery step, the temperature of the ink is made higher than that in the printing step, and the consumption of the ink in the recovery step can be suppressed.

In this embodiment, the first temperature is about 32°C, and the second temperature is about 40°C. The second temperature is preferably a temperature higher than the first temperature by a difference between 2°C (inclusive) and 15°C (inclusive).

When the temperature of the ink increases by a difference of 2°C (inclusive) or more, the viscosity of the ink decreases to such an extent that the discharge conditions change. Therefore, the second temperature is preferably higher than the first temperature by a difference of at least 2°C (inclusive). On the other hand, if the second temperature is raised too much, there is a possibility that the temperature in the shower head 21 will not drop to the first temperature after the recovery step. In this case, it is necessary to provide a cooling period for cooling the ink in the head 21 after the recovery step and before the printing step, or to provide a cooling mechanism. Therefore, the difference between the first temperature and the second temperature is preferably 15°C (inclusive) or less.

Here, FIG. 10 is a graph showing the relationship between the temperature and the viscosity of the edible ink used in the present embodiment. In FIG. 10 , the horizontal axis is the temperature [° C.], and the vertical axis is the ink viscosity [mPa·s]. In addition, the measuring apparatus for measuring the viscosity of the ink of FIG. 10 is a viscometer (VISCOMETER) DV-IIPro by Brookfield.

In the tablet printing apparatus 1 of the present embodiment, the viscosity of the ink suitable for the printing step is 3.9 mPa·s±0.2 mPa·s. Therefore, the first temperature is set to about 32°C. On the other hand, in the cleaning step, the viscosity is preferably set to 3.2 mPa·s±0.2 mPa·s which is about 20% lower than that in the printing step. Therefore, the second temperature is set to about 40°C.

Specifically, in the present embodiment, the ink ejected in the cleaning process is such a small amount that it does not drip from the head 21 and stays on the lower surface of the head 21 . For example, in a tablet printing apparatus 1 having a head 21 of the same size as a conventional printing apparatus that normally ejects about 60 cc of ink in the purge process, the ink ejection amount in the purge step of step S24 may be set to about 1 cc .

<5. Modifications> As mentioned above, although the main embodiment of this invention was described, this invention is not limited to the said embodiment.

In the above-described embodiment, the position of the cap 23 is fixed, and the lower surface of the shower head 21 is covered with the cap 23 when the shower head 21 is lowered. However, a vertical movement mechanism may be provided on the cap 23 , and the lower surface of the shower head 21 may be covered with the cap 23 by raising the cap 23 .

In addition, in the above-mentioned embodiment, the four heads 21 are provided in the printing unit 20 . However, the number of the heads 21 included in the printing unit 20 may be 1 to 3, and may be more than 4.

In addition, in the above-described embodiment, a two-stage structure including one ink storage chamber and a plurality of independent ink chambers 84 is provided in one head 21, but the present invention is not limited to this. For example, a single head may have a three-level structure in which a common ink flow path, a plurality of ink storage chambers for supplying ink from the common ink flow path, and a plurality of independent ink chambers communicated with the ink storage chambers, respectively, may be employed. In addition, the spray head can also have other structures.

In addition, in the above-described embodiment, there is only one head 21 that ejects the same type of ink at the same position in the conveyance direction, but the present invention is not limited to this. A plurality of heads may be combined to form a head unit that ejects the same type of ink at the same position in the conveyance direction.

In addition, although the tablet printing apparatus 1 of the above-described embodiment includes one printing unit that performs printing on the surface of the tablet 9, the present invention is not limited to this. The tablet printing apparatus may include two printing units, a printing unit that performs printing on one surface of the tablet, and a printing unit that performs printing on the other surface (back surface) of the tablet.

In addition, the "tablet" to be treated in the present invention includes, for example, a bare tablet, an orally disintegrating tablet (orally disintegrating (OD) tablet), a film-coated tablet (FC (Film Coating) tablet), a sugar-coated tablet Tablets, split line tablets, etc., but are not necessarily limited to tablets as pharmaceuticals. The tablet printing apparatus of the present invention can also print tablets, which are health foods, or candies such as soft drinks.

In addition, the configuration of the detailed portion of the tablet printing apparatus 1 may be different from the respective figures of the present application. In addition, the respective elements appearing in the above-described embodiments or modifications may be appropriately combined within the range that does not cause inconsistency.

1: tablet printing device 9: Tablets 10: Tablet handling mechanism 11: Pulley 12: carrying belt 13: Motor for transport 14: adsorption hole 15: Suction mechanism 16: Air supply mechanism 20: Printing Department 21: Nozzle 21: Nozzle 22: Nozzle moving mechanism 23: Caps 24: Cleaning unit 25: Erase unit 30: Drying mechanism 51: Move In Agency 52: Moving out of the agency 60: Next door 61: Opening 70: Ink supply mechanism 71: Ink storage part 72: Pressure adjustment mechanism 73: Piping 80: Shell 81: Ink supply port 82: Ink storage room 83: Independent flow path 84: Independent Ink Room 100: Control Department 101: Processor 102: Memory 103: Storage Department 211: Nozzle 221: Arm 222: Arm moving mechanism 240: spout 241: Cleaning Nozzle 242: Cleaning fluid supply part 250: front end 251: Blade 252: Blade moving mechanism 711: Pressure Sensor 731: Solenoid valve 821: Heater 822: Temperature sensor 841: Pressure generating element A1: Printing area A2: Back off area P: computer program P1: Printing position P2: Standby position P3: middle position P4: Erase position Q1: Storage location Q2: Erase location S13, S23, S24, S25, S111, S112, S113, S121, S122, S211, S212, S221, S222: Steps

FIG. 1 is a diagram showing the configuration of a tablet printing apparatus. Fig. 2 is a partial perspective view of the tablet conveying mechanism. Figure 3 is a bottom view of the spray head. FIG. 4 is a block diagram showing the connection between the control unit and each unit in the tablet printing apparatus. FIG. 5 is a partial side view of the printing unit. Fig. 6 is a longitudinal sectional view of the cap. FIG. 7 is a schematic diagram showing the configuration of a head and an ink supply mechanism. FIG. 8 is a flowchart showing the flow of temperature management in the head before the start of the printing step. FIG. 9 is a flowchart showing the flow of the recovery procedure. FIG. 10 is a graph showing the relationship between the temperature and the viscosity of ink.

S211, S212, S221, S222, S23, S24, S25: Steps

Claims (9)

A tablet printing device is an inkjet-type tablet printing device that prints on the surface of a tablet, comprising: an inkjet-type nozzle including a plurality of nozzles capable of ejecting ink; and a pressure adjustment unit capable of adjusting the pressure in the head; a heater capable of raising the temperature of the ink ejected from the nozzles to a first temperature and a second temperature inside the head; and a control unit for controlling the head and the pressure adjustment unit and the heater, and the control unit can perform: a printing step of ejecting the ink at the first temperature from a part of the nozzles to the surface of the tablet; and a recovery step of using the pressure The adjustment unit increases the pressure in the head, and discharges the ink of the second temperature, which is higher than the first temperature, from all the nozzles as discharge objects. The tablet printing apparatus according to claim 1, wherein the ink ejected in the recovery step remains on the lower surface of the ejection head. The tablet printing device according to claim 1 or claim 2, wherein the second temperature is a temperature higher than the first temperature by the difference between 2°C (inclusive) and 15°C (inclusive) . The tablet printing apparatus according to claim 1 or claim 2, wherein the control section includes in the restoring step: a) the step of raising the temperature of the ink in the head to the second temperature by the heater; b) the step of stopping the heater after the step a); and c) the step of After step b), the pressure in the head is increased, and the ink is ejected from all the nozzles as ejection objects. The tablet printing device according to claim 1 or claim 2, wherein the nozzle comprises: a plurality of the nozzles, arranged on the lower surface of the nozzle; a plurality of independent ink chambers, respectively communicating with the nozzles, And it includes an actuator for increasing the pressure inside; and an ink storage chamber, which communicates with the plurality of independent ink chambers, and the heater is arranged inside the ink storage chamber. A maintenance method for a tablet printing device is a maintenance method for an ink jet tablet printing device that prints on the surface of a tablet, the tablet printing device comprising: a nozzle having a plurality of nozzles for ejecting ink, the tablet printing device comprising: The maintenance method of the agent printing device includes: A) a step of raising the temperature of the ink in the print head to a second temperature; and B) after the step A), increasing the pressure in the print head to raise all the and the second temperature is higher than that of the nozzle in the case of printing the tablet The temperature of the ink inside is the temperature at which the first temperature is high. The maintenance method of a tablet printing apparatus according to claim 6, wherein the ink ejected in the step B) stays on the lower surface of the ejection head. The maintenance method for a tablet printing device according to claim 6 or claim 7, wherein the second temperature is higher than the first temperature by a difference between 2°C (inclusive) and 15°C (inclusive). high temperature. The maintenance method for a tablet printing device according to claim 6 or claim 7, wherein in step A), the nozzle is moved from the printing position to the maintenance position, and the ink in the nozzle is moved to the maintenance position at the same time. The temperature is raised to the second temperature, and the step B) includes: B1) confirming that the temperature of the ink in the print head reaches the second temperature and stopping the temperature rise of the ink; B2) in the After step B1), the pressure in the head is increased, and the ink is ejected from all the nozzles as ejection objects; and B3) the step of wiping off the ink remaining on the lower surface of the head.

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