JP2018051843A - Printing device and printing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique which allows an inkjet-type printing device which performs printing processing to a surface of a granular matter to suppress deterioration in printing quality due to floating dust.SOLUTION: The printing device comprises a conveying mechanism 30, a head 721 and an ionizer 71. The conveying mechanism 30 conveys a granular matter 9 from an upstream side to a downstream side in a conveying direction while holding the matter at a holding portion 62. The head 721 has a plurality of nozzles for discharging ink droplets and performs printing processing while discharging ink droplets toward the surface of the granular matter 9 to be conveyed by the conveying mechanism 30. The ionizer 71 has an ion generating portion 711, arranged at an upstream side of the head 721, which generates ion by electric discharge. The ionizer 71 supplies ion to floating dust floating around the granular matter 9. This can destaticize the floating dust and suppress occurrence of printing defect due to electrified floating dust.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a printing apparatus and a printing method for printing on the surface of granular materials such as tablets and tablet confectionery.

  Characters and codes for identifying the product are printed on the surface of the tablet as a medicine. In addition, marks and illustrations may be printed on tablet confectionery. 2. Description of the Related Art Conventionally, a technique for printing on the surface of a granular material such as a tablet or tablet confectionery using an ink jet printing apparatus is known. Such a printing apparatus is described in Patent Document 1, for example.

  In the printing apparatus described in Patent Literature 1, ink is ejected from an inkjet head onto a tablet conveyed by a conveyance mechanism (conveyance conveyor), and printing processing is performed on the tablet.

JP 2013-13711 A

  A powdery substance may float around the granular material transported by the transport mechanism (hereinafter referred to as “floating powder”). In particular, when the granular material is an uncoated tablet (bare tablet) or a ramune confectionery, the granular material is composed of powder as a raw material, so that the powder constituting the granular material may become a floating powder. Moreover, in order to prevent adhesion of particulate matter, when the powder is applied to the surface of the particulate matter, the powder may become floating powder.

  If such suspended powder is charged with static electricity, it may adhere to the vicinity of the nozzles of the inkjet head and cause ink ejection failure. The suspended powder adhering to the vicinity of the nozzle causes, for example, so-called nozzle chipping that prevents the ink from being discharged due to clogging of the nozzle, or shifts the ink landing position by changing the ink discharge direction. On the other hand, the presence of charged floating powder between the nozzle and the granular material may change the ink trajectory after ejection due to the influence of static electricity, thereby shifting the ink landing position. As described above, there is a possibility that the printing quality is deteriorated due to the charging of the floating powder.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a technique for suppressing a decrease in print quality caused by suspended powder in an inkjet printing apparatus.

  In order to solve the above-mentioned problem, the first invention of the present application is a printing apparatus for performing a printing process on the surface of a granular material using an ink jet head, while holding the granular material in a holding unit, A transport mechanism that transports from the upstream side to the downstream side in the transport direction and a plurality of nozzles that eject ink droplets, and prints by ejecting the ink droplets toward the surface of the granular material transported by the transport mechanism An inkjet head that performs processing, and an ionizer that is disposed upstream of the head and has an ion generator that generates ions by discharge, and the ionizer floats around the particulate matter To supply ions.

  A second invention of the present application is the printing apparatus according to the first invention, wherein a distance in the transport direction between the upstream end portion of the head and the ion generating portion is 150 mm or less.

  A third invention of the present application is the printing apparatus according to the first invention or the second invention, wherein a distance in a height direction between the holding portion and the ion generating portion is 150 mm or less.

  A fourth invention of the present application is the printing apparatus according to any one of the first to third inventions, and includes the plurality of ionizers, and the plurality of ionizers are arranged at intervals in the width direction.

  A fifth invention of the present application is the printing apparatus according to any one of the first to fourth inventions, wherein the granular material is a tablet and an uncoated tablet.

  A sixth invention of the present application is a printing method in which a printing process is performed by an inkjet head on the surface of a granular material conveyed from the upstream side to the downstream side in the conveyance direction, and a) from an ion generation part of an ionizer Generating ions and supplying the ions to the suspended powder around the granular material; b) ink from a plurality of nozzles of the head toward the surface of the granular material on the downstream side of the ionizer. And performing a printing process by discharging droplets.

  7th invention of this application is the printing method of 6th invention, Comprising: The distance of the conveyance direction of the upstream edge part of the said head and the said ion generation part is 150 mm or less.

  The eighth invention of the present application is the printing method of the sixth invention or the seventh invention, wherein, in the step a), the distance in the height direction between the granular material and the ion generating part is 150 mm or less.

  A ninth invention of the present application is the printing method according to any of the sixth to eighth inventions, wherein the granular material is a tablet and an uncoated tablet.

  According to the first to ninth inventions of the present application, the suspended powder can be efficiently neutralized. Therefore, it is possible to suppress the occurrence of printing defects due to the charged floating powder.

  In particular, according to the second invention, the third invention, the seventh invention, and the eighth invention of the present application, the effect of neutralizing floating powder is improved. Therefore, it is possible to further suppress printing defects caused by the charged floating powder.

1 is a diagram illustrating a configuration of a printing apparatus. FIG. 6 is a perspective view of the vicinity of a transport drum. It is a bottom view of a printing part. FIG. 3 is a block diagram illustrating connections between a control unit and each unit in the printing apparatus. It is the side view which showed the printing part notionally. It is a figure which shows the relationship between the position of an ionizer, and the adhesion state of the floating powder to a nozzle. It is a figure which shows the relationship between the position of an ionizer, and the adhesion state of the floating powder to a nozzle.

  Embodiments of the present invention will be described below with reference to the drawings. In the following description, a direction in which a plurality of granular materials are transported is referred to as a “transport direction”, and a direction perpendicular to the transport direction is referred to as a “width direction”.

<1. Configuration of printing device>
FIG. 1 is a diagram illustrating a configuration of a printing apparatus 1 according to an embodiment of the present invention. The printing device 1 is a device that prints characters and images such as a product name, a product code, a company name, and a logo mark on the surface of each tablet 9 while conveying a plurality of tablets 9 that are medicines. The tablet 9 may be an uncoated tablet (bare tablet) or a coated tablet such as a film-coated tablet (FC tablet). The tablet 9 may be a capsule including a hard capsule and a soft capsule. The printing object of the printing apparatus of the present invention is not limited to tablets, and may be tablet confectionery such as ramune.

  As illustrated in FIG. 1, the printing apparatus 1 according to the present embodiment includes a supply mechanism 20, a transport mechanism 30, a printing unit 40, an inspection mechanism 50, and a control unit 10.

  The supply mechanism 20 includes a hopper 21, a rectilinear feeder 22, a rotary feeder 23, and an inclined feeder 24. The supply mechanism 20 is a mechanism for delivering the tablet 9 put into the apparatus to the transport mechanism 30.

  The hopper 21 is an input unit for receiving a large number of tablets 9 in the apparatus. The hopper 21 is disposed at the top of the casing 100 of the printing apparatus 1. The hopper 21 has an opening 211 located on the upper surface of the housing 100 and a funnel-shaped inclined surface 212 that gradually converges downward. The plurality of tablets 9 put into the opening 211 flows into the rectilinear feeder 22 along the inclined surface 212.

  The rectilinear feeder 22, the rotary feeder 23, and the inclined feeder 24 are mechanisms that transport the plurality of tablets 9 put into the hopper 21 to the transport mechanism 30. The rectilinear feeder 22 has a flat vibration trough 221. The plurality of tablets 9 supplied from the hopper 21 to the vibration trough 221 are conveyed to the rotary feeder 23 side by the vibration of the vibration trough 221.

  The rotary feeder 23 has a disk-shaped rotary table 231. The plurality of tablets 9 that have dropped from the vibration trough 221 onto the upper surface of the turntable 231 are collected near the outer periphery of the turntable 231 by the centrifugal force generated by the rotation of the turntable 231.

  The inclined feeder 24 has a plate-like slope 241 that extends obliquely downward from the outer periphery of the turntable 231 to a later-described conveying drum 31 of the conveying mechanism 30. FIG. 2 is a perspective view including a part of the inclined feeder 24, a part of the transport drum 31 and the part of the first transport conveyor 32. As shown in FIG. 2, a plurality of (eight in the example of FIG. 2) conveying grooves 242 are provided on the upper surface of the slope 241. The plurality of tablets 9 transported to the outer periphery of the turntable 231 are respectively supplied to any one of the plurality of transport grooves 242 and flow down obliquely downward along the transport grooves 242. As described above, the plurality of tablets 9 are distributed and supplied to the plurality of transport grooves 242 to be aligned in a plurality of transport rows. Then, the plurality of tablets 9 in each conveyance row are supplied to the conveyance drum 31 in order from the first one.

  The transport mechanism 30 includes a transport drum 31, a first transport conveyor 32, a second transport conveyor 33, and a carry-out conveyor 34.

  The transport drum 31 is a mechanism that delivers a plurality of tablets 9 from the inclined feeder 24 to the first transport conveyor 32. The conveyance drum 31 has a substantially cylindrical outer peripheral surface. The conveyance drum 31 is rotated in the direction of the arrow in FIGS. 1 and 2 around the rotation axis extending in the width direction by power obtained from a motor not shown. As shown in FIG. 2, the outer peripheral surface of the transport drum 31 is provided with a plurality of suction portions 310 arranged at substantially equal intervals in the transport direction and the width direction. The plurality of suction units 310 are arranged on the outer peripheral surface of the transport drum 31 at positions in the width direction corresponding to the transport grooves 242 of the inclined feeder 24.

  Each of the suction portions 310 is a through hole provided on the surface of the transport drum 31. A suction mechanism (not shown) is provided inside the transport drum 31. When the suction mechanism is operated, a negative pressure lower than the atmospheric pressure is generated in each of the plurality of suction portions 310. The suction unit 310 sucks and holds the tablets 9 supplied from the inclined feeder 24 one by one by the negative pressure.

  Then, a positive pressure higher than the atmospheric pressure is applied to the suction unit 310 that has moved to a position facing the first transport conveyor 32 on the transport drum 31 to release the suction of the tablet 9. Thus, the transport drum 31 rotates while adsorbing and holding the plurality of tablets 9 supplied from the inclined feeder 24, and delivers these tablets 9 to the first transport conveyor 32. When the tablets 9 are transferred from the transport drum 31 to the first transport conveyor 32, the surface of the tablet 9 that is sucked and held by the transport drum 31 is different from the surface of the tablet 9 that is sucked and held by the first transport conveyor 32. For this reason, the front and back of the tablet 9 are reversed while being held by the transport drum 31 and while being held by the first transport conveyor 32.

  The 1st conveyance conveyor 32 is a 1st conveyance part which has a pair of pulley 61, the conveyance belt 62, and a suction mechanism (not shown). The conveyor belt 62 is looped between the pair of pulleys 61. A part of the conveyance belt 62 is arranged so as to face and face the outer peripheral surface of the conveyance drum 31. One of the pair of pulleys 61 rotates with power obtained from a motor (not shown). As a result, the transport belt 62 rotates in the direction of the arrow in FIGS. At this time, the other of the pair of pulleys 61 is driven to rotate as the conveyor belt 62 rotates.

  As shown in FIG. 2, the conveyance belt 62 is provided with a plurality of suction portions 60. The plurality of suction units 60 are through holes provided on the surface of the transport belt 62, similar to the suction unit 310 of the transport drum 31. The plurality of suction units 60 are arranged in the transport direction at the position in the width direction corresponding to each of the plurality of transport rows. The intervals in the conveyance direction and the width direction of the plurality of suction units 60 on the conveyance belt 62 are equal to the intervals in the conveyance direction and the width direction of the plurality of adsorption units 60 on the conveyance drum 31.

  Similar to the transport drum 31, the first transport conveyor 32 has a suction mechanism (not shown). The suction mechanism generates a negative pressure in the space inside the pulley 61 and the conveyor belt 62. When the suction mechanism is operated, a negative pressure lower than the atmospheric pressure is generated in each of the plurality of suction portions 60. The suction unit 60 sucks and holds the tablets 9 delivered from the transport drum 31 one by one by the negative pressure. Thereby, the 1st conveyance conveyor 32 conveys the some tablet 9 adsorbing-holding in the state aligned in the conveyance direction and the width direction, applying a negative pressure to the some adsorption | suction part 60. As shown in FIG. Thus, the transport belt 62 serves as a holding unit that holds the tablet 9.

  A positive pressure higher than the atmospheric pressure is applied to the suction unit 60 that has moved to a position facing the second transport conveyor 33 on the first transport conveyor 32 to release the suction of the tablets 9. Thereby, the 1st conveyance conveyor 32 delivers the tablet 9 to the 2nd conveyance conveyor 33. FIG. When the tablets 9 are delivered from the first transport conveyor 32 to the second transport conveyor 33, the surface of the tablet 9 that the first transport conveyor 32 sucks and holds and the surface of the tablet 9 that the second transport conveyor 33 sucks and holds are formed. Different. For this reason, the front and back of the tablet 9 are reversed while being held by the first transfer conveyor 32 and while being held by the second transfer conveyor 33.

  The configuration of the second transport conveyor 33 is substantially the same as that of the first transport conveyor 32. Similar to the first conveyor 32, the second conveyor 33 includes a pair of pulleys 61, a conveyor belt 62, and a suction mechanism (not shown). Of the configuration of the second transfer conveyor 33, the description of the same configuration as the first transfer conveyor 32 is omitted.

  A chute 341 that connects the second conveyor 33 and the carry-out conveyor 34 is disposed below the second conveyor 33. A positive pressure higher than the atmospheric pressure is applied to the suction portion 60 that has moved to the position facing the chute 341 on the second conveyor 33, and the suction of the tablets 9 is released. Thereby, the second transport conveyor 33 drops the tablets 9 into the chute 341. Thereby, the tablet 9 is delivered from the second conveyor 33 to the carry-out conveyor 34 via the chute 341.

  The carry-out conveyor 34 is a mechanism for carrying out the plurality of tablets 9 after printing to the outside of the casing 100 of the printing apparatus 1. The upstream end of the carry-out conveyor 34 is located below the chute 341. The downstream end of the carry-out conveyor 34 is located outside the housing 100. The downstream end of the carry-out conveyor 34 is connected to, for example, a packaging device for packaging the tablet 9 after the printing process. For example, a belt conveyance mechanism is used for the carry-out conveyor 34. The plurality of tablets 9 delivered from the second transport conveyor 33 to the carry-out conveyor 34 are carried out of the casing 100 by the carry-out conveyor 34.

  The printing unit 40 includes a first printing unit 41 and a second printing unit 42.

  The first printing unit 41 is a print processing unit for printing an image on one surface of the tablet 9. As shown in FIG. 1, the first printing unit 41 includes two ionizers 71 and a head unit 72 having four heads 721. FIG. 3 is a bottom view of the first printing unit 41. In FIG. 3, the conveyance belt 62 and the plurality of tablets 9 held by the conveyance belt 62 are indicated by a two-dot chain line.

  The two ionizers 71 are arranged on the upstream side of the four heads 721, respectively. The ionizer 71 generates ions by discharge. When the ionizer 71 is driven during the printing process, the ionizer 71 supplies ions to the suspended powder floating around the tablet 9 held on the conveyance belt 62 of the conveyance mechanism 30. Thereby, the ionizer 71 neutralizes the suspended powder. The detailed configuration of the ionizer 71 will be described later.

  Each of the four heads 721 included in the head unit 72 is an ink jet head that performs printing processing by ejecting ink droplets toward the surface of the tablet 9 that is transported by the transport mechanism 30. The four heads 721 eject ink droplets of different colors (for example, cyan, magenta, yellow, and black). A multicolor image is recorded on the surface of the tablet 9 by superimposing single-color images formed by these colors. In addition, the edible ink manufactured with the raw material approved by the food hygiene law is used for the ink discharged from each head 721.

  As shown in an enlarged manner in FIG. 3, a plurality of nozzles 720 capable of ejecting ink droplets are provided on the lower surface of the head 721. In the present embodiment, a plurality of nozzles 720 are two-dimensionally arranged on the lower surface of the head 721 in the transport direction and the width direction. The nozzles 720 are arranged at different positions in the width direction. As described above, when the plurality of nozzles 720 are two-dimensionally arranged, the positions in the width direction of the nozzles 720 can be made closer to each other. However, the plurality of nozzles 720 may be arranged in a line along the width direction.

  As a method for ejecting ink droplets from the nozzle 720, for example, a so-called piezo method is used in which voltage is applied to a piezo element, which is a piezoelectric element, and the ink in the nozzle 720 is pressurized and ejected. Note that the ink droplet ejection method may be a so-called thermal method in which the ink in the nozzle 720 is heated and expanded by energizing the heater.

  The second printing unit 42 is a processing unit for printing an image on the other surface of the tablet 9. Since the configuration of the second printing unit 42 is the same as that of the first printing unit 41, the description thereof is omitted.

  As shown in FIG. 1, the inspection mechanism 50 includes a first appearance inspection camera 51, a second appearance inspection camera 52, a first print inspection camera 53, a third appearance inspection camera 54, and a second print inspection camera 55. And a defective product collection unit 56.

  The first appearance inspection camera 51 is a camera that photographs the surface of the other side of the tablet 9 conveyed by the conveying drum 31. The second appearance inspection camera 52 is a camera that photographs the surface of one side of the tablet 9 conveyed by the first conveyance conveyor 32 on the upstream side of the first printing unit 41. The first appearance inspection camera 51 and the second appearance inspection camera 52 detect the presence / absence of the tablet 9 in each suction portion 60, the presence / absence of the shape defect of each tablet 9, the orientation of each tablet 9, and the like.

  The first print inspection camera 53 is a camera that photographs the surface of one side of the tablet 9 conveyed by the first conveyance conveyor 32 on the downstream side of the first printing unit 41. The first print inspection camera 53 detects the presence or absence of a printing process by the first printing unit 41.

  The third appearance inspection camera 54 is a camera that photographs the surface of the other side of the tablet 9 that is transported by the second transport conveyor 33 on the upstream side of the second printing unit 42. The third appearance inspection camera 54 detects the presence / absence of the shape of the tablet 9, the presence / absence of each tablet 9, the orientation of each tablet 9, and the like at each suction portion of the second conveyor 33.

  The second print inspection camera 55 is a camera that photographs the surface of the other side of the tablet 9 conveyed by the second conveyance conveyor 33 on the downstream side of the second printing unit 42. The second print inspection camera 55 detects the presence or absence of a printing process by the second printing unit 42.

  The defective product collection unit 56 collects the tablets 9 having the shape defect and the printing defect detected by the five cameras 51 to 55. The defective product collection unit 56 includes a pressurizing mechanism (not shown) and a collection box 561. The pressure mechanism releases the suction of the tablet 9 by blowing locally pressurized gas from the inside of the second conveyor 33 to the suction portion 60 holding the tablet 9 in which the defect is detected. To do. Thereby, the tablet 9 in which the defect is detected is collected into the collection box 561.

  The control unit 10 is means for controlling the operation of each unit in the printing apparatus 1. FIG. 4 is a block diagram illustrating the connection between the control unit 10 and each unit in the printing apparatus 1. As conceptually shown in FIG. 1, the control unit 10 is configured by a computer having an arithmetic processing unit 101 such as a CPU, a memory 102 such as a RAM, and a storage unit 103 such as a hard disk drive. A computer program P and data D for executing printing processing are installed in the storage unit 103.

  As shown in FIG. 4, the control unit 10 includes a linear feeder 22, a rotary feeder 23, a transport drum 31 (including a motor and a suction mechanism), a first transport conveyor 32 (including a motor and a suction mechanism), and a second transport conveyor. 33 (including motor and suction mechanism), carry-out conveyor 34, ionizer 71 and head 721 of first printing unit 41 and second printing unit 42, first appearance inspection camera 51, second appearance inspection camera 52, first printing inspection The camera 53, the third appearance inspection camera 54, the second print inspection camera 55, and the defective product collection unit 56 are connected to be able to communicate with each other.

  The control unit 10 temporarily reads the computer program P and data D stored in the storage unit 103 into the memory 102, and the arithmetic processing unit 101 performs arithmetic processing based on the computer program P, whereby each of the above-described units Control the operation. Thereby, the printing process with respect to the some tablet 9 advances.

<2. About the configuration of the printing unit>
Next, a detailed configuration of the printing unit 40 will be described. FIG. 5 is a side view conceptually showing the first printing unit 41. As shown in FIG. 5, the ionizer 71 has an ion generator 711 that is disposed to face the transport belt 62.

  The ionizer 71 generates ions from the ion generator 711 by discharging. For the ionizer 71, for example, TAS-112SPOT of TRINC Co., Ltd. is used. The ionizer 71 is a so-called bipolar DC type ionizer that performs corona discharge by applying a DC voltage to plus and minus bipolar discharge needles. When the ionizer 71 is driven, the ionizer 71 releases positive ions and negative ions from the ion generator 711. Thereby, ions are supplied to the suspended powder that floats around the tablet 9 held on the transport belt 62 of the transport mechanism 30. Thereby, the ionizer 71 neutralizes the suspended powder.

  The suspended powder floating around the tablet 9 is charged with static electricity. If the suspended powder charged around the head 721 is floating, the suspended powder may adhere to the vicinity of the nozzle of the head 721. If the floating powder adheres to the vicinity of the nozzle 720, it may cause nozzle clogging or affect the trajectory of the ink droplets ejected from the nozzle 720, which may cause printing defects. In addition, if the suspended powder charged between the nozzle 720 and the tablet 9 is floating, the ink droplets ejected from the nozzle 720 toward the tablet 9 may change the trajectory due to static electricity, which may cause printing failure. is there.

  By arranging the ionizer 71 on the upstream side of the head 721 and neutralizing the floating powder before the head 721, it is possible to suppress the occurrence of such printing defects.

  Here, the distance in the height direction between the conveyance belt 62 that is the holding part of the tablet 9 and the ion generation part 711 is referred to as a distance D1. The distance in the transport direction between the upstream end of the head unit 72 and the ion generator 711 of the ionizer 71 is referred to as a distance D2. That is, the distance D <b> 2 is a distance in the transport direction between the upstream end of the head 721 on the most upstream side of the head unit 72 and the ion generation unit 711.

  The smaller the distance D1, the smaller the distance between the ion generator 711 and the suspended powder that is the object of charge removal. Thereby, the static elimination effect of floating powder improves. Therefore, the efficiency of suppressing printing defects caused by charged floating powder is improved. In addition, the smaller the distance D2, the easier the floating powder neutralization effect continues to the vicinity of the nozzle 720 of the head 721. Thereby, the printing defect resulting from the charged floating powder can be efficiently suppressed.

  FIGS. 6 and 7 are diagrams showing the results of investigating the relationship between the position of the ionizer 71 and the state of attachment of suspended powder to the nozzle 720 of the head 721. In FIG. 6, the occurrence status of “nozzle chipping” and “end face smear” when the printing process is performed continuously for 10 minutes is displayed for each value of the distance D1 and the distance D2. In general, in a printing apparatus for tablets, the head 721 is cleaned every 10 minutes. FIG. 7 shows the occurrence status of “nozzle chipping” and “end face smear” for each value of the distance D1 and the distance D2 when the printing process is continuously performed for 30 minutes. 6 and 7, the experiment was performed with the distance D1 set to 50 mm, 100 mm, and 150 mm. The experiment was conducted with the distance D2 set to 50 mm, 100 mm, 150 mm, and 180 mm.

  In FIG. 6 and FIG. 7, the “nozzle missing” column indicates the range of the number of nozzles 720 that have caused ejection failure due to floating powder adhering to the nozzles 720. Specifically, “欠 け” indicates that there are no more than three nozzles 720 that cause nozzle missing in one head 721. Nozzle chipping “◯” indicates that within one head 721, there are no more than eight nozzles 720 that have generated nozzle chipping, and this is a usable range. Nozzle chipping “Δ” indicates that there are more than eight nozzles 720 in which nozzle chipping has occurred, and the print quality is in a degraded range.

  In FIG. 6 and FIG. 7, the “end surface dirt” column shows the state of attachment of suspended powder to the end surface of the nozzle 720 in a stepwise manner. When the degree of attachment of the floating powder to the end surface of the nozzle 720 increases, the possibility of an ejection failure in which the trajectory of ink droplets ejected from the nozzle 720 deviates is increased. The end face contamination “◎” indicates a range where the amount of floating powder adhering to the end surface of the nozzle 720 is sufficiently small and hardly affects the trajectory of the ink droplets. “O” on the end face indicates that the amount of the floating powder adhering to the end face of the nozzle 720 is relatively small, and the influence on the trajectory of the ink droplet is relatively small and is in a usable range. The end face contamination “Δ” indicates that the amount of floating powder adhering to the end face of the nozzle 720 is relatively large, the influence on the ink droplet trajectory is relatively large, and the print quality is in a range.

  As shown in FIG. 6 and FIG. 7, the smaller the distance D1 and the distance D2, the less likely nozzle chipping and end face contamination occur. As shown in FIG. 6, as the distance D1 approaches 150 mm, the print quality is likely to be deteriorated due to the adhesion of the floating powder to the nozzle 720.

  As shown in FIG. 6, in order to perform the printing process continuously for 10 minutes, it is preferable to set the distance D1 to 150 mm or less. Further, as shown in FIG. 6, as the distance D2 approaches 150 mm, the print quality is likely to be deteriorated due to the adhesion of the floating powder to the nozzle 720. For this reason, it is preferable that the distance D2 is 150 mm or less. In this way, by setting the distance D1 and the distance D2 to 150 mm or less, the effect of neutralizing the floating powder is sufficiently exhibited, and it is possible to effectively suppress the occurrence of printing defects.

  Further, as shown in FIG. 7, in order to perform the printing process continuously for 30 minutes, it is preferable that the distance D1 and the distance D2 are set to 100 mm or less, respectively. By arranging the ionizer 71 in such a position, the cleaning interval of the head 721 can be changed from every 10 minutes to every 30 minutes. Thereby, the efficiency of the printing process is improved.

  In this embodiment, as shown in FIG. 3, the two ionizers 71 are arranged at an interval in the width direction orthogonal to the transport direction. As described above, by disposing the plurality of ionizers 71 in the width direction, it is possible to suppress the occurrence of unevenness in the charge removal effect in the width direction.

  The ionizer 71 according to the present embodiment can generate an air flow for carrying the generated ions using a built-in fan. In the printing process, the airflow may be generated or the airflow may not be generated. However, when the ionizer 71 generates an airflow, it is necessary to generate the airflow with an airflow that does not affect the ejection of ink droplets in the head 721 (that is, the print quality does not deteriorate).

  In the present embodiment, by arranging a plurality of ionizers 71 in the width direction, a sufficient amount of ions is supplied to each position in the transport direction on the transport belt 62 while suppressing the amount of airflow generated by the ionizer 71. can do. The number of ionizers 71 arranged in the width direction may be one or three or more.

  When the tablet 9 is an uncoated tablet (bare tablet), suspended powder is likely to be generated as compared with the case where the tablet 9 is a coated tablet. For this reason, when the tablet 9 is an uncoated tablet (bare tablet), the printing apparatus 1 which has the static elimination system of this invention is especially useful.

<3. Modification>
As mentioned above, although main embodiment of this invention was described, this invention is not limited to said embodiment.

  The printing apparatus 1 is an apparatus that performs printing on both sides of the tablet 9 by the first printing unit 41 and the second printing unit 42. However, the tablet printing apparatus of the present invention may be an apparatus that performs printing on only one side of the tablet 9.

  Further, the detailed configuration of the printing apparatus 1 may be different from those in the drawings of the present application. Moreover, you may combine suitably each element which appeared in said embodiment and modification in the range which does not produce inconsistency.

DESCRIPTION OF SYMBOLS 1 Printing apparatus 9 Tablet 10 Control part 30 Conveyance mechanism 40 Printing part 41 1st printing part 42 2nd printing part 60 Adsorption part 62 Conveying belt 71 Ionizer 72 Head unit 711 Ion generating part 720 Nozzle 721 Head

Claims (9)

A printing apparatus for performing a printing process on the surface of a granular material using an inkjet head,
A transport mechanism that transports from the upstream side in the transport direction to the downstream side while holding the granular material in the holding unit;
An ink jet head that has a plurality of nozzles that eject ink droplets and that performs a printing process by ejecting the ink droplets toward the surface of the granular material that is transported by the transport mechanism;
An ionizer disposed on the upstream side of the head and having an ion generating part for generating ions by discharge;
Have
The said ionizer is a printing apparatus which supplies ion with respect to the floating powder which floats around the said granular material. The printing apparatus according to claim 1,
The distance in the conveyance direction between the upstream end of the head and the ion generator is 150 mm or less. The printing apparatus according to claim 1 or 2, wherein
The distance in the height direction between the holding unit and the ion generation unit is 150 mm or less. The printing apparatus according to any one of claims 1 to 3,
Having a plurality of said ionizers,
The printing apparatus, wherein the plurality of ionizers are arranged at intervals in the width direction. The printing apparatus according to any one of claims 1 to 4,
The granular material is a tablet and is an uncoated tablet. A printing method in which a printing process is performed by an inkjet head on the surface of a granular material conveyed from the upstream side to the downstream side in the conveyance direction,
a) generating ions from an ion generating part of an ionizer and supplying ions to the suspended powder around the granular material;
b) On the downstream side of the ionizer, a step of performing a printing process by ejecting ink droplets from a plurality of nozzles of the head toward the surface of the granular material;
A printing method comprising: The printing method according to claim 6, comprising:
The distance in the conveyance direction between the upstream end of the head and the ion generator is 150 mm or less. The printing method according to claim 6 or 7, comprising:
In the step a), the distance in the height direction between the granular material and the ion generation unit is 150 mm or less. A printing method according to any one of claims 6 to 8, comprising:
The said granular material is a printing method which is a tablet and is an uncoated tablet.

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