JP7714735B2 - Tablet printing device and tablet printing method - Google Patents

Description

Embodiments of the present invention relate to a tablet printing device and a tablet printing method.

Currently, tablet printing devices that use inkjet heads to print various types of information, such as identification information, on tablets are being developed. Some of these tablet printing devices use inkjet heads to print on tablets that are held by suction through suction holes. In such devices, a camera, detection sensor, control board that controls the inkjet head, a blower used to hold the tablets by suction, a motor used to transport the tablets, and other components are all located at the back of the area where printing is performed by the inkjet head.

The control board, blower, motor, etc. are sources of heat, and the heated air is drawn into the suction hole used to hold the tablets. Because the inkjet head is located above the suction hole, the air flow mentioned above causes the temperature near the inkjet head to rise. When the temperature near the inkjet head rises, the viscosity of the ink inside the inkjet head decreases, making it impossible to eject a fixed amount of ink, or the area around the nozzle dries out, causing the ink to stick to the nozzle. This can lead to poor ejection and printing defects. Alternatively, a rise in temperature near the inkjet head can accelerate the deterioration of the ink inside the inkjet head.

JP 2013-122401 A

The problem that this invention aims to solve is to provide a tablet printing device and tablet printing method that can reduce the occurrence of printing defects and ink degradation.

The tablet printing device according to an embodiment of the present invention is
a conveying section provided in the first area for suction-holding the tablet in the suction hole and conveying the tablet;
an inkjet head provided in the first area and configured to print on the tablets transported by the transport unit;
a heat source provided in a second region connected to the first region and arranged to be aligned with the first region in a direction perpendicular to the conveying direction of the tablet conveyed by the conveying unit;
a cooling unit that supplies gas having a temperature lower than that of the second region to the first region from the first region side toward the second region ;
a moving mechanism provided in the second area and configured to move the inkjet head so as to change a distance between a surface of the inkjet head facing the transport unit and a surface of the transport unit facing the inkjet head;
Equipped with
the cooling unit is provided to blow out the gas while avoiding a surface of the inkjet head moved by the movement mechanism that faces the transport unit,
The inkjet head further includes a partition member, which is a wall for separating the first area from the second area and has an opening for connecting the moving mechanism to the inkjet head.

The tablet printing method according to an embodiment of the present invention comprises:
a conveying unit provided in a first region in the housing suction-holds the tablet in a suction hole and conveys the tablet;
an inkjet head provided in the first region prints on the tablets transported by the transport unit;
a cooling unit that is provided in the housing so as to be aligned with the first region in a direction perpendicular to a conveying direction of the tablet conveyed by the conveying unit, and in a state where a heat source is present in a second region connected to the first region, the cooling unit supplies gas having a temperature lower than that of the second region from the first region side toward the second region while avoiding a surface of the inkjet head on the conveying unit side,
The first area and the second area are separated by a partition member having an opening for connecting an inkjet head provided in the first area to a moving mechanism provided in the second area that changes the distance between the surface of the inkjet head facing the transport unit and the surface of the transport unit facing the inkjet head.

Embodiments of the present invention can reduce the occurrence of printing defects and ink deterioration.

FIG. 1 is a diagram illustrating an example of a schematic configuration of a tablet printing apparatus according to an embodiment. FIG. 1 is a diagram illustrating an example of a schematic configuration of a printing apparatus according to an embodiment. 1 is a cross-sectional view taken along line X1-X1 in FIG. 2, illustrating the cooling function of the tablet printing device according to the embodiment. 3 is a diagram showing an example of a housing of the tablet printing device according to the embodiment, as seen from the direction of arrow Y1 in FIG. 2. FIG. 5A and 5B are diagrams illustrating an example of a partition member according to an embodiment. 5A and 5B are diagrams illustrating an example of a partition member according to an embodiment. 5A and 5B are diagrams illustrating an example of a partition member according to an embodiment. FIG. 2 is a diagram illustrating an example of a control device according to an embodiment. 5A and 5B are diagrams illustrating a retraction function of the inkjet head according to the embodiment. 10 is a flowchart illustrating an example of the flow of a printing process according to the embodiment.

<Embodiment>
An embodiment will be described with reference to the drawings.

(Configuration example of tablet printing device)
An example of the configuration of a tablet printing device 1 according to an embodiment will be described with reference to FIGS. 1 and 2. FIG.

As shown in FIG. 1, the tablet printing device 1 according to the embodiment includes a supply device 10, a printing device 20, a collection device 30, and a control device 40.

The supply device 10 has a hopper 11, an alignment feeder 12, and a delivery feeder 13. The supply device 10 is positioned at one end of the printing device 20 and is configured to be able to supply tablets T, which are printing objects, to the printing device 20. The hopper 11 stores a large number of tablets T and sequentially supplies the stored tablets T to the alignment feeder 12. The alignment feeder 12 aligns the supplied tablets T in a line and transports them in the conveying direction A1 (clockwise direction) toward the delivery feeder 13. The delivery feeder 13 sequentially sucks in and holds each tablet T lined up on the alignment feeder 12 from above, transports the held tablets T in a line to the printing device 20, and delivers them to the printing device 20. The alignment feeder 12 may be, for example, a belt conveying mechanism or a vibrating feeder. The delivery feeder 13 may be, for example, a belt conveying mechanism. The belt conveying mechanism of this delivery feeder 13 rotates in the conveying direction A2 (counterclockwise). The supply device 10 is electrically connected to the control device 40, and its drive is controlled by the control device 40.

The printing device 20 includes a transport unit 21, a detection unit 22, a first imaging unit 23, an inkjet head 24, a second imaging unit 25, a movement mechanism 26, a maintenance unit 27, and a drying unit 28.

As shown in FIG. 2, two of each of the detection unit 22, first imaging unit 23, inkjet head 24, and second imaging unit 25 are provided, for example, but the number is not particularly limited and is set according to the number of transport paths for the tablets T. Note that the configuration of each detection unit 22, each first imaging unit 23, each inkjet head 24, and each second imaging unit 25 is the same, so only one of each will be described below.

Returning to Figure 1, the conveying unit 21 has a conveying belt 21a, a driving pulley 21b, multiple driven pulleys 21c, a motor 21d, a position detector 21e, and a suction chamber 21f. The conveying belt 21a is an endless belt that is stretched over the driving pulley 21b and each driven pulley 21c. The driving pulley 21b and each driven pulley 21c are rotatably mounted on the device main body (not shown), and the driving pulley 21b is connected to the motor 21d. The motor 21d is electrically connected to the control device 40, and its drive is controlled by the control device 40. The position detector 21e is a device such as an encoder and is attached to the motor 21d. The position detector 21e is electrically connected to the control device 40, and transmits a detection signal to the control device 40. The conveying unit 21 moves the conveying belt 21a together with the driven pulleys 21c by rotating the drive pulley 21b using the motor 21d, and conveys the tablets T on the conveying belt 21a in the conveying direction A1 (clockwise direction).

As shown in FIG. 2, the conveyor belt 21a has multiple circular suction holes 21g. Each of these suction holes 21g is a through-hole that adsorbs tablets T and is arranged in two rows along the conveying direction A1 to form two parallel conveying paths. Each suction hole 21g is connected to the suction chamber 21f (see FIG. 1) via a suction path (not shown) formed in the suction chamber 21f, allowing suction force to be generated by the suction chamber 21f. A blower is connected to the suction chamber 21f via a suction pipe (not shown), and operation of the blower reduces the pressure inside the suction chamber 21f. The suction pipe is connected to approximately the center of the side surface of the suction chamber 21f (a surface parallel to the conveying direction A1). The blower is electrically connected to the control device 40, and its operation is controlled by the control device 40. When the pressure inside the suction chamber 21f is reduced, tablets T placed on each suction hole 21g of the conveyor belt 21a are sucked by the suction hole 21g and retained on the conveyor belt 21a.

The detection unit 22 is positioned downstream in the conveying direction A1 from the position where the supply device 10 is provided, and is provided above the conveying path formed by the suction holes 21g. This detection unit 22 detects tablets T that have reached the detection position directly below the detection unit 22 (arrival of tablets T) by emitting and receiving laser light, i.e., the position of tablets T on the conveying belt 21a in the X direction (see Figure 2). The detection unit 22 also detects the height of tablets T on the conveying belt 21a. For example, a displacement sensor is used as the detection unit 22. Various types of laser sensors, such as a reflective laser sensor, are also used as the displacement sensor. The detection unit 22 is electrically connected to the control unit 40 and transmits a detection signal to the control unit 40.

The first imaging unit 23 is positioned downstream in the conveying direction A1 from the position where the detection unit 22 is provided, and is provided above the conveying path formed by the suction holes 21g. Based on the X-direction position information of the tablet T detected by the detection unit 22, the first imaging unit 23 captures an image at the first imaging timing when the tablet T reaches the imaging position directly below the first imaging unit 23, acquires a first image including the top surface of the tablet T, and transmits the acquired first image to the control device 40. The first image is used to detect the position of the tablet T in the X, Y, and θ directions (see Figure 2) and to detect the presence or absence of damage or foreign matter attached to the tablet T (e.g., cracks, chips, dirt, etc.). The first imaging unit 23 can be any camera equipped with an imaging element such as a CCD (charge-coupled device) or a CMOS (complementary metal-oxide semiconductor). The first imaging unit 23 is electrically connected to the control device 40, and its operation is controlled by the control device 40. Illumination for imaging may also be provided as necessary.

Here, the positions of tablet T in the X and Y directions are, for example, positions in the XY coordinate system relative to the center (reference position) of the imaging area of the first imaging unit 23. Furthermore, the position in the θ direction is, for example, a position indicating the degree of rotation of tablet T in a horizontal plane along the XY plane of the imaging area of the first imaging unit 23. This position in the θ direction is detected when tablet T has a directional shape, such as when tablet T has a score line or is molded into an oval, elliptical, rectangular, or other shape. Note that the X and Y directions are positions in the horizontal direction.

The first imaging unit 23 further includes a cover 23a (see Figure 2). The cover 23a corresponds to the first cover and is a member for preventing foreign matter from adhering to the light-receiving portion of the first imaging unit 23. The cover 23a does not contact the conveyor belt 21a and is provided to surround the first imaging unit 23. The lower end of the cover 23a is at the same height as the retracted position H3 of the inkjet head 24, which will be described later (see Figure 9). The lower end of the cover 23a does not necessarily have to be at the same height as the retracted position H3 of the inkjet head 24, as long as it is at a height that does not cause it to come into contact with the tablet T. The cover 23a is made of a metal such as stainless steel, for example.

The inkjet head 24 is positioned downstream in the transport direction A1 from the position where the first imaging unit 23 is provided, and is provided above the transport path formed by the suction holes 21g. The inkjet head 24 has multiple (e.g., hundreds to thousands) nozzles 24a (see Figure 2), and is provided so that the direction in which the nozzles 24a are lined up (nozzle row) is perpendicular (an example of an intersection) to the transport direction A1 in the horizontal plane. The inkjet head 24 ejects ink individually from each nozzle 24a by operating a drive element for each nozzle 24a. This inkjet head 24 can be any inkjet print head having a drive element such as a piezoelectric element, a heat element, or a magnetostrictive element. The inkjet head 24 is electrically connected to a control device 40, and its drive is controlled by the control device 40.

The second imaging unit 25 is positioned downstream in the conveying direction A1 from the position where the inkjet head 24 is provided, and is provided above the conveying path formed by the suction holes 21g. Based on the position information of the tablet T in the X direction detected by the detection unit 22, the second imaging unit 25 performs an image capture at a second imaging timing when the tablet T reaches an imaging position directly below the second imaging unit 25, obtains a second image including the top surface of the tablet T, and transmits the obtained second image to the control device 40. The second image is used to inspect the print pattern printed on the tablet T.
As the second imaging unit 25, various cameras having imaging elements such as CCD or CMOS are used, similar to the above-mentioned first imaging unit 23. The second imaging unit 25 is electrically connected to the control device 40, and its driving is controlled by the control device 40. Illumination for imaging may also be provided as necessary.

The second imaging unit 25 further includes a cover 25a (see Figure 2). The cover 25a corresponds to the second cover and is a member for preventing foreign matter from adhering to the light-receiving portion of the second imaging unit 25. The cover 25a does not contact the conveyor belt 21a and is provided to surround the second imaging unit 25. The lower end of the cover 25a is at the same height as the retracted position H3 of the inkjet head 24 (described below) (see Figure 9). The lower end of the cover 23a does not necessarily have to be at the same height as the retracted position H3 of the inkjet head 24, as long as it is at a height that does not contact the tablet T. The cover 25a is formed of a metal such as stainless steel, for example.

The movement mechanism 26 moves each inkjet head 24 in an elevation direction (up and down in Figure 1). As shown in Figure 2, this movement mechanism 26 has, for example, an arm 26a and an arm movement mechanism 26b. The arm 26a is a holder that holds each inkjet head 24. For example, the arm 26a holds each inkjet head 24 with the ejection surface facing the conveying surface of the conveyor belt 21a. The conveying surface of the conveyor belt 21a is the surface on which tablets T are placed, which is the surface of the conveyor belt 21a facing the inkjet head 24. The ejection surface of the inkjet head 24 is the surface on which the nozzles 24a are formed, which is the surface of the inkjet head 24 facing the conveyor belt 21a. The arm movement mechanism 26b is a mechanism that holds the arm 26a and moves it in an elevation direction. This arm movement mechanism 26b is provided at a position adjacent to the side of the suction chamber 21f (a surface parallel to the conveying direction A1). A linear guide mechanism, for example, is used as the arm movement mechanism 26b. The arm movement mechanism 26b is electrically connected to the control device 40, and its drive is controlled by the control device 40. This movement mechanism 26 can change the distance (separation distance) between the transport surface of the transport belt 21a and the ejection surface of each inkjet head 24 by raising and lowering the arm 26a, i.e., each inkjet head 24, using the arm movement mechanism 26b.

In this embodiment, the maximum raised position of the inkjet head 24 is the maintenance position H2, which will be described later. However, the maximum raised position of the inkjet head 24 is not limited to this. The maximum raised position of the inkjet head 24 may be higher than the maintenance position H2. In other words, the maximum raised position may be a height that prevents the area around the nozzles of the inkjet head 24 from drying out due to the cooling unit 61, which will be described later. However, the lower the maximum raised position of the inkjet head 24, the lower the ceiling height of the cover 53, which will be described later. The lower the ceiling height of the cover 53, the smaller the volume of the space covered by the cover 53. This improves the cooling efficiency of the cooling unit 61, which will be described later.

The maintenance unit 27 performs maintenance operations for each inkjet head 24. Maintenance tasks include, for example, wiping and ink receiving. As shown in FIG. 2, the maintenance unit 27 includes, for example, a wiping unit 27a and a receiving tray 27b. The wiping unit 27a is a cleaning unit that cleans the ejection surface of each inkjet head 24 by reciprocating the maintenance unit 27 in the Y direction (see FIG. 2). The receiving tray 27b is a receiving member that receives droplets ejected from each inkjet head 24. The maintenance unit 27 is located adjacent to the side of the suction chamber 21f (a surface parallel to the conveying direction A1) and is configured to be movable between the conveying surface of the conveyor belt 21a and the ejection surfaces of each inkjet head 24 by a movement mechanism (e.g., a linear guide mechanism) (not shown). During maintenance, the distance between the conveying surface of the conveyor belt 21a and the ejection surfaces of each inkjet head 24 is widened by the movement mechanism 26 by a distance that allows the maintenance unit 27 to move between those surfaces and perform maintenance work.

The drying unit 28 is positioned opposite the conveyor belt 21a, and is provided, for example, below the conveyor unit 21. This drying unit 28 dries the ink applied to each tablet T on the conveyor belt 21a. The drying unit 28 may be any of a variety of dryers, such as a blower that dries using gas such as air, a heater that dries using radiant heat, or a blower that dries using warm or hot air using both gas and a heater. The drying unit 28 is electrically connected to the control device 40, and its operation is controlled by the control device 40.

The recovery device 30 is located downstream in the conveying direction A1 from the position where the drying section 28 is provided, and is provided below the conveying section 21. This recovery device 30 has a reusable product recovery section 31, a defective product recovery section 32, and a non-defective product recovery section 33. The recovery device 30 recovers reusable tablets T using the reusable product recovery section 31, recovers defective tablets T using the defective product recovery section 32, and recovers non-defective tablets T using the non-defective product recovery section 33. For example, reusable tablets are reusable tablets that are unprinted and undamaged with no foreign matter attached. Defective products include unprinted tablets with foreign matter attached and unprinted tablets (printed tablets) that are undamaged and undefective with no foreign matter attached, while non-defective products are unprinted tablets (printed tablets) that pass printing and are undamaged and undefective with no foreign matter attached. Note that the order of the reusable product recovery section 31, defective product recovery section 32, and non-defective product recovery section 33 in the conveying direction A1 is not limited to the order shown in FIG. 1 and may be changed as appropriate. The recovery device 30 is electrically connected to the control device 40, and its operation is controlled by the control device 40.

The reusable product collection section 31 has a spray nozzle 31a and a collection box 31b. The defective product collection section 32 has a spray nozzle 32a and a collection box 32b. The non-defective product collection section 33 has a spray nozzle 33a and a collection box 33b. These spray nozzles 31a, 32a, and 33a basically have the same structure, and the collection boxes 31b, 32b, and 33b also basically have the same structure. Therefore, only the spray nozzle 31a and the collection box 31b will be described as representative examples.

The spray nozzle 31a and collection box 31b are positioned opposite each other across the conveying path where the suction holes 21g of the conveyor belt 21a are aligned. The spray nozzle 31a is located within the suction chamber 21f and, for example, sprays gas (e.g., air) toward the conveyor belt 21a, causing tablets T to fall from the conveyor belt 21a. At this time, the gas sprayed from the spray nozzle 31a passes through the suction holes 21g of the conveyor belt 21a and hits the tablets T. The spray nozzle 31a is electrically connected to the control device 40, and its drive is controlled by the control device 40. The collection box 31b is located directly below the spray nozzle 31a and below the conveyor unit 21. This collection box 31b receives and stores tablets T that have fallen from the conveyor belt 21a due to the gas sprayed from the spray nozzle 31a.

Here, tablets T that have passed through the reusable product recovery section 31 and the defective product recovery section 32 are transported along with the movement of the conveyor belt 21a, and reach a position near the end of the conveyor belt 21a on the driven pulley 21c side. At this position, the suction effect on the tablets T ceases, but gas is sprayed onto the tablets T from above by the spray nozzle 33a, causing the tablets T to fall from the conveyor belt 21a. Therefore, providing the spray nozzle 33a ensures that the tablets T fall from the conveyor belt 21a. The collection box 33b receives and stores tablets T that have fallen from the conveyor belt 21a due to the gas sprayed from the spray nozzle 33a.

The control device 40 controls each part of the tablet printing device 1, such as the supply device 10, printing device 20, and collection device 30, based on various information and programs. The control device 40 also receives detection information (e.g., detection signals) transmitted from the position detector 21e and detection unit 22 of the conveying unit 21, and also receives image information transmitted from the first imaging unit 23 and second imaging unit 25. The control device 40 is realized, for example, by an electronic circuit such as an integrated circuit or a computer.

(Cooling function of tablet printing device)
Next, the cooling function of the tablet printing apparatus 1 will be described with reference to FIGS. 2 to 7. FIG.

As shown in Figures 2 to 4, the tablet printing device 1 has a housing 51. This housing 51 houses each of the components of the tablet printing device 1. These components include the supply device 10, the printing device 20, the collection device 30, and the control device 40. In the example of Figure 3, the cooling unit 61 and heat source 62 are also shown, as well as the conveying unit 21, each inkjet head 24, the movement mechanism 26, and the maintenance unit 27.

The housing 51 has a door 52, a door 55, and a cover 53. The doors 52 and 55 are attached to the housing 51 so that they can be opened and closed. An opening 52a is formed in the door 52. This opening 52a is sized to fit the exterior of the cooling unit 61 and is also formed so that the end of the cooling unit 61 facing the door 52 can be inserted into the opening 52a when the door 52 is closed. A gap member such as a gasket may be provided in this opening 52a. The housing 51 has a holding portion 51a above the inkjet head 24 and above the heat source 62. The holding portion 51a is, for example, a flat plate that covers the inkjet head 24 and the upper sides of the first and second image capture units 23 and 25. The input device 40a and output device 40b, which will be described later, are housed above the holding portion 51a. The detection unit 22, the first and second image capture units 23 and 25 are housed below the holding portion 51a. Additionally, a partition member 54 is provided inside the housing 51 between the transport unit 21 and the heat source 62.

The partition member 54 is a wall separating the first region R1 from the second region R2, preventing heat from the heat source 62 from flowing into the first region R1. The partition member 54 is formed, for example, from a metal plate such as stainless steel. The length of the partition member 54 in the X direction is the same as the length of the conveying section 21 in the X direction. The upper end of the partition member 54 is connected to the ceiling of the housing 51, but does not necessarily have to be connected to the ceiling of the housing 51. A gap may be provided between the upper end of the partition member 54 and the ceiling of the housing 51. A cable connects the first imaging unit 23 or the second imaging unit 25 to the control board. The partition member 54 has a hole (not shown) through which cables can pass. As shown in Figures 4 and 5, the partition member 54 also has an opening 54a. The opening 54a is an opening through which the movement mechanism 26 connects to the inkjet head 24. The opening 54a also serves as an opening for the maintenance unit 27 to move between the first region R1 and the second region R2.

In this embodiment, the opening 54a is a cutout. The outer shape of the opening 54a is T-shaped. For example, a portion of a rectangular or square-shaped partition member 54 is cut out in a T-shape, forming the T-shaped opening 54a in that portion of the partition member 54. Specifically, the opening 54a is formed by cutting downward in the Z direction from the upper end of the partition member 54. The length of the opening 54a in the X direction at the upper end of the partition member 54 is the same as the length of the door 52. The length of the protruding portion of the opening 54a in the X direction is the same as the length of the cover 53 in the X direction. The opening 54a is located at a position where the maintenance unit 27 and the partition member 54 intersect. In other words, the upper end of the partition member 54 at the position where the protruding portion of the opening 54a is located is located at a height that allows the maintenance unit 27 to move between the first region R1 and the second region R2. The opening 54a is a T-shaped notch to avoid interference between the partition member 54 and the holding portion 51a. If there is no holding portion 51a, for example, the opening 54a may be a notch of a shape other than T, or may be a hole of a rectangular, square, circular, or other shape.

The partition member 54 may be formed from a single plate, as shown in FIG. 5, or may be formed by combining multiple plates 54b, as shown in FIG. 6. In this case, there may be a plate 54b that covers the upper part of the holding portion 51a. Also, as shown in FIG. 7, the partition member 54 may be formed from multiple plates 54b and a frame 54c that can be attached to the housing 51. Note that instead of the frame 54c, multiple plates 54b may be attached to pillars or beams of the housing 51.

2 and 3, the cover 53 is a cover member that closes the space above the transport unit 21 from the door 52 side (front side). At least each inkjet head 24 is located in the space enclosed by the cover 53. The cover 53 is attached to the partition member 54 so as to cover a portion of the opening 54a of the partition member 54, and closes the space above the transport unit 21. In other words, the space enclosed by the cover 53 is in communication with the opening 54a of the partition member 54. In this embodiment, the upper part of the opening 54a is separated by the holding portion 51a and cannot be covered by the cover 53. However, the cover 53 may cover the entire opening 54a if it can. The key is that the cover 53 must be able to cover the area into which gas from the second region R2 flows toward the inkjet heads 24.

The cover 53 includes, for example, a main body 53b and a door portion 53c. The main body 53b covers the space above the conveying unit 21 and is a U-shaped member when viewed from the front, with the opening of the U facing downward. The main body 53b is connected to the partition member 54 so as to cover part or all of the opening 54a of the partition member 54 with the U-shaped opening facing downward. Therefore, the main body 53b has two side surfaces perpendicular to the conveying direction A1 and a ceiling connecting these two side surfaces. The ceiling of the main body 53b is higher than the top of the inkjet head 24 when it is in the fully raised position. Furthermore, the ceiling of the main body 53b is located at a height within the range of the lift stroke of the inkjet head 24, higher than the top end of the inkjet head 24 when it is in the fully raised position. The main body 53b is provided so as to fill the space between the cover 23a and the cover 25a.

The door portion 53c is a door that can be opened and closed relative to the main body 53b. The door portion 53c is, for example, box-shaped with one of its four sides missing. The door portion 53c is attached to the end of the main body 53b opposite the partition member 54 via a hinge (not shown), with the missing side facing the inkjet head 24. The door portion 53c is also detachably attached to the cover 25a. Therefore, in this embodiment, the cover 53 corresponds to a third cover that is located between the covers 23a and 25a and covers the space above the conveying unit 21.

The door portion 53c is attached to the cover 25a while the tablet printing device 1 is operating. Furthermore, when installing or removing the inkjet head 24, the door portion 53c is removed from the cover 25a and moves toward the cover 23a via a hinge (not shown). This allows the inkjet head 24 to be installed or removed from the front side. This makes it easy to install and remove the inkjet head 24.

A ventilation section 53a is formed on the door 52-facing surface of the cover 53 (the surface parallel to the conveying direction A1). The top of the ventilation section 53a is at the same height as the ceiling of the main body 53b or several centimeters lower. The ceiling of the main body 53b is also higher than the top of the inkjet head 24 at its maximum raised position by a height within the range of the inkjet head 24's lift stroke. This ventilation section 53a may be, for example, a mesh member such as a wire netting or a punching member such as a punched plate. The ventilation section 53a is used to supply outside air taken in by the cooling section 61 through the ventilation section 53a into the cover 53. The cooling section 61 is provided on the door 52-facing surface of the cover 53 so as to close this ventilation section 53a. It is preferable that the bottom end of the ventilation section 53a be higher in height than the top of the inkjet head 24 at its maximum raised position. If the lower end of the ventilation section 53a is higher than the top of the inkjet head 24, the flow of cooling gas will not be obstructed by the inkjet head 24. This makes it easier for the cooling gas from the cooling section 61 to flow into the second region R2. In this case, it goes without saying that the upper end of the ventilation section 53a is located above the lower end of the ventilation section 53a.

Within the housing 51, there is a first region R1 and a second region R2 connected to (communicating with) the first region R1. The first region R1 is provided with the transport unit 21 and inkjet heads 24, while the second region R2 is provided with a heat source 62. The movement mechanism 26 spans both the first region R1 and the second region R2, and the maintenance unit 27 has a standby position in the second region R2 and a maintenance position in the first region R1. The maintenance position of the maintenance unit 27 is a position below the inkjet heads 24 where maintenance of the inkjet heads 24 (purging, dummy ejection, wiping, etc.) is performed. The standby position of the maintenance unit 27 is the position of the maintenance unit 27 when maintenance of the inkjet heads 24 is not being performed, and is a predetermined position in the second region R2 as shown in Figure 3. The maintenance unit 27 moves between the maintenance position and the standby position, that is, in the left-right direction in Figure 3.

Here, the first region R1 is the region of the housing 51 closer to the door 52 than the partition member 54. The second region R2 is the region of the housing 51 closer to the heat source 62 than the partition member 54.

Each inkjet head 24 is moved in a vertical direction (up and down in Figure 3) by the movement mechanism 26. The vertical movement range Ha of their ejection surfaces is the range between a normal position H1 where each inkjet head 24 is normally located and a maintenance position H2 where the maintenance unit 27 performs maintenance work on each inkjet head 24. The maintenance position H2 is a position where the maintenance unit 27 moves between the transport surface of the transport belt 21a and the ejection surface of each inkjet head 24 to perform maintenance work.

The cooling unit 61 takes in outside air and sends it into the cover 53. The cooling unit 61 may be, for example, a cooling fan that creates an air flow, but is not limited to this. The cooling unit 61 only needs to be able to supply gas to at least the first region R1 at a temperature lower than that of the second region R2, and may be, for example, a supply unit that supplies compressed gas via a tube or the like. The gas may be, for example, air or nitrogen.

The cooling unit 61 is also arranged to face the heat source 62 across the inkjet heads 24 in a direction intersecting the X direction, which is the conveying direction A1 of the tablets T (for example, the Y direction, which is the perpendicular direction). Specifically, the cooling unit 61 is arranged on the end side of the direction in which the inkjet heads 24 are lined up (the Y direction). This is so that the gas supplied by the cooling unit 61 is directed at all of the inkjet heads 24.

The cooling unit 61 also blows and supplies gas in a direction that intersects the tablet T conveyance direction A1 in the horizontal plane (for example, the Y direction, which is a perpendicular direction). Because the gas is supplied toward the second region R2 on the heat source 62 side, it is possible to prevent air from flowing into the suction hole 21g from the second region R2 on the heat source 62 side. If the amount of air flowing into the suction hole 21g from the second region R2 is reduced by the gas supplied from the cooling unit 61, the temperature of the air sucked into the suction hole 21g will decrease, and ultimately the temperature of the first region R1 will also decrease. Note that the gas supply direction may be from above the inkjet head 24 downward by, for example, providing the cooling unit 61 above the inkjet head 24. The gas supply direction is not particularly limited as long as it can lower the temperature of the air flowing into the suction hole 21g.

The lower end of the cooling unit 61 is arranged so that it is always higher than the ejection surface of each inkjet head 24 as it moves up and down, i.e., it is arranged so that it is higher than the upper limit of the movement range Ha of the ejection surface of each inkjet head 24 in the up and down direction. In other words, the cooling unit 61 is arranged so that it blows gas away from the ejection surface of the inkjet head 24 as it is moved by the movement mechanism 26.

The cooling unit 61 is electrically connected to the control device 40, and its operation is controlled by the control device 40. For example, the cooling unit 61 may be operated continuously while the device power is on, or may be operated for a predetermined period of time, or may be stopped for a predetermined period of time. Furthermore, because heat diffusion from the heat source 62 is weak for a predetermined period of time after tablet printing begins (for example, the predetermined period of time required for a predetermined number of tablets T to be printed), the cooling unit 61 may be operated after that predetermined period of time has elapsed. Furthermore, a cooling unit 161 is provided on the second region R2 side of the housing 51.

The cooling unit 161 takes in air from the second region R2 and expels it to the outside of the device. The cooling unit 161 is provided, for example, in a portion of the housing 51 that separates the outside of the device from the second region R2. A cooling fan, for example, is used as the cooling unit 161. However, the cooling unit 161 is not limited to this. The cooling unit 161 may also be a blower or a pump. If the cooling unit 161 is a blower or a pump, the cooling unit 161 is provided outside the device. The cooling unit 161 is then connected via piping to the portion of the housing 51 that contacts the second region R2.

The heat source 62 is a source that generates heat. For example, the heat source 62 is a heat source related to one or both of the conveying operation of the conveying unit 21 and the printing operation of the inkjet head 24. Examples of this heat source 62 include a control board such as the control device 40, a blower used to suction and hold the tablets T, and a motor used to convey the tablets T.

(Configuration example of control device)
Next, an example of the configuration of the control device 40 will be described with reference to FIG.

As shown in FIG. 8, the control device 40 has an image processing unit 41, a memory unit 42, and a control unit 43. An input device 40a and an output device 40b are connected to the control device 40. The input device 40a is realized, for example, by a switch, touch panel, keyboard, mouse, etc. The output device 40b is realized, for example, by a display, lamp, meter, etc.

The image processing unit 41 captures the first image captured by the first imaging unit 23 and the second image captured by the second imaging unit 25, and processes the images using known image processing techniques. For example, the image processing unit 41 processes the first image obtained from the first imaging unit 23 to obtain information on the presence or absence of damage or foreign matter on the tablet T, and further obtains the position of the tablet T in the X, Y, and θ directions. The image processing unit 41 also processes the second image obtained from the second imaging unit 25 to obtain the printing position, shape, and size of the printed pattern (e.g., letters or marks) printed on the tablet T. The image processing unit 41 transmits the obtained information on the presence or absence of damage or foreign matter on the tablet T, the obtained position information of each tablet T in the X, Y, and θ directions, and the printing position, shape, and size information of the printed pattern on each tablet T to the control unit 43.

The memory unit 42 stores processing information, various programs, and the like. For example, it is realized by semiconductor memory elements such as RAM (Random Access Memory) or flash memory, or storage devices such as hard disks or optical disks. The memory unit 42 stores print data related to printing, data on the movement speed of the conveyor belt 21a, and the like. The print data includes information on printing patterns such as characters and marks.

The control unit 43 is a computer such as a CPU (Central Processing Unit), MCU (Micro Control Unit), or MPU (Micro Processing Unit), and controls each unit. For example, the control unit 43 controls the supply device 10, printing device 20, collection device 30, image processing unit 41, and memory unit 42 based on various information and programs stored in the memory unit 42. The control unit 43 also receives detection signals transmitted from the position detector 21e of the conveying unit 21 and the detection unit 22. The control unit 43 is realized, for example, by hardware and/or software.

(Inkjet head movement for maintenance)
For example, when performing maintenance work, the control unit 43 controls the moving mechanism 26 to move the ejection surface of each inkjet head 24 from the normal position H1 to the maintenance position H2. After the ejection surface of each inkjet head 24 has moved to the maintenance position H2, the control unit 43 then moves the maintenance unit 27 to the maintenance position in the Y direction to perform maintenance on the ejection surface of each inkjet head 24. Furthermore, as necessary, the control unit 43 moves the maintenance unit 27 to a position where the tray 27b of the maintenance unit 27 faces the ejection surface of each inkjet head 24, causes each inkjet head 24 to eject ink continuously, and then returns the maintenance unit 27 to its original position.

Here, the normal position H1, maintenance position H2, etc. are typically set in advance and stored, for example, in the memory unit 42. However, the normal position H1, maintenance position H2, etc. may be changed according to predetermined conditions, or may be changed according to a user's input operation on the input device 40a.

(Inkjet head movement due to abnormal tablet height)
Furthermore, during tablet printing, the control unit 43 determines whether the height of the tablet T on the conveyor belt 21a is abnormal based on height information regarding the height of the tablet T detected by the detection unit 22. For example, if the height of the tablet T exceeds a predetermined threshold, the control unit 43 determines that the height of the tablet T on the conveyor belt 21a is abnormal. As shown in FIG. 9 , a tablet T with an abnormal height (hereinafter also referred to as an "abnormal height tablet") is, for example, an upright tablet. An upright tablet T is one whose orientation is perpendicular or inclined to the conveying surface of the conveyor belt 21a. If the tablet T is conveyed by the conveyor belt 21a toward directly below the inkjet head 24 in this orientation, it will collide with the inkjet head 24, whose ejection surface is located at a predetermined normal position H1. The tablet T may be held in an upright position on the conveyor belt 21a due to the suction action of the suction holes 21g. In particular, if the held surface of the tablet T has an R-shape, a point other than the center of the tablet T may be sucked, causing the tablet to be held in an upright position.

The control unit 43 also changes the conveying speed at which the conveyor belt 21a conveys the tablets T, and changes the distance between the conveying surface of the conveyor belt 21a and the ejection surface of the inkjet head 24, based on whether the height of the tablets T on the conveyor belt 21a is abnormal. For example, if the height of the tablets T on the conveyor belt 21a is abnormal, the control unit 43 controls the conveying unit 21 to reduce the conveying speed of the conveyor belt 21a, and controls the moving mechanism 26 to increase the distance between the conveying surface of the conveyor belt 21a and the ejection surface of the inkjet head 24. After that, when a tablet T with an abnormal height passes directly below the inkjet head 24, the control unit 43 controls the moving mechanism 26 to return the inkjet head 24 to its normal position H1, and controls the conveying unit 21 to restore the conveying speed of the conveyor belt 21a.

More specifically, as shown in FIG. 9, the control unit 43 controls the movement mechanism 26 to raise the inkjet head 24 and move the ejection surface of the inkjet head 24 from the predetermined normal position H1 to the predetermined retracted position H3 for a tablet T with an abnormal height. This widens the gap between the conveying surface of the conveyor belt 21a and the ejection surface of the inkjet head 24. Even if the tablet T with an abnormal height is transported by the conveyor belt 21a in this state directly below the inkjet head 24 whose ejection surface is located at the predetermined retracted position H3, the tablet T passes directly below the inkjet head 24 without colliding with the inkjet head 24. Thereafter, at the timing when the tablet T with an abnormal height passes directly below the inkjet head 24, the control unit 43 controls the movement mechanism 26 to lower the inkjet head 24 and move the ejection surface of the inkjet head 24 from the predetermined retracted position H3 to the predetermined normal position H1. This returns the gap between the conveying surface of the conveyor belt 21a and the ejection surface of the inkjet head 24 to its original position.

Here, the predetermined threshold, predetermined normal position H1, predetermined retreat position H3, etc. are typically set in advance and stored, for example, in the memory unit 42. The normal position H1 is the lower limit of the movement range Ha of the inkjet head 24's ejection surface, and the predetermined retreat position H3 is lower than the maintenance position H2, which is the upper limit of the movement range Ha. However, the predetermined threshold, predetermined normal position H1, predetermined retreat position H3, etc. may be changed according to predetermined conditions or according to user input operations via the input device 40a. The predetermined threshold is set to, for example, the thickness of the tablet T + 1 mm. The distance between the printing surface of the tablet T and the ejection surface of the inkjet head 24 is typically about 1 mm, and the thickness of the tablet T is about 2 to 8 mm. Therefore, if the tablet T is 3 mm thick, when the detected height of the tablet T exceeds 4 mm, it exceeds the threshold and is determined to be an abnormally high tablet T, preventing the tablet T from colliding with the inkjet head 24. The predetermined normal position H1 is, for example, a position (e.g., a height position 1 mm away from the printing surface of the tablet T) determined experimentally or theoretically at which the inkjet head 24 does not collide with tablets T lying on the conveyor belt 21a (normal position) and can print normally on the tablets T on the conveyor belt 21a. The predetermined retracted position H3 is a position (e.g., a height position away from the conveyor belt 21a by more than the major axis of the tablet T) at which the inkjet head 24 does not come into contact with tablets T that are at an abnormal height above the conveyor belt 21a. Note that an appropriate margin is provided for both positions.

The control unit 43 also acquires the X-direction position of the tablet T on the conveyor belt 21a based on the detection information transmitted from the detection unit 22, i.e., the timing at which the tablet T on the conveyor belt 21a is detected. Based on this position information indicating the X-direction position of the tablet T, the control unit 43 sets the first imaging timing of the first imaging unit 23, the print start timing of the inkjet head 24, and the second imaging timing of the second imaging unit 25, and generates timing information indicating these timings and stores it in the memory unit 42. The print start timing is the timing at which printing begins on the tablet T that has reached the printing position directly below the inkjet head 24. The control unit 43 can also acquire information such as the amount of movement (amount of rotation) and speed of the conveyor belt 21a based on the detection information transmitted from the position detector 21e.

Furthermore, based on the information on the presence or absence of damage or foreign matter on the tablet T transmitted from the image processing unit 41 (this information is based on the first image), the control unit 43 sets printability information indicating whether or not printing is possible for the tablet T for which such information has been obtained. The control unit 43 then sets printing conditions as printing condition information for the tablet T for which printability has been obtained. At this time, the control unit 43 sets printing conditions for the tablet T for which positional information has been obtained based on the positional information of the tablet T in the X, Y, and θ directions transmitted from the image processing unit 41. For example, the control unit 43 determines the range of nozzles 24a to be used in printing the target tablet T in the inkjet head 24, i.e., the usable nozzle range, based on the positional information of the tablet T in the Y direction and the printing data, and sets printing conditions including the usable nozzle range and printing start timing. Note that if the tablet T has a directional shape, the control unit 43 sets printing conditions corresponding to the position of the tablet T in the θ direction based on the positional information of the tablet T in the θ direction. As an example, the control unit 43 registers 180 different print patterns in the memory unit 42, with the orientation of the print pattern rotated by 1 degree in a range from 0 degrees to 179 degrees, and selects from these print patterns a print pattern with an angle that matches the position of the tablet T in the θ direction, and sets the printing conditions.

In addition, the control unit 43 determines whether the printed pattern has been printed in a predetermined shape and size at a predetermined position on the tablet T, i.e., whether the printed pattern has been printed correctly on the tablet T, based on the printing position information, shape information, and size information of the printed pattern printed on the tablet T transmitted from the image processing unit 41 (this information is based on the second image), and sets print quality information for the tablet T (print status inspection). For example, when determining the shape and size of the printed pattern, the control unit 43 registers a test printed pattern in the memory unit 42 and compares the test printed pattern with the printed pattern on the tablet T after actual printing (the printed pattern printed on the tablet T).

The control unit 43 stores various information (e.g., information on the presence or absence of damage or foreign matter on the tablet T, position information, tablet T height information, timing information, printability information, printing condition information, print quality information, etc.) in the memory unit 42 as appropriate. However, when the target tablet T is collected by the collection device 30, the various information is deleted from the memory unit 42, for example, after a predetermined time (e.g., several seconds) has passed since it fell from the downstream end of the conveying unit 21 in the conveying direction A1. However, if this information is required in a later process, it is possible to leave the various information for each tablet T intact or to store it in storage media outside the device. When storing the various information for each tablet T, this information can be linked to the manufacturing date and time, lot number, etc., and stored so that if a defective tablet T is found after shipment after printing, the cause can be traced back to the original location.

(Printing process)
Next, the printing process performed by the tablet printing apparatus 1 will be described with reference to Fig. 10. This printing process also includes an inspection process. Note that various information, such as data required for printing and data required for retracting the inkjet head 24, is pre-stored in the storage unit 42.

As shown in FIG. 10, in step S1, when a large number of tablets T to be printed are placed in the hopper 11 of the supply device 10, the tablets T begin to be sequentially supplied from the hopper 11 to the alignment feeder 12, which then arranges them in a single line and moves them. The tablets T moving in this single line are then sequentially supplied to the conveyor belt 21a of the printing device 20 by the delivery feeder 13. The conveyor belt 21a rotates in the conveying direction A1 due to the rotation of the drive pulley 21b and each driven pulley 21c by the motor 21d. Therefore, the tablets T supplied onto the conveyor belt 21a are aligned in a single line on the conveyor belt 21a and transported at a predetermined conveying speed.

In step S2, tablet T on conveyor belt 21a is detected by detection unit 22. More specifically, tablet T on conveyor belt 21a is detected by detection unit 22 when it reaches a detection position (e.g., a laser light irradiation position) directly below detection unit 22, and the X-direction position of tablet T on conveyor belt 21a is recognized by control unit 43 based on the timing at which tablet T is detected. Position information indicating the X-direction position of tablet T is then generated by control unit 43 and stored in memory unit 42. Furthermore, the height of tablet T on conveyor belt 21a is detected by detection unit 22, height information regarding the height of tablet T is recognized by control unit 43, and the height information of tablet T is stored in memory unit 42.

In step S3, it is determined whether the height of the tablets T on the conveyor belt 21a is abnormal based on the height information. For example, it is determined whether the height of the tablets T on the conveyor belt 21a exceeds a predetermined threshold. If it is determined that the height of the tablets T on the conveyor belt 21a exceeds the predetermined threshold, it is determined that the height of the tablets T on the conveyor belt 21a is abnormal (Yes in step S3), and processing proceeds to step S11. On the other hand, if it is determined that the height of the tablets T on the conveyor belt 21a does not exceed the predetermined threshold, it is determined that the height of the tablets T on the conveyor belt 21a is normal (No in step S3), and processing proceeds to step S4.

In step S4, the tablet T on the conveyor belt 21a is imaged by the first imaging unit 23. Specifically, the tablet T on the conveyor belt 21a is imaged by the first imaging unit 23 at the first imaging timing when the tablet T reaches the imaging position directly below the first imaging unit 23, and the first image obtained by imaging by the first imaging unit 23 is transmitted to the control device 40. Based on this first image, information on the presence or absence of damage or foreign matter on the tablet T, as well as position information of the tablet T in the X, Y, and θ directions, is generated by the image processing unit 41 and stored in the memory unit 42.

In step S5, the control unit 43 determines whether printing is possible on the target tablet T based on information on the presence or absence of damage or foreign matter on the tablet T. If it is determined that printing is possible on the target tablet T (Yes in step S5), processing proceeds to step S6. Based on information such as the tablet T's position in the X, Y, and θ directions and the print pattern, printing conditions including the nozzle range to be used and print start timing for the tablet T set as printable (printable tablet T) are set in the memory unit 42. The ejection timing for the tablet T (the timing at which ink is ejected onto the tablet T) is determined based on the aforementioned print start timing (the timing at which printing on the tablet T begins). On the other hand, if it is determined that printing is not possible on the target tablet T (No in step S5), processing proceeds to step S9, where operations related to printing and inspection of the target tablet T are restricted. Information on whether printing is possible on the tablet T is stored in the memory unit 42 as appropriate. Restricting operations related to printing and inspection means that at least printing and inspection processes for the target tablet T are not performed.

In step S6, printing is performed by the inkjet head 24 based on the above printing conditions. That is, the control unit 43 controls the inkjet head 24 to print a predetermined printing pattern on the printable tablets T on the conveyor belt 21a. More specifically, the printable tablets T on the conveyor belt 21a that have passed below the first imaging unit 23 are printed by the inkjet head 24 based on the above-mentioned printing conditions at the printing start timing when they reach the printing position directly below the inkjet head 24. In the inkjet head 24, ink is ejected appropriately from each nozzle 24a, and a printing pattern (e.g., numbers, alphabets, katakana, symbols, figures) is printed on the printing surface, which is the top surface of the tablet T.

In step S7, the printed tablet T on the conveyor belt 21a is imaged by the second imaging unit 25. Specifically, the printed tablet T on the conveyor belt 21a is imaged by the second imaging unit 25 at the second imaging timing when the tablet T reaches the imaging position directly below the second imaging unit 25, and the second image obtained by imaging by the second imaging unit 25 is transmitted to the control device 40. This second image is processed by the image processing unit 41 of the control device 40. Specifically, information about the printed pattern printed on the tablet T, i.e., the printing position, shape, and size of the printed pattern, is acquired by the image processing unit 41. The second image transmitted from the second imaging unit 25 is processed by the image processing unit 41, and inspection information indicating the printing position, shape, and size of the printed pattern on the tablet T is generated and stored in the memory unit 42.

In step S8, the control unit 43 performs a print status inspection based on the above inspection information. More specifically, the control unit 43 determines whether the print pattern was printed correctly on the tablet T based on the inspection information related to the print position, shape, and size stored in the memory unit 42, and print pass/fail information indicating whether the tablet T was printed correctly is generated and stored in the memory unit 42. For example, in the print status inspection, the print pattern used for printing is stored in the memory unit 42 as a test print pattern, and pass/fail information related to the specified print position, shape, and size of the test print pattern is compared with inspection information related to the print position, shape, and size of the actual printed print pattern stored in the memory unit 42, to determine whether the print pattern was printed correctly on the tablet T (pass or fail).

In step S9, the tablets T on the conveyor belt 21a are collected by the collection device 30. The ink applied to the tablets T dries naturally during transport and is also dried by the drying section 28. More specifically, when a reused tablet T reaches the reused product collection section 31 as it moves on the conveyor belt 21a, gas is sprayed onto the tablet T from above by the spray nozzle 31a, causing the tablet T to fall from the conveyor belt 21a and be collected in the collection box 31b. Similarly, when a defective tablet T reaches the defective product collection section 32 as it moves on the conveyor belt 21a, gas is sprayed onto the tablet T from above by the spray nozzle 32a, causing the tablet T to fall from the conveyor belt 21a and be collected in the collection box 32b. Furthermore, when a non-defective tablet T reaches a position near the end of the conveyor belt 21a on the driven pulley 21c side, the suction action on the tablet T ceases, and gas is blown onto the tablet T from above by the injection nozzle 33a, causing the tablet T to fall from the conveyor belt 21a and be collected in the collection box 32b. Such control of the blowing of gas is performed by the control unit 43 based on various information, such as position information of the tablet T, height information of the tablet T, printability information, and printability information.

In step S10, the control unit 43 determines whether printing has finished. For example, the number of printed tablets T is counted, and when this number reaches a predetermined production number, printing is determined to have finished. If it is determined that printing has finished (Yes in step S10), processing ends. On the other hand, if it is determined that printing has not finished (No in step S10), processing returns to step S1. Note that the determination of whether printing has finished may be made in response to a user input operation on the input device 40a, for example, when the user presses a print finish button.

If, in step S3 above, it is determined that the height of the tablet T on the conveyor belt 21a is abnormal (Yes in step S3), in step S11, the conveying speed of the conveyor belt 21a is reduced by the control unit 43. For example, the conveying speed may be reduced gradually or in steps from a predetermined normal speed at a constant rate, or may be reduced gradually or in steps at a random rate. The predetermined normal speed is reduced to a predetermined speed, and it is desirable that this predetermined speed be a conveying speed that is approximately 1/10 of the normal speed.

For example, the predetermined speed is determined based on the distance between the position directly below the detection unit 22 on the conveyor belt 21a and the position directly below the inkjet head 24, and the time required for the ejection surface of the inkjet head 24 to move from a predetermined normal position H1 to a predetermined retracted position H3. Note that the distance between the position directly below the detection unit 22 on the conveyor belt 21a and the position directly below the inkjet head 24 is, for example, the distance between the detection position where the detection unit 22 detects a tablet T on the conveyor belt 21a and the position directly below the upstream end of the inkjet head 24 in the conveying direction A1.

In step S12, the inkjet head 24 is raised by the movement mechanism 26. For example, the inkjet head 24 is raised until its ejection surface moves from a predetermined normal position H1 to a predetermined retracted position H3 (see Figure 9). This widens the gap between the conveying surface of the conveyor belt 21a and the ejection surface of the inkjet head 24 to a predetermined retraction gap. This predetermined retraction gap is a gap that allows a tablet T with an abnormal height to pass directly below the inkjet head 24 without colliding with it, even if the tablet T reaches directly below the inkjet head 24 on the conveyor belt 21a in that state.

In step S13, the control unit 43 restricts printing on the tablet T with an abnormal height, i.e., the abnormal-height tablet T, as well as on multiple tablets T located before and after it. For example, the inkjet head 24 is raised by the movement mechanism 26 and ejection is suspended. This prevents the inkjet head 24 from printing on the abnormal-height tablet T and tablets T transported before and after it (i.e., tablets T passing directly below the inkjet head 24 when the inkjet head 24 is positioned higher than the normal position H1). As a result, the occurrence of tablets T with poor printing (rejected printing) can be reduced. In other words, the control unit 43 simultaneously stops printing on the tablets T by the inkjet head 24 when the inkjet head 24 is raised by the movement mechanism 26.

In step S14, the control unit 43 determines whether the height-abnormal tablet T has passed directly below the inkjet head 24. If it is determined that the height-abnormal tablet T has passed directly below the inkjet head 24 (Yes in step S14), the process proceeds to step S15. For example, the control unit 43 determines that the height-abnormal tablet T has passed directly below the inkjet head 24 if a predetermined time has elapsed since the detection unit 22 detected the tablet T on the conveyor belt 21a. Note that whether the height-abnormal tablet T has passed directly below the inkjet head 24 may also be determined by detection by the position detector 22e.

For example, the predetermined time is determined based on the conveying speed of the tablet T (changing conveying speed), the distance between the position directly below the detection unit 22 on the conveying belt 21a and the position directly below the inkjet head 24, and the amount of movement (amount of rotation) of the conveying belt 21a. Note that the distance between the position directly below the detection unit 22 on the conveying belt 21a and the position directly below the inkjet head 24 here is, for example, the distance between the detection position where the detection unit 22 detects the tablet T on the conveying belt 21a and the position directly below the downstream end of the inkjet head 24 in the conveying direction A1.

In step S15, the inkjet head 24 is lowered by the movement mechanism 26. For example, the inkjet head 24 is lowered until its ejection surface moves from a predetermined retracted position H3 to a predetermined normal position H1 (see Figure 9). As a result, the distance between the conveying surface of the conveyor belt 21a and the ejection surface of the inkjet head 24 returns to the predetermined normal distance (the distance when the inkjet head 24 is located at the normal position H1).

In step S16, the control unit 43 returns the conveying speed of the conveyor belt 21a to its original speed, and the process proceeds to step S9. For example, the conveying speed may be increased gradually or in steps at a constant rate to a predetermined normal speed, or may be increased gradually or in steps at a random rate. The predetermined normal speed is set in advance and stored, for example, in the memory unit 42. However, the predetermined normal speed may be changed according to predetermined conditions, or may be changed according to a user's input operation on the input device 40a.

Even during this printing process, the cooling unit 61 (see Figure 3) continues to take in outside air and supply it to the first region R1. The temperature of the air supplied to the first region R1 is at least lower than the temperature in the second region R2. This air that is lower in temperature than the temperature in the second region R2 becomes cooling air. By supplying cooling air to the first region R1, the cooling air comes into contact with each inkjet head 24, cooling each inkjet head 24. The cooling air also passes through each inkjet head 24 and flows toward the suction holes 21g for holding the tablets T, making it difficult for the airflow from the heat source 62 side to be sucked into the suction holes 21g. Alternatively, the air from the heat source 62 side is cooled by the cooling air and sucked into the suction holes 21g. This lowers the temperature of the air flowing near the suction holes 21g, thereby lowering the temperature near the inkjet heads 24.

Here, the target temperature near the inkjet head 24 is preferably, for example, 20 to 25 degrees. Without cooling by the cooling unit 61, the temperature near the inkjet head 24 exceeds 25 degrees. If the temperature near the inkjet head 24 exceeds 25 degrees, the inkjet head 24 is more likely to malfunction (e.g., ink viscosity drops, resulting in poor ejection). Therefore, by supplying cooling air by the cooling unit 61 to lower the temperature near the inkjet head 24, it is possible to prevent the ink viscosity in the inkjet head 24 from decreasing and the ink near the nozzles 24a from drying out, thereby preventing poor ejection and printing defects. Furthermore, it is possible to prevent the temperature of the ink in the inkjet head 24 from rising, maintaining the ink at an appropriate temperature and preventing ink degradation. Experiments have confirmed that supplying cooling air by the cooling unit 61 can lower the temperature near the inkjet head 24 from 28 to 31 degrees to approximately 23 degrees.

Furthermore, a measuring device (not shown) may be provided to measure the temperature near the inkjet head 24, and if the measurement result from this measuring device exceeds a predetermined temperature (e.g., 24°C), the amount of cooling air supplied from the cooling unit 61 may be increased. Alternatively, if the measurement result from the measuring device exceeds the predetermined temperature, printing by the inkjet head 24 may be stopped. In this way, printing defects can be prevented. The measuring device that measures the temperature near the inkjet head 24 may be provided near the inkjet head 24, or it may be provided on the inkjet head 24 itself and measure the surface temperature of the inkjet head 24 itself. In other words, the temperature near the inkjet head 24 includes the temperature of the inkjet head 24 itself.

The cooling unit 61 is also configured to blow cooling air away from the ejection surface of each inkjet head 24 that is moved by the movement mechanism 26. As a result, even when each inkjet head 24 is moved by the movement mechanism 26 to retract from the tablet T or during maintenance, the cooling air blown out from the cooling unit 61 does not directly hit the ejection surface of each inkjet head 24, preventing the ink near the nozzle 24a from drying out and solidifying. This makes it possible to prevent ejection defects and printing failures.

In addition, the air in the second region R2 is exhausted to the outside of the device by the cooling unit 161, creating a negative pressure in the second region R2. Creating a negative pressure in the second region R2 prevents heat generated in the second region R2 from flowing into the first region R1. Creating a negative pressure in the second region R2 also makes it easier for the cooling gas from the cooling unit 61 to flow into the second region R2.

The length of the partition member 54 in the X direction is the same as the length of the conveying unit 21 in the X direction. This prevents air from the second region R2 from flowing into suction holes 21g in the conveying belt 21a that are not sucking up tablets T. The upper end of the partition member 54 is connected to the ceiling of the housing 51. Warm air tends to move toward the top of the space. Therefore, by connecting the upper end of the partition member 54 to the ceiling of the housing 51, it is possible to prevent air heated in the second region R2 from flowing into the first region R1.

In addition, in response to the detection of a height abnormality by the detection unit 22, the control unit 43 reduces the conveying speed of the conveyor belt 21a and further increases the gap between the surface of the inkjet head 24 facing the conveyor belt 21a and the surface of the conveyor belt 21a facing the inkjet head 24. This allows tablets T that are at an abnormal height on the conveyor belt 21a to pass without colliding with the inkjet head 24. This makes it possible to suppress damage to the inkjet head 24 and breakage of the tablets T, thereby minimizing the adverse effects of increased maintenance frequency, extended maintenance time, and tablet breakage, and enabling efficient printing on the tablets T.

The control unit 43 raises the inkjet head 24, and as soon as the tablet T with an abnormal height passes directly below the inkjet head 24, the control unit 43 returns the inkjet head 24 to its original height position (normal position H1), returns the conveying speed of the conveyor belt 21a to normal speed, and resumes printing at the normal conveying speed. Printing by the inkjet head 24 is interrupted only during the raising of the inkjet head 24, the passing of the abnormal-height tablet T below the inkjet head 24, and the lowering of the inkjet head 24. Printing is performed when the inkjet head 24 is in normal position H1, allowing efficient printing of the tablets T. In other words, tablets following the abnormal-height tablet T, which are present at a distance equal to the length of the inkjet head 24 in the conveying direction A1, cannot be printed. However, printing can be resumed after the abnormal-height tablet T has completely passed the downstream end of the inkjet head 24 in the conveying direction A1. This minimizes the number of tablets T that are not printed due to the conveyance of the abnormal-height tablet T. Furthermore, printing and inspection processes will also be restricted for tablets T following the height-abnormal tablet T, and these tablets T will also become non-printed tablets.

As long as the height-abnormal tablet T and any subsequent tablets (tablets present at a distance equal to the length of the inkjet head 24 in the conveying direction A1) have passed the inkjet head 24 and the inkjet head 24 has returned to its normal position H1, the control unit 43 can resume printing on the tablets T using the inkjet head 24. If the conveying speed of the conveyor belt 21a has been reduced, printing may be resumed after the conveying speed is returned to the normal speed as described above, but printing may also be resumed while the conveying speed is reduced, and then the conveying speed may be returned to its original speed while printing continues.

Here, the supply speed at which tablets T are supplied from the supply device 10 to the conveying unit 21 (the conveying speed at which feeders such as the alignment feeder 12 and delivery feeder 13 convey tablets T) is typically set to be slower than the conveying speed at which the conveyor belt 21a conveys tablets T. Therefore, when the control unit 43 reduces the conveying speed of the conveyor belt 21a to maintain a predetermined speed difference between the supply speed of the supply device 10 and the conveying speed of the conveyor belt 21a, it may also reduce the supply speed of the supply device 10. This makes it possible to prevent tablets T from clogging feeders such as the alignment feeder 12 and delivery feeder 13.

The control unit 43 may also control the supply device 10 to stop the supply of new tablets T as soon as a tablet T with an abnormal height is detected. As a result, new tablets T will not be supplied onto the conveyor belt 21a in response to the occurrence of a tablet T with an abnormal height. The maintenance unit 27 of the inkjet head 24 enters between the inkjet head 24 and the conveyor belt 21a to perform maintenance. At this time, the inkjet head 24 retracts to a position higher than the normal position H1 to create space for the maintenance unit 27. Therefore, as soon as the tablets T on the conveyor belt 21a are collected, if new tablets T are not supplied to the conveyor belt 21a, maintenance work on the inkjet head 24 can be performed. Furthermore, maintenance of the conveyor belt 21a (and the suction holes 21g) may also be performed at the same time as maintenance of the inkjet head 24 is performed.

The control unit 43 may also control the recovery device 30 to limit ink ejection from the inkjet head 24 onto tablets T that pass directly below the detection unit 22 during the period when the conveying speed of the conveyor belt 21a is reduced, and to recover tablets T that pass directly below the detection unit 22 during the period when the conveying speed of the conveyor belt 21a is reduced as reusable, non-printed tablets, i.e., reusable products. This allows tablets T that pass directly below the detection unit 22 during the period when the conveying speed of the conveyor belt 21a is reduced to be recovered as reusable products.

In addition, to change the distance between the support surface of the conveyor belt 21a and the ejection surface of the inkjet head 24, the inkjet head 24 is moved by the movement mechanism 26, but this is not limited to this. For example, the conveyor belt 21a may be moved by the movement mechanism 26. This movement of the conveyor belt 21a may be achieved by moving the entire conveyor unit 21 by the movement mechanism 26, or by moving a portion of the conveyor belt 21a facing the inkjet head 24 by the movement mechanism 26.

When the transported object is a tablet T, the speed at which the tablet passes under the inkjet head 24 is orders of magnitude faster than when the transported object is, for example, paper. Furthermore, the relative size difference between the transported object and the inkjet head 24 is large, and the transport interval between each transported object is narrow. Therefore, rather than simply preventing collisions between the transported object and the inkjet head 24, it is important to devise a way to prevent collisions while minimizing the number of tablets T that are affected, such as those that cannot be printed, by retracting the inkjet head 24 to prevent the collision. Furthermore, if a tablet T with an abnormal height is detected and the entire device is stopped and the tablets T on the transport belt 21a are collected as unprinted (unprinted tablets), productivity will decrease significantly. Therefore, the present embodiment described above can solve tablet-specific issues not encountered in paper printing. When printing on tablets T, unlike when printing on paper, a single inkjet head 24 may be used to print on multiple tablets T arranged in a direction perpendicular to the transport direction A1 in a horizontal plane.

As described above, according to the embodiment, the tablet printing device 1 includes a conveying unit 21 provided in the first region R1 that conveys tablets T by suction and holding them in the suction holes 21g; an inkjet head 24 provided in the first region R1 that prints on the tablets T conveyed by the conveying unit 21; a heat source 62 provided in the second region R2 connected to the first region R1; and a cooling unit 61 that supplies gas to the first region R1 at a temperature lower than that of the second region R2. This makes it possible to supply gas to the first region R1 at a temperature lower than that of the second region R2, thereby lowering the temperature near the inkjet head 24 in the first region R1. This prevents a decrease in the viscosity of the ink in the inkjet head 24 and drying of the ink near the nozzles 24a, thereby preventing ejection defects and reducing printing defects. Furthermore, the temperature of the ink in the inkjet head 24 can be prevented from rising, allowing the ink to be maintained at an appropriate temperature, thereby preventing ink deterioration.

<Other Embodiments>
In the above description, printing is performed on tablets T using the tablet printing device 1 (tablet printing method) according to one embodiment, but this can also be rephrased as printing on tablets T using the tablet printing device 1 (tablet printing method) according to one embodiment and manufacturing printed tablets T. In other words, the tablet printing device 1 can be rephrased as a tablet manufacturing device, and the tablet printing method can be rephrased as a tablet manufacturing method.

In addition, while the above explanation exemplifies printing on one side of the tablet T, this is not limited to this. For example, the printing device 20 may be a single unit, and the units may be stacked one on top of the other. The tablet T printed by the upper printing device (first printing device) 20 may be inverted and handed over to the lower printing device (second printing device) 20, and the lower printing device 20 may then print on the tablet T, thereby printing both sides of the tablet T.

In addition, while the above explanation exemplifies conveying tablets T in two rows, this is not limited to this, and the number of rows may be one example, or may be three or more rows, and is not particularly limited. The number of conveyor belts 21a may also be two or more, and is not particularly limited. Furthermore, the number of inkjet heads 24 may also be one, or three or more, and is not particularly limited.

In addition, while the above description exemplifies that the cover 53 is formed from the main body 53b and the door portion 53c, this is not limited to this. For example, the side of the cover 23a facing the inkjet head 24 and the side of the cover 25a facing the inkjet head 24 may function as the side of the main body 53b. Furthermore, the holding portion 51a of the housing 51 may function as the ceiling of the main body 53b. Furthermore, the cover 23a, the cover 25a, and the ceiling of the cover 53 may be integrated. Furthermore, the cover 53 may be integrated without any distinction between the main body 53b and the door portion 53c.

Furthermore, while the above description has exemplified the cover 23a covering the first imaging unit 23 and the cover 25a covering the second imaging unit 25, this is not limiting. For example, the covers 23a and 25a are not required, and the cover 53 may be configured to at least enclose the periphery and upper side of the inkjet head 24 above the transport unit 21.

In the above description, the opening 54a of the partition member 54 is illustrated as having a notch shape, but this is not limiting. For example, if the holding portion 51a is not provided, the opening 54a may be a hole wide enough to allow the maintenance unit 27 to move between the first region R1 and the second region R2. In this case, the lower end of the opening 54a is positioned at a height that allows the maintenance unit 27 to move between the first region R1 and the second region R2. When the partition member 54 is connected to the ceiling of the housing 51, the first region R1 and the second region R2 are substantially separated by the partition member 54. In this case, most of the heat generated in the second region R2 tends to flow into the first region R1 through the opening 54a. However, because cooling gas from the cooling unit 61 is supplied to the space closed by the cover 53, the heat generated in the second region R2 is further prevented from flowing into the first region R1.

Furthermore, in the above description, a print head in which the nozzles 24a are arranged in a single row is used as the inkjet head 24, but this is not limited to this; for example, a print head in which the nozzles 24a are arranged in multiple rows may also be used.

In addition, in the above explanation, the inkjet head 24 is illustrated as being arranged so that the direction in which the nozzles 24a are arranged is perpendicular to the transport direction A1 in a horizontal plane, but this is not limited to this. For example, the nozzles 24a may be arranged so that the direction in which they are arranged is a direction that intersects with the transport direction A1 in a horizontal plane.

In addition, in the above explanation, it was stated that the tablets T were supplied randomly, rather than at regular intervals, onto the conveyor belt 21a, but this is not limited to this and they may also be supplied at regular intervals. In addition, in the above explanation, it was stated that the tablets T were suction-held by the suction holes 21g formed on the conveyor belt 21a, but this is not limited to this and they may be contained and held in a pocket or the like and transported, or they may be held and transported on the conveyor belt 21a by their own weight.

In addition, in the above description, the control unit 43 has been exemplified as determining whether the height of the tablet T is abnormal based on height information regarding the height of the tablet T detected by the detection unit 22, but this is not limited to this. For example, height information may be obtained by detecting the area, length, and shape of the tablet T supplied to the conveyor belt 21a when viewed in a plane based on an image of the tablet T obtained by the first imaging unit 23 (indirectly detecting the height of the tablet T). In other words, the height of the tablet T may be determined to be abnormal when the area or length of the tablet T when viewed in a plane falls below a threshold. Alternatively, the normal position H1 of the inkjet head 24 may be used as a reference, and a position approximately 1 mm lower than the normal position H1 may be set as the threshold.

In the above description, the control unit 43, when the detection unit 22 detects a tablet T with an abnormal height, causes the inkjet head 24 to print until the inkjet head 24 moves to the retracted position H3, or until the tablet T located one tablet upstream of the tablet T with an abnormal height. However, this is not limited to this. For example, when the detection unit 22 detects a tablet T with an abnormal height, printing by the inkjet head 24 may be interrupted and the inkjet head 24 may be moved from the normal position H1 to the retracted position H3. In this case, it is sufficient to reduce the conveying speed of the conveyor belt 21a to a speed that allows the inkjet head 24 to move to the retracted position H3 between the detection of the tablet T with an abnormal height and the arrival of the tablet T with an abnormal height. Alternatively, the inkjet head 24 may be controlled to move to the retracted position H3 so that the tablets T with restricted printing are located just before and after the tablet T with an abnormal height (for example, about 10 tablets, or within the time it is expected that about 10 tablets will be conveyed). In this case, the speed difference before and after the transport speed of the transport belt 21a is reduced is small, allowing for an increase in the number of prints per unit time.

In addition, while the above explanation exemplifies a gradual or stepwise reduction in the conveying speed of the conveyor belt 21a, this is not limiting. The conveying speed may be rapidly reduced to the target conveying speed when the detection unit 22 detects that the height of the tablet T has exceeded a predetermined threshold. When returning the conveying speed of the conveyor belt 21a from a reduced speed to the normal speed, the speed may be gradually or stepwise restored, or rapidly restored, just as when the speed is reduced. In either case, gradually or stepwise changing the conveying speed can prevent the tablet T from separating from the conveyor belt 21a.

The aforementioned tablets T can include tablets used for pharmaceutical, edible, cleaning, industrial, or aromatic purposes. Tablets T can be plain tablets (plain tablets), sugar-coated tablets, film-coated tablets, enteric-coated tablets, gelatin-coated tablets, multi-layered tablets, and dry-coated tablets. Various types of capsule tablets, such as hard capsules and soft capsules, can also be included in the tablets T. Tablets T can be shaped in various ways, such as discs, lenses, triangles, and ovals. When the tablets T to be printed are for pharmaceutical or edible use, edible ink is preferred. Any of synthetic pigment inks, natural pigment inks, dye inks, and pigment inks can be used as the edible ink.

Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments may be embodied in a variety of other forms, and various omissions, substitutions, and modifications may be made without departing from the spirit of the invention. These embodiments and their variations are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as set forth in the claims.

1 Tablet printing device 10 Feeder 11 Hopper 12 Alignment feeder 13 Delivery feeder 20 Printing device 21 Conveying unit 21a Conveyor belt 21b Drive pulley 21c Driven pulley 21d Motor 21e Position detector 21f Suction chamber 21g Suction hole 22 Detection unit 23 First imaging unit 23a Cover 24 Inkjet head 24a Nozzle 25 Second imaging unit 25a Cover 26 Moving mechanism 26a Arm 26b Arm moving mechanism 27 Maintenance unit 27a Wiping unit 27b Receiving tray 28 Drying unit 30 Recovery device 31 Reusable product recovery unit 31a Spray nozzle 31b Recovery box 32 Defective product recovery unit 32a Spray nozzle 32b Recovery box 33 Non-defective product recovery section 33b Recovery box 33a Spray nozzle 40 Control device 40a Input device 40b Output device 41 Image processing section 42 Memory section 43 Control section 51 Housing 51a Holding section 52 Door 52a Opening 53 Cover 53a Ventilation section 53b Main body 53c Door section 54 Partition member 54a Opening 54b Plate 54c Frame 55 Door 61 Cooling section 62 Heat source 161 Cooling section A1 Conveying direction A2 Conveying direction Ha Moving range H1 Normal position H2 Maintenance position H3 Evacuation position T Tablet

Claims (2)

a conveying section provided in the first area for suction-holding the tablet in the suction hole and conveying the tablet;
an inkjet head provided in the first area and configured to print on the tablets transported by the transport unit;
a heat source provided in a second region connected to the first region and arranged to be aligned with the first region in a direction perpendicular to the conveying direction of the tablet conveyed by the conveying unit;
a cooling unit that supplies gas having a temperature lower than that of the second region to the first region from the first region side toward the second region ;
a moving mechanism provided in the second area and configured to move the inkjet head so as to change a distance between a surface of the inkjet head facing the transport unit and a surface of the transport unit facing the inkjet head;
Equipped with
the cooling unit is provided to blow out the gas while avoiding a surface of the inkjet head moved by the movement mechanism that faces the transport unit,
The tablet printing device further includes a partition member that is a wall for separating the first area from the second area and has an opening through which the moving mechanism connects to the inkjet head. a conveying unit provided in a first region in the housing suction-holds the tablet in a suction hole and conveys the tablet;
an inkjet head provided in the first region prints on the tablets transported by the transport unit;
a cooling unit that is provided in the housing so as to be aligned with the first region in a direction perpendicular to a conveying direction of the tablet conveyed by the conveying unit, and in a state where a heat source is present in a second region connected to the first region, the cooling unit supplies gas having a temperature lower than that of the second region from the first region side toward the second region while avoiding a surface of the inkjet head on the conveying unit side,
the first area and the second area are separated by a partition member having an opening for connecting an inkjet head provided in the first area to a movement mechanism provided in the second area and configured to change a distance between a surface of the inkjet head on the transport unit side and a surface of the transport unit on the inkjet head side;
Tablet printing method.