JP2021151740A - Printing device - Google Patents

Abstract

To reduce time required in removing ink.SOLUTION: A pressure generating part 7 and an ink supply part 6 are allowed to execute separately in terms of time: operation by which ink is ejected from an upper printing part 4 into an ink tank 58 through an ejection passage 65A, utilizing a water head difference between the upper printing part 4 and the ink tank 58; and operation by which ink is ejected from a lower printing part 5 into the ink tank 58 through an ejection passage 65B, utilizing a water head difference between the lower printing part 5 and the ink tank 58.SELECTED DRAWING: Figure 2

Description

The present invention relates to a printing apparatus.

There is known a printing apparatus each having an inkjet head and having two printing units arranged one above the other (see Patent Document 1).

In such a printing apparatus, when the inkjet head is replaced or the like, ink may be removed by removing the ink stored in the upper and lower printing units.

Japanese Unexamined Patent Publication No. 2010-99955

In the ink removal in the printing apparatus provided with the upper and lower printing portions as described above, the flow rate of the ink discharged from the lower printing portion is small because the water head difference between the lower printing portion and the ink ejection destination is small. , The time required for ink removal may be longer. When performing work that requires ink removal, if it takes a long time to remove ink, the time required for the entire work becomes long. Therefore, there has been a demand for shortening the time required for removing ink.

The present invention has been made in view of the above, and an object of the present invention is to provide a printing apparatus capable of shortening the time required for ink removal.

According to one aspect of the present invention, a first printing unit that stores ink and prints using the stored ink, and an ink that is arranged at a position lower than the first printing unit, stores ink, and stores the stored ink. A second printing unit for printing using the printing unit, a discharge ink storage unit arranged at a position lower than the second printing unit, a first path connecting the first printing unit and the discharge ink storage unit, and the above. Using the water head difference between the second printing unit and the discharged ink storage unit and the water head difference between the first printing unit and the discharged ink storage unit, the first route is used. Utilizing the operation of discharging ink from the printing unit to the discharged ink storage unit and the water head difference between the second printing unit and the discharged ink storage unit, the second printing unit via the second path. Provided is a printing apparatus including a discharge operation unit that discharges ink to the discharge ink storage unit in a timely manner.

According to another aspect of the present invention, a first printing unit that stores ink and prints using the stored ink, and an ink that is arranged at a position lower than the first printing unit and stores ink and stores the ink. A second printing unit that prints using the above, a discharge ink storage unit that is arranged at a position lower than the second printing unit, and a first path that connects the first printing unit and the discharge ink storage unit. The water head difference between the second printing unit and the discharged ink storage unit, which are connected to each other and are independent of each other, and the first printing unit and the discharged ink storage unit. The operation of discharging ink from the first printing unit to the discharged ink storage unit via the first path and the water head difference between the second printing unit and the discharged ink storage unit are utilized. The printing apparatus is provided, which includes a discharge operation unit that executes an operation of discharging ink from the second printing unit to the discharge ink storage unit in parallel via the second path.

According to another aspect of the present invention, a first printing unit that stores ink and prints using the stored ink, and an ink that is arranged at a position lower than the first printing unit and stores ink and stores the ink. A second printing unit that prints using the above, a discharge ink storage unit arranged at a position lower than the second printing unit, a common path connected to the discharge ink storage unit, the first printing unit, and the above. Utilizing the water head difference between the first branch route connecting the common route, the second branch route connecting the second printing unit and the common route, and the first printing unit and the discharged ink storage unit. Then, the operation of discharging ink from the first printing unit to the discharged ink storage unit via the first branch route and the common route, and the water head difference between the second printing unit and the discharged ink storage unit. The discharge operation unit is provided in parallel with the operation of discharging ink from the second printing unit to the discharge ink storage unit via the second branch path and the common path. In the operation of discharging ink from the second printing unit to the discharged ink storage unit, the unit applies a pressure corresponding to the water head difference between the first printing unit and the second printing unit to the second printing unit. A printing apparatus characterized by the above is provided.

According to the printing apparatus of the present invention, the time required for ink removal can be shortened.

It is a schematic block diagram of the printing apparatus which concerns on 1st Embodiment. It is a schematic block diagram of the upper printing part, the lower printing part, the ink supply part, and the pressure generating part of the printing apparatus shown in FIG. It is a flowchart for demonstrating the operation of ink removal in 1st Embodiment. It is explanatory drawing of the ink flow at the time of ejecting ink from the upper printing part in the operation of removing ink in 1st Embodiment. It is a figure which shows the state of the progress in the process of ejecting ink from the upper printing part in the operation of removing ink in 1st Embodiment. It is explanatory drawing of the ink flow at the time of ejecting ink from the lower printing part by the operation of removing ink in 1st Embodiment. It is a figure which shows the state of the printing apparatus at the time of completion of ink removal in 1st Embodiment. It is a schematic block diagram of the upper printing part, the lower printing part, the ink supply part, and the pressure generating part in 2nd Embodiment. It is explanatory drawing of the flow of ink in the operation of removing ink in 2nd Embodiment. It is a schematic block diagram of the upper printing part, the lower printing part, the ink supply part, and the pressure generating part in 3rd Embodiment. It is explanatory drawing of the flow of ink in the operation of removing ink in 3rd Embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same or equivalent parts and components are designated by the same or equivalent reference numerals throughout the drawings.

The embodiments shown below exemplify an apparatus or the like for embodying the technical idea of the present invention, and the technical idea of the present invention includes the material, shape, structure, arrangement, etc. of each component. Is not specified as the following. The technical idea of the present invention can be modified in various ways within the scope of claims.

[First Embodiment]
FIG. 1 is a schematic configuration diagram of a printing apparatus according to a first embodiment of the present invention. FIG. 2 is a schematic configuration diagram of an upper printing unit, a lower printing unit, an ink supply unit, and a pressure generating unit of the printing apparatus shown in FIG. In the following description, the vertical and horizontal directions of the paper surface in FIG. 1 are defined as the vertical and horizontal directions. Further, the vertical direction in the following description is a vertical direction.

As shown in FIG. 1, the printing apparatus 1 according to the first embodiment includes a web roll support shaft 2, a transport unit 3, upper printing units (corresponding to the first printing unit) 4A to 4E, and a lower printing unit. It includes 5A to 5E (corresponding to the second printing unit), ink supply units 6A to 6E, a pressure generation unit 7, a take-up shaft 8, and a control unit 9. In addition, the subscripts of the alphabet in the symbols of the upper printing units 4A to 4E and the like may be omitted and collectively described.

The web roll support shaft 2 rotatably supports the web roll 10. The web roll 10 is a roll of the web W.

The transport unit 3 pulls out the web W from the web roll 10 and transports the web W toward the take-up shaft 8. The transport unit 3 includes a pair of transport rollers 11. The pair of transfer rollers 11 convey the web W toward the take-up shaft 8 while niping the web W.

The upper printing units 4A to 4E print an image on the surface of the web W. The upper printing units 4A to 4E store inks of different colors, and print on the web W using the stored inks. The upper printing units 4A to 4E are arranged in parallel in the transport direction (left-right direction) of the web W. The details of the upper printing unit 4 will be described later.

The lower printing units 5A to 5E print an image on the back surface of the web W. The lower printing units 5A to 5E each store ink of the same color as the upper printing units 4A to 4E, and print on the web W using the stored ink. The lower printing units 5A to 5E are arranged in parallel in the transport direction (left-right direction) of the web W below the upper printing units 4A to 4E. Details of the lower printing unit 5 will be described later.

The ink supply units 6A to 6E supply ink to the upper printing units 4A to 4E and the lower printing units 5A to 5E, respectively. Details of the ink supply unit 6 will be described later.

The pressure generation unit 7 generates pressure for ink circulation in the pressure tank 31A and the negative pressure tank 33A of the upper printing unit 4 and the pressure tank 31B and the negative pressure tank 33B of the lower printing unit 5, which will be described later. The pressure generating unit 7 is common to the upper printing units 4A to 4E and the lower printing units 5A to 5E. The details of the pressure generating unit 7 will be described later.

The take-up shaft 8 winds and holds the web W printed by the upper printing unit 4 and the lower printing unit 5.

The control unit 9 controls the operation of the entire printing device 1. The control unit 9 includes a CPU, RAM, ROM, a hard disk, and the like.

Next, the details of the upper printing unit 4, the lower printing unit 5, the ink supply unit 6, and the pressure generating unit 7 described above will be described with reference to FIG. Note that FIG. 2 shows an upper printing unit 4, a lower printing unit 5, and an ink supply unit 6 for one color.

As shown in FIG. 2, the upper printing unit 4 includes an inkjet head 21A and an ink circulation mechanism 22A.

The inkjet head 21A ejects the ink supplied by the ink circulation mechanism 22A. The inkjet head 21A includes a plurality of nozzles for ejecting ink, a chamber for storing ink ejected from the nozzles, and a plurality of piezoelectric elements (none of which are shown) arranged in the chamber for ejecting ink from the nozzles. Be prepared. The nozzle is open to the nozzle surface which is the lower surface of the inkjet head 21A.

The ink circulation mechanism 22A supplies ink to the inkjet head 21A while circulating the ink. The ink circulation mechanism 22A includes a pressure tank 31A, a pressure tank liquid level sensor 32A, a negative pressure tank 33A, a negative pressure tank liquid level sensor 34A, ink baths 35A and 36A, an inflow pipe 37A, and an outflow pipe. It includes 38A, ink circulation pipes 39A to 41A, and an ink circulation pump 42A.

The pressure tank 31A stores the ink to be supplied to the inkjet head 21A. The ink in the pressure tank 31A is supplied to the inkjet head 21A via the ink circulation pipe 39A, the ink bath 35A, and the inflow pipe 37A. That is, the pressure tank 31A is arranged on the upstream side of the inkjet head 21A in the ink circulation direction. In the pressure tank 31A, an air layer is formed on the liquid surface of the ink.

The pressure tank liquid level sensor 32A detects whether or not the liquid level height of the ink in the pressure tank 31A has reached the reference height. The pressure tank liquid level sensor 32A outputs a signal indicating "on" when the liquid level height in the pressure tank 31A is equal to or higher than the reference height, and turns "off" when the liquid level in the pressure tank 31A is less than the reference height. The indicated signal is output.

The negative pressure tank 33A stores the ink returned without being consumed by the inkjet head 21A. That is, the negative pressure tank 33A is arranged on the downstream side of the inkjet head 21A in the ink circulation direction. In the negative pressure tank 33A, an air layer is formed on the liquid surface of the ink.

The negative pressure tank liquid level sensor 34A detects whether or not the liquid level height of the ink in the negative pressure tank 33A has reached the reference height. The negative pressure tank liquid level sensor 34A outputs a signal indicating "on" when the liquid level height in the negative pressure tank 33A is equal to or higher than the reference height, and turns "off" when the liquid level in the negative pressure tank 33A is less than the reference height. The indicated signal is output.

The ink bath 35A supplies the ink sent from the pressure tank 31A via the ink circulation pipe 39A to the inkjet head 21A via the inflow pipe 37A.

The ink bath 36A collects the ink not consumed by the inkjet head 21A via the outflow pipe 38A and flows it to the ink circulation pipe 40A.

The inflow pipe 37A forms an ink flow path for allowing the ink supplied by the ink circulation unit 22A to flow into the inkjet head 21A. The inflow pipe 37A connects the inkjet head 21A and the ink bath 35A.

The outflow tube 38A forms an ink flow path that flows out from the inkjet head 21A and goes to the ink bath 36A without being consumed by the inkjet head 21A. The outflow pipe 38A connects the inkjet head 21A and the ink bath 36A.

The ink circulation tube 39A connects the pressure tank 31A and the ink bath 35A. The ink circulation tube 40A connects the ink bath 36A and the negative pressure tank 33A. The ink circulation pipe 41A connects the pressure tank 31A and the negative pressure tank 33A.

The ink circulation pump 42A sends ink from the negative pressure tank 33A to the pressure tank 31A via the ink circulation pipe 41A during ink circulation. Further, when the ink circulation pump 42A supplies ink from the ink supply unit 6 to the ink circulation mechanism 22A, the ink circulation pump 42A has a buffer tank 51A to a pressure tank 31A described later via a part of the connection pipe 54A and the ink circulation pipe 41A described later. Ink is sent to the liquid.

The lower printing unit 5 includes an inkjet head 21B and an ink circulation mechanism 22B.

The inkjet head 21B ejects the ink supplied by the ink circulation mechanism 22B. The inkjet head 21B has the same configuration as the inkjet head 21A of the upper printing unit 4 described above.

The ink circulation mechanism 22B supplies ink to the inkjet head 21B while circulating the ink. The ink circulation mechanism 22B includes a pressure tank 31B, a pressure tank liquid level sensor 32B, a negative pressure tank 33B, a negative pressure tank liquid level sensor 34B, ink baths 35B and 36B, an inflow pipe 37B, and an outflow pipe. It includes 38B, ink circulation tubes 39B to 41B, and an ink circulation pump 42B.

Pressurized tank 31B of ink circulation mechanism 22B, pressurized tank liquid level sensor 32B, negative pressure tank 33B, negative pressure tank liquid level sensor 34B, ink bath 35B, 36B, inflow pipe 37B, outflow pipe 38B, ink circulation pipe 39B to The 41B and the ink circulation pump 42B are the pressure tank 31A, the pressure tank liquid level sensor 32A, the negative pressure tank 33A, the negative pressure tank liquid level sensor 34A, the ink bath 35A, 36A, and the inflow of the ink circulation mechanism 22A described above, respectively. It has the same configuration as the pipe 37A, the outflow pipe 38A, the ink circulation pipes 39A to 41A, and the ink circulation pump 42A.

The ink supply units 6 include buffer tanks 51A and 51B, buffer tank liquid level sensors 52A and 52B, buffer tank air release valves 53A and 53B, buffer tank air release pipes 54A and 54B, and air filters 55A and 55B. Ink supply valves 56A, 56B, connection pipes 57A, 57B, ink tank (corresponding to discharged ink storage) 58, ink supply pumps 59A, 59B, common ink supply pipe (corresponding to common path) 60, and individually. Ink supply pipes 61A and 61B, buffer tank liquid level adjusting valves 62A and 62B, and bypass pipes 63A and 63B are provided.

The buffer tanks 51A and 51B store ink to be supplied to the ink circulation mechanisms 22A and 22B, respectively. The buffer tanks 51A and 51B receive ink from the ink tank 58 and store the supplied ink. In the buffer tanks 51A and 51B, an air layer is formed on the liquid surface of the ink. The buffer tanks 51A and 51B are connected to the ink circulation pipes 41A and 41B via the connection pipes 57A and 57B, respectively. The buffer tanks 51A and 51B are arranged at positions lower (below) than the nozzle surface of the inkjet heads 21A and 21B, respectively.

The buffer tank liquid level sensors 52A and 52B detect whether or not the liquid level height of the ink in the buffer tanks 51A and 51B has reached the reference height, respectively. The buffer tank liquid level sensor 52 outputs a signal indicating "on" when the liquid level height in the buffer tank 51 is equal to or higher than the reference height, and a signal indicating "off" when the liquid level height in the buffer tank 51 is less than the reference height. Is output.

The buffer tank open to the atmosphere valves 53A and 53B open the buffer tank to the atmosphere in order to switch the buffer tanks 51A and 51B between a closed state (a state of being shut off from the atmosphere) and an open state of the atmosphere (a state of being open to the atmosphere), respectively. The air flow path in the pipes 54A and 54B is opened and closed.

The buffer tank air opening pipes 54A and 54B form an air flow path for opening the buffer tanks 51A and 51B to the atmosphere, respectively. One end of the buffer tank open-air pipe 54 is connected to the air layer of the buffer tank 51, and the other end (open end to the atmosphere) is connected to the atmosphere through an air filter 55.

The air filters 55A and 55B prevent dust and the like in the air from entering the buffer tank air opening pipes 54A and 54B, respectively. The air filter 55 is installed at the open end of the buffer tank open to the atmosphere pipe 54.

The ink supply valves 56A and 56B open and close the ink flow path in the connecting pipes 57A and 57B, respectively.

The connection pipes 57A and 57B connect the ink circulation pipes 41A and 41B and the buffer tanks 51A and 51B, respectively. One end of the connection pipe 57 is connected to a portion between the negative pressure tank 33 of the ink circulation pipe 41 and the ink circulation pump 42, and the other end is connected to the buffer tank 51.

The ink tank 58 contains ink used for printing by the inkjet head 21. Further, the ink tank 58 receives and stores the ink discharged from the upper printing unit 4 and the lower printing unit 5 due to the ink removal described later. The ink tank 58 is arranged at a position (lower) lower than the lower printing unit 5 and the buffer tank 51B. The ink tank 58 is always open to the atmosphere.

The ink supply pump 59A sends ink from the ink tank 58 to the buffer tank 51A via the common ink supply pipe 60 and the individual ink supply pipe 61A. The ink supply pump 59A is installed in the individual ink supply pipe 61A. The ink supply pump 59B sends ink from the ink tank 58 to the buffer tank 51B via the common ink supply pipe 60 and the individual ink supply pipe 61B. The ink supply pump 59B is installed in the individual ink supply pipe 61B.

The common ink supply pipe 60 constitutes a common portion between the ink path between the ink tank 58 and the buffer tank 51A and the ink path between the ink tank 58 and the buffer tank 51B. The common ink supply pipe 60 is connected to the ink tank 58. One end of the common ink supply pipe 60 is inserted into the ink tank 58, and the other end is connected to the individual ink supply pipes 61A and 61B.

Here, since the ink paths connected to the ink tank 58 are integrated into one by the common ink supply tube 60, the work of replacing the ink paths when the user replaces the ink tank 58 is simplified. NS.

The individual ink supply tube 61A forms part of the ink path between the ink tank 58 and the buffer tank 51A. The individual ink supply pipe 61A connects the buffer tank 51A and the common ink supply pipe 60. The individual ink supply tube 61B constitutes a part of the ink path between the ink tank 58 and the buffer tank 51B. The individual ink supply pipe 61B connects the buffer tank 51B and the common ink supply pipe 60.

Here, the individual ink supply pipe 61A, the detour pipe 63A, the buffer tank 51A, and the connection pipe 57A form a branch path 64A (corresponding to the first branch path) connecting the upper printing unit 4 and the common ink supply pipe 60. Will be done. Further, the common ink supply pipe 60 and the branch path 64A form a discharge path 65A (corresponding to the first path) connecting the upper printing unit 4 and the ink tank 58.

Further, the individual ink supply pipe 61B, the detour pipe 63B, the buffer tank 51B, and the connection pipe 57B form a branch path 64B (corresponding to the second branch path) connecting the lower printing unit 5 and the common ink supply pipe 60. Will be done. Further, the common ink supply pipe 60 and the branch path 64B form a discharge path 65B (corresponding to the second path) connecting the lower printing unit 5 and the ink tank 58.

The buffer tank liquid level adjusting valves 62A and 62B open and close the ink flow path in the bypass pipes 63A and 63B, respectively.

The bypass pipes 63A and 63B form a route that bypasses the ink supply pumps 59A and 59B, respectively. One end of the detour pipe 63A is connected to a portion between the buffer tank 51A of the individual ink supply pipe 61A and the ink supply pump 59A, and the other end is the ink supply pump 59A of the individual ink supply pipe 61A and the common ink supply pipe 60. It is connected to the part between. One end of the detour pipe 63B is connected to a portion between the buffer tank 51B and the ink supply pump 59B of the individual ink supply pipe 61B, and the other end is the ink supply pump 59B of the individual ink supply pipe 61B and the common ink supply pipe 60. It is connected to the part between.

The pressure generating unit 7 includes a pressurized common air chamber 71, pressurized airtight valves 72A and 72B, pressurized communication pipes 73A and 73B, a pressurized air pump 74, a pressurized pressure generating pipe 75, and a pressurized pressure adjusting unit. Valve 76, pressure pressure adjusting pipe 77, pressure pressure sensor 78, negative pressure common air chamber 79, negative pressure sealing valves 80A, 80B, negative pressure communication pipes 81A, 81B, negative pressure air pump 82. , Atmospheric communication pipe 83, air filter 84, negative pressure pressure adjustment valve 85, negative pressure pressure adjustment pipe 86, negative pressure pressure sensor 87, pressure pressure communication valve 88, and pressure pressure communication pipe 89. To be equipped with.

The pressurized common air chamber 71 is an air chamber for equalizing the pressures of the pressure tank 31A of each upper printing unit 4 and the pressure tank 31B of each lower printing unit 5. The pressurized common air chamber 71 passes through the pressurized communication pipe 73A corresponding to each upper printing unit 4 and the pressure communicating pipe 73B corresponding to each lower printing unit 5, and the pressure tank 31A of each upper printing unit 4 And each lower printing unit 5 is connected to the pressure tank 31B.

The pressure sealing valve 72A switches communication and shutoff between the pressure common air chamber 71 and the pressure tank 31A of the upper printing unit 4 by opening and closing the air flow path in the pressure communication pipe 73A. A pressure sealing valve 72A is provided corresponding to each upper printing unit 4. In FIG. 2, only the pressure sealing valve 72A corresponding to one upper printing unit 4 is shown, and the other pressure sealing valve 72A is not shown.

The pressure sealing valve 72B switches communication and shutoff between the pressure common air chamber 71 and the pressure tank 31B of the lower printing unit 5 by opening and closing the air flow path in the pressure communication pipe 73B. .. A pressure sealing valve 72B is provided corresponding to each lower printing unit 5. In FIG. 2, only the pressure sealing valve 72B corresponding to one lower printing portion 5 is shown, and the other pressure sealing valve 72B is not shown.

The pressure communication pipe 73A communicates the pressure common air chamber 71 with the air layer of the pressure tank 31A of the upper printing unit 4. One pressure communication pipe 73A is provided corresponding to each upper printing unit 4. One end of the pressurized communication pipe 73A is connected to the pressurized common air chamber 71, and the other end is connected to the air layer of the pressurized tank 31A.

The pressure communication pipe 73B communicates the pressure common air chamber 71 with the air layer of the pressure tank 31B of the lower printing unit 5. One pressure communication pipe 73B is provided corresponding to each lower printing unit 5. One end of the pressurized communication pipe 73B is connected to a portion between the pressurized common air chamber 71 and the pressurized closed valve 72A of the pressurized communication pipe 73A, and the other end is connected to the air layer of the pressure tank 31B. There is. In FIG. 2, only the pressure communication pipe 73B corresponding to one lower printing unit 5 is shown, and the other pressure communication pipe 73B is not shown.

The pressurized air pump 74 sends air to the pressurized common air chamber 71 in order to apply a positive pressure to the pressurized tanks 31A and 31B. The pressurized air pump 74 is arranged in the middle of the pressurized pressure generating pipe 75.

The pressurized pressure generating pipe 75 forms an air flow path for sending air to the pressurized common air chamber 71 by the pressurized air pump 74. One end of the pressurized pressure generating pipe 75 is connected to the pressurized common air chamber 71, and the other end is connected to a portion between the negative pressure air pump 82 and the air filter 84 of the atmospheric communication pipe 83.

The pressurizing pressure adjusting valve 76 opens and closes the air flow path in the pressurizing pressure adjusting pipe 77 in order to adjust the pressures of the pressurizing common air chamber 71 and the pressurizing tanks 31A and 31B.

The pressurizing pressure adjusting pipe 77 forms an air flow path for adjusting the pressure of the pressurizing common air chamber 71 and the pressurizing tanks 31A and 31B. One end of the pressurized pressure adjusting pipe 77 is connected to the pressurized common air chamber 71, and the other end is connected to a portion of the atmospheric communication pipe 83 between the negative pressure air pump 82 and the air filter 84.

The pressurizing pressure sensor 78 detects the pressure in the pressurizing common air chamber 71. The pressure in the pressurized common air chamber 71 is equal to the pressure in the pressurized tanks 31A and 31B when the pressurized airtight valves 72A and 72B are open.

The negative pressure common air chamber 79 is an air chamber for equalizing the pressures of the negative pressure tank 33A of each upper printing unit 4 and the negative pressure tank 33B of each lower printing unit 5. The negative pressure common air chamber 79 passes through the negative pressure communication pipe 81A corresponding to each upper printing unit 4 and the negative pressure communication pipe 81B corresponding to each lower printing unit 5, and the negative pressure tank 33A of each upper printing unit 4 And each lower printing unit 5 is connected to a negative pressure tank 33B.

The negative pressure sealing valve 80A switches the communication and shutoff between the negative pressure common air chamber 79 and the negative pressure tank 33A of the upper printing unit 4 by opening and closing the air flow path in the negative pressure communication pipe 81A. A negative pressure sealing valve 80A is provided corresponding to each upper printing unit 4. In FIG. 2, only the negative pressure sealing valve 80A corresponding to one upper printing unit 4 is shown, and the other negative pressure sealing valve 80A is not shown.

The negative pressure sealing valve 80B switches the communication and shutoff between the negative pressure common air chamber 79 and the negative pressure tank 33B of the lower printing unit 5 by opening and closing the air flow path in the negative pressure communication pipe 81B. .. A negative pressure sealing valve 80B is provided corresponding to each lower printing unit 5. In FIG. 2, only the negative pressure sealing valve 80B corresponding to one lower printing portion 5 is shown, and the other negative pressure sealing valve 80B is not shown.

The negative pressure communication pipe 81A communicates the negative pressure common air chamber 79 with the air layer of the negative pressure tank 33A of the upper printing unit 4. One negative pressure communication pipe 81A is provided for each upper printing unit 4. One end of the negative pressure communication pipe 81A is connected to the negative pressure common air chamber 79, and the other end is connected to the air layer of the negative pressure tank 33A.

The negative pressure communication pipe 81B communicates the negative pressure common air chamber 79 with the air layer of the negative pressure tank 33B of the lower printing unit 5. One negative pressure communication pipe 81B is provided for each lower printing unit 5. One end of the negative pressure communication pipe 81B is connected to a portion between the negative pressure common air chamber 79 of the negative pressure communication pipe 81A and the negative pressure sealing valve 80A, and the other end is connected to the air layer of the negative pressure tank 33B. There is. Note that FIG. 2 shows only the negative pressure communication pipe 81B corresponding to one lower printing unit 5, and omits the illustration of the other negative pressure communication pipe 81B.

The negative pressure air pump 82 sucks air from the negative pressure common air chamber 79 in order to apply negative pressure to the negative pressure tanks 33A and 33B. The negative pressure air pump 82 is arranged in the middle of the atmospheric communication pipe 83.

The air communication pipe 83 forms an air flow path for sucking air from the negative pressure common air chamber 79 by the negative pressure air pump 82. One end of the air communication pipe 83 is connected to the negative pressure common air chamber 79, and the other end (open end to the atmosphere) communicates with the atmosphere through the air filter 84. A pressure pressure generating pipe 75, a pressure pressure adjusting pipe 77, and a negative pressure pressure adjusting pipe 86 are connected to the air communication pipe 83. As a result, the pressurized pressure generating pipe 75, the pressurized pressure adjusting pipe 77, and the negative pressure adjusting pipe 86 communicate with the atmosphere.

The air filter 84 prevents dust and the like in the air from entering the air communication pipe 83. The air filter 84 is installed at the open end of the atmospheric communication pipe 83.

The negative pressure pressure adjusting valve 85 opens and closes the air flow path in the negative pressure adjusting pipe 86 in order to adjust the pressures of the negative pressure common air chamber 79 and the negative pressure tanks 33A and 33B.

The negative pressure adjusting pipe 86 forms an air flow path for adjusting the pressure of the negative pressure common air chamber 79 and the negative pressure tanks 33A and 33B. One end of the negative pressure adjusting pipe 86 is connected to the negative pressure common air chamber 79, and the other end is connected to a portion of the atmospheric communication pipe 83 between the negative pressure air pump 82 and the air filter 84.

The negative pressure pressure sensor 87 detects the pressure in the negative pressure common air chamber 79. The pressure in the negative pressure common air chamber 79 is equal to the pressure of the negative pressure tanks 33A and 33B when the negative pressure sealing valves 80A and 80B are open.

The pressure-pressurizing communication valve 88 opens and closes the air flow path in the pressure-pressurizing communication pipe 89 in order to switch between communication and shutoff between the pressurized common air chamber 71 and the negative pressure common air chamber 79.

The applied / negative pressure communication pipe 89 forms an air flow path for communicating the pressurized common air chamber 71 and the negative pressure common air chamber 79. One end of the applied / negative pressure communication pipe 89 is connected to the pressurized common air chamber 71, and the other end is connected to the negative pressure common air chamber 79.

Next, the operation of the printing device 1 will be described.

When a print job is input, the control unit 9 closes the pressing / applying pressure communication valve 88. As a result, the pressure common air chamber 71 and the negative pressure common air chamber 79 are cut off.

In the printing device 1 in the standby state before the print job is input, the pressing / applying pressure communication valve 88 is open. Further, the pressure sealing valves 72A and 72B and the negative pressure sealing valves 80A and 80B are also open. The buffer tank air release valves 53A and 53B, the ink supply valves 56A and 56B, the buffer tank liquid level adjusting valves 62A and 62B, the pressurized pressure adjusting valve 76, and the negative pressure pressure adjusting valve 85 are closed.

Next, the control unit 9 controls the pressurized air pump 74, the pressurized pressure adjusting valve 76, the negative pressure air pump 82, and the negative pressure adjusting valve 85 to the pressurized tanks 31A and 31B and the negative pressure tanks 33A and 33B. Generate each set pressure. As a result, in each of the upper printing unit 4 and the lower printing unit 5, ink flows from the pressure tanks 31A and 31B to the negative pressure tanks 33A and 33B via the inkjet heads 21A and 21B.

Here, the set pressures of the pressure tanks 31A and 31B and the negative pressure tanks 33A and 33B are preset as pressure values for adjusting the nozzle pressures of the inkjet heads 21A and 21B to appropriate values while circulating the ink. It is a thing. The set pressures of the pressurized tanks 31A and 31B are positive pressures, and the set pressures of the negative pressure tanks 33A and 33B are negative pressures.

When the set pressures of the pressurized tanks 31A and 31B and the negative pressure tanks 33A and 33B are generated, the control unit 9 starts executing the print job. Specifically, based on the print job, the control unit 9 causes the web W transported by the transport unit 3 to eject ink from the inkjet heads 21A and 21B to print an image.

During this printing operation, the control unit 9 presses the pressurized air pump 74, the pressurized pressure adjusting valve 76, and the negative pressure air pump so as to maintain the pressures of the pressurized tanks 31A and 31B and the negative pressure tanks 33A and 33B at their respective set pressures. 82 and the negative pressure pressure regulating valve 85 are controlled.

Further, during the printing operation, the control unit 9 performs liquid level maintenance control. The liquid level maintenance control is a control for circulating ink while maintaining the liquid level heights of the pressurized tanks 31A and 31B, the negative pressure tanks 33A and 33B, and the buffer tanks 51A and 51B at the reference height. In the liquid level maintenance control, the control unit 9 sets the ink circulation pump 42A, the ink supply valve 56A, and the ink supply pump 59A according to the liquid level heights of the pressure tank 31A, the negative pressure tank 33A, and the buffer tank 51A. Control. Further, the control unit 9 controls the ink circulation pump 42B, the ink supply valve 56B, and the ink supply pump 59B according to the liquid level heights of the pressure tank 31B, the negative pressure tank 33B, and the buffer tank 51B.

Specifically, in the upper printing unit 4, when both the pressure tank liquid level sensor 32A and the negative pressure tank liquid level sensor 34A are on, the control unit 9 turns off the ink circulation pump 42A and the ink supply valve 56A. To close. Similarly, when the pressure tank liquid level sensor 32A is on and the negative pressure tank liquid level sensor 34A is off, the control unit 9 turns off the ink circulation pump 42A and closes the ink supply valve 56A.

When the pressure tank liquid level sensor 32A is off and the negative pressure tank liquid level sensor 34A is on, the control unit 9 turns on the ink circulation pump 42A and closes the ink supply valve 56A. As a result, the ink is sent from the negative pressure tank 33A to the pressure tank 31A.

When both the pressure tank liquid level sensor 32A and the negative pressure tank liquid level sensor 34A are off, the control unit 9 turns on the ink circulation pump 42A and opens the ink supply valve 56A. As a result, the ink is sent from the buffer tank 51A to the pressure tank 31A.

Further, when the buffer tank liquid level sensor 52A is off, the control unit 9 turns on the ink supply pump 59A. As a result, the ink is sent from the ink tank 58 to the buffer tank 51A. When the buffer tank liquid level sensor 52A is on, the control unit 9 turns off the ink supply pump 59A.

The liquid level maintenance control in the lower printing unit 5 and the buffer tank 51B is the same as the liquid level maintenance control in the upper printing unit 4 and the buffer tank 51A described above.

During the printing operation, the upper printing unit 4 supplies ink from the pressure tank 31A to the inkjet head 21A, and the ink not consumed by the inkjet head 21A is collected in the negative pressure tank 33A. When the pressure tank liquid level sensor 32A is off and the negative pressure tank liquid level sensor 34A is on, the ink circulation pump 42A sends ink from the negative pressure tank 33A to the pressure tank 31A by the above-mentioned liquid level maintenance control. Liquid. Printing is performed while the ink is circulated in this way. The same applies to the lower printing unit 5.

Further, when both the pressure tank liquid level sensor 32A and the negative pressure tank liquid level sensor 34A are turned off in the upper printing unit 4, the ink circulation pump 42A pressurizes from the buffer tank 51A by the above-mentioned liquid level maintenance control. Ink is sent to the tank 31A. As a result, ink is supplied to the ink circulation mechanism 22A. The same applies to the lower printing unit 5.

When the buffer tank liquid level sensor 52A is turned off, the ink supply pump 59A sends ink from the ink tank 58 to the buffer tank 51A by the above-mentioned liquid level maintenance control. As a result, the buffer tank 51A is replenished with ink. The same applies to the buffer tank 51B.

When the printing based on the print job is completed, the control unit 9 ends the liquid level maintenance control and the pressure control by the pressure generation unit 7, and shifts the printing device 1 to the standby state. As a result, a series of operations is completed.

Next, the operation of removing ink in the printing apparatus 1 will be described.

The ink removal is a process of removing the ink stored in the upper printing unit 4 and the lower printing unit 5. Ink removal is performed prior to, for example, when the inkjet head 21 is replaced.

The printing device 1 is in a standby state before the start of ink removal, and as described above, the applying / applying pressure communicating valves 88, the pressure sealing valves 72A and 72B, and the negative pressure sealing valves 80A and 80B are open. The buffer tank air release valves 53A and 53B, the ink supply valves 56A and 56B, the buffer tank liquid level adjusting valves 62A and 62B, the pressurized pressure adjusting valve 76, and the negative pressure pressure adjusting valve 85 are closed. Further, the liquid level heights of the pressurized tanks 31A and 31B, the negative pressure tanks 33A and 33B, and the buffer tanks 51A and 51B are set to the reference heights.

FIG. 3 is a flowchart for explaining the operation of removing ink. The processing of the flowchart of FIG. 3 is started when the start of ink removal is instructed by the operation of the operation input unit (not shown) by the operator who replaces the inkjet head 21 or the like.

Here, in the processing of the flowchart of FIG. 3 described below, the processing for the upper printing unit 4, the lower printing unit 5, and the ink supply unit 6 is all the upper printing units 4A to 4E and the lower printing units 5A to 5E. , And to the ink supply units 6A to 6E.

In step S1 of FIG. 3, the control unit 9 opens the pressurizing pressure adjusting valve 76 and closes the pressurized sealing valve 72B and the negative pressure sealing valves 80A and 80B. As a result, the pressure tank 31A of the upper printing unit 4 is open to the atmosphere, and the negative pressure tank 33A of the upper printing unit 4, the pressure tank 31B of the lower printing unit 5, and the negative pressure tank 33B are sealed. The buffer tanks 51A and 51B are in a sealed state.

Next, in step S2, the control unit 9 opens the ink supply valve 56A and the buffer tank liquid level adjusting valve 62A.

As a result, the ink is started to be discharged from the upper printing unit 4. That is, due to the head difference between the pressure tank 31A and the ink tank 58, as shown in FIG. 4, the ink is ink from the pressure tank 31A via the inkjet head 21A, the negative pressure tank 33A, and the discharge path 65A. Ink flows into the tank 58. Here, the ink flows through the detour pipe 63A in the branch path 64A of the discharge path 65A.

FIG. 5 shows a state in which the ink is being discharged from the upper printing unit 4 in the middle of the process. In the state of FIG. 5, the pressure tank 31A, the inkjet head 21A, the ink baths 35A and 36A, the inflow pipe 37A, the outflow pipe 38A, the ink circulation pipe 39A, and the ink circulation pipe 40A are above the liquid level in the negative pressure tank 33A. Ink is missing from the part. In this state, due to the head difference between the negative pressure tank 33A and the ink tank 58, ink flows from the negative pressure tank 33A to the ink tank 58 via the discharge path 65A.

While the ink is being discharged from the upper printing unit 4, the ink is not discharged from the lower printing unit 5, and the ink is discharged only from the upper printing unit 4.

After the start of ink discharge from the upper printing unit 4, in step S3, the control unit 9 determines whether or not a predetermined upper discharge time has elapsed from the start of ink discharge from the upper printing unit 4. When it is determined that the upper discharge time has not elapsed since the start of ink discharge from the upper printing unit 4 (step S3: NO), the control unit 9 repeats step S3.

Here, the upper discharge time is a preset time as a time required to remove ink from the inkjet head 21A and the ink circulation mechanism 22A of the upper printing unit 4. The upper discharge time is set in advance based on experiments and the like.

When it is determined that the upper discharge time has elapsed from the start of ink discharge from the upper printing unit 4 (step S3: YES), in step S4, the control unit 9 sets the ink supply valve 56A and the buffer tank liquid level adjusting valve 62A. Close. As a result, the ink is discharged from the upper printing unit 4.

Next, in step S5, the control unit 9 closes the pressure sealing valve 72A and opens the pressure sealing valve 72B. As a result, the pressure tank 31B of the lower printing unit 5 is open to the atmosphere, and the pressure tank 31A and the negative pressure tank 33A of the upper printing unit 4 and the negative pressure tank 33B of the lower printing unit 5 are sealed. .. The buffer tanks 51A and 51B are in a sealed state.

Next, in step S6, the control unit 9 opens the ink supply valve 56B and the buffer tank liquid level adjusting valve 62B.

As a result, the ink is started to be discharged from the lower printing unit 5. That is, due to the head difference between the pressure tank 31B and the ink tank 58, as shown in FIG. 6, the ink is ink from the pressure tank 31B via the inkjet head 21B, the negative pressure tank 33B, and the discharge path 65B. Ink flows into the tank 58. Here, the ink flows through the detour pipe 63B in the branch path 64B of the discharge path 65B.

After the start of ink discharge from the lower printing unit 5, in step S7, the control unit 9 determines whether or not a predetermined lower discharge time has elapsed from the start of ink discharge from the lower printing unit 5. When it is determined that the lower discharge time has not elapsed since the start of ink discharge from the lower printing unit 5 (step S7: NO), the control unit 9 repeats step S7.

Here, the lower discharge time is a preset time as a time required to remove ink from the inkjet head 21B and the ink circulation mechanism 22B of the lower printing unit 5. The lower discharge time is preset based on experiments and the like. Since the lower printing unit 5 has a smaller head difference from the ink tank 58 than the upper printing unit 4 and the flow rate of the discharged ink is smaller, the lower discharge time is longer than the upper discharge time.

When it is determined that the lower discharge time has elapsed from the start of ink discharge from the lower printing unit 5 (step S7: YES), in step S8, the control unit 9 determines the ink supply valve 56B and the buffer tank liquid level adjusting valve. Close 62B. As a result, as shown in FIG. 7, the ink is also discharged from the lower printing unit 5.

Next, in step S9, the control unit 9 closes the pressurizing pressure adjusting valve 76 and opens the pressurized sealing valve 72A and the negative pressure sealing valves 80A and 80B. As a result, a series of ink removal operations is completed.

As is clear from the above description, by the processing of steps S1 and S2 of FIG. 3, the ink from the upper printing unit 4 is taken from the upper printing unit 4 via the discharge path 65A by utilizing the head difference between the upper printing unit 4 and the ink tank 58. The operation of discharging the ink to the tank 58 is executed. Further, by the processing of steps S5 and S6 of FIG. 3, ink is transferred from the lower printing unit 5 to the ink tank 58 via the discharge path 65B by utilizing the head difference between the lower printing unit 5 and the ink tank 58. The operation of discharging is executed. The pressure generation unit 7 and the ink supply unit 6 correspond to the discharge operation unit.

As described above, in the printing apparatus 1, when the ink is removed from the upper printing unit 4 and the lower printing unit 5, the operation of discharging the ink from the upper printing unit 4 to the ink tank 58 is performed, and the upper printing unit 4 After the ink is discharged from the ink tank 58, the operation of discharging the ink from the lower printing unit 5 to the ink tank 58 is performed. That is, the operation of discharging the ink from the upper printing unit 4 and the operation of discharging the ink from the lower printing unit 5 are performed separately in time.

Here, unlike the present embodiment, when the ink is discharged from the upper printing unit 4 and the ink is discharged from the lower printing unit 5 at the same time and performed in parallel, the ink is discharged from the upper printing unit 4. Ink may flow from the confluence of the individual ink supply tubes 61A and 61B into the lower printing unit 5 via the individual ink supply tubes 61B. That is, ink may move from the upper printing unit 4 to the lower printing unit 5. The water head difference between the upper printing unit 4 and the ink tank 58 is larger than that of the lower printing unit 5, and the flow rate of the ink discharged from the upper printing unit 4 is larger than that of the ink discharged from the lower printing unit 5. This is because it is larger than the flow rate of.

When the ink moves from the upper printing unit 4 to the lower printing unit 5, the amount of ink that needs to be discharged from the lower printing unit 5 increases by the amount of the movement. Since the water head difference between the lower printing unit 5 and the ink tank 58 is smaller than that of the upper printing unit 4, the flow rate of the discharged ink is small. Therefore, when the ink moves from the upper printing unit 4 to the lower printing unit 5, the time required for removing the ink from the upper printing unit 4 and the lower printing unit 5 becomes longer.

On the other hand, in the present embodiment, as described above, the ink discharge from the upper printing unit 4 and the ink discharge from the lower printing unit 5 are time-separated, so that the upper printing unit 4 is discharged. The movement of ink from the lower printing unit 5 to the lower printing unit 5 is suppressed. Specifically, since the buffer tank liquid level adjusting valve 62B is closed while the ink is being discharged from the upper printing unit 4, the inflow of ink into the lower printing unit 5 is suppressed. As a result, an increase in the amount of ink that needs to be discharged from the lower printing unit 5 is suppressed, so that the ink discharge from the upper printing unit 4 and the ink discharge from the lower printing unit 5 described above are started at the same time. The time required for ink removal can be shortened as compared with the case where the ink is removed in parallel.

Further, as described above, unlike the present embodiment, when the ink discharge from the upper printing unit 4 and the ink discharge from the lower printing unit 5 are started at the same time, the lower printing unit 4 to the lower printing unit 4 starts to discharge the ink. The movement of ink to 5 may cause ink to overflow from the pressure tank 31B opened to the atmosphere in the lower printing unit 5.

On the other hand, in the present embodiment, as described above, the movement of ink from the upper printing unit 4 to the lower printing unit 5 is suppressed, so that the ink overflows from the pressure tank 31B of the lower printing unit 5 It can be suppressed.

[Second Embodiment]
Next, a second embodiment in which a part of the first embodiment described above is modified will be described.

FIG. 8 is a schematic configuration diagram of an upper printing unit, a lower printing unit, an ink supply unit, and a pressure generating unit in the second embodiment.

As shown in FIG. 8, also in the second embodiment, the upper printing unit 4, the lower printing unit 5, and the pressure generating unit 7 have the same configurations as those in the first embodiment described above.

In the ink supply unit 91 of the second embodiment, the common ink supply pipe 60 is omitted from the ink supply unit 6 of the first embodiment described above, and the individual ink supply pipes 61A and 61B are replaced with the ink supply pipes 92A and 92B, respectively. It is a configuration replaced with. The ink supply unit 91 of the second embodiment is also provided one for each ink color, similarly to the ink supply unit 6 of the first embodiment.

The ink supply pipe 92A connects the ink tank 58 and the buffer tank 51A, and constitutes an ink path between them. The ink supply pipe 92A is provided with an ink supply pump 59A, a buffer tank liquid level adjusting valve 62A, and a bypass pipe 63A.

The ink supply pipe 92B connects the ink tank 58 and the buffer tank 51B, and constitutes an ink path between them. The ink supply pipe 92B is provided with an ink supply pump 59B, a buffer tank liquid level adjusting valve 62B, and a bypass pipe 63B.

Here, the ink supply pipe 92A, the detour pipe 63A, the buffer tank 51A, and the connection pipe 57A form an independent path 93A (corresponding to the first path) connecting the upper printing unit 4 and the ink tank 58. Further, the ink supply pipe 92B, the detour pipe 63B, the buffer tank 51B, and the connection pipe 57B form an independent path 93B (corresponding to the second path) connecting the lower printing unit 5 and the ink tank 58. The independent routes 93A and 93B are independent routes. That is, the independent paths 93A and 93B are individually inserted into the ink tank 58 without merging with each other.

Next, the operation of removing ink in the second embodiment will be described.

In the second embodiment as well, as in the first embodiment, in the standby state before the start of ink removal, the applying / negative pressure communicating valves 88, the pressurized sealing valves 72A and 72B, and the negative pressure sealing valves 80A and 80B are opened. ing. The buffer tank air release valves 53A and 53B, the ink supply valves 56A and 56B, the buffer tank liquid level adjusting valves 62A and 62B, the pressurized pressure adjusting valve 76, and the negative pressure pressure adjusting valve 85 are closed. Further, the liquid level heights of the pressurized tanks 31A and 31B, the negative pressure tanks 33A and 33B, and the buffer tanks 51A and 51B are set to the reference heights.

When the start of ink removal is instructed, the control unit 9 opens the pressurizing pressure adjusting valve 76 and closes the negative pressure sealing valves 80A and 80B. As a result, the pressure tank 31A of the upper printing unit 4 and the pressure tank 31B of the lower printing unit 5 are open to the atmosphere, and the negative pressure tank 33A of the upper printing unit 4 and the negative pressure tank 33B of the lower printing unit 5 are opened. It becomes a sealed state. The buffer tanks 51A and 51B are in a sealed state.

Next, the control unit 9 opens the ink supply valves 56A and 56B and the buffer tank liquid level adjusting valves 62A and 62B.

As a result, the ink is discharged from the upper printing unit 4 and the lower printing unit 5 at the same time. Then, as shown in FIG. 9, the ink is discharged from the upper printing unit 4 to the ink tank 58 and the ink is discharged from the lower printing unit 5 to the ink tank 58 in parallel.

That is, in the upper printing unit 4, the ink tank from the pressure tank 31A via the inkjet head 21A, the negative pressure tank 33A, and the independent path 93A due to the head difference between the pressure tank 31A and the ink tank 58. Ink flows to 58. Here, in the independent path 93A, ink flows through the detour pipe 63A.

Further, in the lower printing unit 5, due to the head difference between the pressure tank 31B and the ink tank 58, the ink is ink from the pressure tank 31B via the inkjet head 21B, the negative pressure tank 33B, and the independent path 93B. Ink flows into the tank 58. Here, in the independent path 93B, ink flows through the detour pipe 63B.

When the above-mentioned upper discharge time elapses after the start of ink discharge from the upper printing unit 4 and the lower printing unit 5, the control unit 9 closes the ink supply valve 56A and the buffer tank liquid level adjusting valve 62A. As a result, the ink is discharged from the upper printing unit 4.

Further, when the above-mentioned lower discharge time elapses after the start of ink discharge from the upper printing unit 4 and the lower printing unit 5, the control unit 9 closes the ink supply valve 56B and the buffer tank liquid level adjusting valve 62B. .. As a result, the ink is discharged from the lower printing unit 5.

Next, the control unit 9 closes the pressurizing pressure adjusting valve 76 and opens the negative pressure sealing valves 80A and 80B. As a result, a series of ink removal operations is completed.

As is clear from the above description, in the second embodiment, the pressurizing pressure adjusting valve 76 is opened, the negative pressure sealing valve 80A is closed, and the ink supply valve 56A and the buffer tank liquid level adjusting valve 62A are opened. Then, the operation of discharging the ink from the upper printing unit 4 to the ink tank 58 via the independent path 93A is executed by utilizing the water head difference between the upper printing unit 4 and the ink tank 58. Further, by opening the pressurizing pressure adjusting valve 76, closing the negative pressure sealing valve 80B, and opening the ink supply valve 56B and the buffer tank liquid level adjusting valve 62B, the lower printing unit 5 and the ink tank 58 are connected. An operation of ejecting ink from the lower printing unit 5 to the ink tank 58 via the independent path 93B is executed by utilizing the water head difference between the two. The pressure generation unit 7 and the ink supply unit 91 correspond to the discharge operation unit.

As described above, in the second embodiment, the independent routes 93A and 93B are independent routes. Then, the pressure generating unit 7 and the ink supply unit 91 simultaneously perform an operation of discharging ink from the upper printing unit 4 to the ink tank 58 and an operation of discharging ink from the lower printing unit 5 to the ink tank 58. Let it run.

Since the independent paths 93A and 93B are independent paths, even if the ink is discharged from the upper printing unit 4 to the ink tank 58 and the ink is discharged from the lower printing unit 5 to the ink tank 58 in parallel. In the case of the configuration of the ink supply unit 6 of the first embodiment described above, the ink is discharged from the upper printing unit 4 to the ink tank 58 and the ink is discharged from the lower printing unit 5 to the ink tank 58 in parallel. Such movement of ink from the upper printing unit 4 to the lower printing unit 5 does not occur.

That is, in the second embodiment, the ink is discharged from the upper printing unit 4 to the ink tank 58 and the ink is discharged from the lower printing unit 5 to the ink tank 58 in parallel, and the ink is discharged from the upper printing unit 4 to the lower side. The movement of ink to the side printing unit 5 is suppressed. Therefore, in the second embodiment, in the configuration of the ink supply unit 6 of the first embodiment described above, the ink is discharged from the upper printing unit 4 and the ink is discharged from the lower printing unit 5 in parallel. Compared with, the time required for ink removal can be shortened.

Further, since the movement of ink from the upper printing unit 4 to the lower printing unit 5 is suppressed, the overflow of ink from the pressure tank 31B of the lower printing unit 5 is suppressed.

[Third Embodiment]
Next, a third embodiment in which a part of the first embodiment described above is modified will be described.

FIG. 10 is a schematic configuration diagram of an upper printing unit, a lower printing unit, an ink supply unit, and a pressure generating unit in the third embodiment.

As shown in FIG. 10, also in the third embodiment, the upper printing unit 4, the lower printing unit 5, and the ink supply unit 6 have the same configurations as those in the first embodiment described above.

In the third embodiment, the inkjet heads 21A and 21B correspond to the first inkjet head and the second inkjet head, respectively. Further, the pressurized tank 31A and the negative pressure tank 33A correspond to the first upstream tank and the first downstream tank, respectively. Further, the pressurized tank 31B and the negative pressure tank 33B correspond to the second upstream tank and the second downstream tank, respectively.

The pressure generating unit 7A in the third embodiment includes the upper pressure tank air release valve 96, the upper pressure tank air release pipe 97, and the air filter 98 with respect to the pressure generation unit 7 of the first embodiment described above. Is added.

The upper pressure tank air release valve 96, the upper pressure tank air release pipe 97, and the air filter 98 are provided corresponding to each upper printing unit 4. Note that FIG. 10 shows only the upper pressure tank air release valve 96, the upper pressure tank air release pipe 97, and the air filter 98 corresponding to one upper printing unit 4.

The upper pressure tank air release valve 96 opens and closes the air flow path in the upper pressure tank air release pipe 97 in order to switch the pressure tank 31A of the upper printing unit 4 between the closed state and the atmosphere open state. do.

The upper pressure tank air release pipe 97 forms an air flow path for opening the pressure tank 31A of the upper printing unit 4 to the atmosphere. One end of the upper pressure tank open-air pipe 97 is connected to the air layer of the pressure tank 31A, and the other end (open end to the atmosphere) is connected to the atmosphere through an air filter 98.

The air filter 98 prevents dust and the like in the air from entering the upper pressure tank air opening pipe 97. The air filter 98 is installed at the open end of the upper pressurized tank open pipe 97 to the atmosphere.

Next, the operation of removing ink in the third embodiment will be described.

In the third embodiment, the upper pressure tank air release valve 96 is closed in the standby state before the start of ink removal. Other than this, it is the same as that of the first embodiment, and the negative pressure communication valve 88, the pressure sealing valves 72A and 72B, and the negative pressure sealing valves 80A and 80B are open. The buffer tank air release valves 53A and 53B, the ink supply valves 56A and 56B, the buffer tank liquid level adjusting valves 62A and 62B, the pressurized pressure adjusting valve 76, and the negative pressure pressure adjusting valve 85 are closed. Further, the liquid level heights of the pressurized tanks 31A and 31B, the negative pressure tanks 33A and 33B, and the buffer tanks 51A and 51B are set to the reference heights.

When the start of ink removal is instructed, the control unit 9 closes the pressure sealing valve 72A and the negative pressure sealing valves 80A and 80B.

Next, the control unit 9 controls the pressure air pump 74 and the pressure pressure adjusting valve 76 of the pressure generation unit 7A, and puts the upper printing unit 4 and the lower printing unit 5 in the pressure tank 31B of the lower printing unit 5. Apply pressure equivalent to the head difference between and. Here, since the pressure sealing valve 72A and the negative pressure sealing valves 80A and 80B are closed and the pressure sealing valve 72B is opened, the pressure tank 31A, by the pressure air pump 74 and the pressure pressure adjusting valve 76, Pressure can be generated only in the pressure tank 31B of the 31B and the negative pressure tanks 33A and 33B. The water head difference between the upper printing unit 4 and the lower printing unit 5 corresponds to the height difference between the reference height of the liquid level of the pressure tank 31A and the reference height of the liquid level of the pressure tank 31B.

Next, the control unit 9 opens the upper pressure tank air release valve 96. As a result, the pressure tank 31A is opened to the atmosphere. The pressure tank 31B is in a state where a pressure corresponding to the head difference between the upper printing unit 4 and the lower printing unit 5 is applied by the pressure generating unit 7A, and the negative pressure tanks 33A and 33B are in a closed state. Then, the control unit 9 opens the ink supply valves 56A and 56B and the buffer tank liquid level adjusting valves 62A and 62B.

As a result, the ink is discharged from the upper printing unit 4 and the lower printing unit 5 at the same time. Then, as shown in FIG. 11, the ink is discharged from the upper printing unit 4 to the ink tank 58 and the ink is discharged from the lower printing unit 5 to the ink tank 58 in parallel.

That is, in the upper printing unit 4, due to the head difference between the pressure tank 31A and the ink tank 58, the ink tank from the pressure tank 31A passes through the inkjet head 21A, the negative pressure tank 33A, and the discharge path 65A. Ink flows to 58. Here, the ink flows through the detour pipe 63A in the branch path 64A of the discharge path 65A.

Further, in the lower printing unit 5, the water head difference between the pressure tank 31B and the ink tank 58 and the pressure applied to the pressure tank 31B by the pressure generation unit 7A described above cause the ink jet from the pressure tank 31B. Ink flows to the ink tank 58 via the head 21B, the negative pressure tank 33B, and the discharge path 65B. Here, the ink flows through the detour pipe 63B in the branch path 64B of the discharge path 65B.

When ink is discharged from the pressurizing tank 31B, the ink circulation tube 39B, the ink bath 35B, the inflow tube 37B, and the inkjet head 21B in the lower printing unit 5, the pressurizing tank 31B is opened to the atmosphere via the nozzle of the inkjet head 21B. It becomes a state. Therefore, when the ink is discharged from the pressure tank 31B, the ink circulation pipe 39B, the ink bath 35B, the inflow pipe 37B, and the inkjet head 21B, the pressure application to the pressure tank 31B by the pressure generating unit 7A is completed. .. Until then, the pressure applied to the pressurizing tank 31B by the pressure generating unit 7A described above is continued. After the ink is discharged from the inkjet head 21B, the ink is discharged from the lower printing unit 5 to the ink tank 58 due to the head difference between the lower printing unit 5 and the ink tank 58.

When the above-mentioned upper discharge time elapses after the start of ink discharge from the upper printing unit 4 and the lower printing unit 5, the control unit 9 sets the upper pressure tank air release valve 96, the ink supply valve 56A, and the buffer tank liquid. The surface adjusting valve 62A is closed. As a result, the ink is discharged from the upper printing unit 4.

Further, when the lower discharge time in the third embodiment elapses after the ink discharge from the upper printing unit 4 and the lower printing unit 5 starts, the control unit 9 sends the ink supply valve 56B and the buffer tank liquid level adjusting valve 62B. To close. As a result, the ink is discharged from the lower printing unit 5. Here, the lower ejection time in the third embodiment is preset as the time required to eject ink from the inkjet head 21B and the ink circulation mechanism 22B of the lower printing unit 5 in the ink removing operation in the third embodiment. It is the time that was done. The lower discharge time is preset based on experiments and the like.

Next, the control unit 9 closes the pressure pressure adjusting valve 76 and opens the pressure sealing valve 72A and the negative pressure sealing valves 80A and 80B. As a result, a series of ink removal operations is completed.

As is clear from the above description, in the third embodiment, the upper pressure tank air release valve 96 is opened, the negative pressure sealing valve 80A is closed, and the ink supply valve 56A and the buffer tank liquid level adjusting valve 62A are opened. By doing so, the operation of discharging the ink from the upper printing unit 4 to the ink tank 58 via the discharge path 65A is executed by utilizing the head difference between the upper printing unit 4 and the ink tank 58. Further, the pressure air pump 74 and the pressure pressure adjusting valve 76 apply a pressure equivalent to the water head difference between the upper printing unit 4 and the lower printing unit 5 to the pressure tank 31B, and close the negative pressure sealing valve 80B. By opening the ink supply valve 56B and the buffer tank liquid level adjusting valve 62B, an operation for discharging ink from the lower printing unit 5 to the ink tank 58 via the discharge path 65B is executed. In this operation, in order to discharge ink from the lower printing unit 5 to the ink tank 58, the water head difference between the lower printing unit 5 and the ink tank 58 is used, and the pressurized air pump 74 and the pressurized pressure are adjusted. The pressure applied to the pressurizing tank 31B by the valve 76 is used. The pressure generation unit 7A and the ink supply unit 6 correspond to the discharge operation unit.

As described above, in the third embodiment, the pressure generating unit 7A and the ink supply unit 6 operate to discharge ink from the upper printing unit 4 to the ink tank 58, and from the lower printing unit 5 to the ink tank 58. The operation of ejecting ink is executed in parallel. Then, in the operation of discharging the ink from the lower printing unit 5 to the ink tank 58, the pressure generating unit 7A applies a pressure corresponding to the head difference between the upper printing unit 4 and the lower printing unit 5 to the pressure tank 31B. Give.

By applying the above pressure to the pressure tank 31B, the flow rate of the ink discharged from the upper printing unit 4 and the ink discharged from the lower printing unit 5 until the ink is discharged from the inkjet heads 21A and 21B. Can be equal to the flow rate of. Therefore, while discharging the ink from the upper printing unit 4 and discharging the ink from the lower printing unit 5 at the same time and performing them in parallel, the ink moves from the upper printing unit 4 to the lower printing unit 5. The amount can be reduced. Therefore, since the increase in the amount of ink that needs to be discharged from the lower printing unit 5 can be reduced, the time required for ink removal can be shortened.

Further, since the amount of ink transferred from the upper printing unit 4 to the lower printing unit 5 can be reduced, the overflow of ink from the pressure tank 31B of the lower printing unit 5 can be suppressed.

[Other Embodiments]
As mentioned above, the present invention has been described by the first to third embodiments, but the statements and drawings that form part of this disclosure should not be understood to limit the invention. This disclosure will reveal to those skilled in the art various alternative embodiments, examples and operational techniques.

In the first embodiment described above, in the ink removing operation, the ink is discharged from the upper printing unit 4 and then the ink is discharged from the lower printing unit 5. However, the order of discharging the ink from the lower printing unit 5 and discharging the ink from the upper printing unit 4 may be changed. It suffices that the ink discharge from the upper printing unit 4 and the ink discharge from the lower printing unit 5 are time-separated.

Further, in the second embodiment described above, the ink discharge from the upper printing unit 4 and the ink discharge from the lower printing unit 5 may be time-separated. Even in this case, the movement of ink from the upper printing unit 4 to the lower printing unit 5 is suppressed. Therefore, in the configuration of the ink supply unit 6 of the first embodiment, the ink is discharged from the upper printing unit 4 and the lower printing unit is discharged. Compared with the case where the ink is discharged from No. 5 in parallel, the time required for ink removal can be shortened.

Further, in the third embodiment described above, in the ink removing operation, the upper printing unit 4 puts the pressure tank 31A in the open state to the atmosphere and the negative pressure tank 33A in the closed state. As a result, ink is allowed to flow from the pressure tank 31A to the ink tank 58 via the inkjet head 21A and the negative pressure tank 33A.

However, the pressure tank 31A may be sealed, the negative pressure tank 33A may be open to the atmosphere, and ink may flow from the negative pressure tank 33A to the ink tank 58 via the inkjet head 21A and the pressure tank 31A. .. In this case, as the ink circulation pump 42A, a pump without a check valve may be used. As a result, the ink flowing out from the pressure tank 31A flows from the ink circulation pipe 41A to the branch path 64A.

That is, in the upper printing unit 4, one tank of the pressure tank 31A and the negative pressure tank 33A is in an open state to the atmosphere, the other tank is in a closed state, and the inkjet head 21A is in a closed state from the one tank in an open state to the atmosphere. Ink may flow to the ink tank 58 via the other tank.

Further, in the third embodiment described above, in the ink removing operation, the lower printing unit 5 applies a pressure corresponding to the head difference between the upper printing unit 4 and the lower printing unit 5 to the pressure tank 31B. , The negative pressure tank 33B was sealed. As a result, ink is allowed to flow from the pressure tank 31B to the ink tank 58 via the inkjet head 21B and the negative pressure tank 33B.

However, the pressure tank 31B is sealed, and a pressure corresponding to the head difference between the upper printing unit 4 and the lower printing unit 5 is applied to the negative pressure tank 33 to apply the ink from the negative pressure tank 33B to the ink jet head 21B. Ink may flow to the ink tank 58 via the pressure tank 31B. In this case, as the ink circulation pump 42B, a pump without a check valve may be used. As a result, the ink flowing out from the pressure tank 31B flows from the ink circulation pipe 41B to the branch path 64B. Here, even in this case, the head difference between the upper printing unit 4 and the lower printing unit 5 is the height difference between the reference height of the liquid level of the pressure tank 31A and the reference height of the liquid level of the pressure tank 31B. Corresponds to. This is the same as the height difference between the reference height of the liquid level of the negative pressure tank 33A and the reference height of the liquid level of the negative pressure tank 33B.

That is, in the lower printing unit 5, pressure corresponding to the water head difference between the upper printing unit 4 and the lower printing unit 5 is applied to one of the pressure tank 31B and the negative pressure tank 33B, and the other tank is pressed. In the closed state, ink may flow from one tank to which the pressure is applied to the ink tank 58 via the inkjet head 21B and the other tank in the closed state.

Further, in the third embodiment described above, ink is discharged from the pressure tank 31B, the ink circulation pipe 39B, the ink bath 35B, the inflow pipe 37B, and the inkjet head 21B, and the pressure generation unit 7A applies pressure to the pressure tank 31B. The negative pressure tank 33B may be subjected to a pressure corresponding to the water head difference between the upper printing unit 4 and the lower printing unit 5. Even in this case, the head difference between the upper printing unit 4 and the lower printing unit 5 corresponds to the height difference between the reference height of the liquid level of the pressure tank 31A and the reference height of the liquid level of the pressure tank 31B. .. This is the same as the height difference between the reference height of the liquid level of the negative pressure tank 33A and the reference height of the liquid level of the negative pressure tank 33B.

As a result, even after the ink is discharged from the inkjet heads 21A and 21B, the flow rate of the ink discharged from the upper printing unit 4 and the flow rate of the ink discharged from the lower printing unit 5 can be made equal. As a result, the amount of ink transferred from the upper printing unit 4 to the lower printing unit 5 can be further reduced.

Further, in the ink removing operation in the first to third embodiments described above, the ink may be removed from the buffer tanks 51A and 51B as well.

Further, in the first to third embodiments described above, the two tanks of the pressure tank 31 and the negative pressure tank 33 are connected to the inkjet head 21, and the pressure tank 31, the inkjet head 21 and the negative pressure tank 33 are connected to each other. The printing apparatus 1 that circulates ink between them has been described. However, the present invention is also applicable to a configuration in which ink is circulated between one tank connected to the inkjet head 21 and storing ink ejected from the inkjet head 21 and the inkjet head 21.

Further, in the first to third embodiments described above, the inkjet printing apparatus 1 has been described, but other printing methods using ink may also be used.

As described above, it goes without saying that the present invention includes various embodiments not described here. Therefore, the technical scope of the present invention is defined only by the matters specifying the invention relating to the reasonable claims from the above description.

[Additional Notes]
The present application discloses the following inventions.

(Appendix 1)
The first printing unit, which stores ink and prints using the stored ink,
A second printing unit, which is arranged at a position lower than the first printing unit, stores ink, and prints using the stored ink.
A discharge ink storage unit located at a position lower than the second printing unit, and a discharge ink storage unit.
A first path connecting the first printing unit and the discharged ink storage unit, and
A second path connecting the second printing unit and the discharged ink storage unit, and
An operation of discharging ink from the first printing unit to the discharged ink storage unit via the first path by utilizing the water head difference between the first printing unit and the discharged ink storage unit, and the second operation. The operation of discharging ink from the second printing unit to the discharged ink storage unit via the second path by utilizing the water head difference between the printing unit and the discharged ink storage unit is temporally separated. A printing apparatus characterized in that it is provided with a discharge operation unit to be executed.

(Appendix 2)
The first route is
A common route connected to the discharged ink storage unit and
It has a first branch path connecting the first printing unit and the common path, and has a first branch path.
The second route is
With the common route
The printing apparatus according to Appendix 1, further comprising a second branch path connecting the second printing unit and the common path.

(Appendix 3)
The printing apparatus according to Appendix 1, wherein the first route and the second route are independent routes from each other.

(Appendix 4)
The first printing unit, which stores ink and prints using the stored ink,
A second printing unit, which is arranged at a position lower than the first printing unit, stores ink, and prints using the stored ink.
A discharge ink storage unit located at a position lower than the second printing unit, and a discharge ink storage unit.
A first path connecting the first printing unit and the discharged ink storage unit, and
A second route that connects the second printing unit and the discharged ink storage unit and is independent of the first route, and
An operation of discharging ink from the first printing unit to the discharged ink storage unit via the first path by utilizing the water head difference between the first printing unit and the discharged ink storage unit, and the second operation. Using the water head difference between the printing unit and the discharged ink storage unit, the operation of discharging ink from the second printing unit to the discharged ink storage unit via the second path is executed in parallel. A printing apparatus including a moving unit.

(Appendix 5)
The first printing unit, which stores ink and prints using the stored ink,
A second printing unit, which is arranged at a position lower than the first printing unit, stores ink, and prints using the stored ink.
A discharge ink storage unit located at a position lower than the second printing unit, and a discharge ink storage unit.
A common route connected to the discharged ink storage unit and
A first branch route connecting the first printing unit and the common route,
A second branch route connecting the second printing unit and the common route,
An operation of discharging ink from the first printing unit to the discharged ink storage unit via the first branch path and the common route by utilizing the water head difference between the first printing unit and the discharged ink storage unit. Ink is discharged from the second printing unit to the discharged ink storage unit via the second branch path and the common route by utilizing the water head difference between the second printing unit and the discharged ink storage unit. Equipped with a discharge operation unit that executes the operation in parallel with the operation
In the operation of discharging ink from the second printing unit to the discharged ink storage unit, the discharge operation unit applies a pressure corresponding to the head difference between the first printing unit and the second printing unit to the second printing. A printing device characterized in that it is applied to a part.

(Appendix 6)
The first printing unit is connected to the first inkjet head, a first upstream tank connected to the first inkjet head and stores ink to be supplied to the first inkjet head, and the first inkjet head. It has a first downstream tank that receives the ink returned from the inkjet head,
The second printing unit is connected to the second inkjet head, a second upstream tank connected to the second inkjet head and stores ink to be supplied to the second inkjet head, and the second inkjet head. It has a second downstream tank that receives the ink returned from the inkjet head,
The discharge operation unit is
As an operation of discharging ink from the first printing unit to the discharged ink storage unit, one tank of the first upstream tank and the first downstream tank is opened to the atmosphere, and the other tank is opened to the atmosphere. An operation of flowing ink from one of the tanks in the state to the discharged ink storage unit via the first inkjet head and the other tank in the sealed state is executed.
As an operation of discharging ink from the second printing unit to the discharged ink storage unit, between the first printing unit and the second printing unit in one of the second upstream tank and the second downstream tank. A pressure equivalent to the head difference is applied, the other tank is sealed, and ink is supplied from one of the pressure-applied tanks to the discharged ink storage unit via the second inkjet head and the other tank in the sealed state. The printing apparatus according to Appendix 4, wherein the flow operation is executed.

1 Printing device 2 Web roll support shaft 3 Conveying unit 4, 4A to 4E Upper printing unit 5, 5A to 5E Lower printing unit 6, 6A to 6E, 91 Ink supply unit 7, 7A Pressure generating unit 8 Winding shaft 9 Control Parts 21, 21A, 21B Inkjet head 22A, 22B Ink circulation mechanism 31, 31A, 31B Pressurized tank 32A, 32B Pressurized tank liquid level sensor 33, 33A, 33B Negative pressure tank 34A, 34B Negative pressure tank liquid level sensor 35A, 36A, 35B, 36B Ink bath 37A, 37B Inflow pipe 38A, 38B Outflow pipe 39A-41A, 39B-41B Ink circulation pipe 42, 42A, 42B Ink circulation pump 51, 51A, 51B Buffer tank 52, 52A, 52B Buffer tank liquid Surface sensor 53A, 53B Buffer tank Open to the atmosphere valve 54, 54A, 54B Buffer tank Open to the atmosphere 55, 55A, 55B, 84, 98 Air filter 56A, 56B Ink supply valve 57A, 57B Connection tube 58 Ink tank 59A, 59B Ink supply Pump 60 Common ink supply pipe 61A, 61B Individual ink supply pipe 62A, 62B Buffer tank Liquid level adjustment valve 63A, 63B Bypass pipe 64A, 64B Branch path 65A, 65B Discharge path 71 Pressurized common air chamber 72A, 72B Pressurized closed valve 73A, 73B Pressurized communication pipe 74 Pressurized air pump 75 Pressurized pressure generating pipe 76 Pressurized pressure adjusting valve 77 Pressurized pressure adjusting pipe 78 Pressurized pressure sensor 79 Negative pressure common air chamber 80A, 80B Negative pressure closed valve 81A, 81B Negative pressure communication pipe 82 Negative pressure air pump 83 Atmospheric communication pipe 85 Negative pressure pressure adjustment valve 86 Negative pressure pressure adjustment pipe 87 Negative pressure pressure sensor 88 Negative pressure communication valve 89 Negative pressure communication pipe 92A, 92B Ink supply pipe 93A, 93B Independent path 96 Upper pressure tank air release valve 97 Upper pressure tank air release pipe

Claims (6)

The first printing unit, which stores ink and prints using the stored ink,
A second printing unit, which is arranged at a position lower than the first printing unit, stores ink, and prints using the stored ink.
A discharge ink storage unit located at a position lower than the second printing unit, and a discharge ink storage unit.
A first path connecting the first printing unit and the discharged ink storage unit, and
A second path connecting the second printing unit and the discharged ink storage unit, and
An operation of discharging ink from the first printing unit to the discharged ink storage unit via the first path by utilizing the water head difference between the first printing unit and the discharged ink storage unit, and the second operation. The operation of discharging ink from the second printing unit to the discharged ink storage unit via the second path by utilizing the water head difference between the printing unit and the discharged ink storage unit is temporally separated. A printing apparatus characterized in that it is provided with a discharge operation unit to be executed. The first route is
A common route connected to the discharged ink storage unit and
It has a first branch path connecting the first printing unit and the common path, and has a first branch path.
The second route is
With the common route
The printing apparatus according to claim 1, further comprising a second branch route connecting the second printing unit and the common route. The printing apparatus according to claim 1, wherein the first route and the second route are independent routes from each other. The first printing unit, which stores ink and prints using the stored ink,
A second printing unit, which is arranged at a position lower than the first printing unit, stores ink, and prints using the stored ink.
A discharge ink storage unit located at a position lower than the second printing unit, and a discharge ink storage unit.
A first path connecting the first printing unit and the discharged ink storage unit, and
A second route that connects the second printing unit and the discharged ink storage unit and is independent of the first route, and
An operation of discharging ink from the first printing unit to the discharged ink storage unit via the first path by utilizing the water head difference between the first printing unit and the discharged ink storage unit, and the second operation. Using the water head difference between the printing unit and the discharged ink storage unit, the operation of discharging ink from the second printing unit to the discharged ink storage unit via the second path is executed in parallel. A printing apparatus including a moving unit. The first printing unit, which stores ink and prints using the stored ink,
A second printing unit, which is arranged at a position lower than the first printing unit, stores ink, and prints using the stored ink.
A discharge ink storage unit located at a position lower than the second printing unit, and a discharge ink storage unit.
A common route connected to the discharged ink storage unit and
A first branch route connecting the first printing unit and the common route,
A second branch route connecting the second printing unit and the common route,
An operation of discharging ink from the first printing unit to the discharged ink storage unit via the first branch path and the common route by utilizing the water head difference between the first printing unit and the discharged ink storage unit. Ink is discharged from the second printing unit to the discharged ink storage unit via the second branch path and the common route by utilizing the water head difference between the second printing unit and the discharged ink storage unit. Equipped with a discharge operation unit that executes the operation in parallel with the operation
In the operation of discharging ink from the second printing unit to the discharged ink storage unit, the discharge operation unit applies a pressure corresponding to the head difference between the first printing unit and the second printing unit to the second printing. A printing device characterized in that it is applied to a part. The first printing unit is connected to the first inkjet head, a first upstream tank connected to the first inkjet head and stores ink to be supplied to the first inkjet head, and the first inkjet head. It has a first downstream tank that receives the ink returned from the inkjet head,
The second printing unit is connected to the second inkjet head, a second upstream tank connected to the second inkjet head and stores ink to be supplied to the second inkjet head, and the second inkjet head. It has a second downstream tank that receives the ink returned from the inkjet head,
The discharge operation unit is
As an operation of discharging ink from the first printing unit to the discharged ink storage unit, one tank of the first upstream tank and the first downstream tank is opened to the atmosphere, and the other tank is opened to the atmosphere. An operation of flowing ink from one of the tanks in the state to the discharged ink storage unit via the first inkjet head and the other tank in the sealed state is executed.
As an operation of discharging ink from the second printing unit to the discharged ink storage unit, between the first printing unit and the second printing unit in one of the second upstream tank and the second downstream tank. A pressure equivalent to the head difference is applied, the other tank is sealed, and ink is supplied from one of the pressure-applied tanks to the discharged ink storage unit via the second inkjet head and the other tank in the sealed state. The printing apparatus according to claim 4, wherein the flow operation is performed.

Images