Inkjet printing equipment

Abstract

The present invention provides an inkjet printing device that can reduce ink leakage from nozzles and air intake while minimizing increased working time and wasted ink during the transportation of the device. [Solution] During transport of the inkjet printing apparatus, the head groups 17A to 17C are arranged such that the height difference between the highest head group 17 and the lowest head group 17 is smaller than during printing. The pressurized tanks 31 and negative pressure tanks 33 of the ink towers 4A to 4C are positioned below the head groups 17A to 17C, at a height within a predetermined range where the height difference is smaller than the height difference between the pressurized tanks 31 and negative pressure tanks 33 of the highest ink tower 4C and the lowest ink tower 4A during printing.

Description

Technical Field

[0001] The present invention relates to an inkjet printing apparatus.

Background Art

[0002] There is known an ink circulation type inkjet printing apparatus that circulates ink between an inkjet head and a tank for storing ink, and discharges ink from the inkjet head for printing.

[0003] Also, there is known an inkjet printing apparatus including a plurality of inkjet heads arranged along the vertical direction, each inkjet head discharging ink in the horizontal direction, and capable of printing on a vertical surface such as the side surface of a cardboard box.

[0004] Such an ink circulation type inkjet printing apparatus including a plurality of inkjet heads arranged along the vertical direction is configured such that the head difference between the inkjet head and the tank connected to the inkjet head is the same for all inkjet heads (see Patent Document 1). Thereby, the difference in nozzle pressure between the inkjet heads due to the head difference between the inkjet head and the tank is suppressed to be small, and the nozzle pressure of each inkjet head is kept within a range where stable discharge of ink is possible.

[0005] By the way, when transporting an inkjet printing apparatus, due to the influence of vibrations, impacts, tilting of the apparatus, etc. generated during transportation, the pressure inside the inkjet head may fluctuate, and the meniscus of the ink in the nozzle may be destroyed. When the destruction of the meniscus occurs, ink may flow out of the nozzle or air may be sucked in.

[0006] When an ink-circulating inkjet printing device equipped with multiple inkjet heads, as described above, is transported with the multiple inkjet heads arranged vertically, if the meniscus is damaged and ink leaks from the nozzles, there is a risk that the ink will flow down from the inkjet heads and contaminate the inkjet heads below. Furthermore, if the inkjet heads are capable of ejecting multiple colors of ink, there is a risk of ink mixing occurring in the inkjet heads below.

[0007] Therefore, during transport of the equipment, the nozzle surface of each inkjet head is positioned facing downwards, and the multiple inkjet heads are arranged horizontally.

[0008] However, changing the alignment direction of multiple inkjet heads in this way creates differences in the water head difference between each inkjet head and its tank. This increases the risk that, in at least some inkjet heads, the ink meniscus inside the nozzle may be damaged during transport of the device, leading to ink leakage from the nozzle or air being sucked in.

[0009] In response to this, measures have been taken to suppress ink leakage from the nozzle and air intake due to meniscus damage by using forceps to grip the tube that forms the path connecting the inkjet head and the tank.

[0010] However, if the tube is clamped, even if the clamp is released after transport, the tube may deform at the clamped point, increasing the flow resistance of the tube. This may lead to a decrease in the performance of the device during printing. For example, during printing, if the nozzle pressure falls outside the range where stable ink ejection is possible, the print quality may decrease, or the ink meniscus inside the nozzle may be destroyed, causing ink leakage or air intake from the nozzle.

[0011] Therefore, one method is to remove the ink from the inkjet heads and tanks before transporting the equipment, and then refill them with ink after transport. This method avoids the problems that occur when the tubes are handled with forceps, as described above. [Prior art documents] [Patent Documents]

[0012] [Patent Document 1] Japanese Patent Publication No. 2006-240022 [Overview of the project] [Problems that the invention aims to solve]

[0013] However, as mentioned above, removing ink from inkjet heads and tanks before transporting the equipment is a time-consuming process and results in a large waste of ink.

[0014] The present invention has been made in view of the above, and aims to provide an inkjet printing apparatus that can reduce ink leakage from nozzles and air intake while suppressing the increase in working time and wasted ink during the transportation of the apparatus. [Means for solving the problem]

[0015] To achieve the above objective, the inkjet printing apparatus of the present invention comprises a plurality of ejection units, each having nozzles for ejecting ink and positioned at different heights, for ejecting ink from the nozzles onto a printing medium for printing; and a plurality of storage units connected to each of the plurality of ejection units, for storing ink, and positioned at different heights corresponding to the height of each ejection unit when printing, below the respective ejection unit. The apparatus is characterized in that, during transport, the plurality of ejection units are positioned such that the height difference between the highest and lowest ejection units is smaller than that during printing, and the plurality of storage units are positioned below the plurality of ejection units, within a predetermined height range where the height difference is smaller than that between the highest and lowest storage units when printing. [Effects of the Invention]

[0016] According to the inkjet printing apparatus of the present invention, during the transportation of the apparatus, it is possible to reduce ink leakage from the nozzles and air intake while suppressing the increase in working time and wasted ink. [Brief explanation of the drawing]

[0017] [Figure 1] This is a block diagram showing the configuration of an inkjet printing apparatus according to an embodiment. [Figure 2] Figure 2 is a schematic diagram of the transport and printing sections of the inkjet printing apparatus shown in Figure 1. [Figure 3] Figure 1 is a schematic diagram of the printing section and ink tower of the inkjet printing apparatus shown. [Figure 4] Figure 1 is a schematic diagram of the ink tower configuration of the inkjet printing apparatus shown. [Figure 5] This is an explanatory diagram of the state of the printing unit and ink tower during printing. [Figure 6] This is an explanatory diagram illustrating the condition of the printing unit and ink tower during the transportation of an inkjet printing device. [Figure 7]It is a schematic configuration diagram of an ink supply unit of an inkjet printing apparatus shown in FIG. 1. [Figure 8] It is an explanatory diagram of the state of a printing unit and an ink tower during transportation of an inkjet printing apparatus when the ink tower remains arranged at the height position during printing.

Embodiments for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same or equivalent parts and components throughout the drawings are denoted by the same or equivalent reference numerals.

[0019] The embodiments shown below illustrate apparatuses and the like for embodying the technical idea of this invention. The technical idea of this invention does not specify the materials, shapes, structures, arrangements, etc. of each component part as follows. Various changes can be made to the technical idea of this invention within the scope of the claims.

[0020] FIG. 1 is a block diagram showing the configuration of an inkjet printing apparatus according to an embodiment of the present invention. FIG. 2 is a schematic configuration diagram of a conveyance unit and a printing unit of the inkjet printing apparatus shown in FIG. 1. FIG. 3 is a schematic configuration diagram of a printing unit and an ink tower of the inkjet printing apparatus shown in FIG. 1. FIG. 4 is a schematic configuration diagram of an ink tower of the inkjet printing apparatus shown in FIG. 1. FIG. 5 is an explanatory diagram of the state of a printing unit and an ink tower during printing. FIG. 6 is an explanatory diagram of the state of a printing unit and an ink tower during transportation of the inkjet printing apparatus. FIG. 7 is a schematic configuration diagram of an ink supply unit of the inkjet printing apparatus shown in FIG. 1. In the following description, the up-down, left-right, front-back directions indicated by the arrows in FIG. 2 are taken as the up-down, left-right, front-back directions. The up-down direction is the vertical direction, and the left-right direction and the front-back direction are perpendicular to each other and perpendicular to the up-down direction and parallel to the horizontal direction.

[0021] As shown in Figure 1, the inkjet printing apparatus 1 according to this embodiment comprises a transport unit 2, a printing unit 3, ink towers 4A to 4C, ink supply units 5A to 5D, a maintenance unit 6, and a control unit 7. In the following description, the alphabetical subscripts in the symbols such as ink towers 4A to 4C may be omitted and the units may be referred to collectively.

[0022] The transport unit 2 transports the printing medium 8. The printing medium 8 has a printable surface 8a on which printing is performed by the printing unit 3. The printable surface 8a is a surface perpendicular to the horizontal direction (vertical surface) when the printing medium 8 is placed on the transport unit 2 and transported. The printing medium 8 is, for example, a corrugated cardboard box.

[0023] The printing unit 3 prints on the print surface 8a of the printing medium 8. The printing unit 3 comprises head units 11A and 11B and a head holder 12.

[0024] The print head units 11A and 11B eject ink onto the print surface 8a of the printing medium 8 to perform printing. Each print head unit 11A and 11B ejects two colors of ink. For example, print head unit 11A ejects black and cyan ink, and print head unit 11B ejects magenta and yellow ink. The print head units 11A and 11B have the same configuration except for the colors of ink they eject.

[0025] The printing unit 3 can be manually rotated between the printing position shown by the solid line in Figure 5 and the standby position shown by the dashed line. Alternatively, the printing unit 3 may be configured to be rotatable by a motor or other driving force.

[0026] The printing position described above is the position of the printing unit 3 when printing onto the printing medium 8. When the printing unit 3 is positioned at the printing position, the nozzle surface 16a of the inkjet head 16, which will be described later, is a leftward-facing vertical plane.

[0027] Unless otherwise specified, the printing unit 3 is positioned at the printing location, and the vertical direction of the head units 11A and 11B is assumed to be the vertical direction of the head units 11A and 11B when the printing unit 3 is positioned at the printing location.

[0028] The aforementioned standby position is the position of the printing unit 3 when the inkjet printing device 1 is in a standby state and not operating. Furthermore, when the inkjet printing device 1 is being transported, the printing unit 3 is positioned in the standby position.

[0029] When the printing unit 3 is in the standby position, the nozzle surface 16a of the inkjet head 16 is a downward-facing horizontal plane. Also, when the printing unit 3 is in the standby position, the head groups 17A to 17C, described later, are positioned at the same height as the central head group 17B when the printing unit 3 is in the printing position. Specifically, when the printing unit 3 is in the standby position, the head groups 17A to 17C are positioned such that the height of the nozzle surface 16a of each inkjet head 16 is at the same height as the lower end of the central head group 17B when the printing unit 3 is in the printing position.

[0030] As shown in Figures 2 and 3, the head unit 11 includes a plurality of inkjet heads 16. In this embodiment, the head unit 11 includes six inkjet heads 16. In the head unit 11, the six inkjet heads 16 are each positioned at different heights. Specifically, in the head unit 11, the six inkjet heads 16 are arranged in a staggered pattern along the vertical direction. That is, in the head unit 11, the six inkjet heads 16 arranged along the vertical direction are positioned with their positions in the front-to-back direction alternately offset.

[0031] In this embodiment, the six inkjet heads 16 of the head unit 11 are divided into three head groups (corresponding to ejection sections) 17A to 17C, each containing two inkjet heads 16 and positioned at different heights, as shown in Figure 3. The lower head group 17A consists of the first and second inkjet heads 16 from the bottom. The middle head group 17B consists of the third and fourth inkjet heads 16 from the bottom. The upper head group 17A consists of the fifth and sixth inkjet heads 16 from the bottom.

[0032] The inkjet head 16 ejects two colors of ink. The inkjet head 16 has two rows of nozzles, each consisting of multiple nozzles (not shown) that eject ink, arranged linearly at a predetermined pitch along the vertical direction. The two rows of nozzles eject ink of different colors. The inkjet head 16 has a nozzle surface 16a (see Figure 4, etc.) through which each nozzle in the two rows of nozzles opens.

[0033] The nozzle surface 16a is the left side surface of the inkjet head 16 and is a vertical surface. During printing, the inkjet head 16 ejects ink horizontally from nozzles opening on the nozzle surface 16a to print on the printing medium 8.

[0034] The head holder 12 holds the inkjet heads 16 of the head units 11A and 11B.

[0035] Ink towers 4A to 4C supply ink to head units 11A and 11B. Ink tower 4A supplies ink to each inkjet head 16 of head group 17A in head units 11A and 11B. Ink tower 4B supplies ink to each inkjet head 16 of head group 17B in head units 11A and 11B. Ink tower 4C supplies ink to each inkjet head 16 of head group 17C in head units 11A and 11B.

[0036] Note that in Figure 3, only one of the head units 11A and 11B is shown, and the other head unit 11 is not shown.

[0037] The ink tower 4 comprises ink circulation units 21A to 21D, a pressure generation unit 22, four pressurized air paths 23 (see Figure 4), and four negative pressure air paths 24 (see Figure 4).

[0038] The ink circulation units 21A to 21D circulate the ink and supply it to the inkjet head 16. Each of the ink circulation units 21A to 21D supplies a different color of ink to the inkjet head 16 that ejects the ink of the color held by the respective ink circulation unit 21.

[0039] The ink circulation units 21A and 21B are connected to two inkjet heads 16 of the head group 17 in the head unit 11A that corresponds to the ink tower 4 on which the ink circulation units 21A and 21B are provided, and supply ink to those two inkjet heads 16. The ink circulation units 21C and 21D are connected to two inkjet heads 16 of the nozzle group 17 in the head unit 11B that corresponds to the ink tower 4 on which the ink circulation units 21C and 21D are provided, and supply ink to those two inkjet heads 16.

[0040] Specifically, the ink circulation units 21A and 21B of the ink tower 4A supply ink to the two inkjet heads 16 of the head group 17A in the head unit 11A. The ink circulation units 21C and 21D of the ink tower 4A supply ink to the two inkjet heads 16 of the head group 17A in the head unit 11B.

[0041] Furthermore, the ink circulation units 21A and 21B of the ink tower 4B supply ink to the two inkjet heads 16 of the head group 17B in the head unit 11A. The ink circulation units 21C and 21D of the ink tower 4B supply ink to the two inkjet heads 16 of the head group 17B in the head unit 11B.

[0042] Furthermore, the ink circulation units 21A and 21B of the ink tower 4C supply ink to the two inkjet heads 16 of the head group 17C in the head unit 11A. The ink circulation units 21C and 21D of the ink tower 4C supply ink to the two inkjet heads 16 of the head group 17C in the head unit 11B.

[0043] As shown in Figure 4, the ink circulation unit 21 comprises a pressurized tank 31, a pressurized tank liquid level sensor 32, a negative pressure tank 33, a negative pressure tank liquid level sensor 34, a pressurized ink path 35, a negative pressure ink path 36, a pump liquid delivery path 37, and an ink pump 38. The pressurized tank 31 and the negative pressure tank 33 constitute the storage unit. Here, Figure 4 shows two ink circulation units 21 (for two colors) among the ink circulation units 21A to 21D of the ink tower 4 that supply ink to the same head unit 11.

[0044] The pressurized tank 31 stores the ink supplied to the inkjet head 16. The pressurized tank 31 is subjected to positive pressure by the pressure generation unit 22 to supply ink to the inkjet head 16. The pressurized tank 31 is positioned lower than the lower of the two inkjet heads 16 connected to the ink circulation unit 21, which includes the pressurized tank 31. All of the pressurized tanks 31 in the ink circulation units 21A to 21D of one ink tower 4 are positioned at the same height.

[0045] The pressurized tank liquid level sensor 32 is used to detect whether the liquid level of the ink in the pressurized tank 31 has reached a reference height. The pressurized tank liquid level sensor 32 outputs an "ON" signal when the liquid level in the pressurized tank 31 is above the reference height, and outputs an "OFF" signal when it is below the reference height.

[0046] The negative pressure tank 33 receives and stores ink that is not consumed by the inkjet head 16. The negative pressure tank 33 also stores ink supplied from the ink supply unit 5. The negative pressure tank 33 is supplied with negative pressure by the pressure generation unit 22 to recover ink from the inkjet head 16. The negative pressure tank 33 is composed of a tank of the same shape as the pressurized tank 31 and is located at the same height as the pressurized tank 31.

[0047] The negative pressure tank liquid level sensor 34 is used to detect whether the liquid level of the ink in the negative pressure tank 33 has reached a reference height. The reference height in the negative pressure tank 33 is the same as the reference height in the pressurized tank 31. The negative pressure tank liquid level sensor 34 outputs an "on" signal when the liquid level in the negative pressure tank 33 is at or above the reference height, and outputs an "off" signal when it is below the reference height.

[0048] The pressurized ink path 35 connects the pressurized tank 31 to the two inkjet heads 16. Ink supplied from the pressurized tank 31 to the two inkjet heads 16 flows through the pressurized ink path 35.

[0049] The negative pressure ink path 36 connects the two inkjet heads 16 to the negative pressure tank 33. Ink that is not consumed by the two inkjet heads 16 and is recovered into the negative pressure tank 33 flows through the negative pressure ink path 36.

[0050] The pump delivery path 37 is the path through which ink flows when the ink pump 38 delivers ink from the negative pressure tank 33 to the pressurized tank 31. In the direction of ink circulation, the upstream end of the pump delivery path 37 is connected to the negative pressure tank 33, and the downstream end is connected to the pressurized tank 31.

[0051] The ink pump 38 delivers ink from the negative pressure tank 33 to the pressurized tank 31. The ink pump 38 is located in the middle of the pump delivery path 37.

[0052] The pressure generation unit 22 generates pressure for ink circulation in the pressurized tank 31 and the negative pressure tank 33 of the ink circulation unit 21. Specifically, the pressure generation unit 22 draws air from the negative pressure tank 33 via the negative pressure air path 24 and sends air to the pressurized tank 31 via the pressurized air path 23, thereby applying positive pressure to the pressurized tank 31 and negative pressure to the negative pressure tank 33. The pressure generation unit 22 is common to the ink circulation units 21A to 21D.

[0053] The pressure generating unit 22 is configured to allow each pressurized tank 31 and each negative pressure tank 33 to be switched between a sealed state (isolated from the atmosphere) and an open state (connected to the atmosphere).

[0054] The pressurized air path 23 connects the pressure generation unit 22 to the air layer above the ink level in the pressurized tank 31. One pressurized air path 23 is provided for each of the ink circulation units 21A to 21D.

[0055] The negative pressure air path 24 connects the pressure generation unit 22 to the air layer above the ink level in the negative pressure tank 33. One negative pressure air path 24 is provided for each of the ink circulation units 21A to 21D.

[0056] Here, ink towers 4A to 4C are positioned below the print head groups 17A to 17C that supply ink to them. Furthermore, during printing, ink towers 4A to 4C are positioned such that the height difference between them and the print head groups 17A to 17C that supply ink to them is equal for all of them. Therefore, ink towers 4A to 4C are positioned at different heights corresponding to the heights of the print head groups 17A to 17C. Of the ink towers 4A to 4C, ink tower 4A is positioned at the lowest position, and ink tower 4C is positioned at the highest position.

[0057] Specifically, the height differences Ha, Hb, and Hc shown in Figure 5 are all equal (Ha=Hb=Hc). This minimizes the difference in nozzle pressure between the inkjet heads 16 caused by the head difference between the inkjet head 16 and the pressurized tank 31 and the negative pressure tank 33, keeping the nozzle pressure of each inkjet head 16 within a range that allows for stable ink ejection. Here, the height difference Ha is the height difference between the lower end of the head group 17A and the reference liquid level in the pressurized tank 31 and the negative pressure tank 33 of the ink tower 4A. The height difference Hb is the height difference between the lower end of the head group 17B and the reference liquid level in the pressurized tank 31 and the negative pressure tank 33 of the ink tower 4B. The height difference Hc is the height difference between the lower end of the head group 17C and the reference liquid level in the pressurized tank 31 and the negative pressure tank 33 of the ink tower 4C.

[0058] Note that Figure 5 shows only the pressurized tank 31 and negative pressure tank 33 of one ink circulation unit 21 in each of the ink towers 4A to 4C. The same applies to Figures 6 and 8.

[0059] Ink towers 4A to 4C are all positioned at the same height during transport of the inkjet printing device 1. In this embodiment, during transport of the inkjet printing device 1, ink towers 4A to 4C are all positioned at the height of ink tower 4B during printing, as shown in Figure 6.

[0060] Ink towers 4A and 4C can be manually moved between their respective printing heights and transport heights. Alternatively, ink towers 4A and 4C may be configured to be movable by a motor or other driving force.

[0061] As mentioned above, when transporting the inkjet printing apparatus 1, the printing unit 3 is positioned in a standby position, as shown in Figure 6. When the printing unit 3 is in the standby position, each inkjet head 16 is positioned such that the height of the nozzle surface 16a is at the same height as the lower end of the central head group 17B when the printing unit 3 is in the printing position.

[0062] Therefore, during transport of the inkjet printing apparatus 1, the height difference between the nozzle surface 16a of the inkjet head 16 and the reference liquid level in the pressurized tank 31 and negative pressure tank 33 of the ink towers 4A to 4C is Hb (=Ha=Hc). In other words, the height difference between the nozzle surface 16a of the inkjet head 16 and the reference liquid level in the pressurized tank 31 and negative pressure tank 33 of the ink towers 4A to 4C during transport is the same as the height difference between the lower end of each head group 17 and the reference liquid level in the pressurized tank 31 and negative pressure tank 33 of the corresponding ink tower 4 during printing.

[0063] During transport of the inkjet printing apparatus 1, each pressurized tank 31 and each negative pressure tank 33 are left open to the atmosphere. Therefore, the nozzle pressure of the inkjet head 16 during transport is a value corresponding to the height difference (water head difference) between the nozzle surface 16a and the liquid level of the ink in the pressurized tank 31 and negative pressure tank 33.

[0064] In this embodiment, the height difference Hb (=Ha=Hc) during transport is set to a value within a range where meniscus damage is unlikely to occur even with vibrations during transport. That is, during transport, each pressurized tank 31 and each negative pressure tank 33 are positioned below the head groups 17A to 17C at a predetermined height range where meniscus damage is suppressed even with vibrations during transport. This predetermined range is a height difference smaller than the height difference between the pressurized tank 31 and negative pressure tank 33 of the ink tower 4C, which is at the highest position during printing, and the pressurized tank 31 and negative pressure tank 33 of the ink tower 4A, which is at the lowest position.

[0065] The ink supply units 5A to 5D each supply ink to the negative pressure tanks 33 of the ink circulation units 21A to 21D. In the inkjet printer 1, a common ink supply unit 5 is provided for each ink color in the ink towers 4A to 4C.

[0066] In other words, ink supply unit 5A supplies ink to the ink circulation unit 21A of ink towers 4A to 4C. Ink supply unit 5B supplies ink to the ink circulation unit 21B of ink towers 4A to 4C. Ink supply unit 5C supplies ink to the ink circulation unit 21C of ink towers 4A to 4C. Ink supply unit 5D supplies ink to the ink circulation unit 21D of ink towers 4A to 4C.

[0067] The ink supply unit 5 comprises an ink cartridge 41, an ink supply path 42, and ink supply valves 43A to 43C.

[0068] The ink cartridge 41 contains the ink used for printing by the inkjet head 16. The ink cartridge 41 is positioned higher than the negative pressure tank 33 of the ink tower 4C. The ink in the ink cartridge 41 is supplied to the negative pressure tank 33 of the ink circulation unit 21 via the ink supply path 42.

[0069] The ink supply path 42 connects the ink cartridge 41 to three negative pressure tanks 33, which are the destinations for the ink from the ink cartridge 41. Ink flows from the ink cartridge 41 to the negative pressure tanks 33 in the ink supply path 42. The ink supply path 42 comprises a main path 46 and branch paths 47A to 47C.

[0070] The main path 46 is the path through which ink flows from the ink cartridge 41 to the branch paths 47A to 47C. The upstream end of the main path 46 is connected to the ink cartridge 41, and the downstream end of the main path 46 is connected to the upstream end of branch path 47B and the upstream end of branch path 47C.

[0071] Branch routes 47A to 47C branch off from the main route 46 and are connected to the negative pressure tanks 33 of ink towers 4A to 4C, respectively. The upstream end of branch route 47A is connected to the middle of the main route 46, and the downstream end of branch route 47A is connected to the negative pressure tank 33 of ink tower 4A. The upstream end of branch route 47B is connected to the downstream end of the main route 46, and the downstream end of branch route 47B is connected to the negative pressure tank 33 of ink tower 4B. The upstream end of branch route 47C is connected to the downstream end of the main route 46, and the downstream end of branch route 47C is connected to the negative pressure tank 33 of ink tower 4C.

[0072] The ink supply valves 43A to 43C are located in the branch paths 47A to 47C, respectively, and open and close the ink flow paths within the branch paths 47A to 47C. When supplying ink to the negative pressure tank 33, the ink supply valve 43 is opened.

[0073] The maintenance unit 6 is responsible for maintaining the inkjet head 16. The maintenance unit 6 is movable between a deployed position, where it is positioned when performing maintenance on the inkjet head 16, and a retracted position, where it is moved away from the deployed position. The deployed position is the location of the maintenance unit 6 shown in Figure 6, which is directly below the printing unit 3 located in the standby position. The illustration of the maintenance unit 6 in the retracted position is omitted.

[0074] As shown in Figure 6, the maintenance unit 6 includes an ink receiving unit 51 and a wiper 52.

[0075] The ink receiving section 51 receives ink and other substances removed from the nozzle surface 16a by wiping with the wiper 52 during maintenance of the inkjet head 16.

[0076] The wiper 52 wipes the nozzle surface 16a of the inkjet head 16 to remove ink and other substances from the nozzle surface 16a. The maintenance unit 6 is provided with two wipers 52 for each of the head units 11A and 11B: one for wiping the front three inkjet heads 16 of the six inkjet heads 16 arranged in a staggered pattern, and another for wiping the rear three inkjet heads 16. In other words, the maintenance unit 6 is provided with four wipers 52.

[0077] The control unit 7 controls the operation of each part of the inkjet printing device 1. The control unit 7 is composed of a CPU, RAM, ROM, hard disk, etc.

[0078] Next, the operation of the inkjet printing device 1 will be described.

[0079] When a print job is input, the control unit 7 starts ink circulation in the ink circulation sections 21A to 21D of the ink towers 4A to 4C. Specifically, the control unit 7 uses the pressure generation section 22 of the ink towers 4A to 4C to generate the set pressures for ink circulation in the pressurized tank 31 and the negative pressure tank 33. As a result, ink circulation in the ink circulation sections 21A to 21D begins, and ink flows from the pressurized tank 31 through the inkjet head 16 to the negative pressure tank 33.

[0080] When ink circulation begins, the control unit 7 starts executing the print job. Specifically, the control unit 7 controls the transport unit 2 to transport the print medium 8 and to eject ink from each inkjet head 16 of the head units 11A and 11B to print an image onto the print medium 8.

[0081] During the execution of a print job, ink is supplied from the pressurized tank 31 to the inkjet head 16, and any ink not consumed by the inkjet head 16 is recovered in the negative pressure tank 33. When the pressurized tank liquid level sensor 32 is off and the negative pressure tank liquid level sensor 34 is on, the control unit 7 drives the ink pump 38. This causes ink to be sent from the negative pressure tank 33 to the pressurized tank 31. When the pressurized tank liquid level sensor 32 is on, the control unit 7 stops the ink pump 38. Furthermore, when both the pressurized tank liquid level sensor 32 and the negative pressure tank liquid level sensor 34 are off, the control unit 7 controls the ink replenishment unit 5 to replenish ink to the negative pressure tank 33. In this way, ink is circulated and printing is performed.

[0082] Once printing based on the print job is complete, the control unit 7 controls the pressure generation unit 22 to terminate ink circulation in the ink circulation units 21A to 21D. This completes the series of operations.

[0083] Next, we will describe the condition of the inkjet printing device 1 during transport.

[0084] When transporting the inkjet printing device 1, the printing unit 3 is positioned in a standby position. The maintenance unit 6 is positioned in a deployed position, and the ink receiving unit 51 is positioned directly below each inkjet head 16 with its nozzle surface 16a facing downwards.

[0085] Then, ink towers 4A and 4C are moved to the same height as ink tower 4B. As a result, as shown in Figure 6, the pressurized tanks 31 and negative pressure tanks 33 of ink towers 4A to 4C are all positioned at the same height as the pressurized tanks 31 and negative pressure tanks 33 of ink tower 4B during printing. Consequently, as described above, the pressurized tanks 31 and negative pressure tanks 33 of each ink tower 4 are positioned at a predetermined height range that suppresses meniscus damage even if there is vibration during transport.

[0086] Here, unlike in this embodiment, we assume that the ink towers 4A to 4C remain positioned at their respective printing heights. In this case, as shown in Figure 8, the height difference between the nozzle surface 16a and the reference liquid level in the pressurized tank 31 and negative pressure tank 33 of ink tower 4A is Ha', which is greater than Hb (=Ha=Hc). Also, the height difference between the nozzle surface 16a and the reference liquid level in the pressurized tank 31 and negative pressure tank 33 of ink tower 4C is Hc', which is less than Hb.

[0087] As a result, differences in head difference occur between the inkjet head 16 of head group 17A and the pressurized tank 31 and negative pressure tank 33 of ink tower 4A, between the inkjet head 16 of head group 17B and the pressurized tank 31 and negative pressure tank 33 of ink tower 4B, and between the inkjet head 16 of head group 17C and the pressurized tank 31 and negative pressure tank 33 of ink tower 4C. This increases the risk that the ink meniscus in the nozzles of the inkjet heads 16 of head groups 17A and 17C will be damaged during transport of the inkjet printing device 1, leading to ink leakage from the nozzles or air intake.

[0088] In contrast, in this embodiment, as described above, the pressurized tanks 31 and negative pressure tanks 33 of the ink towers 4A to 4C are arranged at the same height within a predetermined range, thereby reducing ink leakage from the nozzles and air suction due to meniscus damage.

[0089] Furthermore, if meniscus damage occurs and ink leaks out, the leaked ink is received by the ink receiving section 51.

[0090] As explained above, in the inkjet printing apparatus 1, during transport, the printing unit 3 is positioned in a standby position, and the pressurized tanks 31 and negative pressure tanks 33 of the ink towers 4A to 4C are positioned at the same height within the aforementioned predetermined range below the head groups 17A to 17C. This allows the nozzle pressure of the inkjet heads 16 of the head groups 17A to 17C to be set to a value within a range where meniscus damage is less likely to occur even with vibrations during transport. As a result, ink leakage from the nozzles and air intake due to meniscus damage during transport of the inkjet printing apparatus 1 can be reduced.

[0091] Furthermore, there is no need to remove the ink from the ink towers 4A-4C and each inkjet head 16 before transporting the inkjet printer 1 and then refill them after transport. This reduces the amount of work time and wasted ink required when transporting the inkjet printer 1.

[0092] Therefore, the inkjet printing device 1 can reduce ink leakage from the nozzles and air intake during transportation, while suppressing the increase in working time and wasted ink.

[0093] Furthermore, in the inkjet printing apparatus 1, during transport, the pressurized tanks 31 and negative pressure tanks 33 of ink towers 4A to 4C are all positioned at the same height as the pressurized tanks 31 and negative pressure tanks 33 of ink tower 4B during printing. Therefore, during transport, for ink towers 4A to 4C, ink tower 4C, which is positioned higher than ink tower 4B, and ink tower 4A, which is positioned lower than ink tower 4B, only need to be moved to the same height as ink tower 4B. This reduces the space required to move the ink towers 4, thus preventing the apparatus from becoming larger.

[0094] Furthermore, the height positions of the print head groups 17A to 17C during transport are not limited to the height position of print head group 17B during printing. Also, the height positions of the pressurized tanks 31 and negative pressure tanks 33 of ink towers 4A to 4C during transport are not limited to the height positions of the pressurized tanks 31 and negative pressure tanks 33 of ink tower 4B during printing. In addition, the height positions of the pressurized tanks 31 and negative pressure tanks 33 of ink towers 4A to 4C during transport are not all limited to the same height position; they may be positioned within the aforementioned predetermined height range.

[0095] Furthermore, in the above-described embodiment, during printing, each inkjet head 16 constituting each head group 17 of the head unit 11 is positioned at a different height along the vertical direction (up and down direction), and during transport, the printing unit 3 is rotated so that each inkjet head 16 is positioned at the same height along the horizontal direction. However, this is not limited to this, and for example, each inkjet head constituting multiple head groups may be positioned along a direction inclined with respect to the vertical direction during printing, and inclined in a direction closer to the horizontal direction than during printing during transport. It is sufficient that multiple head groups are positioned at different heights during printing, and that during transport, the height difference between the highest and lowest head groups is smaller than during printing.

[0096] Furthermore, in the embodiment described above, the pressurized tank 31 and negative pressure tank 33 (storage unit) of one ink circulation unit 21 were shown to be connected to two inkjet heads 16 of one head group 17 (discharge unit). However, the embodiment is not limited to this, and it is sufficient if one storage unit is connected to each inkjet head of one head group (discharge unit) which includes at least one inkjet head.

[0097] The present invention is not limited to the embodiments described above, and the components can be modified and implemented in practice without departing from the spirit of the invention. Furthermore, various inventions can be formed by appropriately combining the multiple components disclosed in the embodiments. For example, some components may be deleted from all the components shown in the embodiments.

[0098] [Note] This application discloses the following invention:

[0099] (Note 1) Multiple ejection units, each positioned at a different height, each having a nozzle for ejecting ink, and for printing by ejecting ink from the nozzle onto a printing medium, The system comprises multiple storage units, each connected to a corresponding discharge unit, for storing ink, and positioned at different heights below the corresponding discharge unit during printing, corresponding to the height position of the respective discharge unit. During the transport of this device, The plurality of ejection units are arranged such that the height difference between the highest and lowest ejection units is smaller than during printing. The inkjet printing apparatus is characterized in that the plurality of storage units are arranged at a predetermined height range below the plurality of discharge units, where the height difference is smaller than the height difference between the highest storage unit and the lowest storage unit during printing.

[0100] (Note 2) The inkjet printing apparatus according to Appendix 1, characterized in that, during transport of the apparatus, the plurality of storage units are positioned at the height of the storage unit corresponding to the discharge unit that is at the central height position among the plurality of discharge units during printing. [Explanation of symbols]

[0101] 1. Inkjet printing device 2. Conveying section 3 Printing Department 4,4A~4C Ink Tower 5,5A~5D Ink Refill Section 6. Maintenance Department 7 Control Unit 11, 11A, 11B Head Unit 12 Head holders 16 inkjet heads 16a Nozzle surface 17, 17A~17C Head Group 21, 21A~21D Ink circulation section 22 Pressure generation unit 23 Pressurized air path 24. Negative pressure air path 31 Pressurized tank 32 Pressurized tank liquid level sensor 33. Vacuum Tank 34. Vacuum Tank Liquid Level Sensor 35 Pressurized ink path 36. Negative pressure side ink path 37 Pump liquid delivery route 38 Ink pump 41 Ink Cartridges 42 Ink replenishment routes 43, 43A~43C Ink Refill Valve 46 Main Route Branch routes 47, 47A~47C 51 Ink receiving section 52 wipers

Claims

1. Multiple ejection units, each positioned at a different height, each having a nozzle for ejecting ink, and for printing by ejecting ink from the nozzle onto a printing medium, The system comprises multiple storage units, each connected to a corresponding discharge unit, for storing ink, and positioned at different heights below the corresponding discharge unit during printing, corresponding to the height position of the respective discharge unit. During the transport of this device, The plurality of ejection units are arranged such that the height difference between the highest and lowest ejection units is smaller than during printing. The inkjet printing apparatus is characterized in that the plurality of storage units are arranged at a predetermined height range below the plurality of discharge units, where the height difference is smaller than the height difference between the highest storage unit and the lowest storage unit during printing.

2. The inkjet printing apparatus according to claim 1, characterized in that, during transport of the apparatus, the plurality of storage units are positioned at a height corresponding to the storage unit that is at the central height position among the plurality of discharge units during printing.

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