Liquid supply device

Abstract

To provide a liquid supply device that can be suppressed from poorly supplying liquid.SOLUTION: Branch passages 47A-47C are branched from a main passage 46 connected to an ink cartridge 41 and are respectively connected to negative tanks 33 of ink towers 4A-4C arranged at different height positions, at a position lower than a position of the ink cartridge 41. Ink refilling valves 43A-43C are arranged at the branch passages 47A-47C, respectively. A control part controls the ink refilling valves 43A-43C so that ink is supplied from the ink cartridge 41 to the negative tanks 33 of the ink towers 4A-4C. The control part controls the ink refilling valves 43A-43C so that ink is supplied between the negative tanks 33 whose differences in height are above a predetermined value, at different times.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a liquid supply device.

Background Art

[0002] An ink circulation type inkjet printing apparatus is known that applies positive pressure and negative pressure to a pressurized tank and a negative pressure tank connected to an inkjet head respectively to circulate ink, and ejects ink from the inkjet head to perform printing.

[0003] Further, an inkjet printing apparatus is known in which an inkjet head is arranged to be capable of ejecting ink in the horizontal direction, and printing can be performed on a surface perpendicular to the horizontal direction such as the side surface of a corrugated fiberboard box (see Patent Document 1).

[0004] As this type of inkjet printing apparatus, there is one that includes a plurality of inkjet heads arranged along the vertical direction, and ejects ink from the inkjet heads onto a surface of a print medium that is perpendicular to the horizontal direction to perform printing.

[0005] Further, as the above-described ink circulation type inkjet printing apparatus provided with the plurality of inkjet heads arranged along the vertical direction, there is one provided with a plurality of ink towers each having a pressurized tank and a negative pressure tank.

[0006] In this inkjet printing apparatus, the plurality of ink towers are each connected to a predetermined number of inkjet heads. The plurality of ink towers are arranged at different height positions respectively according to the height positions of the inkjet heads connected thereto. Thereby, the difference in nozzle pressure between the inkjet heads caused by the difference in water head pressure between the inkjet heads and the pressurized tank and negative pressure tank is suppressed to be small, and the nozzle pressure of each inkjet head is kept within a range that enables stable ejection.

[0007] Some inkjet printing systems are equipped with an ink supply unit that uses hydrostatic pressure to replenish (supply) ink to multiple ink towers from a single ink cartridge common to all of them. This ink supply unit has multiple branch paths that branch off from the path connected to the ink cartridge, and each branch path is connected to the negative pressure tank of each ink tower. A valve is placed in each branch path, and when the valve is opened, ink flows into the negative pressure tank. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2018-1687 [Overview of the project] [Problems that the invention aims to solve]

[0009] In the aforementioned inkjet printing apparatus, if the valves of multiple branch paths are opened simultaneously to supply ink to multiple negative pressure tanks at the same time, there is a risk of ink supply failure.

[0010] For example, because the hydrostatic pressure between each ink tower's negative pressure tank and the ink cartridge differs, an imbalance in the amount of ink supplied to each negative pressure tank may occur. This can result in some negative pressure tanks not receiving enough ink, potentially causing problems with the operation of the device.

[0011] Furthermore, there is a risk of ink moving from a negative pressure tank located at a higher position with relatively low hydrostatic pressure between it and the ink cartridge to a negative pressure tank located at a lower position with relatively high hydrostatic pressure between it and the ink cartridge. This could result in a negative pressure tank where the ink level decreases, potentially causing problems with the operation of the device.

[0012] The present invention has been made in view of the above, and aims to provide a liquid supply device that can reduce supply failures of liquids such as ink. [Means for solving the problem]

[0013] To achieve the above objective, the liquid supply device of the present invention comprises a liquid storage unit, a plurality of branching paths that branch off from a path connected to the liquid storage unit and are connected to a plurality of tanks arranged at different heights below the liquid storage unit, a plurality of supply valves arranged in each of the plurality of branching paths, and a control unit that controls the plurality of supply valves to supply liquid from the liquid storage unit to each of the plurality of tanks, wherein the control unit controls the plurality of supply valves so as to separate the supply of liquid in time between tanks where the height difference is greater than or equal to a predetermined value. [Effects of the Invention]

[0014] According to the liquid supply device of the present invention, liquid supply failures can be reduced. [Brief explanation of the drawing]

[0015] [Figure 1] This is a block diagram showing the configuration of an inkjet printing apparatus according to an embodiment. [Figure 2] Figure 1 is a schematic diagram of the transport section and head unit of the inkjet printing apparatus shown. [Figure 3] Figure 1 is a schematic diagram of the head unit 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] Figure 1 is a schematic diagram of the ink supply section of the inkjet printing apparatus shown. [Figure 6] This is a flowchart illustrating the ink replenishment process during printing. [Figure 7] This is a flowchart illustrating the ink replenishment process during printing. [Figure 8] This is a flowchart illustrating the operation of the ink supply unit during the initial ink filling process. [Figure 9]This is a flowchart for explaining the operation of the ink supply unit during initial ink filling. [Figure 10] This is a flowchart for explaining the operation of the ink supply unit during initial ink filling. [Figure 11] This is a flowchart for explaining the operation of the ink supply unit during initial ink filling. [Figure 12] This is a flowchart for explaining the operation of the ink supply unit during initial ink filling. [Modes for Carrying Out the Invention]

[0016] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Throughout the respective drawings, the same or corresponding parts and components are denoted by the same or corresponding reference numerals.

[0017] The embodiments shown below exemplify apparatuses and the like for embodying the technical idea of the present invention, and the technical idea of the present invention is not intended to limit the material, shape, structure, arrangement, etc. of each component to those described below. The technical idea of the present invention can be modified in various ways within the scope of the appended claims.

[0018] Figure 1 is a block diagram showing the configuration of an inkjet printing apparatus provided with a liquid supply apparatus according to an embodiment of the present invention. Figure 2 is a schematic configuration diagram of a conveyance unit and a head unit of the inkjet printing apparatus shown in Figure 1. Figure 3 is a schematic configuration diagram of a head unit and an ink tower of the inkjet printing apparatus shown in Figure 1. Figure 4 is a schematic configuration diagram of an ink tower of the inkjet printing apparatus shown in Figure 1. Figure 5 is a schematic configuration diagram of an ink supply unit of the inkjet printing apparatus shown in Figure 1. In the following description, the up, down, left, right, front and rear directions indicated by the arrows in Figure 2 are defined as the up, down, left, right, front and rear directions. The up-down direction is the vertical direction, and the left-right direction and the front-rear direction are directions that are orthogonal to each other, both orthogonal to the up-down direction, and parallel to the horizontal direction.

[0019] As shown in Figure 1, the inkjet printing apparatus 1 according to this embodiment comprises a transport unit 2, head units 3A and 3B, ink towers 4A to 4C, ink supply units 5A to 5D, and a control unit 6. The liquid supply device comprises an ink supply unit 5 and a control unit 6. In the following description, the alphabetical subscripts in the symbols for head units 3A, 3B, etc., may be omitted and the symbols may be referred to collectively.

[0020] The transport unit 2 transports the printing medium 7. The printing medium 7 has a printable surface 7a on which printing is performed by the head unit 3. The printable surface 7a is a surface perpendicular to the horizontal direction (vertical surface) when the printing medium 7 is placed on the transport unit 2 and transported. The printing medium 7 is, for example, a corrugated cardboard box.

[0021] The print head units 3A and 3B perform printing by ejecting ink horizontally toward the print surface 7a of the printing medium 7. Each print head unit 3A and 3B ejects two colors of ink. For example, print head unit 3A ejects black and cyan ink, and print head unit 3B ejects magenta and yellow ink. Print head units 3A and 3B have the same configuration except for the colors of ink they eject.

[0022] As shown in Figures 1 to 3, the head unit 3 includes a plurality of inkjet heads 11. In this embodiment, the head unit 3 includes six inkjet heads 11.

[0023] In the head unit 3, the six inkjet heads 11 are arranged in a staggered pattern along the vertical direction. That is, in the head unit 3, the six inkjet heads 11 arranged along the vertical direction are positioned with their positions in the front-to-back direction alternately offset.

[0024] The inkjet head 11 ejects two colors of ink. The inkjet head 11 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 from each other.

[0025] Ink towers 4A to 4C supply ink to head units 3A and 3B. Ink tower 4A supplies ink to the first and second inkjet heads 11 from the bottom in each of head units 3A and 3B. Ink tower 4B supplies ink to the third and fourth inkjet heads 11 from the bottom in each of head units 3A and 3B. Ink tower 4C supplies ink to the fifth and sixth inkjet heads 11 from the bottom in each of head units 3A and 3B.

[0026] Note that in Figure 3, only one of the head units 3A and 3B, head unit 3, is shown, and the other head unit 3 is not shown.

[0027] Ink towers 4A to 4C are positioned such that the height difference between each tower and the inkjet head 11 that supplies ink is equal for all of them. Therefore, ink towers 4A to 4C are each positioned at different heights. Of ink towers 4A to 4C, ink tower 4A is positioned at the lowest position, and ink tower 4C is positioned at the highest position.

[0028] The ink tower 4 comprises ink circulation sections 21A to 21D, a pressure generation section 22, four pressurized air passages 23 (see Figure 4), and four negative pressure air passages 24 (see Figure 4).

[0029] The ink circulation units 21A to 21D circulate the ink and supply it to the inkjet head 11. Each of the ink circulation units 21A to 21D supplies a different color of ink to the inkjet head 11 that ejects the ink of the color held by the respective ink circulation unit 21.

[0030] The ink circulation units 21A and 21B are connected to two inkjet heads 11 in the head unit 3A, which are positioned at different heights, and supply ink to these two inkjet heads 11. The ink circulation units 21C and 21D are connected to two inkjet heads 11 in the head unit 3B, which are positioned at different heights, and supply ink to these two inkjet heads 11.

[0031] Specifically, the ink circulation units 21A and 21B of the ink tower 4A supply ink to the first and second inkjet heads 11 from the bottom in the head unit 3A. The ink circulation units 21C and 21D of the ink tower 4A supply ink to the first and second inkjet heads 11 from the bottom in the head unit 3B.

[0032] Furthermore, the ink circulation units 21A and 21B of the ink tower 4B supply ink to the third and fourth inkjet heads 11 from the bottom in the head unit 3A. The ink circulation units 21C and 21D of the ink tower 4B supply ink to the third and fourth inkjet heads 11 from the bottom in the head unit 3B.

[0033] Furthermore, the ink circulation units 21A and 21B of the ink tower 4C supply ink to the fifth and sixth inkjet heads 11 from the bottom in the head unit 3A. The ink circulation units 21C and 21D of the ink tower 4C supply ink to the fifth and sixth inkjet heads 11 from the bottom in the head unit 3B.

[0034] As shown in Figure 4, the ink circulation unit 21 includes a pressurized tank 31, a pressurized tank liquid level sensor 32, a negative pressure tank (equivalent to a 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. Note that 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 3.

[0035] The pressurized tank 31 stores the ink supplied to the inkjet head 11. The pressurized tank 31 is subjected to positive pressure by the pressure generation unit 22 to supply ink to the inkjet head 11. The pressurized tank 31 is positioned lower than the lower of the two inkjet heads 11 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.

[0036] 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.

[0037] The negative pressure tank 33 receives and stores ink that is not consumed by the inkjet head 11. 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 11. 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.

[0038] 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.

[0039] The pressurized ink path 35 connects the pressurized tank 31 to the two inkjet heads 11. Ink supplied from the pressurized tank 31 to the two inkjet heads 11 flows through the pressurized ink path 35.

[0040] The negative pressure ink path 36 connects the two inkjet heads 11 to the negative pressure tank 33. Ink that is not consumed by the two inkjet heads 11 and is recovered into the negative pressure tank 33 flows through the negative pressure ink path 36.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] The ink supply units 5A to 5D each supply ink to the negative pressure tanks 33 of the ink circulation units 21A to 21D. The ink supply unit 5 supplies ink to the negative pressure tank 33 using the hydrostatic pressure between the ink cartridge 41 (described later) and the negative pressure tank 33. In the inkjet printing device 1, a common ink supply unit 5 is provided for each ink color in the ink towers 4A to 4C.

[0047] 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.

[0048] The ink supply unit 5 comprises an ink cartridge 41, an ink supply path 42, and ink supply valves (corresponding to supply valves) 43A to 43C.

[0049] The ink cartridge 41 contains the ink used for printing by the inkjet head 11. 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] Here, the three negative pressure tanks 33, each connected to a branching path 47A to 47C, are positioned at different heights, lower than the ink cartridges 41, according to the height positions of the ink towers 4A to 4C to which they are located. Of the three negative pressure tanks 33, each connected to a branching path 47A to 47C, the negative pressure tank 33 connected to branching path 47A is positioned at the lowest position, and the negative pressure tank 33 connected to branching path 47C is positioned at the highest position.

[0054] 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.

[0055] The control unit 6 controls the operation of each part of the inkjet printing device 1. The control unit 6 is composed of a CPU, RAM, ROM, hard disk, etc.

[0056] The control unit 6 circulates ink in the ink circulation sections 21A to 21D of the ink towers 4A to 4C, and prints by ejecting ink from the inkjet heads 11 of the head units 3A and 3B. During the printing operation, the control unit 6 controls the ink supply valves 43A to 43C of the ink supply sections 5A to 5D to supply ink from the ink cartridges 41 to each negative pressure tank 33. During this ink supply operation in printing, the control unit 6 controls the ink supply valves 43A to 43C for each ink supply section 5 so that the supply of ink to the three negative pressure tanks 33, which are the destinations of the ink supplied by the ink supply section 5, is performed in a time-separated manner. That is, for each ink supply section 5, the control unit 6 controls the ink supply valve 43 corresponding to each of the three negative pressure tanks 33 to supply ink to the negative pressure tank 33, performing this process with a time stagger for each negative pressure tank 33. Similarly, during the initial filling of ink, the control unit 6 controls the ink supply valves 43A to 43C to separate the supply of ink to the three negative pressure tanks 33 for each ink supply unit 5 over time.

[0057] Next, the operation of the inkjet printing device 1 will be described.

[0058] When a print job is input, the control unit 6 starts ink circulation in the ink circulation sections 21A to 21D of the ink towers 4A to 4C. Specifically, the control unit 6 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 11 to the negative pressure tank 33.

[0059] When ink circulation begins, the control unit 6 starts executing the print job. Specifically, the control unit 6 controls the transport unit 2 to transport the print medium 7 and to eject ink from each inkjet head 11 of the head units 3A and 3B to print an image onto the print medium 7.

[0060] During the execution of a print job, ink is supplied from the pressurized tank 31 to the inkjet head 11, and any ink not consumed by the inkjet head 11 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 6 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 turns on, the control unit 6 stops the ink pump 38. In this way, ink is circulated and printing is performed.

[0061] Furthermore, during this printing operation, the control unit 6 performs ink replenishment operations using the ink replenishment units 5A to 5D. In these ink replenishment operations, the control unit 6 controls the ink replenishment valves 43A to 43C for each ink replenishment unit 5 to supply ink to the three negative pressure tanks 33, which are the destinations of the ink supplied by that ink replenishment unit 5, in a time-separated manner. Details of this ink replenishment operation will be described later.

[0062] When printing based on a print job is completed, the control unit 6 controls the pressure generation unit 22 to terminate ink circulation in the ink circulation units 21A to 21D.

[0063] Next, we will explain the ink replenishment process described above.

[0064] Figures 6 and 7 are flowcharts illustrating the ink replenishment operation. The flowcharts in Figures 6 and 7 show the operations performed by each of the ink replenishment units 5A to 5D. Therefore, this explanation describes the operation of one ink replenishment unit 5, and the negative pressure tank 33, negative pressure tank liquid level sensor 34, etc., in this explanation refer to those located in the ink circulation unit 21, which is the destination of the ink supplied by the ink replenishment unit 5. The process in the flowcharts of Figures 6 and 7 begins when ink circulation is started.

[0065] In step S1 of Figure 6, the control unit 6 determines whether both the pressurized tank liquid level sensor 32 and the negative pressure tank liquid level sensor 34 of the ink tower 4A are turned off.

[0066] If the control unit 6 determines that both the pressurized tank liquid level sensor 32 and the negative pressure tank liquid level sensor 34 of the ink tower 4A are off (step S1: YES), in step S2, the control unit 6 opens the ink supply valve 43A. As a result, ink is supplied to the negative pressure tank 33 of the ink tower 4A via the branch path 47A by the hydrostatic pressure between the ink cartridge 41 and the negative pressure tank 33 of the ink tower 4A, and by the negative pressure of the negative pressure tank 33.

[0067] Next, in step S3, the control unit 6 determines whether the negative pressure tank liquid level sensor 34 of the ink tower 4A has been turned on or not. If it determines that the negative pressure tank liquid level sensor 34 has not been turned on (step S3: NO), the control unit 6 repeats step S3.

[0068] If the control unit determines that the negative pressure tank liquid level sensor 34 has been turned on (step S3: YES), in step S4, the control unit 6 closes the ink supply valve 43A. This stops the supply of ink from the ink tower 4A to the negative pressure tank 33. After this, the control unit 6 proceeds to step S5.

[0069] If, in step S1, the control unit 6 determines that at least one of the pressurized tank liquid level sensor 32 and the negative pressure tank liquid level sensor 34 of the ink tower 4A is ON (step S1: NO), the control unit 6 proceeds to step S5.

[0070] In step S5, the control unit 6 determines whether both the pressurized tank liquid level sensor 32 and the negative pressure tank liquid level sensor 34 of the ink tower 4B are turned off.

[0071] If the control unit 6 determines that both the pressurized tank liquid level sensor 32 and the negative pressure tank liquid level sensor 34 of the ink tower 4B are off (step S5: YES), in step S6, the control unit 6 opens the ink supply valve 43B. As a result, ink is supplied to the negative pressure tank 33 of the ink tower 4B via the branch path 47B by the hydrostatic pressure between the ink cartridge 41 and the negative pressure tank 33 of the ink tower 4B, and by the negative pressure of the negative pressure tank 33.

[0072] Next, in step S7, the control unit 6 determines whether the negative pressure tank liquid level sensor 34 of the ink tower 4B has been turned on or not. If it determines that the negative pressure tank liquid level sensor 34 has not been turned on (step S7: NO), the control unit 6 repeats step S7.

[0073] If the control unit determines that the negative pressure tank liquid level sensor 34 has been turned on (step S7: YES), in step S8, the control unit 6 closes the ink supply valve 43B. This stops the supply of ink from the ink tower 4B to the negative pressure tank 33. After this, the control unit 6 proceeds to step S9.

[0074] If, in step S5, the control unit 6 determines that at least one of the pressurized tank liquid level sensor 32 and the negative pressure tank liquid level sensor 34 of the ink tower 4B is ON (step S5: NO), the control unit 6 proceeds to step S9.

[0075] In step S9, the control unit 6 determines whether both the pressurized tank liquid level sensor 32 and the negative pressure tank liquid level sensor 34 of the ink tower 4C are turned off.

[0076] If the control unit 6 determines that both the pressurized tank liquid level sensor 32 and the negative pressure tank liquid level sensor 34 of the ink tower 4C are off (step S9: YES), in step S10 of Figure 7, the control unit 6 opens the ink supply valve 43C. As a result, ink is supplied to the negative pressure tank 33 of the ink tower 4C via the branch path 47C by the hydrostatic pressure between the ink cartridge 41 and the negative pressure tank 33 of the ink tower 4C, and by the negative pressure of the negative pressure tank 33.

[0077] Next, in step S11, the control unit 6 determines whether the negative pressure tank liquid level sensor 34 of the ink tower 4C has been turned on or not. If it determines that the negative pressure tank liquid level sensor 34 has not been turned on (step S11: NO), the control unit 6 repeats step S11.

[0078] If the control unit determines that the negative pressure tank liquid level sensor 34 has been turned on (step S11: YES), in step S12, the control unit 6 closes the ink supply valve 43C. This stops the supply of ink from the ink tower 4C to the negative pressure tank 33. After this, the control unit 6 proceeds to step S13.

[0079] In step S9 of Figure 6, if the control unit 6 determines that at least one of the pressurized tank liquid level sensor 32 and the negative pressure tank liquid level sensor 34 of the ink tower 4C is ON (step S9: NO), the control unit 6 proceeds to step S13 of Figure 7.

[0080] In step S13, the control unit 6 determines whether or not the ink circulation has finished. If it determines that the ink circulation has not finished (step S13: NO), the control unit 6 returns to step S1.

[0081] When the control unit 6 determines that ink circulation has finished (step S13: YES), the series of operations ends.

[0082] Next, we will explain the operation of the ink supply unit 5 during the initial filling of ink in the inkjet printing device 1.

[0083] Initial ink filling is performed to fill each ink circulation unit 21 and each inkjet head 11 with ink, starting from a state where there is no ink in each ink circulation unit 21 and each inkjet head 11. Initial ink filling is performed, for example, at the end of maintenance work that involves draining the ink from the ink circulation unit 21 and inkjet head 11, or when the inkjet printing device 1 is completed, in order to make the inkjet printing device 1 ready for printing.

[0084] Figures 8 to 12 are flowcharts illustrating the operation of the ink supply unit 5 during initial ink filling. Similar to the flowcharts in Figures 6 and 7 mentioned earlier, the flowcharts in Figures 8 to 12 show the operations performed by each of the ink supply units 5A to 5D. Therefore, as with the explanation of the flowchart in Figure 6, we will describe the operation of one ink supply unit 5 at a time.

[0085] When the initial ink filling begins, in step S21 of Figure 8, the control unit 6 determines whether the negative pressure tank liquid level sensor 34 of the ink tower 4A is on or not. If it determines that the negative pressure tank liquid level sensor 34 of the ink tower 4A is on (step S21: YES), the control unit 6 proceeds to step S42, which will be described later.

[0086] At the start of the initial filling, the negative pressure tanks 33 of ink towers 4A to 4C are empty, so the negative pressure tank liquid level sensors 34 of ink towers 4A to 4C are off.

[0087] If the control unit 6 determines that the negative pressure tank liquid level sensor 34 of the ink tower 4A is off (step S21: NO), in step S22, the control unit 6 opens the ink supply valve 43A.

[0088] Here, during initial filling, the pressure generation unit 22 applies positive pressure to the pressurized tank 31, while the negative pressure tank 33 is open to the atmosphere. Therefore, when the ink supply valve 43A is opened, ink is supplied to the negative pressure tank 33 of the ink tower 4A via the branch path 47A solely by the hydrostatic pressure between the ink cartridge 41 and the negative pressure tank 33 of the ink tower 4A.

[0089] Next, in step S23, the control unit 6 determines whether a specified time has elapsed since the ink supply valve 43A was opened. Here, the specified time is a preset time for one opening of the ink supply valve 43 until the negative pressure tank liquid level sensor 34 in the ink towers 4A to 4C is first turned on. The specified time is set for each ink tower 4 according to the hydrostatic pressure between the ink cartridge 41 and the negative pressure tank 33 of each ink tower 4, so that the amount of ink supplied when the ink supply valve 43 is opened for the specified time is a predetermined amount.

[0090] If it is determined that the specified time has not elapsed (step S23: NO), in step S24, the control unit 6 determines whether the negative pressure tank liquid level sensor 34 of the ink tower 4A is turned on or off. If it is determined that the negative pressure tank liquid level sensor 34 of the ink tower 4A is off (step S24: NO), the control unit 6 returns to step S23.

[0091] If the control unit determines that the negative pressure tank liquid level sensor 34 of the ink tower 4A has been turned on (step S24: YES), in step S25, the control unit 6 closes the ink supply valve 43A. This stops the supply of ink to the negative pressure tank 33 of the ink tower 4A. After this, the control unit 6 proceeds to step S42, which will be described later.

[0092] In step S23, if it is determined that the specified time has elapsed (step S23: YES), in step S26, the control unit 6 closes the ink supply valve 43A. This stops the supply of ink from the ink tower 4A to the negative pressure tank 33.

[0093] Next, in step S27, the control unit 6 determines whether the negative pressure tank liquid level sensor 34 of the ink tower 4A has been turned on. If it determines that the negative pressure tank liquid level sensor 34 of the ink tower 4A has been turned on (step S27: YES), the control unit 6 proceeds to step S42, which will be described later.

[0094] If the control unit 6 determines that the negative pressure tank liquid level sensor 34 of ink tower 4A is off (step S27: NO), then in step S28 of Figure 9, the control unit 6 determines whether the negative pressure tank liquid level sensor 34 of ink tower 4B is on or off. If the control unit 6 determines that the negative pressure tank liquid level sensor 34 of ink tower 4B is on (step S28: YES), the control unit 6 proceeds to step S44, which will be described later.

[0095] If the control unit 6 determines that the negative pressure tank liquid level sensor 34 of the ink tower 4B is off (step S28: NO), in step S29, the control unit 6 opens the ink supply valve 43B. As a result, ink is supplied to the negative pressure tank 33 of the ink tower 4B via the branch path 47B solely by the hydrostatic pressure between the ink cartridge 41 and the negative pressure tank 33 of the ink tower 4B.

[0096] Next, in step S30, the control unit 6 determines whether a specified time has elapsed since the ink supply valve 43B was opened.

[0097] If it is determined that the specified time has not elapsed (step S30: NO), in step S31, the control unit 6 determines whether the negative pressure tank liquid level sensor 34 of the ink tower 4B is turned on or off. If it is determined that the negative pressure tank liquid level sensor 34 of the ink tower 4B is off (step S31: NO), the control unit 6 returns to step S30.

[0098] If the control unit determines that the negative pressure tank liquid level sensor 34 of ink tower 4B has been turned on (step S31: YES), in step S32, the control unit 6 closes the ink supply valve 43B. This stops the supply of ink to the negative pressure tank 33 of ink tower 4B. After this, the control unit 6 proceeds to step S44, which will be described later.

[0099] In step S30, if it is determined that the specified time has elapsed (step S30: YES), in step S33, the control unit 6 closes the ink supply valve 43B. This stops the supply of ink to the negative pressure tank 33 of the ink tower 4B.

[0100] Next, in step S34, the control unit 6 determines whether the negative pressure tank liquid level sensor 34 of the ink tower 4B has been turned on. If it determines that the negative pressure tank liquid level sensor 34 of the ink tower 4B has been turned on (step S34: YES), the control unit 6 proceeds to step S44, which will be described later.

[0101] If the control unit 6 determines that the negative pressure tank liquid level sensor 34 of ink tower 4B is off (step S34: NO), then in step S35 of Figure 10, the control unit 6 determines whether the negative pressure tank liquid level sensor 34 of ink tower 4C is on or off. If the control unit 6 determines that the negative pressure tank liquid level sensor 34 of ink tower 4C is on (step S35: YES), the control unit 6 proceeds to step S46, which will be described later.

[0102] If the control unit 6 determines that the negative pressure tank liquid level sensor 34 of the ink tower 4C is off (step S35: NO), in step S36, the control unit 6 opens the ink supply valve 43C. As a result, ink is supplied to the negative pressure tank 33 of the ink tower 4C via the branch path 47C solely by the hydrostatic pressure between the ink cartridge 41 and the negative pressure tank 33 of the ink tower 4C.

[0103] Next, in step S37, the control unit 6 determines whether a specified time has elapsed since the ink supply valve 43C was opened.

[0104] If it is determined that the specified time has not elapsed (step S37: NO), in step S38, the control unit 6 determines whether the negative pressure tank liquid level sensor 34 of ink tower 4C is turned on or off. If it is determined that the negative pressure tank liquid level sensor 34 of ink tower 4B is off (step S38: NO), the control unit 6 returns to step S37.

[0105] If the control unit determines that the negative pressure tank liquid level sensor 34 of the ink tower 4C has been turned on (step S38: YES), in step S39, the control unit 6 closes the ink supply valve 43C. This stops the supply of ink to the negative pressure tank 33 of the ink tower 4C. After this, the control unit 6 proceeds to step S46, which will be described later.

[0106] If, in step S37, it is determined that the specified time has elapsed (step S37: YES), then in step S40, the control unit 6 closes the ink supply valve 43C. This stops the supply of ink from the ink tower 4C to the negative pressure tank 33.

[0107] Next, in step S41, the control unit 6 determines whether or not the negative pressure tank liquid level sensor 34 of the ink tower 4C has been turned on.

[0108] If the control unit 6 determines that the negative pressure tank liquid level sensor 34 of the ink tower 4C is off (step S41: NO), it returns to step S21 in Figure 8.

[0109] In step S42 of Figure 8, the control unit 6 determines whether the negative pressure tank liquid level sensor 34 of the ink tower 4B is ON or OFF. If it determines that the negative pressure tank liquid level sensor 34 of the ink tower 4B is OFF (step S42: NO), the control unit 6 proceeds to step S29 of Figure 9.

[0110] If the control unit 6 determines that the negative pressure tank liquid level sensor 34 of ink tower 4B is ON (step S42: YES), in step S43, the control unit 6 determines whether the negative pressure tank liquid level sensor 34 of ink tower 4C is ON or OFF. If the control unit 6 determines that the negative pressure tank liquid level sensor 34 of ink tower 4C is OFF (step S43: NO), the control unit 6 proceeds to step S36 in Figure 10.

[0111] If the control unit 6 determines that the negative pressure tank liquid level sensor 34 of the ink tower 4C is ON (step S43: YES), it proceeds to step S48 in Figure 11, which will be described later.

[0112] In step S44 of Figure 9, the control unit 6 determines whether the negative pressure tank liquid level sensor 34 of the ink tower 4A is ON or OFF. If it determines that the negative pressure tank liquid level sensor 34 of the ink tower 4A is OFF (step S44: NO), the control unit 6 proceeds to step S22 of Figure 8.

[0113] If the control unit 6 determines that the negative pressure tank liquid level sensor 34 of ink tower 4A is ON (step S44: YES), in step S45, the control unit 6 determines whether the negative pressure tank liquid level sensor 34 of ink tower 4C is ON or OFF. If the control unit 6 determines that the negative pressure tank liquid level sensor 34 of ink tower 4C is OFF (step S45: NO), the control unit 6 proceeds to step S36 in Figure 10.

[0114] If the control unit 6 determines that the negative pressure tank liquid level sensor 34 of the ink tower 4C is ON (step S45: YES), it proceeds to step S48 in Figure 11, which will be described later.

[0115] In step S46 of Figure 10, the control unit 6 determines whether the negative pressure tank liquid level sensor 34 of the ink tower 4A is ON or OFF. If it determines that the negative pressure tank liquid level sensor 34 of the ink tower 4A is OFF (step S46: NO), the control unit 6 proceeds to step S22 of Figure 8.

[0116] If the control unit 6 determines that the negative pressure tank liquid level sensor 34 of ink tower 4A is ON (step S46: YES), in step S47, the control unit 6 determines whether the negative pressure tank liquid level sensor 34 of ink tower 4B is ON or OFF. If the control unit 6 determines that the negative pressure tank liquid level sensor 34 of ink tower 4B is OFF (step S47: NO), the control unit 6 proceeds to step S29 in Figure 9.

[0117] If the control unit 6 determines that the negative pressure tank liquid level sensor 34 of ink tower 4B is ON (step S47: YES), it proceeds to step S48 in Figure 11, which will be described later.

[0118] As described above, the process from steps S21 to S47 in Figures 8 to 10 ensures that ink is supplied to the negative pressure tanks 33 of ink towers 4A to 4C in a time-separated manner, and the negative pressure tank liquid level sensors 34 of ink towers 4A to 4C are turned on first. After this, the process proceeds to step S48 in Figure 11.

[0119] Here, after the negative pressure tank liquid level sensor 34 of ink towers 4A to 4C is initially turned on, the ink pump 38 is driven when the pressurized tank liquid level sensor 32 is off and the negative pressure tank liquid level sensor 34 is on, similar to the ink circulation during printing described above. When the pressurized tank liquid level sensor 32 is off and the negative pressure tank liquid level sensor 34 is on, the ink pump 38 is stopped. Also, as described above, positive pressure is applied to the pressurized tank 31, so ink flows out from the pressurized tank 31 towards the inkjet head 11.

[0120] The processes in steps S48 to S59 in Figures 11 and 12 are the same as the processes in steps S1 to S12 in the flowcharts in Figures 6 and 7 described above.

[0121] In step S60 of Figure 12, the control unit 6 determines whether the initial ink filling is complete. Here, the control unit 6 determines that the initial ink filling is complete when the number of times the pressurized tank liquid level sensor 32 has been turned on reaches a predetermined number of times.

[0122] If the control unit 6 determines that the initial ink filling is not complete (step S60: NO), it returns to step S48 in Figure 11.

[0123] When the control unit 6 determines that the initial ink filling is complete (step S60: YES), the series of operations ends.

[0124] As explained above, in the inkjet printing apparatus 1, the control unit 6 controls the ink supply valves 43A to 43C so that the supply of ink to each negative pressure tank 33, which is the destination of the ink supply unit 5, is separated in time for each ink supply unit 5. That is, for each ink supply unit 5, the control unit 6 controls the ink supply valve 43 corresponding to each of the three negative pressure tanks 33 to supply ink to the negative pressure tank 33, and performs this process with a time stagger for each negative pressure tank 33.

[0125] In this embodiment, unlike the present invention, if ink is to be supplied to multiple negative pressure tanks 33 simultaneously, the hydrostatic pressure between each negative pressure tank 33 and the ink cartridge 41 will differ, which may result in a failure to supply ink to the negative pressure tanks 33.

[0126] For example, there is a risk of uneven ink supply to each negative pressure tank 33. This could result in some negative pressure tanks 33 not receiving enough ink, potentially causing problems with the operation of the inkjet printer 1.

[0127] Furthermore, there is a risk of ink movement between the negative pressure tanks 33, from one negative pressure tank 33 located at a higher position with relatively low hydrostatic pressure between it and the ink cartridge 41, to another negative pressure tank 33 located at a lower position with relatively high hydrostatic pressure between it and the ink cartridge 41. This could result in one negative pressure tank 33 experiencing a decrease in ink, potentially causing problems with the operation of the inkjet printing device 1.

[0128] In contrast, the inkjet printing apparatus 1 reduces the aforementioned ink supply failure to the negative pressure tanks 33 by separating the supply of ink to each negative pressure tank 33 by the ink supply unit 5 over time.

[0129] Furthermore, the ink supply valves 43A to 43C may be controlled to separate the supply of ink between negative pressure tanks 33 where the height difference is greater than a predetermined value, and to allow simultaneous supply of ink between negative pressure tanks 33 where the height difference is less than a predetermined value. Here, the predetermined value of the height difference between negative pressure tanks 33 is set based on experiments, etc., as the lower limit of the height difference at which the aforementioned ink supply failure may occur.

[0130] For example, suppose the height difference between ink towers 4A and 4C is greater than or equal to a predetermined value, and the height difference between ink towers 4A and 4B, and between ink towers 4B and 4C are less than a predetermined value. The height difference of the negative pressure tanks 33 included in ink tower 4 is equal to the height difference of ink tower 4. In this case, the ink supply valves 43A to 43C may be controlled to allow for time-separated ink supply between the negative pressure tanks 33 of ink towers 4A and 4C, and simultaneous ink supply between the negative pressure tanks 33 of ink towers 4A and 4B, and between the negative pressure tanks 33 of ink towers 4B and 4C.

[0131] This method also reduces the ink supply failure to the negative pressure tank 33 as described above.

[0132] Furthermore, although the above-described embodiment shows a configuration in which one ink supply unit 5 supplies ink to three negative pressure tanks 33, the number of negative pressure tanks 33 to which the ink is supplied is not limited to this, and any number of such tanks may be used.

[0133] Furthermore, the present invention is applicable not only to ink but also to liquid supply devices that supply any liquid.

[0134] 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.

[0135] [Note] This application discloses the following invention:

[0136] (Note 1) Liquid storage section, Multiple branching paths are connected to multiple tanks that are located at different heights below the liquid storage section, branching off from the path connected to the liquid storage section. Multiple supply valves arranged in each of the aforementioned multiple branch paths, The system includes a control unit that controls the plurality of supply valves to supply liquid from the liquid storage unit to each of the plurality of tanks, The liquid supply device is characterized in that the control unit controls the plurality of supply valves so as to separate the supply of liquid over time between tanks where the height difference is greater than or equal to a predetermined value.

[0137] (Note 2) The liquid supply device according to Appendix 1, characterized in that the control unit controls the plurality of supply valves to supply liquid to each of the plurality of tanks in a timely and separate manner.

[0138] (Note 3) The liquid supply device according to Appendix 1, characterized in that the control unit controls the supply valve corresponding to each of the plurality of tanks to supply liquid to the tank, and performs the process of supplying liquid to the tank at different times for each tank. [Explanation of Symbols]

[0139] 1. Inkjet printing device 2. Conveying section 3,3A,3B Head Unit 4,4A~4C Ink Tower 5,5A~5D Ink Refill Section 6 Control Unit 11 Inkjet heads 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

Claims

[Claim 1] Ink cartridges and Multiple branch paths are connected to multiple tanks that are located at different heights below the ink cartridge, branching off from the path connected to the aforementioned ink cartridge, Multiple supply valves arranged in each of the aforementioned multiple branch paths, Each of the aforementioned multiple tanks is provided with a plurality of liquid level sensors that detect whether or not the liquid level in the tank has reached a reference height, The system includes a control unit that controls the plurality of supply valves to supply liquid from the ink cartridge to each of the plurality of tanks, The control unit performs the following process for each of the plurality of tanks, with a time delay for each tank: opening the supply valve corresponding to the tank to supply liquid to the tank, and closing the supply valve when a specified time has elapsed since the supply valve was opened, or when the liquid level sensor corresponding to the tank detects that the liquid level has reached the reference height, whichever comes first. The liquid supply device is characterized in that the specified time is set for each tank according to the hydrostatic pressure between the ink cartridge and each tank, such that the amount of liquid supplied when the supply valve is opened for the specified time is a predetermined amount.

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