A recirculating ink supply system

Abstract

The application provides a circulating ink supply system. The system comprises a positive pressure source, a negative pressure source and multiple independently arranged color groups; each color group comprises a positive pressure adjusting module, a positive pressure ink box, multiple nozzle modules, a negative pressure adjusting module, a negative pressure ink box, an ink return module and an ink supply module; the positive pressure ink boxes in the multiple color groups are independently connected with the same positive pressure source, and the negative pressure ink boxes in the multiple color groups are independently connected with the same negative pressure source; the positive pressure adjusting module in each color group independently adjusts the positive pressure to reach a preset positive pressure threshold, and the negative pressure adjusting module in each color group independently adjusts the negative pressure to reach a preset negative pressure threshold; the ink supply module is used for supplying ink to the positive pressure ink box; a pressure difference is formed between the positive pressure ink box and the negative pressure ink box, and the ink in the positive pressure ink box flows through the multiple nozzle modules and flows into the negative pressure ink box under the drive of the pressure difference; the ink return module is in communication with the negative pressure ink box and the positive pressure ink box respectively, so that the ink in the negative pressure ink box flows back to the positive pressure ink box.

Description

Technical Field

[0001] This utility model relates to the field of digital printing equipment technology, and in particular to a positive and negative pressure circulating ink supply system suitable for digital printing equipment. Background Technology

[0002] Currently, printheads in digital printing equipment with high resolution and high-frequency ignition characteristics usually require circulating ink supply, that is, the ink inside the printhead needs to flow, and this flow requires stable flow rate and pressure.

[0003] Most digital printing devices on the market use diaphragm pumps to directly power the ink flow within the printhead. Because diaphragm pumps are pulsating, this results in pressure fluctuations in the ink flow within the printhead, thus affecting the printing quality of the digital printing device.

[0004] However, in the case of multiple printheads, traditional ink supply systems still have some drawbacks: (1) Using a single pump to supply ink, and then using a split pipe to distribute the ink to each printhead, makes it difficult for traditional ink supply systems to achieve uniformity.

[0005] (2) Each printhead is equipped with a diaphragm pump. Although this design can achieve uniformity, it will make the installation and control of the traditional ink supply system more complicated and increase the cost of the traditional ink supply system. Therefore, the one-to-one direct ink supply of the diaphragm pump is easy to reduce the printing effect and is not conducive to cost control. Utility Model Content

[0006] The circulating ink supply system provided by this utility model aims to solve at least some of the defects of existing ink supply systems.

[0007] This utility model provides a circulating ink supply system. The circulating ink supply system includes: One positive pressure source, one negative pressure source, and multiple independently configured color groups; The color group includes a positive pressure adjustment module, a positive pressure ink cartridge, multiple printhead modules, a negative pressure adjustment module, a negative pressure ink cartridge, an ink return module, and an ink filling module; Each of the positive pressure ink cartridges in the multiple color groups is independently connected to the same positive pressure source, and each of the negative pressure ink cartridges in the multiple color groups is independently connected to the same negative pressure source. The positive pressure adjustment module in each color group is configured to independently adjust the positive pressure in the corresponding positive pressure ink cartridge to reach a preset positive pressure threshold, and the negative pressure adjustment module in each color group is configured to independently adjust the negative pressure in the corresponding negative pressure ink cartridge to reach a preset negative pressure threshold. The ink supply module is connected to the positive pressure ink cartridge so that the ink supply module supplies ink to the positive pressure ink cartridge; The positive pressure ink cartridge is connected to one end of the plurality of printhead modules, and the other end of the plurality of printhead modules is connected to the negative pressure ink cartridge. At this time, the positive pressure in the positive pressure ink cartridge and the negative pressure in the negative pressure ink cartridge can form a pressure difference between the two ends of the plurality of printhead modules, so that the ink in the positive pressure ink cartridge flows through the printhead module and into the negative pressure ink cartridge under the action of the pressure difference. The ink return module is connected to both the negative pressure ink cartridge and the positive pressure ink cartridge, so that the ink in the negative pressure ink cartridge flows back to the positive pressure ink cartridge.

[0008] In some embodiments, the positive pressure regulating module includes at least: Positive pressure intake valve, positive pressure release valve, and first pressure sensor; The positive pressure intake valve is connected to the positive pressure source and the positive pressure ink cartridge respectively, and the positive pressure release valve is connected to the outside atmosphere and the positive pressure ink cartridge respectively; The first pressure sensor is used to detect the positive pressure inside the positive pressure cartridge and generate a first adjustment signal for controlling the positive pressure intake valve and the positive pressure release valve to switch between an open state and a closed state.

[0009] In some embodiments, when the positive pressure intake valve is switched to the open state, the positive pressure source and the positive pressure ink cartridge are interconnected. When the positive pressure intake valve is switched to the closed state, the positive pressure source and the positive pressure ink cartridge are isolated from each other; When the positive pressure relief valve is switched to the open state, the positive pressure ink cartridge is connected to the outside atmosphere; When the positive pressure release valve is switched to the closed state, the positive pressure ink cartridge is isolated from the outside atmosphere.

[0010] In some embodiments, when the positive pressure inside the positive pressure cartridge is less than the positive pressure threshold, the first adjustment signal controls the positive pressure intake valve to switch to the open state and controls the positive pressure release valve to switch to the closed state, so that the positive pressure gas in the positive pressure source enters the positive pressure cartridge to form positive pressure air until the positive pressure inside the positive pressure cartridge reaches the preset positive pressure threshold.

[0011] In some embodiments, when the positive pressure inside the positive pressure cartridge is greater than the positive pressure threshold, the first adjustment signal controls the positive pressure release valve to switch to the open state and controls the positive pressure air inlet valve to switch to the closed state, so that the positive pressure air inside the positive pressure cartridge is discharged to the outside atmosphere until the positive pressure inside the positive pressure cartridge reaches the preset positive pressure threshold.

[0012] In some embodiments, the negative pressure regulating module includes at least: Negative pressure suction valve, negative pressure release valve, and second pressure sensor; The negative pressure suction valve is connected to the negative pressure source and the negative pressure ink cartridge respectively, and the negative pressure release valve is connected to the outside atmosphere and the negative pressure ink cartridge respectively. The second pressure sensor is used to detect the negative pressure inside the negative pressure ink cartridge and generate a second adjustment signal for controlling the switching between the negative pressure suction valve and the negative pressure release valve in an open or closed state.

[0013] In some embodiments, when the negative pressure suction valve is switched to the open state, the negative pressure source and the negative pressure ink cartridge are interconnected. When the negative pressure suction valve is switched to the closed state, the negative pressure source and the negative pressure ink cartridge are isolated from each other; When the negative pressure release valve is switched to the open state, the negative pressure ink cartridge is connected to the outside atmosphere; When the negative pressure release valve is switched to the closed state, the negative pressure ink cartridge is isolated from the outside atmosphere.

[0014] In some embodiments, when the negative pressure inside the negative pressure ink cartridge is greater than the negative pressure threshold, the second adjustment signal controls the negative pressure release valve to switch to the open state and controls the negative pressure suction valve to switch to the closed state, so that outside air enters the negative pressure ink cartridge to form negative pressure air until the negative pressure inside the negative pressure ink cartridge reaches the preset negative pressure threshold.

[0015] In some embodiments, when the negative pressure in the negative pressure ink cartridge is less than the negative pressure threshold, the second adjustment signal controls the negative pressure extraction valve to switch to the open state and controls the negative pressure release valve to switch to the closed state, so that the negative pressure air in the negative pressure ink cartridge is extracted by the negative pressure source until the negative pressure in the negative pressure ink cartridge reaches the preset negative pressure threshold.

[0016] In some embodiments, the nozzle module includes at least: A positive pressure switch valve, a negative pressure switch valve, and a printhead, wherein the printhead has an ink inlet and an ink outlet, the positive pressure switch valve is connected to the ink inlet of the printhead and the positive pressure ink cartridge respectively, and the negative pressure switch valve is connected to the ink outlet of the printhead and the negative pressure ink cartridge respectively. When both the positive pressure switch valve and the negative pressure switch valve are opened, the positive pressure ink cartridge, the printhead, and the negative pressure ink cartridge are interconnected to form a pressure difference, so that the ink in the positive pressure ink cartridge flows into the printhead through the ink inlet through the pressure difference, and flows out from the ink outlet of the printhead into the negative pressure ink cartridge.

[0017] At least one beneficial effect of the circulating ink supply system provided by this utility model embodiment is that the circulating ink supply system includes a positive pressure source, a negative pressure source, and multiple independently configured color groups. Each color group includes a positive pressure adjustment module, a positive pressure ink cartridge, multiple printhead modules, a negative pressure adjustment module, a negative pressure ink cartridge, an ink return module, and an ink supply module. The positive pressure ink cartridges in the multiple color groups are all independently connected to the same positive pressure source, and the negative pressure ink cartridges in the multiple color groups are all independently connected to the same negative pressure source. This design allows the circulating ink supply system to meet the needs of multiple color groups simultaneously using only one positive pressure source and one negative pressure source, thereby reducing the installation complexity and control complexity of the circulating ink supply system, and thus reducing the cost of the circulating ink supply system. Each color group's positive pressure adjustment module is configured to independently adjust the positive pressure in its corresponding positive pressure cartridge to a preset positive pressure threshold, and each color group's negative pressure adjustment module is configured to independently adjust the negative pressure in its corresponding negative pressure cartridge to a preset negative pressure threshold. This design allows for independent setting of the positive and negative pressures required for ink flow across multiple printhead modules, ensuring uniform ink flow. The positive pressure in the positive pressure cartridge and the negative pressure in the negative pressure cartridge can create a pressure difference across multiple printhead modules, causing the ink in the positive pressure cartridge to flow through the printhead module and into the negative pressure cartridge under the influence of this pressure difference. Therefore, this circulating ink supply system uses positive and negative pressure as the driving force for ink flow within the printhead modules, and the positive and negative pressures are pulse-free, resulting in smoother ink flow within the printhead modules. Attached Figure Description

[0018] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements having the same reference numerals in the drawings are designated as the same elements. Unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0019] Figure 1 This is a connection diagram of the circulating ink supply system provided in this embodiment of the utility model; Figure 2 This is a schematic diagram showing the connection between the color group and the positive pressure source, negative pressure source, degassing negative pressure source, compressed air and pressure regulating valve provided in this embodiment of the utility model; Figure 3 This is a schematic diagram of the ink flow between the positive pressure ink cartridge, the negative pressure ink cartridge, and the printhead according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the flow of ink between the positive pressure ink cartridge, the negative pressure ink cartridge, and the ink return module provided in this embodiment of the utility model; Figure 5This is a connection diagram of the positive pressure source, intake switch valve, intake pump, air filter, positive pressure source release valve and positive pressure source exhaust flow restrictor valve provided in this embodiment of the utility model; Figure 6 This is a connection diagram of the negative pressure source, the air extraction switch valve, the air extraction pump, the negative pressure source release valve, and the negative pressure source air inlet flow limiting valve provided in this embodiment of the utility model.

[0020] Explanation of reference numerals in the attached diagram: 100, Circulating ink supply system; 1, Positive pressure source; 101, Inlet switch valve; 102, Inlet pump; 103, Air filter; 104, Positive pressure source release valve; 105, Positive pressure source exhaust flow restrictor valve; 106, Positive pressure source pressure sensor; 2, Negative pressure source; 201, Extraction switch valve; 202, Extraction pump; 203, Negative pressure source release valve; 204, Negative pressure source inlet flow restrictor valve; 205, Negative pressure source pressure sensor; 3, Color group; 31, Positive pressure ink cartridge; 32, Negative pressure ink cartridge; 331, Positive pressure inlet valve; 332, Positive pressure release valve; 333, First pressure sensor; 334, Positive pressure inlet flow restrictor valve; 335, Positive pressure exhaust flow restrictor valve; 341, Negative pressure extraction valve; 342, Negative pressure release valve; 34 3. Second pressure sensor; 344. Negative pressure exhaust flow limiting valve; 345. Negative pressure air intake flow limiting valve; 351. Positive pressure switch valve; 352. Negative pressure switch valve; 353. Printhead; 354. First filter; 361. First liquid level detector; 362. Ink return switch valve; 363. Ink return pump; 364. Degassing lung; 365. Degassing negative pressure source; 371. Second liquid level detector; 372. Ink filling switch valve; 373. Ink filling pump; 374. Ink tank; 375. Second filter; 381. Ink pressure switch valve; 382. Ink pressure release valve; 383. Pressure regulating valve; 384. Compressed air; 3651. Degassing negative pressure source extraction switch valve; 3652. Degassing negative pressure source extraction pump; 3653. Degassing negative pressure source pressure sensor. Detailed Implementation

[0021] The present invention will now be described in detail with reference to specific embodiments. It should be emphasized that the following description is merely exemplary and is not intended to limit the scope and application of the present invention.

[0022] It should be noted that, unless otherwise explicitly specified and limited, the terms "flow through," "inflow," "eject," "inside," etc., used in this specification indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model. The terms "installation," "fitting," "connection," and "fixing" should be interpreted broadly. For example, "connection" can be a fixed connection or a detachable connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. "Fixing" can be bolt fixing, snap-fit ​​fixing, or glue fixing. The terms "first," "second," "third," and "fourth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," "third," and "fourth" may explicitly or implicitly include one or more of that feature. "A plurality" or "several" means two or more. In addition, "and / or" includes any and all combinations of one or more of the related listed items. For those skilled in the art, the specific meaning of the above terms in this utility model can be understood according to the specific circumstances. To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] In this embodiment, the specific shape, structure, and size of the "circulating ink supply system" are not limited. Those skilled in the art can selectively use any suitable implementation method according to actual needs.

[0024] To facilitate reader understanding, in the appendix Figure 1 To be continued Figure 6 Hollow arrows are used to indicate the direction of gas flow, while solid arrows are used to indicate the direction of ink flow.

[0025] Please see Figures 1-6 The circulating ink supply system 100 includes: a positive pressure source 1, a negative pressure source 2, multiple independently configured color groups 3, an air inlet switch valve 101, an air inlet pump 102, an air filter 103, a positive pressure source release valve 104, a positive pressure source exhaust flow restrictor valve 105, a positive pressure source pressure sensor 106, an air extraction switch valve 201, an air extraction pump 202, a negative pressure source release valve 203, a negative pressure source air inlet flow restrictor valve 204, and a negative pressure source pressure sensor 205.

[0026] It should be noted that positive pressure source 1 is responsible for providing positive pressure gas, which is a type of compressed air.

[0027] The intake switch valve 101 is connected to one end of the intake pump 102 and the positive pressure source 1, respectively. The air filter 103 is connected to the other end of the intake pump 102 and the outside atmosphere. The positive pressure source release valve 104 is connected to one end of the positive pressure source exhaust flow restrictor valve 105 and the positive pressure source 1, and the other end of the positive pressure source exhaust flow restrictor valve 105 is connected to the outside atmosphere.

[0028] In addition, the positive pressure source pressure sensor 106 is used to detect the pressure value of the positive pressure gas in the positive pressure source 1.

[0029] Furthermore, when the positive pressure source pressure sensor 106 detects that the pressure value of the positive pressure gas in the positive pressure source 1 is less than the preset first set value, the intake pump 102 starts to work and simultaneously opens the intake switch valve 101 to allow outside air to enter the positive pressure source 1, thereby increasing the positive pressure of the positive pressure gas in the positive pressure source 1 until the pressure value of the positive pressure gas in the positive pressure source 1 reaches the preset first set value. Then, the intake switch valve 101 is closed, and finally the intake pump 102 stops working.

[0030] To further explain, when the positive pressure source pressure sensor 106 detects that the pressure value of the positive pressure gas in the positive pressure source 1 is greater than the preset first set value, the positive pressure source release valve 104 is opened to allow the positive pressure gas in the positive pressure source 1 to be discharged to the outside atmosphere, thereby reducing the pressure of the positive pressure gas in the positive pressure source 1 until the pressure value of the positive pressure gas in the positive pressure source 1 reaches the preset first set value, and then the positive pressure source release valve 104 is closed.

[0031] Specifically, the function of the positive pressure source exhaust flow limiting valve 105 is to limit the speed at which the positive pressure gas in the positive pressure source 1 is discharged to the outside atmosphere, so as to buffer the pressure adjustment process in the positive pressure source 1 (or avoid pressure adjustment overshoot in the positive pressure source 1).

[0032] In this embodiment, the first set value is usually set to 15 kPa (kPa is kilopascal), which is 10 kPa higher than the positive pressure of the positive air in the positive pressure ink cartridge 31. This design allows the positive gas in the positive pressure source 1 to stably and quickly increase the positive pressure of the positive air in the positive pressure ink cartridge 31, thereby making the positive pressure in the positive pressure ink cartridge 31 non-pulsating.

[0033] It is understandable that the air extraction switch valve 201 is connected to one end of the air extraction pump 202 and the negative pressure source 2 respectively, and the other end of the air extraction pump 202 is connected to the outside atmosphere. The negative pressure source release valve 203 is connected to one end of the negative pressure source inlet flow restriction valve 204 and the negative pressure source 2 respectively, and the other end of the negative pressure source inlet flow restriction valve 204 is connected to the outside atmosphere.

[0034] Among them, the negative pressure source pressure sensor 205 is used to detect the gas pressure value of the positive pressure gas in the negative pressure source 2.

[0035] In addition, when the negative pressure source pressure sensor 205 detects that the air pressure value in the negative pressure source 2 is less than the preset second set value, the air pump 202 starts to work and opens the air pump switch valve 201 at the same time, so that the air in the negative pressure source 2 is drawn out to the outside atmosphere by the air pump 202, thereby increasing the negative pressure in the negative pressure source until the air pressure value in the negative pressure source 2 reaches the preset second set value. Then the air pump switch valve 201 is closed and finally the air pump 202 stops working.

[0036] In addition, when the negative pressure source pressure sensor 205 detects that the air pressure value in the negative pressure source 2 is greater than the preset second set value, the negative pressure source release valve 203 is opened to allow outside air to enter the negative pressure source 2, thereby reducing the negative pressure in the negative pressure source 2 until the air pressure value in the negative pressure source 2 reaches the preset second set value, and then the negative pressure source release valve 203 is closed.

[0037] Specifically, the function of the negative pressure source inlet flow limiting valve 204 is to limit the speed at which outside air enters the negative pressure source 2, so as to buffer the pressure adjustment process in the negative pressure source 2 (or prevent the pressure adjustment in the negative pressure source 2 from overshooting).

[0038] To further explain, the second setting value is usually set to -20KPA, which is -10KPA higher than the negative pressure of the negative air in the negative pressure ink cartridge 32. This design enables the negative pressure in the negative pressure source 2 to stably and quickly increase the negative pressure of the negative air in the negative pressure ink cartridge 32, thereby ensuring that the negative pressure in the negative pressure ink cartridge 32 is not pulsating.

[0039] In this embodiment, color group 3 includes a positive pressure adjustment module, a positive pressure ink cartridge 31, multiple printhead modules, a negative pressure adjustment module, a negative pressure ink cartridge 32, an ink return module, and an ink filling module.

[0040] In this design, the positive pressure ink cartridges 31 in multiple color groups 3 are all independently connected to the same positive pressure source 1, and the negative pressure ink cartridges 32 in multiple color groups 3 are all independently connected to the same negative pressure source 2. This design allows the circulating ink supply system 100 to meet the needs of multiple color groups simultaneously using only one positive pressure source and one negative pressure source, thereby reducing the installation complexity and control complexity of the circulating ink supply system 100, and thus reducing the cost of the circulating ink supply system 100.

[0041] In addition, the positive pressure adjustment module in each color group 3 is configured to independently adjust the positive pressure in the corresponding positive pressure ink cartridge 31 to reach a preset positive pressure threshold, and the negative pressure adjustment module in each color group 3 is configured to independently adjust the negative pressure in the corresponding negative pressure ink cartridge 32 to reach a preset negative pressure threshold. This design allows the positive and negative pressures required when ink flows in multiple printhead modules to be set independently, thereby ensuring the uniformity of ink flow in multiple printhead modules.

[0042] Furthermore, this positive pressure threshold is 10 kPa lower than the first set value mentioned above, while the first set value is 15 kPa, therefore the positive pressure threshold is 5 kPa.

[0043] It should be noted that this negative pressure threshold is -10 kPa higher than the second setting value mentioned above, and the second setting value is -20 kPa. Therefore, this negative pressure threshold is -10 kPa.

[0044] Specifically, the ink supply module is connected to the positive pressure ink cartridge 31 so that the ink supply module supplies ink to the positive pressure ink cartridge 31, and the color of the ink corresponds to the color of each color group 3 (for example, in a red color group, the color of the ink is the corresponding red).

[0045] To further explain, the positive pressure ink cartridge 31 is connected to one end of the multiple printhead 353 modules, and the other end of the multiple printhead 353 modules is connected to the negative pressure ink cartridge 32. At this time, the positive pressure in the positive pressure ink cartridge 31 and the negative pressure in the negative pressure ink cartridge 32 can form a pressure difference between the two ends of the multiple printhead 353 modules, so that the ink in the positive pressure ink cartridge 31 flows through the printhead 353 modules and into the negative pressure ink cartridge 32 under the action of the pressure difference. Therefore, the circulating ink supply system 100 uses positive pressure and negative pressure as the driving force for the ink to flow in the printhead module, and there is no pulse in the positive pressure and negative pressure. This design can make the ink flow in the printhead module more stable.

[0046] In this embodiment, the ink return module is connected to both the negative pressure ink cartridge 32 and the positive pressure ink cartridge 31, so that the ink in the negative pressure ink cartridge 32 flows back to the positive pressure ink cartridge 31.

[0047] In summary, the positive pressure ink cartridge 31 is connected to one end of multiple printhead modules, and the other end of multiple printhead modules is connected to the negative pressure ink cartridge 32. The ink return module is connected to both the negative pressure ink cartridge 32 and the positive pressure ink cartridge 31. This allows ink to flow from the positive pressure ink cartridge 31 through multiple printhead modules, the negative pressure ink cartridge 32, and the ink return module in sequence, and then flow back into the positive pressure ink cartridge 31, thus forming a closed-loop circulating ink supply system.

[0048] In some embodiments, such as Figures 1-6 As shown, the positive pressure regulating module includes at least: a positive pressure intake valve 331, a positive pressure release valve 332, and a first pressure sensor 333.

[0049] The positive pressure intake valve 331 is connected to the positive pressure source 1 and the positive pressure ink cartridge 31, respectively, and the positive pressure release valve 332 is connected to the outside atmosphere and the positive pressure ink cartridge 31, respectively.

[0050] In addition, the first pressure sensor 333 is used to detect the positive pressure inside the positive pressure ink cartridge 31 and generate a first adjustment signal for controlling the positive pressure intake valve 331 and the positive pressure release valve 332 to switch between the open and closed states.

[0051] In some embodiments, such as Figures 1-6 As shown, when the positive pressure intake valve 331 is switched to the open state, the positive pressure source 1 and the positive pressure ink cartridge 31 are connected to each other.

[0052] It should be noted that when the positive pressure intake valve 331 is switched to the closed state, the positive pressure source 1 and the positive pressure ink cartridge 31 are isolated from each other.

[0053] It is understandable that when the positive pressure relief valve 332 is switched to the open state, the positive pressure ink cartridge 31 is connected to the outside atmosphere.

[0054] Specifically, when the positive pressure relief valve 332 is switched to the closed state, the positive pressure ink cartridge 31 is isolated from the outside atmosphere.

[0055] In some embodiments, such as Figures 1-6 As shown, when the positive pressure inside the positive pressure ink cartridge 31 is less than the positive pressure threshold, the first adjustment signal controls the positive pressure intake valve 331 to switch to the open state and controls the positive pressure release valve 332 to switch to the closed state, so that the positive pressure gas in the positive pressure source 1 enters the positive pressure ink cartridge 31 to form positive pressure air until the positive pressure inside the positive pressure ink cartridge 31 reaches the preset positive pressure threshold.

[0056] It should be noted that when the positive pressure inside the positive pressure cartridge 31 is greater than the positive pressure threshold, the first adjustment signal controls the positive pressure release valve 332 to switch to the open state and controls the positive pressure air inlet valve 331 to switch to the closed state, so that the positive pressure air inside the positive pressure cartridge 31 is discharged to the outside atmosphere until the positive pressure inside the positive pressure cartridge 31 reaches the preset positive pressure threshold.

[0057] Understandably, when the positive pressure inside the positive pressure cartridge 31 equals the positive pressure threshold, the first adjustment signal controls both the positive pressure intake valve 331 and the positive pressure release valve 332 to switch to the closed state.

[0058] In this embodiment, the positive pressure ink cartridge 31 is responsible for storing ink and has a positive pressure inside that can force the ink into the printhead module for circulation; the lower part of the cavity of the positive pressure ink cartridge 31 contains ink, while the upper part of the cavity of the positive pressure ink cartridge 31 contains positive pressure air; the positive pressure air in the positive pressure ink cartridge 31 is located above the ink in the positive pressure ink cartridge 31, and both occupy half of the volume of the positive pressure ink cartridge 31.

[0059] Combination Figures 1-6The adjustment process of positive pressure in positive pressure cartridge 31 is described in detail as follows: When the first pressure sensor 333 detects that the positive pressure in positive pressure cartridge 31 is less than the preset positive pressure threshold, the positive pressure intake valve 331 is opened to obtain positive pressure gas from positive pressure source 1 to increase the positive pressure air pressure in positive pressure cartridge 31, so that the positive pressure in positive pressure cartridge 31 reaches the preset positive pressure threshold and then the positive pressure intake valve 331 is closed; When the first pressure sensor 333 detects that the positive pressure in positive pressure cartridge 31 is greater than the positive pressure threshold, the positive pressure release valve 332 is opened to exhaust gas to release the positive pressure air pressure in positive pressure cartridge 31, so that the positive pressure in positive pressure cartridge 31 reaches the preset positive pressure threshold and then the positive pressure release valve 332 is closed.

[0060] In some embodiments, such as Figures 1-6 As shown, the positive pressure regulating module may also include: a positive pressure intake flow restrictor valve 334 and a positive pressure exhaust flow restrictor valve 335.

[0061] The positive pressure intake flow limiting valve 334 is disposed between the positive pressure intake valve 331 and the positive pressure ink cartridge 31, and the positive pressure intake flow limiting valve 334 is used to limit the speed at which the positive pressure gas in the positive pressure source 1 enters the positive pressure ink cartridge 31.

[0062] In addition, the positive pressure exhaust flow limiting valve 335 is disposed between the positive pressure release valve 332 and the positive pressure ink cartridge 31, and the positive pressure exhaust flow limiting valve 335 is used to limit the speed at which the positive pressure air in the positive pressure ink cartridge 31 is discharged from the positive pressure ink cartridge 31 to the outside atmosphere.

[0063] In summary, the positive pressure intake flow restrictor valve 334 and the positive pressure exhaust flow restrictor valve 335 are used to buffer the positive pressure adjustment process in the positive pressure cartridge 31 (or to prevent overshoot of the positive pressure adjustment in the positive pressure cartridge 31).

[0064] In some embodiments, such as Figures 1-6 As shown, the negative pressure regulating module includes at least: a negative pressure suction valve 341, a negative pressure release valve 342, and a second pressure sensor 343.

[0065] Specifically, the negative pressure suction valve 341 is connected to the negative pressure source 2 and the negative pressure ink cartridge 32 respectively, and the negative pressure release valve 342 is connected to the outside atmosphere and the negative pressure ink cartridge 32 respectively.

[0066] To further explain, the second pressure sensor 343 is used to detect the negative pressure inside the negative pressure ink cartridge 32 and generate a second adjustment signal for controlling the switching between the negative pressure suction valve 341 and the negative pressure release valve 342 in an open or closed state.

[0067] In some embodiments, such as Figures 1-6 As shown, when the negative pressure suction valve 341 is switched to the open state, the negative pressure source 2 and the negative pressure ink cartridge 32 are connected to each other.

[0068] When the negative pressure suction valve 341 is switched to the closed state, the negative pressure source 2 and the negative pressure ink cartridge 32 are isolated from each other.

[0069] In addition, when the negative pressure relief valve 342 is switched to the open state, the negative pressure ink cartridge 32 is connected to the outside atmosphere.

[0070] In addition, when the negative pressure relief valve 342 is switched to the closed state, the negative pressure ink cartridge 32 is isolated from the outside atmosphere.

[0071] In some embodiments, such as Figures 1-6 As shown, when the negative pressure inside the negative pressure ink cartridge 32 is greater than the negative pressure threshold, the second adjustment signal controls the negative pressure release valve 342 to switch to the open state and controls the negative pressure suction valve 341 to switch to the closed state, so that the outside atmosphere enters the negative pressure ink cartridge 32 to form negative pressure air, until the negative pressure inside the negative pressure ink cartridge 32 reaches the preset negative pressure threshold.

[0072] It should be noted that when the negative pressure inside the negative pressure ink cartridge 32 is less than the negative pressure threshold, the second adjustment signal controls the negative pressure suction valve 341 to switch to the open state and controls the negative pressure release valve 342 to switch to the closed state, so that the negative pressure air inside the negative pressure ink cartridge 32 is extracted by the negative pressure source 2 until the negative pressure inside the negative pressure ink cartridge 32 reaches the preset negative pressure threshold.

[0073] Understandably, when the negative pressure inside the negative pressure cartridge 32 equals the negative pressure threshold, the second adjustment signal controls both the negative pressure release valve 342 and the negative pressure suction valve 341 to switch to the closed state.

[0074] Combination Figures 1-6 The following describes in detail the adjustment process of negative pressure in negative pressure ink cartridge 32: When the second pressure sensor 343 detects that the negative pressure of the negative air in negative pressure ink cartridge 32 is less than the preset negative pressure threshold, the negative pressure suction valve 341 is opened to discharge the negative pressure air to the negative pressure tank assembly to increase the negative pressure, until the negative pressure of the negative air in negative pressure ink cartridge 32 reaches the preset negative pressure threshold, and then the negative pressure suction valve 341 is closed; When the second pressure sensor 343 detects that the negative pressure of the negative air in negative pressure ink cartridge 32 is greater than the preset negative pressure threshold, the negative pressure release valve 342 is opened to draw in outside atmosphere to release the negative pressure, until the negative pressure of the negative air in negative pressure ink cartridge 32 reaches the preset negative pressure threshold, and then the negative pressure release valve 342 is closed.

[0075] In this embodiment, the negative pressure ink cartridge 32 is responsible for storing ink, and the negative pressure ink cartridge 32 has a negative pressure that provides flow for ink from the printhead module into the negative pressure ink cartridge 32. The lower part of the cavity of the negative pressure ink cartridge 32 contains ink, while the upper part of the cavity contains negative pressure air. The negative pressure air in the negative pressure ink cartridge 32 is located above the ink in the negative pressure ink cartridge 32, and both occupy half the volume of the negative pressure ink cartridge 32.

[0076] In some embodiments, such as Figures 1-6 As shown, the negative pressure regulating module may also include: a negative pressure exhaust flow restrictor valve 344 and a negative pressure intake flow restrictor valve 345.

[0077] The negative pressure exhaust flow limiting valve 344 is located between the negative pressure air extraction valve 341 and the negative pressure ink cartridge 32, and the negative pressure exhaust flow limiting valve 344 is used to limit the speed at which the negative pressure air in the negative pressure ink cartridge 32 is extracted by the negative pressure source 2.

[0078] In addition, the negative pressure intake flow restriction valve 345 is located between the negative pressure release valve 342 and the negative pressure ink cartridge 32, and the negative pressure intake flow restriction valve 345 is used to limit the speed at which outside air enters the negative pressure ink cartridge 32.

[0079] In summary, the negative pressure exhaust flow limiting valve 344 and the negative pressure intake flow limiting valve 345 are used to buffer the negative pressure adjustment process in the negative pressure ink cartridge 32 (or to prevent overshoot of the negative pressure adjustment in the negative pressure ink cartridge 32).

[0080] In some embodiments, such as Figures 1-6 As shown, the nozzle module includes at least: a positive pressure switching valve 351, a negative pressure switching valve 352, and a nozzle 353.

[0081] The printhead 353 has an ink inlet and an ink outlet. The positive pressure switch valve 351 is connected to the ink inlet of the printhead 353 and the positive pressure ink cartridge 31, respectively, and the negative pressure switch valve 352 is connected to the ink outlet of the printhead 353 and the negative pressure ink cartridge 32, respectively.

[0082] In addition, when both the positive pressure switch valve 351 and the negative pressure switch valve 352 are opened, the positive pressure ink cartridge 31, the printhead 353 and the negative pressure ink cartridge 32 are interconnected to form a pressure difference, so that the ink in the positive pressure ink cartridge 31 flows into the printhead 353 through the ink inlet of the printhead 353 through the pressure difference, and flows out from the ink outlet of the printhead 353 into the negative pressure ink cartridge 32.

[0083] Furthermore, both the positive pressure switch valve 351 and the negative pressure switch valve 352 in the printhead module are in the open state during normal cyclic operation. The ink in the positive pressure ink cartridge 31 flows into the ink inlet of the printhead 353 through the positive pressure switch valve 351 and the first filter 354, and then flows into the negative pressure ink cartridge 32 from the ink outlet of the printhead 353 through the negative pressure switch valve 352. This indicates that the flow of ink between the positive pressure ink cartridge 31, the printhead 353 and the negative pressure ink cartridge 32 is driven by the pressure difference formed by the positive and negative pressures.

[0084] In some embodiments, such as Figures 1-6 As shown, the ink return module includes at least: a first liquid level detector 361, an ink return switch valve 362, and an ink return pump 363.

[0085] It should be noted that the ink return switch valve 362 is connected to one end of the ink return pump 363 and the negative pressure ink cartridge 32, and the other end of the ink return pump 363 is connected to the positive pressure ink cartridge 31.

[0086] It is understandable that the ink return switch valve 362 is always in the open state during normal cycle operation, and the first liquid level detector 361 is located inside the negative pressure ink cartridge 32.

[0087] The first liquid level detector 361 is used to detect the first liquid level value of the ink in the negative pressure ink cartridge 32, and the third adjustment signal is generated by the PLC (Programmable Logic Controller) to control the ink return pump 363 to work according to the first liquid level value detected by the first liquid level detector 361.

[0088] In addition, when the first liquid level of the ink in the negative pressure ink cartridge 32 is less than the preset first liquid level threshold (the first liquid level threshold is the lowest liquid level of the ink in the negative pressure ink cartridge 32), the third adjustment signal controls the return ink pump 363 to operate at low power, so that the flow rate of the ink from the positive pressure ink cartridge 31 through the printhead 353 and into the negative pressure ink cartridge 32 is greater than the flow rate of the ink pump 363 from the negative pressure ink cartridge 32, thereby causing the first liquid level of the ink in the negative pressure ink cartridge 32 to gradually increase until the first liquid level of the ink in the negative pressure ink cartridge 32 is greater than the preset first liquid level threshold.

[0089] Furthermore, when the first liquid level of the ink in the negative pressure ink cartridge 32 is greater than the preset second liquid level threshold (the second liquid level threshold is the highest liquid level of the ink in the negative pressure ink cartridge 32), the third adjustment signal controls the return ink pump 363 to operate at high power, so that the flow rate of ink from the positive pressure ink cartridge 31 through the printhead 353 and into the negative pressure ink cartridge 32 is less than the flow rate of ink drawn out of the negative pressure ink cartridge 32 by the return ink pump 363, thereby causing the first liquid level of the ink in the negative pressure ink cartridge 32 to gradually decrease until the first liquid level of the ink in the negative pressure ink cartridge 32 is less than the preset second liquid level threshold.

[0090] In this embodiment, the first liquid level detector 361 is a dual liquid level detector. Therefore, the first liquid level detector 361 has a low liquid level detection float and a high liquid level detection float, while the negative pressure ink cartridge 32 is provided with a low liquid level switch corresponding to the first liquid level threshold and a high liquid level switch corresponding to the second liquid level threshold.

[0091] In summary, when the low-level detection float in the first level detector 361 triggers the low-level switch, the ink return pump 363 operates at a lower power to gradually increase the first level value of the ink in the negative pressure ink cartridge 32 to a level greater than the first level threshold. Only after the high-level detection float in the first level detector 361 triggers the high-level switch does the ink return pump 363 operate at a higher power to gradually decrease the first level value of the ink in the negative pressure ink cartridge 32 to a level less than the second level threshold. When the low-level detection float in the first level detector 361 triggers the low-level switch, the ink return pump 363 switches back to low-power operation. This process repeats to maintain the first level value of the ink in the negative pressure ink cartridge 32 within a certain level range (this level range can be understood as between the highest and lowest level values).

[0092] It should be noted that during the circulation process of ink flowing back from negative pressure ink cartridge 32 to positive pressure ink cartridge 31, ink return pump 363 is used to provide power for the ink.

[0093] In some embodiments, such as Figures 1-6 As shown, the ink return module may also include a degassing component.

[0094] The function of the degassing component is to extract air from the ink to improve the stability of the printed ink output.

[0095] In addition, the degassing component includes a degassing lung 364 and a degassing negative pressure source 365 that provides negative pressure to the degassing lung 364.

[0096] In addition, the function of the degassing lung 364 is to separate the air from the ink through high negative pressure. The degassing negative pressure source 365 is connected to the degassing negative pressure source pressure sensor 3653. When the air pressure in the degassing negative pressure source 365 is less than the set value, the degassing negative pressure source suction pump 3652 works and the degassing negative pressure source suction switch valve 3651 is opened until the air pressure in the degassing negative pressure source 365 reaches the set value and closes the degassing negative pressure source suction switch valve 3651. The degassing negative pressure source suction pump 3652 stops working. Usually, a negative pressure of about -90KPA is required. A negative pressure of about -90KPA needs to be achieved by connecting two degassing negative pressure source suction pumps 3652 in series. The negative pressure does not need to be too accurate. A fluctuation of -5KPA is allowed.

[0097] In some embodiments, such as Figures 1-6 As shown, the ink filling module includes at least: a second liquid level detector 371, an ink filling switch valve 372, an ink filling pump 373, and an ink tank 374.

[0098] Understandably, the ink filling switch valve 372 is connected to one end of the ink filling pump 373 and the positive pressure ink cartridge 31, respectively, and the other end of the ink filling pump 373 is connected to the ink tank 374.

[0099] The second liquid level detector 371 is installed inside the positive pressure ink cartridge 31.

[0100] In addition, the second liquid level detector 371 is used to detect the second liquid level value of the ink in the positive pressure ink cartridge 31, and generates a fourth adjustment signal through the PLC (Programmable Logic Controller) to control the ink filling switch valve 372 and the ink filling pump 373 to work according to the second liquid level value detected by the second liquid level detector 371.

[0101] It should be noted that when the second liquid level value of the ink in the positive pressure ink cartridge 31 is less than the preset third liquid level threshold (the third liquid level threshold is the lowest liquid level value of the ink in the positive pressure ink cartridge 31), the fourth adjustment signal controls the ink filling switch valve 372 and the ink filling pump 373 to open, so that the ink in the ink tank 374 is drawn into the positive pressure ink cartridge 31 until the second liquid level value of the ink in the positive pressure ink cartridge 31 is greater than the preset second liquid level threshold.

[0102] Understandably, when the second ink level in the positive pressure ink cartridge 31 is greater than the preset fourth ink level threshold (the fourth ink level threshold is the highest ink level in the positive pressure ink cartridge 31), the fourth adjustment signal controls the entire circulating ink supply system to stop working and triggers an alarm, prompting the operator to check for faults.

[0103] In this embodiment, the second liquid level detector 371 is also a dual liquid level detector.

[0104] Combination Figures 1-6 Here is a detailed description of the ink filling operation of the ink filling module: When the float of the second liquid level detector 371 in the positive pressure ink cartridge 31 triggers the third liquid level threshold (the third liquid level threshold is the lowest liquid level value of ink in the positive pressure ink cartridge 31), the ink filling pump 373 starts to work, and at the same time the ink filling switch valve 372 opens, and ink is drawn from the ink tank 374 into the positive pressure ink cartridge 31. After the float of the second liquid level detector 371 leaves the third liquid level threshold position and then delays for a few seconds, the ink filling pump 373 stops working, and the ink filling switch valve 372 is closed, thus completing the ink filling operation.

[0105] In some embodiments, such as Figures 1-6 As shown, the circulating ink supply system also includes an ink pressing module.

[0106] The ink pressure module is used to provide greater pressure to clear the nozzles when the printhead 353 is clogged. One end is connected to compressed air 384 and the other end is connected to the positive pressure ink cartridge 31. The input air pressure is limited by the pressure regulating valve 383, usually 100 kPa. When ink pressure is needed, the ink pressure switch valve 381 is opened to inject high-pressure gas into the positive pressure ink cartridge 31. The pressure in the positive pressure ink cartridge 31 is transmitted to the inside of the printhead 353 through the ink path channel of the printhead module, thereby forcing the ink to be discharged from the nozzles of the printhead 353, thus clearing the nozzles of the printhead 353.

[0107] In addition, when the circulating ink supply system clears the nozzles of printhead 353 through the ink pressure module, the circulating ink supply needs to be stopped so that the high pressure provided by the ink pressure module can more effectively clear the nozzle blockage of printhead 353.

[0108] Once the nozzles of printhead 353 are cleared, the pressure release valve 382 is opened to release the excessive pressure in the positive pressure ink cartridge 31 until the positive pressure in the positive pressure ink cartridge 31 returns to the preset positive pressure threshold, and then the ink supply cycle can be restarted.

[0109] In summary, the circulating ink supply system provided by this utility model embodiment includes a positive pressure source, a negative pressure source, and multiple independently configured color groups. Each color group includes a positive pressure adjustment module, a positive pressure ink cartridge, multiple printhead modules, a negative pressure adjustment module, a negative pressure ink cartridge, an ink return module, and an ink supply module. The positive pressure ink cartridges in each of the multiple color groups are independently connected to the same positive pressure source, and the negative pressure ink cartridges in each of the multiple color groups are independently connected to the same negative pressure source. This design allows the circulating ink supply system to simultaneously meet the needs of multiple color groups using only one positive pressure source and one negative pressure source, thereby reducing the installation and control complexity of the circulating ink supply system and ultimately reducing its cost. Each color group's positive pressure adjustment module is configured to independently adjust the positive pressure in its corresponding positive pressure cartridge to a preset positive pressure threshold, and each color group's negative pressure adjustment module is configured to independently adjust the negative pressure in its corresponding negative pressure cartridge to a preset negative pressure threshold. This design allows for independent setting of the positive and negative pressures required for ink flow across multiple printhead modules, ensuring uniform ink flow. The positive pressure in the positive pressure cartridge and the negative pressure in the negative pressure cartridge can create a pressure difference across multiple printhead modules, causing the ink in the positive pressure cartridge to flow through the printhead module and into the negative pressure cartridge under the influence of this pressure difference. Therefore, this circulating ink supply system uses positive and negative pressure as the driving force for ink flow within the printhead modules, and the positive and negative pressures are pulse-free, resulting in smoother ink flow within the printhead modules.

[0110] It should be noted that while the preferred embodiments of this utility model are provided in the specification and accompanying drawings, this utility model can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are not intended to impose additional limitations on the content of this utility model; their purpose is to provide a more thorough and comprehensive understanding of the disclosure of this utility model. Furthermore, the above-described technical features can be combined with each other to form various embodiments not listed above, all of which are considered to be within the scope of this utility model specification. Moreover, those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A recirculating ink supply system characterized by, include: One positive pressure source, one negative pressure source, and multiple independently configured color groups; The color group includes a positive pressure adjustment module, a positive pressure ink cartridge, multiple printhead modules, a negative pressure adjustment module, a negative pressure ink cartridge, an ink return module, and an ink filling module; Each of the positive pressure ink cartridges in the multiple color groups is independently connected to the same positive pressure source, and each of the negative pressure ink cartridges in the multiple color groups is independently connected to the same negative pressure source. The positive pressure adjustment module in each color group is configured to independently adjust the positive pressure in the corresponding positive pressure ink cartridge to reach a preset positive pressure threshold, and the negative pressure adjustment module in each color group is configured to independently adjust the negative pressure in the corresponding negative pressure ink cartridge to reach a preset negative pressure threshold. The ink supply module is connected to the positive pressure ink cartridge so that the ink supply module supplies ink to the positive pressure ink cartridge; The positive pressure ink cartridge is connected to one end of the plurality of printhead modules, and the other end of the plurality of printhead modules is connected to the negative pressure ink cartridge. At this time, the positive pressure in the positive pressure ink cartridge and the negative pressure in the negative pressure ink cartridge can form a pressure difference between the two ends of the plurality of printhead modules, so that the ink in the positive pressure ink cartridge flows through the printhead module and into the negative pressure ink cartridge under the action of the pressure difference. The ink return module is connected to both the negative pressure ink cartridge and the positive pressure ink cartridge, so that the ink in the negative pressure ink cartridge flows back to the positive pressure ink cartridge.

2. The circulating ink supply system of claim 1, wherein, The positive pressure regulating module includes at least: Positive pressure intake valve, positive pressure release valve, and first pressure sensor; The positive pressure intake valve is connected to the positive pressure source and the positive pressure ink cartridge respectively, and the positive pressure release valve is connected to the outside atmosphere and the positive pressure ink cartridge respectively; The first pressure sensor is used to detect the positive pressure inside the positive pressure cartridge and generate a first adjustment signal for controlling the positive pressure intake valve and the positive pressure release valve to switch between an open state and a closed state.

3. The circulating ink supply system according to claim 2, characterized in that, When the positive pressure intake valve is switched to the open state, the positive pressure source and the positive pressure ink cartridge are interconnected; When the positive pressure intake valve is switched to the closed state, the positive pressure source and the positive pressure ink cartridge are isolated from each other; When the positive pressure relief valve is switched to the open state, the positive pressure ink cartridge is connected to the outside atmosphere; When the positive pressure release valve is switched to the closed state, the positive pressure ink cartridge is isolated from the outside atmosphere.

4. The circulating ink supply system according to claim 3, characterized in that, When the positive pressure inside the positive pressure ink cartridge is less than the positive pressure threshold, the first adjustment signal controls the positive pressure intake valve to switch to the open state and controls the positive pressure release valve to switch to the closed state, so that the positive pressure gas in the positive pressure source enters the positive pressure ink cartridge to form positive pressure air until the positive pressure inside the positive pressure ink cartridge reaches the preset positive pressure threshold.

5. The circulating ink supply system according to claim 3, characterized in that, When the positive pressure inside the positive pressure cartridge is greater than the positive pressure threshold, the first adjustment signal controls the positive pressure release valve to switch to the open state and controls the positive pressure air inlet valve to switch to the closed state, so that the positive pressure air inside the positive pressure cartridge is discharged to the outside atmosphere until the positive pressure inside the positive pressure cartridge reaches the preset positive pressure threshold.

6. The circulating ink supply system according to claim 1, characterized in that, The negative pressure regulating module includes at least: Negative pressure suction valve, negative pressure release valve, and second pressure sensor; The negative pressure suction valve is connected to the negative pressure source and the negative pressure ink cartridge respectively, and the negative pressure release valve is connected to the outside atmosphere and the negative pressure ink cartridge respectively. The second pressure sensor is used to detect the negative pressure inside the negative pressure ink cartridge and generate a second adjustment signal for controlling the switching between the negative pressure suction valve and the negative pressure release valve in an open or closed state.

7. The circulating ink supply system according to claim 6, characterized in that, When the negative pressure suction valve is switched to the open state, the negative pressure source and the negative pressure ink cartridge are connected to each other; When the negative pressure suction valve is switched to the closed state, the negative pressure source and the negative pressure ink cartridge are isolated from each other; When the negative pressure release valve is switched to the open state, the negative pressure ink cartridge is connected to the outside atmosphere; When the negative pressure release valve is switched to the closed state, the negative pressure ink cartridge is isolated from the outside atmosphere.

8. The circulating ink supply system according to claim 7, characterized in that, When the negative pressure inside the negative pressure ink cartridge exceeds the negative pressure threshold, the second adjustment signal controls the negative pressure release valve to switch to the open state and controls the negative pressure suction valve to switch to the closed state, so that outside air enters the negative pressure ink cartridge to form negative pressure air until the negative pressure inside the negative pressure ink cartridge reaches the preset negative pressure threshold.

9. The circulating ink supply system according to claim 7, characterized in that, When the negative pressure inside the negative pressure ink cartridge is less than the negative pressure threshold, the second adjustment signal controls the negative pressure extraction valve to switch to the open state and controls the negative pressure release valve to switch to the closed state, so that the negative pressure air inside the negative pressure ink cartridge is extracted by the negative pressure source until the negative pressure inside the negative pressure ink cartridge reaches the preset negative pressure threshold.

10. The circulating ink supply system according to any one of claims 1-9, characterized in that, The nozzle module includes at least: A positive pressure switch valve, a negative pressure switch valve, and a printhead, wherein the printhead has an ink inlet and an ink outlet, the positive pressure switch valve is connected to the ink inlet of the printhead and the positive pressure ink cartridge respectively, and the negative pressure switch valve is connected to the ink outlet of the printhead and the negative pressure ink cartridge respectively. When both the positive pressure switch valve and the negative pressure switch valve are opened, the positive pressure ink cartridge, the printhead, and the negative pressure ink cartridge are interconnected to form a pressure difference, so that the ink in the positive pressure ink cartridge flows into the printhead through the ink inlet through the pressure difference, and flows out from the ink outlet of the printhead into the negative pressure ink cartridge.

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