Nozzle printing ink negative pressure circulation system of digital printing machine

Abstract

The invention relates to a nozzle printing ink negative pressure circulation system of a digital printing machine, which is characterized in that an ink barrel is connected with an ink supply pump, the ink supply pump is connected with an ink supply secondary ink box, a degassing defoaming device is connected between the ink supply pump and the ink supply secondary ink box, and the ink supply secondary ink box is respectively connected with each group of nozzle units through corresponding sub ink supply pipelines; each group of nozzle units is connected with each ink return secondary ink box in a one-to-one correspondence manner, the nozzle negative pressure device comprises an ink supply negative pressure device and an ink return negative pressure device, the ink supply negative pressure device is connected with the ink supply secondary ink box, and each ink return negative pressure device is connected with each ink return secondary ink box in a one-to-one correspondence manner. The negative pressure value of the ink path of each group of nozzle units can be independently and accurately controlled and adjusted in a matched manner, so that the working precision of the plurality of groups of nozzle units is ensured to be consistent, the quality of printed products of the digital printing machine is improved, the problems of line missing, line breaking, line residue, ink dripping, ink residue and the like during working of the digital printing machine are greatly reduced, and the completeness, cleanness and attractiveness of graphic and text information printing are ensured.

Description

Technical Field

[0002] The invention relates to a digital printing machine. Background Art

[0003] The ink precipitation of digital printing machine will block the nozzle of the printhead. When printing with inkjet, there will be problems such as missing lines, broken lines, residual lines, ink dripping, and ink residue, which will lead to defects such as incomplete, unclean, and unsightly printing of graphic information. As an industrial-grade digital printing machine, such defects should not occur. The ink of the printhead of the digital printing machine can circulate under negative pressure. If the ink pressure circuit of the printhead of the digital printing machine is composed of one ink supply pressure, one ink return pressure, and an ink supply tank and an ink return tank, and the negative pressure value of the ink path of the three groups of printheads is controlled and adjusted, the ink pressure circuit of this type of printhead has a single function, and the negative pressure value of the ink path of the three groups of printheads is not easy to control and adjust. After the machine has been working for a long time, the printhead is still prone to ink dripping and ink clogging. Summary of the invention

[0004] In view of the technical problems existing in the background technology, the technical problem solved by the present invention is to provide a digital printing machine's nozzle ink negative pressure circulation system which can independently and accurately coordinate and control the ink path negative pressure value of each group of nozzle units and can accurately control and adjust the balance of the ink path negative pressure values ​​of multiple groups of nozzle units.

[0005] In order to solve the above technical problems, the present invention adopts the following technical scheme: a negative pressure circulation system of ink for a digital printing machine's nozzle, comprising a degassing and defoaming device, a nozzle negative pressure device, an ink supply secondary ink cartridge, an ink return secondary ink cartridge, an ink barrel and a plurality of nozzle unit groups, characterized in that: the ink barrel is connected to an ink supply pump, the ink supply pump is connected to an ink supply secondary ink cartridge, the degassing and defoaming device is connected between the ink supply pump and the ink supply secondary ink cartridge, the ink supply secondary ink cartridge is respectively connected to each group of nozzle units through corresponding sub-ink supply pipelines, each group of nozzle units is connected to each ink return secondary ink cartridge one-to-one, the nozzle negative pressure device comprises an ink supply negative pressure device and an ink return negative pressure device, the ink supply negative pressure device is connected to the ink supply secondary ink cartridge, each set of ink return negative pressure devices is connected to each ink return secondary ink cartridge one-to-one, and an ink return pump is also connected between each ink return secondary ink cartridge and the ink barrel.

[0006] The following various optimizations or supplementary explanations can be made on the above technical solutions respectively.

[0007] For example, the degassing and defoaming device includes a vacuum pump component and a degassing module. The degassing module is arranged in series between the ink supply pump and the secondary ink supply cartridge, and the degassing module is connected to the vacuum pump component; the vacuum pump component includes an oil-water separator and a negative pressure precision regulating valve. The oil-water separator is connected to the negative pressure precision regulating valve, the degassing module is connected to the oil-water separator, and a first ink supply valve is also connected in series between the degassing module and the secondary ink supply cartridge.

[0008] In addition, the degassing and defoaming device also includes an ink supply filter, which is connected in series between the ink supply pump and the degassing module.

[0009] For another example, the vacuum pumping assembly further includes a vacuum generator and a positive pressure precision regulating valve, the negative pressure precision regulating valve is connected to the vacuum generator, and the positive pressure precision regulating valve is arranged between the vacuum generator and the gas source. Alternatively, the vacuum pumping assembly further includes a vacuum pump, and the negative pressure precision regulating valve is connected to the vacuum pump.

[0010] The ink supply negative pressure device independently controls and adjusts the ink supply negative pressure of the secondary ink supply cartridge. The ink supply negative pressure device controls and adjusts the ink supply negative pressure of each group of nozzle units through the secondary ink supply cartridge.

[0011] Among them, a set of ink return negative pressure device independently controls and adjusts the ink return negative pressure of a secondary ink return cartridge, and the ink return negative pressure device and the secondary ink return cartridge are controlled and adjusted one by one. A set of ink return negative pressure device controls and adjusts the ink return negative pressure of a group of nozzle units through a secondary ink return cartridge.

[0012] Among them, an ink supply negative pressure device, an ink supply secondary ink cartridge, an ink supply pipeline, a group of nozzle units, a set of ink return negative pressure devices, and an ink return secondary ink cartridge form a group of independent nozzle negative pressure regulating circulation loops.

[0013] In addition, in a group of independent nozzle negative pressure regulating circulation loops, the negative pressure value of the ink return secondary ink cartridge is greater than the negative pressure value of the ink supply secondary ink cartridge.

[0014] In addition, a first ink return valve is provided between each nozzle unit and each ink return secondary ink cartridge, and a second ink return valve is correspondingly arranged between each ink return secondary ink cartridge and the ink return pump.

[0015] For another example, three groups of nozzle units are arranged, one set of ink supply negative pressure device is connected to one ink supply secondary ink cartridge, one ink supply secondary ink cartridge is connected to three groups of nozzle units respectively, three groups of nozzle units are connected to three ink return secondary ink cartridges respectively, and three ink return secondary ink cartridges are connected to three sets of ink return negative pressure devices respectively.

[0016] In addition, each sub-ink supply pipeline is connected in series with a second ink supply valve and a pre-head filter; and an ink return filter is also connected in series between the ink return pump and the ink barrel.

[0017] The beneficial effects of the present invention are that the ink negative pressure circulation system of the nozzle of the digital printing machine can independently and accurately coordinate and control the ink path negative pressure value of each group of nozzle units to ensure that the ink of the nozzle units is smooth and balanced, without ink dripping or ink blocking; it can accurately control and adjust the balance of the ink path negative pressure values ​​of multiple groups (such as three groups) of nozzle units to ensure that the working accuracy of multiple groups of nozzle units is consistent, improve the print quality of the digital printing machine, and greatly reduce the problems of missing lines, broken lines, residual lines, ink dripping, ink residue, etc. when the digital printing machine is working, ensure the color fidelity of the printing of graphic information, and ensure that the printing of graphic information is complete, clean and beautiful. Its structural design is reasonable, the functions are complete, and the performance is stable. Therefore, compared with the prior art, the present invention has outstanding substantive characteristics and significant progress. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The following describes the relevant details and working principles of the implementation mode and embodiments of the present invention in conjunction with the accompanying drawings.

[0019] Figure 1 It is a schematic diagram of the structure of the present invention.

[0020] In the figure: 1. Positive pressure precision regulating valve; 2. Vacuum generator; 3. Negative pressure precision regulating valve; 4. Oil-water separator; 5. Degassing module; 6. Ink supply filter; 7. Ink supply pump; 8. First ink supply valve; 9. Secondary ink supply cartridge; 10. Second ink supply valve; 11. Pre-head filter; 12. Nozzle unit; 13. First ink return valve; 14. Secondary ink return cartridge; 15. Second ink return valve; 16. Ink return pump; 17. Ink return filter; 18. Ink barrel; 19. Air source; 20. Sub-ink supply pipeline; 21. Nozzle negative pressure device; 22. Vacuum pumping assembly. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention; it is obvious that the described embodiments are only part of the embodiments of the implementation mode of the present invention, rather than all the embodiments, and all other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making creative work are within the scope of protection of the present invention.

[0022] Referring to the accompanying drawings, in the embodiment of the present embodiment, a negative pressure circulation system for ink of a digital printing machine, i.e., a circulation structure, includes a degassing and defoaming device 23, a negative pressure device for the nozzle 21, a plurality of secondary ink supply cartridges 9, secondary ink return cartridges 14, an ink barrel 18, and a plurality of groups of nozzle units 12 (e.g., three groups of nozzle units 12). The nozzle units 12 are arranged one by one with the secondary ink supply cartridges 9.

[0023] Among them, the ink barrel 18 is connected to the ink supply pump 7, the ink supply pump 7 is connected to the ink supply secondary ink cartridge 9, the ink in the ink barrel 18 is supplied to the ink supply secondary ink cartridge 9 through the ink supply pump 7, and a degassing and defoaming device 23 is connected between the ink supply pump 7 and the ink supply secondary ink cartridge 9. The degassing and defoaming device 23 degases and defoams the ink, and extracts the bubbles in the ink to ensure that the ink is bubble-free.

[0024] Among them, the ink supply secondary ink cartridge 9 is respectively connected to each group of nozzle units 12 through the corresponding sub-ink supply pipeline 20. For example, the ink supply secondary ink cartridge 9 is connected to three sub-ink supply pipelines 20, one (root) sub-ink supply pipeline 20 is connected to a group of nozzle units 12 (i.e., digital nozzles), three (root) sub-ink supply pipelines 20 are connected to three groups of nozzle units 12 one by one, and three groups of nozzle units 12 are connected to one ink supply secondary ink cartridge 9.

[0025] Among them, each group of nozzle units 12 is connected to each ink-returning secondary ink cartridge 14 one by one, that is, the ink-returning secondary ink cartridge 14 is connected to the nozzle unit 12, and one ink-returning secondary ink cartridge 14 is connected to one group of nozzle units 12; as shown in the figure, three ink-returning secondary ink cartridges 14 are connected to three groups of nozzle units 12 one by one.

[0026] The nozzle negative pressure device 21 includes an ink supply negative pressure device 211 and a plurality of sets of ink return negative pressure devices 212 .

[0027] The ink supply negative pressure device 211 is connected to the ink supply secondary ink cartridge 9. The ink supply negative pressure device 211 can independently control and adjust the ink supply negative pressure of the ink supply secondary ink cartridge 9. The ink supply negative pressure device 211 controls and adjusts the ink supply negative pressure of multiple groups (such as three groups) of nozzle units 12 through the ink supply secondary ink cartridge 9. One ink supply negative pressure device 211 can uniformly control and adjust the ink supply negative pressure value (numerical value) of each group of nozzle units 12.

[0028] Each set of ink return negative pressure device 212 is connected to each ink return secondary ink cartridge 14 one-to-one, and one set of ink return negative pressure device 212 independently controls and adjusts the ink return negative pressure of one ink return secondary ink cartridge 14. The ink return negative pressure of the three ink return secondary ink cartridges 14 in the figure is independently controlled and adjusted by three sets of ink return negative pressure devices 212. One set of ink return negative pressure device 212 controls and adjusts the ink return negative pressure of a group of nozzle units 12 through one ink return secondary ink cartridge 14. The ink return secondary ink cartridge 14 is connected to the nozzle unit 12, and one ink return secondary ink cartridge 14 is connected to a group of nozzle units 12. The ink return negative pressure device 212 controls and adjusts the ink return negative pressure of one group of nozzle units 12. In the figure, the three ink return secondary ink cartridges 14 are connected to the three groups of nozzle units 12 one-to-one, and the three sets of ink return negative pressure devices 212 control and adjust the ink return negative pressure of the three groups of nozzle units 12.

[0029] An ink return pump 16 is also connected between each ink return secondary ink cartridge 14 and the ink barrel 18 , and the ink return pump 16 cooperates to pump the ink in each ink return secondary ink cartridge 14 back to the ink barrel 18 .

[0030] Among them, the ink supply negative pressure device 211, the ink supply secondary ink cartridge 9, a sub-ink supply pipeline 20, a group of nozzle units 12, a set of ink return negative pressure device 212, and an ink return secondary ink cartridge 14 form a group of independent nozzle negative pressure regulating circulation loops, which can independently and accurately control and adjust the ink path negative pressure pressure of each group of nozzle units 12, ensuring that the ink is smooth and balanced when the nozzle unit 12 piezoelectric works, without ink dripping or ink blocking. For example, in the figure, three groups of nozzle units 12 (i.e., three groups of digital nozzles) have three groups of independent nozzle negative pressure regulating circulation loops (where the ink supply negative pressure device 211 and the ink supply secondary ink cartridge 9 are shared by each group of independent nozzle negative pressure regulating circulation loops), which correspond to each other and independently control the ink path negative pressure pressure of the three groups of nozzle units 12, and can accurately control the balance of the ink path negative pressure pressure values ​​of the three groups of nozzle units 12, ensuring the consistency of the working accuracy of the three groups of nozzles, and improving the quality of printed products of the digital printing machine.

[0031] Before the ink enters the secondary ink supply cartridge 9, the ink is degassed and defoamed by the degassing and defoaming device 23, and the bubbles in the ink are extracted to ensure that the ink is bubble-free.

[0032] The ink negative pressure circulation system of the digital printer can independently and accurately control and adjust the ink path negative pressure of each group of nozzle units 12, ensuring that the ink of the nozzle units 12 is smooth and balanced, without ink dripping or ink blocking; it can accurately control and adjust the balance of the ink path negative pressure values ​​of multiple groups (such as three groups) of nozzle units 12, ensuring the consistency of the working accuracy of multiple groups (such as three groups) of nozzle units 12, improving the print quality of the digital printer, greatly reducing the problems of missing lines, broken lines, residual lines, ink dripping, ink residue, etc. when the digital printer is working, ensuring the color fidelity of the printed graphic information, and ensuring the integrity, cleanliness and beauty of the printed graphic information. Its structural design is reasonable, the functions are complete, and the performance is stable.

[0033] Among them, the nozzle negative pressure device 21 can individually, accurately and efficiently adjust the ink path negative pressure of each group of nozzle units 12 and the (ink supply and ink return) negative pressure value balance of multiple groups (such as three groups) of nozzle units 12; the negative pressure of the ink supply negative pressure device 211 and the three ink return negative pressure devices 212 can be independently detected and adjusted, so that the negative pressure value of each negative pressure device is consistent with the set pressure value.

[0034] The following optimization or further explanation may be performed based on the above embodiments.

[0035] For example, the degassing and defoaming device 23 includes a vacuum pumping component 22 and a degassing module 5. The degassing module 5 is connected in series between the ink supply pump 7 and the ink supply secondary ink cartridge 9, and the degassing module 5 is connected to the vacuum pumping component 22. The vacuum pumping component 22 includes an oil-water separator 4 and a negative pressure precision regulating valve 3. The oil-water separator 4 is connected to the negative pressure precision regulating valve 3, and the degassing module 5 is connected to the oil-water separator 4. The vacuum pumping component 22 cooperates with the air extraction, and the degassing module 5 cooperates with the degassing and defoaming. Under the action of the vacuum pumping component 22, the bubbles extracted from the ink are sucked into the oil-water separator 4 to eliminate the bubbles. A first ink supply valve 8 (such as a two-way valve) is also connected in series between the degassing module 5 and the ink supply secondary ink cartridge 9. The ink after degassing and defoaming (even impurity removal) passes through the first ink supply valve 8 and enters the ink supply secondary ink cartridge 9. When the ink in the ink supply secondary ink cartridge 9 reaches the upper limit, the first ink supply valve 8 is closed to stop supplying ink to the ink supply secondary ink cartridge 9. The first ink supply valve 8 is opened to continue supplying ink. A liquid level sensor can be provided in the ink supply secondary ink cartridge 9 to connect with the first ink supply valve 8 to cooperate in controlling the opening and closing of the first ink supply valve 8. The degassing and defoaming device 23 also includes an ink supply filter 6, which is connected in series between the ink supply pump 7 and the degassing module 5. The ink supply filter 6 cooperates with filtering to make the ink relatively pure and reduce impurities. The bubbles generated during the filtration process can also be defoamed, so that the ink is bubble-free.

[0036] The vacuum pumping assembly 22 also includes a vacuum generator 2 and a positive pressure precision regulating valve 1, and the negative pressure precision regulating valve 3 is connected to the vacuum generator 2. The positive pressure precision regulating valve 1 is arranged between the vacuum generator 2 and the gas source 19; under the pressure control of the positive pressure precision regulating valve 1, air is taken in from the gas source 19 (such as air), the vacuum generator 2 generates a vacuum negative pressure, and the negative pressure precision regulating valve 3 controls the vacuum negative pressure pressure; the vacuum pumping assembly 22 can suck the bubbles in the ink path into the oil-water separator 4 separately for separation. Alternatively, the vacuum pumping assembly 22 also includes a vacuum pump (not shown in the figure), and the negative pressure precision regulating valve 3 is connected to the vacuum pump, and the vacuum pump provides negative pressure air for exhaust.

[0037] Among them, the ink supply negative pressure device 211 independently controls and adjusts the ink supply negative pressure of the ink supply secondary ink cartridge 9; the ink supply negative pressure device 211 controls and adjusts the ink supply negative pressure of each group of nozzle units 12 through the ink supply secondary ink cartridge 9. In the figure, the three groups of nozzle units 12 are individually controlled by the ink supply negative pressure device 211 through the ink supply secondary ink cartridge 9.

[0038] Among them, one set of ink return negative pressure device 212 independently controls and adjusts the ink return negative pressure of one ink return secondary ink cartridge 14, and the ink return negative pressure device 212 and the ink return secondary ink cartridge 14 are controlled and adjusted one by one; one set of ink return negative pressure device 212 controls and adjusts the ink return negative pressure of a group of nozzle units 12 through one ink return secondary ink cartridge 14. In the figure, the ink return negative pressure of three ink return secondary ink cartridges 14 are independently controlled and adjusted by three sets of ink return negative pressure devices 212.

[0039] In a group of independent nozzle negative pressure regulating circulation loops, the negative pressure value (i.e., negative pressure value) of the ink return secondary ink cartridge 14 is greater than the negative pressure value of the ink supply secondary ink cartridge 9, which can be set according to demand, and usually kept slightly greater, so that each nozzle unit 12 can be under the action of negative pressure adsorption force, and after the ink in the ink supply secondary ink cartridge 9 is sucked into the nozzle unit 12 to complete inkjet printing, the excess ink of the nozzle unit 2 is sucked into the ink return secondary ink cartridge 14, and the ink path negative pressure circulates, and the ink in the nozzle unit 12 circulates, which can accurately, individually, and efficiently adjust the ink path negative pressure of each group of nozzles. For example, the ink supply negative pressure is set to -3kpa, and the ink return negative pressure is set to -4kpa.

[0040] In addition, each sub-ink supply pipeline 20 is connected in series with a second ink supply valve 10 (such as a two-way valve) and a pre-head filter 11. Before the ink enters the nozzle unit 12, it is filtered by the pre-head filter 11 to further ensure that the ink is pure and free of impurities. In particular, after the ink is first filtered by the ink supply filter 6 in the degassing and defoaming device 23, the ink is filtered twice by the pre-head filter 11, and the ink is purer and free of impurities. Among them, the first ink supply valve 8 can open and close the ink path when the machine is shut down, and the second ink supply valve 10 can open and close the ink path when it is repaired.

[0041] Multiple (such as three groups) independent nozzle negative pressure regulating circulation loops can accurately control the balance of the ink path negative pressure values ​​of the three nozzle units 12, ensure the consistent working accuracy of the three nozzle units 12, and improve the print quality of the digital printing machine.

[0042] The multiple (three) ink return secondary ink cartridges 14 and (one) ink supply secondary ink cartridge 9 can be a shell structure or designed separately. The ink return secondary ink cartridge 14 and the ink supply secondary ink cartridge 9 can be respectively configured to be connected to their respective safety ink bottles 121 and 91, and the ink supply negative pressure device 211 and the ink return negative pressure device 212 can be respectively connected to the corresponding negative pressure air pumps 2111 and 2121 to provide the negative pressure gas source 19, and even each secondary ink cartridge (including multiple ink return secondary ink cartridges 14 and one ink supply secondary ink cartridge 9) (or each safety ink bottle) and each negative pressure air pump can also be connected in series with each corresponding gas cylinder A, B, C, D (for transfer storage and adjustment of negative pressure gas). In addition, a positive and negative pressure switching valve 2112 (such as a positive and negative pressure switching three-way valve) is connected in series between the ink supply secondary ink cartridge 9 and the gas cylinder D, and a positive pressure air pump 2113 is connected via the positive and negative pressure switching valve; the positive and negative pressure switching valve 2112 switches the ink supply secondary ink cartridge 9 to be connected to the positive pressure air pump 2113, and blows air into the ink supply secondary ink cartridge 9 to blow out the ink in the three groups of nozzle units 9 when pressing the ink; the ink supply secondary ink cartridge 9 is switched to be connected to the gas cylinder D to form a negative pressure pipeline.

[0043] In addition, a first ink return valve 13 (such as a two-way valve) is provided between each nozzle unit 12 and each ink return secondary ink cartridge 14. Under the action of the negative pressure adsorption force of the ink path, after the ink passes through the nozzle unit 12, the ink is sucked into the ink return secondary ink cartridge 14 through the first ink return valve 13. The negative pressure of the ink path circulates, and the negative pressure of the ink path of each group of nozzles can be accurately, individually, and efficiently adjusted. A second ink return valve 15 (such as a two-way valve) is respectively configured between each ink return secondary ink cartridge 14 and the ink return pump 16. One ink return secondary ink cartridge 14 is controlled by the on-off of one second ink return valve 15. The three ink return secondary ink cartridges 14 in the figure are controlled by the on-off of three second ink return valves 15 one by one. When the ink in a certain ink return secondary ink cartridge 14 reaches the upper limit, the second ink return valve 15 corresponding to the ink return secondary ink cartridge 14 is opened, and the ink return pump 16 can cooperate to draw the ink in the ink return secondary ink cartridge 14 back to the ink barrel 18. A liquid level sensor may be provided in the secondary ink return cartridge 14 and connected to the second ink return valve 15 to cooperate with the control of the opening and closing of the second ink return valve 15. An ink return filter 17 is also connected in series between the ink return pump 16 and the ink barrel 18. When the ink return pump 16 pumps the ink back to the ink barrel 18, the ink may also be filtered by the ink return filter 17 to remove impurities. The first ink return valve 13 may also open and close the ink path when the machine is shut down, and the second ink return valve 15 may also open and close the ink path when it is repaired.

[0044] In the figure, three groups of nozzle units 12 are arranged, one set of ink supply negative pressure device 211 is connected to one ink supply secondary ink cartridge 9, one ink supply secondary ink cartridge 9 is respectively connected to three groups of nozzle units 12, three groups of nozzle units 12 are respectively connected to three ink return secondary ink cartridges 14 one by one, and three ink return secondary ink cartridges 14 are respectively connected to three sets of ink return negative pressure devices 212 one by one.

Claims

1. A negative pressure circulation system for ink of a printhead of a digital printing machine, comprising a degassing and defoaming device (23), a printhead negative pressure device (21), a secondary ink supply cartridge (9), a secondary ink return cartridge (14), an ink barrel (18) and a plurality of groups of printhead units (12), characterized in that: The ink barrel (18) is connected to the ink supply pump (7), the ink supply pump (7) is connected to the secondary ink supply cartridge (9), and a degassing and defoaming device (23) is connected between the ink supply pump (7) and the secondary ink supply cartridge (9). The secondary ink supply cartridges (9) are connected to each group of nozzle units (12) via corresponding sub-ink supply pipelines (20). Each group of nozzle units (12) is connected to each ink return secondary ink cartridge (14) in a one-to-one correspondence. The nozzle negative pressure device (21) comprises an ink supply negative pressure device (211) and an ink return negative pressure device (212). The ink supply negative pressure device (211) is connected to the ink supply secondary ink cartridge (9). Each set of ink return negative pressure device (212) is connected to each ink return secondary ink cartridge (14) in a one-to-one correspondence. An ink return pump (16) is also connected between each ink return secondary ink cartridge (14) and the ink barrel (18).

2. The ink negative pressure circulation system for a digital printing machine as claimed in claim 1, characterized in that: The degassing and defoaming device (23) comprises a vacuum pumping component (22) and a degassing module (5). A degassing module (5) is arranged in series between the ink supply pump (7) and the secondary ink supply cartridge (9), and the degassing module (5) is connected to a vacuum pumping component (22); The vacuum pumping assembly (22) comprises an oil-water separator (4) and a negative pressure precision regulating valve (3), the oil-water separator (4) is connected to the negative pressure precision regulating valve (3), and the degassing module (5) is connected to the oil-water separator (4). A first ink supply valve (8) is also connected in series between the degassing module (5) and the secondary ink supply cartridge (9).

3. The ink negative pressure circulation system for a printhead of a digital printing machine as claimed in claim 2, characterized in that: The degassing and defoaming device (23) further comprises an ink supply filter (6), wherein the ink supply filter (6) is connected in series between the ink supply pump (7) and the degassing module (5); The vacuum pumping assembly (22) further comprises a vacuum generator (2) and a positive pressure precision regulating valve (1); the negative pressure precision regulating valve (3) is connected to the vacuum generator (2); and the positive pressure precision regulating valve (1) is arranged between the vacuum generator (2) and the gas source (19); or, The vacuum pumping assembly (22) further comprises a vacuum pump, and the negative pressure precision regulating valve (3) is connected to the vacuum pump.

4. The ink negative pressure circulation system for a printhead of a digital printing machine as claimed in claim 1, characterized in that: The ink supply negative pressure device (211) independently controls and adjusts the ink supply negative pressure of the ink supply secondary ink cartridge (9). The ink supply negative pressure device (211) controls and adjusts the ink supply negative pressure of each group of nozzle units (12) through the ink supply secondary ink cartridge (9).

5. The ink negative pressure circulation system for a printhead of a digital printing machine as claimed in claim 1, characterized in that: A set of ink return negative pressure devices (212) independently controls and adjusts the ink return negative pressure of an ink return secondary ink cartridge (14), and the ink return negative pressure device (212) and the ink return secondary ink cartridge (14) are controlled and adjusted in a one-to-one correspondence. A set of ink return negative pressure devices (212) controls and adjusts the ink return negative pressure of a group of nozzle units (12) via a corresponding ink return secondary ink cartridge (14).

6. The ink negative pressure circulation system for a printhead of a digital printing machine as claimed in claim 1, characterized in that: An ink supply negative pressure device (211), an ink supply secondary ink cartridge (9), an ink supply pipeline (20), a group of nozzle units (12), a set of ink return negative pressure devices (212), and an ink return secondary ink cartridge (14) form a group of independent nozzle negative pressure regulating circulation loops.

7. The ink negative pressure circulation system for a printhead of a digital printing machine as claimed in claim 5, characterized in that: In a group of independent nozzle negative pressure regulating circulation loops, the negative pressure value of the ink return secondary ink cartridge (14) is greater than the negative pressure value of the ink supply secondary ink cartridge (9).

8. The ink negative pressure circulation system for a printhead of a digital printing machine as claimed in claim 1, characterized in that: A first ink return valve (13) is provided between each nozzle unit (12) and each ink return secondary ink cartridge (14). A second ink return valve (15) is correspondingly arranged between each ink return secondary ink cartridge (14) and the ink return pump (16).

9. The ink negative pressure circulation system for a printhead of a digital printing machine as claimed in claim 1, characterized in that: The nozzle units (12) are provided in three groups. A set of ink supply negative pressure devices (211) is connected to an ink supply secondary ink cartridge (9), an ink supply secondary ink cartridge (9) is respectively connected to three groups of nozzle units (12), the three groups of nozzle units (12) are respectively connected to three ink return secondary ink cartridges (14) in a one-to-one correspondence, and the three ink return secondary ink cartridges (14) are respectively connected to three sets of ink return negative pressure devices (212) in a one-to-one correspondence.

10. The ink negative pressure circulation system for a printhead of a digital printing machine as claimed in claim 1, characterized in that: A second ink supply valve (10) and a pre-head filter (11) are connected in series on each sub-ink supply pipeline (20); and an ink return filter (17) is also connected in series between the ink return pump (16) and the ink barrel (18).

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