Liquid circulation mechanism and application thereof

Abstract

The invention discloses a liquid circulation mechanism and application thereof.The liquid circulation mechanism comprises a first pressure tank (1) and a second pressure tank (2), a first exhaust valve (10) is arranged on the first pressure tank (1), a first inner bag (11) is arranged in the first pressure tank (1), the bottom of the first inner bag (11) is communicated with one end of a spray head (3) through a first pipeline (12), a second exhaust valve (20) is arranged on the second pressure tank (2), and the first inner bag (11) is communicated with the other end of the spray head (3) through a second pipeline (12). A second inner bag (21) is arranged in the second pressure tank (2), the bottom of the second inner bag (21) is communicated with the other end of the spray head (3) through a second pipeline (22), and the first pressure tank (1) and the second pressure tank (2) are both connected with high-pressure air sources (4); and the first pressure tank (1) and the second pressure tank (2) are connected with the same high-pressure gas source (4) through a reversing valve (5). The invention has the advantages of low cost and low failure rate.

Description

Technical Field

[0001] This invention belongs to the field of inkjet printing equipment, and particularly relates to a liquid circulation mechanism for inkjet printing equipment and its application. Background Technology

[0002] In existing inkjet printing equipment, to prevent ink sedimentation, drying, and printhead clogging, a circulation mechanism is used to keep the ink flowing. This mechanism, achieved through a pump, includes a first pressure tank and a second pressure tank. The first pressure tank stores ink, and the pump draws ink from it into the printhead. A small amount of ink is ejected through the printhead nozzle, while the remainder flows through the printhead into the second pressure tank. The second pressure tank is connected to the first pressure tank via a return pipe, and ink from the second pressure tank flows back into the first pressure tank through the return pipe. The printhead has two ink inlets / outlets and one ink nozzle.

[0003] The shortcomings of existing circulation mechanisms are as follows: For example, in large character inkjet printers, if a pump is used, the ink decreases during use, requiring an air intake to avoid ink pressure fluctuations caused by negative pressure inside the circulation mechanism. However, a one-way valve cannot be used at the air intake because temperature changes in a closed environment will affect the internal pressure of the pressure tank. Using a one-way valve will not release pressure and will also change the ink supply pressure, affecting the printing effect. Small character inkjet printers face the same problems as large character inkjet printers, and they also need to use a Venturi structure to circulate and draw ink from the recovery tube, which also requires the pressure to remain unchanged. During the ink circulation process, small character inkjet printers also need to continuously consume solvent to adjust the ink concentration.

[0004] Because a one-way valve cannot be installed at the air intake of the circulation mechanism, air can flow bidirectionally at the intake. While this ensures stable internal pressure, the solvents in inks are generally highly volatile, such as acetone, which easily leak from the intake, causing changes in ink viscosity and affecting inkjet printing performance. Therefore, an automatic compensation system is needed to compensate for the lost solvent and maintain stable ink viscosity. However, automatic compensation systems are complex, resulting in high costs and a high failure rate.

[0005] In addition, the working principle of the existing printhead is that ink enters the ink chamber of the printhead, and a solenoid valve is installed at the nozzle of the printhead. The valve core of the solenoid valve extends under the action of the built-in pressure spring, closing the nozzle and preventing the ink from being ejected. When the solenoid valve receives a signal, it opens, the valve core retracts, and the nozzle opens, allowing the ink to be ejected.

[0006] During use, it was discovered that existing printheads, due to the incomplete separation of the ink path and electrical circuit, pose a risk of ink leakage into the circuit. Once ink contaminates the circuit, the solenoid valve will burn out, resulting in a short printhead lifespan. Furthermore, during large character printing, there is prolonged inkjet printing, causing the solenoid valve to remain energized and open for extended periods, which can easily overheat and burn out, a significant reason for the short printhead lifespan.

[0007] The reason why the solenoid valve in the existing nozzle is prone to overheating and burning is that the solenoid valve is built into the nozzle, which has poor heat dissipation conditions and limited size. It needs to be specially customized. The number of turns of the internal winding is generally small and the wire diameter is generally small. It needs to use a large current to obtain sufficient electromagnetic force, and the large current brings high heat, which makes it easy to overheat and burn out. Summary of the Invention

[0008] The purpose of this invention is to provide a liquid circulation mechanism and its application. This invention has the advantages of low cost and low failure rate.

[0009] The technical solution of the present invention is as follows: a liquid circulation mechanism, including a first pressure tank and a second pressure tank. The first pressure tank is provided with a first exhaust valve and a first inner bag. The bottom of the first inner bag is connected to one end of a nozzle through a first pipe. The second pressure tank is provided with a second exhaust valve and a second inner bag. The bottom of the second inner bag is connected to the other end of the nozzle through a second pipe. Both the first pressure tank and the second pressure tank are connected to a high-pressure air source.

[0010] In the aforementioned liquid circulation mechanism, the first pressure tank and the second pressure tank are connected to the same high-pressure gas source through a reversing valve.

[0011] In the aforementioned liquid circulation mechanism, both the first pressure tank and the second pressure tank include a cylinder with an opening at the lower end. A first pipe joint and a second pipe joint are provided on the outside of the cylinder. A base is provided at the lower end of the cylinder. An inner bag interface is provided at the top of the base. A third pipe joint communicating with the inner bag interface is provided on the side wall of the base. The inner bag interface is located inside the cylinder, and the third pipe joint is located outside the cylinder.

[0012] In the aforementioned liquid circulation mechanism, the nozzle includes a main body, the interior of which is provided with a vertical channel, the upper end of which is provided with a stepped hole, and a hollow upper sleeve assembly is provided in the stepped hole. The upper sleeve assembly is connected to the cap by a first spring, the cap is connected to the main body, and the cap is provided with an exhaust hole. The channel is equipped with a spray needle, the upper end of which extends upward into the inner cavity of the upper sleeve assembly. The upper end of the spray needle is connected to the upper sleeve assembly via a second spring. The outer side of the main body is provided with two circulating ink connectors, which are connected to the first pipe and the second pipe respectively; The lower part of the channel is provided with a valve body fixed to the main body. A nozzle that passes through the axially is provided between the valve body and the main body. The lower end of the spray needle enters the nozzle. A fine orifice plate is provided on the lower side of the spray needle. A nozzle is provided on the fine orifice plate. A through hole corresponding to the nozzle is provided at the bottom of the valve body. The outer side of the main body is provided with a pipe joint that connects to the stepped surface of the stepped hole. The pipe joint is connected to a high-pressure air source through a solenoid valve.

[0013] In the aforementioned liquid circulation mechanism, the cap is screwed to the main body, and the bottom of the cap is provided with a first nut that is screwed to the main body.

[0014] In the aforementioned liquid circulation mechanism, the upper sleeve assembly includes an upper sleeve located at the large end of the stepped hole, the lower end of the upper sleeve is inwardly contracted, the upper end of the upper sleeve is screwed with an upper sleeve cover, the inner side of the upper sleeve is provided with two second nuts that connect to the spray needle, the two second nuts are locked to each other, one end of the second spring is connected to the upper sleeve cover, and the other end of the second spring is connected to one of the second nuts. A first sealing ring is provided between the upper sleeve and the main body.

[0015] In the aforementioned liquid circulation mechanism, the small end of the stepped hole is provided with a third nut through which the spray needle passes. The third nut is screwed to the main body, and a second sealing ring is provided on the lower side of the third nut. The second sealing ring blocks the upper end of the channel. The lower end of the nozzle is screwed to the valve body.

[0016] In the aforementioned liquid circulation mechanism, a tubular valve seat is provided on the outer side of the valve body. The upper end of the valve seat extends radially outward to form an upper flange. A fourth nut is provided at the lower end of the main body. The lower end of the fourth nut extends radially inward to form a lower flange. The lower flange presses against the upper flange.

[0017] In the aforementioned liquid circulation mechanism, the lower end of the spray needle is provided with a rubber head.

[0018] The aforementioned liquid circulation mechanism is applied in inkjet printing equipment.

[0019] Compared to existing technologies, this invention incorporates inner bags within two pressure tanks, storing the ink within them. By closing the vent valve on one pressure tank and applying air pressure to its inner bag, the ink is forced out. Simultaneously, the vent valve on the other pressure tank is opened, allowing its inner bag to receive the ink smoothly, thus enabling ink flow between the two inner bags. By switching the pressure between the two pressure tanks, the ink circulates between the two inner bags, resulting in uniform ink mixing without sedimentation or stratification. Because the ink remains sealed throughout the flow process, the solvent does not evaporate or leak, and the ink viscosity remains essentially unchanged. This eliminates the need for a complex automatic compensation system to replenish the solvent, reducing the cost and failure rate of the circulation mechanism.

[0020] Furthermore, this invention improves the printhead structure by completely separating the circuitry and ink path. The pipe connector connects to a high-pressure air source via an external solenoid valve, driving the internal nozzles to move and thus opening and closing the nozzles. Since ink does not contaminate the solenoid valve, it is less prone to burnout, extending the printhead's lifespan. The external solenoid valve also provides excellent heat dissipation, reducing the risk of overheating and burnout, further extending the printhead's lifespan. Moreover, the solenoid valve's weight and size are not limited, requiring no special customization; standard models are sufficient. Its internal coil has more turns and a larger wire diameter, requiring only a small current for operation, resulting in less heat generation and further reducing the risk of burnout. Attached Figure Description

[0021] Figure 1 This is a front view structural diagram of Example 1.

[0022] Figure 2 This is a schematic diagram of the liquid circulation mechanism of Example 1 on a coding and inkjet equipment.

[0023] Figure 3 This is a front view structural diagram of the nozzle of Example 2.

[0024] Figure 4 This is a schematic diagram of the lower part of the nozzle in Example 2.

[0025] The labels in the attached diagram are as follows: 1-First pressure tank, 2-Second pressure tank, 3-Nozzle, 4-High-pressure air source, 5-Reversing valve, 10-First exhaust valve, 11-First inner bag, 12-First pipe, 20-Second exhaust valve, 21-Second inner bag, 22-Second pipe, 30-Cylinder body, 31-First pipe connector, 32-Second pipe connector, 33-Base, 34-Inner bag interface, 35-Third pipe connector. Detailed Implementation

[0026] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the present invention.

[0027] Example 1: A liquid circulation mechanism, such as Figure 1 As shown, the device includes a first pressure tank 1 and a second pressure tank 2 arranged from left to right. Both the first pressure tank 1 and the second pressure tank 2 include a cylindrical body 30 with an opening at the lower end. The cylindrical body 30 is made of a transparent material, such as PC or acrylic. The outside of the cylindrical body 30 is provided with a first pipe joint 31 and a second pipe joint 32. The lower end of the cylindrical body 30 is provided with a base 33. The cylindrical body 30 and the base 33 can be detachably connected by screws. A sealing ring can be provided between the cylindrical body 30 and the base 33 to increase the sealing performance. The top of the base 33 is provided with an inner bag interface 34. The side wall of the base 33 is provided with a third pipe joint 35 that communicates with the inner bag interface 34. The inner bag interface 34 is located inside the cylindrical body 30, and the third pipe joint 35 is located outside the cylindrical body 30.

[0028] The first pressure tank 1 is equipped with a first exhaust valve 10. The air inlet end of the first exhaust valve 10 is connected to the second pipe joint 32 on the left side. The first pressure tank 1 is equipped with a first inner bag 11. The bottom opening of the first inner bag 11 is connected to the inner bag interface 34 on the left side. It can be tightened with a clamp to increase the sealing performance. The first inner bag 11 is connected to one end of the nozzle 3 through the inner bag interface 34 on the left side, the third pipe joint 35 on the left side, and the first pipe 12.

[0029] The second pressure tank 2 is equipped with a second exhaust valve 20. The air inlet end of the second exhaust valve 20 is connected to the second pipe joint 32 on the right side. The second pressure tank 2 is equipped with a second inner bag 21. The bottom opening of the second inner bag 21 is connected to the inner bag interface 34 on the right side. It can be tightened with a clamp to increase the sealing performance. The second inner bag 21 is connected to the other end of the nozzle 3 through the inner bag interface 34 on the right side, the third pipe joint 35 on the right side, and the second pipe 22.

[0030] The first pressure tank 1 and the second pressure tank 2 are connected to the same high-pressure air source 4 via a reversing valve 5. The high-pressure air source can be an air compressor. The reversing valve 5 is connected to the corresponding first pipe joint 31. Without using the reversing valve, the first pressure tank 1 and the second pressure tank 2 can be configured with independent, non-shared high-pressure air sources.

[0031] The aforementioned liquid circulation mechanism is used in inkjet printing equipment to drive ink circulation and prevent the ink from drying out.

[0032] Working principle of Example 1: as follows Figure 1 As shown, the ink circulates back and forth between the first inner bag 11 and the second inner bag 21, and passes through the printhead 3 during the flow, supplying ink to the printhead 3.

[0033] When the ink in the first inner bag 11 flows into the second inner bag 21, the first exhaust valve 10 is closed and the second exhaust valve 20 is open. The airflow from the high-pressure air source 4 is moved to the left by the reversing valve 5 and enters the first pressure tank 1. The internal pressure of the first pressure tank 1 increases, squeezing the first inner bag 11. The ink in the first inner bag 11 enters the second inner bag 21 through the first pipe 12, the printhead 3, and the second pipe 22.

[0034] When the ink in the second inner bag 21 flows into the first inner bag 11, the first exhaust valve 10 is open and the second exhaust valve 20 is closed. The airflow from the high-pressure air source 4 is moved to the right by the reversing valve 5 and enters the second pressure tank 2. The internal pressure of the second pressure tank 2 increases, squeezing the second inner bag 21. The ink in the second inner bag 21 enters the first inner bag 11 through the second pipe 22, the printhead 3, and the first pipe 12.

[0035] In Example 1, the printhead 3 used is not modified and is the same as the printhead of the existing inkjet printing equipment.

[0036] The ink transfers back and forth between the first inner bag 11 and the second inner bag 21, circulating in both directions through the printhead 3. In another embodiment, a one-way valve can be added to the ink pipeline to allow the ink to circulate in one direction from the pipeline to the printhead.

[0037] Example 2: Based on Example 1, the nozzle 3 is improved. The improved nozzle 3 is as follows: Figure 3 and Figure 4 As shown, the main body 40 includes a nozzle. The interior of the main body 40 has a vertical channel 41. The upper end of the channel 41 has a stepped hole 42. An upper sleeve assembly is provided inside the stepped hole 42. The upper sleeve assembly includes an upper sleeve 56 located at the larger end of the stepped hole 42. The lower end of the upper sleeve 56 is inwardly contracted. The bottom surface of the upper sleeve 56 is in contact with the stepped surface of the stepped hole 42. A first sealing ring 59 is provided between the upper sleeve 56 and the main body 40. An upper sleeve cover 57 is screwed to the upper end of the upper sleeve 56. The upper sleeve 56 is connected to a screw cap 44 through a spiral first spring 43. The screw cap 44 is screwed to the main body 40. The screw cap 44 has an exhaust hole 45. The bottom of the screw cap 44 is provided with a first nut 55 screwed to the main body 40. The screw cap 44 and the first nut 55 are locked together.

[0038] The channel 41 is equipped with a spray needle 46, the diameter of which is smaller than that of the channel 41. The lower end of the spray needle 46 is equipped with a rubber head 66, and the upper end of the spray needle 46 extends upward into the upper sleeve 56. The inner side of the upper sleeve 56 is equipped with two second nuts 58 that connect to the spray needle 46. The two second nuts 58 are locked to each other. The upper end of the spray needle 46 is equipped with a spiral second spring 47. One end of the second spring 47 is connected to the upper sleeve cover 57, and the other end of the second spring 47 is connected to one of the second nuts 58.

[0039] The small end of the stepped hole 42 is provided with a third nut 60 through which the spray needle 46 passes. The third nut 60 is slidably connected to the spray needle 46 and screwed to the main body 40. A second sealing ring 61 is provided on the lower side of the third nut 60, and the second sealing ring 61 blocks the upper end of the channel 41.

[0040] The outer side of the main body 40 is provided with two circulating ink connectors 48, both of which are connected to the channel 41. The two circulating ink connectors 48 are respectively connected to the first pipe 12 and the second pipe 22. The outer side of the main body 40 is provided with a pipe connector 54 that connects to the stepped surface of the stepped hole 42. The pipe connector 54 is connected to the high-pressure air source 4 through a solenoid valve.

[0041] A valve body 49 is provided below the channel 41. A tubular valve seat 62 is provided on the outside of the valve body 49. The valve seat 62 is fixed to the valve body 49. The upper end of the valve seat 62 extends radially outward to form an upper flange 63. A fourth nut 64 is provided at the lower end of the main body 40. The lower end of the fourth nut 64 extends radially inward to form a lower flange 65. The lower flange 65 presses against the upper flange 63.

[0042] A nozzle 50 is axially connected between the main body 40 and the valve body 49. The upper end of the nozzle 50 is screwed to the lower end of the channel 41, and the lower end of the nozzle 50 is screwed to the valve body 49. A fine-hole plate 51 is provided on the lower side of the spray needle 46. The fine-hole plate 51 is clamped between the nozzle 50 and the valve body 49. The fine-hole plate 51 is provided with a nozzle 52. The bottom of the valve body 49 is provided with a through hole 53 corresponding to the nozzle 52. The lower end of the spray needle 46 enters the nozzle 50 and blocks the nozzle 52 through the rubber head 66.

[0043] The working principle of the printhead 3: Pressurized ink enters from one of the circulating ink connectors 48, fills the channel 41, and exits from the other circulating ink connector 48. Due to the elastic force of the second spring 47, the nozzle 46 presses down on the nozzle 66, the nozzle 52 is blocked, and the ink cannot be sprayed out.

[0044] When inkjet printing is required, the solenoid valve is opened, and compressed air is introduced into the high-pressure air source 4-way connector 54. The compressed air enters the stepped hole 42, pushing the upper sleeve 56 upward. The first spring 43 is compressed. Since the second sealing ring 61 blocks the channel 41, the gas pressure will not affect the ink pressure, ensuring stable inkjet printing.

[0045] After the upper sleeve 56 moves upward to a certain extent, the second nut 58 drives the nozzle 46 to move upward, the second spring 47 is compressed, the nozzle 46 drives the head 66 to move upward, the nozzle 52 opens, the ink in the channel 41 passes through the nozzle 50 and is ejected from the nozzle 52. After the ink is sprayed, the solenoid valve is closed. Under the action of the first spring 43 and the second spring 47, the nozzle 46 moves downward and the nozzle 52 is closed again.

[0046] In Example 2, pipe connector 54 also needs to be connected to the air source through a solenoid valve to realize the opening and closing of compressed air. However, since the solenoid valve is located outside the nozzle, the heat dissipation effect is good and the size and weight are not limited. A conventional solenoid valve can be used with more turns and a larger wire diameter. A small current can obtain enough electromagnetic force to drive its valve core to move and realize the opening and closing of the air passage, so it is not easy to overheat and burn out.

[0047] The best application scenario for this invention is to use it in conjunction with online inspection equipment on a production line for defect marking. When the online inspection equipment detects a defect in a product (including copper wire, fabric, cable, etc.) produced continuously on the production line, it sprays ink to form a linear mark, i.e., a large character ink line, at the defect location of the product, which facilitates subsequent quality inspection. The defect marking does not require high inkjet precision.

[0048] When ink flows and transfers between the two inner bags, it passes through the printhead 3. A certain pressure needs to be maintained within the channel 41 of the printhead 3 to ensure that the ink is ejected normally after the nozzle 46 moves upward. The exhaust cross-sections of the first exhaust valve 10 and the second exhaust valve 20 should be relatively small, with a microporous structure. The size of the exhaust cross-section affects the ink pressure within the channel 41. For example, when ink flows from the first inner bag 11 to the second inner bag 21, the first exhaust valve 10 is closed, and the second exhaust valve 20 is open. Compressed air enters the first pressure tank 1, reducing the volume of the first inner bag 11. The ink from the first inner bag 11 enters the second inner bag 21, increasing its volume. The air in the second pressure tank 2 is compressed and discharged through the second exhaust valve 20. The exhaust cross-section of the second exhaust valve 20 should be relatively small to minimize air discharge resistance. A certain pressure is maintained in the second pressure tank 2, and a certain pressure is maintained inside the second inner bag 21, thus maintaining a certain pressure within the channel 41 of the printhead 3.

[0049] Alternatively, another implementation method can be adopted, in which the exhaust cross-section of the first exhaust valve 10 and the second exhaust valve 20 is not restricted, the first exhaust valve 10 and the second exhaust valve 20 are conventional on / off valves, and both the first exhaust valve 10 and the second exhaust valve 20 are equipped with overflow valves at their outlet ends. Figure 1 As shown: When the ink in the first inner bag 11 flows into the second inner bag 21, the first exhaust valve 10 is closed, and compressed air enters the first pressure tank 1. The volume of the first inner bag 11 decreases, and the ink in the first inner bag 11 enters the second inner bag 21. The air inside the second pressure tank 2 is discharged through the second exhaust valve 20 and the corresponding overflow valve. The air inside the second pressure tank 2 is maintained at a certain pressure by the overflow valve on the right, so that a certain pressure is maintained in the channel 41 of the printhead 3. This increases the cost to some extent, but the pressure stabilization effect is better, which helps to control the ink ejection accuracy. The overflow pressure of the overflow valve should be less than the pressure of the compressed air.

[0050] In the description of the embodiments, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. They are only for the convenience of describing the embodiments 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.

Claims

1. A liquid circulation mechanism, comprising a first pressure tank (1) and a second pressure tank (2), characterized in that: The first pressure tank (1) is equipped with a first exhaust valve (10), and the first pressure tank (1) is equipped with a first inner bag (11). The bottom of the first inner bag (11) is connected to one end of the nozzle (3) through the first pipe (12). The second pressure tank (2) is equipped with a second exhaust valve (20), and the second pressure tank (2) is equipped with a second inner bag (21). The bottom of the second inner bag (21) is connected to the other end of the nozzle (3) through the second pipe (22). Both the first pressure tank (1) and the second pressure tank (2) are connected to a high-pressure air source (4).

2. The liquid circulation mechanism according to claim 1, characterized in that: The first pressure tank (1) and the second pressure tank (2) are connected to the same high-pressure gas source (4) through a reversing valve (5).

3. The liquid circulation mechanism according to claim 1, characterized in that: The first pressure tank (1) and the second pressure tank (2) both include a cylinder (30) with an opening at the lower end. The cylinder (30) is provided with a first pipe joint (31) and a second pipe joint (32) on the outside. The lower end of the cylinder (30) is provided with a base (33). The top of the base (33) is provided with an inner bag interface (34). The side wall of the base (33) is provided with a third pipe joint (35) that connects to the inner bag interface (34). The inner bag interface (34) is located inside the cylinder (30), and the third pipe joint (35) is located outside the cylinder (30).

4. The liquid circulation mechanism according to claim 1, characterized in that: The nozzle (3) includes a main body (40), the interior of the main body (40) is provided with a vertical channel (41), the upper end of the channel (41) is provided with a stepped hole (42), a hollow upper sleeve assembly is provided in the stepped hole (42), the upper sleeve assembly is connected to the cap (44) through a first spring (43), the cap (44) is connected to the main body (40), and the cap (44) is provided with an exhaust hole (45). The channel (41) is provided with a spray needle (46), the upper end of the spray needle (46) extends upward into the inner cavity of the upper sleeve assembly, and the upper end of the spray needle (46) is connected to the upper sleeve assembly through a second spring (47). Two circulating ink connectors (48) are provided on the outside of the main body (40), and the two circulating ink connectors (48) are respectively connected to the first pipe (12) and the second pipe (22); Below the channel (41) is a valve body (49) fixed to the main body (40). Between the valve body (49) and the main body (40) is an axially penetrating nozzle (50). The lower end of the spray needle (46) enters the nozzle (50). The lower side of the spray needle (46) is provided with a fine hole plate (51). The fine hole plate (51) is provided with a nozzle (52). The bottom of the valve body (49) is provided with a through hole (53) corresponding to the nozzle (52). The outer side of the main body (40) is provided with a pipe joint (54) that connects to the stepped surface of the stepped hole (42). The pipe joint (54) is connected to the high-pressure gas source (4) through a solenoid valve.

5. The liquid circulation mechanism according to claim 4, characterized in that: The cap (44) is screwed to the body (40), and the bottom of the cap (44) is provided with a first nut (55) screwed to the body (40).

6. The liquid circulation mechanism according to claim 4, characterized in that: The upper sleeve assembly includes an upper sleeve (56) located at the large end of the stepped hole (42). The lower end of the upper sleeve (56) is tapered inward. An upper sleeve cover (57) is screwed onto the upper end of the upper sleeve (56). Two second nuts (58) for connecting the nozzle (46) are provided on the inner side of the upper sleeve (56). The two second nuts (58) are locked to each other. One end of the second spring (47) is connected to the upper sleeve cover (57), and the other end of the second spring (47) is connected to one of the second nuts (58). A first sealing ring (59) is provided between the upper sleeve (56) and the main body (40).

7. The liquid circulation mechanism according to claim 4, characterized in that: The small end of the stepped hole (42) is provided with a third nut (60) through which the spray needle (46) passes. The third nut (60) is screwed to the main body (40). A second sealing ring (61) is provided on the lower side of the third nut (60). The second sealing ring (61) blocks the upper end of the channel (41). The lower end of the nozzle (50) is screwed to the valve body (49).

8. The liquid circulation mechanism according to claim 4, characterized in that: The valve body (49) has a tubular valve seat (62) on its outer side. The upper end of the valve seat (62) extends radially outward to form an upper flange (63). The lower end of the main body (40) has a fourth nut (64). The lower end of the fourth nut (64) extends radially inward to form a lower flange (65). The lower flange (65) presses against the upper flange (63).

9. The liquid circulation mechanism according to claim 4, characterized in that: The lower end of the spray needle (46) is provided with a rubber head (66).

10. The application of the liquid circulation mechanism according to any one of claims 1 to 9 in a coding / inkjet equipment.

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