Printing head with stable pressure intensity

Abstract

The utility model relates to a printing head with stable pressure. The printing head with the stable pressure intensity comprises a secondary ink box, a pressure supply pump, a spray head and a circulating pump, an ink containing cavity is formed in the secondary ink box and communicated with the external atmosphere through a vent hole, the pressure supply pump is communicated with an ink outlet of the secondary ink box and conveys ink to the spray head, and the circulating pump is communicated with the ink outlet of the secondary ink box and conveys the ink to the spray head. The circulating pump is communicated with an ink return port of the secondary ink box, ink is recovered from the spray head and then conveyed into the secondary ink box, and the pressure supply pump, the spray head and the circulating pump synchronously move along with the secondary ink box. The printing head with the stable pressure intensity has the advantages of being easy to control and stable in ink jet effect.

Description

Technical Field

[0001] This utility model relates to the field of printers, and in particular to a pressure-stable printhead. Background Technology

[0002] Piezoelectric inkjet printers (PIJ printers) use the vibration of piezoelectric crystals to compress ink, causing tiny amounts of ink to be expelled from the printhead and form droplets. Therefore, for PIJ printing to achieve high-precision coding, it is necessary to maintain a stable pressure at the printhead. However, the printhead is very sensitive to pressure changes, and many parameters affect pressure. Existing printheads use software control to adjust other parameters promptly when one parameter changes. However, this control method is complex, the adjustment effect is poor, and the coding stability still does not meet market requirements. Utility Model Content

[0003] Therefore, the purpose of this utility model is to provide a pressure-stable printhead, which has the advantages of simple control and stable inkjet effect.

[0004] A pressure-stabilized printhead includes a secondary ink cartridge, a pressure pump, a printhead, and a circulation pump. The secondary ink cartridge has an ink-containing chamber that is connected to the external atmosphere through a vent. The pressure pump is connected to the ink outlet of the secondary ink cartridge and delivers ink to the printhead. The circulation pump is connected to the ink return port of the secondary ink cartridge and recovers ink from the printhead and delivers it back to the secondary ink cartridge. The pressure pump, printhead, and circulation pump move synchronously with the secondary ink cartridge.

[0005] The pressure-stable printhead described in this invention can effectively ensure a stable pressure value near the printhead, thereby guaranteeing the printing effect of the printhead.

[0006] Furthermore, the secondary ink cartridge, pressure pump, printhead, and circulation pump are fixedly connected to each other, forming an integrated structure. This makes the printhead structure compact, ensuring that parameters do not change abruptly when the printhead moves or vibrates, thus improving the stability of the printhead pressure.

[0007] Furthermore, it also includes a pressure pump buffer and a circulation pump buffer. The two ends of the pressure pump buffer are connected to the pressure pump and the ink supply pipeline, respectively, and the other end of the ink supply pipeline is connected to the printhead. The two ends of the circulation pump buffer are connected to the circulation pump and the ink return pipeline, respectively, and the other end of the ink return pipeline is connected to the printhead. The buffers reduce the pressure fluctuations in the ink path caused by the pump during operation, thereby improving the stability of the pressure at the printhead.

[0008] Furthermore, it also includes a first pressure sensor that measures the pressure across a cross-section inside the pressure pump buffer where the ink flow rate is near static. This sensor detects the ink pressure in real time, improving the stability of the pressure in the ink path.

[0009] Furthermore, it also includes a second pressure sensor that measures the pressure in the ink return pipe. This facilitates control of the circulation pump, thereby maintaining a constant pressure value at the printhead.

[0010] Furthermore, a first solenoid valve is installed on the ink supply pipe, and a second solenoid valve is installed on the ink return pipe. Both the first and second solenoid valves are normally closed. A bridging pipe is connected in parallel in the circuit, with one end connected upstream of the first solenoid valve and the other end connected downstream of the second solenoid valve. A third solenoid valve, also normally closed, is installed in the bridging pipe. This structure ensures stable ink flow during startup and adjusts the pressure value measured by the sensor to ensure that the pressure value at the printhead meets production requirements, while also preventing impact on the printhead during startup.

[0011] Furthermore, it also includes a primary ink cartridge, which comprises a primary cartridge body, a primary level sensor, and an ink supply pump. The primary cartridge body holds ink, the primary level sensor detects the ink level in real time, and the ink supply pump's inlet extends below the ink level, its supply end communicating with the secondary ink cartridge, thereby drawing ink from the primary cartridge body into the secondary ink cartridge. This primary ink cartridge holds a relatively large amount of ink, ensuring the printhead can perform printing operations for extended periods without frequent ink refills.

[0012] Furthermore, the secondary ink cartridge includes a secondary cartridge body and a secondary ink level sensor. The ink-containing cavity and vent are located in the secondary cartridge body, and the secondary ink level sensor is used to detect the ink level in the secondary cartridge body in real time. This secondary ink cartridge carries only a small amount of ink sufficient to satisfy the closed-loop ink path, thereby reducing the mass of the printhead, reducing the vibration amplitude of the printhead, and improving the stability of ink pressure.

[0013] Furthermore, the secondary ink cartridge also includes a filter, which is located at the ink outlet of the secondary cartridge and connected to the pressure pump via a pipeline. The filter is used to filter the ink flowing out of the secondary ink cartridge, preventing dirt and grime from flowing into the ink path and causing printhead clogging.

[0014] Furthermore, the secondary ink cartridge also includes a heater and a temperature sensor. The heater heats the ink in the secondary ink cartridge, and the temperature sensor detects the temperature of the ink in the secondary ink cartridge. This structure ensures that the ink is at a suitable operating temperature, guaranteeing printing quality.

[0015] To better understand and implement this invention, the following detailed description is provided in conjunction with the accompanying drawings. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of the print head described in this utility model;

[0017] Explanation of reference numerals in the attached diagram: 11. Primary cartridge; 12. Primary level sensor; 13. Ink supply pump; 21. Secondary cartridge; 211. Vent; 22. Secondary level sensor; 23. Filter; 24. Heater; 25. Temperature sensor; 3. Pressure pump; 31. Pressure pump buffer; 32. First pressure sensor; 33. Ink supply pipe; 4. Printhead; 5. Circulation pump; 51. Circulation pump buffer; 52. Second pressure sensor; 53. Ink return pipe; 6. Jumper pipe; 7. First solenoid valve; 8. Second solenoid valve; 9. Third solenoid valve. Detailed Implementation

[0018] Please see Figure 1 , Figure 1 This is a schematic diagram of the printhead structure described in this utility model. This utility model discloses a pressure-stable printhead, including a primary ink cartridge and a coding assembly connected to the primary ink cartridge. This coding assembly is based on the PIJ printing principle and performs coding printing on the target product.

[0019] The primary ink cartridge includes a primary cartridge body 11, a primary ink level sensor 12, and an ink supply pump 13. The primary cartridge body 11 holds a relatively large amount of ink, ensuring the printhead can perform long printing operations without frequent ink refills. The primary ink level sensor 12 detects the ink level in real time. When it detects a low ink level in the primary cartridge body 11, it promptly outputs an ink refill prompt signal to the controller, reminding the user to add ink. The ink supply pump 13 extends below the ink level and its supply end is connected to the inkjet printing assembly, thereby drawing ink from the primary cartridge body 11 into the inkjet printing assembly.

[0020] The inkjet printing assembly is an integrated structure, comprising a secondary ink cartridge, a pressure pump 3, a printhead 4, and a circulation pump 5, which are connected sequentially via ink pipelines. Ink flows from the secondary ink cartridge, through the pressure pump 3, and into the printhead 4. Excess ink returns to the secondary ink cartridge via the circulation pump 5, forming a closed-loop ink flow circuit. The secondary ink cartridge, pressure pump 3, printhead 4, and circulation pump 5 are integrated into a single unit, secured together by fasteners or other structural components, or fixedly mounted on the same bracket. This ensures that movement of one component will cause movement of the others, thereby maintaining relatively stable parameters.

[0021] The integrated structure consists of a secondary ink cartridge, a pressure pump 3, a printhead 4, and a circulation pump 5, which are fixedly connected to each other to form a whole. These parts can be directly fixed to each other, or the structure can also include a bracket, which can be a housing or other structure. The secondary ink cartridge, pressure pump 3, printhead 4, and circulation pump 5 are all fixedly mounted on the bracket and move with the bracket, thereby ensuring that the parameters are relatively stable and avoiding the impact of high-speed reciprocating bending or movement of the pipeline on the pressure of the printhead 4.

[0022] The secondary ink cartridge includes a secondary cartridge body 21, a secondary ink level sensor 22, and a filter 23. The secondary ink cartridge contains an ink-holding chamber for holding a small amount of ink, which is connected to the ink supply end of the ink supply pump 13 via a pipe. The secondary ink level sensor 22 is used to detect the ink level in the secondary cartridge body 21 in real time. When the ink level is insufficient, the ink supply pump 13 can replenish the secondary ink cartridge with ink from the primary ink cartridge until the ink level in the secondary cartridge body 21 reaches the target height. This ensures that the printhead can print for extended periods while reducing the ink load on the printhead itself, reducing the printhead's weight, and improving printing stability.

[0023] The top of the secondary cartridge 21 has a vent 211, which allows the interior of the secondary cartridge 21 to contact atmospheric pressure. This vent 211 connects the ink chamber to the external atmosphere, providing a constant atmospheric pressure reference value at the ink level. Thus, when the printhead moves up and down at high speed during printing, the pressure of the ink paths and components inside the printhead is related to this reference value, maintaining a relatively stable pressure. This significantly improves the stability of ink ejection during operation.

[0024] The secondary ink cartridge also includes a heater 24 and a temperature sensor 25. After the printhead starts, the temperature sensor continuously monitors the ink temperature in the secondary cartridge in real time. When the detected temperature is below 5°C, the heater starts to heat the ink, keeping the temperature above 5°C; when the detected temperature is above 50°C, the temperature sensor outputs an audible and visual alarm signal to the controller to remind the user that the ink temperature is too high. This temperature value is not limited to 5°C and 50°C; its specific value is determined by the characteristics of the ink itself during actual use.

[0025] The filter 23 is located at the ink outlet of the secondary cartridge 21 and is connected to the pressure pump 3 via a pipeline. The filter 23 is used to filter the ink flowing out of the secondary ink cartridge to prevent dirt and grime from flowing into the ink path and clogging the printhead 4.

[0026] The pressure pump 3 draws ink from the secondary ink cartridge. The drawn ink passes through the ink path sequentially via the pressure pump 3, the pressure pump buffer 31, and the ink supply pipe 33 before entering the printhead 4. The pressure pump 3 provides a constant pressure and controls the ink flow rate, ensuring that the pressure at the printhead 4 reaches the required value for inkjet printing. Simultaneously, the pressure pump buffer 31 buffers upstream pressure fluctuations, preventing the secondary ink cartridge and other structures from affecting the ink path pressure during operation. The ink supply pipe 33 connects the printhead 4 and the pressure pump buffer 31. The pressure pump buffer 31 can be a flexible hose, a component with an air cavity, or a flexible container, acting as a buffer to reduce pressure fluctuations in the ink path caused by the pressure pump 3 during operation, thus improving the pressure stability at the printhead 4.

[0027] The printhead 4 adopts the piezoelectric inkjet printhead 4 of PIJ technology, which can be selected and designed according to existing technologies, and will not be elaborated here. Since the pressure at the printhead 4 determines the inkjet effect, a first pressure sensor 32 is also provided at the pressure pump buffer 31 to keep the ink pressure supplied to the printhead 4 at a stable value. The first pressure sensor 32 is used to detect the position of minimum flow rate in the pressure pump buffer 31. The pressure pump buffer 31 and the first pressure sensor 32 work in a closed loop to adjust the ink pressure in time, so that the first pressure sensor 32 is maintained at a constant value, thereby keeping the ink pressure supplied to the printhead 4 at a stable value.

[0028] In this embodiment, if the first pressure sensor 32 is to detect the position with the minimum flow rate, it should be placed in the pressure pump buffer 31 as much as possible. That is, the first pressure sensor 32 should measure the cross-section where the ink flow rate is close to static (i.e., the cross-section of the water column measured by the first pressure sensor 32 should be as large as possible) to obtain a stable pressure value.

[0029] Ink not ejected from printhead 4 flows back into the secondary ink cartridge via the return ink pipe 53, passing sequentially through the circulation pump buffer 51, the circulation pump 5, and the return ink port of the secondary ink cartridge. The circulation pump 5 ensures the ink flows back at a controlled rate, further controlling the pressure at printhead 4. The circulation pump buffer 51, located near the printhead 4, can be a component with an air cavity or a flexible container, mitigating pressure fluctuations in the circuit caused by the circulation pump 5 and improving the stability of the pressure at printhead 4. The pressure control at printhead 4 by the circulation pump 5 and the pressure supply pump 3 is as follows: when the pressure at printhead 4 is too low, the circulation pump 5 reduces its speed, while the pressure supply pump 3 increases its speed, thus increasing the pressure at the pressure supply pump buffer 31 and achieving pressure boosting at printhead 4; when the pressure at printhead 4 is too high, the circulation pump 5 increases its speed, rapidly increasing the ink flow rate, while the pressure supply pump 3 reduces its speed, thus decreasing the pressure at the pressure supply pump buffer 31 and achieving pressure reduction at printhead 4.

[0030] To detect the pressure near the nozzle 4, a second pressure sensor 52 is also installed, which works in a closed loop with the circulation pump 5. The second pressure sensor 52 detects the pressure in the ink return pipe 53. The cross-section of the detected liquid should be the same as or have a similar area to the cross-section of the pipe flowing through the nozzle 4, thereby improving the accuracy of the measured pressure value and facilitating the control of the circulation pump 5 so that the nozzle 4 is kept at a constant pressure value.

[0031] Preferably, the ink supply pipe 33 and the ink return pipe 53 are connected by a jumper pipe 6. A first solenoid valve 7 is installed on the ink supply pipe 33, and a second solenoid valve 8 is installed on the ink return pipe 53. Both the first solenoid valve 7 and the second solenoid valve 8 are normally closed. The jumper pipe 6 is connected in parallel in the circuit, with one end connected upstream of the first solenoid valve 7 and the other end connected downstream of the second solenoid valve 8. A third solenoid valve 9 is installed in the jumper pipe 6, and the third solenoid valve 9 is also normally closed. When starting operation, the third solenoid valve 9 is opened first, and the first solenoid valve 7 and the second solenoid valve 8 are closed, allowing the ink to circulate without passing through the printhead 4, thus unloading the impact load. After the pressure in the circuit stabilizes, the third solenoid valve 9 is closed, and the first solenoid valve 7 and the second solenoid valve 8 are opened, allowing the ink to flow through the printhead 4 for inkjet printing.

[0032] In this embodiment, the pressure difference relative to atmospheric pressure required for the nozzle to operate normally is -15 mbar. The pressure at the nozzle is defined as P. head The pressure of the pressure pump is P. p1 (i.e., the pressure value obtained by the first pressure sensor), the nozzle and the pressure value measured by the first pressure sensor P p1 The height difference between the liquid levels is h, the ink flow velocity is v, and the ink density is ρ. At this time... The printhead pressure is only related to the height difference, the pressure of the pressure pump, and the ink flow rate. Therefore, to ensure the stability of these parameters, the printhead is made as a single unit to avoid sudden changes in parameters. During use, the pressure pump provides a relatively constant pressure compared to atmospheric pressure and works with the circulation pump to control the ink flow rate. As the ink flows through the printhead, some ink is sprayed onto the product packaging, while excess ink flows back into the secondary ink cartridge, achieving a closed-loop circulation of ink.

[0033] The pressure-stable printhead described in this invention can effectively ensure a stable pressure value near the printhead, thereby guaranteeing the printing effect of the printhead.

[0034] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, the term "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0035] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0036] In this application, unless otherwise expressly specified and limited, the use of descriptions such as "above" or "below" the second feature indicates that the first and second features are in direct contact or indirect contact via an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. Similarly, "below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0037] The embodiments described above are merely examples of several implementations of this utility model, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the utility model patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this utility model, and this utility model also intends to include these modifications and variations.

Claims

1. A pressure-stable printhead, characterized by: The ink cartridge comprises a secondary ink cartridge, a pressure supply pump, a nozzle and a circulation pump, the secondary ink cartridge is internally provided with an ink storage cavity, the ink storage cavity is communicated with the external atmosphere through a vent hole, the pressure supply pump is communicated with an ink outlet of the secondary ink cartridge and delivers ink to the nozzle, the circulation pump is communicated with an ink return port of the secondary ink cartridge and delivers the ink from the nozzle to the secondary ink cartridge, and the pressure supply pump, the nozzle and the circulation pump move synchronously with the secondary ink cartridge.

2. A pressure-stable printhead according to claim 1, wherein: The secondary ink cartridge, the pressure supply pump, the nozzle and the circulation pump are fixedly connected with each other to form an integrated structure.

3. A pressure-stable printhead according to claim 1 or 2, characterized in that: The ink cartridge further comprises a pressure supply pump buffer and a circulation pump buffer, the pressure supply pump buffer is communicated with the pressure supply pump and an ink supply pipeline at two ends, the other end of the ink supply pipeline is communicated with the nozzle, the circulation pump buffer is communicated with the circulation pump and an ink return pipeline at two ends, and the other end of the ink return pipeline is communicated with the nozzle.

4. A pressure-stable printhead according to claim 3, wherein: The ink cartridge further comprises a first pressure sensor, which measures the pressure of the cross section of the ink flow in the pressure supply pump buffer close to static state.

5. A pressure-stable printhead according to claim 4, wherein: The ink cartridge further comprises a second pressure sensor, which measures the pressure in the ink return pipeline.

6. A pressure-stable printhead according to claim 5, wherein: The ink supply pipeline is provided with a first electromagnetic valve, the ink return pipeline is provided with a second electromagnetic valve, the first electromagnetic valve and the second electromagnetic valve are both normally closed structures, a cross connection pipeline is connected in parallel in the loop, one end of the cross connection pipeline is communicated with the upstream of the first electromagnetic valve, the other end is communicated with the downstream of the second electromagnetic valve, and a third electromagnetic valve is arranged in the cross connection pipeline, the third electromagnetic valve is a normally closed structure.

7. A pressure-stable printhead according to claim 6, wherein: The ink cartridge further comprises a primary ink cartridge, the primary ink cartridge comprises a primary cartridge body, a primary liquid level sensor and an ink supply pump, the primary cartridge body is used for containing ink, the sensing end of the primary liquid level sensor detects the ink level in real time, the ink inlet end of the ink supply pump is inserted below the ink level, and the ink outlet end is communicated with the secondary ink cartridge, so as to pump the ink in the primary cartridge body into the secondary ink cartridge.

8. A pressure-stable printhead according to claim 6, wherein: The secondary ink cartridge comprises a secondary cartridge body and a secondary liquid level sensor, the ink storage cavity and the vent hole are arranged in the secondary cartridge body, and the secondary liquid level sensor is used for detecting the ink level in the secondary cartridge body in real time.

9. A pressure-stable printhead according to claim 8, wherein: The secondary ink cartridge further comprises a filter, which is arranged at the ink outlet of the secondary cartridge body and communicated with the pressure supply pump through a pipeline.

10. A pressure-stable printhead according to claim 9, wherein: The secondary ink cartridge further comprises a heater and a temperature sensor, the heater heats the ink in the secondary ink cartridge, and the temperature sensor detects the temperature of the ink in the secondary ink cartridge.

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