Ink mixing device, digital printing machine, ink mixing method and cleaning method

Abstract

The invention discloses an ink mixing device, a digital printing machine, an ink mixing method and a cleaning method. The device comprises a plurality of basic color ink bottles and at least one transparent ink bottle, the ink mixer is provided with a plurality of ink inlets which are respectively connected with the basic color ink bottle and the transparent ink bottle; an ink outlet and an ink return opening are further formed; a first outlet of the three-way valve is connected with an ink return port of the ink mixer; an inlet of the circulating pump is connected with the ink outlet of the ink mixer, and an outlet of the circulating pump is connected with an inlet of the three-way valve; the buffer is provided with an ink inlet and an ink outlet, the ink inlet is connected to the second outlet of the three-way valve, and the ink outlet is connected with a spray head; wherein at least one of the buffer and the nozzle is provided with an ink discharge port, and the ink discharge port is provided with a first valve. The ink mixing device of the digital printing machine is simple in structure, uniform in ink mixing and convenient to clean. Moreover, the ink is not easy to dissolve in air during mixing, and the jet printing quality can be improved.

Description

Technical Field

[0001] The present application relates to the field of digital inkjet printing technology, and specifically, to an ink mixing device for a digital printer, a digital printer, an ink mixing method, and a cleaning method. Background Art

[0002] In digital inkjet printing technology, in order to achieve printing of different colors, generally several basic color inks (usually C, M, Y, K) are mixed in proportion to print the target color. For patterns with relatively rich colors, different basic color inks are sprayed onto the substrate by the print head in proportion respectively, and the mixing effect is achieved on the substrate. For the printing requirement of a large area of a single color, the basic color inks are mixed in proportion in advance to obtain the ink of the target color, and then sprayed onto the substrate by the print head, which has higher efficiency and printing effect.

[0003] In order to achieve the mixing of basic color inks of multiple colors, a patent document with the publication number KR20180063640A discloses an intelligent ink mixing system that can match colors and prepare inks without replacement and a print head having this system. However, in this ink mixing system, the inks of each color and the transparent ink are mixed evenly in the ink mixer by means of stirring blades provided in the ink mixer. This solution results in a complex structure of the ink mixer, low reliability, and it is difficult to clean the residual ink in the ink mixer when different colors need to be printed. In addition, this solution is realized by mechanical stirring, and air is easily dissolved in the ink during the stirring process. After the air enters the print head, it will affect the printing quality. Summary of the Invention

[0004] The technical problem to be solved by the present application is to provide an ink mixing device for a digital printer, a digital printer, an ink mixing method, and a cleaning method, which have a simple structure, are uniform in ink mixing, and are easy to clean.

[0005] To solve the above technical problem, an embodiment of the present application provides an ink mixing device for a digital printer, including: A plurality of basic color ink bottles and at least one transparent ink bottle; An ink mixer, provided with a plurality of ink inlets respectively connected to the basic color ink bottles and the transparent ink bottle; also provided with an ink outlet, a return ink port, and a ventilation hole; A three-way valve, the first outlet of which is connected to the return ink port of the ink mixer; A circulation pump, the inlet of which is connected to the ink outlet of the ink mixer, and the outlet of which is connected to the inlet of the three-way valve; A buffer, provided with an ink inlet and an ink outlet, the ink inlet is connected to the second outlet of the three-way valve, and the ink outlet is connected to a print head; wherein, At least one of the buffer and the print head is provided with a drain port, and a first valve is provided on the drain port.

[0006] Further, a mixing channel is provided in the ink mixer. One end of the mixing channel communicates with the inner cavity of the ink mixer, and the other end is connected to the ink outlet. A turbulence generator is provided in the mixing channel.

[0007] Further, a metering pump is provided between the ink inlet of the ink mixer and the basic color ink bottle and / or the transparent ink bottle.

[0008] Further, an air vent hole is also provided on the ink mixer.

[0009] Further, a cleaning liquid inlet is also provided on the ink mixer, and a cleaning liquid pump is provided on the connecting pipeline of the cleaning liquid inlet.

[0010] Further, a second valve is provided between the ink outlet of the buffer and the inkjet head.

[0011] Further, a first liquid sensor is provided between the ink inlet of the buffer and the three-way valve. A second liquid sensor is provided in the buffer. A third liquid sensor is provided at the ink outlet of the buffer. A fourth liquid sensor and a safety bottle are also provided on the air vent hole.

[0012] Further, a positive pressure interface and / or a negative pressure interface is also provided on the buffer, and a third valve is provided on the positive pressure interface and / or the negative pressure interface.

[0013] Further, an ink discharge pump is also connected to the ink discharge port.

[0014] Further, a second ink inlet is also provided on the buffer.

[0015] Further, there are multiple inkjet heads.

[0016] An embodiment of the present application also provides a digital inkjet printer including the above ink mixing device.

[0017] An embodiment of the present application also provides an ink mixing method based on the above ink mixing device, including: Injecting the basic color ink and the transparent ink in the basic color ink bottle and the transparent ink bottle into the ink mixer in proportion; Controlling the three-way valve to connect the inlet and the first outlet, and turning on the circulation pump. The circulation pump circulates the ink in the ink mixer between the ink outlet and the ink return port to mix the ink evenly; Controlling the three-way valve to connect the inlet and the second outlet, and supplying the ink in the ink mixer to the inkjet head through the buffer.

[0018] An embodiment of the present application also provides a cleaning method for the above ink mixing device, including: Injecting cleaning liquid into the ink mixer; Control the three-way valve to connect the inlet and the first outlet, and turn on the circulation pump. The circulation pump circulates the cleaning liquid in the ink mixer between the ink outlet and the ink return port to clean the ink mixer. Control the three-way valve to connect the inlet and the second outlet, discharge the cleaning liquid in the ink mixer into the buffer, and then discharge it through the nozzle and the ink discharge port. Repeat the above steps until the ink content in the discharged cleaning liquid is lower than the preset value.

[0019] Further, the cleaning liquid is transparent ink, and is injected into the ink mixer through a transparent ink bottle; or, the cleaning liquid is injected into the ink mixer through a cleaning liquid inlet provided on the ink mixer.

[0020] Further, a positive pressure interface is provided on the buffer, and positive pressure is provided to the buffer through the positive pressure interface, and the waste ink or cleaning liquid in the buffer is discharged by using the positive pressure.

[0021] Further, an ink discharge pump is connected to the ink discharge port, and the waste ink or cleaning liquid in the buffer is discharged by using the ink discharge pump.

[0022] Further, before injecting the cleaning liquid into the ink mixer, it further includes the step of discharging the waste ink in the ink mixer and the buffer.

[0023] The ink mixing device of the digital inkjet printer of the present application has a simple structure, mixes the ink evenly, and has the effect of being easy to clean. Moreover, air is not easily dissolved when mixing the ink, which can improve the printing quality. Description of the Drawings

[0024] Figure 1 is a schematic diagram of the first embodiment of the ink mixing device of the digital inkjet printer of the present application.

[0025] Figure 2 is a schematic diagram of the second embodiment of the ink mixing device of the digital inkjet printer of the present application.

[0026] Figure 3 is a schematic diagram of the third embodiment of the ink mixing device of the digital inkjet printer of the present application.

[0027] Figure 4 is a schematic diagram of the fourth embodiment of the ink mixing device of the digital inkjet printer of the present application.

[0028] Figure 5 is a cross-sectional view of an embodiment of the ink mixer in the ink mixing device of the digital inkjet printer of the present application.

[0029] In the figure: 1. Vent hole; 2. Fourth liquid sensor; 3. Safety bottle; 4. Positive pressure interface and / or negative pressure interface; 5. First liquid sensor; 6. Second liquid sensor; 7. Third liquid sensor; 8. Second valve; 9. First valve; 10. Third valve; 11. Ink discharge pump; 12. Ink mixer; 13. Inner cavity; 14. Ink mixing channel; 15. Turbulence generator; 16. Ink outlet; 17. Ink return port. Detailed implementation manners

[0030] The following further describes the present application with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand the present application and be able to implement it, but the specific embodiments cited are not intended to limit the present application.

[0031] As Figures 1-4 shown, an embodiment of the ink mixing device of the digital inkjet printer of the present application includes: Multiple basic color ink bottles and at least one transparent ink bottle; The ink mixer 12 is provided with a plurality of ink inlets respectively connected to the basic color ink bottles and the transparent ink bottle; it is also provided with an ink outlet 16, an ink return port 17 and a vent hole 1; A three-way valve, the first outlet of which is connected to the ink return port 17 of the ink mixer 12; A circulation pump, the inlet of which is connected to the ink outlet 16 of the ink mixer 12, and the outlet is connected to the inlet of the three-way valve; A buffer, which is provided with an ink inlet and an ink outlet, the ink inlet is connected to the second outlet of the three-way valve, and the ink outlet is connected to a nozzle; wherein, At least one of the buffer and the nozzle is provided with an ink discharge port, and a first valve 9 is arranged on the ink discharge port.

[0032] The embodiment of the present application includes an ink mixing device with multiple basic color ink bottles and transparent ink bottles. The ink mixer 12 is provided with an ink inlet, an ink outlet 16 and an ink return port 17, and forms a circulation channel through a three-way valve connected to a circulation pump. The buffer is connected to the nozzle and is configured with an ink discharge port. Among them, the basic color ink bottles are used to store basic color inks, the transparent ink bottles are used to adjust the ink concentration or clean the pipeline, the ink inlets are used as input interfaces for different inks, the ink outlet 16 forms the starting point of the flow with the inlet of the circulation pump, and the ink return port 17 constitutes the end point of the circulation loop. The three-way valve is used to switch the ink flow direction, the first outlet is connected to the ink return port 17 to form a closed loop, and the second outlet leads to the buffer.

[0033] The basic color ink bottle refers to a container for storing un-mixed basic color inks. For example, it includes ink bottles for storing four colors of C, M, Y, and K respectively. Specifically, it can be realized by using a corrosion-resistant plastic bottle body with a sealing cover to ensure the independent storage of different color inks.

[0034] When performing a printing operation, the base color inks of different colors in each base color ink bottle and the transparent ink in the transparent ink bottle are injected into the ink mixer 12 in proportion. Control the three-way valve to connect the inlet and the first outlet, and turn on the circulation pump. The circulation pump makes the ink in the ink mixer 12 circulate between the ink outlet 16 and the ink return port 17. After circulating for a certain period of time, the ink is evenly mixed. After the ink is evenly mixed, control the three-way valve to connect the inlet and the second outlet, and supply the ink in the ink mixer 12 to the nozzle through the buffer.

[0035] In the embodiment of the present application, the circulation pump is used to make the ink in the ink mixer 12 form a circulating flow and be evenly mixed during the circulating flow process. Compared with the existing mechanical stirring methods such as setting stirring blades in the ink mixer 12, no other components need to be set in the ink mixer 12 in the embodiment of the present application. The structure is simple, easy to process, and easy to clean when the color needs to be switched. At the same time, compared with the mechanical stirring method, the ink mixing solution in the embodiment of the present application is less likely to dissolve air into the ink, so as to avoid the dissolved air affecting the printing quality.

[0036] In order to achieve ink mixing better and more efficiently, as Figure 5 shown, in the embodiment of the present application, an ink mixing channel 14 is provided in the ink mixer 12. One end of the ink mixing channel 14 is communicated with the inner cavity 13 of the ink mixer 12, and the other end is connected to the ink outlet 16; a turbulence generator 15 is provided in the ink mixing channel 14. The turbulence generator 15 makes the ink flowing through the ink mixing channel 14 generate turbulence to accelerate the mixing of the ink. The turbulence generator 15 can be any structure that can make the ink generate turbulence. For example, it can be the Figure 5 shown spiral blade structure, or it can be a protrusion provided on the inner wall of the ink mixing channel 14, etc.

[0037] It can be understood that although the embodiment of the present application is configured with multiple base color ink bottles and transparent ink bottles, when performing a printing operation, it is not necessarily required to use all the ink bottles. That is, the proportion of the ink in any ink bottle can be 0. For example, if a target color is exactly obtained by using two base color inks each accounting for 50%, only these two base color inks are selected and injected into the ink mixer 12, and other base color inks do not need to be injected. The function of the transparent ink is that when the color to be printed is relatively light, if the transparent ink is not added, it is necessary to reduce the density of the printed ink dots to achieve a light color vision, but the printing quality of this method is poor. After adding the transparent ink, there is no need to reduce the number of printed ink dots, making the printed color more uniform and saturated.

[0038] The functions of the buffer in the embodiment of the present application are: first, the pressure in the buffer is easier to control, so that the ink can be stably supplied to the nozzle; second, it can ensure long-term continuous ink supply. Since the volume of the ink mixer 12 cannot be too large, it usually cannot meet the amount of ink required for a printing operation. After the ink that has been mixed evenly for the first time is injected into the buffer, the printing operation can be started at this time. During the operation, the ink passage from the ink mixer 12 to the buffer is first disconnected, and then the ink mixing operation can continue in the ink mixer 12. After the mixing is even, the ink passage from the ink mixer 12 to the buffer is opened again, and the mixed ink is injected into the buffer. In this cycle, long-term continuous ink supply can be achieved.

[0039] After the printing operation is completed, if the color of the next printing is different, the ink mixing device, nozzle and pipelines need to be cleaned. The details are as follows: Injecting cleaning liquid into the ink mixer 12; The three-way valve is controlled to connect the inlet and the first outlet, and the circulation pump is turned on. The circulation pump allows the cleaning liquid in the ink mixer 12 to circulate between the ink outlet 16 and the ink return port 17 to clean the ink mixer 12; Control the three-way valve to connect the inlet and the second outlet, discharge the cleaning liquid in the ink mixer 12 to the buffer, and then discharge it through the nozzle and the ink outlet; Repeat the above steps until the ink content in the discharged cleaning fluid is lower than the preset value.

[0040] Of course, if there is still waste ink in the ink mixer 12 , the buffer, the nozzle and the pipeline, the waste ink in the ink mixer 12 , the buffer, the nozzle and the pipeline needs to be discharged before the cleaning liquid is injected into the ink mixer 12 .

[0041] A metering pump may be provided between the ink inlet of the ink mixer 12 and the basic color ink bottle and / or the transparent ink bottle. A metering pump refers to a fluid delivery device that can accurately control the amount of liquid delivered, and may be implemented using a peristaltic pump. The device receives control instructions through signals and can adjust the pumping speed in real time to ensure that the volume of ink delivered per unit time meets a preset value. Specifically, the metering pump is installed in the conveying pipeline between the base color ink bottle and the ink mixer 12, or is installed on the conveying paths of both the base color ink bottle and the transparent ink bottle at the same time. When color mixing is required, the control system sends signals to each metering pump according to the ratio of the target color, so as to pump the corresponding amount of base color ink and / or transparent ink. For example, when it is necessary to prepare a mixture containing 30% cyan base color ink and 70% transparent ink, the metering pump corresponding to the cyan base color ink bottle and the metering pump corresponding to the transparent ink bottle pump cyan ink and transparent ink into the ink mixer 12 at a rate ratio of 3:7. The embodiment of the present application realizes the closed-loop control of the injection amount by setting a metering pump in the conveying path. For example, when it is detected that there is a deviation in the color after a certain mixing, the rotation speed of the corresponding metering pump can be automatically adjusted to compensate for the error. The function of setting the vent hole 1 on the ink mixer 12 is to balance the internal and external air pressures of the ink mixer 12. When injecting ink or cleaning liquid into the ink mixer 12, the air in the ink mixer 12 is discharged through the vent hole 1; when discharging the ink or cleaning liquid in the ink mixer 12, air enters the ink mixer 12 through the vent hole 1. A microporous filter membrane can be set on the vent hole 1. The microporous filter membrane allows gas to escape but prevents liquid leakage, and can also prevent impurities in the air from entering the ink mixing bottle. During the ink circulation process, the air dissolved in the ink may be precipitated and accumulated in the ink mixer 12. In this embodiment, the accumulated air in the ink mixer 12 can also be discharged through the vent hole 1 to prevent the air from entering the nozzle with the ink and affecting the printing effect. When the amount of ink overflowing from the vent hole 1 is large, the microporous filter membrane cannot completely prevent the ink from overflowing. Therefore, in the embodiment of the present application, a fourth liquid sensor 2 and a safety bottle 3 can also be set on the vent hole 1. When the fourth liquid sensor 2 detects liquid, it sends a signal to control the metering pump or the cleaning liquid pump to stop working and no longer inject liquid into the ink mixer 12 to prevent liquid from overflowing. If the ink overflows due to some factors, it can be received by the safety bottle 3.

[0042] In the embodiment of the present application, the cleaning liquid can be transparent ink and is injected into the ink mixer 12 through the transparent ink bottle to complete the cleaning. In other embodiments of the present application, a cleaning liquid inlet can also be set on the ink mixer 12, and a cleaning liquid pump is set on the connecting pipeline of the cleaning liquid inlet. By setting an independent cleaning liquid inlet in this embodiment, the cleaning liquid can be injected into the ink mixer 12 more quickly. The cleaning liquid can be transparent ink or other liquids, such as ultrapure water, deionized water, etc.

[0043] In an embodiment of the present application, a second valve 8 may also be provided between the ink outlet of the buffer and the nozzle. During the cleaning operation, the second valve 8 can be closed first to cut off the passage from the buffer to the nozzle. At this time, other components except the nozzle can be cleaned with a relatively large cleaning pressure and flow rate, with high cleaning efficiency and good cleaning effect. After cleaning other components, the second valve 8 is then opened to clean the nozzle with a relatively low cleaning pressure and flow rate to avoid damaging the nozzle due to excessive pressure and flow rate. In addition, the second valve 8 can also prevent air from entering the nozzle.

[0044] In an embodiment of the present application, a first liquid sensor 5 is provided between the ink inlet of the buffer and the three-way valve, a second liquid sensor 6 is provided in the buffer, and a third liquid sensor 7 is provided at the ink outlet of the buffer. Among them, the first liquid sensor 5 can be implemented by a flow meter or a photoelectric sensor, and is used to detect the flow state of ink or cleaning liquid during the transportation from the ink mixer 12 to the buffer. The second liquid sensor 6 can be implemented by a float sensor or a capacitive liquid level sensor, and is used to monitor the liquid level height in the buffer. The third liquid sensor 7 can be implemented by a flow meter or a photoelectric sensor, and is used to monitor the flow of ink or cleaning liquid output to the nozzle. Specifically, the first liquid sensor 5 detects the flow signal of ink transported from the ink mixer 12 to the buffer, and serves as a start signal for corresponding steps during the printing operation or the cleaning operation. The second liquid sensor 6 continuously monitors the liquid level height in the buffer. During the printing operation, when the liquid level in the buffer exceeds the preset upper limit, a trigger signal is sent to stop ink mixing. When the liquid level in the buffer is lower than the preset lower limit, a trigger signal is sent to perform the ink mixing operation and inject the uniformly mixed ink into the buffer until the liquid level in the buffer reaches the preset upper limit. During the cleaning operation, the second liquid sensor 6 is used to detect whether the waste ink or cleaning liquid in the buffer has been emptied. The third liquid sensor 7 detects the flow state at the ink outlet and serves as a start signal for corresponding steps during the printing operation or the cleaning operation.

[0045] The embodiment of the present application solves the problem that the flow state of ink and the liquid level of the buffer in the ink mixing device cannot be monitored in real time. During the cleaning process, the completion state of cleaning is determined through the cooperation of multiple sensors to ensure that the residual ink or cleaning liquid is completely discharged, improving the stability and reliability of the system operation.

[0046] In the embodiments of the present application, a positive pressure interface and / or a negative pressure interface 4 may also be provided on the buffer. A third valve 10 is provided on the positive pressure interface and / or the negative pressure interface 4. Among them, the negative pressure interface is connected to an external negative pressure source, and the negative pressure source can be specifically implemented by a vacuum pump or a negative pressure generator, and is used to provide negative pressure to the buffer. The first function of the negative pressure is that the mixed ink can be sucked into the buffer from the ink mixer 12 by using the negative pressure. The second function of the negative pressure is to form a certain suction force on the ink in the nozzle to prevent the ink in the nozzle from flowing out.

[0047] The positive pressure interface is connected to a positive pressure source, and the positive pressure source can be implemented by an air pump or a compressed air pipeline, and is used to apply a controllable positive pressure to the inside of the buffer to accelerate the discharge of waste liquid. Only one of the positive pressure interface and the negative pressure interface can be provided, or both can be provided, or the two can share one interface. When positive pressure is required, the interface is connected to the positive pressure source, and when negative pressure is required, the interface is switched to the negative pressure source.

[0048] In the embodiments of the present application, an ink discharge pump 11 may also be connected to the ink discharge port. The ink discharge pump 11 is used to accelerate the discharge of waste ink or cleaning liquid from the ink discharge port. Specifically, when the buffer or the nozzle needs to discharge waste ink, the ink discharge pump 11 forms a fluid path with the ink discharge port. After the pump body starts, a suction force is generated to forcibly drive the waste ink to be discharged from the ink discharge port. During the cleaning stage, the cleaning liquid enters the buffer after circulating through the ink mixer 12, and the continuous operation of the ink discharge pump 11 causes the cleaning liquid to be quickly discharged from the ink discharge port, improving the cleaning efficiency.

[0049] Both the positive pressure interface of the buffer and the ink discharge pump 11 can play a role in accelerating the discharge of waste ink and cleaning liquid. Either one can be provided, or both can be provided simultaneously to work together. When only the ink discharge pump 11 is used, the positive pressure interface can be communicated with the atmosphere to balance the air pressure inside and outside the buffer.

[0050] In the embodiments of the present application, a second ink inlet is also provided on the buffer. The second ink inlet is used to directly inject the pre-mixed ink into the buffer, that is, path 3, providing an additional option for users. During the cleaning operation, the cleaning liquid can also be injected through the second ink inlet.

[0051] In the embodiments of the present application, there are multiple nozzles, and the multiple nozzles are connected in parallel. The multiple nozzles can perform the printing task simultaneously, increasing the printing area for simultaneous printing and improving the printing efficiency.

[0052] The following further illustrates the present application through specific embodiments.

[0053] As Figure 1As shown, in this embodiment, the ink mixing device includes four basic color ink bottles and one transparent ink bottle. A metering pump is provided between each ink bottle and the ink mixer 12. The ink mixer 12 is provided with a vent hole 1 and a cleaning liquid inlet. A cleaning liquid pump is provided on the connecting pipeline of the cleaning liquid inlet. A fourth liquid sensor 2 is provided on the vent hole 1 and is connected to a safety bottle 3. In this embodiment, there are N nozzles (N is a natural number greater than 1). Each nozzle is respectively connected to a buffer through an independent pipeline. A second valve 8 is provided on the pipeline between the ink outlet of the buffer and each nozzle; a drain port is provided on each nozzle and the buffer. Among them, the drain ports of multiple nozzles are connected in parallel and then a first valve 9 is provided. The drain port of the buffer is independently provided with a first valve 9; a first liquid sensor 5 is provided between the ink inlet of the buffer and the three-way valve. A second liquid sensor 6 is provided in the buffer. A third liquid sensor 7 is provided at each ink outlet of the buffer; the buffer is provided with an interface for sharing positive pressure and negative pressure. A third valve 10 is provided on the interface. The buffer is also provided with a second ink inlet.

[0054] Based on the ink mixing device of this embodiment, its cleaning method includes: 101. Close the second valve 8 from the buffer to each nozzle, open the first valve 9 on the drain port of the buffer, control the three-way valve to connect the inlet and the second outlet, that is, path 2, turn on the circulation pump, discharge the waste ink in the ink mixer 12 into the buffer, input positive pressure into the buffer through the positive pressure interface, and discharge the waste ink in the buffer through the drain port; detect the discharge situation of the waste ink through the first liquid sensor 5 and the second liquid sensor 6. When neither the first liquid sensor 5 nor the second liquid sensor 6 detects liquid, delay for a preset time (such as several seconds). At this time, the waste ink has been completely discharged; turn off the circulation pump and the positive pressure input of the buffer, and close the first valve 9 on the drain port of the buffer; 102. Turn on the cleaning liquid pump, inject cleaning liquid into the ink mixer 12, control the three-way valve to connect the inlet and the first outlet, that is, path 1, turn on the circulation pump to make the cleaning liquid form a cycle to clean the ink mixer 12. After the cleaning liquid in the ink mixer 12 reaches the preset amount, turn off the cleaning liquid pump (which can be achieved by controlling the running time of the cleaning liquid pump); 103. After the circulation pump runs for a certain time, control the three-way valve to connect the inlet and the second outlet, that is, path 2, and inject the cleaning liquid in the ink mixer 12 into the buffer; 104. If the amount of cleaning liquid in the buffer does not reach the preset value, repeat the above steps 102 and 103; if the amount of cleaning liquid in the buffer reaches the preset value, turn off the circulation pump; 105. Input positive pressure into the buffer through the positive pressure interface, and discharge the cleaning liquid in the buffer through the ink discharge port; detect the discharge situation of the cleaning liquid through the first liquid sensor 5 and the second liquid sensor 6. When neither the first liquid sensor 5 nor the second liquid sensor 6 detects liquid, delay for a preset time (such as several seconds). At this time, the cleaning liquid has been completely discharged; close the positive pressure input of the circulation pump and the buffer, and close the first valve 9 on the ink discharge port of the buffer. 106. Repeat the above steps 102 to 105 until the ink content in the cleaning liquid discharged from the ink discharge port of the buffer is lower than the preset value and will not affect the next use. 107. Execute steps 102 to 104, turn on the positive pressure input of the buffer, turn on the second valve 8 from the buffer to each nozzle and the first valve 9 on the ink discharge port of the nozzle, so that the cleaning liquid in the buffer is discharged through the nozzle. 108. Detect the discharge situation of the cleaning liquid through the third liquid sensor 7. When the third liquid sensor 7 does not detect liquid, turn off the positive pressure input of the buffer, and turn off the second valve 8 from the buffer to each nozzle and the first valve 9 on the ink discharge port of the nozzle. 109. Repeat steps 107 to 108 until the ink content in the cleaning liquid discharged from the ink discharge port of the nozzle is lower than the preset value and will not affect the next use, and the cleaning is completed.

[0055] In this embodiment, if all the mixed ink is just used up at the end of the printing, that is, there is no waste ink in both the ink mixer 12 and the buffer, and step 101 does not need to be executed. The cleaning liquid remaining in the nozzle can be discharged from the nozzle orifice in the form of empty spraying (that is, not spraying on the printing substrate) before the printing operation.

[0056] As Figure 2 shown, in this embodiment, the difference between the ink mixing device and the Figure 1 embodiment shown is that the second valve 8 from the buffer to each nozzle is removed. Based on this, its cleaning method includes: 201. Close the first valve 9 on the ink discharge port of the nozzle, open the first valve 9 on the ink discharge port of the buffer, control the three-way valve to connect the inlet and the second outlet, that is, path 2, turn on the circulation pump, discharge the waste ink in the ink mixer 12 into the buffer, input positive pressure into the buffer through the positive pressure interface, and discharge the waste ink in the buffer through the ink discharge port; detect the discharge situation of the waste ink through the first liquid sensor 5 and the second liquid sensor 6. When neither the first liquid sensor 5 nor the second liquid sensor 6 detects liquid, delay for a preset time (such as several seconds). At this time, the waste ink has been completely discharged; close the circulation pump and the positive pressure input of the buffer, and close the first valve 9 on the ink discharge port of the buffer. Turn on the cleaning liquid pump, inject cleaning liquid into the ink mixer 12, control the three-way valve to connect the inlet and the first outlet, that is, path 1, turn on the circulation pump to form a circulation of the cleaning liquid to clean the ink mixer 12, and turn off the cleaning liquid pump after the cleaning liquid in the ink mixer 12 reaches a preset amount (which can be achieved by controlling the running time of the cleaning liquid pump); After the circulation pump runs for a certain period of time, control the three-way valve to connect the inlet and the second outlet, that is, path 2, and inject the cleaning liquid in the ink mixer 12 into the buffer; If the amount of cleaning liquid in the buffer does not reach the preset value, repeat steps 202 and 203 above; if the amount of cleaning liquid in the buffer reaches the preset value, turn off the circulation pump; Input positive pressure into the buffer through the positive pressure interface, and discharge the cleaning liquid in the buffer through the ink discharge port; detect the discharge condition of the cleaning liquid through the first liquid sensor 5 and the second liquid sensor 6. When neither the first liquid sensor 5 nor the second liquid sensor 6 detects liquid, delay for a preset time (such as several seconds). At this time, the cleaning liquid has been completely discharged; turn off the circulation pump and the positive pressure input of the buffer, and close the first valve 9 on the ink discharge port of the buffer; Repeat steps 202 to 205 above until the ink content in the cleaning liquid discharged from the ink discharge port of the buffer is lower than the preset value and will not affect the next use; Execute steps 202 to 204, turn on the first valve 9 on the ink discharge port of the nozzle, and discharge the cleaning liquid in the buffer through the nozzle; Detect the discharge condition of the cleaning liquid through the third liquid sensor 7. When the third liquid sensor 7 does not detect liquid, turn off the positive pressure input of the buffer and close the first valve 9 on the ink discharge port of the nozzle; Repeat steps 207 to 208 until the ink content in the cleaning liquid discharged from the ink discharge port of the nozzle is lower than the preset value and will not affect the next use, and the cleaning is completed.

[0057] In this embodiment, if all the mixed ink is just used up at the end of the printing, that is, there is no waste ink in the ink mixer 12 and the buffer, and step 201 does not need to be executed. The cleaning liquid remaining in the nozzle can be discharged from the nozzle holes in the form of empty spraying (that is, not spraying on the printing substrate) before the printing operation.

[0058] As Figure 3 shown, in this embodiment, the difference between the ink mixing device and the Figure 1 embodiment shown is that ink discharge pumps 11 are respectively arranged at the ink discharge ports of the buffer and the nozzle. Based on this, its cleaning method includes: 301. Close the second valve 8 from the buffer to each nozzle, open the first valve 9 on the ink discharge port of the buffer, control the three-way valve to connect the inlet and the second outlet, that is, path 2, turn on the circulation pump, discharge the waste ink in the ink mixer 12 into the buffer, open the ink discharge pump 11 on the ink discharge port of the buffer, and discharge the waste ink in the buffer through the ink discharge port; detect the waste ink discharge situation through the first liquid sensor 5 and the second liquid sensor 6. When neither the first liquid sensor 5 nor the second liquid sensor 6 detects liquid, delay for a preset time (such as several seconds). At this time, the waste ink has been completely discharged; turn off the circulation pump and the ink discharge pump 11 on the ink discharge port of the buffer, and close the first valve 9 on the ink discharge port of the buffer; 302. Turn on the cleaning liquid pump, inject cleaning liquid into the ink mixer 12, control the three-way valve to connect the inlet and the first outlet, that is, path 1, turn on the circulation pump to make the cleaning liquid circulate to clean the ink mixer 12, and turn off the cleaning liquid pump after the cleaning liquid in the ink mixer 12 reaches the preset amount (which can be achieved by controlling the running time of the cleaning liquid pump); 303. After the circulation pump runs for a certain time, control the three-way valve to connect the inlet and the second outlet, that is, path 2, and inject the cleaning liquid in the ink mixer 12 into the buffer; 304. If the amount of cleaning liquid in the buffer does not reach the preset value, repeat the above steps 302 and 303; if the amount of cleaning liquid in the buffer reaches the preset value, turn off the circulation pump; 305. Turn on the ink discharge pump 11 on the ink discharge port of the buffer, and discharge the cleaning liquid in the buffer through the ink discharge port; detect the cleaning liquid discharge situation through the first liquid sensor 5 and the second liquid sensor 6. When neither the first liquid sensor 5 nor the second liquid sensor 6 detects liquid, delay for a preset time (such as several seconds). At this time, the cleaning liquid has been completely discharged; turn off the circulation pump, the first valve 9 on the ink discharge port of the buffer, and the ink discharge pump 11; 306. Repeat the above steps 302 to 305 until the ink content in the cleaning liquid discharged from the ink discharge port of the buffer is lower than the preset value and will not affect the next use; 307. Execute steps 302 to 304, turn on the second valve 8 from the buffer to each nozzle, the first valve 9 and the ink discharge pump 11 on the ink discharge port of the nozzle, and make the cleaning liquid in the buffer discharge through the nozzle; 308. Detect the cleaning liquid discharge situation through the third liquid sensor 7. When the third liquid sensor 7 does not detect liquid, close the second valve 8 from the buffer to each nozzle, the first valve 9 and the ink discharge pump 11 on the ink discharge port of the nozzle; 309. Repeat steps 307 to 308 until the ink content in the cleaning liquid discharged from the ink discharge port of the nozzle is lower than the preset value and will not affect the next use, and the cleaning is completed.

[0059] In this embodiment, if all the mixed ink is exactly used up at the end of the printing, that is, there is no waste ink in the ink mixer 12 and the buffer, and step 301 does not need to be executed. The cleaning liquid remaining in the nozzle can be discharged from the nozzle holes of the nozzle in the form of empty spraying (i.e., not spraying on the printing substrate) before the printing operation.

[0060] In this embodiment, when the drain pump 11 is turned on, the positive pressure input of the buffer can also be turned on, and the positive pressure and the drain pump 11 cooperate to complete the liquid discharge, improving the efficiency; correspondingly, when the drain pump 11 is turned off, the positive pressure input of the buffer is also turned off synchronously.

[0061] As Figure 4 shown, in this embodiment, the difference between the ink mixing device and the Figure 3 embodiment shown is that the second valve 8 from the buffer to each nozzle is removed. Based on this, its cleaning method includes: 401. Close the first valve 9 at the drain port of the nozzle, open the first valve 9 at the drain port of the buffer, control the three-way valve to connect the inlet and the second outlet, that is, path 2, turn on the circulation pump, discharge the waste ink in the ink mixer 12 into the buffer, open the drain pump 11 at the drain port of the buffer, and discharge the waste ink in the buffer through the drain port; detect the discharge situation of the waste ink through the first liquid sensor 5 and the second liquid sensor 6. When neither the first liquid sensor 5 nor the second liquid sensor 6 detects liquid, delay for a preset time (for example, several seconds). At this time, the waste ink has been completely discharged; turn off the circulation pump and the drain pump 11 at the drain port of the buffer, and close the first valve 9 at the drain port of the buffer; 402. Turn on the cleaning liquid pump, inject cleaning liquid into the ink mixer 12, control the three-way valve to connect the inlet and the first outlet, that is, path 1, turn on the circulation pump to form a circulation of the cleaning liquid to clean the ink mixer 12, and turn off the cleaning liquid pump after the cleaning liquid in the ink mixer 12 reaches the preset amount (which can be achieved by controlling the running time of the cleaning liquid pump); 403. After the circulation pump runs for a certain time, control the three-way valve to connect the inlet and the second outlet, that is, path 2, and inject the cleaning liquid in the ink mixer 12 into the buffer; 404. If the amount of cleaning liquid in the buffer does not reach the preset value, repeat steps 402 and 403 above; if the amount of cleaning liquid in the buffer reaches the preset value, turn off the circulation pump; 405. Turn on the drain pump 11 at the drain port of the buffer, and discharge the cleaning liquid in the buffer through the drain port; detect the discharge situation of the cleaning liquid through the first liquid sensor 5 and the second liquid sensor 6. When neither the first liquid sensor 5 nor the second liquid sensor 6 detects liquid, delay for a preset time (for example, several seconds). At this time, the cleaning liquid has been completely discharged; turn off the circulation pump, the first valve 9 at the drain port of the buffer, and the drain pump 11; 406. Repeat the above steps 402 to 405 until the ink content in the cleaning liquid discharged from the ink discharging port of the buffer is lower than the preset value and will not affect the next use; 407. Execute steps 402 to 404, open the first valve 9 and the ink discharging pump 11 on the ink discharging port of the nozzle, and discharge the cleaning liquid in the buffer through the nozzle; 408. Detect the discharge condition of the cleaning liquid through the third liquid sensor 7. When the third liquid sensor 7 cannot detect the liquid, close the first valve 9 and the ink discharging pump 11 on the ink discharging port of the nozzle; 409. Repeat steps 407 to 408 until the ink content in the cleaning liquid discharged from the ink discharging port of the nozzle is lower than the preset value and will not affect the next use, and the cleaning is completed.

[0062] In this embodiment, if all the mixed ink is just used up at the end of the printing, that is, there is no waste ink in both the ink mixer 12 and the buffer, and step 401 does not need to be executed. The cleaning liquid remaining in the nozzle can be discharged from the nozzle holes in the form of empty spraying (i.e., not spraying on the printing substrate) before the printing operation.

[0063] In this embodiment, when the ink discharging pump 11 is opened, the positive pressure input of the buffer can also be opened, and the liquid discharge is jointly completed by the positive pressure and the ink discharging pump 11 to improve the efficiency; correspondingly, when the ink discharging pump 11 is closed, the positive pressure input of the buffer is also synchronously closed.

[0064] In the above embodiments, ink discharging ports are provided on both the buffer and the nozzle. The advantage is that the ink discharging port on the nozzle can be closed first, and the ink discharging port on the buffer is opened. At this time, other components except the nozzle can be cleaned with a larger cleaning pressure and flow rate, with high cleaning efficiency and good cleaning effect. After cleaning other components, the ink discharging port on the nozzle is opened, and the ink discharging port on the buffer is closed, and the nozzle is cleaned with a lower cleaning pressure and flow rate to avoid damaging the nozzle due to excessive pressure and flow rate. In other embodiments, an ink discharging port can also be provided only on the buffer, and when the nozzle needs to be cleaned, the waste ink or cleaning liquid is discharged through the nozzle holes. Of course, an ink discharging port can also be provided only on the nozzle, and both the waste ink and the cleaning liquid are discharged from the ink discharging port on the nozzle.

[0065] The above-described embodiments are only preferred embodiments given to fully illustrate the present application, and the protection scope of the present application is not limited thereto. Equivalent substitutions or transformations made by those skilled in the art on the basis of the present application are within the protection scope of the present application. The protection scope of the present application is subject to the claims.

Claims

1. An ink mixing device for a digital printing machine, characterized in that, Comprising: A plurality of basic color ink bottles and at least one transparent ink bottle; An ink mixer, provided with a plurality of ink inlets respectively connected to the basic color ink bottles and the transparent ink bottle; also provided with an ink outlet, an ink return port and a vent hole; A three-way valve, whose first outlet is connected to the ink return port of the ink mixer; A circulation pump, whose inlet is connected to the ink outlet of the ink mixer and whose outlet is connected to the inlet of the three-way valve; A buffer, provided with an ink inlet and an ink outlet, the ink inlet is connected to the second outlet of the three-way valve, and the ink outlet is connected with a print head; wherein, At least one of the buffer and the print head is provided with a drain port, and a first valve is provided on the drain port.

2. The ink mixing device of the digital printing machine according to claim 1, characterized in that, An ink mixing channel is provided in the ink mixer, one end of the ink mixing channel communicates with the inner cavity of the ink mixer, and the other end is connected to the ink outlet; a turbulence generator is provided in the ink mixing channel.

3. The ink mixing device of the digital printing machine according to claim 1, characterized in that, A metering pump is provided between the ink inlet of the ink mixer and the basic color ink bottle and / or the transparent ink bottle.

4. The ink mixing device of the digital printing machine according to claim 1, characterized in that, The ink mixer is also provided with a vent hole.

5. The ink mixing device of the digital printing machine according to claim 1, characterized in that, The ink mixer is also provided with a cleaning liquid inlet, and a cleaning liquid pump is provided on the connecting pipeline of the cleaning liquid inlet.

6. The ink mixing device of the digital printing machine according to claim 1, characterized in that, A second valve is provided between the ink outlet of the buffer and the print head.

7. The ink mixing device of the digital printing machine according to claim 1, characterized in that, A first liquid sensor is provided between the ink inlet of the buffer and the three-way valve, a second liquid sensor is provided in the buffer, a third liquid sensor is provided at the ink outlet of the buffer, and a fourth liquid sensor and a safety bottle are also provided on the vent hole.

8. The ink mixing device of the digital printing machine according to claim 1, characterized in that, The buffer is also provided with a positive pressure interface and / or a negative pressure interface, and a third valve is provided on the positive pressure interface and / or the negative pressure interface.

9. The ink mixing device of the digital printing machine according to claim 1, characterized in that, A drain pump is also connected to the drain port.

10. The ink mixing device of the digital printing machine according to claim 1, characterized in that, The buffer is also provided with a second ink inlet.

11. The ink mixing device of the digital printing machine according to any one of claims 1-10, characterized in that, There are a plurality of the print heads.

12. A digital printing machine comprising the ink mixing device according to any one of claims 1-11.

13. A method for mixing ink based on the ink mixing device according to any one of claims 1-11, characterized in that, Comprising: Inject the basic color ink and the transparent ink in the basic color ink bottle and the transparent ink bottle into the ink mixer in proportion; Control the three-way valve to connect the inlet and the first outlet, and turn on the circulation pump. The circulation pump circulates the ink in the ink mixer between the ink outlet and the ink return port to mix the ink evenly; Control the three-way valve to connect the inlet and the second outlet, and supply the ink in the ink mixer to the print head through the buffer.

14. A cleaning method for the ink mixing device according to claim 1, characterized in that, Comprising: Inject cleaning liquid into the ink mixer; Control the three-way valve to connect the inlet and the first outlet, and turn on the circulation pump. The circulation pump circulates the cleaning liquid in the ink mixer between the ink outlet and the ink return port to clean the ink mixer; Control the three-way valve to connect the inlet and the second outlet, and discharge the cleaning liquid in the ink mixer to the buffer, and then discharge it through the print head and the drain port; Repeat the above steps until the ink content in the discharged cleaning liquid is lower than a preset value.

15. The cleaning method according to claim 14, wherein, The cleaning liquid is transparent ink and is injected into the ink mixer through the transparent ink bottle; or, the cleaning liquid is injected into the ink mixer through the cleaning liquid inlet provided on the ink mixer.

16. The cleaning method according to claim 14, wherein, A positive pressure interface is provided on the buffer, and positive pressure is provided to the buffer through the positive pressure interface, and the waste ink or cleaning liquid in the buffer is discharged by using the positive pressure.

17. The cleaning method according to claim 14, wherein A drain pump is connected to the drain port, and the waste ink or cleaning liquid in the buffer is discharged by using the drain pump.

18. The cleaning method according to claim 14, wherein Before injecting the cleaning liquid into the ink mixer, it further includes the step of discharging the waste ink in the ink mixer and the buffer.

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