Liquid supply device

Abstract

The invention relates to a liquid supply device which comprises a liquid supply cavity filled with hydraulic oil, a solution bladder is arranged in the hydraulic oil of the liquid supply cavity, an inner cavity is formed in the solution bladder, the inner cavity is filled with a coating ink solution, and the outer wall of the solution bladder elastically deforms along with the pressure of the hydraulic oil. When the pressure of the hydraulic oil is reduced, the volume of the inner cavity is increased, otherwise, when the pressure of the hydraulic oil is increased, the volume of the inner cavity is reduced, and a liquid inlet and a liquid outlet which are communicated with the inner cavity are respectively formed in the solution bladder; the liquid inlet and the liquid outlet are respectively communicated with a liquid inlet pipeline and a liquid outlet pipeline which are arranged outside the liquid supply cavity, and the liquid inlet pipeline is communicated with a container filled with a coating ink solution; a pushing device capable of changing the pressure of hydraulic oil in the liquid supply cavity is further arranged on the liquid supply cavity. The hydraulic buffering principle is utilized, hydraulic fluctuation in the coating process is reduced, and the high-hydraulic-pressure and high-precision coating requirements are met.

Description

Technical Field

[0001] The present invention belongs to the technical field of thin film coating equipment, and particularly relates to a liquid supply device. Background Art

[0002] Slot coating is widely used in the display industry, semiconductor industry, solar thin film battery industry, etc. due to its advantages of high coating accuracy, high coating speed, good uniformity of coating film quality, wide applicability of coating liquid viscosity, and high material utilization rate. As a device for directly transporting the solution, the liquid supply device plays a decisive role in the stability of the coating liquid output. In the large-scale mass production of perovskite thin film coating, it is required that the coating film thickness is very thin (generally the dry film thickness is below 1 μm), and a high-precision liquid supply device needs to be matched. During the actual coating process, due to factors such as the properties of the solution, the mechanical structure design of the device itself, and the external environment, the coating liquid output cannot always be maintained in a stable state, resulting in insufficient uniformity of the coating film or poor coating repeatability. The solution is uniformly extruded from the fine slot of the coating head after being ejected by the liquid supply device. The liquid supply device will be subject to great resistance from the solution pipeline and the coating head. Therefore, in addition to high precision, the liquid supply device also needs to have the characteristics of high hydraulic pressure and high stability. The commonly used liquid supply devices are mainly screw-type, plunger-type or diaphragm-type direct liquid supply injection pumps. There are flow fluctuations and hydraulic pressure fluctuations during the liquid supply process of these injection pumps, resulting in uneven and unstable liquid supply. When applied to slot coating, the liquid output at the die head is uneven, resulting in uneven coating film and coating stripe defects, and it is difficult to meet the coating requirements of high hydraulic pressure and high precision at the same time. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a liquid supply device, which uses the principle of hydraulic buffering to reduce the hydraulic pressure fluctuations during the coating process and achieve the coating requirements of high hydraulic pressure and high precision.

[0004] The present invention is realized as follows: A liquid supply device is provided, which includes a liquid supply cavity filled with hydraulic oil. A solution bladder is arranged in the hydraulic oil of the liquid supply cavity. An inner cavity is arranged in the solution bladder, and the inner cavity is filled with coating ink solution. The outer wall of the solution bladder undergoes elastic deformation according to the magnitude of the hydraulic oil pressure, so that the volume of the inner cavity of the solution bladder also changes accordingly. When the pressure of the hydraulic oil decreases, the volume of the inner cavity increases; conversely, when the pressure of the hydraulic oil increases, the volume of the inner cavity decreases. An inlet and an outlet communicating with the inner cavity are respectively arranged on the solution bladder. The inlet and the outlet are respectively communicated with an inlet pipeline and an outlet pipeline arranged outside the liquid supply cavity. The inlet pipeline is communicated with a container filled with coating ink solution; A pushing device capable of changing the hydraulic oil pressure in the liquid supply cavity is also arranged on the liquid supply cavity.

[0005] Furthermore, a hydraulic oil inlet and a hydraulic oil outlet are respectively arranged on the liquid supply cavity, and a pressure relief valve is also arranged. The height of the hydraulic oil inlet in the liquid supply cavity is lower than that of the hydraulic oil outlet in the liquid supply cavity.

[0006] The present invention is implemented as follows. Another liquid supply device is also provided, which includes a liquid supply cavity filled with hydraulic oil and at least one buffer tank filled with buffer oil. Each buffer tank is sequentially connected to each other through an intermediate pipeline. An oil inlet pipeline is arranged between the buffer tank at the forefront and the liquid supply cavity for communication. A solution bladder is arranged in the hydraulic oil of the liquid supply cavity. An inner cavity is arranged in the solution bladder, and the inner cavity is filled with coating ink solution. The outer wall of the solution bladder undergoes elastic deformation with the change of the pressure of the hydraulic oil, so that the volume of the inner cavity of the solution bladder also changes accordingly. When the pressure of the hydraulic oil decreases, the volume of the inner cavity increases; on the contrary, when the pressure of the hydraulic oil increases, the volume of the inner cavity decreases. A liquid inlet and a liquid outlet communicating with the inner cavity are respectively arranged on the solution bladder. The liquid inlet and the liquid outlet are respectively communicated with a liquid inlet pipeline and a liquid outlet pipeline arranged outside the liquid supply cavity. The liquid inlet pipeline is communicated with a container filled with coating ink solution; a buffer bladder is respectively arranged in the buffer oil of each buffer tank. A buffer inner cavity is respectively arranged in each buffer bladder. The buffer inner cavity at the forefront is filled with hydraulic oil, and the remaining buffer inner cavities are filled with buffer oil. The outer wall of each buffer bladder undergoes elastic deformation with the change of the pressure of the buffer oil in the corresponding buffer tank, so that the volume of the buffer inner cavity of the corresponding buffer bladder also changes accordingly. When the pressure of the buffer oil in the corresponding buffer tank decreases, the volume of the corresponding buffer inner cavity increases; on the contrary, when the pressure of the buffer oil in the corresponding buffer tank increases, the volume of the corresponding buffer inner cavity decreases. A pushing device capable of changing the pressure of the buffer oil in the last buffer tank is also arranged on the last buffer tank.

[0007] Furthermore, a buffer oil inlet and a buffer oil outlet are respectively arranged on the last buffer tank, and a pressure relief valve is also arranged. The height of the buffer oil inlet in the buffer tank is lower than that of the buffer oil outlet in the buffer tank.

[0008] Specifically, in the above two liquid supply devices, the pushing device includes a piston, a push rod, a lead screw slider and a servo motor. A piston cavity is arranged in the liquid supply cavity. The piston is connected to the push rod. A lead screw cooperating with the lead screw slider is arranged on the push rod. The servo motor drives the piston to move in the piston cavity through the lead screw slider, so as to change the pressure of the hydraulic oil in the liquid supply cavity.

[0009] Specifically, in the above two liquid supply devices, the solution bladder is a coiled curved pipe, and the liquid inlet and the liquid outlet are respectively arranged at the head and the tail of the curved pipe.

[0010] Specifically, in the above two liquid supply devices, a solution valve is provided on the liquid inlet pipe, and a three-way valve is provided on the liquid outlet pipe. One outlet of the three-way valve is communicated with a return pipe, and the return pipe is communicated with a container filled with a coating ink solution.

[0011] Specifically, in the above two liquid supply devices, a bubble detection device is also provided on the liquid outlet pipe.

[0012] Specifically, in the above two liquid supply devices, the position of the liquid inlet on the solution bladder is lower than the position of the liquid outlet on the solution bladder.

[0013] Compared with the prior art, the liquid supply device of the present invention has the following characteristics: 1. The method of using hydraulic oil + solution bladder + pushing device is adopted to reduce the instability of the liquid supply flow caused by the mechanical fluctuations and precision problems of the pushing device. Hydraulic oil has the ability to absorb mechanical vibrations or fluctuations, and plays a buffering role in case of "jamming" during the movement process.

[0014] 2. The liquid supply is driven by hydraulic pressure. The internal pressure generated by the hydraulic pressure is very large, which can overcome the loads caused by the coating head and the solution pipeline, etc., and ensure the continuity and stability of the liquid supply process.

[0015] 3. It meets the high-hydraulic-pressure and high-precision liquid supply requirements for industrial coating. The mechanical vibrations / fluctuations generated by the large pushing device are buffered by the hydraulic oil, and the solution bladder can be slowly squeezed by the hydraulic oil to achieve a stable liquid outlet process at a very low flow rate.

[0016] 4. The liquid supply process can achieve full continuous liquid supply to ensure that there is no fluctuation in the liquid supply process. The periodic fluctuations of the pushing device will be "damped" by the liquid hydraulic oil under a large volume of hydraulic oil. The periodic fluctuations of the pushing device are also reflected in the periodic fluctuation law of the force applied to the hydraulic oil. The contact area between the solution bladder and the hydraulic oil is very large, and the average surface of the solution bladder acts on the fluctuating force received by the hydraulic oil, reducing the pressure applied per unit area of the solution bladder and further weakening the influence on the solution.

[0017] 5. The solution bladder is arranged in a folded paper-like manner, increasing the surface area of contact between the solution bladder and the hydraulic oil, and also increasing the length of the solution bladder in terms of length. After increasing the surface area of the solution bladder, the pressure and deformation per unit area are reduced. Increasing the length of the solution bladder increases the storage capacity of the solution bladder and further reduces the deformation of the solution bladder per unit volume of the solution. During the liquid supply process, the deformation of the solution bladder is very small, ensuring the stability of the flow rate and direction of the solution in the solution bladder during the liquid supply process, and thus ensuring the stability of the liquid outlet of the liquid supply device.

[0018] 6. The solution bladder can be designed to be very large, and the amount of solution required for coating the thin film, especially the perovskite thin film, is very small. It can hold a solution volume sufficient for more than 1000 coating times.

[0019] 7. The solution bladder is uniformly acted upon by the hydraulic oil pressure everywhere, which can ensure a continuous and stable liquid discharging process. There is no problem of difficult and unstable liquid discharging caused by an overly large volume of the solution bladder.

[0020] 8. The solution in the solution bladder can supply the solution multiple times without interruption, and the solution valve between the liquid supply device and the coating die head is in a long-term connected state without switching. The solution continuously flows without interruption while the solution valve does not operate, avoiding the deposition of the solution at the solution valve.

[0021] 9. A multi-stage hydraulic oil cavity is designed to further reduce the fluctuation of the coating ink solution output by the liquid supply device during the working process. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic structural principle diagram of Embodiment 1 of the liquid supply device of the present invention; Figure 2 It is a schematic structural principle diagram of Embodiment 2 of the liquid supply device of the present invention; Figure 3 It is a schematic structural principle diagram of Embodiment 3 of the liquid supply device of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. Embodiment 1

[0024] Please refer to Figure 1 and Figure 2 As shown, the first preferred embodiment of the liquid supply device of the present invention includes a liquid supply cavity 1 filled with hydraulic oil, and a solution bladder 2 is arranged in the hydraulic oil of the liquid supply cavity 1.

[0025] An inner cavity A is arranged in the solution bladder 2, and the inner cavity A is filled with the coating ink solution. The outer wall of the solution bladder 2 undergoes elastic deformation with the change of the hydraulic oil pressure, so that the volume of the inner cavity A of the solution bladder 2 also changes accordingly. When the pressure of the hydraulic oil decreases, the volume of the inner cavity A increases; conversely, when the pressure of the hydraulic oil increases, the volume of the inner cavity A decreases.

[0026] An inlet 3 and an outlet 4 communicating with the inner cavity A are respectively arranged on the solution bladder 2. The inlet 3 and the outlet 4 are respectively communicated with an inlet pipeline 5 and an outlet pipeline 6 arranged outside the liquid supply cavity 1, and the inlet pipeline 5 is communicated with a container 7 filled with coating ink solution. A pushing device 8 capable of changing the pressure of the hydraulic oil in the liquid supply cavity 1 is further arranged on the liquid supply cavity 1.

[0027] The solution bladder 2 is prepared from an elastoplastic corrosion-resistant material, and the outer wall of the solution bladder 2 is continuously extruded by hydraulic oil to cause elastoplastic deformation. After the solution bladder 2 is extruded and deformed by hydraulic oil, the volume of the inner cavity A becomes smaller, and the coating ink solution in the inner cavity A is extruded to the use load. Figure 1 In, the outlet pipeline 6 is communicated with the use load (i.e., the coating die head B), and the coating die head B then performs high-precision coating on the substrate C.

[0028] A hydraulic oil inlet 11 and a hydraulic oil outlet 10 are respectively arranged on the liquid supply cavity 1, and a pressure relief valve 12 is further arranged. The height of the hydraulic oil inlet 11 on the liquid supply cavity 1 is lower than the height of the hydraulic oil outlet 10 on the liquid supply cavity 1. The pressure relief valve 12 is located at the top of the liquid supply cavity 1.

[0029] The pushing device 8 includes a piston 81, a push rod 82, a lead screw slider 83 and a servo motor 84. A piston cavity 13 is arranged in the liquid supply cavity 1. The piston 81 is connected with the push rod 82. A lead screw (not shown in the figure) cooperating with the lead screw slider 83 is arranged on the push rod 82. The servo motor 84 drives the piston 81 to move in the piston cavity 13 through the lead screw slider 83, so as to change the pressure of the hydraulic oil in the liquid supply cavity 1.

[0030] A solution valve 17 is arranged on the inlet pipeline 5, and a three-way valve 14 is arranged on the outlet pipeline 6. One outlet of the three-way valve 14 is communicated with a return pipe 15, and the return pipe 15 is communicated with the container 7 filled with coating ink solution.

[0031] A bubble detection device 16 is further arranged on the outlet pipeline 6, and once bubbles are sensed, an air discharge operation is performed.

[0032] The position of the inlet 3 on the solution bladder 2 is lower than the position of the outlet 4 on the solution bladder 2, ensuring that the hydraulic oil can completely fill the liquid supply cavity 1. Since the hydraulic oil has basically no loss during the working process, the hydraulic oil only needs to be loaded for the first time and does not need to be loaded subsequently.

[0033] The liquid supply cavity 1 is prepared from materials such as metal alloy, plastic, and plastic, and has the characteristics of wear resistance and high pressure resistance. The inner cavity A of the solution bladder 2 has a maximum solution loading capacity and a maximum extrusion amount. When the loading capacity of the solution bladder 2 is exceeded, the solution bladder 2 may be squeezed and broken. Similarly, when the solution bladder 2 is squeezed to the limit, the solution distribution will be unstable, resulting in excessive internal pressure in the liquid supply cavity 1 and causing the hydraulic oil to be discharged from the pressure relief valve 12. These two problems are solved by controlling the maximum movement stroke of the push rod 82 of the pushing device 8 to control the extrusion amount and the back suction amount of the solution bladder 2. In order to avoid the generation of bubbles in the solution bladder 2 during the liquid supply process, which affects the liquid outlet stability of the liquid supply device, the present invention sets the liquid outlet 4 at the highest point in the height direction of the solution bladder 2, and sets the liquid inlet 3 at the lowest point of the solution bladder 2. Under this design, the coating ink solution flows in from the liquid inlet 3 and flows out from the liquid outlet 4, which is beneficial to discharging the bubbles in the solution bladder 2.

[0034] The liquid supply uniformity and stability of the solution bladder 2 mainly depend on the uniform deformation of the outer wall of the solution bladder 2, and the deformation amount per unit length in the pipe diameter direction should not be too large to ensure the stability of the solution flow rate and the solution hydraulic pressure when the solution flows. The hydraulic oil itself can absorb the mechanical vibration of the pushing device 8 and the fluctuations caused by insufficient accuracy during the movement process, and can continuously apply stable hydraulic pressure to the solution bladder 2.

[0035] Adopting the structure of the solution bladder 2 in this embodiment can achieve the coating of the coating ink solution with high precision and high stability. Embodiment 2

[0036] Please refer to Figure 1 and Figure 2 As shown, the second preferred embodiment of the liquid supply device of the present invention. The difference between the structure of the liquid supply device in this embodiment and that in Embodiment 1 is that: the solution bladder 2 is a coiled curved pipe, and the liquid inlet 3 and the liquid outlet 4 are respectively arranged at the head and tail ends of the curved pipe. In order to ensure the pressure stability of the solution bladder 2 during the liquid supply process and reduce the deformation amount per unit pipe diameter direction, it can be achieved by increasing the surface area of the solution bladder in contact with the hydraulic oil and increasing the length of the solution flow path. Setting the solution bladder 2 as a coiled curved pipe not only increases the surface area of the solution bladder 2 but also increases the length of the solution bladder 2.

[0037] Adopting the structure of the solution bladder 2 in this embodiment can achieve the coating of the coating ink solution with high precision and high stability.

[0038] The other structures are the same as those of the liquid supply device in Embodiment 1 and will not be described in detail. Embodiment 3

[0039] Please refer to Figure 1 and Figure 2As shown, it is the third preferred embodiment of the liquid supply device of the present invention. In order to ensure the stability of the extrusion process of the hydraulic oil on the solution bladder 2 and reduce the overall tremor or fluctuation of the hydraulic oil caused by the mechanical fluctuation of the pushing device 8, and enhance the hydraulic stability of the liquid supply process, at least one buffer chamber is added between the pushing device 8 and the solution bladder 2 of the liquid supply device in Embodiment 2.

[0040] The liquid supply device of this embodiment includes a liquid supply cavity 1 filled with hydraulic oil and at least one buffer tank 9 filled with buffer oil. Each buffer tank 9 is sequentially connected to each other through an intermediate pipeline (not shown in the figure). An oil inlet pipeline 18 is provided between the buffer tank 9 at the frontmost end and the liquid supply cavity 1 to communicate with each other. A solution bladder 2 is arranged in the hydraulic oil of the liquid supply cavity 1.

[0041] An inner cavity A is arranged in the solution bladder 2, and the inner cavity A is filled with coating ink solution. The outer wall of the solution bladder 2 undergoes elastic deformation with the change of the pressure of the hydraulic oil, so that the volume of the inner cavity A of the solution bladder 2 also changes accordingly. When the pressure of the hydraulic oil decreases, the volume of the inner cavity A increases; on the contrary, when the pressure of the hydraulic oil increases, the volume of the inner cavity A decreases.

[0042] A liquid inlet 3 and a liquid outlet 4 communicating with the inner cavity A are respectively arranged on the solution bladder 2. The liquid inlet 3 and the liquid outlet 4 are respectively communicated with a liquid inlet pipeline 5 and a liquid outlet pipeline 6 arranged outside the liquid supply cavity 1, and the liquid inlet pipeline 5 is communicated with a container filled with coating ink solution. A hydraulic oil outlet 10 is arranged on the liquid supply cavity 1.

[0043] A buffer bladder 91 is respectively arranged in the buffer oil of each buffer tank 9. A buffer inner cavity D is respectively arranged in each buffer bladder 91. The buffer inner cavity D at the frontmost end is filled with hydraulic oil, and the remaining buffer inner cavities are filled with buffer oil. The outer wall of each buffer bladder 91 undergoes elastic deformation with the change of the pressure of the buffer oil in the corresponding buffer tank 9, so that the volume of the buffer inner cavity D of the corresponding buffer bladder 91 also changes accordingly. When the pressure of the buffer oil in the corresponding buffer tank 9 decreases, the volume of the corresponding buffer inner cavity D increases; on the contrary, when the pressure of the buffer oil in the corresponding buffer tank 9 increases, the volume of the corresponding buffer inner cavity D decreases. A pushing device 8 capable of changing the pressure of the buffer oil in the last buffer tank 9 is also arranged on the last buffer tank 9.

[0044] A buffer oil inlet 92 and a buffer oil outlet 93 are respectively arranged on the last buffer tank 9. A pressure relief valve 12 is also arranged, and a hydraulic oil inlet pipe 94 is also arranged. The height of the buffer oil inlet 92 on the buffer tank 9 is lower than the height of the buffer oil outlet 93 on the buffer tank 9, and the height of the hydraulic oil inlet pipe 94 on the buffer tank 9 is lower than the height of the oil inlet pipeline 18 on the buffer tank 9.

[0045] In this embodiment, the hydraulic oil is loaded into the liquid supply cavity 1 in a manner similar to the loading of the coating ink solution into the inner cavity A of the solution bladder 2 in Embodiment 1, and is supplied by using the buffer bladder 91 provided in the buffer tank 9.

[0046] By adopting the structure of the buffer tank 9 in this embodiment, the coating of the coating ink solution can be achieved under low flow rate, high precision and high stability.

[0047] Other structures are the same as those of the liquid supply device in Embodiment 1 and will not be described in detail.

[0048] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A liquid supply device, characterized in that, it includes a liquid supply cavity filled with hydraulic oil, a solution bladder is arranged in the hydraulic oil of the liquid supply cavity, an inner cavity is arranged in the solution bladder, and the inner cavity is filled with coating ink solution. The outer wall of the solution bladder undergoes elastic deformation with the magnitude of the hydraulic oil pressure, so that the volume of the inner cavity of the solution bladder also changes accordingly. When the pressure of the hydraulic oil decreases, the volume of the inner cavity increases; conversely, when the pressure of the hydraulic oil increases, the volume of the inner cavity decreases. An inlet and an outlet communicating with the inner cavity are respectively arranged on the solution bladder, and the inlet and the outlet are respectively communicated with an inlet pipeline and an outlet pipeline arranged outside the liquid supply cavity. The inlet pipeline is communicated with a container filled with coating ink solution; a pushing device capable of changing the pressure of the hydraulic oil in the liquid supply cavity is also arranged on the liquid supply cavity.

2. The liquid supply device according to claim 1, characterized in that, a hydraulic oil inlet and a hydraulic oil outlet are respectively arranged on the liquid supply cavity, and a pressure relief valve is also arranged. The height of the hydraulic oil inlet in the liquid supply cavity is lower than the height of the hydraulic oil outlet in the liquid supply cavity.

3. A liquid supply device, characterized in that, it includes a liquid supply cavity filled with hydraulic oil and at least one buffer tank filled with buffer oil. Each buffer tank is sequentially connected to each other through an intermediate pipeline. An oil inlet pipeline is arranged between the buffer tank at the frontmost end and the liquid supply cavity for communication. A solution bladder is arranged in the hydraulic oil of the liquid supply cavity, an inner cavity is arranged in the solution bladder, and the inner cavity is filled with coating ink solution. The outer wall of the solution bladder undergoes elastic deformation with the magnitude of the hydraulic oil pressure, so that the volume of the inner cavity of the solution bladder also changes accordingly. When the pressure of the hydraulic oil decreases, the volume of the inner cavity increases; conversely, when the pressure of the hydraulic oil increases, the volume of the inner cavity decreases. An inlet and an outlet communicating with the inner cavity are respectively arranged on the solution bladder, and the inlet and the outlet are respectively communicated with an inlet pipeline and an outlet pipeline arranged outside the liquid supply cavity. The inlet pipeline is communicated with a container filled with coating ink solution; buffer bladders are respectively arranged in the buffer oil of each buffer tank, buffer inner cavities are respectively arranged in each buffer bladder, the frontmost buffer inner cavity is filled with hydraulic oil, and the remaining buffer inner cavities are filled with buffer oil. The outer wall of each buffer bladder undergoes elastic deformation with the magnitude of the buffer oil pressure in the corresponding buffer tank, so that the volume of the corresponding buffer inner cavity also changes accordingly. When the pressure of the buffer oil in the corresponding buffer tank decreases, the volume of the corresponding buffer inner cavity increases; conversely, when the pressure of the buffer oil in the corresponding buffer tank increases, the volume of the corresponding buffer inner cavity decreases. A pushing device capable of changing the pressure of the buffer oil in the last buffer tank is also arranged on the last buffer tank.

4. The liquid supply device according to claim 3, characterized in that, a buffer oil inlet and a buffer oil outlet are respectively arranged on the last buffer tank, and a pressure relief valve is also arranged. The height of the buffer oil inlet in the buffer tank is lower than the height of the buffer oil outlet in the buffer tank.

5. The liquid supply device according to any one of claims 1 to 4, characterized in that, The pushing device includes a piston, a push rod, a lead screw slider and a servo motor. A piston chamber is arranged in the liquid supply cavity. The piston is connected to the push rod. A lead screw that cooperates with the lead screw slider is arranged on the push rod. The servo motor drives the piston to move in the piston chamber through the lead screw slider, thereby changing the pressure of the hydraulic oil in the liquid supply cavity.

6. The liquid supply device according to any one of claims 1 to 4, characterized in that the solution bladder is a coiled curved tube, and the liquid inlet and the liquid outlet are respectively arranged at the head and the tail ends of the curved tube.

7. The liquid supply device according to any one of claims 1 to 4, characterized in that a solution valve is arranged on the liquid inlet pipeline, a three-way valve is arranged on the liquid outlet pipeline, one outlet of the three-way valve is communicated with a return pipe, and the return pipe is communicated with a container filled with a coating ink solution.

8. The liquid supply device according to any one of claims 1 to 4, characterized in that a bubble detection device is further arranged on the liquid outlet pipeline.

9. The liquid supply device according to any one of claims 1 to 4, characterized in that the position of the liquid inlet on the solution bladder is lower than the position of the liquid outlet on the solution bladder.

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