Device and method for controlling constant tension of film

Abstract

The present invention discloses a device and method for constant tension control of a film. The present invention adjusts the water storage amount in the tension roller, so that the film can complete real-time and arbitrary tension value adjustment constant tension control without stopping the machine; the water storage space in the tension roller is divided into a plurality of water storage compartments, and the water storage compartments can be filled one by one. The water storage cavity filled with water does not have the problem of water flowing to one side of the tension roller due to insufficient installation level; when affected by external vibration, the shaking is also greatly reduced; setting the water storage space in the tension roller as a plurality of water storage compartments can greatly reduce the problem of uneven weight distribution in the tension roller caused by large-scale shaking of the water medium in the tension roller due to mechanical vibration or insufficient installation level during the working process of the tension roller, so as to ensure the processing quality of the film.

Description

Technical Field

[0001] The invention relates to a device and method for controlling constant tension of a film. Background Art

[0002] In the packaging industry, films are constantly in motion during production. As the film moves, the diameter of the film sleeve constantly changes. This change in diameter causes changes in film tension. Increases or decreases in film tension can alter the film's physical properties, affecting the performance and appearance of the finished product. This requires a control method in packaging production that can automatically adjust the tension applied to the film during its movement, maintaining a constant tension at all times.

[0003] In the prior art, during film operation, the film tension is typically changed by adjusting the position or pressure of a reference roller, or a tension control device, such as a tension sensor and a tension wheel, is typically used to monitor and adjust the film tension. Based on the feedback signal from the sensor, the system can automatically adjust the position and speed of the tension wheel to achieve the desired tension. For example, patent application CN 204957924U provides a digital printing machine and a constant tension cloth feeding system thereof. The constant tension cloth feeding system includes a cloth feeding frame, a counterweight mechanism, a constant tension roller, a sliding mechanism, and a transmission mechanism. The counterweight mechanism and the sliding mechanism are both arranged on the transmission mechanism, the constant tension roller is fixed to the sliding mechanism, and the transmission mechanism is fixed to the cloth feeding frame. When setting the cloth feeding tension, the weight of the counterweight mechanism can be configured according to the properties of the fabric, and the transmission mechanism controls the sliding mechanism to slide according to the weight of the counterweight mechanism. The tension of the constant tension roller is adjusted by sliding the sliding mechanism, thereby achieving the tension adjustment of the cloth feeding system according to different fabrics. This patent adjusts the tension by mechanically setting a counterweight on the constant tension roller. Since the mechanical counterweight is composed of different weights, the tension adjustment is jumpy and cannot accurately achieve any value of tension adjustment. For example, patent CN205820495U provides an automatic tension control device for an automatic paper splicer. Each of the two sliders is provided with a vertical downward suspension rod. The other end of the suspension rod is fixed with a water tank with a regular shape. The water tank is provided with an inlet pipe and an outlet pipe. The outlet pipe is set at the bottom of the water tank. The inlet pipe is connected to the water outlet of the first water pump, and the outlet pipe is connected to the water inlet of the second water pump. The two water pumps are connected to the water tank through water pipes. The power supply of the water pump is connected to the circuit controller. The bottom of the water tank is provided with a water pressure sensor, which is connected to the terminal controller. This patent increases the counterweight by increasing the amount of water in the water tank, and a water tank is suspended on the guide roller by a hanger. The equipment will inevitably vibrate during operation, which will cause the suspended water tank to swing greatly, which will have a serious impact on the stability of the guide rail operation and may easily cause the slider to get stuck. Hanging a water tank on the guide roller by a hanger may also interfere with the guidance of the guide roller.

[0004] Patent CN213679094 U provides a printing press unwinding tension control device. During printing, the second guide roller is lifted by the tension of the printing paper, compressing the spring and maintaining a certain height. When the tension of the printing paper becomes smaller, it is insufficient to maintain the original height of the second guide roller, causing it to move downward under the action of its own gravity and the elastic force of the spring, causing the connecting block to press down the right end of the first movable plate, while the left end of the first movable plate is tilted to lift the right end of the second movable plate, causing its left end to descend. The contact button is pressed down, and then the solenoid valve is energized. The pressure pump injects water in the water tank into the cavity through the water injection pipe, increasing the weight of the drive roller to compensate for the weight lost by the printing paper roll, maintaining a constant speed of the drive roller, and then maintaining the tension of the printing paper at a constant value. In this patent, the weight of the driving roller is set in a separate cavity that can accommodate water, so as to achieve the adjustment of the driving roller weight. However, since the driving roller is installed horizontally, it is difficult to ensure absolute levelness during installation, and the cavity is not filled with water most of the time. When the driving roller is not installed horizontally, the water will inevitably be concentrated on the lower side, and the weight distribution of the driving roller will also be seriously uneven. When affected by external vibrations, the large fluctuation of the water in the cavity will also cause uneven weight distribution of the driving roller.

[0005] Therefore, we propose a device and method for constant tension control of a film to solve the above problems. Summary of the Invention

[0006] (1) Purpose of the invention

[0007] The present invention is to avoid the shortcomings of the above-mentioned prior art and provide a device and method for constant tension control of film. On the basis of realizing arbitrary tension value adjustment, the problem of uneven weight distribution on the tension roller caused by mechanical vibration or insufficient installation level during the tension adjustment process is reduced, so as to improve the quality of film production.

[0008] (2) Technical solution

[0009] To achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0010] A device for controlling constant tension of a film, comprising a film support, a film roll rotatably arranged on the film support via an axis pin for film unwinding;

[0011] The main support is composed of a left support and a right support. A film guide roller 1, a tension roller, and a film guide roller 2 are arranged between the left support and the right support. The film is drawn out from the film roll and supported by the film guide roller 1, the tension roller, and the film guide roller 2 in sequence. An upper fixed seat and a lower fixed seat are fixed on the left support and the right support. A sliding shaft is arranged between the upper fixed seat and the lower fixed seat. A slider fixing flange is passed through each sliding shaft. A weighing sensor is arranged on each of the two slider fixing flanges. A slider is arranged on each of the slider fixing flanges. The slider is slidably sleeved on the sliding shaft.

[0012] The invention is characterized in that the tension roller is hollow, a drainage passage is set in the middle of the tension roller, and a plurality of water storage grids are axially arranged inside the tension roller and outside the drainage passage, the water storage grids are symmetrically distributed around the center of the tension roller, and a water inlet pressure valve is provided on the side of each water storage grid, the water inlet pressure valve is set to open unidirectionally under a certain pressure, the opening pressure of all water inlet pressure valves is set to be the same, and the opening pressure of the water inlet pressure valve is set to open only when the outer water storage grid is full of water; a water inlet pipe extends from each end side of the tension roller and is connected to the water inlet pressure valve on the water storage grid near the two end sides; a water outlet pressure valve that can be connected to the drainage passage is provided on the inner wall of each water storage grid, and the water outlet pressure valve is set to open unidirectionally under a certain pressure, and the opening pressure of the water outlet pressure valve is set to be greater than the opening pressure of the water inlet pressure valve, and the opening pressure increases from the outer water outlet pressure valve to the inner water outlet pressure valve;

[0013] A water tank is fixedly mounted on the main bracket, and is provided with a water inlet, a water outlet and a water replenishment port. The water inlet is connected to a water inlet pump, which is used to connect with two water inlet pipes to supply water to each water storage grid. The water outlet is connected to a drainage pump, which is used to connect with the two ports of the drainage passage.

[0014] Furthermore, an upper end position detection sensor, a middle end position detection sensor, and a lower end position detection sensor are provided on the side plates of the sliding shaft.

[0015] Furthermore, the volume of each water storage grid is the same to ensure the balance of weight on both sides of the tension roller.

[0016] Furthermore, the number of water storage grids is an odd number.

[0017] Furthermore, the number of water storage grids is 5.

[0018] Furthermore, a water filling port is provided on the water tank, and the water filling port is used to fill the water tank with water.

[0019] Furthermore, it also includes a controller, which is electrically connected to the weighing sensor, the water inlet pump, and the water discharge pump.

[0020] Furthermore, pressure sensors electrically connected to the controller are provided at the ports of the outlet pump and the inlet pump. The outlet pump and the inlet pump are configured as variable frequency pumps, which can adjust the pumping pressure and flow.

[0021] A method for controlling constant tension of a film, the method comprising the following steps: during a film roll unwinding movement, the film roll is constantly pulled by the weight of a tension roller, a weighing sensor constantly detects changes in the weight of the tension roller itself, when the pulling force exerted by the tension roller on the film is less than the tension requirement of the film, a device automatically starts a water inlet pump on a water tank, and fills a water storage grid of the tension roller with water through water inlet pipes on both sides of the tension roller, and stops filling water when the weight requirement is reached; when the pulling force exerted by the tension roller on the film exceeds the tension requirement of the film, a drainage pump on the water tank is automatically started, and water is drained from the tension roller through the drainage pump, and stops draining water when the weight requirement is reached, constantly adjusting changes in the weight of the tension roller to maintain the tension exerted on the film unchanged and in a constant state;

[0022] The step of filling the water storage compartment of the tension roller with water includes: after the water inlet pump is started, the water inlet pressure of the water inlet pipe is made greater than the opening pressure of the water inlet pressure valve and less than the opening pressure of the water outlet pressure valve, and water is fed into the outermost water storage compartment through the water inlet pipe, and the outermost water storage compartments on both sides are fed with water simultaneously; when the outer water storage compartment is full of water, water is fed into the adjacent water storage compartment until the weight requirement of the tension roller is met and then the water feeding is stopped;

[0023] The method and steps for releasing water from the tension roller are as follows: after the drainage pump is started, the negative pressure value in the drainage pipe is made greater than the opening pressure of the water outlet pressure valve, so that the water in the tension roller is discharged and the weight of the tension roller is reduced; when slow drainage is required, the drainage pump will be turned on at the initial stage of drainage to set the negative pressure value in the drainage pipe to be greater than the opening pressure of the outermost water outlet pressure valve and less than the opening pressure of the water outlet pressure valve adjacent to the outermost water outlet. At this time, only the outermost water outlet pressure valve is open, the outermost water storage grid is in the drainage state, and the inner water outlet pressure valves are all closed; after the outermost water storage grid is emptied, if drainage still needs to be continued, the drainage pump is controlled to gradually increase the drainage pressure. The negative pressure value in the water pipe causes the water outlet pressure valve adjacent to the outermost side to open, and the water storage grid adjacent to the outermost side is also in a drainage state, while the water outlet pressure valve further inside remains closed; if more drainage is needed, and so on, after the water storage grid on the outside has been drained, the negative pressure value in the drain pipe is increased to drain the adjacent water storage grids, and the drainage is stopped after the weight requirement of the tension roller is met; when rapid drainage is required, the negative pressure value in the drain pipe can be controlled to be directly greater than the opening pressure of all water outlet pressure valves, so that all water outlet pressure valves are in an open state, all water storage grids are drained synchronously, and the water in the tension roller is quickly discharged.

[0024] (3) Technical effects

[0025] Compared with the prior art, the present invention has the following beneficial and significant technical effects:

[0026] 1. The present invention adjusts the water storage volume within the tension roller to achieve real-time, arbitrary tension value adjustment and constant tension control for the film without shutting down. The water storage space within the tension roller is divided into several water compartments, which can be filled one by one. A fully filled water chamber does not have the problem of water flowing to one side of the tension roller due to insufficient leveling. When subjected to external vibrations, the same weight of water in a fully filled water chamber will experience significantly less swaying than in an underfilled chamber. Therefore, configuring the water storage space within the tension roller as a plurality of water compartments can significantly reduce the problem of uneven weight distribution within the tension roller caused by mechanical vibrations during operation or insufficient leveling, thereby ensuring film processing quality.

[0027] 2. The opening pressure of the water outlet pressure valve is set to increase from the outer side to the inner side. According to the drainage needs, the drainage can be set to slow drainage mode and fast drainage mode by adjusting the water outlet pressure to meet the drainage needs of different conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic structural diagram of a device for controlling constant tension of a film.

[0029] Figure 2 It is a structural diagram of the tension roller. DETAILED DESCRIPTION

[0030] In order to better understand the present invention, the contents of the present invention are further explained in conjunction with the embodiments below. In the accompanying drawings, the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be understood as limiting the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. The structure and technical solution of the present invention are further described in detail below in conjunction with the accompanying drawings, and an embodiment of the present invention is given.

[0031] Figure 1-2 shows a device for constant tension control of a film, which includes a film support 15, on which a film roll 13 rotates at a uniform speed via an axle pin 14 to unwind the film; and a main support, which is composed of a left support 1 and a right support 20, between which a film guide roller 12, a tension roller 5, and a film guide roller 2 19 are arranged. The film is drawn out from the film roll 13 and is supported by the film guide roller 12, the tension roller 5, and the film guide roller 2 19 in sequence, forming a film unwinding path. The film unwinding path is shown in the attached figure. Figure 1 As shown by the specific arrows in .

[0032] The left bracket 1 and the right bracket 20 are both fixed with an upper fixing seat 5 and a lower fixing seat 12. Figure 1 As shown, the sliding shaft 10 is fixed to the left bracket 1 through the upper fixing seat 3 and the lower fixing seat 12, and the same structure is set on the right side to fix it to the right bracket 20; the sliding shaft 10 is passed through a slider fixing flange 8, and the slider fixing flange 8 is also set on the right sliding shaft, ultimately ensuring that the left and right slider fixing flanges can move freely up and down along the left and right sliding shafts; weighing sensors 6 are set on the two slider fixing flanges 8, and sliders 7 are set on the slider fixing flanges 8; upper end position detection sensors 4, middle end position detection sensors 9, and lower end position detection sensors 11 are set on the side panels of the sliding shaft 10 to detect the upper and lower limit positions and the position in use of the slider fixing flange 8.

[0033] The tension roller 5 is a constant tension roller. Figure 2 The diagram shows the structure of the tension roller 5. The tension roller 5 is hollow in design. A drainage passage 52 is provided in the middle of the tension roller 5. A plurality of water storage grids are provided inside the tension roller 5 and outside the drainage passage 52 along the axial direction. The water storage grids are symmetrically distributed around the center of the tension roller, and the volume of each water storage grid is the same to ensure the balance of weight on both sides of the tension roller. Preferably, the number of water storage grids is an odd number. Figure 2 In the embodiment shown, there are 5 water storage grids. In order to explain the working process of the tension roller later, Figure 2 As shown, the five water storage grids are coded as 1, 2, 3, 2, and 1 from left to right. A water inlet pressure valve 53 is provided on the side of each water storage grid. The water inlet pressure valve is configured to open unidirectionally under a certain pressure, and the opening pressure of all the water inlet pressure valves 53 is set to the same; a water inlet pipe 51 extends from each end side of the tension roller 5 and is connected to the water inlet pressure valve 53 on the water storage grid near the two end sides; a water outlet pressure valve that can be connected to the drainage passage 52 is provided on the inner wall of each water storage grid, and the water outlet pressure valve is configured to open unidirectionally under a certain pressure. The pressure at which the water outlet pressure valve opens the water outlet pressure is set to be greater than the opening pressure of the water inlet pressure valve, as shown in FIG. Figure 2As shown, a first water outlet pressure valve 55 is provided inside the water storage compartment numbered 1, a second water outlet pressure valve 56 is provided inside the water storage compartment numbered 2, and a third water outlet pressure valve 57 is provided inside the water storage compartment numbered 3.

[0034] By dividing the water storage space within the tension roller 5 into several compartments, each compartment can be filled individually. A full water storage chamber eliminates the problem of water flowing to one side of the tension roller due to insufficient leveling. When subjected to external vibrations, the same weight of water in a full water storage chamber will experience significantly less swaying than in an underfilled chamber. Therefore, configuring the water storage space within the tension roller 5 into multiple compartments significantly reduces the problem of uneven weight distribution within the tension roller caused by mechanical vibrations during operation or insufficient leveling, thereby ensuring film processing quality.

[0035] Figure 2 Only an embodiment of 5 water storage compartments is shown. The problem of uneven weight distribution of the tension roller can be further reduced by increasing the number of water storage compartments. The more water storage compartments there are, the smaller the volume of a single water storage compartment will be. The smaller the volume is, the smaller the impact of uneven gravity distribution caused by the water storage compartments that are not full of water will be.

[0036] Also includes Figure 1-2 The water tank not shown in the figure is fixed on the main bracket, and is provided with a water inlet, a water outlet and a water replenishing port. The water inlet is connected to a water inlet pump, which is used to communicate with the two water inlet pipes 51 to supply water to each water storage grid. The water outlet is connected to a drainage pump, which is used to communicate with the two ports of the drainage passage 52, and the water replenishing port is used to replenish water to the water tank.

[0037] The device is set to have symmetrical and synchronous water inlet and outlet on both sides, which can maximize the balance of gravity on both sides of the tension roller.

[0038] The device for controlling the constant tension of the film also includes a controller, which is electrically connected to the weighing sensor 6, the water inlet pump, and the drainage pump. The electrical connection method can be selected through wire connection or wireless connection according to the equipment layout requirements.

[0039] The method for controlling the constant tension of a film is as follows: during the film unwinding movement of the film roll 13, the film roll 13 is always pulled by the weight of the tension roller 5, and the weighing sensor 6 constantly detects the change in the weight of the tension roller 5 itself. When the traction force of the tension roller 5 on the film is less than the tension requirement of the film, the device automatically starts the water inlet pump on the water tank, and injects water into the water storage grid of the tension roller through the water inlet pipe 51 on both sides of the tension roller 5. When the weight requirement is met, the water injection is stopped; when the traction force of the tension roller 5 on the film exceeds the tension requirement of the film, the drainage pump on the water tank is automatically started, and the water in the tension roller 5 is drained through the drainage pump. When the weight requirement is met, the water discharge is stopped, and the weight change of the tension roller 5 is constantly adjusted to maintain the tension on the film unchanged and in a constant state.

[0040] by Figure 2 A specific embodiment with 5 water storage compartments is given for illustration. The method of injecting water into the tension roller 5 is as follows: after the water inlet pump is started, the water inlet pressure of the water inlet pipe is greater than the opening pressure of the water inlet pressure valve 53 and less than the opening pressure of the water outlet pressure valve. The water inlet pressure valve 53 on the upper outer wall of the water storage compartment coded 1 is opened through the water inlet pipe to inject water into the water storage compartment coded 1, and the water storage compartments coded 1 on both sides are simultaneously injected with water; the opening pressure of the water inlet pressure valve 53 is set to be opened only when the outer water storage compartment is full of water. When the water storage compartment of code 1 is full of water, the water inlet pressure valve 53 between the water storage compartment of code 1 and the water storage compartment of code 2 is opened, and water starts to flow into the water storage compartment of code 2; when the water storage compartment of code 2 is full of water, the water inlet pressure valve 53 between the water storage compartment of code 2 and the water storage compartment of code 3 is opened, and water starts to flow into the water storage compartment of code 3. If there are more water-inlet compartments, and so on, after the outer water storage compartments are full of water, water will flow into the adjacent water storage compartments until the weight requirement of the tension roller is met and the water flow stops.

[0041] by Figure 2A specific embodiment with 5 water storage grids is given for illustration. Specifically, the method of draining water into the tension roller 5 is as follows: after the drainage pump is started, the negative pressure value in the drainage pipe is made greater than the opening pressure of the water outlet pressure valve, so that the water in the tension roller is discharged and the weight of the tension roller is reduced. As a more preferred solution, the opening pressure increases from the outer water outlet pressure valve to the inner water outlet pressure valve, that is, the opening pressures of each pressure valve are in the order of water inlet pressure valve 53 < first water outlet pressure valve 55 < second water outlet pressure valve 56 < third water outlet pressure valve 57. When slow drainage is required, the drainage pump will be turned on at the beginning of drainage to set the negative pressure value in the drainage pipe to be greater than the opening pressure of the first water outlet pressure valve 55 and less than the opening pressure of the second water outlet pressure valve 56. At this time, only the first water outlet pressure valve 55 is open, the water storage grid coded 1 is in the drainage state, and the second water outlet pressure valve 56 and the third water outlet pressure valve 57 are closed. During the drainage process, the water can be drained to the maximum extent possible. The degree ensures the number of water storage grids that are full of water and maintains the balance of gravity on both sides of the tension roller; after the water storage grid coded 1 is emptied, if it is still necessary to continue draining, control the drainage pump to gradually increase the negative pressure value in the drainage pipe, so that the negative pressure value in the drainage pipe is greater than the opening pressure of the second water outlet pressure valve 56 and less than the opening pressure of the third water outlet pressure valve 57. At this time, the second water outlet pressure valve 56 is open, the water storage grid coded 2 is also in the drainage state, and the third water outlet pressure valve 57 is still closed; if more drainage is needed, and so on, after the outer water storage grids are drained, the negative pressure value in the drainage pipe is increased to drain the adjacent water storage grids until the weight requirement of the tension roller is met and the drainage is stopped.

[0042] When rapid drainage is required, the negative pressure value in the drainage pipe can be controlled to be directly greater than the opening pressure of the third water outlet pressure valve 57, so that the first water outlet pressure valve 55, the second water outlet pressure valve 56, and the third water outlet pressure valve 57 are all in the open state, all water storage grids are drained synchronously, and the water in the tension roller 5 is quickly discharged.

[0043] In order to better control and monitor the pressure of the outlet pump and the inlet pump, pressure sensors electrically connected to the controller are provided at the ports of the outlet pump and the inlet pump. The outlet pump and the inlet pump are set as variable frequency pumps, which can adjust the pumping pressure and flow.

[0044] The above embodiments fully and effectively achieve the objectives of the present invention. Those skilled in the art will appreciate that the present invention includes, but is not limited to, the contents described in the accompanying drawings and the above specific embodiments. Although the present invention has been described with reference to the embodiments currently considered to be the most practical and preferred, it should be understood that the present invention is not limited to the disclosed embodiments, and any modifications that do not deviate from the functional and structural principles of the present invention are intended to be included within the scope of the claims.

Claims

1. A device for controlling constant tension of a film, the device comprising a film support, a film roll rotatably mounted on the film support via a shaft pin for film unwinding; The main support is composed of a left support and a right support. A film guide roller 1, a tension roller, and a film guide roller 2 are arranged between the left support and the right support. The film is drawn out from the film roll and supported by the film guide roller 1, the tension roller, and the film guide roller 2 in sequence. An upper fixed seat and a lower fixed seat are fixed on the left support and the right support. A sliding shaft is arranged between the upper fixed seat and the lower fixed seat. A slider fixing flange is passed through each sliding shaft. A weighing sensor is arranged on each of the two slider fixing flanges. A slider is arranged on each of the slider fixing flanges. The slider is slidably sleeved on the sliding shaft. It is characterized by: The tension roller is hollow, and a drainage passage is set in the middle of the tension roller. A plurality of water storage grids are axially arranged inside the tension roller and outside the drainage passage. The water storage grids are symmetrically distributed around the center of the tension roller, and a water inlet pressure valve is provided on the side of each water storage grid. The water inlet pressure valve is set to open unidirectionally under a certain pressure, and the opening pressure of all water inlet pressure valves is set to be the same. The opening pressure of the water inlet pressure valve is set to open only when the outer water storage grid is full of water; a water inlet pipe extends from each end side of the tension roller and is connected to the water inlet pressure valve on the water storage grid near the two end sides; a water outlet pressure valve that can be connected to the drainage passage is provided on the inner wall of each water storage grid; the water outlet pressure valve is set to open unidirectionally under a certain pressure, and the opening pressure of the water outlet pressure valve is set to be greater than the opening pressure of the water inlet pressure valve, and the opening pressure increases from the outer water outlet pressure valve to the inner water outlet pressure valve; A water tank is fixedly mounted on the main bracket, and is provided with a water inlet, a water outlet and a water replenishment port. The water inlet is connected to a water inlet pump, which is used to connect with two water inlet pipes to supply water to each water storage grid. The water outlet is connected to a drainage pump, which is used to connect with the two ports of the drainage passage.

2. The device for constant tension control of a film according to claim 1, characterized in that: An upper end position detection sensor, a middle end position detection sensor, and a lower end position detection sensor are arranged on the side plates of the sliding shaft.

3. The device for constant tension control of a film according to claim 1, characterized in that: The volume of each water storage grid is the same to ensure the balance of weight on both sides of the tension roller.

4. The device for constant tension control of a film according to claim 1, characterized in that: The number of water storage grids is an odd number.

5. The device for constant tension control of a film according to claim 4, characterized in that: There are 5 water storage grids.

6. The device for constant tension control of a film according to claim 1, characterized in that: A water filling port is also provided on the water tank, and the water filling port is used to fill the water tank with water.

7. The device for constant tension control of a film according to claim 1, characterized in that: The utility model also includes a controller, which is electrically connected with the weighing sensor, the water inlet pump and the water discharge pump.

8. The device for constant tension control of a film according to claim 1, characterized in that: Pressure sensors electrically connected to the controller are provided at the ports of the outlet pump and the inlet pump. The outlet pump and the inlet pump are configured as variable frequency pumps, which can adjust the pumping pressure and flow.

9. A method for constant tension control of a film, the method using the device for constant tension control of a film according to claims 1-8, characterized in that: The method comprises the following steps: when the film roll is in the process of unwinding, the film roll is always pulled by the weight of the tension roller, the weighing sensor constantly detects the change of the weight of the tension roller itself, when the pulling force of the tension roller on the film is less than the tension requirement of the film, the device automatically starts the water inlet pump on the water tank, and fills the water storage grid of the tension roller with water through the water inlet pipes on both sides of the tension roller, and stops filling water after the weight requirement is met; when the pulling force of the tension roller on the film exceeds the tension requirement of the film, the drainage pump on the water tank is automatically started, and the water in the tension roller is drained through the drainage pump, and stops draining water after the weight requirement is met, and constantly adjusts the change of the weight of the tension roller to maintain the tension on the film unchanged and in a constant state; The step of filling the water storage compartment of the tension roller with water includes: starting the water inlet pump so that the water inlet pressure of the water inlet pipe is greater than the opening pressure of the water inlet pressure valve and less than the opening pressure of the water outlet pressure valve, and then filling water into the outermost water storage compartment through the water inlet pipe, and the outermost water storage compartments on both sides are filled with water simultaneously; when the outer water storage compartment is full of water, water is then added to the adjacent water storage compartments, and water is stopped after the water supply is met due to the weight of the tension roller; The method and steps for releasing water from the tension roller are as follows: after the drainage pump is started, the negative pressure value in the drainage pipe is made greater than the opening pressure of the water outlet pressure valve, so that the water in the tension roller is discharged and the weight of the tension roller is reduced; when slow drainage is required, the drainage pump will be turned on at the initial stage of drainage to set the negative pressure value in the drainage pipe to be greater than the opening pressure of the outermost water outlet pressure valve and less than the opening pressure of the water outlet pressure valve adjacent to the outermost water outlet. At this time, only the outermost water outlet pressure valve is open, the outermost water storage grid is in the drainage state, and the inner water outlet pressure valves are all closed; after the outermost water storage grid is emptied, if drainage still needs to be continued, the drainage pump is controlled to gradually increase the drainage pressure. The negative pressure value in the water pipe causes the water outlet pressure valve adjacent to the outermost side to open, and the water storage grid adjacent to the outermost side is also in a drainage state, while the water outlet pressure valve further inside remains closed; if more drainage is needed, and so on, after the water storage grid on the outside has been drained, the negative pressure value in the drain pipe is increased to drain the adjacent water storage grids, and the drainage is stopped after the weight requirement of the tension roller is met; when rapid drainage is required, the negative pressure value in the drain pipe can be controlled to be directly greater than the opening pressure of all water outlet pressure valves, so that all water outlet pressure valves are in an open state, all water storage grids are drained synchronously, and the water in the tension roller is quickly discharged.

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