A feeding system for powder material and control method thereof

Abstract

The present application discloses a feeding system for powder materials and a control method thereof, relating to the technical field of packaging equipment. The feeding system includes a main feeding pipeline, a spiral feeder, a first regulating valve, a first control valve, a return air blanking barrel assembly, a return air regulating pipeline, and a weighing sensor. The discharge port of the spiral feeder is connected to the side of the main feeding pipeline, and the return air blanking barrel assembly is connected to the bottom of the main feeding pipeline. The first regulating valve is connected to the main feeding pipeline and is located on the upper side of the spiral feeder. The main feeding pipeline and the return air blanking barrel assembly are connected via a first control valve. The return air regulating pipeline is connected to the side of the return air blanking barrel assembly, and the pressure in the return air regulating pipeline is controlled by adjusting the degree of connectivity between the return air regulating pipeline and the outside atmosphere. The weighing sensor is located at the bottom of the return air blanking barrel assembly and is used to weigh the powder falling from the bottom of the return air blanking barrel assembly. This solves the problem of poor metering accuracy caused by unstable fluidizing gas pressure.

Description

Technical Field

[0001] The present invention relates to the technical field of packaging equipment, and in particular to a feeding system for powder materials and a control method thereof. Background Art

[0002] In the prior art, there are four main feeding methods for packaging equipment according to the different material properties: (1) gravity arc plate feeding, which is suitable for feeding granular materials; (2) double screw feeding, which is suitable for feeding powder materials, but has the disadvantage of slow feeding speed; (3) gravity plus screw feeding, which is also suitable for feeding powder materials and can take into account both feeding speed and metering accuracy; (4) flexible screw feeding, which is suitable for powder materials that are easy to stick and compact.

[0003] For powder packaging, in order to take into account both feeding speed and metering accuracy, a gravity plus spiral feeding method is generally adopted. In order to further increase the powder feeding speed, the powder is usually fluidized before feeding. However, during the feeding process, the fluidizing gas content in the powder constantly changes, which will cause the fluidizing gas pressure entering the packaging bag to fluctuate, resulting in inaccurate metering accuracy.

[0004] In order to solve the above problems, it is urgent to propose a feeding system that can meet the powder feeding speed, avoid fluidizing gas pressure fluctuations, and ensure metering accuracy. Summary of the Invention

[0005] The technical problem solved by the present invention is to overcome the deficiencies of the prior art, provide a feeding system for powder materials and a control method thereof, and solve the problem of poor metering accuracy caused by unstable fluidizing gas pressure.

[0006] The technical solution of the present invention is:

[0007] A feeding system for powder material, comprising a main discharge pipeline, a spiral feeder, a first regulating valve, a first control valve, a return air blanking barrel assembly, a return air regulating pipeline and a weighing sensor; the discharge port of the spiral feeder is connected to the side of the main discharge pipeline, and the return air blanking barrel assembly is connected to the bottom of the main discharge pipeline; the first regulating valve is connected to the main discharge pipeline and is located on the upper side of the spiral feeder; the main discharge pipeline and the return air blanking barrel assembly are connected via the first control valve; the return air regulating pipeline is connected to the side of the return air blanking barrel assembly, and the pressure in the return air regulating pipeline is controlled by adjusting the degree of connectivity between the return air regulating pipeline and the outside atmosphere; a container for holding powder material is flexibly connected to the bottom of the return air blanking barrel assembly, and the weighing sensor is located at the bottom of the return air blanking barrel assembly and is used to weigh the container and the powder material located in the container.

[0008] The main discharge pipeline is connected to the feed port of the spiral feeder through a side branch pipe, and the connecting end of the side branch pipe and the main discharge pipeline is located above the first regulating valve.

[0009] The return air blanking cylinder assembly includes an outer cylinder and an inner cylinder. The inner cylinder is connected to the main discharge pipeline through a first control valve. The outer cylinder is sleeved on the outside of the inner cylinder. The top of the outer cylinder is connected to the top of the inner cylinder. A sandwich return air channel is formed between the inner cylinder and the outer cylinder, the bottom of which is connected to a feeding system for powder. The side walls of the outer cylinder are respectively connected to and communicated with a pressure sensor and a return air regulating pipeline. The pressure sensor is used to detect the pressure in the return air regulating pipeline.

[0010] The return air regulating pipeline includes a return air main pipeline, a side return air pipeline, an air pipeline, an exhaust pipeline, a second control valve and a second regulating valve. The side wall of the return air main pipeline is connected and communicated with the outer cylinder through the side return air pipeline. The second control valve and the second regulating valve are both arranged on the return air main pipeline and are respectively located on both sides of the side return air pipeline. The air pipeline is connected and communicated with one end of the return air main pipeline through the second control valve, and the exhaust pipeline is connected and communicated with the other end of the return air main pipeline through the second regulating valve.

[0011] It also includes the controller, the weighing sensor transmits the weight value to the controller, the pressure sensor transmits the pressure value to the controller, the controller analyzes and judges according to the weight value and pressure value, and further controls the actions of the first regulating valve, the first control valve, the second control valve, the second regulating valve and the spiral motor.

[0012] A method for controlling a feeding system for powder material, according to any of the above-mentioned feeding systems for powder material, comprising:

[0013] S1: The weighing weights are set to a first preset weight value, a second preset weight value, a third preset weight value and a target weight value, respectively, with the first preset weight value < the second preset weight value < the third preset weight value < the target weight value, and the pressure values ​​are set to a first preset pressure value and a second preset pressure value, respectively;

[0014] S2: Open the first regulating valve, open the first control valve, and open the second regulating valve;

[0015] S3: Obtain the weighing weight value and the pressure value in the bag;

[0016] S311: When the weighing weight reaches a first preset weight value, the first regulating valve is adjusted to 1 / 2 opening, and the second regulating valve is adjusted to 1 / 2 opening;

[0017] S312: When the weighing weight reaches a second preset weight value, the first regulating valve is completely closed and the second control valve is opened until all the powder in the return air blanking cylinder assembly falls into the container and a second weight value is obtained, and the screw feeder starts to operate;

[0018] S313. When the weighing weight reaches the third preset weight value, the screw feeder stops working, the first control valve is closed, and the second regulating valve is closed until all the powder in the return air blanking barrel assembly falls into the container to obtain the actual weight value.

[0019] In step S3, the third preset weight value = the target weight value - the drop amount, where the drop amount is the total weight of the powder still in the main discharge pipeline when the first control valve is closed; the second preset weight value is the target weight value - the drop amount - the fine addition amount, where the fine addition amount is the total weight of the powder delivered by the screw feeder, generally 3% to 5% of the target weight value; the first preset weight value is the target weight value - the drop amount - the fine addition amount - the medium addition amount, where the medium addition amount is the total weight of the powder falling into the container from the main discharge pipeline when the first regulating valve is opened to 1 / 2, generally 10% to 12% of the target weight value; the first preset pressure value is 90-95% of the bursting pressure of the ton bag to prevent the ton bag from bursting; and the second preset pressure value is equal to the atmospheric pressure value.

[0020] In step S312, before closing the first regulating valve, the return air blanking barrel assembly is controlled to have a first preset pressure value; during the operation of the screw feeder, the return air blanking barrel assembly is controlled to have a second preset pressure value.

[0021] In step S3, if the weighed weight is less than the first preset weight value and the pressure value is greater than the first preset pressure value, the opening of the first regulating valve is reduced; if the weighed weight is less than the first preset weight value and the pressure value is less than the second preset pressure value, the opening of the second regulating valve is reduced; if the weighed weight is greater than the first preset weight value and the pressure value is greater than the first preset pressure value, the opening of the second regulating valve is increased; if the weighed weight is greater than the first preset weight value and the pressure value is less than the second preset pressure value, the opening of the second regulating valve is reduced.

[0022] The second preset weight value and the third preset weight value can be dynamically corrected. The controller obtains the second weight value and the actual weight value and stores them; calculates the average of multiple consecutive actual weight values ​​before the current feeding, the drop correction value = the average value - the target weight value, and corrects the third preset value according to the drop correction value; calculates the average of multiple consecutive second weight values ​​before the current feeding operation, the fine addition correction value = the average value of the second weight value - the third preset weight value, and corrects the second preset weight value according to the fine addition correction value.

[0023] In summary, this application has at least the following beneficial technical effects:

[0024] 1. The present invention uses a unique return air structure design to discharge a large amount of fluidizing gas in a timely manner during the rapid feeding stage, and relies on the added air to balance the pressure in the bag during the precise feeding stage, thus ensuring the feeding and weighing accuracy;

[0025] 2. The present invention uses a pressure sensor to monitor the pressure inside the bag and controls the opening of the first regulating valve and the second regulating valve according to the pressure value, ensuring that the pressure inside the bag is maintained at a normal state and effectively avoiding the influence of fluidizing gas pressure fluctuation on the weighing accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a structural diagram of a feeding system for powder provided in a specific embodiment of the present invention;

[0027] Figure 2 1 is a flow chart of a feeding control method provided by a specific embodiment of the present invention;

[0028] Figure 3 and Figure 4 1 is a flow chart of a method for controlling pressure in a bag provided by a specific embodiment of the present invention;

[0029] Figure 5 This is a structural block diagram of a feeding system control for powder provided in a specific embodiment of the present invention;

[0030] Figure 6 This is a schematic diagram of the relative positions of an emergency air storage device, a return air blanking barrel assembly, and a return air regulating pipeline for emergency exhaust of powder materials provided by a specific embodiment of the present invention;

[0031] Figure 7 It is a cross-sectional view of an emergency gas storage container provided by a specific embodiment of the present invention.

[0032] In the accompanying drawings, they are marked as:

[0033] 1. Main discharge pipeline; 11. Side branch pipe;

[0034] 2. Screw feeder;

[0035] 3. The first regulating valve;

[0036] 4. First control valve;

[0037] 5. Return air blanking cylinder assembly; 51. Outer cylinder, 52. Inner cylinder;

[0038] 6. Return air conditioning pipeline; 61. Air-to-air pipeline; 62. Second control valve; 63. Second regulating valve; 64. Exhaust pipeline; 65. Return air main pipeline; 66. Side return air pipeline;

[0039] 7. Pressure sensor;

[0040] 8. Weighing sensor;

[0041] 9. Emergency gas storage device; 91. Gas storage container; 92. Third control valve; 93. Gas storage discharge pipeline; 94. Gas storage intake pipeline; 95. Intake valve; 96. Torsion spring; 97. Rotating shaft. DETAILED DESCRIPTION

[0042] The present application is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0043] This embodiment discloses a feeding system for powder material and a control method thereof.

[0044] like Figure 1 As shown, a feeding system for powder materials, such as Figure 1 As shown, it includes a main discharge pipeline 1, a screw feeder 2, a first regulating valve 3, a first control valve 4, a return air discharge barrel assembly 5, a return air regulating pipeline 6, a pressure sensor 7 and a weighing sensor 8.

[0045] A screw feeder 2 is mounted on the side of the main discharge line 1. The upper sidewall of the main discharge line 1 is connected to the feed port of the screw feeder 2 via a side branch pipe 11. The lower sidewall of the main discharge line 1 is connected to the discharge port of the screw feeder 2. A first regulating valve 3 is installed on the main discharge line between the upper and lower sidewalls. The main discharge line 1 is connected to the return air discharge barrel assembly 5 via a first control valve 4. A container for holding powder is flexibly connected to the bottom of the main discharge line 1. In this embodiment, the container is a ton bag.

[0046] The return air blanking cylinder assembly 5 includes an outer cylinder 51 and an inner cylinder 52. A sandwich return air channel is formed between the inner cylinder 52 and the outer cylinder 51. The inner cylinder 52 is connected to the main blanking pipeline 1 through the first control valve 4. The side walls of the outer cylinder 51 are respectively connected and connected to the pressure sensor 7 and the return air adjustment pipeline 6.

[0047] The return air regulating duct 6 includes a return air main duct 65. The side wall of the return air main duct 65 is connected and communicated with the outer cylinder 51 of the return air blanking barrel assembly 5 through the side return air duct 66. The second control valve 62 and the second regulating valve 63 are both arranged on the return air main duct 65 and are respectively located on both sides of the side return air duct. The air duct 61 is connected and communicated with the return air main duct 65 through the second control valve 62. The exhaust duct 64 is connected and communicated with the return air main duct 65 through the second regulating valve 63. The exhaust duct 64 is connected to the dust collector for continuously extracting the fluidizing gas in the return air blanking barrel assembly 5.

[0048] The weighing sensor 8 is placed directly below the main unloading pipeline 1, and is used to bear the weight of the ton bag and the split inside the ton bag, and output the weighing signal of the powder in the ton bag.

[0049] The structural arrangement of the return air blanking barrel assembly 5 and the return air regulating pipeline 6 enables the fluidizing gas to drive the powder to fall into the ton bag along the main discharge pipeline 1, and then the fluidizing gas rises from the bottom of the interlayer between the outer cylinder 51 and the inner cylinder 52. This process greatly reduces the powder entrained in the fluidizing gas. The fluidizing gas then enters the side return air pipeline and the return air main pipeline 65, and is finally discharged from the exhaust pipeline 64.

[0050] like Figure 5 As shown, the weighing sensor transmits the weight value to the controller, and the pressure sensor transmits the pressure value to the controller. The controller analyzes and judges according to the weight value and pressure value, and further controls the actions of the first regulating valve, the first control valve, the second control valve, the second regulating valve and the screw motor.

[0051] like Figure 6 and Figure 7 As shown, the emergency gas storage device 9 includes a gas storage container 91, and both ends of the gas storage discharge pipeline 93 are connected to the return air main pipeline 65 and the gas storage container 91 respectively. A third control valve 92 is arranged on the gas storage discharge pipeline 93, and one end of the gas storage intake pipeline 94 is connected to the outer cylinder 51 of the return air blanking barrel assembly 5, and the other end extends into the gas storage container 91. An intake valve 95 is arranged at the end of the gas storage intake pipeline 94, and the intake valve 95 is connected to the end of the gas storage intake pipeline 94 through a rotating shaft 97. The intake valve 95 can rotate around the rotating shaft 97. Torsion springs 96 are sleeved on both sides of the rotating shaft, and one end of the torsion spring 96 is connected to the intake valve 95, and the other end is connected to the end of the gas storage intake pipeline 94. The intake valve 95 is pressed against the end face of the gas storage intake pipeline 96 with a certain pressing force under the torsion force of the torsion spring 96.

[0052] Working principle:

[0053] Initially, all valves are closed and the screw motor is stopped. When feeding begins, the first regulating valve 3, the first control valve 4, and the second regulating valve 63 are all opened. Fluidized powder rapidly enters the packaging bag from top to bottom through the main discharge pipe 1. A large amount of fluidizing gas in the powder is rapidly discharged from the interlayer channel between the outer cylinder 51 and the inner cylinder 52 of the return air discharge cylinder 5 through the main return air line 65, the second regulating valve 63, and the exhaust pipe 64, ensuring the discharge speed. A load cell 8 is used for weighing and measurement, and a pressure sensor monitors the pressure in the bag in real time. When the weighing weight reaches the set coarse addition value, the first regulating valve 3 is closed by 1 / 2; when the weighing weight reaches the set medium addition value, the first regulating valve 3 is completely closed, the screw feeder 2 starts working, the second control valve 62 is opened, and the powder mixed with a small amount of fluidizing gas flows evenly into the packaging bag through the screw feeder 2. Some air enters through the air pipe 61 to balance the pressure in the bag. The replenished air and fluidizing gas are discharged together through the second regulating valve 63 and the exhaust pipe 64; when the weighing weight reaches the set fine addition value, the screw feeder 2 stops working, the first control valve 4 is closed, the second regulating valve 63 is closed, and the powder in the pipeline below the first control valve 4 falls into the packaging bag. The weighing weight value just reaches the set target weight value, and the fluidizing gas in the bag is connected to the atmosphere, ensuring the weighing accuracy.

[0054] During the entire feeding process, when the pressure inside the bag fluctuates, the openings of the first regulating valve 3 and the second regulating valve 63 are slightly adjusted to ensure that the pressure inside the bag is stable.

[0055] During the initial feeding, if there is too much fluidizing gas in the powder, which has exceeded the adjustment range of the first regulating valve 3 and the second regulating valve 63, and the instantaneous pressure of the fluidizing gas in the ton bag is greater than the bursting pressure of the ton bag, the air inlet valve 95 will open under the action of the fluidizing gas pressure, releasing part of the fluidizing gas into the gas storage container 91, and at the same time quickly reducing the fluidizing gas pressure in the ton bag to avoid the ton bag from bursting. At the same time, since the fluidizing gas is mostly inert gas, the fluidizing gas stored in the gas storage container 91 can open the third control valve 92 when the pressure value in the bag is less than the second preset pressure value, and replenish the ton bag or discharge it through the exhaust pipe 64 to prevent the fluidizing gas from leaking into the indoor air and avoid suffocation of on-site operators.

[0056] like Figure 2 、 Figure 3 and Figure 4 As shown, a control method for powder feeding includes:

[0057] Step S1, initialization settings, setting the weighing weight to a first preset weight value, a second preset weight value, a third preset weight value and a target weight value, and setting the pressure value to a first preset pressure value and a second preset pressure value;

[0058] Among them, the target weight value is the target weight of the ton bag; the third preset weight value = target weight value - drop amount, the drop amount is the total weight of the powder that is still in the main discharge pipeline and has not fallen into the ton bag when the first control valve is closed; the second preset weight value is the target weight value - drop amount - fine addition amount, the fine addition amount is the total weight of the powder delivered by the screw feeder, generally 3% to 5% of the target weight value; the first preset weight value is the target weight value - drop amount - fine addition amount - medium addition amount, the medium addition amount is the total weight of the powder that falls into the container from the main discharge pipeline when the opening of the first regulating valve is 1 / 2, generally 10% to 12% of the target weight value; the first preset pressure value is 95% of the ton bag bursting pressure, so that the ton bag does not burst; the second preset pressure value is equal to the atmospheric pressure value.

[0059] Step S2: open the first regulating valve, open the first control valve, and open the second regulating valve;

[0060] Step S3, obtaining the weighing weight value and the pressure value inside the bag;

[0061] Step S311: When the weighing weight reaches a first preset weight value, the first regulating valve is adjusted to 1 / 2 opening, and the second regulating valve is adjusted to 1 / 2 opening. During this process, the return air blanking cylinder assembly is controlled to have a first preset pressure value, so that the powder can be packaged at a faster speed;

[0062] Step S312: When the weighing weight reaches a second preset weight value, the first regulating valve is completely closed and the second control valve is opened until all the powder in the return air blanking barrel assembly falls into the container and a second weight value is obtained. When the pressure in the return air blanking barrel assembly is controlled to a second preset pressure value, the screw feeder starts to operate. In multiple consecutive feeding operations of the same batch, the screw feeder maintains the same feeding speed to ensure that the drop value is basically consistent.

[0063] Step S313: until the weighing weight reaches the third preset weight value, the screw feeder stops working, the first control valve is closed, and the second regulating valve is closed; until all the powder in the return air blanking barrel assembly falls into the container, the actual weight value is obtained.

[0064] In step S3,

[0065] When the weighing weight is less than the first preset weight value and the pressure value is greater than the first preset pressure value, the opening of the first regulating valve is reduced;

[0066] When the weighing weight is less than the first preset weight value and the pressure value is less than the second preset pressure value, the third control valve is opened and the opening of the second regulating valve is reduced;

[0067] When the weighing weight is greater than the first preset weight value and the pressure value is greater than the first preset pressure value, the opening of the second regulating valve is increased;

[0068] When the weighing weight is greater than the first preset weight value and the pressure value is less than the second preset pressure value, the third control valve is opened and the opening of the second regulating valve is reduced.

[0069] The second preset weight value and the third preset weight value can be dynamically modified. The controller obtains the second weight value and the actual weight value and stores them.

[0070] The correction method for the third preset weight value is:

[0071] According to four consecutive actual weight values ​​before the current feeding operation, an average of the four consecutive actual weight values ​​before the current feeding operation is obtained;

[0072] Calculate the drop correction value, drop correction value = average value - target weight value;

[0073] The third preset weight value is corrected according to the drop correction value. The third preset weight value of the current feeding operation=the third preset weight value before the current feeding operation-the drop correction value.

[0074] The correction method for the second preset weight value is:

[0075] Calculate the average of the four consecutive second weight values ​​before the current feeding operation based on the four consecutive second weight values ​​before the current feeding operation;

[0076] Calculate the fine addition correction value, which is the fine addition correction value = the average of the second weight values ​​- (the third preset weight value);

[0077] The second preset weight value is corrected according to the fine-added correction value. The second preset weight value of the current feeding operation = the second preset weight value before the current feeding operation - the fine-added correction value.

[0078] Although the present invention is disclosed above in terms of preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be based on the scope defined by the claims of the present invention.

Claims

1. A feeding system for powder, characterized by: It comprises a main feeding pipeline (1), a screw feeder (2), a first regulating valve (3), a first control valve (4), a return air feeding cylinder assembly (5), a return air regulating pipeline (6) and a weighing sensor (8); The discharge port of the screw feeder (2) is connected to the side of the main discharge pipe (1), and the return air discharge cylinder assembly (5) is connected to the bottom of the main discharge pipe (1); The first regulating valve (3) is connected to the main discharge pipeline (1) and is located on the upper side of the screw feeder (2); the main discharge pipeline (1) and the return air discharge cylinder assembly (5) are connected via the first control valve (4); The return air regulating pipe (6) is connected to the side of the return air blanking barrel assembly (5); the pressure in the return air regulating pipe (6) is controlled by adjusting the degree of connection between the return air regulating pipe (6) and the outside atmosphere; The bottom of the return air blanking barrel assembly (5) is softly connected to a container for holding powder, and a weighing sensor (8) is located at the bottom of the return air blanking barrel assembly (5) and is used to weigh the container and the powder in the container; The return air blanking cylinder assembly (5) comprises an outer cylinder (51) and an inner cylinder (52), the inner cylinder (52) and the main discharge pipe (1) are connected via a first control valve (4), the outer cylinder (51) is sleeved on the outer side of the inner cylinder (52), the top of the outer cylinder (51) is connected to the top of the inner cylinder (52), and an interlayer return air channel is formed between the inner cylinder (52) and the outer cylinder (51), the bottom of which is connected to a feeding system for powder material, and the side wall of the outer cylinder (51) is connected to and communicated with a pressure sensor (7) and a return air regulating pipe (6), respectively, and the pressure sensor (7) is used to detect the pressure in the return air regulating pipe (6); The return air regulating pipeline (6) comprises a return air main pipeline (65), a side return air pipeline (66), an air pipeline (61), an exhaust pipeline (64), a second control valve (62) and a second regulating valve (63). The side wall of the return air main pipeline (65) is connected and communicated with the outer cylinder (51) through the side return air pipeline (66). The second control valve (62) and the second regulating valve (63) are both arranged on the return air main pipeline (65) and are respectively located on both sides of the side return air pipeline (66). The air pipeline (61) is connected and communicated with one end of the return air main pipeline (65) through the second control valve (62), and the exhaust pipeline (64) is connected and communicated with the other end of the return air main pipeline (65) through the second regulating valve (63).

2. A feeding system for powder according to claim 1, characterized in that: The main discharge pipeline (1) is connected to the feed port of the screw feeder (2) via a side branch pipe (11), and the connection end between the side branch pipe (11) and the main discharge pipeline (1) is located above the first regulating valve (3).

3. A feeding system for powder according to claim 1, characterized in that: The invention also includes a controller. The weighing sensor (8) transmits the weight value to the controller, and the pressure sensor (7) transmits the pressure value to the controller. The controller analyzes and judges the weight value and the pressure value, and further controls the first regulating valve (3), the first control valve (4), the second control valve (62), the second regulating valve (63) and the screw motor.

4. A method for controlling a feeding system for powder materials, according to any one of claims 1 to 3, characterized in that: include S1: The weighing weights are set to a first preset weight value, a second preset weight value, a third preset weight value and a target weight value, respectively, with the first preset weight value < the second preset weight value < the third preset weight value < the target weight value, and the pressure values ​​are set to a first preset pressure value and a second preset pressure value, respectively; S2: Open the first regulating valve (3), open the first control valve (4), and open the second regulating valve (63); S3: Obtain the weighing weight value and the pressure value in the bag; S311, when the weighing weight reaches a first preset weight value, the first regulating valve (3) is adjusted to 1 / 2 opening, and the second regulating valve (63) is adjusted to 1 / 2 opening; S312, when the weighing weight reaches a second preset weight value, the first regulating valve (3) is completely closed, and the second control valve (62) is opened until all the powder in the return air drop barrel assembly (5) falls into the container, and a second weight value is obtained, and the screw feeder (2) starts to operate; S313: When the weighing weight reaches the third preset weight value, the screw feeder (2) stops working, the first control valve (4) is closed, and the second regulating valve (63) is closed until all the powder in the return air drop barrel assembly (5) falls into the container, and the actual weight value is obtained.

5. The control method for a feeding system for powder materials according to claim 4, characterized in that: In step S3, the third preset weight value = the target weight value - the drop amount, where the drop amount is the total weight of the powder still in the main discharge pipeline when the first control valve is closed; the second preset weight value is the target weight value - the drop amount - the fine addition amount, where the fine addition amount is the total weight of the powder delivered by the screw feeder; The first preset weight value is the target weight value - drop amount - fine addition amount - medium addition amount. The medium addition amount is the total weight of the powder dropped into the container from the main discharge pipe when the first regulating valve is opened to 1 / 2. The fine addition amount is 3% to 5% of the target weight value, and the medium addition amount is 10% to 12% of the target weight value. The first preset pressure value is 90-95% of the bursting pressure of the ton bag so that the ton bag does not burst; the second preset pressure value is equal to the atmospheric pressure value.

6. The control method for a feeding system for powder materials according to claim 4, characterized in that: In the step S312, before closing the first regulating valve (3), the return air blanking barrel assembly (5) is controlled to have a first preset pressure value; during the operation of the screw feeder (2), the return air blanking barrel assembly (5) is controlled to have a second preset pressure value.

7. The control method for a feeding system for powder materials according to claim 4, characterized in that: In step S3, if the weighed weight is less than the first preset weight value and the pressure value is greater than the first preset pressure value, the opening of the first regulating valve (3) is reduced; When the weighed weight is less than a first preset weight value and the pressure value is less than a second preset pressure value, the opening of the second regulating valve (63) is reduced; When the weighed weight is greater than a first preset weight value and the pressure value is greater than a first preset pressure value, the opening of the second regulating valve (63) is increased; When the weighed weight is greater than the first preset weight value and the pressure value is less than the second preset pressure value, the opening of the second regulating valve (63) is reduced.

8. The control method for a powder feeding system according to claim 4, characterized in that: The second preset weight value and the third preset weight value can be dynamically modified, and the controller obtains the second weight value and the actual weight value and stores them; Calculate the average of the actual weight values ​​before the current feeding, the drop correction value = average value - target weight value, and correct the third preset value according to the drop correction value; Calculate the average of the second weight values ​​before the current feeding operation, the fine correction value = the average of the second weight value - the third preset weight value, and correct the second preset weight value according to the fine correction value.

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