Filter

Abstract

The invention relates to a filter. The filter comprises a filter main body, an upper plunger body and a lower plunger body, one side of the filter main body is provided with a feed port for feeding raw materials, the other side of the filter main body is provided with a discharge port for discharging the raw materials, the filter main body is provided with an upper plunger channel, a lower plunger channel, an upper inlet channel, an upper outlet channel, a lower inlet channel and a lower outlet channel, and the upper plunger channel and the lower plunger channel both penetrate through the filter main body; the upper plunger channel is communicated with the feed port through an upper inlet channel and is communicated with the discharge port through an upper outlet channel; the lower plunger channel is communicated with the feed port through a lower inlet channel and is communicated with the discharge port through a lower outlet channel; the upper plunger body is provided with an upper channel, an upper filter screen is arranged in the upper channel, the upper plunger body is arranged in the upper plunger channel in a sliding mode, the lower plunger body is provided with a lower channel, a lower filter screen is arranged in the lower channel, and the lower plunger body is arranged in the lower plunger channel in a sliding mode. The filter screen is provided with the upper filter screen and the lower filter screen, so that non-stop screen replacement is realized by alternate screen replacement.

Description

Technical Field

[0001] The present invention relates to the technical field of nonwoven fabrics, and more particularly to a filter. Background Art

[0002] In the production process of spunbond nonwoven fabrics, some impurities such as dust, metal shavings, plastic fragments, etc. may be mixed in during the production and transportation of raw polymers. If these impurities enter the spinning process, they will cause the spinneret to be blocked, affecting the continuity and uniformity of spinning, and thus affecting the quality of the nonwoven fabric. Therefore, a filter is required to remove large particles and uneven substances in the melt, making the melt more uniform.

[0003] Because the filter needs to be cleaned after a period of use, but spunbond non-woven fabrics need to run continuously during the production process. Once stopped, it will affect the production progress and increase production costs.

[0004] Therefore, how to replace or clean the filter without stopping the filter is exactly the technical problem to be solved by this application. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention proposes a filter having an upper filter screen and a lower filter screen, so that the screens can be replaced alternately without stopping the machine.

[0006] The present invention provides a filter, and the technical solution is as follows: A filter comprises a filter body, an upper plunger body and a lower plunger body; A feed port for raw materials is provided on one side of the filter body, and a discharge port for raw materials is provided on the other side. The filter body is provided with an upper plunger channel, a lower plunger channel, an upper inlet channel, an upper outlet channel, a lower inlet channel and a lower outlet channel. Both the upper plunger channel and the lower plunger channel are provided through the filter body. The upper plunger channel is connected to the feed port through the upper feed channel, and is connected to the discharge port through the upper discharge channel; The lower plunger channel is connected to the feed port through the lower feed channel, and is connected to the discharge port through the lower discharge channel; The upper plunger body is provided with an upper channel, in which an upper filter screen is arranged, and the upper plunger body is slidably arranged in the upper plunger channel. When one end of the upper channel is connected with the upper inlet channel and the other end is connected with the upper outlet channel, the raw material is filtered through the upper filter screen and then flows to the discharge port; The lower plunger body is provided with a lower channel, in which a lower filter screen is arranged, and the lower plunger body is slidably arranged in the lower plunger channel. When one end of the lower channel is connected with the lower inlet channel and the other end is connected with the lower outlet channel, the raw material is filtered through the lower filter screen and flows to the discharge port.

[0007] In summary, the above technical solution has the following beneficial effects: the filter of the present application is provided with a filter screen, and when the upper channel and the lower channel are both connected, after the raw material enters from the feed port, it can pass through the upper feed channel, the upper filter screen and the upper outlet channel in sequence, and finally exit from the outlet, or it can pass through the lower feed channel, the lower filter screen and the lower outlet channel in sequence, and finally exit from the outlet. When the upper plunger body is moved so that the upper channel is not connected, or the lower plunger body is moved so that the lower channel is not connected, the raw material cannot pass through the corresponding filter screen.

[0008] During normal operation, the upper and lower plunger bodies are moved to the appropriate positions in the filter body, so that the upper and lower channels are connected. At this time, the feed port is divided into two by the upper and lower channels, and finally merged into a discharge port. When the polymer material passes through, the dirt will be intercepted on one side of the upper and lower filter screens. After the equipment has been running for a period of time, when the pressure difference before and after the filter gradually increases and reaches a critical value that is considered to be set, the program will prompt to replace the filter screen. At this time, the operator controls the hydraulic cylinder through the control program to push the upper plunger body or the lower plunger body out of the filter body, so that the filter screen is completely exposed, remove the dirty filter screen and replace it with a new one, and then push the plunger body with the replaced filter screen back into the filter body through program control, thus completing the net replacement of one plunger body, and then controls the hydraulic cylinder through the control program to push the other plunger body out of the filter body, so that the filter screen is completely exposed, remove the dirty filter screen and replace it with a new one, and then push the plunger with the replaced filter screen back into the filter body through program control, thus completing the net replacement process of the entire filter. The entire net replacement process can ensure that the filter has at least one passage for the polymer melt to pass through, thereby realizing non-stop net replacement. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is a schematic diagram of a filter body of a filter; Figure 2 A schematic diagram of a longitudinal cross-sectional view of a filter body of a filter; Figure 3 is a schematic diagram of a cross-section of a filter body of a filter; Figure 4 A schematic diagram of an upper plunger body and a lower plunger body of a filter; Figure 5 A schematic diagram of an upper filter screen and a lower filter screen of a filter; Figure 6 A schematic diagram of a control module of a filter; Figure 7 The figure is a schematic diagram of an upper plunger channel and a lower plunger channel of a filter.

[0010] : Illustration symbols: 10, filter body; 11, feed port; 12, discharge port; 13, upper plunger channel; 14, lower plunger channel; 15, upper inlet channel; 16, upper outlet channel; 17, lower inlet channel; 18, lower outlet channel; 20, upper plunger body; 21, upper channel; 211, upper large channel; 212, upper small channel; 30, lower plunger body; 31, lower channel; 311, lower large channel; 312, lower small channel; 40, upper filter screen; 41, upper pressure plate; 50, lower filter screen; 51, lower pressure plate; 60, hydraulic station; 61, upper hydraulic cylinder; 62, lower hydraulic cylinder; 70, protective cover; 80, control module; 81, upper inlet pressure sensor; 82, upper outlet pressure sensor; 83, lower inlet pressure sensor; 84, lower outlet pressure sensor. DETAILED DESCRIPTION

[0011] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0012] like Figure 1-Figure 5 As shown, a filter comprises a filter body 10, an upper plunger body 20 and a lower plunger body 30; a feed port 11 for feeding raw materials is provided on one side of the filter body 10, and a discharge port 12 for discharging raw materials is provided on the other side; an upper plunger channel 13, a lower plunger channel 14, an upper feed channel 15, an upper discharge channel 16, a lower feed channel 17 and a lower discharge channel 18 are provided on the filter body 10, and the upper plunger channel 13 and the lower plunger channel 14 are both provided through the filter body 10; the upper plunger channel 13 is connected to the feed port 11 through the upper feed channel 15, and is connected to the discharge port 12 through the upper discharge channel 16; the lower plunger channel 14 is connected to the feed port 11 through the lower feed channel 17, and is connected to the discharge port 12 through the lower discharge channel 18. The outlet channel 18 is connected with the material outlet 12; the upper plunger body 20 is provided with an upper channel 21, in which an upper filter screen 40 is arranged, and the upper plunger body 20 is slidably arranged in the upper plunger channel 13. When one end of the upper channel 21 is connected with the upper inlet channel 15 and the other end is connected with the upper outlet channel 16, the raw material is filtered through the upper filter screen 40 and flows to the material outlet 12; the lower plunger body 30 is provided with a lower channel 31, in which a lower filter screen 50 is arranged, and the lower plunger body 30 is slidably arranged in the lower plunger channel 14. When one end of the lower channel 31 is connected with the lower inlet channel 17 and the other end is connected with the lower outlet channel 18, the raw material is filtered through the lower filter screen 50 and flows to the material outlet 12.

[0013] The filter of the present application is provided with a filter screen. When the upper channel 21 and the lower channel 31 are both connected, the raw material can pass through the upper inlet channel 15, the upper filter screen 40 and the upper outlet channel 16 in sequence after entering from the feed port 11, and finally exit from the outlet port 12. It can also pass through the lower inlet channel 17, the lower filter screen 50 and the lower outlet channel 18 in sequence, and finally exit from the outlet port 12. When the upper plunger body 20 is moved so that the upper channel 21 is not connected, or the lower plunger body 30 is moved so that the lower channel 31 is not connected, the raw material cannot pass through the corresponding filter screen.

[0014] During normal operation, the upper plunger body 20 and the lower plunger body 30 are moved to appropriate positions in the filter body 10, so that the upper channel 21 and the lower channel 31 are connected. At this time, the feed port 11 is divided into two by the upper channel 21 and the lower channel 31, and finally merged into a discharge port 12. When the polymer material passes through, the dirt will be intercepted on one side of the upper filter screen 40 and the lower filter screen 50. After the equipment has been running for a period of time, when the pressure difference before and after the filter gradually increases and reaches a critical value that is considered to be set, the program will prompt to replace the filter screen. At this time, the operator controls the hydraulic cylinder through the control program to push the upper plunger body 20 or the lower plunger body 30 out of the filter body 10, so that the filter screen is completely exposed, the dirty filter screen is removed and replaced with a new filter screen, and then the plunger body with the replaced filter screen is pushed back into the filter body 10 through program control, thus completing the net replacement of one plunger body, and then the hydraulic cylinder is controlled through the control program to push another plunger body out of the filter body 10, so that the filter screen is completely exposed, the dirty filter screen is removed and replaced with a new filter screen, and then the plunger with the replaced filter screen is pushed back into the filter body 10 through program control, thus completing the net replacement process of the entire filter. The entire net replacement process can ensure that the filter has at least one passage for the polymer melt to pass through, thereby realizing non-stop net replacement.

[0015] like Figure 2-Figure 5 As shown, the aperture of the upper channel 21 facing the feed port 11 is larger than the aperture of the upper channel 21 facing the discharge port 12, thereby forming an upper large channel 211 and an upper small channel 212; the upper filter screen 40 is arranged in the upper large channel 211, and the outer diameter of the upper filter screen 40 is larger than the inner diameter of the upper small channel 212, thereby being stuck in the upper large channel 211, and an upper pressure plate 41 that contacts the upper filter screen 40 is arranged in the upper small channel 212, and the upper pressure plate 41 has a porous structure, which is used to support the upper filter screen 40 and allow the raw materials to flow through; The aperture of the lower channel 31 facing the feed port 11 is larger than the aperture of the lower channel 311 facing the discharge port 12, thereby forming a lower large channel 311 and a lower small channel 312; the lower filter screen 50 is arranged in the lower large channel 311, and the outer diameter of the lower filter screen 50 is larger than the inner diameter of the lower small channel 312, so that it is stuck in the lower small channel 312, and a lower pressure plate 51 that contacts the lower filter screen 50 is arranged in the lower small channel 312, and the lower pressure plate 51 has a porous structure for supporting the lower filter screen 50 and allowing raw materials to flow through.

[0016] The upper pressure plate 41 and the lower pressure plate 51 are used to respectively resist the upper filter screen 40 and the lower filter screen 50 to prevent deformation of the middle part of the upper filter screen 40 and the lower filter screen 50. The upper pressure plate 41 and the upper small channel 212 are connected by interference fit, and the lower pressure plate 51 and the lower small channel 312 are connected by interference fit, so as to ensure that the position remains unchanged, or the upper pressure plate 41 is fixed in the upper small channel 212, and the lower pressure plate 51 is fixed in the lower small channel 312.

[0017] The upper filter screen 40 and the lower filter screen 50 are both formed by overlapping multiple layers of metal screens with the same outer edge size.

[0018] Preferably, each layer of metal mesh is woven in a mat-shaped manner, and the metal mesh is a stainless steel mat-shaped mesh, and its warp and weft wire diameters and densities have a large contrast, so that the filtering accuracy is much higher than that of ordinary square hole mesh, and it is suitable for precision filtration and separation. Of course, the filter mesh can be constructed with other metal materials or other weaving methods, such as copper, steel and other materials, and the weaving methods such as square hole mesh, dense mesh and hexagonal mesh are used. Preferably, each layer of metal mesh is fixedly connected.

[0019] like Figure 4 As shown, the upper large channel 211 is formed with an upper large entrance on the upper piston body 20, and the interface between the upper small channel 212 and the upper large channel 211 is flush with the lowest point of the upper large entrance; the lower large channel 311 is formed with a lower large entrance on the lower piston body 30, and the interface between the lower small channel 312 and the lower large channel 311 is flush with the lowest point of the lower large entrance.

[0020] This arrangement allows the upper filter 40 to be higher than the lowest point of the upper large entrance, and the lower filter 50 to be higher than the lowest point of the lower large entrance, thereby facilitating the placement of the upper filter 40 and the lower filter 50 by hand, and facilitating the adjustment of the upper filter 40 and the lower filter 50.

[0021] like Figure 3As shown, the inner diameter of the upper inlet channel 15 facing the upper plunger channel 13 is larger than the inner diameter of the side facing the feed port 11; the inner diameter of the upper outlet channel 16 facing the upper plunger channel 13 is larger than the inner diameter of the side facing the feed port 11; the inner diameter of the lower inlet channel 17 facing the lower plunger channel 14 is larger than the inner diameter of the side facing the feed port 11; the inner diameter of the lower outlet channel 18 facing the lower plunger channel 14 is larger than the inner diameter of the side facing the feed port 11.

[0022] The upper inlet channel 15 , the upper outlet channel 16 , the lower inlet channel 17 and the lower outlet channel 18 are of the same shape and size and are completely symmetrical, so that the raw materials at the feed port 11 can be evenly distributed to the upper inlet channel 15 and the lower inlet channel 17 , and all are in the shape of a trumpet with a gradually increasing opening, so that the raw materials can be evenly diffused into the upper channel 21 and the lower channel 31 .

[0023] It also includes a hydraulic station 60, an upper hydraulic cylinder 61 and a lower hydraulic cylinder 62. The hydraulic station 60 is connected to the upper hydraulic cylinder 61 and the lower hydraulic cylinder 62 through hydraulic oil pipes, respectively, and is used to control the movement of the upper hydraulic cylinder 61 and the lower hydraulic cylinder 62; the upper hydraulic cylinder 61 is connected to the upper plunger body 20, and is used to drive the upper plunger body 20 to move in the upper plunger channel 13; the lower hydraulic cylinder 62 is connected to the lower plunger body 30, and is used to drive the lower plunger body 30 to move in the lower plunger channel 14.

[0024] The function of the hydraulic station 60 is to provide power for reciprocating motion to the hydraulic cylinder; the hydraulic station 60 is connected to the upper hydraulic cylinder 61 and the lower hydraulic cylinder 62 through hydraulic oil pipes, and the circulating oil circuit of the upper hydraulic cylinder 61 and the circulating oil circuit of the lower hydraulic cylinder 62 are independent of each other; the upper hydraulic cylinder 61 and the lower hydraulic cylinder 62 mainly perform reciprocating motion, and the upper hydraulic cylinder 61 and the lower hydraulic cylinder 62 are arranged in parallel in the height direction; the upper plunger body 20 and the lower plunger body 30 are arranged in parallel in the height direction, and the control module 80 controls the movement of the upper hydraulic cylinder 61 and the lower hydraulic cylinder 62 through the hydraulic station 60, thereby driving the upper plunger body 20 and the lower plunger body 30 to move respectively.

[0025] A protective cover 70 is also included, and the protective cover 70 is arranged on the side of the filter body 10 facing the upper hydraulic cylinder 61 and the side of the filter body 10 away from the upper hydraulic cylinder 61. The protective cover 70 is mainly used to isolate high temperature and moving parts to prevent personal injury.

[0026] like Figure 6As shown, an upper inlet pressure sensor 81 is provided on the side of the upper filter 40 facing the feed port 11, and an upper outlet pressure sensor 82 is provided on the side facing the feed port 12; a lower inlet pressure sensor 83 is provided on the side of the lower filter 50 facing the feed port 11, and a lower outlet pressure sensor 84 is provided on the side facing the feed port 12; the control module 80 is preset with an upper pressure difference value and a lower pressure difference value, and when the pressure difference detected by the upper inlet pressure sensor 81 and the upper outlet pressure sensor 82 is greater than the upper pressure difference value, a signal for replacing the upper filter 40 is generated; when the pressure difference detected by the lower inlet pressure sensor 83 and the lower outlet pressure sensor 84 is greater than the lower pressure difference value, a signal for replacing the lower filter 50 is generated.

[0027] Of course, two pressure sensors can be set at the feed port 11 and the discharge port 12 respectively. In order to better judge the filtering conditions of the two filter screens, four pressure sensors are set to make judgments, so that the flow pressure of the upper channel 21 and the lower channel 31 are kept consistent as much as possible. If the pressures are different, the flow in the channel with a larger pressure is larger, the filter screen is more likely to be blocked, and finally the pressure difference between the two channels is greater. The control module 80 judges the use of the upper filter screen 40 and the lower filter screen 50 through the pressure sensor, so as to accurately judge whether the filter screen needs to be replaced.

[0028] like Figure 7 As shown, the upper plunger body 20 is provided with two upper channels 21. When one upper channel 21 is located in the upper plunger channel 13 and is connected with the upper inlet channel 15 and the upper outlet channel 16, the other upper channel 21 is located outside the upper plunger channel 13. The lower plunger body 30 is provided with two lower channels 31. When one lower channel 31 is located in the lower plunger channel 14 and is connected with the lower inlet channel 17 and the lower outlet channel 18, the other lower channel 31 is located outside the lower plunger channel 14.

[0029] Although the equipment can be kept running when the filters are replaced one by one, the fluidity of the filters is already very poor when the filters need to be replaced, and the pressure difference on both sides of the filters also exceeds the preset pressure difference value. At this time, if the filter is replaced to close one channel, the other filter needs to withstand a larger pressure difference, and it will affect the raw material flow rate of the discharge port 12. Therefore, the present application sets two upper channels 21 and two lower channels 31. When the upper filter 40 in one upper channel 21 needs to be replaced and removed, the filter in the other upper channel 21 will be connected to the upper inlet channel 15 and the upper outlet channel 16, thereby avoiding the lower filter 50 from being subjected to too much pressure difference, and the flow rate of the filter discharge port 12 can be kept unchanged. The same is true when the lower filter 50 needs to be replaced. The setting of the other two upper channels 21 and two lower channels 31 can prevent sudden failures of the filters. At this time, if there is no time to replace the upper filter 40 or the lower filter 50, another upper filter 40 and the lower filter 50 can be used to ensure the continuous operation of the equipment.

[0030] The above are only preferred embodiments of the present invention. The protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A filter, characterized in that: It comprises a filter body (10), an upper plunger body (20) and a lower plunger body (30); A feed port (11) for feeding raw materials is provided on one side of the filter body (10), and a discharge port (12) for discharging raw materials is provided on the other side. The filter body (10) is provided with an upper plunger channel (13), a lower plunger channel (14), an upper inlet channel (15), an upper outlet channel (16), a lower inlet channel (17) and a lower outlet channel (18). The upper plunger channel (13) and the lower plunger channel (14) are both provided through the filter body (10); The upper plunger channel (13) is connected to the feed port (11) through the upper feed channel (15), and is connected to the discharge port (12) through the upper discharge channel (16); The lower plunger channel (14) is connected to the feed port (11) through the lower feed channel (17), and is connected to the discharge port (12) through the lower discharge channel (18); The upper plunger body (20) is provided with an upper channel (21), an upper filter screen (40) is arranged in the upper channel (21), and the upper plunger body (20) is slidably arranged in the upper plunger channel (13). When one end of the upper channel (21) is connected to the upper inlet channel (15) and the other end is connected to the upper outlet channel (16), the raw material is filtered through the upper filter screen (40) and then flows to the discharge port (12); The lower plunger body (30) is provided with a lower channel (31), and a lower filter screen (50) is arranged in the lower channel (31). The lower plunger body (30) is slidably arranged in the lower plunger channel (14). When one end of the lower channel (31) is connected to the lower inlet channel (17) and the other end is connected to the lower outlet channel (18), the raw material is filtered through the lower filter screen (50) and then flows to the discharge port (12).

2. A filter according to claim 1, characterized in that: The aperture of the upper channel (21) facing the feed port (11) is larger than the aperture of the upper channel (21) facing the discharge port (12), thereby forming an upper large channel (211) and an upper small channel (212); The upper filter screen (40) is arranged in the upper large channel (211); the outer diameter of the upper filter screen (40) is larger than the inner diameter of the upper small channel (212), so that the upper filter screen (40) is stuck in the upper large channel (211); an upper pressure plate (41) is arranged in the upper small channel (212) to contact the upper filter screen (40); the upper pressure plate (41) has a porous structure and is used to support the upper filter screen (40) and allow the raw materials to flow through; The aperture of the lower channel (31) facing the feed port (11) is larger than the aperture of the lower channel (31) facing the discharge port (12), thereby forming a lower large channel (311) and a lower small channel (312); The lower filter screen (50) is arranged in the lower large channel (311); the outer diameter of the lower filter screen (50) is larger than the inner diameter of the lower small channel (312), so that the lower filter screen (50) is stuck in the lower small channel (312); a lower pressure plate (51) in contact with the lower filter screen (50) is arranged in the lower small channel (312); the lower pressure plate (51) has a porous structure and is used to support the lower filter screen (50) and allow raw materials to flow through.

3. A filter according to claim 2, characterized in that: The upper filter screen (40) and the lower filter screen (50) are both formed by overlapping multiple layers of metal screens with the same outer edge size.

4. A filter according to claim 2, characterized in that: The upper large channel (211) is formed with an upper large entrance on the upper plunger body (20), and the interface between the upper small channel (212) and the upper large channel (211) is flush with the lowest point of the upper large entrance; The lower large channel (311) is formed with a lower large inlet on the lower plunger body (30), and the interface between the lower small channel (312) and the lower large channel (311) is flush with the lowest point of the lower large inlet.

5. A filter according to claim 1, characterized in that: The inner diameter of the upper feed channel (15) facing the upper plunger channel (13) is larger than the inner diameter of the side facing the feed port (11); The inner diameter of the upper outlet channel (16) facing the upper plunger channel (13) is larger than the inner diameter of the side facing the feed port (11); The inner diameter of the lower inlet channel (17) facing the lower plunger channel (14) is larger than the inner diameter of the side facing the feed port (11); The inner diameter of the lower outlet channel (18) facing the lower plunger channel (14) is larger than the inner diameter of the side facing the feed port (11).

6. A filter according to any one of claims 1 to 5, characterized in that: It also includes a hydraulic station (60), an upper hydraulic cylinder (61) and a lower hydraulic cylinder (62); the hydraulic station (60) is connected to the upper hydraulic cylinder (61) and the lower hydraulic cylinder (62) through hydraulic oil pipes, respectively, and is used to control the movement of the upper hydraulic cylinder (61) and the lower hydraulic cylinder (62); The upper hydraulic cylinder (61) is connected to the upper plunger body (20) and is used to drive the upper plunger body (20) to move in the upper plunger channel (13); The lower hydraulic cylinder (62) is connected to the lower plunger body (30) and is used to drive the lower plunger body (30) to move in the lower plunger channel (14).

7. A filter according to claim 6, characterized in that: The invention also comprises a protective cover (70), wherein the protective cover (70) is arranged on a side of the filter body (10) facing the upper hydraulic cylinder (61) and a side of the filter body (10) away from the upper hydraulic cylinder (61).

8. A filter according to claim 6, characterized in that: The hydraulic station (60) is connected to a control module (80); an upper inlet pressure sensor (81) is provided on the side of the upper filter screen (40) facing the feed port (11), and an upper outlet pressure sensor (82) is provided on the side facing the discharge port (12); A lower inlet pressure sensor (83) is provided on the side of the lower filter screen (50) facing the feed inlet (11), and a lower outlet pressure sensor (84) is provided on the side facing the outlet (12); The control module (80) is preset with an upper pressure difference value and a lower pressure difference value, and when the pressure difference value detected by the upper inlet pressure sensor (81) and the upper outlet pressure sensor (82) is greater than the upper pressure difference value, a signal for replacing the upper filter screen (40) is generated; When the pressure difference detected by the lower inlet pressure sensor (83) and the lower outlet pressure sensor (84) is greater than the lower pressure difference, a signal for replacing the lower filter screen (50) is generated.

9. A filter according to claim 1, characterized in that: The upper plunger body (20) is provided with two upper channels (21). When one upper channel (21) is located inside the upper plunger channel (13) and is connected to the upper inlet channel (15) and the upper outlet channel (16), the other upper channel (21) is located outside the upper plunger channel (13); The lower plunger body (30) is provided with two lower channels (31). When one lower channel (31) is located inside the lower plunger channel (14) and is connected to the lower inlet channel (17) and the lower outlet channel (18), the other lower channel (31) is located outside the lower plunger channel (14).

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