Aggregate powder screening device for preparing asphalt mixture

Abstract

The utility model discloses an aggregate powder screening device for preparing an asphalt mixture, relates to the technical field of asphalt preparation, and aims to solve the problems that a roller needs to be replaced and the process is too tedious when the particle size of the screened aggregate needs to be changed. According to the technical scheme, the screening device is characterized by comprising a device body with a roller, the roller comprises a plurality of screening frames which are detachably connected with one another, a plurality of screening holes with the same size are formed in the screening frames, the screening holes in every two adjacent screening frames are different in size, and the screening frames are arranged from large to small according to the diameters of the screening holes. According to the aggregate screening device, aggregate can be screened according to the particle size requirement of the aggregate through the screening holes with different sizes in the screening frames, the problem that a roller is replaced when the screening particle size of the aggregate needs to be changed is solved, operation steps are reduced, working efficiency is improved, meanwhile, the particle size precision can be improved when the aggregate is screened, and the screening quality of the aggregate is improved. And the asphalt mixture is stirred more uniformly.

Description

Technical Field

[0001] This utility model relates to the field of asphalt preparation technology, and more specifically, it relates to an aggregate screening device for asphalt mixture preparation. Background Technology

[0002] Asphalt mixture is a material obtained by mixing aggregates, asphalt, fillers, etc. in a certain proportion. It is often used for road base paving. During the preparation of asphalt mixture, a screening machine is usually used to screen the aggregates to make the aggregate particle size more uniform, so that the asphalt and aggregates can be mixed more evenly in the subsequent mixing of asphalt mixture.

[0003] Publication No. CN217392906U discloses an aggregate screening machine. Its technical solution includes a base, a support box at the bottom of the base, supports symmetrically arranged on the inner walls of the base, a roller at the top of the symmetrical supports, a screening trough on the surface of the roller, the screening trough being located at the top of the support box, a feed pipe on one side of the roller, a guide plate on the side of the roller away from the feed pipe, a motor on one side of the base, a rotating shaft at the output end of the motor, a transmission device sleeved on the surface of the rotating shaft, a transmission shaft inserted at one end of the transmission device, gears on both sides of the transmission shaft, a gear ring meshing on one side of the gear, and the inner wall of the gear ring being fixedly connected to the outer wall of the roller.

[0004] The above-mentioned technical solution, when screening aggregates, involves pouring the aggregates into a drum and then driving the drum to rotate. The aggregates are screened using the screening troughs on the drum. The drum replaces the use of ordinary flat screening machines, greatly extending the service life of the screening machine, reducing vibration and noise transmission, and improving work efficiency. However, when using drums to screen aggregates, only aggregates of the corresponding particle size can be screened according to the size of the screening troughs on the drum. If it is necessary to change the particle size of the aggregates after screening, the drum needs to be replaced, which is too cumbersome.

[0005] Therefore, a new solution is needed to address this problem. Utility Model Content

[0006] To address the shortcomings of existing technologies, the purpose of this utility model is to provide an aggregate screening device for asphalt mixture preparation, which solves the problem that when it is necessary to change the particle size of the aggregate after screening, the drum needs to be replaced, which is too cumbersome.

[0007] The above-mentioned technical objective of this utility model is achieved through the following technical solution: an aggregate screening device for asphalt mixture preparation, comprising a device body with a drum, the drum comprising a plurality of screening frames detachably connected to each other, the screening frames having a plurality of screening holes of the same size, the plurality of screening frames being arranged in descending order of the diameter of the screening holes, a through groove being formed on the side of the plurality of screening frames away from their own openings, a rotating plate being fixedly connected to the side of the screening frame with the smallest diameter of the screening holes, the rotating plate being rotatably connected to the device body, a motor being fixedly connected to one side of the rotating plate, the output end of the motor passing through the rotating plate and being fixedly connected to one of the screening frames, the device body being provided with a drive assembly for driving the plurality of screening frames to rotate, and a first control assembly for controlling the opening and closing of the screening holes and a second control assembly for controlling the opening and closing of the through groove being provided inside the screening frames.

[0008] By adopting the above technical solution, when aggregate screening is required, the aggregate is poured into a screening frame with the largest screening aperture. Then, according to the required aggregate particle size, the first control component at the corresponding screening frame is opened, opening the screening aperture. Next, the second control component opens the through-slot, allowing communication between the aggregate in the screening frame with the largest screening aperture and the screening frame itself. Then, the drive component drives the rotating plate to rotate, simultaneously moving several screening frames and tilting them. The aggregate within the screening frames is then subjected to this tilting action. The aggregate is inclined and moves into the screening frame where the screening holes are open, and accumulates in the screening frame. Then the motor is started, driving the output end of the motor to rotate several screening frames, and screening the aggregate through the screening holes. This achieves the effect of screening the aggregate. Through the screening holes of different sizes on several screening frames, the aggregate can be screened according to the required particle size, avoiding the problem of replacing the roller when the aggregate screening particle size needs to be changed. This saves operation steps, improves work efficiency, and also increases the accuracy of the aggregate particle size during screening, making the asphalt mixture more uniform.

[0009] The present invention is further configured such that: the driving component includes a cylinder fixedly connected to the device body, and an arc plate is rotatably connected to the output end of the cylinder. The arc plate is in contact with the side wall of the screening frame located at the largest sieve hole diameter. When the cylinder is in a retracted state, the rotating plate is vertically arranged.

[0010] By adopting the above technical solution, when several screening frames are tilted, the cylinder is activated, driving the output end of the cylinder to extend upwards, and at the same time driving the arc plate to move in the same direction. The arc plate drives the screening frame located at the largest screening hole diameter to move upwards. At this time, the other screening frames are affected and also move, and drive the rotating plate to rotate, thereby achieving the effect of driving several screening frames to tilt.

[0011] The present invention is further configured such that: the first control component includes a rotating ring rotatably connected within the screening frame, the rotating ring having a plurality of through holes of the same size as the screening holes, a connecting plate fixedly connected to the side wall of the rotating ring, and a sliding groove for the connecting plate to slide on the side wall of the screening frame, a first limiting plate and a second limiting plate fixedly connected to the two sides of the sliding groove, the first limiting plate and the second limiting plate respectively having limiting elements for limiting the movement of the connecting plate, when one side wall of the connecting plate and the limiting plate contacts each other, the through holes and the side wall of the screening holes are interconnected, and when the connecting plate and the second limiting plate contact each other, the through holes and the screening holes are staggered.

[0012] By adopting the above technical solution, when several screening holes on the screening frame are in the open state, the connecting plate is moved to move towards the first limiting plate. At the same time, the connecting plate drives the rotating ring to slide and rotate. When the connecting plate and the first limiting plate come into contact with each other, the connecting plate and the first limiting plate are fixed together by the limiting member. At this time, the through hole on the rotating ring and the screening hole are interconnected, so that the screening hole is in the open state. When it is necessary to close the screening hole, the connecting plate is moved towards the second limiting plate, and the connecting plate and the second limiting plate come into contact with each other. At the same time, the connecting plate and the second limiting plate are fixed together by the limiting member. At this time, the through hole on the rotating ring and the screening hole are staggered, so that the screening hole is in the closed state, thereby achieving the effect of controlling the opening and closing of the screening hole.

[0013] The present invention is further configured such that: the limiting member includes two elastic plates respectively fixedly connected to the side walls of limiting plate one and limiting plate two, there is a gap between the two elastic plates, and a locking block is fixedly connected to the side wall of the elastic plate; when the connecting plate moves into the gap, the locking block and the connecting plate engage with each other.

[0014] By adopting the above technical solution, when the connecting plate moves in the direction of limiting plate one or limiting plate two, the connecting plate will come into contact with the two elastic plates. Then, a pushing force is applied to the connecting plate, causing the connecting plate to enter the gap formed by the two elastic plates. At this time, the connecting plate is affected by the locking block and locks with the locking block, thereby achieving the effect of fixing the connecting plate and limiting plate one or limiting plate two.

[0015] The present invention is further configured such that: the second control component includes a screening plate fixedly connected to one end of the rotating ring, and a second through groove is provided on the screening plate. When one side wall of the connecting plate and the limiting plate are in contact with each other, the side walls of the first through groove and the second through groove are staggered. When the connecting plate and the limiting plate are in contact with each other, the first through groove and the second through groove are interconnected.

[0016] By adopting the above technical solution, when the rotating ring of the connecting plate rotates, the rotating ring drives the screening plate to rotate. When one side wall of the connecting plate and the limiting plate comes into contact with each other, the side walls of through groove one and through groove two are staggered, and through groove one is in a closed state. When the connecting plate and the limiting plate two come into contact with each other, through groove one and through groove two are interconnected, and through groove one is in an open state. This achieves the effect of controlling the opening and closing of through groove one.

[0017] The present invention is further configured such that: a plurality of mounting plates are fixedly connected to the outer walls of two adjacent screening frames, and threaded holes are provided on the plurality of mounting plates, bolts are threadedly connected to the threaded holes, and nuts are threadedly connected to the bolts.

[0018] By adopting the above technical solution, it is easy to replace or maintain the screening frame individually, and it is also easy to clean the aggregate remaining in the screening frame, thereby improving the service life of the screening frame.

[0019] The present invention is further configured such that a limiting groove for sliding of the arc plate is provided on the outer wall of the screening frame with the largest screening hole diameter.

[0020] By adopting the above technical solution, it is possible to prevent the arc plate from separating from the outer wall of the screening frame located at the maximum screening hole diameter when it moves, thus avoiding affecting normal use.

[0021] In summary, this utility model has the following beneficial effects: when aggregate screening is required, the aggregate can be screened according to the required particle size through the screening holes of different sizes on several screening frames, avoiding the problem of replacing the roller when the aggregate screening particle size needs to be changed, reducing operation steps, improving work efficiency, and also increasing the accuracy of the aggregate particle size during screening, making the asphalt mixture more uniformly mixed. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the external structure of this utility model;

[0023] Figure 2 A cross-sectional view of this utility model Figure 1 ;

[0024] Figure 3 This is a schematic diagram of the structure of the screening frame, connecting plate, limiting plate one, and limiting plate two in this utility model;

[0025] Figure 4 A cross-sectional view of this utility model Figure 2 ;

[0026] Figure 5 This is a schematic diagram of the structure of the screening frame, connecting plate, limiting plate one, limiting plate two, rotating ring, and screening plate in this utility model;

[0027] Figure 6 A cross-sectional view of this utility model Figure 3 .

[0028] In the diagram: 1. Device body; 2. Screening frame; 3. Screening hole; 4. Through groove one; 5. Rotating plate; 6. Motor; 7. Cylinder; 8. Arc plate; 9. Rotating ring; 10. Through hole; 11. Connecting plate; 12. Slide groove; 13. Limiting plate one; 14. Limiting plate two; 15. Elastic plate; 16. Locking block; 17. Screening plate; 18. Through groove two; 19. Mounting plate; 20. Threaded hole; 21. Bolt; 22. Nut; 23. Limiting groove. Detailed Implementation

[0029] To enable those skilled in the art to better understand the technical solution of this utility model, the present utility model will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of this application can be combined with each other.

[0030] In the description of this utility model, it should be noted that the terms "upper", "lower", "inner", "outer", "top / bottom", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0031] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed," "equipped with," "sleeved / connected," "connected," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0032] An aggregate screening device for asphalt mixture preparation, such as Figures 1-6As shown, the device includes a main body 1 with a roller. The roller includes several screening frames 2 that are detachably connected to each other. Several screening holes 3 of the same size are opened on the screening frames 2. The screening frames 2 are arranged in descending order of the diameter of the screening holes 3. A through groove 4 is opened on the side of the screening frames 2 away from their own openings. A rotating plate 5 is fixedly connected to the side of the screening frame 2 with the smallest diameter screening hole 3. The rotating plate 5 is rotatably connected to the main body 1. A motor 6 is fixedly connected to the side of the rotating plate 5. The output end of the motor 6 passes through the rotating plate 5 and is fixedly connected to one of the screening frames 2. The main body 1 is provided with a drive assembly for driving the screening frames 2 to rotate. The screening frames 2 are provided with a first control assembly for controlling the opening and closing of the screening holes 3 and a second control assembly for controlling the opening and closing of the through groove 4.

[0033] When aggregate screening is required, the aggregate is poured into the screening frame 2 with the largest screening hole 3. Then, according to the required aggregate particle size, the first control component at the corresponding screening frame 2 is opened, so that the screening hole 3 on the screening frame 2 is open. Then, the second control component opens the through groove 4, so that the aggregate in the screening frame 2 with the largest screening hole 3 and the screening frame 2 are interconnected. Then, the drive component drives the rotating plate 5 to rotate, and at the same time, the rotating plate 5 drives several screening frames 2 to move, so that several screening frames 2 tilt. At the same time, the aggregate in the screening frame 2 is limited by the tilt. The aggregate is moved into the screening frame 2 with the screening holes 3 in the open state and accumulates in the screening frame 2. Then, the motor 6 is started, driving the output end of the motor 6 to drive several screening frames 2 to rotate, and screen the aggregate through the screening holes 3. This achieves the effect of screening the aggregate. Through the screening holes 3 of different sizes on several screening frames 2, the aggregate can be screened according to the required particle size, avoiding the problem of replacing the roller when the aggregate screening particle size needs to be changed. This saves operation steps, improves work efficiency, and can also increase the accuracy of the aggregate particle size during screening, making the asphalt mixture more uniform.

[0034] like Figure 2As shown, the driving assembly includes a cylinder 7 fixedly connected to the device body 1. An arc-shaped plate 8 is rotatably connected to the output end of the cylinder 7. The arc-shaped plate 8 and the side wall of the screening frame 2 with the largest diameter of the screening hole 3 are in contact with each other. When the cylinder 7 is in the retracted state, the rotating plate 5 is vertically set. When several screening frames 2 are tilted, the cylinder 7 is activated, driving the output end of the cylinder 7 to extend upward. At the same time, the arc-shaped plate 8 is driven to move in the same direction. The arc-shaped plate 8 drives the screening frame 2 with the largest diameter of the screening hole 3 to move upward. At this time, the other screening frames 2 are affected and also move, driving the rotating plate 5 to rotate. This achieves the effect of driving several screening frames 2 to tilt. A limiting groove 23 for the arc-shaped plate 8 to slide is provided on the outer wall of the screening frame 2 with the largest diameter of the screening hole 3. This can prevent the arc-shaped plate 8 from separating from the outer wall of the screening frame 2 with the largest diameter of the screening hole 3 when it moves, thus avoiding affecting normal use.

[0035] like Figures 2-6 As shown, the first control component includes a rotating ring 9 rotatably connected within the screening frame 2. The rotating ring 9 has several through holes 10 of the same size as the screening holes 3. A connecting plate 11 is fixedly connected to the side wall of the rotating ring 9. A sliding groove 12 is provided on the side wall of the screening frame 2 for the connecting plate 11 to slide. A first limiting plate 13 and a second limiting plate 14 are fixedly connected to both sides of the sliding groove 12, respectively. The first limiting plate 13 and the second limiting plate 14 are respectively provided with limiting elements for restricting the movement of the connecting plate 11. When the connecting plate 11... When the connecting plate 11 and the second limiting plate 14 are in contact with each other, the through hole 10 and the sieve hole 3 are interconnected. When the connecting plate 11 and the second limiting plate 14 are in contact with each other, the through hole 10 and the sieve hole 3 are staggered. The limiting component includes two elastic plates 15 that are fixedly connected to the side walls of the first limiting plate 13 and the second limiting plate 14 respectively. There is a gap between the two elastic plates 15. A locking block 16 is fixedly connected to the side wall of the elastic plate 15. When the connecting plate 11 moves into the gap, the locking block 16 and the connecting plate 11 are locked together.

[0036] When the screening holes 3 on the screening frame 2 are in the open state, the connecting plate 11 is moved to move towards the limiting plate 13. At the same time, the connecting plate 11 drives the rotating ring 9 to slide and rotate. When the connecting plate 11 and the limiting plate 13 come into contact with each other, the connecting plate 11 enters the gap formed by the two elastic plates 15. At this time, the connecting plate 11 is affected by the locking block 16 and locks with the locking block 16. At this time, the through hole 10 on the rotating ring 9 and the screening hole 3 are interconnected, so that the screening hole 3 is in the open state. When it is necessary to close the screening hole 3, the connecting plate 11 is moved towards the limiting plate 14, and the connecting plate 11 and the limiting plate 14 come into contact with each other. At the same time, the connecting plate 11 locks with the locking block 16. At this time, the through hole 10 on the rotating ring 9 and the screening hole 3 are staggered, so that the screening hole 3 is in the closed state. This achieves the effect of controlling the opening and closing of the screening hole 3.

[0037] like Figures 3-6 As shown, the second control component includes a screening plate 17 fixedly connected to one end of the rotating ring 9. The screening plate 17 has a through groove 18. When the side walls of the connecting plate 11 and the first limiting plate 13 are in contact with each other, the side walls of the first through groove 4 and the second through groove 18 are staggered. When the connecting plate 11 and the second limiting plate 14 are in contact with each other, the first through groove 4 and the second through groove 18 are connected to each other. When the connecting plate 11 rotates with the rotating ring 9, the rotating ring 9 drives the screening plate 17 to rotate. When the side walls of the connecting plate 11 and the first limiting plate 13 are in contact with each other, the side walls of the first through groove 4 and the second through groove 18 are staggered. At this time, the first through groove 4 is in a closed state. When the connecting plate 11 and the second limiting plate 14 are in contact with each other, the first through groove 4 and the second through groove 18 are connected to each other. At this time, the first through groove 4 is in an open state, thereby achieving the effect of controlling the opening and closing of the first through groove 4.

[0038] like Figures 1-2 As shown, several mounting plates 19 are fixedly connected to the outer walls of two adjacent screening frames 2. Threaded holes 20 are opened on the mounting plates 19, and bolts 21 are threaded into the threaded holes 20. Nuts 22 are threaded onto the bolts 21. This facilitates the individual replacement or maintenance of the screening frames 2, and also facilitates the cleaning of the aggregate remaining in the screening frames 2, thereby improving the service life of the screening frames 2.

[0039] The working principle of this utility model is as follows: When aggregate needs to be screened, the aggregate is poured into the screening frame 2 with the largest screening hole 3. Then, according to the required aggregate particle size, the connecting plate 11 at the corresponding screening frame 2 is moved, causing the connecting plate 11 to move towards the limiting plate 13. At the same time, the connecting plate 11 drives the rotating ring 9 to slide and rotate. When the connecting plate 11 and the limiting plate 13 come into contact with each other, the connecting plate 11 and the limiting plate 13 are fixed to each other by the limiting member. At this time, the through hole 10 on the rotating ring 9 and the screening hole 3 are interconnected, so that the screening hole 3 is in the open state. Then, the side walls of the connecting plate 11 and the limiting plate 14 on the other screening frames 2 come into contact with each other, so that the side walls of the through groove 1 4 and the through groove 2 18 are interconnected. At this time, the through groove 1 4 is in the open state, so that the aggregate in the screening frame 2 with the largest screening hole 3 and the screening frame 2 at this time are interconnected.

[0040] After adjusting the required aperture on the screening frame 2, start the cylinder 7, causing its output end to extend upwards. Simultaneously, this moves the arc plate 8 in the same direction. The arc plate 8 then moves the screening frame 2 located at the largest screening aperture 3 upwards. At this time, the other screening frames 2 are also affected and move, causing the rotating plate 5 to rotate. This tilts several screening frames 2, restricting the aggregate within them and forcing it to move towards the screening frame 2 where the screening aperture 3 is open. The aggregate is piled up inside the screen 2, and then the motor 6 is started. The output end of the motor 6 drives several screening frames 2 to rotate and screen the aggregate through the screening holes 3. This achieves the effect of screening the aggregate. Through the screening holes 3 of different sizes on several screening frames 2, the aggregate can be screened according to the required particle size. This avoids the problem of replacing the roller when the aggregate screening particle size needs to be changed, saves operation steps, improves work efficiency, and can also increase the accuracy of the aggregate particle size during screening, making the asphalt mixture more uniform.

[0041] The above description is merely a preferred embodiment of this utility model. The protection scope of this utility model is not limited to the above embodiments. All technical solutions falling within the scope of this utility model's concept are protected. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principle of this utility model should also be considered within the protection scope of this utility model.

Claims

1. An aggregate screening device for asphalt mixture preparation, comprising a device body (1) with rollers, characterized in that: The roller includes several screening frames (2) that are detachably connected to each other. Several screening holes (3) of the same size are opened on the screening frames (2). The screening frames (2) are arranged in descending order of the diameter of the screening holes (3). A through groove (4) is opened on the side of the screening frames (2) away from their own openings. A rotating plate (5) is fixedly connected to one side of the screening frame (2) with the smallest diameter of the screening holes (3). The rotating plate (5) is rotatably connected to the device body (1). A motor (6) is fixedly connected to one side of the rotating plate (5). The output end of the motor (6) passes through the rotating plate (5) and is fixedly connected to one of the screening frames (2). The device body (1) is provided with a drive assembly for driving the several screening frames (2) to rotate. The screening frames (2) are provided with a first control assembly for controlling the opening and closing of the screening holes (3) and a second control assembly for controlling the opening and closing of the through groove (4).

2. The aggregate screening device for asphalt mixture preparation according to claim 1, characterized in that: The drive assembly includes a cylinder (7) fixedly connected to the device body (1). The output end of the cylinder (7) is rotatably connected to an arc plate (8). The arc plate (8) and the side wall of the screening frame (2) with the largest aperture of the screening hole (3) are in contact with each other. When the cylinder (7) is in a retracted state, the rotating plate (5) is vertically arranged.

3. The aggregate screening device for asphalt mixture preparation according to claim 1, characterized in that: The first control component includes a rotating ring (9) rotatably connected to the screening frame (2). The rotating ring (9) has several through holes (10) of the same size as the screening holes (3). A connecting plate (11) is fixedly connected to the side wall of the rotating ring (9). A sliding groove (12) for the connecting plate (11) to slide is provided on the side wall of the screening frame (2). A first limiting plate (13) and a second limiting plate (14) are fixedly connected to both sides of the sliding groove (12). The first limiting plate (13) and the second limiting plate (14) are respectively provided with limiting members for limiting the movement of the connecting plate (11). When the side walls of the connecting plate (11) and the first limiting plate (13) are in contact with each other, the through holes (10) and the side walls of the screening holes (3) are interconnected. When the connecting plate (11) and the second limiting plate (14) are in contact with each other, the through holes (10) and the screening holes (3) are staggered.

4. The aggregate screening device for asphalt mixture preparation according to claim 3, characterized in that: The limiting component includes two elastic plates (15) that are fixedly connected to the side walls of limiting plate one (13) and limiting plate two (14) respectively. There is a gap between the two elastic plates (15). A locking block (16) is fixedly connected to the side wall of the elastic plate (15). When the connecting plate (11) moves into the gap, the locking block (16) and the connecting plate (11) engage with each other.

5. The aggregate screening device for asphalt mixture preparation according to claim 3, characterized in that: The second control component includes a screening plate (17) fixedly connected to one end of the rotating ring (9). The screening plate (17) has a through groove (18). When the side walls of the connecting plate (11) and the limiting plate (13) are in contact with each other, the side walls of the through groove (4) and the through groove (18) are staggered. When the connecting plate (11) and the limiting plate (14) are in contact with each other, the through groove (4) and the through groove (18) are connected to each other.

6. The aggregate screening device for asphalt mixture preparation according to claim 1, characterized in that: Several mounting plates (19) are fixedly connected to the outer walls of two adjacent screening frames (2). Threaded holes (20) are opened on the mounting plates (19). Bolts (21) are threaded in the threaded holes (20). Nuts (22) are threaded on the bolts (21).

7. The aggregate screening device for asphalt mixture preparation according to claim 2, characterized in that: A limiting groove (23) for sliding of the arc plate (8) is provided on the outer wall of the screening frame (2) with the largest aperture of the screening hole (3).

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