A steel ball screening device

Abstract

The invention relates to a device for producing steel balls, in particular to a steel ball screening device, comprising a screener, a pushing device and a conveying device. The pushing device is used to push the steel balls to move in a screening slot, so as to prevent the steel balls from directly rushing through the screening slot by inertia, thereby ensuring the accuracy of the steel ball screening size. The efficiency of steel ball screening is changed by replacing the number of baffles and the number of crawlers arranged on the driving wheel and the auxiliary driving wheel on the pushing device, so that a plurality of steel balls of different sizes can be screened at the same time. The width of a limiting bottom plate in the screening slot decreases in sequence, so that steel balls of smaller sizes are screened first and steel balls of larger sizes are screened last. Steel balls of different sizes are obtained as required, so as to meet a variety of steel ball screening requirements. The size of the screened steel balls is changed by changing the width of the limiting bottom plate, that is, the limiting bottom plate is detachably designed, and limiting bottom plates of different widths can be replaced, so as to meet the purpose of screening steel balls of different sizes.

Description

Technical Field

[0001] The invention relates to the field of steel ball screening, in particular to a steel ball screening device. Background Art

[0002] The traditional method of screening steel balls in a steel ball coal mill is to open the mill inlet door after the coal mill is shut down, unload the steel balls, and then use a forklift or a small loader to transport them to the screening site for manual screening. This screening process causes high labor intensity for construction workers, a poor working environment, occupies a large amount of manpower and mechanical resources, and has low labor efficiency. It is also easy to cause dust pollution in the construction area, which endangers the health of workers. There are also steel ball screening machines in the prior art, but the cost of this equipment is relatively expensive, and the size of the steel balls that can be screened is relatively single, which cannot meet a variety of actual needs. As a result, when the factory has more sizes to be screened, it is necessary to repeat the screening multiple times or purchase equipment of different specifications, which is costly and not conducive to industrial application. In order to solve the above series of problems caused by manual screening of steel balls, it is very necessary to design an automatic steel ball screening machine to replace the traditional method of manual screening of steel balls and improve the existing mechanical screening method.

[0003] After searching, it was found that in the document with the announcement number CN117900133B, a screening device for grinding steel ball production includes a base, a motor is welded on the outer wall of one side of the base, a rotating wheel is welded on the main shaft of the motor, the rotating wheel rotates and is inserted in the base, and a plurality of scrapers with equidistant circumferential distribution are welded on the inner wall of the rotating wheel, and an inclined material distribution trough 1, a material discharging chute and a material distribution trough 2 are welded in sequence from top to bottom on the inner wall of the side of the base away from the motor, and a hinged slide is provided on the inner wall of the side of the material distribution trough away from the material discharging chute. In the present invention, the anti-stuck mechanism is set, so that the ratchet can drive the roller to rotate, so that the two rollers rotate in the opposite direction, and the steel ball stuck between the two rollers can be turned out, thereby avoiding the situation that the steel ball is stuck between the two rollers, and the second screening mechanism is set, so that the two screening rods are distributed in an eight-shaped pattern, avoiding the situation that the steel ball is stuck between the two screening rods. However, this device cannot screen steel balls of various sizes, and the size of the steel balls that can be screened at the same time is relatively single, which cannot meet the current industrial needs. Summary of the invention

[0004] The object of the present invention is to provide a steel ball screening device to solve the problems raised in the above background technology.

[0005] In order to achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a steel ball screening device, including a screener, a pushing device, and a conveying device. The screener includes a baffle, a screening slot, a limiting bottom plate, a material port bottom plate, and a baffle slot. The pushing device includes a crawler and a pushing plate, wherein several baffles are placed in parallel, and a screening slot is formed between two adjacent baffles. Several baffle slots corresponding to the baffles are arranged on the material port bottom plate, and the front and rear ends of the baffles are respectively connected with the baffle slots by clamping. The steel ball feeding place is the feeding port bottom plate, and the other end is the material outlet bottom plate. Slots are arranged on both sides of the lower end of the baffle, and blocks corresponding to the slots are arranged on the limiting bottom plate. The limiting bottom plate cooperates with the slots on the baffle through the blocks thereon, and the limiting bottom plate is detachably connected to the baffle. Two limiting bottom plates are arranged between two adjacent baffles, and a gap is left between the two limiting bottom plates. The pushing device is arranged above the screener, and several pairs of driving wheels and auxiliary wheels are arranged on the pushing device. The movable wheel comprises a plurality of driving wheels, a plurality of pairs of driving wheels and an auxiliary driving wheel, and the plurality of driving wheels are fixedly connected to each other by a transmission shaft, and the plurality of auxiliary driving wheels are fixedly connected to each other by a transmission shaft, and each pair of driving wheels and the auxiliary driving wheel are respectively connected to a track, and the distance between the plurality of tracks is the same as the thickness of the baffle plate, and a plurality of push plates are arranged on the track at intervals, and the width of the push plates is less than the width of the screening slot, and the height of the push plates is less than the height of the track from the limiting bottom plate. The number of tracks is the same as the number of screening slots, and each track is located directly above its corresponding screening slot, and the push plate on the lower track is located inside the screening slot and above the limiting bottom plate. The screener and the pushing device are fixed by a supporting frame, and the conveying device is located below the screener, and the conveying direction of the conveying device below the screener in the vertical direction is perpendicular to the screening direction of the screener, and the conveying direction of the conveying device located below the material port bottom plate is the same as the screening direction of the screener.

[0006] Furthermore, the screen is placed at an inclined angle, the feed position of the steel balls entering the screen is lower than the position of the other end of the screen, and the pushing device has the same inclination angle as the screen.

[0007] Furthermore, the length of the limiting bottom plate is shorter than that of the baffle, and the width of the limiting bottom plate is different. The limiting bottom plate is arranged on the baffle in a stepped manner according to the width, and the width of the limiting bottom plate arranged at the front end of the baffle is wider than that of the limiting bottom plate arranged at the rear end of the baffle.

[0008] Furthermore, a steel ball screening device also includes a partition plate, the height of the partition plate is the same as that of the limiting bottom plate, and the width is the same as the interval width between two adjacent baffles. Card blocks are arranged on both sides of the partition plate, which can cooperate with the card slots on the corresponding two adjacent baffles. The partition plate is detachably connected to the two adjacent baffles, and the partition plate is arranged between the limiting bottom plates of different widths in the same screening slot.

[0009] Furthermore, the conveying device also includes flexible materials and protective plates. Flexible materials are arranged on the surface of the conveying belt of the conveying device. A protective plate is respectively arranged on the two sides of the conveying device. The top surface height of the protective plate is higher than the highest position of the conveying belt. The conveying device is located below the screener in the vertical direction, and at least one side in the vertical direction is located below the partition plate, and its width is wider than the length of the limiting bottom plate above it. The conveying device is located below the bottom plate of the discharge port, and its width is wider than the width of the screener.

[0010] Furthermore, a steel ball screening device also includes a feed hopper, which is fixed by a support frame, wherein the feed hopper includes a hopper, the upper end of the hopper is open, and the lower end is fixedly connected to a plurality of conveying pipes, the upper ends of the conveying pipes are respectively provided with detachable upper covers, and the lower ends of the conveying pipes are provided with a lower opening on the side, the feed hopper is arranged above the screener, and the lower opening is correspondingly arranged above the horizontal position of the screening slot.

[0011] Compared with the prior art, the present invention has the following advantages:

[0012] (1) The present invention can directly pour the steel balls to be screened and transported into the hopper through the hopper on the feed hopper to start screening and transportation, without the need for preliminary preparation work, which greatly reduces labor costs and reduces the learning cost of using the equipment, so that workers can use the equipment with zero learning cost. In addition, the conveying pipe on the feed hopper is also provided with a detachable upper cover. When used in different usage scenarios, for example, when the number of steel balls to be screened is small and there is no need to use multiple screening slots, only the required number of conveying pipes need to be opened to limit the input number of steel balls, thereby matching the number of screening slots set.

[0013] (2) The present invention places the screener and the pushing device at an angle, and uses the pushing device to push the steel ball to move in the screening slot, thereby preventing the steel ball from directly rushing through the screening slot by inertia, thereby causing errors in the size of the screened steel ball, thereby ensuring the accuracy of the steel ball screening size.

[0014] (3) The screener of the present invention can change the efficiency of steel ball screening by replacing the number of baffles and the number of tracks provided on the driving wheel and the auxiliary driving wheel on the pushing device, thereby meeting different work needs, minimizing energy consumption, and complying with the concept of green environmental protection.

[0015] (4) The present invention can screen multiple steel balls of different sizes at the same time. The width of the limiting bottom plate in the screening groove decreases successively, so that the smaller steel balls are screened first and the larger steel balls are screened last. Steel balls of different sizes can be obtained as needed, thereby meeting various steel ball screening requirements.

[0016] (5) The present invention can change the purpose of screening the size of steel balls by changing the width of the limiting bottom plate, that is, the limiting bottom plate is detachable and can be replaced with limiting bottom plates of different widths to meet the purpose of screening steel balls of different sizes.

[0017] (6) The partition plate of the present invention can ensure that the steel ball on it will not fall. The partition plate is set at the vertical position between the intervals of the conveying devices to ensure that the steel ball falls directly on the flexible material of the conveying device when it falls. Even if it bounces, it will be blocked by the protective plate to prevent the steel ball from rolling down. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic diagram of a steel ball screening device.

[0019] Figure 2 A schematic diagram of the decomposition of a steel ball screening equipment.

[0020] Figure 3 Partial schematic diagram of the propulsion device.

[0021] Figure 4 Schematic diagram of the filter.

[0022] Figure 5 Schematic diagram of the feed port bottom plate.

[0023] Figure 6 Schematic diagram of baffle, limiting bottom plate and partition board.

[0024] Figure 7 Partial schematic diagram of the feed hopper.

[0025] Among them, 1. feed hopper, 11. hopper, 12. conveying pipe, 121. upper cover, 122. lower opening, 2. screener, 21. baffle, 211. card slot, 22. screening slot, 23. limit bottom plate, 231. card block, 24. material port bottom plate, 241. baffle slot, 242. feed port bottom plate, 243. discharge port bottom plate, 25. partition plate, 3. pushing device, 31. crawler, 32. push plate, 33. driving wheel, 34. auxiliary wheel, 4. conveying device, 41. flexible material, 42. protective plate,

[0026] 5. Support frame. DETAILED DESCRIPTION

[0027] The present invention aims to provide a steel ball screening device to address the deficiencies of the prior art, which is specifically implemented by the following technical solutions:

[0028] Reference Figure 1 , Figure 2 , Figure 3This embodiment provides a steel ball screening device, including a screener 2, a pushing device 3, and a conveying device 4. The screener 2 includes a baffle 21, a screening slot 22, a limiting bottom plate 23, a material port bottom plate 24, and a baffle slot 241. The pushing device 3 includes a crawler 31 and a push plate 32.

[0029] Reference Figure 4 , Figure 5 , Figure 6 , wherein several baffles 21 are placed in parallel, and a screening slot 22 is formed between two adjacent baffles 21. A plurality of baffle slots 241 corresponding to the baffles 21 are provided on the material port bottom plate 24. The front and rear ends of the baffle 21 are respectively connected with the baffle slots 241 by snapping. The steel ball feeding place is the feeding port bottom plate 242, and the other end is the discharging port bottom plate 243. The two ends of the baffle 21 are placed in the baffle slots 241. The number of baffles 21 is placed according to the required number, thereby forming the basic shape of the screening slot.

[0030] Reference Figure 5 , Figure 6 , slots 211 are provided on both sides of the lower end of the baffle 21, and blocks 231 corresponding to the slots 211 are provided on the limiting bottom plate 23. The limiting bottom plate 23 cooperates with the slots 211 on the baffle 21 through the blocks 231 thereon, and the limiting bottom plate 23 and the baffle 21 are detachably connected, and two limiting bottom plates 23 are provided between two adjacent baffles 21, and a gap is left between the two limiting bottom plates 23. The limiting bottom plate 23 is clamped on the baffle 21, and different lengths can be selected according to different needs, or the limiting bottom plates 23 can be set at different positions. The specific installation method is: first, one end of the baffle 21 is placed on a material port bottom plate 24, and then the required limiting bottom plate 23 is inserted thereon, and a certain distance is reserved at the end so that the baffle 21 can place the other end on another material port bottom plate 24.

[0031] Reference Figure 1 , Figure 2 , Figure 3 The pushing device 3 is arranged above the screen 2, and is provided with a plurality of pairs of driving wheels 33 and auxiliary wheels 34. The pairs of driving wheels 33 and auxiliary wheels 34 are arranged at intervals and in parallel, and the driving wheels 33 are fixedly connected by a transmission shaft, and the auxiliary wheels 34 are fixedly connected by a transmission shaft. Each pair of driving wheels 33 and auxiliary wheels 34 is respectively connected with a crawler belt 31. The number of driving wheels 33, auxiliary wheels 34 and crawler belt 31 can be set according to different actual needs to ensure that the pushing device 3 will not have an idling part, so as to achieve the purpose of energy saving.

[0032] Reference Figure 1 , Figure 2 , Figure 3The distance between the plurality of crawlers 31 is the same as the thickness of the baffle 21, so that the crawlers 31 can avoid the baffle 21, and the pushing device 3 can move freely on the screen 2. A plurality of push plates 32 are arranged on the crawler 31 at intervals. The width of the push plates 32 is smaller than the width of the screening slot 22, and the height of the push plates 32 is smaller than the height of the crawler 31 from the limiting bottom plate 23, so as to prevent the steel ball from being stuck in the screening slot 22 due to various reasons when the push plates 32 push the steel ball, and thus causing the steel ball to be unable to move. The number of crawlers 31 is the same as the number of screening slots 22, and each Each track 31 is located directly above its corresponding screening slot 22. The push plate 32 on the lower track 31 is located inside the screening slot 22 and above the limiting bottom plate 23. The driving wheel 33 drives the track 31 to rotate, and the auxiliary wheel 34 plays a role in positioning and auxiliary rotation. The rotation of the track 31 drives the push plate 32 thereon to move along the movement path of the track 31. Because the pushing device 3 is arranged above the screen 2 and is parallel to it, the push plate 32 can move along its path in the screening slot 22, thereby pushing the steel ball therein to move.

[0033] If the steel ball is stuck on the screening groove 22 or the limiting bottom plate 23 due to various unexpected reasons, it must be stuck at the widest part of the steel ball or at a position very close to the widest part. Therefore, when the steel ball is stuck, the distance that it can be higher than the screening groove 22 or the limiting bottom plate 23 is half of the height of the steel ball. Therefore, as long as the height of the push plate 32 is less than the height of the track 31 from the limiting bottom plate 23, and less than half of the height from the track 31 to the limiting bottom plate 23, it can be ensured that even if the steel ball is stuck at its highest position, the push plate 32 can push the steel ball behind onto the stuck steel ball to prevent equipment operation failure caused by the steel ball getting stuck. Moreover, the limiting bottom plate 23 has a certain length. As long as not all of a section of the limiting plate is stuck by the steel ball, the equipment can operate normally.

[0034] Reference Figure 1 The screener 2 and the pusher 3 are fixed by a support frame 5, and the support frame 5 can be adjusted in height, width and other dimensions as needed.

[0035] Reference Figure 1 , Figure 2 The conveying device 4 is located below the screener 2. The conveying direction of the conveying device 4 below the screener 2 in the vertical direction is perpendicular to the screening direction of the screener 2. The conveying direction of the conveying device 4 below the material port bottom plate 24 is the same as the screening direction of the screener 2, so that the steel balls screened out on the screener 2 can be transported to the corresponding position by the conveying device 4 below it. If there are steel balls falling from the discharge port bottom plate 243, they will fall into the conveying device 4 below the material port bottom plate 24, so that the steel balls will not fall disorderly.

[0036] Reference Figure 2The screener 2 is placed at an inclined angle, and the feed position of the steel ball entering the screener 2 is lower than the position of the other end of the screener 2. The pushing device 3 has the same inclination angle as the screener 2. The screener 2 is placed at an inclination, so that the steel ball cannot rush through the screener 2 by inertia, thereby ensuring the accuracy of screening. The pushing device 3 has the same inclination angle as the screener 2, and the steel ball that cannot move by gravity is pushed by the pushing device 3 to push the steel ball through the screener 2, thereby ensuring the accuracy of screening.

[0037] Reference Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 The length of the limiting bottom plate 23 is shorter than that of the baffle 21, and the width of the limiting bottom plate 23 is different. The limiting bottom plate 23 is arranged on the baffle 21 in a stepped manner according to the width. The width of the limiting bottom plate 23 arranged at the front end of the baffle 21 is wider than the limiting bottom plate 23 arranged at the rear end of the baffle 21. The limiting bottom plate 23 is arranged in a stepped manner, that is, the limiting bottom plate 23 at the front end is wider and the rear end is narrower. The limiting bottom plate 23 may not be arranged at the position closest to the discharge port bottom plate 243. In this way, the path that the steel ball passes through can be ensured, and the sizes of the steel balls that can pass through are from small to large. The smaller steel balls will fall at the position of the limiting bottom plate 23 at the front, and the larger steel balls will fall at the limiting bottom plate 23 at the rear position. Finally, the steel ball that can pass through the discharge port bottom plate 243 is the largest steel ball.

[0038] The stepped and detachable limiting bottom plate 23 enables the device to screen steel balls of various sizes, can be set according to actual needs, adapt to various actual situations, and has strong market adaptability.

[0039] Reference Figure 5 A steel ball screening device also includes a partition plate 25, the partition plate 25 has the same height as the limiting bottom plate 23, and its width is the same as the interval width between two adjacent baffles 21. Blocks 231 are arranged on both sides of the partition plate 25, which can cooperate with the slots 211 on the two adjacent baffles 21 corresponding to them. The partition plate 25 is detachably connected to the two adjacent baffles 21. The partition plate 25 makes a section of the position between each limiting bottom plate 23 where the steel ball cannot fall, so that when the conveyor device 4 below catches the fallen steel ball, because there is a part of the area between the conveyor device 4 where the conveyor belt cannot be set, when the steel ball falls in this vertical direction, the conveyor device 4 cannot catch the steel ball. After the partition plate 25 is set, the partition plate 25 can fill this distance, and the steel ball cannot fall from the partition plate 25, ensuring that the conveyor device 4 can catch all the steel balls falling from the screener 2.

[0040] Reference Figure 2The conveying device 4 also includes a flexible material 41 and a protective plate 42. The flexible material 41 is arranged on the conveyor belt surface of the conveying device 4. A protective plate 42 is arranged on the two sides of the conveying device 4 respectively. The top surface height of the protective plate 42 is higher than the highest position of the conveyor belt. The conveying device 4 is located below the screener 2 in the vertical direction. At least one side in the vertical direction is located below the partition plate 25, and its width is wider than the length of the limiting bottom plate 23 above it. The conveying device 4 located below the discharge port bottom plate 243 is wider than the width of the screener 2, which ensures that the conveying device 4 can catch all the steel balls dropped from the screener 2, and the steel balls will not collapse disorderly in the conveying device 4.

[0041] Reference Figure 1 , Figure 2 , Figure 7 , and also includes a feed hopper 1, wherein the feed hopper 1 is fixed by a support frame 5, the feed hopper 1 includes a hopper 11, the upper end of the hopper 11 is open, and a plurality of conveying pipes 12 are fixedly connected to the lower end, and a detachable upper cover 121 is respectively provided on the upper end of the conveying pipe 12, and a lower opening 122 is provided on the side of the lower end of the conveying pipe 12. The feed hopper 1 is arranged above the screener 2, and the lower opening 122 is correspondingly arranged above the horizontal position of the screening slot 22, so that the worker can directly pour the steel balls into the hopper 11, and the subsequent equipment can automatically complete the work, and the detachable upper cover 121 can make the feed hopper 1 match the size of the screener 2 and the pushing device 3.

Claims

1. A steel ball screening device, comprising a screener (2), a pushing device (3), and a conveying device (4), characterized in that: The screener (2) comprises a baffle (21), a screening slot (22), a limiting bottom plate (23), a material port bottom plate (24), a baffle slot (241), The pushing device (3) comprises a crawler belt (31) and a push plate (32), wherein A plurality of baffles (21) are placed in parallel and symmetrically along the rolling direction of the steel ball, and a screening groove (22) is formed between two adjacent baffles (21). A plurality of baffle grooves (241) corresponding to the baffles (21) are provided on the material inlet bottom plate (24). The front and rear ends of the baffle plate (21) are respectively connected to the baffle plate grooves (241) by snapping. The steel ball feeding place is the feeding port bottom plate (242), and the other end is the discharging port bottom plate (243). Slots (211) are provided on both sides of the lower end of the baffle (21). A clamping block (231) corresponding to the clamping slot (211) is provided on the limiting bottom plate (23). The limiting bottom plate (23) cooperates with the clamping groove (211) on the baffle plate (21) through the clamping block (231) thereon. The limiting bottom plate (23) is detachably connected to the baffle plate (21). A limiting bottom plate (23) is respectively provided on adjacent baffles (21), and a gap is provided between the two limiting bottom plates (23). The pushing device (3) is arranged above the filter (2). The pushing device (3) is provided with a plurality of pairs of driving wheels (33) and auxiliary driving wheels (34). A plurality of pairs of driving wheels (33) and auxiliary driving wheels (34) are arranged in parallel and at intervals. A plurality of driving wheels (33) are fixedly connected via a transmission shaft. A plurality of auxiliary wheels (34) are fixedly connected via a transmission shaft. Each pair of driving wheels (33) and auxiliary wheels (34) is connected to a crawler belt (31). The distance between the plurality of crawlers (31) is the same as the thickness of the baffle (21). A plurality of push plates (32) are arranged at intervals on the crawler (31), the width of the push plates (32) is smaller than the width of the screening slot (22), and the height of the push plates (32) is smaller than the height of the crawler (31) from the limiting bottom plate (23). The number of crawlers (31) is the same as the number of screening slots (22), and each crawler (31) is located directly above its corresponding screening slot (22). The push plate (32) on the lower crawler (31) is located inside the screening slot (22) and above the limiting bottom plate (23). The filter (2) and the push device (3) are fixed by a support frame (5). The conveying device (4) is located below the filter (2). The conveying device (4) is located below the screen (2) in the vertical direction, and its conveying direction is perpendicular to the screening direction of the screen (2). The conveying device (4) located below the material port bottom plate (24) has a conveying direction that is the same as the screening direction of the screener (2). A plurality of limiting bottom plates (23) of different widths are provided in each screening slot (22). The width of the limit bottom plate (23) decreases in the rolling direction of the steel ball. The limiting bottom plates (23) arranged on adjacent baffles (21) are arranged symmetrically.

2. A steel ball screening device according to claim 1, characterized in that: The screen (2) is placed at an inclined angle, and the position of the feeding point where the steel balls enter the screen (2) is lower than the position of the other end of the screen (2). The pushing device (3) and the screen (2) have the same inclination angle.

3. The steel ball screening device according to claim 1, characterized in that: It also includes a partition plate (25), the partition plate (25) has the same height as the limiting bottom plate (23), and the same width as the interval width between two adjacent baffles (21). The partition plate (25) is provided with clamping blocks (231) on both sides thereof, which can be matched with the clamping slots (211) on the two adjacent baffle plates (21) corresponding thereto, and the partition plate (25) and the two adjacent baffle plates (21) are detachably connected. The partition plate (25) is arranged between the limiting bottom plates (23) of different widths in the same screening slot (22).

4. The steel ball screening device according to claim 3, characterized in that: The conveying device (4) further comprises a flexible material (41), a protective plate (42), A flexible material (41) is provided on the surface of the conveyor belt of the conveyor device (4). A protective plate (42) is provided on each of two side surfaces of the conveyor device (4), and the top surface height of the protective plate (42) is higher than the highest position of the conveyor belt. The conveying device (4) is located below the screen (2) in the vertical direction, and at least one side thereof is located below the partition plate (25) in the vertical direction, and its width is wider than the length of the limiting bottom plate (23) above it. The conveying device (4) located below the discharge port bottom plate (243) has a width wider than the width of the screen (2).

5. The steel ball screening device according to claim 1, characterized in that: It also includes a feed hopper (1), wherein The feed hopper (1) is fixed by a support frame (5). The feed hopper (1) comprises a hopper (11), the upper end of the hopper (11) is open, and the lower end is fixedly connected to a plurality of conveying pipes (12). The upper ends of the delivery pipes (12) are respectively provided with detachable upper covers (121). A lower opening (122) is provided on the side of the lower end of the delivery pipe (12). The feed hopper (1) is arranged above the screen (2), and the lower opening (122) is correspondingly arranged above the horizontal position of the screening slot (22).

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