A rapping screen

Abstract

The utility model provides a kind of to strike screen, belong to powder screening equipment, this to strike screen includes screening container, base and be set on the base: clamping device, including moving flat plate, upper buckle cover, lower plate and height adjusting mechanism, moving flat plate can be horizontally moved to set on base, upper buckle cover and lower plate are spaced apart and are installed on moving flat plate by height adjusting mechanism, screening container is arranged between upper buckle cover and lower plate, height adjusting mechanism adjusts the height of lower plate and makes lower plate and upper buckle cover clamp screening container;Drive arrangement, including driving source, horizontal vibration mechanism and vertical to strike mechanism, horizontal vibration mechanism and vertical to strike mechanism are all with driving source transmission connection, driving source drives moving flat plate horizontal swing by horizontal vibration mechanism, driving source drives vertical to strike mechanism vertical to strike the top of screening container.The utility model's to strike screen realizes the compound motion of horizontal swing and vertical to strike, effectively improves screening efficiency and precision.

Description

Technical Field

[0001] This utility model relates to the technical field of powder screening equipment, and in particular to a tapping screen. Background Technology

[0002] In additive manufacturing, chemical, and pharmaceutical powder processing industries, precise control of the particle size of powder materials is required.

[0003] Especially in the additive printing manufacturing industry, traditional vibrating screens have low precision in the post-processing inspection of powders used for 3D printing. For powders with a fineness of less than 180 mesh (approximately 100 micrometers), the accuracy of vibrating sieving is low. Particles smaller than 53 micrometers cannot be accurately measured using a sieve analyzer. Finer particles tend to aggregate or adhere to the sieve surface, leading to inaccurate particle size distribution results. Sieving also increases powder loss and waste, and the overall equipment has poor stability, leading to loosening after prolonged operation. The sieving process is discontinuous and unstable. Furthermore, replacing screens, disassembling, and reinstalling typically rely on bolts and nuts, which is inefficient and increases labor costs.

[0004] Therefore, traditional vibrating screening equipment can no longer meet the needs of industries such as additive manufacturing, chemical industry, and food industry for efficient and accurate screening.

[0005] In view of this, based on years of experience in production and design in this and related fields, the inventor has designed a tapping screen through repeated experiments in order to solve the problems existing in the prior art. Utility Model Content

[0006] The purpose of this invention is to provide a tapping screen that combines vibration and tapping, which greatly shortens the screening time and improves screening efficiency.

[0007] To achieve the above objectives, this utility model proposes a tapping screen, wherein the tapping screen includes a screening container, a base, and components disposed on the base:

[0008] The clamping device includes a movable plate, an upper cover, a lower plate, and a height adjustment mechanism. The movable plate is horizontally movable on the machine base. The upper cover and the lower plate are spaced apart vertically and mounted on the movable plate through the height adjustment mechanism. The screening container is disposed between the upper cover and the lower plate. The height adjustment mechanism adjusts the height of the lower plate and clamps the screening container between the lower plate and the upper cover.

[0009] The driving device includes a driving source, a horizontal vibration mechanism, and a vertical striking mechanism. Both the horizontal vibration mechanism and the vertical striking mechanism are connected to the driving source. The driving source drives the moving plate to swing horizontally through the horizontal vibration mechanism, and the driving source drives the vertical striking mechanism to strike the top of the screening container vertically.

[0010] As described above, in the impact screen, the height adjustment mechanism includes two adjusting bolts and two guide rods. The two guide rods are vertically arranged and spaced apart. The bottom end of each guide rod is fixedly connected to the moving plate, and the top end of each guide rod is fixedly connected to the upper cover. The two ends of the lower plate are respectively penetrated by the two guide rods and slidably engaged with them. The two adjusting bolts are respectively located on both sides of the screening container. Each adjusting bolt penetrates the lower plate and is threadedly engaged with it. The bottom end of each adjusting bolt is rotatably mounted on the moving plate.

[0011] In the slapping sieve described above, the lower plate is provided with a support seat for supporting the sieving container, and the support seat has an upward-opening receiving cavity.

[0012] In the impact sieve described above, an elastic buffer is also provided between the lower plate and the support.

[0013] The impact screen as described above, wherein the horizontal vibration mechanism comprises:

[0014] The first rotating shaft is vertically arranged and rotatably mounted on the base;

[0015] An eccentric block is fixedly mounted on the first rotating shaft;

[0016] The connecting component has one end fixedly connected to the movable plate and the other end abutting against the outer edge of the eccentric block;

[0017] The drive source is connected to the first rotating shaft and drives the eccentric block to rotate eccentrically through the first rotating shaft. The eccentric block pushes the moving plate to sway horizontally through the connecting component.

[0018] The striking sieve as described above, wherein the vertical striking mechanism includes:

[0019] The second rotating shaft is arranged parallel to the first rotating shaft and is rotatably mounted on the base;

[0020] A gear transmission assembly is meshed between the first rotating shaft and the second rotating shaft, and transmits the rotation of the first rotating shaft to the second rotating shaft;

[0021] The track block is fixedly mounted on the second rotating shaft, and the top surface of the track block is provided with an annular inclined track;

[0022] The rotating block is slidably disposed within the annular inclined track;

[0023] A top rod is vertically arranged, with its bottom end fixedly connected to the rotating block and its top end provided with a striking block. The top rod moves up and down periodically with the rotating block and drives the striking block to strike the top end of the screening container.

[0024] As described above, in the tapping screen, the base includes a base plate and a bracket and a fixing frame fixedly connected to the base plate. The bracket has a horizontally arranged upper plate, and the fixing frame is located below the upper plate. The upper and lower ends of the first rotating shaft and the upper and lower ends of the second rotating shaft are rotatably mounted on the upper plate and the fixing frame respectively through bearings.

[0025] In the slapping screen described above, the drive source is fixedly connected to the base plate and located below the fixed frame, and the first rotating shaft passes through the fixed frame and is drively connected to the output end of the drive source.

[0026] In the tapping screen described above, the driving source is an electric motor.

[0027] The tapping sieve described above, wherein the screening container comprises:

[0028] A sieve frame is a cylindrical body that is open at the top and bottom.

[0029] A sieve is disposed within the sieve frame;

[0030] A cover plate is detachably installed on the top of the screen frame and closes its upper opening;

[0031] The receiving tray is detachably and sealingly connected to the bottom of the screen frame and closes its lower opening.

[0032] Compared with the prior art, the present invention has the following features and advantages:

[0033] The impact sieve proposed in this utility model achieves precise and controllable vertical impact synchronized with horizontal reciprocating vibration through a driving device. While maintaining the original high-efficiency screening characteristics of the impact sieve, it greatly improves screening accuracy and stability. Furthermore, the clamping device facilitates the quick assembly and disassembly of the screening container, further reducing powder loss and operational complexity.

[0034] The tapping screen proposed in this utility model has both vibration and impact operation modes, which greatly improves screening efficiency and accuracy, significantly reduces powder loss, meets environmental protection and emission reduction requirements, and its highly reliable structure and fast operation characteristics ensure stability and convenience in continuous industrial production.

[0035] The tapping sieve proposed in this invention has high powder sieving efficiency and is suitable for the rapid development of industries such as additive manufacturing, chemical industry, and food industry.

[0036] The tapping sieve proposed in this utility model can significantly enhance the uniform distribution of materials on the sieve surface and the sieve passage efficiency, completely solving the problem of easy agglomeration and adhesion of ultrafine powders. Through the optimization of the overall structure, the sieve accuracy, stability and ease of operation are improved simultaneously. Attached Figure Description

[0037] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of this invention in any way. Furthermore, the shapes and proportions of the components in the drawings are merely illustrative to aid in understanding the invention and do not specifically limit the shapes and proportions of the components. Those skilled in the art, under the guidance of this invention, can select various possible shapes and proportions to implement this invention according to specific circumstances.

[0038] Figure 1 This is a perspective view of the tapping sieve proposed in this utility model;

[0039] Figure 2 This is a side view of the tapping sieve in this utility model;

[0040] Figure 3 This is a schematic diagram of the transmission mechanism of the tapping screen in this utility model.

[0041] Explanation of reference numerals in the attached figures

[0042] 1. Base plate; 2. Bracket; 3. Drive source; 4. Eccentric block; 5. Lower part of the first rotating shaft; 6. Right gear; 7. Upper part of the first rotating shaft; 8. Right bearing; 9. Upper plate; 10. Left bearing; 11. Push rod; 12. Slide groove; 13. Rotating block; 14. Track block; 15. Left gear; 16. Second rotating shaft; 17. Fixing frame; 18. Connecting block; 19. Moving plate; 20. Lower plate;

[0043] 21. Elastic buffer; 22. Support seat; 23. Screening container; 24. Cover plate; 25. Top cover; 26. Beating block; 27. Guide rod; 28. Adjusting bolt; 29. ​​Slide rail; 100. Beating screen. Detailed Implementation

[0044] The details of this utility model can be more clearly understood by referring to the accompanying drawings and the description of specific embodiments. However, the specific embodiments of this utility model described herein are for illustrative purposes only and should not be construed as limiting the utility model in any way. Under the teachings of this utility model, those skilled in the art can conceive of any possible modifications based on this utility model, and these should all be considered to fall within the scope of this utility model.

[0045] like Figures 1 to 3 As shown, this utility model proposes a tapping screen 100, which includes a screening container 23, a base, and components mounted on the base:

[0046] The clamping device includes a movable plate 19, an upper cover 25, a lower plate 20, and a height adjustment mechanism. The movable plate 19 is horizontally movable on the machine base. The upper cover 25 and the lower plate 20 are spaced apart vertically and are mounted on the movable plate through the height adjustment mechanism. The screening container 23 is disposed between the upper cover 25 and the lower plate 20. The height adjustment mechanism adjusts the height of the lower plate 20 and clamps the screening container 23 between the upper cover 25 and the lower plate 20.

[0047] The driving device includes a driving source 3, a horizontal vibration mechanism and a vertical striking mechanism. Both the horizontal vibration mechanism and the vertical striking mechanism are connected to the driving source 3. The driving source 3 drives the moving plate 19 to swing horizontally through the horizontal vibration mechanism, and the driving source 3 drives the vertical striking mechanism to strike the top of the screening container 23 vertically.

[0048] The impact sieve 100 proposed in this utility model uses a drive device to drive both the horizontal vibration mechanism and the vertical impact mechanism through the same drive source, realizing a compound motion of horizontal shaking and vertical impact at the top during the sieving process. This effectively prevents sieve hole clogging and improves sieving efficiency and accuracy. At the same time, the height adjustment mechanism in the clamping device can press the sieving containers 23 of different specifications to ensure the overall sealing of the sieving containers 23 to reduce powder escape, and realize quick assembly and disassembly. Thus, based on structural integration, it takes into account sieving reliability, ease of operation and adaptability.

[0049] In an optional embodiment of this utility model, the height adjustment mechanism includes two adjusting bolts 28 and two guide rods 27. The two guide rods 27 are vertically arranged and spaced apart. The bottom end of each guide rod 27 is fixedly connected to the moving plate 19, and the top end of each guide rod 27 is fixedly connected to the upper cover 25. The two ends of the lower plate 20 are respectively penetrated by the guide rods 27 and slidably engaged with the guide rods 27. The two adjusting bolts 28 are respectively located on both sides of the screening container 23. Each adjusting bolt 28 penetrates the lower plate 20 and is threadedly engaged with the lower plate 20. The bottom end of each adjusting bolt 28 is rotatably mounted on the moving plate 19.

[0050] In use, rotating the two adjusting bolts 28 drives the lower plate 20 to move up and down, thereby pressing or loosening the screening container 23 placed between the lower plate 20 and the upper cover 25. The adjusting bolts 28, located on both sides of the screening container 23, allow for height adjustment of the lower plate 20, ensuring that the lower plate 20 applies a uniform pressing force to the screening container 23, effectively guaranteeing the overall sealing of the screening container 23 during the screening process and preventing powder leakage. The guide rod 27 supports and positions the upper cover 25, and guides and limits the lower plate 20, ensuring that the upper cover 25 and the lower plate 20 are always parallel.

[0051] In an optional embodiment of this utility model, a support seat 22 for supporting the screening container 23 is provided on the lower plate 20, and the support seat 22 has an upward-opening receiving cavity. During assembly, the screening container 23 is placed into the receiving cavity of the support seat 22, and the receiving cavity forms a circumferential limit on the screening container 23, so that the screening container 23 is stably attached to the support seat 22.

[0052] In an optional embodiment, an elastic buffer 21 is further provided between the lower plate 20 and the support 22. When the driving device drives the vertical striking mechanism to vertically strike the screening container 23, the elastic buffer 21 undergoes corresponding elastic deformation with the strike, which can buffer the vibration and impact force of the vertical striking mechanism on the screening container 23 and the support 22 during the screening process, ensuring that the support 22 and the screening container 23 in the accommodating cavity always maintain a relatively stable positional relationship. By adopting a multi-layer buffer structure composed of the lower plate 20, the elastic buffer 21, and the support 22, the impact vibration generated during the screening process is effectively absorbed, providing stable flexible support for the screening container 23.

[0053] In one optional embodiment of this utility model, the horizontal vibration mechanism includes:

[0054] The first rotating shaft is vertically set and rotatably mounted on the machine base;

[0055] Eccentric block 4 is fixedly mounted on the first rotating shaft;

[0056] The connecting component has one end fixedly connected to the movable plate 19 and the other end abutting against the outer edge of the eccentric block 4;

[0057] The drive source 3 is connected to the first rotating shaft and drives the eccentric block 4 to rotate eccentrically through the first rotating shaft. The eccentric block 4 pushes the moving plate 19 to sway horizontally through the connecting component.

[0058] In this embodiment, the eccentric block 4 is driven to rotate eccentrically by the first rotating shaft, and the rotation of the eccentric block 4 is converted into the horizontal reciprocating sway of the moving plate 19 by the connecting component. This horizontal vibration mechanism has direct transmission and compact structure, and can generate uniform vibration force, effectively promoting the distribution and screening of materials on the screen surface, and significantly improving screening efficiency and accuracy.

[0059] In an alternative embodiment of this implementation, the eccentric block 4 and the movable plate 19 are connected by a connecting block 18.

[0060] In one optional embodiment, the vertical striking mechanism includes a second rotating shaft 16, a gear transmission assembly, a track block 14, a rotating block 13, a striking block 26, and a top rod 11. The second rotating shaft 16 is arranged parallel to the first rotating shaft and is rotatably mounted on the base. The gear transmission assembly is meshed between the first rotating shaft and the second rotating shaft 16 and transmits the rotation of the first rotating shaft to the second rotating shaft 16. The track block 14 is fixedly mounted on the second rotating shaft 16, and the top surface of the track block 14 is provided with an annular inclined track. The rotating block 13 is slidably arranged in the annular inclined track. The top rod 11 is vertically arranged, and the bottom end of the top rod 11 is fixedly connected to the rotating block 13. The top end of the top rod 11 is provided with a striking block 26. The top rod 11 moves up and down periodically with the rotating block 13 and drives the striking block 26 to strike the top of the screening container 23.

[0061] By adopting the above structure, the power of the horizontal vibration mechanism is transmitted to the vertical striking mechanism through the gear transmission assembly, realizing the simultaneous driving of two motions by a single drive source 3, reducing the complexity of the equipment and energy consumption. At the same time, the rotational motion is converted into the precise up-and-down movement of the push rod 11 through the annular inclined track on the top surface of the track block 14, thereby driving the striking block 26 to produce regular striking action. This mechanical transmission method ensures the stability of the striking force and frequency, effectively prevents screen clogging, and significantly improves the screening efficiency and accuracy of ultrafine powders.

[0062] Furthermore, the gear transmission assembly includes a meshing left gear 15 and a right gear 6, with the right gear 6 fixedly sleeved on the lower part 5 of the first rotating shaft and the left gear 15 fixedly sleeved on the second rotating shaft 16.

[0063] In an optional example, the base includes a base plate 1, a bracket 2 and a fixing frame 17. The bracket 2 and the fixing frame 17 are fixedly connected to the base plate 1. The bracket 2 has a horizontally arranged upper plate 9 and a side wall for supporting the upper plate 9. The fixing frame 17 is located below the upper plate 9. The upper and lower ends of the first rotating shaft and the upper and lower ends of the second rotating shaft 16 are rotatably mounted on the upper plate 9 and the fixing frame 17 respectively through the left bearing 10.

[0064] Furthermore, the bracket 2 and the fixing frame 17 can be welded to the base plate 1 to form a stable support structure.

[0065] Preferably, the drive source 3 is located below the fixed frame 17 and is fixedly installed on the base plate 1. The output end of the drive source 3 is connected to the lower part 5 of the first rotating shaft, and the upper part 7 of the first rotating shaft can be rotatably mounted on the upper plate 9 through the right bearing 8.

[0066] Specifically, the bottom end of the first rotating shaft passes through the fixed frame 17 and is connected to the output shaft of the drive source 3 via a coupling. When the drive source 3 is started, power is directly transmitted to the first rotating shaft through the output shaft, causing the first rotating shaft to rotate continuously.

[0067] In one alternative example, the rotating block 13 is T-shaped, with a vertical part and a horizontal part arranged perpendicularly to each other. The bottom end of the vertical part of the rotating block 13 is slidably engaged with the annular inclined track. The side wall of the bracket 2 has a vertically arranged groove 12. One end of the horizontal part of the rotating block 13 is fixedly connected to the vertical part, and the other end of the horizontal part of the rotating block 13 is inserted into the groove 12 and slidably engaged with the groove 12, thereby ensuring that the rotating block 13 can only move up and down.

[0068] In an optional embodiment of this utility model, the drive source 3 is an electric motor. Electric motors are characterized by stable speed and precise control. By using an electric motor as the drive source, a stable and reliable power input is provided to the tapping screen 100, ensuring continuous and stable operation of both horizontal vibration and vertical tapping motions. This guarantees the consistency of motion parameters during the screening process, thereby effectively improving screening accuracy and repeatability.

[0069] In an optional example, a slide rail 29 is provided on the base plate 1, and the movable plate 19 is mounted on the base plate 1 via the slide rail 29. The movable plate 19 can move horizontally on the base plate 1 through the sliding engagement between the movable plate 19 and the slide rail 29.

[0070] In one optional embodiment, the screening container 23 includes a screen frame, a screen mesh, a cover plate 24, and a receiving tray. The screen frame is a cylindrical body with openings at the top and bottom. The screen mesh is disposed inside the screen frame. The cover plate 24 is detachably placed on the top of the screen frame and closes its upper opening. The receiving tray is detachably and sealingly connected to the bottom of the screen frame and closes its lower opening. With the above-described structure, the cover plate 24 and the receiving tray of the screening container 23 are detachably connected to the screen frame. After assembly, the cover plate 24 can be pressed tightly by the upper cover 25, and the receiving tray is fixed by the support 22. In this way, the cover plate 24, the receiving tray, and the screen frame together form a sealed container, effectively preventing powder from escaping from the top and bottom during the screening process and reducing material loss. At the same time, the modular structural design makes screen replacement, material loading and unloading, and container cleaning operations more convenient, significantly improving the flexibility of equipment use and maintenance efficiency, while ensuring that the screening process is carried out in a closed environment.

[0071] The specific working process of the tapping sieve 100 proposed in this utility model is as follows:

[0072] Step 1: Place the powder into the sieving container 23, seal the top of the sieving container 23 with the cover plate 24, and place the entire sieving container 23 on the support 22; adjust the height of the lower plate 20 by adjusting the adjusting bolts 28 on the left and right sides of the sieving container 23 until the upper cover 25 is in close contact with the cover plate 24, and then fix the position of the adjusting bolts 28 so that the lower plate 20 and the upper cover 25 press the cover plate 24 tightly, ensuring that the cover plate 24 seals the top of the sieving container 23.

[0073] Step 2: Start the motor to drive the lower part 5 of the first rotating shaft, the eccentric block 4, the right gear 6, the upper part 7 of the first rotating shaft and the right bearing 8 to rotate. The left gear 15, which meshes with the right gear 6, also rotates synchronously. The left gear 15 drives the track block 14 to rotate. The track block 14 drives the rotating block 13 to move along the annular inclined track. The rotating block 13 drives the top rod 11 to move up and down and pushes the paddle block 26 to strike the upper cover 25.

[0074] The eccentric block 4 pushes the moving plate 19 to shake through the connecting block 18, which drives the entire sieving container 23 to shake for high-precision powder sieving until the sieving is completed.

[0075] Step 3: Stop the motor, adjust the lower plate 20 by adjusting bolt 28, and remove the screening container 23 for data statistics.

[0076] Step 4: Repeat steps 1 to 3 above to achieve continuous production.

[0077] The detailed explanations of the above embodiments are intended only to explain the present invention so as to facilitate a better understanding of the present invention. However, these descriptions should not be construed as limiting the present invention for any reason. In particular, the various features described in different embodiments can be arbitrarily combined with each other to form other embodiments. Unless there is an explicit description to the contrary, these features should be understood to be applicable to any embodiment, and not limited to the described embodiments.

Claims

1. A tapping sieve, characterized in that, The tapping screen includes a screening container, a base, and components mounted on the base: The clamping device includes a movable plate, an upper cover, a lower plate, and a height adjustment mechanism. The movable plate is horizontally movable on the machine base. The upper cover and the lower plate are spaced apart vertically and mounted on the movable plate through the height adjustment mechanism. The screening container is disposed between the upper cover and the lower plate. The height adjustment mechanism adjusts the height of the lower plate and clamps the screening container between the lower plate and the upper cover. The driving device includes a driving source, a horizontal vibration mechanism, and a vertical striking mechanism. Both the horizontal vibration mechanism and the vertical striking mechanism are connected to the driving source. The driving source drives the moving plate to swing horizontally through the horizontal vibration mechanism, and the driving source drives the vertical striking mechanism to strike the top of the screening container vertically.

2. The tapping sieve as described in claim 1, characterized in that, The height adjustment mechanism includes two adjusting bolts and two guide rods. The two guide rods are vertically arranged and spaced apart. The bottom end of each guide rod is fixedly connected to the moving plate, and the top end of each guide rod is fixedly connected to the upper cover. The two ends of the lower plate are respectively penetrated by the two guide rods and are slidably engaged with the guide rods. The two adjusting bolts are respectively located on both sides of the screening container. Each adjusting bolt penetrates the lower plate and is threadedly engaged with the lower plate. The bottom end of each adjusting bolt is rotatably mounted on the moving plate.

3. The tapping sieve as described in claim 1, characterized in that, The lower plate is provided with a support seat for supporting the screening container, and the support seat has an upward-opening receiving cavity.

4. The tapping sieve as described in claim 3, characterized in that, An elastic buffer is also provided between the lower plate and the support.

5. The tapping sieve as described in claim 1, characterized in that, The horizontal vibration mechanism includes: The first rotating shaft is vertically arranged and rotatably mounted on the base; An eccentric block is fixedly mounted on the first rotating shaft; The connecting component has one end fixedly connected to the movable plate and the other end abutting against the outer edge of the eccentric block; The drive source is connected to the first rotating shaft and drives the eccentric block to rotate eccentrically through the first rotating shaft. The eccentric block pushes the moving plate to sway horizontally through the connecting component.

6. The tapping sieve as described in claim 5, characterized in that, The vertical striking mechanism includes: The second rotating shaft is arranged parallel to the first rotating shaft and is rotatably mounted on the base; A gear transmission assembly is meshed between the first rotating shaft and the second rotating shaft, and transmits the rotation of the first rotating shaft to the second rotating shaft; The track block is fixedly mounted on the second rotating shaft, and the top surface of the track block is provided with an annular inclined track; The rotating block is slidably disposed within the annular inclined track; A top rod is vertically arranged, with its bottom end fixedly connected to the rotating block and its top end provided with a striking block. The top rod moves up and down periodically with the rotating block and drives the striking block to strike the top end of the screening container.

7. The tapping sieve as described in claim 6, characterized in that, The base includes a base plate and a bracket and a fixing frame fixedly connected to the base plate. The bracket has a horizontally arranged upper plate, and the fixing frame is located below the upper plate. The upper and lower ends of the first rotating shaft and the upper and lower ends of the second rotating shaft are rotatably mounted on the upper plate and the fixing frame respectively through bearings.

8. The tapping sieve as described in claim 7, characterized in that, The drive source is fixedly connected to the base plate and located below the fixed frame. The first rotating shaft passes through the fixed frame and is connected to the output end of the drive source.

9. The tapping sieve as described in claim 1 or 8, characterized in that, The driving source is an electric motor.

10. The tapping sieve as described in claim 1, characterized in that, The screening container includes: A sieve frame is a cylindrical body that is open at the top and bottom. A sieve is disposed within the sieve frame; A cover plate is detachably installed on the top of the screen frame and closes its upper opening; The receiving tray is detachably and sealingly connected to the bottom end of the screen frame and closes its lower opening.

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