Sandstone belt conveyor feeding device for stock bin

Abstract

The gravel belt conveyor feeding device comprises a box body, a discharging port is formed in the left side of the upper end of the box body, a feeding port is formed in the right side of the upper end of the box body, the discharging port, the box body and the feeding port are sequentially communicated, a net plate is arranged at the upper end of the box body, and a discharging port is formed in the lower end of the box body. The screen plate is located at the lowest position of a communicating port of the discharging port and the feeding port, a plurality of fans are evenly arranged on the top wall in the box body and the side wall located above the screen plate, a water sprayer and a water filter are arranged on the lower portion in the box body, the water filter is located at the bottom of the box body, and the water sprayer is located at the bottom of the box body. And the water outlet end of the water filter is connected with the water sprayer through a communicating pipe. According to the gravel feeding device, dust removal is conducted on the placed gravel, then the gravel subjected to dust removal is sent out of the gravel belt conveyor, and therefore in the gravel feeding process, a large amount of dust cannot be generated on the gravel belt conveyor, and then work of the gravel belt conveyor is effectively guaranteed.

Description

Technical Field

[0001] This invention relates to the field of construction technology, and in particular to a sand and gravel conveyor belt feeding device for silos. Background Technology

[0002] The sand and gravel belt conveyor is a continuous conveying equipment specifically designed for transporting sand and gravel aggregates. It is widely used in silo feeding systems in industries such as building materials and mining. This equipment uses a rubber belt as the carrier, transmits power through a drive drum, and utilizes idler rollers to support the belt, forming a closed-loop circuit to achieve efficient and stable transport of sand and gravel materials from the feeding point to the silo. Its structure includes key components such as the belt, drive unit, tensioning device, idler rollers, and cleaners. It features high conveying capacity, stable operation, and easy maintenance. Considering the characteristics of sand and gravel materials, the belt is typically made of wear-resistant and tear-resistant material and can be flexibly arranged for horizontal or inclined conveying according to site requirements, effectively improving the automation level and production efficiency of silo feeding.

[0003] However, when feeding sand and gravel onto the conveyor belt, it is often done manually. Workers use shovels to scoop sand and gravel from the hopper onto the conveyor belt. This method often generates a lot of dust. This dust adheres to the drive system of the conveyor belt, and over the years, it will cause drive failures, thus affecting the construction efficiency of the project. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address the shortcomings of the prior art by providing a sand and gravel conveyor belt feeding device for a silo. The device removes dust from the sand and gravel that is placed in the silo and then sends the dust-removed sand and gravel onto the sand and gravel conveyor belt. This prevents the generation of a large amount of dust on the sand and gravel conveyor belt during the sand and gravel feeding process, thereby effectively ensuring the operation of the sand and gravel conveyor belt.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a feeding device for a sand and gravel conveyor belt for a silo, comprising a box body, an outlet provided on the upper left side of the box body, and an inlet provided on the upper right side of the box body, wherein the outlet, the box body, and the inlet are connected in sequence, a mesh plate is provided at the upper end of the box body, the mesh plate is located at the lowest point of the connection between the outlet and the inlet, a plurality of fans are evenly arranged on the top wall of the box body and the side wall above the mesh plate, a water sprayer and a water filter are provided at the lower part of the box body, the water filter is located at the bottom of the box body, and the water outlet of the water filter is connected to the water sprayer through a connecting pipe.

[0006] Furthermore, an irregular support platform is provided inside the box, one end of which is fixed to the side wall of the box. A universal steering head is provided on the top of the irregular support platform, and the universal steering head is connected to the water sprayer. The cross-sectional area of ​​the upper end of the irregular support platform is smaller than that of the lower end.

[0007] Furthermore, the irregular support platform is provided with a longitudinally penetrating channel, through which the connecting pipe passes.

[0008] Furthermore, an annular guide block is provided at the bottom edge of the housing, the guide block surrounds the water filter, the guide block is sealed to the side of the housing, the highest point of the outer side of the guide block contacts the housing, and the lowest point of the outer side of the guide block contacts the water filter.

[0009] Furthermore, one end of the mesh plate is hinged to the inner wall of the box body via a hinge, the hinge being located at the lower end of the discharge port, and the other end of the mesh plate is in contact with the top of the box body. An electric push rod that reciprocates upwards is provided inside the box body, and a support plate is provided at the push rod head of the electric push rod. When the electric push rod retracts, the support plate contacts the mesh plate, and the mesh plate is in a horizontal state.

[0010] Furthermore, the diameter of the mesh plate is greater than the distance between the mesh plate and the top of the box.

[0011] Furthermore, a buffer pad is provided on the side of the support plate that faces the mesh plate.

[0012] Furthermore, the inner wall of the housing is provided with a plurality of connecting rods, each of which is located above the mesh plate. The other end of the connecting rod is connected to the same connecting plate, and the connecting plate has a plurality of through holes, each of which is provided with a fan.

[0013] Furthermore, the inlet is connected to the housing via an arc-shaped connecting pipe, and a feeding mechanism for intermittent feeding is provided at the bottom of the inlet.

[0014] Furthermore, the feeding mechanism includes a fixed plate fixed to the bottom of the feed inlet, a longitudinal fixed opening on one side of the fixed plate, a rotating plate at the upper end of the fixed plate, a longitudinal rotating opening on one side of the rotating plate, the fixed opening and the rotating opening being opposite each other and having the same diameter, a downward-opening groove at the bottom center of the rotating plate, and a motor fixed at the top center of the fixed plate, the output shaft of the motor being connected to the central axis of the rotating plate, and the motor being located inside the groove.

[0015] Compared with the prior art, the present invention has the following advantages: This invention provides a feeding device for a sand and gravel conveyor belt in a silo. By employing a closed box structure and multiple fans located above the mesh plate and on the top wall, negative pressure or airflow disturbance is created during the falling sand and gravel, initially separating and collecting the light dust mixed in the material. Simultaneously, a water sprayer located at the lower part of the box sprays water mist onto the surface of the sand and gravel flowing over the mesh plate, achieving deep dust suppression through the adsorption of water molecules and dust. The water used for dust removal is filtered by a water filter and then returned to the water sprayer for recycling through a connecting pipe, effectively avoiding water waste. Most importantly, the device constructs a complete closed dust removal path between the discharge port and the inlet, ensuring that the sand and gravel are efficiently purified before falling into the conveyor belt. This fundamentally eliminates the deposition and adhesion of dust on the surface of the conveyor belt drive system, idlers, and transmission components, eliminating potential hazards such as drive jamming, bearing wear, and electrical faults caused by dust accumulation. It significantly reduces the frequency of equipment maintenance and the failure rate, ensuring the stability and reliability of the sand and gravel conveyor belt during long-term operation, and thus effectively guaranteeing the continuity and overall efficiency of engineering construction.

[0016] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0018] Figure 2 for Figure 1 Enlarged view of point A in the middle.

[0019] Figure 3 for Figure 1 Enlarged view of point B in the middle.

[0020] Figure 4 This is a schematic diagram of the feed inlet structure in this invention.

[0021] Figure 5 This is a schematic diagram of the rotating disk in this invention.

[0022] Explanation of reference numerals in the attached figures: 1. Box body; 2. Electric push rod; 3. Connecting pipe; 4. Feed inlet; 5. Discharge mechanism; 5-1. Fixed plate; 5-2. Fixed opening; 5-3. Rotating plate; 5-4. Motor; 5-5. Groove; 5-6. Rotating opening; 6. Irregular support platform; 7. Discharge port; 8. Water sprayer; 9. Universal steering head; 10. Connecting pipe; 11. Guide block; 12. Water filter; 13. Box body; 14. Mesh plate; 15. Support plate; 16. Connecting rod; 17. Connecting plate; 18. Fan; 19. Through hole. Detailed Implementation

[0023] like Figure 1-5 As shown, the present invention provides a feeding device for a sand and gravel conveyor belt in a silo, comprising a housing 1. A discharge port 7 is provided on the upper left side of the housing 1, and a feed port 4 is provided on the upper right side of the housing 1. The discharge port 7, the housing 1, and the feed port 4 are connected in sequence. A mesh plate 14 is provided at the upper end of the housing 1, and the mesh plate 14 is located at the lowest point of the connection between the discharge port 7 and the feed port 4. Multiple fans 18 are evenly arranged on the top wall inside the housing 1 and the side wall above the mesh plate 14. A water sprayer 8 and a water filter 12 are provided at the lower part inside the housing 1. The water filter 12 is located at the bottom of the housing 1, and the water outlet of the water filter 12 is connected to the water sprayer 8 through a connecting pipe 10.

[0024] This invention provides a feeding device for a sand and gravel conveyor belt in a seed material silo, comprising a housing 1. The housing 1, serving as the main load-bearing structure of the entire device, adopts a sealed design to create a relatively enclosed dust-free working space. In existing technologies, when manually shoveling material onto a sand and gravel conveyor belt, a large amount of dust is stirred up during the throwing process. This dust adheres to the surfaces of moving parts such as the drive rollers, idlers, and transmission bearings of the conveyor belt for extended periods, exacerbating mechanical wear and potentially leading to poor heat dissipation or even electrical malfunctions in the drive system. This invention, by setting up a sealed housing 1, confines the dust generated during the feeding process within the housing 1, effectively blocking the diffusion path of dust into the conveyor belt's working environment.

[0025] Specifically, a discharge port 7 is located on the upper left side of the housing 1, and a feed port 4 is located on the upper right side of the housing 1. The discharge port 7, housing 1, and feed port 4 are connected sequentially. The feed port 4 is used to receive sand and gravel materials from the upstream silo or conveyor equipment, while the discharge port 7 is connected to the feed end of the sand and gravel conveyor belt. The sand and gravel enter the housing 1 through the feed port 4, undergo dust removal treatment inside the housing 1, and are then output to the conveyor belt through the discharge port 7. A mesh plate 14 is located at the lower end of the housing 1, at the connection point between the discharge port 7 and the feed port 4. The mesh plate 14 ensures that the sand and gravel entering from the feed port 4 first fall onto the surface of the mesh plate 14. The mesh plate 14 serves to support and disperse the material, forming a uniform material layer distribution on the mesh plate 14, providing a good material condition for subsequent dust removal treatment.

[0026] Multiple fans 18 are evenly arranged on the top wall and side wall above the mesh plate 14 inside the housing 1. When sand and gravel fall onto the mesh plate 14, the multiple fans 18 start simultaneously, forming a directional airflow field in the area above the mesh plate 14. According to the principles of fluid mechanics, when the airflow flows over the surface of the sand and gravel, it will carry smaller, lighter dust particles away from the surface of the sand and gravel, causing them to move with the airflow towards the lower part of the housing 1 or a specific dust collection area, thereby achieving preliminary dust separation. The fans 18 are evenly arranged to ensure that the sand and gravel in each area of ​​the mesh plate 14 are effectively covered by the airflow, avoiding the problem of incomplete dust removal caused by blind spots in the airflow.

[0027] Inside the housing 1, a water sprayer 8 and a water filter 12 are installed at the bottom. The water filter 12 is located at the bottom of the housing 1, and its outlet is connected to the water sprayer 8 via a connecting pipe 10. After initial dust removal by the fan 18, the sand and gravel continue to move on the mesh plate 14 or fall to the action area of ​​the water sprayer 8 under its own gravity. The water sprayer 8 sprays a fine water mist onto the surface of the sand and gravel. Based on the principles of dust wetting and cohesion, the water mist particles collide, adsorb, and agglomerate with the dust particles, causing the dust to become heavier and settle with the water flow, thus achieving deep capture of residual fine dust on the surface of the sand and gravel. The sprayed water carries the dust downwards, is filtered and purified by the water filter 12, and then flows back to the water sprayer 8 for recycling through the connecting pipe 10. This water circulation system design makes full use of water resources, avoids water waste in continuous spraying operations, reduces the operating cost of the device, and conforms to the design concept of energy conservation and environmental protection.

[0028] As a further improvement of the present invention, an irregular support platform 6 is provided inside the housing 1. One end of the irregular support platform 6 is fixed to the side wall of the housing 1, and a universal steering head 9 is provided on the top of the irregular support platform 6. The universal steering head 9 is connected to a water sprayer 8. The cross-sectional area of ​​the upper end of the irregular support platform 6 is smaller than that of the lower end. This trapezoidal or conical structure, which is smaller at the top and larger at the bottom, gives the irregular support platform 6 a lower center of gravity and higher structural stability, and can stably support the water sprayer 8. The universal steering head 9 allows the water sprayer 8 to flexibly adjust the spray angle in multiple degrees of freedom. The operator can adjust the water sprayer 8 to the optimal spray position according to the actual working conditions such as the particle size distribution, falling trajectory, and dust content of the sand and gravel, so that the water mist covers the surface of the sand and gravel at the optimal angle, which significantly improves the targeting and effectiveness of the spray dust removal.

[0029] Furthermore, a longitudinally penetrating channel is provided within the irregular support platform 6, through which the connecting pipe 10 passes. This built-in channel design completely conceals the connecting pipe 10 within the internal cavity of the irregular support platform 6. On the one hand, the structure of the irregular support platform 6 provides physical protection for the connecting pipe 10, preventing impact or wear during the falling sand and gravel. On the other hand, it makes the internal layout of the device more compact and neat, eliminating the potential for entanglement, snagging, or interference caused by exposed pipes, thereby improving the operational safety and maintenance convenience of the equipment.

[0030] A ring-shaped guide block 11 is provided at the bottom edge of the housing 1, surrounding the water filter 12 and sealed to the side of the housing 1. The highest point of the outer side of the guide block 11 contacts the housing 1, and the lowest point of the outer side of the guide block 11 contacts the water filter 12. The guide block 11 adopts a ring-shaped inclined structure, with its surface extending downwards from the side wall of the housing 1 towards the water filter 12. When the sprayed water flows along the side wall or bottom of the housing 1, the guide block 11 collects and guides the flow, allowing the water containing dust to flow smoothly to the inlet of the water filter 12, preventing water from accumulating in the dead corners at the bottom edge of the housing 1 or overflowing into non-collection areas, thus ensuring the smoothness and efficiency of the water circulation system.

[0031] Considering that the mesh plate 14 may become clogged due to sand and gravel particles embedding in the mesh during long-term operation, thus affecting airflow efficiency and sand and gravel falling speed, the present invention optimizes the structure of the mesh plate 14. One end of the mesh plate 14 is hinged to the inner wall of the box 1 via a hinge joint located at the lower end of the discharge port 7, and the other end of the mesh plate 14 contacts the top of the box 13. An upward reciprocating electric push rod 2 is installed inside the box 13, and a support plate 15 is provided at the push rod head of the electric push rod 2. When the electric push rod 2 is in the retracted state, the support plate 15 contacts the mesh plate 14, and the mesh plate 14 remains horizontal. At this time, the sand and gravel can be evenly distributed on the surface of the mesh plate 14 for dust removal. When the electric push rod 2 extends, the push rod head pushes the support plate 15 upward. The support plate 15 pushes the screen plate 14 to rotate upward around the hinge at a certain angle, causing the screen plate 14 to tilt. The sand and gravel on the screen plate 14 slide towards the discharge port 7 under the action of gravity. At the same time, the reciprocating motion of the electric push rod 2 causes the screen plate 14 to vibrate periodically. This vibration helps to clear the blocked mesh holes and realize the self-cleaning function of the screen plate 14. By controlling the extension frequency and stroke of the electric push rod 2, the vibration amplitude and frequency can be flexibly adjusted according to the actual blockage of the screen plate 14, effectively preventing the adverse effects of screen plate 14 blockage on dust removal effect and feeding efficiency.

[0032] The diameter of the mesh plate 14 is greater than the distance between the mesh plate 14 and the top of the housing 1. This dimensional relationship ensures that when the mesh plate 14 tilts due to the push of the electric push rod 2, the free end of the mesh plate 14 has sufficient space to move and will not interfere with or collide with the top of the housing 1, ensuring smooth execution of the vibration and tilting movements of the mesh plate 14. A buffer pad is provided on the side of the support plate 15 facing the mesh plate 14. The buffer pad can be made of rubber, polyurethane, or other materials with good elasticity and wear resistance. When the electric push rod 2 pushes the mesh plate 14, the buffer pad can effectively absorb and buffer the impact force, reducing the rigid contact between the mesh plate 14 and the support plate 15. This reduces operating noise and extends the service life of the electric push rod 2, the support plate 15, and the mesh plate 14.

[0033] To optimize the installation layout of the fans 18 and improve the uniformity of the airflow field, multiple connecting rods 16 are installed on the inner wall of the housing 1. Each connecting rod 16 is located above the mesh plate 14, and the other end of the connecting rod 16 is connected to the same connecting plate 17. The connecting plate 17 has multiple through holes 19, and each through hole 19 houses a fan 18. Through the suspended support structure formed by the connecting rods 16 and the connecting plate 17, multiple fans 18 are centrally installed at a predetermined height above the mesh plate 14. This centralized installation method facilitates unified control, centralized power supply, and synchronous maintenance of the fans 18. At the same time, the array distribution of multiple fans 18 on the connecting plate 17 ensures uniform airflow coverage above the mesh plate 14, further improving the stability and consistency of dry dust removal.

[0034] The feed inlet 4 is connected to the housing 1 via an arc-shaped connecting pipe 3. The arc-shaped connecting pipe 3 allows the sand and gravel to fall smoothly along an arc-shaped trajectory as they enter the housing 1 from the feed inlet 4. Compared to right-angle or acute-angle turning structures, the arc-shaped pipe effectively reduces the impact force and number of impacts between the sand and gravel and the pipe wall, thereby reducing the amount of dust generated during the fall of the sand and gravel. The bottom of the feed inlet 4 is equipped with an intermittent feeding mechanism 5. This feeding mechanism 5 can control the flow rate and feeding rhythm of sand and gravel entering the housing 1 according to the dust removal load and sand and gravel processing capacity inside the housing 1. This avoids overloading the screen plate 14 or causing a sudden increase in the dust removal load of the fan 18 and water sprayer 8 due to a large amount of material fed at one time, ensuring the continuity and stability of the dust removal operation and making the entire feeding process more stable and controllable.

[0035] Specifically, the feeding mechanism 5 includes a fixed plate 5-1 fixed to the bottom of the feed inlet 4. A longitudinal fixed opening 5-2 is provided on one side of the fixed plate 5-1. A rotating plate 5-3 is located at the upper end of the fixed plate 5-1. A longitudinal rotating opening 5-6 is provided on one side of the rotating plate 5-3. The fixed opening 5-2 and the rotating opening 5-6 are opposite each other and have the same diameter. A downward-opening groove 5-5 is provided at the center of the bottom of the rotating plate 5-3. A motor 5-4 is fixed at the center of the top of the fixed plate 5-1. The output shaft of the motor 5-4 is connected to the central axis of the rotating plate 5-3, and the motor 5-4 is located inside the groove 5-5. During operation, the motor 5-4 drives the rotating plate 5-3 to rotate around its axis. When the rotating opening 5-6 rotates to a position coinciding with the fixed opening 5-2, the sand and gravel in the feed inlet 4 fall into the housing 1 through both openings. When the rotating opening 5-6 rotates to a position deviating from the fixed opening 5-2, the feeding channel is blocked, and feeding stops. By controlling the speed and start-stop cycle of motors 5-4, intermittent and quantitative feeding of sand and gravel can be achieved. This feeding method not only ensures that the sand and gravel have sufficient residence time in the box 1 to complete adequate dry and wet dust removal, but also effectively avoids the problem of sand and gravel accumulation and blockage at the feed inlet 4 due to continuous feeding, making the entire feeding process automated and controllable.

[0036] In summary, this invention constructs a closed-loop feeding system integrating dry airflow dust removal and wet water mist dust removal through the coordinated operation of multiple components, including the housing 1, fan 18, water sprayer 8, water filter 12, mesh plate 14, and feeding mechanism 5. After entering through the inlet 4, the sand and gravel undergo preliminary dust removal via the airflow field generated by the fan 18, followed by deep dust removal via the water mist field generated by the water sprayer 8. The purified sand and gravel are then discharged from the outlet 7 to the sand and gravel conveyor belt. Throughout the dust removal process, the dust generated is effectively controlled within the housing 1 and collected by the circulating water system in the water filter 12 for filtration, preventing leakage into the working environment of the conveyor belt. This invention fundamentally solves the technical problem of excessive dust generation and adhesion to the drive system, idlers, and transmission components of conveyor belts caused by manual feeding in existing technologies. It eliminates the potential hazards of drive jamming, bearing wear, and electrical faults caused by dust accumulation, significantly reduces the maintenance frequency and failure rate of sand and gravel conveyor belts, ensures the stability and reliability of the equipment during long-term operation, and effectively guarantees the continuity and overall efficiency of engineering construction. It has extremely high practical value and promising prospects for widespread application.

[0037] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the present invention. Any simple modifications, alterations, or equivalent structural changes made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A material feeding device for a sand and gravel conveyor belt, characterized in that, The box includes a housing (1), with a discharge port (7) on the upper left side and a feed port (4) on the upper right side. The discharge port (7), the housing (1), and the feed port (4) are connected in sequence. A mesh plate (14) is provided at the upper end of the housing (1). The mesh plate (14) is located at the lowest point of the connection between the discharge port (7) and the feed port (4). Multiple fans (18) are evenly arranged on the top wall inside the housing (1) and the side wall above the mesh plate (14). A water sprayer (8) and a water filter (12) are provided at the lower part inside the housing (1). The water filter (12) is located at the bottom of the housing (1). The water outlet of the water filter (12) is connected to the water sprayer (8) through a connecting pipe (10).

2. The sand and gravel conveyor belt feeding device for a silo according to claim 1, characterized in that, An irregular support platform (6) is provided inside the box (1). One end of the irregular support platform (6) is fixed to the side wall of the box (1). A universal steering head (9) is provided on the top of the irregular support platform (6). The universal steering head (9) is connected to the water sprayer (8). The cross-sectional area of ​​the upper end of the irregular support platform (6) is smaller than the cross-sectional area of ​​the lower end.

3. A material feeding device for a sand and gravel conveyor belt according to claim 2, characterized in that, The irregular support platform (6) has a longitudinally penetrating channel, through which the connecting pipe (10) passes.

4. A sand and gravel conveyor belt feeding device for a silo according to claim 3, characterized in that, The bottom edge of the housing (1) is provided with an annular guide block (11), which surrounds the water filter (12). The guide block (11) is sealed to the side of the housing (1). The highest point of the outer side of the guide block (11) is in contact with the housing (1), and the lowest point of the outer side of the guide block (11) is in contact with the water filter (12).

5. A material feeding device for a sand and gravel conveyor belt according to claim 1, characterized in that, One end of the mesh plate (14) is hinged to the inner wall of the box (1) by a hinge. The hinge is located at the lower end of the discharge port (7). The other end of the mesh plate (14) is in contact with the top of the box (13). An electric push rod (2) that pushes upwards and back is provided inside the box (13). A support plate (15) is provided at the push rod head of the electric push rod (2). When the electric push rod (2) retracts, the support plate (15) contacts the mesh plate (14) and the mesh plate (14) is in a horizontal state.

6. A material feeding device for a sand and gravel conveyor belt according to claim 5, characterized in that, The diameter of the mesh plate (14) is greater than the distance between the mesh plate (14) and the top of the box (1).

7. A sand and gravel conveyor belt feeding device for a silo according to claim 6, characterized in that, A buffer pad is provided on the side of the support plate (15) facing the mesh plate (14).

8. A sand and gravel conveyor belt feeding device for a silo according to claim 1, characterized in that, The inner wall of the box (1) is provided with a plurality of connecting rods (16), each of the connecting rods (16) is located above the mesh plate (14), and the other end of the connecting rod (16) is connected to the same connecting plate (17). The connecting plate (17) is provided with a plurality of through holes (19), and the fan (18) is provided in each of the through holes (19).

9. A sand and gravel conveyor belt feeding device for a silo according to claim 1, characterized in that, The feed inlet (4) is connected to the box body (1) through an arc-shaped connecting pipe (3), and the bottom of the feed inlet (4) is provided with a feeding mechanism (5) for intermittent feeding.

10. A material feeding device for a sand and gravel conveyor belt according to claim 9, characterized in that, The feeding mechanism (5) includes a fixed plate (5-1) fixed at the bottom of the feed inlet (4). A longitudinal fixed opening (5-2) is provided on one side of the fixed plate (5-1). A rotating plate (5-3) is provided at the upper end of the fixed plate (5-1). A longitudinal rotating opening (5-6) is provided on one side of the rotating plate (5-3). The fixed opening (5-2) and the rotating opening (5-6) are opposite to each other and have the same diameter. A downward-opening groove (5-5) is provided at the center of the bottom of the rotating plate (5-3). A motor (5-4) is fixed at the center of the top of the fixed plate (5-1). The output shaft of the motor (5-4) is connected to the central axis of the rotating plate (5-3). The motor (5-4) is located inside the groove (5-5).

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