Rainwater collecting and gravel separating device
The cylinder is rotated by the impact of rainwater flow on the blades. Combined with the design of the mesh cylinder and guide blades, efficient separation of sand and gravel in hillside rainwater is achieved, solving the problem of sand and gravel impurities affecting irrigation transportation and effects, and realizing energy-saving and environmentally friendly multi-stage filtration separation.
Patent Information
- Application Number
- CN202422936969.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-29
- Publication Date
- 2025-10-10
- Estimated Expiration
- 2034-11-29
AI Technical Summary
When collecting rainwater on hillsides or side slopes, the presence of sand and gravel impurities makes irrigation and transportation inconvenient and affects the irrigation effect. Existing technologies are difficult to effectively separate them.
The blades are impacted by the flow of rainwater to drive the cylinder to rotate, and the mesh cylinder is used to separate sand and gravel from rainwater. Combined with the design of guide blades and inclined plates, sand and gravel impurities are discharged through the discharge port, and rainwater is discharged through the mesh holes.
It achieves efficient separation of sand and gravel from rainwater, simplifies the transportation process, improves irrigation effect, saves energy and is environmentally friendly, does not require an additional power source, and separates sand and gravel of different particle sizes through multi-stage filtration.
Smart Images
Figure CN223416861U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model belongs to rainwater treatment technical field, concretely relates to a rainwater collection sandstone separation device. BACKGROUND
[0002] In order to realize water resource conservation and reuse, rainwater is often collected, filtered and treated for irrigation or other purposes. In mountainous or side slope areas, rainwater flows down from the top of the mountain or slope through the ditch. Before collection, impurities such as branches and leaves mixed in the rainwater are removed. Then, sand and gravel need to be separated. Subsequently, they are transported to the corresponding position for irrigation use. If there are too many sand and gravel impurities, on the one hand, it is not convenient for irrigation and transportation, and on the other hand, the sand and gravel impurities will affect the subsequent irrigation effect. SUMMARY
[0003] The utility model discloses a rainwater collection sandstone separation device. The water flow impacts the cylinder and the mesh cylinder to rotate, and then the mesh cylinder separates sand and gravel from rainwater. Subsequently, under the action of the guide vane, the sand and gravel impurities in the mesh cylinder are transported to the inclined plate and then discharged from the impurity discharge port for treatment. The rainwater after separation of sand and gravel is discharged from the water outlet for subsequent treatment.
[0004] To achieve the above purpose, the technical scheme of the utility model is as follows:
[0005] A rainwater collection sandstone separation device includes a box body and a cover body arranged obliquely along the water flow direction. The cover body is provided with a water inlet at the upstream end. The box body is provided with a water outlet at the lower part of the downstream end. A rotating shaft and a separation assembly are arranged in the box body. The separation assembly includes a power element and a separation element. The power element includes a cylinder and multiple blades. The multiple blades are fixed circumferentially between the rotating shaft and the inner wall of the cylinder and correspond to the water inlet. The water inlet rainwater flow impacts the blades to drive the cylinder to rotate. Rainwater enters the cylinder from the water inlet. After separation of sand and gravel particles, it is discharged from the water outlet.
[0006] The separating piece comprises a mesh cylinder and a plurality of guide vanes, the plurality of guide vanes are arranged in a spiral shape on the inner wall of the mesh cylinder, the mesh cylinder is used for separating sand and stones in rainwater, and the guide vanes are used for guiding the sand and stones in the mesh cylinder to the downstream end; the box body is further provided with a debris removal assembly, the debris removal assembly comprises an inclined plate, a supporting plate and a debris removal opening formed on one side of the box body, the inclined plate is arranged obliquely in the box body, the debris removal opening is arranged at the tail end of the inclined plate, the inclined plate is fixedly connected with the downstream end side plate of the box body and the supporting plate on the two sides, respectively, an arc-shaped groove is formed on the upper side of the supporting plate, one end of the mesh cylinder is coaxially fixedly connected with a cylinder body, and the other end is located in the arc-shaped groove; after the rainwater enters the mesh cylinder, the water flow falls from the mesh holes of the mesh cylinder into the box body, and then is discharged; the sand and stone particles and the like are discharged into the debris removal assembly under the guidance of the guide vanes and the self-gravity, and are discharged through the debris removal opening.
[0007] Preferably, the box body is fixedly provided with a supporting frame at both ends, the supporting frame is fixedly provided with a bearing seat, the rotating shaft is rotatably connected with the bearing seat through the bearing after extending out of the box body, and effective support and installation of the box body are realized through the supporting frame.
[0008] Preferably, a first sleeve is fixedly sleeved on the rotating shaft, the vane is fixedly arranged between the first sleeve and the cylinder body, the vane extends along the axial direction of the cylinder body and is arranged in an inclined manner along the circumferential direction of the cylinder body, so that the vane rotates synchronously with the rotating shaft under the impact of the water flow.
[0009] Preferably, a plurality of second sleeves are fixedly sleeved on the rotating shaft in sequence, an annular supporting ring is arranged on the outer side of each second sleeve, the annular supporting ring is fixedly connected with the inner wall of the mesh cylinder, and a plurality of supporting rods are fixedly arranged along the circumferential direction between each annular supporting ring and the corresponding second sleeve, so as to guarantee the overall structural strength of the mesh cylinder through cooperation of the supporting rods and the annular supporting ring.
[0010] Preferably, a guide plate is fixedly arranged between the supporting plate and the end side plate of the box body, the guide plate is located on the side, away from the debris removal opening, of the mesh cylinder, the guide plate is in an arc shape and extends along the circumferential direction of the mesh cylinder, the guide plate is located above the inclined plate and is fixedly provided with a supporting plate between the guide plate and the inclined plate, the guide plate is used for limiting the sand and stone particles and the like in the mesh cylinder, so as to guarantee that the sand and stone particles and the like slide and roll along the inclined surface of the inclined plate and then are discharged from the debris removal opening of the box body.
[0011] Preferably, a plurality of fan-shaped plates are fixedly provided on the outer arc surface of the mesh cylinder, and the plurality of fan-shaped plates are distributed in a spiral shape. The cover body is penetrated by a plurality of tubes from top to bottom, and the lower ends of the tubes are provided with strip through grooves, and each strip through groove passes through the lower end of the corresponding tube along the circumference of the mesh cylinder. Each of the fan-shaped plates is matched with the strip through groove of the corresponding tube, and a ball is movably provided in each of the tubes. During the rotation of the mesh cylinder, when the fan-shaped plate moves into the tube body, the ball is lifted up, and when the fan-shaped plate leaves the tube body, the ball falls and hits the mesh cylinder, causing the mesh cylinder to vibrate to avoid blockage of the mesh cylinder or residual sand and gravel particles therein.
[0012] Through the above technical solution, the beneficial effects of the utility model are:
[0013] 1. The utility model utilizes the kinetic energy of rainwater flowing down the hillside to impact the blades and drive the cylinder and the net cylinder to rotate, so that the rainwater falls into the box from the mesh holes of the net cylinder and is discharged. The sand and gravel particles and other impurities are transported to the inclined plate by their own weight under the action of the rotation of the net cylinder with the guide blades, and then discharged along the inclined plate through the impurity discharge port, thereby realizing the separation of sand and gravel particles in the rainwater.
[0014] 2. The utility model is arranged in multiple pieces and tilted along the hillside. There is a height difference between two adjacent sand and gravel separation devices to ensure that the water flow impacts the blades to drive the separation component of the next sand and gravel separation device to rotate, and the mesh apertures on the mesh cylinders of the multiple sand and gravel separation devices decrease in sequence to achieve multi-stage filtration of rainwater and separate sand and gravel particles of different particle sizes contained therein.
[0015] 3. The utility model uses the kinetic energy of rainwater flowing down from a high place to impact the blades, so that the blades rotate with the cylinder, and the cylinder rotates with the net cylinder. There is no need to set up a separate power element, which is energy-saving and environmentally friendly.
[0016] 4. The utility model arranges a plurality of guide blades distributed in a spiral shape in the mesh cylinder. During the rotation of the mesh cylinder, on the one hand, the sand and gravel particles and impurities in the mesh cylinder roll downstream along the inclined mesh cylinder under their own gravity. On the other hand, the guide blades transport the sand and gravel particles and impurities downstream, and then the sand and gravel particles and impurities in the mesh cylinder are transported to the top of the inclined plate and then roll down and discharged from the box through the impurity discharge port.
[0017] 5. The utility model arranges a tube body on the cover body, and a sphere is arranged in the tube body. The sphere falls on the top of the mesh tube under the action of gravity. As the mesh tube rotates, when the fan-shaped plate passes through the strip groove and enters the tube body, the sphere is pushed upward. When the fan-shaped plate passes through the strip groove and leaves the tube body, the sphere falls and hits the mesh tube, causing the mesh tube to vibrate, effectively avoiding clogging of the mesh tube and facilitating the sand and gravel impurities in the mesh tube to roll downstream.
[0018] 6,The utility model discloses a guide plate is arranged on the inclined plate, the arc direction of guide plate is identical with the net cylinder lateral wall, and guide plate is located the net cylinder side away from the impurity discharge port one side, and then the sandstone particle that exports from the net cylinder to the inclined plate under the action of guide plate can not be accumulated in the end of the inclined plate away from the impurity discharge port, and then be favorable to the impurity such as sandstone particle on the inclined plate and is discharged from the impurity discharge port. BRIEF DESCRIPTION OF DRAWINGS
[0019] Figure 1 It is the structure diagram of the utility model Figure 1 .
[0020] Figure 2 It is the structure diagram of the utility model Figure 2 .
[0021] Figure 3 It is the structure diagram of the utility model Figure 3 .
[0022] Figure 4 It is the structure diagram of the utility model after removing the cover body.
[0023] Figure 5 It is the structure diagram of the utility model box Figure 1 .
[0024] Figure 6 It is the structure diagram of the utility model box Figure 2 .
[0025] Figure 7 It is the structure diagram of the utility model cover body Figure 1 .
[0026] Figure 8 It is the structure diagram of the utility model cover body Figure 2 .
[0027] Figure 9 It is the structure diagram of the utility model separation component.
[0028] Figure 10 It is the utility model Figure 1 The enlarged view of A.
[0029] Figure 11 It is the utility model Figure 8 The enlarged view of B.
[0030] The numbers in the accompanying drawings are: 1 for the box body, 2 for the cover body, 3 for the water inlet, 4 for the water outlet, 5 for the rotating shaft, 6 for the cylinder body, 7 for the blade, 8 for the mesh cylinder, 9 for the guide blade, 10 for the inclined plate, 11 for the support plate, 12 for the debris discharge port, 13 for the support frame, 14 for the bearing seat, 15 for the annular support ring, 16 for the support rod, 17 for the guide plate, 18 for the support plate, 19 for the fan-shaped plate, 20 for the tube body, 21 for the strip groove, and 22 for the sphere. DETAILED DESCRIPTION
[0031] The present invention will be further described below with reference to the accompanying drawings and specific embodiments:
[0032] like Figures 1 to 11 As shown, this embodiment provides a rainwater collection and gravel separation device, which is provided in multiple arrangements and is tilted in sequence from top to bottom along the slope of the hillside. Each rainwater collection and gravel separation device comprises a box body 1 and a cover body 2 tilted along the direction of water flow. A water inlet 3 is provided at the upstream end of the cover body 2, and a water outlet 4 is provided at the lower portion of the downstream end of the box body 1. Two adjacent sand and gravel separation devices are connected by pipes, that is, the water outlet 4 is connected to the water inlet 3 adjacent to the downstream thereof. A rotating shaft 5 and a separation component sleeved on the rotating shaft 5 are rotatably provided in the box body 1, as shown in FIG. Figure 2 As shown, support frames 13 are fixedly provided at both ends of the box body 1, and bearing seats 14 are fixedly provided on the support frames 13. After the two ends of the rotating shaft 5 extend out of the box body 1, they are rotatably connected to the bearing seats 14 through bearings. Both ends of the rotating shaft 5 pass through the cover body 2, and the support frame 13 makes it easy to install and support the sand and gravel separation device.
[0033] like Figure 1 or Figure 9 As shown, the separation component includes a power part and a separation part, and the power part includes a cylinder 6 and a plurality of blades 7. The plurality of blades 7 are fixedly arranged circumferentially between the rotating shaft 5 and the inner wall of the cylinder 6 and correspond to the water inlet 3. The rainwater flow at the water inlet 3 impacts the blades 7 to drive the cylinder 6 to rotate. A first sleeve is fixedly provided on the rotating shaft 5, and the blades 7 are fixedly arranged between the first sleeve and the cylinder 6. The blades 7 extend axially along the cylinder 6 and are arranged obliquely along the circumference of the cylinder 6. After the rainwater flowing down the ditch along the hillside first passes through a filter screen or a filter plate to simply separate the dead branches and leaves or large-sized stones therein, it is transported to the water inlet 3 located upstream through a pipeline inclined along the hillside. The kinetic energy of the rainwater entering the box 1 at the water inlet 3 impacts the blades 7 in the cylinder 6, and then the blades 7 drive the cylinder 6 to rotate.
[0034] like Figure 1As shown, the separation piece includes a mesh cylinder 8 and a plurality of guide vanes 9, the mesh cylinder 8 is a cylinder structure with a plurality of mesh holes on the side wall, the mesh hole diameter of the mesh cylinder 8 on which a plurality of sand and stone separation devices are arranged in turn from top to bottom along the slope gradient decreases in turn, the mesh cylinder 8 is coaxially fixedly connected with the cylinder body 6, the rainwater in the cylinder body 6 continues to flow forward to the mesh cylinder 8, after entering the mesh cylinder 8, the rainwater falls through the mesh hole of the side wall of the mesh cylinder 8 into the box body 1, and flows out through the water outlet 4, and is transported to the water inlet 3 of the next sand and stone separation device through the pipeline, while the sand and stone particles with a certain particle size mixed in the rainwater are left in the mesh cylinder 8, and since the box body 1 is inclined, the mesh cylinder 8 is also inclined, the sand and stone particles in the mesh cylinder 8 roll downstream under the action of their own gravity, a plurality of the guide vanes 9 are arranged in a spiral shape on the inner wall of the mesh cylinder 8, the mesh cylinder 8 is used for separating sand and stone in rainwater, and the guide vanes 9 are used for guiding the sand and stone in the mesh cylinder 8 to the downstream end, in the process of rotation of the mesh cylinder 8, the mesh cylinder 8 rotates with the plurality of guide vanes 9, and then under the action of the guide vanes 9, the sand and stone particles in the mesh cylinder 8 are transported downstream.
[0035] As shown in the figure, Figure 4-6 As shown, the box body 1 is also provided with a impurity removal assembly, the impurity removal assembly includes an inclined plate 10, a support plate 11 and an impurity removal opening 12 opened on one side of the box body 1, the box body 1 is inclinedly provided with the inclined plate 10, the end of the inclined plate 10 is provided with the impurity removal opening 12, the both sides of the inclined plate 10 are fixedly connected with the downstream end side plate of the box body 1 and the support plate 11 respectively, the upper side of the support plate 11 is provided with an arc-shaped groove, one end of the mesh cylinder 8 is coaxially fixedly connected with the cylinder body 6, and the other end is located in the arc-shaped groove, the sand and stone particles in the mesh cylinder 8 are transported to above the inclined plate 10 along with the rotation of the mesh cylinder 8, and roll or slide along the inclined surface of the inclined plate 10 to the impurity removal opening 12 to be discharged, the sand and stone particles on the inclined plate 10 are limited by the support plate 11 and the downstream end side plate of the box body 1, so as to avoid falling into the box body 1, a guide plate 17 is fixedly arranged between the support plate 11 and the end side plate of the box body 1, the guide plate 17 is located on the side of the mesh cylinder 8 away from the impurity removal opening 12, the guide plate 17 is arc-shaped and the arc-shaped direction extends along the circumference of the mesh cylinder 8, a support plate 18 is fixedly arranged between the guide plate 17 and the inclined plate 10 located above the guide plate 17, the guide plate 17 is supported by the support plate 18, the sand and stone particles discharged from the mesh cylinder 8 fall on the guide plate 17, since the inclination gradient of the guide plate 17 is much larger than that of the inclined plate 10, the sand and stone particles roll or slide to the side of the inclined plate 10 close to the impurity removal opening 12, which is conducive to the discharge of the sand and stone particles above the inclined plate 10.
[0036] The rotating shaft 5 is sequentially fixed with a plurality of second sleeves, and each second sleeve is provided with an annular support ring 15 which is fixedly connected with the inner wall of the mesh cylinder 8, and a plurality of support rods 16 are fixedly arranged between each annular support ring 15 and the corresponding second sleeve in the circumferential direction, the annular support ring 15 is supported by the second sleeve mounting support rod 16, and then the annular support ring 15 and the mesh cylinder 8 are fixedly connected by bolts, thereby effectively ensuring the structural strength of the mesh cylinder 8 and avoiding deformation, thereby ensuring the smooth operation of the sand and stone separation of rainwater.
[0037] As shown in Figure 1 With Figure 3 As shown, a plurality of fan-shaped plates 19 are fixedly arranged on the outer arc surface of the mesh cylinder 8, and the plurality of fan-shaped plates 19 are distributed in a spiral shape, as shown in Figure 7-8 A plurality of pipe bodies 20 are vertically and longitudinally arranged on the cover body 2, and a strip-shaped through slot 21 is formed in the lower end of each pipe body 20, each strip-shaped through slot 21 longitudinally and circumferentially penetrates the lower end of the corresponding pipe body 20, each fan-shaped plate 19 is correspondingly matched with the strip-shaped through slot 21 of the corresponding pipe body 20, and a spherical body 22 is movably arranged in each pipe body 20, as shown in Figure 3 As shown, when the fan-shaped plate 19 rotates into the corresponding pipe body 20, the arc side surface of the fan-shaped plate 19 contacts and pushes up the spherical body 22 in the pipe body 20, and as the mesh cylinder 8 continues to rotate, the fan-shaped plate 19 leaves the pipe body 20, and the spherical body 22 falls under the action of gravity, hits the mesh cylinder 8, and then the mesh cylinder 8 vibrates, on the one hand, effectively reducing the blockage of the mesh cylinder 8, and on the other hand, facilitating the downstream conveying of sand and stone particles and the like.
[0038] In use, the rainwater flowing along the ditch of the slope is first separated from the dry branches, fallen leaves or large-diameter stones and the like by the filter screen or the filter plate, and then is conveyed to the water inlet 3 located in the upstream by the pipeline arranged obliquely along the slope, the rainwater enters the cylinder body 6 from the water inlet 3 and impacts the blade 7 in the cylinder body 6, and then the blade 7 drives the cylinder body 6 and the mesh cylinder 8 to rotate, the rainwater in the cylinder body 6 continues to flow forward into the mesh cylinder 8, and after entering the mesh cylinder 8, the rainwater falls through the mesh holes in the side wall of the mesh cylinder 8 into the box body 1 and flows out through the water outlet 4, while the sand and stone particles mixed in the rainwater are left in the mesh cylinder 8, thereby realizing the separation of sand and stone particles in the rainwater.
[0039] Meanwhile, since the box body 1 is arranged obliquely, the mesh cylinder 8 is arranged obliquely, and the sand particles and the like in the mesh cylinder 8 roll downstream under the action of gravity, and in the process of rotation of the mesh cylinder 8, the guide vanes 9 also have the conveying effect on the rolling of the sand particles, and at the same time, with the rotation of the mesh cylinder 8, when the sector plate 19 rotates to the corresponding pipe body 20, the sector plate 19 pushes up the ball 22 in the pipe body 20 upward, and with the continuous rotation of the mesh cylinder 8, the sector plate 19 leaves the pipe body 20, and the ball 22 falls under the action of gravity, hits the mesh cylinder 8, and then the mesh cylinder 8 vibrates, and with the multiple balls 22 hitting and vibrating the mesh cylinder 8 in turn, on the one hand, the clogging of the mesh cylinder 8 is effectively reduced, and on the other hand, the sand particles and the like in the mesh cylinder 8 are beneficial to be conveyed downstream, and the sand particles and the like in the mesh cylinder 8 are conveyed to the downstream end of the mesh cylinder 8 and fall on the inclined plate 10, and under the guiding action of the inclined plate 10 and the upper side inclined surface of the guide plate 17, the sand particles and the like roll or slide to the impurity discharge port 12 and are discharged from the box body 1.
[0040] It should be noted that the rainwater collecting sand and stone separating device of the utility model is arranged as multiple and arranged obliquely from top to bottom along the slope gradient of a hill, the water outlet 4 of the sand and stone separating device located in the upstream is connected to the water inlet 3 of the sand and stone separating device adjacent thereto in the downstream through a pipeline, and the mesh hole diameters on the mesh cylinders 8 of the multiple sand and stone separating devices arranged obliquely from top to bottom along the slope gradient of a hill are reduced in turn, and in actual use, the sand particles and the like of different particle sizes are separated by the multiple sand and stone separating devices, and complete separation is ensured.
[0041] The above-described embodiments are only preferred embodiments of the utility model, and are not intended to limit the implementation range of the utility model, so equivalent changes or modifications made according to the structure, features and principles described in the patent range of the utility model should be included in the patent range of the utility model application.
Claims
1. A rainwater collection and gravel separation device, characterized in that: The invention comprises a box body (1) and a cover body (2) arranged obliquely along the direction of water flow, a water inlet (3) being arranged at the upstream end of the cover body (2), and a water outlet (4) being arranged at the lower part of the downstream end of the box body (1), a rotating shaft (5) and a separation component sleeved on the rotating shaft (5) being rotatably arranged in the box body (1), the separation component comprising a power part and a separation part, the power part comprising a cylinder body (6) and a plurality of blades (7), the plurality of blades (7) being fixedly arranged circumferentially between the rotating shaft (5) and the inner wall of the cylinder body (6) and corresponding to the water inlet (3), and rainwater flow from the water inlet (3) impacting the blades (7) drives the cylinder body (6) to rotate; The separation element comprises a mesh cylinder (8) and a plurality of guide blades (9), wherein the plurality of guide blades (9) are spirally arranged on the inner wall of the mesh cylinder (8), the mesh cylinder (8) is used to separate sand and gravel in rainwater, and the guide blades (9) are used to guide the sand and gravel in the mesh cylinder (8) to the downstream end; The box body (1) is further provided with a debris discharge component, which comprises an inclined plate (10), a support plate (11) and a debris discharge port (12) opened on one side of the box body (1). The inclined plate (10) is tiltedly arranged in the box body (1), and the debris discharge port (12) is provided at the end of the inclined plate (10). Both sides of the inclined plate (10) are fixedly connected to the downstream side plate of the box body (1) and the support plate (11), respectively. An arc groove is provided on the upper side of the support plate (11), and one end of the net cylinder (8) is coaxially fixedly connected to the cylinder body (6), and the other end is located in the arc groove.
2. A rainwater collection and gravel separation device according to claim 1, characterized in that: Support frames (13) are fixedly provided at both ends of the box body (1), and bearing seats (14) are fixedly provided on the support frames (13). After extending out of the box body (1), both ends of the rotating shaft (5) are rotatably connected to the bearing seats (14) via bearings.
3. The rainwater collection and gravel separation device according to claim 1, characterized in that: A first sleeve is fixedly sleeved on the rotating shaft (5), and the blades (7) are fixedly arranged between the first sleeve and the cylinder (6). The blades (7) extend axially along the cylinder (6) and are arranged obliquely along the circumference of the cylinder (6).
4. The rainwater collection and gravel separation device according to claim 1, characterized in that: A plurality of second sleeves are fixedly sleeved on the rotating shaft (5) in sequence, and an annular support ring (15) is provided on the outside of each second sleeve. The annular support ring (15) is fixedly connected to the inner wall of the net cylinder (8), and a plurality of support rods (16) are fixedly provided between each annular support ring (15) and the corresponding second sleeve along the circumference thereof.
5. The rainwater collection and gravel separation device according to claim 1, characterized in that: A guide plate (17) is fixedly provided between the support plate (11) and the end side plate of the box body (1). The guide plate (17) is located on the side of the net cylinder (8) away from the impurity discharge port (12). The guide plate (17) is arc-shaped and the arc direction extends along the circumference of the net cylinder (8). The guide plate (17) is located above the inclined plate (10) and a support plate (18) is fixedly provided between the guide plate (17) and the inclined plate (10).
6. The rainwater collection and gravel separation device according to claim 1, characterized in that: A plurality of fan-shaped plates (19) are fixedly provided on the outer arc surface of the net cylinder (8), and the plurality of fan-shaped plates (19) are distributed in a spiral shape. A plurality of tubes (20) are passed through the cover body (2) from top to bottom, and a strip-shaped through-slot (21) is provided at the lower end of each tube (20). Each strip-shaped through-slot (21) passes through the lower end of the corresponding tube (20) along the circumference of the net cylinder. Each fan-shaped plate (19) is matched with the strip-shaped through-slot (21) of the corresponding tube (20), and a sphere (22) is movably provided in each tube (20).