High-quality tin powder screening device

Abstract

The invention relates to the related technical field of metal powder screening, and discloses a high-quality tin powder screening device which comprises a support, a feeding mechanism and a screening mechanism, the feeding mechanism and the screening mechanism are installed on the support, the feeding mechanism is connected with the screening mechanism, and the screening mechanism is connected with the feeding mechanism. The screening mechanism comprises a screening cylinder, an anti-blocking gas hood, a central pipe, a blower device, a negative pressure pipe and a return pipe, a screening cylinder body is provided with a plurality of screening holes, the anti-blocking gas hood comprises an inner shade arranged in the screening cylinder and an outer shade arranged outside the screening cylinder, a flow channel gap is formed between the inner shade and the outer shade, and the central pipe is connected with the central pipe. Air flow in the center pipe flows back into the flow channel gap through the backflow pipe, high-speed air flow is formed in the center pipe, air in the flow channel gap flows into the center pipe through the negative pressure pipe and drives sand on the screening barrel to be separated from the screening barrel, and therefore the anti-blocking effect is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field related to the screening of metal powders, and more specifically, particularly relates to a high-quality tin powder screening device. Background Art

[0002] After the formation of metal powders, different requirements are imposed on particles of different diameters. Existing metal powder screening devices usually use sieves with different pore diameters to screen them. During the screening process, blockages will inevitably occur. After the particles block the sieve holes, the screening efficiency is greatly reduced. To reduce the risk of blockage, existing technologies usually install vibration generating devices on the sieve, and by vibrating, the blocked particles are separated from the sieve holes. However, the following technical problems exist in the existing technologies.

[0003] During the screening of existing metal powders, a large amount of metal powders will accumulate on the sieve. As the amount of accumulated metal powders increases, the gravity borne by the sieve increases, and its own inertia increases, making it more difficult to vibrate. Therefore, the effect of the vibration generator is reduced, and it is more likely to be blocked, reducing the screening efficiency.

[0004] To improve the screening efficiency, some people have proposed to use the effect of negative pressure to increase the screening speed. Similarly, due to a large amount of powders accumulating on the sieve, a large number of particles block the sieve holes of the sieve, and the negative pressure cannot well increase the powder screening speed.

[0005] Therefore, in view of this, research and improvement are carried out on the existing structure and deficiencies, and a high-quality tin powder screening device is provided, with the expectation of achieving a more practical value. Summary of the Invention

[0006] The present invention provides a high-quality tin powder screening device to overcome the above defects in the prior art.

[0007] The purpose and efficacy of a high-quality tin powder screening device of the present invention are achieved by the following specific technical means: A high-quality tin powder screening device, comprising a bracket, a feeding mechanism and a screening mechanism. The feeding mechanism and the screening mechanism are installed on the bracket. The feeding mechanism is connected to the screening mechanism. The screening mechanism includes a screening cylinder, an anti-blocking air hood, a central pipe, a blowing device, a negative pressure pipe and a return pipe. The screening cylinder body has a number of screening holes. The anti-blocking air hood includes an inner mask arranged inside the screening cylinder and an outer mask arranged outside the screening cylinder. A flow channel gap is formed between the inner mask and the outer mask, and the lower sides of the inner mask and the outer mask are open so that the lower side of the screening cylinder is exposed. The central pipe is arranged at the center of the screening cylinder. One end of the negative pressure pipe is connected to the central pipe, and the other end of the negative pressure pipe is connected to the inner mask. The negative pressure pipe communicates the flow channel gap and the central pipe. The blowing device is arranged at one end of the central pipe and communicates with the central pipe. The end of the central pipe away from the blowing device is connected to the return pipe. The upper end of the return pipe extends upward and is connected to the outer mask. The central pipe communicates with the flow channel gap through the return pipe, and the air pressure gradually decreases from the outside to the inside in the flow channel gap.

[0008] A further technical solution is that the return pipe includes an air flow deceleration box with a gradually increasing inner diameter, a sand discharge pipe and an exhaust pipe. The end of the air flow deceleration box with a smaller inner diameter has a connector, and the connector is rotatably connected to one end of the central pipe. The upper end of the air flow deceleration box communicates with the exhaust pipe, and the upper end of the exhaust pipe is connected to the outer mask through a pipe so that the exhaust pipe communicates with the flow channel space. The lower side of the air flow deceleration box is connected to the sand discharge pipe, and the lower side outlet of the sand discharge pipe extends towards the inside of the screening cylinder.

[0009] A further technical solution is that a sealing door is swingably arranged on the inner wall of the exhaust pipe, and a first telescopic rod is hingedly arranged on the inner wall of the exhaust pipe. The end of the first telescopic rod is hinged to the sealing door; and / or, a sand sealing door is swingably arranged in the sand discharge pipe, and a second telescopic rod is hingedly arranged on the inner wall of the sand discharge pipe. The end of the second telescopic rod is hinged to the sand sealing door.

[0010] A further technical solution is that the number of the screening cylinders is multiple. The screening cylinder with a larger diameter is sleeved outside the screening cylinder with a smaller diameter. A buffer body is connected between two adjacent screening cylinders, and a screening gap is formed between two adjacent screening cylinders. Different screening spaces communicate with different pipes.

[0011] Further technical solution: The high-quality tin powder screening device further includes a vibration unit. The vibration unit includes an elastic rod fixedly connected to the outside of the central tube. An installation space is provided inside the elastic rod. A striker, a collision block, a return spring and an electromagnet are arranged in the installation space. The striker is embedded inside the elastic rod, with one end extending outward and connecting to the screening cylinder, and the other end located inside the installation space. The return spring is arranged between the collision block and the striker, and the electromagnet is arranged on one side close to the collision block.

[0012] Further technical solution: The outside of the anti-blocking air hood is connected to the support. A rotating box is arranged between the central tube and the negative pressure tube. The rotating box is rotatably connected to the outside of the central tube. The central tube is provided with ventilation holes, and the ventilation holes communicate with the rotating box. The outside of the rotating box communicates with the negative pressure tube; and / or, the outer end of the negative pressure tube inclines towards the direction of the air blowing device, so as to form an acute angle between the negative pressure tube and the central tube.

[0013] Further technical solution: The outer cover is provided with a plurality of air inlet holes opening outward. An air inlet box is arranged outside the outer cover. The air inlet box is connected to the exhaust pipe through a pipeline; and / or, the exhaust pipe is arranged vertically, and the inner wall of the exhaust pipe has a plurality of protruding bodies for blocking sand, and the protruding bodies are distributed alternately at intervals up and down.

[0014] Further technical solution: The feeding mechanism includes a feeding funnel, a feeding pipe body, a power rod, a sand shielding piece and blades. The upper side of the feeding pipe body is connected to the feeding funnel. A sand shielding piece is installed inside the feeding pipe body. The sand shielding piece has a central hole, and the power rod is rotatably arranged in the central hole. The blades are sleeved outside the power rod, and one end of the power rod is connected to the central tube.

[0015] Further technical solution: The high-quality tin powder screening device further includes a power device. The power device includes a power box, a motor, a first pulley, a second pulley and a belt. The power box is connected to one end of the feeding pipe. The first pulley and the second pulley are rotatably arranged inside the power box. The belt connects the first pulley and the second pulley. The motor is installed on the power box, the shaft of the motor is connected to the first pulley, and the shaft of the second pulley is connected to the power rod.

[0016] Compared with the prior art, the present invention has the following beneficial effects: In a high-quality tin powder screening device of the present invention, by setting a screening cylinder, an outer mask, an inner mask, a central tube, and a negative pressure tube, the screening cylinder rotates to screen the powder, and sands of different particle sizes are separated by the screening cylinder. To reduce the blockage of the screening cylinder, a blowing device sends air flow into the central tube, and the air flow in the central tube returns to the flow channel gap through a return pipe to complete a cycle. During this process, a high-speed air flow is formed in the central tube. The negative pressure tube is connected to the central tube. Since the flow velocity in the central tube is high and the air pressure is low, the gas in the flow channel gap flows into the central tube through the negative pressure tube and drives the sands on the screening cylinder to break away from the screening cylinder to achieve the anti-blocking effect. Since the inner mask and the outer mask are close to each other, the gap formed between them is small, and the negative pressure in the negative pressure tube can better act on the inner wall of the screening cylinder, resulting in a better adsorption effect. In addition, due to the rotation of the screening cylinder itself, the part of the screening cylinder rotating to the lower side screens the powder, and the part on the upper side of the screening cylinder does not contact a large amount of powder. The negative pressure tube acts on the upper part of the screening cylinder to adsorb it to achieve a good blocking effect.

[0017] In a high-quality tin powder screening device of the present invention, by setting an air flow deceleration box, a mixture of gas and powder flows in the central tube. The high-speed flowing mixture enters the air flow deceleration box. Since the internal volume of the air flow deceleration box gradually increases, the air flow velocity decreases. Under the action of gravity, the powder deposits downward, and the air separates on the upper side. The powder accumulates at the bottom of the air flow deceleration box and enters the sand discharge pipe, and the sand is re-discharged into the interior of the screening cylinder through the sand discharge pipe.

[0018] In a high-quality tin powder screening device of the present invention, by setting an elastic rod, a striker, and a collision block, the electromagnet in the elastic rod drives the collision block to reciprocate in the installation space. The collision block continuously impacts the striker, and the striker transmits the vibration to the screening cylinder. During this process, a return spring is used to reset the collision block. The screening cylinder is vibrated, and the sands blocking the holes are shaken out, achieving the effect of reducing blockage. Brief Description of the Drawings

[0019] Figure 1 is the overall structural schematic diagram of the present invention; Figure 2 is the front view structural schematic diagram of the present invention; Figure 3 is Figure 2 the longitudinal sectional view of Figure 4 is the structural schematic diagram of the screening mechanism 12 in the present invention; Figure 5 is the left view of the screening mechanism 12 in the present invention; Figure 6 is the right view of the screening mechanism 12 in the present invention; Figure 7 is Figure 4 the longitudinal sectional view of the screening mechanism 12 in Figure 8 is Figure 5 a longitudinal sectional view of the screening mechanism 12 in the middle.

[0020] Description of the reference numerals: 10 bracket, 11 feeding mechanism, 12 screening mechanism, 13 screening cylinder, 14 central pipe, 15 negative pressure pipe, 16 return pipe, 17 screening holes, 18 inner mask, 19 outer mask, 20 flow path gap, 21 air flow deceleration box, 22 sand discharge pipe, 23 exhaust pipe, 24 sealing door, 25 first telescopic rod, 26 sand sealing door, 27 second telescopic rod, 28 elastic rod, 29 rotating box, 30 air inlet holes, 31 air inlet box, 32 feeding funnel, 33 feeding pipe body, 34 power rod, 35 sand shielding piece, 36 blades, 37 power box, 38 motor, 39 first pulley, 40 second pulley, 41 belt. Detailed implementation manners

[0021] The following further describes the implementation manners of the present invention in detail in conjunction with the drawings and embodiments. The following embodiments are used to illustrate the present invention, but cannot be used to limit the scope of the present invention.

[0022] In the description of the present invention, unless otherwise specified, "a plurality of" means two or more; the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "inner", "outer", "front end", "rear end", "head", "tail", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0023] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations. Embodiment 1

[0024] As shown in the attached Figure 1 to the attached Figure 8 shown: A high-quality tin powder screening device, as shown in Figure 1 and Figure 2As shown, it includes a bracket 10, a feeding mechanism 11 and a screening mechanism 12. The feeding mechanism 11 and the screening mechanism are installed on the bracket 10. The feeding mechanism 11 is connected to the screening mechanism 12. Figure 4 , Figure 5 and Figure 7 As shown, the screening mechanism 12 includes a screening drum 13, an anti-blocking air cover, a central tube 14, an air blowing device, a negative pressure tube 15 and a return tube 16. The screening drum 13 body has a plurality of screening holes 17. The anti-blocking air cover includes an inner mask 18 arranged in the screening drum and an outer mask 19 arranged outside the screening drum. A flow channel gap 20 is formed between the inner mask 18 and the outer mask 19, and the lower sides of the inner mask 18 and the outer mask 19 are open to expose the lower side of the screening drum to the outside. The central tube 14 is arranged at the screening drum 13. Center, one end of the negative pressure tube 15 is connected to the central tube 14, the other end of the negative pressure tube 15 is connected to the inner mask 18, the negative pressure tube 15 connects the flow channel gap 20 and the central tube 14, the blowing device is arranged at one end of the central tube 14 and connected to the central tube 14, the end of the central tube 14 away from the blowing device is connected to the return pipe 16, the upper end of the return pipe 16 extends upward and is connected to the outer mask 19, the central tube 14 is connected to the flow channel gap 20 through the return pipe 16, and the air pressure in the flow channel gap 20 gradually decreases from the outside to the inside.

[0025] In this embodiment, the tin powder or other powder to be screened is injected into the feeding mechanism 11, and the feeding mechanism 11 transports the powder to the inside of the screening cylinder. Sands of different particle sizes are separated by the screening cylinder. In order to reduce the blockage of the screening cylinder, the blowing device sends the airflow into the central tube 14, and a high-speed airflow is formed in the central tube 14. The negative pressure tube 15 is connected to the central tube 14. Since the central tube 14 has a high flow rate and a low air pressure, the gas in the flow channel gap 20 flows into the central tube 14 through the negative pressure tube 15, and drives the sand on the screening cylinder to leave the screening cylinder, so as to achieve the effect of preventing blockage. The airflow in the central tube 14 flows back to the flow channel gap 20 through the return pipe 16 to complete a cycle. In this process, since the inner mask 18 and the outer mask 19 are close to each other, the gap formed between the two is small, and the negative pressure in the negative pressure pipe 15 can better act on the inner wall of the screening cylinder, and the adsorption effect is better. Since the screening cylinder rotates itself, the screening cylinder rotates to the lower part to screen the powder, and the upper part of the screening cylinder does not contact a large amount of powder. The negative pressure pipe 15 acts on the upper part of the screening cylinder to adsorb it to achieve a good blocking effect.

[0026] Preferably, Figure 6 and Figure 7As shown, the reflux pipe 16 includes an air flow deceleration box 21 with a gradually increasing inner diameter, a sand discharge pipe 22, and an exhaust pipe 23. One end of the air flow deceleration box 21 with a smaller inner diameter has a joint, and the joint is rotatably connected to one end of the central pipe 14. The upper end of the air flow deceleration box 21 communicates with the exhaust pipe 23, and the upper end of the exhaust pipe 23 is connected to the outer mask 19 through a pipe so that the exhaust pipe 23 communicates with the flow channel space. The lower side of the air flow deceleration box 21 is connected to the sand discharge pipe 22, and the lower side outlet of the sand discharge pipe 22 extends towards the inside of the screening cylinder 13.

[0027] In this embodiment, a mixture of gas and powder flows through the central pipe 14. The mixture flowing at a high speed enters the air flow deceleration box 21. Since the internal volume of the air flow deceleration box 21 gradually increases, the air flow speed decreases. Under the action of gravity, the powder deposits downward, and the air is separated on the upper side. The powder accumulates at the bottom of the air flow deceleration box 21 and enters the sand discharge pipe 22, and the sand is re-discharged into the inside of the screening cylinder 13 through the sand discharge pipe.

[0028] Preferably, a sealing door 24 is swingably arranged on the inner wall of the exhaust pipe 23, a first telescopic rod 25 is hingedly arranged on the inner wall of the exhaust pipe 23, and the end of the first telescopic rod 25 is hinged to the sealing door 24.

[0029] As Figure 7 shown, in this embodiment, a sand sealing door 26 is swingably arranged in the sand discharge pipe 22, a second telescopic rod 27 is hingedly arranged on the inner wall of the sand discharge pipe 22, and the end of the second telescopic rod 27 is hinged to the sand sealing door 26.

[0030] In this embodiment, the first telescopic rod 25 expands and contracts to adjust the angle of the sealing door 24, thereby realizing the opening or closing of the exhaust pipe 23. The second telescopic rod 27 expands and contracts to adjust the angle of the sand sealing door 26, thereby realizing the opening or closing of the sand discharge pipe 22.

[0031] During normal operation, the exhaust pipe 23 is opened and the sand discharge pipe 22 is closed. The powder deposits downward, and the air is separated on the upper side. The air is discharged through the exhaust pipe 23 to complete the separation effect of air and powder. When the powder accumulates for a period of time, the exhaust pipe 23 is closed and the sand discharge pipe 22 is closed. The air pressure in the air flow deceleration box 21 increases to a set value, and the sand discharge pipe 22 starts, thereby quickly discharging the powder.

[0032] Preferably, the number of the screening cylinders 13 is multiple. As Figure 8 shown, in this embodiment, there are two screening cylinders 13. The screening cylinder 13 with a larger diameter is sleeved outside the screening cylinder 13 with a smaller diameter. A buffer body is connected between adjacent two screening cylinders 13, and a screening gap is formed between adjacent two screening cylinders 13. Different screening spaces communicate with different pipes.

[0033] In this embodiment, different screening cylinders 13 have screening holes with different diameters, and from the inside to the outside, the diameters of the screening holes gradually decrease to screen powders with different particle sizes. After screening, powders with different particle sizes are discharged through different pipelines.

[0034] Preferably, as Figure 7 shown, the high-quality tin powder screening device further includes a vibration unit. The vibration unit includes an elastic rod 28 fixedly connected to the outside of the central tube 14. The elastic rod 28 has an installation space inside. A striker, a collision block, a return spring, and an electromagnet are arranged in the installation space. The striker is embedded inside the elastic rod 28, one end extends outward and is connected to the screening cylinder 13, and the other end is located inside the installation space. A return spring is arranged between the collision block and the striker, and the electromagnet is arranged on one side close to the collision block.

[0035] In this embodiment, the electromagnet drives the collision block to reciprocate in the installation space. The collision block continuously impacts the striker, and the striker transmits the vibration to the screening cylinder. During this process, the return spring is used to reset the collision block. The screening cylinder is vibrated, and the sand blocked in the holes is shaken out, achieving the effect of reducing blockage.

[0036] Preferably, the outside of the anti-blocking air hood is connected to the bracket 10. A rotating box 29 is arranged between the central tube 14 and the negative pressure tube 15. The rotating box 29 is rotatably connected to the outside of the central tube 14. The central tube 14 is provided with ventilation holes, and the ventilation holes communicate with the rotating box 29. The outside of the rotating box 29 communicates with the negative pressure tube 15.

[0037] As Figure 7 shown, in this embodiment, the outer end of the negative pressure tube 15 is inclined towards the direction of the air blowing device, so that an acute angle is formed between the negative pressure tube 15 and the central tube 14.

[0038] Preferably, the outer shield 19 is provided with a plurality of air intake holes 30 opening outwards. An air intake box 31 is arranged outside the outer shield 19, and the air intake box 31 is connected to the exhaust pipe 23 through a pipeline.

[0039] As Figure 7 shown, in this embodiment, the exhaust pipe 23 is arranged vertically, and the inner wall of the exhaust pipe 23 has a plurality of protruding bodies for blocking sand, and the protruding bodies are alternately distributed at intervals up and down.

[0040] In this embodiment, the air flow flows upwards in the air flow deceleration box 21. Some of the sand grains carried in the air flow touch the protruding bodies, thereby reducing the upward movement speed of the sand grains. The plurality of protruding bodies continuously hinder the upward trend of the sand grains, playing a role in further separation.

[0041] Preferably, as Figure 3As shown, the feeding mechanism 11 includes a feeding funnel 32, a feeding tube body 33, a power rod 34, a sand shielding piece 35 and a blade 36. The upper side of the feeding tube body 33 is connected to the feeding funnel 32. A sand shielding piece 35 is installed in the feeding tube body 33. The sand shielding piece 35 has a center hole. The power rod 34 is rotatably arranged in the center hole. The outer side of the power rod 34 is covered with a blade 36. One end of the power rod 34 is connected to the center tube 14.

[0042] Preferably, Figure 3 As shown, the high-quality tin powder screening device also includes a power device, which includes a power box 37, a motor 38, a first pulley 39, a second pulley 40 and a belt 41. The power box 37 is connected to one end of the feeding tube, and the first pulley 39 and the second pulley 40 are rotatably arranged in the power box 37. The belt 41 connects the first pulley 39 and the second pulley 40. The motor 38 is installed on the power box 37, and the shaft of the motor 38 is connected to the first pulley 39, and the shaft of the second pulley 40 is connected to the power rod 34.

[0043] In this embodiment, the motor 38 is started to drive the first pulley 39, the belt 41, and the second pulley 40 to move. The second pulley 40 drives the power rod 34 to rotate, and the power rod 34 drives the blades 36 to rotate to transport the powder to be screened.

[0044] Specific use of the present invention: The first step is to inject the tin powder or other powder to be screened into the feed hopper 32, start the motor 38, drive the first pulley 39, the belt 41, and the second pulley 40 to move, the second pulley 40 drives the power rod 34 to rotate, the power rod 34 drives the blade 36 to rotate, and the powder is input into the interior of the screening cylinder.

[0045] In the second step, the power rod 34 drives the central tube 14 to rotate, and the central tube 14 drives the screening cylinder to rotate through the elastic rod 28 to screen the powder. Sand of different particle sizes is separated by the screening cylinder. In order to reduce the blockage of the screening cylinder, the blowing device sends the airflow into the central tube 14, and the airflow in the central tube 14 flows back to the flow channel gap 20 through the return pipe 16 to complete a cycle. In this process, a high-speed airflow is formed in the central tube 14, and the negative pressure pipe 15 is connected to the central tube 14. Since the central tube 14 has a high flow rate and low air pressure, the gas in the flow channel gap 20 flows into the central tube 14 through the negative pressure pipe 15, and drives the sand on the screening cylinder to leave the screening cylinder to achieve the effect of anti-blocking. Since the inner mask 18 and the outer mask 19 are close to each other, the gap formed between the two is small, and the negative pressure in the negative pressure pipe 15 can better act on the inner wall of the screening cylinder, and the adsorption effect is better.

[0046] Step 3: The electromagnet inside the elastic rod 28 drives the striker to reciprocate within the installation space. The striker continuously impacts the firing pin, and the firing pin transmits the vibration to the screening cylinder. During this process, the return spring is used to reset the striker. The screening cylinder is vibrated, and the sand blocking the holes is shaken out, achieving the effect of reducing blockage.

[0047] Step 4: A mixture of gas and powder flows through the central pipe 14. The mixture flowing at high speed enters the air flow deceleration box 21. Since the internal volume of the air flow deceleration box 21 gradually increases, the air flow speed decreases. Under the action of gravity, the powder deposits downward, and the air separates on the upper side. The powder accumulates at the bottom of the air flow deceleration box 21 and enters the sand discharge pipe 22, and the sand is re-discharged into the interior of the screening cylinder 13 through the sand discharge pipe.

[0048] The embodiments of the present invention are given for purposes of illustration and description, and are not exhaustive or limit the invention to the disclosed form. Many modifications and variations are obvious to those of ordinary skill in the art. The embodiments are chosen and described in order to better explain the principles of the invention and its practical application, and to enable those of ordinary skill in the art to understand the invention and design various embodiments with various modifications suitable for a particular purpose.

Claims

1. A high-quality tin powder screening device, comprising a bracket, a feeding mechanism and a screening mechanism, characterized in that: A feeding mechanism and the screening mechanism are installed on the bracket. The feeding mechanism is connected to the screening mechanism. The screening mechanism includes a screening cylinder, an anti-blocking air hood, a central pipe, a blowing device, a negative pressure pipe, and a return pipe. The body of the screening cylinder has a number of screening holes. The anti-blocking air hood includes an inner mask disposed inside the screening cylinder and an outer mask disposed outside the screening cylinder. A flow channel gap is formed between the inner mask and the outer mask, and the lower sides of the inner mask and the outer mask are open so that the lower side of the screening cylinder is exposed. The central pipe is disposed at the center of the screening cylinder. One end of the negative pressure pipe is connected to the central pipe, and the other end of the negative pressure pipe is connected to the inner mask. The negative pressure pipe communicates the flow channel gap and the central pipe. The blowing device is disposed at one end of the central pipe and communicates with the central pipe. The end of the central pipe away from the blowing device is connected to the return pipe. The upper end of the return pipe extends upward and is connected to the outer mask. The central pipe communicates with the flow channel gap through the return pipe, and the air pressure gradually decreases from the outside to the inside in the flow channel gap.

2. The high-quality tin powder screening device according to claim 1, wherein: The return pipe includes an air flow deceleration box with a gradually increasing inner diameter, a sand discharge pipe, and an exhaust pipe. The end of the air flow deceleration box with a smaller inner diameter has a joint, and the joint is rotatably connected to one end of the central pipe. The upper end of the air flow deceleration box communicates with the exhaust pipe, and the upper end of the exhaust pipe is connected to the outer mask through a pipe so that the exhaust pipe communicates with the flow channel space. The lower side of the air flow deceleration box is connected to the sand discharge pipe, and the lower side outlet of the sand discharge pipe extends towards the inside of the screening cylinder.

3. A high-quality tin powder screening device according to claim 2, characterized in that: A sealing door is swingably disposed on the inner wall of the exhaust pipe, and a first telescopic rod is hingedly disposed on the inner wall of the exhaust pipe. The end of the first telescopic rod is hinged to the sealing door; and / or, a sand sealing door is swingably disposed in the sand discharge pipe, and a second telescopic rod is hingedly disposed on the inner wall of the sand discharge pipe. The end of the second telescopic rod is hinged to the sand sealing door.

4. A high-quality tin powder screening device according to claim 1, characterized in that: The number of the screening cylinders is multiple. The screening cylinder with a larger diameter is sleeved outside the screening cylinder with a smaller diameter. A buffer is connected between two adjacent screening cylinders, and a screening gap is formed between two adjacent screening cylinders. Different screening spaces communicate with different pipes.

5. A high-quality tin powder screening device according to claim 1, characterized in that: The high-quality tin powder screening device further includes a vibration unit. The vibration unit includes an elastic rod fixedly connected to the outside of the central pipe. An installation space is provided inside the elastic rod. A striker, a collision block, a return spring, and an electromagnet are disposed in the installation space. The striker is embedded inside the elastic rod, extends outward at one end and is connected to the screening cylinder, and is located inside the installation space at the other end. The return spring is disposed between the collision block and the striker, and the electromagnet is disposed on the side close to the collision block.

6. The high-quality tin powder screening device according to claim 1, characterized in that: The outer side of the anti-blocking air hood is connected to the bracket. A rotating box is arranged between the central pipe and the negative pressure pipe. The rotating box is rotatably connected to the outside of the central pipe. The central pipe is provided with ventilation holes, and the ventilation holes communicate with the rotating box. The outside of the rotating box communicates with the negative pressure pipe; and / or, the outer end of the negative pressure pipe inclines towards the direction of the air blowing device, so that an acute angle is formed between the negative pressure pipe and the central pipe.

7. A high-quality tin powder screening device according to claim 1, characterized in that: The outer shield is provided with a plurality of air inlet holes opening outwards. An air inlet box is arranged outside the outer shield, and the air inlet box is connected to the exhaust pipe through a pipeline; and / or, the exhaust pipe is arranged vertically, and the inner wall of the exhaust pipe has a plurality of protruding bodies for blocking sand, and the protruding bodies are distributed alternately at intervals up and down.

8. The high-quality tin powder screening device according to claim 1, characterized in that: The feeding mechanism includes a feeding funnel, a feeding pipe body, a power rod, a sand shielding piece and blades. The upper side of the feeding pipe body is connected to the feeding funnel. A sand shielding piece is installed in the feeding pipe body. The sand shielding piece has a central hole, and the power rod is rotatably arranged in the central hole. The blades are sleeved on the outside of the power rod, and one end of the power rod is connected to the central pipe.

9. A high-quality tin powder screening device according to claim 8, characterized in that: The high-quality tin powder screening device further includes a power device. The power device includes a power box, a motor, a first pulley, a second pulley and a belt. The power box is connected to one end of the feeding pipe. The first pulley and the second pulley are rotatably arranged in the power box. The belt connects the first pulley and the second pulley. The motor is installed on the power box, the shaft of the motor is connected to the first pulley, and the shaft of the second pulley is connected to the power rod.

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