Plastic pellet vertical conveying pipe control structure with automatic control of bifurcated flow channel on and off

Abstract

A control structure for a vertical conveying pipe for plastic pellets that automatically controls the on / off state of a bifurcated flow channel comprises a vertical conveying pipe located above a material barrel, wherein the lower section of the vertical conveying pipe bifurcates into two bifurcated flow channels, namely a suction channel and a discharge channel; the discharge channel is provided with a one-way valve plate; a hollow valve block is rotatably mounted inside the vertical conveying pipe, wherein the axis of rotation of the hollow valve block extends longitudinally, and the central axis of the axis of rotation of the hollow valve block is located at the top edge of the partition wall; the hollow valve block comprises three valve plates connected together to form a triangular prism shape, wherein the three valve plates are respectively referred to as a first valve plate, a second valve plate, and a third valve plate, wherein the third edge line is close to and parallel to the axis of rotation of the hollow valve block; the third edge line is located at the lowest point of the entire hollow valve block, and the first edge line is further to the left than the second edge line; and an air permeable net is provided in the middle portion of each of the second and third valve plates. The present invention can automatically control the on / off state of the bifurcated flow channel during the suction and discharge process of the vertical conveying pipe.

Description

Technical Field

[0001] The invention belongs to the technical field of plastic production and processing equipment, and in particular relates to a plastic pellet vertical conveying pipe control structure capable of automatically controlling the on-off of a bifurcated flow channel. Background Art

[0002] The raw material for plastic products is plastic pellets, stored in containers called barrels, typically located in the factory's storage area. During production, an extruder in the factory's production area melts and extrudes the plastic pellets. A hopper is located above the extruder, and the pellets enter the extruder through the discharge port. Before the extruder's hopper is depleted of pellets, the hopper needs to be refilled. This process uses vacuum pressure to draw the pellets from the storage barrel into the extruder's hopper in the production area. This process is called suction, or feeding. Typically, the storage area is located far from the production area, with the horizontal distance between the hopper and barrel often reaching tens of meters or even longer.

[0003] Furthermore, during the production process, it is often necessary to change materials (i.e., change the type of plastic pellets). At this time, there is likely to be a large amount of the original type of plastic pellets remaining in the hopper. Therefore, the original type of plastic pellets need to be discharged from the hopper above the extruder. This process is called material withdrawal, or also called material return. To achieve this, the traditional method requires opening a material withdrawal port at the bottom of the hopper with a valve. Normally, the valve at the material withdrawal port is closed. When withdrawing material, the valve is opened, and the accumulated plastic pellets in the hopper automatically flow out through the material withdrawal port. Workers use bags to catch the plastic pellets at the material withdrawal port, then transfer the bagged plastic pellets to the side of the material barrel dozens of meters away, and finally pour them into the barrel. This is obviously quite laborious.

[0004] To solve this problem, the applicant developed a plastic pellet feeding mechanism with a material return function and applied for an invention patent, with the authorized publication number CN118769512B. The characteristic of the technical solution is that it can realize both feeding and material return functions by using only a total horizontal conveying pipe of several tens of meters long, without the need for a tens of meters long exhaust pipe to transmit power. This not only reduces the number of pipes, but also reduces the number of turns in the conveying pipe, which is conducive to the smooth flow of the conveying pipe and is not easy to be blocked. Figure 1 、 Figure 2As shown. Since the structure of CN118769512B has only one main conveying pipe, and the suction port of the material pipe needs to be inserted into the plastic pellet pile inside the barrel 2 when feeding, and the discharge port of the material pipe needs to leave the plastic pellet pile and be located above the plastic pellet pile when withdrawing, the vertical material conveying pipe 8 located above the barrel 2 forms a Y-shaped bifurcated structure, that is, it bifurcates into a withdrawal channel 72 and a suction channel 41, the lower end pipe opening of the suction channel 41 is located at the lower part of the barrel 2, the lower end pipe opening 720 of the withdrawal channel 72 is located above the barrel 2, and the lower end pipe opening 720 of the withdrawal channel is also provided with a valve. In this way, when sucking, the valve of the lower end pipe opening 720 of the withdrawal channel is closed, and the two-way fan 30 starts the exhaust mode to form a negative pressure in the hopper 1, and the negative pressure is transmitted to the barrel 2 by the downstream section 42 of the suction channel, the horizontal conveying pipe 9, the vertical material conveying pipe 8, and the suction channel 41, thereby realizing suction. The suction path and direction are as shown in FIG. Figure 1 As shown by the arrow; when the material is withdrawn, the valve of the pipe mouth 720 at the lower end of the withdrawal channel is opened, and the two-way fan 30 blows the plastic pellets in the hopper 1 to the upstream section 71 of the withdrawal channel, and then the plastic pellets flow horizontally along the horizontal conveying pipe 9, and then the plastic pellets flow downward along the vertical conveying pipe 8. When the material is withdrawn, the plastic pellets falling from the top are divided into two parts. The first part falls directly into the plastic pellet accumulation body from the withdrawal channel 72, and the second part falls into the tube cavity of the suction channel 41 and gradually accumulates in the tube cavity of the suction channel 41 until the suction channel 41 is filled with plastic pellets. Only then do all the plastic pellets flowing down from the vertical conveying pipe 8 pass through the withdrawal channel 72 and fall into the plastic pellet accumulation body. The withdrawal path and direction are shown in FIG. Figure 2 As indicated by the arrow.

[0005] After practice, the applicant found that the above structure still has the following two aspects to be improved: First, during the material return process, the suction channel 41 is filled with plastic particles, and it also needs to continue to withstand the downward impact of the subsequent plastic particle fluid falling from above, making the plastic particles in the suction channel 41 more and more dense, which may cause the plastic particles to block the suction channel 41, and after blockage, it needs to be manually cleared; Second; Since the valve of the pipe mouth 720 at the lower end of the return channel is dozens of meters away from the hopper 1, and the area for controlling the suction or return of materials is mainly next to the hopper 1, before each suction or return of materials, the worker needs to walk dozens of meters from the side of the hopper 1 to the side of the barrel 2 to open or close the valve of the pipe mouth 720 at the lower end of the return channel, and then walk back to the side of the hopper 1 to operate, which is more troublesome. Summary of the Invention

[0006] The purpose of the present invention is to overcome the above shortcomings and provide a plastic pellet vertical conveying pipe control structure that automatically controls the on-off state of the bifurcated flow channel, which can automatically control the on-off state of the bifurcated flow channel during the material suction and discharge process of the vertical conveying pipe.

[0007] Its purpose can be achieved according to the following scheme: a control structure for a vertical feeding pipe of plastic pellets that automatically controls the on and off of a bifurcated flow channel, comprising a vertical feeding pipe located above a barrel, wherein the lower section of the vertical feeding pipe is bifurcated into two bifurcated flow channels, the two bifurcated flow channels being a suction channel and a return channel respectively, the outlet at the bottom end of the suction channel being located at the lower part of the inner cavity of the barrel, and the outlet at the bottom end of the return channel being located above the barrel; it is characterized in that the cross section of the vertical feeding pipe is rectangular, the vertical feeding pipe is provided with a front side wall, a rear side wall, a left side wall and a right side wall, a partition wall is provided in the center of the inner cavity of the vertical feeding pipe, the partition wall is parallel to the left side wall and the right side wall, the bottom edge of the left half of the front side wall, the bottom edge of the left half of the rear side wall and the bottom edge of the left side wall are higher than the bottom edge of the partition wall, and the front side wall is provided with a partition wall. The bottom edge of the right half of the wall, the bottom edge of the right half of the rear side wall, and the bottom edge of the right side wall are flush with the bottom edge of the partition wall. The space enclosed by the right half of the front side wall, the right half of the rear side wall, the right side wall and the partition wall forms the material suction channel, and the space enclosed by the left half of the front side wall, the left half of the rear side wall, the left side wall and the partition wall forms the material withdrawal channel; the material withdrawal channel is provided with a one-way valve disc, the opening direction of the one-way valve disc is downward rotation; a hollow valve block is rotatably installed inside the vertical material delivery pipe, the rotating shaft of the hollow valve block extends in the longitudinal direction, and the central axis of the rotating shaft of the hollow valve block is located at the top edge of the partition wall; the longitudinal length of the hollow valve block is equivalent to the longitudinal dimension of the vertical material delivery pipe cavity; the hollow valve block includes three valve plates connected together to form a triangular prism shape, The three valve plates are respectively called the first valve plate, the second valve plate, and the third valve plate. The boundary line between the first valve plate and the second valve plate is called the first ridge line, the boundary line between the first valve plate and the third valve plate is called the second ridge line, and the boundary line between the second valve plate and the third valve plate is called the third ridge line. The third ridge line is close to and parallel to the rotating axis of the hollow valve block; the third ridge line is located at the lowest point of the entire hollow valve block, and the first ridge line is further to the left than the second ridge line; a breathable net is provided in the middle of the second valve plate and the third valve plate;

[0008] When the first ridge rotates to contact the left side wall, the first valve plate forms an acute angle less than 60° with the left side wall above the first ridge, and the center of gravity of the entire hollow valve block is located to the left of the plane where the partition wall is located and close to the plane where the partition wall is located;

[0009] When the second ridge rotates to contact the right side wall, the center of gravity of the entire hollow valve block is located on the right side of the plane where the partition wall is located. The first valve plate forms an obtuse angle with the right side wall above the second ridge, and the third valve plate forms an acute angle with the right side wall below the second ridge.

[0010] A counterweight is provided at the upper right corner of the hollow valve block.

[0011] When the first ridge line rotates to contact the left side wall, the transverse distance between the second ridge line and the right side wall is equal to 0.8 to 1.0 times the transverse width of the suction channel.

[0012] When the second ridge line rotates to contact the right side wall, the transverse distance between the first ridge line and the left side wall is equal to 0.8 to 1.0 times the transverse width of the material withdrawal channel.

[0013] The present invention has the following advantages and effects:

[0014] 1. The present invention can automatically control the on-off state of the bifurcated flow channel during the material suction / return process of the vertical material conveying pipe. Specifically, during the material suction process, the one-way valve disc is sucked up by the negative pressure and maintained in the closed position, the first edge of the hollow valve block automatically keeps in contact with the left wall of the material delivery pipe, and the material return channel is automatically disconnected to prevent outside air from entering the material delivery pipe from the bottom port of the material return channel to maintain the vacuum degree of the material delivery pipe, and an ascending channel for plastic pellets to flow upward is formed between the third valve plate of the hollow valve block and the right side wall, and the ascending channel is opposite to the material suction channel, so that the material suction channel remains unobstructed, thereby achieving continuous material suction; during the material withdrawal process, the second edge of the hollow valve block automatically keeps in contact with the right side wall of the material delivery pipe, and the hollow valve block disconnects the material suction channel to prevent plastic pellets from continuously falling into the material suction channel and continuously impacting the plastic pellets in the material suction channel, thereby avoiding blockage of the material suction channel, and a descending channel for plastic pellets to flow downward is formed between the second valve plate of the hollow valve block and the left side wall, and the descending channel is opposite to the material withdrawal channel, so that the material withdrawal channel remains unobstructed, thereby achieving continuous material withdrawal;

[0015] 2. During the above process, the on-off state of the bifurcated flow channel does not require any human intervention or any electric mechanism intervention. The entire mechanism is simple and ingenious, avoiding the trouble of workers walking back and forth, and there is no need to build a remote control electric control system. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the material suction path and direction in the structure disclosed in CN118769512B.

[0017] Figure 2 This is a schematic diagram of the material return path and direction in the structure disclosed in CN118769512B.

[0018] Figure 3 It is a schematic diagram of the overall structure of a specific embodiment of the present invention.

[0019] Figure 4 yes Figure 3 Schematic diagram of the enlarged structure of the hollow valve block.

[0020] Figure 5 yes Figure 4 Schematic diagram of the three-dimensional structure of the hollow valve block.

[0021] Figure 6 yes Figure 3 Schematic diagram of the middle DD section.

[0022] Figure 7 yes Figure 3 Schematic diagram of the changing state of the hollow valve block after it is rotated to the left.

[0023] Figure 8 The present invention is a schematic diagram of the overall structure of an automatic feeding and withdrawing system for plastic pellets according to a specific embodiment of the present invention.

[0024] Figure 9 This is a schematic diagram of the first starting state of the material suction process in a specific embodiment of the present invention.

[0025] Figure 10 yes Figure 9 Schematic diagram of the changed state after further evolution of the shown state.

[0026] Figure 11 middle Figure 10 The schematic diagram of the changing state after further evolution of the shown state is also a schematic diagram of the specific embodiment of the present invention in the continuous material suction process.

[0027] Figure 12 2 is a schematic diagram of the second starting state of the material suction process in a specific embodiment of the present invention.

[0028] Figure 13 yes Figure 12 Schematic diagram of the changed state after further evolution of the shown state.

[0029] Figure 14 middle Figure 13 Schematic diagram of the changed state after further evolution of the shown state.

[0030] Figure 15 middle Figure 14 The schematic diagram of the changing state after further evolution of the shown state is also a schematic diagram of the specific embodiment of the present invention in the continuous material suction process.

[0031] Figure 16 This is a schematic diagram of the first starting state of the material return process in a specific embodiment of the present invention.

[0032] Figure 17 yes Figure 16 The schematic diagram of the changed state after further evolution of the shown state is also a schematic diagram of the specific embodiment of the present invention in the process of continuous material withdrawal.

[0033] Figure 18 This is a schematic diagram of the second starting state of the material withdrawal process in a specific embodiment of the present invention.

[0034] Figure 19 yes Figure 18 Schematic diagram of the changed state after further evolution of the shown state.

[0035] Figure 20 yes Figure 19 The schematic diagram of the changed state after further evolution of the shown state is also a schematic diagram of the specific embodiment of the present invention in the process of continuous material withdrawal. DETAILED DESCRIPTION

[0036] Figure 3 、 Figure 7 、 Figure 6 The plastic pellet vertical feeding pipe control structure shown in the figure automatically controls the on and off of the bifurcated flow channel, including a vertical feeding pipe 8 located above the material barrel 2, and the lower section of the vertical feeding pipe 8 is bifurcated into two bifurcated flow channels, the two bifurcated flow channels are respectively a suction channel 41 and a return channel 72, the cross section of the vertical feeding pipe 8 is rectangular, the vertical feeding pipe 8 is provided with a front side wall 81, a rear side wall 82, a left side wall 83, and a right side wall 84, a partition wall 85 is provided in the center of the inner cavity of the vertical feeding pipe 8, the partition wall 85 is parallel to the left side wall 83 and the right side wall 84, the front side wall 81 is divided into a front side wall left half 811 and a front side wall right half 812, the rear side wall 82 is divided into a rear side wall left half 821 and a rear side wall right half 822, the bottom edge of the front side wall left half 811, the bottom edge of the rear side wall left half 821, and the bottom edge of the left side wall 83 are higher than the bottom edge of the partition wall 85 The bottom edge of the right half of the front side wall 812, the bottom edge of the right half of the rear side wall 822, and the bottom edge of the right side wall 84 are flush with the bottom edge of the partition wall 85. The space enclosed by the right half of the front side wall 812, the right half of the rear side wall 822, the right side wall 84 and the partition wall 85 forms the suction channel 41, and the space enclosed by the left half of the front side wall 811, the left half of the rear side wall 821, the left side wall 83 and the partition wall 85 forms the return channel 72; the outlet at the bottom end of the suction channel 41 is located at the lower part of the inner cavity of the barrel 2, and the outlet at the bottom end of the return channel 72 is located above the barrel 2. The return channel 72 is provided with a one-way valve disc 5, and the one-way valve disc 5 is provided with a valve disc rotating shaft 50. The extension direction of the valve disc rotating shaft 50 is horizontal and longitudinal. The opening direction of the one-way valve disc 5 is downward counterclockwise rotation, and the closing direction of the one-way valve disc 5 is upward clockwise rotation.

[0037] Figure 3 、 Figure 4 、 Figure 5As shown, a hollow valve block 6 is rotatably mounted inside the vertical feed pipe 8. The rotating shaft 60 of the hollow valve block extends in the longitudinal direction, and the central axis of the rotating shaft 60 of the hollow valve block is located at the top edge of the partition wall 85. The longitudinal length of the hollow valve block 6 is equivalent to the longitudinal dimension of the lumen of the vertical feed pipe 8. The hollow valve block 6 includes three valve plates. The three valve plates are respectively called the first valve plate 61, the second valve plate 62, and the third valve plate 63. The three valve plates are connected together to form a triangular prism shape. The boundary line between the first valve plate 61 and the second valve plate 62 is called the first ridge line 64, the boundary line between the first valve plate 61 and the third valve plate 63 is called the second ridge line 65, and the boundary line between the second valve plate 62 and the third valve plate 63 is called the third ridge line 66. A counterweight block 69 is provided at the upper right corner of the hollow valve block 6; the third ridge line 66 is close to and parallel to the rotating shaft 60 of the hollow valve block; the third ridge line 66 is located at the lowest point of the entire hollow valve block 6, and the first ridge line 64 is further to the left than the second ridge line 65; a first air permeable net 67 is provided in the middle part of the second valve plate 62, and a second air permeable net 68 is provided in the middle part of the third valve plate 63; the mesh holes of the first air permeable net 67 and the second air permeable net 68 can be ventilated and transmit negative pressure, but cannot allow plastic particles to pass through;

[0038] When the hollow valve block 6 rotates around its rotation axis 60 and drives the first edge line 64 to rotate to contact the left side wall 83 of the vertical material conveying pipe 8, the angle formed by the first valve plate 61 and the left side wall 83 above the first edge line 64 (as shown in FIG. Figure 7 ∠A in the figure) is an acute angle of 45°, and the center of gravity of the entire hollow valve block 6 (as shown in Figure 7 The second ridgeline 65 is located on the left side of the plane where the partition wall 85 is located and is close to the plane where the partition wall 85 is located. The lateral distance between the second ridgeline 65 and the right side wall 84 is equal to 0.9 times the lateral width of the suction channel. Figure 7 、 Figure 5 As shown;

[0039] When the hollow valve block 6 rotates around its rotation axis 60 and drives the second edge line 65 to rotate to contact the right side wall 84 of the vertical material conveying pipe 8, the center of gravity of the entire hollow valve block 6 (such as Figure 3 The first valve plate 61 and the right side wall 84 above the second ridge line 65 form an angle (as shown in point G in FIG. Figure 3 ∠B in the figure) is an obtuse angle, and the angle formed by the third valve plate 63 and the right side wall 84 below the second ridge line 65 (as shown in FIG. Figure 3 ∠C in the middle is an acute angle, and the lateral distance between the first ridge line 64 and the left side wall 83 is equal to 0.9 times the lateral width of the material return channel 72.

[0040] The above embodiment is applied in the automatic feeding and withdrawing system of plastic pellets, such as Figure 8As shown, the system is provided with a hopper 1, a two-way fan 30, and a horizontal conveying pipe 9. The suction port of the hopper 1 is connected to the first end of the horizontal conveying pipe 9 (located at one end of the production area) through the downstream section 42 of the suction channel and the three-way valve 91. The discharge port of the hopper 1 is connected to the first end of the horizontal conveying pipe 9 through the upstream section 71 of the discharge channel and the three-way valve 91. The second end of the horizontal conveying pipe 9 (located at one end of the storage area) is connected to the upper end of the vertical conveying pipe 8. The air duct of the two-way fan 30 extends into the interior of the hopper 1. The relevant flow channel structure between the two-way fan 30 and the upper end of the vertical conveying pipe 8 is the same as the structure disclosed in CN118769512B.

[0041] The above embodiment can automatically control the on-off state of the bifurcated flow channel during the material suction and withdrawal process of the vertical material conveying pipe, that is, during material suction, the material suction channel is automatically kept unobstructed while the material withdrawal channel is kept disconnected, and during material withdrawal, the material withdrawal channel is automatically kept unobstructed while the material suction channel is kept disconnected, as follows:

[0042] 1. Suction process:

[0043] 1. If in the initial state, the first edge line 64 of the hollow valve block 6 is against the left side wall 83 of the vertical feed pipe 8 (such as Figure 9 As shown), when the negative pressure generated by the two-way fan 30 is transmitted to the vertical conveying pipe 8, the one-way valve plate 5 is sucked up and rotates clockwise around its rotation axis, and the return channel 72 remains disconnected (as shown). Figure 10 As shown in FIG5 ), the suction channel 41 remains unobstructed, and an ascending channel for the plastic pellets to flow upward is formed between the third valve plate 63 of the hollow valve block and the right side wall 84. Therefore, the negative pressure can continuously suck the plastic pellets upward through the suction channel 41, the ascending channel between the third valve plate 63 and the right side wall 84, as shown in FIG5 . Figure 11 As shown, the plastic pellets are then continuously sucked into the hopper 1 through the horizontal conveying pipe 9 and the downstream section 42 of the suction channel;

[0044] 2. If in the initial state, the second edge line 65 of the hollow valve block 6 is against the right side wall 84 of the vertical feed pipe 8 (such as Figure 12 As shown), when the negative pressure generated by the two-way fan 30 is transmitted to the vertical conveying pipe 8, the one-way valve plate 5 is first sucked up and rotates clockwise around its rotation axis, and the return channel 72 remains closed (as shown). Figure 13 As shown), the negative pressure is then transmitted to the suction channel 41 through the first air permeable mesh 67 in the middle of the second valve plate 62 and the second air permeable mesh 68 in the middle of the third valve plate 63. The plastic pellets in the barrel 2 are sucked upward and collide with the third valve plate 63 of the hollow valve block, as shown. Figure 14As shown, under the action of the impact force and the counterclockwise torque generated by the air pressure difference on the solid part of the third valve plate 63, the hollow valve block 6 rotates counterclockwise to the left around its rotation axis 60 until the first edge line 64 abuts against the left side wall 83 of the vertical material conveying pipe 8. After that, the suction channel 41 remains unobstructed and the material return channel 72 remains disconnected. The negative pressure can continuously suck the plastic particles upward through the suction channel 41, the rising channel between the third valve plate 63 and the right side wall 84, and the material suction continues. Figure 15 shown.

[0045] 2. Material return process:

[0046] 1. If in the initial state, the second edge line 65 of the hollow valve block 6 is against the right side wall 84 of the vertical feed pipe 8 (such as Figure 16 As shown), when the plastic pellets flowed from the hopper 1 reaches the upper end of the vertical feed pipe 8, the plastic pellets flow downward and hit the first valve plate 61 of the hollow valve block. The impact force generates a weak rightward horizontal component force, the hollow valve block 6 remains stationary, and the suction channel 41 remains disconnected, as shown in FIG. Figure 16 As shown, the material return channel 72 remains unobstructed, so the plastic pellets can continue to fall into the material barrel below through the material return channel 72, as shown in FIG. Figure 17 As shown;

[0047] 2. If in the initial state, the first edge line 64 of the hollow valve block 6 is against the left side wall 83 of the vertical feed pipe 8 (such as Figure 18 As shown in FIG5 , when the plastic pellets flowed from the hopper 1 reaches the upper end of the vertical feed pipe 8, the plastic pellets flow downward and hit the first valve plate 61 of the hollow valve block. The impact force of the falling plastic pellets and the gravity of the plastic pellets can generate a large rightward horizontal component force on the first valve plate 61. Since the center of gravity G of the hollow valve block 6 is close to the plane where the partition wall 85 is located and is close to the critical state of left-right balance, the hollow valve block 6 quickly rotates clockwise to the right, as shown in FIG5 . Figure 19 As shown, under the action of the gravity torque of the hollow valve block 6 itself and the impact force of the plastic pellets, the hollow valve block 6 quickly rotates to the right to the limit position, so that the second edge line 65 is close to the right side wall 84 of the vertical feed pipe 8, as shown in FIG. Figure 20 As shown, the suction channel 41 remains disconnected, while the return channel 72 remains unobstructed, so that the plastic pellets can continue to fall into the bucket below through the return channel 72.

[0048] As can be seen from the above, in the above process, the change of the on-off state of the bifurcated flow channel (ie, the material suction channel 41 and the material return channel 72) does not require any manual intervention or any electric mechanism intervention.

[0049] In the above embodiment, when the first ridge line 64 rotates to contact the left side wall, the first valve plate 61 and the left side wall 83 above the first ridge line 64 form an acute angle (such as Figure 7 The angle ∠A) can be changed to 40° or 58°, and the lateral distance between the second ridge line 65 and the right side wall 84 can be changed to be equal to 0.8 times or 1.0 times the lateral width of the suction channel 41.

[0050] In the above embodiment, when the second edge line 65 rotates to contact the right side wall 84 , the lateral distance between the first edge line 64 and the left side wall 83 can be changed to be equal to 0.8 times or 1.0 times the lateral width of the material withdrawal channel 72 .

Claims

1. A control structure for a vertical plastic pellet conveying pipe with automatic control of the opening and closing of a bifurcated flow channel, comprising a vertical conveying pipe located above a barrel, the lower section of the vertical conveying pipe bifurcating into two bifurcated flow channels, the two bifurcated flow channels being a suction channel and a discharge channel, respectively. The outlet at the bottom end of the suction channel is located at the lower portion of the barrel cavity, and the outlet at the bottom end of the discharge channel is located above the barrel; characterized in that: The cross section of the vertical material conveying pipe is rectangular, and the vertical material conveying pipe is provided with a front side wall, a rear side wall, a left side wall, and a right side wall. A partition wall is provided in the center of the inner cavity of the vertical material conveying pipe, and the partition wall is parallel to the left side wall and the right side wall. The bottom edge of the left half of the front side wall, the bottom edge of the left half of the rear side wall, and the bottom edge of the left wall are higher than the bottom edge of the partition wall, and the bottom edge of the right half of the front side wall, the bottom edge of the right half of the rear side wall, and the bottom edge of the right wall are flush with the bottom edge of the partition wall. The space enclosed by the right half of the front side wall, the right half of the rear side wall, the right side wall, and the partition wall forms the material suction channel. The space enclosed by the left half of the front side wall, the left half of the rear side wall, the left side wall and the partition wall forms the material return channel; the material return channel is provided with a one-way valve disc, the opening direction of the one-way valve disc is downward rotation; a hollow valve block is rotatably installed inside the vertical material delivery pipe, the rotating shaft of the hollow valve block extends in the longitudinal direction, the central axis of the rotating shaft of the hollow valve block is located at the top edge of the partition wall, and a counterweight block is provided at the upper right corner of the hollow valve block; the longitudinal length of the hollow valve block is equivalent to the longitudinal dimension of the lumen of the vertical material delivery pipe; the hollow valve block includes three valve plates connected together to form a triangular prism shape, The three valve plates are respectively called the first valve plate, the second valve plate, and the third valve plate. The boundary line between the first valve plate and the second valve plate is called the first ridge line, the boundary line between the first valve plate and the third valve plate is called the second ridge line, and the boundary line between the second valve plate and the third valve plate is called the third ridge line. The third ridge line is close to and parallel to the rotating axis of the hollow valve block; the third ridge line is located at the lowest point of the entire hollow valve block, and the first ridge line is further to the left than the second ridge line; a breathable net is provided in the middle of the second valve plate and the third valve plate; When the first ridge rotates to contact the left side wall, the first valve plate forms an acute angle less than 60° with the left side wall above the first ridge, and the center of gravity of the entire hollow valve block is located to the left of the plane where the partition wall is located and close to the plane where the partition wall is located; When the second ridge rotates to contact the right side wall, the center of gravity of the entire hollow valve block is located on the right side of the plane where the partition wall is located. The first valve plate forms an obtuse angle with the right side wall above the second ridge, and the third valve plate forms an acute angle with the right side wall below the second ridge.

2. The plastic pellet vertical conveying pipe control structure for automatically controlling the opening and closing of the bifurcated flow channel according to claim 1 is characterized in that: When the first ridge line rotates to contact the left side wall, the transverse distance between the second ridge line and the right side wall is equal to 0.8 to 1.0 times the transverse width of the suction channel.

3. The plastic pellet vertical conveying pipe control structure for automatically controlling the opening and closing of the bifurcated flow channel according to claim 1 is characterized in that: When the second ridge line rotates to contact the right side wall, the transverse distance between the first ridge line and the left side wall is equal to 0.8 to 1.0 times the transverse width of the material withdrawal channel.

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