Ton bag packaging machine with dustproof structure

Abstract

The present application relates to the packaging technical field, disclose a kind of ton bag packaging machine with dustproof structure, including column leg, and located the platform of column leg upper end, the bottom end of the inside of column leg is equipped with belt conveyor, the upper end of the inside of platform is equipped with conical bunker, the upper end of conical bunker is generated with feeding port and inspection cover respectively, the output end of conical bunker is connected with hose in the inside of platform, the lower end of hose is connected with mobile type hanging belt assembly, the lower end of mobile type hanging belt assembly is connected with dustproof bag clamping mechanism, the inside of platform is equipped with hydraulic cylinder in four corners.The present application integrates bag clamping, filling and sealing functions, each process is carried out in a sealed or controlled environment, from loading to sealing the whole process without dust, significantly improve the cleanliness of workshop, and reduce the manual participation, improve the automation level of packaging.

Description

Technical Field

[0001] This invention relates to the field of packaging technology, and in particular to a ton bag packaging machine with a dustproof structure. Background Technology

[0002] Ton bags are mainly used for packaging and transporting bulk materials. They can hold powdery, granular, or lumpy items and serve as flexible containers in logistics and warehousing. In the field of large-bag packaging of powdery or granular materials, traditional ton bag packaging machines commonly suffer from the following problems: First, during the filling process, the lack of a reliable seal between the ton bag opening and the discharge pipe allows dust generated when material falls to easily leak out through the gaps in the bag opening, severely polluting the working environment and endangering the health of operators. Second, the attachment of the ton bag lifting straps relies heavily on manual operation, and the hooks lack anti-slip structures, making it easy for the straps to slip off during bag lifting or filling, posing a safety hazard. Third, the bag sealing process after filling usually requires manual adjustment of the bag opening and the use of external heat sealing equipment, which is not only inefficient but also prone to material leakage and dust dispersion during the sealing process. Furthermore, many existing devices lack a bag pre-expansion mechanism, and insufficient bag expansion affects the filling speed and density. Summary of the Invention

[0003] The purpose of this invention is to provide a ton bag packaging machine with a dustproof structure to solve the problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention provides the following technical solution: A ton bag packaging machine with a dustproof structure includes upright legs and a platform located at the upper end of the upright legs. A belt conveyor is installed at the bottom inner side of the upright legs. A conical hopper is installed at the upper inner side of the platform. A feeding port and an inspection cover are respectively generated at the upper end of the conical hopper. The output end of the conical hopper passes through the inner side of the platform and is connected to a flexible hose. The lower end of the flexible hose is connected to a movable hanging assembly. The lower end of the movable hanging assembly is connected to a dustproof bag clamping mechanism. Hydraulic cylinders are installed at the four corners of the inner side of the platform. The output end of each hydraulic cylinder is connected to one corner of the upper end of the movable hanging assembly.

[0005] As a further embodiment of the present invention: the dustproof bag clamping mechanism includes a feeding pipe, a negative pressure suction cup is installed at the upper part of the outer side of the feeding pipe, a sealing plate is fixedly connected to the outer side of the negative pressure suction cup, and a bag clamping assembly is rotatably connected to the lower end of the sealing plate located outside the feeding pipe.

[0006] As a further embodiment of the present invention: a set of connecting arms is rotatably connected to both ends of the outer side of the bag clamping assembly, and a sealing assembly is fixedly connected to the lower end of each set of connecting arms. A cylinder is rotatably connected between each connecting arm and the bag clamping assembly.

[0007] As a further embodiment of the present invention: the bag clamping assembly includes a set of clamping arms one and a set of clamping arms two. A cylinder two is rotatably connected to the upper end of each set of clamping arms one and the upper end of each set of clamping arms two. An elastic band is fixedly connected to the lower end of each clamping arm one and the corresponding clamping arm two. An elastic sheet is fixedly connected to the lower end of each clamping arm one and clamping arm two.

[0008] As a further embodiment of the present invention: the sealing assembly includes a strip-shaped opening box and a hot melt device embedded in the inner side of the strip-shaped opening box from one side, a hot melt plate is embedded and installed on one side of the hot melt device, and a fixing ear is fixedly connected to the front and rear sides of the upper end of the strip-shaped opening box.

[0009] As a further embodiment of the present invention: both the front and rear ends of one side of the hot melter are fixedly connected to the second fixing lug; gearboxes are installed on the front and rear sides of the strip-shaped open box near the corresponding second fixing lug; gear one and gear two are installed on the inner side of the gearbox and mesh with each other; a rotating shaft is fixedly connected to the center of gear two through the outer side of the gearbox; one end of the rotating shaft is fixedly connected to the corresponding second fixing lug; a connecting shaft at the center of gear one is fixedly connected to a connecting rod through the outer side of the gearbox; one end of the connecting rod is rotatably connected to an electric cylinder; and one end of the electric cylinder is rotatably connected to the lower end of the outer side of the strip-shaped open box.

[0010] As a further embodiment of the present invention: each of the clamping arms 1 and each of the clamping arms 2 is provided with a lug 2 near the cylinder 2, the lug 2 is rotatably connected to the upper end of the cylinder 1, and each of the clamping arms 1 and each of the clamping arms 2 is provided with a lug 1 near the elastic plate, the lug 1 is rotatably connected to the upper end of the connecting arm.

[0011] As a further embodiment of the present invention: the movable strap assembly includes a flat plate, a connecting pipe is installed through the middle of the upper end of the flat plate, and hooks are fixedly connected to the four corners of the lower end of the flat plate. A motor is installed on the outside of the hooks, and a limit block is fixedly connected to the output end of the motor.

[0012] As a further embodiment of the present invention: a flange is provided at the upper end of the feeding pipe, an air pipe is installed on the inner side wall of the feeding pipe, and an air inlet is provided at one end of the air pipe through the inner side wall of the feeding pipe.

[0013] Compared with the prior art, the present invention has the following beneficial effects: This invention integrates bag clamping, filling, and sealing functions into one unit. Each process is carried out in a sealed or controlled environment, resulting in a dust-free process from filling to sealing. This significantly improves the cleanliness of the workshop, reduces manual intervention, and enhances the automation level of packaging. The elastic sheets and bands in the bag clamping assembly tightly grip the bag opening onto the feeding pipe, while a negative pressure suction cup adsorbs the outside of the bag opening, forming a dual-sealing structure of mechanical clamping and negative pressure adsorption. This effectively prevents dust leakage during the filling process, achieving clean production. The sealing assembly uses a flip-up hot-melt plate structure. When not welding, the hot-melt plate is stored in a strip-shaped open box, preventing burns to workers or damage to the bag body and protecting the hot-melt plate itself. During welding, an electric cylinder and gear transmission smoothly flip the hot-melt plate out, directly heat-sealing the bag opening. The entire sealing process is dust-free and sealed. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of a ton bag packaging machine with a dustproof structure. Figure 2 This is a schematic diagram of a ton bag packaging machine with a dustproof structure during the filling of ton bags; Figure 3 This is a schematic diagram of the installation of the dustproof bag clamping mechanism and the movable hanging strap assembly in a ton bag packaging machine with a dustproof structure. Figure 4 This is a schematic diagram of a movable hanging strap assembly in a ton bag packaging machine with a dustproof structure. Figure 5 for Figure 4 A magnified structural diagram of part A in the middle; Figure 6 This is a schematic diagram of the dustproof bag clamping mechanism in a ton bag packaging machine with a dustproof structure. Figure 7 This is a schematic diagram of the bag clamping assembly in a ton bag packaging machine with a dustproof structure. Figure 8 This is a partial cross-sectional view of the sealing assembly in a ton bag packaging machine with a dustproof structure. Figure 9 for Figure 8 A magnified structural diagram of part B.

[0015] In the diagram: 1. Belt conveyor; 2. Support leg; 3. Dustproof bag clamping mechanism; 31. Feeding pipe; 32. Sealing assembly; 321. Strip-shaped opening box; 322. Hot melt plate; 323. Hot melt machine; 324. Fixing lug 1; 325. Connecting rod; 326. Electric cylinder; 327. Gear 1; 328. Gear 2; 329. Gearbox; 330. Rotating shaft; 331. Fixing lug 2; 33. Cylinder 1; 34. Connecting arm; 35. Bag clamping assembly; 351. Clamping arm 1; 35 2. Clamping arm two; 353. Elastic band; 354. Elastic sheet; 355. Shaft lug one; 356. Cylinder two; 357. Shaft lug two; 36. Sealing plate; 37. Negative pressure suction cup; 38. Flange; 39. Air pipe; 310. Air inlet; 4. Movable hanging belt assembly; 41. Flat plate; 42. Connecting pipe; 43. Hook; 44. Motor; 45. Limit block; 5. Hose; 6. Platform; 7. Hydraulic cylinder; 8. Inspection cover; 9. Feeding port; 10. Conical hopper; 11. Ton bag. Detailed Implementation

[0016] Please see Figures 1-9In this embodiment of the invention, a ton bag packaging machine with a dustproof structure includes a column support leg 2 and a platform 6 located at the upper end of the column support leg 2. A belt conveyor 1 is installed at the bottom inner side of the column support leg 2. The belt conveyor 1 can also adopt an electric roller conveyor structure, which facilitates connection with subsequent palletizing or handling stations to achieve automatic conveying. A conical hopper 10 is installed at the upper inner side of the platform 6. The upper end of the conical hopper 10 has a feeding port 9 and an inspection cover 8 respectively. The feeding port 9 is connected to an external raw material conveying pump. The raw materials can be continuously fed into the conical hopper 10. After opening the inspection cover 8, the condition inside the conical hopper 10 can be inspected. The output end of the conical hopper 10 is connected to a flexible hose 5 through the inner side of the platform 6. The flexible hose 5 is made of wear-resistant and flexible material, which can adapt to the lifting and lowering displacement of the movable strap assembly 4. The lower end of the flexible hose 5 is connected to the movable strap assembly 4, and the lower end of the movable strap assembly 4 is connected to the dustproof bag clamping mechanism 3. Hydraulic cylinders 7 are installed at the four corners of the inner side of the platform 6. Each hydraulic cylinder 7 outputs... The outlet ends are all connected to one corner of the upper end of the movable hanging strap assembly 4; four hydraulic cylinders 7 are controlled by a synchronous circuit to ensure the smooth lifting and lowering of the flat plate 41; the bag opening of the ton bag 11 is fitted onto the dustproof bag clamping mechanism 3 and fixed, and then the lifting strap of the ton bag 11 is hung on the movable hanging strap assembly 4; then, the movable hanging strap assembly 4 is lifted and lowered by the hydraulic cylinders 7, so that the ton bag 11 can be raised to a suitable height for easy loading; at this time, the valve at the bottom of the conical hopper 10 is opened, which is preferably a pneumatic gate valve. It can achieve rapid opening and closing and precise feeding control; the raw materials in the conical hopper 10 pass through the hose 5, the movable hanging belt assembly 4 and the dustproof bag clamping mechanism 3 in sequence, and enter the ton bag 11. The dustproof bag clamping mechanism 3 can ensure that there is no dust during the material feeding process; after the material is filled, the dustproof bag clamping mechanism 3 melts and seals the bag opening of the ton bag 11, thereby ensuring that there is no dust during the entire material filling process; after the material is filled, the belt conveyor 1 transports the ton bag 11 to the side away from the column support leg 2 for easy handling.

[0017] exist Figure 3 , Figure 4 and Figure 5The mobile strap assembly 4 includes a flat plate 41. A connecting pipe 42 is installed through the middle of the upper end of the flat plate 41, and hooks 43 are fixedly connected to the four corners of the lower end of the flat plate 41. The upper end of the connecting pipe 42 is connected to the hose 5. The output end of each hydraulic cylinder 7 is connected to the four corners of the upper end of the flat plate 41. Therefore, the hydraulic cylinder 7 can drive the entire mobile strap assembly 4 to move up and down to adjust the height of the mobile strap assembly 4, so as to facilitate hanging the strap part of the ton bag 11 on the hook 43. A motor 44 is installed on the outside of the hook 43. The output end of the motor 44 is fixedly connected to the limit block 45. The motor 44 drives the limit block 45 to rotate, thereby opening the opening of the hook 43, so that the strap part of the ton bag 11 can be hung on the hook 43. The motor 44 drives the limit block 45 to rotate in the opposite direction. At this time, the limit block 45 can seal the opening of the hook 43 to prevent the strap of the ton bag 11 from falling off the hook 43.

[0018] exist Figure 1 , Figure 3 and Figure 6 In the middle, the dustproof bag clamping mechanism 3 includes a feeding pipe 31. A negative pressure suction cup 37 is installed at the upper part of the outer side of the feeding pipe 31. The negative pressure suction cup 37 is connected to a negative pressure pump outside the negative pressure pump, and the negative pressure suction cup 37 is arranged in a ring to form a balanced suction force on the bag opening. A sealing plate 36 is fixedly connected to the outer side of the negative pressure suction cup 37. The lower end of the sealing plate 36 is rotatably connected to a bag clamping assembly 35 outside the feeding pipe 31. A set of connecting arms 34 is rotatably connected to both ends of the outer side of the bag clamping assembly 35. A sealing assembly 32 is fixedly connected to the lower end of each set of connecting arms 34. A cylinder 33 is rotatably connected between each connecting arm 34 and the bag clamping assembly 35.

[0019] exist Figure 3 , Figure 6 and Figure 7In the bag clamping assembly 35, there is a set of clamping arms 351 and a set of clamping arms 352. A cylinder 356 is rotatably connected to the upper end of each set of clamping arms 351 and the upper end of each set of clamping arms 352. The cylinder 356 allows either the clamping arms 351 or the clamping arms 352 to rotate relative to each other, specifically at the junction of the clamping arms 351 and 352 with the sealing plate 36. An elastic band 353 is fixedly connected to the lower end of each clamping arm 351 and its corresponding clamping arm 352. The elastic band 353 is preferably made of high-temperature resistant, highly elastic silicone or rubber material to ensure effective clamping of the bag opening and long-term use. Each clamping arm 351... An elastic plate 354 is fixedly connected to the lower end of both the first clamping arm 351 and the second clamping arm 352. The bag opening of the ton bag 11 is fitted onto the feeding pipe 31. When the second cylinder 356 retracts, each set of clamping arms 351 and 352 rotate relative to each other. At this time, each set of elastic plates 354 moves closer to each other and pulls the elastic band 353. The elastic band 353 clamps the outside of the bag opening of the ton bag 11, so that the bag opening of the ton bag 11 is tightly attached to the feeding pipe 31. At the same time, the negative pressure pump generates negative pressure on the negative pressure suction cup 37, which generates suction on the upper end of the bag opening of the ton bag 11. This can effectively prevent dust from overflowing from the bag opening when filling the ton bag 11, thus avoiding environmental pollution.

[0020] exist Figure 6 , Figure 8 and Figure 9In the process, the sealing assembly 32 includes a strip-shaped opening box 321 and a heat fusion device 323 embedded in the inner side of the strip-shaped opening box 321 from one side. A heat fusion plate 322 is embedded and installed on one side of the heat fusion device 323, wherein the heat fusion plate 322 is connected to an external power source. Fixing ears 324 are fixedly connected to the front and rear sides of the upper end of the strip-shaped opening box 321, wherein the fixing ears 324 are fixedly connected to the lower end of the connecting arm 34. Fixing ears 331 are fixedly connected to the front and rear ends of one side of the heat fusion device 323. The front and rear sides of the strip-shaped opening box 321 near the corresponding fixing ears 331 are also equipped with... A gearbox 329 is installed, featuring a sealed design to effectively prevent dust from entering the transmission pair and ensure the reliability of the gear transmission. Inside the gearbox 329 are meshing gears 327 and 328. A rotating shaft 330 is fixedly connected to the center of gear 328, extending through the outer side of the gearbox 329. One end of the rotating shaft 330 is fixedly connected to a corresponding fixing lug 331. A connecting rod 325 is fixedly connected to the center of gear 327, extending through the outer side of the gearbox 329. The connecting rod 325 and the fixing lug 331... 1. Located on the front and rear sides of gearbox 329 respectively; one end of connecting rod 325 is rotatably connected to electric cylinder 326, and one end of electric cylinder 326 is rotatably connected to the lower end of the outer side of strip-shaped open box 321. By extending or retracting electric cylinder 326, connecting rod 325 can be pulled or pushed. Connecting rod 325 drives gear one 327 to rotate within a certain angle range. Gear one 327 meshes with gear two 328, thereby driving shaft 330 to rotate. Shaft 330 drives fixed ear two 331 and hot melt device 323 to rotate together, thereby causing hot melt device 323 to flip, and thus... The hot melt plate 322 can be flipped out from the inside of the strip-shaped opening box 321 or stored inside the strip-shaped opening box 321. When the hot melt plate 322 is flipped out from the inside of the strip-shaped opening box 321, the hot melt temperature can be set according to the material of the inner bag of the ton bag and automatically maintained by the temperature control system. The opening of the ton bag 11 can be hot melt welded through the hot melt plate 322. When the hot melt plate 322 is stored inside the strip-shaped opening box 321, it can be protected to prevent the hot melt plate 322 from burning the staff or damaging other parts of the ton bag 11.

[0021] exist Figure 6 and Figure 7In this assembly, each clamping arm 351 and each clamping arm 352 is provided with a lug 357 near the cylinder 356. The lug 357 is rotatably connected to the upper end of the cylinder 33. Each clamping arm 351 and each clamping arm 352 is provided with a lug 355 near the elastic plate 354. The lug 355 is rotatably connected to the upper end of the connecting arm 34. When the bag clamping assembly 35 clamps the bag opening of the ton bag 11, the extension of the cylinder 33 drives the sealing assembly 32 away from the bag opening of the ton bag 11, which can reduce interference during bag clamping. When the heat melter 323 flips and the heat melt plate 322 faces the strip-shaped opening box... On the outside of 321; and after the bag clamping assembly 35 and the negative pressure suction cup 37 release the fixation on the bag opening of the ton bag 11; the cylinder 1 33 retracts, pulling the connecting arm 34, and the connecting arm 34 drives the sealing assembly 32, so that the two sealing assemblies 32 come closer; when the two hot melt plates 322 come into contact with the bag opening of the ton bag 11 and squeeze the bag opening, the bag opening can be melted and welded together, thus ensuring that the entire process from filling to sealing is in a sealed state, so that there is no dust in the filling workshop; by setting the action interlock between cylinder 1 33 and cylinder 2 356, the orderly cycle of bag clamping - filling - loosening clamping - hot melt sealing can be realized, greatly improving the degree of automation.

[0022] exist Figure 3 and Figure 6 In the middle, the upper end of the feeding pipe 31 is provided with a flange 38, which is fixedly connected to the lower end of the connecting pipe 42, thereby fixing the dustproof bag clamping mechanism 3 and the movable hanging strap assembly 4 together. An air pipe 39 is installed on the inner side wall of the feeding pipe 31. One end of the air pipe 39 passes through the inner side wall of the feeding pipe 31 and is provided with an air inlet 310, which is connected to an external compressed air pipeline. When the bag opening of the ton bag 11 is covered on the feeding pipe 31 and the hanging strap is hung on the hook 43, compressed air is blown into the air inlet 310 and the air pipe 39 in sequence through the compressed air pipeline. The compressed air enters the ton bag 11 from the feeding pipe 31, causing the ton bag 11 to expand, thereby facilitating the filling of the ton bag 11. The air outlet of the air pipe 39 can extend in the direction of the axis of the feeding pipe 31 to avoid direct impact on the bag wall. The compressed air pressure value can be adjusted according to the size and material of the ton bag to achieve flexible expansion.

[0023] In addition, this ton bag packaging machine can be equipped with a PLC integrated control system to coordinate and control various hydraulic cylinders, air cylinders, electric cylinders and valves, and set up position sensors and temperature sensors to monitor the bag opening clamping status and heat melt temperature in real time, thereby realizing a fully automated bag hanging, inflation, filling, sealing and conveying process, further reducing manual intervention and improving packaging quality and production efficiency.

[0024] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A ton bag packaging machine with a dustproof structure, comprising a column support leg (2) and a platform (6) located at the upper end of the column support leg (2), wherein a belt conveyor (1) is installed at the bottom end of the inner side of the column support leg (2), characterized in that, A conical hopper (10) is installed on the upper inner side of the platform (6). A feeding port (9) and an inspection cover (8) are generated on the upper end of the conical hopper (10). The output end of the conical hopper (10) passes through the inner side of the platform (6) and is connected to a hose (5). The lower end of the hose (5) is connected to a movable hanging assembly (4). The lower end of the movable hanging assembly (4) is connected to a dustproof bag clamping mechanism (3). Hydraulic cylinders (7) are installed at the four corners of the inner side of the platform (6). The output end of each hydraulic cylinder (7) is connected to one corner of the upper end of the movable hanging assembly (4).

2. The ton bag packaging machine with a dustproof structure according to claim 1, characterized in that, The dustproof bag clamping mechanism (3) includes a feeding pipe (31), a negative pressure suction cup (37) is installed on the upper part of the outer side of the feeding pipe (31), a sealing plate (36) is fixedly connected to the outer side of the negative pressure suction cup (37), and a bag clamping assembly (35) is rotatably connected to the lower end of the sealing plate (36) located on the outer side of the feeding pipe (31).

3. A ton bag packaging machine with a dustproof structure according to claim 2, characterized in that, Both ends of the outer side of the bag clamping assembly (35) are rotatably connected to a set of connecting arms (34), and a sealing assembly (32) is fixedly connected to the lower end of each set of connecting arms (34). A cylinder (33) is rotatably connected between each connecting arm (34) and the bag clamping assembly (35).

4. A ton bag packaging machine with a dustproof structure according to claim 2, characterized in that, The bag clamping assembly (35) includes a set of clamping arms one (351) and a set of clamping arms two (352). A cylinder two (356) is rotatably connected to the upper end of each set of clamping arms one (351) and the upper end of each set of clamping arms two (352). An elastic band (353) is fixedly connected to the lower end of each clamping arm one (351) and the corresponding clamping arm two (352). An elastic sheet (354) is fixedly connected to the lower end of each clamping arm one (351) and clamping arm two (352).

5. A ton bag packaging machine with a dustproof structure according to claim 3, characterized in that, The sealing assembly (32) includes a strip-shaped opening box (321) and a heat melter (323) embedded in the inside of the strip-shaped opening box (321) from one side. A heat melt plate (322) is embedded in one side of the heat melter (323). Fixing ears (324) are fixedly connected to the front and rear sides of the upper end of the strip-shaped opening box (321).

6. A ton bag packaging machine with a dustproof structure according to claim 5, characterized in that, The front and rear ends of the hot melter (323) are fixedly connected to the second fixed lug (331). Gearboxes (329) are installed on the front and rear sides of the strip-shaped open box (321) near the corresponding second fixed lug (331). Gears 1 (327) and 2 (328) are installed on the inner side of the gearbox (329) and are meshed with each other. A rotating shaft (330) is fixedly connected through the outer side of the gearbox (329) at the center of the second gear (328). One end of the rotating shaft (330) is fixedly connected to the corresponding second fixed lug (331). A connecting shaft at the center of the first gear (327) is fixedly connected through the outer side of the gearbox (329) to a connecting rod (325). One end of the connecting rod (325) is rotatably connected to an electric cylinder (326). One end of the electric cylinder (326) is rotatably connected to the lower end of the outer side of the strip-shaped open box (321).

7. A ton bag packaging machine with a dustproof structure according to claim 4, characterized in that, Each of the first clamping arm (351) and each of the second clamping arm (352) is provided with a lug (357) near the second cylinder (356), the lug (357) being rotatably connected to the upper end of the first cylinder (33), and each of the first clamping arm (351) and each of the second clamping arm (352) is provided with a lug (355) near the elastic sheet (354), the lug (355) being rotatably connected to the upper end of the connecting arm (34).

8. A ton bag packaging machine with a dustproof structure according to claim 1, characterized in that, The movable strap assembly (4) includes a flat plate (41), a connecting pipe (42) is installed through the middle of the upper end of the flat plate (41), and hooks (43) are fixedly connected to the four corners of the lower end of the flat plate (41). A motor (44) is installed on the outside of the hooks (43), and a limit block (45) is fixedly connected to the output end of the motor (44).

9. A ton bag packaging machine with a dustproof structure according to claim 2, characterized in that, The upper end of the feed pipe (31) is provided with a flange (38), and an air pipe (39) is installed on the inner side wall of the feed pipe (31). One end of the air pipe (39) passes through the inner side wall of the feed pipe (31) and is provided with an air inlet (310).

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