Powder tank truck tank and powder tank truck thereof

Abstract

The invention provides a powder tank truck tank and powder tank truck, including support frame, both sides of which are equipped with support wheels, and the upper end is connected with the tank, one end of which is rotatably connected with the lower side of one end of the tank, and the tank extends out of the support frame at this end, and the lower side of this end is equipped with a towing frame; the upper end of the tank is provided with a feeding port and a sealing cover, and a discharge pipe is obliquely arranged downward at the end away from the towing frame, and a free end of the discharge pipe is detachably connected with a sealing plug, and the end is concave to form a mounting groove, and a driving motor is arranged in the groove, and a spiral discharge rod is rotatably connected in the discharge pipe and extends into the tank, and a power output shaft of the driving motor is connected with one end of the spiral discharge rod extending into the tank; the tank is provided with mounting frames at both sides of the towing frame, and each mounting frame is rotatably connected with a vertical rotating hydraulic supporting cylinder, and the telescopic shaft extends downward and is connected with a supporting seat, and the upper end of the hydraulic supporting cylinder is provided with a connecting push plate towards one side of the support frame, and the mounting frame is provided with a supporting plate near the connecting push plate, and a plurality of elastic rubber supporting pieces are connected between the two. The invention lifts one end of the tank and cooperates with the spiral discharge, which can avoid powder blockage and improve the discharging efficiency.

Description

Technical Field

[0001] This invention belongs to the field of powder storage and transportation technology, and relates to a powder tanker tank and the powder tanker truck itself. Background Technology

[0002] In the field of bulk material transportation, with the continuous upgrading of industrialization and logistics systems, the demand for closed, large-scale, and efficient transportation of powdery solid materials (such as cement, fly ash, slag powder, limestone powder, flour, and chemical raw materials) is increasing. Traditional transportation methods mostly use bagged or open-top trucks for transshipment, which is not only labor-intensive and inefficient in loading and unloading, but also easily causes material dust, loss, and environmental pollution, making it difficult to meet the requirements of modern green logistics and safe production standards.

[0003] To address the aforementioned issues, powder tank trucks were developed. Their typical structure includes a chassis, a sealed horizontal cylindrical tank, a fluidized bed device, a compressed air system, an air circuit control unit, and unloading pipelines. During operation, a controlled-pressure compressed air is injected into the tank via an onboard air compressor, causing the powder on the fluidized bed at the bottom of the tank to enter a near-fluid state under the interaction of the gas and solid phases. This allows for fluidized transport and gravity-assisted unloading via the pressure difference. This technology significantly improves the airtightness, automation, and operational efficiency of powder transportation, and has become a key piece of equipment in the powder logistics chain of industries such as building materials, energy, food, and chemicals.

[0004] However, compared to liquid media, powders are typical non-Newtonian, multiphase discrete systems, and their flow behavior is highly dependent on physical properties such as particle size distribution, moisture content, particle shape, surface roughness, and bulk density. Especially under static storage or low-pressure fluidization conditions, because the discharge port cannot be too large, powder is prone to phenomena such as arching, rat holes, material adhering to the wall, and uneven fluidization at the discharge port, leading to a significant deterioration in overall flowability. In practice, it is common to see smooth discharge at the beginning, followed by a sharp drop in rate or even complete stagnation; in severe cases, stable material arches form inside the tank or local failure of the fluidized bed occurs, causing discharge interruption and increased residue, which not only affects turnover efficiency but also increases the frequency of manual tank cleaning and safety risks. Summary of the Invention

[0005] The purpose of this invention is to provide a powder tanker body and the powder tanker itself. By raising one end of the tank body and coordinating it with a screw unloading method, the problem of powder blockage can be effectively avoided and the powder discharge efficiency can be improved.

[0006] To solve the above technical problems, the present invention provides a powder tanker body, including a support frame, support wheels are installed on both sides of the support frame, the upper end of the support frame is connected to the tank body, the upper side of one end of the support frame is rotatably connected to the lower side of one end of the tank body, the end of the tank body away from the rotation extends out of the support frame, and a towing frame for connecting to the powder tanker is provided on the lower side of the end of the tank body extending out of the support frame.

[0007] The upper end of the tank is provided with a feeding port, and a sealing cap is connected to the feeding port. A discharge pipe is provided at the end of the tank away from the traction frame, which is inclined outward and downward. A sealing plug is detachably connected to the free end of the discharge pipe. The end of the tank away from the traction frame is recessed inward to form an installation groove. A drive motor is installed in the installation groove. A spiral discharge rod is rotatably connected in the discharge pipe. The spiral discharge rod extends into the tank. The power output shaft of the drive motor is connected to the end of the spiral discharge rod that extends into the tank.

[0008] The tank body is provided with mounting brackets on both sides of the traction frame. Each mounting bracket is rotatably connected to a hydraulic support cylinder that can rotate vertically. The telescopic axis of the hydraulic support cylinder is downward and rotatably connected to a support seat. Each hydraulic support cylinder has a connecting push plate on the side facing the support frame. Each mounting bracket is provided with a support plate near the corresponding connecting push plate. Multiple elastic rubber support plates are connected between each connecting push plate and the corresponding support plate.

[0009] By adopting the above technical solution, during powder unloading operations, the vehicle is first parked at the unloading position. Then, the hydraulic support cylinders on both sides are extended. After the support base contacts the ground, the telescopic shaft continues to extend, lifting the end of the tank equipped with the traction frame upwards. This results in the tank being tilted, with the end further away from the discharge pipe higher and the end closer to the discharge pipe lower. At this time, the powder inside the tank naturally gathers towards the discharge pipe under the action of gravity, reducing the gravitational resistance that needs to be overcome during the powder discharge process. Afterwards, the sealing plug of the discharge pipe is opened, and the drive motor is started to drive the screw discharge rod to rotate. The screw discharge rod continuously pushes the powder accumulated at the discharge pipe outwards. Combined with the tilted posture of the tank, this effectively avoids the formation of a material arch at the discharge port, ensuring a smooth and stable unloading process. After unloading is completed, the hydraulic support cylinders are shortened in the reverse direction, and the tank gradually falls back to a horizontal state. The connecting shaft at the traction frame is re-inserted into the connecting slot of the traction base to complete the positioning. Finally, the hydraulic support cylinders are reset to complete the unloading operation.

[0010] The invention is further configured such that the feeding port is rectangular, the sealing cover includes two cover plates respectively hinged to opposite sides of the feeding port, the sum of the lengths of the two cover plates is equal to the length of the feeding port, a push-pull hydraulic support rod is rotatably connected between the outer side of each cover plate and the outer side of the upper end of the tank body, and the remaining two sides of the feeding port are connected to flexible sealing membranes, and the two sides of each flexible sealing membrane are connected to the edge of the corresponding cover plate.

[0011] The present invention is further configured such that each cover plate has a rubber sealing strip on its free edge.

[0012] The present invention is further configured such that each flexible sealing membrane is made of elastic silicone material.

[0013] The invention is further configured such that a spray pipe is provided on both sides of the feeding port at the top of the tank body, and each spray pipe is connected to a plurality of nozzles distributed along its length. Each nozzle faces outward toward the inner wall of the tank body. A diversion pipe is provided at one end of the tank body. One end of each spray pipe extends out of the tank body and is connected to the diversion pipe. A high-pressure air pump is installed outside the tank body. A connecting pipe is connected to the middle of the diversion pipe. The free end of the connecting pipe is connected to the outlet end of the high-pressure air pump.

[0014] The present invention is further configured such that the inner wall of the tank is provided with multiple arc-shaped guide strips distributed along its length on both sides of the feeding port, and the lower edge of each arc-shaped guide strip is inclined towards the discharge pipe.

[0015] The present invention is further configured such that the free end of the connecting pipe is provided with a connector that can be detachably connected to the outlet end of the high-pressure air pump.

[0016] The present invention is further configured such that a pressure safety valve is provided on the outside of the tank.

[0017] The present invention is further configured such that each elastic rubber support sheet is vertically arranged.

[0018] This invention also discloses a powder tanker truck body, including a powder tanker truck body and a tractor unit. The rear of the tractor unit is provided with a traction seat that cooperates with the supporting frame. The upper end of the traction seat is rotatably connected to a horizontally rotatable connecting seat. The upper end of the rotating connecting seat has a downward-facing connecting slot. The lower side of the tractor unit has a downward-facing connecting shaft that cooperates with the connecting slot. The inner diameter of the connecting slot is larger than the diameter of the connecting shaft.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] Firstly, this invention, through the rotating connection structure between the support frame and the tank body, and in conjunction with the hydraulic support cylinders on both sides, can flexibly lift the end of the tank body near the traction frame during unloading operations, causing the entire tank body to tilt towards the discharge pipe. With the help of gravity, the powder naturally gathers towards the discharge pipe, significantly reducing the resistance that needs to be overcome during the powder discharge process. Combined with the active pushing action of the spiral discharge rod, it can effectively break up the material arch formed at the discharge port, avoid powder blockage, ensure a smooth unloading process, reduce the residual powder rate in the tank, reduce the frequency of manual tank cleaning, and improve turnover efficiency.

[0021] Secondly, the present invention provides an elastic rubber support plate between the hydraulic support cylinder and the mounting frame. When the vehicle is in motion, the elastic rubber support plate can buffer the vibration load transmitted from the tank to the hydraulic support cylinder, preventing the rigid structure from being damaged by bumps during the process, thus improving the stability and service life of the structure.

[0022] Thirdly, this invention features a high-pressure spray pipe and nozzle at the top of the tank. After unloading, high-pressure air can be used to blow down the inner wall of the tank, removing powder adhering to it and further reducing residual powder. Combined with the guiding effect of the arc-shaped guide strip, the blown-down powder can smoothly converge and be discharged through the discharge pipe, improving the tank cleaning effect. Simultaneously, automatic tank cleaning and automatic air blowing further reduce workload. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0024] Figure 2 Used to display the connecting shaft at the lower end of the traction frame;

[0025] Figure 3 It is a partial cross-sectional view used to show the spiral discharge rod inside the discharge pipe;

[0026] Figure 4 It is a partial sectional view used to show the nozzle and arc-shaped guide strip inside the tank;

[0027] Figure 5 Used to demonstrate the connection between the sealing cap and the feeding port;

[0028] Figure 6 Used to demonstrate the connection between the hydraulic support cylinder and the tank;

[0029] Figure 7 Used to demonstrate the rotating connecting seat on the traction seat.

[0030] The components include: 1. Traction head; 2. Traction seat; 3. Rotary connecting seat; 4. Connecting slot; 5. Support frame; 6. Support wheels; 7. Tank body; 8. Traction frame; 9. Connecting shaft; 10. Pneumatic safety valve; 11. Feed port; 12. Cover plate; 13. Rubber sealing strip; 14. Push-pull hydraulic support rod; 15. Flexible sealing membrane; 16. Discharge pipe; 17. Sealing plug; 18. Mounting slot; 19. Drive motor; 20. Spiral discharge rod; 21. Spray pipe; 22. Nozzle; 23. Diverter pipe; 24. High-pressure air pump; 25. Connecting pipe; 26. Connector; 27. Arc-shaped guide strip; 28. Mounting frame; 29. ​​Hydraulic support cylinder; 30. Support seat; 31. Connecting push plate; 32. Support plate; 33. Elastic rubber support sheet. Detailed Implementation

[0031] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a further detailed explanation of the powder tanker body and the powder tanker truck proposed in this invention. The advantages and features of this invention will become clearer from the following description. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, used only to facilitate and clarify the illustration of the embodiments of this invention. The same or similar reference numerals in the drawings represent the same or similar parts.

[0032] Example, refer to Figure 1-7 A powder tanker tank body 7 includes a tractor head 1. The rear of the tractor head 1 is provided with a traction seat 2 that cooperates with a support frame 5. The upper end of the traction seat 2 is rotatably connected to a rotating connecting seat 3 that can rotate horizontally. The upper end of the rotating connecting seat 3 is provided with a connecting slot 4 facing downward.

[0033] The system includes a support frame 5, with two support wheels 6 mounted on both sides. A horizontally positioned tank body 7 is connected to the upper end of the support frame 5. The upper side of one end of the support frame 5 is rotatably connected to the lower side of one end of the tank body 7. The end of the tank body 7 away from the rotatable end extends out of the support frame 5, allowing the end of the tank body 7 extending out of the support frame 5 to be supported upwards. A towing frame 8, which connects to the powder tanker, is located on the lower side of the end of the tank body 7 extending out of the support frame 5. A connecting shaft 9, which mates with a connecting slot 4, is located on the lower side of the towing frame 8. The connecting shaft 9 has a circular cross-section, while the connecting slot 4 has a strip-shaped cross-section that mates with the connecting shaft 9. The inner diameter of the connecting slot is larger than the diameter of the connecting shaft 9, facilitating the downward insertion of the connecting shaft 9 into the connecting slot 4, thus connecting the towing frame 8 to the towing seat 2.

[0034] A pressure safety valve 10 is installed on the outside of the tank body 7. If the air pressure inside the tank body 7 is too high, the pressure will be automatically released through the pressure safety valve 10. A feeding port 11 is located at the top of the tank body. The feeding port 11 is rectangular and connected to a sealing cover. The sealing cover consists of two cover plates 12 hinged to opposite sides of the feeding port 11. The sum of the lengths of the two cover plates 12 is equal to the length of the feeding port 11. Each cover plate 12 has a rubber sealing strip 13 on its free edge to increase the sealing performance of the feeding port 11. A push-pull hydraulic support rod 14, extending along the length of each cover plate 12, is rotatably connected between the outer side of each cover plate 12 and the outer side of the upper end of the tank body 7. 1. Each of the remaining two sides is connected to a flexible sealing membrane 15 made of elastic silicone material. Both sides of each flexible sealing membrane 15 are connected to the edge of the corresponding cover plate 12. When the hydraulic support rod 14 is pushed and pulled to shorten, the cover plate 12 is pulled to rotate outward and open the feeding port 11. When the hydraulic support rod 14 is pushed and pulled to extend, the cover plate 12 is pushed to close and cover the feeding port 11. When the two cover plates 12 open outward, the flexible sealing membrane 15 is in a taut state. When the cover plate 12 closes inward, the flexible sealing membrane 15 retracts inward and enters the feeding port 11.

[0035] A discharge pipe 16 is installed at the end of the tank body 7 furthest from the traction frame 8, angled downwards and outwards. A sealing plug 17 is detachably connected to the free end of the discharge pipe 16. The end of the tank body 7 furthest from the traction frame 8 is recessed inwards to form a mounting groove 18. A drive motor 19 is installed in the mounting groove 18. A spiral discharge rod 20 is rotatably connected inside the discharge pipe 16, extending into the tank body 7. The power output shaft of the drive motor 19 is connected to the end of the spiral discharge rod 20 that extends into the tank body 7. When the drive motor 19 drives the spiral discharge rod 20 to rotate, it continuously pushes and conveys the powder in the tank body 7 outwards, preventing bridging of the powder within the discharge pipe 16 and ensuring smooth discharge.

[0036] Inside the tank body 7, on both sides of the feeding port 11, there is a spray pipe 21 extending along its length. Each spray pipe 21 is connected to multiple nozzles 22 distributed along its length. Each nozzle 22 faces outward toward the inner wall of the tank body 7. A diversion pipe 23 is provided at one end of the tank body 7. One end of each spray pipe 21 extends out of the tank body 7 and connects to the diversion pipe 23. A high-pressure air pump 24 is installed outside the tank body 7. A connecting pipe 25 is connected to the middle of the diversion pipe 23. The free end of the connecting pipe 25 is provided with a connector 26 that can be detachably connected to the outlet end of the high-pressure air pump 24. On both sides of the feeding port 11, the inner wall of the tank body 7 is provided with multiple arc-shaped guide strips 27 distributed along its length. The lower edge of each arc-shaped guide strip 27 is inclined toward the discharge pipe 16. When the high-pressure air pump 24 operates and the nozzle 22 blows air onto the inner wall of the tank 7, it can dry the water inside the tank 7 after cleaning, reducing powder adhering to the wall. During discharge, the air blowing can move the powder adhering to the wall towards the discharge pipe 16, allowing the powder inside the tank 7 to be discharged more fully. At the same time, it can also disconnect the connector 26 to connect to high-pressure water for automatic cleaning of the inner wall of the tank 7.

[0037] On both sides of the tank body 7 at the towing frame 8, there is a mounting frame 28. Each mounting frame 28 is rotatably connected to a vertically rotatable hydraulic support cylinder 29. The telescopic axis of the hydraulic support cylinder 29 is downward and rotatably connected to a support seat 30. A connecting push plate 31 is provided on the upper end of each hydraulic support cylinder 29 facing the side of the support frame 5. A support plate 32 is provided on each mounting frame 28 near the corresponding connecting push plate 31. Multiple elastic rubber support plates 33 are connected between each connecting push plate 31 and the corresponding support plate 32. Each elastic rubber support plate 33 is vertically arranged. When unloading or replacing tank 7 is required, hydraulic support cylinder 29 extends, gradually bringing support base 30 into contact with the ground. Then, hydraulic support cylinder 29 continues to extend, causing one end of tank 7 to rotate upward. During the rotation of tank 7, hydraulic support cylinder 29 rotates to an inclined position, causing elastic rubber support sheet 33 to bend through connecting push plate 31. When one end of tank 7 is supported, the powder inside tank 7 can continuously gather towards discharge pipe 16. When hydraulic support cylinder 29 shortens, tank 7 gradually rotates downward to a horizontal position, and connecting shaft 9 is inserted downward into connecting slot 4. Hydraulic support cylinder 29 returns to a vertical downward position. At the same time, under the action of elastic rubber support sheet 33, hydraulic support cylinder 29 is less prone to swaying during vehicle movement.

[0038] Working principle: When unloading powder, first park the vehicle at the unloading position, then control the extension of the hydraulic support cylinders 29 on both sides. After the support seat 30 contacts the ground, the telescopic shaft continues to extend, lifting the end of the tank 7 equipped with the traction frame 8 upwards. This makes the tank 7 tilted, with the end away from the discharge pipe 16 higher and the end closer to the discharge pipe 16 lower. At this time, the powder in the tank 7 naturally gathers towards the discharge pipe 16 under the action of gravity, reducing the gravitational resistance that needs to be overcome during the powder discharge process. Then, open the sealing plug 17 of the discharge pipe 16 and start the drive motor 19 to drive the screw discharge rod 20. As the spiral discharge rod 20 rotates, it continuously pushes the powder accumulated at the discharge pipe 16 outwards. Combined with the tilted posture of the tank 7, this effectively prevents the powder from forming an arch at the discharge port, ensuring a smooth and stable unloading process. If further reduction of powder residue in the tank 7 is required, the high-pressure air pump 24 can be activated. Compressed air is delivered to the two side nozzles 21 via the connecting pipe 25 and the diverting pipe 23, and finally sprayed from each nozzle 22, blowing off the powder adhering to the side wall of the tank 7. With the tilting guidance of the arc-shaped guide strip 27, the powder can smoothly slide to the discharge pipe 16 for discharge, further reducing the residue rate in the tank. After unloading, the reverse control hydraulic support cylinder 29 shortens, and the tank 7 gradually returns to a horizontal state. The connecting shaft 9 at the traction frame 8 is re-inserted into the connecting slot 4 of the traction seat 2 to complete positioning. Finally, the hydraulic support cylinder 29 is reset to complete the unloading operation. The entire process requires no manual intervention for tank cleaning, improving unloading efficiency and reducing safety risks.

[0039] It should also be noted that all terms such as "set up" and similar descriptive words in this application (especially the specification) indicate that two structures have or exist a connection relationship. However, the specific means by which the two are connected are not limited in detail, and are usually conventional connection methods. That is, the means should be understood as prior art and do not need to be elaborated. For example, "m is set up with n" only indicates that structure m has structure n, and whether the two are connected by welding, riveting, adhesive, or integral molding is within the scope of protection of this application. Similarly, "x is rotatably set up with y" only indicates that y and x can rotate relative to each other, and whether the two are connected by a bearing, or whether y directly passes through x and is rotatably connected to x, or other feasible methods, are all within the scope of protection of this application.

[0040] The above description is merely a description of preferred embodiments of the present invention and is not intended to limit the scope of the present invention in any way. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the protection scope of the claims.

Claims

1. A powder tanker body, comprising a support frame (5), wherein support wheels (6) are mounted on both sides of the support frame (5), characterized in that, The upper end of the support frame (5) is connected to the tank body (7). The upper side of one end of the support frame (5) is rotatably connected to the lower side of one end of the tank body (7). The end of the tank body (7) away from the rotation extends out of the support frame (5). A towing frame (8) connected to the powder tanker is provided on the lower side of the end of the tank body (7) extending out of the support frame (5). The upper end of the tank (7) is provided with a feeding port (11), and a sealing cap is connected to the feeding port (11). The end of the tank (7) away from the traction frame (8) is provided with a discharge pipe (16) that slopes outward and downward. The free end of the discharge pipe (16) is detachably connected with a sealing plug (17). The end of the tank (7) away from the traction frame (8) is recessed inward to form an installation groove (18). A drive motor (19) is installed in the installation groove (18). A spiral discharge rod (20) is rotatably connected in the discharge pipe (16). The spiral discharge rod (20) extends into the tank (7). The power output shaft of the drive motor (19) is connected to the end of the spiral discharge rod (20) that extends into the tank (7). The tank (7) is provided with mounting brackets (28) on both sides of the traction frame (8). Each mounting bracket (28) is rotatably connected to a hydraulic support cylinder (29) that can rotate vertically. The telescopic axis of the hydraulic support cylinder (29) is downward and rotatably connected to a support seat (30). Each hydraulic support cylinder (29) is provided with a connecting push plate (31) on the side facing the support frame (5). Each mounting bracket (28) is provided with a support plate (32) near the corresponding connecting push plate (31). Each connecting push plate (31) and the corresponding support plate (32) are connected with multiple elastic rubber support plates (33).

2. The tank body of a powder tanker truck according to claim 1, characterized in that, The feeding port (11) is rectangular. The sealing cover includes two cover plates (12) that are respectively hinged to opposite sides of the feeding port (11). The sum of the lengths of the two cover plates (12) is equal to the length of the feeding port (11). Each cover plate (12) has a push-pull hydraulic support rod (14) rotatably connected between its outer side and the outer side of the upper end of the tank (7). The remaining two sides of the feeding port (11) are connected to flexible sealing membranes (15). Each flexible sealing membrane (15) has its two sides connected to the edge of the corresponding cover plate (12).

3. The tank body of a powder tanker truck according to claim 2, characterized in that, Each cover plate (12) has a rubber sealing strip (13) on its free edge.

4. The tank body of a powder tanker truck according to claim 2, characterized in that, Each flexible sealing membrane (15) is made of elastic silicone material.

5. The tank body of a powder tanker truck according to claim 1, characterized in that, The top of the tank (7) is provided with spray pipes (21) arranged along its length on both sides of the feeding port (11). Each spray pipe (21) is connected to multiple nozzles (22) distributed along its length. Each nozzle (22) faces outward toward the inner wall of the tank (7). A diversion pipe (23) is provided at one end of the tank (7). One end of each spray pipe (21) extends out of the tank (7) and is connected to the diversion pipe (23). A high-pressure air pump (24) is installed outside the tank (7). A connecting pipe (25) is connected to the middle of the diversion pipe (23). The free end of the connecting pipe (25) is connected to the outlet end of the high-pressure air pump (24).

6. The tank body of a powder tanker truck according to claim 5, characterized in that, The inner wall of the tank (7) is provided with multiple arc-shaped guide strips (27) distributed along its length on both sides of the feeding port (11), and the lower edge of each arc-shaped guide strip (27) is inclined towards the discharge pipe (16).

7. The tank body of a powder tanker truck according to claim 5, characterized in that, The free end of the connecting pipe (25) is provided with a connector (26) that can be detachably connected to the outlet end of the high-pressure air pump (24).

8. The tank body of a powder tanker truck according to claim 1, characterized in that, A pressure safety valve (10) is provided on the outside of the tank (7).

9. The tank body of a powder tanker truck according to claim 1, characterized in that, Each elastic rubber support sheet (33) is set vertically.

10. A powder tanker truck body, comprising the powder tanker truck body according to any one of claims 1-9, characterized in that, It also includes a tractor unit (1), the rear of which is provided with a traction seat (2) that cooperates with the support frame (5). The upper end of the traction seat (2) is rotatably connected to a rotating connecting seat (3) that can rotate horizontally. The upper end of the rotating connecting seat (3) is provided with a connecting slot (4) facing downward. The lower side of the traction frame (8) is provided with a connecting shaft (9) that cooperates with the connecting slot (4). The inner diameter of the connecting slot (4) is larger than the diameter of the connecting shaft (9).

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