A device for avoiding inner-arc wrinkling of a large-diameter thin-wall elbow

Abstract

The utility model provides a kind of equipment to avoid large-diameter thin-wall elbow inner arc wrinkle, including medium-frequency elbow machine main body, pipe chuck and swing arm;The medium-frequency elbow machine main body is arranged on horizontal ground, and the pipe to be processed is worn out by medium-frequency electric induction heating area, and the pipe is clamped and fixed by pipe chuck through the pipe wearing end;The pipe chuck is equipped with fixed part, opening and closing part and opening and closing control oil cylinder, the fixed part is equipped with the fixed part base parallel with horizontal ground, and roller assembly is assembled on the fixed part base, and the roller assembly is driven to run by hydraulic motor;The swing arm is equipped with the swing arm seat matched with medium-frequency elbow machine main body, and swing arm one end is fixedly assembled with pipe chuck.The utility model controls the inner and outer arc plastic deformation stress in the pipe bending process, solves the problem of large-diameter thin-wall elbow inner arc wrinkle, and achieves the purpose of improving product quality and reducing production cost.

Description

Technical Field

[0001] This utility model relates to the field of thin-walled pipe bending technology, specifically to a device for preventing wrinkling on the inner arc of large-diameter thin-walled pipes. Background Technology

[0002] Currently, large-diameter thin-walled bends are widely used in oil and gas pipelines, as well as in the chemical and shipbuilding industries. Because their processing is not suitable for anti-wrinkle plates and other measures used in small-diameter cold-bending processes, they are mostly processed using medium-frequency bending. This involves locally heating the pipe material to be bent using a medium-frequency induction coil until it reaches a plastic state, then bending is achieved by the swinging of a rotating arm driven by mechanical thrust. However, for bends with a wall thickness to diameter ratio of less than 2% and a bending radius less than 5D (D being the pipe diameter), internal arc wrinkling (referred to as excessive waviness in the SY / T-5257 standard) frequently occurs during bending, failing to meet relevant technical standards. Subsequent repair of these internally wrinkled bends is necessary. Repairing internal arc wrinkling in bends typically involves grinding the highest point while maintaining the minimum wall thickness, sometimes requiring adjustments to the wall thickness of the original pipe material. This is not only time-consuming and labor-intensive but also increases production costs, severely impacting the company's economic benefits.

[0003] To address the issue of inner arc wrinkling during medium-frequency bending of large-diameter thin-walled pipes, domestic and international manufacturers typically narrow the red-hot area of ​​the pipe by controlling the width of the medium-frequency induction heating band (i.e., the red-hot zone of the pipe). However, due to the influence of pipe temperature conduction, induction coil operating frequency, and shape and size, it is difficult to control the width of the heating band within the required range, making the effect of preventing inner arc wrinkling unstable. In addition, some manufacturers have also used double-sided water spraying to cool the induction coil and other heating components, which leads to increased energy consumption and production costs. Utility Model Content

[0004] This invention provides a device to prevent wrinkling on the inner arc of large-diameter thin-walled bends. It aims to solve the problem of wrinkling on the inner arc of large-diameter thin-walled bends by balancing the plastic deformation stress of the inner and outer arcs during the bending process, thereby improving product quality and reducing production costs.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A device for preventing wrinkling on the inner arc of large-diameter thin-walled pipe bends includes a medium-frequency pipe bending machine body, a pipe clamp, and a rotating arm; The main body of the medium frequency pipe bending machine is arranged on a horizontal ground. The pipe to be processed passes through the medium frequency induction heating area, and the end of the pipe is clamped and fixed by a pipe clamp. The pipe clamp is provided with a fixing part, an opening and closing part and an opening and closing control cylinder. The opening and closing part is driven by the opening and closing control cylinder to clamp the protruding end of the pipe in the mold hole surrounded by the fixing part and the opening and closing part. The fixing part is provided with a fixing part base parallel to the horizontal ground. A roller assembly is mounted on the fixing part base. The roller assembly is driven to rotate by a hydraulic motor. The rotating arm is equipped with a rotating arm seat that is fitted to the main body of the medium frequency pipe bending machine, and one end of the rotating arm is fixedly assembled with the pipe clamp.

[0006] The aforementioned device for preventing wrinkling of the inner arc of large-diameter thin-walled bends comprises two sets of roller assemblies, each driven by a hydraulic motor. Two hydraulic motor control circuits are connected in parallel within the hydraulic control system of the hydraulic motors. Each hydraulic motor control circuit is equipped with a gear pump and a three-position four-way directional valve. The gear pumps in both hydraulic motor control circuits are driven by the output shaft of the same motor. The three-position four-way directional valve is installed on the oil line between the gear pump and the hydraulic motor.

[0007] The aforementioned equipment for preventing wrinkling of the inner arc of large-diameter thin-walled bends is further equipped with on / off valves and pressure relief valves in the two sets of hydraulic motor control oil circuits, which are connected in series.

[0008] In the aforementioned equipment for preventing wrinkling of the inner arc of large-diameter thin-walled bends, both the three-position four-way directional valve and the on / off valve are electromagnetic control valves.

[0009] The aforementioned device for preventing wrinkling of the inner arc of large-diameter thin-walled bends includes a roller assembly with rollers and a roller mounting frame. The roller mounting frame has a top plate and two side plates, and the roller mounting frame is connected to the fixing base of the pipe clamp through the top plate. The rollers are pivotally connected to the two side plates of the roller mounting frame through roller shafts, and one end of the roller shaft is fixedly connected to the power output end of a hydraulic motor.

[0010] The aforementioned device for preventing wrinkling of the inner arc of large-diameter thin-walled bends includes a roller assembly with a roller angle adjustment mechanism. This mechanism comprises a roller mounting bracket rotating shaft, bolt connectors, and an arc-shaped elongated hole on the top plate of the roller mounting bracket. The rotating shaft of the roller mounting bracket is rotatably assembled with a shaft hole on the fixing base of the pipe clamp, and its lower end is fixed to the top plate of the roller mounting bracket. A screw in the bolt connector passes through the arc-shaped elongated hole on the top plate of the roller mounting bracket and the fixing base of the pipe clamp, thus assembling the roller mounting bracket and the fixing base of the pipe clamp together via the bolt connector.

[0011] This invention provides a device for preventing wrinkling on the inner arc of large-diameter thin-walled pipe bends. Compared with existing technologies, its advantages lie in the following: two sets of hydraulic motors drive two sets of rollers mounted on the base of the pipe clamp fixing part, which in turn provide rotational power to the rotating arm via the rollers and the pipe clamp. Simultaneously, during the plastic deformation of the pipe, the pipe clamp provides tension to the pipe it holds, thus balancing the plastic deformation stress of the inner and outer arcs during pipe bending and preventing instability and wrinkling caused by material compression due to the release of stress on the inner arc of the pipe. Tests have proven that the device described in this invention effectively solves the problem of wrinkling on the inner arc of large-diameter thin-walled pipe bends, and the produced bent pipe products meet relevant standards. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the bending process for large-diameter thin-walled pipes; Figure 2 This is a front view of the device for preventing wrinkling on the inner arc of large-diameter thin-walled bends as described in this utility model; Figure 3 yes Figure 2 Top view; Figure 4 yes Figure 2 Side view; Figure 5 yes Figure 4 Schematic diagram of the cross-sectional structure of the middle AA section; Figure 6 yes Figure 5 Schematic diagram of the cross-sectional structure of the middle BB section; Figure 7 This is a schematic diagram of the hydraulic control system for a hydraulic motor. Figure 8 This is a stress distribution diagram under the action of the swing arm torque during the pipe bending process; Figure 9 This is a stress distribution diagram of the pipe under the propulsion force of a medium-frequency pipe bending machine; Figure 10 yes Figure 8 and Figure 9 Schematic diagram of stress superposition in the middle tube; Figure 11 This is a schematic diagram of the tensile stress of the pipe under roller drive; Figure 12 yes Figure 10 and Figure 11 Schematic diagram of stress superposition in the middle pipe (the stress of the pipe is balanced by this utility model).

[0013] Explanation of each label in the diagram: 1 represents the pipe material, and 1-1 represents the red-hot area of ​​the pipe material; 2 is a swing arm; 3 is the pipe clamp, 3-1 is the fixing part, 3-1-1 is the base of the fixing part, 3-2 is the opening and closing part, and 3-3 is the opening and closing control cylinder; 4 is the swivel arm seat; 5 is the roller assembly, 5-1 is the roller, 5-2 is the roller shaft, 5-3 is the roller mounting bracket, 5-3-1 is the arc-shaped elongated hole, 5-4 is the roller mounting bracket rotating shaft, and 5-5 is the bolt connector; 6 represents the main body of the medium-frequency pipe bending machine; 7 represents a hydraulic motor; 8 represents the hydraulic control system of the hydraulic motor, 8-1 represents the motor, 8-2 represents the gear pump, 8-3 represents the on / off valve, 8-4 represents the pressure relief valve, and 8-5 represents the three-position four-way directional valve. Detailed Implementation

[0014] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0015] See Figure 1. Figure 8 , Figure 9 , Figure 10 Currently, the bending process for large-diameter thin-walled pipes generally adopts medium-frequency bending technology. This involves locally heating the pipe 1 to be bent using a medium-frequency induction coil until it reaches a red-hot state, and then bending the pipe 1 by swinging the rotating arm 2 under mechanical thrust. However, for bends with a wall thickness to diameter ratio of less than 2% and a bending radius of less than 5D, during the bending process, the compressive stress σ4 generated in the inner arc region of pipe 1 is the sum of the compressive stress σ1 generated by the inner arc compression deformation and the compressive stress σ3 generated by the pipe's advancement. Meanwhile, the tensile stress σ5 generated in the outer arc region of pipe 1 is the difference between the tensile stress σ2 generated by the outer arc stretching deformation and the compressive stress σ3 generated by the pipe's advancement. Since the absolute value of the compressive stress σ4 generated in the inner arc region of pipe 1 is much greater than the tensile stress σ5 generated in the outer arc region, the inner arc region may experience instability and wrinkling due to material compression during the pipe bending process. In the SY / T-5257 standard, this inner arc wrinkling phenomenon is referred to as excessive waviness. Such products do not meet the standard requirements and require subsequent repair. Repairing inner arc wrinkles in bends typically involves grinding the highest points while ensuring the minimum wall thickness, sometimes requiring thickening the main pipe wall. This is not only time-consuming and labor-intensive but also increases production costs, severely impacting the company's economic benefits.

[0016] See Figure 2 , Figure 3 , Figure 4To address the problem of inner arc wrinkling during the bending process of large-diameter thin-walled pipes, this invention provides a device to prevent inner arc wrinkling in large-diameter thin-walled pipes. It includes a medium-frequency pipe bending machine body 6, a pipe clamp 3, and a rotating arm 2. The medium-frequency pipe bending machine body 6 is positioned on a horizontal surface. The pipe to be processed 1 passes through the induction heating area of ​​the medium-frequency pipe bending machine body 6, and the end of the pipe 1 is clamped and fixed by the pipe clamp 3. The pipe clamp 3 is equipped with a fixing part 3-1, an opening and closing part 3-2, and an opening and closing control cylinder 3-3. The opening and closing control cylinder... The hydraulic cylinder 3-3 drives the opening and closing part 3-2 to clamp the protruding end of the pipe 1 in the mold hole surrounded by the fixing part 3-1 and the opening and closing part 3-2. The fixing part 3-1 is provided with a fixing base 3-1-1 parallel to the horizontal ground. Roller assembly 5 is mounted on the fixing base 3-1-1. The number of roller assembly 5 is preferably two sets. Each set of roller assembly 5 is driven by a set of hydraulic motors 7. The rotating arm 2 is provided with a rotating arm seat 4 that is matched with the main body 6 of the medium frequency pipe bending machine. One end of the rotating arm 2 is fixedly assembled with the pipe clamp 3.

[0017] See Figure 4 , Figure 5 , Figure 6 The device for preventing wrinkling of the inner arc of large-diameter thin-walled bends according to this utility model includes a roller 5-1, a roller mounting frame 5-3, and a roller angle adjustment mechanism in each roller assembly 5. The roller mounting frame 5-3 has a top plate and two side plates, and the roller mounting frame 5-3 is connected to the fixing base 3-1-1 of the pipe clamp 3 through the top plate. The roller 5-1 is pivotally connected to the two side plates of the roller mounting frame 5-3 through a roller shaft 5-2, and one end of the roller shaft 5-2 is fixedly connected to the power output end of the hydraulic motor 7. The roller angle adjustment mechanism includes a roller mounting frame rotating shaft. 5-4, bolt connector 5-5, and an arc-shaped elongated hole 5-3-1 opened on the top plate of the roller mounting bracket 5-3. The rotating shaft 5-4 of the roller mounting bracket is rotatably assembled with the shaft hole provided on the fixing base 3-1-1 of the pipe clamp 3. Its lower end is fixed to the top plate of the roller mounting bracket 5-3. The screw in the bolt connector 5-5 passes through the arc-shaped elongated hole 5-3-1 on the top plate of the roller mounting bracket 5-3 and the fixing base 3-1-1 of the pipe clamp 3. The roller mounting bracket 5-3 and the fixing base 3-1-1 of the pipe clamp 3 are assembled by the bolt connector 5-5. This utility model uses an adjustment mechanism to ensure that the extended axis of the roller shaft 5-2 intersects the rotation center O of the rotating arm seat 4, thereby ensuring that the roller 5-1 rotates around the rotation center O of the rotating arm seat 4 while rotating around the roller shaft 5-2, and the running trajectory curve is concentric with the curve of the bent pipe 1.

[0018] See Figure 2 , Figure 3 , Figure 4 , Figure 7The device for preventing wrinkling of the inner arc of large-diameter thin-walled bends described in this utility model has two sets of roller assemblies 5 driven by two sets of hydraulic motors 7. Two sets of hydraulic motor control oil circuits are set in parallel in the hydraulic control system 8 of the hydraulic motors. In each set of hydraulic motor control oil circuits, a gear pump 8-2, a three-position four-way directional valve 8-5, an on / off valve 8-3, and a pressure relief valve 8-4 are respectively provided. The gear pumps 8-2 in the two sets of hydraulic motor control oil circuits are driven by the output shaft of the same motor 8-1. The motor 8-1 is provided with synchronous output shafts extending in two directions. The three-position four-way directional valve 8-5 and the on / off valve 8-3 are electromagnetic control valves. The three-position four-way directional valve 8-5, the on / off valve 8-3, and the pressure relief valve 8-4 are installed in the oil circuit between the gear pump 8-2 and the hydraulic motor 7.

[0019] See Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 11 , Figure 12 The device for preventing wrinkling of the inner arc of large-diameter thin-walled bent pipes described in this utility model uses two sets of hydraulic motors 7 to drive two sets of rollers 5-1 installed on the fixing base 3-1-1 of the pipe clamp 3. The rollers 5-1 and the pipe clamp 3 provide rotational power to the rotating arm 2. At the same time, during the plastic deformation of the pipe, the pipe clamp 3 provides tension to the pipe 1 it holds. Therefore, during the bending process of the pipe 1, the compressive stress σ4 in the inner arc area of ​​the pipe 1 is partially offset by the tensile stress σ6 generated by the roller power. Meanwhile, the tensile stress in the outer arc area of ​​the pipe 1 is superimposed with the tensile stress σ6 generated by the roller power, so that the final compressive stress generated in the inner arc area of ​​the pipe 1 is close to the final tensile stress generated in the outer arc area of ​​the pipe 1. This balances the plastic deformation stress of the inner and outer arcs during the bending process of the pipe 1, and avoids the instability and wrinkling phenomenon caused by material extrusion due to the release of the inner arc stress of the pipe.

[0020] See Figure 2 , Figure 3 , Figure 4 , Figure 7 When using this invention to bend large-diameter thin-walled pipes, the roller assembly 5 driven by the hydraulic motor 7 provides a tension L to the pipe 1 through the pipe clamp 3. This balances the stress distribution in the inner and outer arc regions of the pipe 1 during plastic deformation, caused by the superposition of the medium-frequency pipe bending machine's propulsion force T and the swing arm torque M. This prevents instability and wrinkling of the inner arc of the pipe due to material compression. Furthermore, it adjusts the working state of the hydraulic motor control circuit to match the bending process of the pipe 1. Taking a φ914×10 thin-walled steel pipe as the raw material and a bending radius of 3D (2742mm) as a specific embodiment, the specific bending operation steps are as follows: a. Motor and Gear Pump Selection: Based on the dimensions and performance parameters of the large-diameter thin-walled pipe product, the stress distribution in the inner and outer arc regions of the pipe during bending is analyzed when using the existing medium-frequency bending process (i.e., without roller assemblies). Based on this stress distribution, the required tension value provided by the rollers to balance the stress distribution is determined when using the device described in this invention to prevent wrinkling of the inner arc of the large-diameter thin-walled pipe. Then, the rated power of motor 8-1 and the rated pressure and flow rate of the two gear pumps 8-2 are selected to match this tension value. In this embodiment: The bending modulus W of steel pipes = =6348953.1mm 3 The maximum yield strength ReH of the red-hot zone of the steel pipe is calculated as 60MPa. Therefore, the moment required for the bending deformation of the pipe is M=W×ReH=6348953.1×60 / 1000=380937.2nm. Considering that the bending moment borne by the entire cross-sectional area meets the yield strength requirement, the maximum bending moment is set to 2M=761874.4nm. Since the bending radius of pipe 1 is R=2.742m, the thrust required for the plastic deformation of the pipe is T=2M / R=277853.5n, that is, T=27.8 tons. Based on the measured data, the friction coefficient of the swing arm was calculated and determined to be 0.05 (when the roller 5-1 is not working, the swing arm is passively operated under the thrust of the medium frequency pipe bending machine). The weight of the swing arm is about 40 tons. The friction resistance of the swing arm is calculated to be 2 tons. Adding the thrust required for the plastic deformation of the pipe, the total thrust is about 29.8 tons. The cross-sectional area of ​​the steel pipe is S = π (R 2 -r 2 ) = 3.14 × (457) 2 -447 2 =28385mm 2 The compressive stress generated by the thrust is 29.8 × 10⁻⁶. 4 / 28385=10.56MPa. The corresponding tensile stress σ5 on the outer arc is 60-10.56=49.44MPa, and the compressive stress σ4 on the inner arc is 70.56MPa; To reduce the difference between the compressive stress of the inner arc and the tensile stress of the outer arc, and to balance the stress distribution during the pipe bending process, a tensile force L of 2 to 5 tons is set to be provided by the roller assembly 5, and a motor 8-1 with a rated power of 5.5KW and two gear pumps 8-2 with a rated pressure of not less than 12MPa and a rated flow rate of 14L / min are selected. b. Roller Angle Adjustment: After completing the connection of the roller assembly, hydraulic motor, and hydraulic motor control system, adjust the position of the rotating arm seat 4 according to the dimensional parameters of the large-diameter thin-walled pipe product, and determine the rotation center of the rotating arm as point O (see Appendix). Figure 3The rotation radius of the rotating arm (R=2.742m) is determined, and the angle of roller 5-1 is adjusted according to the rotation center and rotation radius of the rotating arm so that the movement trajectory curve of roller 5-1 is concentric with the arc curve of the pipe bending. c. Adjustment of the tension of the roller assembly under no-load condition: In the control oil circuit of the two sets of hydraulic motors 7, the valve core of one three-position four-way reversing valve moves to the middle position, and the valve core of the other three-position four-way reversing valve moves to the left position. Start motor 8-1. At this time, only one set of hydraulic motors drives one set of rollers to rotate, providing the power required for the swing arm 2 to swing. Use the on-off valve 8-3 and the pressure relief valve 8-4 to adjust the pressure of the hydraulic oil circuit so that the power provided by roller 5-1 to the swing arm 2 is consistent with the resistance of the swing arm. The swing arm 2 swings at a uniform speed. Repeat the above operation steps to adjust the power provided by the other set of rollers to the swing arm so that both sets of rollers can independently drive the swing arm to swing at a uniform speed. d. Pipe bending: The pipe 1 passing through the medium frequency induction heating area of ​​the medium frequency pipe bending machine is clamped by the pipe clamp 3. Under the combined action of the propulsion force of the medium frequency pipe bending machine and the driving force of the rollers, the rotating arm 2 rotates and swings. During this process, the valve core of the three-position four-way reversing valve 8-3 in the control oil circuit of the two sets of hydraulic motors 7 is in the left position. The motor 8-1 runs, and the two sets of hydraulic motors 7 drive the two sets of rollers 5-1 to run respectively, and provide tension to the pipe 1 through the pipe clamp 3. e. Arm Return: After the bending operation is completed, the pipe clamp 3 is driven by the opening and closing control cylinder 3-3 to open the opening and closing part 3-2, so that the pipe clamp 3 can be opened and the bent workpiece can be taken out. Then, the valve core of the three-position four-way reversing valve 8-5 in the hydraulic circuit controlled by the two sets of hydraulic motors moves to the right position, the on-off valve 8-3 is closed, the pressure relief valve does not work, the motor 8-1 runs, and after the three-position four-way valve 8-5 reverses, the two sets of hydraulic motors 7 drive the two sets of rollers 5-1 to rotate in opposite directions, and the arm 2 swings back to the center at a set speed, entering the next working cycle.

Claims

1. A device for preventing wrinkling on the inner arc of a large-diameter thin-walled bend pipe, characterized in that: Includes the main body of the medium frequency pipe bending machine (6), the pipe clamp (3) and the rotating arm (2); The main body (6) of the medium frequency pipe bending machine is arranged on a horizontal ground. The pipe (1) to be processed passes through the medium frequency induction heating area, and the end of the pipe (1) is clamped and fixed by the pipe clamp (3). The pipe clamp (3) is provided with a fixing part (3-1), an opening and closing part (3-2) and an opening and closing control cylinder (3-3). The opening and closing part (3-2) is driven by the opening and closing control cylinder (3-3) to clamp the protruding end of the pipe (1) in the mold hole surrounded by the fixing part (3-1) and the opening and closing part (3-2). The fixing part (3-1) is provided with a fixing part base (3-1-1) parallel to the horizontal ground. A roller assembly (5) is mounted on the fixing part base (3-1-1). The roller assembly (5) is driven to run by a hydraulic motor (7). The rotating arm (2) is equipped with a rotating arm seat (4) that is fitted to the main body (6) of the medium frequency pipe bending machine, and one end of the rotating arm (2) is fixedly assembled with the pipe clamp (3).

2. The device for preventing wrinkling on the inner arc of large-diameter thin-walled bends according to claim 1, characterized in that: The number of roller assemblies (5) is two sets. The two sets of roller assemblies (5) are driven by two sets of hydraulic motors (7). Two sets of hydraulic motor control oil circuits are set in parallel in the hydraulic control system (8) of the hydraulic motors. A gear pump (8-2) and a three-position four-way directional valve (8-5) are set in each set of hydraulic motor control oil circuits. The gear pump (8-2) in the two sets of hydraulic motor control oil circuits is driven by the output shaft of the same motor (8-1). The three-position four-way directional valve (8-5) is installed in the oil circuit between the gear pump (8-2) and the hydraulic motor (7).

3. The device for preventing wrinkling on the inner arc of large-diameter thin-walled bends according to claim 2, characterized in that: The two sets of hydraulic motor control circuits are also equipped with on / off valves (8-3) and pressure relief valves (8-4).

4. The device for preventing wrinkling on the inner arc of large-diameter thin-walled bends according to claim 3, characterized in that: Both the three-position four-way directional valve (8-5) and the on / off valve (8-3) are electromagnetic control valves.

5. The device for preventing wrinkling on the inner arc of a large-diameter thin-walled bend according to claim 2, 3, or 4, characterized in that: The roller assembly (5) is provided with a roller (5-1) and a roller mounting bracket (5-3); the roller mounting bracket (5-3) is provided with a top plate and two side plates, and the roller mounting bracket (5-3) is connected to the fixing base (3-1-1) of the pipe clamp (3) through the top plate; the roller (5-1) is pivotally connected to the two side plates of the roller mounting bracket (5-3) through the roller shaft (5-2), and one end of the roller shaft (5-2) is fixedly connected to the power output end of the hydraulic motor (7).

6. The device for preventing wrinkling on the inner arc of a large-diameter thin-walled bend according to claim 5, characterized in that: The roller assembly (5) is also provided with a roller angle adjustment mechanism, which includes a roller mounting bracket rotating shaft (5-4), a bolt connector (5-5), and an arc-shaped elongated hole (5-3-1) opened on the top plate of the roller mounting bracket (5-3). The roller mounting bracket rotating shaft (5-4) is rotatably assembled with the shaft hole provided on the fixing part base (3-1-1) of the pipe clamp (3), and its lower end is fixed on the top plate of the roller mounting bracket (5-3). The screw in the bolt connector (5-5) passes through the arc-shaped elongated hole (5-3-1) on the top plate of the roller mounting bracket (5-3) and the fixing part base (3-1-1) of the pipe clamp (3), and the roller mounting bracket (5-3) is assembled with the fixing part base (3-1-1) of the pipe clamp (3) through the bolt connector (5-5).

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