A back-retractable c-shaped airbag threading device and method for variable cross-section pipeline

Abstract

The application discloses a back-rolling C-shaped air bag wire threading device for a variable cross-section pipeline and a method thereof. The device comprises a receiving cavity, a rotating shaft, an air bag body, a reset driving mechanism and a pneumatic system. The cross-section of the air bag body is C-shaped, the bottom wall is thicker than the two side flaps, the free edge of the flaps is provided with a flexible magnetic strip, the free end is provided with a flexible conical guide head and a traction ring which are communicated with the air cavity. When the air bag body is inflated, the flaps bend inward and wrap the original wire, and the flexible conical guide head pulls the original wire through the variable cross-section pipeline. After the wire threading is completed, the air bag body is depressurized or collapsed under negative pressure, and the rotating shaft is reversely wound and recovered by the reset driving mechanism, so that the original wire remains in the pipeline. The application can improve the stability of the original wire threading, reduce the swing, sliding and contact with the pipeline wall, and facilitate the repeated use of the wire threading carrier.

Description

Technical Field

[0001] This invention belongs to the technical field of conveying, threading and guiding equipment for flexible linear materials such as fibers and yarns, and relates to a rewindable C-shaped airbag threading device and method for threading flexible filament bundles such as carbon fiber filaments through a variable cross-section pipe. Background Technology

[0002] In the production of carbon fiber and other continuous fiber materials, precursor fibers typically need to be threaded through steam drawing pipes, heat treatment furnaces, or other enclosed process channels to establish a continuous fiber path. Some steam drawing pipes have variable cross-section structures, with expansion cone sections, straight sections, and contraction cone sections along their inner circumference. The precursor fibers must be threaded from the inlet end to the outlet end of the pipe before entering subsequent production processes. Carbon fiber precursor fibers are usually formed by bundling multiple monofilaments and have high axial tensile strength. However, their surface is prone to fuzzing, dispersion, or damage when subjected to scratching, shearing, or localized concentrated compression. Therefore, during the threading process, it is necessary not only to ensure the precursor fibers pass smoothly through long enclosed pipes but also to reasonably limit the lateral movement and localized stress on the precursor fibers.

[0003] Existing methods for threading wire through pipes mainly include rigid pusher, wire or wire rope traction, and airflow. Rigid pusher typically uses a rod-like component to push the wire forward from the inlet end; wire or wire rope traction usually involves first passing a traction component through the pipe, then connecting the end of the wire to the traction component and pulling it to the outlet end; airflow uses airflow within the pipe to move the wire forward. In addition, existing technologies also include methods that utilize inflatable components moving within the pipe to push or pull flexible linear materials such as cables and wire bundles.

[0004] For example, Chinese utility model patent CN202247063U discloses a traction device for guiding fibers through a low-temperature carbonization furnace during carbon fiber production. This traction device consists of multiple interconnected high-temperature resistant metal rings forming a chain. The chain passes through the furnace body, with its two ends, located outside the furnace inlet and outlet, interconnected. During fiber threading, the fiber bundle is attached to the metal ring at the inlet side. By pulling the chain, the fiber bundle passes through the furnace body and reaches the outlet end, where it is then removed from the metal ring. This traction device can be retained within the high-temperature furnace body for an extended period and can be reused for subsequent fiber threading.

[0005] However, existing rigid push rods are easily restricted by the radial direction of the pipe wall when passing through the contraction section, and may deviate in the expansion section due to the lack of radial support; steel wire, steel wire rope or metal ring chain traction devices mainly transmit traction force through point connection between the end of the original wire and the traction component, and the main body of the original wire lacks continuous restraint along the length direction, which may cause swinging, slippage or contact with the pipe wall when passing through the expansion cone section and the contraction cone section; during the airflow blowing process, the change of the pipe flow cross section can easily cause changes in airflow velocity and pressure distribution, and may cause the original wire composed of multiple single wires to diverge; ordinary local inflation pushing components usually only act on the end of the original wire, and it is difficult to form a releasable and relatively uniform constraint on the main body of the original wire during the threading process. For flexible inflatable carriers stored using a winding method, their release requires a conversion from tangential motion around the rotation axis to axial motion along the pipe. If the storage end and outlet lack appropriate radial constraints and smooth guidance, ineffective expansion at the fixed end, folding, scraping, or local accumulation at the outlet can easily occur. After threading, the threading carrier needs to be released from the constraint on the original filament and withdrawn from the pipe to prevent the original filament already threaded into the pipe from being brought back during carrier recovery. The existing solutions described above are insufficient to simultaneously meet the requirements of stable passage in variable cross-section pipes, continuous protection of the original filament body, orderly release of the threading carrier, and separation and recovery after threading.

[0006] Therefore, a wire threading device and method suitable for variable cross-section pipes is needed, which can smoothly transform the wire threading carrier from a wound state to a state of being released along the pipe axis. During the threading process, a releasable continuous constraint is formed on the main body of the wire, and it can adapt to the pipe diameter changes between the expansion cone section, the straight cylinder section and the contraction cone section. After the wire reaches the pipe outlet, the constraint relationship between the wire threading carrier and the wire can be released and the wire threading carrier can be rewound and stored, so that the wire is retained in the variable cross-section pipe. Summary of the Invention

[0007] In view of this, the purpose of the present invention is to provide a retractable C-shaped airbag threading device and method for variable cross-section pipes, so as to solve the problems of existing rigid push rods, steel wire ropes, metal ring chains or partially inflatable pushing components, which are difficult to simultaneously meet the requirements of adaptive passage of variable cross-section pipes, continuous limiting of the main body of the main body of the main body and orderly recovery of the threading carrier during the threading process. The main body is easily swayed, slipped or contacted with the pipe wall between the expansion cone section, the straight section and the contraction cone section when the flexible inflatable carrier is released from the coiled state to the axial direction of the pipe. The flexible inflatable carrier is prone to ineffective expansion at the fixed end or folding, scraping and local accumulation at the outlet of the receiving cavity. After the threading is completed, the threading carrier is difficult to reliably release the constraint on the main body and independently exit the pipe, and is prone to bringing back the main body that has been threaded into the pipe.

[0008] This invention does not simply utilize inflatable components to push or pull the raw filament through a pipe. Instead, it addresses the interaction between the raw filament insertion and anti-detachment, airbag inflation and coverage, directional release of the wound airbag, adaptation to the variable cross-section pipe, and release and recovery processes after threading. It combines an airbag body with a C-shaped cross-section and an air chamber connected along its length, flexible magnetic strips of opposite poles located on the inner sides of the free edges of the wing walls on both sides of the C-shaped opening, a differential wall thickness structure where the bottom wall thickness is greater than the wing wall thickness, a flexible conical guide head connected to the air chamber of the airbag body and equipped with a coaxial traction ring, a storage structure that forms radial constraints on the fixed end of the airbag body and the inner coil section, an arc-shaped guide lip for smoothly transitioning the airbag body from the tangential direction of the rotation axis to the axial direction of the pipe, and a pneumatic supply and exhaust structure and a reset and rewinding structure that cooperate with the rotation axis. Through the cooperation of the above structures, the airbag body forms a pre-limiting position for the filament without clamping it when it is not inflated. When inflated, the filament body is continuously covered by the inward deformation of the side wing walls, and the head of the filament is pulled through the variable cross-section pipe by the flexible conical guide head. After the filament reaches the outlet and is disconnected from the traction ring, the airbag body releases the covering by depressurization or negative pressure suction and is wound back up under the action of reset drive, thereby improving the stability of the filament in the process of threading, releasing and retrieving in the variable cross-section pipe.

[0009] To achieve the above objectives, the technical solution of the present invention is implemented as follows: This invention provides a rewindable C-shaped airbag threading device for variable cross-section pipes, used to thread the raw filament through the variable cross-section pipe. The threading device includes a receiving cavity, a rotating shaft, an airbag body, a reset drive mechanism, and a pneumatic system.

[0010] The receiving cavity accommodates the airbag body in its wound state and the corresponding rotating support component. The rotating shaft supports the airbag body and enables its release and rewinding. The pneumatic system changes the pressure state within the airbag body. The reset drive mechanism drives the rotating shaft to rotate in the opposite direction after yarn threading is completed. These components work together to allow the same airbag body to sequentially complete the processes of yarn insertion, inflation, axial release, pressure depressurization, and winding recovery.

[0011] The receiving cavity is located at the inlet end of the variable cross-section pipe, and the rotating shaft is rotatably connected inside the receiving cavity. The axis of the rotating shaft is perpendicular to the axis of the variable cross-section pipe.

[0012] By making the axis of the rotating shaft perpendicular to the axis of the variable cross-section pipe, the airbag wound on the rotating shaft can be released layer by layer from the outer periphery of the rotating shaft to the inlet end of the variable cross-section pipe, and at the outlet of the receiving cavity, the direction of movement around the rotating shaft is changed to the axial direction of movement along the variable cross-section pipe.

[0013] The airbag is a single-lobed, sheet-like inflatable structure extending along its length. The fixed end of the airbag is fixedly connected to the rotating shaft. The main body of the airbag is spirally wound around the rotating shaft. The free end of the airbag is positioned from the outlet of the receiving cavity toward the variable cross-section pipe.

[0014] The fixed end is used to establish the mechanical and pneumatic connection between the airbag body and the rotating shaft, and the free end is the leading end of the airbag body as it advances along the variable cross-section pipe. The airbag body adopts a single-lobed sheet structure, which allows it to maintain a relatively stable winding layer along the axial direction of the rotating shaft in the winding state, and to form a continuous covering structure along the length of the original filament after being released.

[0015] The interior of the airbag forms an air cavity that communicates along the length of the airbag. The cross-section of the airbag perpendicular to its length is C-shaped with an opening. The C-shaped cross-section includes a bottom wall portion located away from the opening and two wing wall portions extending from both sides of the bottom wall portion toward the opening. The wall thickness of the bottom wall portion is greater than the wall thickness of the two wing wall portions.

[0016] The opening of the C-shaped cross-section forms a channel for the insertion of the precursor filament and the detachment of the airbag from the precursor filament. The bottom wall portion is used to support the precursor filament, and the two wing-shaped wall portions are located on both sides of the precursor filament. The bottom wall portion and the two wing-shaped wall portions together form the air cavity, and gas can flow in the air cavity along the length direction of the airbag, so that different length positions of the airbag form an interconnected pressure state.

[0017] Within the pre-formed C-shaped profile of the airbag, the larger wall thickness of the bottom wall provides it with relatively greater resistance to deformation, while the smaller wall thickness of the two winglets provides it with relatively lower bending stiffness. Therefore, when the pressure within the air cavity increases, the two winglet walls are more prone to bending deformation relative to the bottom wall, and under the combined guidance of the C-shaped profile and the flexible magnetic strip, they move towards the inner side of the C-shaped cross-section. This prevents the airbag from merely undergoing overall radial bulging without effectively covering the original filament.

[0018] Flexible magnetic strips are respectively provided on the inner side of the free edges of the two wing wall portions. The two flexible magnetic strips are arranged with opposite poles facing each other. When the airbag is not inflated, the two flexible magnetic strips bring the free edges of the two wing wall portions closer to each other and leave a separable opening between the two wing wall portions.

[0019] The magnetic attraction of the two flexible magnetic strips maintains the relative proximity of the free edges of the two vane walls, preventing the filament placed inside the C-shaped cross-section from easily detaching through the opening. Simultaneously, the two flexible magnetic strips are not permanently fixed together; the operator can separate the two vane walls to insert the filament or to separate the airbag from the filament after depressurization. The flexible magnetic strips bend with the vane walls to avoid creating rigid obstructions when the airbag is wound around or passes through variable cross-section pipes.

[0020] The two wing-shaped wall portions deform preferentially relative to the bottom wall portion when the airbag is inflated, and bend toward the inside of the C-shaped cross-section.

[0021] In the inflated state, the walls of the two vanes bend inward from both sides of the profilament, allowing the main body of the profilament to be contained within the enclosed space formed by the C-shaped airbag along its length. This enclosed space primarily restricts the lateral escape and excessive swinging of the profilament, rather than using rigid components to create localized concentrated clamping of the profilament. As a result, while the head of the profilament is tractioned, the main body of the profilament can obtain flexible restraints that are continuously distributed along its length.

[0022] The free end of the airbag is provided with a flexible conical guide head, which is connected to the air cavity of the airbag. A traction ring is coaxially provided at the tip of the flexible conical guide head.

[0023] The flexible conical guide head inflates synchronously with the airbag body, forming an outer contour that gradually increases in size from the tip towards the main body of the airbag. This outer contour reduces the possibility of abrupt contact between the free end and the tube wall when passing through a position where the tube diameter changes. The traction ring is used to connect the raw filament head. It is located at the tip of the flexible conical guide head and is coaxial with the flexible conical guide head, so that the position of the traction force on the raw filament head is close to the central axis of the flexible conical guide head, reducing the offset of the traction force relative to the center of the guide head. The raw filament head can be connected to the traction ring through a loop, slip knot, or other connection method that can be disengaged at the outlet end.

[0024] The pneumatic system is connected to the air chamber of the airbag via a gas channel formed within the rotating shaft.

[0025] Thus, the pneumatic system can continuously supply air to the airbag during the rotation of the rotating shaft and the layer-by-layer release of the airbag, and can depressurize or suction the airbag after the threading is completed, so that the airbag maintains the required inflation state during the release process and is converted into a low-pressure or collapsed state that is easy to bend and roll before rewinding.

[0026] The reset drive mechanism is connected to the rotating shaft and applies a rewind torque to the rotating shaft that is opposite to the release direction of the airbag.

[0027] When the airbag is released into the variable cross-section pipe, the airbag overcomes the rewinding torque and drives the rotating shaft to rotate; after the airbag is depressurized or vacuumed and the original yarn is unwrapped, the rewinding torque drives the rotating shaft to rotate in the opposite direction, so that the airbag is rewound onto the rotating shaft.

[0028] Furthermore, the tube wall of the airbag body is provided with an axial extension induction structure, the axial extension induction structure including annular corrugated folds spaced apart along the length direction of the airbag body, and a high-strength fiber woven mesh layer embedded in the tube wall of the airbag body.

[0029] The annular corrugated creases form pre-defined folds that compress along the length of the airbag when it is not inflated or in a rolled-up state. When the airbag is inflated, the annular corrugated creases unfold sequentially, causing the airbag to extend along its length. The high-strength fiber woven mesh layer limits excessive radial expansion of the airbag and, in conjunction with the annular corrugated creases, ensures that the deformation generated during inflation is primarily used for the axial extension and orderly release of the airbag.

[0030] In an embodiment that optimizes this solution, the airbag body forms a gradually decreasing wall thickness structure from the fixed end to the free end along its length direction, with the wall thickness of the fixed end being 1.5mm to 3.0mm and the minimum wall thickness of the free end being 0.3mm to 0.8mm.

[0031] The fixed end bears the combined effects of connection with the rotating shaft, air passage, and inner coil winding. A larger wall thickness improves the connection stability and resistance to local bulging at the fixed end. The free end needs to pass through an expansion cone section, a straight section, and a contraction cone section. A smaller wall thickness improves its bending compliance and adaptability to changes in pipe diameter. The wall thickness gradually decreases from the fixed end to the free end, which reduces deformation concentration caused by abrupt changes in wall thickness between adjacent areas.

[0032] Preferably, the flexible conical guide head is integrally formed with the airbag body, the wall thickness of the flexible conical guide head is greater than the wall thickness of the adjacent airbag body; the maximum outer diameter of the flexible conical guide head is smaller than the minimum inner diameter of the variable cross-section pipe, the traction ring is a flexible rope ring, and the center of the ring hole of the traction ring is located on the central axis of the flexible conical guide head.

[0033] The flexible conical guide head is integrally molded with the airbag body, creating a continuous air cavity and a continuous flexible wall surface between them, reducing the possibility of air leakage or the formation of rigid steps at independent connection points. The flexible conical guide head uses a relatively large wall thickness, giving it a higher shape retention capability after inflation than adjacent airbag bodies; its maximum outer diameter is smaller than the minimum inner diameter of the variable cross-section pipe, allowing the flexible conical guide head to pass through the minimum cross-section of the pipe under normal inflation conditions. The flexible cord loop can deform with the flexible conical guide head and can be released from the profilole head during the handover step.

[0034] Furthermore, an annular space is formed between the inner wall of the receiving cavity and the outer periphery of the rotating shaft, and the fixed end of the airbag and the inner coiled section adjacent to the fixed end are accommodated in the annular space; the outlet of the receiving cavity is provided with an arc-shaped guide lip, which extends smoothly from the annular space toward the inner periphery of the variable cross-section pipe.

[0035] The radial dimension of the annular space is adapted to the airbag in its coiled state, allowing the inner wall of the receiving cavity to form an outer circumferential constraint on the fixed end and the inner coiled section, reducing the likelihood of the positive pressure gas preferentially causing radial expansion of the fixed end or the inner coiled section. After the airbag is released tangentially along the rotation axis within the annular space, it contacts the arc-shaped guide lip and gradually turns towards the axial direction of the variable cross-section pipe along the arc-shaped inner surface of the guide lip, thereby reducing the formation of sharp bends, internal flattening, or local accumulation of the airbag at the outlet of the receiving cavity.

[0036] In one optional embodiment, the rotating shaft is a hollow shaft body, one end of the rotating shaft is provided with a first air hole extending along its axial direction, the outer periphery of the rotating shaft is provided with a second air hole communicating with the first air hole, the fixed end of the airbag body is provided with a third air hole corresponding to and communicating with the second air hole; the first air hole is connected to the pneumatic system through a rotary joint, and the other end of the rotating shaft is closed.

[0037] The first, second, and third air holes are sequentially connected to form a channel for air supply, exhaust, and negative pressure suction between the pneumatic system and the air chamber of the airbag. The fixed side of the rotary joint is connected to the pneumatic system, and the rotating side is connected to the rotating shaft, ensuring that the air path connection does not become entangled with the rotating shaft when it rotates. The other end of the rotating shaft is closed, allowing gas entering through the first air hole to enter the airbag through the second and third air holes, reducing gas escape from the end of the rotating shaft.

[0038] Preferably, the reset drive mechanism includes a spiral spring, the inner hook end of the spiral spring is connected to the rotating shaft, and the outer straight hook end of the spiral spring is connected to the receiving cavity; the inner diameter of the spiral spring is larger than the outer diameter of the rotating shaft, and there is a radial gap of 2mm to 5mm between the spiral spring and the rotating shaft.

[0039] When the airbag is released, it causes the rotating shaft to rotate relative to the receiving cavity, causing the inner hook end of the spiral spring to rotate relative to the outer straight hook end and store elastic potential energy. After the airbag is depressurized or the negative pressure suction is completed, the spiral spring releases the elastic potential energy to drive the rotating shaft to rotate in the opposite direction. The radial clearance is a reserved space for the radial deformation of the spiral spring during the winding and releasing process, reducing direct friction or mutual jamming between the spiral spring and the rotating shaft.

[0040] In one specific embodiment, the pneumatic system includes a positive pressure air source, a negative pressure air source, an exhaust port, a reversing valve, and a controller; the reversing valve is provided with a first interface communicating with the positive pressure air source, a second interface communicating with the negative pressure air source, a third interface communicating with the exhaust port, and a working interface communicating with the gas passage of the rotating shaft; the reversing valve has a working position that allows the working interface to communicate with the first interface, the second interface, or the third interface respectively, and a pressure-holding position that closes the working interface.

[0041] When the working interface is connected to the first interface, the positive pressure air source supplies air to the airbag body; when the reversing valve is in the pressure-holding position, the airbag body is disconnected from the positive pressure air source, the negative pressure source, and the exhaust port to maintain the airbag body's inflation state; when the working interface is connected to the third interface, the gas inside the airbag body is discharged through the exhaust port; when the working interface is connected to the second interface, the negative pressure source draws air from the airbag body. The controller is used to control the reversing valve to switch the corresponding working position according to different stages of the threading process.

[0042] In one optional embodiment, when the airbag is in an uninflated state, the opening width of the C-shaped cross-section is 1.2 to 1.5 times the equivalent diameter of the original filament bundle to be threaded.

[0043] The equivalent diameter of the original filament bundle refers to the diameter obtained by converting the cross-section of the original filament bundle into a circular cross-section of equal area. The opening width is larger than the equivalent diameter of the original filament bundle, allowing the original filament bundle to be inserted into the airbag body through the opening; after the two flexible magnetic strips attract each other, the free edges of the two wing wall portions move closer to each other, reducing the effective passage width of the opening, thereby reducing the possibility of the original filament bundle coming out of the opening in the uninflated state.

[0044] Furthermore, the flexible magnetic strip is embedded inside the free edge of the wing wall, and a PTFE anti-adhesion coating is provided on the side of the flexible magnetic strip facing the inside of the airbag body.

[0045] The flexible magnetic strip is embedded within the vane wall, allowing it to bend along with the vane wall and reducing direct scraping of the magnetic strip edge against the filament. The PTFE anti-stick coating forms a low-friction contact surface facing the filament, reducing frictional resistance as the filament moves relative to the airbag and as the airbag retracts from the outside of the filament.

[0046] Optionally, the airbag body is made of highly elastic wear-resistant rubber or polyurethane elastomer.

[0047] Highly elastic and wear-resistant rubber or polyurethane elastomers can produce recoverable elastic deformation when inflated under positive pressure, and return to a flexible state that is easy to roll up after depressurization or negative pressure suction. At the same time, they can withstand the friction generated by the airbag repeatedly passing through the outlet of the storage cavity and the variable cross-section pipe.

[0048] Preferably, the angle between the braided threads of the high-strength fiber woven mesh layer and the length direction of the airbag body is 54°44′±5°.

[0049] The high-strength fiber woven mesh layer adapts to the inflation deformation of the airbag by changing the angle between the woven threads, and restricts the circumferential expansion of the airbag; the woven mesh layer works together with the annular corrugated creases to allow the airbag to gradually extend along the length direction while maintaining the C-shaped cross-section coverage.

[0050] Furthermore, the receiving cavity includes a base, an upper cover plate disposed above the base, and an outlet plate disposed between the base and the variable cross-section pipe; the rotating shaft is rotatably connected to the base, and the arc-shaped guide lip is formed on the outlet plate.

[0051] The base supports the rotating shaft and forms the main space of the receiving cavity. The upper cover plate closes the upper part of the receiving cavity and allows for the installation or maintenance of internal components. The outlet plate is located at the transition position where the airbag enters the variable cross-section pipe from the receiving cavity. The arc-shaped guide lip and the outlet plate form a relatively fixed positional relationship, ensuring the stability of the airbag's release and retraction paths.

[0052] In an embodiment that optimizes this solution, the upper cover plate has a wire pressing groove corresponding to the C-shaped cross-section opening of the airbag body. The width of the wire pressing groove is greater than the opening width of the C-shaped cross-section and less than the axial width of the airbag body wound on the rotating shaft.

[0053] When the raw yarn is loaded, it can enter the receiving cavity through the pressing groove and then be placed inside the bottom wall through the C-shaped opening of the airbag body. The width of the pressing groove is smaller than the axial width of the airbag body in the wound state, so that the airbag body wound on the rotating shaft is axially restricted by the upper cover plate, reducing the possibility of the airbag body as a whole coming out of the pressing groove.

[0054] Preferably, the radius of curvature of the arc-shaped guide lip is not less than twice the minimum bending radius of the airbag body, and the center of the arc of the arc-shaped guide lip is located on the axis of the variable cross-section pipe.

[0055] The minimum bending radius of the airbag body refers to the minimum bending radius that the airbag body can form without causing irreversible wrinkling, air cavity blockage, or structural damage. The arc-shaped guide lip adopts a curvature radius of not less than twice this minimum bending radius, enabling the airbag body to complete the turning along a relatively gentle arc path; the center of the arc of the arc-shaped guide lip is located on the axis of the variable cross-section pipe, so that the release direction of the airbag body after turning through the arc-shaped guide lip corresponds to the axis of the variable cross-section pipe.

[0056] In one specific application, the variable cross-section pipe is a carbon fiber precursor steam drawing pipe, which includes an expansion cone section, a straight section and a contraction cone section along the direction of precursor fiber travel.

[0057] The inner diameter of the expanding cone section gradually increases along the direction of the filament's travel, while the inner diameter of the contracting cone section gradually decreases along the same direction. The inner diameter of the straight section remains essentially consistent along its length. The flexible conical guide head and the airbag adapt to the changes in the inner diameter of different tube sections through their own flexible deformation. The airbag forms a continuous flexible covering on the carbon fiber filament body to reduce the divergence, lateral swaying, or localized scraping of the filament at the locations where the tube diameter changes.

[0058] Furthermore, the controller stores air pressure control parameters corresponding to the expansion cone section, the straight section, and the contraction cone section respectively; the controller increases the intake pressure when the airbag enters the contraction cone section, maintains the preset intake pressure when the airbag enters the expansion cone section, and adjusts the intake pressure to the preset normal air pressure when the airbag enters the straight section.

[0059] When the airbag enters the contraction cone section, its resistance increases as the pipe's inner diameter decreases. The controller compensates for this resistance by increasing the inlet pressure. When the airbag enters the expansion cone section, the preset inlet pressure is maintained to preserve the airbag's axial extension and its coverage of the filament. When the airbag enters the straight section, the inlet pressure is adjusted to a preset conventional pressure to accommodate the relatively stable passage conditions of this pipe section. All pressure control parameters can be predetermined and stored in the controller based on the airbag's dimensions, material, the inner diameter of the variable cross-section pipe, and the filament specifications.

[0060] Furthermore, the rotating shaft is connected to an encoder, and the controller obtains the release length of the airbag body based on the number of rotations of the rotating shaft detected by the encoder, and compares the release length with the preset position parameters of each pipe segment of the variable cross-section pipe.

[0061] The controller pre-stores the correspondence between the number of rotations of the rotating shaft and the deployment length of the airbag, and determines the current deployment length of the airbag based on the rotation signal output by the encoder. The preset position parameters include the axial distance from the inlet end of the variable cross-section pipe to the starting or ending position of each expansion cone section, straight cylinder section, and contraction cone section. The controller determines the pipe section where the flexible conical guide head is located by comparing the deployment length of the airbag with the preset position parameters.

[0062] Preferably, a pressure sensor is installed in the pipeline of the pneumatic system, and the controller corrects the release position of the airbag obtained by the encoder based on the air pressure change detected by the pressure sensor.

[0063] When the airbag passes through pipe sections of different diameters, its deformation state and travel resistance change, causing corresponding changes in the pressure or pressure change trend in the pneumatic system pipeline. The controller compares the pressure value or pressure change trend detected by the pressure sensor with the preset pressure judgment parameter, and combines the comparison result with the release position obtained by the encoder to reduce the cumulative position error caused by changes in the airbag winding layer diameter, elastic elongation, or local slippage.

[0064] The present invention also provides a method for threading wire using a retractable C-shaped airbag for variable cross-section pipes, which is implemented using a receiving cavity, a rotating shaft, an airbag body, a reset drive mechanism, and a pneumatic system.

[0065] The threading method utilizes the different cross-sectional shapes of the airbag body under uninflated, positive pressure inflation, pressure holding, pressure release, and negative pressure suction states to enable the airbag body to sequentially complete the insertion of the raw filament, the wrapping of the raw filament, the threading inside the tube, the release of the raw filament, and the retrieval of the airbag.

[0066] The airbag body has an air cavity that is connected along its length. The cross-section of the airbag body is C-shaped with an opening. The wall thickness of the bottom wall on the side of the C-shaped cross-section away from the opening is greater than the wall thickness of the two wing wall portions located on both sides of the opening. Flexible magnetic strips with opposite poles are respectively provided on the inner side of the free edges of the two wing wall portions.

[0067] The thickness difference between the bottom wall and the wing wall gives the two wing walls a lower bending stiffness than the bottom wall. Two flexible magnetic strips are used to keep the two sides of the opening close to each other in the uninflated state and to guide the free edges of the two wing walls to move toward each other during inflation.

[0068] The threading method includes a threading step, an inflation threading step, a handover step, and a release and recovery step.

[0069] The above steps are performed sequentially. The handover step is performed after the inflation and threading step is completed, and the release and recovery step is performed after the head of the raw yarn is disconnected from the traction ring, so as to avoid the airbag body being unwrapped or starting to rewind before the raw yarn is handed over.

[0070] In the yarn feeding step, the main body of the raw yarn is placed inside the bottom wall through the C-shaped cross-section opening of the airbag body. The two flexible magnetic strips attract each other and bring the free edges of the two wing wall portions closer to each other. The head of the raw yarn is connected to the traction ring at the tip of the flexible conical guide head located at the free end of the airbag body.

[0071] During the yarn feeding step, the air bladder remains uninflated, allowing the operator to separate the two vane walls and continuously feed the main yarn into the air bladder. The connection between the yarn head and the traction ring can withstand the axial traction force during the threading process and can be released after the flexible conical guide head reaches the outlet end.

[0072] In the inflation and threading step, positive pressure gas is introduced into the air chamber of the airbag through the pneumatic system. The two wing wall portions bend towards the inside of the C-shaped cross section relative to the bottom wall portion and cover the main body of the raw filament. The flexible conical guide head expands, and the airbag is released layer by layer by the rotating shaft and moves along the variable cross section pipe. The traction ring pulls the head of the raw filament to move synchronously with the flexible conical guide head.

[0073] Positive pressure gas enters the airbag body through the gas channel within the rotating shaft, causing the flexible conical guide head to form a guiding outer contour and gradually unfolding the annular corrugated folds of the airbag body. As the airbag body extends axially, it overcomes the rewinding torque applied by the reset drive mechanism and drives the rotating shaft to rotate, thus releasing the filament layer by layer. The axial traction of the filament head is undertaken by a traction ring, while the filament body is covered along its length by a C-shaped airbag body, ensuring that the traction of the head and the limiting of the body are synchronized.

[0074] In the handover step, after the flexible conical guide head reaches the outlet end of the variable cross-section pipe, the airbag is kept in an inflated state, and the connection between the profilament head and the traction ring is released.

[0075] Maintaining the inflation state of the airbag ensures continued coverage of the filament body and release of the rotation axis during the disconnection process, reducing the likelihood of the reset drive mechanism prematurely rewinding the airbag. After the filament head is disconnected from the traction ring, axial traction force is no longer transmitted between the filament and the airbag via the traction ring.

[0076] In the release and recovery step, after disconnecting the connection between the profilament head and the traction ring, the airbag body is depressurized or a negative pressure is applied to separate the two wing wall portions and remove the covering of the profilament body, causing the flexible conical guide head to collapse. The reset drive mechanism drives the rotating shaft to rotate in the opposite direction, winding and recovering the airbag body into the receiving cavity, and leaving the profilament in the variable cross-section pipe.

[0077] Depressurization reduces the pressure difference between the inside and outside of the airbag, and the two vane walls are released from their inflated state due to material elasticity and the C-shaped pre-formed contour. Negative pressure suction further removes residual gas from the air chamber, causing the airbag and flexible conical guide head to collapse into a state that facilitates bending and winding. During rewinding, the filament head remains at the outlet end of the variable cross-section pipe, the airbag moves relative to the filament along its C-shaped opening and is withdrawn from the outside of the filament, and then rewinds onto the rotating shaft through the arc-shaped guide lip.

[0078] Furthermore, the pneumatic system performs positive pressure inflation in the inflation and insertion step, closes the air passage connected to the airbag body and maintains pressure in the handover step, and sequentially performs depressurization by connecting to the exhaust port and suction by connecting to the negative pressure source in the release and recovery step; the reset drive mechanism drives the rotating shaft to rotate in the opposite direction after the airbag body completes negative pressure suction.

[0079] Positive pressure inflation is used to form the airbag body into an axially extended and filament-covered state; pressure holding is used to maintain the state of the airbag body during the junction of the filament heads; pressure relief is used to reduce the internal pressure of the airbag body; and negative pressure suction is used to further expel the residual gas inside the airbag body. Setting the reverse winding after negative pressure suction can reduce the occurrence of coiling, folding, local bulging, or air passage blockage when there is still a lot of gas inside the airbag body.

[0080] In an embodiment that optimizes this solution, the variable cross-section pipe includes an expanding cone section, a straight section, and a contracting cone section; in the inflation and insertion step, the airbag increases the intake pressure when entering the contracting cone section, maintains a preset intake pressure when entering the expanding cone section, and adjusts the intake pressure to a preset normal air pressure when entering the straight section.

[0081] The air pressure regulation is based on maintaining the axial extension of the airbag, ensuring the flexible wrapping of the filament by the two vane walls, and allowing the flexible conical guide head to continue moving forward. When entering the contraction cone section, the intake pressure is increased to compensate for the increased travel resistance due to the reduced pipe diameter; when entering the expansion cone section, the preset intake pressure is maintained to avoid significant fluctuations in the axial extension state of the airbag caused by the increased pipe diameter; when entering the straight section, the preset normal air pressure is restored.

[0082] Furthermore, the number of rotations of the rotating shaft is detected by an encoder, the release length of the airbag is obtained based on the number of rotations, and the release length is compared with the preset position parameters of each pipe segment of the variable cross-section pipe to determine the pipe segment where the flexible conical guide head is located.

[0083] During implementation, a preset correspondence between the number of rotations and the release length can be established based on the initial winding state of the airbag, the size of the rotating shaft, and the thickness of the airbag. The controller calls the correspondence based on the cumulative number of rotations detected by the encoder to obtain the release length of the airbag, and performs air pressure control corresponding to different pipe sections accordingly.

[0084] In one optional embodiment, a pressure sensor installed in the pneumatic system pipeline detects the air pressure change inside the airbag body, determines the state of the airbag body entering the contraction cone section or the expansion cone section based on the air pressure change, and adjusts the intake pressure based on the determination result.

[0085] The controller can compare the real-time pressure, pressure change, or pressure change trend detected by the pressure sensor with preset judgment parameters. When the airbag enters the contraction cone section and the travel resistance increases, or when it enters the expansion cone section and the deformation conditions change, the pressure response in the pneumatic system changes accordingly. Based on this, the controller judges the passage status of the airbag and adjusts the air path status between the positive pressure air source and the airbag.

[0086] Preferably, the pressure holding duration is 5 to 30 seconds, the pressure release duration is 1 to 3 seconds, and the negative pressure suction duration is 1 to 5 seconds.

[0087] The pressure holding time allows time for the disconnection of the raw yarn head from the traction ring; the pressure relief time allows most of the positive pressure gas inside the airbag to be discharged through the exhaust port; and the negative pressure suction time allows the airbag to collapse further. The specific durations, within the above range, are selected based on the air chamber volume, gas flow rate, pipe length, and the material elasticity of the airbag.

[0088] In one optional embodiment, the reset drive mechanism includes a spiral spring; when the airbag is released by the rotating shaft, it drives the rotating shaft to rotate in the forward direction and causes the spiral spring to store energy; after the airbag is depressurized or completes negative pressure suction, the spiral spring releases its elastic potential energy and drives the rotating shaft to rotate in the reverse direction.

[0089] The energy storage process of the spiral spring is synchronized with the release process of the airbag, and the release process of the spiral spring is synchronized with the rewinding process of the airbag, thus eliminating the need for a separate traction component at the outlet end of the variable cross-section pipe to pull back the airbag.

[0090] Preferably, after disconnecting the connection between the raw filament head and the traction ring in the handover step, the raw filament head is kept stationary at the outlet end of the variable cross-section pipe until the airbag body is fully wound and retracted.

[0091] Keeping the head of the primary filament stationary, the airbag body moves axially from the outlet end to the inlet end relative to the primary filament as it rewinds. The main body of the primary filament gradually detaches from the airbag body through the C-shaped opening, thereby allowing the airbag body to be recovered while the primary filament remains inside the variable cross-section pipe.

[0092] Furthermore, the outlet of the receiving cavity is provided with an arc-shaped guide lip; in the inflation and insertion step, the free end of the airbag gradually changes from the tangential release direction around the rotation axis to the axial movement direction along the arc-shaped guide lip; in the release and recovery step, the airbag gradually changes from the axial recovery direction of the variable cross-section pipe to the tangential winding direction around the rotation axis along the arc-shaped guide lip.

[0093] The arc-shaped guide lip forms a shared bidirectional guide surface during the deployment and retraction of the airbag, allowing the airbag to complete the directional change along a smooth arc path during both opposite movements, reducing local compression and scratching of the airbag by the outlet edge of the storage cavity.

[0094] In one specific embodiment, the precursor fiber is a 3K to 24K carbon fiber precursor fiber, and when the airbag is in an uninflated state, the opening width of the C-shaped cross-section is 1.2 to 1.5 times the equivalent diameter of the carbon fiber precursor fiber.

[0095] For carbon fiber precursors with different K numbers, the corresponding equivalent diameter can be determined according to the actual cross-sectional dimensions of the precursor bundle, and the C-shaped cross-sectional dimensions of the airbag and the opening width in the uninflated state can be selected accordingly, so as to take into account both the convenience of precursor insertion and the anti-detachment requirements in the uninflated state.

[0096] Preferably, a pressure sensor is installed in the pipeline of the pneumatic system. During the negative pressure suction process, the pressure sensor detects the pressure inside the airbag and stops the negative pressure suction when the pressure inside the airbag reaches a preset negative pressure value.

[0097] The preset negative pressure value is stored in the controller and corresponds to the pressure state where the airbag and flexible conical guide head have collapsed to a level where they can be wound back up. Determining the stop time of negative pressure suction by using a pressure sensor can prevent insufficient suction from causing the airbag to remain inflated, and can also reduce ineffective suction after the airbag has reached the rewinding condition.

[0098] Compared to existing technologies, this invention combines a rollable C-shaped airbag, a flexible magnetic strip of opposite poles located on the free edge of the vane wall, a differential wall thickness structure where the bottom wall is thicker than the vane wall, a flexible conical guide head and traction ring, a receiving cavity and a rotating shaft, a pneumatic system, and a reset drive mechanism. This allows the precursor filament to be inserted into the airbag through the C-shaped opening, and the flexible magnetic strip forms a pre-limiting anti-detachment mechanism when the airbag is not inflated. After the airbag is inflated, the vane walls on both sides bend inwards relative to the bottom wall, forming a continuous wrapping around the precursor filament along its length. Simultaneously, the flexible conical guide head and traction ring pull the precursor filament head through the expanding conical section, the straight section, and the contracting conical section, thereby reducing the swaying and slippage caused by point-to-point traction at the precursor filament end. The system addresses the issues of dispersion and contact with the pipe wall; the receiving cavity constrains the fixed end and inner coil section of the airbag; the arc-shaped guide lip guides the airbag to smoothly transition between the tangential direction of the rotation axis and the axial direction of the pipe; the hollow rotating shaft and rotary joint ensure that the air path remains open during the release and recovery of the airbag, which helps improve the orderly release of the airbag and the stability of passing through the variable cross-section pipe; after the filament reaches the pipe outlet and is disconnected from the traction ring, the airbag is de-encased by the pressure relief or negative pressure suction, and the reset drive mechanism drives the rotating shaft to rotate in the opposite direction, winding and recovering the airbag into the receiving cavity, so that the filament remains in the variable cross-section pipe. This system simultaneously ensures continuous protection during the filament threading process, adaptability to variable cross-section, separation and recovery of the threading carrier, and reuse. Attached Figure Description

[0099] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of the first structure before threading in this invention; Figure 2 This is a top view of the present invention before threading the silk; Figure 3 for Figure 2 A schematic diagram of the AA-direction cross-section structure; Figure 4 for Figure 2 Schematic diagram of the BB-direction cross-section structure; Figure 5 This is a schematic diagram of the second structure before threading in this invention; Figure 6 for Figure 5 A magnified view of a portion of point X in the middle; Figure 7 This is a schematic diagram of the airbag body of the present invention in a wound state; Figure 8 This is a schematic diagram of the spiral spring of the present invention; Figure 9This is a schematic diagram of the airbag body of the present invention in its deployed state; Figure 10 This is a schematic diagram of the structure after the wire is threaded in this invention; Figure 11 for Figure 10 A magnified view of a portion of point Y in the middle; Figure 12 This is a schematic diagram illustrating the working principle of the pneumatic system of the present invention.

[0100] Explanation of reference numerals in the attached figures: 1. Storage cavity; 11. Top cover plate; 111. Wire pressing groove; 12. Outlet plate; 121. Arc-shaped guide lip; 13. Base; 2. Rotating shaft; 21. First vent; 22. Second vent; 3. Airbag body; 31. Fixed end; 311. Third air hole; 32. Free end; 321. Flexible conical guide head; 3211. Traction ring; 33. Flexible magnetic strip; 34. Annular corrugated crease; 4. Spiral spring; 41. Inner hook end; 42. Outer straight hook end; 5. Pneumatic system; 51. Rotary joint; 6. Variable cross-section pipe; 61. Expansion cone section; 62. Straight cylinder section; 63. Contraction cone section; P1, First Interface; P2, Second Interface; P3, Third Interface; P4, Working Interface. Detailed Implementation

[0101] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0102] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0103] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0104] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. Example 1

[0105] Reference Figures 1 to 11 This embodiment provides a rewindable C-shaped airbag threading device for variable cross-section pipes, used to thread carbon fiber precursors through a variable cross-section pipe 6. The variable cross-section pipe 6 can be a steam drawing pipe for carbon fiber precursors, and is provided with an expansion cone section 61, a straight section 62, and a contraction cone section 63 along the direction of precursor travel. The inner diameter of the expansion cone section 61 gradually increases along the direction of precursor travel, the inner diameter of the contraction cone section 63 gradually decreases along the direction of precursor travel, and the inner diameter of the straight section 62 remains basically consistent along its length.

[0106] The threading device includes a receiving cavity 1, a rotating shaft 2, an airbag body 3, a reset drive mechanism, and a pneumatic system 5. The receiving cavity 1 is located at the inlet end of the variable cross-section pipe 6 and is used to accommodate the airbag body 3 in a wound state. The rotating shaft 2 is rotatably connected to the receiving cavity 1, and the axis of the rotating shaft 2 is perpendicular to the axis of the variable cross-section pipe 6. The fixed end 31 of the airbag body 3 is fixed to the rotating shaft 2, the main body of the airbag body 3 is spirally wound around the rotating shaft 2, and the free end 32 of the airbag body 3 is located from the outlet of the receiving cavity 1 toward the variable cross-section pipe 6.

[0107] Reference Figures 2 to 6 The receiving cavity 1 includes a base 13, an upper cover plate 11, and an outlet plate 12. The base 13 forms the main space of the receiving cavity 1 and provides rotational support for the rotating shaft 2; the upper cover plate 11 is located above the base 13 and is used to close the upper part of the receiving cavity 1; the outlet plate 12 is located between the base 13 and the variable cross-section pipe 6 and forms a transition position for the airbag 3 to enter the variable cross-section pipe 6 from the receiving cavity 1.

[0108] An annular space is formed between the inner wall of the receiving cavity 1 and the outer periphery of the rotating shaft 2. The fixed end 31 of the airbag body 3 and the inner coiled section adjacent to the fixed end 31 are accommodated in the annular space. The radial dimension of the annular space is adapted to the airbag body 3 in the coiled state, so that the inner wall of the receiving cavity 1 can form an outer peripheral restriction on the fixed end 31 and the inner coiled section, reducing the radial expansion of the fixed end 31 or the inner coiled section when the airbag body 3 is inflated.

[0109] The upper cover plate 11 has a wire-pressing groove 111, the position of which corresponds to the C-shaped cross-sectional opening of the airbag body 3 in the wound state. The width of the wire-pressing groove 111 is greater than the width of the C-shaped cross-sectional opening of the airbag body 3 when it is not inflated, and less than the axial width of the airbag body 3 wound on the rotating shaft 2. When the raw wire is loaded, the raw wire can enter the receiving cavity 1 through the wire-pressing groove 111 and be placed inside the airbag body 3 through the C-shaped cross-sectional opening of the airbag body 3; at the same time, the upper cover plate 11 can restrict the airbag body 3 in the wound state, reducing the possibility of the airbag body 3 as a whole coming out through the wire-pressing groove 111.

[0110] An arc-shaped guide lip 121 is formed on the outlet plate 12, extending smoothly from the annular space within the receiving cavity 1 towards the inner circumference of the variable cross-section pipe 6. The center of the arc of the arc-shaped guide lip 121 is located on the axis of the variable cross-section pipe 6, and its radius of curvature is not less than twice the minimum bending radius of the airbag 3. When the airbag 3 is released, its direction of motion gradually changes from the tangential direction of the rotation axis 2 to the axial direction of the variable cross-section pipe 6 along the arc-shaped guide lip 121; when the airbag 3 is retracted, its direction of motion gradually changes from the axial direction of the variable cross-section pipe 6 to the tangential direction of the rotation axis 2 along the arc-shaped guide lip 121. Thus, the airbag 3 completes the direction change along a continuous arc-shaped surface during both release and retraction.

[0111] Reference Figure 3 , Figure 4 and Figure 7 The rotating shaft 2 is a hollow shaft. One end of the rotating shaft 2 has a first vent 21 extending axially along its axis, and the outer periphery of the rotating shaft 2 has a second vent 22 communicating with the first vent 21. The fixed end 31 of the airbag body 3 has a third vent 311. When the fixed end 31 of the airbag body 3 is fixed to the rotating shaft 2, the third vent 311 is opposite to and communicates with the second vent 22, so that the first vent 21, the second vent 22, the third vent 311, and the air cavity inside the airbag body 3 are sequentially connected. The end of the rotating shaft 2 away from the inlet of the first vent 21 is closed, so that the gas entering the first vent 21 enters the airbag body 3 through the second vent 22 and the third vent 311.

[0112] The first air vent 21 is connected to the pneumatic system 5 via a rotary joint 51. One side of the rotary joint 51 is connected to the pipeline of the pneumatic system 5, and the other side is connected to the rotating shaft 2, so that the rotating shaft 2 can rotate relative to the receiving cavity 1 during the release or retraction of the airbag body 3, while maintaining the air passage between the pneumatic system 5 and the airbag body 3.

[0113] The airbag body 3 is a single-lobed, sheet-like inflatable structure extending along its length, with a single air cavity forming inside that communicates along the length of the airbag body 3. The airbag body 3 is pre-formed into a C-shape with a longitudinal opening during manufacturing. The cross-section of the airbag body 3 perpendicular to its length includes a bottom wall and two wing-shaped wall portions. The bottom wall is located away from the opening of the C-shaped cross-section, and the two wing-shaped wall portions extend from both sides of the bottom wall towards the opening. The bottom wall and the two wing-shaped wall portions together form the air cavity. The opening of the C-shaped cross-section is used for inserting the raw yarn and for separating the airbag body 3 from the raw yarn after yarn threading.

[0114] Within the same C-shaped cross-section, the wall thickness of the bottom wall is greater than that of the two wing-shaped walls. The bottom wall has relatively greater resistance to deformation, while the two wing-shaped walls have relatively lower bending stiffness. In the uninflated state, the two wing-shaped walls maintain a pre-formed bent shape facing inwards towards the opening of the C-shaped cross-section. When positive pressure gas is introduced into the air chamber, the bottom wall provides relatively stable support for the airbag body 3, and the two wing-shaped walls preferentially undergo bending deformation relative to the bottom wall, moving inwards towards the inside of the C-shaped cross-section along their pre-formed direction.

[0115] The airbag body 3 can also have a gradually varying wall thickness along its length. Specifically, the wall thickness of the airbag body 3 gradually decreases from the fixed end 31 to the free end 32, with the wall thickness of the fixed end 31 being 1.5mm to 3.0mm and the minimum wall thickness of the free end 32 being 0.3mm to 0.8mm. The larger wall thickness of the fixed end 31 is used to meet the requirements of fixing the airbag body 3 to the rotating shaft 2 and ensuring airflow connectivity, while the smaller wall thickness of the free end 32 allows it to flexibly deform with the change in diameter of the variable cross-section pipe 6.

[0116] Flexible magnetic strips 33 are embedded on the inner sides of the free edges of the two wing wall sections. The two flexible magnetic strips 33 have opposite poles and are arranged along the length of the airbag body 3. When the airbag body 3 is not inflated, the two flexible magnetic strips 33 attract each other, bringing the free edges of the two wing wall sections closer together, but an opening that can be manually separated is still maintained between the two wing wall sections. When the primary filament is inserted, the two flexible magnetic strips 33 can be partially separated, allowing the primary filament to enter the inner side of the bottom wall section through the C-shaped opening; after the primary filament is inserted, the two flexible magnetic strips 33 attract each other again, forming an anti-detachment restriction for the primary filament.

[0117] The magnetic attraction provided by the two flexible magnetic strips 33 is used to keep the two vane walls close to each other, rather than to form a rigid clamp on the filament. After the airbag 3 is inflated, the two thinner vane walls bend further inwards towards the C-shaped cross-section under positive pressure, forming a continuous flexible wrapping from both sides of the filament; after the airbag 3 is depressurized, the two vane walls release the inflated wrapping state under the action of material elasticity and C-shaped pre-formed contour, and the two flexible magnetic strips 33 can separate from each other along with the vane walls, so that the airbag 3 can roll back and withdraw relative to the filament.

[0118] A PTFE anti-stick coating is provided on the side of the flexible magnetic strip 33 facing the inside of the airbag body 3. The PTFE anti-stick coating forms the contact surface facing the original filament, which is used to reduce the friction between the original filament and the flexible magnetic strip 33 and the free edge of the wing wall. The airbag body 3 can be made of highly elastic wear-resistant rubber or polyurethane elastomer, so that the airbag body 3 can produce recoverable elastic deformation when inflated under positive pressure, and can be converted into a state that is easy to bend and roll after depressurization or negative pressure suction.

[0119] Reference Figure 6 , Figure 7 and Figure 9 The airbag body 3 has an axial extension induction structure on its tube wall. The axial extension induction structure includes multiple annular corrugated folds 34 and a high-strength fiber woven mesh layer. The multiple annular corrugated folds 34 are spaced apart along the length of the airbag body 3 and can be in a compressed state when the airbag body 3 is not inflated or rolled up, and gradually unfold along the length of the airbag body 3 when the airbag body 3 is inflated.

[0120] A high-strength fiber woven mesh layer is embedded within the tube wall of the airbag 3 during its molding process. The angle between the woven threads of the mesh layer and the length direction of the airbag 3 is 54°44′±5°. The high-strength fiber woven mesh layer restricts the circumferential expansion of the airbag 3 and, in conjunction with the annular corrugated folds 34, allows the airbag 3 to extend along its length after inflation. After the receiving cavity 1 forms a radial constraint on the fixed end 31 and the inner coiled section, the portion of the airbag 3 located outside the outlet of the receiving cavity 1 preferentially extends axially. The displacement generated by this axial extension drives the rotating shaft 2 to rotate, causing the airbag 3 to be released layer by layer from the rotating shaft 2.

[0121] A flexible conical guide head 321 is provided at the free end 32 of the airbag body 3. The flexible conical guide head 321 is integrally formed with the airbag body 3 and communicates with the air cavity of the airbag body 3. The wall thickness of the flexible conical guide head 321 is greater than the wall thickness of the adjacent airbag body 3, so that the flexible conical guide head 321 has a higher shape retention capability than the adjacent airbag body 3 after inflation. The maximum outer diameter of the flexible conical guide head 321 is smaller than the minimum inner diameter of the variable cross-section pipe 6, so that it can still pass through the minimum cross-section of the variable cross-section pipe 6 after inflation and shaping.

[0122] The flexible conical guide head 321 gradually increases in size from the tip towards the main body of the airbag 3. When the flexible conical guide head 321 passes through the expanding conical section 61, the straight section 62 and the contracting conical section 63, its flexible outer wall can deform accordingly with the pipe diameter and contact state to guide the free end 32 of the airbag 3 to continue moving forward.

[0123] The tip of the flexible conical guide head 321 is provided with a traction ring 3211, which is a flexible rope loop, and the center of its loop hole is located on the central axis of the flexible conical guide head 321. The lead wire head can be connected to the traction ring 3211 by a slip knot or other connection method that can be released at the outlet end of the variable cross-section pipe 6. The traction ring 3211 is coaxially arranged with the flexible conical guide head 321, so that the force-bearing position of the lead wire head is close to the central axis of the flexible conical guide head 321.

[0124] Reference Figure 4 and Figure 8 In this embodiment, the reset drive mechanism uses a spiral spring 4. The inner hook end 41 of the spiral spring 4 is connected to the rotating shaft 2, and the outer straight hook end 42 of the spiral spring 4 is connected to the seat 13 of the receiving cavity 1. The inner diameter of the spiral spring 4 is larger than the outer diameter of the rotating shaft 2, and a radial gap of 2mm to 5mm is maintained between the spiral spring 4 and the rotating shaft 2.

[0125] As the airbag 3 is released layer by layer by the rotating shaft 2, the rotating shaft 2 rotates in the positive direction relative to the base 13, causing the inner hook end 41 of the spiral spring 4 to rotate relative to the outer straight hook end 42, thus gradually storing elastic potential energy in the spiral spring 4. After the airbag 3 is depressurized or completes negative pressure suction, the spiral spring 4 releases its elastic potential energy and applies a rewind torque to the rotating shaft 2 in the opposite direction to the release direction of the airbag 3, thereby driving the rotating shaft 2 to rotate in the opposite direction. The radial clearance provides space for the radial deformation of the spiral spring 4 during winding and release, thereby reducing interference between the spiral spring 4 and the rotating shaft 2. Example 2

[0126] Reference Figure 12 The pneumatic system 5 includes a positive pressure air source, a negative pressure air source, an exhaust port, a reversing valve, and a controller. The reversing valve includes a first interface P1, a second interface P2, a third interface P3, and a working interface P4. The first interface P1 is connected to the positive pressure air source, the second interface P2 is connected to the negative pressure air source, the third interface P3 is connected to the exhaust port, and the working interface P4 is connected to the air chamber of the airbag body 3 via the gas passage in the rotary joint 51 and the rotating shaft 2.

[0127] The reversing valve has a positive pressure inflation position, a negative pressure suction position, a pressure relief position, and a pressure holding position. When the reversing valve is in the positive pressure inflation position, the first port P1 is connected to the working port P4, and the positive pressure gas enters the air chamber of the airbag body 3 in sequence through the working port P4, the rotary joint 51, the first air hole 21, the second air hole 22, and the third air hole 311; at this time, the second port P2 and the third port P3 are isolated from the working port P4.

[0128] When the reversing valve is in the pressure-holding position, the working interface P4 is closed, isolating the airbag 3 from the positive pressure source, negative pressure source, and exhaust port to maintain the inflation state of the airbag 3. When the reversing valve is in the pressure-relief position, the third interface P3 connects to the working interface P4, and the positive pressure gas in the airbag 3 is discharged through the exhaust port. When the reversing valve is in the negative pressure suction position, the second interface P2 connects to the working interface P4, and the negative pressure source extracts the residual gas in the airbag 3 through the gas channel in the rotating shaft 2.

[0129] The controller is electrically connected to the reversing valve and controls the reversing valve to sequentially switch between positive pressure inflation, pressure holding, pressure relief, and negative pressure suction positions according to the yarn threading process. The pressure of the positive pressure gas is predetermined based on the material and cross-sectional dimensions of the airbag body 3, the inner diameter of the variable cross-section pipe 6, and the specifications of the raw yarn, so that the flexible conical guide head 321 can maintain its conical profile, and the walls of the two vanes can bend inward toward the C-shaped cross-section, while avoiding rigid concentrated compression of the raw yarn.

[0130] In one embodiment, the rotating shaft 2 is connected to an encoder, which is used to detect the cumulative number of rotations of the rotating shaft 2. The controller pre-stores the correspondence between the initial winding state of the rotating shaft 2, the size of the rotating shaft 2, the thickness of the airbag 3 and the deployment length of the airbag 3, and obtains the deployment length of the airbag 3 based on the cumulative number of rotations detected by the encoder.

[0131] The controller also pre-stores the axial distances from the inlet end of the variable cross-section pipe 6 to the starting or ending positions of each expansion cone section 61, straight section 62, and contraction cone section 63. The controller compares the release length of the airbag 3 with the preset position parameters of each pipe section to determine the pipe section where the flexible conical guide head 321 is located.

[0132] A pressure sensor can also be installed in the piping of the pneumatic system 5. The pressure sensor detects the real-time pressure in the airbag 3 or the piping connected to the airbag 3. The controller compares the detected pressure value, pressure change, or pressure change trend with preset judgment parameters, and, in conjunction with the release position obtained by the encoder, corrects the judgment result of the pipe section where the flexible conical guide head 321 is located.

[0133] When the flexible conical guide head 321 enters the contraction cone section 63, the resistance to passage of the airbag body 3 increases, and the controller increases the intake pressure according to the preset air pressure control parameters. When the flexible conical guide head 321 enters the expansion cone section 61, the controller maintains the preset intake pressure. When the flexible conical guide head 321 enters the straight section 62, the controller adjusts the intake pressure to the preset normal air pressure. The air pressure control parameters corresponding to each pipe section are predetermined and stored in the controller based on the size and material of the airbag body 3, the diameter of the variable cross-section pipe 6, and the specifications of the original wire. Example 3

[0134] This embodiment provides a method for threading variable cross-section pipes using a retractable C-shaped airbag employing the aforementioned threading device. Taking the threading of 3K to 24K carbon fiber precursors as an example, when the airbag body 3 is in an uninflated state, the opening width of its C-shaped cross-section is set to 1.2 to 1.5 times the equivalent diameter of the carbon fiber precursor to be threaded. The equivalent diameter is the diameter obtained by converting the actual cross-section of the precursor bundle into a circular cross-section of equal area.

[0135] The method includes a yarn feeding step, an air-inflating threading step, a handover step, and a release and recovery step, as detailed below. Step 1: Threading Step

[0136] Before threading the wire, the reversing valve is closed at the working interface P4. The airbag 3 remains uninflated and is wound around the rotating shaft 2. The C-shaped cross-section opening of the airbag 3 corresponds to the wire pressing groove 111 of the upper cover plate 11.

[0137] The operator partially separates the flexible magnetic strips 33 at the free edges of the two vane walls through the pressing groove 111, and inserts the main body of the raw wire into the inner side of the bottom wall section by section along the accessible C-shaped cross-section opening of the airbag body 3. After the raw wire is inserted, the two flexible magnetic strips 33 move closer to each other again under the action of opposite pole magnetic attraction, keeping the free edges of the two vane walls close together, and leaving a separable opening between the two vane walls.

[0138] The head of the raw filament is connected to the traction ring 3211 at the tip of the flexible conical guide head 321. The connection between the head of the raw filament and the traction ring 3211 is designed to be detachable at the outlet end of the variable cross-section pipe 6, so that the connection can transmit axial traction force during the inflation and threading process and can be released during the handover step. Step 2: Inflation and threading steps

[0139] The controller controls the reversing valve to switch to the positive pressure inflation position, so that the first interface P1 is connected to the working interface P4. The positive pressure gas enters the air chamber of the airbag body 3 in sequence through the rotary joint 51, the first air hole 21, the second air hole 22 and the third air hole 311.

[0140] After the pressure inside the airbag 3 increases, the flexible conical guide head 321 is inflated and formed. The two wing wall portions deform preferentially relative to the bottom wall portion because their wall thickness is less than that of the bottom wall portion. Under the combined action of the C-shaped preformed profile and the two flexible magnetic strips 33, they bend toward the inside of the C-shaped section, forming a continuous flexible wrapping of the original filament body from both sides.

[0141] The annular corrugated folds 34 of the airbag body 3 gradually unfold under positive pressure. The high-strength fiber woven mesh layer restricts the excessive circumferential expansion of the airbag body 3, causing the portion of the airbag body 3 located outside the outlet of the receiving cavity 1 to extend along its length. When the airbag body 3 extends, it overcomes the rewinding torque applied by the spiral spring 4 and drives the rotating shaft 2 to rotate in the forward direction, thereby releasing it layer by layer from the rotating shaft 2; at the same time, the spiral spring 4 stores elastic potential energy as it rotates with the rotating shaft 2.

[0142] After the airbag body 3 is tangentially released from the rotating shaft 2, it gradually transitions to axial movement along the variable cross-section pipe 6 via the arc-shaped guide lip 121. The flexible conical guide head 321 moves forward as the leading end of the airbag body 3, and the traction ring 3211 pulls the filament head to move synchronously. The C-shaped cross-section of the airbag body 3 extends continuously along the filament body to form a flexible limit on the filament body while the filament head is subjected to axial traction.

[0143] The flexible conical guide head 321 passes sequentially through the expanding conical section 61, the straight section 62, and the contracting conical section 63. Its maximum outer diameter is smaller than the minimum inner diameter of the variable cross-section pipe 6, and it can adapt to the changes in the inner diameter of different pipe sections by utilizing its own flexibility. The controller determines the pipe section where the flexible conical guide head 321 is located based on the length of the airbag 3 released by the encoder and the pressure change detected by the pressure sensor, and adjusts the intake pressure according to the preset air pressure control parameters. Step 3: Handover Procedures

[0144] When the flexible conical guide head 321 reaches the outlet end of the variable cross-section pipe 6, the controller controls the reversing valve to switch from the positive pressure inflation position to the pressure holding position, and closes the working interface P4, so that the airbag body 3 continues to be inflated.

[0145] With the airbag 3 still inflated, disconnect the connection between the profilograph head and the traction ring 3211. After disconnection, keep the profilograph head at the outlet end of the variable cross-section pipe 6, and prevent the profilograph head from moving towards the inlet end with the airbag 3 during subsequent recovery. The pressure holding time can be set to 5 to 30 seconds to allow time for disconnecting the profilograph head from the traction ring 3211. Step 4: Release and Recycling Steps

[0146] After the raw yarn head is disconnected from the traction ring 3211, the controller first controls the reversing valve to switch to the pressure relief position, so that the third interface P3 is connected to the working interface P4. The positive pressure gas in the airbag body 3 is discharged to the third interface P3 in sequence through the third air hole 311, the second air hole 22, the first air hole 21, the rotary joint 51 and the working interface P4, and the pressure relief time is 1 second to 3 seconds.

[0147] After the pressure difference between the inside and outside of the airbag 3 decreases, the two wing walls release the air covering of the raw filament body under the action of material elasticity and C-shaped pre-formed contour. Subsequently, the controller controls the reversing valve to switch to the negative pressure suction position, connecting the second interface P2 with the working interface P4, and the negative pressure source extracts the residual gas in the airbag 3 and the flexible conical guide head 321. The negative pressure suction time is 1 second to 5 seconds, or it stops when the pressure sensor detects that the internal pressure of the airbag 3 has reached the preset negative pressure value.

[0148] After the negative pressure suction is completed, the flexible conical guide head 321 collapses, and the airbag 3 is converted into a state that is easy to bend and coil. The spiral spring 4 releases the elastic potential energy stored during the release of the airbag 3, driving the rotating shaft 2 to rotate in the opposite direction. The airbag 3 is retracted from the outlet side to the inlet side of the variable cross-section pipe 6, and moves relative to the stationary filament along its C-shaped cross-section opening, so that the filament body gradually detaches from the airbag 3.

[0149] When the airbag 3 reaches the outlet of the receiving cavity 1, it gradually changes from the axial recovery direction of the variable cross-section pipe 6 to the tangential winding direction of the rotating shaft 2 via the arc-shaped guide lip 121, and is wound layer by layer onto the rotating shaft 2. After the airbag 3 is recovered, the original filament is retained in the variable cross-section pipe 6, thus completing one filament threading process.

[0150] When threading the yarn again in a subsequent process, the yarn to be threaded can be placed back into the air bladder 3 which is in a wound state, and the above-mentioned yarn release step, inflation threading step, handover step and release and recovery step can be repeated.

[0151] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A rewindable C-shaped airbag threading device for variable cross-section pipes, used to thread the raw filament through a variable cross-section pipe (6), characterized in that, It includes a storage cavity (1), a rotating shaft (2), an airbag body (3), a reset drive mechanism, and a pneumatic system (5); The receiving cavity (1) is located at the inlet end of the variable cross-section pipe (6), and the rotating shaft (2) is rotatably connected to the receiving cavity (1). The axis of the rotating shaft (2) is perpendicular to the axis of the variable cross-section pipe (6). The airbag body (3) is a single-lobed sheet-like inflatable structure extending along the length direction. The fixed end (31) of the airbag body (3) is fixedly connected to the rotating shaft (2). The main body of the airbag body (3) is spirally wound around the rotating shaft (2). The free end (32) of the airbag body (3) is set from the outlet of the receiving cavity (1) toward the variable cross-section pipe (6). The interior of the airbag (3) forms an air cavity that communicates along the length direction of the airbag (3). The cross section of the airbag (3) perpendicular to its length direction is C-shaped with an opening. The C-shaped cross section includes a bottom wall portion located away from the opening and two wing wall portions extending from both sides of the bottom wall portion toward the opening. The wall thickness of the bottom wall portion is greater than the wall thickness of the two wing wall portions. Flexible magnetic strips (33) are respectively provided on the inner side of the free edges of the two wing wall portions. The two flexible magnetic strips (33) are arranged with opposite poles facing each other. When the airbag (3) is not inflated, the two flexible magnetic strips (33) bring the free edges of the two wing wall portions closer to each other and retain the separable opening between the two wing wall portions. When the airbag (3) is inflated, the two wing wall portions deform preferentially relative to the bottom wall portion and bend toward the inside of the C-shaped section; The free end (32) of the airbag body (3) is provided with a flexible conical guide head (321), the flexible conical guide head (321) is connected to the air cavity of the airbag body (3), and the tip of the flexible conical guide head (321) is coaxially provided with a traction ring (3211). The pneumatic system (5) is connected to the air cavity of the airbag body (3) through the gas channel formed inside the rotating shaft (2); The reset drive mechanism is connected to the rotating shaft (2) and applies a rewinding torque to the rotating shaft (2) that is opposite to the release direction of the airbag (3).

2. The rewindable C-shaped airbag threading device for variable cross-section pipes according to claim 1, characterized in that, The airbag body (3) has an axial extension induction structure on its tube wall. The axial extension induction structure includes annular corrugated creases (34) spaced apart along the length of the airbag body (3) and a high-strength fiber woven mesh layer embedded in the tube wall of the airbag body (3).

3. The rewindable C-shaped airbag threading device for variable cross-section pipes according to claim 1, characterized in that, The airbag body (3) has a gradually decreasing wall thickness structure from the fixed end (31) to the free end (32) along its length direction. The wall thickness of the fixed end (31) is 1.5mm to 3.0mm, and the minimum wall thickness of the free end (32) is 0.3mm to 0.8mm.

4. The rewindable C-shaped airbag threading device for variable cross-section pipes according to claim 1, characterized in that, The flexible conical guide head (321) is integrally formed with the airbag body (3). The wall thickness of the flexible conical guide head (321) is greater than the wall thickness of the adjacent airbag body (3). The maximum outer diameter of the flexible conical guide head (321) is smaller than the minimum inner diameter of the variable cross-section pipe (6). The traction ring (3211) is a flexible rope ring. The center of the ring hole of the traction ring (3211) is located on the central axis of the flexible conical guide head (321).

5. The rewindable C-shaped airbag threading device for variable cross-section pipes according to claim 1, characterized in that, The inner wall of the receiving cavity (1) and the outer periphery of the rotating shaft (2) form an annular space. The fixed end (31) of the airbag body (3) and the inner coil section adjacent to the fixed end (31) are accommodated in the annular space. The outlet of the receiving cavity (1) is provided with an arc-shaped guide lip (121). The arc-shaped guide lip (121) extends smoothly from the annular space toward the inner periphery of the variable cross-section pipe (6).

6. The rewindable C-shaped airbag threading device for variable cross-section pipes according to claim 1, characterized in that, The rotating shaft (2) is a hollow shaft. One end of the rotating shaft (2) is provided with a first air hole (21) extending along its axial direction. The outer periphery of the rotating shaft (2) is provided with a second air hole (22) communicating with the first air hole (21). The fixed end (31) of the airbag body (3) is provided with a third air hole (311) corresponding to and communicating with the second air hole (22). The first air hole (21) is connected to the pneumatic system (5) through a rotary joint (51). The other end of the rotating shaft (2) is closed.

7. The rewindable C-shaped airbag threading device for variable cross-section pipes according to claim 1, characterized in that, The reset drive mechanism includes a spiral spring (4), the inner hook end (41) of the spiral spring (4) is connected to the rotating shaft (2), and the outer straight hook end (42) of the spiral spring (4) is connected to the receiving cavity (1); the inner diameter of the spiral spring (4) is larger than the outer diameter of the rotating shaft (2), and there is a radial gap of 2mm to 5mm between the spiral spring (4) and the rotating shaft (2).

8. The rewindable C-shaped airbag threading device for variable cross-section pipes according to claim 1, characterized in that, The pneumatic system (5) includes a positive pressure air source, a negative pressure air source, an exhaust port, a reversing valve, and a controller; the reversing valve is provided with a first interface connected to the positive pressure air source, a second interface connected to the negative pressure air source, a third interface connected to the exhaust port, and a working interface connected to the gas passage of the rotating shaft (2); the reversing valve has a working position that allows the working interface to be connected to the first interface, the second interface, or the third interface respectively, and a pressure-holding position that closes the working interface.

9. A method for threading wire using a retractable C-shaped airbag for variable cross-section pipes, characterized in that, It is implemented using a storage cavity (1), a rotating shaft (2), an airbag body (3), a reset drive mechanism, and a pneumatic system (5); The airbag body (3) has an internal air cavity that is connected along its length. The cross-section of the airbag body (3) is C-shaped with an opening. The wall thickness of the bottom wall on the side of the C-shaped cross-section away from the opening is greater than the wall thickness of the two wing wall portions located on both sides of the opening. Flexible magnetic strips (33) with opposite poles are respectively provided on the inner side of the free edges of the two wing wall portions. The method includes: In the yarn feeding step, the main body of the raw yarn is placed inside the bottom wall through the C-shaped cross-section opening of the airbag body (3). The two flexible magnetic strips (33) attract each other and bring the free edges of the two wing wall parts closer to each other. The head of the raw yarn is connected to the traction ring (3211) at the tip of the flexible conical guide head (321) set at the free end (32) of the airbag body (3). In the inflation and threading step, positive pressure gas is introduced into the air chamber of the airbag (3) through the pneumatic system (5). The two wing wall portions bend towards the inside of the C-shaped cross section relative to the bottom wall portion and cover the main body of the raw filament. The flexible conical guide head (321) expands. The airbag (3) is released layer by layer by the rotating shaft (2) and moves along the variable cross section pipe (6). The traction ring (3211) pulls the head of the raw filament to move synchronously with the flexible conical guide head (321). In the handover step, after the flexible conical guide head (321) reaches the outlet end of the variable cross-section pipe (6), the airbag body (3) is kept in an inflated state, and the connection between the raw filament head and the traction ring (3211) is released. In the release and recovery step, after disconnecting the connection between the profilament head and the traction ring (3211), the airbag body (3) is depressurized or negative pressure is applied to separate the two wing wall portions and remove the covering of the profilament body, causing the flexible conical guide head (321) to collapse. The reset drive mechanism drives the rotating shaft (2) to rotate in the opposite direction, winding the airbag body (3) back into the receiving cavity (1) and leaving the profilament in the variable cross-section pipe (6).

10. The method for threading wire using a retractable C-shaped airbag for variable cross-section pipes according to claim 9, characterized in that, The pneumatic system (5) performs positive pressure inflation in the inflation and insertion step, closes the air passage connected to the airbag body (3) and maintains pressure in the handover step, and sequentially performs pressure relief through the exhaust port and suction through the negative pressure source in the release and recovery step; the reset drive mechanism drives the rotating shaft (2) to rotate in the opposite direction after the airbag body (3) completes negative pressure suction.

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