A complex space double-layer pipe integral bending forming tool and method

Abstract

The present application belongs to the technical field of metal plastic forming and numerical control bending processing, and discloses a complex space double-layer pipe integral bending forming tool and method. The front-end clamping mechanism, the movable hydraulic internal expansion driving module and the rear-end double-motor independent driving module are connected with the control unit. The front-end clamping mechanism clamps one end of the outer wall of the outer pipe. The movable hydraulic internal expansion driving module is arranged in the inner cavity of the inner pipe. The high-pressure flexible hydraulic hose in the movable hydraulic internal expansion driving module is connected with the hydraulic cylinder cavity through the oil circuit. The piston is arranged in the hydraulic cylinder cavity. The tapered mandrel is connected with the piston. The split cylinder clamp is installed on the tapered mandrel. The outer pipe driving motor in the rear-end double-motor independent driving module is connected with the outer pipe. The inner pipe driving motor is connected with the high-pressure flexible hydraulic hose. The present application realizes the inner and outer pipe feeding decoupling control and the precise control of the cross-section quality, achieves the high-precision integral forming of the complex space double-layer pipe, and significantly improves the integral forming quality of the double-layer pipe.

Description

Technical Field

[0001] This invention belongs to the field of metal plastic forming and CNC bending processing technology, and in particular, it relates to a tooling and method for integral bending forming of complex spatial double-layer tubes. Background Technology

[0002] In the fields of modern aerospace, energy and power, and precision instrument manufacturing, complex space double-layer tubes are widely used in critical components such as engine fuel lines, nuclear reactor cooling circuits, and high-precision optical instrument supports due to their combined functions of media isolation, thermal compensation, structural reinforcement, and signal shielding. These components typically require strict coaxiality and spatial trajectory consistency between the inner and outer tubes, and must meet high sealing and fatigue strength requirements after forming.

[0003] Existing pipe bending processes and fixtures are mostly designed for single-layer pipes. When directly applied to the bending of double-layer pipes, they face significant technical challenges. Traditional bending equipment typically uses a single drive source to simultaneously feed the inner and outer pipes, or uses a front-end clamping method to fix the pipe blank. However, due to the fundamental differences in the stress state, neutral layer offset, and elongation between the inner and outer pipes during bending deformation, this forced synchronous driving method easily leads to relative slippage between the inner and outer pipes. This relative movement not only disrupts the pre-set fit between the layers but also often causes axial compression wrinkling or tensile thinning of the inner pipe, severely weakening the structural integrity of the pipeline.

[0004] Furthermore, existing double-layer tube forming processes, especially for processing continuous multi-bend components, have significant limitations. Current processes typically rely solely on a front-end clamping mechanism to fix the outer tube, while the movement of the inner tube depends entirely on a rear-end mechanism for feeding. During complex bending deformation, the lack of effective synchronous constraints on the inner tube's local area leads to a completely uncontrollable relative slippage between the inner and outer tubes due to this non-cooperative driving method of "outer tube clamping, inner tube pushing." This uncontrollable interlayer slippage not only disrupts the original structural matching relationship of the double-layer tube but also severely reduces the controllability of overall forming accuracy, making it difficult for the product to meet the stringent quality standards of high-end equipment manufacturing.

[0005] Therefore, there is an urgent need to propose a brand-new forming fixture that can effectively solve the problems of uncontrollable sliding of inner and outer tubes and low forming accuracy, thereby improving the accuracy and stability of overall bending forming of complex spatial double-layer tubes. Summary of the Invention

[0006] The purpose of this invention is to provide a tooling and method for integral bending and forming of complex spatial double-layer tubes, which solves the problems of uncontrollable sliding of inner and outer tubes and low forming accuracy in the prior art.

[0007] To achieve the above objectives, the present invention employs the following technical solution: In the first aspect, this application proposes a complex spatial double-layer tube integral bending forming tooling, including a front clamping mechanism, a movable hydraulic internal expansion drive module, a rear dual-motor independent drive module and a control unit. The front clamping mechanism, the movable hydraulic internal expansion drive module and the rear dual-motor independent drive module are all connected to the control unit. The front clamping mechanism clamps one end of the outer wall of the outer tube. The movable hydraulic internal expansion drive module is set in the inner cavity of the inner tube. The movable hydraulic internal expansion drive module includes a high-pressure flexible hydraulic hose and a hydraulic cylinder cavity. The high-pressure flexible hydraulic hose is connected to the hydraulic cylinder cavity through an oil circuit. A piston is set in the hydraulic cylinder cavity. A tapered mandrel is connected to the piston. A segmented collet is installed on the tapered mandrel. The rear dual-motor independent drive module includes an outer tube drive motor and an inner tube drive motor. The outer tube drive motor is connected to the outer tube, and the inner tube drive motor is connected to the high-pressure flexible hydraulic hose.

[0008] Furthermore, a dedicated support mechanism for the front-end outer tube is provided on one side of the front-end clamping mechanism, which supports the outer wall of the outer tube.

[0009] Furthermore, a rear support mechanism is provided at the other end of the outer tube, and the rear support mechanism is provided with two independent support units, which respectively support the outer walls of the outer tube and the inner tube.

[0010] Furthermore, the front-end clamping mechanism includes a clamping sleeve, a drive disk, and a jaw body. The jaw body is a two-lobed chuck, and the clamping sleeve is arranged around the outside of the jaw body. The lobed chuck is connected to one end of the drive disk.

[0011] Furthermore, the split chuck includes a left clamp and a right clamp, the inner arc surfaces of which match the outer diameter of the outer tube.

[0012] Furthermore, both the outer tube drive motor and the inner tube drive motor are servo motors. The output end of the outer tube drive motor is connected to the outer tube through a transmission mechanism, and the output end of the inner tube drive motor is connected to the high-pressure flexible hydraulic hose through a transmission mechanism.

[0013] Furthermore, the control unit includes a control unit and a CNC numerical control system. The hydraulic control system is connected to the other end of the drive disc and the high-pressure flexible hydraulic hose. The CNC numerical control system is independently connected to the outer tube drive motor and the inner tube drive motor.

[0014] Furthermore, the movable hydraulic internal expansion drive module is axially arranged in the inner cavity of the inner tube, and the high-pressure flexible hydraulic hose is a multi-layer steel wire braided telescopic structure.

[0015] Secondly, this application proposes a method for integral bending and forming of complex spatial double-layer tubes based on the aforementioned tooling, comprising: The double-layer tube blank is placed outside the movable hydraulic internal expansion drive module, and the front end of the double-layer tube blank is sent into the front clamping mechanism. The front clamping mechanism only holds the end of the outer tube and keeps the end of the inner tube in a non-contact state. The control unit injects high-pressure medium into the hydraulic cylinder cavity of the movable hydraulic internal expansion drive module inside the inner tube through the oil circuit, which pushes the piston to drive the conical mandrel to move, lift up the dividing collet and tighten the inner wall of the inner tube, thereby establishing a transmission interface with friction between the inner tube and the movable hydraulic internal expansion drive module. The control unit controls the rotation of the main shaft of the pipe bending machine according to the trajectory parameters of the current bending pass. The outer tube drive motor drives the outer tube to be fed in, and the inner tube drive motor drives the high-pressure flexible hydraulic hose according to the preset speed ratio. The movable hydraulic internal expansion drive module in the expansion state drives the inner tube to bend synchronously in the bending deformation zone through friction, eliminating interlayer slippage and completing the bending and forming of the current pass. After the current bending pass is completed, the control unit controls the hydraulic circuit to depressurize, drives the piston to move the conical mandrel back, releases the radial support force on the dividing sleeve, and restores the inner tube to a free state; the inner tube drive motor drives the depressurized movable hydraulic internal expansion drive module to move axially inside the inner tube, and transports it to the starting point of the next bending pass. After reaching the predetermined position, the hydraulic circuit is repressurized, pushing the piston to drive the conical mandrel forward, radially lifting the dividing collet and tightening the inner wall of the inner tube, re-establishing the friction transmission connection between the inner and outer tubes, and re-establishing the friction transmission interface. The control unit calls the bending process parameters for the next pass, repeats the coordinated bending process, and cycles in this way until all bending passes of the double-layer tube blank are completed. After all bending processes are completed, the front clamping mechanism is released, and the inner tube drive motor drives the depressurized movable hydraulic internal expansion drive module to be completely extracted, thus removing the formed complex spatial double-layer tube.

[0016] Furthermore, the CNC numerical control system in the control unit preloads a spatial bending trajectory algorithm, calculates the difference in plastic elongation between the outer tube and the inner tube in real time based on different bending angles and bending radii, and issues different motion commands to the outer tube drive motor and the inner tube drive motor respectively, actively compensating for the difference in elongation and suppressing interlayer slippage and misalignment between the inner and outer tubes during bending.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a complex spatial double-layer tube integral bending forming fixture. The front-end clamping mechanism only grips the outer tube end, maintaining non-contact with the inner tube, fundamentally releasing the axial constraint of the inner tube. The rear-end dual-motor independent drive module independently drives the outer tube and the inner expansion module via separate outer and inner tube drive motors, achieving decoupled control of the inner and outer tube feeding. The movable hydraulic inner expansion drive module uses a high-pressure flexible hydraulic hose combined with a tapered mandrel and a segmented collet mechanical locking structure to establish a reliable friction transmission interface within the inner tube cavity. The synergistic effect of these three components allows the fixture to utilize the internal expansion friction to drag the inner tube for synchronous deformation during bending. Simultaneously, the dual-motor speed ratio control actively compensates for the difference in plastic elongation between the inner and outer tubes, fundamentally solving the problems of interlayer movement, wrinkling, or tearing caused by forced synchronous feeding in traditional fixtures. Furthermore, the segmented collet can be adjusted in size according to different inner tube diameters, giving the fixture strong versatility and adaptability. The dedicated front-end outer tube support mechanism and the rear-end support mechanism provide stable support throughout the long double-layer tube process, further ensuring forming accuracy. This invention releases the axial constraint of the inner tube by clamping the outer tube on one side at the front end, and works in conjunction with the independent drive of the dual motors at the rear end and the synergistic effect of the movable hydraulic internal expansion drive module. This achieves decoupling control of the inner and outer tube feeding and precise control of the cross-sectional quality. Without changing the main structure of the existing bending machine tool, it achieves high-precision integral forming of complex spatial double-layer tubes, significantly improving the overall forming quality of the double-layer tubes.

[0018] Furthermore, by adding a dedicated support mechanism for the outer tube on one side of the front clamping mechanism, an auxiliary support is provided to the outer wall of the outer tube during the bending process. This effectively counteracts the radial off-center load generated when the main shaft of the tube bending machine rotates and the outer tube is fed in, preventing the outer tube from being locally crushed or unstable and deformed in the clamping section. At the same time, the positioning stiffness of the front end of the outer tube is further improved, ensuring that the outer tube maintains a stable cross-sectional shape in the bending deformation zone. This provides a reliable external reference for the precise coordinated movement of the inner tube and the inner expansion drive module, thereby significantly improving the dimensional accuracy of the first section of the complex space double-layer tube bending and forming.

[0019] Furthermore, a rear support mechanism containing two independent support units is set at the rear end to independently support the outer wall of the outer tube and the inner tube respectively. This not only prevents the swaying and twisting of the tail of the tube due to gravity or torque during bending, but also avoids forced constraint interference between the two tube layers. This independent support design, in conjunction with the rear dual-motor independent drive module, ensures that the outer tube and the inner tube each have independent degrees of freedom of movement at the rear end, thereby effectively eliminating the additional stress caused by the constraint coupling at the tail end and significantly improving the forming stability and interlayer position consistency of the tube in the rear section during multiple bending passes.

[0020] Furthermore, the inner arc surfaces of the left and right clamping blocks of the split clamp are designed to match the outer diameter of the outer tube, increasing the contact area between the clamping blocks and the outer tube. This ensures that the clamping force is evenly distributed around the outer wall of the outer tube, preventing damage such as indentations or pits on the outer tube surface caused by localized stress concentration. At the same time, this matching inner arc surface design allows for quick adaptation to outer tubes of different diameters by changing the clamping blocks, improving the versatility and flexibility of the tooling. Moreover, since the clamping process only grips the outer tube, the inner tube is not constrained by the clamping force in the axial direction, creating favorable conditions for the inner tube to be freely fed into the bending deformation zone by the internal expansion drive module.

[0021] Furthermore, servo motors are used as the outer tube drive motor and the inner tube drive motor, and the outer tube and the high-pressure flexible hydraulic hose are driven independently through a transmission mechanism. The high response speed and high control precision of the servo motors enable the control unit to make precise speed ratio adjustments between the outer tube feed speed and the inner tube drive speed based on real-time bending trajectory parameters. This drive scheme ensures that the axial feed amount of the outer tube and the inner tube can be differentiated according to their respective plastic elongation characteristics in each bending pass, thereby realizing the decoupled control of the inner and outer tube motion at the power source level and providing a precise execution basis for suppressing interlayer misalignment.

[0022] Furthermore, by designing the control unit as a combination of a hydraulic control system and a CNC numerical control system, the hydraulic control system precisely adjusts the pressure of the drive disc and the inner expansion hydraulic cylinder to ensure the reliability of the outer tube clamping and the inner tube expansion, while the CNC numerical control system independently controls the outer tube drive motor and the inner tube drive motor respectively, realizing real-time coordination between the bending trajectory parameters and the movement of the two motors. This dual-system hierarchical control architecture not only utilizes the advantages of the hydraulic system's large output force and good stability, but also leverages the CNC system's high precision in trajectory planning and multi-axis linkage, enabling the tooling to automatically adapt to the process requirements of different bending radii and bending angles, significantly improving the automation level and process consistency of complex spatial double-layer tube forming.

[0023] Furthermore, a movable hydraulic internal expansion drive module is axially positioned within the inner tube cavity, employing a high-pressure flexible hydraulic hose with a multi-layered steel wire braided telescopic structure. This hose possesses both high-pressure sealing performance to transmit hydraulic pressure to drive the conical mandrel and segmented collets to tighten the inner wall, and the ability to achieve axial extension and bending follow-up under the traction of the inner tube drive motor, adapting to the axial displacement and curvature changes generated by the inner tube in the bending deformation zone. Simultaneously, the multi-layered steel wire braided structure enhances the hose's tensile strength and fatigue resistance, ensuring reliable operation under repeated pressurization, depressurization, and axial movement cycles, avoiding premature failure of ordinary hoses under high-pressure cycles, and greatly improving the tooling's durability and long-term stability.

[0024] This invention also provides a method for integral bending of complex spatial double-layer tubes. In each bending pass, the control unit injects high-pressure medium into the movable hydraulic internal expansion drive module inside the inner tube through the oil circuit. This pushes the piston to drive the conical mandrel to radially lift the dividing sleeve and tighten the inner wall of the inner tube. This allows the internal expansion module, which is in an expanded state, to drive the inner tube to bend synchronously through friction in the bending deformation zone, eliminating interlayer slippage between the inner and outer tubes. After the current pass is completed, the hydraulic circuit is depressurized to restore the inner tube to a free state. The inner tube drive motor can then axially move the depressurized internal expansion module inside the inner tube to the starting point of the next pass, realizing flexible displacement of the internal expansion module between multiple bending passes. This invention, without altering the main structure of existing bending machines, employs a high-pressure, multi-layered steel wire braided flexible hydraulic hose as the internal expansion medium. Combined with a mechanical locking structure of a conical mandrel and a dividing collet, it achieves high-precision forming of complex spatial double-layer tubes in multiple passes and at multiple angles. This ensures both uniform distribution of the internal expansion force and reliable connection between the inner tube and the internal expansion device through the radial support of the dividing collet, preventing hose slippage or inner tube deformation and effectively suppressing interlayer slippage and misalignment between the inner and outer tubes during bending. Furthermore, the size of the dividing collet can be adjusted according to different inner tube diameters, exhibiting strong versatility and adaptability.

[0025] Furthermore, the CNC system in the control unit is pre-loaded with a spatial bending trajectory algorithm. Based on different bending angles and radii, it calculates the difference in plastic elongation between the outer and inner tubes in real time, and issues different motion commands to the outer tube drive motor and the inner tube drive motor respectively to actively compensate for the difference in elongation. This intelligent speed ratio compensation mechanism actively eliminates the difference in axial length caused by the different bending radii of the inner and outer tubes at the control strategy level. This ensures that the inner tube always maintains coordinated deformation with the outer tube during the bending deformation process. It can effectively suppress interlayer slippage and misalignment without relying on mechanical forced synchronization, fundamentally improving the geometric accuracy and internal quality consistency of the overall forming of double-layer tubes under complex spatial multi-bend trajectories. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the complex spatial double-layer tube integral bending forming tooling of the present invention.

[0028] Figure 2 This is a diagram of the gripper body of the present invention.

[0029] Figure 3This is a structural diagram of the movable hydraulic internal expansion drive module of the present invention.

[0030] Figure 4 This is a schematic diagram illustrating the working principle of the movable hydraulic internal expansion drive module of the present invention.

[0031] Figure 5 This is a flowchart of the complex spatial double-layer tube integral bending forming method of the present invention.

[0032] Among them: 1-front end clamping mechanism, 2-front end outer tube dedicated support mechanism, 3-movable hydraulic internal drive module, 4-rear end dual motor independent drive module, 5-rear end support mechanism, 6-outer tube, 7-inner tube, 8-outer tube drive motor, 9-inner tube drive motor, 10-high pressure flexible hydraulic hose, 11-clamping sleeve, 12-drive disc, 13-segmented collet, 14-conical mandrel, 15-piston, 16-hydraulic cylinder cavity, 17-segmented chuck, 18-left clamping block, 19-right clamping block, 20-gripper body, 21-oil circuit. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0034] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0035] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0036] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing the present 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 present invention. Furthermore, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0037] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0038] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" 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 can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0039] The present invention will now be described in further detail with reference to the accompanying drawings: See Figure 1 This invention provides a complex spatial double-layer tube integral bending forming fixture. The fixture is installed on a common base, and arranged sequentially from front to back along the axis of the double-layer tube are a front clamping mechanism 1, a front outer tube dedicated support mechanism 2, a rear support mechanism 5, and a rear dual-motor independent drive module 4. The double-layer tube consists of an outer tube 6 and an inner tube 7 fitted inside the outer tube 6. A movable hydraulic internal expansion drive module 3 is completely housed in the hollow cavity of the inner tube 7. The control unit is equipped with a CNC numerical control system and a hydraulic control system. The rear dual-motor independent drive module 4 is connected to the CNC numerical control system, and the front clamping mechanism 1 and the movable hydraulic internal expansion drive module 3 are connected to the hydraulic control system.

[0040] The front clamping mechanism 1 is located at the front end of the double-layer tube and only clamps the front outer wall of the outer tube 6. The front clamping mechanism 1 as a whole maintains a gap with the end of the inner tube 7 and does not make any contact, thereby releasing the axial extension and contraction freedom of the inner tube 7.

[0041] like Figure 2As shown, the front-end clamping mechanism 1 includes a clamping sleeve 11, a drive disk 12, and a jaw body 20. The jaw body 20 adopts a two-part split chuck 17 structure, which includes a left clamping block 18 and a right clamping block 19. The inner arc surfaces of the left clamping block 18 and the right clamping block 19 are matched with the outer diameter of the outer tube 6, and the clamping range only acts on the outer wall of the outer tube 6. The left clamping block 18 and the right clamping block 19 will not touch the inner tube 7 during the inward clamping process. One end of the drive disk 12 is connected to the split chuck 17, and the other end of the drive disk 12 is connected to the hydraulic control system, which drives the left clamping block 18 and the right clamping block 19 to open and close by hydraulic power. The clamping sleeve 11 is arranged around the outside of the jaw body 20 to limit the radial displacement of the left clamping block 18 and the right clamping block 19, ensuring clamping coaxiality and positioning accuracy.

[0042] Throughout the entire process of continuous multi-bend processing of the pipeline, the front clamping mechanism 1 continuously locks and fixes the front end of the outer tube 6, while the end of the inner tube 7 is in a non-contact floating state and will not be rigidly jammed, thus avoiding wrinkling and cracking defects in the inner tube due to axial forced constraint during the bending deformation process.

[0043] The front-end outer tube special support mechanism 2 is arranged behind the front-end clamping mechanism 1. It only lifts and supports the outer wall of the outer tube 6 from the outside and does not touch the inner tube 7. The annular gap between the inner and outer tubes is not interfered with by the support structure. It only bears the radial load during the bending process of the outer tube 6 and does not constrain the deformation of the inner tube 7.

[0044] The rear support mechanism 5 is arranged in the tail area of ​​the double-layer pipe, and two sets of independent support units are set up: one set of support units supports the outer wall of the outer pipe 6, and the other set of support units supports the outer wall of the inner pipe 7, so that the outer pipe 6 and the inner pipe 7 are independently radially supported separately, and the inner and outer pipe supports do not interfere with each other.

[0045] The rear-end dual-motor independent drive module 4 is installed at the tail of the tooling and includes an outer tube drive motor 8 and an inner tube drive motor 9. Both motors are servo motors and are independently connected to the CNC numerical control system, with the two drive transmission chains being independent of each other.

[0046] The output end of the outer tube drive motor 8 is connected to the tail end clamping assembly of the outer tube 6 through a matching transmission mechanism, and the axial feeding speed and feeding stroke of the outer tube 6 are controlled independently; the output end of the inner tube drive motor 9 is connected to the tail high-pressure flexible hydraulic hose 10 of the movable hydraulic internal expansion drive module 3 through a transmission structure, and the axial position and moving speed of the movable hydraulic internal expansion drive module 3 are controlled independently.

[0047] The CNC system preloads a spatial bending trajectory algorithm, calculates the difference in plastic elongation between the outer tube 6 and the inner tube 7 in real time based on different bending angles and bending radii, and issues different motion commands to the outer tube drive motor 8 and the inner tube drive motor 9 respectively, actively compensating for the difference in elongation rate and suppressing interlayer slippage and misalignment between the inner and outer tubes during bending.

[0048] like Figure 3 As shown, the movable hydraulic internal expansion drive module 3 is placed axially inside the inner tube 7. From front to back along the axial direction, it includes a dividing collet 13, a tapered mandrel 14, a piston 15, and a hydraulic cylinder cavity 16. A high-pressure flexible hydraulic hose 10 is connected to the rear end of the hydraulic cylinder cavity 16. The piston 15 is installed inside the hydraulic cylinder cavity 16. The tapered mandrel 14 is connected to the piston 15. The dividing collet 13 is installed on the tapered mandrel 14.

[0049] The high-pressure flexible hydraulic hose 10 adopts a multi-layer steel wire braided telescopic structure. The high-pressure flexible hydraulic hose 10 is connected to the hydraulic cylinder cavity 16 through the oil passage 21, continuously delivering high-pressure hydraulic oil to the hydraulic cylinder cavity 16. The high-pressure flexible hydraulic hose 10 extends outward along the tail of the double-layer tube, and the rear end is fixedly connected to the output end of the inner tube drive motor 9. The movable hydraulic internal expansion drive module 3 can follow the inner tube drive motor 9 and move axially inside the inner tube 7.

[0050] like Figure 4 As shown, the working process of the movable hydraulic internal expansion drive module 3 is divided into two working conditions: expansion and contraction. 1) Hydraulic pressing operation (expansion state): High-pressure oil enters the hydraulic cylinder cavity 16 through oil circuit 21, pushing the piston 15 and the conical mandrel 14 to move forward axially; the outer conical surface of the conical mandrel 14 presses against the inner wall of the dividing collet 13, causing the dividing collet 13 to expand radially outward, and the outer peripheral wall tightly presses against the inner wall of the inner tube 7. Relying on the frictional force of the contact surface, the movable hydraulic internal expansion drive module 3 and the inner tube 7 form an integrated force transmission structure. When the outer tube 6 is bent and fed in, the frictional force drags the inner tube 7 to deform synchronously, avoiding the inner tube 7 from being fed in sluggishly and the tube wall from becoming unstable and wrinkling.

[0051] 2) Hydraulic decompression condition (contraction state): The hydraulic cylinder cavity 16 is decompressed, the hydraulic thrust disappears, the piston 15 drives the conical mandrel 14 to retract backward, the radial tension is removed, the dividing collet 13 retracts radially, the outer wall of the dividing collet 13 separates from the inner wall of the inner tube 7, and the friction transmission connection is released; at this time, the movable hydraulic internal expansion drive module 3 no longer constrains the inner tube 7, and under the traction of the inner tube drive motor 9, the entire movable hydraulic internal expansion drive module 3 can slide freely along the inner cavity of the inner tube 7 and move to the next bending start point.

[0052] This invention also provides a method for integral bending and forming of complex spatial double-layer tubes, such as... Figure 5 As shown, it includes the following steps: S1. Billet Clamping and Initial State Setting: The double-layer billet is placed outside the movable hydraulic internal expansion drive module 3, and the front end of the billet is fed into the front clamping mechanism 1. The front clamping mechanism 1 is controlled to operate so that its left clamping block 18 and right clamping block 19 only clamp the end of the outer tube 6, keeping the end of the inner tube 7 in a non-contact state, thereby releasing the axial constraint of the inner tube 7 at the clamping point. At the same time, the rear outer tube drive motor 8 and inner tube drive motor 9 lock the tail ends of the outer tube 6 and inner tube 7 respectively through independent clamping components. Subsequently, high-pressure medium is injected into the movable hydraulic internal expansion drive module 3, causing it to elastically expand and adhere tightly to the inner wall of the inner tube 7, thereby establishing a high-friction transmission interface between the inner tube 7 and the movable hydraulic internal expansion drive module 3.

[0053] S2. Bending Process Coordination: The CNC system controls the rotation of the tube bending machine spindle according to the trajectory parameters of the current bending pass. During this process, the outer tube drive motor 8 drives the outer tube 6 to feed in, and the inner tube drive motor 9 drives the high-pressure flexible hydraulic hose 10 at the tail end of the inner tube 7 according to the preset speed ratio; at the same time, the movable hydraulic internal expansion drive module 3, which is in an expanded state, drives the inner tube 7 to bend synchronously in the bending deformation zone through friction, eliminating interlayer slippage and completing the bending forming of the current pass.

[0054] S3. Depressurization and displacement of movable hydraulic internal expansion drive module 3: After the current bending is completed, the hydraulic control system controls the hydraulic circuit to depressurize, driving piston 15 to drive tapered mandrel 14 to retract, releasing the radial support force on the dividing collet 13, and restoring the inner tube 7 to a free state; then, the inner tube drive motor 9 drives the depressurized movable hydraulic internal expansion drive module 3 to move axially inside the inner tube 7, transporting it to the starting point of the next bending; after reaching the predetermined position, the hydraulic circuit is repressurized, pushing piston 15 to drive tapered mandrel 14 forward, radially lifting the dividing collet 13 and tightening the inner wall of the inner tube 7, re-establishing the friction transmission connection between the inner and outer tubes.

[0055] S4. Next Forming Cycle and Unloading: After the movable hydraulic internal expansion drive module 3 reaches the new position, it is repressurized and expanded, and the friction transmission interface is re-established. The CNC system calls the bending process parameters for the next cycle and repeats the collaborative bending process of step S2. This cycle continues until all bending cycles of the pipe are completed. After all bending processes are completed, the front clamping mechanism 1 is released, and the inner tube drive motor 9 drives the depressurized movable hydraulic internal expansion drive module 3 to be completely extracted, removing the formed complex spatial double-layer tube.

[0056] The present invention will be further described in detail below through specific embodiments: Example 1: This embodiment provides a method for continuous multi-bend forming of complex spatial double-layer tubes based on forming fixtures. The following describes the operation steps using the three-bend forming of a double-layer tube as an example: S1. Billet clamping and internal expansion pre-setting: The double-layer billet is placed outside the segmented collet 13 of the movable hydraulic internal expansion drive module 3. The front end of the billet is fed into the front clamping mechanism 1, and the front clamping mechanism 1 is activated so that its left clamping block 18 and right clamping block 19 clamp the end of the outer tube 6, while ensuring that the left clamping block 18 and right clamping block 19 do not contact the inner tube 7. Subsequently, the tail end of the billet is connected to the clamping assemblies of the outer tube drive motor 8 and the inner tube drive motor 9, respectively. At this time, the hydraulic control system controls the hydraulic circuit to inject high-pressure medium into the hydraulic cylinder cavity 16 through the oil circuit 21 into the high-pressure flexible hydraulic hose 10, pushing the piston 15 to drive the conical mandrel 14 to move, lifting the segmented collet 13 and supporting the inner wall of the inner tube 7, so that the movable hydraulic internal expansion drive module 3 and the inner tube 7 form a rigid friction connection. The movable hydraulic internal expansion drive module 3 is located at the starting point of the first bend.

[0057] S2. First Pass of Coordinated Bending: The CNC system controls the spindle rotation of the pipe bending machine according to the preset first bending trajectory. During this process, the outer tube drive motor 8 drives the outer tube 6 at a predetermined speed, while the inner tube drive motor 9 drives the high-pressure flexible hydraulic hose 10 at an independent, matched speed based on the difference in elongation between the inner and outer tubes 6. Simultaneously, the movable hydraulic internal expansion drive module 3, in a taut state, uses the friction between the segmented collet 13 and the inner wall of the inner tube 7 to force the inner tube 7 to bend and deform synchronously with the outer tube 6. The front clamping mechanism 1 keeps the outer tube 6 fixed, ensuring accurate bending point positioning.

[0058] S3. Depressurization and Displacement of the Movable Hydraulic Internal Expansion Drive Module 3: After the first bending pass is completed, the hydraulic control system depressurizes the hydraulic circuit, pushing the piston 15 to retract the conical mandrel 14, releasing the radial support force on the dividing collet 13, and restoring the inner tube 7 to a free state. Subsequently, the inner tube drive motor 9 drives the depressurized movable hydraulic internal expansion drive module 3 to move axially inside the inner tube 7, transporting it to the starting point of the second bending pass.

[0059] S4. Second-pass coordinated bending: After the movable hydraulic internal expansion drive module 3 reaches the second-pass bending starting point, the hydraulic control system re-injects high-pressure medium into the high-pressure flexible hydraulic hose 10, pushing the piston 15 to drive the conical mandrel 14 to lift the dividing collet 13 and tighten the inner wall of the inner tube 7, re-establishing the friction transmission connection between the inner and outer tubes. The CNC numerical control system controls the spindle rotation of the pipe bending machine according to the preset second-pass bending trajectory, repeating the coordinated bending process of step S2.

[0060] S5. Third-stage Cooperative Bending and Final Unloading: After the second bending is completed, the depressurization and relocation operation of the movable hydraulic internal expansion drive module 3 in step S3 is repeated to transport the movable hydraulic internal expansion drive module 3 to the starting point of the third bending. Subsequently, the cooperative bending process in step S4 is repeated to complete the third bending. After all bending processes are completed, the front clamping mechanism 1 is released, and the inner tube drive motor 9 drives the depressurized movable hydraulic internal expansion drive module 3 to be completely extracted, removing the formed complex spatial double-layer tube.

[0061] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A tooling for integral bending and forming of a complex spatial double-layer tube, characterized in that, It includes a front clamping mechanism (1), a movable hydraulic internal expansion drive module (3), a rear dual-motor independent drive module (4) and a control unit. The front clamping mechanism (1), the movable hydraulic internal expansion drive module (3) and the rear dual-motor independent drive module (4) are all connected to the control unit. The front clamping mechanism (1) clamps one end of the outer wall of the outer tube (6). The movable hydraulic internal expansion drive module (3) is set in the inner cavity of the inner tube (7). The movable hydraulic internal expansion drive module (3) includes a high-pressure flexible hydraulic hose (10) and a hydraulic cylinder cavity (16). The high-pressure flexible hydraulic hose (10) is connected to the hydraulic cylinder cavity (16) through the oil circuit (21). A piston (15) is set in the hydraulic cylinder cavity (16). A tapered mandrel (14) is connected to the piston (15). A split collet (13) is installed on the tapered mandrel (14). The rear dual-motor independent drive module (4) includes an outer tube drive motor (8) and an inner tube drive motor (9). The outer tube drive motor (8) is connected to the outer tube (6), and the inner tube drive motor (9) is connected to the high-pressure flexible hydraulic hose (10).

2. The complex spatial double-layer tube integral bending forming tooling according to claim 1, characterized in that, A front-end clamping mechanism (1) is provided with a front-end outer tube special support mechanism (2) on one side, which supports the outer wall of the outer tube (6).

3. The complex spatial double-layer tube integral bending forming tooling according to claim 1, characterized in that, The other end of the outer tube (6) is provided with a rear support mechanism (5), which contains two independent support units that support the outer walls of the outer tube (6) and the inner tube (7) respectively.

4. The complex spatial double-layer tube integral bending forming tooling according to claim 1, characterized in that, The front clamping mechanism (1) includes a clamping sleeve (11), a drive disk (12) and a jaw body (20). The jaw body (20) is a two-lobed split jaw (17). The clamping sleeve (11) is arranged around the outside of the jaw body (20). The split jaw (17) is connected to one end of the drive disk (12).

5. The complex spatial double-layer tube integral bending forming tooling according to claim 4, characterized in that, The split chuck (17) includes a left chuck (18) and a right chuck (19), the inner arc surfaces of which match the outer diameter of the outer tube (6).

6. The complex spatial double-layer tube integral bending forming tooling according to claim 1, characterized in that, Both the outer tube drive motor (8) and the inner tube drive motor (9) are servo motors. The output end of the outer tube drive motor (8) is connected to the outer tube (6) through a transmission mechanism, and the output end of the inner tube drive motor (9) is connected to the high-pressure flexible hydraulic hose (10) through a transmission mechanism.

7. The complex spatial double-layer tube integral bending forming tooling according to claim 1, characterized in that, The control unit includes a control unit and a CNC numerical control system. The hydraulic control system is connected to the other end of the drive disc (12) and the high-pressure flexible hydraulic hose (10). The CNC numerical control system is independently connected to the outer tube drive motor (8) and the inner tube drive motor (9).

8. The complex spatial double-layer tube integral bending forming tooling according to claim 1, characterized in that, The movable hydraulic internal expansion drive module (3) is axially arranged in the inner cavity of the inner tube (7), and the high-pressure flexible hydraulic hose (10) is a multi-layer steel wire braided telescopic structure.

9. A method for integral bending and forming of a complex spatial double-layer tube using the tooling described in any one of claims 1 to 8, characterized in that, include: The double-layer tube blank is placed outside the movable hydraulic internal expansion drive module (3), and the front end of the double-layer tube blank is sent into the front clamping mechanism (1). The front clamping mechanism (1) only holds the end of the outer tube (6) and keeps the end of the inner tube (7) in a non-contact state. The control unit injects high-pressure medium into the hydraulic cylinder cavity (16) of the movable hydraulic internal expansion drive module (3) inside the inner tube (7) through the oil circuit (21), pushing the piston (15) to drive the conical spindle (14) to move, lifting the dividing collet (13) and tightening the inner wall of the inner tube (7), thereby establishing a transmission interface with friction between the inner tube (7) and the movable hydraulic internal expansion drive module (3); The control unit controls the rotation of the main shaft of the pipe bending machine according to the trajectory parameters of the current bending pass. The outer tube drive motor (8) drives the outer tube (6) to be fed in, and the inner tube drive motor (9) drives the high-pressure flexible hydraulic hose (10) according to the preset speed ratio. The movable hydraulic internal expansion drive module (3) in the expansion state drives the inner tube (7) to bend synchronously in the bending deformation zone through friction, eliminating interlayer slippage and completing the bending and forming of the current pass. After the current bending is completed, the control unit controls the hydraulic circuit to depressurize, drives the piston (15) to drive the conical mandrel (14) to retract, releases the radial support force on the dividing collet (13), and restores the inner tube (7) to a free state; the inner tube drive motor (9) drives the depressurized movable hydraulic internal expansion drive module (3) to move axially inside the inner tube (7) and transport it to the starting point of the next bending. After reaching the predetermined position, the hydraulic circuit is repressurized, pushing the piston (15) to drive the conical mandrel (14) forward, which radially lifts the dividing collet (13) and tightens the inner wall of the inner tube (7), re-establishing the friction transmission connection between the inner and outer tubes, and re-establishing the friction transmission interface. The control unit calls the bending process parameters for the next pass, repeats the coordinated bending process, and cycles in this way until all bending passes of the double-layer tube blank are completed. After all bending processes are completed, the front clamping mechanism (1) is released, and the inner tube drive motor (9) drives the depressurized movable hydraulic internal expansion drive module (3) to be completely extracted, and the formed complex space double-layer tube is taken out.

10. The method for integral bending and forming of complex spatial double-layer tubes according to claim 9, characterized in that, The CNC numerical control system in the control unit preloads the spatial bending trajectory algorithm, calculates the difference in plastic elongation between the outer tube (6) and the inner tube (7) in real time according to different bending angles and bending radii, and issues different motion commands to the outer tube drive motor (8) and the inner tube drive motor (9) respectively, actively compensates for the difference in elongation, and suppresses interlayer slippage and misalignment between the inner and outer tubes during bending.

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