Small bending radius pipe bending device and its usage method

Abstract

This invention provides a small-bending-radius pipe bending device and its usage method, comprising: an upper support plate, a push rod, a hydraulic pressure boosting pipe, a guide sleeve, a bending die, a sealing joint, a sealing ring, rubber balls, a pressure sensor, a hydraulic push cylinder, a movable ball joint, and a hydraulic pressure booster. The method includes the following steps: first, the straight pipe to be processed is installed inside the bending die and fitted against the guide sleeve; several rubber balls are filled into the inner cavity of the straight pipe; the gaps in the inner cavity of the straight pipe are filled using the hydraulic pressure booster; a press is started to apply downward pressure to the push rod; the filling pressure is set to provide pressure support inside the pipe, and as the push rod moves downward, the pipe begins to bend and form; after completing a 90° bend, the filling pressure is gradually increased for pressure shaping. This invention increases the internal support pressure of the pipe by using rubber balls and hydraulic filling of the gaps; and increases the length of the straight section while achieving uniform force distribution during the bending process by employing differential friction.

Description

Technical Field

[0001] This invention relates to the field of aerospace technology, specifically to a small-bending-radius tube bending device and its usage method. Background Technology

[0002] The layout space for pipelines in spacecraft, especially launch vehicles, is becoming increasingly compact, leaving less and less room for choice in layout options. For pipeline system design, a smaller relative bending radius R / D (R is the bending radius of the bend, D is the outer diameter of the bend) (R / D≤1.5) for pipe bends and a longer straight section effectively reduces the number of welds and is therefore more valuable. This is especially true in the design of pressurization and delivery system pipelines, where thin-walled conduits with small bending radii are widely used to save space and reduce welds. Using thin-walled (t<1.5mm) conduits with small bending radii can significantly save space and reduce the weight of the pipeline system. This advantage is particularly important for launch vehicle pipeline systems, especially as the proportion of extremely small bending radius bends (R / D≈1) is increasing year by year, leading to increasing manufacturing difficulties for such products in actual production. Currently, the production of these conduits uses a process of half-pipe welding + straight pipe butt welding, a process heavily reliant on manual operation. The large number of structurally complex conduits rely solely on manual repair, welding, and assembly. This type of operation results in low manufacturing efficiency, low product quality stability, long processing cycles (more than 15 hours), and high processing costs, which affect the progress of aerospace product development and production.

[0003] Research indicates that small-bending-radius pipes can currently be processed using a push-bending process. This process is simple and convenient, and it is particularly effective in preventing thinning on the outer side of the pipe during bending, achieving a bending radius of less than 1D. However, increasing the straight segment length is the biggest challenge in the push-bending process. Generally, the straight segment length L is within 1D; further increases in length can easily lead to outer thinning and cracking, inner wrinkling, and cross-sectional distortion defects.

[0004] The invention patent (publication number CN114346026A) invented a push-bending device. This method uses the friction generated by the contact between the tube blank and the bending die wheel to reduce the thickening and wrinkling defects on the inner side of the bent part of the tube. However, it cannot solve the thinning and tearing defects on the outer side, and the quality of the finished product is not high enough.

[0005] The invention patent (publication number CN110814121B) discloses a method for bending a small diameter pipe with a small bending radius and a small diameter pipe. The method is mainly for bending a small diameter pipe using a low melting point metal as a filling medium. During the bending process, a partition layer needs to be set to isolate the low melting point metal from the pipe blank. The metal also needs to be heated and separated afterward. However, the filling effect is not flexible enough.

[0006] The invention patent (publication number CN100384558C) invented a thin-walled tube variable curvature push-bending process and mold. The method uses a hydraulic press as the loading method. There is no filling medium inside the tube during the push-bending process, which is not suitable for tubes with high precision requirements.

[0007] The invention patent (publication number CN109158458B) discloses a method for hydraulically bending pipes using a composite filling medium. This method uses a composite approach of filling the inside of the pipe with polyurethane rings and liquid action, and then uses a pressure bending process for forming. However, the polyurethane ring filling is prone to creating local suspended areas, which is not suitable for pipes with small bending radii.

[0008] Therefore, there is a need to provide a small bending radius tube bending device and its usage method, which can reduce circumferential and longitudinal welds through integral forming, and effectively improve product accuracy and reliability. Summary of the Invention

[0009] To address the shortcomings of existing technologies, the purpose of this invention is to provide a small-bending-radius pipe bending device and its usage method.

[0010] According to the present invention, a small bending radius tube bending device includes: a push rod, a bending die, rubber balls, a hydraulic push cylinder, a movable ball joint, and a hydraulic booster. The bending die is installed on the lower table of a hydraulic press. A guide sleeve is installed inside the bending die. The guide sleeve includes a vertical section and a bending section. The straight tube to be processed is installed in the vertical section of the guide sleeve and the two are fitted together. The straight tube is filled with a plurality of rubber balls.

[0011] The upper end of the push rod is fastened to the lower side of the upper table of the hydraulic press, and the lower end of the push rod extends into the guide sleeve and abuts against the upper end of the straight pipe through the upper seal.

[0012] The output end of the hydraulic booster is connected to a hydraulic booster pipe, which extends through the upper seal into a straight pipe.

[0013] The spherical end of the movable ball joint is pressed against the lower end of the straight pipe through the lower seal, and the other end of the movable ball joint is connected to the hydraulic jacking cylinder.

[0014] Preferably, the inner cavity profile of the curved section of the guide sleeve includes only the outer curved profile, and the outer friction coefficient of the inner cavity profile of the guide sleeve is 0.8, and the inner friction coefficient is 1.6.

[0015] Preferably, the guide sleeve is fitted to the bending die, and the inner cavity of the bending die includes a vertical section, a curved section and a horizontal section, with the curved section of the guide sleeve smoothly connected to the horizontal section of the bending die.

[0016] Preferably, the movable ball joint extends inward from the horizontal section opening of the bending die to connect with the straight pipe, and the diameter of the spherical end of the movable ball joint matches the inner diameter of the guide sleeve.

[0017] Preferably, the upper sealing element includes a sealing joint and a sealing ring. The sealing joint is disposed inside the upper end of the straight pipe, and one or more sealing rings are disposed on the periphery of the sealing joint. The sealing joint is sealed to the straight pipe through the sealing rings.

[0018] Preferably, the sealing joint has a through hole at its center, and the hydraulic booster pipe extends through the through hole into the straight pipe, with the hydraulic booster pipe and the through hole being interference fit.

[0019] Preferably, the lower seal includes a rubber block, which is installed inside the lower end of the straight pipe and is sealed to the straight pipe.

[0020] Preferably, the push rod is fastened to the underside of the upper table of the hydraulic press via an upper support plate.

[0021] Preferably, a pressure sensor is installed inside the movable ball joint.

[0022] A method of using a small bending radius pipe bending device according to the present invention, applied to the aforementioned small bending radius pipe bending device, includes the following steps:

[0023] Step S1: Install the straight pipe to be processed into the bending die and fit it with the guide sleeve; install the movable ball joint at the lower opening of the bending die.

[0024] Step S2: Fill the inner cavity of the straight tube to be processed with multiple rubber balls and compact them, and install the lower end of the push rod on the upper end of the straight tube to be processed.

[0025] Step S3: The hydraulic booster injects water into the straight pipe to be processed through the hydraulic booster pipe to fill the gaps in the inner cavity of the straight pipe. The press is started to apply a preset downward pressure F to the push rod and presses it down at a constant preset speed. The filling pressure P is set. 初始 Apply pressure support to the inside of the straight pipe;

[0026] Step S4, in hydraulic P 初始 With the support of the push rod, the straight tube begins to bend and take shape as it moves downward. The movable ball joint applies an outward force to support the rubber ball and liquid inside the straight tube and moves backward. After completing the 90° bend, the filling pressure is gradually increased to pressurize and shape the inside of the straight tube. After the shaping is completed, the pressure is unloaded, and the rubber ball and the formed bent tube parts are taken out to complete the processing procedure.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. This invention increases the internal support pressure of the pipe by using rubber balls and hydraulic filling of the gaps, thereby improving the rigidity of the straight section of the pipe and effectively preventing instability and wrinkling during bending. By using differential friction, the friction coefficient of the straight section of the pipe is reduced, and the friction coefficients of the inner and outer sides of the bend are adjusted differently, increasing the length of the straight section while achieving uniform stress during bending. The integral forming reduces circumferential and longitudinal welds, improves product precision and reliability, and greatly simplifies the production process.

[0029] 2. This invention uses liquid filling to form a tube that has been bent and formed by filling it with liquid to achieve pressure expansion. The structure of the rubber ball provides better filling effect and reduces the likelihood of suspended areas. The surface of the bent tube is then molded to improve the molding accuracy of the formed parts, reduce springback, and achieve high-precision processing. Attached Figure Description

[0030] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0031] Figure 1 This is a cross-sectional view of the small bending radius tube bending device in Embodiment 1, which is the main embodiment of the present invention.

[0032] Figure 2 This invention is mainly embodied in Figure 1 A magnified view of part A in the middle;

[0033] Figure 3 This is a schematic diagram illustrating the formed bent pipe, which is the main feature of this invention.

[0034] Figure 4 This is a schematic diagram illustrating step S1 in embodiment 2 of the present invention;

[0035] Figure 5 This is a schematic diagram illustrating step S2 in embodiment 2 of the present invention;

[0036] Figure 6 This is a schematic diagram illustrating step S3 in embodiment 2 of the present invention;

[0037] Figure 7 This is a schematic diagram illustrating step S4 in embodiment 2 of the present invention.

[0038] As shown in the figure:

[0039] Upper support plate 1, push rod 2, hydraulic booster pipe 3

[0040] 4. Guide sleeve; 5. Bending die; 6. Sealing joint

[0041] 7. Sealing ring; 8. Rubber ball; 9. Pressure sensor

[0042] Hydraulic jacking cylinder 10, movable ball joint 11, hydraulic booster 12 Detailed Implementation

[0043] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0044] Example 1

[0045] like Figure 1-3 As shown, a small bending radius pipe bending device according to the present invention includes: a push rod 2, a bending die 5, rubber balls 8, a hydraulic jacking cylinder 10, a movable ball joint 11, and a hydraulic booster 12. The bending die 5 is installed on the lower table of the hydraulic press. A guide sleeve 4 is installed inside the bending die 5. The guide sleeve 4 includes a vertical section and a bending section. The straight pipe to be processed is installed in the vertical section of the guide sleeve 4 and the two are fitted together. The straight pipe is filled with a plurality of rubber balls 8. The upper end of the push rod 2 is fastened to the lower side of the upper table of the hydraulic press. The lower end of the push rod 2 extends into the guide sleeve 4 and is pressed against the upper end of the straight pipe through an upper seal. The output end of the hydraulic booster 12 is connected to a hydraulic booster pipe 3, which extends into the straight pipe through the upper seal. The spherical end of the movable ball joint 11 is pressed against the lower end of the straight pipe through a lower seal. The other end of the movable ball joint 11 is connected to the hydraulic jacking cylinder 10.

[0046] This application applies to the processing of thin-walled stainless steel bent pipes for launch vehicle pressurization and delivery systems. It primarily addresses the problem of limited straight section length and the resulting wrinkling and distortion defects in existing small-bending-radius pipe processing. Under existing process constraints, this application combines push-bending forming with liquid-filling forming technology. First, rubber balls 8 are used to fill and compact the inside of the pipe, ensuring uniform stress during push-bending. Then, liquid is injected to achieve pressurized expansion, and the surface of the bent pipe is shaped using a mold.

[0047] R is the bending radius of the bend, D is the outer diameter of the bend, and L is the length of the straight segment.

[0048] Rubber balls 8 are filled inside the pipe, and liquid is used to fill the gaps in the rubber balls 8, which increases the overall support area inside the pipe, improves the rigidity of the straight section of the pipe, and effectively prevents instability and wrinkling during bending. The length L of the straight section is increased from 1D to 2-3D.

[0049] The inner cavity profile of the curved section of guide sleeve 4 only includes the outer curved profile. The friction coefficient of the outer side of the inner cavity profile of guide sleeve 4 is 0.8, and the friction coefficient of the inner side is 1.6, resulting in differential lubrication. The inner cavity profile of guide sleeve 4 is designed and arranged in the straight section and on the outer side of the curve, with a roughness of 0.8, which effectively reduces the friction coefficient of the straight section and the outer side of the pipe during the bending process, achieves differential friction, and increases the effective length of the straight section.

[0050] The guide sleeve 4 is fitted to the bending die 5. The inner cavity of the bending die 5 includes a vertical section, a curved section and a horizontal section. The curved section of the guide sleeve 4 is smoothly connected to the horizontal section of the bending die 5.

[0051] The movable ball joint 11 extends inward from the horizontal section opening of the bending die 5 to connect with the straight pipe, and the diameter of the spherical end of the movable ball joint 11 matches the inner diameter of the guide sleeve 4.

[0052] The upper sealing element includes a sealing joint 6 and a sealing ring 7. The sealing joint 6 is located inside the upper end of the straight pipe, and one or more sealing rings 7 are provided on the periphery of the sealing joint 6. The sealing joint 6 is sealed to the straight pipe through the sealing rings 7.

[0053] The sealing joint 6 has a through hole at its center, through which the hydraulic booster pipe 3 extends into the straight pipe. The hydraulic booster pipe 3 is interference-fitted with the through hole. The hydraulic booster 12 can linearly adjust the internal pressure P of the pipe to control the internal support force of the pipe during the bending process.

[0054] The lower seal includes a rubber block, which is installed inside the lower end of the straight pipe and is sealed to the straight pipe.

[0055] The push rod 2 is fastened to the lower side of the upper table of the hydraulic press via the upper support plate 1.

[0056] The movable ball joint 11 is equipped with a pressure sensor 9, which can monitor and adjust the jacking force in real time during the bending process to control the bending deformation of the pipe during the bending process.

[0057] This application improves the internal support pressure of the pipe by using "rubber ball 8 + hydraulic filling gap", thereby increasing the rigidity of the straight section of the pipe and effectively preventing instability and wrinkling during bending. The length L of the straight section is increased from 1D to 2-3D.

[0058] This application reduces the friction coefficient of the straight section of the pipe by using differential friction, and adjusts the friction coefficients of the inner and outer sides of the bend differently, thereby increasing the length of the straight section and achieving uniform force distribution during the bending process.

[0059] This application utilizes liquid filling forming to achieve pressure expansion of the tube after push bending by filling it with liquid. The structure of the rubber ball 8 provides better filling effect and reduces the likelihood of suspended areas. The surface of the bent tube is then molded and shaped, improving the molding accuracy of the formed parts, reducing springback, and achieving high-precision processing.

[0060] Example 2

[0061] Based on Example 1, such as Figure 4-7 As shown, the method of using a small bending radius pipe bending device according to the present invention includes the following steps:

[0062] Step S1: Securely install the bending die 5 on the upper side of the lower table of the hydraulic press and fix it with a pressure plate; install the straight pipe to be processed inside the bending die 5 and fit it against the guide sleeve 4; install one end of the movable ball joint 11 at the lower opening of the bending die 5 and fit it against the lower end of the straight pipe to be processed through a rubber block, and install the other end on the hydraulic push cylinder 10; install the pressure sensor 9 in the movable ball joint 11.

[0063] Step S2: Fill the inner cavity of the straight tube to be processed with multiple rubber balls 8 and compact them; fasten the upper support plate 1 to the lower side of the upper table of the hydraulic press and fix it with a pressure plate; fasten the upper end of the push rod 2 to the upper support plate 1, install the sealing joint 6 at the lower end of the push rod 2, install the sealing joint 6 at the upper end of the straight tube to be processed, and fit it tightly with the inner wall of the straight tube through the sealing ring 7;

[0064] Step S3: Water is injected into the hydraulic booster pipe 3 through the hydraulic booster 12 to fill the gaps in the inner cavity of the straight pipe to be processed. The press is started to apply a preset downward pressure F to the push rod 2 and presses it down at a constant preset speed. The filling pressure P is set. 初始 Apply pressure support to the inside of the straight pipe;

[0065] Step S4, in hydraulic P 初始 With the support of the push rod 2, the straight tube begins to bend and form as it moves downward; the movable ball joint 11 applies an outward force to support the rubber ball 8 and the liquid inside the straight tube, and moves backward accordingly; after completing the 90° bending and forming, the filling pressure P is gradually increased to pressurize and shape the inside of the straight tube; after the shaping is completed, the pressure P is unloaded, the rubber ball 8 and the formed bent tube parts are taken out, and the processing procedure is completed.

[0066] This application, through integral forming, reduces circumferential and longitudinal welds, which can effectively improve product precision and reliability.

[0067] This application breaks through the manufacturing bottleneck of traditional processes constrained by "thin walls, small bending radius, and high dimensional accuracy", realizes the overall flexible processing of the conduit, eliminates 3 welds, and improves the dimensional accuracy from 2mm to 0.5mm, greatly improving product reliability.

[0068] This application improves processing efficiency by over 40%, which can shorten the supply chain and development cycle. Based on the overall small bending radius bend structure of this application, the traditional model of aerospace product structural design and manufacturing has been changed, and the production process has been greatly simplified. The traditional conduit development and production process has been reduced from 14 steps to 7 steps, shortening the supply chain and development cycle, accelerating the speed of component production and system integration, and improving processing efficiency by over 40%, thus providing technical support for promoting the efficient development of aerospace models.

[0069] This application integrates and applies a variety of advanced technologies, and solves the product structure design constrained by traditional manufacturing processes through a flexible approach. It liberates design thinking and concepts, breaks the high dependence on existing process levels, and is a powerful measure to achieve overall high-reliability manufacturing.

[0070] This application presents a small bending radius tube integral forming device and its application method based on push-bending-hydraulic composite forming. Through integrated innovation of configuration design and manufacturing process, it breaks through the integral forming of long straight sections of power ducts with 1D bending radius. It effectively reduces welds, improves product dimensional accuracy and efficiency, and achieves the development goals of lightweight and high performance. It breaks through the limitations of traditional manual operation and other single manufacturing technologies. By using composite forming technology that combines push-bending manufacturing technology and liquid filling forming technology, it achieves a breakthrough in thin-walled tube bending technology for aircraft and has important application prospects in future aircraft structural design and manufacturing.

[0071] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application 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. Therefore, they should not be construed as limitations on this application.

[0072] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A small bending radius pipe bending device, characterized in that, include: Push rod (2), bending die (5), rubber ball (8), hydraulic push cylinder (10), movable ball joint (11) and hydraulic booster (12). The bending die (5) is installed on the lower table of the hydraulic press. A guide sleeve (4) is installed inside the bending die (5). The guide sleeve (4) includes a vertical section and a bending section. The straight pipe to be processed is installed in the vertical section of the guide sleeve (4) and the two are fitted together. The straight pipe is filled with multiple rubber balls (8). The upper end of the push rod (2) is fastened to the lower side of the upper table of the hydraulic press, and the lower end of the push rod (2) extends into the guide sleeve (4) and abuts against the upper end of the straight pipe through the upper seal; The output end of the hydraulic booster (12) is connected to a hydraulic booster pipe (3), which extends through the upper seal into the straight pipe. The spherical end of the movable ball joint (11) is pressed against the lower end of the straight pipe through the lower seal, and the other end of the movable ball joint (11) is connected to the hydraulic push cylinder (10); The inner cavity profile of the curved section of the guide sleeve (4) includes only the outer curved profile. The outer friction coefficient of the inner cavity profile of the guide sleeve (4) is 0.8, and the inner friction coefficient is 1.

6.

2. The small bending radius pipe bending device as described in claim 1, characterized in that, The guide sleeve (4) is fitted to the bending mold (5). The inner cavity of the bending mold (5) includes a vertical section, a curved section and a horizontal section. The curved section of the guide sleeve (4) is smoothly connected to the horizontal section of the bending mold (5).

3. The small bending radius pipe bending device as described in claim 2, characterized in that, The movable ball joint (11) extends inward from the horizontal section opening of the bending die (5) to connect with the straight pipe, and the diameter of the spherical end of the movable ball joint (11) matches the inner diameter of the guide sleeve (4).

4. The small bending radius pipe bending device as described in claim 1, characterized in that, The upper sealing element includes a sealing joint (6) and a sealing ring (7). The sealing joint (6) is disposed inside the upper end of the straight pipe, and one or more sealing rings (7) are disposed on the periphery of the sealing joint (6). The sealing joint (6) is sealed to the straight pipe through the sealing rings (7).

5. The small bending radius pipe bending device as described in claim 4, characterized in that, The sealing joint (6) has a through hole in the center, and the hydraulic booster pipe (3) extends through the through hole into the straight pipe. The hydraulic booster pipe (3) is interference-fitted with the through hole.

6. The small bending radius pipe bending device as described in claim 1, characterized in that, The lower seal includes a rubber block, which is installed inside the lower end of the straight pipe and is sealed to the straight pipe.

7. The small bending radius pipe bending device as described in claim 1, characterized in that, The push rod (2) is fastened to the lower side of the upper table of the hydraulic press by the upper support plate (1).

8. The small bending radius pipe bending device as described in claim 1, characterized in that, A pressure sensor (9) is installed inside the movable ball section (11).

9. A method of using a small bending radius pipe bending device, characterized in that, The small bending radius tube bending device according to any one of claims 1-8 includes the following steps: Step S1: Install the straight pipe to be processed into the bending die (5) and fit it with the guide sleeve (4); install the movable ball joint (11) at the lower opening of the bending die (5); Step S2: Fill the inner cavity of the straight tube to be processed with multiple rubber balls (8) and compact them, and install the lower end of the push rod (2) on the upper end of the straight tube to be processed; Step S3: The hydraulic booster (12) injects water into the straight pipe to be processed through the hydraulic booster pipe (3) to fill the gaps in the inner cavity of the straight pipe to be processed. The press is started to apply a preset downward pressure F to the push rod (2) and presses it down at a constant preset speed. The filling pressure P is set. 初始 Apply pressure support to the inside of the straight pipe; Step S4, in hydraulic P 初始 With the support of the push rod (2), the straight tube begins to bend and form as it moves down. The movable ball joint (11) applies an outward force to support the rubber ball (8) and liquid inside the straight tube, and moves back to complete the bending 90° forming. Then, the filling pressure is gradually increased to pressurize and shape the inside of the straight tube. After the shaping is completed, the pressure is unloaded, and the rubber ball (8) and the formed bent tube parts are taken out to complete the processing procedure.

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