An internally expanding thin walled pipe fitting mandrel device

Abstract

This invention discloses an internally expanding thin-walled tube mandrel device, comprising: a core cable assembly, a core ball assembly, and an adjusting assembly. The core ball includes an elastic outer shell and several particles filled within the elastic shell. When the adjusting assembly is adjusted, the core ball, which is inserted through a soft core cable, is simultaneously squeezed, causing the core balls to deform radially along each other, so that the outer wall of the core ball abuts against or moves away from the inner wall of the thin-walled tube to be bent. The core ball utilizes a combination structure of an elastic outer shell filled with particles, combined with the adjusting assembly. During entry and exit from the tube cavity, the diameter of the core ball is reduced to prevent scratching the tube wall. During bending, the core ball is locked, increasing its diameter to fully conform to the tube wall and achieve full support, thereby improving the bending quality. Furthermore, annular hemispherical components are added between adjacent core balls to further enable the extrusion force of the adjusting assembly to be rapidly and evenly transmitted between each core ball, thus ensuring that the diameter of each core ball remains consistent even after the diameter increases, further improving the processing quality of the bent tube.

Description

Technical Field

[0001] This invention relates to the field of pipe bending auxiliary device technology, and in particular to an internal expansion type thin-walled pipe mandrel device. Background Technology

[0002] Thin-walled pipe bends, characterized by their hollow cross-section, lightweight design, low energy consumption, and high efficiency, are widely used in aerospace, shipbuilding, automotive, and precision instrument industries. The forming process of complex pipe bends (such as thin-walled, small-diameter, and large-bending-angle bends) often suffers from defects such as wrinkling and cross-sectional flattening distortion. Inserting a mandrel into the pipe blank to be bent can effectively reduce wrinkling and cross-sectional flattening distortion during the bending process. Therefore, studying the structure and performance of mandrels is of great significance for improving the quality and efficiency of pipe bending. Currently, the more mature mandrel devices used in production mainly include rigid mandrels and flexible mandrels. Rigid mandrels have a fixed diameter, while flexible mandrels have a variable diameter.

[0003] In the pipe bending process, it is generally necessary to first send the mandrel device into the cavity of the pipe to be bent. For thin-walled or easily damaged pipes, the rigid mandrel will scratch the inner wall of the cavity during the sending process, resulting in defects on the inner wall of the bent pipe. However, using a flexible mandrel can avoid the defects of the rigid mandrel. For example, Chinese patent (publication number: CN110216178B) discloses a slider-type cross-section fully supported mandrel structure with a ratchet-based reverse-stop rotation diameter change mechanism. It includes a mandrel hinge and a straight shank, connected by a quick-release universal joint. The mandrel hinge's rotating shaft is sequentially equipped with a connecting rod mounting plate, a ratchet, a reverse ratchet, a bearing, and a limiting retaining ring. A pawl mounting bracket is mounted on the outer ring of the bearing. The connecting rod mounting plate and the pawl mounting bracket are hinged to long and short connecting rods, respectively. The long and short connecting rods are hinged to the outer ring slider component. The relative rotation of the pawl mounting bracket and the rotating shaft drives the connecting rod mechanism, which in turn moves the slider component to achieve diameter change. The ratchet device limits the diameter reduction during use. The slider component consists of a Z-shaped structure composed of two layers of arc-shaped blocks; one layer has a slider positioning pin, and the other layer has a slider positioning pin groove. This mandrel's diameter is adjustable to accommodate the processing needs of circular cross-section tubes of different sizes, and the adjustment process is simple and quick, improving efficiency while saving production costs.

[0004] In this design, the mandrel joint can be tightened during the insertion or removal of the mandrel device from the tube cavity, reducing its diameter and preventing scratches on the tube wall. However, when the mandrel joint is opened, gaps exist between adjacent mandrel joints. These gaps can cause localized collapse during the bending process, resulting in substandard quality of the bent tube.

[0005] Based on the above requirements, there is an urgent need to develop a mandrel device that can both change diameter to facilitate the entry and exit of the mandrel into the tube cavity and provide full cross-sectional support for the tube wall during the bending process. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide an internally expanding thin-walled tube mandrel device to solve the technical problem that existing variable-diameter mandrels cannot achieve full support of the tube wall when unfolded.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] An embodiment of the present invention provides an internally expanding thin-walled tube mandrel device, comprising:

[0009] A core cable assembly, the core cable assembly including a flexible core cable and a first threaded rod connected to the rear end of the flexible core cable;

[0010] A core ball assembly, comprising a plurality of core balls arranged linearly in a front-to-back manner, wherein the plurality of core balls are threaded through the flexible core cable; and

[0011] An adjustment assembly includes a limiting block and an adjustment member. The limiting block is connected to the front end of the flexible core cable and abuts against the foremost core ball. The adjustment member is screwed to the first threaded rod and abuts against the foremost core ball.

[0012] The core ball includes an elastic shell and several particles filled in the elastic shell. When the relative position of the adjusting member and the first threaded rod is adjusted, the core ball passing through the soft core cable is squeezed synchronously, causing the core balls to deform radially along the core ball due to mutual compression, so that the outer wall of the core ball abuts against or moves away from the inner wall of the thin-walled tube to be bent.

[0013] The outer wall of the core sphere is a spherical annular wall.

[0014] The hardness of the elastic outer shell is not less than 60 HRC.

[0015] The particles are rubber particles with a Poisson's ratio of not less than 0.475, expanded polytetrafluoroethylene particles, hydroxyapatite calcium microspheres, or metal spheres.

[0016] Among them, an annular hemispherical component is provided between adjacent core balls, and the annular hemispherical component is inserted through the flexible core cable.

[0017] The annular hemispherical component has a spherical surface and a planar portion opposite to the spherical surface. The spherical surface is disposed towards the side closer to the adjusting member, and the planar portion is disposed towards the side farther from the adjusting member.

[0018] The core ball has two oppositely distributed and equally sized front and rear sidewalls, and the outer contour of the planar portion is smaller than the outer contour of the rear sidewall.

[0019] The thickness of the annular hemispherical component is no greater than one-fifth of the distance between the front sidewall and the rear sidewall.

[0020] The first threaded rod is further provided with a locking assembly at its rear end, which is used to lock the core ball assembly at the set position of the thin-walled tube to be bent.

[0021] The locking assembly includes: a connector, a second threaded rod connected to the rear end of the connector, and a locking member screwed to the second threaded rod; the front end of the connector is fixedly connected to the rear end of the first threaded rod, and the tapered sidewall of the locking member is used to clamp the opening of the thin-walled pipe fitting that is to be bent.

[0022] The internal expansion thin-walled tube mandrel device of the present invention employs a combination structure of a mandrel ball with an elastic outer shell and granules inside, combined with an adjustment component. During the insertion and exit of the tube, the diameter of the mandrel ball is reduced to prevent scratching the tube wall. During tube bending, the mandrel ball is locked, increasing its diameter to fully conform to the tube wall and achieve full support, thereby improving the bending quality. Furthermore, annular hemispherical components are added between adjacent mandrel balls to further enable the extrusion pressure of the adjustment component to be rapidly and evenly transmitted between each mandrel ball, thus ensuring that the diameter of each mandrel ball remains consistent even after the diameter increases, further improving the processing quality of the bent tube.

[0023] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention, it can be implemented according to the contents of the specification. In order to make the above and other objects, features and advantages of the present invention more obvious and understandable, preferred embodiments are described in detail below. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the overall structure of the internally expanding thin-walled tube mandrel device according to an embodiment of the present invention;

[0025] Figure 2 This is a cross-sectional view of the internally expanding thin-walled tube mandrel device according to an embodiment of the present invention;

[0026] Figure 3 for Figure 2 A magnified schematic diagram of section A in the middle;

[0027] Figure 4 This is a schematic diagram of the assembly state of the internal expansion thin-walled tube mandrel device and the thin-walled tube to be bent before bending, according to an embodiment of the present invention.

[0028] Explanation of reference numerals in the attached figures:

[0029] Internal expansion thin-walled tube fitting mandrel device 100, core ball 1, limiting block 2, soft core cable 3, first threaded rod 4, adjusting component 5, connecting component 6, second threaded rod 7, locking component 8, annular hemispherical component 9, elastic shell 11, particle 12, end face 81, flat part 91, spherical part 92, spherical annular wall 111, front side wall 112, rear side wall 113, thin-walled tube fitting 200, bent pipe section 201, non-bent pipe section 202, pipe opening 203. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] 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. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," 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 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. Therefore, they should not be construed as limitations on this invention.

[0033] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0034] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral molding; 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; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0035] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0036] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. The illustrative expressions of the above terms in this specification should not be construed as necessarily referring to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0037] Currently, the more mature mandrel devices used in production mainly include rigid mandrels and flexible mandrels. Rigid mandrels have a fixed diameter, while flexible mandrels have a variable diameter. However, in existing solutions, during the mandrel device's insertion or removal from the tube cavity, the mandrel joint can be tightened to reduce its diameter and prevent scratching the tube wall. However, when the mandrel joint is open, gaps exist between adjacent joints. These gaps can cause localized collapse during pipe bending, resulting in substandard quality of the bent pipe fitting. To address these issues, this embodiment discloses an internally expanding thin-walled pipe fitting mandrel device 100.

[0038] Please see Figures 1 to 4 This embodiment provides an internally expanding thin-walled tube mandrel device 100, which is used to provide full support to the inner cavity of the tube wall during the bending process of the thin-walled tube 200, and to prevent defects such as wrinkles or collapse at the bending point.

[0039] The internally expanded thin-walled tube mandrel assembly 100 includes:

[0040] The core cable assembly includes a flexible core cable 3 and a first threaded rod 4 connected to the rear end of the flexible core cable 3.

[0041] The core ball assembly includes a plurality of core balls 1 arranged linearly in front and behind, and the plurality of core balls 1 are threaded through the flexible core cable 3;

[0042] An adjustment assembly, comprising a limiting block 2 and an adjustment member 5, wherein the limiting block 2 is connected to the front end of the flexible core cable 3 and abuts against the foremost core ball 1, and the adjustment member 5 is screwed to the first threaded rod 4 and abuts against the foremost core ball 1;

[0043] The core ball 1 includes an elastic outer shell 11 and a plurality of particles 12 filled in the elastic outer shell 11. When the relative position of the adjusting member 5 and the first threaded rod 4 is adjusted, the core ball 1 passing through the soft core cable 3 is squeezed synchronously, so that the core balls 1 are squeezed against each other and deformed radially along the core ball 1, so that the outer wall 111 of the core ball 1 abuts against or moves away from the inner wall of the thin-walled tube 200 to be bent.

[0044] In this embodiment, the core ball 1 is improved to a slightly deformable core ball structure. Before entering the cavity of the thin-walled tube 200, the internally expanding thin-walled tube core rod device 100 loosens several core balls 1 that are threaded onto the soft core cable 3 by adjusting the component. At this time, under the elastic shell 11 and the particle 12 filling the inside, the core ball 1 enters a state without external pressure, the diameter of the core ball 1 becomes smaller, and a gap is left between it and the inner wall of the cavity of the thin-walled tube 200. In this state, no damage caused by hard contact will occur when entering or exiting the cavity of the thin-walled tube 200. When the internally expanding thin-walled tube core rod device 100 is in the process of bending the thin-walled tube 200, the core balls 1 connected in series are squeezed synchronously by adjusting the distance between the adjusting component 5 and the limiting component 2. The adjacent core balls 1 squeeze each other, so that the elastic shell 11 deforms and extends radially in the core ball, making its diameter larger and fully fitting the cavity of the thin-walled tube 200, providing comprehensive support for the tube wall. Compared with existing mandrel devices, since the outer wall of the elastic outer shell 11 of the core ball 1 expands outward as a whole during the deformation process, the outer wall surface expands synchronously while the diameter increases, and it can still maintain a full and tight fit and support for the tube wall, and there will be no collapse or wrinkling defects of the thin-walled tube 200 caused by local gaps.

[0045] Please refer to it again. Figure 1 and Figure 3 The core ball 1 has a disc-shaped structure. When not subjected to external pressure, the elastic outer shell 11 of the core ball 1 includes a spherical annular wall 111, and a front sidewall 112 and a rear sidewall 113 connected to the spherical annular wall 111. The front sidewall 112 and the rear sidewall 113 are oppositely distributed and of the same size. The spherical annular wall 111, together with the front sidewall 112 and the rear sidewall 113, forms a sealed cavity filled with particles 12, which can move within the sealed cavity. Of course, the core ball 1 also has a perforation along its central axis for threading the flexible core cable 3.

[0046] The soft core cable 3 can be made of steel wire rope, carbon fiber filament, or other high-strength, high-toughness, and bendable cables. During the bending process of the auxiliary thin-walled tube 200, the core ball 1 will be pressed and drive the soft core cable 3 to bend synchronously. This can maintain uniform support for the tube wall during the bending process and also bend along with the tube.

[0047] The adjustment component includes a limiting member 2 and an adjusting member 5, which are located at both ends of the core ball assembly. By adjusting the distance between the adjusting member 5 and the limiting member 2, the core ball 1 can be squeezed or released synchronously, thereby achieving radial expansion and contraction of the core ball 1.

[0048] The limiting member 2 is fixedly connected to the front end of the flexible core cable 3, and the limiting member 2 at least partially abuts against the front side wall of the core ball 1 located at the foremost end. The adjusting member 5 can be a screw-on member such as a nut that is screwed to the first threaded rod 4. When the adjusting member 5 is adjusted to reduce the distance between it and the limiting member 2, the adjusting member 5 is always subjected to the axial reaction force of the core ball 1. This reaction force will keep the adjusting member 5 fixed in its current position relative to the first threaded rod 4 after the external force is released, so that the adjusting member 5 and the first threaded rod 4 can be conveniently locked without other locking mechanisms.

[0049] In this embodiment, the hardness of the elastic outer shell 11 is not less than 60 HRC. HRC represents the hardness value measured using a diamond cone indenter with a 150 kg load and a 120° apex angle, and is applicable to high-hardness materials such as quenched steel and tool steel. A hardness value of not less than 60 HRC falls into the ultra-high hardness range, indicating that the elastic outer shell has extremely strong resistance to plastic deformation. Under the action of this high-hardness elastic outer shell 11, the thin-walled tube 200 can provide sufficient support for the cavity during bending, preventing collapse or wrinkling.

[0050] Of course, it is understood that in other embodiments, depending on the hardness of the thin-walled tube 200 and the required support force for bending, it is sufficient to use an elastic outer shell 11 with a hardness greater than that required for support force, and it is not limited to the hardness value of the material in this embodiment.

[0051] In this embodiment, the particle 12 is a rubber particle, expanded polytetrafluoroethylene particle, hydroxyapatite calcium microsphere, or metal sphere with a Poisson's ratio of not less than 0.475. Poisson's ratio is defined as the absolute value of the ratio of transverse strain to longitudinal strain when a material is under uniaxial tension or compression. The larger the Poisson's ratio, the smaller the deformation of the material itself under stress. In this embodiment, material particles with a Poisson's ratio of not less than 0.475 are used, indicating that the particle 12 is difficult to deform under stress, and can only undergo small displacement of adjacent particles 12, while the particle 12 itself hardly deforms. Therefore, the particle 12 with this Poisson's ratio can not only undergo small displacement synchronously with the radial extension of the elastic shell 11, but also provide stable and high-strength support after deformation.

[0052] Please refer to it again. Figures 1 to 3 An annular hemispherical component 9 is also provided between adjacent core balls 1, and the annular hemispherical component 9 is threaded through the flexible core cable 3. The annular hemispherical component 9 has at least one partial spherical structure, the highest point of which abuts against the adjacent core ball 1, so as to evenly transmit the extrusion pressure of the adjusting component to the adjacent core balls 1, and avoid the core balls 1 at the foremost and rearmost ends having large deformations, while the core balls 1 in the middle have small deformations, resulting in a situation where the overall diameter of the core ball assembly after extrusion is not uniform.

[0053] Through long-term practice, it has been found that when adjusting the distance between the adjusting component 5 and the limiting component 2, the component located at the very front (i.e., Figure 2 The core ball 1 (shown at the far left) and the core ball located at the far end (i.e., the core ball at the far right) Figure 2 The rightmost core ball 1 (shown in the diagram) exhibits a more pronounced radial deformation compared to the other core balls, resulting in an overall waist-shaped outer surface of the core ball assembly. During the bending of the thin-walled tube 200, the central support is weaker, leading to a smaller cross-sectional diameter at the center of the bend compared to other locations. This results in inconsistent inner diameters within the tube after bending. The reason for this is that the core balls 1 at the foremost and rearmost ends experience greater stress during the reduction of the distance between the adjusting component 5 and the limiting component 2. This embodiment addresses this by adding an annular hemispherical component 9 between adjacent core balls 1 to evenly distribute the extrusion pressure towards the center, thereby reducing the smaller radial deformation of the central core ball 1 and ultimately achieving an approximately cylindrical structure with uniform diameter on the outer surface of the entire core ball assembly.

[0054] Specifically, such as Figure 3 As shown, the annular hemispherical component 9 has a spherical portion 92 and a flat portion 91 opposite to the spherical portion 92. The spherical portion 92 is disposed towards the side closer to the adjusting member 5, and the flat portion 91 is disposed towards the side farther from the adjusting member 5. The annular hemispherical component 9 has a through hole in its middle for threading a flexible cable 3. The flat portion 91 of the annular hemispherical component 9 abuts against the core ball 1 located at its front end, and the spherical portion 92 abuts against the core ball 1 located at its rear end. This structural design facilitates the uniform transmission of axial pressure between adjacent core balls 1.

[0055] Furthermore, the core sphere 1 has two oppositely distributed and equally sized front sidewalls 112 and rear sidewalls 113. The outer contour of the planar portion 91 of the annular hemisphere 9 is smaller than the outer contour of the rear sidewall 113 or the front sidewall 112. The front sidewalls 112 and rear sidewalls 113 are equally sized circular planes, and the planar portion 91 of the annular hemisphere 9 is also a circular plane. The annular hemisphere 9 and the core sphere 1 are coaxially inserted into the flexible core cable 3. Therefore, the area of ​​the planar portion 91 is smaller than the area of ​​the front sidewall 112 or the rear sidewall 113.

[0056] The thickness of the annular hemispherical component 9 is no greater than one-fifth of the distance between the front sidewall 112 and the rear sidewall 113. The thickness of the annular hemispherical component 9 refers to its maximum thickness along the length of the flexible core cable 3, and the distance between the front sidewall 112 and the rear sidewall 113 is also the thickness of the core ball 1. Setting the thickness of the annular hemispherical component 9 to within one-fifth of the thickness of the core ball 1 ensures good transmission of compressive force between adjacent core balls 1 without affecting the radial extension of the core ball 1 itself.

[0057] In other embodiments, the aforementioned annular hemispherical component 9 may also be replaced by a double spherical component or a conical component, and the thickness of the double spherical component or the conical component and the thickness of the core ball 1 satisfy the above-mentioned proportional relationship.

[0058] Please refer to it again. Figures 1 to 4 The first threaded rod 4 is further provided with a locking assembly at its rear end. The locking assembly is used to lock the core ball assembly at a set depth position of the thin-walled tube 200 to be bent. That is, after the core ball assembly and the adjusting assembly are inserted into the cavity of the thin-walled tube 200 to a set depth, the locking assembly locks the core ball assembly and the adjusting assembly at the current depth to prevent them from moving and causing the bending position of the thin-walled tube 200 to shift.

[0059] Specifically, the locking assembly includes: a connector 6, a second threaded rod 7 connected to the rear end of the connector 6, and a locking member 8 screwed to the second threaded rod 7; the front end of the connector 6 is fixedly connected to the rear end of the first threaded rod 4, and the end face 81 of the locking member 8 abuts against the pipe opening 203 of the thin-walled pipe fitting 200 to be bent, or the locking member 8 is fixedly connected to a positioning member in the pipe bending equipment.

[0060] One end of the connector 6 is fixedly connected to the first threaded rod 4, and the other end is fixedly connected to the second threaded rod 7. The length of the connector 6 is determined by the distance between the bending position of the thin-walled tube 200 and the rear end of the tube opening 203.

[0061] like Figure 4 As shown, this is a schematic diagram of the assembly state of the internal expansion thin-walled tube mandrel device 100 and the thin-walled tube 200 before bending processing in this embodiment. At this time, the mandrel assembly and the adjustment assembly have been inserted into the tube cavity of the thin-walled tube 200. Rotate the locking member 8 and adjust the relative distance between the locking member 8 and the mandrel assembly until the locking member 8 is positioned at the tube opening 203 at the rear end of the thin-walled tube 200, or the mandrel assembly is locked at a preset depth of the thin-walled tube 200 by connecting the locking assembly with the positioning member of the tube bending equipment.

[0062] The thin-walled tube 200 includes a bent section 201 and a non-bent section 202 at the rear end, with an opening 203 at the end of the non-bent section 202. During the bending process, the core ball assembly is supported on the inner wall of the cavity of the bent section 201.

[0063] Please refer to it again. Figures 1 to 4 The following is a brief description of the auxiliary processing of the internal expansion thin-walled tube mandrel device 100 in the tube bending process of this embodiment:

[0064] First, adjust the distance between the adjusting component 5 and the limiting component 2 to increase the gap between them so that each core ball 1 is in a non-compressed state. At this time, the diameter of the core ball 1 is small. The core ball assembly and the adjusting assembly are transported to the set depth of the thin-walled tube 200. A certain gap is reserved between the outer wall of the core ball 1 and the cavity of the thin-walled tube 200, so that the feeding resistance is small and the cavity wall will not be scratched.

[0065] Then, by inserting a Phillips screwdriver or a small robotic arm into the tube cavity and rotating the adjusting member 5, the distance between the adjusting member 5 and the limiting member 4 is reduced. The adjacent core balls 1 are forced to extend radially due to axial compression until their spherical annular wall 111 fully fits the tube cavity wall. In order to accurately adjust the adjusting member 5 to expand the core balls 1 to the set diameter, a scale line can also be set on the outer wall of the first threaded rod 4. The zero scale line is when the adjacent core balls 1 are in a natural and abutting state. Before the mandrel device is sent into the tube cavity, the adjusting member 5 needs to be adjusted to the zero scale line. The adjustment scale value of the adjusting member 5 is set according to the experimentally measured data for the tube cavities of different thin-walled tubes 200, so as to quickly and conveniently realize the adjustment of the mandrel device.

[0066] Then, adjust the relative position of the locking member 8 and the second threaded rod 7 so that the end face 81 of the locking member 8 is positioned at the pipe opening 203 of the thin-walled pipe 200, and finally fix the core ball assembly at the cavity of the thin-walled pipe 200 at a set depth, or fix the locking member 8 by the positioning part of the pipe bending equipment.

[0067] Finally, control the pipe bending machine to bend the thin-walled pipe 200. After completion, reverse the operation and remove the mandrel device 100 of the internally expanded thin-walled pipe.

[0068] The internal expansion thin-walled tube mandrel device of this embodiment uses a combination structure of elastic shell and granules inside the mandrel ball, combined with an adjustment component. During the insertion and exit of the tube, the diameter of the mandrel ball is reduced to prevent scratching the tube wall. During bending, the mandrel ball is locked, increasing its diameter to fully conform to the tube wall and achieve full support, thereby improving the bending quality. Furthermore, annular hemispherical components are added between adjacent mandrel balls to further ensure that the extrusion pressure from the adjustment component is quickly and evenly transmitted between each mandrel ball, thus maintaining diameter consistency even after the diameter increases, further improving the processing quality of the bent tube.

[0069] The above examples are merely illustrative of the technical content of the present invention to facilitate easier understanding by the reader, but do not imply that the implementation of the present invention is limited to these examples. Any technical extensions or re-creations made based on the present invention are protected by the present invention. The scope of protection of the present invention is defined by the claims.

Claims

1. An inside expanding thin walled pipe fitting mandrel apparatus, characterized by, include: A core cable assembly, the core cable assembly including a flexible core cable and a first threaded rod connected to the rear end of the flexible core cable; A core ball assembly, comprising a plurality of core balls arranged linearly in a front-to-back manner, wherein the plurality of core balls are threaded through the flexible core cable; as well as An adjustment assembly includes a limiting block and an adjustment member. The limiting block is connected to the front end of the flexible core cable and abuts against the foremost core ball. The adjustment member is screwed to the first threaded rod and abuts against the foremost core ball. The core ball comprises an elastic outer shell and several particles filled within the elastic outer shell. When the relative position of the adjusting member and the first threaded rod is adjusted, the core ball passing through the flexible core cable is simultaneously squeezed, causing the core balls to deform radially along each other, so that the outer wall of the core ball abuts against or moves away from the inner wall of the thin-walled tube to be bent. An annular hemispherical member is also provided between adjacent core balls. The annular hemispherical member passes through the flexible core cable and has a spherical part and a planar part opposite to the spherical part. The spherical part is oriented towards the side closer to the adjusting member, and the planar part is oriented away from the adjusting member. The outer wall of the core ball is a spherical annular wall. The core ball has two oppositely distributed and equally sized front and rear side walls. The outer contour of the planar part is smaller than the outer contour of the rear side wall. The thickness of the annular hemispherical member is not greater than one-fifth of the distance between the front and rear side walls.

2. An inside expanding thin walled pipe mandrel apparatus as claimed in claim 1 wherein, The hardness of the elastic outer shell is not less than 60 HRC.

3. The internally expanding thin-walled tube mandrel device according to claim 2, characterized in that, The particles are rubber particles with a Poisson's ratio of not less than 0.475, expanded polytetrafluoroethylene particles, hydroxyapatite calcium microspheres, or metal spheres.

4. The inside expanding thin walled pipe mandrel apparatus of claim 1 wherein, The rear end of the first threaded rod is also provided with a locking component, which is used to lock the core ball assembly at a set depth position of the thin-walled tube to be bent.

5. An inside expanding thin walled pipe mandrel apparatus as claimed in claim 4 wherein, The locking assembly includes: a connector, a second threaded rod connected to the rear end of the connector, and a locking member screwed to the second threaded rod; the front end of the connector is fixedly connected to the rear end of the first threaded rod, and the tapered sidewall of the locking member is used to clamp the opening of the thin-walled pipe fitting that is to be bent.

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