Sealing end joint structure for high-molecular perfluoropolymer pipe connection

Abstract

The invention belongs to the technical field of macromolecule pipe connection, and particularly relates to a sealing end connection structure for macromolecule perfluoropolymer pipe connection, which comprises a metal joint assembly, a perfluoropolymer pipe and a welding part, the metal joint assembly comprises a joint body and a compression nut, the inner wall of the joint body is provided with a positioning cavity along the axial direction, and the positioning cavity is provided with a positioning hole; one end of the connector body is a connector of a metal part to be connected, an internal thread is arranged at the other end of the connector body, an external thread matched with the internal thread is arranged on the inner wall of the pressing nut, one end of the pressing nut extends into the positioning cavity, an arc-shaped pressing face is arranged at the end of the pressing nut, and the perfluoropolymer pipe is inserted into the positioning cavity. An annular sealing groove is formed in the end part of the perfluoropolymer pipe; permanent sealing, high-strength connection, structural strength multiplication and stretching resistance of the perfluoropolymer pipe and the metal part are achieved, meanwhile, the assembly process is simplified, and the perfluoropolymer pipe is suitable for large-scale production.

Description

Technical Field

[0001] This invention belongs to the field of polymer pipe connection technology, specifically referring to a sealed end connection structure for connecting perfluoropolymer pipes. Background Technology

[0002] Polytetrafluoroethylene (PTFE), perfluoroalkoxy resin (PFA), and other high-molecular-weight perfluoropolymer materials are widely used in semiconductor, pharmaceutical, and chemical industries as core pipeline components for transporting corrosive media and high-purity fluids due to their excellent chemical inertness, wide temperature range stability (-200℃ to 260℃), low coefficient of friction, and high purity. In the semiconductor industry, PTFE pipes often need to be connected to metal fittings, valves, reaction vessels, and other metal components to form a complete fluid transport system. The sealing performance, pressure resistance, and structural reliability of these connections directly determine the system's operational safety and fluid purity.

[0003] Existing connection methods between PTFE pipes and metal components mainly include compression fitting, crimping, and adhesive bonding. Compression fitting forms a seal by clamping the PTFE pipe to the outer wall, but it relies on precise assembly torque. Insufficient torque can easily lead to leakage, while excessive torque can damage the inner wall of the PTFE pipe. Furthermore, the "clamp line seal" has extremely low tolerance for surface defects in the pipe, resulting in poor sealing reliability and making it unsuitable for extreme scenarios such as high pressure and vacuum. Crimping uses external pressure to bond the PTFE pipe to the metal joint, but its sealing surface is located on the outside of the joint, making it prone to loosening under pressure impact. It also has limited pressure resistance, and the crimping tools are highly specialized, hindering large-scale assembly. While adhesive bonding can achieve surface sealing, the adhesive can easily contaminate the transported medium, failing to meet the high purity requirements of the semiconductor industry. Additionally, the adhesive layer has poor resistance to high and low temperatures and corrosion, resulting in a short service life. Summary of the Invention

[0004] To address the problems of low sealing reliability, insufficient pressure resistance, difficult assembly, and easy contamination of media in existing connection methods, this invention provides a sealed end structure for connecting perfluoropolymer tubes, achieving permanent sealing and high-strength connection between the perfluoropolymer tube and metal components, doubling the structural strength, significantly increasing tensile strength, simplifying the assembly process, and adapting to large-scale production.

[0005] To achieve the above functions, the technical solution adopted by the present invention is as follows: A sealing end connection structure for a polymer perfluoropolymer tube connection includes a metal connector assembly, a perfluoropolymer tube, and a welding part. The metal connector assembly includes a connector body and a clamping nut. A positioning cavity is formed along the axial direction on the inner wall of the connector body. One end of the connector body is an interface for the metal component to be connected, and the other end is provided with an internal thread. The inner wall of the clamping nut is provided with an external thread adapted to the internal thread. One end of the clamping nut extends into the positioning cavity and has an arc-shaped clamping surface at its end. The perfluoropolymer tube is inserted into the positioning cavity. An annular sealing groove is formed at the end of the perfluoropolymer tube. The annular sealing groove is filled with a perfluoropolyether-based sealant. Through the threaded engagement between the clamping nut and the connector body, the arc-shaped clamping surface applies axial pressure to the annular sealing groove, causing the arc-shaped clamping surface to be press-fitted into the annular sealing groove, forming an initial seal.

[0006] As a preferred embodiment of the present invention, the inner wall of the positioning cavity has multiple sets of annular protrusions arranged axially, and the annular protrusions are interference-fitted with the outer wall of the perfluoropolymer tube.

[0007] As a preferred embodiment of the present invention, the connector body is provided with a tapered guide surface, and the inner wall of the tapered guide surface is connected to the clamping nut.

[0008] As a preferred technical solution of the present invention, the welding part is located at the connection between the joint body and the clamping nut, and the two are fused into an integral structure by laser welding. When the pressure in the pipeline increases, the outer wall of the perfluoropolymer tube adheres to the inner wall of the positioning cavity and the conical guide surface to form a secondary self-tightening seal.

[0009] Compared with the prior art, the present invention achieves the following beneficial effects by adopting the above structure: 1. Through the collaborative design of "initial sealing and secondary self-tightening sealing", a multi-layer sealing system is constructed. In the initial stage, with the help of the threaded engagement between the clamping nut and the connector body, the arc-shaped clamping surface is pressed into the annular sealing groove filled with perfluoropolyether-based sealant. Utilizing the compatibility of the sealant and the tightness of the interference fit, the first sealing barrier is quickly formed, effectively blocking the leakage path of the medium. When the pressure in the pipeline increases, the perfluoropolymer tube undergoes slight deformation under pressure. Its outer wall tightly fits the annular protrusion on the inner wall of the positioning cavity and the conical guide surface of the connector body, automatically enhancing the sealing effect and forming a secondary self-tightening seal. The higher the pressure, the tighter the seal. 2. The multiple sets of annular protrusions axially arrayed on the inner wall of the positioning cavity, which are interference fit with the outer wall of the perfluoropolymer tube, not only enable precise positioning of the tube during the assembly stage and prevent axial displacement of the tube, but also significantly improve the structure's pull-out resistance through the interlocking action of the protrusions with the outer wall of the tube, avoiding loosening of the connection due to media impact, vibration and other factors. At the same time, the connection between the joint body and the clamping nut is laser welded to form an integrated structure, completely eliminating the gap between the two, eliminating the risk of leakage at the connection, further enhancing the rigidity and stability of the overall structure, and extending the service life of the end connection structure. 3. Perfluoropolyether-based sealants have good compatibility with perfluoropolymer tubing materials and will not react chemically. This ensures the durability of the sealing effect and avoids corrosion or aging damage to the tubing caused by the sealant. The tapered guide surface design achieves a smooth connection with the clamping nut, preventing the formation of eddies at the connection point during medium flow and reducing pressure loss. On the other hand, it provides a guide for the deformation of the perfluoropolymer tubing, ensuring that the tubing can fit evenly to form a self-tightening seal when the pressure increases. At the same time, it reduces local stress concentration between the tubing and the joint, protecting the perfluoropolymer tubing from damage due to excessive stress. 4. The structure is simple and the assembly process does not require complicated special equipment. It only requires initial clamping through threaded connection and then fixed by laser welding. The operation process is simple and easy to learn. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the overall structure of a sealed end connection structure for a polymer perfluoropolymer tube connection proposed in this invention. Figure 2 This is a cross-sectional view of a metal connector assembly with a sealed end structure for connecting a perfluoropolymer tube, as proposed in this invention. Figure 3 for Figure 2 Enlarged view of a portion of point A in the middle; Figure 4 This is a schematic diagram of the compression nut of a sealing end connection structure for a polymer perfluoropolymer tube connection proposed in this invention.

[0011] Among them, 1. Metal connector assembly, 101. Connector body, 102. Compression nut, 103. Positioning cavity, 104. Internal thread, 105. External thread, 106. Arc-shaped compression surface, 107. Annular sealing groove, 108. Annular protrusion, 109. Conical guide surface, 2. Perfluoropolymer tube, 3. Welded part. Detailed Implementation

[0012] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0013] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for 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 the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The invention will be further described in detail below with reference to the accompanying drawings.

[0014] like Figures 1-4 As shown, the present invention provides a sealed end connection structure for connecting a perfluoropolymer tube, comprising a metal connector assembly 1, a perfluoropolymer tube 2, and a welding part 3.

[0015] like Figures 1-4 As shown, the metal connector assembly 1 includes a connector body 101 and a clamping nut 102, both of which are made of corrosion-resistant stainless steel. The inner wall of the connector body 101 has a positioning cavity 103 along the axial direction. The inner diameter of the positioning cavity 103 is adapted to the outer diameter of the perfluoropolymer tube 2, and its axial length is 50-80mm to ensure sufficient positioning length after the tube is inserted. One end of the connector body 101 is the interface of the metal component to be connected, which adopts a standardized thread structure to facilitate docking with other metal components in the pipeline system. The inner wall of the other end is machined with an internal thread 104 for mating with the clamping nut 102.

[0016] like Figures 2-4 As shown, the inner wall of the clamping nut 102 is machined with an external thread 105 that matches the internal thread 104 of the connector body 101. One end of the nut extends into the positioning cavity 103, and the end is integrally formed with an arc-shaped clamping surface 106. The arc of the arc-shaped clamping surface 106 is R3-R5mm, which matches the groove shape of the annular sealing groove 107 to ensure that it can fully fit the groove wall during interference compression. The perfluoropolymer tube 2 is made of polytetrafluoroethylene (PTFE) material, and the outer diameter of the tube is 20-30mm. An annular sealing groove 107 is opened circumferentially at its end. The width of the sealing groove is 3-5mm and the depth is 2-4mm. The groove is filled with a perfluoropolyether-based sealant. This sealant has high temperature resistance, chemical corrosion resistance, and excellent compatibility with the perfluoropolymer tube 2 material.

[0017] like Figures 2-4 As shown, there are 6 sets of annular protrusions 108 arranged axially on the inner wall of the positioning cavity 103. The height of each set of annular protrusions 108 is 0.5-1mm and the width is 2-3mm. The distance between two adjacent sets of annular protrusions 108 is 8-12mm. The annular protrusions 108 are interference-fitted with the outer wall of the perfluoropolymer tube 2. The interference is controlled at 0.1-0.2mm, which can achieve tight positioning without damaging the tube due to excessive interference. The end of the connector body 101 near the clamping nut 102 is machined with a tapered flow guide surface 109. Its inner wall is smoothly connected to the end of the clamping nut 102 to avoid throttling or eddies when the medium flows.

[0018] Assembly process: First, the two ends of the perfluoropolymer tube are pretreated by machining an annular sealing groove 107 to ensure that the groove wall is smooth and burr-free. Then, a perfluoropolyether-based sealant is evenly filled into the annular sealing groove 107, with the filling amount slightly higher than the groove opening to avoid insufficient sealant during subsequent pressing.

[0019] Insert the end of the perfluoropolymer tube 2 into the positioning cavity 103 of the connector body 101. During the insertion process, ensure that the outer wall of the tube is tightly fitted with the annular protrusion 108 on the inner wall of the positioning cavity 103. The interference fit of the annular protrusion 108 is used to achieve the initial positioning of the tube and prevent the tube from moving axially. Then, put the clamping nut 102 on the outside of the perfluoropolymer tube 2 and rotate the clamping nut 102 to make it engage with the internal thread 104 of the connector body 101. The clamping nut 102 is driven to move into the positioning cavity 103 through the thread drive until the arc-shaped clamping surface 106 of the clamping nut 102 is aligned with the annular sealing groove 107 and axial pressure is applied. Continue tightening the clamping nut 102 until the arc-shaped clamping surface 106 is pressed into the annular sealing groove 107 with an interference fit. The interference fit is controlled at 0.2-0.3mm. At this time, the sealant is evenly filled into the gap between the arc-shaped clamping surface 106 and the groove wall under pressure, forming an initial seal. Finally, laser welding equipment is used to perform laser welding at the joint between the connector body 101 and the clamping nut 102. The welding power is 1500-2000W and the welding speed is 3-5mm / s, fusing the two into an integral structure and completing the assembly. After welding, the welded part 3 needs to be visually inspected to ensure that there are no defects such as pores and cracks, and to ensure the integrity of the structure.

[0020] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention; the actual structure is not limited thereto. In conclusion, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the invention, such designs should fall within the protection scope of the present invention.

Claims

1. A sealed end connection structure for connecting perfluoropolymer tubing, characterized in that: The assembly includes a metal connector assembly (1), a perfluoropolymer tube (2), and a welding part (3). The metal connector assembly (1) includes a connector body (101) and a clamping nut (102). The inner wall of the connector body (101) is provided with a positioning cavity (103) along the axial direction. One end of the connector body (101) is an interface for the metal parts to be connected, and the other end is provided with an internal thread (104). The inner wall of the clamping nut (102) is provided with an external thread (105) that matches the internal thread (104). One end of the clamping nut (102) extends into the positioning cavity (103) and the end is provided with an arc-shaped clamping surface (106). The perfluoropolymer tube (2) is inserted into the positioning cavity (103). The end of the perfluoropolymer tube (2) is provided with an annular sealing groove (107), and the annular sealing groove (107) is filled with a perfluoropolyether-based sealant.

2. The sealed end connection structure for a polymer perfluoropolymer tube connection according to claim 1, characterized in that: The positioning cavity (103) has multiple sets of annular protrusions (108) arranged axially on its inner wall, and the annular protrusions (108) are interference-fitted with the outer wall of the perfluoropolymer tube (2).

3. The sealed end connection structure for a polymer perfluoropolymer tube connection according to claim 1, characterized in that: The connector body (101) is provided with a tapered guide surface (109), and the inner wall of the tapered guide surface (109) is connected to the clamping nut (102).

4. The sealed end connection structure for a polymer perfluoropolymer tube connection according to claim 1, characterized in that: The welding part (3) is located at the junction of the connector body (101) and the clamping nut (102), and the two are fused into an integral structure by laser welding.

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