External thread movable joint with inverted trapezoidal thread

Abstract

The utility model discloses an external thread movable joint with an inverted trapezoidal thread, which relates to the field of pipeline joints, and is provided with a first thread section, a second thread section and a third thread section from top to bottom, an annular first sealing ring groove is arranged on the wall between the first thread section and the second thread section, and a second sealing ring groove is arranged on the wall between the second thread section and the third thread section. The third threaded section is an inverted trapezoidal thread, and a central through hole is formed in the middle of the movable joint. The external threads of the movable joint are designed, high joint sealing performance is achieved through thread fit, the reliability of threaded connection is guaranteed through interference fit of the inverted trapezoidal threads at one end, it can be guaranteed that the movable joint is not prone to loosening in a vibration environment, the sealing groove is additionally formed between the two threads at the other end, and the sealing performance of the movable joint is improved. The movable joint is used for mounting a sealing ring, so that the possibility of sealing failure is reduced, and the use reliability of the movable joint in a working scene in a vibration environment is realized.

Description

Technical Field

[0001] This utility model relates to the field of engineering components, specifically to a live joint with an inverted trapezoidal threaded external thread in the field of pipe joints. Background Technology

[0002] External threaded unions, as common pipe connection components, are widely used in building water supply and drainage, industrial piping systems, HVAC, and other fields. Currently, the DN25×3 / 4 external threaded union on the market has revealed numerous problems in practical use. Traditional unions have deficiencies in sealing performance, and are prone to leakage when subjected to long-term pressure and temperature changes, or when transporting corrosive media. This not only wastes resources but may also lead to safety accidents. Furthermore, the existing union installation and disassembly processes are cumbersome, requiring significant time and manpower, which greatly reduces work efficiency in large-scale pipeline installation and maintenance.

[0003] Although the "merchant" disclosed in announcement number CN119826004A ensures good sealing performance through its double-layer sealing structure, it raises the requirements for the processing and manufacturing of themerchant, and is complex to install, time-consuming, costly, and difficult to replace and maintain. Utility Model Content

[0004] The purpose of this invention is to provide a union with an inverted trapezoidal threaded external thread, which can firmly fix the union to the pipeline through the interference fit of the inverted trapezoidal thread, and at the same time, it is not easy for the threaded connection of the union to loosen under vibration, thus preventing water leakage. A further purpose of this invention is to provide two sections of thread on the other end of the union, and to provide a sealing groove for installing a sealing ring between the two sections of thread. Under vibration, the union can maintain good sealing performance. Even if loosening occurs, the sealing ring can still seal, and the two nuts may not loosen at the same time, making it more secure and less prone to sealing failure. At the same time, the installation steps of this invention only require tightening the threads at both ends of the union to achieve reliable installation, and the middle step can be used as a clamping and force application point for installation tools, making installation more convenient and simple.

[0005] The present invention achieves its purpose by adopting the following technical solutions.

[0006] A union with an inverted trapezoidal external thread is provided. The union has a first threaded section, a second threaded section, and a third threaded section from top to bottom. An annular first sealing groove is provided on the wall between the first threaded section and the second threaded section. The third threaded section is an inverted trapezoidal thread. A central through hole is provided in the middle of the union.

[0007] Furthermore, the diameter of the middle step is greater than the diameter of the first threaded segment and the second threaded segment.

[0008] Preferably, a middle step is provided between the second threaded segment and the third threaded segment.

[0009] Furthermore, the first threaded segment and the second threaded segment have the same thread direction.

[0010] Furthermore, the inverted trapezoidal teeth of the third thread segment are provided on the inverted trapezoidal thread end face.

[0011] Preferably, the diameter of the first threaded segment is equal to the diameter of the second threaded segment.

[0012] Furthermore, the second threaded segment contacts the first step surface of the middle step.

[0013] Furthermore, the distance d between the outer walls of adjacent inverted trapezoidal teeth is equal to the width a of the outer wall of the inverted trapezoidal teeth.

[0014] Preferably, the angle α between the sidewall of the inverted trapezoidal tooth and the end face of the inverted trapezoidal thread is in the range of 45° to 75°.

[0015] Furthermore, an annular second sealing groove is provided at the end face of the live joint near the third threaded section.

[0016] This utility model has the following beneficial effects:

[0017] Compared to existing technologies that ensure the sealing performance of the union through a multi-layer sealing structure, this invention designs the external thread of the union to achieve a higher joint sealing performance through threaded engagement. One end uses an interference fit of an inverted trapezoidal thread to ensure the reliability of the threaded connection and prevent the union from loosening easily in a vibration environment. The other end adds a sealing groove between the two threads to install a sealing ring, reducing the possibility of seal failure and ensuring the reliability of the union in working environments under vibration. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the main structure of this utility model.

[0019] Figure 2 This is a cross-sectional structural diagram of the present invention.

[0020] Figure 3 for Figure 2 A magnified view of a portion of point A in the middle.

[0021] In the figure, 1-first threaded section, 2-second threaded section, 3-third threaded section, 4-middle step, 5-first sealing ring groove, 6-inverted trapezoidal tooth, 7-second sealing ring groove, 8-first stepped surface, 9-second stepped surface, 10-inverted trapezoidal thread end face, 11-center through hole. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0023] Example 1:

[0024] like Figures 1 to 3 As shown, a union with an inverted trapezoidal external thread is provided. The union has a first threaded section 1, a second threaded section 2, and a third threaded section 3 from top to bottom. An annular first sealing groove 5 is provided on the wall between the first threaded section 1 and the second threaded section 2. The third threaded section 3 is an inverted trapezoidal thread. A central through hole is provided in the middle of the union.

[0025] This utility model provides a union with an inverted trapezoidal external thread, mainly used for connection points in water pipes in buildings. The main body of the union is made of a corrosion-resistant high-strength alloy. A central through hole 11 running along the axis is provided at the center of the union, providing a flow channel for water within the pipe. From top to bottom, the outer side of the union has a first threaded section 1, a second threaded section 2, and a third threaded section 3.

[0026] The first thread segment 1 and the second thread segment 2 are two adjacent external threads, such as Figure 1 As shown, the diameters of the first thread segment 1 and the second thread segment 2 are equal. The thread directions of the first thread segment 1 and the second thread segment 2 are the same. In the prior art, for the convenience of manufacturing process, the first thread segment 1 and the second thread segment 2 are generally designed as a single thread segment to reduce processing steps and reduce process difficulty. However, a single thread segment is prone to causing the nut to loosen under vibration environment, resulting in the failure of the seal at the joint.

[0027] Because the first threaded segment 1 and the second threaded segment 2 are two separate threads with the same direction of rotation, the preferred machining method is to machine the first sealing ring groove 5 at the middle position of the same threaded segment. The connection between the pipe and this union can be installed and fixed by two nuts. Since the two nuts independently engage with the first threaded segment 1 and the second threaded segment 2, and because the first threaded segment 1 and the second threaded segment 2 are independent of each other, the two nuts engaged with the two threads are affected differently under vibration. This reduces the likelihood of a single-nut connection where vibration causes the nut to fail to seal, leading to the overall seal failure of the union.

[0028] To prevent the seal from failing due to both nuts loosening simultaneously, a sealing ring groove 5 is provided between the two threaded sections to install a sealing ring for supplementary sealing after the first threaded section 1. Conventional unions often require extensive wrapping of PTFE tape around both ends of the thread to improve sealing performance and reduce water leakage from the union. While this invention also requires additional sealing materials during installation, compared to existing technologies where auxiliary sealing also fails when the thread loosens, this invention, due to the presence of the first sealing ring groove 5, is less prone to direct seal failure.

[0029] The first sealing ring groove 5 can be used for O-rings or other types of elastic sealing elements. When the union is connected to the mounting nut of the external pipe through the first threaded section 1 and the second threaded section 2, the sealing ring of the first sealing ring groove 5 is compressed to form a radial static seal, thereby reliably preventing fluid medium from leaking from the gap between the first threaded section 1 and the second threaded section 2.

[0030] A middle step 4 is provided between the lower part of the second threaded section 2 and the upper part of the third threaded section 3, as shown below. Figure 1 and Figure 2 As shown, the diameter of the intermediate step 4 is larger than the diameters of the first threaded segment 1 and the second threaded segment 2. Specifically, the end thread of the second threaded segment 2 connects to the first step surface 8 located on the upper surface of the intermediate step 4. The intermediate step 4 serves as a structural transition connecting segments of different diameters. The first step surface 8 also serves as an axial positioning reference surface for the second threaded segment 2 and the internal thread during installation, and bears the axial load from the mating components.

[0031] like Figure 1 and Figure 2 As shown, the outer perimeter of the middle step 4 has a polygonal structure, or is designed with other structures that facilitate tool clamping. This design allows operators to easily use tools such as wrenches to install or remove the union, ensuring the connection achieves the required tightness.

[0032] The third threaded segment 3 constitutes another innovative point of this utility model, and the third threaded segment 3 is designed as an inverted trapezoidal thread structure. For example... Figure 2 and Figure 3 As shown, the inverted trapezoidal tooth 6 is located on the annular end face 10 of a radial flange at the lower part of the union. Figure 3As shown, there is an included angle α between the sidewall of each inverted trapezoidal tooth 6 and the end face 10 of the inverted trapezoidal thread. The value of the included angle α is preferably set between 45° and 75°. This angle range is chosen based on achieving a better embedding effect and self-locking performance. A smaller angle makes it easier for the tooth tip to cut into the mating material and form a deeper embedding, but it requires a larger installation force, and the stress is more concentrated at the tooth root, making it more prone to fracture and thus causing the live joint to be scrapped.

[0033] Larger angles result in relatively lower installation force, but may correspondingly weaken the embedding depth and self-locking effect. The distance d between the outer walls of two adjacent inverted trapezoidal teeth 6, i.e., the width of the tooth groove, is equal to the width a of the outer wall of a single inverted trapezoidal tooth 6, i.e., the width of the tooth tip. The equality of the tooth groove width and the tip width facilitates the fit between the third thread segment 3 and the internal thread, as well as the interference fit between the internal and external threads, and generates uniform radial pressure between the teeth and the mating surfaces, thereby enhancing the stability of the connection and its resistance to pull-out.

[0034] When the third thread section 3 of the union is screwed into the inner hole of the pipe, due to the structure of the inverted trapezoidal teeth 6 and the interference fit, the cutting edge and bevel of the teeth will produce a certain degree of plastic deformation on the inner wall material of the pipe, that is, a cutting or extrusion action will occur. This allows the inverted trapezoidal teeth 6 to be firmly embedded in the inner wall of the pipe, forming an extremely tight embedded connection with high friction and mechanical interlocking characteristics. It can generate a large fastening force and withstand a large axial pull-out force and torsional load, ensuring that the union is firmly fixed to the pipe and is not easy to fall off or rotate relative to each other, resulting in good anti-vibration loosening performance. The interference fit and embedding characteristics of the inverted trapezoidal thread make it difficult for the connection to loosen even in the environment of strong vibration or impact, thus effectively avoiding fluid leakage problems that may be caused by loose connection. This plays an important role in vibrating equipment or systems with frequent vibration.

[0035] To further improve the sealing performance of the union and enhance the sealing effect of the third threaded section 3 connected to the pipe, as follows: Figure 2 As shown, at the lowest point of the union joint, on the end face of the union joint where the third threaded section 3 is located, an annular second sealing groove 7 is also formed. The second sealing groove 7 is located on the end face. After the third threaded section 3 is connected to the pipe, the sealing ring installed here can serve as the first sealing point on the end face of the pipe, acting as an additional sealing barrier. This can prevent water from flowing to the position where the third threaded section 3 and the pipe thread are installed.

[0036] Example 2:

[0037] The main structure of the live joint in this embodiment is the same as that in Embodiment 1. The dynamic assembly process of the first threaded section 1, the second threaded section 2, and the first sealing ring groove 5 of this utility model when assembled with an external nut is specifically described.

[0038] like Figures 1 to 3 As shown, a union with an inverted trapezoidal external thread is provided. The union has a first threaded section 1, a second threaded section 2, and a third threaded section 3 from top to bottom. An annular first sealing groove 5 is provided on the wall between the first threaded section 1 and the second threaded section 2. The third threaded section 3 is an inverted trapezoidal thread. A central through hole is provided in the middle of the union.

[0039] This utility model provides a union with an inverted trapezoidal external thread, mainly used for connection points in water pipes in buildings. The main body of the union is made of a corrosion-resistant high-strength alloy. A central through hole 11 running along the axis is provided at the center of the union, providing a flow channel for water within the pipe. From top to bottom, the outer side of the union has a first threaded section 1, a second threaded section 2, and a third threaded section 3.

[0040] The first thread segment 1 and the second thread segment 2 are two adjacent external threads, such as Figure 1 As shown, the diameters of the first thread segment 1 and the second thread segment 2 are equal. The thread directions of the first thread segment 1 and the second thread segment 2 are the same. In the prior art, for the convenience of manufacturing process, the first thread segment 1 and the second thread segment 2 are generally designed as a single thread segment to reduce processing steps and reduce process difficulty. However, a single thread segment is prone to causing the nut to loosen under vibration environment, resulting in the failure of the seal at the joint.

[0041] Because the first threaded segment 1 and the second threaded segment 2 are two separate threads with the same direction of rotation, the preferred machining method is to machine the first sealing ring groove 5 at the middle position of the same threaded segment. The connection between the pipe and this union can be installed and fixed by two nuts. Since the two nuts independently engage with the first threaded segment 1 and the second threaded segment 2, and because the first threaded segment 1 and the second threaded segment 2 are independent of each other, the two nuts engaged with the two threads are affected differently under vibration. This reduces the likelihood of a single-nut connection where vibration causes the nut to fail to seal, leading to the overall seal failure of the union.

[0042] To prevent the seal from failing due to both nuts loosening simultaneously, a sealing ring groove 5 is provided between the two threaded sections to install a sealing ring for supplementary sealing after the first threaded section 1. Conventional unions often require extensive wrapping of PTFE tape around both ends of the thread to improve sealing performance and reduce water leakage from the union. While this invention also requires additional sealing materials during installation, compared to existing technologies where auxiliary sealing also fails when the thread loosens, this invention, due to the presence of the first sealing ring groove 5, is less prone to direct seal failure.

[0043] The first sealing ring groove 5 can be used for O-rings or other types of elastic sealing elements. When the union is connected to the mounting nut of the external pipe through the first threaded section 1 and the second threaded section 2, the sealing ring of the first sealing ring groove 5 is compressed to form a radial static seal, thereby reliably preventing fluid medium from leaking from the gap between the first threaded section 1 and the second threaded section 2.

[0044] A middle step 4 is provided between the lower part of the second threaded section 2 and the upper part of the third threaded section 3, as shown below. Figure 1 and Figure 2 As shown, the diameter of the intermediate step 4 is larger than the diameters of the first threaded segment 1 and the second threaded segment 2. Specifically, the end thread of the second threaded segment 2 connects to the first step surface 8 located on the upper surface of the intermediate step 4. The intermediate step 4 serves as a structural transition connecting segments of different diameters. The first step surface 8 also serves as an axial positioning reference surface for the second threaded segment 2 and the internal thread during installation, and bears the axial load from the mating components.

[0045] like Figure 1 and Figure 2 As shown, the outer perimeter of the middle step 4 has a polygonal structure, or is designed with other structures that facilitate tool clamping. This design allows operators to easily use tools such as wrenches to install or remove the union, ensuring the connection achieves the required tightness.

[0046] The third threaded segment 3 constitutes another innovative point of this utility model, and the third threaded segment 3 is designed as an inverted trapezoidal thread structure. For example... Figure 2 and Figure 3 As shown, the inverted trapezoidal tooth 6 is located on the annular end face 10 of a radial flange at the lower part of the union. Figure 3As shown, there is an included angle α between the sidewall of each inverted trapezoidal tooth 6 and the end face 10 of the inverted trapezoidal thread. The value of the included angle α is preferably set between 45° and 75°. This angle range is chosen based on achieving a better embedding effect and self-locking performance. A smaller angle makes it easier for the tooth tip to cut into the mating material and form a deeper embedding, but it requires a larger installation force, and the stress is more concentrated at the tooth root, making it more prone to fracture and thus causing the live joint to be scrapped.

[0047] Larger angles result in relatively lower installation force, but may correspondingly weaken the embedding depth and self-locking effect. The distance d between the outer walls of two adjacent inverted trapezoidal teeth 6, i.e., the width of the tooth groove, is equal to the width a of the outer wall of a single inverted trapezoidal tooth 6, i.e., the width of the tooth tip. The equality of the tooth groove width and the tip width facilitates the fit between the third thread segment 3 and the internal thread, as well as the interference fit between the internal and external threads, and generates uniform radial pressure between the teeth and the mating surfaces, thereby enhancing the stability of the connection and its resistance to pull-out.

[0048] When the third thread section 3 of the union is screwed into the inner hole of the pipe, due to the structure of the inverted trapezoidal teeth 6 and the interference fit, the cutting edge and bevel of the teeth will produce a certain degree of plastic deformation on the inner wall material of the pipe, that is, a cutting or extrusion action will occur. This allows the inverted trapezoidal teeth 6 to be firmly embedded in the inner wall of the pipe, forming an extremely tight embedded connection with high friction and mechanical interlocking characteristics. It can generate a large fastening force and withstand a large axial pull-out force and torsional load, ensuring that the union is firmly fixed to the pipe and is not easy to fall off or rotate relative to each other, resulting in good anti-vibration loosening performance. The interference fit and embedding characteristics of the inverted trapezoidal thread make it difficult for the connection to loosen even in the environment of strong vibration or impact, thus effectively avoiding fluid leakage problems that may be caused by loose connection. This plays an important role in vibrating equipment or systems with frequent vibration.

[0049] To further improve the sealing performance of the union and enhance the sealing effect of the third threaded section 3 connected to the pipe, as follows: Figure 2 As shown, at the lowest point of the union joint, on the end face of the union joint where the third threaded section 3 is located, an annular second sealing groove 7 is also formed. The second sealing groove 7 is located on the end face. After the third threaded section 3 is connected to the pipe, the sealing ring installed here can serve as the first sealing point on the end face of the pipe, acting as an additional sealing barrier. This can prevent water from flowing to the position where the third threaded section 3 and the pipe thread are installed.

[0050] In this embodiment, the third threaded segment 3 is first connected to one end of the pipe by clamping the middle step 4 with a wrench or other installation tools. After the union is fixed to a pipe, the first threaded segment 1 and the second threaded segment 2 are then connected to another section of pipe that needs to be connected. The sealing ring is placed in the first sealing ring groove 5, and then the nut is screwed from the first threaded segment 1 into the second threaded segment 2, with the end face of the nut abutting against the first step surface 8 of the middle step 4. During installation, care must be taken to avoid the sealing ring from rolling into the threads during nut installation.

[0051] When the first nut passes through the first threaded section 1 and begins to engage with the second threaded section 2, the second nut on the pipeline generally also begins to contact the first threaded section 1. At this time, as the first nut is screwed into the second threaded section 2, the second nut also needs to be screwed into the first threaded section 1. When the end face of the first nut abuts against the first step surface 8 of the middle step 4, the second nut continues to be screwed in until the end face of the second nut abuts against the end face of the first nut, completing the installation process of the threads at both ends of the union and the pipeline.

[0052] This utility model discloses a union with an inverted trapezoidal external thread. By designing the first threaded section 1 and the second threaded section 2 with opposite thread directions and setting the third threaded section 3 as an inverted trapezoidal thread, and by providing a first sealing ring groove 5 at the middle of the union and a second sealing ring groove 7 at the surface of the third threaded section 3, the sealing performance of the union is further enhanced. The design of the first and second threaded sections ensures that the union maintains high stability and excellent anti-loosening performance under vibration conditions when connected to external pipelines or equipment, while the first sealing ring provides a reliable seal. The inverted trapezoidal thread of the third threaded section 3, through an interference fit with the external pipeline or equipment, achieves a firm and reliable fixed installation effect, also possessing strong anti-vibration loosening ability, effectively preventing leakage problems caused by loose connections. Therefore, the union provided by this utility model can better adapt to more severe working environments, especially those with continuous or strong vibrations, and scenarios where the liquid temperature inside the pipe may change abruptly, thereby improving the overall reliability of the connection, sealing performance, and ultimate service life.

Claims

1. A union with an inverted trapezoidal external thread, characterized in that, The union has a first threaded section (1), a second threaded section (2), and a third threaded section (3) from top to bottom. The wall between the first threaded section (1) and the second threaded section (2) is provided with an annular first sealing groove (5). The third threaded section (3) is an inverted trapezoidal thread. The union has a central through hole in the middle.

2. A union with an inverted trapezoidal external thread as described in claim 1, characterized in that, A middle step (4) is provided between the second threaded section (2) and the third threaded section (3).

3. A union with an inverted trapezoidal external thread as described in claim 2, characterized in that, The diameter of the middle step (4) is greater than the diameter of the first threaded section (1) and the second threaded section (2).

4. A union with an inverted trapezoidal external thread as described in claim 1, characterized in that, The first thread segment (1) and the second thread segment (2) have the same thread direction.

5. A live joint with an inverted trapezoidal external thread as described in claim 1, 2, 3, or 4, characterized in that, The inverted trapezoidal teeth (6) of the third thread segment (3) are provided on the inverted trapezoidal thread end face (10).

6. A live joint with an inverted trapezoidal external thread as described in claim 1, 2, 3, or 4, characterized in that, The diameter of the first threaded segment (1) is equal to the diameter of the second threaded segment (2).

7. A union with an inverted trapezoidal external thread as described in claim 3, characterized in that, The second threaded segment (2) contacts the first step surface of the middle step (4).

8. A union with an inverted trapezoidal external thread as described in claim 5, characterized in that, The distance d between the outer walls of adjacent inverted trapezoidal teeth (6) is equal to the width a of the outer wall of the inverted trapezoidal teeth (6).

9. A union with an inverted trapezoidal external thread according to claim 5, characterized in that, The angle α between the sidewall of the inverted trapezoidal tooth (6) and the end face (10) of the inverted trapezoidal thread ranges from 45° to 75°.

10. A live joint with an inverted trapezoidal external thread as described in claim 1, 2, 3, 4, 7, 8, or 9, characterized in that, A second sealing groove (7) is provided at the end face of the live joint near the third threaded section (3).

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