A full plastic sealed joint assembly of PPR pipe

Abstract

The utility model relates to the technical field of PPR pipe joint, more particularly to a kind of PPR pipe full plastic sealing joint assembly, outer thread plastic fittings include first inner cladding, inner thread plastic fittings include second inner cladding, first inner cladding is butted with the cavity inner wall of outer thread insert, the cavity inner wall of inner thread insert is divided into thread section and fixed section, second inner cladding is butted with fixed section. The end face of first inner cladding is provided with sealing ring, when outer thread insert is connected with inner thread insert thread, sealing ring is butted with the end face of second inner cladding. The utility model can effectively plug leakage passage, simultaneously need not rely on raw material band and other auxiliary sealing material to carry out sealing installation, effectively improve sealing installation qualified rate.

Description

Technical Field

[0001] This utility model relates to the field of PPR pipe fitting technology, and more specifically, to a PPR pipe all-plastic sealed fitting assembly. Background Technology

[0002] In building water supply and heating systems, polypropylene random copolymer (PPR) piping systems are widely used due to their advantages such as corrosion resistance, high temperature resistance, and easy installation. The key connecting component of this system—the PPR pipe fitting—generally adopts a plastic-steel composite structure. Specifically, this structure typically includes an external threaded insert, an internal threaded insert, and corresponding plastic fittings covering them (e.g., an external threaded plastic fitting covering the external threaded insert, and an internal threaded plastic fitting covering the internal threaded insert). The plastic fittings are formed by injection molding the metal inserts to create the fitting body. During installation, regardless of the type of metal insert used, current technology typically involves first wrapping auxiliary sealing materials such as PTFE tape around the external threaded insert before threading the internal threaded insert.

[0003] Currently, copper alloys are the mainstream material for metal inserts. Copper alloy inserts have the advantages of a large coefficient of thermal expansion, good thermal conductivity, and excellent thread sealing performance, and the holding pressure required for injection molding is relatively low. However, copper alloy materials are expensive, and their inherent brittleness can easily lead to cracking and failure of the insert during processing or use, affecting the reliability of the joint.

[0004] To reduce costs and mitigate brittleness, stainless steel inserts have been proposed as an alternative. While stainless steel inserts are less expensive and less prone to cracking, they have significant drawbacks in practical applications: Firstly, the high hardness of stainless steel often results in sharp edges on the threads formed during machining. When using PTFE tape for sealing, these sharp threads easily scratch or cut the tape. Once the PTFE tape is damaged, its sealing function fails, leading to fluid leakage at the connection. This results in a low first-time installation success rate (typically only about 70%), requiring installers to repeatedly disassemble, rewrap the PTFE tape, and attempt installation again, making the process cumbersome and inefficient. To address the sharp thread issue, the industry has attempted shot blasting to polish the stainless steel threads. However, firstly, due to the strict requirements on the thread profile angle of the sealed pipe, which cannot vary significantly, excessive grinding is not advisable. The grinding process requires strict supervision by the operators, demanding a high level of experience. Secondly, the small thread diameter and pitch make it difficult for the shot blasting medium to effectively and evenly reach all sharp edges and corners of the thread crest and flanks, resulting in significant grinding dead zones. Therefore, the actual effect of shot blasting is not ideal and cannot reliably eliminate the problem of sharp threads. Furthermore, the coefficient of thermal expansion of stainless steel is much lower than that of PPR plastic, and its thermal conductivity is also poor. This significant difference in physical properties necessitates the application of higher pressure (usually twice the pressure of copper alloy inserts) during injection molding to achieve initial bonding. More importantly, the mismatch in expansion coefficients leads to insufficient bonding strength at the bonded plastic-steel interface. Under operating conditions (especially hot and cold cycling), interface separation easily occurs, forming leakage channels. Liquid leakage at the plastic-steel interface then seriously affects system safety. Utility Model Content

[0005] The purpose of this invention is to overcome the problems of low sealing installation qualification rate and easy leakage of stainless steel inserts in existing PPR pipe joints, and to provide a PPR pipe all-plastic sealing joint assembly that can effectively block leakage channels, and at the same time, it does not need to rely on auxiliary sealing materials such as PTFE tape for sealing installation, thus effectively improving the sealing installation qualification rate.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by this utility model is as follows: A PPR pipe all-plastic sealing joint assembly is provided, including an external thread insert, an internal thread insert, an external thread plastic fitting, and an internal thread plastic fitting. The external thread plastic fitting includes a first inner covering layer, and the internal thread plastic fitting includes a second inner covering layer. The first inner covering layer abuts against the inner wall of the cavity of the external thread insert. The inner wall of the cavity of the internal thread insert is divided into a threaded section and a fixed section. The second inner covering layer abuts against the fixed section. A sealing ring is installed on the end face of the first inner covering layer. When the external thread insert and the internal thread insert are threadedly connected, the sealing ring abuts against the end face of the second inner covering layer.

[0007] In the operation of the above scheme, the first inner covering layer of the external threaded plastic fitting tightly covers and adheres to the inner wall of the cavity of the external threaded insert, while the second inner covering layer of the internal threaded plastic fitting tightly covers and adheres to the fixing section of the inner wall of the cavity of the internal threaded insert. These two inner covering layers, made of PPR plastic, are equivalent to the internal isolation layers of the insert, completely covering the inner surface of the metal insert and completely preventing the fluid from directly contacting the metal insert itself, ensuring that the fluid medium flowing through the joint only contacts the PPR plastic material. At the same time, a sealing ring is installed on the end face of the first inner covering layer of the external threaded plastic fitting. When the external threaded insert and the internal threaded insert are threaded together and tightened, the sealing ring is axially compressed and tightly pressed against the end face of the second inner covering layer, forming an elastic sealing barrier between the mating end faces of the first and second inner covering layers, completely sealing the gap between the mating end faces, and cutting off the path for fluid leakage through the poor interface of the plastic-steel bond at the source. The entire assembly features a dual sealing mechanism during use: firstly, an initial seal provided by the threaded engagement between the metal inserts; and secondly, a crucial seal formed by the sealing ring between the plastic end faces, blocking potential leakage channels. Therefore, even if microscopic gaps exist in the metal threaded connection or potential separation gaps exist at the plastic-steel interface, the fluid cannot reach these areas due to the blocking effect of the first inner sheath, the sealing ring, and the second inner sheath. This allows the connector assembly to achieve excellent sealing performance without relying on auxiliary sealing materials such as PTFE tape during installation, significantly improving the first-time installation success rate.

[0008] Furthermore, a first groove is provided on one end face of the external thread insert, and a first protrusion is provided on the first inner covering layer. The first protrusion is inserted into the first groove. After the first protrusion is inserted into the first groove, the relative position of the first inner covering layer and the external thread insert can be fixed, preventing the first inner covering layer from falling off after injection molding, which is more conducive to the plastic wrapping the metal.

[0009] Furthermore, the external thread insert has several anti-rotation protrusions on the end face away from the first groove, and the anti-rotation protrusions are inserted into the first inner covering layer. During the threaded connection process, it is necessary to screw the external thread insert or the internal thread insert. The first inner covering layer has a groove, and the anti-rotation protrusions are inserted into the groove to prevent the external thread insert from rotating relative to the first inner covering layer during the screwing process.

[0010] Furthermore, the external threaded plastic fitting also includes a first outer covering layer, which is connected to the first inner covering layer. The first outer covering layer abuts against the outer wall of the external threaded insert. The first outer covering layer is the basic structure of the plastic-steel joint. The first outer covering layer wraps the metal external threaded insert on the outside to prevent the external threaded insert from being corroded by external substances.

[0011] Furthermore, both the outer and inner covering layers have first water-stopping protrusions, and the inner and outer walls of the external threaded insert have first water-stopping grooves. The first water-stopping protrusions are inserted into the first water-stopping grooves. During the injection molding process, the plastic flows into the first water-stopping grooves to form the first water-stopping protrusions, which can reduce the generation of internal stress during the injection molding process, avoid air entrapment, and prevent voids, resulting in insufficient bonding between the plastic and the metal.

[0012] Furthermore, it also includes a socket tube body, wherein the first outer covering layer and the second inner covering layer are respectively fixedly connected to the socket tube body; the socket tube body is the interface of the connecting component, and the pipe is connected to the socket tube body through processes such as hot-melt socketing, so as to realize the basic function of connecting the pipe of the connecting component.

[0013] Furthermore, a second groove is provided on the fixing segment, and a second protrusion is provided on the second inner covering layer, the second protrusion being inserted into the second groove. The second protrusion, inserted into the second groove, also fixes the second inner covering layer to the wall surface of the fixing segment, preventing it from falling off after injection molding.

[0014] Furthermore, the internally threaded plastic fitting also includes a second outer covering layer, which is fixedly connected to the second inner covering layer. The outer wall surface of the threaded section abuts against the second outer covering layer. The second outer covering layer covers the outer wall of the fixed section, thus protecting the surface of the metal part and improving its corrosion resistance.

[0015] Furthermore, the outer wall surface of the threaded section is provided with a second water-stop groove, and the second outer covering layer is provided with a second water-stop protrusion, which is inserted into the second water-stop groove; the second water-stop groove on the outer wall surface also reduces the stress during the injection molding process and avoids insufficient bonding force between the plastic and the metal.

[0016] Furthermore, the fixed section has several anti-rotation grooves on the side away from the second groove, and the second inner covering layer is connected to the anti-rotation grooves; during injection molding, the molten material enters the anti-rotation grooves to form a fixed shape, preventing the internal thread insert from rotating relative to the second inner covering layer during the twisting process.

[0017] Compared with the prior art, the beneficial effects of this utility model are: 1. The externally threaded plastic fitting includes a first inner covering layer, and the internally threaded plastic fitting includes a second inner covering layer. The first inner covering layer abuts against the inner wall of the cavity of the externally threaded insert. The inner wall of the cavity of the internally threaded insert is divided into a threaded section and a fixed section. The second inner covering layer abuts against the fixed section. A sealing ring is installed on the end face of the first inner covering layer. When the externally threaded insert and the internally threaded insert are threadedly connected, the sealing ring abuts against the end face of the second inner covering layer. The first inner covering layer, the sealing ring, and the second inner covering layer completely isolate fluid from potential leakage channels, and fluid cannot reach these areas. This allows the connector assembly to achieve excellent sealing performance without relying on auxiliary sealing materials such as PTFE tape during installation, significantly improving the first-time installation success rate.

[0018] 2. A first groove is provided on one end face of the external thread insert, and a first protrusion is provided on the first inner covering layer, the first protrusion being inserted into the first groove; a second groove is provided on the fixed section, and a second protrusion is provided on the second inner covering layer, the second protrusion being inserted into the second groove. The second protrusion being inserted into the second groove prevents the first and second inner covering layers from falling off after injection molding, and is more conducive to the plastic encapsulating the metal. Attached Figure Description

[0019] Figure 1 A schematic diagram of the internal structure of a PPR pipe all-plastic sealed joint assembly; Figure 2 A schematic diagram of the combined installation of an external thread insert and an external thread plastic fitting for a PPR pipe all-plastic sealing joint assembly; Figure 3 for Figure 2 A magnified view of a section at point A in the middle; Figure 4 A perspective view of an external threaded insert for a PPR pipe all-plastic sealing joint assembly; Figure 5 A schematic diagram of the structure of a PPR pipe all-plastic sealing joint assembly with an internal thread insert and an internal thread plastic fitting. Figure 6 for Figure 5 A magnified view of a section at point B in the middle; Figure 7 This is a perspective view of an internal thread insert for a PPR pipe all-plastic sealing joint assembly.

[0020] In the attached diagram: 100, external thread insert; 110, first groove; 120, first water-stop groove; 130, anti-rotation protrusion; 200, internal thread insert; 210, threaded section; 211, second water-stop groove; 220, fixed section; 221, second groove; 222, anti-rotation groove; 300, external thread plastic fitting; 310, first inner covering layer; 311, first protrusion; 320, first outer covering layer; 330, first water-stop protrusion; 400, internal thread plastic fitting; 410, second inner covering layer; 411, second protrusion; 420, second outer covering layer; 421, second water-stop protrusion; 500, sealing ring; 600, socket tube body. Detailed Implementation

[0021] The present invention will be further described below with reference to specific embodiments. The accompanying drawings are for illustrative purposes only, representing schematic diagrams rather than actual physical objects, and should not be construed as limiting the scope of this patent. To better illustrate the embodiments of the present invention, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0022] In the accompanying drawings of this utility model, the same or similar reference numerals correspond to the same or similar components. In the description of this utility model, it should be understood that if terms such as "upper," "lower," "left," and "right" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing this utility model 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, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting this patent. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0023] Example 1 This embodiment is a first embodiment of a PPR pipe all-plastic sealed joint assembly, such as... Figures 1 to 3 as well as Figures 5 to 6 As shown, the device includes an externally threaded insert 100, an internally threaded insert 200, an externally threaded plastic fitting 300, and an internally threaded plastic fitting 400. The externally threaded plastic fitting 300 includes a first inner covering layer 310, and the internally threaded plastic fitting 400 includes a second inner covering layer 410. The first inner covering layer 310 abuts against the inner wall of the cavity of the externally threaded insert 100. The inner wall of the cavity of the internally threaded insert 200 is divided into a threaded section 210 and a fixed section 220. The second inner covering layer 410 abuts against the fixed section 220. A sealing ring 500 is installed on the end face of the first inner covering layer 310. When the externally threaded insert 100 and the internally threaded insert 200 are threadedly connected, the sealing ring 500 abuts against the end face of the second inner covering layer 410.

[0024] Specifically, a first groove 110 is provided on one end face of the external thread insert 100, and a first protrusion 311 is provided on the first inner covering layer 310. The first protrusion 311 is inserted into the first groove 110. After the first protrusion 311 is inserted into the first groove 110, the relative position of the first inner covering layer 310 and the external thread insert 100 can be fixed, preventing the first inner covering layer 310 from falling off after injection molding, which is more conducive to the plastic wrapping the metal.

[0025] Specifically, the external threaded plastic fitting 300 also includes a first outer covering layer 320, which is connected to the first inner covering layer 310. The first outer covering layer 320 abuts against the outer wall of the external threaded insert 100. The first outer covering layer 320 is the basic structure of the plastic-steel joint. The first outer covering layer 320 wraps the metal external threaded insert 100 on the outside to prevent the external threaded insert 100 from being corroded by external substances.

[0026] Specifically, the fixed section 220 is provided with a second groove 221, and the second inner covering layer 410 is provided with a second protrusion 411, which is inserted into the second groove 221. The second protrusion 411 is inserted into the second groove 221, which also fixes the second inner covering layer 410 to the wall of the fixed section 220 to prevent it from falling off after injection molding.

[0027] Specifically, the internally threaded plastic fitting 400 also includes a second outer covering layer 420, which is fixedly connected to the second inner covering layer 410. The outer wall surface of the threaded section 210 abuts against the second outer covering layer 420. The second outer covering layer 420 covers the outer wall of the fixed section 220, thus protecting the surface of the metal part and improving its corrosion resistance.

[0028] The working principle of a PPR pipe all-plastic sealed joint assembly in this embodiment is as follows: For the fixing section 220 of both the external thread insert 100 and the internal thread insert 200, an interlocking structure to enhance the bonding strength between the plastic and steel is adopted. A first groove 110 is pre-set on the end face of the external thread insert 100 facing the mating end, and a first protrusion 311 is formed on the corresponding first inner covering layer 310. A second groove 221 is pre-set on the end face of the inner wall of the cavity of the fixing section 220 of the internal thread insert 200, and a second protrusion 411 is formed on the corresponding second inner covering layer 410. During injection molding, the molten plastic flows into these grooves, and after cooling, a firmly fitted mechanical interlocking structure is formed, effectively preventing the inner covering layer from loosening from the inner wall of the metal insert under subsequent thermal cycling, fluid pressure, or external force.

[0029] Meanwhile, the external threaded plastic fitting 300 is integrally formed by a first inner covering layer 310 and a first outer covering layer 320. The first inner covering layer 310 covers the inner wall of the external threaded insert 100, while the first outer covering layer 320 tightly covers its outer wall. The internal threaded plastic fitting 400 is integrally formed by a second inner covering layer 410 and a second outer covering layer 420. The second inner covering layer 410 covers the inner wall of the fixing section 220 of the internal threaded insert 200, while the second outer covering layer 420 tightly covers its outer wall. These inner and outer covering layers work together: the inner covering layer ensures that the fluid medium flowing through the inside of the fitting only contacts the PPR plastic, completely isolating it from contact with the inner surface of the metal insert and its plastic-steel interface; the first outer covering layer 320 and the second outer covering layer 420 adhere to the outer walls of the external threaded insert 100 and the internal threaded insert 200, isolating the external environment from corroding the outer wall of the metal insert.

[0030] In terms of sealing mechanism, a sealing ring 500 is installed on the end face of the first inner covering layer 310 of the externally threaded plastic fitting 300. When the externally threaded insert 100 and the internally threaded insert 200 are threadedly connected and tightened, the sealing ring 500 is axially compressed and tightly pressed against the end face of the second inner covering layer 410, forming an elastic sealing barrier between the mating end faces of the first inner covering layer 310 and the second inner covering layer 410. This forms a double seal: the threaded engagement between the metal inserts provides an initial seal, while the seal formed by the sealing ring 500 between the plastic end faces can block any potential leakage channels.

[0031] The beneficial effects of this embodiment are as follows: The fixing sections 220 of both the external threaded insert 100 and the internal threaded insert 200 employ a mechanical interlocking structure of grooves and protrusions, ensuring a durable, stable, and tight coverage of the inner wall by the inner coating layer. During installation, the joint assembly achieves excellent sealing performance and a high first-time installation success rate without relying on auxiliary sealing materials such as PTFE tape. Furthermore, the outer coating layer significantly improves overall corrosion resistance and service life.

[0032] Example 2 This embodiment is a second embodiment of a PPR pipe all-plastic sealed joint assembly, such as... Figure 1 , Figure 4 and Figure 7 As shown, the difference from Embodiment 1 is as follows: Specifically, the external thread insert 100 has several anti-rotation protrusions 130 on the end face away from the first groove 110. The anti-rotation protrusions 130 are inserted into the first inner covering layer 310. During the threaded connection process, it is necessary to screw the external thread insert 100 or the internal thread insert 200. The first inner covering layer 310 has a groove, and the anti-rotation protrusions 130 are inserted into the groove to prevent the external thread insert 100 from rotating relative to the first inner covering layer 310 during the screwing process.

[0033] Specifically, a number of anti-rotation grooves 222 are provided on the side of the fixed section 220 away from the second groove 221, and the second inner covering layer 410 is connected to the anti-rotation grooves 222. When the fixed section 220 is injection molded, the molten material enters the anti-rotation grooves 222 to form a fixed shape, preventing the internal thread insert 200 from rotating relative to the second inner covering layer 410 during the twisting process.

[0034] The working principle of a PPR pipe all-plastic sealed joint assembly in this embodiment is as follows: The external threaded insert 100 and the internal threaded insert 200 are respectively provided with anti-rotation protrusions 130 and anti-rotation grooves 222. During injection molding, the molten plastic fills, covers, or fits these structures, forming a strong mechanical interlock. This creates a rigid circumferential connection between the metal insert and the plastic layer. During thread tightening, the installation torque applied to the plastic portion can be directly and effectively transmitted to the metal insert, driving the threads to engage.

[0035] The beneficial effects of this embodiment are as follows: the external thread insert 100 and the internal thread insert 200 are respectively provided with anti-rotation protrusion 130 and anti-rotation groove 222 structures, which eliminate the shear stress borne by the plastic-steel joint interface during screwing, prevent the first inner covering layer 310 and the second inner covering layer 410 from loosening, falling off or being damaged during installation, and ensure that the installation operation is smooth and controllable, ultimately improving the sealing reliability and installation efficiency.

[0036] Example 3 This embodiment is a third embodiment of a PPR pipe all-plastic sealed joint assembly, such as... Figure 1 , Figure 2 and Figure 5 As shown, the difference from Embodiment 1 is as follows: Specifically, a first water-stopping protrusion 330 is provided on the wall surface of both the first outer covering layer 320 and the first inner covering layer 310, and a first water-stopping groove 120 is provided on both the inner and outer wall surfaces of the external thread insert 100. The first water-stopping protrusion 330 is inserted into the first water-stopping groove 120. During the injection molding process, the plastic flows into the first water-stopping groove 120 to form the first water-stopping protrusion 330, which can reduce the generation of internal stress during the injection molding process, avoid air entrapment, and prevent voids, resulting in insufficient bonding force between the plastic and the metal.

[0037] Specifically, the outer wall of the threaded section 210 is provided with a second water-stop groove 211, and the second outer covering layer 420 is provided with a second water-stop protrusion 421, which is inserted into the second water-stop groove 211. The second water-stop groove 211 on the outer wall of the threaded section 210 also reduces the stress during the injection molding process and avoids insufficient bonding between the plastic and the metal.

[0038] Specifically, it also includes a socket tube body 600, with the first outer covering layer 320 and the second inner covering layer 410 fixedly connected to the socket tube body 600 respectively; the socket tube body 600 is the interface of the connection component, and the pipe is connected to the socket tube body 600 through processes such as hot-melt socketing, so as to realize the basic function of pipe connection of the connection component.

[0039] The working principle of a PPR pipe all-plastic sealed joint assembly in this embodiment is as follows: The inner and outer walls of the external thread insert 100 and the outer wall of the threaded segment 210 of the internal thread insert 200 are pre-set with arc-shaped first water-stop groove 120 and second water-stop groove 211. When the internal stress of the plastic melt is too large during injection molding, the melt can fully flow into and fill these grooves, and after cooling, it forms a plastic water-stop protrusion that fits tightly with it.

[0040] The beneficial effects of this embodiment are: the first water-stop groove 120 and the second water-stop groove 211 improve the fluidity and filling behavior of molten plastic on the metal surface, effectively reduce the internal stress caused by flow resistance or poor venting during injection molding, and avoid air entrapment and the resulting defects such as holes and shrinkage marks.

[0041] In the specific implementation of the above embodiments, the technical features can be combined in any non-contradictory way. For the sake of brevity, not all possible combinations of the above technical features are described. However, as long as the combination of these technical features is not contradictory, it should be considered to be within the scope of this specification.

[0042] Obviously, the above embodiments of this utility model are merely examples for clearly illustrating this utility model, and are not intended to limit the implementation of this utility model. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this utility model should be included within the protection scope of the claims of this utility model.

Claims

1. A PPR pipe all-plastic sealing joint assembly, comprising an external thread insert (100), an internal thread insert (200), an external thread plastic fitting (300), and an internal thread plastic fitting (400), characterized in that, The external threaded plastic fitting (300) includes a first inner covering layer (310), and the internal threaded plastic fitting (400) includes a second inner covering layer (410). The first inner covering layer (310) abuts against the inner wall of the cavity of the external threaded insert (100). The inner wall of the cavity of the internal threaded insert (200) is divided into a threaded section (210) and a fixed section (220). The second inner covering layer (410) abuts against the fixed section (220). A sealing ring (500) is installed on the end face of the first inner covering layer (310). When the external threaded insert (100) and the internal threaded insert (200) are threadedly connected, the sealing ring (500) abuts against the end face of the second inner covering layer (410).

2. The PPR pipe all-plastic sealing joint assembly according to claim 1, characterized in that, A first groove (110) is provided on one end face of the external thread insert (100), and a first protrusion (311) is provided on the first inner covering layer (310), and the first protrusion (311) is inserted into the first groove (110).

3. The PPR pipe all-plastic sealing joint assembly according to claim 2, characterized in that, The external thread insert (100) has a plurality of anti-rotation protrusions (130) on the side face away from the first groove (110), and the anti-rotation protrusions (130) are inserted into the first inner covering layer (310).

4. A PPR pipe all-plastic sealing joint assembly according to any one of claims 1-3, characterized in that, The external threaded plastic fitting (300) further includes a first outer covering layer (320), which is connected to the first inner covering layer (310), and the first outer covering layer (320) abuts against the outer wall of the external threaded insert (100).

5. The PPR pipe all-plastic sealing joint assembly according to claim 4, characterized in that, The first outer covering layer (320) and the first inner covering layer (310) are provided with a first water-stopping protrusion (330), and the inner and outer walls of the external threaded insert (100) are provided with a first water-stopping groove (120), and the first water-stopping protrusion (330) is inserted into the first water-stopping groove (120).

6. The PPR pipe all-plastic sealing joint assembly according to claim 4, characterized in that, It also includes a socket tube body (600), wherein the first outer covering layer (320) and the second inner covering layer (410) are respectively fixedly connected to the socket tube body (600).

7. The PPR pipe all-plastic sealing joint assembly according to claim 1, characterized in that, The fixed section (220) is provided with a second groove (221), and the second inner covering layer (410) is provided with a second protrusion (411), which is inserted into the second groove (221).

8. A PPR pipe all-plastic sealing joint assembly according to claim 7, characterized in that, The internally threaded plastic fitting (400) also includes a second outer covering layer (420), which is fixedly connected to the second inner covering layer (410), and the outer wall surface of the threaded segment (210) abuts against the second outer covering layer (420).

9. A PPR pipe all-plastic sealing joint assembly according to claim 8, characterized in that, The outer wall of the threaded section (210) is provided with a second water-stop groove (211), and the second outer covering layer (420) is provided with a second water-stop protrusion (421), which is inserted into the second water-stop groove (211).

10. A PPR pipe all-plastic sealing joint assembly according to any one of claims 7-9, characterized in that, The fixed section (220) has a plurality of anti-rotation grooves (222) on the side away from the second groove (221), and the second inner covering layer (410) is connected to the anti-rotation grooves (222).

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