Double-walled plastic corrugated pipe

Abstract

Double-walled plastic corrugated pipe, wherein the double-walled plastic corrugated pipe comprises an inner wall and an outer wall, characterized in that the double-walled plastic corrugated pipe has a main pipe section, wherein a transition pipe section is connected to each of the two ends of the main pipe section and a solid-wall pipe section is connected to the outer end of each transition pipe section, wherein in the main pipe section the wave crest height of the outer wall is constant, the wave spacing is constant and the outer wall thickness is constant, and in the direction from the main pipe section to the solid-wall pipe section in the transition pipe section the wave crest height of the outer wall gradually decreases, the wave spacing gradually decreases and the outer wall thickness gradually increases.

Description

Technical field

[0001] The present invention belongs to the technical field of plastic pipes and relates in particular to a double-walled corrugated plastic pipe. State of the art

[0002] HDPE, short for "High Density Polyethylene," is a thermoplastic resin with high crystallinity and non-polar properties. It is used to manufacture plastic pipes. Compared to conventional pipe materials such as cast iron and galvanized steel, HDPE plastic pipes offer significant advantages, including low weight, corrosion resistance, low flow resistance, energy savings, easy and quick installation, and lower costs. Therefore, they are the preferred material in pipeline construction and are increasingly replacing conventional double-walled corrugated plastic pipes.

[0003] Currently, most double-walled corrugated pipes on the market are formed by extrusion using high-density polyethylene as the main raw material, with a smooth inner wall and a corrugated outer wall. In ordinary double-walled corrugated pipes, the crest height of adjacent corrugations on the outer wall is generally unchanged, as is the corrugation spacing. They can be broadly divided into two main types: double-walled corrugated pipes with sockets (push-fit connections) and double-walled corrugated pipes without sockets. The state of the art is that corrugated pipes can generally withstand higher external pressures, but rarely higher internal pressures. Furthermore, double-walled corrugated pipes manufactured using state-of-the-art technology are uniform in their design, and production costs are high.

[0004] Common connection types between double-walled plastic corrugated pipes are a clamp connection, a heating element welding connection and a push-fit connection.

[0005] In a clamp connection, the pipes to be joined are clamped together using a clamp; it is typically used for connecting double-walled corrugated pipes without a socket. Although clamp connections offer good stability and tightness, the price of individual clamp components is relatively high.

[0006] In a push-fit connection, a double-walled corrugated pipe without a socket is inserted into the socket (push-fit socket) of a double-walled corrugated pipe with a socket. A sealing ring is provided between the socket and the push-fit end to prevent leaks at the connection point. However, with previously known double-walled plastic corrugated pipes with sockets, assembly during insertion is difficult, and problems such as cracking at the socket can easily occur. Furthermore, the sealing ring tends to age with increasing use, which can easily lead to loosening of the pipe connection and leakage of fluid. In addition, the manufacture of double-walled plastic corrugated pipes with sockets requires cutting off a section in the socket area according to the installation dimensions; the cut-off section must be disposed of as waste, resulting in material waste.

[0007] Hot plate welding essentially comprises socket welding and butt welding. In this process, the two pipes to be joined are each heated to a molten state using a heating element and then joined, thus creating a single unit from two double-walled corrugated plastic pipes. Hot plate welding results in a high fusion density and strength, offering a high degree of joint reliability. However, it places high demands on the wall thickness of the double-walled corrugated plastic pipe in the weld area; if the wall thickness is too thin, cracking can easily occur, or the weld may not be reliable. Content of the present invention

[0008] The technical problem underlying the present invention is to provide a double-walled plastic corrugated pipe in which the wall thickness in the connection area of ​​the double-walled plastic corrugated pipe is increased so that the connection of the double-walled plastic corrugated pipe is reliable.

[0009] A double-walled plastic corrugated pipe, wherein the double-walled plastic corrugated pipe comprises an inner wall and an outer wall, characterized in that that the double-walled plastic corrugated pipe has a main pipe section, wherein a transition pipe section is connected to each of the two ends of the main pipe section and a solid wall pipe section is connected to the outer end of each transition pipe section, wherein in the main pipe section the wave crest height of the outer wall is constant, the wave spacing is constant and the outer wall thickness is constant, and wherein in the direction from the main pipe section to the solid wall pipe section in the transition pipe section the wave crest height of the outer wall gradually decreases, the wave spacing gradually decreases and the outer wall thickness gradually increases.

[0010] Preferably, the inner wall thickness of the double-walled plastic corrugated pipe is the same in the main pipe section, in the transition pipe section and in the solid wall pipe section.

[0011] Preferably, in the transition pipe section, the inner wall thickness of the double-walled plastic corrugated pipe increases gradually, and in the solid-wall pipe section, the inner wall thickness of the double-walled plastic corrugated pipe is greater than the inner wall thickness in the transition pipe section and the inner wall thickness in the main pipe section.

[0012] Preferably, two adjacent double-walled plastic corrugated tubes are joined together by butt welding using a heating element, with one end section of the solid wall tube section being designed as the welding end.

[0013] In comparison to the prior art, the present invention has the following advantageous effects: 1) The double-walled corrugated plastic pipe has a main pipe section with a transition pipe section connected to each end of the main pipe section. A solid-wall pipe section is connected to the outer end of each transition pipe section. When joining the double-walled corrugated plastic pipe, one end of the solid-wall pipe section serves as the welding interface for a hot-plate or electrofusion welding process. This connection exhibits good weldability and is not prone to cracking. The weld is reliable, and the weld seam formed by hot-plate butt welding is not easily separated due to ground movement or load-bearing effects. Furthermore, the welding process is simple, assembly is convenient, the quality of the pipe connection is high, no additional fittings are required, and the overall project costs are low.This solves the problems existing in the prior art of corrugated pipe assembly, namely low connection strength and aging of sealing rings. 2) The outer wall of the main pipe section features annular corrugations, thus retaining the advantages of conventional corrugated pipes, particularly low weight, high pressure resistance, high toughness, high vibration and shock resistance, and high external pressure resistance. Due to the increased outer wall thickness of the solid-wall pipe section, its strength is higher than that of conventional corrugated pipes, and good resistance to internal and external pressure is achieved. In the transition pipe section, the corrugation spacing of the outer wall gradually decreases, the crest height gradually decreases, and the outer wall thickness gradually increases, resulting in a gradual transition to a double-walled solid-wall pipe structure without corrugations. This combines the advantages of the main pipe section and the solid-wall pipe section, while simultaneously achieving a beneficial transition effect, thus resulting in good overall annular flexibility.Consequently, the double-walled plastic corrugated pipe can withstand both higher external and higher internal pressures simultaneously and offers the advantages of low weight, high pressure resistance, high toughness, high vibration and shock resistance, and overall good ring flexibility.

[0014] In summary, the increased wall thickness of the solid-wall pipe section ensures a reliable connection of the double-walled plastic corrugated pipe, allowing the double-walled plastic corrugated pipe to withstand both higher external and higher internal pressures, while also offering the advantages of low weight, high pressure resistance, high toughness, high vibration and shock resistance, and overall good ring flexibility. Brief description of the characters Fig. Figure 1 is a schematic structural representation of the double-walled plastic corrugated tube according to the first embodiment of the present invention; Fig. Figure 2 is a schematic structural representation of the double-walled plastic corrugated tube according to the second embodiment of the present invention.

[0015] In the figures a - inner wall, b - outer wall, 1 - main pipe section, 2 - transition pipe section, 3 - solid wall pipe section, T1 - wave spacing, T2 - wave spacing, H1 - wave crest height, H2 - wave crest height. Detailed descriptions

[0016] The technical solution of the present invention is described in detail below with reference to the figures and specific embodiments in order to further clarify the purpose, solution and effect of the present invention; however, this does not serve as a limitation of the scope of protection of the attached claims of the present invention. Example 1

[0017] Fig. Figure 1 is a schematic structural representation of the double-walled plastic corrugated pipe according to the first embodiment of the present invention. The double-walled plastic corrugated pipe comprises an inner wall a and an outer wall b. The double-walled plastic corrugated pipe has a main pipe section 1, a transition pipe section 2, and a solid-wall pipe section 3, with a transition pipe section 2 being connected to each end of the main pipe section 1 and a solid-wall pipe section 3 being connected to the outer end of each transition pipe section 2. In the main pipe section 1, the corrugation height H1 of the outer wall b is the same, the corrugation spacing T1 is the same, and the outer wall thickness is constant. In the transition pipe section 2, in the direction from the main pipe section 1 to the solid-wall pipe section 3, the corrugation height H2 of the outer wall gradually decreases, the corrugation spacing T2 gradually decreases, and the outer wall thickness of the outer wall b gradually increases.The inner wall thickness (a) of the double-walled plastic corrugated pipe is the same in the main pipe section 1, the transition pipe section 2, and the solid-wall pipe section 3. The main pipe section 1 retains the advantages of conventional corrugated pipes, in particular low weight, high pressure resistance, high toughness, high vibration and shock resistance, and high external pressure resistance. Due to the increased outer wall thickness (b) in the solid-wall pipe section 3, its strength is higher than that of conventional corrugated pipes, and good resistance to internal and external pressure is achieved. In the transition pipe section 2, the corrugation spacing (T2) of the outer wall (b) gradually decreases, the crest height (H2) gradually decreases, and the outer wall thickness (b) gradually increases, thus transitioning into a double-walled solid-wall pipe structure (3) without corrugations.This allows the transition pipe section 2 to combine the advantages of the main pipe section 1 and the solid-wall pipe section 3, achieving a beneficial transition effect and resulting in good overall ring flexibility. Consequently, the double-walled corrugated plastic pipe can withstand both higher external and higher internal pressures simultaneously and offers the advantages of low weight, high pressure resistance, high toughness, high vibration and shock resistance, and overall good ring flexibility.

[0018] Two adjacent double-walled corrugated plastic pipes are joined by butt welding using a hot plate, with one end section of the solid-wall pipe section serving as the weld end. Specifically, when joining double-walled corrugated pipes with a length L1, one end section of the solid-wall pipe section 3 at one end of a double-walled corrugated pipe is butt-welded to the other end section of the solid-wall pipe section 3 at the end of another double-walled corrugated pipe, resulting in a reliable connection. The weld formed by butt welding is resistant to soil movement or traffic loads. Furthermore, the welding process is simple, assembly is convenient, the quality of the pipe connection is high, no additional fittings are required, and the overall project costs are low.

[0019] With conventional double-walled corrugated plastic pipes with sockets, it is necessary to cut off a section in the socket area according to the connection parameters to create a push-fit socket connection. However, since in the present embodiment, a butt welding process is used to join two adjacent double-walled corrugated plastic pipes, the creation of a socket structure is not required. Accordingly, it is also not necessary to cut off excess material in the socket area during the manufacturing of the double-walled corrugated plastic pipe, thus shortening the production cycle and simplifying the cutting process. Example 2

[0020] Exemplary embodiment 2 differs from exemplary embodiment 1 in that, as in Fig.As shown in Figure 2, the inner wall thickness a of the double-walled corrugated plastic pipe gradually increases in transition pipe section 2 and solid-wall pipe section 3. The increase in inner wall thickness a begins in transition pipe section 2, where the inner and outer walls are thickened uniformly, forming an angle α, thus gradually transitioning into solid-wall pipe section 3. This results in a thickened solid-wall pipe section, significantly improving properties such as weldability, pressure resistance, and crack resistance.

[0021] The two double-walled corrugated pipes according to embodiments 1 and 2 are used as follows: The double-walled corrugated pipe according to embodiment 1 is suitable for applications where there are no stringent requirements for pipe performance, such as secondary lines, where the individual sections of the double-walled corrugated pipe are manufactured at a constant speed during forming. This is achieved by calculating the corrugation shape to ensure that the amount of material (volume) within the corrugation per unit length of the pipe remains strictly constant, thus enabling constant manufacturing speed. The double-walled plastic corrugated pipe according to embodiment 2 is suitable for main lines where there are stringent requirements for pipe performance.Since the inner and outer walls change simultaneously in the transition pipe section, a process with a consistently variable production speed is required for forming the double-walled plastic corrugated pipe. By appropriately combining the two double-walled plastic corrugated pipes according to embodiments 1 and 2, the advantages of reliable performance and low overall project costs can be achieved.

[0022] The present invention is not limited to the embodiments described above. All improvements based on the idea, principles, structure, and methods of the present invention fall within the scope of protection of the present invention.

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