Metal pipe joint structure for plastic-lined metal pipe processing and matching diameter-reducing die

Abstract

A metal pipe joint structure for plastic-lined metal pipe processing, comprising at least two thin-walled metal pipes, wherein each thin-walled metal pipe has a reduced-diameter section integrally formed at one end, a necking chamfer being formed between the reduced-diameter section and the thin-walled metal pipe, and said thin-walled metal pipe has an internal chamfer matching the necking chamfer formed at the other end; in a connected state, the reduced-diameter section of one thin-walled metal pipe is inserted into the end of the adjacent thin-walled metal pipe having the internal chamfer, and the corresponding necking chamfer and internal chamfer of the two adjacent thin-walled metal pipes are fitted against each other. The present joint structure allows a joint section to remain directly in a finished plastic-lined metal pipe, thereby eliminating the need to discard the joint section and avoiding waste caused by scrap disposal.

Description

Metal pipe fitting structure and matching diameter reduction mold for processing plastic-lined metal pipes Technical Field

[0001] This utility model belongs to the field of plastic and metal composite pipe processing technology. More specifically, it relates to a production process for a continuously produced plastic-lined thin-walled metal composite pipe, which is a structural improvement of connecting the two metal pipes during production. Background Technology

[0002] In the existing manufacturing process of plastic-lined thin-walled metal composite pipes, as shown in Figure 1, two metal pipes are connected together by a double-ended internal support plastic connector. This double-ended internal support plastic connector is a disposable process component, which is cut off when the composite pipe is cut to length after cooling and shaping, and is discarded along with the external composite pipe section.

[0003] Because the composite pipe section discarded by this method is made of complex materials and difficult to separate, it can often only be treated as plastic waste, resulting in high process costs.

[0004] In summary, there is an urgent need for a new self-connecting pipe structure for metal pipes that can be directly embedded in the finished composite pipe, eliminating the need for fixed-length thin-walled metal pipes and allowing for free cutting of the composite pipe length.

[0005] Utility Model Content

[0006] In order to solve the above-mentioned technical problems, the purpose of this utility model is to provide a metal pipe connection structure for processing plastic-lined metal pipes and a matching diameter reduction mold.

[0007] As a first aspect, this utility model provides a metal pipe connection structure for processing plastic-lined metal pipes, including at least two thin-walled metal pipes. One end of each thin-walled metal pipe is integrally formed with a reduced diameter section, and a constriction chamfer is formed between the reduced diameter section and the thin-walled metal pipe. The other end of the thin-walled metal pipe is formed with an inner chamfer that matches the constriction chamfer. In the connected state, the reduced diameter section of the thin-walled metal pipe is inserted into the end of the adjacent thin-walled metal pipe with the inner chamfer, and the constriction chamfers and inner chamfers of the two adjacent thin-walled metal pipes fit together.

[0008] According to this utility model, the outer diameter of the reduced diameter section corresponds to the inner diameter of the thin-walled metal tube, thereby achieving a transitional fit connection between two adjacent thin-walled metal tubes.

[0009] According to this utility model, the chamfer angle of the reduced diameter section is 15° to 45°, and the length of the reduced diameter section is 1 / 4 to 1 / 2 of the outer diameter of the thin-walled metal tube.

[0010] According to this utility model, the width of the inner chamfer is equal to the wall thickness of the thin-walled metal tube.

[0011] According to this utility model, the reduced diameter section is formed by cold extrusion compression process, and the inner and outer wall surfaces are flat.

[0012] As a second aspect, this utility model also provides a diameter reduction mold for processing diameter reduction sections, including a mold barrel and a mandrel assembled with the mold barrel; the inner cavity of the mold barrel includes a large mold barrel cavity, a flared mold barrel cavity, a small mold barrel cavity, and a positioning cavity formed sequentially along its axial direction; the mandrel has a free end and a positioning seat integrally formed with the free end, and is inserted into the cavity of the mold barrel from one end of the positioning cavity, with the positioning seat and the positioning cavity transitionally fitted to achieve transitional assembly of the mandrel and the mold barrel.

[0013] According to this utility model, further, the inner diameter of the large cavity of the mold barrel is 0.2mm to 2mm larger than the outer diameter of the thin-walled metal tube; the inclination angle of the flared cavity of the mold barrel is consistent with the constriction angle of the constriction section of the thin-walled metal tube; the small cavity of the mold barrel forms a taper, and the transition point with the flared cavity of the mold barrel is the large diameter; the large diameter of the small cavity of the mold barrel is consistent with the outer diameter of the constriction section.

[0014] According to this utility model, the taper of the small cavity of the mold barrel is 1:8 to 1:32.

[0015] According to this utility model, the free end face of the mandrel extends beyond the large diameter end of the horn cavity of the mold barrel, forming a uniform annular cavity; the free end is cylindrical, and its outer diameter is 0.2mm to 2mm smaller than the inner diameter of the reduced diameter section.

[0016] According to this utility model, the free end of the mandrel is an inverted frustum shape, with its open end being the larger diameter and its taper being 1:8 to 1:32. When the diameter reduction mold is withdrawn, it expands to compensate for the elastic deformation of the metal and smooths the outer wall surface of the diameter reduction section.

[0017] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0018] 1. This utility model relates to a self-connection method for thin-walled metal pipes. Because the metal pipe wall is very thin, only 0.2mm to 0.5mm, and a self-reducing, transition-fitting socket-type connecting pipe is used, it satisfies the requirement for continuous and stable connection of thin-walled metal pipes in continuous production of plastic-lined metal pipes. This does not affect the outer diameter of the plastic-lined metal pipe, nor does it significantly affect its bore diameter. The connecting pipe section can be directly retained in the finished plastic-lined metal pipe, thus eliminating the waste of discarding the connecting pipe section; it eliminates the requirement for the thin-walled metal pipe to be used to a fixed length based on the finished pipe length; and it allows for free cutting of the finished pipe to the desired length.

[0019] 2. The radial reduction of the thin-walled metal tube's constricted section in this invention is only twice the wall thickness, and the reduction length is only 1 / 4 to 1 / 2 of the tube diameter. Therefore, the constriction mold is simple, the constriction process is convenient, and the stability is good. This metal tube connection structure has a short connection time, does not increase additional working hours, and does not affect production efficiency.

[0020] 3. The diameter reduction mold of this utility model is pre-formed into a diameter reduction section by cold extrusion molding of a diameter reduction mold with a matching mandrel in the mold barrel, and the outer wall surface of the diameter reduction section is flattened by expanding the inverted frustum structure at the free end to compensate for the elastic deformation of the metal. Attached Figure Description

[0021] Figure 1 is a schematic diagram of a bimetallic tube connection structure in the prior art;

[0022] Figure 2a is a schematic diagram of the metal pipe connection structure processed by the plastic-lined metal pipe of this utility model.

[0023] Figure 2b is a magnified view of part A in Figure 2a;

[0024] Figure 3 is a schematic diagram of the reduced diameter section structure of the metal pipe connector structure processed by the plastic-lined metal pipe of this utility model.

[0025] Figure 4 is a schematic diagram of the inner chamfer structure of the metal pipe connecting structure processed by the plastic-lined metal pipe of this utility model.

[0026] Figure 5 is a schematic diagram of the diameter reduction mold of this utility model.

[0027] The reference numerals in the attached drawings are as follows: 1-copper-lined tube, 2-thin-walled copper tube, 21-reduced diameter section, 22-inner chamfer, 3-mold barrel, 31-large cavity of mold barrel, 32-flare cavity of mold barrel, 33-small cavity of mold barrel, 34-positioning cavity, 4-core rod, 41-free end, 42-positioning seat. Detailed Implementation

[0028] The technical solution of this utility model will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of this utility model will become clearer from the following description. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of this utility model.

[0029] Please refer to Figures 2a to 5. A metal pipe connection structure for processing plastic-lined metal pipe is provided. A reduced diameter section 21 is pre-formed at one end of the thin-walled metal pipe by cold extrusion molding with a matching mandrel. The reduced diameter section 21 forms a chamfer with the thin-walled metal pipe, with a chamfer angle of 15° to 45°. The outer diameter of the reduced diameter section 21 corresponds to the inner diameter of the thin-walled metal pipe. The length of the reduced diameter section 21 is 1 / 4 to 1 / 2 of the outer diameter of the thin-walled metal pipe. It is formed by cold extrusion compression molding, and the inner and outer wall surfaces are smooth. At the other end of the thin-walled metal pipe, an inner chamfer 22 is pre-formed to match the chamfer of the reduced diameter section of another thin-walled metal pipe. The width of the inner chamfer 22 is the entire wall thickness. It is machined by cutting to remove burrs. The reduced diameter section 21 at one end of a thin-walled metal tube is inserted into the end of another thin-walled metal tube with an inner chamfer 22. After being inserted to the bottom, a stable connection is achieved, where the reduced diameter section 21 of one thin-walled metal tube transitions with the inner diameter of the other thin-walled metal tube, and the chamfer of the reduced diameter section of one thin-walled metal tube is flush with the inner chamfer 22 of the other thin-walled metal tube.

[0030] The reducing mold required for the diameter reduction section 21 consists of a mold barrel 3 and a mandrel 4. The inner cavity of the mold barrel 3 is divided into a cylindrical large cavity 31, a middle mold barrel flared cavity 32, a small cavity 33, and a bottom positioning cavity 34. The inner diameter of the large cavity 31 is 0.2mm to 2mm larger than the outer diameter of the thin-walled metal tube. The inclination angle of the mold barrel flared cavity 32 is consistent with the reducing angle of the diameter reduction section of the thin-walled metal tube. The small cavity 33 forms a taper, and the transition point with the mold barrel flared cavity 32 is the large diameter. The large diameter of the small cavity 33 is consistent with the outer diameter of the diameter reduction section 21. The taper of the small cavity 33 is 1:8 to 1:32. The mold barrel 3 and the mandrel 4 are installed through a transition fit via the positioning cavity 34 of the mold barrel and the positioning seat 42 of the mandrel. The end of the mandrel 4 facing the large cavity 31 of the mold barrel is a free end 41, with a rounded end of 1mm to 3mm and an end face extending 3mm to 6mm beyond the large end of the flared cavity 32 of the mold barrel, forming a uniform annular cavity. The free end 41 is cylindrical, with an outer diameter 0.2mm to 2mm smaller than the inner diameter of the reduced diameter section 21. After the thin-walled metal tube is reduced by the reducing mold, it relies on the springback of the residual metal elastic deformation to pre-form a reduced diameter section with the required smooth inner and outer wall surfaces. When needed, the free end 41 of the mandrel is a frustum-shaped inverted cone with a large diameter at the opening and a taper of 1:8 to 1:32. When the reducing mold is withdrawn, it expands to compensate for the springback of the metal elastic deformation, thus achieving the required smooth inner and outer wall surfaces of the reduced diameter section.

[0031] Example:

[0032] A connecting structure for a thin-walled copper tube 2 produced continuously from polypropylene (PP-R) lined copper pipe (hereinafter referred to as PP-R lined copper pipe) 1 is disclosed, used for the self-connection of two thin-walled copper pipe 2 sections in the continuous production process of PP-R lined copper pipe 1. The outer diameter of the thin-walled copper pipe 2 is 10mm to 50mm, and its wall thickness is 0.2mm to 0.5mm. One end of the thin-walled copper pipe 2 is pre-formed into a reduced-diameter section 21 by cold extrusion molding using a die barrel 3 and a mandrel 4, and the other end is pre-formed with an inner chamfer 22. A reduced-diameter section 21 and the thin-walled copper pipe 1 form a reduced-diameter chamfer a1 with an angle of 15° to 45°; the outer diameter d1 of the reduced-diameter section 21 and the inner diameter D of the pipe are in a transition fit; the length L of the reduced-diameter section 21 is 1 / 4 to 1 / 2 of the outer diameter d of the thin-walled copper pipe 2; the reduced-diameter section 21 is formed by cold extrusion compression molding, and the inner and outer wall surfaces are smooth. The angle a2 of the inner chamfer 22 corresponds to and matches the chamfer angle of the reduced diameter section 21 of the other thin-walled copper tube 2; the width of the inner chamfer 22 is the entire wall thickness, and it is machined by cutting to remove burrs. The reduced diameter section 21 at one end of the thin-walled copper tube 2 is inserted into the end of the other thin-walled copper tube 2 with the inner chamfer 22. After being fully inserted, a stable connection is achieved where the inner diameter transition of the reduced diameter section 21 of one thin-walled metal tube is flush with that of the other thin-walled copper tube 2, and the chamfer of the reduced diameter section of one thin-walled copper tube 2 is flush with the inner chamfer 22 of the other thin-walled copper tube 2.

[0033] The reducing mold required for the diameter reduction section 21 consists of a mold barrel 3 and a mandrel 4. The inner cavity of the mold barrel 3 is divided into a cylindrical large cavity 31, a middle mold barrel flared cavity 32, a small cavity 33, and a bottom positioning cavity 34. The inner diameter D2 of the large cavity 31 is 0.2mm to 2mm larger than the outer diameter d of the thin-walled copper tube 2. The inclination angle a3 of the flared cavity 32 is consistent with the reduction angle a1 of the diameter reduction section 21 of the thin-walled copper tube 2. The small cavity 33 forms a taper, and the transition point with the flared cavity 32 is the large diameter D3. The large diameter D3 of the small cavity is consistent with the outer diameter d1 of the diameter reduction section 21. The taper of the small cavity 33 is 1:8 to 1:32. The mold barrel 3 and the mandrel 4 are installed through a transition fit via the positioning cavity 34 of the mold barrel 3 and the positioning seat 42 of the mandrel 4. The end of the mandrel 4 facing the large cavity 31 of the mold barrel is a free end 41, with the opening rounded by 1mm to 3mm, and the end face extending 3mm to 6mm beyond the large end of the horn cavity 32, forming a uniform annular cavity. The free end 41 is cylindrical, and its outer diameter d2 is 0.2mm to 2mm smaller than the inner diameter D1 of the reduced diameter section 21. After the thin-walled copper tube 2 is reduced by the reducing mold, it relies on the springback of the residual metal elastic deformation to pre-form the required reduced diameter section 21 with smooth inner and outer wall surfaces. When needed, the free end 41 of the mandrel 4 is a frustum-shaped inverted cone, with its opening being the large diameter and its taper being 1:8 to 1:32. When the reducing mold is withdrawn, it expands to compensate for the springback of the metal elastic deformation, thus achieving the required smooth inner and outer wall surfaces of the reduced diameter section 21.

[0034] The working principle of this utility model is as follows: This metal pipe connector structure is suitable for connecting thin-walled metal pipes in the continuous production of plastic-lined metal pipes. One end of the thin-walled metal pipe is pre-formed into a reduced-diameter section by cold extrusion molding using a reducing die, so that its outer diameter dimension transitions with the inner diameter dimension of the pipe, and the inner and outer wall surfaces are smooth. An inner chamfer is pre-formed at the other end of the thin-walled metal pipe, matching the reduction angle of the reduced-diameter section of another thin-walled metal pipe. The reduced-diameter section of one thin-walled metal pipe is inserted into the end of another thin-walled metal pipe with the inner chamfer. After being fully inserted, a stable connector is achieved with a smooth transition between the two pipes and the inner chamfer and the reduced-diameter chamfer interface are flush.

[0035] This metal pipe connection structure is a self-connection of thin-walled metal pipes. Simultaneously, due to the very thin wall thickness of the metal pipe (only 0.2mm to 0.5mm), and the use of a self-reducing, transitional fit socket connection, it satisfies the requirement for continuous and stable connection of thin-walled metal pipes in the continuous production of plastic-lined metal pipes. This does not affect the outer diameter of the plastic-lined metal pipe, nor does it significantly affect its nominal diameter. Therefore, the connecting pipe section can be directly retained in the finished plastic-lined metal pipe, eliminating the waste of discarding the connecting pipe section; it eliminates the need for the thin-walled metal pipe to be used to a fixed length based on the finished pipe length; and the finished pipe length can be freely cut.

[0036] The radial reduction of the thin-walled metal pipe section required by this metal pipe connection method is only twice the wall thickness, and the reduction length is only 1 / 4 to 1 / 2 of the pipe diameter. Therefore, the reduction mold is simple, the reduction process is convenient, and the stability is good. This metal pipe connection method can also be completed within the processing time of one metal pipe length, without increasing extra working time or affecting production efficiency.

[0037] The above description is only a description of the preferred embodiment of the present utility model and is not intended to limit the scope of the present utility model in any way. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the protection scope of the claims.

Claims

1. A metal pipe joint structure for a plastic-lined metal pipe process, characterized by, It includes at least two thin-walled metal tubes, each of which has a reduced diameter section integrally formed at one end, and a constricted chamfer is formed between the reduced diameter section and the thin-walled metal tube. The other end of the thin-walled metal tube has an inner chamfer that matches the constricted chamfer. In the connected state, the reduced diameter section of the thin-walled metal tube is inserted into the end of the adjacent thin-walled metal tube with the inner chamfer, and the constricted chamfers and inner chamfers of the two adjacent thin-walled metal tubes fit together.

2. The plastic-lined metal pipe processed metal pipe joint structure according to claim 1, wherein, The outer diameter of the reduced diameter section corresponds to the inner diameter of the thin-walled metal tube, enabling a transitional fit connection between two adjacent thin-walled metal tubes.

3. The plastic-lined metal pipe processed metal pipe joint structure according to claim 1 or 2, wherein The chamfer angle of the reduced diameter section is 15° to 45°, and the length of the reduced diameter section is 1 / 4 to 1 / 2 of the outer diameter of the thin-walled metal tube.

4. The plastic-lined metal pipe processed metal pipe joint structure according to Claim 1, wherein The width of the inner chamfer is equal to the wall thickness of the thin-walled metal tube.

5. The plastic-lined metal pipe fabricated metal pipe nipple structure as recited in claim 1, wherein, The reduced diameter section is formed by cold extrusion compression process, and the inner and outer wall surfaces are smooth.

6. A reducing die for machining a reducing section, characterized in that, It includes a mold barrel and a mandrel assembled with the mold barrel; the inner cavity of the mold barrel includes a large mold barrel cavity, a flared mold barrel cavity, a small mold barrel cavity and a positioning cavity formed sequentially along its axial direction; the mandrel has a free end and a positioning seat integrally formed with the free end, and is inserted into the cavity of the mold barrel from one end of the positioning cavity, with the positioning seat and the positioning cavity transitionally fitted to achieve transitional assembly of the mandrel and the mold barrel.

7. The reducing die of claim 6 wherein, The inner diameter of the large cavity of the mold barrel is 0.2mm to 2mm larger than the outer diameter of the thin-walled metal tube; the inclination angle of the flared cavity of the mold barrel is consistent with the constriction angle of the constriction section of the thin-walled metal tube; the small cavity of the mold barrel forms a taper, and the transition point with the flared cavity of the mold barrel is the large diameter; the large diameter of the small cavity of the mold barrel is consistent with the outer diameter of the constriction section.

8. The reducing die of claim 7 wherein, The taper of the small cavity of the mold barrel is 1:8 to 1:

32.

9. The reducing die of claim 6 wherein, The free end face of the mandrel extends beyond the large diameter end of the horn cavity of the mold barrel, forming a uniform annular cavity; the free end is cylindrical, and its outer diameter is 0.2mm to 2mm smaller than the inner diameter of the narrowed section.

10. The reducing die of claim 6 wherein, The free end of the mandrel is an inverted frustum shape, with its open end being the larger diameter and its taper being 1:8 to 1:

32. When the diameter reduction mold is withdrawn, it expands to compensate for the elastic deformation of the metal and smooths the outer wall surface of the diameter reduction section.

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