Double-wall corrugated pipe forming die

Abstract

The present invention relates to a double-wall corrugated pipe forming die, which comprises a feeding spiral part, an intermediate heating part and a discharging die part arranged in sequence from front to back. The intermediate heating part includes an inner pipe, an intermediate pipe and an outer pipe sleeved in sequence from inside to outside; the discharging die part includes an inner core die, an intermediate core die and an outer die sleeve sleeved in sequence from inside to outside. The inner core die and the intermediate core die define an inner discharging channel, and the intermediate core die and the outer die sleeve define an outer discharging channel. The inner discharging channel and the outer discharging channel respectively have an inner annular discharging port and an outer annular discharging port; the intermediate core die is fixedly connected to the intermediate pipe. The inner core die includes an inner core main body fixedly connected to the inner pipe and an inner core mouth part defining the rear boundary of the inner annular discharging port. The inner core mouth part and the inner core main body form a thread connection that can move in the front-rear direction to adjust the width of the inner annular discharging port. The outer die sleeve and the outer pipe form a thread connection that can move in the front-rear direction to adjust the width of the outer annular discharging port.

Description

Technical Field

[0001] The present invention relates to the field of plastic extrusion, and more particularly to a double-wall corrugated pipe forming die. Background Art

[0002] The double-wall corrugated pipe has an outer wall with an annular structure and a smooth inner wall. Due to its physical and chemical characteristics such as strong external pressure resistance, low engineering cost, light weight, small friction coefficient, and low temperature resistance, it is increasingly widely used in related fields such as water supply and drainage, sewage discharge, and exhaust.

[0003] The double-wall corrugated pipe forming die is used for the preliminary forming of the double-wall corrugated pipe. It generally includes an outer die assembly for forming the outer wall of the double-wall corrugated pipe and an inner die assembly for forming the inner wall of the double-wall corrugated pipe. The inner die assembly defines an inner discharge channel with an inner annular discharge port, and the outer die assembly defines an outer discharge channel with an outer annular discharge port. The widths of the inner and outer annular discharge ports determine the widths of the inner and outer walls of the formed double-wall corrugated pipe.

[0004] Based on the following facts and problems, the present invention is proposed: The inner die assembly of the traditional double-wall corrugated pipe forming die includes an inner core die and an inner mouth die, and the outer die assembly includes an outer core die and an outer mouth die. Both the inner and outer mouth dies include a main body part and a mouth part that can move back and forth relative to the main body part (for adjusting the widths of the inner and outer discharge ports). The number of components is large and the connection structure is relatively complex, so the processing and assembly costs are relatively high. In addition, due to the large accumulated processing deviations of each component, there may be situations such as irregular inner and outer annular discharge ports and offset of the axis lines of each component, making it difficult to adjust the widths of the inner and outer annular discharge ports (i.e., adjust the inner and outer wall thicknesses of the formed double-wall corrugated pipe) and difficult to adjust the eccentricity. Summary of the Invention

[0005] Therefore, the object of the present invention is to provide a double-wall corrugated pipe forming die with fewer components, a relatively simple structure, and easy adjustment of the widths of the inner and outer annular discharge ports.

[0006] To achieve the above object, the present invention provides the following technical solution: A double-wall corrugated pipe forming die, which defines a longitudinally extending axis line extending from front to back and includes a feeding spiral part, an intermediate heating part, and a discharging die part arranged in sequence from front to back. The intermediate heating part includes an inner pipe, an intermediate pipe, and an outer pipe sleeved from inside to outside in sequence. The inner pipe and the intermediate pipe jointly define an inner heating channel, and the intermediate pipe and the outer pipe jointly define an outer heating channel. The discharging die part includes an inner core die, an intermediate core die, and an outer die sleeve sleeved from inside to outside in sequence. The inner core die and the intermediate core die jointly define an inner discharging channel connected to the inner heating channel, and the intermediate core die and the outer die sleeve jointly define an outer discharging channel connected to the outer heating channel. The inner discharging channel and the outer discharging channel respectively have an inner annular discharging port and an outer annular discharging port. The inner annular discharging port and the annular discharging port respectively have a first width and a second width in the front-rear direction. The intermediate core die is fixedly connected to the intermediate pipe. The inner core die includes an inner core main body fixedly connected to the inner pipe and an inner core mouth part defining the rear boundary of the inner annular discharging port. The inner core mouth part and the inner core main body form a threaded connection that can move in the front-rear direction to adjust the first width. The outer die sleeve and the outer pipe form a threaded connection that can move in the front-rear direction to adjust the second width.

[0007] In the above technical solution, preferably, the inner core main body has a first annular inclined surface formed on the outer wall. The inner core mouth part has a second annular inclined surface formed on the outer wall and adjacent to the first annular inclined surface. The intermediate core die has a third annular inclined surface formed on the inner wall surface. The first annular inclined surface, the second annular inclined surface, and the third annular inclined surface all incline backward and outward and jointly define the inner discharging channel. Further preferably, the inner core mouth part is sleeved on the outside of the inner core main body. The inner core main body has a first annular contact surface formed on the outer wall and adjacent to the rear side of the first annular inclined surface. The first annular contact surface extends in the front-rear direction and is provided with a first thread. The inner core mouth part is formed with a second annular contact surface located on the inner wall. The second annular contact surface extends in the front-rear direction and is provided with a second thread adapted to the first thread.

[0008] In the above technical solution, preferably, the intermediate core mold has a fourth annular inclined surface formed on the outer wall, the outer die has a fifth annular inclined surface formed on the inner wall, and the outer discharge channel is defined by the fourth annular inclined surface and the fifth annular inclined surface. Further preferably, the outer tube has a third annular contact surface formed on the outer wall at the rear end, the third annular contact surface extends back and forth and is provided with a third thread, the outer die has a fourth annular contact surface formed on the inner wall and adjacent to the front side of the fifth annular inclined surface, and both the fourth annular inclined surface and the fifth annular inclined surface are inclined backward and outward and jointly define the outer discharge channel.

[0009] In the above technical solution, preferably, a plurality of first locking bolts arranged circumferentially around the longitudinal axis are provided on the inner core mouth or / and the inner core body, and each of the first locking bolts can move along the radial direction and has a first locking position for fixing the inner core mouth and a first release position for allowing the inner core mouth to move back and forth.

[0010] In the above technical solution, preferably, a plurality of second locking bolts arranged circumferentially around the longitudinal axis are provided on the outer die or / and the outer tube, and each of the second locking bolts can move along the radial direction and has a second locking position for fixing the outer die and a second release position for allowing the outer die to move back and forth.

[0011] In the above technical solution, preferably, a concentricity adjusting mechanism is further provided on the intermediate heating part. The concentricity adjusting mechanism includes a plurality of first adjusting bolts that can apply pressure to the intermediate tube and a plurality of second adjusting bolts that can apply force to the inner tube. The plurality of first adjusting bolts and the plurality of second adjusting bolts are both arranged circumferentially around the longitudinal axis. Further preferably, a plurality of first threaded grooves adapted to the plurality of first adjusting bolts are formed on the outer tube, and each of the first adjusting bolts is threadedly connected to the corresponding first threaded groove and the bottom of each first adjusting bolt abuts against the intermediate tube. Further preferably, a plurality of second threaded grooves adapted to the plurality of second adjusting bolts are formed on the outer tube, a plurality of flat grooves are formed on the intermediate tube and are aligned with the plurality of second threaded grooves in the radial direction, and the concentricity adjusting mechanism further includes a plurality of sliding members located in the plurality of flat grooves. Each of the sliding members can move radially, and each of the second adjusting bolts is threadedly connected to the corresponding second threaded groove and the bottom of each second adjusting bolt abuts against the corresponding sliding member to apply pressure to the inner tube via the corresponding sliding member.

[0012] Compared with the prior art, the double-wall corrugated pipe forming die provided by the present invention only has an inner core die, an intermediate core die, an outer die at the discharge port and necessary connecting parts at the discharge port die part. Among them, both the intermediate core die and the outer die are integral structural parts. The number of components at the discharge port die part of the double-wall corrugated pipe forming die is small, the assembly is simple, the production and assembly costs can be reduced, and the difficulties in adjusting the width and eccentricity of the inner and outer annular discharge ports caused by the accumulation of component processing errors can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a side view of the double-wall corrugated pipe forming die provided by the present invention;

[0014] Figure 2 is Figure 1 a cross-sectional view of the double-wall corrugated pipe forming die shown along the A-A direction;

[0015] Figure 3 is Figure 2 a partial enlarged view of the B position shown;

[0016] Figure 4 is Figure 2 a partial enlarged view of the C position shown;

[0017] Figure 5 is Figure 1 a schematic side view of the concentricity adjustment mechanism of the double-wall corrugated pipe forming die shown;

[0018] Figure 6 is Figure 1 a cross-sectional view of the discharge port die part of the double-wall corrugated pipe forming die shown;

[0019] Figure 7 is Figure 6 a partial enlarged view of the D position shown.

[0020] Labels in the figure:

[0021] 100. Double-wall corrugated pipe forming die;

[0022] 1. Feed screw part; 11. Inner screw bushing; 111. First spiral groove; 112. Inner plasticizing channel;

[0023] 12. Outer screw bushing; 121. Second spiral groove; 122. Outer plasticizing channel;

[0024] 13. Outer limiting bushing; 14. End cover; 15. First feed pipe; 16. Second feed pipe;

[0025] 2. Intermediate heating section; 21. Inner tube; 22. Intermediate tube; 221. Flat groove; 23. Outer tube; 231. First thread groove; 232. Second thread groove; 233. Third annular contact surface; 24. Inner heating channel; 25. Outer heating channel; 26. First heating coil;

[0026] 3. Discharge port die section;

[0027] 31. Inner core die; 311. Inner core body; 312. Inner core opening; 313. First annular inclined surface; 314. Second annular inclined surface; 315. First annular contact surface; 316. Second annular contact surface; 317. First locking bolt;

[0028] 32. Intermediate core die; 321. Third annular inclined surface; 322. Fourth annular inclined surface;

[0029] 33. Outer die; 331. Fifth annular inclined surface; 332. Fourth annular contact surface;

[0030] 34. Inner discharge channel; 35. Outer discharge channel; 36. Second heating coil;

[0031] 41. First adjusting bolt; 42. Second adjusting bolt; 43. Sliding member;

[0032] Y. Longitudinal axis line. Detailed implementation manners

[0033] To describe in detail the technical content, structural features, achieved objectives and effects of the invention, the technical solutions in the embodiments of the present application will be described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. In the following description, for the purpose of explanation, many specific details are set forth to provide a detailed description of various exemplary embodiments or implementation modes of the invention. However, various exemplary embodiments can also be implemented without these specific details or in the case of one or more equivalent arrangements. In addition, various exemplary embodiments can be different, but do not have to be exclusive. For example, without departing from the inventive concept, the specific shapes, structures and characteristics of the exemplary embodiments can be used or implemented in another exemplary embodiment.

[0034] In addition, in the present application, spatial relative terms such as "under", "below", "beneath", "lower", "above", "upper", "on", "higher", "side" (e.g., as in "side wall") are used to describe the relationship between one element and another (other) element as shown in the drawings. The spatial relative terms are intended to include different orientations of the device in use, operation, and / or manufacture in addition to the orientation depicted in the drawings. For example, if the device in the drawings is flipped, an element described as "under" or "beneath" another element or feature will then be positioned "above" the other element or feature. Thus, the exemplary term "under" can include both upper and lower orientations. In addition, the device can be positioned otherwise (e.g., rotated 90 degrees or at other orientations), and accordingly, the spatial relative descriptors used herein are to be interpreted.

[0035] In the present invention, the term "head" means the most upstream end of a channel, groove, or solid part in terms of the flow direction of the material; the term "tail" means the most downstream end of a channel, groove, or solid part in terms of the flow direction of the material.

[0036] Figure 1-2 The double-wall corrugated pipe forming die 100 (hereinafter referred to as the forming die) provided by the present invention is shown. The forming die 100 is adjacent to the downstream of a corresponding extruder to receive molten corrugated pipe material (including inner wall material and outer wall material). As shown in the figure, the forming die 100 defines a longitudinal axis Y extending in the front-rear direction and includes a feeding spiral part 1, an intermediate heating part 2, and a discharging die part 3 arranged in sequence along the longitudinal axis Y.

[0037] The feeding spiral part 1 is used to receive the molten corrugated pipe material and preliminarily plasticize and enhance the material. Figure 3 Combined with, the feeding spiral part 1 is fixedly supported on a frame 4. The feeding spiral part 1 includes an inner spiral sleeve 11, an outer spiral sleeve 12, and an outer defining sleeve 13 that are sleeved in sequence from the inside to the outside and all extend along the longitudinal axis Y. A plurality of first spiral grooves 111 extending in a spiral posture along the longitudinal axis Y are formed on the outer wall of the inner spiral sleeve 11. Each of the first spiral grooves 111 is configured such that the groove depth gradually decreases along the flow direction of the inner wall material. The inner spiral sleeve 11 and the outer spiral sleeve 12 jointly define an inner plasticizing channel 112. The plurality of first spiral grooves 111 form a part of the inner plasticizing channel 112. After the inner wall material enters the forming die 100, it is divided into multiple strands of material flows by the plurality of first spiral grooves 111 at the head of the inner plasticizing channel 112 and moves in a spiral shape. Then, the multiple strands of material flows merge into one strand at the tail of the plurality of first spiral grooves 111, thereby completing the preliminary enhanced plasticization of the material.

[0038] On the outer wall of the outer spiral shaft sleeve 12, a plurality of second spiral grooves 121 are formed, which extend spirally along the longitudinal axis Y. Each of the second spiral grooves 121 is configured such that the groove depth gradually decreases along the direction of material flow. The outer spiral shaft sleeve 12 and the outer limiting sleeve define an outer plasticizing channel 122, and these plurality of second spiral grooves 121 form a part of the outer plasticizing channel 122. Similarly, after the outer wall material enters the molding die 100, it is divided into strand flows by the plurality of second spiral grooves 121 at the head of the outer plasticizing channel 122 and moves spirally. Then, the multiple strand flows merge into one at the tail of the plurality of second spiral grooves 121, thereby completing the preliminary enhanced plasticization of the material.

[0039] Continue to refer to Figure 1 , the molding die 100 further includes an end cap 14, a first feed pipe 15, and a second feed pipe 16 provided at the feed spiral part 1. The end cap 14 is used to close the front parts of the inner spiral shaft sleeve 11, the outer spiral shaft sleeve 12, and the outer limiting shaft sleeve 13. The first and second feed pipes are respectively for the inner wall material and the outer wall material to flow into the inner plasticizing channel 112 and the outer plasticizing channel 122.

[0040] Combined with Figure 4 , the intermediate heating part 2 is used to continuously heat the corrugated pipe material. The intermediate heating part 2 includes an inner pipe 21, an intermediate pipe 22, and an outer pipe 23 that are sleeved from the inside to the outside in sequence. The inner pipe 21, the intermediate pipe 22, and the outer pipe 23 all extend along the longitudinal axis. The head of the inner pipe 21 and the head of the intermediate pipe 22 are respectively fixedly connected to the tail of the inner spiral shaft sleeve 11 and the tail of the outer spiral shaft sleeve 12. The inner pipe 21 and the intermediate pipe 22 define an inner heating channel 24 for the inner wall material to flow through, and the head of the inner heating channel 24 is connected to the tail of the inner plasticizing channel 112. The head of the outer pipe 23 is fixedly connected to the tail of the outer limiting shaft sleeve 13. The inner wall surface of the outer pipe 23 and the outer wall surface of the intermediate pipe 22 jointly define an outer heating channel 25 for the outer wall material to flow through, and the head of the outer heating channel 25 is connected to the tail of the outer plasticizing channel 122. The intermediate heating part 2 is provided with a plurality of first heating coils 26 that tightly surround the outer pipe 23 from the outside to continuously heat the corrugated pipe material in the inner and outer heating channels.

[0041] Combined with Figure 6, the die part 3 of the discharge port includes an inner core die 31, an intermediate core die 32, and an outer port die 33 that are sleeved from the inside to the outside in sequence. The head of the inner core die 31 and the head of the intermediate core die 32 are respectively fixedly connected to the tail of the inner tube 21 and the tail of the intermediate tube 22. The outer wall surface of the inner core die 31 and the inner wall surface of the intermediate core die 32 jointly define an inner discharge channel 34 that communicates with the inner heating channel 24. The inner plasticizing channel 112, the inner heating channel 24, and the inner discharge channel 34 constitute an inner material flow path for the inner wall material to flow into and out of the molding die 100. The head of the outer port die 33 is fixedly connected to the tail of the outer tube 23. The inner wall surface of the outer port die 33 and the outer wall surface of the intermediate core die 32 jointly define an outer discharge channel 35 that communicates with the outer heating channel 25. Similarly, the outer plasticizing channel 122, the outer heating channel 25, and the outer discharge channel 35 constitute an inner material flow path for the outer wall material to flow into and out of the molding die 100. Among them, the die part 3 of the discharge port is further provided with a second heating coil that sleeves the outer port die 33 from the periphery to maintain the material temperature and flow inside the die part 3 of the discharge port.

[0042] To ensure the concentricity among the inner core die 31, the intermediate core die 32, and the outer port die 33, that is, to ensure the uniform wall thickness of the inner and outer walls of the double-wall corrugated pipe, the present invention is provided with a concentricity adjustment mechanism in the intermediate heating part 2 of the molding die 100. Refer to Figure 3-4 , in the outer tube 23 of the intermediate heating part 2 of the molding die 100 provided in this embodiment, four first thread grooves 231 arranged circumferentially at equal intervals and four second thread grooves 232 arranged circumferentially at equal intervals are opened. The first and second thread grooves penetrate the outer tube 23 and are arranged alternately at intervals in sequence. Four flat grooves 221 that are arranged circumferentially at equal intervals and penetrate the intermediate tube 22 are opened on the intermediate tube 22. Each of the first thread grooves 231, each of the second thread grooves 232, and each of the flat grooves 221 are located in the same radial plane. The four flat grooves 221 are configured to be respectively aligned with the four second thread grooves 232 in the radial direction.

[0043] The eccentric mechanism includes first adjusting bolts 41 respectively located at four first threaded grooves 231, four second adjusting bolts 42 respectively located at four second threaded grooves 232, and four sliding members 43 respectively located in four flat grooves 221. Each sliding member 43 forms a sliding connection with the corresponding flat groove 221. The first and second adjusting bolts each include a nut (not shown in the figure) exposed from the outer tube 23 for the user to rotate the adjusting bolt, a threaded portion (not shown in the figure) threadedly connected to the corresponding spiral groove, and an abutting portion (not shown in the figure) located below the threaded portion and at least partially extending into the outer heating channel 25. Among them, the abutting portions of the four first adjusting bolts 41 all abut against the outer wall of the intermediate tube 22, and the abutting portions of the four second adjusting bolts 42 abut against the outer surface of the corresponding sliding member 43 and make the corresponding sliding member 43 contact the wall surface of the inner tube 21. It can be understood that by means of the first and second adjusting bolts, the axial center line positions of the inner core die 31 and the intermediate core die 32 can be adjusted, so as to ensure that the wall thickness of the formed double-wall corrugated pipe is uniform. In other embodiments, any number of first and second adjusting bolts can also be arranged, but to ensure that the axial center line positions of the inner core die and the intermediate core die can be adjusted in all directions, the number of the first adjusting bolts and the second adjusting bolts should be no less than three; in other embodiments, the first and second threaded grooves can also be arranged in different radial planes, but it can be understood that the second threaded groove and the flat groove should be arranged in the same radial plane.

[0044] The forming die 100 provided in this embodiment arranges the concentricity adjusting mechanism on the intermediate heating portion 2, which can make each adjusting bolt away from the outlet of the discharge port die portion 3, so as to avoid leaving welding marks on the inner wall and / or outer wall of the formed double-wall corrugated pipe and ensure the external pressure resistance of the double-wall corrugated pipe. In addition, since the eccentric mechanism is located in front of the discharge port die portion 3, when adjusting the axial center line positions of the inner core die 31 and the intermediate core die 32, the forming die 100 can be operated without stopping.

[0045] Continue to refer to Figure 4 、 Figure 6 and Figure 7 , the inner core die 31 includes an inner core main body 311 fixedly connected to the inner tube 21 and an inner core mouth portion 312 sleeved outside the inner core main body 311. The inner core main body 311 has a first annular inclined surface 313 formed on the outer wall surface, the inner core mouth portion 312 has a second annular inclined surface 314 formed on the outer wall and adjacent to the rear side of the first annular inclined surface 313, and the intermediate core die 32 has a third annular inclined surface 321 formed on the inner wall surface. The inner discharge channel 34 is jointly defined by the first, second, and third annular inclined surfaces. Among them, the tail of the inner discharge channel 34 forms an inner annular discharge port (not shown in the figure), the inner annular discharge port has a first width in the front-rear direction and the rear boundary of the inner annular discharge port is defined by the second annular inclined surface 314.

[0046] The inner core body 311 and the inner core opening 312 form a threaded connection that enables the inner core opening 312 to move back and forth, so that the inner core opening 312 can adjust the first width of the inner annular discharge port (i.e., adjust the inner wall thickness of the formed double-wall corrugated pipe). Specifically, the inner core body 311 has a first annular contact surface 315 formed on the outer wall and located behind the first annular inclined surface 313. The first annular contact surface 315 extends back and forth and has a first thread (not shown in the figure); the inner core opening 312 has a second annular contact surface 316 formed on the inner wall surface. The second annular contact surface extends back and forth and has a second thread adapted to the first thread. A threaded connection between the inner core body 311 and the inner core opening 312 is formed via the first and second threads.

[0047] Further, a plurality of first locking bolts 317 arranged circumferentially around the longitudinal axis Y are provided inside the inner core opening 312. Each first locking bolt 317 can move along the radial direction and has a locking position where it abuts against the first annular contact surface 315 of the inner core body 311 to lock the inner core opening 312 and a release position where it disengages from the first annular contact surface 315 of the inner core body 311 to allow the inner core opening 312 to move. In other embodiments, the first locking bolt may also be arranged on the inner core body.

[0048] Similarly, a fourth annular inclined surface 322 is formed on the outer wall of the intermediate core mold 32, and a fifth annular inclined surface 331 is formed on the inner wall surface of the outer mouth mold 33. The outer discharge channel 35 is defined by the fourth and fifth annular inclined surfaces. The tail of the outer discharge channel 35 forms an outer annular discharge port (not marked in the figure), and the outer annular discharge port has a second width in the front-rear direction.

[0049] The outer mouth mold 33 and the outer pipe 23 form a threaded connection that enables the outer mouth mold 33 to move back and forth, so that the outer mouth mold 33 can adjust the second width of the outer annular discharge port (i.e., adjust the outer wall thickness of the formed double-wall corrugated pipe). Specifically, the outer mouth mold 33 has a fourth annular contact surface 332 formed on the inner wall surface and adjacent to the front side of the fifth annular inclined surface 331. The fourth annular contact surface 332 extends back and forth and is provided with a fourth thread; a third annular contact surface 233 is formed on the outer wall of the rear end of the outer pipe 23. The third annular contact surface 233 extends back and forth and is provided with a third thread adapted to the fourth thread. The third and fourth threads form a threaded connection between the outer pipe 23 and the outer mouth mold 33.

[0050] Further, the forming die 100 is further provided with a plurality of second locking bolts (not shown in the figure) located on the outer pipe 23 or / and the outer mouth mold 33. The plurality of second locking bolts are arranged circumferentially around the longitudinal axis Y, and each locking bolt has a second locking position for locking the movement of the outer mouth mold 33 and a second release position for allowing the outer mouth mold 33 to move back and forth.

[0051] Compared with the traditional forming die for double-wall corrugated pipes, the discharging port die part 3 of the present forming die 100 is only provided with an inner core die 31, an intermediate core die 32, an outer port die 33 and necessary fastening parts. Among them, both the intermediate core die 32 and the outer port die 33 are integral structures. Thereby, the number of components of the discharging port die part 3 is reduced and the processing and assembly costs of the components are lowered. In addition, the accumulated processing errors of the components are also smaller, which is beneficial to adjusting the first and second widths.

[0052] In addition, it can be understood that both the inner and outer discharging channels are straight inclined channels. Compared with the discharging channels in the prior art, the inner and outer discharging channels provided in this embodiment have smaller overall pressure losses. After passing through the inner and outer discharging channels, the corrugated pipe material still has a relatively large total pressure (including dynamic pressure and static pressure), so as to ensure reliable combination of the inner and outer walls of the formed double-wall corrugated pipe.

[0053] The foregoing has shown and described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and the descriptions in the specification only illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements. The scope of protection claimed by the present invention is defined by the appended claims, the specification and their equivalents.

Claims

1. A double-wall corrugated pipe forming die, which defines a longitudinally extending axis line extending from front to back and includes a feeding spiral part, an intermediate heating part, and a discharging die part arranged in sequence from front to back. It is characterized in that, The middle heating part includes an inner pipe, a middle pipe and an outer pipe which are sleeved in sequence from inside to outside. The inner pipe and the middle pipe jointly define an inner heating channel, and the middle pipe and the outer pipe jointly define an outer heating channel. The discharge port die part includes an inner core die, a middle core die and an outer port die which are sleeved in sequence from inside to outside. The inner core die and the middle core die jointly define an inner discharge channel communicating with the inner heating channel, and the middle core die and the outer port die jointly define an outer discharge channel communicating with the outer heating channel. The inner discharge channel and the outer discharge channel respectively have an inner annular discharge port and an outer annular discharge port. The inner annular discharge port and the annular discharge port respectively have a first width and a second width in the front-rear direction. The middle core die is fixedly connected to the middle pipe. The inner core die includes an inner core main body fixedly connected to the inner pipe and an inner core mouth part defining the rear boundary of the inner annular discharge port. The inner core mouth part and the inner core main body form a threaded connection that can move in the front-rear direction to adjust the first width. The outer port die and the outer pipe form a threaded connection that can move in the front-rear direction to adjust the second width. The inner core main body has a first annular inclined surface formed on the outer wall. The inner core mouth part has a second annular inclined surface formed on the outer wall and adjacent to the first annular inclined surface. The middle core die has a third annular inclined surface formed on the inner wall surface. The first annular inclined surface, the second annular inclined surface and the third annular inclined surface all incline backward and outward and jointly define the inner discharge channel. The middle core die has a fourth annular inclined surface formed on the outer wall. The outer port die has a fifth annular inclined surface formed on the inner wall. The fourth annular inclined surface and the fifth annular inclined surface both incline backward and outward and jointly define the outer discharge channel.

2. The double-wall corrugated pipe forming die according to claim 1, characterized in that, The inner core mouth part is sleeved outside the inner core main body. The inner core main body has a first annular contact surface formed on the outer wall and adjacent to the rear side of the first annular inclined surface. The first annular contact surface extends in the front-rear direction and is provided with a first thread. The inner core mouth part is formed with a second annular contact surface located on the inner wall. The second annular contact surface extends in the front-rear direction and is provided with a second thread adapted to the first thread.

3. The double-wall corrugated pipe forming die according to claim 1, characterized in that, The outer pipe has a third annular contact surface formed on the outer wall of the rear end. The third annular contact surface extends in the front-rear direction and is provided with a third thread. The outer port die has a fourth annular contact surface formed on the inner wall and adjacent to the front side of the fifth annular inclined surface. The fourth annular contact surface extends in the front-rear direction and is provided with a fourth thread adapted to the third thread.

4. The double-wall corrugated pipe forming die according to claim 1, characterized in that, A plurality of first locking bolts arranged circumferentially around the longitudinal axis are arranged on the inner core mouth part or / and the inner core main body. Each of the first locking bolts can move along the radial direction and has a first locking position for fixing the inner core mouth part and a first release position for allowing the inner core mouth part to move back and forth.

5. The double-wall corrugated pipe forming die according to claim 1, characterized in that, A plurality of second locking bolts arranged circumferentially around the longitudinal axis are provided on the outer die or / and the outer tube, and each of the second locking bolts can move along the radial direction and has a second locking position for fixing the outer die and a second release position for allowing the outer die to move back and forth.

6. The double-wall corrugated pipe forming die according to claim 1, characterized in that, A concentricity adjusting mechanism is further provided on the intermediate heating part. The concentricity adjusting mechanism includes a plurality of first adjusting bolts capable of applying pressure to the intermediate tube and a plurality of second adjusting bolts capable of applying a force to the inner tube. The plurality of first adjusting bolts and the plurality of second adjusting bolts are both arranged circumferentially around the longitudinal axis.

7. The double-wall corrugated pipe forming die according to claim 6, characterized in that, A plurality of first threaded grooves adapted to the plurality of first adjusting bolts are formed on the outer tube. Each of the first adjusting bolts is threadedly connected to the corresponding first threaded groove, and the bottom of each of the first adjusting bolts abuts against the intermediate tube.

8. The double-wall corrugated pipe forming die according to claim 7, characterized in that, A plurality of second threaded grooves adapted to the plurality of second adjusting bolts are formed on the outer tube. A plurality of flat grooves radially aligned with the plurality of second threaded grooves are formed on the intermediate tube. The concentricity adjusting mechanism further includes a plurality of sliding members located in the plurality of flat grooves. Each of the sliding members can move radially. Each of the second adjusting bolts is threadedly connected to the corresponding second threaded groove, and the bottom of each of the second adjusting bolts abuts against the corresponding sliding member to apply pressure to the inner tube via the corresponding sliding member.

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