Baking device for detecting high temperature resistance of polyethylene pipe

Abstract

This invention provides a baking device for testing the high-temperature resistance of polyethylene pipes, belonging to the field of plastic pipe manufacturing technology. It includes a housing, two pipe supports, an air circulation channel, and an internal heating channel. Each of the two pipe supports is equipped with a pipe fitting support and multiple elastic support blocks. The air circulation channel includes an inlet channel and a return air channel. A heating element is installed in the inlet channel, and the outlet of the inlet channel connects to the lower part of the heating chamber. The inlet of the return air channel connects to the upper part of the heating chamber. The internal heating channel includes an inlet hose connecting the outlet end of the inlet channel to the inner cavity of the pipe fitting support and an outlet hole opened on the side wall of the pipe fitting support. The baking device for testing the high-temperature resistance of polyethylene pipes provided by this invention, with its air circulation channel and internal heating channel, can simultaneously heat the inner and outer sides of the pipe sample, avoiding uneven temperatures on the inner and outer sides of the pipe sample or significant differences from the application environment, thereby improving the accuracy of the test.

Description

Technical Field

[0001] This invention belongs to the field of plastic pipe manufacturing technology, and more specifically, relates to a baking device for testing the high-temperature resistance of polyethylene pipes. Background Technology

[0002] Plastic pipes are widely used in daily production, especially high-temperature resistant engineering plastic pipes, which possess the highest thermal conductivity, lowest coefficient of linear expansion, and excellent electrical properties. During the production process, the quality of high-temperature resistant engineering plastic pipes needs to be inspected. Currently, in most cases, pipe samples are placed in a high-temperature medium and heated through the medium. However, because the internal medium fluctuations of the pipe sample are relatively small, uneven heating occurs between the inner and outer sides of the sample during the heating process. This differs significantly from the environmental conditions of the high-temperature flowing medium inside the pipe in actual applications, resulting in poor accuracy of the test results. Summary of the Invention

[0003] The purpose of this invention is to provide a baking device for testing the high-temperature resistance of polyethylene pipes, which aims to solve the problems of small fluctuations in the medium inside the pipe sample, uneven heating on the inside and outside of the pipe sample, and poor testing accuracy in existing pipe samples.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A baking device for testing the high-temperature resistance of polyethylene pipes is provided, comprising a chamber, two pipe supports, an air circulation channel, and an internal heating channel. The chamber has a heating chamber containing two symmetrically arranged pipe supports. Each of the two pipe supports has a pipe fitting support and multiple elastic support blocks circumferentially arranged around the pipe fitting support on opposite sides. The elastic support blocks have radial freedom along the pipe fitting support and are used to abut against the inner wall of the pipe sample. The air circulation channel includes an inlet channel and a return air channel. The inlet channel contains a heating component, and its outlet connects to the lower part of the heating chamber. The inlet of the return air channel connects to the upper part of the heating chamber. The internal heating channel includes an inlet hose connecting the outlet end of the inlet channel and the inner cavity of the pipe fitting support, and an outlet hole opened on the side wall of the pipe fitting support.

[0005] In another embodiment of this application, the pipe support includes a solid shaft and an outer sleeve. The end of the solid shaft is connected to the pipe bracket, and the outer sleeve is fitted over the outside of the solid shaft. A buffer cavity exists between the outer sleeve and the solid shaft. The buffer cavity is connected to the outlet end of the flexible hose. The air outlet is opened on the outer sleeve and connects the heating cavity and the buffer cavity.

[0006] In another embodiment of this application, the length of the solid shaft is greater than the length of the outer sleeve; an annular hole is provided on the end plate of the end of the outer sleeve away from the tube support, and the annular hole connects the buffer cavity and the heating cavity.

[0007] In another embodiment of this application, the pipe support is provided with a longitudinally extending guide groove, and a longitudinally extending threaded drive rod is provided in the guide groove; the pipe support also includes a guide seat that passes through the guide groove, and the ends of the solid shaft and the outer sleeve are fixed on the guide seat; the threaded drive rod passes through the guide seat to drive the pipe support to move up and down; a vent hole is provided in the guide seat, one end of the vent hole is connected to the air inlet hose, and the other end of the vent hole is connected to the buffer cavity.

[0008] In another embodiment of this application, the guide seat is a T-shaped seat, which includes a vertically connected support part and a mounting part. The support part passes through the guide groove, and the threaded drive rod passes through the support part longitudinally. The ends of the solid shaft and the outer sleeve are both fixed to the mounting part on the side away from the support part. A connecting cavity is provided in the mounting part. The longitudinal section of the connecting cavity is circular, and the diameter of the connecting cavity is larger than the outer diameter of the buffer cavity. The connecting cavity connects the vent hole and the buffer cavity.

[0009] In another embodiment of this application, the air intake channel includes a preheating section, a heating section, and a lower air intake jacket connected in sequence. The preheating section and the heating section are located behind the heating chamber. A heat exchange device is provided in the preheating section. The heating assembly is located in the heating section. The lower air intake jacket is located below the heating chamber and is separated from the heating chamber by a lower partition. The lower partition has multiple vent holes. The inlet end of the air intake hose extends into the lower air intake jacket.

[0010] In another embodiment of this application, the return air channel includes an upper return air jacket, a return air duct, and an exhaust duct; the upper return air jacket is located above the heating chamber and is connected to the upper part of the heating chamber by means of an upper partition; the upper return air jacket is connected to the return air duct, and the return air duct is connected to the medium inlet of the heat exchange device; the exhaust duct is connected to the medium outlet of the heat exchange device, and the outlet end of the exhaust duct extends out of the outside of the housing.

[0011] In another embodiment of this application, the return air duct further includes two side return air jackets, which are located on both sides of the heating cavity. The upper part of the side return air jacket is connected to the upper return air jacket, and the lower part of the side return air jacket is connected to the return air duct.

[0012] In another embodiment of this application, the pipe support is slidably disposed on the upper end of the lower partition plate. The lower end of the lower partition plate has a driving assembly, which includes a threaded rod and a driving motor. The threaded rod has two symmetrically arranged threaded portions with opposite thread directions. The two pipe supports are respectively connected to the two threaded portions. The driving motor drives the threaded rod to rotate forward or backward to drive the two pipe supports closer or further away.

[0013] In another embodiment of this application, temperature sensors are provided on both the end of the pipe support and the inner wall of the box.

[0014] The beneficial effects of the baking device for testing the high-temperature resistance of polyethylene pipes provided by this invention are as follows: Compared with the prior art, the baking device for testing the high-temperature resistance of polyethylene pipes of this invention, by setting a pipe support in the heating chamber of the chamber, ensures the stability of the pipe during the test by supporting the inside of the pipe sample; by setting an air circulation channel and an internal heating channel in the chamber, it is possible to simultaneously heat the inside and outside of the pipe sample, which is more conducive to simulating the application environment of real-world scenarios and avoids the problem of uneven temperature on the inside and outside of the pipe sample or large differences from the application environment, thereby improving the accuracy of the test. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the baking device for testing the high-temperature resistance of polyethylene pipes provided in an embodiment of the present invention;

[0017] Figure 2 This is a side sectional view of a baking apparatus for testing the high-temperature resistance of polyethylene pipes provided in an embodiment of the present invention.

[0018] Figure 3 for Figure 2 Enlarged view of point A in the middle;

[0019] Figure 4 This is a schematic diagram of the structure of the guide seat provided in an embodiment of the present invention.

[0020] In the diagram: 1. Box body; 2. Heating chamber; 3. Pipe sample; 4. Lower air inlet jacket; 5. Upper return air jacket; 6. Lower partition; 7. Upper partition; 8. Solid shaft; 9. Outer sleeve; 10. Support block; 11. Telescopic rod; 12. Flexible hose; 13. Guide seat; 14. Threaded drive rod; 15. Laser emitting device; 16. Laser receiving device; 17. Threaded rod; 18. Sliding rod; 19. Connecting block; 20. Limiting plate; 21. Rotating shaft; 22. Roller shaft; 23. Elastic rod; 24. Striking rod; 25. First motor; 26. Side return air jacket; 27. Return air duct; 28. Pipe support; 29. ​​Electric heater; 30. Heat exchanger; 31. Exhaust duct; 32. Air inlet; 33. Buffer chamber; 34. Vent hole; 35. Connecting chamber. Detailed Implementation

[0021] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0022] Please see Figures 1 to 4 The baking apparatus for testing the high-temperature resistance of polyethylene pipes provided by the present invention will now be described. The baking apparatus for testing the high-temperature resistance of polyethylene pipes includes a housing 1, two pipe supports 28, an air circulation channel, and an internal heating channel. The housing 1 has a heating chamber 2, which contains two symmetrically arranged pipe supports 28. Each of the two pipe supports 28 has a pipe fitting support and multiple elastic support blocks arranged around the outer periphery of the pipe fitting support. The elastic support blocks have radial freedom along the pipe fitting support and are used to abut against the inner wall of the pipe sample 3. The air circulation channel includes an air inlet channel and a return air channel. The air inlet channel contains a heating component, and its outlet connects to the lower part of the heating chamber 2. The inlet of the return air channel connects to the upper part of the heating chamber 2. The internal heating channel includes an air inlet hose 12 connecting the outlet end of the air inlet channel and the inner cavity of the pipe fitting support, and an air outlet hole opened on the side wall of the pipe fitting support.

[0023] The chamber 1 is equipped with two pipe supports 28 for fixing the pipe sample 3. The two pipe supports 28 are symmetrically arranged in the heating chamber 2 inside the chamber 1. The pipe fitting support connected to the pipe support 28 is located inside the pipe support 28 and is symmetrically arranged. The pipe fitting support is used to extend into the inner cavity of the pipe sample. The elastic support block on the outside of the pipe fitting support is radially retractable. The end of the elastic support block away from the pipe fitting support abuts against the inner wall of the pipe sample and applies force in different directions at the same time. The purpose of fixing the pipe sample is achieved by applying pressure to the inner wall of the pipe sample.

[0024] During the heating process, the air in the intake channel is heated by the heating component. The heated high-temperature air is divided into two parts. The first part enters the heating chamber 2 to heat the air inside the heating chamber 2. The second part enters the inner cavity of the pipe support through the intake hose 12 and is released to the outside through the air outlet on the side wall of the pipe support. The second part of high-temperature air enters the inner cavity of the pipe sample through the air outlet and moves radially outward with the pipe sample. It then passes through the gap between two adjacent elastic support blocks and is discharged into the heating chamber 2 through the opening at the end of the pipe sample. During this process, as the air temperature in the heating chamber 2 rises, the temperature in the inner cavity of the pipe sample 3 also rises, enabling temperature control of the inner and outer sides of the pipe sample 3 to better simulate the application environment in real-world scenarios.

[0025] The baking device for testing the high-temperature resistance of polyethylene pipes provided by this invention, compared with the prior art, ensures the stability of the pipe during the test by setting a pipe support 28 in the heating chamber 2 of the chamber 1 to support the inside of the pipe sample 3; and by setting an air circulation channel and an internal heating channel in the chamber 1, it is possible to heat the inside and outside of the pipe sample 3 simultaneously, which is more conducive to simulating the application environment of real-world scenarios and avoids the problem of uneven temperature on the inside and outside of the pipe sample 3 or large differences from the application environment, thereby improving the accuracy of the test.

[0026] like Figure 1 and Figure 2 As shown, the elastic support blocks are arranged circumferentially along the pipe support, and multiple elastic support blocks are evenly distributed on the outer side of the pipe support, with gaps between the multiple elastic support blocks. Figure 2 As shown, taking the example of three elastic support blocks on the outer side of the pipe fitting support, the included angle between the extension length directions of any two elastic support blocks is equal. Furthermore, the pipe fitting support has a degree of freedom along its extension length direction, i.e., the radial direction of the corresponding pipe fitting support.

[0027] Specifically, a telescopic rod 11 is provided on the outside of the pipe fitting support. The telescopic rod 11 includes an outer rod fixed to the outer wall of the pipe fitting support and an inner rod slidably connected to the outer rod, with the inner rod and outer rod arranged coaxially. A spring is installed in the hollow cavity of the outer rod, with one end of the spring abutting against the outer wall of the pipe fitting support and the other end abutting against the end of the inner rod; the spring is always in a compressed state. When there is no external force, the telescopic rod 11 is in its longest state. A support block 10 is connected to the free end of the inner rod, and the outer wall of the support block 10 is an outwardly convex arc or semi-circular shape. In application, pressing the support block 10 causes the support block 10 to press the inner rod inward until the outer side of the support block 10 abuts against the inner wall of the pipe sample 3.

[0028] An elastic membrane is wrapped around the circumference of the elastic support block. The elastic membrane protects the structure of the telescopic rod 11 without affecting its extension and retraction.

[0029] like Figure 1 , Figure 2 and Figure 4 As shown, the pipe support includes a solid shaft 8 and an outer sleeve 9. The end of the solid shaft 8 is connected to the pipe support 28. The outer sleeve 9 is sleeved on the outside of the solid shaft 8, and there is a buffer cavity 33 between the outer sleeve 9 and the solid shaft 8. The buffer cavity 33 is connected to the outlet end of the hose 12. The air outlet is opened on the outer sleeve 9 and connects the heating cavity 2 and the buffer cavity 33.

[0030] The ends of both the solid shaft 8 and the outer sleeve 9 are connected to the tube support 28. The solid shaft 8 and the outer sleeve 9 are coaxially arranged, forming an annular buffer cavity 33 between them. Multiple air outlets are provided on the outer sleeve 9, connecting the buffer cavity 33 and the heating cavity 2. These outlets are used to transport the high-temperature air from the buffer cavity 33 to the inner cavity of the tube sample 3 and allow it to move along the length of the tube sample 3 until it enters the heating cavity 2. The multiple air outlets are evenly distributed on the outer sleeve 9.

[0031] In addition, the length of the solid shaft 8 is greater than the length of the outer sleeve 9; an annular hole is formed on the end plate of the outer sleeve 9 at the end away from the tube support 28, and the annular hole connects the buffer chamber 33 and the heating chamber 2. The free end of the solid shaft 8 extends out of the outer sleeve 9, and an annular stepped surface is formed between the side wall of the solid shaft 8 and the end face of the outer sleeve 9. An annular hole is formed on this annular stepped surface, and the annular hole penetrates the end plate of the outer sleeve 9. Part of the high-temperature air in the buffer chamber 33 is discharged through the air outlet, and the other part is discharged through the annular hole.

[0032] like Figure 1 and Figure 2 As shown, the pipe support 28 has a longitudinally extending guide groove, and a longitudinally extending threaded drive rod 14 is provided in the guide groove; the pipe support also includes a guide seat 13 that passes through the guide groove, and the ends of the solid shaft 8 and the outer sleeve 9 are fixed on the guide seat 13; the threaded drive rod 14 passes through the guide seat 13 to drive the pipe support to move up and down; a vent hole 34 is provided in the guide seat 13, one end of the vent hole 34 is connected to the air inlet hose 12, and the other end of the vent hole 34 is connected to the buffer chamber 33.

[0033] The pipe support 28 is arranged longitudinally, and a guide groove is formed in the middle of the pipe support 28. The length direction of the guide groove is vertical, and the depth direction of the guide groove is consistent with the thickness direction of the pipe support 28 and extends through the pipe support 28. One end of the guide seat 13 is connected to the solid shaft 8 and the outer sleeve 9, and the other end of the guide seat 13 passes through the guide groove and extends from the other side of the pipe support 28. A vent hole 34 is formed inside the guide seat 13. One end of the vent hole 34 is connected to the buffer cavity 33, and the other end of the vent hole 34 is located on the end face of the guide seat 13 away from the solid shaft 8 and is connected to the air inlet hose 12.

[0034] Specifically, the guide seat 13 is a T-shaped seat, which includes a vertically connected support part and a mounting part. The support part passes through the guide groove, and the threaded drive rod 14 passes through the support part longitudinally. The ends of the solid shaft 8 and the outer sleeve 9 are both fixed on the side of the mounting part away from the support part. A connecting cavity 35 is provided in the mounting part. The longitudinal section of the connecting cavity 35 is circular, and the diameter of the connecting cavity 35 is larger than the outer diameter of the buffer cavity 33. The connecting cavity 35 is connected to the buffer cavity 33.

[0035] The support section passes through the guide groove and is slidably connected to the inner wall of the guide groove. The threaded drive rod 14, which is inside the guide groove, passes through the support section and is threadedly connected to it. During adjustment, the support section and the entire pipe fitting are raised and lowered by adjusting the forward or reverse rotation of the threaded drive rod 14.

[0036] A vent hole 34 is provided in a part of the support and mounting part of the guide seat 13, and a connecting cavity 35 is provided on the side of the mounting part near the solid shaft 8. The connecting cavity 35 is connected to the buffer cavity 33 by means of the vent hole provided in the mounting part.

[0037] Optionally, to improve detection accuracy and simulate the environmental characteristics of vibration and impact, a rotating shaft 21 is installed above the pipe support, with the length direction of the rotating shaft 21 aligned with the length direction of the pipe support. A roller 22 is fitted onto the rotating shaft 21, and an elastic rod 23 and a striking rod 24 are provided on the outer side of the roller 22. The elastic rod 23 can be made of materials such as rubber. When the rotating shaft 21 rotates, the elastic rod 23 strikes the pipe sample 3, applying a vibrational force to the pipe sample 3. The striking rod 24 is made of rigid material, and its striking action on the pipe sample 3 creates an external force, allowing observation of the characteristics of the pipe sample 3 under the action of the external force. A first motor 25 is connected to the end of the rotating shaft 21.

[0038] To facilitate control of the vibration frequency, multiple mounting holes are provided on the outer side of the roller 22. These mounting holes have internal threads, while the ends of the elastic rod 23 and the striking rod 24 are both provided with external threads. The elastic rod 23 and the striking rod 24 are mounted on the roller 22 via these threads. The number of elastic rods 23 and the striking rod 24 is not fixed.

[0039] The mounting holes arranged in a ring around the roller 22 are arranged in a row, and the included angle between the projections of two adjacent rows of mounting holes is 30°-45°.

[0040] To facilitate observation and detection of the deformation of the pipe sample 3, a laser emitting device 15 and a laser receiving device 16 are respectively installed on the lower part of the two pipe supports 28. Before detection, the laser lines generated by the laser emitting device 15 and the laser receiving device 16 are located below the lower end face of the pipe sample 3. When the pipe sample 3 deforms under the action of external force, the upper part of the pipe sample 3 is struck by the striking rod 24, causing the pipe sample 3 to deform, and the lower end of the pipe sample 3 blocks the laser line.

[0041] The distance between the laser line and the lower end face of the tubular sample 3 is within the allowable deformation range, while also preventing the vibration generated by the elastic rod 23 from affecting the accuracy of the test. The distance between the laser line and the lower end face of the tubular sample 3 is achieved by controlling the height of the threaded drive rod 14 to raise and lower the tubular sample 3.

[0042] Optionally, two pipe supports 28 are slidably disposed within the heating chamber 2, and the two pipe supports 28 slide horizontally to achieve relative proximity or distance.

[0043] During testing, first, the pipe sample 3 is fixed, with one end secured to one of the pipe supports. The other end of the sample is then fixed to another pipe support by adjusting the distance between the two pipe supports 28. Next, the threaded drive rod 14 is adjusted to move the pipe support 28 downwards until the distance between the lower end of the pipe support 28 and the laser line emitted by the laser emitting device 15 reaches the allowable deformation range. Then, elastic rods 23 and striking rods 24 of appropriate length and number are selected. Finally, the chamber door 1 is closed, and the air circulation channel and the internal heating channel are opened to begin the testing.

[0044] like Figure 1 and Figure 2 As shown, the air intake channel includes a preheating section, a heating section, and a lower air intake jacket connected in sequence. The preheating section and the heating section are located behind the heating chamber 2. A heat exchange device 30 is installed in the preheating section. The heating assembly is located in the heating section. The lower air intake jacket is located below the heating chamber 2 and is separated from the heating chamber 2 by a lower partition 6. The lower partition 6 has multiple vent holes. The inlet end of the air intake hose 12 extends into the lower air intake jacket. The heating assembly is an electric heater 29, such as an electric heating wire.

[0045] An air inlet 32, which communicates with the air intake channel, is provided on the back panel of the housing 1. Fresh air entering the air intake channel passes sequentially through the heat exchanger 30 and the heating element, and after being heated, it enters the lower air intake jacket and enters the heating chamber 2 through the vent holes on the lower partition 6; at the same time, some high-temperature air enters the air intake hose 12 through the inlet. A flow valve is provided at the inlet end of the air intake hose 12.

[0046] The return air duct includes an upper return air jacket 5, a return air duct 27, and an exhaust duct 31. The upper return air jacket 5 is located above the heating chamber 2 and is connected to the upper part of the heating chamber 2 by means of an upper partition 7. The upper return air jacket 5 is connected to the return air duct 27, which is connected to the medium inlet of the heat exchange device 30. The exhaust duct 31 is connected to the medium outlet of the heat exchange device 30, and the outlet end of the exhaust duct 31 extends out of the outer side of the housing 1.

[0047] High-temperature air enters the heating chamber 2 from the lower intake jacket and then enters the upper return air jacket 5. Since the air temperature entering the upper return air jacket 5 and the return air duct 27 is relatively high, the outlet end of the return air duct 27 is connected to the heat exchanger 30. The return air is used as a heat source for the preheating section to preheat the fresh air, further saving thermal energy and reducing energy waste. The heat exchanger 30 can be a plate heat exchanger, with corrugated plates inside.

[0048] Furthermore, the return air duct also includes two side return air jackets 26, which are located on both sides of the heating chamber 2. The upper part of the side return air jackets 26 is connected to the upper return air jacket 5, and the lower part of the side return air jackets 26 is connected to the return air duct 27. The return air in the upper return air jacket 5 enters the two side return air jackets 26 from both sides of the upper return air jacket 5, moves downward along the side return air jackets 26, and enters the return air duct 27 from the lower part of the side return air jackets 26.

[0049] Two side return air jackets 26 are located on both sides of the heating cavity 2, which improves the heat preservation performance of the heating cavity 2.

[0050] The pipe support 28 is slidably disposed on the upper end of the lower partition 6. The lower end of the lower partition 6 has a drive assembly, which includes a threaded rod 17 and a drive motor. The threaded rod 17 has two symmetrically arranged threaded portions with opposite thread directions. The two pipe supports 28 are respectively connected to the two threaded portions. The drive motor drives the threaded rod 17 to rotate forward or backward to drive the two pipe supports 28 closer or further away.

[0051] A movable groove is provided on the lower partition plate 6, and the movable groove is arranged along the connecting line of the pipe support 28. A connecting block 19 is provided at the lower end of the pipe support 28, and the connecting block 19 passes through the movable groove and is connected to the threaded rod 17.

[0052] Optionally, a limiting plate 20 is installed at the end of the moving slot, the limiting plate 20 extends downward into the lower air inlet jacket 4, and the end of the threaded rod 17 is rotatably mounted on the limiting plate 20.

[0053] Optionally, a slide bar 18 is also installed between the two limiting plates 20, with the slide bar 18 located below the threaded rod 17. The connecting block 19 is slidably connected to the slide bar 18, improving the stability of the movement of the connecting block 19.

[0054] Temperature sensors are provided at the ends of the pipe support and on the inner side wall of the housing 1. Temperature sensor points are also provided at the free end of the pipe support and on the side wall of the middle part of the housing 1. Each point is equipped with a temperature sensor to detect the air temperature at each point.

[0055] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A baking apparatus for testing the high-temperature resistance of polyethylene pipes, characterized in that, The device includes a housing (1), two pipe supports (28), an air circulation channel, and an internal heating channel. The housing (1) has a heating chamber (2), which has two symmetrically arranged pipe supports (28). Each of the two pipe supports (28) has a pipe fitting support and multiple elastic support blocks arranged around the outer periphery of the pipe fitting support. The elastic support blocks have a degree of freedom along the radial direction of the pipe fitting support and are used to abut against the inner wall of the pipe sample (3). The air circulation channel includes an air inlet channel and a return air channel. The air inlet channel is equipped with a heating component, and the outlet of the air inlet channel is connected to the lower part of the heating chamber (2). The inlet of the return air channel is connected to the upper part of the heating chamber (2). The internal heating channel includes an air inlet hose (12) connecting the outlet end of the air inlet channel and the inner cavity of the pipe fitting support, and an air outlet hole opened on the side wall of the pipe fitting support. The pipe support includes a solid shaft (8) and an outer sleeve (9). The end of the solid shaft (8) is connected to the pipe support (28). The outer sleeve (9) is sleeved on the outside of the solid shaft (8), and there is a buffer cavity (33) between the outer sleeve (9) and the solid shaft (8). The buffer cavity (33) is connected to the outlet end of the hose (12). The air outlet is opened on the outer sleeve (9) and connects the heating cavity (2) and the buffer cavity (33). The pipe support (28) has a longitudinally extending guide groove, and a longitudinally extending threaded drive rod (14) is provided in the guide groove; the pipe support also includes a guide seat (13) that passes through the guide groove, and the ends of the solid shaft (8) and the outer sleeve (9) are fixed on the guide seat (13); the threaded drive rod (14) passes through the guide seat (13) to drive the pipe support to move up and down; a vent hole (34) is provided in the guide seat (13), one end of the vent hole (34) is connected to the air inlet hose (12), and the other end of the vent hole (34) is connected to the buffer chamber (33).

2. The baking apparatus for testing the high-temperature resistance of polyethylene pipes as described in claim 1, characterized in that, The length of the solid shaft (8) is greater than the length of the outer tube (9); an annular hole is provided on the end plate of the outer tube (9) away from the tube support (28), and the annular hole connects the buffer cavity (33) and the heating cavity (2).

3. The baking apparatus for testing the high-temperature resistance of polyethylene pipes as described in claim 1, characterized in that, The guide seat (13) is a T-shaped seat. The guide seat (13) includes a support part and a mounting part connected vertically. The support part passes through the guide groove, and the threaded drive rod (14) passes through the support part longitudinally. The ends of the solid shaft (8) and the outer sleeve (9) are fixed on the side of the mounting part away from the support part. A connecting cavity (35) is provided in the mounting part. The longitudinal section of the connecting cavity (35) is circular, and the diameter of the connecting cavity (35) is larger than the outer diameter of the buffer cavity (33). The connecting cavity (35) connects the vent hole (34) and the buffer cavity (33).

4. The baking apparatus for testing the high-temperature resistance of polyethylene pipes as described in claim 1, characterized in that, The air intake channel includes a preheating section, a heating section and a lower air intake jacket connected in sequence. The preheating section and the heating section are located behind the heating chamber (2). A heat exchange device (30) is provided in the preheating section. The heating component is located in the heating section. The lower air intake jacket is located below the heating chamber (2) and is separated from the heating chamber (2) by a lower partition (6). A plurality of vent holes are provided on the lower partition (6). The inlet end of the air intake hose (12) extends into the lower air intake jacket.

5. The baking apparatus for testing the high-temperature resistance of polyethylene pipes as described in claim 4, characterized in that, The return air channel includes an upper return air jacket (5), a return air duct (27), and an exhaust duct (31); the upper return air jacket (5) is located above the heating chamber (2) and is connected to the upper part of the heating chamber (2) by means of an upper partition (7); the upper return air jacket (5) is connected to the return air duct (27), and the return air duct (27) is connected to the medium inlet of the heat exchange device (30); the exhaust duct (31) is connected to the medium outlet of the heat exchange device (30), and the outlet end of the exhaust duct (31) extends out of the outside of the housing (1).

6. The baking apparatus for testing the high-temperature resistance of polyethylene pipes as described in claim 5, characterized in that, The return air duct also includes two side return air jackets (26), which are located on both sides of the heating chamber (2). The upper part of the side return air jacket (26) is connected to the upper return air jacket (5), and the lower part of the side return air jacket (26) is connected to the return air duct (27).

7. The baking apparatus for testing the high-temperature resistance of polyethylene pipes as described in claim 5, characterized in that, The pipe support (28) is slidably disposed on the upper end of the lower partition (6). The lower end of the lower partition (6) has a drive assembly, which includes a threaded rod (17) and a drive motor. The threaded rod (17) has two symmetrically arranged threaded portions with opposite thread directions. The two pipe supports (28) are respectively connected to the two threaded portions. The drive motor drives the threaded rod (17) to rotate forward or backward to drive the two pipe supports (28) to move closer or further away.

8. The baking apparatus for testing the high-temperature resistance of polyethylene pipes as described in claim 1, characterized in that, Temperature sensors are provided on the end of the pipe support and on the inner wall of the box (1).

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