Injection molding mold for a side armrest

Abstract

The utility model discloses a side handrail injection moulding mould, include: base, place on the mesa support whole mould, lower mould, solid link in the base, upper die, buckle on the lower mould and can move relative to the lower mould, movable plate, be located on the base and can move in the space between the base and the lower mould, a plurality of thimble, be located on the movable plate and be provided on the lower mould, the lower mould and upper die buckle and form the mould cavity, and the thimble is provided in the mould cavity, the side handrail injection moulding mould still include: injection tube, be provided in the mould cavity of lower mould, sealing rod, be provided in the injection tube, one end of injection tube is equipped with injection port, and injection tube can move relative to sealing rod, so that injection tube has at least sealing rod is in the closed state of injection port and sealing rod is removed from the injection state of injection port, the through hole that is equipped with for injection tube to pass through is set up on movable plate, the injection port of the application has good sealing effect, and product forming quality is stable.

Description

Technical Field

[0001] This utility model belongs to the field of mold technology, and in particular relates to an injection molding mold for a side armrest. Background Technology

[0002] As a core component of furniture (such as sofas and office chairs), medical devices (such as wheelchairs and nursing beds), and transportation vehicles (such as cars and electric mobility scooters), side armrests need to combine structural strength (to support the weight of the human body) with a smooth appearance (to fit the overall design). Their injection molding often uses tough plastics such as PP and ABS, and they often have complex structures such as grooves, connecting holes, and curved surfaces. This places stringent requirements on the mold's "injection sealing," "structural coordination," and "smooth demolding": it is necessary to ensure that the molten plastic accurately fills the mold cavity without overflow, avoid interference between injection components and demolding components (such as ejector pins and moving plates), and ensure the efficiency of changeover during mass production. Otherwise, it is easy to cause defects such as burrs, missing material, and deformation in the product, increasing subsequent processing costs. Existing injection molding dies for side handrails have significant defects in their injection and demolding structural design, making it difficult to balance molding quality and production efficiency. Specific problems are as follows: First, existing molds mostly use fixed gates or simple valve gates: Fixed gates lack an active sealing structure, and after injection molding, the molten plastic remaining in the mold cavity easily overflows from the gate, forming burrs on the side handrail surface, requiring additional trimming. Although valve gates have seals, they are mostly made of rubber, which is prone to aging and deformation under long-term exposure to high-temperature molten plastic, leading to seal failure. Furthermore, the seals do not fit well with the gate, and there is still a risk of material leakage during high-pressure injection molding, affecting the appearance accuracy and assembly fit of the side handrail.

[0003] Secondly, the existing sealing structure cannot meet the high-pressure requirements of side armrest injection molding (the molten plastic needs high pressure to fill the complex cavity): if the pressure is too high, the seal will be easily opened, resulting in material leakage; if the pressure is too low, the filling will not be full. At the same time, plastic residue is easy to accumulate in the gap between the injection tube and the seal. After long-term use, it will cause the gate to be blocked, requiring frequent disassembly and cleaning of the mold. This not only increases maintenance costs, but also makes it difficult to restore the sealing accuracy after cleaning, resulting in fluctuations in the quality of subsequent molded products and a high scrap rate. Utility Model Content

[0004] The summary section of this application is intended to provide a brief overview of the concepts, which will be described in detail in the detailed description section below. This summary section is not intended to identify key or essential features of the claimed technical solutions, nor is it intended to limit the scope of the claimed technical solutions.

[0005] In order to overcome the problems of poor sealing effect of injection port and unstable molding quality in the prior art, this utility model provides a side armrest injection molding mold.

[0006] To achieve the above objectives, this utility model adopts the following technical solution: a side armrest injection molding die, comprising: The base is placed on the table to support the entire mold; The lower mold is fixedly connected to the base; The upper mold is fastened to the lower mold and can move relative to the lower mold; The movable plate is located on the base and can move within the space between the base and the lower mold; Several ejector pins are mounted on the movable plate and pass through the lower mold; The lower mold and the upper mold are engaged to form a mold cavity, and ejector pins are inserted into the mold cavity; The side armrest injection molding mold also includes: Injection tubes are inserted into the cavity of the lower mold. A sealing rod is inserted inside the injection-molded tube; One end of the injection tube is provided with an injection port, and the injection tube can move relative to the sealing rod, so that the injection tube has at least a closed state in which the sealing rod is in the injection port and an injection state in which the sealing rod moves out of the injection port; the movable plate is provided with a through hole for the injection tube to pass through.

[0007] Furthermore, the side armrest injection molding mold also includes: A support platform is mounted on the base; Pad blocks are placed on the support platform; The lower mold is fixed to the pad block, which separates the movable cavity between the support platform and the lower mold. The movable plate is located in the movable cavity and moves within it.

[0008] Furthermore, the side armrest injection molding mold also includes a movable block, with a movable groove at the bottom of the support platform, the movable block being located within the movable groove, and the injection tube connected to the movable block.

[0009] Furthermore, a guide rod is connected inside the movable groove, and a guide hole is provided on the movable block, through which the guide rod passes.

[0010] Furthermore, the guide rod is threaded into the movable groove, and one end of the guide rod is provided with an end block. When the movable block is placed on the end block, the injection tube is in a sealed state.

[0011] Furthermore, one end of the injection tube is recessed towards the central axis to form an injection port, and the diameter of the sealing rod corresponds to the inner diameter of the injection port.

[0012] Furthermore, the injection port has an hourglass-shaped structure, including a guide section, a connecting section, and a discharge section. The guide section and the discharge section are connected by the connecting section. The sealing rod is provided with a sealing end, which is inserted into the discharge section. The side wall of the connecting section is provided with a guide groove.

[0013] Furthermore, the base is provided with a connecting groove, and a mounting block is provided in the connecting groove. The mounting block is fixed to the base by bolts. The mounting block is provided with a mounting groove, one end of the sealing rod is fixed to the mounting groove, and a limiting plate is provided on the end of the sealing rod connected to the mounting groove.

[0014] Furthermore, the bottom of the base is connected to a first guide seat and a second guide seat. The first guide seat has a first guide hole, the second guide seat has a second guide hole, and the base has a through cavity. The first guide hole, the second guide hole, and the through cavity are coaxially arranged. The movable block has a push block, which passes through the through cavity. The projection of the first guide seat on the base at least partially overlaps with the mounting block.

[0015] Furthermore, the side wall of the injection-molded pipe is provided with an annular groove, and an insulation layer and an outer shell are provided on the annular groove. The insulation layer is wrapped around the inner wall of the annular groove, and the outer shell is placed on the annular groove.

[0016] The advantages of this utility model are: The injection tube and the sealing rod slide together, and when closed, the sealing rod is embedded in the injection port to form a rigid seal. Compared with existing fixed gates or rubber seals, the rigid sealing structure can withstand the high temperature erosion and high pressure impact of molten plastic for a long time, avoiding residual plastic overflow after injection molding. This reduces burrs on the side armrest surface from the source, eliminates subsequent trimming processes, and reduces processing costs. At the same time, the sealing rod and the injection port have a high degree of fit, which is suitable for the high pressure filling requirements of tough plastics such as PP and ABS, ensuring the flatness of the side armrest appearance and the fit of the assembly.

[0017] The precise fit between the sealing rod and the injection tube reduces gaps, preventing the accumulation of plastic residue and lowering the risk of gate blockage. Compared to existing molds where residue accumulation in gaps requires frequent disassembly and cleaning, this structure can extend the mold cleaning cycle, reducing maintenance time and costs. At the same time, the dual guarantee of rigid sealing and uniform filling can avoid problems such as high-pressure leakage or low-pressure material shortage, ensuring consistent molding quality for each batch of side armrests, reducing scrap due to appearance defects or structural material shortages, improving the finished product qualification rate, and adapting to the quality requirements of side armrests in different scenarios such as furniture, medical devices, and transportation. Attached Figure Description

[0018] The accompanying drawings, which form part of this application, are used to provide a further understanding of the application and to make other features, objects, and advantages of the application more apparent. The illustrative embodiments and descriptions of this application are used to explain the application and do not constitute an undue limitation of the application.

[0019] Furthermore, throughout the accompanying drawings, the same or similar reference numerals denote the same or similar elements. It should be understood that the drawings are schematic, and the elements are not necessarily drawn to scale.

[0020] In the attached diagram: Figure 1This is a schematic diagram of the side armrest injection molding die in one embodiment of the present invention.

[0021] Figure 2 for Figure 1 A cross-sectional view of the movable block of the side armrest injection molding die in the illustrated embodiment.

[0022] Figure 3 for Figure 2 Enlarged view of point A in the image.

[0023] Figure 4 for Figure 1 A cross-sectional view of the injection tube of the side armrest injection molding die in the illustrated embodiment.

[0024] Figure 5 for Figure 4 Enlarged view of point B in the image.

[0025] Figure 6 for Figure 4 Enlarged view of point C in the image.

[0026] The meanings of the reference numerals in the figure are as follows: 101. Lower mold; 102. Upper mold; 103. Base; 104. Support seat; 105. Pad; 106. Movable block; 107. Guide rod; 108. End block; 109. Mounting block; 110. Push block; 111. First guide seat; 112. Second guide seat; 113. First guide hole; 114. Second guide hole; 115. Injection tube; 116. Sealing rod; 1161. Sealing end; 117. Injection port; 1171. Guide part; 1172. Discharge part; 1173. Connecting part; 1174. Guide groove; 118. Insulation layer; 119. Outer shell; 120. Limiting plate; 121. Movable plate; 122. Ejector pin; 123. Through cavity. Detailed Implementation

[0027] Embodiments of this disclosure will now be described in more detail with reference to the accompanying drawings. While some embodiments of this disclosure are shown in the drawings, it should be understood that this disclosure can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of this disclosure. It should be understood that the accompanying drawings and embodiments of this disclosure are for illustrative purposes only and are not intended to limit the scope of protection of this disclosure.

[0028] It should also be noted that, for ease of description, only the parts relevant to the utility model are shown in the accompanying drawings. Unless otherwise specified, the embodiments and features described in this disclosure can be combined with each other.

[0029] It should be noted that the concepts of "first" and "second" mentioned in this disclosure are used only to distinguish different devices, modules or units, and are not used to limit the order of functions performed by these devices, modules or units or their interdependencies.

[0030] It should be noted that the terms "a" and "a plurality of" used in this disclosure are illustrative rather than restrictive, and those skilled in the art should understand that, unless otherwise expressly indicated in the context, they should be understood as "one or more".

[0031] The names of messages or information exchanged between multiple devices in the embodiments of this disclosure are for illustrative purposes only and are not intended to limit the scope of such messages or information.

[0032] This disclosure will now be described in detail with reference to the accompanying drawings and embodiments.

[0033] like Figures 1-6 As shown, a side armrest injection molding die includes a base 103, a lower mold 101, an upper mold 102, a movable plate 121, a plurality of ejector pins 122, an injection tube 115, and a sealing rod 116.

[0034] The base 103 is placed on the table to support the entire mold; the lower mold 101 is fixed to the base 103; the upper mold 102 is fastened to the lower mold 101 and can move relative to the lower mold 101; the movable plate 121 is provided on the base 103 and can move within the space between the base 103 and the lower mold 101; the ejector pin 122 is provided on the movable plate 121 and passes through the lower mold 101; after the lower mold 101 and the upper mold 102 are fastened together, a mold cavity is formed, and the ejector pin 122 passes through the mold cavity. Inside the cavity; the injection tube 115 passes through the cavity of the lower mold 101; the sealing rod 116 passes through the injection tube 115; one end of the injection tube 115 is provided with an injection port 117, and the injection tube 115 can move relative to the sealing rod 116, so that the injection tube 115 has at least a closed state in which the sealing rod 116 is in the injection port 117 and an injection state in which the sealing rod 116 is moved out of the injection port 117; the movable plate 121 is provided with a through hole for the injection tube 115 to pass through.

[0035] The working process of this side armrest injection molding mold is as follows: When injection molding is required, the injection tube 115 moves relative to the sealing rod 116, the sealing rod 116 moves out from the injection port 117, and the injection tube 115 enters the injection state. At this time, the molten plastic enters the mold cavity through the injection tube 115 and the injection port 117, and the plastic is precisely filled into the mold cavity through the injection tube 115.

[0036] After injection molding is completed, the injection tube 115 moves again relative to the sealing rod 116, the sealing rod 116 is reinserted into the injection port 117, and the injection tube 115 enters a closed state.

[0037] When demolding is required, the movable plate 121 moves within the movable cavity between the base 103 and the lower mold 101, causing the ejector pin 122, which is inserted into the mold cavity, to move and push the molded side armrest out of the mold cavity. Because the precise fit between the sealing rod 116 and the injection tube 115 reduces the gap, it avoids the accumulation of plastic residue and reduces the risk of gate blockage. During demolding, issues such as gate blockage will not affect the smoothness of demolding, ensuring that each demolding is successful, further improving production efficiency and product quality.

[0038] Furthermore, the side armrest injection molding mold also includes a support base 104 and a pad 105. The support base is mounted on the base 103; the pad 105 is mounted on the support base; the lower mold 101 is fixedly connected to the pad 105. The pad 105 separates a movable cavity between the support base and the lower mold 101, and the movable plate 121 is located within the movable cavity and moves within it. The arrangement of the support base 104 and the pad 105 optimizes the overall structural layout of the mold. The support base provides a more stable support foundation for the entire mold, enabling the mold to withstand greater pressure during injection molding without easily shaking or deforming. The pad 105 cleverly separates the movable cavity between the support base and the lower mold 101, creating space for the movement of the movable plate 121. The smooth movement of the movable plate 121 within the movable cavity ensures that the ejector pin 122 can accurately eject the molded side armrest from the mold cavity, improving the efficiency and accuracy of demolding.

[0039] Furthermore, the side armrest injection molding mold also includes a movable block 106. A movable groove is provided at the bottom of the support platform, and the movable block 106 is located within the movable groove. The injection tube 115 is connected to the movable block 106. The movement of the movable block 106 within the movable groove provides power and support for the state switching of the injection tube 115. When the movable block 106 moves within the movable groove, it drives the connected injection tube 115 to move relative to the sealing rod 116, thereby achieving the switching between the closed state and the injection state of the injection tube 115. Since a guide rod 107 is connected within the movable groove, and a guide hole is provided on the movable block 106, the guide rod 107 passes through the guide hole, making the movement of the movable block 106 more stable and accurate. The guide rod 107 is threaded into the movable groove, and an end block 108 at one end provides a limit for the movement of the movable block 106. When the movable block 106 is placed on the end block 108, the injection tube 115 is in a sealed state, ensuring the sealing performance during the injection process. Furthermore, one end of the injection tube 115 is recessed towards the central axis to form an injection port 117, and the diameter of the sealing rod 116 corresponds to the inner diameter of the injection port 117. This correspondence allows the sealing rod 116 to be tightly inserted into the injection port 117, achieving a good sealing effect. When the injection tube 115 is in a closed state, the tight fit between the sealing rod 116 and the injection port 117 effectively prevents leakage of molten plastic, ensuring the stability of the injection molding process and product quality.

[0040] Preferably, the injection port 117 has an hourglass-shaped structure, including a guide portion 1171, a connecting portion 1173, and a discharge portion 1172. The guide portion 1171 and the discharge portion 1172 are connected by the connecting portion 1173. The sealing rod 116 is provided with a sealing end 1161, which is inserted into the discharge portion 1172. The connecting portion 1173 has a guide groove 1174 on its side wall. The guide portion 1171 can guide the molten plastic to enter the injection port 117 more smoothly, reducing the resistance and turbulence of the plastic during entry, allowing the plastic to flow into the mold cavity in a more orderly manner. The connecting portion 1173 serves as a transition and connection, connecting the guide portion 1171 and the discharge portion 1172 to ensure the continuity of plastic flow. The sealing end 1161 inserted into the discharge portion 1172 further enhances the sealing effect.

[0041] During injection molding, the guide groove 1174 guides the flow direction of the plastic, allowing it to be more evenly distributed within the mold cavity and preventing localized material shortages or accumulation. Simultaneously, the guide groove 1174 can also buffer the pressure of the plastic to a certain extent, reducing the impact on the injection port 117 and the sealing rod 116, thus extending their service life. When the injection tube 115 moves, the guide groove 1174 allows the sealing end 1161 to be directly inserted into the discharge section 1172, ensuring the sealing effect of the sealing rod 116 on the discharge port.

[0042] Furthermore, the base 103 is provided with a connecting groove, and a mounting block 109 is provided in the connecting groove. The mounting block 109 is fixed to the base 103 by bolts. The mounting block 109 is provided with a mounting groove, and one end of the sealing rod 116 is fixed to the mounting groove. A limiting plate 120 is provided on the end of the sealing rod 116 connected to the mounting groove. The setting of the limiting plate 120 ensures the stability and accuracy of the installation of the sealing rod 116, prevents the sealing rod 116 from shifting or shaking during use, and ensures its fitting accuracy with the injection tube 115. When the sealing rod 116 is installed in the mounting groove of the mounting block 109, the limiting plate 120 can fit tightly with the mounting block 109, restricting the axial and radial movement of the sealing rod 116, so that the sealing rod 116 always maintains the correct position and posture during the sealing and injection state switching of the injection tube 115.

[0043] Furthermore, the bottom of the base 103 is connected to a first guide seat 111 and a second guide seat 112. The first guide seat 111 has a first guide hole 113, and the second guide seat 112 has a second guide hole 114. The base 103 has a through cavity 123. The first guide hole 113, the second guide hole 114, and the through cavity 123 are coaxially arranged. The movable block 106 has a push block 110, which passes through the through cavity 123. The projection of the first guide seat 111 on the base 103 at least partially overlaps with the mounting block 109. The push block 110 can move smoothly within the first guide hole 113, the second guide hole 114, and the through cavity 123. Since the three are coaxially arranged, the linearity and stability of the movement of the movable block 106 are ensured, thereby ensuring the accuracy of the movement of the injection tube 115 relative to the sealing rod 116, making the switching of the injection tube 115 between the closed state and the injection state more reliable.

[0044] Mounting block 109 is bolted to base 103, providing stable support for sealing rod 116. The first guide seat 111 partially overlaps with mounting block 109, forming a mutually restraining and supporting relationship between the two, which further improves the mold's ability to withstand pressure and vibration during injection molding and reduces the possibility of component loosening or displacement caused by external forces.

[0045] Furthermore, the injection molding tube 115 has an annular groove on its side wall, on which an insulation layer 118 and an outer shell 119 are provided. The insulation layer 118 wraps around the inner wall of the annular groove, and the outer shell 119 covers the annular groove. The insulation layer 118 effectively reduces heat loss from the molten plastic inside the injection molding tube 115, allowing the plastic to maintain a suitable temperature and fluidity during the injection molding process. This helps the plastic to fill the mold cavity more evenly, improving the molding quality of the side armrest. The outer shell 119 protects the insulation layer 118 and the injection molding tube 115, preventing damage to the insulation layer 118 from external factors, and also enhancing the overall structural strength of the injection molding tube 115.

[0046] In actual operation, when injection molding is required, the movable block 106 is pushed to move along the guide rod 107, which in turn moves the injection tube 115 relative to the sealing rod 116, causing the sealing rod 116 to move out of the injection port 117, and the injection tube 115 enters the injection state. At this time, the molten plastic enters the mold cavity through the injection port 117 of the injection tube 115. Since the injection port 117 adopts an hourglass-shaped structure, the guide part 1171 can effectively guide the plastic, allowing it to smoothly enter the connecting part 1173, and then evenly fill the mold cavity through the discharge part 1172. The guide groove 1174 on the side wall of the connecting part 1173 further ensures the stability of the plastic flow and avoids problems such as plastic accumulation or poor flow.

[0047] After injection molding is completed, the movable block 106 is pushed in the reverse direction, so that the movable block 106 is placed back on the end block 108 of the guide rod 107. At this time, the injection tube 115 returns to the closed state, and the sealing rod 116 is embedded again into the injection port 117 to achieve rigid sealing and prevent the residual molten plastic in the mold cavity from overflowing.

[0048] After the side armrest is formed, the movable plate 121 moves in the movable cavity between the base 103 and the lower mold 101, driving the ejector pin 122 to pass through the mold cavity and push the formed side armrest out of the mold cavity, thus completing the demolding process.

[0049] This side armrest injection molding die, through the coordinated operation of its various components, not only solves the problems of poor sealing effect and unstable molding quality of the injection port 117 in the existing technology, but also improves production efficiency and reduces production costs, and can meet the high-quality requirements of different industries such as furniture, medical devices, and transportation for side armrests.

[0050] The above description is merely a selection of preferred embodiments of this disclosure and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the utility model involved in the embodiments of this disclosure is not limited to the technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the above-described inventive concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in the embodiments of this disclosure.

Claims

1. A side armrest injection molding die, comprising: The base (103) is placed on the table to support the entire mold; The lower mold (101) is fixedly connected to the base (103); The upper mold (102) is fastened to the lower mold (101) and is movable relative to the lower mold (101); A movable plate (121) is provided on the base (103) and is movable within the space between the base (103) and the lower mold (101); A number of ejector pins (122) are disposed on the movable plate (121) and pass through the lower mold (101); The lower mold (101) and the upper mold (102) are fastened together to form a mold cavity, and the ejector pin (122) is inserted into the mold cavity; Its features are: The side armrest injection molding mold also includes: The injection tube (115) is inserted into the mold cavity of the lower mold (101); A sealing rod (116) is inserted into the injection tube (115); The injection tube (115) has an injection port (117) at one end. The injection tube (115) can move relative to the sealing rod (116) so that the injection tube (115) has at least a closed state in which the sealing rod (116) is in the injection port (117) and an injection state in which the sealing rod (116) is moved out of the injection port (117). The movable plate (121) has a through hole through which the injection tube (115) passes.

2. The side armrest injection molding die according to claim 1, characterized in that: Also includes: A support platform is provided on the base (103); A pad (105) is provided on the support platform; The lower mold (101) is fixed to the pad (105), the pad (105) separates a movable cavity between the support platform and the lower mold (101), and the movable plate (121) is located in the movable cavity and moves within the movable cavity.

3. The side armrest injection molding die according to claim 2, characterized in that: It also includes a movable block (106), the bottom of the support platform is provided with a movable groove, the movable block (106) is located in the movable groove, and the injection tube (115) is connected to the movable block (106).

4. The side armrest injection molding die according to claim 3, characterized in that: A guide rod (107) is connected inside the movable groove, and a guide hole is provided on the movable block (106), through which the guide rod (107) passes.

5. The side armrest injection molding die according to claim 4, characterized in that: The guide rod (107) is threaded into the movable groove. One end of the guide rod (107) is provided with an end block (108). When the movable block (106) is placed on the end block (108), the injection tube (115) is in a sealed state.

6. The side armrest injection molding die according to claim 1, characterized in that: One end of the injection tube (115) is recessed towards the central axis to form the injection port (117), and the diameter of the sealing rod (116) corresponds to the inner diameter of the injection port (117).

7. The side armrest injection molding die according to claim 6, characterized in that: The injection port (117) has an hourglass-shaped structure. The injection port (117) includes a guide part (1171), a connecting part (1173), and a discharge part (1172). The guide part (1171) and the discharge part (1172) are connected by the connecting part (1173). The sealing rod (116) is provided with a sealing end (1161), which is inserted into the discharge part (1172). The connecting part (1173) has a guide groove (1174) on its side wall.

8. The side armrest injection molding die according to claim 3, characterized in that: The base (103) is provided with a connecting groove, and a mounting block (109) is provided in the connecting groove. The mounting block (109) is fixed to the base (103) by bolts. The mounting block (109) is provided with a mounting groove, and one end of the sealing rod (116) is fixed to the mounting groove. A limiting plate (120) is provided on the end of the sealing rod (116) connected to the mounting groove.

9. The side armrest injection molding die according to claim 8, characterized in that: The base (103) is connected to a first guide seat (111) and a second guide seat (112) at its bottom. The first guide seat (111) is provided with a first guide hole (113), and the second guide seat (112) is provided with a second guide hole (114). The base (103) is provided with a through cavity (123). The first guide hole (113), the second guide hole (114) and the through cavity (123) are coaxially arranged. The movable block (106) is provided with a push block (110), which passes through the through cavity (123). The projection of the first guide seat (111) on the base (103) overlaps at least partially with the mounting block (109).

10. The side armrest injection molding die according to claim 1, characterized in that: The injection-molded tube (115) has an annular groove on its side wall. The annular groove is provided with a heat insulation layer (118) and an outer shell (119). The heat insulation layer (118) wraps around the inner wall of the annular groove, and the outer shell (119) covers the annular groove.

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