Bridge sling end waterproof sleeve-sheath integrated forming method

Abstract

The application relates to a bridge sling cable end waterproof sleeve-sheath integrated forming method and belongs to the technical field of bridges. A sling sheath is formed on the surface of a sling body by extrusion in an extrusion device, air cooling and water cooling are carried out, the sling body after extrusion is cut according to the anchoring length, and the sling sheaths on both sides of the sling body after extrusion are removed; anchorages and conical supporting cylinders are installed at both ends of the sling body, the steel wire bundles at both ends of the sling are spread into broom shapes, and anchor pouring is completed; a molten waterproof sleeve raw material is put into a conical half-sleeve extrusion forming die to be extruded, a half-conical sheath is formed; the two half-conical sheaths are arranged on the outer periphery of the conical supporting cylinder to form a half-sleeve conical waterproof sleeve, and a straight section gap is reserved between the half-sleeve conical waterproof sleeve and the sling sheath; the half-sleeve conical waterproof sleeve is axially welded, and the sling sheath is circumferentially welded. The application forms an integrated piece through the welding of the half-sleeve conical waterproof sleeve and the sling sheath, and the sealing waterproof property is improved.

Description

Technical Field

[0001] This invention relates to an integrated molding method for waterproof sleeves and sheaths at the ends of bridge suspension cables, belonging to the field of bridge technology. Background Technology

[0002] The suspension cable is a component connecting the main cable and the main beam of a suspension bridge. The cable body is made of high-strength hot-dip galvanized steel wire twisted and then hot-extruded with a double-layer high-density polyethylene sheath. Anchorages are fitted at both ends, and anchoring material is cast. The anchor body is formed through mechanical interlocking, friction, and adhesion between the anchoring material and the steel wire, achieving anchorage with the main cable clamps and the main beam steel structure. To achieve the assembly of the cable anchorages and the casting of the anchor body, the high-density polyethylene sheath needs to be peeled off within a certain length at both ends of the cable. This peeled section becomes a weak point in the hot-extruded high-density polyethylene cable protection. Traditional methods use steel connecting cylinders combined with rubber sealing rings for waterproofing, which has a certain sealing effect. However, for ultra-long-span suspension bridges, under cable vibration and complex dynamic loads, the sealing structure often cannot completely prevent moisture ingress. Therefore, the design unit proposed using a high-density polyethylene conical waterproof sleeve structure integrally formed with the cable sheath, but conventional cable extrusion processes cannot form this structure. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide an integrated molding method for waterproof sleeve and sheath at the cable end of a bridge suspension bridge, which realizes the integration of the conical waterproof sleeve at the cable end of the suspension bridge and the cable sheath, thereby improving the sealing and waterproof performance of the cable end.

[0004] The technical solution adopted by the present invention to solve the above problems is: an integrated molding method for a waterproof sleeve-sheath at the end of a bridge suspension cable, the molding method comprising the following steps: Step 1: The sling sheath is extruded onto the surface of the sling body in a dual-cavity co-extrusion extrusion machine. After extrusion, air cooling and water cooling are performed in sequence, with the cooling temperature distributed in a stepped manner. Step 2: Cut the extruded sling body according to the anchoring length, and remove the sling sheaths from both ends of the extruded sling body so that both ends of the sling body are exposed. Step 3: Install anchors and conical support cylinders at both ends of the sling body, spread the steel wire bundles at both ends of the sling into a broom shape, and complete the anchoring. Step 4: The waterproof sleeve raw material is fully melted through a screw extruder, and then the molten waterproof sleeve raw material is put into a conical half sleeve extrusion mold for extrusion to form two conical sleeves. Step 5: Place the two halves of the conical sheath around the outer perimeter of the conical support cylinder to form a half-conical waterproof sheath, and leave a straight section gap between the front end of the half-conical waterproof sheath and the end of the sling sheath respectively; Step Six: Axially weld the two halves of the conical waterproof sleeve to make them a single piece; then circumferentially weld the conical waterproof sleeve to the sling sheath to make them a single piece.

[0005] The temperature of the sling body after extrusion in step one is 150℃~180℃. It is then air-cooled to 100℃~130℃ for 1~2 minutes, and then water-cooled in a water tank to 50℃~80℃ for 10~20 minutes.

[0006] In step one, the extrusion temperature is divided into the feeding section, melting section, equalization section, die neck section, die head section, and extrusion section. The temperature of the feeding section is 120℃~160℃, the temperature of the melting section is 170℃~210℃, the temperature of the equalization section is 200℃~240℃, the temperature of the die neck section is 195℃~235℃, the temperature of the die head section is 165℃~195℃, and the temperature of the extrusion section is 150℃~180℃.

[0007] Step one involves extruding the sling sheath using an extrusion die. The extrusion die includes a core die, a middle die, and an outer die. The middle die is fitted around the core die, and the outer die is fitted around the middle die. The structural dimensions of the extrusion die are as follows: The inner diameter d0 of the small end of the core die is 1.05~1.10d. The outer diameter of the small end of the core die is d1 = d0 + (6~10) mm; In the formula: d0 is the inner diameter of the small end of the mandrel; d is the outer diameter of the suspension cable wire bundle; The length of the shaping section L3 = (16~20) * (t1 + t2) The length of the compressed section L2 = (1.5~2.5)d0 In the formula: L3 is the length of the shaping section of the extrusion die; t1 is the thickness of the inner sheath; t2 is the thickness of the outer sheath. L2 is the length of the compression section of the extrusion die, and d0 is the inner diameter of the small end of the mandrel. The compression cone angle β1 of the core die is 30°~60°; The outer diameter of the large end of the core die is D1 = d1 + 2L2Tanβ1.

[0008] Inner diameter of small end of middle die ; In the formula: d2 is the inner diameter of the center die; d1 is the outer diameter of the core die; d is the outer diameter of the sling wire bundle; t1 is the thickness of the inner sheath; The inner diameter of the large end of the die In the formula: The inner diameter of the large end of the die; The outer diameter of the large end of the core die; The angle difference between the inner cone angle β2 of the center die and the outer cone angle β1 of the core die is 3°~6°; Outer die small end inner diameter

[0009] In the formula: d4 is the inner diameter of the small end of the outer die; d3 is the outer diameter of the middle die; d is the outer diameter of the suspension cable wire bundle; t1 is the thickness of the inner high-density polyethylene layer; t2 is the thickness of the outer high-density polyethylene layer. Outer diameter of the large end of the outer mold ; The angle difference between the outer cone angle β3 and the inner cone angle β2 of the central die is 1°~4°.

[0010] The angle difference between the inner cone angle β4 of the outer die and the outer cone angle β3 of the middle die is 4°~7°.

[0011] In step four, the conical half-sleeve extrusion die includes an upper punch and a lower die. The top surface of the lower die has a downwardly recessed extrusion cavity. The upper punch serves as the extrusion core, and molten high-density polyethylene is placed inside the extrusion cavity. The upper punch presses against the molten high-density polyethylene. A pressure plate is provided on the top surface of the upper punch, and a reaction plate is provided on the pressure plate. The reaction plate is connected to the lower die by symmetrically arranged positioning pins. A threaded through hole is opened in the center of the reaction plate, and a T-bolt is screwed into the threaded through hole.

[0012] The upper punch matches the inner cavity of the semi-conical sheath, and the extrusion cavity of the lower die matches the outer periphery of the semi-conical sheath.

[0013] The extrusion cavity of the lower die has an exhaust hole with a diameter of 2mm to 6mm.

[0014] The method for determining the dimensions of the lower die is as follows: Inner diameter of large end of die ; Inner diameter of small end of die ; Die large end height ; Die small end height ; Length of the conical cavity section of the die ; Length of straight section of die ; The method for determining the structural dimensions of the upper punch is as follows: outer diameter of the large end of the punch ; outer diameter of small end of punch ; Length of punch cone cavity ; Length of straight section of punch ; Where S is the extrusion shrinkage rate of high-density polyethylene; Δ 1、 Δ 2、 Δ 3、 Δ4, Δ5, Δ 6、 Δ7 and Δ8 are the design tolerances for the corresponding dimensions of the conical waterproof sleeve.

[0015] The high-density polyethylene has an extrusion shrinkage rate of 1.5-3%.

[0016] Compared with the prior art, the advantages of the present invention are as follows:

[0017] By combining step-by-step molding and welding processes, the integrated molding of high-density polyethylene conical waterproof sleeves and polyethylene cable sheaths at the cable ends of suspension bridges has been achieved for the first time.

[0018] By fusion welding the half-conical waterproof sleeve to the sling sheath, a continuous and seamless polyethylene protective layer is formed, which avoids the problem of easy leakage under vibration and dynamic load of traditional steel connecting cylinder with rubber sealing ring, and improves the sealing and waterproof performance of the sling end.

[0019] The sheath was axially and circumferentially welded using an extrusion welding gun. The heating temperature of the welding rod and the base material, as well as the thickness of the molten layer, were controlled to ensure that the strength and fatigue strength of the welded area were not lower than those of the base material. Tests verified that there was no cracking or separation under 95% breaking load, thus enhancing the mechanical properties of the welded part.

[0020] The method of using a half-type conical waterproof sleeve, clamp positioning, and digital display dual-heating extrusion welding gun ensures reliable construction and facilitates on-site operation. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the operation of a dual-cavity co-extrusion extruder used in an integrated molding method for waterproof sleeve-sheath at the end of a bridge suspension cable according to an embodiment of the present invention. Figure 2 This is a schematic diagram of a cross-section of the extrusion die; Figure 3 This is a schematic diagram of the suspension cable after anchoring. Figure 4 A schematic diagram of installing waterproof sleeves and sheaths on the suspender cable body after anchoring; Figure 5 This is a schematic diagram of an integrated waterproof cover and sheath. Figure 6 This is a cross-sectional view of the sling body with a waterproof sleeve and sheath. Figure 7 A structural diagram of a conical half-sleeve extrusion die; Figure 8 for Figure 7 AA diagram; Figure 9 for Figure 7 Schematic diagram of BB in the middle; Figure 10 for Figure 7 Schematic diagram of CC in the middle; Figure 11 This is a schematic diagram of the lower die; Figure 12 This is a side view of the lower die; Figure 13 This is a schematic diagram of the upper punch; Figure 14 Figure 11 shows the cone-shaped waterproof sleeve; Figure 15 This is a cross-sectional view of the large end of the conical waterproof sleeve; Figure 16 This is a cross-sectional view of the small end of the tapered waterproof sleeve; In the figure, 1 is a conical waterproof sleeve, 2 is a sling sheath, 2.1 is an inner sheath, 2.2 is an outer sheath, 3 is a wire bundle, 4 is an axial weld, 5 is a circumferential weld, 6 is a large end positioning clamp, 7 is a small end positioning clamp, 8 is a reaction plate, 9 is a T-bolt, 10 is a pressure plate, 11 is a positioning post, 12 is a vent hole, 13 is a lower die, 14 is an extrusion cavity, 15 is an extrusion die, 15.1 is a core die, 15.2 is a middle die, 15.3 is an outer die, 16 is a water tank, 17 is a conical support cylinder, 18 is an anchor, and 19 is an upper punch. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0023] The integrated molding method of waterproof sleeve-sheath at the end of a bridge suspension cable in this embodiment includes the following steps: Step 1: As Figure 1 As shown, a high-density polyethylene sling sheath 2 is extruded onto the surface of the sling body on a dual-cavity co-extrusion extruder. After extrusion, air cooling and water cooling are performed sequentially, with the cooling temperature distributed in a stepped manner.

[0024] Step Two: As Figure 3 As shown, the extruded sling body is cut according to the anchoring length, and the high-density polyethylene sling sheaths at both ends of the extruded sling body are removed, leaving both ends of the sling body exposed.

[0025] Step 3: As Figure 4 As shown, anchors 18 and conical support cylinders 17 are installed at both ends of the exposed sling body, and the steel wire bundles 3 at both ends of the sling are spread out in a broom shape and the anchoring is completed.

[0026] Step 4: High-density polyethylene particles are fully melted through a screw extruder, and then the molten high-density polyethylene is placed into a conical half-sleeve extrusion mold for extrusion to form a semi-conical sheath.

[0027] Step 5: As Figure 5 As shown, the two halves of the conical sheath are attached to the outer periphery of the conical support cylinder using large-end clamps and small-end clamps, forming a half-type conical waterproof sleeve 1. The outer dimensions of the conical support cylinder 17 match the conical inner cavity dimensions of the conical waterproof sleeve, with a conical inner cavity dimensional tolerance of +0.2~+0.5mm; and a straight section of 20mm~30mm is reserved between the front end of the half-type conical waterproof sleeve and the end of the sling sheath.

[0028] Step Six: As Figure 6 As shown, the two halves of the conical waterproof sleeve are axially welded together to make them a single piece; then the conical waterproof sleeve and the sling sheath are circumferentially welded together to make them a single piece.

[0029] In step one above, granular high-density polyethylene material is fed from the hopper of the extruder into the barrel. Driven by the rotating screw of the extruder, it is conveyed forward along the rotating groove of the screw. At the same time, the high-density polyethylene material is gradually melted and plasticized into a viscous flow state due to the heating of the barrel and the shear friction heat of the screw on the high-density polyethylene material. Then, under the extrusion action of the screw, the high-density polyethylene material melt passes through the extrusion die with a certain orifice. The sling wire bundle, which has been twisted and wrapped, is inserted into the core of the extruder head, so that the high-density polyethylene material melt is applied to the wire bundle 3, forming a high-density polyethylene sling sheath with a uniform cross-sectional shape. After extrusion, the sling body is immediately shaped and cooled after leaving the extrusion mold. The cooling temperature is stepped, as follows: after leaving the extrusion mold, the temperature of the extruded sling body is 150℃~180℃. It is then air-cooled to 100℃~130℃ for 1~2 minutes, and then placed in water tank 16 to cool to 50℃~80℃ for 10~20 minutes. This process avoids deformation, denting or twisting of the sheath under its own weight.

[0030] The principles for determining the main process parameters of high-density polyethylene sling sheaths are as follows: I. Extrusion Temperature Control: This application uses high-density polyethylene particles as the raw material for the sheath, and the moisture content of the polyethylene particles is controlled to be <0.3%. The extrusion temperature is divided into the feeding section, melting section, equalization section, die neck section, die head section, and extrusion section. The temperature settings for each section are as follows: The feeding section mainly generates sufficient thrust, mechanical shearing, and mixing. If the temperature is too high, the plastic will melt prematurely, which will not only lead to decomposition during the extrusion process but also cause "slippage," resulting in fluctuations in extrusion pressure; premature melting will also lead to insufficient mixing and uneven plasticization. Therefore, the temperature of the feeding section is generally 120℃~160℃. The melting section achieves plasticization, and a certain temperature must be reached to ensure that most of the plastic components are plasticized; the temperature is set at 170℃~210℃. The equalization section ensures that the plastic is fully plasticized, and a slight increase in temperature is necessary; the temperature is set at 200℃~240℃. The neck section should maintain the temperature of the equalizing section or be slightly lower. The plastic exiting the screen changes from rotary motion to linear motion and has dispersed into strips. It must be compacted in its molten state. Too much temperature reduction will not meet the extrusion molding requirements. The temperature should be set to 195℃~235℃. The die head section continues extrusion to compact the plastic. Here, the plastic has a fixed surface layer in long-term contact with the inner wall of the die head. If the temperature is too high, it will cause plastic decomposition or even scorching. The temperature should be set to 165℃~195℃. Increasing the temperature in the extrusion section can make the surface glossy, but excessive temperature will cause surface decomposition, making cooling difficult, making the product difficult to shape, and prone to sagging, leading to eccentricity or flattening deformation of the high-density polyethylene sheath. The temperature should be set to 150℃~180℃.

[0031] II. Control of Traction Speed: High-density polyethylene (HDPE) sling sheath extrusion molding is a continuous production process, requiring a traction device and controlled traction speed. A higher traction speed reduces the sheath thickness and sling diameter, but increases the longitudinal tensile strength of the sling sheath. To ensure the integrity of the sling body, the traction speed cannot be too high. Typically, the traction speed is equal to or slightly greater than the extrusion speed. The ratio of traction speed to extrusion speed is called the traction ratio; in this application, the traction ratio is 1.1 to 1.3.

[0032] III. Figure 2 As shown, the extrusion die is designed as a channel for the flow of high-density polyethylene melt. The shape of this channel gradually transitions from the circular cross-section of the barrel to the shape of a double-layer polyethylene sleeve.

[0033] The extrusion die is used to form a high-density polyethylene (HDPE) sling sheath. Since the sling body is protected by a double-layer HDPE sheath, the extrusion die 15 includes a core die 15.1, a middle die 15.2, and an outer die 15.3. The middle die 15.2 is fitted around the core die 15.1, and the outer die 15.3 is fitted around the middle die 15.2. The inner diameter of the core die needs to accommodate the sling wire bundle. The cavity dimensions of the core die and the middle die determine the extrusion thickness and quality of the inner HDPE layer; the cavity dimensions of the middle die and the outer die determine the extrusion thickness and quality of the outer HDPE layer. The diameter of the extrusion die is determined based on the outer diameter of the sling wire bundle and the extrusion thickness. Due to die expansion and cooling contraction effects, the inner diameter of the extrusion die is not equal to the outer diameter of the sling. When designing the extrusion die, the main dimensions are the inner diameter, the length of the shaping section, the length of the compression section, and the compression cone angle; other dimensions only need to meet the installation requirements of the extruder. The main dimensions of the extrusion die are determined using the following empirical formulas.

[0034] 1. Core mold dimensions The inner diameter d0 of the small end of the core die is 1.05~1.10d. The outer diameter of the small end of the core die is d1 = d0 + (6~10) mm; In the formula: d0 is the inner diameter of the small end of the mandrel; d is the outer diameter of the suspension cable wire bundle; The length of the shaping section L3 = (16~20) * (t1 + t2) The length of the compressed section L2 = (1.5~2.5)d0 In the formula: L3 is the length of the shaping section (straight section) of the core die (middle die, outer die); t1 is the thickness of the inner sheath, and t2 is the thickness of the outer sheath; L2 is the length of the compression section of the mandrel (middle mandrel, outer mandrel), and d0 is the inner diameter of the small end of the mandrel.

[0035] The compression cone angle β1 of the core die is 30°~60°; The outer diameter of the large end of the core die is D1 = d1 + 2L2Tanβ1.

[0036] 2. Die dimensions The inner diameter of the small end (shaping section) of the middle die is determined by the stretch ratio of the inner sheath. The stretch ratio is the ratio of the cross-sectional area of ​​the annular gap of the middle die and the core die to the cross-sectional area of ​​the sheath after forming. The calculation formula is as follows: =1.2~1.5 Where: I is the inner sheath stretch ratio; d2 is the inner diameter of the middle die; d1 is the outer diameter of the core die; d is the outer diameter of the sling wire bundle; t1 is the thickness of the inner sheath; Inner diameter of small end of middle die ; The inner diameter of the large end of the die is mainly determined by the compression ratio of the inner sheath flow channel. The compression ratio is the ratio of the maximum material flow cross-section of the die head (large end of the compression section) to the cross-sectional area of ​​the annular interval between the die and the core die during molding. It determines the degree of compaction of the inner high-density polyethylene melt during sheath extrusion molding. The compression ratio ε is 2.5 to 6.0.

[0037] =2.5~6.0 In the formula: ε is the compression ratio; The inner diameter of the large end of the die; The outer diameter of the large end of the core die; The inner cone angle β2 of the center die needs to have an angle difference of 3°~6° with the outer cone angle β1 of the core die, i.e., β2-β1=3°~6°. This angle difference allows the extrusion pressure of the sling sheath to gradually increase, achieving a dense inner sheath protective layer and a tight bond with the bare sling.

[0038] The inner diameter of the large end of the die .

[0039] 3. External mold dimensions The inner diameter of the small end of the outer die is determined by the stretch ratio of the outer sheath. The stretch ratio is the ratio of the cross-sectional area of ​​the annular gap of the outer die and the middle die to the cross-sectional area of ​​the outer sheath after forming. The calculation formula is as follows: =1.2~1.5 In the formula: I is the outer sheath stretch ratio; d4 is the inner diameter of the small end (shaping section) of the outer die, mm; d3 is the outer diameter of the middle die, mm; d is the outer diameter of the sling wire bundle, mm; t1 is the thickness of the inner high-density polyethylene, mm; t2 is the thickness of the outer high-density polyethylene, mm.

[0040] Outer die small end inner diameter

[0041] The inner diameter of the large end of the outer die is mainly determined by the compression ratio of the inner polyethylene sheath flow channel. It is the ratio of the cross-sectional area of ​​the annular gap between the outer die and the middle die during the forming process, which determines the degree of compaction of the outer high-density polyethylene melt during the extrusion molding of the sling sheath. High-density polyethylene ε = 2.5~6.0.

[0042] =2.5~6.0 Outer diameter of the large end of the outer mold

[0043] The angle difference between the outer cone angle β3 and the inner cone angle β2 of the middle die is 1°~4°, and the angle difference between the inner cone angle β4 of the outer die and the outer cone angle β3 of the middle die is 4°~7°. This angle difference allows the extrusion pressure of the outer sheath of the sling to gradually increase, achieving the purpose of a dense outer sheath protective layer and a tight bond with the inner sheath.

[0044] To ensure the uniform and smooth flow of molten high-density polyethylene sheathing material along the die head's flow channel and its successful extrusion, the inner cavity of the extrusion die should be smooth and streamlined, without any abrupt expansions, contractions, dead zones, or stagnant areas to prevent overheating and decomposition. The surface roughness Ra of the extrusion die's inner cavity should be less than 1.6–3.2 μm.

[0045] The extrusion die material should be selected as wear-resistant alloy steel with high hardness, not less than 40HRC, and hard chrome plated. The thickness of the hard chrome plating layer is generally 0.02 to 0.03 mm.

[0046] In step four above, high-density polyethylene (HDPE) particles are first fully melted using a small screw extruder. Then, the molten HDPE rod is placed into a conical half-sleeve extrusion die, with dimensions determined according to the design dimensions of the HDPE conical waterproof sleeve, for extrusion molding. The screw extrusion temperature in the small screw extruder is set to 220~280°C to prevent insufficient temperature during subsequent die extrusion molding.

[0047] like Figure 7-16 As shown, the conical half-sleeve extrusion die includes a conical upper punch 19 and a semi-circular lower die 13. The top surface of the lower die 13 has a downwardly recessed extrusion cavity 14. The upper punch 19 serves as the extrusion core, and molten high-density polyethylene is placed inside the extrusion cavity. The upper punch presses against the molten high-density polyethylene. A pressure plate 10 is placed on the top surface of the upper punch. The bottom surface of the pressure plate 10 has an inwardly recessed arc surface that mates with the upper punch, and the top surface of the pressure plate is flat. A reaction plate 8 is provided on the pressure plate 10. The reaction plate 8 is connected to the lower die by symmetrically arranged positioning pins 11, and the reaction plate 8 mates with the plane of the pressure plate 10. A threaded through hole is provided in the center of the reaction plate; a T-bolt 9 is screwed into the threaded through hole. During operation, the T-bolt is tightened, and the extrusion force of the T-bolt is transmitted to the upper punch through the pressure plate. The upper punch applies the extrusion force to the molten high-density polyethylene, and after extrusion molding and cooling, a high-density polyethylene semi-conical sheath is formed.

[0048] The upper punch matches the inner cavity of the semi-conical sheath, and the extrusion cavity of the lower die matches the outer periphery of the semi-conical sheath.

[0049] The extrusion cavity of the lower die has an exhaust hole 12 with a diameter of 2mm to 6mm to prevent gas from forming wrinkles and other defects on the surface of the semi-conical sheath during the extrusion process.

[0050] The method for determining the dimensions of a tapered half-sleeve extrusion die is as follows: The method for determining the dimensions of the lower die is as follows: Inner diameter of large end of die ; Inner diameter of small end of die ; Die large end height ; Die small end height ; Length of the conical cavity section of the die ; Length of straight section of die ; The method for determining the structural dimensions of the upper punch is as follows: outer diameter of the large end of the punch ; outer diameter of small end of punch ; Length of punch cone cavity ; Length of straight section of punch ; Where S is the extrusion shrinkage rate of high-density polyethylene; typically 1.5~3%; Δ 1、 Δ 2、 Δ 3、 Δ4, Δ5, Δ 6、 Δ7 and Δ8 are the design tolerances for the corresponding dimensions of the conical waterproof sleeve. The above D... 1t D 2t d 1t d 2t H 1t H 2t All are structural dimensions of a semi-conical sheath.

[0051] In step six above, a digital display dual-heating extrusion welding torch is used for welding. Before the molten electrode is pressed onto the base material, the area of ​​the base material to be welded is preheated to its melting temperature to achieve a molten state. Then, pressure is applied to the molten electrode for welding. During extrusion welding, the electrode and the sheath are heated by different methods. The high-density electrode is heated by conduction in the extruder cavity and the molten guide leading to the welding shoe. In addition, the electrode is subjected to shear friction heat under the shearing action of the extruder screw, with a temperature of 240~280℃. The polyethylene sheath to be welded is heated by convection through the hot air outlet of the extrusion welding torch, with a hot air temperature of 260~300℃, ensuring that the molten layer thickness of the sheath in the welding area is not less than 0.5mm. During extrusion welding, the application of construction pressure and welding pressure ensures close contact between the molten high-density polyethylene electrode and the molten surface of the half-conical sheath to be welded, promoting diffusion and entanglement between macromolecular chains. The strength, fatigue strength, and watertightness of the welded position shall not be lower than the strength and watertightness of the high-density sheath body.

[0052] An extrusion welding torch was used to weld the straight section of the conical protective sleeve to the sling sheath, achieving an integrated structure of the high-density conical waterproof sleeve and the sling sheath. The sling was stretched to over 95% of its breaking load (≥4406KN) during the static load test, and no cracking or detachment was observed at the welded parts of the conical waterproof sleeve.

[0053] This application, through a process combining step-by-step molding and welding, achieves for the first time the integrated molding of high-density polyethylene conical waterproof sleeves and polyethylene cable sheaths at the cable ends of suspension bridges. By fusion welding the half-type conical waterproof sleeve and the cable sheath, a continuous, seamless polyethylene protective layer is formed, avoiding the leakage problems of traditional steel connecting cylinders with rubber sealing rings under vibration and dynamic loads, thus improving the sealing and waterproofing performance of the cable ends.

[0054] In addition to the above embodiments, the present invention also includes other embodiments. All technical solutions formed by equivalent transformation or equivalent substitution should fall within the protection scope of the claims of the present invention.

Claims

1. A method for integrally molding a waterproof sleeve and sheath for bridge cable ends, characterized in that: The molding method includes the following steps: Step 1: The sling sheath is extruded onto the surface of the sling body in a dual-cavity co-extrusion extrusion machine. After extrusion, air cooling and water cooling are performed in sequence, with the cooling temperature distributed in a stepped manner. Step 2: Cut the extruded sling body according to the anchoring length, and remove the sling sheaths from both ends of the extruded sling body so that both ends of the sling body are exposed. Step 3: Install anchors and conical support cylinders at both ends of the sling body, spread the steel wire bundles at both ends of the sling into a broom shape, and complete the anchoring. Step 4: Place the molten waterproof sleeve raw material into a conical half sleeve extrusion mold for extrusion to form a semi-conical sleeve; Step 5: Place the two halves of the conical sheath around the outer perimeter of the conical support cylinder to form a half-conical waterproof sheath, and leave a straight section gap between the front end of the half-conical waterproof sheath and the end of the sling sheath respectively; Step Six: Axially weld the two halves of the conical waterproof sleeve to make them a single piece; then circumferentially weld the conical waterproof sleeve to the sling sheath to make them a single piece.

2. The method for integrated molding of waterproof sleeve and sheath at the end of a bridge suspension cable according to claim 1, characterized in that: The temperature of the sling body after extrusion in step one is 150℃~180℃. It is then air-cooled to 100℃~130℃ for 1~2 minutes, and then water-cooled in a water tank to 50℃~80℃ for 10~20 minutes.

3. The integrated molding method for waterproof sleeve-sheath at the end of bridge suspension cable according to claim 1, characterized in that: In step one, the extrusion temperature is divided into the feeding section, melting section, equalization section, die neck section, die head section, and extrusion section. The temperature of the feeding section is 120℃~160℃, the temperature of the melting section is 170℃~210℃, the temperature of the equalization section is 200℃~240℃, the temperature of the die neck section is 195℃~235℃, the temperature of the die head section is 165℃~195℃, and the temperature of the extrusion section is 150℃~180℃.

4. The integrated molding method for waterproof sleeve-sheath at the end of bridge suspension cable according to claim 1, characterized in that: Step one involves extruding the sling sheath using an extrusion die. The extrusion die includes a core die, a middle die, and an outer die. The middle die is fitted around the core die, and the outer die is fitted around the middle die. The structural dimensions of the extrusion die are as follows: The inner diameter d0 of the small end of the core die is 1.05~1.10d. The outer diameter of the small end of the core die is d1 = d0 + (6~10) mm; In the formula: d0 is the inner diameter of the small end of the mandrel; d is the outer diameter of the suspension cable wire bundle; The length of the shaping section L3 = (16~20) * (t1 + t2) The length of the compressed section L2 = (1.5~2.5)d0 In the formula: L3 is the length of the shaping section of the extrusion die; t1 is the thickness of the inner sheath; t2 is the thickness of the outer sheath. L2 is the length of the compression section of the extrusion die, and d0 is the inner diameter of the small end of the mandrel. The compression cone angle β1 of the core die is 30°~60°; The outer diameter of the large end of the core die is D1 = d1 + 2L2Tanβ1; Inner diameter of small end of the die ; In the formula: d2 is the inner diameter of the center die; d1 is the outer diameter of the core die; d is the outer diameter of the sling wire bundle; t1 is the thickness of the inner sheath; The inner diameter of the large end of the die ; In the formula: The inner diameter of the large end of the die; The outer diameter of the large end of the core die; The angle difference between the inner cone angle β2 of the center die and the outer cone angle β1 of the core die is 3°~6°; Outer die small end inner diameter ; In the formula: d4 is the inner diameter of the small end of the outer die; d3 is the outer diameter of the middle die; d is the outer diameter of the suspension cable wire bundle; t1 is the thickness of the inner high-density polyethylene layer; t2 is the thickness of the outer high-density polyethylene layer. Outer diameter of the large end of the outer mold ; The angle difference between the outer cone angle β3 and the inner cone angle β2 of the central die is 1°~4°; The angle difference between the inner cone angle β4 of the outer die and the outer cone angle β3 of the middle die is 4°~7°.

5. The integrated molding method for waterproof sleeve-sheath at the end of bridge suspension cable according to claim 1, characterized in that: In step four, the conical half-sleeve extrusion die includes an upper punch and a lower die. The top surface of the lower die has a downwardly recessed extrusion cavity. The upper punch serves as the extrusion core, and molten high-density polyethylene is placed inside the extrusion cavity. The upper punch presses against the molten high-density polyethylene. A pressure plate is provided on the top surface of the upper punch, and a reaction plate is provided on the pressure plate. The reaction plate is connected to the lower die by symmetrically arranged positioning pins. A threaded through hole is opened in the center of the reaction plate, and a T-bolt is screwed into the threaded through hole.

6. The integrated molding method for waterproof sleeve-sheath at the end of bridge suspension cable according to claim 5, characterized in that: The upper punch matches the inner cavity of the semi-conical sheath, and the extrusion cavity of the lower die matches the outer periphery of the semi-conical sheath.

7. The integrated molding method for waterproof sleeve-sheath at the end of bridge suspension cable according to claim 5, characterized in that: The extrusion cavity of the lower die has an exhaust hole with a diameter of 2mm to 6mm.

8. The integrated molding method for waterproof sleeve-sheath at the end of bridge suspension cable according to claim 5, characterized in that: The dimensions of the lower die are as follows: ； ； ； ； ； ； The method for determining the structural dimensions of the upper punch is as follows: ； ； ； ； Where S is the extrusion shrinkage rate of high-density polyethylene; Δ 1、 Δ 2、 Δ 3、 Δ4, Δ5, Δ 6、 Δ7 and Δ8 are the design tolerances for the corresponding dimensions of the conical waterproof sleeve.

9. The integrated molding method for waterproof sleeve-sheath at the end of bridge suspension cable according to claim 8, characterized in that: The high-density polyethylene has an extrusion shrinkage rate of 1.5-3%.

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