CN113724927B - Manufacturing method of prefabricated branch cable and prefabricated branch cable - Google Patents
Manufacturing method of prefabricated branch cable and prefabricated branch cable Download PDFInfo
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- CN113724927B CN113724927B CN202111069788.8A CN202111069788A CN113724927B CN 113724927 B CN113724927 B CN 113724927B CN 202111069788 A CN202111069788 A CN 202111069788A CN 113724927 B CN113724927 B CN 113724927B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B7/00—Insulated conductors or cables characterised by their form
- H01B7/17—Protection against damage caused by external factors, e.g. sheaths or armouring
- H01B7/18—Protection against damage caused by wear, mechanical force or pressure; Sheaths; Armouring
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B13/00—Apparatus or processes specially adapted for manufacturing conductors or cables
- H01B13/22—Sheathing; Armouring; Screening; Applying other protective layers
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B7/00—Insulated conductors or cables characterised by their form
- H01B7/02—Disposition of insulation
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B7/00—Insulated conductors or cables characterised by their form
- H01B7/17—Protection against damage caused by external factors, e.g. sheaths or armouring
- H01B7/18—Protection against damage caused by wear, mechanical force or pressure; Sheaths; Armouring
- H01B7/24—Devices affording localised protection against mechanical force or pressure
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B7/00—Insulated conductors or cables characterised by their form
- H01B7/17—Protection against damage caused by external factors, e.g. sheaths or armouring
- H01B7/28—Protection against damage caused by moisture, corrosion, chemical attack or weather
- H01B7/282—Preventing penetration of fluid, e.g. water or humidity, into conductor or cable
- H01B7/2825—Preventing penetration of fluid, e.g. water or humidity, into conductor or cable using a water impermeable sheath
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B7/00—Insulated conductors or cables characterised by their form
- H01B7/17—Protection against damage caused by external factors, e.g. sheaths or armouring
- H01B7/29—Protection against damage caused by extremes of temperature or by flame
- H01B7/292—Protection against damage caused by extremes of temperature or by flame using material resistant to heat
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A30/00—Adapting or protecting infrastructure or their operation
- Y02A30/14—Extreme weather resilient electric power supply systems, e.g. strengthening power lines or underground power cables
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- Injection Moulding Of Plastics Or The Like (AREA)
Abstract
The invention discloses a manufacturing method of a prefabricated branch cable and the prefabricated branch cable, wherein the manufacturing method of the prefabricated branch cable comprises the following steps: a1, stripping an insulating layer and a protective layer at a connecting part of a main line cable and stripping an insulating layer and a protective layer at a connecting end of a branch line cable; a2, connecting the conductor of the branch line cable connecting end to the conductor of the main line cable connecting part; a3, clamping the C-shaped connecting piece to a joint between the branch line cable and the main line cable; a4, wrapping an insulating wrapping layer at the connection part of the trunk cable; a5, moving the main line cable, the branch line cable, the C-shaped connecting piece and the insulating wrapping layer into an injection mold, injecting the hot-melted polyolefin into the injection mold through a screw injection molding machine, and solidifying after pressure maintaining and cooling to form a branch connecting body; a6, opening the injection mold, and taking out the prefabricated branch cable after the manufacture; the advantages are that the tensile strength and sealing performance of the connection between the main line and the branch line are effectively improved.
Description
Technical Field
The invention belongs to the technical field of cable preparation, and particularly relates to a manufacturing method of a prefabricated branch cable and the prefabricated branch cable.
Background
The prefabricated branch cable is prefabricated at a specified position of the main line cable by a factory according to the distribution design requirement, has good power supply reliability, and is widely applied to places with branch cable requirements such as middle and high-rise buildings, electric shafts and the like.
After the trunk line and the branch line of the prefabricated branch cable are connected by a crimping method, a branch connecting body is generally injection molded at the connecting position to protect the connecting position of the trunk line and the branch line, however, the tensile strength and the sealing performance of the branch connecting body obtained by the conventional injection molding method are poor, and when the prefabricated branch cable is paved, the phenomenon of unstable connection of the trunk line and the branch line is caused by the pulling force or the repeated bending of the branch line, so that the use of the branch cable is affected.
Disclosure of Invention
The invention aims to provide a manufacturing method of a prefabricated branch cable and the prefabricated branch cable, and the manufacturing method effectively improves tensile strength and sealing performance of a joint of a trunk line and a branch line.
The technical scheme adopted for solving the technical problems is as follows: a method of making a prefabricated drop cable comprising the steps of:
a1, stripping an insulating layer and a protective layer at a connecting part of a trunk cable to expose a conductor at the connecting part of the trunk cable, and stripping an insulating layer and a protective layer at a connecting end of a branch cable to expose a conductor at the connecting end of the branch cable;
a2, connecting the conductor of the branch line cable connecting end to the conductor of the main line cable connecting part;
a3, clamping the C-shaped connector at the joint between the branch line cable and the main line cable, and crimping the C-shaped connector to the conductor of the branch line cable and the conductor of the main line cable through a symmetrical confining pressure cold-pressing die;
a4, wrapping the connection part of the trunk cable to tightly combine the C-shaped connecting piece, the branch cable and the trunk cable;
a5, moving the connection part of the trunk cable, the connection end of the branch cable, the C-shaped connecting piece and the insulating wrapping layer into an injection mold, injecting the hot-melted polyolefin into the injection mold through a screw injection molding machine, wrapping the hot-melted polyolefin on the connection part of the trunk cable, the connection end of the branch cable, the C-shaped connecting piece and the insulating wrapping layer, and performing pressure maintaining and cooling to solidify to form a branch connecting body;
a6, opening the injection mold, and taking out the prefabricated branch cable after the manufacture;
in the step A3, a plurality of ridges distributed along the length direction of the trunk cable are arranged on the compression joint surface of the symmetrical confining pressure cold pressing die, the extending direction of the ridges is intersected with the extending direction of the trunk cable, the height of the ridges is 5-8 mm, and the width of the ridges is 3-5 mm; after the C-shaped connector is crimped, the clearance of the conductor monofilament is less than or equal to 3 percent.
Preferably, in the step A1, the length of the exposed conductor at the trunk cable connection portion is 1.5 to 2.5 times the length of the C-shaped coupling member.
Preferably, in the step A3, the thickness of the opening of the C-shaped coupling is smaller than the thickness of the rest of the C-shaped coupling.
Preferably, in the step A3, the width of the opening of the C-shaped connector is denoted as L1, the diameter of the main line cable is denoted as L2, the diameter of the branch line cable is denoted as L3, when L2 is more than or equal to L3, 4mm is less than or equal to L1-L2 is less than or equal to 6mm, and when L2 is less than or equal to L3, 4mm is less than or equal to L1-L3 is less than or equal to 6mm.
Preferably, in the step A3, a distance between an end of the branch cable connection end and the C-shaped coupling member is denoted as L4, and L4 satisfies: l4 is more than or equal to 8mm and less than or equal to 12mm.
Preferably, in the step A4, the insulating wrapping layer comprises a hot melt adhesive tape, a tetrafluoroethylene heat-shrinkable tape and a glass fiber tape which are distributed from inside to outside.
Preferably, in the step A6, the method specifically includes the following steps:
b1, heating and hot-melting polyolefin plastic in a charging barrel to obtain a flowing state, wherein the flowing temperature of the polyolefin is 160-180 ℃, and the temperature of a nozzle is lower than 180 ℃ of the highest flowing temperature of the polyolefin;
b2, pushing the die assembly and the injection seat to move forward through the screw rod, so that the nozzle is tightly attached to a sprue channel of the injection mold;
b3, introducing pressure oil into the injection cylinder to enable the screw rod to advance, injecting hot-melted polyolefin into the closed injection mold, wherein the filling injection pressure is 140-160 MPa, and the polyolefin flow speed is 40g/s until 94-96% of the cavity of the injection mold is filled;
b4, adopting abrupt change screw type injection molding, pushing the screw forwards to continuously apply pressure which is 83-87% of the maximum pressure of filling polyolefin melt until the hot melt polyolefin in the sprue is solidified and sealed;
and B5, cooling the injection mold for 30-120 s, wherein the temperature in the cavity of the injection mold is lower than 110 ℃.
Preferably, in the step B4, the average pressure in the cavity of the injection mold is 20 to 45MPa.
The invention also provides a prefabricated branch cable which comprises a main line cable and a branch line cable, and is manufactured by the manufacturing method of the prefabricated branch cable.
Compared with the prior art, the prefabricated branch cable obtained by the manufacturing method of the prefabricated branch cable has the advantages that the reduction rate of the tensile strength of the conductor is less than or equal to 8-10% of the original value, the tensile strength is better, and the branch connector in the immersion voltage test is better than the branch connector of the conventional prefabricated branch cable and has better tightness.
Drawings
FIG. 1 is a schematic view of a prefabricated drop cable according to the present invention;
FIG. 2 is a schematic illustration of a compression molding of a C-shaped coupling according to the present invention;
fig. 3 is a schematic view of a screw injection molding machine.
In the figure: 1. a main line cable; 2. a branch line cable; 3. a C-shaped coupling; 4. symmetrically confining pressure cold pressing dies; 5. a ridge; 6. an insulating wrapping layer; 7. a branch connecting body.
Detailed Description
The invention is described in further detail below with reference to the embodiments of the drawings.
In the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "center", "upper", "lower", "left", "right", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings, are merely for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the apparatus or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention.
Embodiment one: as shown in fig. 1 to 3, a method for manufacturing a prefabricated branch cable includes the steps of:
a1, stripping an insulating layer and a protective layer at a connecting part of a trunk cable to expose a conductor at the connecting part of the trunk cable, and stripping an insulating layer and a protective layer at a connecting end of a branch cable to expose a conductor at the connecting end of the branch cable;
a2, connecting the conductor of the branch line cable connecting end to the conductor of the main line cable connecting part;
a3, clamping the C-shaped connector at the joint between the branch line cable and the main line cable, and crimping the C-shaped connector to the conductor of the branch line cable and the conductor of the main line cable through a symmetrical confining pressure cold-pressing die;
a4, wrapping the connection part of the trunk cable to tightly combine the C-shaped connecting piece, the branch cable and the trunk cable;
a5, moving the connection part of the trunk cable, the connection end of the branch cable, the C-shaped connecting piece and the insulating wrapping layer into an injection mold, injecting the hot-melted polyolefin into the injection mold through a screw injection molding machine, wrapping the hot-melted polyolefin on the connection part of the trunk cable, the connection end of the branch cable, the C-shaped connecting piece and the insulating wrapping layer, and performing pressure maintaining and cooling to solidify to form a branch connecting body;
a6, opening the injection mold, and taking out the prefabricated branch cable after the manufacture;
in the step A3, a plurality of ridges distributed along the length direction of the trunk cable are arranged on the compression joint surface of the symmetrical confining pressure cold pressing die, the extending direction of the ridges is intersected with the extending direction of the trunk cable, the height of the ridges is 5-8 mm, and the width of the ridges is 3-5 mm; after the C-shaped connector is crimped, the clearance of the conductor monofilament is less than or equal to 3 percent.
The convex ridge design of the inner wall of the symmetrical confining pressure die enables the C-shaped connecting piece to be in contact extrusion firstly, so that the problem that the inner wall plane of the C-shaped connecting piece is in pressure connection with a conductor in a common manufacturing process, the conductor is easy to slip due to insufficient pressure force, or the conductor is deformed and interference due to overlarge pressure force, so that the section of the conductor is insufficient is avoided. The clamping force 880KN of the symmetrical confining pressure die in the design, the inner wall and the C-shaped connecting piece form corresponding convex ridges meshed with each other, firm compression connection is enhanced, enough pressure force and contact surface are ensured, the C-shaped connecting piece enables the conductor of the main line cable and the conductor of the branch line cable to be tightly and firmly connected, the conductor monofilament clearance after pressure connection is only 3%, the hot air bad conductor in the gap in the current process is reduced, the line temperature is reduced, the heat-resistant safety coefficient is improved, the equivalent length conductor resistance of the contact resistance is met, the conductor tensile strength of the branch line cable after connection is not less than 80% of the conductor tensile strength before connection, the compression connection does not reduce the original actual sectional area of the conductor of the main line cable and the conductor of the branch line cable, and in addition, the opening part after pressure connection allows a basic closed state with 1-2 mm thin seams to be reserved.
In step A1, the length of the exposed conductor at the connection part of the main line cable is 1.5-2.5 times of the length of the C-shaped connector. If the length of the exposed conductor at the connection part of the trunk cable is too short, the connection operation of the trunk cable, the branch cable and the C-shaped connecting piece is inconvenient, and even the crimping operation is affected; if the length of the exposed conductor at the trunk cable connection site is too long, more C-shaped connector wrapping insulating layer material may be consumed, and even the quality of injection molding and cladding of the branch connector is affected, preferably, the length of the exposed conductor at the trunk cable connection site is 2 times that of the C-shaped connector.
In the step A3, the thickness of the opening of the C-shaped connecting piece is smaller than that of the rest parts of the C-shaped connecting piece, the opening of the C-shaped connecting piece is easy to be closed when the cold pressing mold is in compression joint, and meanwhile, due to the fact that a certain material thickness is inherent in the rest parts of the C-shaped connecting piece, the C-shaped connecting piece can bear enough cold pressing force to perform plastic change, and the C-shaped connecting piece is favorable for firmly compacting and connecting conductors of the branch line cable and conductors of the main line cable. In addition, the C-shaped connecting piece is made of copper or copper alloy materials, does not contain components which generate harmful corrosiveness and cause cracking in use, has the room temperature tensile strength of 2.16-2.45 Mpa, the elongation of 45-50%, and the Brinell Hardness (HB) of 35-45, and has certain plasticity.
In the step A3, the width of the opening of the C-shaped connector is recorded as L1, the diameter of the main line cable is recorded as L2, the diameter of the branch line cable is recorded as L3, when L2 is more than or equal to L3, L1-L2 is more than or equal to 4mm and less than or equal to 6mm, and when L2 is less than or equal to L3, L1-L3 is more than or equal to 4mm and less than or equal to 6mm, so that the C-shaped connector can be conveniently clamped on the branch line cable and the main line cable. Typically, when L2.gtoreq.L3, L1-L2=5 mm, and when L2 < L3, L1-L3=5 mm.
In step A3, the spacing between the end of the branch cable connection and the C-shaped coupling is noted as L4, L4 satisfying: l4 is more than or equal to 8mm and less than or equal to 12mm, so that stable and firm crimping is facilitated, and L4 is preferably 10mm.
In the step A4, the insulating wrapping layer comprises a hot melt adhesive tape, a tetrafluoroethylene heat-shrinkable tape and a glass fiber tape which are distributed from inside to outside.
The melt viscosity of the hot melt adhesive tape is 8000CPs/180 ℃, the softening point is 85+/-5 ℃, the initial viscosity is more than 20# copper balls, the peel strength is more than 4.3N/in2, the melting temperature is 160-180 ℃, the solid content is 100%, and the hot melt adhesive tape has gap filling property and sealing property. The hot melt adhesive tape clings to the C-shaped connecting piece and the conductor and is wrapped by 30 degrees obliquely, the insulating material with the characteristics of soft and sticky is beneficial to good contact wrapping with the dissimilar metal material, and the heat resistance index is enough to bear the heat of the conductor once the conductor heats up.
The tetrafluoroethylene thermal shrinkage belt has the working temperature reaching 250 ℃, has good mechanical toughness, can keep 5 percent of elongation even if the temperature is reduced to-196 ℃, and has the advantages of no toxicity, no pollution to contacted media, no aging, good flexibility, high compressibility and good creep resistance. The tetrafluoroethylene thermal shrinkage belt is left inclined at 30 degrees outside the hot melt adhesive tape and the wrapping design of the physical and mechanical properties of the material enhances the insulation stability of the connector.
The glass fiber belt is made of alkali-free glass fiber, si-0 is used as a chain, and the bond energy of the alkali-free glass fiber belt is larger than that of a C-C chain of an organic fiber material, so that the alkali-free glass fiber belt has better high-temperature resistance, can work for a long time at 538 ℃, has no great change of strength at a high temperature of 250 ℃, has good mechanical strength (the fiber strength is 2000-3000MPa and the elongation is 3%), has good chemical stability and insulating property, is firm and has no air hole, and does not absorb water and steam. The glass fiber belt is wrapped by being inclined by 30 degrees right outside the tetrafluoroethylene thermal shrinkage belt, and the material is high-temperature resistant and waterproof under the conditions of moisture, high temperature and even fire caused by the external environment of the cable, so that the material is more beneficial to resisting high temperature and water resistance.
The design of the insulating wrapping layer can avoid the problem that the normal use of the conductor is affected when the injection part is not closed and blemished or damaged after the C-shaped connector is in compression joint in the common manufacturing process and then the connector is directly injection molded. The integrated application design of the characteristics of tightness, flexibility and waterproofness of the hot melt adhesive tape, the tetrafluoroethylene thermal shrinkage tape and the glass fiber tape overlapped with the flat wrapping with the tensile force of about 30MPa and the covering rate of 20 percent promotes the improvement of the performance of the insulating wrapping layer, and has firm tightness.
Embodiment two: the rest is the same as in embodiment one, except that in step A6, the following steps are specifically included:
b1, heating and hot-melting polyolefin plastic in a charging barrel to obtain a flowing state, wherein the flowing temperature of the polyolefin is 160-180 ℃, and the temperature of a nozzle is lower than 180 ℃ of the highest flowing temperature of the polyolefin;
b2, pushing the die assembly and the injection seat to move forward through the screw rod, so that the nozzle is tightly attached to a sprue channel of the injection mold;
b3, introducing pressure oil into the injection cylinder to enable the screw rod to advance, injecting hot-melted polyolefin into the closed injection mold, wherein the filling injection pressure is 140-160 MPa, and the polyolefin flow speed is 40g/s until 94-96% of the cavity of the injection mold is filled;
b4, adopting abrupt change screw type injection molding, pushing the screw forwards to continuously apply pressure which is 83-87% of the maximum pressure of filling polyolefin melt until the hot melt polyolefin in the sprue is solidified and sealed;
and B5, cooling the injection mold for 30-120 s, wherein the temperature in the cavity of the injection mold is lower than 110 ℃.
In the step B4, the average pressure in the cavity of the injection mold is 20-45 MPa.
The injection molding material is polyolefin, has light weight and small density (0.83-0.96 g/cm < 3 >), has good insulation performance on electricity and heat, has the same type as the outer sheath material of the main line cable and the outer sheath material of the branch line cable, ensures the air tightness and the water tightness of the branch connecting body material and the main line cable and the branch line cable after being effectively adhered, resists pressure AC3500V after the branch connecting body is molded, is not broken down after being pressed for 5min, and has insulation resistance of more than or equal to 200MΩ.
In step B1, the nozzle temperature is lower than the highest temperature of the polyolefin flow, in order to prevent the "casting" of the melt in the through nozzle, which may occur when the fluid flows out of the nozzle opening at a certain speed, the nozzle temperature should not be too low, which would otherwise cause premature solidification of the melt to clog the nozzle, or to affect the performance of the coupling body due to the injection of the premature solidification material into the film cavity.
The screw injection molding machine is adopted to inject the molten material, the pressure born by the molten material at the top of the screw during the backward movement of the screw rotation is plasticizing pressure (also called back pressure), when the rotating speed is unchanged, the plasticizing pressure is increased to strengthen the shearing action, the temperature of the molten body is improved, the even and uniform mixing of the molten body and the discharge of gas in the molten body are facilitated, the lower the quality of the branched connecting body is ensured, the better the lower the temperature is, the better the lower the quality is, the injection molding pressure is, the plasticizing pressure of the polyolefin molten body is generally not more than 20kg/cm < 2 >, but the lower plasticizing pressure can reduce the plasticizing efficiency, the countercurrent and the leakage flow are increased, and the driving power is increased. The plasticizing pressure overcomes the flowing resistance of plastic flowing from a charging barrel to a cavity, the filling speed of the molten material is increased, the molten material is compacted, the size of the branch connecting body is different, the small size is about 2min, the large size is about 10-15 min, the injection molding time is the time required for filling the cavity with plastic melt, the reasonable injection molding time is favorable for ideal filling of the melt, the reasonable injection molding time has important significance for improving the surface quality of the branch connecting body and reducing the dimensional tolerance, and the polyolefin injection molding time is about 1/10-1/15 of the cooling time and is far lower than the cooling time.
In step B3, sufficient pressure and velocity must be ensured during the filling process, the distribution trend of the cavity pressure of the polyolefin melt in the flow direction gradually decreases, the pressure is maximum at the cavity inlet, decreases to zero at the melt front, the pressure decreases linearly in isothermal conditions, and the pressure deviates from decreasing linearly due to the influence of temperature in non-isothermal conditions. The temperature profile of the polyolefin melt gradually decreases from the center of the cavity to the wall, but the front is affected by the fountain flow, the temperature profile is uniform, the temperature of the melt at the center remains substantially the same at the inlet, the temperature at the die wall gradually decreases from the inlet, and increases at the front.
In step B4, the melt is compacted by continuously applying pressure to increase the polyolefin density to compensate for the shrinkage behavior of the polyolefin. In the pressure maintaining process, the mold cavity is filled with polyolefin, abrupt screw injection is adopted, the compression section is shorter and accounts for 5-15% of the total length of the screw, the energy conversion is more intense during plasticizing, the plasticizing pressure, namely the back pressure, of the polyolefin melt at the top of the screw is higher when the screw rotates and retreats, after the mold is closed, the mold locking force supplied to the mold is larger than the expansion force of the polyolefin melt in the cavity of the molding mold, so that the pressure of the molten polyolefin plastic entering the cavity is resisted, and the bad situation of branch connecting bodies caused by mold slotting is prevented.
In the pressure maintaining stage, the average pressure in the film cavity is generally between 20 and 45MPa, and the polyolefin has partial compressible characteristic due to quite high pressure, so that the polyolefin is more compact, has higher density and is filled with 85 percent of the maximum pressure in a region with higher pressure; in the lower pressure region, the polyolefin is relatively loose and has a relatively low density, and the time is generally between 20 and 120 seconds according to the size of the joint body and the thickness of the outer sheath layer. Therefore, the density distribution changes along with the position and time, the polyolefin flow speed in the pressure maintaining process is extremely low, the flow does not play a leading role, and the pressure becomes a main factor affecting the pressure maintaining process.
In step B5, the cooling time should be terminated on the basis of ensuring that no variation is caused when the joint body is demolded, and the temperature of the plastic polyolefin in the demolding stage should be cooled below 110 ℃ softening temperature of the polyolefin so as to prevent the relaxation phenomenon of the branched joint body caused by residual stress or the warping and deformation caused by the demolding external force.
Embodiment III: a prefabricated branch cable comprises a main line cable 1 and a branch line cable 2, and is manufactured by the manufacturing method of the prefabricated branch cable.
In this embodiment, the trunk cable 1 and the branch cable 2 are each a conductor, a polyethylene wrapping insulating layer and a polyolefin outer sheath, the polyethylene wrapping insulating layer is wrapped on the outer side of the conductor, and the polyolefin outer sheath is wrapped on the outer side of the polyethylene wrapping insulating layer.
Compared with the conventional prefabricated branch cable, the prefabricated branch cable has the following advantages that see table 1:
TABLE 1
The invention has been described above by way of example with reference to the accompanying drawings, it is clear that the implementation of the invention is not limited to the above-described manner, but it is within the scope of the invention to apply the inventive concept and technical solution to other situations as long as various improvements made by the inventive concept and technical solution are adopted or without any improvement.
Claims (8)
1. The manufacturing method of the prefabricated branch cable is characterized by comprising the following steps of:
a1, stripping an insulating layer and a protective layer at a connecting part of a trunk cable to expose a conductor at the connecting part of the trunk cable, and stripping an insulating layer and a protective layer at a connecting end of a branch cable to expose a conductor at the connecting end of the branch cable;
a2, connecting the conductor of the branch line cable connecting end to the conductor of the main line cable connecting part;
a3, clamping the C-shaped connector at the joint between the branch line cable and the main line cable, and crimping the C-shaped connector to the conductor of the branch line cable and the conductor of the main line cable through a symmetrical confining pressure cold-pressing die;
a4, wrapping the connection part of the trunk cable to tightly combine the C-shaped connecting piece, the branch cable and the trunk cable;
a5, moving the connection part of the trunk cable, the connection end of the branch cable, the C-shaped connecting piece and the insulating wrapping layer into an injection mold, injecting the hot-melted polyolefin into the injection mold through a screw injection molding machine, wrapping the hot-melted polyolefin on the connection part of the trunk cable, the connection end of the branch cable, the C-shaped connecting piece and the insulating wrapping layer, and performing pressure maintaining and cooling to solidify to form a branch connecting body;
a6, opening the injection mold, and taking out the prefabricated branch cable after the manufacture;
in the step A3, a plurality of ridges distributed along the length direction of the trunk cable are arranged on the compression joint surface of the symmetrical confining pressure cold pressing die, the extending direction of the ridges is intersected with the extending direction of the trunk cable, the height of the ridges is 5-8 mm, and the width of the ridges is 3-5 mm; after the C-shaped connecting piece is in crimping, the clearance of the conductor monofilament is less than or equal to 3%;
the step A5 specifically comprises the following steps:
b1, heating and hot-melting the polyolefin plastic in a charging barrel to obtain a flowing state, wherein the flowing temperature of the polyolefin is 160-180 ℃, and the temperature of a nozzle is lower than 180 ℃ of the highest flowing temperature of the polyolefin;
b2, pushing the die assembly and the injection seat to move forward through the screw rod, so that the nozzle is tightly attached to a sprue channel of the injection mold;
b3, introducing pressure oil into the injection cylinder to enable the screw rod to advance, injecting hot-melted polyolefin into the closed injection mold, wherein the filling injection pressure is 140-160 MPa, and the polyolefin flow speed is 40g/s until the injection mold cavity is full of 94-96%;
b4, adopting abrupt change screw type injection molding, pushing the screw forwards to continuously apply pressure which is 83-87% of the maximum pressure of filling polyolefin melt until the hot melt polyolefin in the sprue is solidified and sealed;
and B5, cooling the injection mold for 30-120 s, wherein the temperature in the cavity of the injection mold is lower than 110 ℃.
2. The method of manufacturing a prefabricated drop cable according to claim 1, wherein in step A1, the length of the exposed conductor at the trunk cable connection is 1.5 to 2.5 times the length of the C-shaped connector.
3. The method of manufacturing a prefabricated drop cable as claimed in claim 1, wherein in step A3, the thickness of the C-shaped connector at the opening is smaller than the thickness of the remainder of the C-shaped connector.
4. The method of manufacturing a prefabricated drop cable according to claim 1, wherein in step A3, the width of the opening of the C-shaped connector is denoted as L1, the diameter of the trunk cable is denoted as L2, the diameter of the branch cable is denoted as L3, 4mm is equal to or less than L1-L2 is equal to or less than 6mm when L2 is equal to or greater than L3, and 4mm is equal to or less than L1-L3 is equal to or less than 6mm when L2 is equal to or less than L3.
5. The method of manufacturing a prefabricated drop cable according to claim 1, wherein in step A3, the spacing between the end of the stub cable connection end and the C-shaped coupling member is denoted as L4, L4 satisfying: l4 is more than or equal to 8mm and less than or equal to 12mm.
6. The method according to claim 1, wherein in the step A4, the insulating wrapping layer comprises a hot melt adhesive tape, a tetrafluoroethylene heat shrinkable tape, and a glass fiber tape distributed from inside to outside.
7. The method of manufacturing a prefabricated drop cable according to claim 1, wherein in step B4, the average pressure in the cavity of the injection mold is 20 to 45MPa.
8. A prefabricated drop cable comprising a trunk cable and a branch cable, characterized in that it is manufactured by a method of manufacturing a prefabricated drop cable according to any one of claims 1-7.
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| CN114300913A (en) * | 2022-01-05 | 2022-04-08 | 四川新蓉电缆有限责任公司 | Processing method of injection-molding-free pre-branch connecting body |
| CN114898914B (en) * | 2022-05-27 | 2023-11-14 | 四川蓝电电缆科技有限公司 | Prefabricated branch cable and manufacturing method thereof |
| CN114883031B (en) * | 2022-05-27 | 2023-11-10 | 四川蓝电电缆科技有限公司 | Outdoor prefabricated branch cable connector and manufacturing method thereof |
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| JP2005354758A (en) * | 2004-06-08 | 2005-12-22 | Yazaki Corp | Branch cable |
| CN101286631B (en) * | 2008-06-03 | 2010-10-13 | 上海亚龙工业（集团）有限公司 | Environment friendly and clean type prefabricated branch cable and method for producing the same |
| CN101673600B (en) * | 2009-07-21 | 2011-10-05 | 江苏海达电缆有限公司 | Method for manufacturing prefabricated branch cable |
| CN103985436A (en) * | 2014-05-04 | 2014-08-13 | 南安市国高建材科技有限公司 | Environment-friendly clean prefabricated branch cable and manufacturing method thereof |
| JP6782104B2 (en) * | 2015-06-29 | 2020-11-11 | 矢崎エナジーシステム株式会社 | Branch cable |
| CN109903919A (en) * | 2017-12-07 | 2019-06-18 | 孙强 | A kind of environmental protection low pressure aluminium alloy pre-branched cable |
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