A polytetrafluoroethylene pipe isostatic forming device and forming process thereof

Abstract

The present invention relates to a polytetrafluoroethylene pipe isostatic forming device and a forming process thereof, comprising a tubular outer mold, a central pressure tube, a head module and a rubber membrane cylinder; the specific process is as follows: S1: forming device station distribution; S2: polytetrafluoroethylene powder feeding; S3: head locking and sealing; S4: pressure molding; S5: pressure holding molding; S6: pressure relief and material taking; S7: sintering; the pipe is formed by internal pressure molding of the polytetrafluoroethylene pipe, and the central pressure tube can meet the high-pressure water flow while ensuring the rapid assembly and locking of the head module; when disassembling and installing the head module, it is only necessary to loosen or tighten the tightening nut, which improves the loading and unloading efficiency and is convenient to operate; the molding device adopts a multi-station structure to complete the powder feeding, device locking, pressure molding, pressure holding molding and pressure relief and material taking of the polytetrafluoroethylene pipe at each station; fully realizes the streamlined production, and the efficiency is greatly improved.

Description

Technical Field

[0001] The invention relates to the technical field of polytetrafluoroethylene pipe forming, in particular to a polytetrafluoroethylene pipe isostatic forming device and a forming process thereof. Background Art

[0002] Polytetrafluoroethylene (PTFE) is a high-molecular-weight polymer made from tetrafluoroethylene (PTFE). It is white, waxy, translucent, and highly resistant to heat and cold. It is resistant to acids, alkalis, and various organic solvents, and is virtually insoluble in all solvents. PTFE also offers high-temperature resistance and a very low coefficient of friction, making it an ideal coating for easy-to-clean water pipe linings, in addition to its lubricating properties.

[0003] Existing PTFE-lined pipes generally adopt an isobaric process, that is, during the manufacturing process, the steel shell of the pipe itself is used as part of the mold, and high-pressure water is filled into the interior. The high-pressure water isobaricly generates high pressure in the mold cavity, thereby pressing the powdered PTFE into the pipe. Generally, in this molding device, the end face of the molding cavity is provided with multiple fixedly connected plate structures, which are fixed to the end face by bolts. This structure is not only very troublesome to add and remove the PTFE, but also prone to poor sealing problems due to the multiple plate structures. Therefore, there is a need for a PTFE isobaric molding device that is easy to assemble and disassemble and has strong sealing performance.

[0004] For example, the polytetrafluoroethylene isostatic pressing device and the pipe lining method using the device disclosed in Chinese patent CN201210075199.5 provide a polytetrafluoroethylene isostatic pressing device with an ingenious concept, high strength of the formed tube and good performance, and a lining method that can tightly line the polytetrafluoroethylene formed tube in the pipeline, which solves the technical problems existing in the prior art such as low density of the polytetrafluoroethylene lining, poor tensile strength, and poor anti-permeability due to insufficient forming pressure of the polytetrafluoroethylene formed tube. The mold is placed as a whole under the liquid level of the high-pressure chamber of the isostatic press, and the high-pressure chamber is pressurized to the process pressure to cold-press the polytetrafluoroethylene blank, that is, the isostatic pressing process is adopted, and the mold blank is sintered and then stretched and placed in the pipeline. After heating, the polytetrafluoroethylene tube blank has memory rebound, so that the lining polytetrafluoroethylene tube is tightly lined in the pipeline, the lining has good high temperature and high pressure resistance, and meets the full vacuum use requirements under high temperature conditions of 232°C; Figure 1 As shown: 1 is the tubular inner mold; 2 is the tubular outer mold; 3 is the upper sealing ring; 4 is the lower sealing ring; 5 is the annular packing cavity; 6 is the elastic mold layer; 7 is the annular pressure plate; 8 is the sealing ring; 9 is the upper positioning flange; 10 is the upper and lower equal position flanges; 21 is the through hole;

[0005] In the above patent, the molding of polytetrafluoroethylene adopts an external pressure molding method. The device requires the mold to be immersed in a large high-pressure chamber. The equipment required for the entire molding occupies a large area and is very troublesome to take and place the entire mold. In addition, multiple flange structures are set on the end. The sealing after adding polytetrafluoroethylene and the removal of the formed pipe require a large number of installation and removal bolt structures, which is very troublesome. The device is difficult to meet the requirements of continuous flow production, resulting in low production efficiency. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a polytetrafluoroethylene pipe isostatic molding device and its molding process; it can solve the problems of the general use of high-pressure chamber pressurized molds and external pressure molding, which results in large equipment footprint, low production efficiency, and inconvenience in adding raw materials and removing pipes.

[0007] In order to solve the above technical problems, the technical solution of the present invention is: a polytetrafluoroethylene pipe isostatic molding device, the innovation of which is that it includes a tubular outer mold, a central pressure tube, a head module and a rubber membrane cylinder;

[0008] The tubular outer mold has a cylindrical inner cavity and is open at both ends; the central pressure tube is coaxially arranged with the tubular outer mold, and a pipe forming cavity is formed between the outer wall of the central pressure tube and the inner wall of the tubular outer mold; a plurality of pressure through holes are evenly arranged in the circumferential direction in the middle area of ​​the central pressure tube; threaded sections are provided at both ends of the pressure through holes on the central pressure tube, and the outer diameter of the threaded sections is smaller than the outer diameter of the pressure through holes on the central pressure tube;

[0009] The head module has a pair and is respectively arranged at the two ends of the tubular outer mold; the head module includes a first pressure plate, a second pressure plate, a spring, a tightening nut and a locking bolt; the first pressure plate is arranged on the end faces of the two ends of the tubular outer mold, and the first pressure plate is annular in structure; the first pressure plate is nested on the central pressurized tube; the inner contour of the first pressure plate is sealed to the outer wall of the central pressurized tube; the bottom end of the first pressure plate is sealed to the end face of the tubular outer mold; a countersunk threaded hole is provided on the upper surface of the first pressure plate; a groove is provided on the lower surface of the first pressure plate to accommodate the end of the rubber membrane cylinder;

[0010] The second pressure plate is arranged above the first pressure plate; the second pressure plate is annular in structure, and a pair of bolt holes are symmetrically arranged in the circumferential direction of the central hole of the upper plate; the second pressure plate is nested on the central pressure tube and a gap is left between the second pressure plate and the outer wall of the central pressure tube;

[0011] The locking bolt passes through the bolt hole of the second pressure plate, and the bottom end of the locking bolt is connected to the countersunk threaded hole on the first pressure plate; the spring is nested on the locking bolt and is located between the second pressure plate and the first pressure plate; a connecting nut is provided at the top of the locking bolt and is connected to the locking bolt to press the second pressure plate against the top of the spring; the tightening nut is provided above the second pressure plate, and the tightening nut cooperates with the threaded section on the central pressure tube to press the first pressure plate against the end surface of the tubular outer mold;

[0012] The rubber diaphragm cylinder is nested on the central pressure tube and is located outside the pressure through hole of the central pressure tube. The end face of the rubber diaphragm cylinder is embedded in the groove of the first pressure plate; a powder molding cavity is formed between the outer wall of the rubber diaphragm cylinder and the inner wall of the tubular outer mold.

[0013] Furthermore, a rubber membrane hoop is provided at the end of the rubber membrane cylinder, which is fixed on the central pressure tube and embedded in the groove of the first pressure plate; the rubber membrane is fixed by the rubber membrane hoop to ensure that the rubber membrane is supported.

[0014] Furthermore, a first sealing groove is provided on the inner wall of the central opening of the first pressure plate, a second sealing groove is provided on the lower surface of the first pressure plate, and sealing rubber is provided in both the first sealing groove and the second sealing groove; the sealing effect is ensured by using a sealing strip and a sealing groove in combination.

[0015] Furthermore, a high-pressure water pipe quick connector is provided at the end of the central pressure pipe; the high-pressure water pipe quick connector can be directly plugged into the high-pressure water pipeline, enabling rapid injection of high-pressure water.

[0016] A polytetrafluoroethylene pipe isostatic molding process, the innovation of which lies in: the specific molding process is as follows:

[0017] S1: Molding device station distribution: The polytetrafluoroethylene pipe isostatic molding device is placed on a rotary turntable, and a powder feeding station, a head fixing station, a pressurizing molding station, a pressure maintaining station, and a pressure relief and material removal station are formed on the rotary turntable;

[0018] S2: PTFE powder feeding: At the molding powder feeding station on the rotary turntable, open the head module at one end of the molding device and use the guide hopper to add PTFE powder from the side into the powder molding cavity;

[0019] S3: Head locking and sealing: The rotary turntable drives the molding device after the material is added to rotate to the head fixing position, and tightens the tightening nut to press the head module onto the end face of the tubular outer mold;

[0020] S4: Pressurized molding: The rotary turntable drives the molding device with the head locked to the pressurized molding station. The high-pressure water pipe is connected to the high-pressure water pipe quick connector of the central pressurized pipe on the molding device. The high-pressure water valve is opened to fill the central pressurized pipe with high-pressure water at a pressure of 25-30 MPa. The high-pressure water passes through the pressurized through-hole of the central pressurized pipe to pressurize the inner wall of the rubber diaphragm cylinder, so that the rubber diaphragm cylinder evenly compresses the polytetrafluoroethylene powder, and the polytetrafluoroethylene pipe is formed.

[0021] S5: Pressure holding molding: The molding device that has completed high-pressure water pressurization is rotated to the pressure holding station through the rotary turntable and the pressure is held for 10-30 seconds;

[0022] S6: Pressure relief and material removal: The molding device that has completed pressure-maintaining molding is rotated to the pressure relief and material removal station via the rotary turntable; the head module at the other end of the molding device is opened to remove the molded polytetrafluoroethylene pipe;

[0023] S7: Sintering: Place the obtained polytetrafluoroethylene pipe in a sintering furnace for sintering at a temperature of 360-375°C, keep it warm for 7-10 hours, and then cool it down; after cooling to room temperature, take out the polytetrafluoroethylene pipe and perform trimming.

[0024] The advantages of the present invention are:

[0025] 1) The present invention adopts the method of internal pressure forming of polytetrafluoroethylene pipe to form the pipe. In this device, a pressure through hole is directly opened on the central pressure pipe and a threaded section is set at the end. It serves as a high-pressure pipe and also as a locking structure of the head module, which can not only meet the requirements of high-pressure water flow passing through but also ensure the rapid assembly and locking of the head module. In addition, when disassembling and installing the head module in this device, it is only necessary to loosen or tighten the tightening nut, without additional bolt assembly and disassembly, which improves the assembly and disassembly efficiency and is convenient to operate.

[0026] 2) The polytetrafluoroethylene pipe forming device of the present invention adopts a multi-station structure to complete the powder feeding, device locking, pressure molding, pressure-maintaining molding and pressure relief material removal of the polytetrafluoroethylene pipe at each station; it fully realizes streamlined production and greatly improves efficiency. Compared with the traditional device that uses a single mold placed inside and outside the high-pressure chamber for pressure molding, the molding device and molding process can increase the molding efficiency of the polytetrafluoroethylene pipe by more than 3 times; the molding device has a simple structure, is easy to operate, is quickly put into production, occupies a small area, and the molded polytetrafluoroethylene pipe meets the performance requirements of similar products. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] Figure 1This is a schematic diagram of the structure of a conventional external pressure polytetrafluoroethylene pipe forming device.

[0029] Figure 2 The figure is a schematic structural diagram of a polytetrafluoroethylene pipe isostatic forming device of the present invention.

[0030] Figure 3 The present invention is a flow chart of the isostatic molding process of polytetrafluoroethylene pipes.

[0031] Figure 4 The present invention is a schematic diagram of a flow-type station production structure of a polytetrafluoroethylene pipe isostatic forming device. DETAILED DESCRIPTION

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0033] Example 1

[0034] like Figures 2 to 3 The device shown is a polytetrafluoroethylene pipe isostatic molding device, which includes a tubular outer mold 1, a central pressure tube 2, a head module 3 and a rubber membrane cylinder 4.

[0035] The tubular outer mold 1 has a cylindrical inner cavity and is open at both ends; the central pressure tube 2 is coaxially arranged with the tubular outer mold 1, and a pipe forming cavity is formed between the outer wall of the central pressure tube 2 and the inner wall of the tubular outer mold 1; a number of pressure through holes 21 are evenly arranged in the circumferential direction in the middle area of ​​the central pressure tube 2; threaded sections are provided at both ends of the pressure through hole 21 on the central pressure tube 2, and the outer diameter of the threaded section is smaller than the outer diameter of the pressure through hole 21 on the central pressure tube 2; it is convenient for the disassembly and assembly of the head module on the central pressure pipe; a high-pressure water pipe quick connector is provided at the end of the central pressure pipe 2; the high-pressure water pipe quick connector can be directly plugged into the high-pressure water pipe, and high-pressure water can be injected quickly.

[0036] The head module 3 has a pair and is respectively arranged at the two ends of the tubular outer mold 1; the head module 3 includes a first pressure plate 31, a second pressure plate 32, a spring 33, a tightening nut 34 and a locking bolt 35; the first pressure plate 31 is arranged on the end faces of the two ends of the tubular outer mold 1, and the first pressure plate 31 is annular in structure; the first pressure plate 31 is nested on the central pressurized tube 2; the inner wall of the central opening of the first pressure plate 31 is provided with a first sealing groove, and the lower surface of the first pressure plate 31 is provided with a second sealing groove, and sealing rubber is provided in the first sealing groove and the second sealing groove; a countersunk threaded hole is provided on the upper surface of the first pressure plate 31; a groove for accommodating the end of the rubber membrane cylinder 4 is provided on the lower surface of the first pressure plate 31.

[0037] The second pressure plate 32 is arranged above the first pressure plate 31; the second pressure plate 32 has an annular structure, and a pair of bolt holes are symmetrically arranged circumferentially around the center hole of the upper plate; the second pressure plate 32 is nested on the central pressure tube 2 and a gap is left between the second pressure plate 32 and the outer wall of the central pressure tube 2.

[0038] The locking bolt 35 passes through the bolt hole of the second pressure plate 32, and the bottom end of the locking bolt 35 is connected to the countersunk threaded hole on the first pressure plate 31; the spring 33 is nested on the locking bolt 35 and is located between the second pressure plate 32 and the first pressure plate; a connecting nut is provided at the top of the locking bolt 35 and is connected to the locking bolt 35 to realize the second pressure plate 32 being pressed against the top of the spring 33; the tightening nut 34 is provided above the second pressure plate 32, and the tightening nut 34 cooperates with the threaded section on the central pressure pipe 2 to realize the first pressure plate 31 being pressed against the end face of the tubular outer mold; when disassembling and installing the head module 3, it is only necessary to loosen or tighten the tightening nut, without additional bolt loading and unloading, which improves loading and unloading efficiency and is convenient to operate.

[0039] The rubber diaphragm cylinder 4 is nested on the central pressure tube 2 and the rubber diaphragm cylinder 4 is located on the outside of the pressure through hole of the central pressure tube 2. The end face of the rubber diaphragm cylinder 4 is embedded in the groove of the first pressure plate 31; a powder molding cavity is formed between the outer wall of the rubber diaphragm cylinder 4 and the inner wall of the tubular outer mold; a rubber diaphragm hoop is provided at the end of the rubber diaphragm cylinder 4, which is fixed on the central pressure tube 2 and embedded in the groove of the first pressure plate 31.

[0040] A pressurized through hole is directly opened on the central pressurized pipe 2 and a threaded section is set at the end. It serves as a high-pressure pipeline and also as a locking structure of the head module. It can meet the needs of high-pressure water flow while ensuring the rapid assembly and locking of the head module 3.

[0041] A polytetrafluoroethylene pipe isostatic forming process uses a single polytetrafluoroethylene pipe isostatic forming device to form the polytetrafluoroethylene pipe. The specific forming process is as follows:

[0042] S1: PTFE powder feeding: Open the head module at one end of the molding device and use the guide hopper to add PTFE powder from the side into the powder molding cavity;

[0043] S2: Head locking and sealing: Tighten the tightening nut to press the head module onto the end surface of the tubular outer mold;

[0044] S3: Pressurized molding: Connect the high-pressure water pipe to the high-pressure water pipe quick connector of the central pressure pipe on the molding device, open the high-pressure water valve and fill the central pressure pipe with high-pressure water at a pressure of 25 MPa; the high-pressure water passes through the pressure through-hole of the central pressure pipe to pressurize the inner wall of the rubber diaphragm so that the rubber diaphragm evenly compresses the polytetrafluoroethylene powder to form the polytetrafluoroethylene pipe; and maintain the pressure for 30 seconds;

[0045] S4: Depressurizing and removing materials: Open the head module at the other end of the molding device to remove the molded polytetrafluoroethylene pipe;

[0046] S5: Sintering: The obtained polytetrafluoroethylene pipe is placed in a sintering furnace for sintering at a temperature of 360° C., kept warm for 7 hours, and then cooled; after cooling to room temperature, the polytetrafluoroethylene pipe is taken out for trimming.

[0047] Example 2

[0048] like Figures 2 to 4 A polytetrafluoroethylene pipe isostatic molding device comprises a tubular outer mold 1, a central pressure tube 2, a head module 3 and a rubber membrane cylinder 4.

[0049] The tubular outer mold 1 has a cylindrical inner cavity and is open at both ends; the central pressure tube 2 is coaxially arranged with the tubular outer mold 1, and a pipe forming cavity is formed between the outer wall of the central pressure tube 2 and the inner wall of the tubular outer mold 1; a number of pressure through holes 21 are evenly arranged in the circumferential direction in the middle area of ​​the central pressure tube 2; threaded sections are provided at both ends of the pressure through hole 21 on the central pressure tube 2, and the outer diameter of the threaded section is smaller than the outer diameter of the pressure through hole 21 on the central pressure tube 2; it is convenient for the disassembly and assembly of the head module on the central pressure pipe; a high-pressure water pipe quick connector is provided at the end of the central pressure pipe 2; the high-pressure water pipe quick connector can be directly plugged into the high-pressure water pipe, and high-pressure water can be injected quickly.

[0050] The head module 3 has a pair and is respectively arranged at the two ends of the tubular outer mold 1; the head module 3 includes a first pressure plate 31, a second pressure plate 32, a spring 33, a tightening nut 34 and a locking bolt 35; the first pressure plate 31 is arranged on the end faces of the two ends of the tubular outer mold 1, and the first pressure plate 31 is annular in structure; the first pressure plate 31 is nested on the central pressurized tube 2; the inner wall of the central opening of the first pressure plate 31 is provided with a first sealing groove, and the lower surface of the first pressure plate 31 is provided with a second sealing groove, and sealing rubber is provided in the first sealing groove and the second sealing groove; a countersunk threaded hole is provided on the upper surface of the first pressure plate 31; a groove for accommodating the end of the rubber membrane cylinder 4 is provided on the lower surface of the first pressure plate 31.

[0051] The second pressure plate 32 is arranged above the first pressure plate 31; the second pressure plate 32 has an annular structure, and a pair of bolt holes are symmetrically arranged circumferentially around the center hole of the upper plate; the second pressure plate 32 is nested on the central pressure tube 2 and a gap is left between the second pressure plate 32 and the outer wall of the central pressure tube 2.

[0052] The locking bolt 35 passes through the bolt hole of the second pressure plate 32, and the bottom end of the locking bolt 35 is connected to the countersunk threaded hole on the first pressure plate 31; the spring 33 is nested on the locking bolt 35 and is located between the second pressure plate 32 and the first pressure plate; a connecting nut is provided at the top of the locking bolt 35 and is connected to the locking bolt 35 to realize the second pressure plate 32 being pressed against the top of the spring 33; the tightening nut 34 is provided above the second pressure plate 32, and the tightening nut 34 cooperates with the threaded section on the central pressure pipe 2 to realize the first pressure plate 31 being pressed against the end face of the tubular outer mold; when disassembling and installing the head module 3, it is only necessary to loosen or tighten the tightening nut, without additional bolt loading and unloading, which improves loading and unloading efficiency and is convenient to operate.

[0053] The rubber diaphragm cylinder 4 is nested on the central pressure tube 2 and the rubber diaphragm cylinder 4 is located on the outside of the pressure through hole of the central pressure tube 2. The end face of the rubber diaphragm cylinder 4 is embedded in the groove of the first pressure plate 31; a powder molding cavity is formed between the outer wall of the rubber diaphragm cylinder 4 and the inner wall of the tubular outer mold; a rubber diaphragm hoop is provided at the end of the rubber diaphragm cylinder 4, which is fixed on the central pressure tube 2 and embedded in the groove of the first pressure plate 31.

[0054] A pressurized through hole is directly opened on the central pressurized pipe 2 and a threaded section is set at the end. It serves as a high-pressure pipeline and also as a locking structure of the head module. It can meet the needs of high-pressure water flow while ensuring the rapid assembly and locking of the head module 3.

[0055] A polytetrafluoroethylene pipe isostatic molding process, the specific molding process is as follows:

[0056] S1: Molding device station layout: The polytetrafluoroethylene pipe isostatic molding device is placed on the rotary turntable 5, and a powder feeding station, a head fixing station, a pressurizing molding station, a pressure maintaining station, and a pressure relief and material removal station are formed on the rotary turntable 5;

[0057] S2: Adding polytetrafluoroethylene powder: At the molding powder adding station on the rotary turntable 5, open the head module 3 at one end of the molding device and use the guide hopper to add polytetrafluoroethylene powder from the side into the powder molding cavity;

[0058] S3: Head locking and sealing: The rotary turntable 5 drives the forming device after the material is added to rotate to the head fixing position, and tightens the tightening nut so that the head module is pressed against the end surface of the tubular outer mold;

[0059] S4: Pressurized molding: The rotary turntable 5 drives the molding device with the sealed end locked to the pressurized molding station. The high-pressure water pipe 6 is connected to the high-pressure water pipe quick connector of the central pressurized pipe on the molding device. The high-pressure water valve is opened to fill the central pressurized pipe with high-pressure water at a pressure of 30 MPa. The high-pressure water passes through the pressurized through hole of the central pressurized pipe to pressurize the inner wall of the rubber diaphragm cylinder 4, so that the rubber diaphragm cylinder 4 evenly compresses the polytetrafluoroethylene powder, thereby molding the polytetrafluoroethylene pipe.

[0060] S5: Pressure-holding molding: The molding device that has completed high-pressure water pressurization is rotated to the pressure-holding station through the rotary turntable and the pressure is held for 30 seconds;

[0061] S6: Pressure relief and material removal: The molding device that has completed pressure-maintaining molding is rotated to the pressure relief and material removal station via the rotary turntable; the head module at the other end of the molding device is opened to remove the molded polytetrafluoroethylene pipe;

[0062] S7: Sintering: Place the obtained polytetrafluoroethylene pipe in a sintering furnace for sintering at a temperature of 375° C., keep the temperature for 10 hours, and then cool; after cooling to room temperature, take out the polytetrafluoroethylene pipe and perform trimming.

[0063] Example 1 and Example 2 can respectively realize the production and flow-type production of a single polytetrafluoroethylene pipe using a single polytetrafluoroethylene pipe isostatic molding device, and the product performance of the two embodiments meets the quality requirements of conventional polytetrafluoroethylene pipes. The molding process adopted in Example 2 can increase the production efficiency of polytetrafluoroethylene pipes by more than 3 times.

[0064] Those skilled in the art will appreciate that the present invention is not limited to the foregoing embodiments. The foregoing embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A polytetrafluoroethylene pipe isostatic forming device, characterized by: It includes a tubular outer mold, a central pressure pipe, a head module and a rubber membrane cylinder; The tubular outer mold has a cylindrical inner cavity and is open at both ends; the central pressure tube is coaxially arranged with the tubular outer mold, and a pipe forming cavity is formed between the outer wall of the central pressure tube and the inner wall of the tubular outer mold; a plurality of pressure through holes are evenly arranged in the circumferential direction in the middle area of ​​the central pressure tube; threaded sections are provided at both ends of the pressure through holes on the central pressure tube, and the outer diameter of the threaded sections is smaller than the outer diameter of the pressure through holes on the central pressure tube; The head module has a pair and is respectively arranged at the two ends of the tubular outer mold; the head module includes a first pressure plate, a second pressure plate, a spring, a tightening nut and a locking bolt; the first pressure plate is arranged on the end faces of the two ends of the tubular outer mold, and the first pressure plate is annular in structure; the first pressure plate is nested on the central pressurized tube; the inner contour of the first pressure plate is sealed to the outer wall of the central pressurized tube; the bottom end of the first pressure plate is sealed to the end face of the tubular outer mold; a countersunk threaded hole is provided on the upper surface of the first pressure plate; a groove is provided on the lower surface of the first pressure plate to accommodate the end of the rubber membrane cylinder; The second pressure plate is arranged above the first pressure plate; the second pressure plate is annular in structure, and a pair of bolt holes are symmetrically arranged in the circumferential direction of the central hole of the upper plate; the second pressure plate is nested on the central pressure tube and a gap is left between the second pressure plate and the outer wall of the central pressure tube; The locking bolt passes through the bolt hole of the second pressure plate, and the bottom end of the locking bolt is connected to the countersunk threaded hole on the first pressure plate; the spring is nested on the locking bolt and is located between the second pressure plate and the first pressure plate; a connecting nut is provided at the top of the locking bolt and is connected to the locking bolt to press the second pressure plate against the top of the spring; the tightening nut is provided above the second pressure plate, and the tightening nut cooperates with the threaded section on the central pressure tube to press the first pressure plate against the end surface of the tubular outer mold; The rubber diaphragm cylinder is nested on the central pressure tube and is located outside the pressure through hole of the central pressure tube. The end face of the rubber diaphragm cylinder is embedded in the groove of the first pressure plate; a powder molding cavity is formed between the outer wall of the rubber diaphragm cylinder and the inner wall of the tubular outer mold.

2. The polytetrafluoroethylene pipe isostatic forming device according to claim 1, characterized in that: The end of the rubber diaphragm cylinder is provided with a rubber diaphragm hoop, which is fixed on the central pressure tube and embedded in the groove of the first pressure plate.

3. The polytetrafluoroethylene pipe isostatic forming device according to claim 1, characterized in that: A first sealing groove is provided on the inner wall of the central opening of the first pressing plate, a second sealing groove is provided on the lower surface of the first pressing plate, and sealing rubber is provided in both the first sealing groove and the second sealing groove.

4. The polytetrafluoroethylene pipe isostatic forming device according to claim 1, characterized in that: The end of the central pressure pipe is provided with a high-pressure water pipe quick interface.

5. A polytetrafluoroethylene pipe isostatic forming process based on the polytetrafluoroethylene pipe isostatic forming device according to claim 1, characterized in that: The specific molding process is as follows: S1: Molding device station distribution: The polytetrafluoroethylene pipe isostatic molding device is placed on a rotary turntable, and a powder feeding station, a head fixing station, a pressurizing molding station, a pressure maintaining station, and a pressure relief and material removal station are formed on the rotary turntable; S2: PTFE powder feeding: At the molding powder feeding station on the rotary turntable, open the head module at one end of the molding device and use the guide hopper to add PTFE powder from the side into the powder molding cavity; S3: Head locking and sealing: The rotary turntable drives the molding device after the material is added to rotate to the head fixing position, and tightens the tightening nut to press the head module onto the end face of the tubular outer mold; S4: Pressurized molding: The rotary turntable drives the molding device with the head locked to the pressurized molding station. The high-pressure water pipe is connected to the high-pressure water pipe quick connector of the central pressurized pipe on the molding device. The high-pressure water valve is opened to fill the central pressurized pipe with high-pressure water at a pressure of 25-30 MPa. The high-pressure water passes through the pressurized through-hole of the central pressurized pipe to pressurize the inner wall of the rubber diaphragm cylinder, so that the rubber diaphragm cylinder evenly compresses the polytetrafluoroethylene powder, and the polytetrafluoroethylene pipe is formed. S5: Pressure holding molding: The molding device that has completed high-pressure water pressurization is rotated to the pressure holding station through the rotary turntable and the pressure is held for 10-30 seconds; S6: Pressure relief and material removal: The molding device that has completed pressure-maintaining molding is rotated to the pressure relief and material removal station via the rotary turntable; the head module at the other end of the molding device is opened to remove the molded polytetrafluoroethylene pipe; S7: Sintering: Place the obtained polytetrafluoroethylene pipe in a sintering furnace for sintering at a temperature of 360-375°C, keep it warm for 7-10 hours, and then cool it down; after cooling to room temperature, take out the polytetrafluoroethylene pipe and perform trimming.

Images