A method for molding polytetrafluoroethylene bushings for plug valves

Abstract

This invention relates to the field of plastic parts manufacturing and discloses a method for molding a polytetrafluoroethylene (PTFE) bushing for a plug valve, comprising the following steps: S1: First, filler is added to PTFE and thoroughly mixed, and the PTFE powder is dried in a low-temperature drying oven; S2: Then, an inner sleeve and an outer sleeve are prepared using a cold pressing sintering process; S3: Then, fiber filaments are wound around the outer surface of the inner sleeve; S4: Finally, the inner sleeve and the outer sleeve are joined together, and PTFE powder is filled in the gap between them. The bushing is then produced by cold pressing sintering again. The method for molding a PTFE bushing for a plug valve proposed in this invention uses a batch preparation method for the inner and outer sleeves, winds fiber filaments around the outer wall of the inner sleeve, and finally joins the inner and outer sleeves and performs a second sintering to achieve the purpose of preparing a high-strength bushing.

Description

Technical Field

[0001] This invention relates to the field of plastic parts manufacturing, and more specifically, to a method for molding a polytetrafluoroethylene bushing for a plug valve. Background Technology

[0002] Polytetrafluoroethylene, abbreviated as PTFE, is commonly known as the "King of Plastics." It is a high-molecular polymer made by polymerizing tetrafluoroethylene as a monomer. It is white, waxy, translucent, and has excellent heat and cold resistance, and can be used for extended periods at temperatures ranging from -180 to 260ºC. This material is resistant to acids, alkalis, and various organic solvents, and is almost insoluble in all solvents.

[0003] PTFE is widely used, and its application in the valve industry is also quite common. In order to prepare a PTFE bushing for a plug valve with high strength, it is necessary to add reinforcing fiber filaments inside the bushing.

[0004] The current method generally involves sintering the bushing into shape in one go, making it difficult to add fiber filaments. Summary of the Invention

[0005] This invention provides a method for molding a polytetrafluoroethylene (PTFE) bushing for a plug valve, comprising the following steps:

[0006] S1: First, add the filler to the PTFE and mix thoroughly. Then, store the PTFE powder in a low-temperature drying oven for drying.

[0007] S2: Then, the inner sleeve and outer sleeve are prepared by cold pressing and sintering process;

[0008] S3: Then, wrap the outer surface of the inner sleeve with fiber filaments;

[0009] S4: Finally, the inner and outer sleeves are joined together, and PTFE powder is filled into the gap between them. The cold pressing and sintering process is used again to produce the bushing.

[0010] Preferably, when preparing the inner sleeve, a combined mold is used for batch production. The combined mold includes a lower mold and an upper mold. The lower mold includes a mold base, a mating mold, and various sub-molds. Each sub-mold is detachably installed on the mold base. The sub-molds are used to combine with the mating mold to form the inner sleeve cavity. During the cold pressing and sintering process, each sub-mold is installed on the mold base to achieve batch production of the inner sleeve in one go.

[0011] When winding fiber filaments on the outer surface of the inner sleeve, the mating mold detaches from the mold base, and then each sub-mold detaches from the mold base in sequence and is transferred to the winding mechanism. After the winding is completed, it is transferred and assembled into another mold base.

[0012] Preferably, the upper mold includes a cold-pressing upper mold and a sintering upper mold. The cold-pressing upper mold is used to cooperate with the lower mold to press PTFE powder into shape, and the sintering upper mold is used to cooperate with the lower mold to achieve sintering.

[0013] Preferably, the mold base has equally spaced slides, one end of which is open and the other end is closed. The open ends of each slide are located on the same side of the mold base, and the slides are distributed in parallel. Each sub-mold is slidably assembled in the slide.

[0014] Preferably, the sub-mold includes a slider and a core assembled together, the slider and the slide rail are matched, the upper surface of each slider and the upper surface of the mold base are located in the same plane, and the plane is seamless;

[0015] The core includes a cylindrical part and a mating block part. The slider has a hole that matches the cylindrical part, and the lower surface of the slider has a mating groove that matches the mating block part.

[0016] Furthermore: The lower mold is sequentially transported to the feeding mechanism, pressing mechanism and demolding mechanism by a conveying mechanism. The feeding mechanism is used to discharge PTFE powder into the cavity. The cold pressing upper mold is arranged in the pressing mechanism. The pressing mechanism adjusts the lifting of the cold pressing upper mold to press the PTFE powder in the cavity into shape. The demolding mechanism is used to separate the mating mold from the mold base so that the inner sleeve stays on the sub-mold.

[0017] Furthermore: The material transfer mechanism is used to take each sub-mold out of each slide in turn and transfer it into the winding mechanism. After the fiber filament is wound inside each sub-mold, each sub-mold is transferred into another mold base and assembled into each slide in turn.

[0018] Preferably, each sub-mold has a magnet c on its adjacent side, the corresponding magnets are opposite in polarity, and the closed end of the slide also has a magnet for adsorbing the sub-mold.

[0019] Preferably, the bottom of the mating block b is provided with a mating groove, which matches the cylindrical part. The top of the cylindrical part has an electrical contact protrusion, and the mating groove has an electrical contact groove, which matches the electrical contact protrusion and the electrical contact groove.

[0020] Preferably, the material transfer mechanism has a mating column that matches a connecting groove. The top of the mating column has a magnetic protrusion, and the connecting groove has an adsorption groove that mates with the magnetic protrusion.

[0021] The beneficial effects of the present invention are as follows: The method for molding polytetrafluoroethylene bushings for plug valves proposed in this invention adopts a batch preparation method for inner and outer sleeves, and winds fiber filaments around the outer wall of the inner sleeve. Finally, the inner and outer sleeves are joined and sintered twice to achieve the purpose of preparing high-strength bushings. Attached Figure Description

[0022] Figure 1This is a flowchart of a method for molding a polytetrafluoroethylene bushing for a plug valve, as proposed in this invention.

[0023] Figure 2 This is a schematic diagram of the lower mold used in the polytetrafluoroethylene bushing molding method for a plug valve proposed in this invention.

[0024] Figure 3 This is a schematic diagram of the structure of the mold base and the mating mold when they are separated in the polytetrafluoroethylene bushing molding method of the plug valve proposed in this invention;

[0025] Figure 4 This is a top view of the mold base and sub-mold combined together in a method for molding a polytetrafluoroethylene bushing for a plug valve proposed in this invention.

[0026] Figure 5 This is a schematic diagram of the sub-mold used in the molding method of polytetrafluoroethylene bushing for a plug valve proposed in this invention.

[0027] Figure 6 This is a schematic diagram of the bottom of the sub-mold used in the polytetrafluoroethylene bushing molding method for a plug valve proposed in this invention.

[0028] Figure 7 This is a schematic diagram of the lower mold and cold-pressed upper mold used in a method for molding a polytetrafluoroethylene bushing for a plug valve proposed in this invention.

[0029] Figure 8 This is a schematic diagram of the lower mold and sintering upper mold used in a method for molding a polytetrafluoroethylene bushing for a plug valve proposed in this invention.

[0030] Figure 9 This is a schematic diagram of the structure when multiple combined molds are stacked and combined in a method for molding a PTFE bushing for a plug valve proposed in this invention.

[0031] In the diagram: 1. Mold; 2. Lower mold; 21. Mold base; 211. Slide rail; 22. Sub-mold; 221. Slider; 221a. Guide groove; 221b. Guide bar; 221c. Magnet; 222. Core; 222a. Cylindrical part; 222a1. Electrical contact protrusion; 222a2. Connecting groove; 222a3. Electrical contact groove; 222a4. Adsorption groove; 222b. Mold block part; 3. Cold pressing upper mold; 4. Sintering upper mold. Detailed Implementation

[0032] The subject matter described herein will now be discussed with reference to exemplary embodiments. It should be understood that these embodiments are discussed merely to enable those skilled in the art to better understand and implement the subject matter described herein, and are not intended to limit the scope, applicability, or examples set forth in the claims. The function and arrangement of the elements discussed may be changed without departing from the scope of this specification. Various processes or components may be omitted, substituted, or added as needed in the various examples. Furthermore, features described in some examples may be combined in other examples.

[0033] Example 1

[0034] Reference Appendix Figure 1-9 This embodiment proposes a method for molding a polytetrafluoroethylene bushing for a plug valve, comprising the following steps:

[0035] S1: First, add the filler to the PTFE and mix thoroughly. Then, store the PTFE powder in a low-temperature drying oven for drying.

[0036] Furthermore, a mixing device is used to mix the filler and PTFE powder. After mixing, the mixture is screened using a sieve. During the sieving process, the sieve is kept clean, and other impurities are strictly avoided from being introduced.

[0037] S2: Then, the inner sleeve and outer sleeve are prepared by cold pressing and sintering process.

[0038] The specific process for preparing the inner sleeve is as follows:

[0039] First, assemble each sub-mold 22 onto the mold base 21, referring to the attached diagram. Figure 4 As shown, the purpose of first assembling the lower mold 2 is to then assemble the mating mold 1 onto the mold base 21.

[0040] The lower mold 2, which is assembled, is moved into the feeding mechanism by a conveying mechanism. It should be noted that the conveying mechanism has components that keep the mold base 21 and the mating mold 1 in position and fixed.

[0041] The feeding mechanism fills the cavity with PTFE powder. After filling, the conveying mechanism moves the lower mold 2 to the pressing mechanism. The pressing mechanism has a cold pressing upper mold 3. The pressing mechanism adjusts the lifting of the cold pressing upper mold 3 to press the PTFE powder in the cavity into shape.

[0042] Then, the sintering upper mold 4 is placed on the mating mold 1 to cover the upper end of the cold-pressed inner sleeve;

[0043] Then, the lower mold 2 and the upper sintering mold 4, which are assembled together on the conveying mechanism, are removed in sequence and stacked together, so that the electrical contact protrusion 222a1 on each cylindrical part 222a engages with the electrical contact groove 222a3 of the upper layer. Then, the assembled mold is transferred to the sintering mechanism to achieve sintering by applying pressure.

[0044] After sintering is completed, the lower mold 2 is removed and reinstalled in the conveying mechanism. The conveying mechanism transports the lower mold 2 through the demolding mechanism. The demolding mechanism is used to remove the mating mold 1 on the lower mold 2, so that the outer surface of the inner sleeve is exposed.

[0045] Using a similar method, the outer sleeve is prepared. The difference from the inner sleeve is that after the outer sleeve is formed, it remains on the mold, and the inner surface of the outer sleeve is exposed.

[0046] S3: Then, wrap the outer surface of the inner sleeve with fiber filaments.

[0047] Specifically, the conveying direction of the conveying mechanism is perpendicular to the groove direction of the slide 211 on the mold base 21, and the lower mold 2 is conveyed in a suspended state. The material transfer mechanism is used to remove and convey each sub-mold 22.

[0048] The material transfer mechanism has multiple conveyor lines, the number and position of which match the slides 211 in the mold base 21;

[0049] Each conveyor line has a material transfer assembly, which includes a vertical mating column. The upper end of the mating column matches the mating groove 222a2, and the mating column has a magnetic protrusion that matches the adsorption groove 222a4.

[0050] The conveyor line sequentially transports the material transfer assembly to the bottom of the mold base 21. The mating column rises and inserts into the mating groove 222a2. The magnetic protrusion and the adsorption groove 222a4 engage and hold the material transfer assembly and the sub-mold 22 from the mold base 21. The conveyor line then transfers the sub-mold 22 to the winding mechanism. The mating column can drive the sub-mold 22 to move, coordinating with the winding operation. After the winding is completed, the conveyor line transfers the sub-mold 22 to the corresponding slide 211 of another empty mold base 21. When the sub-mold 22 is transported to the end of the mold base 21, the mating column descends and disengages from the sub-mold 22.

[0051] Repeat the above steps to remove each sub-mold 22 from the mold base 21 on the conveying mechanism in sequence, complete the winding process, and then reassemble them onto another empty mold base 21. After the other empty mold base 21 is filled with sub-molds 22, another conveying mechanism will transport them away to the next process.

[0052] S4: Finally, the inner and outer sleeves are joined together, and PTFE powder is filled into the gap between them. The cold pressing and sintering process is used again to produce the bushing.

[0053] When preparing the inner sleeve, a combination mold is used for batch production. The combination mold includes a lower mold 2 and an upper mold. The lower mold 2 includes a mold base 21, a mating mold 1, and various sub-molds 22. Each sub-mold 22 is detachably installed on the mold base 21. The sub-molds 22 are used to combine with the mating mold 1 to form the inner sleeve cavity. During the cold pressing and sintering process, each sub-mold 22 is installed on the mold base 21 to achieve batch production of the inner sleeve in one go.

[0054] When winding fiber filaments on the outer surface of the inner sleeve, the mating mold 1 disengages from the mold base 21, and then each sub-mold 22 disengages from the mold base 21 in sequence and is transferred to the winding mechanism. After the winding is completed, it is transferred and assembled into another mold base 21.

[0055] The upper mold includes a cold pressing upper mold 3 and a sintering upper mold 4. The cold pressing upper mold 3 is used to cooperate with the lower mold 2 to press PTFE powder into shape, and the sintering upper mold 4 is used to cooperate with the lower mold 2 to achieve sintering.

[0056] The mold base 21 has equally spaced slides 211. One end of each slide 211 is open and the other end is closed. The open ends of each slide 211 are located on the same side of the mold base 21. The slides 211 are distributed in parallel, and each sub-mold 22 is slidably assembled in the slide 211.

[0057] The sub-mold 22 includes a slider 221 and a core 222 combined together. The slider 221 and the slide 211 are matched. The upper surface of each slider 221 and the upper surface of the mold base 21 are located in the same plane, and the plane is seamless.

[0058] The core 222 includes a cylindrical part 222a and a mating block part 222b. The slider 221 has a hole that matches the cylindrical part 222a. The lower surface of the slider 221 has a mating groove that matches the mating block part 222b.

[0059] The lower mold 2 is conveyed sequentially to the feeding mechanism, pressing mechanism and demolding mechanism. The feeding mechanism is used to discharge PTFE powder into the cavity. The cold pressing upper mold 3 is arranged in the pressing mechanism. The pressing mechanism adjusts the lifting of the cold pressing upper mold 3 to press the PTFE powder in the cavity into shape. The demolding mechanism is used to remove the mating mold 1 from the mold base so that the inner sleeve stays on the sub-mold 22.

[0060] The material transfer mechanism is used to take each sub-mold 22 out of each slide rail 211 in sequence and transfer it into the wire winding mechanism. Fiber filaments are wound inside each sub-mold 22. After winding is completed, each sub-mold 22 is transferred into another mold base 21 and assembled into each slide rail 211 in sequence.

[0061] Each sub-mold 22 has a magnet 221c on its adjacent side, and the corresponding magnets are opposite in polarity. The closed end of the slide 211 also has a magnet for adsorbing the sub-mold 22.

[0062] The bottom of the mating block 222b is provided with a mating groove 222a2, which matches the cylindrical part 222a. The top of the cylindrical part 222a has an electrical contact protrusion 222a1, and the mating groove 222a2 has an electrical contact groove 222a3, which matches the electrical contact protrusion 222a1 and the electrical contact groove 222a3.

[0063] The material transfer mechanism has a mating column that matches the mating groove 222a2. The top of the mating column has a magnetic protrusion, and the mating groove 222a2 has an adsorption groove that matches the magnetic protrusion.

[0064] The present invention proposes a method for molding polytetrafluoroethylene bushings for plug valves, which involves batch preparation of inner and outer sleeves, winding fiber filaments around the outer wall of the inner sleeve, and finally joining the inner and outer sleeves and sintering them a second time to achieve the purpose of preparing high-strength bushings.

[0065] The embodiments of this embodiment have been described above with reference to the accompanying drawings. However, this embodiment is not limited to the specific implementation methods described above. The specific implementation methods described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this embodiment without departing from the spirit of this embodiment and the scope of protection of the claims, and all of these forms are within the protection scope of this embodiment.

Claims

1. A method for molding a polytetrafluoroethylene bushing for a plug valve, characterized in that, Includes the following steps: S1: First, add the filler to the PTFE and mix thoroughly. Then, store the PTFE powder in a low-temperature drying oven for drying. S2: Then, the inner sleeve and outer sleeve are prepared by cold pressing and sintering process; S3: Then, wrap the outer surface of the inner sleeve with fiber filaments; S4: Finally, the inner and outer sleeves are joined together, and PTFE powder is filled in the gap between them. The cold pressing and sintering process is used again to produce the bushing. When preparing the inner sleeve, a combination mold is used for batch production. The combination mold includes a lower mold (2) and an upper mold. The lower mold (2) includes a mold base (21), a mating mold (1) and various sub-molds (22). Each sub-mold (22) is detachably installed on the mold base (21). The sub-molds (22) are used to combine with the mating mold (1) to form the inner sleeve cavity. During the cold pressing and sintering process, each sub-mold (22) is installed on the mold base (21) to achieve batch production of the inner sleeve in one go. When winding fiber filaments on the outer surface of the inner sleeve, the matching mold (1) is disengaged from the mold base (21), and then each sub-mold (22) is disengaged from the mold base (21) in sequence and transferred to the winding mechanism. After the winding is completed, it is transferred and assembled into another mold base (21). The upper mold includes a cold pressing upper mold (3) and a sintering upper mold (4). The cold pressing upper mold (3) is used to cooperate with the lower mold (2) to press PTFE powder into shape, and the sintering upper mold (4) is used to cooperate with the lower mold (2) to achieve sintering.

2. The method for molding a polytetrafluoroethylene bushing for a plug valve according to claim 1, characterized in that, The mold base (21) has equally spaced slides (211). One end of each slide (211) is open and the other end is closed. The open ends of each slide (211) are located on the same side of the mold base (21). Each slide (211) is distributed in parallel. Each sub-mold (22) is slidably assembled in the slide (211).

3. The method for molding a polytetrafluoroethylene bushing for a plug valve according to claim 2, characterized in that, The sub-mold (22) includes a slider (221) and a core (222) assembled together. The slider (221) and the slide (211) are matched. The upper surface of each slider (221) and the upper surface of the mold base (21) are located in the same plane, and the plane is seamless. The core (222) includes a cylindrical part (222a) and a mating block part (222b). The slider (221) has a hole that matches the cylindrical part (222a). The lower surface of the slider (221) has a mating groove that matches the mating block part (222b).

4. The method for molding a polytetrafluoroethylene bushing for a plug valve according to claim 3, characterized in that, The lower mold (2) is conveyed sequentially to the feeding mechanism, pressing mechanism and demolding mechanism. The feeding mechanism is used to discharge PTFE powder into the cavity. The cold pressing upper mold (3) is arranged in the pressing mechanism. The pressing mechanism adjusts the lifting of the cold pressing upper mold (3) to press the PTFE powder in the cavity into shape. The demolding mechanism is used to remove the mating mold (1) from the mold base so that the inner sleeve stays on the sub-mold (22).

5. The method for molding a polytetrafluoroethylene bushing for a plug valve according to claim 4, characterized in that, The material transfer mechanism is used to take each sub-mold (22) out of each slide (211) in turn and transfer it into the winding mechanism. Fiber filaments are wrapped inside each sub-mold (22). After the winding is completed, each sub-mold (22) is transferred into another mold base (21) and assembled into each slide (211) in turn.

6. The method for molding a polytetrafluoroethylene bushing for a plug valve according to claim 5, characterized in that, Each sub-mold (22) has a magnet (221c) on its adjacent side, and the corresponding magnets are opposite in polarity. The closed end of the slide (211) also has a magnet for adsorbing the sub-mold (22).

7. The method for molding a polytetrafluoroethylene bushing for a plug valve according to claim 6, characterized in that, The bottom of the mating block (222b) is provided with a mating groove (222a2), which matches the cylindrical part (222a). The top of the cylindrical part (222a) has an electrical contact protrusion (222a1), and the mating groove (222a2) has an electrical contact groove (222a3). The electrical contact protrusion (222a1) and the electrical contact groove (222a3) match.

8. The method for molding a polytetrafluoroethylene bushing for a plug valve according to claim 7, characterized in that, The material transfer mechanism has a mating column that matches the mating groove (222a2). The top of the mating column has a magnetic protrusion, and the mating groove (222a2) has an adsorption groove that matches the magnetic protrusion.

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