Thermoplastic forming device and method for forcibly manufacturing movable piston guide rod bushing

Abstract

The invention relates to the technical field of macromolecule-metal matrix composite production equipment, and discloses a thermoplastic forming device and method for a guide rod bush of a forcibly manufactured movable piston, the thermoplastic forming device comprises a forming module and a punch part which is coaxially arranged, the forming module comprises a fixed die and a movable die, the fixed die is provided with a containing cavity used for containing the forcibly manufactured movable piston, and the movable die is provided with a cavity used for containing the forcibly manufactured movable piston; the accommodating cavity is provided with an upper opening, and a mold unloading hole communicated with the accommodating cavity is formed in the lower end of the fixed mold; the movable mold is cylindrical, a vertically-through thermoplastic cavity is formed in the center of the movable mold, the movable mold is arranged in the containing cavity in a sliding mode, the lower end of the movable mold abuts against the upper end of a piston seat of the forcibly-manufactured movable piston, and a guide rod of the forcibly-manufactured movable piston penetrates through the thermoplastic cavity from bottom to top; the punch part is located above the movable die and arranged in the containing cavity in a sliding mode, a through guide hole is formed in the punch part along the axis, and the guide hole is in sliding fit with a guide rod for forcibly manufacturing the movable piston. By adopting the forming device and method, the bonding strength of the plastic bushing and the metal matrix is improved, the service life is long, the yield is high, the operation is simple and convenient, and the production cost is low.

Description

Technical Field

[0001] The present invention relates to the technical field of production equipment for polymer-metal matrix composites, and particularly to a thermoplastic forming device and forming method for a forced-actuating piston guide rod bushing. Background Art

[0002] The blank structure of the forced-actuating piston in the oxygen tank exhaust valve of spacecraft XX model is shown in Figure 1 As shown, it is a key component of the exhaust valve. The forced-actuating piston includes a piston seat and a guide rod connected thereto. A bushing ring is circumferentially provided on the guide rod. The design requirement is to bond a polytetrafluoroethylene plastic bushing on the bushing ring of the forced-actuating piston guide rod, that is, to thermoplast the polytetrafluoroethylene plastic bushing on the bushing ring. Compared with the metal-metal mating pair without a bushing, the bushing of the forced-actuating piston can not only prevent adhesive wear between metals, but also the bushing has resistance to foreign matters. Even if foreign matters enter the gap of the guide rod, it can reduce or eliminate the influence of foreign matters on the movement of the guide rod, thereby improving the movement flexibility and reliability of the exhaust valve.

[0003] Polytetrafluoroethylene plastic is chemically inert and belongs to a material that is difficult to bond. The bonding of polytetrafluoroethylene plastic to metal includes cold bonding and thermoplasting. Cold bonding with an adhesive is prone to problems such as debonding in later use; thermoplasting requires sufficient melting and plasticization under heating conditions, and also requires the plastic to be fully compressed during thermoplastic forming to ensure good bonding with the metal matrix.

[0004] Due to the relatively large metal skeleton of the forced-actuating piston and the slender guide rod, the bonding strength between the thermoplastic bushing on the guide rod and the metal matrix often fails to meet the process requirements, resulting in a low yield rate and increased production costs. Summary of the Invention

[0005] The present invention provides a thermoplastic forming device and forming method for a forced-actuating piston guide rod bushing. The forced-actuating piston produced by this thermoplastic forming device and forming method has a high bonding strength between the plastic bushing and the metal matrix, a long service life, a high yield rate, simple operation, and low production costs.

[0006] The above object of the invention is achieved by the following technical solutions:

[0007] A thermoplastic forming device for a forced-actuating piston guide rod bushing, comprising a forming module and a punch head coaxially arranged. The forming module includes a fixed mold and a movable mold. The fixed mold is provided with a receiving cavity for accommodating the forced-actuating piston. The receiving cavity has an upper opening, and a demolding hole communicating with the receiving cavity is opened at the lower end of the fixed mold. The movable mold is cylindrical, and a thermoplastic cavity penetrating up and down is provided in the center of the movable mold. The movable mold is slidably arranged in the receiving cavity, and the lower end of the movable mold abuts against the upper end of the piston seat of the forced-actuating piston. The guide rod of the forced-actuating piston passes upward through the thermoplastic cavity. The punch head is located above the movable mold and is slidably arranged in the receiving cavity. A through guiding hole is provided along the axis of the punch head, and the guiding hole is slidably adapted to the guide rod of the forced-actuating piston.

[0008] In the above thermoplastic forming device for a forced-actuating piston guide rod bushing, the thermoplastic cavity is cylindrical or tapered with a larger upper part and a smaller lower part, and the axis of the thermoplastic cavity is coaxial with the axis of the movable mold.

[0009] In the above thermoplastic forming device for a forced-actuating piston guide rod bushing, the movable mold includes two or three mating movable mold bodies.

[0010] In the above thermoplastic forming device for a forced-actuating piston guide rod bushing, the movable mold is divided into two mating movable mold bodies along the plane where its axis is located; the two movable mold bodies are of the same size and shape.

[0011] In the above thermoplastic forming device for a forced-actuating piston guide rod bushing, the movable mold is divided into three mating movable mold bodies along the plane where its axis is located; the three movable mold bodies are of the same size and shape.

[0012] In the above thermoplastic forming device for a forced-actuating piston guide rod bushing, opposite parting grooves are provided on both sides of the mating surface of two adjacent movable mold bodies, and two opposite parting grooves enclose a parting cavity.

[0013] In the above thermoplastic forming device for a forced-actuating piston guide rod bushing, the parting cavity is a wedge-shaped cavity with a larger outer part and a smaller inner part.

[0014] In the above thermoplastic forming device for a forced-actuating piston guide rod bushing, two parting cavities are provided, and the two parting cavities are located at the lower end of the movable mold.

[0015] In the above thermoplastic forming device for a forced-actuating piston guide rod bushing, the punch head includes a punch and a pressure plate coaxially fixed, and the punch is slidably arranged in the receiving cavity.

[0016] A thermoplastic forming method for a forced-actuating piston guide rod bushing includes the following steps:

[0017] a. Surface treatment of the guide rod of the forced-actuating piston: Use white corundum sand #16 - #24 to blast the bushing ring, and the pressure of compressed air is 0.3 - 0.4 MPa;

[0018] b. Clean the blasted surface: Clean the forced-actuating piston with gasoline, acetone, and alcohol in sequence, dry the cleaned forced-actuating piston in an oven at 50 - 60 °C for 30 min, and let it cool to room temperature after drying;

[0019] c. Prepare the primer: Mix 0.5 - 1 g of chromium trioxide, 3 - 5 ml of distilled water, and 0.8 - 1.3 g of phosphoric acid evenly, filter 10 - 17 g of polytetrafluoroethylene with a clean nylon thickener, and add the mixed acid solution to the polytetrafluoroethylene suspension and stir evenly for use;

[0020] d. Apply the primer: Apply the primer evenly on the blasted surface, apply 2 - 3 coats, dry it in an oven at 50 - 60 °C for 30 min, and store the forced-actuating piston in a desiccator after drying for use;

[0021] e. Thermoplastic molding: Place the forced-actuating piston with the primer applied and dried in the accommodating cavity of the fixed mold, then place the moving mold in the accommodating cavity above the forced-actuating piston, add polytetrafluoroethylene to the thermoplastic cavity of the moving mold, finally place the punch at the opening of the accommodating cavity, place the molding module in the molding machine, heat up to 330 ± 5 °C and keep it at a constant temperature for 20 min;

[0022] f. Cold pressing and forming: Move the molding module to the cold press, apply a pressure of 30 - 50 MPa, wait for the molding module to cool below 60 °C, take out the forced-actuating piston with the moving mold, and after demolding the moving mold, obtain the blank of the forced-actuating piston with a polytetrafluoroethylene bushing.

[0023] In summary, the beneficial technical effects of the present invention are as follows:

[0024] By setting the molding module and the coaxial punch head, the molding module includes a fixed mold and a moving mold. The fixed mold is provided with an accommodating cavity that slidably fits with the piston seat of the forced-actuating piston. The opening of the accommodating cavity faces upward, and the lower end of the fixed mold is provided with a demolding hole communicating with the accommodating cavity; the moving mold slides in the accommodating cavity, and a thermoplastic cavity penetrating up and down is provided in the center of the moving mold. The punch head is provided with a guiding hole adapted to the guide rod of the forced-actuating piston along the axial direction, and the punch of the punch head slides at the opening of the accommodating cavity. Using this device and molding method can improve the bonding strength between the plastic bushing and the metal matrix, increase the service life, have a high yield rate, be easy to operate, and reduce production costs. Description of the Drawings

[0025] Figure 1 is a schematic structural diagram of the forced-actuating piston;

[0026] Figure 2It is a schematic structural diagram of the present invention;

[0027] Figure 3 It is a schematic structural diagram of putting plastic substrate particles into the thermoplastic cavity of the present invention;

[0028] Figure 4 It is a side view of the moving mold of an embodiment of the present invention;

[0029] Figure 5 It is Figure 4 a schematic structural diagram of the moving mold body;

[0030] Figure 6 It is a side view of the moving mold of another embodiment of the present invention;

[0031] Figure 7 It is Figure 6 a schematic structural diagram of the moving mold body;

[0032] Figure 8 It is a schematic structural diagram of the blank part of the forced-actuating piston after thermoplastic forming of the present invention;

[0033] Figure 9 It is Figure 8 a schematic structural diagram of the finished product after machining.

[0034] As shown in the figure, 1. Forced-actuating piston; 11. Piston seat; 12. Guide rod; 121. Bushing ring; 2. Forming module; 21. Fixed mold; 211. Accommodating cavity; 212. Mold unloading hole; 22. Moving mold; 221. Moving mold body; 2211. Opposing surface; 222. Thermoplastic cavity; 223. Parting groove; 2231. Parting cavity; 3. Punch head part; 31. Punch; 311. Necking step; 32. Pressure plate; 33. Guide hole; 4. Bottom plate; 5. Plastic substrate. Detailed implementation manners

[0035] The following further elaborates on the present invention in conjunction with the attached Figure 2-9 for a more detailed description.

[0036] As Figure 2As shown in the figure, a thermoplastic forming device for a forced actuation piston guide rod bushing includes a forming module 2 and a punch head 3 arranged coaxially. The forming module 2 includes a fixed mold 21 and a movable mold 22, which are arranged coaxially. The fixed mold 21 is provided with a receiving cavity 211 for accommodating the forced actuation piston 1. The receiving cavity 211 has an upper opening, and a demolding hole 212 communicating with the receiving cavity 211 is opened at the lower end of the fixed mold 21. The movable mold 22 is cylindrical, and a thermoplastic cavity 222 penetrating up and down is provided in the center of the movable mold 22. The movable mold 22 is slidably arranged in the receiving cavity 211. The lower end of the movable mold 22 abuts against the upper end of the piston seat 11 of the forced actuation piston 1. The guide rod 12 of the forced actuation piston 1 passes through the thermoplastic cavity 222 from bottom to top. The punch head 3 is located above the movable mold 22 and is slidably arranged in the receiving cavity 211. A through guiding hole 33 is provided along the axis of the punch head 3, and the guiding hole 33 is slidably adapted to the guide rod 12 of the forced actuation piston 1.

[0037] As Figure 2 shown, the punch head 3 of this embodiment includes a punch 31 and a pressure plate 32 fixedly connected coaxially. The punch 31 is slidably arranged at the opening of the receiving cavity 211. In order to reduce the contact area between the punch 31 and the receiving cavity 211 and reduce the friction force, a necking step 311 is provided at one end of the punch 31 close to the pressure plate 32.

[0038] In order to avoid damaging the forced actuation piston 1 when the movable mold 22 is pushed out of the fixed mold 21, a circular bottom plate 4 is provided between the bottom of the receiving cavity 211 and the piston seat 11 of the forced actuation piston 1. By pushing the bottom plate 4 through the push rod passing through the demolding hole 212, the forced actuation piston 1 and the movable mold 22 are pushed out of the receiving cavity 211 of the fixed mold 21.

[0039] The thermoplastic cavity 222 is cylindrical or conical with a larger upper part and a smaller lower part, and the axis of the thermoplastic cavity 222 is coaxial with the axis of the movable mold 22.

[0040] In this embodiment, the thermoplastic cavity 222 is selected to be conical with a larger upper part and a smaller lower part. This structure can reduce the amount of plastic substrate 5 put in, reduce the production cost, and at the same time, the demolding of the movable mold body 221 is more convenient and fast.

[0041] In order to facilitate the demolding of the movable mold 22, the movable mold 22 includes two or three mating movable mold bodies 221.

[0042] As Figure 4 、 5 shown, in one embodiment, the movable mold 22 is divided into two mating movable mold bodies 221 along the plane where its axis is located. The two movable mold bodies 221 have the same size and shape.

[0043] As Figure 6 、 7As shown, in another embodiment, the moving die 22 is divided into three mating moving die bodies 221 along the plane where its axis is located, and the three moving die bodies 221 are of the same size and shape.

[0044] As Figure 4-7 shown, in order to facilitate the demolding operation of the moving die 22, opposite parting grooves 223 are provided on both sides of the mating surface 2211 of two adjacent moving die bodies 221, and the two opposite parting grooves 223 enclose a parting cavity 2231.

[0045] Furthermore, the parting cavity 2231 is a wedge-shaped cavity with a larger outer part and a smaller inner part. This structure facilitates the insertion of a demolding tool into the parting cavity 2231 to pry the moving die body 221, realizing the rapid demolding operation of the mating moving die bodies 221.

[0046] As Figure 4 、 5 shown, the moving die 22 includes two mating moving die bodies 221, and two parting cavities 2231 are provided. The two parting cavities 2231 are symmetrically distributed at the lower end of the moving die 22.

[0047] As Figure 6 、 7 shown, the moving die 22 includes three mating moving die bodies 221, and three parting cavities 2231 are provided. The three parting cavities 2231 are all located at the lower end of the moving die 22.

[0048] When the device is in use, first slide the forced actuation piston 1 at the bottom of the accommodation cavity 211, then sequentially place the moving die bodies 221 into the accommodation cavity 211 for mating. The guide rod 12 of the forced actuation piston 1 passes through the thermoplastic cavity 222 of the moving die 22. Put the weighed plastic substrate 5 into the thermoplastic cavity 222, and finally slide the punch 31 at the opening of the accommodation cavity 211. Place the forming module 2 into a molding machine for heating. After the plastic substrate 5 melts, transfer it to a press, and apply a specified pressure to the pressure plate 32 through the press to ensure that the melt of the plastic substrate 5 fills the bushing ring 121 under the action of pressure. After the forming module 2 cools, eject the forced actuation piston 1 and the moving die 22 from the accommodation cavity 211 of the fixed die 21 through the demolding hole 212, and insert a demolding tool into the wedge-shaped parting cavity 2231 to separate and demold the adjacent moving die bodies 221. Finally, take out the blank of the forced actuation piston 1 with a plastic substrate bushing, and remove the excess plastic substrate 5 through machining to complete the forced actuation piston 1 part with specified precision.

[0049] Figure 3 is a schematic structural view of the thermoplastic cavity 222 with plastic substrate 5 particles placed in it. The plastic substrate 5 is made of perfluoroethylenepropylene plastic.

[0050] A method for thermoplastic molding of a forced actuation piston guide rod bushing according to the present invention includes the following steps:

[0051] a. Surface treatment of the guide rod 12 of the forced-actuating piston 1: Use white corundum sand of 16# - 24# to blow sand at its bushing ring, and the pressure of compressed air is 0.3 - 0.4 MPa;

[0052] b. Clean the sand-blasted surface: Clean the forced-actuating piston 1 successively with gasoline, acetone, and alcohol once each. Dry the cleaned forced-actuating piston 1 in an oven at 50 - 60 °C for 30 min, and let the dried forced-actuating piston 1 cool to room temperature;

[0053] c. Prepare the primer: Mix 0.5 - 1 g of chromium trioxide, 3 - 5 ml of distilled water, and 0.8 - 1.3 g of phosphoric acid evenly. Filter 10 - 17 g of polytetrafluoroethylene with a clean nylon thickener, and add the mixed acid solution to the polytetrafluoroethylene suspension and stir evenly for use. The preparation sequence cannot be reversed;

[0054] d. Apply the primer: Apply the primer evenly on the sand-blasted surface, apply 2 - 3 coats, and dry it in an oven at 50 - 60 °C for 30 min. After drying, store the forced-actuating piston 1 in a desiccator for use;

[0055] e. Thermoplastic molding: Place the forced-actuating piston 1 coated with primer and dried in the accommodating cavity 211 of the fixed mold. Then place the moving mold 22 in the accommodating cavity 211 above the forced-actuating piston 1. Add polytetrafluoroethylene to the thermoplastic cavity 222 of the moving mold 22. Finally, place the punch 31 at the opening of the accommodating cavity 211, place the molding module 2 in the molding machine, heat up to 330 ± 5 °C and keep it at a constant temperature for 20 min;

[0056] f. Cold pressing and forming: Move the molding module 2 to a cold press, apply a pressure of 30 - 50 MPa. Wait until the molding module 2 cools to below 60 °C, take out the forced-actuating piston 1 with the moving mold 22, and demold the moving mold 22 to obtain the blank of the forced-actuating piston 1 with a polytetrafluoroethylene bushing.

[0057] For the forced-actuating piston 1 produced by this forming device and forming method, under the specified pressure and temperature tests, the leakage rate and service life of the valve both meet the relevant requirements of the spacecraft.

[0058] The embodiments of this specific implementation manner are all preferred embodiments of the present invention, and do not limit the protection scope of the present invention accordingly. Therefore, all equivalent changes made according to the structure, shape, and principle of the present invention should be covered within the protection scope of the present invention.

Claims

1. A thermoplastic molding device for a forced brake piston guide rod bushing, characterized in that: The invention comprises a forming module and a coaxially arranged punching head, wherein the forming module comprises a fixed module and a movable module, wherein the fixed module is provided with a receiving chamber for receiving a forced braking piston, the receiving chamber has an upper opening, and a demolding hole communicating with the receiving chamber is provided at the lower end of the fixed module; the movable module is cylindrical, and a thermoplastic chamber penetrating from top to bottom is provided at the center of the movable module, the movable module is slidably arranged in the receiving chamber, the lower end of the movable module abuts against the upper end of the piston seat of the forced braking piston, and the guide rod of the forced braking piston passes through the thermoplastic chamber from bottom to top; the punching head is located above the movable module and is slidably arranged in the receiving chamber, and a through guide hole is provided along the axis of the punching head, and the guide hole is slidably adapted to the guide rod of the forced braking piston.

2. The thermoplastic molding device for forced braking piston guide rod bushing according to claim 1, characterized in that: The thermoplastic cavity is cylindrical or conical with a larger top and a smaller bottom, and the axis of the thermoplastic cavity is coaxial with the axis of the movable mold.

3. The thermoplastic molding device for forced braking piston guide rod bushing according to claim 1, characterized in that: The movable mold comprises two or three movable mold bodies which are matched with each other.

4. The thermoplastic molding device for forced braking piston guide rod bushing according to claim 3, characterized in that: The movable mold is divided into two matched movable mold bodies along the plane where the axis of the movable mold is located; the two movable mold bodies have the same size and shape.

5. The thermoplastic molding device for forced braking piston guide rod bushing according to claim 3, characterized in that: The movable mold is divided into three matched movable mold bodies along the plane where the axis of the movable mold is located; the three movable mold bodies are of the same size and shape.

6. The thermoplastic molding device for forced braking piston guide rod bushing according to claim 4 or 5, characterized in that: Two opposite mold splitting grooves are provided on both sides of the mating surfaces of two adjacent movable mold bodies, and the two opposite mold splitting grooves surround a mold splitting cavity.

7. The thermoplastic molding device for forced braking piston guide rod bushing according to claim 6, characterized in that: The mold splitting cavity is a wedge-shaped cavity that is larger on the outside and smaller on the inside.

8. The thermoplastic molding device for forced braking piston guide rod bushing according to claim 6, characterized in that: Two mold splitting cavities are provided, and the two mold splitting cavities are located at the lower end of the movable mold.

9. The thermoplastic molding device for forced braking piston guide rod bushing according to claim 1, characterized in that: The punch part comprises a punch and a pressure plate which are coaxially fixedly connected, and the punch is slidably arranged in the accommodating cavity.

10. A thermoplastic molding method for a forced brake piston guide rod bushing, characterized in that: The following steps are involved: a. Surface treatment of the guide rod of the forced actuator piston: Use 16#-24# white corundum sand to sandblast the bushing ring, and the pressure of the compressed air is 0.3~0.4MPa; b. Clean the sandblasting surface: Use gasoline, acetone and alcohol to clean the forced actuator piston once each, dry the cleaned forced actuator piston at 50-60°C for 30 minutes, and let the dried forced actuator piston dry to room temperature; c. Prepare primer: mix 0.5-1g chromium trioxide, 3-5ml distilled water, 0.8-1.3g phosphoric acid evenly, filter 10-17g fluoroethylene propylene with clean nylon, add the mixed acid solution into the fluoroethylene propylene suspension, stir evenly and set aside; d. Primer: Apply the primer evenly on the sandblasted surface for 2 to 3 times, and dry it in a 50-60℃ oven for 30 minutes. After drying, store the forced actuator piston in a dryer for later use; e. Thermoplastic: Place the primed and dried forced actuating piston in the accommodation cavity of the fixed mold, then place the movable mold in the accommodation cavity above the forced actuating piston, add polyperfluoroethylene propylene into the thermoplastic cavity of the movable mold, finally place the punch at the opening of the accommodation cavity, place the molding module in the molding machine, heat it to 330±5℃ and keep it constant for 20 minutes; f. Cold pressing: Move the molding module to the cold press machine, apply a pressure of 30-50MPa, wait for the molding module to cool to below 60°C, take out the forced brake piston with the movable mold, demold the movable mold to obtain the forced brake piston blank with a polyperfluoroethylene propylene bushing.

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