Installation Method of Polytetrafluoroethylene Composite Sealing Ring and Damper

Abstract

The present invention belongs to the field of mechanical component installation, and relates to a method for installing a polytetrafluoroethylene combined sealing ring and a damper. The polytetrafluoroethylene combined sealing ring is composed of an O-ring and a polytetrafluoroethylene support ring arranged therein. Among them, the inner ring of the polytetrafluoroethylene combined sealing ring has an annular cutting edge. When installing the present invention, first bend the support ring into a heart shape, press flat the protrusion after placing it in the piston installation groove, apply lubricating oil to the piston rod and the guiding tooling, first conduct a reverse trial installation, reversely sleeve the piston with the support ring onto the piston rod, and then conduct the formal installation, install the piston onto the piston rod forward, and complete the assembly of the polytetrafluoroethylene combined sealing ring. The present invention utilizes the structural characteristics and material characteristics of the polytetrafluoroethylene stepped ring itself to solve its installation problem, maximally avoid damage to parts during the installation process, ensure the sealing quality and qualification rate of the product, and save the production preparation time.

Description

Technical Field

[0001] The present invention belongs to the field of mechanical component installation, and relates to a method for installing a polytetrafluoroethylene combined sealing ring and a damper. Background Art

[0002] Polytetrafluoroethylene (PTFE for short), commonly known as "the king of plastics", is a high molecular polymer obtained by polymerizing tetrafluoroethylene as a monomer. It is white waxy, translucent, with excellent heat and cold resistance, and can be used for a long time at -180 to 2600 °C. It is widely used in making various sealing rings, such as a polytetrafluoroethylene lip sealing ring for multi-medium sealing in CN207470776U, and a composite polytetrafluoroethylene and elastomer lip seal and a method for manufacturing the same in EP31356A1.

[0003] A certain polytetrafluoroethylene combined sealing ring is composed of a rubber elastomer and a low-friction polytetrafluoroethylene stepped ring. It is applied to mechanical components that require high sealing, installed around the piston rod, and has toughness, wear resistance, and self-lubrication while playing a sealing role. Among them, the outer diameter of the polytetrafluoroethylene stepped ring is larger than the inner hole diameter of the installation part. Its material properties have both toughness and elasticity, and it is prone to plastic deformation. It cannot be folded and installed like a rubber sealing ring. Improper installation is extremely likely to cause plastic deformation or edge damage, thereby affecting the sealing performance and the locking force of the damper, reducing reliability. Therefore, how to ensure the integrity of the polytetrafluoroethylene stepped ring during installation and prevent it from deforming and being damaged is one of the key technologies in the installation process.

[0004] The prior art lacks an effective and reliable installation method for this type of polytetrafluoroethylene combined sealing ring with a specific structure. During installation in the prior art, it is necessary to heat the polytetrafluoroethylene stepped ring to make it deform, then install and heat-insulate. The process is complex and the implementation conditions are harsh, and there is a high rejection rate, becoming a process problem that is difficult to break through and has a great impact on the sealing effect. Summary of the Invention

[0005] The object of the present invention is to provide a method for installing a polytetrafluoroethylene combined sealing ring that can operate conveniently at room temperature and has a high reliability and qualified rate.

[0006] In addition, a damper using a polytetrafluoroethylene combined sealing ring installed by this installation method is also provided.

[0007] The technical solution of the present invention is: a method for installing a polytetrafluoroethylene combined sealing ring, wherein the polytetrafluoroethylene combined sealing ring is composed of an O-ring and a polytetrafluoroethylene support ring arranged therein, wherein the inner ring of the polytetrafluoroethylene combined sealing ring has an annular cutting edge. When installing the polytetrafluoroethylene combined sealing ring, the support ring is first bent into a heart shape, placed in a piston mounting groove, and then the protrusion is flattened, lubricating oil is applied to the piston rod and the guide tooling, a reverse test assembly is first performed, the piston with the support ring is reversely sleeved on the piston rod, and then a formal installation is performed, the piston is forwardly installed on the piston rod, and the assembly of the polytetrafluoroethylene combined sealing ring is completed.

[0008] The support ring is formed into a heart shape by a support ring bending tool, and the bending tool includes three bending rods, and the three bending rods are arranged in a finished shape using one in front and two in the back. Both ends of the two bending rods on both sides are connected to the middle bending rod by hinges, and handles are set at the ends of the two bending rods on both sides.

[0009] The upper and lower hinge structures and sizes of the bending rod are consistent, so that the bending of the support ring by the bending rod can be accurately controlled.

[0010] The support ring to be bent is arranged on the outside of the bottom hinge of the three bending rods, two bending rods are on the inside of the support ring, and the middle bending rod is on the outside of the support ring. The support ring is rotated through the handle according to the tooling, driving the three bending rods to rotate relative to each other, so as to realize the bending of the support ring into a heart shape.

[0011] The guide fixture comprises a guide fixture structure, a conical guide and a clamping bolt. The bottom of the conical guide is a notch structure that docks with the step at the end of the guide fixture structure, and the top of the conical guide is a cone structure with a bolt hole, through which the clamping bolt passes and is connected to the guide fixture as a whole, forming a rod structure.

[0012] The O-type sealing ring is made of nitrile rubber, the material grade is 5171, and the material grade of the polytetrafluoroethylene support ring is SFB-2.

[0013] The radial dimension of the upper end surface of the cutting edge of the support ring is 31.5 mm, and the distance from the top surface of the support ring is 1 mm, the distance from the lower end surface of the support ring is 2.25 mm, and the inclination angle of the cutting edge is 10°.

[0014] The two polytetrafluoroethylene combined sealing rings are used in series connection.

[0015] During reverse test assembly, the stop piston is reversely mounted on the piston rod, and the cutting edge direction of the support ring follows the conical surface of the guide tooling, so that the protrusions generated by the support ring during the process of installing the stop piston can be evenly flattened.

[0016] A damper has two polytetrafluoroethylene combined sealing rings installed by the above method connected in series between its piston rod and the stop piston.

[0017] The technical effects of the present invention are as follows: The method for quickly installing the PTFE combined sealing ring of the present invention is simple and easy to learn, with low cost, and does not require heating equipment or special media. By utilizing the structural and material characteristics of the PTFE cascade ring itself, a specific installation process is designed. Under normal temperature environment, it can achieve the quick installation of the PTFE combined sealing ring, effectively solving the technical problems of the existing installation methods, such as low efficiency, high cost, and easy damage to components. And by using simple tools, the installation can be quickly implemented, effectively ensuring the sealing quality and qualification rate of the product, saving the production preparation time, and playing a positive role in promoting the installation process of the product with guaranteed quality and quantity. Description of the Drawings

[0018] Figure 1 Structural diagram of the PTFE combined sealing ring;

[0019] Figure 2 is Figure 1 cross-sectional view of;

[0020] Figure 3 Structural diagram of the PTFE support ring;

[0021] Figure 4 Schematic diagram before installation of the installation tooling;

[0022] Figure 5 Schematic diagram of reverse torsion of the installation tooling;

[0023] Figure 6 Schematic diagram of the structure where the support ring is twisted into a heart shape;

[0024] Figure 7 Schematic diagram of the support ring being inserted into the seal installation groove;

[0025] Figure 8 is the schematic diagram of the support ring being flattened;

[0026] Figure 9 Schematic diagram of the structure of the guiding tooling;

[0027] Figure 10 Flowchart of the installation method of the PTFE combined sealing ring according to the embodiment of the present invention;

[0028] Figure 11 Schematic diagram of reverse installation;

[0029] Figure 12 Schematic diagram of the damper seal with the PTFE combined sealing ring installed;

[0030] Figure 13 Comparison chart of the combined seal of the CF ring - original O-ring and the locking force curve of the original seal (temperature: -40°C);

[0031] Figure 14 CF Ring - Comparison Chart of Combined Sealing between Original O - ring and Locking Force Curve of Original Seal (Temperature: 20°C);

[0032] Figure 15 CF Ring - Comparison Chart of Combined Sealing between Original O - ring and Locking Force Curve of Original Seal (Temperature: 50°C).

[0033] Among them, 1 - O - ring, 2 - support ring, 3 - bent column, 4 - hinge, 5 - handle, 6 - compression bolt, 7 - conical guide, 8 - guide tooling structure, 9 - piston rod, 10 - PTFE combined seal ring. Specific Embodiment

[0034] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0035] Please refer to Figure 1 and Figure 2 , the PTFE combined seal ring of the present invention adopts a combined seal design and is composed of a PTFE support ring and a nitrile rubber O - ring. Among them, the material of the nitrile rubber O - ring is Test 5171, which is an annular seal ring. The PTFE support ring, with the material of SFB - 2, is arranged inside the O - ring, and the O - ring provides rigid support for the support ring. The material hardness, elasticity, and compression ratio of the two match each other to form an effective seal structure.

[0036] In this embodiment, please refer to Figure 3 , the PTFE support ring is of a trapezoidal step structure with an annular cutting edge in the middle. Among them, the radial dimension of the upper end face of the annular cutting edge is, and the distance from the top surface of the support ring is 1 mm, the distance from the lower end face of the support ring is 2.25 mm, and the inclination angle of the cutting edge is 10°. Its dimension design, including the thickness, size, and inclination angle of the cutting edge, is mainly to make the support ring have a suitable compression ratio and elongation rate to meet the requirements of sealing performance and reliability in addition to meeting the installation requirements.

[0037] As shown in Table 1, the following gives the design of the dimensions, compression ratio, and elongation rate of three groups of seal rings and support rings. In this embodiment, the seal ring data of the first group is preferably selected. This parameter is small, and its size, elongation rate, compression ratio, and sealing performance can meet better process requirements.

[0038] Table 1 Compression Ratio of O - ring of CF Ring

[0039]

[0040] When installing the polytetrafluoroethylene combined sealing ring of the present invention, due to the toughness of the support ring, it cannot be easily bent by fingers and inserted into the sealing groove like a rubber sealing ring. Therefore, it is necessary to design an installation form suitable for the material of the support ring to ensure successful installation without damaging the support ring.

[0041] The present invention specially designs two special tools, namely a support ring installation tool and a guide tool.

[0042] See also Figure 4 The support ring installation tooling includes three bending rods, which are hard metal rods. The three bending rods are arranged in a finished product shape with one in front and two in the back. Both ends of the two bending rods on both sides are connected to the middle bending rod by hinges, and handles are provided at the ends of the two bending rods on both sides. The support ring to be bent is placed outside the hinge at the bottom of the three bending rods, wherein the two bending rods are on the inner side of the support ring and the middle bending rod is on the outer side of the support ring. The support ring is rotated by the handle according to the tooling, driving the three bending rods to rotate relatively, so that the support ring can be bent into a heart shape, which can reduce the outer diameter of the support ring, and can be placed in the sealing groove, and then unfolded, so that it can be completely installed in the sealing groove without the risk of edge damage.

[0043] See also Figure 9 The guide fixture includes a guide fixture structure, a conical guide and a clamping bolt. The bottom of the conical guide is a notch structure that docks with the step at the end of the guide fixture structure. The top of the conical guide is a cone structure with a bolt hole, which is passed through by the clamping bolt and connected to the guide fixture as a whole to form a rod structure. When installed, hydraulic oil is applied.

[0044] See also Figure 10 The process is as follows:

[0045] Step 1: Bending the support ring

[0046] When the support ring is bent, the two bending rods on both sides are driven by the handle to twist in the opposite direction and bend toward the middle, so that the three bending rods are arranged in a parallel row, and the support ring is initially bent. Figure 5 Then continue to twist the handle in the opposite direction, so that the two bending rods on both sides pass over the middle bending rod and form an inverse T-shape. The middle bending rod supports the support ring, and the bending columns on both sides twist the support ring to form a heart shape. Figure 6, thus effectively reducing the size of the support ring and facilitating installation. In the present invention, three cylindrical bent rods are used to bend the support ring into a heart shape by reverse torsion. The force is gentle and the force application is relatively uniform. While bending it into a heart shape to reduce the size for easy installation, it can effectively avoid damage to the cutting edge of the support ring and ensure the installation quality.

[0047] Step 2: Installation of the support ring

[0048] Please refer to Figure 7 and Figure 8 , then hold the handle and place the bottom heart-shaped support ring into the installation groove of the stop piston. At this time, the support ring is bent into a heart shape, and its size is significantly smaller than the original circle here, enabling it to be conveniently installed in the sealing installation groove. And because it is bent into a heart shape, after removing the support ring tooling, it can naturally spring back to achieve effective installation.

[0049] Step 3: Lubrication before installation

[0050] The end of the piston rod part has a step. Direct installation is likely to cause the sealing tip of the support ring to get stuck at the step, resulting in impossible installation or even scrapping. Therefore, using the guiding tooling, apply hydraulic oil to the piston rod and the guiding tooling during installation to make the installation process smooth and uniform.

[0051] Step 4: Reverse trial installation

[0052] Please refer to Figure 11 , before the formal installation, first conduct a reverse trial installation, that is, reverse the stop piston onto the piston rod. The purpose is to combine the structural characteristics of the support ring, and the cutting edge direction of the support ring conforms to the conical surface of the guiding tooling, so that the protrusions generated during the process of installing the support ring into the stop piston can be flattened more fully and evenly, ensuring its roundness, so as to prevent jamming due to circumferential non-uniformity during the formal installation.

[0053] In addition, since in the reverse trial installation in Step 4, the sealing cutting edge can be further flattened fully and evenly, so, in this step, just apply pressure with fingers to flatten it, without using a hard tool, which can avoid damaging the sealing cutting edge.

[0054] Step 5: Forward installation

[0055] After the reverse trial installation, then install the stop piston onto the piston rod forward to complete the assembly of the CF ring. After the reverse trial installation, the protrusions of the support ring are fully flattened and the circumferential direction is more uniform. Then, during the formal installation, it can prevent the cutting edge of the support ring from being damaged by the piston rod step.

[0056] Please refer to Figure 12, which is a schematic structural diagram of a damper installed by using the above-mentioned installation method of the polytetrafluoroethylene combined sealing ring. Since the polytetrafluoroethylene combined sealing ring adopts the above-mentioned specific structural dimensions, it has specific elongation and compression ratios. After adopting the above-mentioned specific installation method, the locking force of the obtained damper is significantly improved, and it has good sealing performance.

[0057] Next, the locking forces of the dampers with the sealing rings of the present invention and the original sealing rings of the prior art are tested at three temperatures of -40°C, 20°C, and 50°C respectively. It can be seen that the locking force of the damper with the combined sealing ring installed by the installation method of the present invention is significantly greater than that of the original scheme, as shown in Figure 13 , Figure 14 , Figure 15 . Therefore, it effectively solves the technical problem that the product quality cannot be guaranteed due to the installation method of the prior art.

[0058] In addition, the present invention has played an important role in the development of a new sealing form for the hydraulic damper of the escape system of a certain type of manned space rocket. It gets rid of the environment and equipment required for the installation of such polytetrafluoroethylene stepped rings in the past. The operation is simple and easy to learn, and the cost is relatively low. There is no need for heating equipment and special media. Combining the concept of cost reduction and efficiency improvement, it can utilize the structural and material characteristics of the polytetrafluoroethylene stepped ring itself. At normal temperature, the rapid installation of the polytetrafluoroethylene combined sealing ring is realized, solving its installation problem, minimizing the damage to parts during the installation process, ensuring the sealing quality and qualification rate of the product, saving the production preparation time, and finally passing various verifications such as high and low pressure sealing tests, high and low temperature multiple reciprocating actuation tests, and rapid impact tests. The polytetrafluoroethylene combined sealing ring installed in this way can fully meet the use requirements of the product under various working conditions, and has substantial technical characteristics and remarkable technical progress compared with the prior art.

[0059] The above is only a specific embodiment of the present invention. The present invention is described in detail, and the unelaborated parts are conventional technologies. However, the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention. The protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A method for installing a polytetrafluoroethylene combined sealing ring, characterized in that, The polytetrafluoroethylene combined sealing ring is composed of an O-ring and a polytetrafluoroethylene support ring arranged therein, wherein the inner ring of the polytetrafluoroethylene combined sealing ring has an annular cutting edge. When installing it, first bend the support ring into a heart shape, put it into the piston installation groove, and then flatten the protrusion. Apply lubricating oil on the piston rod and the guide tooling, first perform a reverse test installation, reversely put the piston with the support ring on the piston rod, and then perform formal installation, install the piston forward on the piston rod, and complete the assembly of the polytetrafluoroethylene combined sealing ring.

2. The method according to claim 1, wherein The support ring is formed into a heart shape by a support ring bending tool, and the bending tool includes three bending rods, and the three bending rods are arranged in a finished shape using one in front and two in the back. Both ends of the two bending rods on both sides are connected to the middle bending rod by hinges, and handles are set at the ends of the two bending rods on both sides.

3. The method according to claim 2, characterized in that, The upper and lower hinge structures and sizes of the bending rod are consistent, so that the bending of the support ring by the bending rod can be accurately controlled.

4. The method according to claim 3, characterized in that, The support ring to be bent is arranged on the outside of the bottom hinge of the three bending rods, two bending rods are on the inside of the support ring, and the middle bending rod is on the outside of the support ring. The support ring is rotated through the handle according to the tooling, driving the three bending rods to rotate relative to each other, so as to realize the bending of the support ring into a heart shape.

5. The method according to claim 4, wherein The guide tooling includes a guide tooling structure, a conical guide and a clamping bolt; wherein the bottom of the conical guide is a notch structure that docks with the end step of the guide tooling structure, and the top of the conical guide is a cone structure with a bolt hole, through which the clamping bolt passes and is connected to the guide tooling as a whole to form a rod structure.

6. The method according to claim 1, wherein The O-type sealing ring is made of nitrile rubber, the material grade is 5171, and the material grade of the polytetrafluoroethylene support ring is SFB-2.

7. The method according to claim 2, wherein The radial dimension of the upper end surface of the cutting edge of the support ring is 31.5 mm, and the distance from the top surface of the support ring is 1 mm, the distance from the lower end surface of the support ring is 2.25 mm, and the inclination angle of the cutting edge is 10°.

8. The method according to claim 1, wherein The two polytetrafluoroethylene combined sealing rings are used in series connection.

9. The method according to claim 1, characterized in that, During reverse test assembly, the stop piston is reversely mounted on the piston rod, and the cutting edge direction of the support ring follows the conical surface of the guide tooling, so that the protrusions generated by the support ring during the process of installing the stop piston can be evenly flattened.

10. A damper, characterized in that, Two polytetrafluoroethylene combined sealing rings installed by the method of any one of claims 1 to 9 are arranged in series between the piston rod and the stop piston.

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