A new type of pressure air cylinder structure

Abstract

The application discloses a novel pressure air cylinder structure and belongs to the technical field of railway vehicle equipment, comprising an air cylinder body, a maintenance hole is formed in the end of the air cylinder body, a threaded flange seat is welded at the maintenance hole, and the maintenance hole is sealed by a set of bolts and a flange plate; a sealing gasket is arranged between the flange plate and the flange seat, and an elastic washer is arranged between the bolt and the flange plate; the detachable flange sealing structure is arranged at the end of the air cylinder, a maintenance channel convenient for construction and maintenance is formed, high-performance protective coating spraying can be implemented on the inside of the air cylinder, the corrosion resistance is improved, the internal corrosion problem of the air cylinder is effectively solved, and the service life and operation safety and reliability of the product are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of rail vehicle equipment technology, and specifically to a novel pressure cylinder structure. Background Technology

[0002] As a key component of the braking system of rail vehicles, the pressure cylinder is mainly used to store and supply compressed air, and its performance and reliability are directly related to the overall operational safety of the vehicle. Currently, common pressure cylinder structures include... Figure 1 As shown, compressed air is stored inside the cylinder for a long time. Due to changes in ambient temperature and pressure, condensation is easily generated on the inner wall of the cylinder, leading to internal corrosion problems and seriously affecting the service life and safety performance of the air cylinder.

[0003] In existing technologies, pressure air cylinders typically only have an RC3 / 4 specification air inlet at the end, and internal corrosion protection mainly relies on a phosphating process using manganese-based phosphating solutions. While this treatment method can improve corrosion resistance to some extent, its salt spray test time is usually only around 48 hours, resulting in limited corrosion resistance and making it difficult to meet the long-term use requirements in highly corrosive environments.

[0004] Therefore, how to improve the existing structure and effectively enhance the corrosion resistance of the pressure cylinder has become an important technical problem that needs to be solved by those skilled in the art. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to address the shortcomings of existing technologies by providing a novel pressure cylinder structure, which improves upon existing structures and effectively enhances the corrosion resistance of the pressure cylinder.

[0006] Technical solution: The present invention discloses a novel pressure cylinder structure, including a cylinder body, an inspection hole at the end of the cylinder body, a flange seat welded at the inspection hole, and threads on the flange seat; it also includes a flange for sealing the inspection hole, the flange is connected to the flange seat by a set of bolts, a sealing gasket is provided between the flange and the flange seat, and an elastic washer is provided between the bolts and the flange. Bolts are screwed through the flange and into the flange seat threads. By applying preload, the flange, gasket, and flange seat are compressed into a single unit. Under this pressure, the gasket undergoes elastic deformation, filling all microscopic imperfections and forming a reliable static seal to prevent internal compressed air leakage. The elastic washer, under pressure after bolt preload, exhibits a sustained rebound force due to its upturned opening or wavy structure, effectively counteracting the tendency of bolts to loosen due to vibration and pressure fluctuations.

[0007] The weld dimension g between the flange seat and the cylinder body satisfies: g ≥ 0.7t, where t is the thickness of the thinner plate in the weldment. Ensuring the throat thickness of the weld is sufficient to transfer the structural load, the weld dimension is linked to the thickness t of the thinner plate, guaranteeing that the weld strength matches the strength of the base material (cylinder body and flange seat). This makes the area an equal-strength design, ensuring that stress is borne by the structure itself when subjected to internal pressure, rather than concentrated in the weak weld.

[0008] Furthermore, the inspection hole has a diameter of 200mm; this diameter provides a sufficiently large channel that allows the spray gun of the spraying equipment to extend and move flexibly during the construction phase, ensuring that the anti-corrosion coating can be evenly sprayed onto every corner of the air cylinder, including the far end and the inner wall, facilitating subsequent internal visual inspection, cleaning, or maintenance.

[0009] Furthermore, there are 12 bolts, all M8 bolts, evenly distributed circumferentially on the flange. The number and specifications of the bolts are calculated based on the total force (28.27 kN) exerted by the gas on the flange under a working pressure of 0.9 MPa. The reasonable distribution of the 12 M8 bolts provides sufficient total preload to tighten the gasket and resist the internal pressure attempting to pry open the flange.

[0010] Furthermore, the bolt installation preload range is 10.6kN~18.4kN, and the bolt installation torque range is 17N·m~24 N·m. The preload is the core of the bolted connection. The lower limit of this range (10.6kN) ensures that the gasket can still maintain sufficient residual clamping force without leakage under internal pressure. The upper limit (18.4kN) prevents the bolt from elongating and yielding, the thread from stripping, or the flange from deforming due to excessive preload. Torque is a measurable parameter used on the production site to control the preload.

[0011] Furthermore, the flange can be made of low-carbon steel or carbon structural steel; the flange mainly bears the bending and compressive stresses caused by bolt preload and internal air pressure. The selected low-carbon steel or carbon structural steel (such as Q235B, yield strength ≥235MPa) has a strength far exceeding the design calculation value (145.13MPa), which fully meets the mechanical requirements for pressure bearing and fastening.

[0012] Furthermore, a protective coating is sprayed onto the inner wall of the air cylinder body; through the openable flange structure, a dense, continuous, and firm organic coating (such as epoxy or polyurethane paint) can be formed inside the air cylinder. This coating completely isolates the metal cylinder body from the humid compressed air and condensate inside, fundamentally preventing electrochemical corrosion, increasing the salt spray test time, and greatly extending the service life of the air cylinder.

[0013] Furthermore, the flange is located outside the air cylinder body during assembly. This design allows the bolt tightening operation to be performed outside the air cylinder, and the flange can be removed directly without having to reach inside the air cylinder.

[0014] Beneficial effects: Compared with the prior art, the advantages of the present invention are as follows: This invention addresses the issue of internal corrosion by incorporating an inspection port at the end of the air cylinder body and a detachable flange connection structure. Traditional air cylinders, due to their enclosed structure, can only undergo limited phosphating treatments. This new structure, with its openable flange, allows for internal construction, enabling the application of high-performance protective coatings using advanced processes such as spraying. This significantly enhances the air cylinder's corrosion resistance (salt spray test time), fundamentally solving the internal corrosion problem and greatly extending its service life. Furthermore, the flange structure is not merely an opening; precise pre-tightening force is applied using a specific number and specification of bolts, combined with a sealing gasket, to create a reliable, leak-free static seal under a working pressure of 0.9 MPa inside the air cylinder. Simultaneously, the inspection port design facilitates the full lifecycle management of the air cylinder. Attached Figure Description

[0015] Figure 1 This is a structural diagram of the prior art mentioned in the background section; Figure 2 This is a schematic diagram of the structure of the present invention; Figure 3 This is a schematic diagram of the flange structure in this invention; Figure 4 This is a schematic diagram of the flange seat weld in this invention. Detailed Implementation

[0016] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings, but the scope of protection of the present invention is not limited to the embodiments described.

[0017] Example 1 like Figures 2-4 As shown, a new type of pressure cylinder structure is characterized by a core improvement in the detachable sealing structure at the end, which enables high-quality corrosion protection inside the cylinder.

[0018] The pressure cylinder structure in this embodiment mainly includes a cylinder body 1, a flange seat 2, a flange 3, bolts 4, a sealing gasket 5, and an elastic washer 6. The cylinder body 1 is composed of a steel pipe and end caps at both ends. A circular inspection hole with a diameter of Φ200mm is provided on one end cap. This hole size has been optimized to allow spraying equipment and personnel to enter for internal coating and inspection.

[0019] A flange seat 2 is fixed to the edge of the inspection hole by welding. The flange seat 2 has an internally threaded hole. The connection weld 7 between the flange seat 2 and the cylinder body 1 is crucial. Its weld size g must meet the requirement of g ≥ 0.7t, where t is the thickness of the thinner plate at the weld joint between the cylinder body 1 and the flange seat 2. In this embodiment, the type and size of the weld strictly follow the TB / T 1900 standard to ensure that the weld strength is equivalent to that of the cylinder body and can withstand the internal pressure.

[0020] Flange 3 serves as a cover plate to seal the inspection port. Flange 3 is preferably made of economical and practical Q235B low-carbon steel, whose yield strength (≥235 MPa) is much higher than the design requirement of 145.13 MPa, fully meeting the pressure requirements.

[0021] During assembly, flange 3 is located outside the air cylinder body 1. A rubber sealing gasket 5 is placed between flange 3 and flange seat 2. Subsequently, 12 M8 bolts 4 are evenly distributed along the circumference of flange 3 to secure flange 3, sealing gasket 5, and flange seat 2 together. To ensure the connection is secure, a spring washer 6 conforming to GB / T 93 standard is installed between the head of each bolt 4 and the contact surface of flange 3.

[0022] The tightening of bolt 4 is crucial for ensuring reliable sealing. In this embodiment, the pre-tightening force of bolt 4 is controlled within the range of 10.6 kN to 18.4 kN, achieved by applying an installation torque of 17 N·m to 24 N·m using a torque wrench. This parameter range is calculated based on the total force exerted by the gas on flange 3 of 28.27 kN under the highest test pressure of the air cylinder (0.9 MPa), taking into account the connection stiffness. This pre-tightening force ensures that the sealing gasket 5 is fully compressed to prevent leakage, while also preventing damage to the bolts or flange due to overload.

[0023] In this embodiment, the calculation process for each parameter is as follows: Bolts are used to mount components such as the cover plate onto the flange on the air cylinder. Therefore, the external load on the components is the force exerted by the gas inside the air cylinder on the cover plate. F = 0.9 × π ​​× 100² = 28.27 kN Since the connecting parts are made of soft material, and the stiffness ratio of the bolted connection is taken as 0.3 according to mechanical design, the external load acting on the bolt is: F1 = F × 0.3 = 8.48 kN The load on a single bolt is: FA1 = F1 / 12 = 0.71kN Structural analysis shows that the external load is in the axial direction of the bolt. Therefore, the minimum preload of the bolt should be >0.71kN to ensure stable contact between the connection surfaces.

[0024] Since the cover plate is relatively lightweight, the lateral load caused by vibration due to the cover plate mass is ignored. Therefore, the bolt preload (torque) design at this location mainly considers overcoming the external load brought by the test wind pressure and the strength of components such as the cover plate.

[0025] Initially, M8 bolts were selected. Based on a thread friction coefficient of 0.15, a bearing surface friction coefficient of 0.15, and a bolt mounting hole diameter of 9 mm, calculations were performed using 50%–70% of the bolt's guaranteed load, resulting in a torque range of 17–24 N·m. The resulting preload ranged from 10.6 to 18.4 kN, which is greater than the external load acting on the bolt, thus meeting the design requirements.

[0026] Based on a maximum preload of 18.4 MPa, to reduce the requirements for the cover plate material, a flat washer (GB / T97.1) is added under the bolt to improve the surface bearing capacity. At this point, the compressive stress on the lower surface of the bolt head is 145.13 MPa. The cover plate can be made of a material with a yield strength greater than 145.13 MPa.

[0027] 18.4 / (Π×(15.57^2-9^2) / 4)=145.13 MPa The type and dimensions of flange seat welds shall comply with TB / T 1900, and the weld dimension g shall be ≥0.7t.

[0028] Workflow: 1. First, complete the assembly welding of the air cylinder body 1 and the end cap with the flange seat 2.

[0029] 2. The inner wall of the air cylinder body 1 is pre-treated (e.g., sandblasting to remove rust) through the Φ200mm inspection hole.

[0030] 3. Through this inspection hole, use a spraying device to evenly spray a high-performance epoxy protective coating onto the inner wall of the air cylinder body 1. Because the opening is large enough, it can ensure that the coating covers the entire surface without any dead corners.

[0031] 4. After the coating has cured, install the sealing gasket 5, flange 3 and bolts 4 with elastic washers 6 according to the above method, and tighten them to the specified torque (17~24 N·m) to form the final product.

[0032] As described above, although the invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the invention itself. Various changes in form and detail may be made without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A novel pressure cylinder structure, comprising a cylinder body (1), characterized in that: The air cylinder body (1) has an inspection hole at its end, and a flange seat (2) is welded to the inspection hole. The flange seat (2) is threaded. It also includes a flange (3) for sealing the inspection hole. The flange (3) is connected to the flange seat (2) by a set of bolts (4). A sealing gasket (5) is provided between the flange (3) and the flange seat (2). An elastic washer (6) is provided between the bolts (4) and the flange (3). The weld (7) between the flange seat (2) and the cylinder body (1) has a dimension g that satisfies: g ≥ 0.7t, where t is the thickness of the thin plate in the weldment.

2. The novel pressure cylinder structure according to claim 1, characterized in that: The diameter of the inspection hole is 200mm.

3. The novel pressure cylinder structure according to claim 2, characterized in that: The number of bolts (4) is 12, which are evenly distributed around the circumference of the flange; the bolts (4) are M8 bolts.

4. The novel pressure cylinder structure according to claim 3, characterized in that: The installation preload of the bolt (4) ranges from 10.6kN to 18.4kN, and the installation torque of the bolt (4) ranges from 17 N·m to 24 N·m.

5. The novel pressure cylinder structure according to claim 1, characterized in that: The flange (3) can be made of low-carbon steel or carbon structural steel.

6. The novel pressure cylinder structure according to claim 1, characterized in that: The inner wall of the air cylinder body (1) is coated with a protective coating.

7. The novel pressure cylinder structure according to claim 1, characterized in that: The flange (3) is located outside the air cylinder body (1) during assembly.

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