In-line spring flame arrestor

Abstract

The present application aims to provide a series spring type flame arrester with high reliability and long service life, which is not easy to be damaged. The series spring type flame arrester comprises a shell, an overpressure valve arranged in the interior of the shell, a negative pressure valve arranged outside the shell, and a fixed shaft fixedly installed on the shell, the overpressure valve and the negative pressure valve are installed on the fixed shaft in a sliding manner along the axial direction, the interior limiting spring and the exterior limiting spring capable of stretching and contracting along the axial direction are arranged on the fixed shaft in a series connection manner, the interior limiting spring is used for abutting against the overpressure valve to limit the sliding range of the overpressure valve on the fixed shaft, and the exterior limiting spring is used for abutting against the negative pressure valve to limit the sliding range of the negative pressure valve on the fixed shaft.

Description

Technical Field

[0001] The present invention relates to a series spring type flame arrester, which can be used in fuel systems of civil transport aircraft, for example. Background Art

[0002] Flame arresters are used in the vent system of fuel tanks on civil aircraft, for example, to prevent external flames from entering the fuel tank. They also need to protect the fuel tank from overpressure and underpressure, preventing damage to the fuel tank structure due to excessive positive or negative pressure. Flame arresters are typically installed above the vent port of the fuel tank. Existing flame arresters come in two forms: Figure 1 External spring loaded flame arrester shown and Figure 2 External rocker-arm flame arrestor shown.

[0003] However, the two types of flame arresters mentioned above may be subjected to excessive positive and negative pressure when subjected to complex air flow fields, causing the valves to have excessive actuation frequency or amplitude, exceeding the tolerance value of the device itself, thereby causing strength damage. Figure 1 In the external spring type flame arrester shown, if the swing amplitude of the rocker arm is too large or the frequency is too high, the external spring type valve may be damaged. Figure 2 In the external rocker arm flame arrester shown, if the swing amplitude of the rocker arm is too large or the frequency is too high, the fixing plate of the flame arrester valve plate may be damaged or even fall off.

[0004] That is, the valve damage problem of the flame suppressor mostly occurs in the moving parts, and the variable flow field during flight can easily cause it to be subjected to excessive positive and negative pressure, too frequent cyclic fluctuations, and repeated deflection and impact of the moving surface of the spring or rocker arm, which can easily cause fatigue damage and damage.

[0005] In summary, whether it is an external spring-type flame arrester or an external rocker-arm flame arrester, the valve is relatively easy to be damaged. At present, there is no mature improvement solution to solve the problem of damage to the actuating valve of the flame arrester. In order to ensure that the valve of the flame arrester has high reliability and long service life, optimization and improvement are urgently needed. Summary of the Invention

[0006] In view of the above problems, an object of the present invention is to provide a series spring type flame arrester with a valve that is not easily damaged, high reliability and long service life.

[0007] In order to achieve the above-mentioned purpose of the present invention, the present invention provides a series spring type flame suppressor, comprising: a shell; an overpressure valve arranged inside the shell; a negative pressure valve arranged outside the shell; and a fixed shaft fixedly installed on the shell, the overpressure valve and the negative pressure valve are installed on the fixed shaft in a manner that can slide along the axial direction, and an internal limit spring and an external limit spring that can be extended and retracted along the axial direction are arranged on the fixed shaft in a series connection manner, the internal limit spring is used to abut against the overpressure valve to limit the sliding range of the overpressure valve on the fixed shaft, and the external limit spring is used to abut against the negative pressure valve to limit the sliding range of the negative pressure valve on the fixed shaft.

[0008] The tandem spring-loaded flame arrester of the present invention utilizes a fixed axis, or fixed shaft, to ensure that the motion paths of the overpressure and negative pressure valves, as well as the internal and external limit springs, are controlled along the axis. This means that, under both overpressure and negative pressure conditions in the fuel tank, the overpressure and negative pressure valves move along the axis, resulting in a simple, reliable, and damage-free operation. Furthermore, the internal and external limit springs, respectively, limit the sliding range of the overpressure and negative pressure valves, preventing excessive movement and damaging them, thereby improving reliability and device life.

[0009] Preferably, a sealing ring for an overpressure valve is installed on the overpressure valve, and a sealing ring for a negative pressure valve is installed on the negative pressure valve. The sealing ring for the overpressure valve is located between the overpressure valve and the inner surface of the outer shell to seal the overpressure valve and the inner surface of the outer shell, and the sealing ring for the negative pressure valve is located between the negative pressure valve and the outer surface of the outer shell to seal the negative pressure valve and the outer surface of the outer shell.

[0010] The tandem spring-loaded flame arrester of the present invention utilizes sealing rings for the overpressure and negative pressure valves to prevent gas leakage from the gaps between the overpressure and negative pressure valves and the fixed shaft. This allows the overpressure and negative pressure valves to be sealed against the housing while ensuring free movement. Furthermore, precise vertical positioning of the fixed shaft along its axis ensures a complete seal with the housing surface.

[0011] Preferably, the sealing ring for the overpressure valve is composed of two sealing rings, an inner sealing ring and an outer sealing ring, which are embedded in the sealing groove of the valve disc of the overpressure valve itself; the sealing ring for the negative pressure valve is composed of two sealing rings, an inner sealing ring and an outer sealing ring, which are embedded in the sealing groove of the valve disc of the negative pressure valve itself.

[0012] To prevent external leakage caused by the inevitable play between the valve discs and the fixed shaft of the overpressure and negative pressure valves, the tandem spring-loaded flame arrester of the present invention utilizes a double inner and outer sealing ring, consisting of two sealing rings, the overpressure and negative pressure valve seals, to control leakage within the valve bodies of the overpressure and negative pressure valves, preventing leakage outside the valve bodies. This ensures the airtightness of the tandem spring-loaded flame arrester. This ensures that the overpressure and negative pressure valve seals are sealed and fully secured.

[0013] Preferably, vent holes are respectively provided at positions of the shell corresponding to the overpressure valve and the negative pressure valve, the vent holes are composed of four sector-shaped surfaces, and an axis mounting hole is formed in the center of the four sector-shaped surfaces. The fixed shaft passes through the axis mounting hole and is installed on the shell, and the fixed shaft is connected to the shell by the cross spacing parts between the four sector-shaped surfaces.

[0014] According to the series spring-type flame arrester of the present invention, air is taken in or out through the four sector-shaped surfaces of the vent hole, and the fixed shaft is firmly connected to the housing by means of the cross-spaced portions between the four sector-shaped surfaces. Therefore, it is possible to ensure the strength and flatness of the mounting portion of the fixed shaft while ensuring the air intake or exhaust volume, thereby simultaneously meeting the requirements for air intake or exhaust volume and the requirements for mounting flatness.

[0015] Preferably, the four sector-shaped surfaces of the vent hole and the shaft mounting hole are formed by laser cutting.

[0016] According to the series spring type flame arrester of the present invention, it is possible to ensure that the installation plane of the fixed shaft and the housing remain in the same plane without deviation.

[0017] Preferably, an external limit spring fixing portion is provided on the outside of the position of the outer shell corresponding to the negative pressure valve, and the external limit spring fixing portion is formed into a half I-shape, is located outside the negative pressure valve and the external limit spring, and is for the fixed shaft to pass through, and the external limit spring fixing portion is formed as the fixed end of the external limit spring.

[0018] According to the series spring type flame arrester of the present invention, since the external limit spring fixing portion is formed as the fixed end of the external limit spring, the negative pressure valve and the end of the fixed shaft can be protected from deformation due to external forces during manufacturing, installation and transportation.

[0019] Preferably, the external limit spring fixing portion is integrally formed with the housing.

[0020] The series spring type flame arrester according to the present invention can ensure that the shell is not easily deformed and can accurately position the fixed shaft to ensure that the axis of the fixed shaft is perpendicular to the plane of the shell.

[0021] Preferably, the overpressure valve, the negative pressure valve and the fixed shaft are made of self-lubricating metal materials.

[0022] The series spring type flame arrester according to the present invention can reduce sliding friction loss to the greatest extent and improve the reliability and service life of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a perspective view showing the structure of a conventional external spring-type flame arrester.

[0024] Figure 2 This is a perspective view showing the structure of a conventional external rocker-arm flame arrester.

[0025] Figure 3 FIG. 1 is a schematic diagram schematically showing the structure of a series spring type flame arrester according to an embodiment of the present invention.

[0026] Figure 4 FIG. 1 is an exploded schematic diagram schematically showing the structures of various parts of a series spring-type flame arrester according to an embodiment of the present invention.

[0027] Figure 5 FIG. 1 is a schematic diagram schematically showing a series spring-type flame arrester in an overpressure exhaust state according to an embodiment of the present invention.

[0028] Figure 6 FIG. 1 is a schematic diagram schematically showing a series spring-type flame arrester in a negative pressure suction state according to an embodiment of the present invention.

[0029] Figure 7 The figure is a perspective view showing the structure of a series spring type flame arrester according to an embodiment of the present invention, wherein a rectangular opening is cut out on the oblique left side to facilitate viewing of the internal structure.

[0030] Figure 8 The figure is a perspective view showing the structure of a housing of a series spring type flame arrester according to an embodiment of the present invention, wherein a rectangular opening is cut out on the oblique right side to facilitate viewing of the internal structure.

[0031] Figure 9 It is a side view showing the structure of a housing of a series spring type flame arrester according to an embodiment of the present invention.

[0032] Figure 10 This is a front view showing the structure of a series spring type flame arrester according to an embodiment of the present invention, wherein a rectangular opening is cut out on the front side to facilitate viewing of the internal structure.

[0033] (Explanation of Symbols)

[0034] 100 Series Spring-Loaded Flame Arrestor

[0035] 1. Housing

[0036] 11 Installation bottom

[0037] 12 Housing body

[0038] 121 vent

[0039] 122 Shaft mounting hole

[0040] 123 Fireproof Honeycomb

[0041] 124 External limit spring fixing portion

[0042] 2 Overpressure valve

[0043] 3 Negative pressure valve

[0044] 4 fixed axis

[0045] 5 Internal limit spring

[0046] 6 External limit spring

[0047] 7 Sealing ring for overpressure valve

[0048] 8. Sealing ring for negative pressure valve DETAILED DESCRIPTION

[0049] Various embodiments of the present invention will now be described in detail, examples of which are shown in the accompanying drawings and described below. Although the present invention will be described in conjunction with exemplary embodiments, it should be appreciated that this description is not intended to limit the invention to those exemplary embodiments. On the contrary, the present invention is intended to cover not only those exemplary embodiments, but also various alternatives, modifications, equivalents, and other embodiments that may be included within the spirit and scope of the invention as defined by the appended claims.

[0050] Next, combine Figures 3 to 10 A series spring type flame arrester 100 according to an embodiment of the present invention will be described. Figure 3 FIG. 1 is a schematic diagram schematically showing the structure of a series spring type flame arrester 100 according to an embodiment of the present invention. Figure 4 1 is an exploded schematic diagram schematically showing the structure of each component of the series spring type flame arrester 100 according to an embodiment of the present invention. Figure 5 FIG. 1 is a schematic diagram schematically showing the serial spring type flame arrester 100 according to the embodiment of the present invention in an overpressure exhaust state. Figure 6FIG. 1 is a schematic diagram schematically showing the serial spring type flame arrester 100 according to the embodiment of the present invention in a negative pressure suction state. Figure 7 1 is a perspective view showing the structure of a series spring-type flame arrester 100 according to an embodiment of the present invention, wherein a rectangular opening K is cut out on the oblique left side to facilitate viewing of the internal structure (it should be noted that the rectangular opening K does not actually exist and is cut out only to facilitate viewing of the internal structure). Figure 8 1 is a perspective view showing the structure of the housing 1 of the series spring type flame arrester 100 according to the embodiment of the present invention, wherein a rectangular opening K is cut out on the oblique right side to facilitate viewing of the internal structure. Figure 9 1 is a side view showing the structure of the housing 1 of the series spring type flame arrester 100 according to the embodiment of the present invention. Figure 10 1 is a front view showing the structure of a series spring type flame arrester 100 according to an embodiment of the present invention, wherein a rectangular opening K is cut out on the front side to facilitate viewing of the internal structure.

[0051] The series spring-loaded flame arrester 100 according to an embodiment of the present invention is used, for example, in fuel tanks of civilian aircraft to prevent external flames from entering the fuel tank. It also protects the fuel tank from overpressure and negative pressure, preventing damage from excessive positive or negative pressure. The series spring-loaded flame arrester 100 according to an embodiment of the present invention is installed, for example, above the fuel tank's vent.

[0052] (Overall structure of series spring type flame arrester 100)

[0053] like Figures 3 to 10 As shown, a series spring-type flame arrester 100 according to an embodiment of the present invention includes a housing 1, an overpressure valve 2 disposed within the housing 1, a negative pressure valve 3 disposed outside the housing 1, and a fixed shaft 4 fixedly mounted to the housing 1. The overpressure valve 2 and the negative pressure valve 3 are mounted on the fixed shaft 4 so as to be slidable along the axial direction. An internal limit spring 5 and an external limit spring 6, which are extendable and retractable along the axial direction, are disposed in series on the fixed shaft 4. The internal limit spring 5 is configured to abut against the overpressure valve 2 to limit the sliding range of the overpressure valve 2 on the fixed shaft 4, while the external limit spring 6 is configured to abut against the negative pressure valve 3 to limit the sliding range of the negative pressure valve 3 on the fixed shaft 4.

[0054] Specifically, if Figure 5 As shown, the overpressure valve 2 on the left is used to move to the right by squeezing the internal limit spring 5 when the pressure in the fuel tank is too high, thereby achieving the function of exhausting gas. Figure 6 As shown, the negative pressure valve 3 on the right is used to move to the right by squeezing the external limit spring 6 when the pressure in the fuel tank is too low, thereby achieving the function of inhaling gas.

[0055] Thus, in the series-spring flame arrester 100 according to the embodiment of the present invention, a fixed axis, namely, fixed axis 4, ensures that the motion trajectories of the overpressure valve 2 and negative pressure valve 3, as well as the internal limit spring 5 and external limit spring 6, are controlled and aligned along the axis. That is, under conditions of overpressure or negative pressure in the fuel tank, the overpressure valve 2 and negative pressure valve 3 move along the axis, which is simple, reliable, and damage-free. Furthermore, by limiting the sliding range of the overpressure valve 2 and negative pressure valve 3, respectively, the internal limit spring 5 and external limit spring 6 prevent excessive movement of the overpressure valve 2 and negative pressure valve 3, preventing damage to the valves and improving reliability and device life.

[0056] Furthermore, the internal limit spring 5 and the external limit spring 6 are fixed by using a fixed shaft 4, which can save space and weight.

[0057] In addition, in the series spring type flame suppressor 100 of the embodiment of the present invention, a sealing ring 7 for an overpressure valve is installed on the overpressure valve 2, and a sealing ring 8 for a negative pressure valve is installed on the negative pressure valve 3. The sealing ring 7 for the overpressure valve is located between the overpressure valve 2 and the inner surface of the outer shell 1 to seal the overpressure valve 2 and the inner surface of the outer shell 1, and the sealing ring 8 for the negative pressure valve is located between the negative pressure valve 3 and the outer surface of the outer shell 1 to seal the negative pressure valve 3 and the outer surface of the outer shell 1.

[0058] Thus, the overpressure valve sealing ring 7 and the negative pressure valve sealing ring 8 prevent gas leakage from the gaps between the overpressure valve 2 and the negative pressure valve 3 and the fixed shaft 4, ensuring that the overpressure valve 2 and the negative pressure valve 3 are freely movable while being sealed against the housing 1. Furthermore, the precise vertical positioning of the fixed shaft 4 along its axis ensures a complete seal with the surface of the housing 1.

[0059] Preferably, in this embodiment, Figure 3 、 Figure 4 As shown, the sealing ring 7 for the overpressure valve is composed of two sealing rings, an inner sealing ring and an outer sealing ring, which are embedded in the sealing groove of the valve disc of the overpressure valve 2 itself. The sealing ring 8 for the negative pressure valve is composed of two sealing rings, an inner sealing ring and an outer sealing ring, which are embedded in the sealing groove of the valve disc of the negative pressure valve 3 itself.

[0060] To prevent external leakage caused by the inevitable play between the valve discs of overpressure valve 2 and negative pressure valve 3 and fixed shaft 4, double seals, such as overpressure valve seal ring 7 and negative pressure valve seal ring 8, are used to contain the leakage within the valve bodies of overpressure valve 2 and negative pressure valve 3, preventing leakage outside the valve bodies of overpressure valve 2 and negative pressure valve 3. This ensures the airtightness of the series spring-loaded flame arrester 100. This ensures the sealing and complete fixation of overpressure valve seal ring 7 and negative pressure valve seal ring 8.

[0061] In addition, preferably, an inner sealing ring (not shown) smaller than the inner peripheral sealing ring of the overpressure valve sealing ring 7 and the negative pressure valve sealing ring 8 is further provided inside the overpressure valve 2 and the negative pressure valve 3 respectively.

[0062] In summary, in the series spring-loaded flame arrester 100 of the present invention, the central fixed shaft 4 is fixed to the left and right fixed planes of the outer shell 1 and is integrally connected to the structure of the outer shell 1. Both the overpressure valve 2 and the negative pressure valve 3 can slide freely along the axis. This ensures that the outer shell 1 is always in the same plane, ensuring the precise positioning of the fixed shaft 4 to meet the requirements of the overpressure valve sealing ring 7 and the negative pressure valve sealing ring 8 to seal both surfaces simultaneously. The series spring-loaded flame arrester 100 of the present invention can prevent excessive movement of the valve discs of the overpressure valve 2 and the negative pressure valve 3, thereby increasing the life of the equipment and achieving a good seal with the outer shell 1.

[0063] (Specific structure of the series spring type flame arrester 100)

[0064] In this embodiment, for example Figure 8 as well as Figure 9 As shown, housing 1 includes a mounting base 11 and a housing body 12 disposed upright on mounting base 11. Housing body 12 is formed into a substantially rectangular parallelepiped shape. The in-line spring-loaded flame arrester 100 according to an embodiment of the present invention is mounted, for example, above the vent of a fuel tank on a civil aircraft via mounting base 11.

[0065] Vent holes 121 are provided in the housing 1 (specifically, the housing body 12) at locations corresponding to the overpressure valve 2 and the negative pressure valve 3. These vent holes 121 are formed of four sector-shaped surfaces, each with a shaft mounting hole 122 formed in its center. The fixed shaft 4 is mounted to the housing 1 through these shaft mounting holes 122. The fixed shaft 4 is connected to the housing 1 (specifically, the housing body 12) via the cross-shaped spacing between the four sector-shaped surfaces. Thus, the fixed shaft 4 is secured between the two sidewalls of the housing body 12 and maintains a seal with the housing 1. This seal can be achieved, for example, by local welding or gluing, thereby preventing gas within the housing 1 from leaking to the outside.

[0066] Thus, air is introduced or exhausted through the four sectors of the vent hole 121, and the fixed shaft 4 is securely connected to the housing body 12 by the cross-shaped spacing between the four sectors. This ensures both the strength and flatness of the mounting portion of the fixed shaft 4 while ensuring sufficient air intake or exhaust volume, thereby simultaneously meeting both the air intake or exhaust volume requirements and the mounting flatness requirements.

[0067] Preferably, the four sector surfaces of the vent hole 121 and the shaft mounting hole 122 are formed by laser cutting, thereby ensuring that the mounting plane of the fixed shaft 4 and the side wall surface of the housing body 12 remain in the same plane without deviation.

[0068] A fireproof honeycomb 123 is provided in the upper region of the housing body 12 to prevent flames from entering the fuel tank.

[0069] Furthermore, an external limit spring fixing portion 124 is provided on the exterior of the housing 1 (specifically, the housing body 12) at a position corresponding to the negative pressure valve 3. This external limit spring fixing portion 124 is formed, for example, in the shape of a half I-beam and is located outside the negative pressure valve 3 and the external limit spring 6, through which the fixed shaft 4 passes. This external limit spring fixing portion 124 serves as the fixed end of the external limit spring 6, protecting the ends of the negative pressure valve 3 and the fixed shaft 4 from deformation due to external forces during manufacturing, installation, and transportation.

[0070] Preferably, the external limit spring fixing portion 124 is integrally formed with the housing body 12. This ensures that the housing 1 is not easily deformed, and the fixed shaft 4 can be accurately positioned. The fixed shaft 4, which passes through the housing body 12, is fixed to the external limit spring fixing portion 124 to ensure that the axis of the fixed shaft 4 is perpendicular to the side wall of the housing body 12. The moving trajectories of the overpressure valve 2 and the negative pressure valve 3 are along the axis direction, making the overpressure valve 2 and the negative pressure valve 3 less susceptible to damage.

[0071] The overpressure valve 2 and the negative pressure valve 3 are formed into a circle, and the overpressure valve sealing ring 7 and the negative pressure valve sealing ring 8 are also formed into a circle. The outer shapes of the overpressure valve 2 and the negative pressure valve 3 are slightly larger than the outer shapes of the outer peripheral sealing rings of the overpressure valve sealing ring 7 and the negative pressure valve sealing ring 8.

[0072] Preferably, the overpressure valve 2, the negative pressure valve 3 and the fixed shaft 4 are made of self-lubricating metal materials, which can minimize sliding friction loss and improve product reliability and life.

[0073] (Variation)

[0074] The present invention is described above by way of example with reference to the accompanying drawings. It is apparent that the specific implementation of the present invention is not limited to the above-mentioned embodiments.

[0075] (1) In the above embodiment, the serial spring type flame arrester 100 of the present invention is used in a fuel tank of a civil aircraft. However, the serial spring type flame arrester 100 of the present invention can also be used in any location where flames need to be blocked, such as a fuel tank of other equipment.

[0076] (2) In the above embodiment, the structure for sealing the overpressure valve 2 and the negative pressure valve 3 respectively using the sealing ring 7 for the overpressure valve and the sealing ring 8 for the negative pressure valve is described, but the structure for sealing the overpressure valve 2 and the negative pressure valve 3 is not particularly limited, and other sealing forms may also be used.

[0077] In addition, the structure in which the sealing ring 7 for the overpressure valve and the sealing ring 8 for the negative pressure valve are respectively installed on the overpressure valve 2 and the negative pressure valve 3 in a snap-fit ​​manner is described, but the sealing ring 7 for the overpressure valve and the sealing ring 8 for the negative pressure valve can also be installed in other forms.

[0078] (3) In the above embodiment, the external limit spring fixing portion 124 is described as being formed in a half-I-shape. However, the shape of the external limit spring fixing portion 124 is not particularly limited and may be in another shape such as a box. Furthermore, the external limit spring fixing portion 124 may be formed separately from the housing 1.

[0079] (4) In the above embodiment, the overpressure valve 2, the negative pressure valve 3 and the fixed shaft 4 are described as being made of self-lubricating metal materials, but the overpressure valve 2, the negative pressure valve 3 and the fixed shaft 4 can also be made of ordinary metal materials and lubricating oil, etc. can be added between them.

[0080] Although the structure and working principle of the present invention have been described above in conjunction with preferred embodiments, those skilled in the art will recognize that the above examples are for illustration only and are not intended to limit the present invention. Therefore, modifications and variations may be made to the present invention within the spirit of the claims, and such modifications and variations will fall within the scope of the claims.

Claims

1. A series spring type flame arrester, characterized in that: include: shell; an overpressure valve disposed inside the housing; a negative pressure valve disposed on the outside of the housing; as well as a fixed shaft fixedly mounted on the housing, The overpressure valve and the negative pressure valve are mounted on the fixed shaft in a manner that allows them to slide along the axial direction. An internal limit spring and an external limit spring are provided on the fixed shaft in a serially connected manner and are capable of extending and retracting along the axial direction. The internal limit spring is used to abut against the overpressure valve to limit the sliding range of the overpressure valve on the fixed shaft. The external limit spring is used to abut against the negative pressure valve to limit the sliding range of the negative pressure valve on the fixed shaft.

2. The series spring type flame arrester according to claim 1, characterized in that: A sealing ring for an overpressure valve is installed on the overpressure valve, and a sealing ring for a negative pressure valve is installed on the negative pressure valve. The overpressure valve sealing ring is located between the overpressure valve and the inner surface of the shell to seal the overpressure valve and the inner surface of the shell. The sealing ring for the negative pressure valve is located between the negative pressure valve and the outer surface of the shell to seal the negative pressure valve and the outer surface of the shell.

3. The series spring type flame arrester according to claim 2, characterized in that: The overpressure valve sealing ring is composed of an inner sealing ring and an outer sealing ring which are embedded in the sealing groove of the valve disc of the overpressure valve. The sealing ring for the negative pressure valve is composed of two sealing rings, an inner peripheral sealing ring and an outer peripheral sealing ring, which are embedded in the sealing groove of the valve plate of the negative pressure valve.

4. The series spring type flame arrester according to claim 1, characterized in that: Ventilation holes are respectively provided at positions of the housing corresponding to the overpressure valve and the negative pressure valve. The vent hole is composed of four sector-shaped surfaces, and a shaft mounting hole is formed in the center of the four sector-shaped surfaces. The fixed shaft passes through the shaft mounting hole and is installed on the shell. The fixed shaft is connected to the shell by the cross spacing part between the four sector-shaped surfaces.

5. The series spring type flame arrester according to claim 4, characterized in that: The four sector-shaped surfaces of the vent hole and the shaft mounting hole are formed by laser cutting.

6. The series spring type flame arrester according to claim 1, characterized in that: An external limit spring fixing portion is provided on the outside of the position of the shell corresponding to the negative pressure valve. The external limit spring fixing portion is formed into a half I-shape and is located outside the negative pressure valve and the external limit spring, and is for the fixed shaft to pass through. The external limit spring fixing portion is formed as a fixed end of the external limit spring.

7. The series spring type flame arrester according to claim 6, characterized in that: The external limit spring fixing portion is integrally formed with the housing.

8. The series spring type flame arrester according to claim 1, characterized in that: The overpressure valve, the negative pressure valve and the fixed shaft are made of self-lubricating metal materials.

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