A high-service-life composite double check valve

Abstract

This application discloses a high-service-life composite double check valve, relating to the field of valves, comprising a valve body, a valve cover, a valve plate, and a compression spring. The valve plate has a first-pass opening, and a guide tube communicating with the first-pass opening is provided on the side of the valve plate near the inlet end of the valve body. The guide tube has an inner edge on the side away from the valve plate, and a first-pass valve plate is provided inside the guide tube, abutting against the inner edge of the guide tube. The compression spring includes a first compression spring and a second compression spring arranged concentrically, with a neutral pressure plate connecting the first compression spring and the second compression spring. The end of the second compression spring away from the neutral pressure plate is connected to the first-pass valve plate, and the neutral pressure plate abuts against the edge of the first-pass opening. The first compression spring is in a pre-compressed deformation state. Under a fixed service life, the first-pass valve plate and the valve plate respectively function as opening and closing elements, reducing the time that a single opening and closing element is subjected to fluid scouring, thereby extending the service life of the check valve.

Description

Technical Field

[0001] This application relates to the field of valves, and more particularly to a composite double check valve with a long service life. Background Technology

[0002] A check valve is a valve whose opening and closing element is a circular valve disc that relies on its own weight and the pressure of the medium to prevent backflow. Check valves can be classified into lift check valves, swing check valves, and butterfly check valves based on their structure. Lift check valves are the most common type. They come in vertical and horizontal versions, with horizontal check valves being more suitable for horizontal pipelines. In production practice, horizontally installed pipelines far outnumber vertically installed pipelines; therefore, horizontal lift check valves are more commonly used in production.

[0003] Lift check valves have a simple structure and are relatively reliable in operation. However, when the check valve is in a condition where the fluid pressure changes frequently, the valve plate of the check valve is subjected to increased fluid scouring, which increases the wear and tear on the check valve and shortens its service life. Summary of the Invention

[0004] To address the issue of shortened service life of lift check valves under conditions of frequent fluid pressure changes, this application provides a composite double check valve with a long service life.

[0005] The composite double check valve with a long service life provided in this application adopts the following technical solution: A high-service-life composite double check valve includes a valve body, a valve cover, a valve plate, and a compression spring. The valve body has an inlet, an outlet, a valve cover opening, and a valve port. The valve cover is connected to the valve cover opening portion of the valve body. The valve plate is used to close the valve port. The valve plate has a first-pass opening. A guide tube communicating with the first-pass opening is provided on the side of the valve plate near the inlet end of the valve body. An inner edge is provided on the side of the guide tube away from the valve plate. A first-pass valve plate is provided inside the guide tube, and the first-pass valve plate abuts against the inner edge of the guide tube. The compression spring includes a first compression spring and a second compression spring arranged concentrically. A neutral pressure plate is connected between the first compression spring and the second compression spring. The end of the first compression spring away from the neutral pressure plate is connected to the valve cover. The end of the second compression spring away from the neutral pressure plate is connected to the first-pass valve plate. The neutral pressure plate abuts against the edge of the first-pass opening. The first compression spring is in a pre-compression deformation state.

[0006] By adopting the above technical solution, when the check valve in this application is working, the first spring forces the valve plate to seal the valve port of the valve body, and the second spring first passes through the valve plate to seal the first passage on the valve plate. Since the first spring is in a pre-compression deformed state, when the fluid pressure entering the valve body is low, the valve plate is not enough to drive it to open, and the first passage valve plate will open before the valve plate, allowing the fluid to pass through the valve body from the first passage on the valve plate. As the fluid pressure entering the valve body increases, the opening degree of the first passage valve plate increases, and at the same time, the deformation of the second spring increases. When the deformation of the second spring increases to the same as the pre-compression deformation of the first spring, the first and second springs can act simultaneously, causing the valve plate to open, thereby opening the valve port. By adding a first passage and a first passage valve plate for closing the first passage, this application enables the check valve to open different opening and closing parts under different pressure ranges. Thus, given a fixed service life for the check valve, the first valve plate and the second valve plate each perform the functions of the opening and closing elements, which can reduce the time that a single opening and closing element is subjected to fluid scouring, thus helping to extend the service life of the check valve.

[0007] Optionally, the center pressure plate is provided with a guide structure, which is connected to the valve cover; the first compression spring and the second compression spring are connected as a whole to form an integral compression spring, and the center pressure plate is connected to the integral compression spring.

[0008] By adopting the above technical solution, the first and second compression springs are connected as a single compression spring, which is then connected to the intermediate pressure plate. Under the action of the guide structure, the intermediate pressure plate is difficult to move helically along the single compression spring, thus maintaining a relatively fixed position on the single compression spring and achieving the connection between the intermediate pressure plate and the single compression spring. Connecting the first and second compression springs as a single compression spring simplifies the equipment structure and reduces the likelihood of connection failure at the joints between the intermediate pressure plate and the first or second compression spring.

[0009] Optionally, the guiding structure is a guide rod, and the center pressure plate is provided with a guide hole adapted to the guide rod. At least three guide rods are provided, and the three guide rods are arranged in a circumferential array along the center line of the first compression spring. The guide rods abut against the outer circumferential surface of the first compression spring. By adopting the above technical solution, the three guide rods can surround the first compression spring. When all three guide rods abut against the outer circumference of the first compression spring, the three guide rods can jointly guide the first compression spring, which helps to ensure the stability of the first compression spring during the extension and retraction process.

[0010] Optionally, the valve plate has a through hole for the guide rod to pass through, with one end of the guide rod away from the valve cover located inside the through hole.

[0011] By adopting the above technical solution, the guide rod is connected to the through hole on the valve plate, so that the guide rod guides the lifting and lowering movement of the valve plate. The end of the guide rod away from the valve cover is located in the through hole, which can avoid the guide rod from interfering with the valve plate.

[0012] Optionally, the guide rod is threadedly connected to the valve cover, the guide rod is a round rod, the end of the guide rod away from the valve cover is provided with a longitudinal section, the through hole is a square hole, and the longitudinal section abuts against one inner side of the through hole.

[0013] By adopting the above technical solution, the guide rod is threadedly connected to the valve cover, making disassembly and assembly relatively convenient. The longitudinal section of the guide rod abuts against the inner surface of the through hole, which can prevent the guide rod from rotating around its own axis, thereby reducing the possibility of the guide rod becoming loose and improving the stability of the guide rod.

[0014] Optionally, the inner diameter of the guide tube and the diameter of the pre-flow valve plate are both larger than the inner diameter of the pre-flow port, and the pre-flow valve plate can block the pre-flow port from bottom to top.

[0015] By adopting the above technical solution, as the pressure of the fluid medium entering the valve body gradually increases, the compression of the second compression spring gradually increases, causing the first-pass valve plate to gradually approach the first-pass port. When the first-pass valve plate abuts the edge of the first-pass port, the first-pass valve plate blocks the first-pass port, thereby reducing the scouring effect of the fluid on the second and first compression springs.

[0016] Optionally, the diameter of the pre-flow valve plate is smaller than the inner diameter of the guide tube, the pre-flow valve plate and the inner wall of the guide tube form an annular gap that can avoid the guide rod, and the peripheral side wall of the guide tube and the inner edge are transitioned with a rounded corner, so that the inner peripheral surface of the guide tube and the upper surface of the inner edge form an inner rounded corner, and the radius of the inner rounded corner is greater than or equal to the width of the annular gap.

[0017] By adopting the above technical solution, the inner radius of the guide tube can make the first-pass valve plate position in the center of the guide tube, so that the first-pass valve plate can avoid the guide rod.

[0018] Optionally, a limiting cylinder is provided on the side of the valve plate near the valve cover. The cylinder wall of the limiting cylinder is provided with holes for fluid to pass through. The limiting cylinder is used to limit the minimum distance between the valve plate and the valve cover.

[0019] By adopting the above technical solution, the limiting cylinder can limit the minimum distance between the valve plate and the valve cover, thereby limiting the maximum deformation of the first compression spring and protecting the first compression spring.

[0020] Optionally, the outer diameter of the limiting cylinder is greater than or equal to the outer diameter of the valve plate; the valve cover is provided with an elastic protective membrane, the elastic protective membrane includes multiple valves, the multiple valves are arranged in an array around the central circumference of the limiting cylinder, and the valves abut against the outer circumferential surface of the limiting cylinder; when the valve plate moves to a position close to the valve cover, the valves can extend from the limiting cylinder to the sealing surface of the valve plate.

[0021] By adopting the above technical solution, the elastic protective membrane remains in contact with the outer circumferential surface of the limiting cylinder. When the valve plate and the limiting cylinder move towards the valve cover, each valve of the flexible protective membrane gradually extends along the outer circumferential surface of the limiting cylinder to the sealing surface of the valve plate. The fluid flowing through the valve body can force the valve to abut against the sealing surface of the valve plate, thereby reducing the erosion of the valve plate sealing surface by the fluid and improving the service life of the valve plate.

[0022] Optionally, the valve cover is provided with a connecting cylinder, the connecting cylinder is provided with a hole for fluid to pass through, the inner diameter of the connecting cylinder is larger than the outer diameter of the limiting cylinder, the lower edge of the connecting cylinder is provided with an outwardly flared outer edge, one side of the valve is connected and fixed to the outer edge, and the valve is bent downward and abuts against the outer peripheral surface of the limiting cylinder.

[0023] By adopting the above technical solution, during valve installation, it is first connected to the outer edge of the connecting cylinder, and then bent downwards to abut against the outer circumferential surface of the limiting cylinder. The downward bending part of the valve produces elastic deformation, so that the valve can maintain its abutment against the limiting cylinder.

[0024] In summary, this application includes at least one of the following beneficial technical effects: This application adds a pre-flow port and a pre-flow valve plate for closing the pre-flow port, allowing the check valve to open different opening and closing elements under different pressure ranges. Thus, with a fixed service life of the check valve, the pre-flow valve plate and the valve plate respectively perform the functions of the opening and closing elements, reducing the time that individual opening and closing elements are subjected to fluid erosion, which helps extend the service life of the check valve. The elastic protective membrane remains in contact with the outer circumferential surface of the limiting cylinder. When the valve plate and the limiting cylinder move towards the valve cover, each valve of the flexible protective membrane gradually extends along the outer circumferential surface of the limiting cylinder to the sealing surface of the valve plate. The fluid flowing through the valve body can force the valve to abut against the sealing surface of the valve plate, thereby reducing the erosion of the valve plate sealing surface by the fluid and improving the service life of the valve plate. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the composite double check valve in the closed state according to Example 1.

[0026] Figure 2 This is a schematic diagram of Embodiment 1 used to illustrate the connection relationship between the valve plate and other components.

[0027] Figure 3 This is a schematic diagram of the composite double check valve of Example 1 in the valve plate open state.

[0028] Figure 4 This is a schematic diagram of the composite double check valve in the closed state according to Example 2.

[0029] Figure 5 This is a schematic diagram of the composite double check valve in the valve plate open state of Example 2.

[0030] Explanation of reference numerals in the attached figures: 1. Valve body; 11. Inlet; 12. Outlet; 13. Valve cover port; 14. Valve port; 2. Valve cover; 21. Connecting cylinder; 211. Outer edge; 3. Valve plate; 31. First through port; 32. Through hole; 33. Limiting cylinder; 4. Compression spring; 41. First compression spring; 42. Second compression spring; 43. Center pressure plate; 431. Guide hole; 44. Guide rod; 441. Longitudinal section; 442. Locking nut; 5. Flow guide cylinder; 51. Inner edge; 52. Inner rounded corner; 6. First through valve plate; 7. Elastic protective membrane; 71. Valve valve. Detailed Implementation

[0031] The following is in conjunction with the appendix Figure 1-5 This application will be described in further detail. Example 1

[0032] This application discloses a long-service-life composite double check valve. (Refer to...) Figure 1 The high-service-life composite double check valve includes a valve body 1, a valve cover 2, a valve plate 3, and a compression spring 4. The valve body 1 has a horizontal structure and has an inlet 11, an outlet 12, a valve cover port 13, and a valve port 14. The valve cover 2 is bolted to the valve cover port 13 of the valve body 1. The valve port 14 is located inside the valve body 1. The valve plate 3 is used to close the valve port 14 inside the valve body 1 to separate the inlet 11 and the outlet 12 of the valve body 1.

[0033] Reference Figure 1 and Figure 2The valve plate 3 is provided with a first passage 31. A guide tube 5 communicating with the first passage 31 is provided on the side of the valve plate 3 near the inlet 11 end of the valve body 1. The end of the guide tube 5 away from the valve plate 3 is provided with an inner edge 51. A first passage valve plate 6 is provided on the inner side of the guide tube 5. The first passage valve plate 6 abuts against the inner edge 51 of the guide tube 5. The compression spring 4 includes a first compression spring 41 and a second compression spring 42 arranged concentrically. A middle pressure plate 43 is connected between the first compression spring 41 and the second compression spring 42. The middle pressure plate 43 is a ring structure. The first compression spring 41 and the second compression spring 42 are fixedly connected to the middle pressure plate 43 respectively. The end of the first compression spring 41 away from the middle pressure plate 43 is connected to the valve cover 2. The end of the second compression spring 42 away from the middle pressure plate 43 is connected to the first passage valve plate 6. The middle pressure plate 43 abuts against the edge of the first passage 31. The first compression spring 41 is in a pre-compression deformation state, and the second compression spring 42 is in a relaxed state.

[0034] In this embodiment, the second compression spring 42 can also be set to a pre-compression deformation state. The ratio of the pre-compression deformation force of the second compression spring 42 to the pre-compression deformation force of the first compression spring 41 is less than the ratio of the area of ​​the middle pressure plate 43 to the area of ​​the valve plate 3 (including the first opening 31).

[0035] Reference Figure 1 and Figure 2 The intermediate pressure plate 43 is equipped with a guide structure, which is a guide rod 44 with a circular cross-section. The guide rod 44 is parallel to the center line of the second compression spring 42. The end of the guide rod 44 near the valve cover 2 has an external thread, and the guide rod 44 is threadedly connected to the valve cover 2. The guide rod 44 is threadedly connected to a locking nut 442, which abuts against the inner surface of the valve cover 2. The intermediate pressure plate 43 is equipped with guide holes 431 that are adapted to the guide rods 44. There are four guide rods 44, which are distributed at the four corners. The four guide rods 44 are arranged in a circumferential array along the center line of the first compression spring 41, and the guide rods 44 abut against the outer circumferential surface of the first compression spring 41. The guide rods 44 can simultaneously guide the intermediate pressure plate 43 and the first compression spring 41, so that the first compression spring 41 remains stable during the expansion and contraction deformation process.

[0036] The guide rod 44 has two parallel longitudinal sections 441 at its end away from the valve cover 2. The valve plate 3 has a through hole 32 for the guide rod 44 to pass through. The through hole 32 is a square hole or an oblong hole. The two longitudinal sections 441 of the guide rod 44 abut against the two inner sides of the through hole 32, and the guide rod 44 passes into the inside of the guide tube 5. One side of the guide hole 431 is connected to the through opening 31. The guide rod 44 cooperates with the through hole 32 to guide the lifting and lowering movement of the valve plate 3.

[0037] The inner diameter of the guide tube 5 and the diameter of the pilot valve plate 6 are both larger than the inner diameter of the pilot opening 31. The pilot valve plate 6 can block the pilot opening 31 from bottom to top. The diameter of the pilot valve plate 6 is smaller than the inner diameter of the guide tube 5, so that the pilot valve plate 6 and the inner wall of the guide tube 5 form an annular gap that can avoid the guide rod 44. The peripheral side wall of the guide tube 5 and the inner edge 51 are connected by a rounded corner, so that the inner peripheral surface of the guide tube 5 and the upper surface of the inner edge 51 form an inner rounded corner 52. The radius of the rounded corner 52 is greater than or equal to the width of the annular gap mentioned above, so that the pilot valve plate 6 can be located at the center of the guide tube 5 under the guidance of the inner rounded corner 52, so as to avoid the guide rod 44.

[0038] Reference Figure 2 and Figure 3 The implementation principle of the high-service-life composite double check valve in this application embodiment is as follows: When the check valve in this application is working, the first compression spring 41 forces the valve plate 3 to seal the valve port 14 of the valve body 1, and the second compression spring 42 first passes through the valve plate 6 to seal the first passage 31 on the valve plate 3. Since the first compression spring 41 is in a pre-compression deformation state, when the fluid pressure entering the valve body 1 is small, the valve plate 3 is not enough to drive the valve plate 3 to open, and the first passage valve plate 6 will open before the valve plate 3, so that the fluid passes through the valve body 1 from the first passage 31 on the valve plate 3. As the fluid pressure entering the valve body 1 increases, the opening degree of the first passage valve plate 6 increases, and at the same time, the deformation of the second compression spring 42 increases. When the deformation of the second compression spring 42 increases to be the same as the pre-compression deformation of the first compression spring 41, the first compression spring 41 and the second compression spring 42 can act simultaneously to open the valve plate 3, thereby opening the valve port 14.

[0039] This application adds a pilot port 31 and a pilot valve plate 6 for closing the pilot port 31, enabling the check valve to open different opening and closing elements under different pressure ranges. Thus, with a fixed service life of the check valve, the pilot valve plate 6 and the valve plate 3 respectively perform the functions of the opening and closing elements, reducing the time that individual opening and closing elements are subjected to fluid erosion and helping to extend the service life of the check valve. Example 2

[0040] Reference Figure 4 and Figure 5 The difference between this embodiment and embodiment 1 is that in this embodiment, a limiting cylinder 33 is provided on the side of the valve plate 3 near the valve cover 2. The cylinder wall of the limiting cylinder 33 is evenly provided with holes for fluid to pass through. The limiting cylinder 33 is used to limit the minimum distance between the valve plate 3 and the valve cover 2. The outer diameter of the limiting cylinder 33 is greater than or equal to the outer diameter of the valve plate 3.

[0041] The valve cover 2 is provided with a connecting cylinder 21. The cylinder wall of the connecting cylinder 21 is evenly provided with holes for fluid to pass through. The inner diameter of the connecting cylinder 21 is larger than the outer diameter of the limiting cylinder 33. The lower edge of the connecting cylinder 21 is provided with an outwardly flared outer edge 211. The connecting cylinder 21 is provided with an elastic protective membrane 7. The elastic protective membrane 7 includes multiple valves 71. The multiple valves 71 are arranged in an array around the central circumference of the limiting cylinder 33. One side of the valve 71 is fixedly connected to the outer edge 211 of the connecting cylinder 21. After the valve 71 is bent downward, it abuts against the outer circumferential surface of the limiting cylinder 33. When the valve plate 3 moves to a position close to the valve cover 2, the valve 71 can extend from the limiting cylinder 33 to the sealing surface of the valve plate 3.

[0042] The implementation principle of this embodiment is as follows: During the use of the check valve, the limiting cylinder 33 can limit the maximum deformation of the first compression spring 41, which is beneficial to protecting the first compression spring 41. The elastic protective membrane 7 remains in contact with the outer peripheral surface of the limiting cylinder 33. When the valve plate 3 and the limiting cylinder 33 move towards the valve cover 2, each valve 71 of the flexible protective membrane gradually extends along the outer peripheral surface of the limiting cylinder 33 to the sealing surface of the valve plate 3. The fluid flowing through the valve body 1 can force the valve 71 to abut against the sealing surface of the valve plate 3, thereby reducing the erosion of the sealing surface of the valve plate 3 by the fluid and improving the service life of the valve plate 3. Example 3

[0043] The difference between this embodiment and embodiment 1 is that in this embodiment, the first compression spring 41 and the second compression spring 42 are connected as a whole to form an integral compression spring 4. One end of the integral compression spring 4 is fixedly connected to the valve cover 2, and the middle pressure plate 43 is connected to the integral compression spring 4 through it. Under the action of the guide structure, the middle pressure plate 43 is difficult to move spirally along the integral compression spring 4, so that the middle pressure plate 43 maintains a relatively fixed position on the integral compression spring 4, thereby realizing the connection between the middle pressure plate 43 and the integral compression spring 4.

[0044] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A high-service-life composite double check valve, comprising a valve body (1), a valve cover (2), a valve plate (3), and a compression spring (4), wherein the valve body (1) has an inlet (11), an outlet (12), a valve cover opening (13), and a valve port (14), the valve cover (2) is connected to the valve cover opening (13) of the valve body (1), and the valve plate (3) is used to close the valve port (14), characterized in that: The valve plate (3) is provided with a first passage (31). A guide tube (5) communicating with the first passage (31) is provided on the side of the valve plate (3) near the inlet (11) end of the valve body (1). An inner edge (51) is provided on the side of the guide tube (5) away from the valve plate (3). A first passage valve plate (6) is provided on the inner side of the guide tube (5). The first passage valve plate (6) abuts against the inner edge (51) of the guide tube (5). The compression spring (4) includes a first compression spring (41) arranged concentrically. The first spring (41) and the second spring (42) are connected by a middle pressure plate (43). The end of the first spring (41) away from the middle pressure plate (43) is connected to the valve cover (2), and the end of the second spring (42) away from the middle pressure plate (43) is connected to the pilot valve plate (6). The middle pressure plate (43) abuts against the edge of the pilot opening (31), and the first spring (41) is in a pre-compression deformation state.

2. The composite double check valve with a long service life according to claim 1, characterized in that: The middle pressure plate (43) is provided with a guide structure, which is connected to the valve cover (2); the first pressure spring (41) and the second pressure spring (42) are connected as a whole to form an integral pressure spring (4), and the middle pressure plate (43) and the integral pressure spring (4) are connected through it.

3. The composite double check valve with a long service life according to claim 2, characterized in that: The guiding structure is a guide rod (44), and the middle pressure plate (43) is provided with a guide hole (431) adapted to the guide rod (44). There are at least three guide rods (44), and the three guide rods (44) are arranged in a circumferential array along the center line of the first compression spring (41). The guide rods (44) abut against the outer circumferential surface of the first compression spring (41).

4. The composite double check valve with a long service life according to claim 3, characterized in that: The valve plate (3) has a through hole (32) through which the guide rod (44) passes, and the end of the guide rod (44) away from the valve cover (2) is located in the through hole (32).

5. A high-service-life composite double check valve according to claim 4, characterized in that: The guide rod (44) is threadedly connected to the valve cover (2). The guide rod (44) is a round rod. The end of the guide rod (44) away from the valve cover (2) is provided with a longitudinal section (441). The through hole (32) is a square hole. The longitudinal section (441) abuts against one inner side of the through hole (32).

6. The composite double check valve with a long service life according to claim 4, characterized in that: The inner diameter of the guide tube (5) and the diameter of the first-pass valve plate (6) are both larger than the inner diameter of the first-pass opening (31), and the first-pass valve plate (6) can block the first-pass opening (31) from bottom to top.

7. A high-service-life composite double check valve according to claim 6, characterized in that: The diameter of the first-pass valve plate (6) is smaller than the inner diameter of the guide tube (5). The first-pass valve plate (6) and the inner wall of the guide tube (5) form an annular gap that can avoid the guide rod (44). The peripheral side wall of the guide tube (5) and the inner edge (51) are connected by a rounded corner, so that the inner peripheral surface of the guide tube (5) and the upper surface of the inner edge (51) form an inner rounded corner (52). The radius of the rounded corner (52) is greater than or equal to the width of the annular gap.

8. The composite double check valve with a long service life according to claim 1, characterized in that: The valve plate (3) is provided with a limiting cylinder (33) on the side near the valve cover (2). The cylinder wall of the limiting cylinder (33) is provided with holes for fluid to pass through. The limiting cylinder (33) is used to limit the minimum distance between the valve plate (3) and the valve cover (2).

9. A high-service-life composite double check valve according to claim 8, characterized in that: The outer diameter of the limiting cylinder (33) is greater than or equal to the outer diameter of the valve plate (3); the valve cover (2) is provided with an elastic protective membrane (7), the elastic protective membrane (7) includes multiple valves (71), the multiple valves (71) are arranged in a circular array around the center of the limiting cylinder (33), the valves (71) abut against the outer circumferential surface of the limiting cylinder (33); when the valve plate (3) moves to a position close to the valve cover (2), the valves (71) can extend from the limiting cylinder (33) to the sealing surface of the valve plate (3).

10. A high-service-life composite double check valve according to claim 9, characterized in that: The valve cover (2) is provided with a connecting cylinder (21), the connecting cylinder (21) is provided with a hole for fluid to pass through, the inner diameter of the connecting cylinder (21) is larger than the outer diameter of the limiting cylinder (33), the lower edge of the connecting cylinder (21) is provided with an outwardly turned outer edge (211), one side of the valve (71) is connected and fixed to the outer edge (211), and the valve (71) is bent downward and abuts against the outer peripheral surface of the limiting cylinder (33).

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