Chatter prevention device

Abstract

To provide a chattering prevention device which prevents chattering when a non-return valve is opened.SOLUTION: The present invention relates to a chattering prevention device 3 provided in a dash pot which controls opening / closing of a valve body of a non-return valve. The dash pot comprises a cylinder 23 including a piston 27 and a plurality of first passages 70A communicating an inner pressure side and an outer pressure side of the cylinder in response to movement of the piston. The chattering prevention device comprises: a spool which is provided at the inner pressure side of the cylinder and linked with the movement of the piston; a spool presser in which the spool is stored; and a second passage 70D communicating the inner pressure side and the outer pressure side of the cylinder in response to the movement of the spool. A bypass passage 51 is provided in the second passage, and a check valve 50 by which circulation of oil is stopped when closing the valve body of the non-return valve and the oil is circulated when opening the valve body is provided in the bypass passage.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a chattering prevention device.

Background Art

[0002] For example, Patent Document 1 discloses a check valve provided with a dashpot and a chattering prevention device. The chattering prevention device of Patent Document 1 is configured to prevent chattering during valve closing by providing a flow path that is linked to a piston in a cylinder of the dashpot and that connects the inner pressure side and the outer pressure side of the cylinder before a valve body of the check valve contacts a valve seat.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Here, chattering of the check valve can occur not only during valve closing but also during valve opening. Similar to chattering during valve closing, chattering during valve opening also causes problems such as damage to the valve body and piston because the valve body and valve seat rapidly contact each other multiple times or the piston rapidly moves up and down in the cylinder.

[0005] In view of such problems, an object of the present invention is to provide a chattering prevention device that prevents chattering during valve opening of a check valve.

Means for Solving the Problems

[0006] To achieve the above objective, the present invention provides a check valve in which a swingable valve body is provided in a valve casing, and the valve is opened and closed by swinging the valve body toward and toward a valve seat, wherein a chattering prevention device is provided in a dashpot that controls the opening and closing of the valve body, the dashpot comprising a cylinder equipped with a piston, and a plurality of first passages that connect the internal pressure side and the external pressure side of the cylinder in accordance with the movement of the piston, the chattering prevention device comprising a spool provided on the internal pressure side of the cylinder and linked to the movement of the piston, a spool retainer that houses the spool, and a second passage that connects the internal pressure side and the external pressure side of the cylinder in accordance with the movement of the spool, a bypass passage provided in the second passage, and a check valve provided in the bypass passage that stops the flow of oil when the valve body of the check valve is closed and allows oil to flow when the valve body is open.

[0007] According to the present invention, when the valve is opened, oil flows into the internal pressure side via a bypass passage equipped with a check valve, in addition to the second passage, thus increasing the flow rate of oil that flows into the internal pressure side. As a result, the rotation speed of the valve body can be increased, and chattering when the check valve is opened can be prevented.

[0008] Furthermore, it is preferable that the spool is configured such that, immediately before the valve body of the check valve seats on the valve seat, the first flow path closest to the chattering prevention device among the plurality of first flow paths is in communication and the second flow path is closed.

[0009] According to the present invention, the movement of the piston just before full closure can be made gentler, and the impact of the valve body seating can be mitigated. [Effects of the Invention]

[0010] According to the present invention, chattering when the check valve opens can be prevented. [Brief explanation of the drawing]

[0011] [Figure 1] This is a front view of the valve opening and closing structure of the check valve according to this embodiment. [Figure 2] This is a side view of the valve opening and closing structure of the check valve according to this embodiment. [Figure 3] This is a side cross-sectional view of the dashpot and chatter prevention device according to this embodiment. [Figure 4] This is a cross-sectional view of the chatter prevention device according to this embodiment. [Figure 5] This is a side view of the spool according to this embodiment. [Figure 6] This is a hydraulic circuit diagram of the dashpot and chatter prevention device according to this embodiment. [Figure 7] This graph shows the relationship between valve closing time or valve opening time and the degree of valve opening. [Figure 8] This is an enlarged view of the graph in Figure 7. [Figure 9] This is an enlarged view of the graph in Figure 8. [Modes for carrying out the invention]

[0012] Embodiments of the present invention will be described in detail below with reference to the drawings. Figure 1 is a front view of the valve opening and closing structure of the check valve according to this embodiment. Figure 2 is a side cross-sectional view of the valve opening and closing structure of the check valve according to this embodiment. The valve opening and closing structure 100 of the check valve consists of a check valve 1, a dashpot 2, and a chattering prevention device 3.

[0013] (Check valve 1) The check valve 1 is installed in piping (not shown) on the discharge side of a pump (not shown) and prevents backflow caused by negative pressure inside the piping due to the pump stopping. The check valve 1 is a swing type with a valve body that swings on a shaft, and the valve body 12 contains an upper valve body 11a, a lower valve body 11b, an upper valve seat 13a for the upper valve body 11a, and a lower valve seat 13b for the lower valve body 11b. In the center of the lower valve body 11b is a small valve body 11, a valve seat 13, an arm 14, and a rotating shaft 15. The valve body 12 is a box-shaped member with a hollow section that houses the upper valve body 11a, the lower valve body 11b, and the valve body 11, and is equipped with flanges 12a, 12b (see Figure 2) for connecting to piping, and has a removable cover 16 on the top.

[0014] The upper valve body 11a and the lower valve body 11b are plate-shaped members that are pivotably mounted on a shaft (not shown). The upper valve seat 13a and the lower valve seat 13b are frame-shaped members provided within the valve casing 12 and are parts that contact or separate from the upper valve body 11a and the lower valve body 11b in their respective circumferential directions. The valve body 11 is a plate-shaped member that opens and closes an opening formed in the center of the lower valve body 11b, and the valve seat 13 is provided on the edge of the opening. The arm 14 is a member that connects the valve body 11 and the rotating shaft 15. The rotating shaft 15 is a shaft member that pivots the valve body 11 around its axis via the arm 14.

[0015] The check valve 1 has a swingable valve body 11 inside the valve casing 12, and the valve opens and closes by swinging the valve body 11 toward and away from the valve seat 13. When the pressure of the water flowing into the valve casing 12 is above a predetermined value, the valve body 11 is pushed up and separated from the valve seat 13 by the water pressure, and the opening of the valve seat 13 opens. As a result, water passes through the opening and flows out into the piping connected to the flange 12a. If the water pressure increases further, the upper valve body 11a and the lower valve body 11b open, and the openings of the upper valve seat 13a and the lower valve seat 13b open. On the other hand, when the pressure of the water flowing into the valve casing 12 decreases, the upper valve body 11a and the lower valve body 11b descend by their own weight, and the openings of the upper valve seat 13a and the lower valve seat 13b close. Furthermore, if the pressure of the water flowing into the valve casing 12 is below a predetermined value, the valve body 11 descends by its own weight and closes the opening of the valve seat 13. This prevents water from flowing back.

[0016] (Dashpot 2) The dashpot 2 is a buffer device that controls the opening and closing of the valve body 11. FIG. 3 is a side cross-sectional view of the dashpot and the chattering prevention device according to this embodiment. The dashpot 2 includes a weight 21, an upper lid 22, a cylinder 23, a crank 24, a crank pin 25, a piston rod 26, a piston 27, needle valves 30A, 30B, 30C, and flow paths 70A, 70B, 70C.

[0017] The weight 21 is a counterweight for maintaining the balance position of the dashpot 2 with respect to the rocking of the valve body 11. The upper lid 22 is a housing that constitutes approximately the upper half of the dashpot 2. The cylinder 23 is a cylindrical housing that constitutes the lower half of the dashpot 2. The upper part of the cylinder 23 and the lower part of the upper lid 22 are connected by a fastener. Ports 23a to 23e penetrating in the radial direction are formed in the side wall of the cylinder 23. Ports 23d and 23e are formed facing each other at the upper part of the cylinder 23. Ports 23a and 23b are formed near the middle of the cylinder 23. Port 23b is formed below port 23a. Port 23c is formed below port 23b and at the lower part of the cylinder 23.

[0018] The crank 24 is a member that converts the rotation of the rotating shaft 15 into the vertical reciprocating motion of the piston 27. The crank pin 25 is a member that rotatably connects the crank 24 and the piston rod 26. The piston rod 26 is a rod that moves up and down according to the rotation of the crank 24. The piston 27 is a member that circulates the oil in the cylinder 23 by sliding along the inner peripheral surface of the cylinder 23. The piston 27 is connected to the lower end of the piston rod 26 and moves up and down according to the rotation of the crank 24. <U+ <U+

[0019] <U+ A cylinder valve 60 is provided on the lower surface of the piston 27. As shown in Figure 4, the cylinder valve 60 comprises a valve body 61, a spring retainer 62, a coil spring 63, and a fastener 64. The valve body 61 is substantially disc-shaped and covers a plurality of through holes 27a formed circumferentially in the bottom of the piston 27. The spring retainer 62 is positioned below the valve body 61 and spaced apart from it. The coil spring 63 is interposed between the valve body 61 and the spring retainer 62 and biases the valve body 61 upward relative to the spring retainer 62. The fastener 64 is a component that fastens the components constituting the cylinder valve 60 to the piston 27.

[0020] Under normal conditions, the cylinder valve 60 is closed due to the biasing force of the coil spring 63, which causes the valve body 61 to contact the piston 27. However, when the pressure in the space formed by the chattering prevention device 3, cylinder 23, and piston 27 (internal pressure) falls below a predetermined value, the valve body 61 moves away from the piston 27 against the biasing force of the coil spring 63, opening the valve. When the valve is open, oil from the external pressure side of the cylinder 23 flows through the through hole 27a to the internal pressure side (downwards the piston 27). The fastener 64 is the part that contacts the spool 34 of the chattering prevention device 3 when the piston 27 moves downward.

[0021] As shown in Figure 3, the cylinder 23 is equipped with needle valves 30A, 30B, and 30C for each of the multiple first flow paths (70A, 70B, 70C) that connect the internal pressure side and the external pressure side via the piston 27. Flow path 70A is a pipe connecting port 23a and port 23d. Flow path 70B is a pipe connecting port 23b and port 23d. Flow path 70C is a pipe connecting port 23c and port 23e. The needle valves 30A, 30B, and 30C are flow control valves that adjust the flow rate of each flow path 70A, 70B, and 70C according to the movement speed of the piston 27. The dashpot 2 can flow the oil from the cylinder 23 in three stages using the three flow paths 70A, 70B, and 70C.

[0022] In this embodiment, a needle valve is used for flow rate adjustment, but other types of valves may be used. In this embodiment, "multiple first flow paths" refers to three flow paths 70A, 70B, and 70C.

[0023] When the valve body 11 is in the open position, the piston 27 is located at the top of the cylinder 23 via the rotating shaft 15, crank 24, crank pin 25, and piston rod 26 (see dashed line of piston 27 in Figure 3).

[0024] On the other hand, when the valve body 11 begins to close and the piston 27 moves downward, the oil on the internal pressure side of the cylinder 23 flows out from ports 23a to 23c and flows into the external pressure side through needle valves 30A, 30B, and 30C via passages 70A, 70B, and 70C, through ports 23d and 23e. More specifically, as the piston 27 descends, the pressure at the bottom of the cylinder 23, i.e., the internal pressure side pressure, increases, and the oil on the internal pressure side of the cylinder 23 flows to the external pressure side via passages 70A, 70B, and 70C. When the piston 27 descends and passes through port 23a, the oil that flowed from the internal pressure side to the external pressure side of the cylinder 23 via passage 70A stops, and the oil on the internal pressure side of the cylinder 23 flows to the external pressure side via passages 70B and 70C. As the piston 27 descends further and passes through port 23b, the oil that flowed from the internal pressure side to the external pressure side of the cylinder 23 via passage 70B stops, and the oil from the internal pressure side of the cylinder 23 flows to the external pressure side via passage 70C. In other words, the flow rate of oil flowing from the internal pressure side to the external pressure side of the cylinder 23 can be adjusted by the movement of the piston 27. Thus, the dashpot 2 can reduce the impact of closing the valve body 11 through this three-stage buffering action, thereby avoiding the so-called water hammer phenomenon. In addition, since the flow rate of each passage 70A, 70B, and 70C can be adjusted by the needle valves 30A, 30B, and 30C, the time of each stage, that is, the descent speed of the piston 27 at each stage, can be adjusted.

[0025] (Chatter prevention device 3) The chattering prevention device 3 is a device installed at the bottom of the dashpot 2. Figure 4 is a cross-sectional view of the chattering prevention device according to this embodiment. The chattering prevention device 3 comprises a spacer flange 31, a spool retainer 32, a guide tube 33, a spool 34, a nut 35, a spool holder 36, a coil spring 37, a stopper 38, and a plug 39. The chattering prevention device 3 also comprises a needle valve 30 and a flow path 70D (see Figure 3)D.

[0026] As shown in Figure 4, the spacer flange 31 is a connecting member between the spool retainer 32 and the dashpot 2. The spool retainer 32 is a cylindrical member that houses the guide tube 33 and the spool 34. The spool retainer 32 constitutes the side wall surface of the exterior of the chattering prevention device 3. The upper surface of the spool retainer 32 and the lower surface of the spacer flange 31 are joined. A port 32a is formed in the side wall of the spool retainer 32, penetrating in the radial direction. In addition, a recess 32b is formed on the inner circumferential surface of the spool retainer 32, communicating with the port 32a and extending in the vertical direction. The port 32a communicates with the port 23e of the cylinder 23 via a flow path 70D (see Figure 3) made of piping. The flow path 70D (second flow path) is a flow path that opens and closes in accordance with the movement of the spool 34, and flows the oil of the cylinder 23 from the internal pressure side to the external pressure side (and vice versa). The needle valve 30D is installed in the flow path 70D and is a flow control valve that adjusts the flow rate of the flow path 70D.

[0027] In this embodiment, a needle valve is used, but other types of valves may be used. In this embodiment, "second flow path" refers to flow path 70D.

[0028] Figure 6 is a hydraulic circuit diagram of the dashpot and chatter prevention device according to this embodiment. As shown in Figure 6, a bypass passage 51 is formed in the passage 70D (in this embodiment, inside the needle valve 30D). A check valve 50 is also provided in the bypass passage 51. The check valve 50 blocks the passage when the valve body 11 closes (when oil flows from port 32a to port 23e) and opens the passage when the valve body 11 opens (when oil flows from port 23e to port 32a). In this embodiment, the check valve 50 and the bypass passage 51 are provided inside the needle valve 30D, but they may also be provided outside the needle valve 30D in a part of the passage 70D.

[0029] As shown in Figure 4, the guide tube 33 is a cylindrical member that guides the spool 34 so that it can slide up and down. The guide tube 33 has a projection 33a that protrudes radially inward and circumferentially, and ports 33b and 33c that penetrate radially. The inner diameter of the projection 33a is approximately the same as the outer diameter of the first small diameter portion 342 of the spool 34, which will be described later. Port 33b is formed below the projection 33a. Both ports 33b and 33c communicate with the recess 32b and port 32a, respectively.

[0030] The spool 34 is a roughly cylindrical body that adjusts the amount of oil on the internal pressure side and the external pressure side in the cylinder 23 by moving up and down. The nut 35 is a member for fastening the guide tube 33 to the spool retainer 32. The spool holder 36 is a bottomed cylindrical member that houses the guide tube 33 and the lower part of the spool 34. The coil spring 37 has one end in contact with the spool holder 36 and the other end in contact with a part of the spool 34. The coil spring 37 is an elastic member that biases the spool 34 upward relative to the spool holder 36. The stopper 38 is provided at the upper end of the guide tube 33, and the head 341 of the spool 34 (described later) can be inserted through it, but the first small diameter portion 342 cannot be inserted through it. In other words, the stopper 38 is a member that determines the upper limit of the vertical movement of the spool 34. The plug 39 is attached to the lower part of the spool holder 36.

[0031] (Spool 34) Figure 5 is a side view of the spool according to this embodiment. The spool 34 consists of a head portion 341, a first small diameter portion 342, a first large diameter portion 343, a second small diameter portion 344, a second large diameter portion 345, and a third small diameter portion 346, and is integrally molded. The spool 34 is positioned inside the hollow portion of the guide tube 33 with the head portion 341 facing upwards.

[0032] The head portion 341 is the part that contacts the fastener 64 (see Figure 4) of the cylinder valve 60. The first small diameter portion 342, the second small diameter portion 344, and the third small diameter portion 346 are of the same diameter and are smaller in diameter than the first large diameter portion 343 and the second large diameter portion 345. The first large diameter portion 343 and the second large diameter portion 345 are of the same diameter and are the same diameter as the inner diameter of the guide tube 33. The other end of the coil spring 37 contacts the lower end of the second large diameter portion 345.

[0033] A cross-shaped communication hole 40a is formed in the first small-diameter portion 342, penetrating in the radial direction. A cross-shaped communication hole 40b is formed in the second small-diameter portion 344, penetrating in the radial direction. In addition, a communication hole 40c is formed that connects from approximately the axial center of the first small-diameter portion 342 to the lower end of the third small-diameter portion 346. The communication holes 40a to 40c are in communication with each other.

[0034] [Fully open] Next, the operation and effects of the valve opening and closing structure 100 of the check valve according to this embodiment will be described. When the valve body 11 is in the fully open state, the piston 27 is located at the top of the cylinder 23. The spool 34 is biased upward by the coil spring 37 and is in contact with the stopper 38, and the first large diameter portion 343 is in contact with the projection 33a.

[0035] [Prevention of chattering when the valve is closed] As the valve body 11 moves in the closing direction, the piston 27 descends accordingly, and the dashpot 2 begins the slow closing action of the valve body 11. If the chattering prevention device 3 is not provided, the pressure on the internal pressure side of the cylinder 23 will rise, and the rotational speed of the valve body 11 will slow down just before closing, causing chattering to occur.

[0036] In contrast, as in this embodiment, when the chattering prevention device 3 is provided, the spool 34 is pushed down by the fastener 64 provided at the lower end of the piston 27 (i.e., the piston 27 and the spool 34 are linked), and the communication hole 40a of the first small diameter portion 342 and the port 33b of the guide tube 33 are connected. More specifically, the oil pushed by the piston 27 flows from the upper part of the guide tube 33 through the communication hole 40a, communication hole 40c, communication hole 40b, port 33b, and port 32a, flows into the flow path 70D, and through the needle valve 30D, the oil flows into the external pressure side of the piston 27 from port 23e. As a result, the valve body 11 can increase its rotational speed when closing the valve, thus preventing chattering when closing the valve.

[0037] [When fully closed] Figures 3 and 4 show the valve body 11 in the fully closed position. When fully closed, the spool 34 is pushed to its lowest position by the fastener 64. At this time, the communication hole 40a is covered by the projection 33a, so no oil flows into the spool 34 or the passage 70D. In other words, the passage 70D is closed. On the other hand, oil is flowing through the passage 70C. In other words, the internal pressure side and the external pressure side of the cylinder 23 are in a state of equal pressure.

[0038] [Prevention of chattering when the valve is open] Immediately after the valve body 11 opens from the fully closed position, in addition to the flow path 70C which was originally open, the spool 34 moves upward as the piston 27 rises, so that the internal pressure side of the cylinder 23 and the flow path 70D are connected. As a result, oil flows from the external pressure side to the internal pressure side of the piston 27 through the flow paths 70C and 70D, the piston 27 moves upward, and the valve body 11 gradually opens.

[0039] However, immediately after the valve body 11 opens, the rotational speed of the valve body 11 does not increase, which may cause chattering. In this embodiment, however, since the needle valve 30D is provided with a bypass passage 51, in addition to the flow rate through the needle valve 30D, the flow rate through the bypass passage 51 flows into the passage 70D, allowing more oil to flow from port 23e to port 32a. This increases the movement speed of the piston 27 and increases the speed of the valve body 11, thus preventing chattering. Furthermore, as the speed at which the valve body 11 rotates in the opening direction increases, the flow rate from passages 70C and 70D becomes insufficient, and when the internal pressure side of the cylinder 23 becomes negative pressure, the cylinder valve 60 opens. In other words, the valve body 61 moves downward against the biasing force of the coil spring 63, and oil from the external pressure side moves to the internal pressure side through the through hole 27a. As a result, the piston 27 rises rapidly, and the valve body 11 becomes fully open.

[0040] [Just before fully closed] As already explained, when the valve body 11 is closed, the spool 34 descends, and the communication hole 40a of the first small diameter portion 342 and the port 33b of the guide tube 33 communicate with each other, causing the oil on the internal pressure side of the cylinder 23 to move to the external pressure side via the flow path 70D. As a result, chattering during valve closing is prevented. However, if the speed of the valve body 11 is increased, the valve body 11 may hit the valve seat 13 forcefully when seating, potentially damaging both. Therefore, in this embodiment, a damage prevention mechanism is provided to prevent such damage.

[0041] The damage prevention mechanism closes the passage 70D from just before to when the valve body 11 is fully closed. If the passage 70D is open from just before to when the valve body 11 is fully closed, oil will flow from the internal pressure side to the external pressure side in both passages 70C and 70D, causing the speed of the valve body 11 to increase. Therefore, in the damage prevention mechanism of this embodiment, after preventing chattering, the passage 70D is closed again so that the speed of the valve body 11 decreases slightly. As a result, from just before to when the valve body 11 is fully closed, oil moves from the internal pressure side to the external pressure side only in passage 70C, which allows the piston 27 to descend slowly, and the valve body 11 seats at a slower rotational speed again. This prevents damage to the valve body 11 and other components.

[0042] [Relationship between time and opening degree] Next, the timing of each function's operation will be explained. Figure 7 is a graph showing the relationship between the valve closing time or valve opening time and the valve body opening degree. Figure 8 is an enlarged view of the graph in Figure 7. Figure 9 is an enlarged view of the graph in Figure 8. In Figures 7 to 9, the solid line represents the valve closing time in the embodiment. The dashed line represents the valve opening time in the embodiment. The dotted line represents the valve opening time in the comparative example. The opening degree refers to the percentage of the valve body 11 that is open, with an opening degree of 100 degrees representing full open and an opening degree of 0 degrees representing full closed. The relationship between time and opening degree shown below is merely an example and can be set as appropriate.

[0043] [When closing] In Figure 7, from time ta0 to ta1, all passages 70A, 70B, and 70C are in a flow state, and the oil on the internal pressure side of cylinder 23 flows to the external pressure side via passages 70A, 70B, and 70C. At time ta1 (inflection point S1), the piston 27 blocks port 23a, so passages 70B and 70C become flow states, and the oil on the internal pressure side flows to the external pressure side via passages 70B and 70C. Also, at time ta2 (inflection point S2), the piston 27 blocks port 23b, so only passage 70C becomes flow state, and the oil on the internal pressure side flows to the external pressure side only via passage 70C.

[0044] Furthermore, at time ta3 (inflection point S3), when the piston 27 descends and presses against the spool 34, the flow path 70D becomes flowing, and the oil on the internal pressure side of the cylinder 23 flows to the external pressure side via the flow paths 70C and 70D. The chattering prevention device 3 operates between inflection point S3 and inflection point S4 (see Figure 9), which will be described later. The start time of the chattering prevention action can be set, for example, when the opening degree of the valve body 11 is 4 degrees.

[0045] Furthermore, as shown in Figure 9, at time ta4 (inflection point S4), when the piston 27 descends further and presses against the spool 34, oil does not flow through the passage 70D, and only the passage 70C becomes a flowing state. As a result, the oil on the internal pressure side of the cylinder 23 flows to the external pressure side only through the passage 70C. This activates the damage prevention mechanism, which reduces the rotation speed of the valve body 11 again just before full closure. The damage prevention mechanism operates from the inflection point S4 to full closure (ta5).

[0046] [When opening] Next, we will explain what happens when the valve body 11 opens from a fully closed position. As shown in Figure 9, between time tb0 and time tb1 (inflection point S5), the mechanism operates in the opposite direction to the damage prevention mechanism. That is, oil does not flow through the passage 70D, and only the passage 70C is in a flow state. As the piston 27 rises, oil from the external pressure side of the cylinder 23 flows into the internal pressure side through the passage 70C. Since oil flows only through the passage 70C and the piston 27 is slowly pushed up, the valve body 11 also opens slowly.

[0047] Between time tb1 and time tb2 (inflection point S6), the spool 34 rises along with the rise of the piston 27, and the spool 34 and the passage 70D become connected, allowing oil to flow from the external pressure side to the internal pressure side of the cylinder 23 through passages 70C and 70D. As a result, the piston 27 (valve body 11) rotates slightly faster than before the inflection point S5.

[0048] Between time tb2 and time tb3 (inflection point S7), the check valve 50 of the needle valve 30D is in communication, and in addition to the flow rate through the needle valve 30D, the flow rate through the bypass passage 51 flows into the passage 70D, and oil flows from the external pressure side to the internal pressure side of the cylinder 23 through this passage 70D. As a result, as shown from inflection point S6 to inflection point S7 in Figure 8, a large amount of oil flows into the internal pressure side in a short time, so the rotation speed of the valve body 11 increases. This prevents chattering when the valve is opened. For example, the dashed line in Figure 8 shows the valve opening in the comparative example (without bypass channel 51). Comparing the opening degree at time tb3 between the example and the comparative example, it is clear that the opening degree is larger in the example.

[0049] As shown in Figure 7, between time tb3 and time tb4 (inflection point S8), the cylinder valve 60 is opened, and oil from the external pressure side of the cylinder 23 flows into the internal pressure side through the through hole 27a, causing the piston 27 to rise rapidly and reach a fully open state at time tb4.

[0050] According to the embodiment described above, when the valve is opened, oil flows to the internal pressure side via the bypass passage 51 in addition to the passage 70D (second passage), so the flow rate of oil flowing to the internal pressure side of the cylinder 23 when the valve is opened can be increased. As a result, the rotation speed of the valve body 11 can be increased, and chattering when the check valve 1 is opened can be prevented.

[0051] Furthermore, according to this embodiment, the spool 34 is configured such that, just before the valve body 11 of the check valve 1 seats on the valve seat 13, the passage 70C (first passage) closest to the chattering prevention device 3 among the multiple passages (first passage) opens and the passage 70D (second passage) closes. This makes it possible to slow down the operation of the piston 27 just before full closure, and reduces damage to the valve body 11, etc. Also, since no oil flows through the spool 34, the synchronization between the pressure pulsation of the fluid inside the pipe that occurs when the check valve 1 is closed and the opening and closing operation of the valve body 11 can be mitigated, and the operation of the check valve 1 becomes stable. In this embodiment, as shown in Figure 1, the upper and lower divided parent-child check valve consists of an upper valve body 11a, a lower valve body 11b, and a valve body 11 (the lower valve body 11b is a child valve body), but it may also be a check valve having only a valve body 11.

[0052] While embodiments of the present invention have been described above, design modifications can be made as appropriate, provided they do not contradict the spirit of the invention. For example, the diameter, shape, and position of the communication holes 40a to 40c of the spool 34 can be appropriately changed according to the ports of the guide tube 33. [Explanation of Symbols]

[0053] 100 Valve opening and closing structure 1. Check valve 2 Dashpots 3. Anti-chattering device 11 Valve body 11a Upper valve body 11b Lower valve body 12 valve boxes 12a, 12b flange 13 valve seats 13a Upper valve seat 13b Lower valve seat 14 Arms 15 Rotation axis 16 Lid 21 weights 22 Top lid 23 liters Ports 23a-23e 24 Crank 25 Crankpin 26 Piston Rod 27 Pistons 28 Coil springs 29 Spring support 30A, 30B, 30C Needle Valves 30D Needle Valve 34 spools 40a~40c communication hole 50 Check valve 51 Bypass channel 70A, 70B, 70C channels (first channel) 70D channel (second channel)

Claims

[Claim 1] In a check valve in which a swingable valve body is provided inside the valve casing, and the valve is opened and closed by the swinging of the valve body to bring the valve body into contact with and separate from the valve seat, a chatter prevention device is provided on the dashpot that controls the opening and closing of the valve body, The dashpot comprises a cylinder with a piston, and a plurality of first passages that connect the internal pressure side and the external pressure side of the cylinder in accordance with the movement of the piston. The chattering prevention device is provided on the internal pressure side of the cylinder and includes a spool that moves in conjunction with the movement of the piston, a spool retainer that houses the spool, and a second flow path that connects the internal pressure side and the external pressure side of the cylinder in accordance with the movement of the spool. A bypass passage is provided in the second passage, and a check valve is provided in the bypass passage that stops the flow of oil when the valve body of the check valve is closed and allows oil to flow when the valve body is open. The chatter prevention device is characterized in that, immediately before the valve body of the check valve seats on the valve seat, the spool is configured such that the first flow path closest to the chatter prevention device among a plurality of first flow paths is in communication and the second flow path is closed.

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