JP5937790B2 - Check valve with built-in liquid seal prevention mechanism - Google Patents

Description

  The present invention, for example, in an apartment house or the like, from a plurality of LP gas containers to the consumer side (for example, each household) LP gas (LPG: Liquefied Petroleum Gas: liquefied gas) via a collecting pipe and an automatic switching regulator The present invention relates to a check valve with a built-in liquid seal prevention mechanism used in a supplied LP gas supply system.

  Patent Document 1 describes a “safety device for a high-pressure gas container”. This device is implemented with a check valve that prevents back flow of gas into the gas container.

  FIG. 6 shows a check used in an LP gas supply system for supplying LP gas to a consumer side from a plurality of LP gas containers through a collecting pipe and an automatic switching regulator in business use or in an apartment house. A valve 301 is shown. The check valve 301 includes a valve body 303, a valve seat 305, and a spring 307 that biases the valve body 303 in a direction away from the valve seat 305.

  This check valve 301 is installed between the other end of the high-pressure hose whose one end is connected to the on-off valve provided in each LP gas container and the collecting pipe, and when the on-off valve and the high-pressure hose are not connected. When a predetermined differential pressure is generated on the upstream side and the downstream side of the check valve, the valve body 303 is pressed against the valve seat 305 against the urging force of the spring 307 to prevent the LP gas from being released into the atmosphere.

Japanese Utility Model Publication No. 57-139800

  In the LP gas supply system using the check valve 301 described above, there is a possibility that the following problems may occur when the consuming side does not use LP gas.

  For example, if the LP gas supply system is exposed to sunlight during the daytime in fine weather, the temperature and pressure (vapor pressure) of the LP gas container, which has a larger heat collection area than the collecting pipe, rises first, and there is a temperature difference between the collecting pipe and Occurs. In the case of LP gas, it is known that if the temperature difference is 3 ° or more, a reliquefaction phenomenon occurs in which the gas liquefies by the amount exceeding the saturated vapor pressure. If LP gas generated by the phenomenon stays in the lower part and this state continues for 30 minutes to 1 hour, the collecting pipe may be filled with LP gas.

  In the LP gas supply system, since the LP gas container is exchanged according to a predetermined delivery plan, the LP gas container may be exchanged with the collecting pipe filled with LP gas as described above. The manual on-off valve 309 is closed, the high-temperature used LP gas container is removed, and after installing a new LP gas container, the on-off valve 309 is opened.

  New LP gas containers that have not been exposed to sunlight for a long time, such as used LP gas containers, are at a lower temperature and lower pressure than the collecting pipe. Generally, the check valve 301 has a pressure difference between the collecting pipe and the LP gas container. Is set to close when 0.02 MPa or more, and the check valve 301 is instantaneously closed by LP gas flowing from the high-pressure side collecting pipe toward the low-pressure side LP gas container. The check valve 301 is attached between the collecting pipe and each LP gas container, and the check valve 301 is closed by all the replaced LP gas containers. It is blocked and enters a liquid seal state filled with LP gas.

  If the collecting pipe that is closed and liquid-sealed continues to be exposed to sunlight, the internal pressure (hydraulic pressure) may rise abnormally and reach a high pressure exceeding 5 MPa. Automatic switching adjustment connected to the collecting pipe When such a high pressure is applied to the vessel, the precise adjustment unit may be damaged, resulting in a malfunction in the pressure adjustment function.

  The conventional check valve 301 does not have a function of preventing the collecting pipe from being in a liquid-sealed state.

  Therefore, the present invention prevents the collecting pipe from being liquid-sealed in an LP gas supply system that supplies LP gas from a plurality of LP gas containers to the consuming side via the collecting pipe and the automatic switching regulator. The purpose is to provide a check valve with a built-in liquid seal prevention mechanism.

The check valve with a built-in liquid seal prevention mechanism according to the present invention includes a plurality of LP gas containers for supplying LP gas, a collecting pipe for collecting gas from the LP gas container, and an LP gas disposed on the collecting pipe on the consumption side. A check valve with a built-in liquid seal prevention mechanism disposed between an LP gas container and a collecting pipe of an LP gas supply system having an automatic switching regulator to supply the pressure on the collecting pipe side. A check valve that operates when the pressure difference between the pressure on the LP gas container side and the pressure on the collecting pipe side exceeds the first set value to prevent backflow to the LP gas container side, and the pressure difference. And a relief valve that operates when the second set value greater than the first set value is exceeded to allow backflow, and the check valve includes the first small diameter portion, the second small diameter portion, and the first and second small diameter portions. position through holes is formed having a large diameter portion inner diameter than these large between the 2 small diameter portion Rutotomoni, a groove packing is provided an elastic member on the outside portion of the position of the second small diameter portion is formed, the relief valve is movably arranged a relief valve in the large diameter portion of the through-hole of the check valve Body, a seat packing attached to the relief valve body, and a biasing means that biases the relief valve body toward one end of the through hole, and the pressure difference does not exceed the second set value. When the pressure difference exceeds the second set value when the sheet packing is pressed against the first small diameter portion by the urging means and seals one end of the through hole, the urging force of the urging means is resisted. The relief valve body and the seat packing move from the first small diameter portion to the second small diameter portion and move in a direction to open one end of the through hole.

  According to this check valve with a built-in liquid seal prevention mechanism, the check valve is formed with a through hole having a first small diameter portion, a second small diameter portion, and a large diameter portion, and the relief valve is a pressure on the LP gas container side. Is lower than the pressure on the collecting pipe side, and the pressure difference between the pressure on the LP gas container side and the pressure on the collecting pipe side does not exceed the second set value, the sheet packing is pressed against the first small diameter part by the urging means Is positioned so as to seal one end of the through-hole, and when the pressure difference exceeds the second set value, the relief valve body and the seat packing resist the biasing force of the biasing means. To the second small diameter portion side to move in a direction to open one end of the through hole. For this reason, when the pressure difference does not exceed the second set value, the sheet packing is pressed against the first small diameter portion by the biasing means, and the through hole is closed. Therefore, backflow is prevented by the check valve when the pressure difference exceeds the first set value. On the other hand, when the pressure difference exceeds the second set value, the relief valve body and the seat packing move from the first small diameter portion to the second small diameter portion side against the urging force of the urging means and Since one end is opened, backflow is allowed through the through hole. From these, while preventing the backflow, the backflow is allowed when the inside of the collecting tube is in a liquid-sealed state and becomes a higher pressure. Therefore, in the LP gas supply system that supplies LP gas to the consumption side from the plurality of LP gas containers via the collecting pipe and the automatic switching regulator, it is possible to prevent the collecting pipe from being in a liquid-sealed state.

  In the check valve with a built-in liquid seal prevention mechanism of the present invention, it is preferable that the urging means is a coil spring, and the relief valve element has a recess into which the coil of the coil spring is inserted.

  According to this check valve with a built-in liquid seal prevention mechanism, the relief valve body has a recess into which the coil spring coil is inserted, so that the positional relationship between the relief valve body and the coil spring is stabilized by the recess. Further, it is possible to prevent a situation where the position of the coil spring is shifted and the urging force against the relief valve body becomes unstable.

  In the check valve with a built-in liquid seal prevention mechanism according to the present invention, the check valve further includes a valve seat formed with a first small diameter portion and fixed to one end side of the through hole. Preferably, the first small diameter portion is formed so as to penetrate from the tip end portion of the valve seat toward one end side of the through hole.

  According to this check valve with a built-in liquid seal prevention mechanism, the valve seat has a protruding shape that projects in a tapered manner toward the other end side of the through hole, and the first small diameter portion extends from the tip end of the protrusion to one end side of the through hole. When the relief valve element is pressed against one end of the through hole, the seat packing bites into the tapered protrusion and seals the first small diameter portion. Become. Thereby, when the pressure difference exceeds the first set value, the degree of sealing between the valve seat and the seat packing can be further increased.

Further, in the check valve with a built-in liquid seal prevention mechanism of the present invention, the relief valve body is formed with another recess to which the seat packing is attached on the side opposite to the formation side of the recess into which the coil spring is inserted, It is preferable that an air vent hole for connecting the recess and the other recess is formed.

According to this check valve with a built-in liquid seal prevention mechanism, an air vent hole for venting air that connects the recess and the other recess is formed, so that the seat packing is assembled in close contact with the other recess. be able to.

  According to the check valve with a built-in liquid seal prevention mechanism of the present invention, it is possible to prevent the collecting pipe from being in a liquid sealed state.

It is a block diagram of the LP gas supply system containing the check valve with a built-in liquid seal prevention mechanism according to the present embodiment. It is an external view which shows the detail of the check valve 1 with a liquid seal prevention mechanism shown in FIG. It is AA sectional drawing of the check valve 1 with a built-in liquid seal prevention mechanism shown in FIG. It is AA sectional drawing of the check valve 1 with a built-in liquid seal prevention mechanism shown in FIG. 2, Comprising: It is sectional drawing which shows the state by which the check valve 17 was closed. It is AA sectional drawing of the check valve 1 with a liquid seal prevention mechanism shown in FIG. 2, Comprising: It is sectional drawing which shows the state in which the relief valve 19 was open | released. It is a block diagram which shows a prior art example.

  Hereinafter, embodiments of the check valve with a built-in liquid seal prevention mechanism according to the present invention will be described. FIG. 1 is a configuration diagram of an LP gas supply system including a check valve with a built-in liquid seal prevention mechanism according to the present embodiment.

  As shown in FIG. 1, the LP gas supply system 15 includes a plurality of LP gas containers 3, 5, 7, 9, a collecting pipe 11, an automatic switching adjuster 13, a check valve 1 with a built-in liquid seal prevention mechanism, It has.

  The plurality of LP gas containers 3, 5, 7, and 9 are containers in which LP gas is stored, respectively, and supply LP gas to the consumer side (for example, each household). The collecting pipe 11 is a pipe for collecting LP gas from the LP gas containers 3, 5, 7, and 9.

  The automatic switching adjuster 13 is disposed on the collecting pipe 11, and the automatic switching adjuster 13 is connected to each household side through an outflow port. This automatic switching adjuster 13 is disposed at the central portion of the collecting pipe 11 and switches the left and right collecting pipes 11 (LP gas containers 3 and 5 and LP gas containers 7 and 9), and by a pressure adjusting function. Maintain the pressure of LP gas sent to home properly.

  The check valve 1 with a built-in liquid seal prevention mechanism is a valve disposed between each LP gas container 3, 5, 7, 9 and the collecting pipe 11, and more specifically, each LP gas container 3, 5, 7 , 9 and the high pressure hose 39 extending from the on-off valve 37 and the collecting pipe 11. When replacing the LP gas containers 3, 5, 7, 9, etc., the operator operates the check valve 1 with a built-in liquid seal prevention mechanism to prevent backflow, and in this state the LP gas containers 3, 5 , 7 and 9 will be replaced.

  In the example shown in FIG. 1, the LP gas supply system 15 includes four LP gas containers 3, 5, 7, and 9, but is not limited to four, and may be three or less, Five or more may be sufficient.

  FIG. 2 is an external view showing details of the check valve 1 with a built-in liquid seal prevention mechanism shown in FIG. As shown in FIG. 2, the check valve 1 with a built-in liquid seal prevention mechanism includes a plug 23 and a case main body 45. The plug 23 and the case body 45 are separate members, and the check valve 1 with a built-in liquid seal prevention mechanism is configured by combining these separate members. Here, the plug 23 and the case body 45 may be an integral body.

  The case body 45 includes an on-off valve 51 and a lever 53. The operator or the like operates the lever 53 to close the on-off valve 51 and operate the check valve 1 with a built-in liquid seal prevention mechanism to prevent backflow. In this state, the LP gas containers 3 and 5 , 7 and 9 will be replaced.

  3 is a cross-sectional view taken along line AA of the check valve 1 with a built-in liquid seal prevention mechanism shown in FIG. As shown in FIG. 3, the check valve 1 with a built-in liquid seal prevention mechanism includes a check valve 17 and a relief valve 19. In the check valve 17, the pressure on the LP gas containers 3, 5, 7, 9 side becomes lower than the pressure on the collecting pipe 11 side, and the pressure on the LP gas containers 3, 5, 7, 9 side and the pressure on the collecting pipe 11 side When the pressure difference between and exceeds the first set value, it operates to prevent backflow to the LP gas containers 3, 5, 7, 9 side. The relief valve 19 operates when the pressure difference exceeds a second set value that is larger than the first set value, such as in a liquid-sealed state, and allows backflow.

  Hereinafter, the check valve 17 and the relief valve 19 will be described in detail. The check valve 17 includes a valve body 21, a coil spring 27, and a packing 43. The valve body 21 is a main body portion of the check valve 17 and has a substantially conical shape. The conical tip side of the valve body 21 has a shape that matches a valve seat 25 formed on the plug 23. The coil spring 27 is an urging member disposed between a notch 25 a formed in the valve seat 25 and the valve body 21. The packing 43 is an elastic member such as rubber provided on the distal end side of the valve body 21.

  Since the configuration is as described above, when the pressure difference is equal to or smaller than the first set value, the valve body 21 and the valve seat 25 are separated by the urging force of the coil spring 27 as shown in FIG. For this reason, the gas from the LP gas containers 3, 5, 7, 9 side is supplied to the collecting pipe 11.

  FIG. 4 is a cross-sectional view taken along the line AA of the check valve 1 with a built-in liquid seal prevention mechanism shown in FIG. 2 and shows a state where the check valve 17 is closed. As shown in FIG. 4, when the pressure difference exceeds the first set value, the valve body 21 moves toward the valve seat 25 against the urging force of the coil spring 27 and closes the flow path. Thereby, the backflow from the collecting pipe 11 side is prevented.

  Here, a through hole 29 is formed in the valve body 21 of the check valve 17. The relief valve 19 includes a valve body (relief valve body) 31 and a seat packing 32. The valve body 31 is a member that is movably disposed in the through hole 29 and is made of, for example, brass. The valve body 31 has a first recess 31 a on one end side of the through hole 29 and a second recess 31 b on the other end side. A sheet packing 32 is attached in close contact with the first recess 31a. The sheet packing 32 is made of a cylindrical synthetic rubber or the like. When the pressure difference does not exceed the second set value, such a valve body 31 is positioned so that the seat packing 32 seals one end of the through hole 29, and the pressure difference reaches the second set value. When exceeding, the sheet packing 32 moves in a direction to open one end of the through hole 29.

  The through hole 29 has a first small diameter portion 29a, a second small diameter portion 29b, and a large diameter portion 29c. The first small diameter portion 29a is formed at one end of the through hole 29, and the second small diameter portion 29b is formed at the other end of the through hole. The large diameter portion 29c is located between the first small diameter portion 29a and the second small diameter portion 29b, and has an inner diameter larger than both. The check valve 17 includes a cylindrical valve seat 35, and the first small diameter portion 29a is formed in the valve seat 35 as an inner portion of the cylinder. The valve seat 35 is made of, for example, brass.

  The relief valve 19 has a coil spring (biasing means) 41. The coil spring 41 is a biasing member that biases the valve body 31 toward one end of the through hole 29. Specifically, one end of the coil spring 41 is in contact with a step located at the boundary between the second small diameter portion 29b and the opening 29d, and the other end is inserted into the second recess 31b of the valve body 31. It has become.

  Due to such a configuration, the valve body 31 is biased toward the one end side of the through hole 29 by the coil spring 41 when the pressure difference does not exceed the second set value, and the seat packing 32 is 1 It is positioned so as to be sealed against one end of the through hole 29 by being pressed against the small diameter portion 29a.

  FIG. 5 is a cross-sectional view of the check valve 1 with a built-in liquid seal prevention mechanism shown in FIG. 2 taken along line AA, showing a state in which the relief valve 19 is opened. As shown in FIG. 5, when the pressure difference exceeds the second set value, the valve body 31 and the seat packing 32 resist the biasing force of the coil spring 41 from the first small diameter portion 29a to the second small diameter portion 29b. It moves to the side and opens one end of the through hole 29. Thereby, the LP gas in a liquid-sealed state enters from one end (collection tube side) of the through hole 29 and escapes to the other end (container side) of the through hole 29 via the large diameter portion 29c and the small diameter portion 29b. It will be. Thereby, it can prevent that the collecting pipe 11 will be in a liquid-sealed state.

  Furthermore, as shown in FIGS. 3 to 5, the valve seat 35 has a protruding shape that protrudes in a tapered manner toward the other end side of the through hole 29. The first small diameter portion 29 a is formed so as to penetrate from the tip end portion of the protrusion toward one end side of the through hole 29. For this reason, as shown in FIG. 4, when the pressure difference exceeds the first set value, the sheet packing 32 bites into the tapered protrusion and holds the first small diameter portion 29 a in a sealed state. The degree of sealing between the valve seat 35 and the seat packing 32 can be further increased.

  In addition, the valve body 31 is formed with an air vent hole 31c that connects the first recess 31a and the second recess 31b. The air vent hole 31c is a hole for venting air interposed between the seat packing 32 and the first recess 31a of the valve body 31. Thereby, it can assemble | attach in the state which adhered both. When the sheet packing 32 is fixed to the valve body 31, a baking process or adhesion using an adhesive is performed. In particular, when baking, a compound of chemical and synthetic rubber is applied to the first recess 31a, and the sheet packing 32 is attached to the first recess 31a, and heated in a furnace at 180 ° C. for about 10 minutes, for example. Thereby, the compound of synthetic rubber is melted, and the seat packing 32 is in close contact with the valve body 31. In addition, when adhering the sheet packing 32 to the valve body 31, the sheet packing 32 may be adhered as it is without performing the baking process or the bonding using the adhesive. By doing so, the number of steps required for baking and bonding can be reduced.

  In the above, the first set value is set by adjusting the biasing force of the coil spring 27, and the second set value is set by adjusting the biasing force of the coil spring 41. The first set value is the same as the conventional check valve (for example, about 0.01 to 0.02 MPa), and the second set value is a value that is reasonably larger than the first set value ( For example, it is set to about 1.5 to 3.0 MPa.

  Next, the operation of the check valve 1 with a built-in liquid seal prevention mechanism according to this embodiment will be described. First, when the pressure difference is equal to or less than the first set value, such as when LP gas is used on the consumption side, the check valve 17 is opened by the coil spring 27 and the LP gas containers 3, 5, 7, LP gas is supplied from 9 to the collecting pipe 11 (see FIG. 3).

  If the pressure difference exceeds the first set value, the check valve 17 is closed against the biasing force of the coil spring 27, and the collecting pipe 11 is connected to the LP gas containers 3, 5, 7, and 9. Backflow is prevented (see FIG. 4).

  Further, if the pressure difference exceeds the second set value, the relief valve 19 is opened against the biasing force of the coil spring 41, and the backflow from the collecting pipe 11 to the LP gas containers 3, 5, 7, 9 is performed. (See FIG. 5). For this reason, it is avoided that the inside of the collecting pipe 11 is in a liquid-sealed state, and even if the collecting pipe 11 is exposed to sunlight, the internal pressure does not rise abnormally, and the function of the automatic switching adjuster 13 is damaged. There is no.

  Thus, according to the check valve 1 with a built-in liquid seal prevention mechanism according to the present embodiment, the check valve 21 has a through hole having the first small diameter portion 29a, the second small diameter portion 29b, and the large diameter portion 29c. 29, and the pressure of the LP gas containers 3, 5, 7, 9 is lower than the pressure on the collecting pipe 11 side, and the pressure on the LP gas containers 3, 5, 7, 9 side of the relief valve 19 and the collecting pipe If the pressure difference with the pressure on the 11th side does not exceed the second set value, the sheet packing 32 is pressed against the first small diameter portion 29a by the coil spring 41 so as to seal one end of the through hole 29, When the pressure difference exceeds the second set value, the valve body 31 and the seat packing 32 move from the first small diameter portion 29a toward the second small diameter portion 29b against the urging force of the coil spring 41, and the through hole 29 It moves in the direction which opens one end of. For this reason, when the pressure difference does not exceed the second set value, the sheet packing 32 is pressed against the first small diameter portion 29a by the coil spring 41, and the through hole 29 is closed. Therefore, when the pressure difference exceeds the first set value, the check valve 17 prevents backflow. On the other hand, when the pressure difference exceeds the second set value, the valve body 31 and the seat packing 32 move from the first small diameter portion 29a toward the second small diameter portion 29b against the urging force of the coil spring 41 and penetrate therethrough. Since one end of the hole 29 is opened, backflow is allowed through the through hole 29. From these, while preventing the backflow, the backflow is allowed when the inside of the collecting pipe 11 is in a liquid-sealed state and becomes a higher pressure. Therefore, in the LP gas supply system 15 that supplies LP gas from the plurality of LP gas containers 3, 5, 7, 9 through the collecting pipe 11 and the automatic switching regulator 13, the collecting pipe 11 is liquid-sealed. It is possible to prevent the situation from occurring.

  Further, since the valve body 31 has the second recess 31b into which the coil of the coil spring 41 is inserted, the positional relationship between the valve body 31 and the coil spring 41 is stabilized by the second recess 31b. It is possible to prevent a situation in which the position is shifted and the urging force against the valve body 31 becomes unstable.

  Further, the valve seat 35 has a protruding shape that projects in a tapered manner toward the other end side of the through hole 29, and the first small diameter portion 29 a is formed to penetrate from the protruding tip portion toward one end side of the through hole 29. Therefore, when the valve body 31 is pressed against one end side of the through-hole 29, the sheet packing 32 bites into the tapered protrusion and seals the first small diameter portion 29a. Thereby, even when the pressure difference exceeds the first set value, the check valve 17 can further prevent backflow.

  Further, since the air vent hole 31c for venting air interposed between the valve body 31 and the seat packing 32 is formed when the seat packing 32 is fixed, the seat packing 32 is in close contact with the valve body 31. Can be assembled with.

  As described above, the present invention has been described based on the embodiment, but the present invention is not limited to the above embodiment, and may be modified without departing from the gist of the present invention.

  For example, although the valve seat 35 is one member, it is not limited to this and may be configured by combining two members.

  Furthermore, in the present embodiment, it is preferable that the sliding dimension (sliding area) between the valve body 31 and the large diameter portion 29c is longer. Thereby, the play between both can be suppressed and the adhesiveness of the sheet packing 32 and the valve body 31 can be improved. Specifically, it is preferable that the sliding dimension of both is 2.8 mm or more. This is because if the thickness is less than 2.8 mm, the possibility of looseness increases.

Further, the moving directions of the check valve 17 and the relief valve 19 that move according to the pressure difference may be reversed. For example, the relief valve 19 moves to the other end side of the through hole 29 when the pressure difference exceeds the second set value, but moves to one end side to open the through hole 29. It may be.

DESCRIPTION OF SYMBOLS 1 Check valve with built-in liquid seal prevention mechanism 3, 5, 7, 9 LP gas container 11 Collecting pipe 13 Automatic switch regulator 15 LP gas supply system 17 Check valve 19 Relief valve 21 Valve body 23 Plug 25 Valve seat 27 Coil spring 29 Through-hole 29a 1st small diameter part 29b 2nd small diameter part 29c Large diameter part 29d Opening part 31 Valve body (valve body for relief)
31a 1st recessed part 31b 2nd recessed part (recessed part)
31c Air vent hole 35 Valve seat 41 Coil spring (biasing means)

Claims (4)

LP gas having a plurality of LP gas containers for supplying LP gas, a collecting pipe for collecting the gas from the LP gas container, and an automatic switching regulator arranged on the collecting pipe for supplying LP gas to a consumer side A check valve with a built-in liquid seal prevention mechanism disposed between the LP gas container and the collecting pipe of the supply system,
When the pressure on the LP gas container side becomes lower than the pressure on the collecting pipe side and the pressure difference between the pressure on the LP gas container side and the pressure on the collecting pipe side exceeds a first set value, the LP gas container side operates. A check valve that prevents backflow to the gas container,
A relief valve that operates when the pressure difference exceeds a second set value that is greater than the first set value to allow backflow;
The check valve is formed with a through hole having a first small diameter portion, a second small diameter portion, and a large diameter portion that is located between the first and second small diameter portions and has an inner diameter larger than these. In addition, a groove in which a packing that is an elastic member is provided is formed at an outer portion of the position of the second small diameter portion,
The relief valve comprises: a relief valve body that is movably disposed in the large diameter portion of the through hole of the check valve; a seat packing attached to the relief valve body; and the relief valve body. An urging means for urging one end of the through hole, and when the pressure difference does not exceed the second set value, the urging means presses the sheet packing against the first small-diameter portion. The relief valve body and the seat packing against the urging force of the urging means when the pressure difference exceeds the second set value. The check valve with a built-in liquid seal prevention mechanism moves from the first small-diameter portion to the second small-diameter portion and moves in a direction to open one end of the through hole. The biasing means is a coil spring,
The check valve with a built-in liquid seal prevention mechanism according to claim 1, wherein the relief valve body has a recess into which a coil of the coil spring is inserted. The check valve further includes a valve seat in which the first small diameter portion is formed and fixed to one end side of the through hole,
The valve seat has a protruding shape that protrudes in a tapered shape toward the other end side of the through-hole,
The check valve with a built-in liquid seal prevention mechanism according to claim 1, wherein the first small-diameter portion is formed so as to penetrate from a tip end portion of the protrusion of the valve seat toward one end side of the through hole. . In the relief valve body, another recess to which the seat packing is attached is formed on the side opposite to the recess forming side into which the coil spring is inserted, and an air vent that connects the recess and the other recess is formed. The check hole with a built-in liquid seal prevention mechanism according to claim 2 , wherein a use hole is formed.

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