JP2007278484A - Overflow preventing valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the occurrence of improper overflow preventing operation by stabilizing a flow amount in a normal condition while reliably shutting off a fluid take-out passage during excessive flow-out. <P>SOLUTION: An inlet passage 5, an overflow preventing valve chamber 6 and an outlet passage 7 are formed in sequence in a housing 4. An overflow preventing valve seat 8 is formed around the opening of the outlet passage 7 facing the overflow preventing valve chamber 6. An overflow preventing member 14 inserted into the overflow preventing valve chamber 6 is changed over between a valve opening attitude Y where it is isolated from the overflow preventing valve seat 8 and a valve closing attitude where it abuts on the overflow preventing valve seat 8. A rod part 23 formed at the front end of the overflow preventing member 14 is protruded into the outlet passage 7. Between the outer peripheral face of the rod part 23 and the inner peripheral face of the outlet passage 7, a minimum opening distribution part 27 is formed for restricting the flow amount of fluid. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an overflow prevention valve that prevents an excessive fluid outflow by shutting off the fluid extraction path in the event of an abnormal flow out of fluid due to damage or the like of devices connected to the fluid extraction path. The present invention relates to an overflow prevention valve that can stably shut off a fluid take-out path in the event of excessive outflow, stabilizes the flow rate during normal times, and suppresses the occurrence of malfunctions of overflow prevention.

  In recent years, development of vehicles using hydrogen gas as fuel with little environmental pollution has been underway. The hydrogen gas storage container is desired to have a large capacity and a small size, and accordingly, the storage gas pressure is also required to be increased to a high pressure such as 70 MPa.

The flow rate taken out from the gas container increases to a predetermined amount or more when an abnormality such as gas leakage from the pipe occurs. Therefore, the gas extraction path from the gas container is usually provided with an overflow prevention valve, for example, on the container valve, and when the extraction flow rate increases abnormally, the overflow prevention valve is closed to shut off the gas extraction path. It is configured as follows.
Conventionally, as an overflow prevention valve that shuts off the gas extraction path when the extraction flow rate increases abnormally, an overflow prevention member is inserted into the overflow prevention valve chamber, and this overflow prevention member is repressed by a valve opening spring. There is an overflow prevention valve that can be switched between a valve opening posture that is separated from the overflow prevention valve seat and a valve closing posture that is in contact with the overflow prevention valve seat as the take-off flow rate increases (patented) Reference 1).

  That is, for example, as shown in FIG. 4, this overflow prevention valve (50) is provided with an inlet passage (52), an overflow prevention valve chamber (53) and an outlet passage (54) in the housing (51) in this order. A gas extraction passage (59) is formed, an overflow prevention valve seat (55) is formed in the overflow prevention valve chamber (53), and an overflow prevention member (56) is installed in the overflow prevention valve chamber (53). The overflow prevention member (56) is inserted and elastically pressed by a valve opening spring (57) in the valve opening direction away from the overflow prevention valve seat (55).

  In the normal state, the above-described overflow prevention member (56) is elastically pressed by the valve opening spring (57) and is separated from the overflow prevention valve seat (55) by a predetermined dimension. Therefore, when taking out the stored gas from the gas container (58) through the gas extraction path (59), a predetermined flow rate that passes through the gap between the overflow prevention member (56) and the overflow prevention valve seat (55). Gas is removed.

  On the other hand, if an overflow occurs at the time of taking out the gas, the internal pressure of the outlet passage (54) is lower than a predetermined differential pressure compared to the internal pressure of the inlet passage (52). The prevention member (56) moves toward the valve closing side against the elastic force of the valve opening spring (57), contacts the overflow prevention valve seat (55), and the gas extraction path (59) is shut off.

JP 2003-314798 A

  In the above-described overflow prevention valve, the smallest opening flow portion having the smallest opening area in the take-out path in the valve opening posture is formed between the overflow prevention valve seat and the overflow prevention member facing the minimum opening circulation portion. The gas flow rate taken out via the overflow prevention valve is determined by the opening area of the opening circulation portion and the opening shape. At this time, in the case of a gas having a small molecular weight such as hydrogen gas, the flow rate varies greatly depending on the slight difference in the opening area of the minimum opening circulation portion and the opening shape.

  However, the forward / backward movement of the overflow prevention member depends on the balance of the biasing force of the valve opening spring, the internal pressure of the outlet passage, and the like. When this overflow prevention member is slightly displaced in the forward / backward direction, the minimum opening circulation portion formed between the overflow prevention valve seat and the overflow prevention member has an opening area or an opening shape. Are likely to fluctuate and it is not easy to stabilize them.

In addition, in order for the overflow prevention member to operate smoothly when an overflow occurs, the contact portion between the overflow prevention member and the overflow prevention valve chamber is formed to be small, for example, near the rear end of the overflow prevention member. Only one part is slid and supported on the inner surface of the overflow prevention valve chamber. For this reason, the overflow prevention member has a problem that the tip side facing the overflow prevention valve seat is likely to be shaken, and it is difficult to stabilize the opening area and the opening shape of the minimum opening circulation portion.
As a result, in the conventional overflow prevention valve described above, the gas flow rate passing through the minimum opening circulation portion is not stable, and the internal pressure of the outlet passage is lowered due to this flow rate variation, and malfunction of overflow prevention is caused. There was a possibility of producing.

  The technical problem of the present invention is to solve the above-mentioned problems and to reliably shut off the fluid extraction path at the time of excessive outflow, to stabilize the flow rate flowing out from the outlet path in normal times, and to prevent malfunction of overflow prevention. The object is to provide a suppressed overflow prevention valve.

In order to solve the above-described problems, the present invention is configured as follows, for example, based on FIGS. 1 to 3 showing an embodiment of the present invention.
That is, the present invention relates to an overflow prevention valve, wherein an inlet passage (5), an overflow prevention valve chamber (6), and an outlet passage (7) are formed in order in a housing (4), and the above-described overflow prevention valve chamber is formed. An overflow prevention valve seat (8) is formed around the outlet passage (7) opening facing (6), and the overflow prevention member (14) is placed in the overflow prevention valve chamber (6). Inserted into the flow prevention valve seat (8) so as to be able to contact and separate, and the above-described overflow prevention member (14) is elastically pressed by the valve opening spring (13) and separated from the overflow prevention valve seat (8). The pressure difference between the valve posture (Y) and the internal pressure of the inlet passage (5) and the internal pressure of the outlet passage (7), which is lower than this, is against the elastic pressure of the valve opening spring (13). An overflow prevention valve configured to be switchable to a closed position (X) in contact with the overflow prevention valve seat (8), wherein a rod-like portion ( 23), and this rod-like portion (23) is plunged into the outlet passage (7), and the outer peripheral surface of the rod-like portion (23) and the outlet A minimum opening circulation portion (27) for limiting the fluid flow rate is formed between the inner peripheral surface of the passage (7).

  In the normal state, the above-described overflow prevention member is held in the valve opening posture separated from the overflow prevention valve seat by the elastic force of the valve opening spring, and the fluid flows between the overflow prevention member and the overflow prevention valve seat. It flows out at a predetermined flow rate from the outlet passage through the gap and the minimum opening circulation portion in order. At this time, since the minimum opening circulation portion is formed between the outer peripheral surface of the rod-shaped portion at the tip of the overflow prevention member and the inner peripheral surface of the outlet passage, the overflow prevention member is slightly moved in the advancing / retreating direction. Therefore, the minimum opening circulation portion is always maintained at a constant opening area, and the fluid flowing out from the outlet passage is stably maintained at a predetermined flow rate corresponding to the opening area. In the unlikely event that an overflow occurs due to damage to the fluid device, etc., the internal pressure of the outlet passage decreases and the overflow prevention member moves forward. At this time, the minimum opening circulation portion is maintained at a constant opening area, but the overflow prevention member abuts against the overflow prevention valve seat by advancing, thereby shutting off the flow path and stopping the outflow of fluid.

  The minimum opening circulation portion formed between the outer peripheral surface of the rod-shaped portion and the inner peripheral surface of the outlet passage is formed, for example, by forming an annular protrusion on the outer peripheral surface of the rod-shaped portion. You may form a minimum distribution | circulation part between the inner peripheral surfaces. However, if an annular protrusion is formed on the inner surface of the outlet passage and formed between the inner surface of the annular protrusion and the outer peripheral surface of the rod-shaped portion, the minimum opening flow portion can be easily formed and the rod-shaped The minimum opening circulation part can be set to a predetermined opening area or opening shape simply by changing the outer shape of the part, which is preferable.

  Further, the above-described overflow prevention member is formed at the front end portion of the overflow prevention member when the two portions near the front end and the rear end portion are supported by sliding on the inner surface of the overflow prevention valve chamber. The rod-shaped portion is preferable because there is no risk of causing runout and the opening shape is maintained constant.

  The above-described overflow preventing member can be constituted by a cylindrical sleeve and a shaft portion inserted into the sleeve so as to be able to advance and retract. That is, the sleeve is configured to be able to contact and separate from the overflow prevention valve seat, and the rod-shaped portion is formed at the tip of the shaft portion, and the rod-shaped portion protrudes from the tip opening of the sleeve. The two positions of the front and rear portions of the shaft portion are slid and supported on the inner peripheral surface of the sleeve, and the shaft portion is advanced to the inner peripheral surface of the sleeve. A second valve seat for sealing contact is formed, and biasing means for biasing the shaft portion toward the second valve seat side is provided, and the shaft portion is retracted against the biasing force of the biasing means. If it does, it will comprise so that said bar-shaped part may move and the opening area of said minimum opening circulation part may become large.

  With this configuration, when the fluid is normally taken out, the shaft portion moves forward and comes into contact with the second valve seat, and is formed between the outer peripheral surface of the rod-shaped portion and the inner peripheral surface of the outlet passage. A flow rate corresponding to the opening area of the minimum opening circulation portion is taken out. On the other hand, when the fluid is filled from the opposite direction, the shaft portion is pressed backward against the elastic force of the urging spring with the filling pressure, whereby the opening area of the minimum opening circulation portion is Is larger, and the flow rate passing therethrough can be increased to fill at high speed, which is preferable.

  In this case, a small-diameter return push rod is formed on the tip side of the rod-shaped portion, and when the shaft portion moves forward and is switched to the valve closing posture, the tip of the return push rod is used as a return means. When the shaft portion is further retracted from the valve opening posture, the outer peripheral surface of the return push rod faces the inner peripheral surface of the outlet passage that forms the minimum opening circulation portion. The return push rod can be easily returned to the normal state from the closed position by linking the return means to the tip of the return push rod, for example, a closing member of the stop valve, and the return push rod has a small diameter. Thus, when filling, the shaft portion is further retracted from the valve opening posture, and the outer peripheral surface of the small-diameter return push rod faces the inner peripheral surface of the outlet passage, thereby opening the opening area of the minimum opening flow portion. Can be easily increased.

Since the present invention is configured and operates as described above, the following effects can be obtained.
In the unlikely event that an overflow occurs due to damage to the fluid equipment, etc., the overflow prevention member moves forward and contacts the overflow prevention valve seat, thereby blocking the flow path and stopping the outflow of fluid reliably. it can. In addition, in the normal state, the minimum opening flow portion is formed between the outer peripheral surface of the rod-shaped portion at the tip of the overflow prevention member and the inner peripheral surface of the outlet passage, so that the overflow prevention member moves in the forward and backward direction. Even if it is slightly deviated, the minimum opening circulation portion can always be maintained at a constant opening area. As a result, the fluid flowing out from the outlet passage can be stably maintained at a predetermined flow rate, and the occurrence of malfunction for preventing overflow can be suppressed.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 and 2 show a first embodiment of the present invention, FIG. 1 is a cross-sectional view of an overflow prevention valve in a normal state, FIG. 2 is an operation explanatory view of the overflow prevention valve, and FIG. FIG. 2B is a cross-sectional view of the overflow prevention valve at the time of gas filling.

  As shown in FIG. 1, this overflow prevention valve (1) is incorporated in a valve device (3) attached to the gas container (2), and an inlet passage (5) and an overflow are formed in the housing (4). A gas extraction passage (18) is formed which is provided with a prevention valve chamber (6) and an outlet passage (7) in this order. An overflow prevention valve seat (8) is formed around the opening of the outlet passage (7) facing the overflow prevention valve chamber (6). The inlet channel (5) communicates with the gas container (2), and the outlet channel (7) passes through the shut-off valve chamber (10) of the shut-off valve (9) and the gas outlet (11). Communicating with

  The overflow prevention valve chamber (6) is sealed by a receiving member (12) screwed and fixed to the housing (4), and the overflow prevention member ( 14) is inserted in the overflow prevention valve seat (8) so as to be able to advance and retract. The overflow prevention member (14) is composed of a cylindrical sleeve (15) having both ends opened and a shaft portion (16) inserted so as to be able to advance and retreat. A valve opening posture (Y) separated from the prevention valve seat (8) and received by the receiving member (12), and a valve closing posture (X) in contact with the overflow prevention valve seat (8); Is switched to.

  The above-described overflow prevention member (14) is supported at the front end portion (14a) and the rear end portion (14b) so as to be slidable on the inner surface of the overflow prevention valve chamber (6). The valve opening spring (13) disposed between the overflow prevention member (14) and the inner surface of the overflow prevention valve chamber (6) is elastically pressed away from the overflow prevention valve seat (8). is there. Of the overflow prevention member (14), a seal member (19) is attached to the front end of the sleeve (15) so as to face the overflow prevention valve seat (8). When the overflow prevention member (14) moves forward against the elastic force of the valve opening spring (13), the seal member (19) comes into contact with the overflow prevention valve seat (8) in a tightly sealed manner.

  On the other hand, the shaft portion (16) includes a small-diameter front portion (16a) and a larger-diameter rear portion (16b), and is slid on the inner peripheral surface of the sleeve (15). It is supported. Further, a second seal member (20) is attached to a step portion at the front end of the rearward portion (16b), and a second valve seat (21 on the inner peripheral surface of the sleeve (15) at a position facing the second seal member (21). ) Is formed. An urging spring (22) having a smaller elastic force than the valve opening spring (13) is disposed between the shaft portion (16) and the receiving member (12). The shaft (16) is biased toward the second valve seat (21) by a spring (22).

  The small-diameter forward portion (16a) of the shaft portion (16) has a distal end projecting from the distal end opening of the sleeve (15), and the projecting portion is formed in the rod-shaped portion (23). It rushes into the exit channel (7). A small-diameter return push rod (24) is formed at the tip of the rod-like portion (23), and the rod-like portion (23), that is, the shaft portion (16), moves forward together with the sleeve (15) to close the above-mentioned closing. When switched to the valve posture (X), the tip of the return push rod (24) is configured to enter the closing valve chamber (10). The closing member (25) inserted into the shut-off valve chamber (10) constitutes a return means, and is linked to the tip of the return push rod (24) that has entered the shut-off valve chamber (10). It is.

  An annular protrusion (26) is formed on the inner surface of the outlet passage (7), and an inlet passage is formed between the inner surface of the annular protrusion (26) and the outer peripheral surface of the rod-shaped portion (23). A minimum opening circulation portion (27) having the smallest opening area is formed in the gas extraction passage (18) from (5) to the outlet passage (7). That is, the opening area of the minimum opening flow portion (27) is the opening area between the above-described overflow prevention valve seat (8) and the seal member (19) at the tip of the sleeve (15) in the valve opening posture (Y). Therefore, the flow rate of the gas flowing through the gas extraction passage (18) is limited by the opening area and the opening shape of the minimum opening circulation portion (27).

Next, based on FIG. 1 and FIG. 2, operation | movement of said overflow prevention valve is demonstrated.
(1) At the time of gas extraction at normal time As shown in FIG. 1, the overflow prevention member (14) is elastically pressed by the valve opening spring (13) and is separated from the overflow prevention valve seat (8). The valve opening posture (Y) is maintained. When the closing member (25) of the above-described closing valve (9) is opened in this state, the stored gas in the gas container (2) flows into the inlet passage (5), the overflow prevention valve chamber (6), and the outlet passage (7 ) And the shut-off valve chamber (10) in this order, and is taken out from the gas outlet (11). At this time, since the opening area of the minimum opening circulation portion (27) is the smallest in the gas extraction passage (18), it flows out from the overflow prevention valve chamber (6) to the outlet passage (7). The flow rate of the extracted gas is set by the minimum opening circulation portion (27).

  The minimum opening circulation portion (27) is formed between the outer peripheral surface of the rod-shaped portion (23) and the inner surface of the annular protrusion (26). In addition, the overflow prevention member (14) is slidably supported on the inner surface of the overflow prevention valve chamber (6) at two positions, the front end portion (14a) and the rear end portion (14b). The shaft portion (16) is supported on the inner peripheral surface of the sleeve (15) at two locations, a small-diameter front portion (16a) and a large-diameter rear portion (16b). As a result, it is possible to reduce the possibility that the rod-like portion (23) at the tip of the shaft portion (16) will run out, and the rod-like portion (23) and the overflow prevention member (14) forming the rod-like portion (23) are slightly shifted in the advancing and retracting direction. The minimum opening circulation part (27) is always maintained in a constant opening area and opening shape even if it is tilted.

(2) At the time of overflow On the other hand, if an overflow occurs because the gas equipment attached to the downstream side of the valve device (3) is damaged, the internal pressure of the outlet passage (7) is increased along with the excessive outflow of gas. The overflow prevention member (14) is pressed toward the overflow prevention valve seat (8) by the gas pressure flowing into the overflow prevention valve chamber (6) from the inlet passage (5). Then, when a differential pressure greater than a predetermined pressure is generated between the internal pressure of the inlet passage (5) and the internal pressure of the low outlet passage (7), the overflow prevention member (14) is the elastic pressure of the valve opening spring (13). As shown in FIG. 2A, the valve moves forward against the force, and is switched to the valve closing posture (X) in contact with the overflow prevention valve seat (8). At this time, the minimum opening flow part (27) is maintained at a constant opening area, but when the overflow prevention member (14) comes into contact with the overflow prevention valve seat (8), the gas extraction passage (18). Is shut off, thereby stopping the outflow of gas to the outlet channel (7).

  In this valve closing posture (X), as shown in FIG. 2 (a), the tip of the return push rod (24) formed at the tip of the rod-like portion (23) enters the valve closing chamber (10). And it faces the closing member (25). When the closing member (25) is closed in this state, the return push rod (24) is pressed by the closing member (25), and the overflow prevention member (14) is separated from the overflow prevention valve seat (8). To do. As a result, the outlet passage (7), the overflow prevention valve chamber (6), and the inlet passage (5) on the upstream side of the shutoff valve chamber (10) have equal pressure, and the overflow prevention member (14) is The valve opening spring (13) is returned to the valve opening posture (Y) shown in FIG. Then, after the cause of the excessive outflow is resolved, when the shut-off valve (9) is opened, the stored gas in the gas container (2) is transferred to the inlet channel (as in the normal state). 5), the overflow prevention valve chamber (6), the outlet passage (7), and the shut-off valve chamber (10), which are taken out from the gas outlet (11) in this order.

(3) Gas filling When filling the gas container (2) with a gas, a filling device (not shown) is connected to the gas outlet (11), and the closing valve (9) is opened. Since the above-described overflow prevention member (14) is separated from the overflow prevention valve seat (8), the fresh gas flows into the closing valve chamber (10), the outlet passage (7), and the overflow prevention valve chamber (6). The gas container (2) is filled through the inlet channel (5) in order.

  At this time, since the shaft portion (16) is pressed by the filling gas pressure, the shaft portion (16) retreats against the elastic force of the biasing spring (22) as shown in FIG. 2 (b). By the retraction of the shaft portion (16), the rod-like portion (23) is removed from the position facing the annular protrusion (26), and the small-diameter return push rod (24) formed at the tip of the rod-like portion (23). The outer peripheral surface faces this annular protrusion (26). For this reason, the opening area of the minimum opening circulation part (27) formed inside the annular protrusion (26) is increased, and the flow rate of the fresh gas is increased to quickly enter the gas container (2). Can be filled.

FIG. 3 is a cross-sectional view of an overflow prevention valve showing a second embodiment of the present invention.
In the second embodiment, the rod-like portion (23) is integrally formed at the tip of the overflow preventing member (14). In the second embodiment, a filling path (not shown) separate from the gas extraction path (18) is provided in the housing (4).

  In the second embodiment, two portions of the overflow prevention member (14), the front end portion (14a) and the rear end portion (14b), are slid onto the inner peripheral surface of the overflow prevention valve chamber (6). Since the rod-like portion (23) is integrally formed at the tip of the overflow prevention member (14), the annular protrusion (26) formed on the inner surface of the outlet passage (7) is supported. On the other hand, the occurrence of runout can be prevented more stably, and the extracted gas flowing out from the outlet passage (7) can be stably maintained at a predetermined flow rate. The other configuration is the same as that of the first embodiment described above, and functions in the same manner, so that the description is omitted.

  The overflow prevention valve described in each of the above embodiments is exemplified to embody the technical idea of the present invention, and includes an overflow prevention member, a valve opening spring, a minimum opening circulation portion, a sleeve and a shaft. The shape, structure, arrangement, etc. of each member, such as the portion, return push rod, return means, etc. are not limited to these embodiments, and various modifications can be made within the scope of the claims of the present invention Needless to say, the gas to be handled is not limited to a specific type.

For example, in each of the above-described embodiments, the annular protrusion is formed on the inner surface of the outlet passage. Alternatively, the annular protrusion may be formed on the outer peripheral surface of the rod-shaped portion. Depending on the inner diameter of the outlet channel, this annular projection can be omitted.
Further, in each of the above embodiments, the closing member is configured as a return means, and the return push rod is formed at the tip of the rod-shaped portion. However, in the present invention, the return means may be provided separately. It is formed according to the structure of the return means, and the formation position is not limited to the tip side of the overflow prevention member.

  The overflow prevention valve of the present invention can be used in, for example, a hydrogen supply device because it can stably shut off the fluid take-out path at the time of excessive outflow and can stabilize the flow rate and suppress the occurrence of malfunction of overflow prevention. Although it is particularly suitable for a container valve of a gas container, it is also suitably used for other valve devices and midway of piping.

It is sectional drawing of the overflow prevention valve in the normal time which shows 1st Embodiment of this invention. FIG. 2A is a cross-sectional view of the overflow prevention valve at the time of excessive outflow, and FIG. 2B is a cross-sectional view of the overflow prevention valve at the time of filling. . It is sectional drawing of the overflow prevention valve in the normal time which shows 2nd Embodiment of this invention. It is sectional drawing of the overflow prevention valve which shows a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Overflow prevention valve 4 ... Housing 5 ... Inlet passage 6 ... Overflow prevention valve chamber 7 ... Outlet passage 8 ... Overflow prevention valve seat
13 ... Valve opening spring
14… Overflow prevention member
14a ... Near the tip
14b: Rear end portion
15… Sleeve
16 ... Shaft
16a ... Front side
16b ... Rear part
21 ... Second valve seat
22 ... Biasing means (biasing spring)
23… Bar-shaped part
24 ... Push bar for return
25 ... Return means (closing member)
26 ... annular protrusion
27 ... Minimum opening circulation part X ... Valve closed posture Y ... Valve open posture

Claims (5)

An inlet passage (5), an overflow prevention valve chamber (6), and an outlet passage (7) are formed in this order in the housing (4), and the outlet passage (7) facing the overflow prevention valve chamber (6). An overflow prevention valve seat (8) is formed around the opening,
An overflow prevention member (14) is inserted into the overflow prevention valve chamber (6) so as to be able to contact with and separate from the overflow prevention valve seat (8).
The valve opening posture (Y) in which the overflow prevention member (14) is elastically pressed by the valve opening spring (13) and separated from the overflow prevention valve seat (8), and the internal pressure of the inlet passage (5). Closed position in contact with the overflow prevention valve seat (8) against the elastic pressure of the valve-opening spring (13) due to a differential pressure greater than a predetermined pressure between the pressure and the internal pressure of the outlet passage (7) lower than this (X) is an overflow prevention valve configured to be switchable,
A rod-like portion (23) is formed at the tip of the overflow prevention member (14), and the rod-like portion (23) is plunged into the outlet passage (7),
An overflow prevention valve characterized in that a minimum opening flow portion (27) for restricting a fluid flow rate is formed between the outer peripheral surface of the rod-like portion (23) and the inner peripheral surface of the outlet passage (7).   An annular protrusion (26) is formed on the inner peripheral surface of the outlet passage (7), and the minimum opening is formed between the inner surface of the annular protrusion (26) and the outer peripheral surface of the rod-shaped part (23). The overflow prevention valve according to claim 1, wherein a circulation part (27) is formed.   The above-described overflow prevention member (14) is supported by sliding the front end portion (14a) and the rear end portion (14b) on the inner peripheral surface of the overflow prevention valve chamber (6). The overflow prevention valve according to claim 1 or 2. The overflow prevention member (14) is composed of a cylindrical sleeve (15) and a shaft portion (16) inserted into the sleeve so as to be able to advance and retreat, and the sleeve (15) is provided with the overflow prevention valve seat. (8) The rod-like portion (23) is formed at the tip of the shaft portion (16), and the rod-like portion (23) is formed from the tip opening of the sleeve (15). Protruding,
Two parts of the front part (16a) and the rear part (16b) of the shaft part (16) are supported by sliding on the inner peripheral surface of the sleeve (15),
A second valve seat (21) is formed on the inner peripheral surface of the sleeve (15) to be in sealing contact at a position where the shaft (16) has advanced,
There is provided an urging means (22) for urging the shaft portion (16) toward the second valve seat (21), and the shaft portion (16) against the urging force of the urging means (22). 4. The excessive structure according to claim 1, wherein the rod-shaped part (23) moves and the opening area of the minimum opening circulation part (27) increases when the reverse is moved. 5. Flow prevention valve.   A return push rod (24) with a small diameter is formed on the distal end side of the rod-like portion (23), and when the shaft portion (16) moves forward and is switched to the valve closing posture (X), this return The distal end of the push rod (24) is configured to be able to be linked with the return means (25), and when the shaft portion (16) is further retracted from the valve opening posture (Y), the minimum opening flow portion (27 The overflow prevention valve according to claim 4, wherein the outer peripheral surface of the return push rod (24) is made to face the inner peripheral surface of the outlet passage (7) forming the).

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