CA1261808A - Ball valve - Google Patents
Ball valveInfo
- Publication number
- CA1261808A CA1261808A CA000478731A CA478731A CA1261808A CA 1261808 A CA1261808 A CA 1261808A CA 000478731 A CA000478731 A CA 000478731A CA 478731 A CA478731 A CA 478731A CA 1261808 A CA1261808 A CA 1261808A
- Authority
- CA
- Canada
- Prior art keywords
- body cavity
- chamber
- diameter
- communication
- piston
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
- F16K39/00—Devices for relieving the pressure on the sealing faces
- F16K39/06—Devices for relieving the pressure on the sealing faces for taps or cocks
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- Engineering & Computer Science (AREA)
- General Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Safety Valves (AREA)
- Taps Or Cocks (AREA)
Abstract
ABSTRACT
A ball valve having a housing; a movable ball for opening and closing a fluid passage within the housing; an annular seat retainer fitted in the housing around the fluid passage in opposed relation to, the ball; an annular valve seat mounted on the seat retainer in opposed relation to the ball; a stepped portion formed in the outer peripheral portion of the seat retainer where the seat retainer is in sliding contact with the inner wall surface of the housing, the stepped portion extending from a surface portion having a diameter larger than a seal point diameter of the valve seat to a surface portion having a diameter smaller than said seal point diameter, said larger- and smaller-diameter surface portions forming a sealed chamber in conjunction with the inner wall of the housing which is in sliding contact therewith, the sealed chamber serving as an O-ring slot: and an O-ring fitted in said O-ring slot, characterized in that:
a change-over valve having a main cylinder and a sub cylinder is used; a main piston which is axially movable within the main cylinder and a sub piston which is axially movable within the sub cylinder are coupled together; and the interior of the main cylinder is partitioned by the main piston into a primary chamber which communicates with the fluid passage and a secondary chamber which communicates with the body cavity, while the interior of the sub cylinder is partitioned by the sub piston into a communication chamber which communicates with the primary chamber or the atmosphere and a control chamber which communicates with the body cavity, the sub piston being biased toward the control chamber by means of a compression spring in the communication chamber, whereby when the fluid pressure is higher than the internal pressure of the body cavity and the body cavity internal pressure is within an allowable range, the sub piston is held in said biased position to cut off the communication between the fluid passage and the body cavity, while when the body cavity internal pressure reaches a predetermined level, the sub piston is moved against the compression spring to bring the body cavity into communication with the fluid passage through said primary chamber.
A ball valve having a housing; a movable ball for opening and closing a fluid passage within the housing; an annular seat retainer fitted in the housing around the fluid passage in opposed relation to, the ball; an annular valve seat mounted on the seat retainer in opposed relation to the ball; a stepped portion formed in the outer peripheral portion of the seat retainer where the seat retainer is in sliding contact with the inner wall surface of the housing, the stepped portion extending from a surface portion having a diameter larger than a seal point diameter of the valve seat to a surface portion having a diameter smaller than said seal point diameter, said larger- and smaller-diameter surface portions forming a sealed chamber in conjunction with the inner wall of the housing which is in sliding contact therewith, the sealed chamber serving as an O-ring slot: and an O-ring fitted in said O-ring slot, characterized in that:
a change-over valve having a main cylinder and a sub cylinder is used; a main piston which is axially movable within the main cylinder and a sub piston which is axially movable within the sub cylinder are coupled together; and the interior of the main cylinder is partitioned by the main piston into a primary chamber which communicates with the fluid passage and a secondary chamber which communicates with the body cavity, while the interior of the sub cylinder is partitioned by the sub piston into a communication chamber which communicates with the primary chamber or the atmosphere and a control chamber which communicates with the body cavity, the sub piston being biased toward the control chamber by means of a compression spring in the communication chamber, whereby when the fluid pressure is higher than the internal pressure of the body cavity and the body cavity internal pressure is within an allowable range, the sub piston is held in said biased position to cut off the communication between the fluid passage and the body cavity, while when the body cavity internal pressure reaches a predetermined level, the sub piston is moved against the compression spring to bring the body cavity into communication with the fluid passage through said primary chamber.
Description
TITLE OF TH E INVENTION
BALL VALVE
1 BACKGROUND OF THE_INVENTION
1. Field of the Invention The present invention relates to a ball valve for use in pipelines, etc, and more particularly to a double seal type ball valve in which in the event of an abnormal increase of the internal pressure of a body cavity, the body cavi~y is brought into communication with a fluid passage, thereby suppressing such abnormal pressure increase in the body cavity.
BALL VALVE
1 BACKGROUND OF THE_INVENTION
1. Field of the Invention The present invention relates to a ball valve for use in pipelines, etc, and more particularly to a double seal type ball valve in which in the event of an abnormal increase of the internal pressure of a body cavity, the body cavi~y is brought into communication with a fluid passage, thereby suppressing such abnormal pressure increase in the body cavity.
2. Description of the Prior Art In ball valves of the type in which a ball is held within a housing rotatably by a stem and a fluid passage is opened and closed by rotation of the ball, there are known, as typical sealing methods, a single seal type and a double seal~type as disclosed in the "Piping Technique" March 1979 Number, pp. 78-89.
BRIEF DESCRIPTION OF THE~DRAWINGS
Fig. 1 is a sectional view of a principal portion of a conventional single seal type ball valve;
Fig. ~ and 3 are sectional views of a principal portion of a conventional double seal type A
*
1 ball valve;
Fig. 4 is a sectional view of a principal portion of a ball valve according to an embodiment of the present invention;
Fig. 5 is a sectional view of a change-over valve used therein, showing operation;
Figs. 6 and 7 are sectional views showing other examples of change-over valves in the ball valve of Fig. 4;
Fig. 8 is a sectional view of a principal portion of a ball valve according to another embodiment of the present invention;
Fig. 9 is a sectional view of a change-over valve used therein, showing operation;
Fig. 10 is a sectional view showing a detailed example of the change-over valve; and Fig. 11 is a sectional view of a principal portion showing another example of a change-over valve in the ball valve of Fig. 8.
Fig. 1 is a sectional~view of a principal portion of a conventional si~ngle seal type ball valve, in which a ball 2 as a valving member is ~nclosed in a housing l so as to be rotatable about~a stem (not shown) to open and close a fluid passage 3 formed within the - 2 _ A ~
1 housing. An annular seat retainer 4 is fitted in the housing so as to surround the fluid passage, and an annular valve seat 6 is mounted opposite to the ball in a position between the seat retainer 4 and an outer ring 5 fi~ed thereto The outer ring 5 is urged from its back toward the ball by means of compression springs 7 at ~redetermined intervals in the circumferential direction, whereby the annular valve seat 6 is brought ` into abutment with the ball surface to provide a seal between the seat retainer and the ball.
In an outer peripheral surface portion of the seat retainer 4 where the seat retainer is in sliding contact with the inner wall surface of the housing there is mounted an O-ring 8 in a position having an outside diameter D2 larger than a seal point diameter Dl of the va~ve seat to seal between the housing and seat retainer. In the ball valve of Fig. 1, moreover, a sealant passage 9 for injecting a sealant from an injector (not shown) to the seal point is open in the vicinity Oe the inside of the valve seat in order to make up for the sealing function temporarily in the event of damage of the seat.
In such single seal type, therefore, when fluid pres~sure is applied to the fluid passage and a 8~
1 primary side fluid pressure Pl is higher than a secondary side fluid pressure P2, a self-compressing force which is proportional to the product of the area of an annular portion whose width corresponds to the difference between the seal point diameter Dl o~ the valve seat 6 and the outside diame~er D2 Of the seat retainer in the position of the O-ring, and a differential pressure between the fluid pressure Pl and the internal pressure P3 of the body cavity, namely:
4(D2 ~ Dl)(Pl P3) is exerted on the seat retainer from the back thereof, so that the valve seat is brought into close contact with the ball. In this way, the priMary side fluid is sealed.
On the other hand, in the event the primary side fluid leaks to the body cavity, causing the internal pressure P3 of the body cavity to rise higher than the secondary side fluid pressure P2, the following force:
4~(D2 ~ Dl)(P3 - P2) is exerted on the seat retainer as a decompressing force for forcing back the seat retainer toward its back side.
Therefore, when this decompressing force becomes larger than the compresslve force of the compression spring 7, ~4 ~{ . .
1 the valve seat moves back from the ball, allowing the internal pressure of the body cavity to be released to the secondary side to prevent an abnormal increase of the internal pressure of the body cavity.
Thus, according to the single seal type, an abnormal increase of the internal pressure of the body cavity can be prevented by making the body cavity communicate with the secondary side. But, the fluid sealing is performed on the primary side alone.
As a sealing method capable of sealing fluid on both primary and secondary sides, there is known a double seal type as shown in Fig. 2. According to this sealing method, a stepped portion is formed in the outer peripheral portion of the seat retainer 4 where the seat retainer is in sliding contact with the inner wall surface of the housing 1, the stepped portion extending from the surface having a larger diameter D2 than the seal point diameter Dl of the valve seat 6 to the surface having a smaller diameter D3 than the seal point diameter Dl. These larger and smaller diameter surfaces form a sealed chamber in conjunction with the inner wall surface of the housing which is in sliding contact therewith. The sealed chamber serves as an O-ring slot 11 in which is fitted an O-ring 8 to seal between the _ 5 _ A
1 housing 1 and the seat retainer 6.
Therefore, on the primary side in normal condition, the primary side fluid pressure Pl is higher than the internal pressure P3 of the body cavity 10, so S that a self-compressing force of:
~ ~ 2 4(D2 ~ Dl)(Pl - P2) is exerted on the back of the seat retainer, thus causing the valve seat 6 to seal the primary side fluid.
On the other hand, in the event the interval pressure of the body cavity increases due to leak of the primary side fluid to the body cavity or due to la temperature rise and the body cavity internal pressure P3 becomes higher than the secondary side fluid pressure P2 in an allowable range, the body cavity internal pressure is conducted to the O-ring slot 11, so that the O-ring 8 is pushed a~ainst the right-hand housing wall in the O-ring slot 11 as shown in Fig. 3 and the body cavity internal pressure acts on as far s the smaller-diameter surface of diameter~D3. As a result~ a self-compressing force of:
4~D2 - D3)(P3 P2) is exerted on the back of the seat retainer 4, thus oausing the valve seat 6 to seal the secondary side fluid. In other words! the leakage of fluid from the ~ -~ 6 -A ` : ~
8~
1 primary to the secondary side is prevented.
Thus, according to such double seal method, the body cavity is closed pressurewise, so particularly in the case where the fluid is non-compressible liquid and, for example, in the event the primary side- liquid leaks to the body cavity in excess of a certain limit, the internal pressure of the body cavity will increase to an abnormal extent and result in damage of the valve.
Such an abnormal pressure increase in the body cavity can be avoided by attaching a relief valve to the body cavity, but this does not apply in the case where the fluid is inflammable. Also in the case of a deficient capacity of the relief valve, regardless of the kind of fluid, the valve will be damaged.
SUMMARY OF THE INVENTION
Accordingly, it lS the object of the present invention to provide a double seal type ball valve in which when the internal pressure of the body cavity becomes higher than a predetermined level, the body cavity is brought into communication with the fluid passage by utilizatlon of this pressure to prevent an abnormal pressure increase in the body cavity.
Accordlng;to one aspect of the present A
1 invention there is provided a ball valve having a housing; a movable ball for opening and closing a fluid passage within the housing; an annular seat retainer fitted in the housing around the fluid passage in opposed relation to the ball; an annular valve.seat mounted on the seat retainer in opposed relation to the ball; a stepped portion formed in the outer peripheral portion of the seat retainer where the seat retainer is in sliding contact with the inner wall surface of the housing, the stepped portion extending from a surface portion having a diameter larger than a seal point diameter of the valve seat to a surface portion having a diameter smaller than the seal point diameter, the larger- and smaller-diameter surface portions forming a sealed chamber In conjunction with the housing inner wall surface which is in sliding contact therewith, the sealed chamber serving as an O-ring slot; and an O-ring fitted in the O~ring slot, characterized in that a change-over valve having a maln cylinder and a sub cylinder is used; a main piston which is axially movable within the main cylinder and a sub piston which is axially movable withln the~sub cylinder are coupled together; and the interior of the main cylinder is partitioned by the main piston into a primary chamber : - 8 -A
1 which communicates with the fluid passage and a secondary chamber which communicates with the body cavity, while the interior of the sub cylinder is partitioned by the sub piston into a communication chamber which communicates with the primary chamber or the atmosphere and a control chamber which communicates with the body cavity, the sub piston being urged toward the control chamber by means of a compression spring in the communication chamber, whereby when the fluid pressure is higher than the internal pressure of the body cavity and the body cavity internal pressure is within an allowable range, the sub piston is held in the above biased position to cut off the communication between the fluid passage and the body cavity, while when the body cavity internal pressure reaches a predetermined level, the sub piston is moved against the compression spring to bring the body cavity into communication with the fluid passage through the primary chamber.
Thus, according to the ball valve just described above, in both the case where the fluid pressure is higher than the internal pressure o~ the body cavlty and the case where the body cavity internal pressure is higher than the fluid pressure but is within A
.
8~
1 a predetermined allowable range, the communication between the fluid passage and the body cavity is cut off, so that a self-compressing force is exerted on the seat retainer to seal the fluid on both primary and secondary sides. On the other hand, in the event the internal pressure of the body cavity increases to an abnormal extent beyond the predetermined allowable range, the sub and main pistons are operated by such pressure applied to the control chamber, allowing the body cavity to communicate with the fluid passage through the primary chamber in the main cylinder~ so that the body cavity internal pressure is released to the fluid passage to suppres.s the abnormal pressure increase.
According to another aspect of the present invention there is provided a ball valve having a housing; a movable ball for opening and closing a fluid passage within the housing; an annular seat retainer fitted in the housing around the fluid passage in opposed relation to the ball; an annular valve seat mounted on the seat retainer in opposed relation to the ball; a stepped portion formed in the outer peripheral portion of the seat retainer where the seàt retainer is in sliding contact with the inner wall surface of the A : `
1 housing, the stepped portion extending from a surface portion having a diameter larger than a seal point diameter of the valve seat to a surface portion having a diameter smaller than the seal point diameter, the S larger-and smaller-diameter surface portions f;orming a sealed chamber in conjunction with the housing inner wall surface which is in sliding contact therewith, the sealed chamber serving as an O-ring slot; and an O-ring fitted in the O-ring slot, characterized in that a change-over valve having a small-diameter portion and a large-diameter portion is used, the small-diameter portion having a communication port which communicates wi.h a body cavity; a piston rod is provided axially movably within the cylinder; a body cavity communication chamber which communicates with the body cavity through the communication port of the small-diameter portion is formed by the piston rod, the piston rod having a communication port formed in the peripheral surface thereof; further, within the large-diameter portion of the cylinder, a first large-diameter piston is formed at an end of the piston rod on the side opposite to the body cavity communication chamber to define a control chamber which communicates with the body cavity, and a second large-diameter piston is formed in a position A
1 adjacent to the first large-diameter piston to define a fluid passage communication chamber between it and the first large-diameter piston; a communication passage for communication from the fluid passage communication chamber to the comm~nication port of the piston rod is formed within the piston rod; a atmosphere chamber partitioned from the fluid passage communication chamber by the second large-diameter piston is formed within the large-diameter portion of the cylinder; and a compression spring for urging the piston rod toward the control chamber is mounted within the cylinder, when the internal pressure of the body cavity is within an allowable range, the piston rod is held in the biased position to disconnect the communication port of the piston rod from the communication port of the small-diameter portion, while when the internal pressure of the body c~vity reaches a predetermined level, the piston rod is moved toward the body cavity communication chamber against the compression spring by virtue of a differential pressuee between the control chamber and the body c~avity communication chamber to connect both communication ports with each other to thereby communicate the body cavity with the fluid passage.
Thus, accordingly to this ball valve, when the .
l internal pressure of the body cavity is within a predetermined allowable range, the fluid passage and the body cavity are out of communication, so a self-compressing force is exerted on the seat retainer to seal the fluid on both primary and secondary si~es, while when the body cavity internal pressure increases to an abnormal extent beyond the predetermined allowable range, the piston rod in the change-over valve is moved by the foregoing pressu~e applied to the control chamber to-let the fluid passage communication chamber communicate through the communication passage to the communication port of the small-diameter portion which communicates with the body cavity, so that the internal pressure of the body cavity is released to the fluid passage to suppress the abnormal pressure increase.
Further, the change-over valve responds to only the internal pressure of the body cavity independently of the fluid pressure.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Embodiments of the present invention will be described in detail hereinunder with reference to the accompanying drawings.
1 Referrin~ first to Fig. 4~ ~here is illustrated in section a principal portion o~ a hall valve according to an embodiment of the present invention, in which an annular sea~ retainer 4 is fitted in a housing 1 around a fluid passage 3, and between the seat retainer 4 and an outer ring 5 fixed thereto is mounted an annular valve seat 6 in opposed rel~tion to a ball 2., The outer ring 5 is urged from its back toward the ball by means of compression springs 7 which are mounted on the inner wall surface of the housing at predetermined intervals in the circumferential direction, whereby the annular valve seal is brought into abutment with the ball surface to seal between the seat retainer and the ballO
In the outer peripheral surface portion of the seat retainer 4 where the seat retainer is in sliding contact with the inner wall surface of the housing 1, there is formed a stepped portion which comprises a surface having a diameter D2 larger than a seal point diameter Dl of:the valve seat 6 and a surface having a diameter D3 smaller than the seal point diameter D
The larger- and smaller-diameter surfaces which constitute the stepped portion from a sealed chamber in conjunction with the housing inner wall surface which is .
:~ - 14 -.
.~a..~ o~
1 in sliding contact therewith. The sealed chamber serves as an O-ring slot 11~ in which is fitted an 0-ring 8 to seal between the housing 1 and the seat retainer 4.
The ball valve is further provided with a change-over valve 31. The change-over valve 31 has a main`cylinder 32 and a sub cylinder 33, and within these cylinders are disposed axially movable main piston 35 and sub piston 36 which are integrally formed at both ends of a rod 34~ The main piston 35 partitions the interior of the main cylinder into a primary chamber 40 which communicates with the fluid passage 3 through a conduit 44 and a secondary chamber 42 which communicate.s with a body cavity 10 through conduits 46 and 45. The sub piston 36 partitions the interior of the sub cylinder into a communication chamber 41 which communicates with the.primary chamber through a port 37 and a control chamber 43 which communicates with the body cavity through conduits 48 and 45.
Further, the main cylinder is connected to a conduit 47 which brings the primary chamber or secondary chamber into communication with the body cavity through conduit ~S according to ~the operation of the main pistonO When the fluid pressure is higher than the internal pressure oE the body cavity and when the body : -- 15 --1 cavity internal pressure is within a predetermined allowable range, the main piston is positioned on the right side in the figure to cut off communication between the primary and secondary chambers, namely, S between the fluid passage and the body cavity,~in the main cylinderO
In the sub cylinder, the sub piston 36 is urged toward the control chamber by means of a compression spring 38. The strength of the compression spring is set so that the sub piston can operate or move to the left in the figure when the body cavity internal pressure P3 exceeds the predetermined allowable range and reaches a predetermined level P3'. A sub piston diameter d2 in the sub cylinder is selected so that it lS is larger than a main piston diameter dl in the main cylinder. Therefore,.when the body cavity internal pressure reaches the predetermined level P3', the sub piston moves to the left in the figure against the compression spring and sctuates the main plston in the 20 . primary chamber, so that the conduit 44 which conducts to the~fluid psssage comes into communicstion with the conduit 47~ ;
Thus, according to the above ball valve, when .
the prlmary side flu1d prsssure Pl is higher than the .
- 16 - :
: ~
.
1 body cavity internal pressure P3, the main piston 34 of the main cylinder is positioned on the right side in FigO 4 and the body cavity is disconnected from the fluid passagep so that, as previously noted, a self-compressing force of 4(D2 ~ Dl)(Pl P3) acts on the bac~ of the seat retainer and the valve seat is thereby brought into close contact with the ball to seal the primary side fluido Also when the internal pressure P3 oF the body cavity 10 i5 higher than the fluid pressure P2 in the secondary side fluid passage 3 but is within the predetermined allowable range, the sub piston is still held in the right-hand position by the compression spring 38 as shown in Fig. 4 so that a self-compression force of~ .
4(Dl - D3)(P3 ; P2) acts on the back of the seat retainer to seal the secondary side fluid~
On the other hand, when the internal pressure of the body cavity 10 increases to an abnormal extent beyond the predetermined ~allowable range and reaches the predetermined level P3', this pressure is applied to the control chamber 43 and so the sub piston moves to the :
1 left against the compression spring 38 as shown in Fig.
5, so that in the primary chamber the conduit 47 comes into communication with the condui~ 44 which conducts to the fluid passage 3~ ~hat is, the body cavity 10 comes into communication with the secondary fluid passage 3, allowing the body cavity internal pressure to be released to the secondary side, and thus the abnormal pressure increase in suppressed.
Since in this way the body cavity is communicated with the secondary side fluid passage to reduce its internal pressure rapidlyO the operation of the cbange-over valve 31 can be stabilized by incorporating a throttle valve 51 with check valve in the conduit 48 as shown in FigO 6~
In the above description, the body cavity is brought into communication with the secondary side fluid passage when its internal pressure exceeds the allowable range and rea~hes the predetermined abnormal level. In this case, however, the body cavity may be communicated with the primary side fluid passageO
: Referring now to Fig. 7~ there is illustrated in section another example of the change-over valve 31 in the ~ball valve described above, in which a ~
communication ohamber S0 whioh~does not communioate with ; - 18 --1 the primary chamber.40 of the main cylinder but communicates s with the atmosphere through a port 49 is formed in place of the communication chamber 41 in the sub cylinde.rO Its operation is just the same as in the s change-over valve previously described except :that the communication chamber 50 is communicated with the atmosphere instead of being made equal in pressure with the primary chamber~
Thus~ according to the ball valve of the above embodiment, in the event of an abnormal increase of the body cavity internal pressure, the body cavity is brought into communication with the fluid passage hy utilizing this pressure in the change~over valve, whereby the abnormal pressure increase in the body cavity can be suppressedO
Another embodiment of the present invention will be described below wi.th reference to Figs. 8 through 11.
Referring to Figu 4, there is illustrated in sect.ion a principal portion of a ball according to another embodiment of the invention~ in which an annular retairer 4 is fitted in a housing 1 around a fluid passage 3, and between the seat retainer 4 and an outer ring 5 fixed thereto is mounted an annular valve seat 6 l in opposed relation,to a ball 2. The outer ring 5 is urged toward the ball from its back by means of compression springs 7 which are mounted on the inner wall surface of the housing at predetermined intervals in the circumferential direction, whereby the a,nnular valve seat is brought into abutment with the ball surface to seal between the seat retainer and the ballO
In the outer peripheral surface portion of the seat retainer 4 where ~he seat retainer is in sliding contact with the inner wall surface of the housing l there is formed a stepped portion which comprises a surface having a diameter D2 larger than a seal point diameter Dl of the valve seat 6 and a surface baving a diameter D3 smaller than the seal point diameter Dl.
lS - These larger- and smaller diameter surfaces which constitute the stepped portion form a sealed çhamber in conjunction with the housing inner wall surface which is in sliding contact therewith. This sealed chamber serves as an O-ring slot l1 in which is mounted on O-20 ring 8 to seal between the housing l and the seat retainer 4O
The ball valve of this embodiment is provided with a change-over valve 31. The change-over valve 31 has a cylinder 34 which comprises a small-diameter : - 20 -:
1 portion 32 having a~diameter dl and a larger-diameter portion 33 having a diameter d2, the small-diameter portion 32 being in communica~ion with a body cavity 10 through a communication port 51 and then through conduits 61 and 62. The cylinder 34 houses th rein a piston rod 35 axially movablyO In the small-diameter portion 32 of the cylinder~ the piston rod has a small-diameter piston 36 whose end face in the small-diameter cylinder portion has the diameter dl~ and a bod~ cavity communication chamber 37 which communicates with the body cavity through the communication port 51 is formed.
In the small-diameter cylinder portion, moreover, the piston rod has an annular communication port 38 formed in the peripheral surface thereof, which communicates with a fluid passage communication chamber ~1 through a communication passage`46 as will be described later.
In the large-diameter portion 33 of the cylinder, the piston 35 has a first large-diameter piston 39 of diameter d2 formed at an end opposite to the foregoing end face of the small-diameter piston, and there is formed a con~rol chamber 43 which is connected to the conduit 62 through a communication port 52, a conduit 64 and a flow control valve 49 and thereby communicated with the body cavity. The flow control 1 valve 49 may be mounted within the cylinder 340 Further, the piston rod has a second large-diameter piston 44 oE diameter d~ in a position ad~acent to the large-diameter piston 39, and between the first and second large-diameter pistons in ~he large-diameter portion of the cylinder is formed an annular fluid passage communication chamber 41 having an inside diameter of d3 which communicates with the fluid passage
BRIEF DESCRIPTION OF THE~DRAWINGS
Fig. 1 is a sectional view of a principal portion of a conventional single seal type ball valve;
Fig. ~ and 3 are sectional views of a principal portion of a conventional double seal type A
*
1 ball valve;
Fig. 4 is a sectional view of a principal portion of a ball valve according to an embodiment of the present invention;
Fig. 5 is a sectional view of a change-over valve used therein, showing operation;
Figs. 6 and 7 are sectional views showing other examples of change-over valves in the ball valve of Fig. 4;
Fig. 8 is a sectional view of a principal portion of a ball valve according to another embodiment of the present invention;
Fig. 9 is a sectional view of a change-over valve used therein, showing operation;
Fig. 10 is a sectional view showing a detailed example of the change-over valve; and Fig. 11 is a sectional view of a principal portion showing another example of a change-over valve in the ball valve of Fig. 8.
Fig. 1 is a sectional~view of a principal portion of a conventional si~ngle seal type ball valve, in which a ball 2 as a valving member is ~nclosed in a housing l so as to be rotatable about~a stem (not shown) to open and close a fluid passage 3 formed within the - 2 _ A ~
1 housing. An annular seat retainer 4 is fitted in the housing so as to surround the fluid passage, and an annular valve seat 6 is mounted opposite to the ball in a position between the seat retainer 4 and an outer ring 5 fi~ed thereto The outer ring 5 is urged from its back toward the ball by means of compression springs 7 at ~redetermined intervals in the circumferential direction, whereby the annular valve seat 6 is brought ` into abutment with the ball surface to provide a seal between the seat retainer and the ball.
In an outer peripheral surface portion of the seat retainer 4 where the seat retainer is in sliding contact with the inner wall surface of the housing there is mounted an O-ring 8 in a position having an outside diameter D2 larger than a seal point diameter Dl of the va~ve seat to seal between the housing and seat retainer. In the ball valve of Fig. 1, moreover, a sealant passage 9 for injecting a sealant from an injector (not shown) to the seal point is open in the vicinity Oe the inside of the valve seat in order to make up for the sealing function temporarily in the event of damage of the seat.
In such single seal type, therefore, when fluid pres~sure is applied to the fluid passage and a 8~
1 primary side fluid pressure Pl is higher than a secondary side fluid pressure P2, a self-compressing force which is proportional to the product of the area of an annular portion whose width corresponds to the difference between the seal point diameter Dl o~ the valve seat 6 and the outside diame~er D2 Of the seat retainer in the position of the O-ring, and a differential pressure between the fluid pressure Pl and the internal pressure P3 of the body cavity, namely:
4(D2 ~ Dl)(Pl P3) is exerted on the seat retainer from the back thereof, so that the valve seat is brought into close contact with the ball. In this way, the priMary side fluid is sealed.
On the other hand, in the event the primary side fluid leaks to the body cavity, causing the internal pressure P3 of the body cavity to rise higher than the secondary side fluid pressure P2, the following force:
4~(D2 ~ Dl)(P3 - P2) is exerted on the seat retainer as a decompressing force for forcing back the seat retainer toward its back side.
Therefore, when this decompressing force becomes larger than the compresslve force of the compression spring 7, ~4 ~{ . .
1 the valve seat moves back from the ball, allowing the internal pressure of the body cavity to be released to the secondary side to prevent an abnormal increase of the internal pressure of the body cavity.
Thus, according to the single seal type, an abnormal increase of the internal pressure of the body cavity can be prevented by making the body cavity communicate with the secondary side. But, the fluid sealing is performed on the primary side alone.
As a sealing method capable of sealing fluid on both primary and secondary sides, there is known a double seal type as shown in Fig. 2. According to this sealing method, a stepped portion is formed in the outer peripheral portion of the seat retainer 4 where the seat retainer is in sliding contact with the inner wall surface of the housing 1, the stepped portion extending from the surface having a larger diameter D2 than the seal point diameter Dl of the valve seat 6 to the surface having a smaller diameter D3 than the seal point diameter Dl. These larger and smaller diameter surfaces form a sealed chamber in conjunction with the inner wall surface of the housing which is in sliding contact therewith. The sealed chamber serves as an O-ring slot 11 in which is fitted an O-ring 8 to seal between the _ 5 _ A
1 housing 1 and the seat retainer 6.
Therefore, on the primary side in normal condition, the primary side fluid pressure Pl is higher than the internal pressure P3 of the body cavity 10, so S that a self-compressing force of:
~ ~ 2 4(D2 ~ Dl)(Pl - P2) is exerted on the back of the seat retainer, thus causing the valve seat 6 to seal the primary side fluid.
On the other hand, in the event the interval pressure of the body cavity increases due to leak of the primary side fluid to the body cavity or due to la temperature rise and the body cavity internal pressure P3 becomes higher than the secondary side fluid pressure P2 in an allowable range, the body cavity internal pressure is conducted to the O-ring slot 11, so that the O-ring 8 is pushed a~ainst the right-hand housing wall in the O-ring slot 11 as shown in Fig. 3 and the body cavity internal pressure acts on as far s the smaller-diameter surface of diameter~D3. As a result~ a self-compressing force of:
4~D2 - D3)(P3 P2) is exerted on the back of the seat retainer 4, thus oausing the valve seat 6 to seal the secondary side fluid. In other words! the leakage of fluid from the ~ -~ 6 -A ` : ~
8~
1 primary to the secondary side is prevented.
Thus, according to such double seal method, the body cavity is closed pressurewise, so particularly in the case where the fluid is non-compressible liquid and, for example, in the event the primary side- liquid leaks to the body cavity in excess of a certain limit, the internal pressure of the body cavity will increase to an abnormal extent and result in damage of the valve.
Such an abnormal pressure increase in the body cavity can be avoided by attaching a relief valve to the body cavity, but this does not apply in the case where the fluid is inflammable. Also in the case of a deficient capacity of the relief valve, regardless of the kind of fluid, the valve will be damaged.
SUMMARY OF THE INVENTION
Accordingly, it lS the object of the present invention to provide a double seal type ball valve in which when the internal pressure of the body cavity becomes higher than a predetermined level, the body cavity is brought into communication with the fluid passage by utilizatlon of this pressure to prevent an abnormal pressure increase in the body cavity.
Accordlng;to one aspect of the present A
1 invention there is provided a ball valve having a housing; a movable ball for opening and closing a fluid passage within the housing; an annular seat retainer fitted in the housing around the fluid passage in opposed relation to the ball; an annular valve.seat mounted on the seat retainer in opposed relation to the ball; a stepped portion formed in the outer peripheral portion of the seat retainer where the seat retainer is in sliding contact with the inner wall surface of the housing, the stepped portion extending from a surface portion having a diameter larger than a seal point diameter of the valve seat to a surface portion having a diameter smaller than the seal point diameter, the larger- and smaller-diameter surface portions forming a sealed chamber In conjunction with the housing inner wall surface which is in sliding contact therewith, the sealed chamber serving as an O-ring slot; and an O-ring fitted in the O~ring slot, characterized in that a change-over valve having a maln cylinder and a sub cylinder is used; a main piston which is axially movable within the main cylinder and a sub piston which is axially movable withln the~sub cylinder are coupled together; and the interior of the main cylinder is partitioned by the main piston into a primary chamber : - 8 -A
1 which communicates with the fluid passage and a secondary chamber which communicates with the body cavity, while the interior of the sub cylinder is partitioned by the sub piston into a communication chamber which communicates with the primary chamber or the atmosphere and a control chamber which communicates with the body cavity, the sub piston being urged toward the control chamber by means of a compression spring in the communication chamber, whereby when the fluid pressure is higher than the internal pressure of the body cavity and the body cavity internal pressure is within an allowable range, the sub piston is held in the above biased position to cut off the communication between the fluid passage and the body cavity, while when the body cavity internal pressure reaches a predetermined level, the sub piston is moved against the compression spring to bring the body cavity into communication with the fluid passage through the primary chamber.
Thus, according to the ball valve just described above, in both the case where the fluid pressure is higher than the internal pressure o~ the body cavlty and the case where the body cavity internal pressure is higher than the fluid pressure but is within A
.
8~
1 a predetermined allowable range, the communication between the fluid passage and the body cavity is cut off, so that a self-compressing force is exerted on the seat retainer to seal the fluid on both primary and secondary sides. On the other hand, in the event the internal pressure of the body cavity increases to an abnormal extent beyond the predetermined allowable range, the sub and main pistons are operated by such pressure applied to the control chamber, allowing the body cavity to communicate with the fluid passage through the primary chamber in the main cylinder~ so that the body cavity internal pressure is released to the fluid passage to suppres.s the abnormal pressure increase.
According to another aspect of the present invention there is provided a ball valve having a housing; a movable ball for opening and closing a fluid passage within the housing; an annular seat retainer fitted in the housing around the fluid passage in opposed relation to the ball; an annular valve seat mounted on the seat retainer in opposed relation to the ball; a stepped portion formed in the outer peripheral portion of the seat retainer where the seàt retainer is in sliding contact with the inner wall surface of the A : `
1 housing, the stepped portion extending from a surface portion having a diameter larger than a seal point diameter of the valve seat to a surface portion having a diameter smaller than the seal point diameter, the S larger-and smaller-diameter surface portions f;orming a sealed chamber in conjunction with the housing inner wall surface which is in sliding contact therewith, the sealed chamber serving as an O-ring slot; and an O-ring fitted in the O-ring slot, characterized in that a change-over valve having a small-diameter portion and a large-diameter portion is used, the small-diameter portion having a communication port which communicates wi.h a body cavity; a piston rod is provided axially movably within the cylinder; a body cavity communication chamber which communicates with the body cavity through the communication port of the small-diameter portion is formed by the piston rod, the piston rod having a communication port formed in the peripheral surface thereof; further, within the large-diameter portion of the cylinder, a first large-diameter piston is formed at an end of the piston rod on the side opposite to the body cavity communication chamber to define a control chamber which communicates with the body cavity, and a second large-diameter piston is formed in a position A
1 adjacent to the first large-diameter piston to define a fluid passage communication chamber between it and the first large-diameter piston; a communication passage for communication from the fluid passage communication chamber to the comm~nication port of the piston rod is formed within the piston rod; a atmosphere chamber partitioned from the fluid passage communication chamber by the second large-diameter piston is formed within the large-diameter portion of the cylinder; and a compression spring for urging the piston rod toward the control chamber is mounted within the cylinder, when the internal pressure of the body cavity is within an allowable range, the piston rod is held in the biased position to disconnect the communication port of the piston rod from the communication port of the small-diameter portion, while when the internal pressure of the body c~vity reaches a predetermined level, the piston rod is moved toward the body cavity communication chamber against the compression spring by virtue of a differential pressuee between the control chamber and the body c~avity communication chamber to connect both communication ports with each other to thereby communicate the body cavity with the fluid passage.
Thus, accordingly to this ball valve, when the .
l internal pressure of the body cavity is within a predetermined allowable range, the fluid passage and the body cavity are out of communication, so a self-compressing force is exerted on the seat retainer to seal the fluid on both primary and secondary si~es, while when the body cavity internal pressure increases to an abnormal extent beyond the predetermined allowable range, the piston rod in the change-over valve is moved by the foregoing pressu~e applied to the control chamber to-let the fluid passage communication chamber communicate through the communication passage to the communication port of the small-diameter portion which communicates with the body cavity, so that the internal pressure of the body cavity is released to the fluid passage to suppress the abnormal pressure increase.
Further, the change-over valve responds to only the internal pressure of the body cavity independently of the fluid pressure.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Embodiments of the present invention will be described in detail hereinunder with reference to the accompanying drawings.
1 Referrin~ first to Fig. 4~ ~here is illustrated in section a principal portion o~ a hall valve according to an embodiment of the present invention, in which an annular sea~ retainer 4 is fitted in a housing 1 around a fluid passage 3, and between the seat retainer 4 and an outer ring 5 fixed thereto is mounted an annular valve seat 6 in opposed rel~tion to a ball 2., The outer ring 5 is urged from its back toward the ball by means of compression springs 7 which are mounted on the inner wall surface of the housing at predetermined intervals in the circumferential direction, whereby the annular valve seal is brought into abutment with the ball surface to seal between the seat retainer and the ballO
In the outer peripheral surface portion of the seat retainer 4 where the seat retainer is in sliding contact with the inner wall surface of the housing 1, there is formed a stepped portion which comprises a surface having a diameter D2 larger than a seal point diameter Dl of:the valve seat 6 and a surface having a diameter D3 smaller than the seal point diameter D
The larger- and smaller-diameter surfaces which constitute the stepped portion from a sealed chamber in conjunction with the housing inner wall surface which is .
:~ - 14 -.
.~a..~ o~
1 in sliding contact therewith. The sealed chamber serves as an O-ring slot 11~ in which is fitted an 0-ring 8 to seal between the housing 1 and the seat retainer 4.
The ball valve is further provided with a change-over valve 31. The change-over valve 31 has a main`cylinder 32 and a sub cylinder 33, and within these cylinders are disposed axially movable main piston 35 and sub piston 36 which are integrally formed at both ends of a rod 34~ The main piston 35 partitions the interior of the main cylinder into a primary chamber 40 which communicates with the fluid passage 3 through a conduit 44 and a secondary chamber 42 which communicate.s with a body cavity 10 through conduits 46 and 45. The sub piston 36 partitions the interior of the sub cylinder into a communication chamber 41 which communicates with the.primary chamber through a port 37 and a control chamber 43 which communicates with the body cavity through conduits 48 and 45.
Further, the main cylinder is connected to a conduit 47 which brings the primary chamber or secondary chamber into communication with the body cavity through conduit ~S according to ~the operation of the main pistonO When the fluid pressure is higher than the internal pressure oE the body cavity and when the body : -- 15 --1 cavity internal pressure is within a predetermined allowable range, the main piston is positioned on the right side in the figure to cut off communication between the primary and secondary chambers, namely, S between the fluid passage and the body cavity,~in the main cylinderO
In the sub cylinder, the sub piston 36 is urged toward the control chamber by means of a compression spring 38. The strength of the compression spring is set so that the sub piston can operate or move to the left in the figure when the body cavity internal pressure P3 exceeds the predetermined allowable range and reaches a predetermined level P3'. A sub piston diameter d2 in the sub cylinder is selected so that it lS is larger than a main piston diameter dl in the main cylinder. Therefore,.when the body cavity internal pressure reaches the predetermined level P3', the sub piston moves to the left in the figure against the compression spring and sctuates the main plston in the 20 . primary chamber, so that the conduit 44 which conducts to the~fluid psssage comes into communicstion with the conduit 47~ ;
Thus, according to the above ball valve, when .
the prlmary side flu1d prsssure Pl is higher than the .
- 16 - :
: ~
.
1 body cavity internal pressure P3, the main piston 34 of the main cylinder is positioned on the right side in FigO 4 and the body cavity is disconnected from the fluid passagep so that, as previously noted, a self-compressing force of 4(D2 ~ Dl)(Pl P3) acts on the bac~ of the seat retainer and the valve seat is thereby brought into close contact with the ball to seal the primary side fluido Also when the internal pressure P3 oF the body cavity 10 i5 higher than the fluid pressure P2 in the secondary side fluid passage 3 but is within the predetermined allowable range, the sub piston is still held in the right-hand position by the compression spring 38 as shown in Fig. 4 so that a self-compression force of~ .
4(Dl - D3)(P3 ; P2) acts on the back of the seat retainer to seal the secondary side fluid~
On the other hand, when the internal pressure of the body cavity 10 increases to an abnormal extent beyond the predetermined ~allowable range and reaches the predetermined level P3', this pressure is applied to the control chamber 43 and so the sub piston moves to the :
1 left against the compression spring 38 as shown in Fig.
5, so that in the primary chamber the conduit 47 comes into communication with the condui~ 44 which conducts to the fluid passage 3~ ~hat is, the body cavity 10 comes into communication with the secondary fluid passage 3, allowing the body cavity internal pressure to be released to the secondary side, and thus the abnormal pressure increase in suppressed.
Since in this way the body cavity is communicated with the secondary side fluid passage to reduce its internal pressure rapidlyO the operation of the cbange-over valve 31 can be stabilized by incorporating a throttle valve 51 with check valve in the conduit 48 as shown in FigO 6~
In the above description, the body cavity is brought into communication with the secondary side fluid passage when its internal pressure exceeds the allowable range and rea~hes the predetermined abnormal level. In this case, however, the body cavity may be communicated with the primary side fluid passageO
: Referring now to Fig. 7~ there is illustrated in section another example of the change-over valve 31 in the ~ball valve described above, in which a ~
communication ohamber S0 whioh~does not communioate with ; - 18 --1 the primary chamber.40 of the main cylinder but communicates s with the atmosphere through a port 49 is formed in place of the communication chamber 41 in the sub cylinde.rO Its operation is just the same as in the s change-over valve previously described except :that the communication chamber 50 is communicated with the atmosphere instead of being made equal in pressure with the primary chamber~
Thus~ according to the ball valve of the above embodiment, in the event of an abnormal increase of the body cavity internal pressure, the body cavity is brought into communication with the fluid passage hy utilizing this pressure in the change~over valve, whereby the abnormal pressure increase in the body cavity can be suppressedO
Another embodiment of the present invention will be described below wi.th reference to Figs. 8 through 11.
Referring to Figu 4, there is illustrated in sect.ion a principal portion of a ball according to another embodiment of the invention~ in which an annular retairer 4 is fitted in a housing 1 around a fluid passage 3, and between the seat retainer 4 and an outer ring 5 fixed thereto is mounted an annular valve seat 6 l in opposed relation,to a ball 2. The outer ring 5 is urged toward the ball from its back by means of compression springs 7 which are mounted on the inner wall surface of the housing at predetermined intervals in the circumferential direction, whereby the a,nnular valve seat is brought into abutment with the ball surface to seal between the seat retainer and the ballO
In the outer peripheral surface portion of the seat retainer 4 where ~he seat retainer is in sliding contact with the inner wall surface of the housing l there is formed a stepped portion which comprises a surface having a diameter D2 larger than a seal point diameter Dl of the valve seat 6 and a surface baving a diameter D3 smaller than the seal point diameter Dl.
lS - These larger- and smaller diameter surfaces which constitute the stepped portion form a sealed çhamber in conjunction with the housing inner wall surface which is in sliding contact therewith. This sealed chamber serves as an O-ring slot l1 in which is mounted on O-20 ring 8 to seal between the housing l and the seat retainer 4O
The ball valve of this embodiment is provided with a change-over valve 31. The change-over valve 31 has a cylinder 34 which comprises a small-diameter : - 20 -:
1 portion 32 having a~diameter dl and a larger-diameter portion 33 having a diameter d2, the small-diameter portion 32 being in communica~ion with a body cavity 10 through a communication port 51 and then through conduits 61 and 62. The cylinder 34 houses th rein a piston rod 35 axially movablyO In the small-diameter portion 32 of the cylinder~ the piston rod has a small-diameter piston 36 whose end face in the small-diameter cylinder portion has the diameter dl~ and a bod~ cavity communication chamber 37 which communicates with the body cavity through the communication port 51 is formed.
In the small-diameter cylinder portion, moreover, the piston rod has an annular communication port 38 formed in the peripheral surface thereof, which communicates with a fluid passage communication chamber ~1 through a communication passage`46 as will be described later.
In the large-diameter portion 33 of the cylinder, the piston 35 has a first large-diameter piston 39 of diameter d2 formed at an end opposite to the foregoing end face of the small-diameter piston, and there is formed a con~rol chamber 43 which is connected to the conduit 62 through a communication port 52, a conduit 64 and a flow control valve 49 and thereby communicated with the body cavity. The flow control 1 valve 49 may be mounted within the cylinder 340 Further, the piston rod has a second large-diameter piston 44 oE diameter d~ in a position ad~acent to the large-diameter piston 39, and between the first and second large-diameter pistons in ~he large-diameter portion of the cylinder is formed an annular fluid passage communication chamber 41 having an inside diameter of d3 which communicates with the fluid passage
3 through a communication port 53 and a conduit 63.
Within the piston rod 35 is formed a communication passage 46 for communication between the fluid passage communication chamber and the communication port 38.
Further, the second large-diameter piston 44 defines and forms an atmosphere chamber 42 of an inside . diameter d3 within the large-diameter portion of the cylinder separately from the control chamber 43~ In the atmosphere chamber 42 which is in communication with the .
atmosphere through a communication port 54, there is mounted a compression spring 47 which urges the second-diameter piston 44 toward the control chamber 43. When the body cavity internal pressure P3 is within the predetermined allowable range, the compression spring 47 holds the`piston rod 35 in the biased rightmost position as shown~in the figure. In this position of the piston ~ 22 -1 rod, the communication port 51 which communieates with the body cavity 10 and the communication port 38 on the position rod are disconnected from each other by the wall of tlle small-diameter cylinder portion to thereby eut off eommunication between the fluid passage:
eommunication chamber 41 and the body cavityO
The strength of the compression spring 47 is selected so that when the body eavity internal pressure P3 exeeeds the predetermined allowable range and reaches the predetermined level P3', the piston rod can be moved toward the body cavity communication chamber 37, namely to the left in the figure~ by virtue of a differential pressure between the pressure applied to the samll-diameter piston 36 and that applied to the large-diameter piston 39. Accordingly, when the internal pressure of the body eavity reaches the predetermined level P3', the piston rod 35 moves to the left against the eompression spring 47 until the eommunication port 38 faees the communieation port 51 in the small-diameter portion 32 of the cylinder, as shown in Fig. 9. ~ In this way, the fluid passage communieation chamber 41 is eommunieated with the eommunieation port Sl through the eommunieatlon passage 46 and then with the body eavity 10 tbrough conduits 61 and 62.
~ 23 -.
Q~
1 In the ball yalve of this embodiment, therefore, the change-over valve responds to only the internal pressure of the body cavity~ More particularly, when the internal pressure P3 of the body cavity is within the predetermined range, the piston rod is biased and held in the rightmost position by the compression spring 46 as shown in Fig. 8, so that a self-compressing force is exerted on the back of the seat retainer to seal fluid~
In the event the internal pressure of the body cavity increases to an abnormal extent beyond the predetermined allowable range and reaches the predetermined level P3', this pressure is applied to the control chamber 43, causing the piston rod to move to lS the le~t against the compression spring 47 as shown in Fig. 9r sO that the fluid passage communication chamber 41 is brought into communication through the passage 46 with the communication port 51 which communicates with the body cavity, thereby allowing the body cavity internal pressure to be released to the fluid passage to suppress the abnormal pressure increase.
Even i the:body cavity comes into communication with the fluid passage in this`way and its internal pressure is thereby reduced, the change-over . ~ - 24 -1 valve 31 continues ~o,operate stably because the control chamber 49 is connected to the conduit 62 through the flow control valve 49 as previously noted.
Fign 10 is a sectional view showing a detailed example of the change-over valve shown in Fig.,~8.
In a change-over valve 101 illustrated in Fig.
10, an inner drum 103 is fitted in an outer drum 102, which inner drum forms a cylinder 106 comprising a small-diameter cylinder portion 104 and a large-diameter cylinder portion 105. This cylinder houses therein a piston rod 107 axially movably. The piston rod 107 is formed with a small-diameter piston 106 having an end face of diameter dl facing the interior of the small- ' diameter cylinder portion. By the small-diameter piston 106 is defined a body cavity communication chamber 108 within the small-diameter cylinder portion. The body cavity communication chamber 108 is connected through a communication port 109 to a conduit 62 which communicates with the body cavity. Further, the piston rod end face is formed with a notch 115 to maintain the communication between the communication port 109 and the body cavity communication chamber 108 even when the piston rod operates upon an abnormal increase of the body cavity internal pressure and comes into close : :
~ ~ 25 -1 contact with the opening end ~f the port 109 located within the cylinder, as will be described later.
Between the outer wall of the small-diameter cylinder portion 104 and ~he outer drum 102 is formed an annular flow control chamber 111 around the body cavit~
communication chamber. The flow control chamber 111 is communicated with the body cavity communication chamber 108 doubly through a communication port 112 and a connection port 113 which are formed in the small-diameter cylinder portion~ As to the flow control chamber, a more de~ailed description will be given later.
In the large-diameter cylinder portion 105, the piston rod 107 has a large-diameter piston 121 formed at an end thereof on the side opposite to the body cavity communication chamber, and a control chamber 122 is defined thereby. Within the piston rod is formed a communication passage 123 which is open to the body cavity communication chamber 108 at one end thereof and open to the control chamber 122 at the other end thereof through a check valve 126, the check valve 126 being supported by a spring support 125 having a communication port 124~ The~ communiaation passage 123 provide communication between~ the hody cavity communlcation ~ ~ 26 -.. :
1 chamber 108 and the~control chamber 1220 The spring support 125 is supported by a cylinder bottom 114 through a shaft 127.
In the inner drum 103 is formed a flow control S passage 131 extending from the control chamber;~22 to the flow control chamber lllo At an end portion of the flow control passage 131 which is open to the flow control chamber 111, there is provided a flow control valve 132. The internal pressure of the control chamber is conducted into the flow control chamber 111 while being regulated by the flow control valve 132. The valve 132 is operated with, for example~ a lock nut 133 which is provided on the outside of the outer drum.
The piston rod is further provided with a second large-diameter piston 141 in a position adjacent to the first large~diameter piston 105c In the large-diameter cylinder portion is formed a fluid passage communication chamber 142 between the first and second large-diameter pistons 121 and 141, the chamber 142 between the first and second~large-diameter pistons 121 and 141~ the chamber 142 being in communication with the fluid passage 3 through communication ports 145 and 146.
Also formed in the piston rod is a communication passage 143 which is open to the fluid 1 passage communication chamber 142 at OnQ end thereof and is communicated at the other end thereof with an annular communication port 144 formed in the peripheral surface of the piston rod in the small-diameter cylinder portion. ~;
Further, the second large-diameter piston 141 dèfines an atmosphere chamber 151 in the large-diameter cylinder portion separately from the control chamber 1220 The atmosphere chamber 151 communicates ~it~ the atmosphere through atmosphere communication ports 152 and 153. Within the atmosphere chamber 151 is mounted a compression spring 154 to bias the second large~diameter piston to move ~he piston rod to its rightmost position as shown in the figure when the body cavity internal pressure P3 is within a predetermined allowable range r thereby disconnecting.the fluid passage communication chamber 142 and the body cavity 10 from each other.
The strength of the compression spring 154 is set so that when the body cavity internal pressure P3 exceeds the predetermined allowable range and reaches a predetermined level P3', the piston rod can be operated, namely, can be~moved to the left in the figure toward the body cavity communication chamber 108. In this way, when the~body cavity int~ernal pressure Feaches the : - 28 - ~
0~
1 predetermined level~P3', the piston rod moved to the left against the compression spring 154, allowing the communication port 144 to face the connection port 113, so that the fluid passage communication port 142 is communicated with the connection port 132 through the communication passage 143 and further with the body cavity 10 through the body cavity communication chamber 108 and the communication port 109. The compression spring 154 may be disposed in any other suitable position then the atmosphere chamber in the cylinder.
~ The change-over valve thus constructed operates in the following manner.
When the internal pressure P3 of the body cavity 10 is within the predetermined allowable range, the piston rod 107 is held resiliently in its rightmost position as shown in Fig. 8, and the body cavity internal pressure conducted from the body cavity communication port 109 into the body cavity communication chamber 108 is partly transmitted to the control chamber 122 through the communication passage 123 formed in the piston rod and the check valve 126 and partly transmitted from~the body cavity communication chamber to the flow control chamber 111 through the communication port 112 and connection port 132. On the .
' ;
1 other hand, ~he fluid ~ressure of the fluid passage is transmitted to the fluid passage communication chamber 142 through the communication port 146 of the outer drum and the communication port 145 of the large-diameter S cylinder portion. In this case, the fluid pressure has no influence on the operation of the piston rod because the fluid passage communication chamber 142 is formed within the piston rod/ nor does the atmosphere chamber affect the operation of the piston rod at allO Thus, when the body cavity internal pressure is within the predetermined allowable range, the body cavity is disconnected from the fluid passage, so a self-compressing force acts on the back of the seat retainer as previously noted, thus causing the valve seat to seal the primary or secondary side fluid.
On the other hand, in the event the internal pressure of the body cavity 10 exceeds to an abnormal extent beyond the predetermined allowable range and reaches the predetermined level P3', a differential pressure between the pressure applied to the first large-diameter piston in the control chamber and that applied to the small-diameter piston in the body cavity communicatlon chamber, na~eLy:
.
: - 30 : ,
Within the piston rod 35 is formed a communication passage 46 for communication between the fluid passage communication chamber and the communication port 38.
Further, the second large-diameter piston 44 defines and forms an atmosphere chamber 42 of an inside . diameter d3 within the large-diameter portion of the cylinder separately from the control chamber 43~ In the atmosphere chamber 42 which is in communication with the .
atmosphere through a communication port 54, there is mounted a compression spring 47 which urges the second-diameter piston 44 toward the control chamber 43. When the body cavity internal pressure P3 is within the predetermined allowable range, the compression spring 47 holds the`piston rod 35 in the biased rightmost position as shown~in the figure. In this position of the piston ~ 22 -1 rod, the communication port 51 which communieates with the body cavity 10 and the communication port 38 on the position rod are disconnected from each other by the wall of tlle small-diameter cylinder portion to thereby eut off eommunication between the fluid passage:
eommunication chamber 41 and the body cavityO
The strength of the compression spring 47 is selected so that when the body eavity internal pressure P3 exeeeds the predetermined allowable range and reaches the predetermined level P3', the piston rod can be moved toward the body cavity communication chamber 37, namely to the left in the figure~ by virtue of a differential pressure between the pressure applied to the samll-diameter piston 36 and that applied to the large-diameter piston 39. Accordingly, when the internal pressure of the body eavity reaches the predetermined level P3', the piston rod 35 moves to the left against the eompression spring 47 until the eommunication port 38 faees the communieation port 51 in the small-diameter portion 32 of the cylinder, as shown in Fig. 9. ~ In this way, the fluid passage communieation chamber 41 is eommunieated with the eommunieation port Sl through the eommunieatlon passage 46 and then with the body eavity 10 tbrough conduits 61 and 62.
~ 23 -.
Q~
1 In the ball yalve of this embodiment, therefore, the change-over valve responds to only the internal pressure of the body cavity~ More particularly, when the internal pressure P3 of the body cavity is within the predetermined range, the piston rod is biased and held in the rightmost position by the compression spring 46 as shown in Fig. 8, so that a self-compressing force is exerted on the back of the seat retainer to seal fluid~
In the event the internal pressure of the body cavity increases to an abnormal extent beyond the predetermined allowable range and reaches the predetermined level P3', this pressure is applied to the control chamber 43, causing the piston rod to move to lS the le~t against the compression spring 47 as shown in Fig. 9r sO that the fluid passage communication chamber 41 is brought into communication through the passage 46 with the communication port 51 which communicates with the body cavity, thereby allowing the body cavity internal pressure to be released to the fluid passage to suppress the abnormal pressure increase.
Even i the:body cavity comes into communication with the fluid passage in this`way and its internal pressure is thereby reduced, the change-over . ~ - 24 -1 valve 31 continues ~o,operate stably because the control chamber 49 is connected to the conduit 62 through the flow control valve 49 as previously noted.
Fign 10 is a sectional view showing a detailed example of the change-over valve shown in Fig.,~8.
In a change-over valve 101 illustrated in Fig.
10, an inner drum 103 is fitted in an outer drum 102, which inner drum forms a cylinder 106 comprising a small-diameter cylinder portion 104 and a large-diameter cylinder portion 105. This cylinder houses therein a piston rod 107 axially movably. The piston rod 107 is formed with a small-diameter piston 106 having an end face of diameter dl facing the interior of the small- ' diameter cylinder portion. By the small-diameter piston 106 is defined a body cavity communication chamber 108 within the small-diameter cylinder portion. The body cavity communication chamber 108 is connected through a communication port 109 to a conduit 62 which communicates with the body cavity. Further, the piston rod end face is formed with a notch 115 to maintain the communication between the communication port 109 and the body cavity communication chamber 108 even when the piston rod operates upon an abnormal increase of the body cavity internal pressure and comes into close : :
~ ~ 25 -1 contact with the opening end ~f the port 109 located within the cylinder, as will be described later.
Between the outer wall of the small-diameter cylinder portion 104 and ~he outer drum 102 is formed an annular flow control chamber 111 around the body cavit~
communication chamber. The flow control chamber 111 is communicated with the body cavity communication chamber 108 doubly through a communication port 112 and a connection port 113 which are formed in the small-diameter cylinder portion~ As to the flow control chamber, a more de~ailed description will be given later.
In the large-diameter cylinder portion 105, the piston rod 107 has a large-diameter piston 121 formed at an end thereof on the side opposite to the body cavity communication chamber, and a control chamber 122 is defined thereby. Within the piston rod is formed a communication passage 123 which is open to the body cavity communication chamber 108 at one end thereof and open to the control chamber 122 at the other end thereof through a check valve 126, the check valve 126 being supported by a spring support 125 having a communication port 124~ The~ communiaation passage 123 provide communication between~ the hody cavity communlcation ~ ~ 26 -.. :
1 chamber 108 and the~control chamber 1220 The spring support 125 is supported by a cylinder bottom 114 through a shaft 127.
In the inner drum 103 is formed a flow control S passage 131 extending from the control chamber;~22 to the flow control chamber lllo At an end portion of the flow control passage 131 which is open to the flow control chamber 111, there is provided a flow control valve 132. The internal pressure of the control chamber is conducted into the flow control chamber 111 while being regulated by the flow control valve 132. The valve 132 is operated with, for example~ a lock nut 133 which is provided on the outside of the outer drum.
The piston rod is further provided with a second large-diameter piston 141 in a position adjacent to the first large~diameter piston 105c In the large-diameter cylinder portion is formed a fluid passage communication chamber 142 between the first and second large-diameter pistons 121 and 141, the chamber 142 between the first and second~large-diameter pistons 121 and 141~ the chamber 142 being in communication with the fluid passage 3 through communication ports 145 and 146.
Also formed in the piston rod is a communication passage 143 which is open to the fluid 1 passage communication chamber 142 at OnQ end thereof and is communicated at the other end thereof with an annular communication port 144 formed in the peripheral surface of the piston rod in the small-diameter cylinder portion. ~;
Further, the second large-diameter piston 141 dèfines an atmosphere chamber 151 in the large-diameter cylinder portion separately from the control chamber 1220 The atmosphere chamber 151 communicates ~it~ the atmosphere through atmosphere communication ports 152 and 153. Within the atmosphere chamber 151 is mounted a compression spring 154 to bias the second large~diameter piston to move ~he piston rod to its rightmost position as shown in the figure when the body cavity internal pressure P3 is within a predetermined allowable range r thereby disconnecting.the fluid passage communication chamber 142 and the body cavity 10 from each other.
The strength of the compression spring 154 is set so that when the body cavity internal pressure P3 exceeds the predetermined allowable range and reaches a predetermined level P3', the piston rod can be operated, namely, can be~moved to the left in the figure toward the body cavity communication chamber 108. In this way, when the~body cavity int~ernal pressure Feaches the : - 28 - ~
0~
1 predetermined level~P3', the piston rod moved to the left against the compression spring 154, allowing the communication port 144 to face the connection port 113, so that the fluid passage communication port 142 is communicated with the connection port 132 through the communication passage 143 and further with the body cavity 10 through the body cavity communication chamber 108 and the communication port 109. The compression spring 154 may be disposed in any other suitable position then the atmosphere chamber in the cylinder.
~ The change-over valve thus constructed operates in the following manner.
When the internal pressure P3 of the body cavity 10 is within the predetermined allowable range, the piston rod 107 is held resiliently in its rightmost position as shown in Fig. 8, and the body cavity internal pressure conducted from the body cavity communication port 109 into the body cavity communication chamber 108 is partly transmitted to the control chamber 122 through the communication passage 123 formed in the piston rod and the check valve 126 and partly transmitted from~the body cavity communication chamber to the flow control chamber 111 through the communication port 112 and connection port 132. On the .
' ;
1 other hand, ~he fluid ~ressure of the fluid passage is transmitted to the fluid passage communication chamber 142 through the communication port 146 of the outer drum and the communication port 145 of the large-diameter S cylinder portion. In this case, the fluid pressure has no influence on the operation of the piston rod because the fluid passage communication chamber 142 is formed within the piston rod/ nor does the atmosphere chamber affect the operation of the piston rod at allO Thus, when the body cavity internal pressure is within the predetermined allowable range, the body cavity is disconnected from the fluid passage, so a self-compressing force acts on the back of the seat retainer as previously noted, thus causing the valve seat to seal the primary or secondary side fluid.
On the other hand, in the event the internal pressure of the body cavity 10 exceeds to an abnormal extent beyond the predetermined allowable range and reaches the predetermined level P3', a differential pressure between the pressure applied to the first large-diameter piston in the control chamber and that applied to the small-diameter piston in the body cavity communicatlon chamber, na~eLy:
.
: - 30 : ,
4(d2 dl~oP'3 overcomes the biasing force of the compression spring 154, so ~hat the piston rod moves to the left in the figure, allowing the communication port 144 o the communication passage in the piston rod to face the connection port 113 of the small-diameter cylinder portion. Consequently, the body cavity is brought into communication with the fluid passage communication chamber and its internal pressure is released to the fluid passage side to suppress the abnormal pressure increase.
When the internal pressure of the body cavity is thus released, the interrlal pressure of the control chamber 122 is prevented by the check valve 126 from reverse-flowing into the body cavity communication chamber through the communication passage 123 in the piston rod. Also, the back flow through the communication passage 131 into the flow control chamber 11 is prevented hy the flow control valve 132~
Therefore, the body cavity internal pressure which has been transmitted into the control chamber is maintained over a certain period of time. That is, the body cavity internal pressure can be~fully released because the 1 piston rod is not immediately returned to its original rightmost position by the compression spring.
Referring now to Fig~ 11, there is illustrated in section a principal portion of another example of a change-over valve in the ball valve of this embodiment, in whicp the same components as ~hose shown in Fig. 10 are indicated by the same re~erence numerals. This change-over valve comprises the components of the change-over valve of Fig. 10 plus some additional members, so only the additional members will be explained below.
In the change-over valve illustrated in Fig.
11, the outer drum 102 extends beyond the control chamber 122, and a gas seal chamber 203 is formed by the outer drum and a cylinder bottom 2020 A shaft 204 which supports the spring support 125 is extended as far as the cylinder bottom 202 and fixed thereto, and a movable piston 201 is mounted on the shaft 204 to partition between the control chamber and the gas seal chamber. The gas seal chamber 203 is charged with gas at an appropriate pressure according to the predetermined pressure level P3~o This change-over valve operates in the following manner~ As the internal pressure o~ the body l cavity increases and is transmitted to the control chamber, the internal pressure of the control chamber increases and at the same time the movable piston moves toward the cylinder bottom, namely, to the right in the figure while increasing the internal pressure of the gas seal chamber to take balance with the internal pressure of the control chamber. Then, when the body cavity internal pressure reaches the predetermined level, it is communicated with the fluid passage communication chamber 142 and released. At this time, the control chamber pressure is also reduced, but the gas seal chamber expands because the gas in the gas seal chamber is a compressible fluid, so that the movable piston moves toward the control chamber in response to the pressure drop in the same chamber, thereby compensating for the said pressure drop. Thus, in addition to the preventlon of the pressure drop by the check valve 126 and that by the flow control valve 132, the pressure drop in the control chamber effectively prevented by the volume-variable gas seal chamber adjacent to the control chamber when the internal pressure of the body cavity is released to the fluid passage, and so the piston rod 107 is prevented from rapidly returning to its initial biased position. Consequently, the operation o~ the :
1 piston rod is stabilized and the internal pressure of the body cavity is fully released.
This change-over valve is effective particularly where the fluid being conveyed is a non-compressible liquid. Becausel in the case of liquid, the pressure or the amount of liquid in the control chamber is reduced relatively rapidly when the internal pressure of the body cavity is released to the fluid passage, but the gas seal chamber expands so the pressure drop is prevented in response to the contraction of the control chamber~
Thus, according to the double seal type ball valve of the invention described above, in the event of an abnormal increase of the internal pressure of the body cavity, the body cavity is brought into communication with the fluid passage by utilization of such pressure in the change-over valve, so it is possible to suppress the abnormal pressure increase in the body cavity.
Moreover, by the provision of the gas seal chamber defined by the movable piston adjacently to the control chamber, the pressure drop in the control chamber at the time of release of the body cavity internal pressure is prevented to ensure an effective release of such internal pressureO
- 3~ -
When the internal pressure of the body cavity is thus released, the interrlal pressure of the control chamber 122 is prevented by the check valve 126 from reverse-flowing into the body cavity communication chamber through the communication passage 123 in the piston rod. Also, the back flow through the communication passage 131 into the flow control chamber 11 is prevented hy the flow control valve 132~
Therefore, the body cavity internal pressure which has been transmitted into the control chamber is maintained over a certain period of time. That is, the body cavity internal pressure can be~fully released because the 1 piston rod is not immediately returned to its original rightmost position by the compression spring.
Referring now to Fig~ 11, there is illustrated in section a principal portion of another example of a change-over valve in the ball valve of this embodiment, in whicp the same components as ~hose shown in Fig. 10 are indicated by the same re~erence numerals. This change-over valve comprises the components of the change-over valve of Fig. 10 plus some additional members, so only the additional members will be explained below.
In the change-over valve illustrated in Fig.
11, the outer drum 102 extends beyond the control chamber 122, and a gas seal chamber 203 is formed by the outer drum and a cylinder bottom 2020 A shaft 204 which supports the spring support 125 is extended as far as the cylinder bottom 202 and fixed thereto, and a movable piston 201 is mounted on the shaft 204 to partition between the control chamber and the gas seal chamber. The gas seal chamber 203 is charged with gas at an appropriate pressure according to the predetermined pressure level P3~o This change-over valve operates in the following manner~ As the internal pressure o~ the body l cavity increases and is transmitted to the control chamber, the internal pressure of the control chamber increases and at the same time the movable piston moves toward the cylinder bottom, namely, to the right in the figure while increasing the internal pressure of the gas seal chamber to take balance with the internal pressure of the control chamber. Then, when the body cavity internal pressure reaches the predetermined level, it is communicated with the fluid passage communication chamber 142 and released. At this time, the control chamber pressure is also reduced, but the gas seal chamber expands because the gas in the gas seal chamber is a compressible fluid, so that the movable piston moves toward the control chamber in response to the pressure drop in the same chamber, thereby compensating for the said pressure drop. Thus, in addition to the preventlon of the pressure drop by the check valve 126 and that by the flow control valve 132, the pressure drop in the control chamber effectively prevented by the volume-variable gas seal chamber adjacent to the control chamber when the internal pressure of the body cavity is released to the fluid passage, and so the piston rod 107 is prevented from rapidly returning to its initial biased position. Consequently, the operation o~ the :
1 piston rod is stabilized and the internal pressure of the body cavity is fully released.
This change-over valve is effective particularly where the fluid being conveyed is a non-compressible liquid. Becausel in the case of liquid, the pressure or the amount of liquid in the control chamber is reduced relatively rapidly when the internal pressure of the body cavity is released to the fluid passage, but the gas seal chamber expands so the pressure drop is prevented in response to the contraction of the control chamber~
Thus, according to the double seal type ball valve of the invention described above, in the event of an abnormal increase of the internal pressure of the body cavity, the body cavity is brought into communication with the fluid passage by utilization of such pressure in the change-over valve, so it is possible to suppress the abnormal pressure increase in the body cavity.
Moreover, by the provision of the gas seal chamber defined by the movable piston adjacently to the control chamber, the pressure drop in the control chamber at the time of release of the body cavity internal pressure is prevented to ensure an effective release of such internal pressureO
- 3~ -
Claims (5)
1. A ball valve having a housing; a movable ball for opening and closing a fluid passage within the housing; an annular seat retainer fitted in the housing around the fluid passage in opposed relation to the ball; an annular valve seat mounted on the seat retainer in opposed relation to the ball; a stepped portion formed in the outer peripheral portion of the seat retainer where the seat retainer is in sliding contact with the inner wall surface of the housing, the stepped portion extending from a surface portion having a diameter larger than a seal point diameter of the valve seat to a surface portion having a diameter smaller than said seal point diameter, said larger- and smaller-diameter surface portions forming a sealed chamber in conjunction with the inner wall of the housing which is in sliding contact therewith, the sealed chamber serving as an O-ring slot; and an O-ring fitted in said O-ring slot, characterized in that:
a change-over valve having a main cylinder and a sub cylinder is used; a main piston which is axially movable within the main cylinder and a sub piston which is axially movable within the sub cylinder are coupled together; and the interior of the main cylinder is partitioned by the main piston into a primary chamber which communicates with the fluid passage and a secondary chamber which communicates with the body cavity, while the interior of the sub cylinder is partitioned by the sub piston into a communication chamber which communicates with the primary chamber or the atmosphere and a control chamber which communicates with the body cavity, the sub piston being biased toward the control chamber by means of a compression spring in the communication chamber, whereby when the fluid pressure is higher than the internal pressure of the body cavity and the body cavity internal pressure is within an allowable range, the sub piston is held in said biased position to cut off the communication between the fluid passage and the body cavity, while when the body cavity internal pressure reaches a predetermined level, the sub piston is moved against the compression spring to bring the body cavity into communication with the fluid passage through said primary chamber.
a change-over valve having a main cylinder and a sub cylinder is used; a main piston which is axially movable within the main cylinder and a sub piston which is axially movable within the sub cylinder are coupled together; and the interior of the main cylinder is partitioned by the main piston into a primary chamber which communicates with the fluid passage and a secondary chamber which communicates with the body cavity, while the interior of the sub cylinder is partitioned by the sub piston into a communication chamber which communicates with the primary chamber or the atmosphere and a control chamber which communicates with the body cavity, the sub piston being biased toward the control chamber by means of a compression spring in the communication chamber, whereby when the fluid pressure is higher than the internal pressure of the body cavity and the body cavity internal pressure is within an allowable range, the sub piston is held in said biased position to cut off the communication between the fluid passage and the body cavity, while when the body cavity internal pressure reaches a predetermined level, the sub piston is moved against the compression spring to bring the body cavity into communication with the fluid passage through said primary chamber.
2. A ball valve having a housing; a movable ball for opening and closing a fluid passage within the housing; an annular seat retainer fitted in the housing around the fluid passage in opposed relation to the ball; an annular valve seat mounted on the seat retainer in opposed relation to the ball; a stepped portion formed in the outer peripheral portion of the seat retainer where the seat retainer is in sliding contact with the inner wall surface of the housing, the stepped portion extending from a surface portion having a diameter larger than a seal point diameter of the valve seat to a surface portion having a diameter smaller than said seal point diameter, said larger- and smaller-diameter surface portions forming a sealed chamber in conjunction with the inner wall of the housing which is in sliding contact therewith, the sealed chamber serving as an O-ring slot; and an O-ring fitted in said O-ring slot, characterized in that:
a change-over valve having a small-diameter portion and a large-diameter portion is used, the small-diameter portion having a communication port which communicates with a body cavity; a piston rod is provided axially movably within the cylinder; a body cavity communication chamber which communicates with the body cavity through said communication port of the small-diameter portion is formed by the piston rod, the piston rod having a communication port formed in the peripheral surface thereof; further, within the larger-diameter portion of the cylinder, a first large-diameter piston is formed at an end of the piston rod an the side opposite to said body cavity communication chamber to define a control chamber which communicates with the body cavity, and a second large-diameter piston; is formed in a position adjacent to said first large-diameter piston to define a fluid passage communication chamber between it and the first large-diameter piston;
a communication passage for communication from said fluid passage communication chamber to said communication port of the piston rod is formed within the piston rod; an atmosphere chamber partitioned from said fluid passage communication chamber by the second large-diameter piston is formed within the large-diameter portion of the cylinder; and a compression spring for biasing the piston rod toward said control chamber is mounted within the cylinder, whereby when the internal pressure of the body cavity is within an allowable range, the piston rod is held in said biased position to disconnect the communication port of the piston rod from the communication port of the small-diameter portion, while when the internal pressure of the body cavity reaches a predetermined level, the piston rod is moved toward said body cavity communication chamber against said compression spring by virtue of a differential pressure between said control chamber and said body cavity communication chamber to connect both said communication ports with each other to thereby communicate the body cavity with the fluid passage.
a change-over valve having a small-diameter portion and a large-diameter portion is used, the small-diameter portion having a communication port which communicates with a body cavity; a piston rod is provided axially movably within the cylinder; a body cavity communication chamber which communicates with the body cavity through said communication port of the small-diameter portion is formed by the piston rod, the piston rod having a communication port formed in the peripheral surface thereof; further, within the larger-diameter portion of the cylinder, a first large-diameter piston is formed at an end of the piston rod an the side opposite to said body cavity communication chamber to define a control chamber which communicates with the body cavity, and a second large-diameter piston; is formed in a position adjacent to said first large-diameter piston to define a fluid passage communication chamber between it and the first large-diameter piston;
a communication passage for communication from said fluid passage communication chamber to said communication port of the piston rod is formed within the piston rod; an atmosphere chamber partitioned from said fluid passage communication chamber by the second large-diameter piston is formed within the large-diameter portion of the cylinder; and a compression spring for biasing the piston rod toward said control chamber is mounted within the cylinder, whereby when the internal pressure of the body cavity is within an allowable range, the piston rod is held in said biased position to disconnect the communication port of the piston rod from the communication port of the small-diameter portion, while when the internal pressure of the body cavity reaches a predetermined level, the piston rod is moved toward said body cavity communication chamber against said compression spring by virtue of a differential pressure between said control chamber and said body cavity communication chamber to connect both said communication ports with each other to thereby communicate the body cavity with the fluid passage.
3. A ball valve as set forth in claim 2, wherein said control chamber is in communication with the body cavity through a flow control valve.
4. A ball valve having a housing; a movable ball for opening and closing a fluid passage within the housing; an annular seat retainer fitted into the housing around the fluid passage in opposed relation to the ball; an annular valve seat mounted on the seat retainer in opposed relation to the ball; a stepped portion formed in the outer peripheral portion of the seat retainer where the seat retainer is in sliding contact with the inner wall surface of the housing, the stepped portion extending from a surface portion having a diameter larger than a seal point diameter of the valve seat to a surface portion having a diameter smaller than said seal point diameter, said larger- and smaller-diameter surface portions forming a sealed chamber in conjunction with the inner wall of the housing which is in sliding contract therewith, the sealed chamber serving as an O-ring slot; and an O-ring fitted in said O-ring slot, characterized in that:
a change-over valve having a small-diameter portion and a large-diameter portion is used, the small-diameter portion having a communication port which communicates with a body cavity; a piston rod is provided axially movably within the cylinder; a body cavity communication chamber which communicates with the body cavity through said communication port of the small-diameter portion is formed by the piston rod, the piston rod having a communication port formed in the peripheral surface thereof, further, within the larger-diameter portion of the cylinder, a first large-diameter piston is formed at an end of the piston rod on the side opposite to said, body cavity communication chamber to define a control chamber which communicates with the body cavity; a gas seal chamber is formed adjacently to said control chamber but separately from said control chamber through said movable piston; and a second large-diameter piston is formed in a position adjacent to said first large diameter piston to define a fluid passage communication chamber between it and the first large-'diameter piston; a communication passage for communication from said fluid passage communication chamber to said communication port of the piston rod is formed within the piston rod; an atmosphere chamber partitioned from said fluid passage communication chamber by the second large-diameter piston is formed within the large-diameter portion of the cylinder; and a compression spring for biasing the piston rod toward said control chamber is mounted within the cylinder, whereby when the internal pressure of the body cavity is within an allowable range, the piston rod is held in said biased position to disconnect the communication port of the piston rod from the communication port of the small-diameter portion, while when the internal pressure of the body cavity reaches a predetermined level, the piston rod is moved toward said body cavity communication chamber against said compression spring by virtue of a differential pressure between said control chamber and said body cavity communication chamber to connect both said communication ports with each other to thereby communicate the body cavity with the fluid passage, and at the same time a pressure drop in said control chamber is compensated for by expansion of said gas seal chamber caused by movement of said movable piston.
a change-over valve having a small-diameter portion and a large-diameter portion is used, the small-diameter portion having a communication port which communicates with a body cavity; a piston rod is provided axially movably within the cylinder; a body cavity communication chamber which communicates with the body cavity through said communication port of the small-diameter portion is formed by the piston rod, the piston rod having a communication port formed in the peripheral surface thereof, further, within the larger-diameter portion of the cylinder, a first large-diameter piston is formed at an end of the piston rod on the side opposite to said, body cavity communication chamber to define a control chamber which communicates with the body cavity; a gas seal chamber is formed adjacently to said control chamber but separately from said control chamber through said movable piston; and a second large-diameter piston is formed in a position adjacent to said first large diameter piston to define a fluid passage communication chamber between it and the first large-'diameter piston; a communication passage for communication from said fluid passage communication chamber to said communication port of the piston rod is formed within the piston rod; an atmosphere chamber partitioned from said fluid passage communication chamber by the second large-diameter piston is formed within the large-diameter portion of the cylinder; and a compression spring for biasing the piston rod toward said control chamber is mounted within the cylinder, whereby when the internal pressure of the body cavity is within an allowable range, the piston rod is held in said biased position to disconnect the communication port of the piston rod from the communication port of the small-diameter portion, while when the internal pressure of the body cavity reaches a predetermined level, the piston rod is moved toward said body cavity communication chamber against said compression spring by virtue of a differential pressure between said control chamber and said body cavity communication chamber to connect both said communication ports with each other to thereby communicate the body cavity with the fluid passage, and at the same time a pressure drop in said control chamber is compensated for by expansion of said gas seal chamber caused by movement of said movable piston.
5. A ball valve as set forth in claim 4, wherein said control chamber is in communication with the body cavity through a flow control valve.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP59-137590 | 1984-07-02 | ||
| JP13759084A JPS6117772A (en) | 1984-07-02 | 1984-07-02 | Ball valve |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1261808A true CA1261808A (en) | 1989-09-26 |
Family
ID=15202261
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000478731A Expired CA1261808A (en) | 1984-07-02 | 1985-04-10 | Ball valve |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPS6117772A (en) |
| CA (1) | CA1261808A (en) |
| FI (1) | FI81661C (en) |
| SU (1) | SU1639437A3 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5432127A (en) * | 1989-06-30 | 1995-07-11 | Texas Instruments Incorporated | Method for making a balanced capacitance lead frame for integrated circuits having a power bus and dummy leads |
| JP2531880Y2 (en) * | 1989-12-13 | 1997-04-09 | 株式会社キッツ | Abnormal pressure absorption device for ball valve |
| RU2740327C1 (en) * | 2020-01-22 | 2021-01-13 | Рустам Фаритович Мамлеев | Pipeline gate |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5022505Y2 (en) * | 1971-03-31 | 1975-07-08 | ||
| JPS49100624A (en) * | 1973-01-29 | 1974-09-24 |
-
1984
- 1984-07-02 JP JP13759084A patent/JPS6117772A/en active Pending
-
1985
- 1985-04-10 CA CA000478731A patent/CA1261808A/en not_active Expired
- 1985-04-12 FI FI851472A patent/FI81661C/en not_active IP Right Cessation
- 1985-05-23 SU SU853895849A patent/SU1639437A3/en active
Also Published As
| Publication number | Publication date |
|---|---|
| FI81661C (en) | 1990-11-12 |
| FI851472L (en) | 1986-01-03 |
| JPS6117772A (en) | 1986-01-25 |
| SU1639437A3 (en) | 1991-03-30 |
| FI81661B (en) | 1990-07-31 |
| FI851472A0 (en) | 1985-04-12 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |