MXPA98000693A - Hemisfer ball valve - Google Patents

Abstract

The present invention relates to a valve for controlling the flow of fluid and having open and closed positions, characterized in that it comprises: a) a box that provides a chamber in its interior and a passage of fluid flow therethrough with portions of inlet and outlet to, and from the chamber adjacent to the lower end of the box, the box also has an opening at its upper end communicating with the chamber; b) a removable bonnet on the box, sealing the opening at the upper end and having a passage extending therethrough from the chamber; c) means securing the bonnet to the box; d) a generally hemispherical plug member that is seated rotationally in the chamber and having a rotation axis aligned with the chamber; the center of the opening in the box, the opening in the box and the plug member are dimensioned in a cooperative manner to allow removal of the plug member therethrough, the plug member having: i) a portion bottom spherical having a passage of anticlinal fluid flow therethrough with inlet and outlet ends, the inlet and outlet ends of the plug member are aligned with the inlet and outlet portions of the flow passage in and out of the chamber in the open position of the valve and displaced from the inlet and outlet portions of the flow passage in the closed position of the valve, the flow passage extends through the axis of rotation, and ii) an upper portion; ) removable valve seats placed in the box inside the chamber and extending around the inlet and outlet portions of the flow passage, the wall of the box chamber has concave annular recesses around the inlet and outlet portions with transverse axes extending perpendicularly to the flow axes of the adjacent end portions of the anticlinal flow passage through the plug and the po Inlet and outlet flows of the flow passage in and out of the chamber, the valve seats are seated in the annular concave recesses and extend outward from the recesses in the chamber, the valve seats include a concave surface in sealing coupling With the surface of the lower portion of the plug member, the valve seats are dimensioned and configured for easy insertion and easy removal from the arcuate annular recesses in the chamber through the opening in the box; the cap member about its axis of rotation between the open and closed positions of the valve, the means for rotating have a portion disposed outwardly of the box and the bonnet and are operatively connected to the upper portion of the ball member through of the passage in the bone

Description

HEMISPHERIC BALL VALVE DESCRIPTION OF THE INVENTION: The present invention relates to ball valves, and more particularly, to ball valves for use with high pressure and / or high temperature fluids. Ball valves have wide application in the control of fluids in various industrial applications. Such valves generally have a spherical ball with a passage therethrough which allows the flow of fluid to pass through the valve when the valve is opened. When the valve is closed by the rotation of the ball, the valve sits around the fluid passage in the box seal against the surface of the ball member to prevent the passage of fluid through the valve. Under less demanding operating conditions, various metal alloys can be selected for the components so that the valve has a long life without the need for frequent replacement of parts. However, valves used in combination with highly corrosive and / or high temperature fluids, such as those found in the power generation and chemical industries, have a relatively short life due to the erosion of the valve components, particularly in the areas around the valve seat and in the flow passages. Eventually this erosion requires the removal of the entire valve from the line and replacement. To facilitate service within the line without needing to remove the valve from its operating position, some valve bodies have been designed with an opening that allows the ball member and the valve seat to be removed. Commonly referred to as an upper inlet ball valve, this type of valve is illustrated in US Patent No. 4,802,652. However, there is a need for ball valves that are not only easy to repair, but also have a long service life without frequent replacement of parts. It is an object of the present invention to provide a novel ball valve in which erosion is reduced. It is also another object to provide a ball valve where the valve seat can be easily removed and replaced. Another object is to provide a valve wherein the valve seat is mov between the valve body and the ball to accommodate dimensional variations and to ensure a good sealing action with the ball. However, another object of the invention is to provide a ball valve that employs a valve seat with novel inserts that act against the ball.

Another object is to provide a ball valve with a highly effective valve bonnet / valve seal. It has been found that the above and mentioned objects can be reached immediately in a valve to control the flow of fluid having opening and closing positions, and that it includes a box that provides a chamber, a remov bonnet in the box, and a seated ball. rotationally in the camera. The box has a fluid passage passage extending therethrough with inlet and outlet portions to and from the chamber adjacent its lower end, and an opening communicating at its upper end with the chamber. The remov bonnet on the box seals the opening at the upper end of the box, and has a passage through it for the camera, and is fixed to the box. The ball has an axis of rotation aligned with the center of the opening in the box, and the opening in the box is dimensioned cooperating with respect to the ball to allow removal of the ball therethrough. The ball includes an upper portion and a spheroidal lower portion having an anticlinal fluid passage with inlet and outlet ends. These ends of the passage in the ball are aligned with the inlet and outlet portions of the fluid passage of the chamber in the open position of the valve and move from the inlet and outlet portions of the passage in the closed position of the valve. The fluid flow path extends through the axis of rotation of the ball. The valve seats are remov seated in the housing within the chamber and extend around the inlet and outlet portions of the fluid passage. The valve seat includes a concave surface in the sealing coupling with the surface of the lower portion of the ball, and have dimensions and configurations to be inserted in the chamber through the opening of the box. Means are provided for rotating the ball about its axis of rotation between the open and closed positions of the valve, and means for rotating having a portion disposed away from the box and the bonnet, and functionally connected to the upper portion of the ball through the step in the bonnet. Preferably the means for rotating includes a valve rod that extends within the passage of the bonnet and connected to one end of the upper portion of the ball. It is desirable that the valve stem be formed separately from, but coupled to, the ball, so that it can move coaxially to obtain maximum sealing around the rod. Preferably the action of the anticlinal fluid passing through the ball has a pair of Arched legs intersecting the axis of rotation of the ball member to form an inverted U-shaped fluid passage through the ball. The valve seat is oriented at an angle of approximately 45 ° to the axis of rotation of the ball. Alternatively, the anticlinal passage through the ball may have an inverted V configuration, and the valve seat at an angle of 45 ° to the axis of rotation of the ball. It is desirable that the valve includes deflectable means guiding the ball toward the valve seats. These deflectable means may comprise a coil spring or at least one elastically deflectable annular member. In a preferred embodiment, the passage in the bonnet is configured to provide a shoulder, and the valve includes an annular seal first disposed around the valve stem and against the shoulder. The valve stem has a collar within the passage in the bonnet and is disposed below and leaning against the annular seal, and a second annular seal is disposed around the rod below the collar. A packing collar is disposed around the valve stem below the second annular seal and on the elastic deflecting means, and the internal pressure at the bottom of the bonnet and the deflectable member guides the rod and packing collar against the second seal and the collar to perform a herraetizing action around the stem inside the bonnet. Preferably, the valve seat has convex surfaces on the generally annular concave surfaces in the box chamber around the inlet and outlet portions of the flow passage. The valve seat may include a slot that extends around the circumference of the body. it provides some elastic deflection on the peripheral portion of the valve seat and pressure in the passageway in the body to guide the concave sealing surface against the surface of the lower portion of the valve member. Generally, the inlet portion of the flow passage extends from an inlet port, and the outlet portion of the flow passage extends from an outlet port. In an alternative mode, the ports are in planes oriented at an angle to each other. Preferably the planes are oriented at an angle of 45 * to the axis of rotation of the ball and 90 ° to each other. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a cross-sectional view of a ball valve of the present invention, with the ball in the valve opening position; Figure 2 is a cross-sectional view of the circular section of figure 1; Figure 3 is an elevation view of the ball of the valve of Figure 1; Figure 4 is a partial sectional view of the ball along line 4-4 of Figure 3; Figure 5 is a highly enlarged elevation view of the partial section of the valve seat of Figure 1; Figure 6 is a cross-sectional view of another embodiment of the valve of the present invention using a flow passage through the ball with a different configuration; Figure 7 is a vertical cross-sectional view of another embodiment of a ball valve with a flow passage wherein the inlet and outlet ports a are regularly oriented. Considering Figure 1, there is illustrated a ball valve according to the present invention, and comprising a valve body 10, a ball 14, a fluid flow passage 15, a bonnet 12, and a valve rod 16. As best seen in Figure 2, the valve body 10 has a chamber 18 and inlet and outlet ports 20, 22 which communicate with the inlet and outlet portions 24, 26 or legs of the flow passage 15 provided by the aligned portions 28. The valve body 10 has an opening 31 at its upper end communicating with the chamber 18, and a collar 30 on the body 10 extending around the opening end 31 thereof. As seen in Figure 1, the bonnet 12 sits on the collar 30 over the opening 31 and is secured to the body 10 by fasteners 32. As illustrated in Figures 3 and 4, the ball 14 has a lower spherical portion 34. through which extends a convexly arched flow passage 36 having the shape of an inverted U. When the valve is in the open position, the ends of the passage 36 are aligned with the inlet and outlet portions 24, 26 of the flow passage 15 in the valve body 10 to allow flow through the valve, as shown. in Figure 1. The valve is closed by rotating the ball 14 90 ° from an open position to seal step 15 when moving the ends of the arched passage 36 of the inlet and outlet portions 24, 26 of step 15. The ball 14 can be rotated by a handle 38 which engages with the valve rod 16. The inverted V-flow passage 36 is basically arranged in the lower spherical portion. 34 of the ball 14, as illustrated in Figures 3 and 4. The configurations and dimensions of the lower spheroidal portion 34 of the ball 14 cooperate with the body opening 31 to allow easy removal through the opening 31. As illustrated in Figure la, the bonnet 12 has a dependent sealing flange 51, which extends into the opening 31 and seals against the valve body 10 to seal the valve chamber 18. As shown in Figure 2, the Valve seats 42, 44 are disposed around the inlet and outlet portions 24, 26 of the passageway 15 on the upstream and downstream sides of the chamber 18. As shown in FIGS. A and 5, the valve seats are improved. 42, 44 have a concave sealing surface 46 which is cooperatively configured with respect to the convex surface of the ball 14. The opposing seating surface 48 is convexly curved and slidably seats in concave recesses 50 around the entry and exit portions 22, 24 of the passageway. 15. The concave sealing surface 46 and the convex seating surface 48 allow the seats 42, 44 to slide and adjust themselves between the concave surfaces 50 of the body 10 and the spheroidal portion 34 of the ball 14. This feature self-adjusting compensates for minimal dimensional differences between the inter-adjusting portions of the valve seats 42 and 44, the valve body 10 and the ball 14. The valve seats 42, 44 also have a slot 52, which extends around of the circumference thereof as illustrated in Figures IA and 5. Slot 52 allows the peripheral portion of seats 42, 44 to deflect under a high pressure forcing the sealing surfaces 46 of the seats 42, 44 against the ball 14.

The removal of the bonnet Ia 2, allows entry from the top, in-line access to both the ball 14 and the annular seats 42, 44 having cooperating dimensions and also configurations to allow insertion and removal through the opening 31 in the valve body 10. This construction allows the ball 14, and the seats 42, 44 to be replaced by simply removing the bonnet 12 from the body 10 as long as the valve remains in place in the operating line where it is installed. The bonnet 12 is removably connected to the collar 30 of the valve body 10 by the brackets 54 and nuts 56, and this connection can be sealed with rings or fittings on or 58, as shown in Figure 6 or with any other seal activated by pressure such as a Graylock seal (not shown). The upper portion 60 of the ball 14 is generally cylindrical and extends within the bonnet 12, and is preferably coupled to a separate valve rod 16 as illustrated in FIGS. 1 and 7, although it may have an integral valve rod 16a as shown in Figure 6. In any embodiment, the rod 16 sits within a cylindrical passage 62 in the bonnet 12. As illustrated in Figure 1, the annular neck seals 64, 66 are provided around the periphery of the collar. valve stem 16 and down a shoulder 68 in step 62. The rod 16 is coupled to the valve member 14 by the coupler 61 having a recess seating the lug 63 on the ball 14 and a bore 65 seating the lower end of the valve. rod to perform a coupling drive effect between them. In the preferred embodiment illustrated in Figure 1, the valve stem 16 has a collar 70 having annular neck seals 64, 66 above and below it. The seals 64, 66 are compressed axially by the guiding force of the Belleville fittings 72, whose force is transmitted upwards through the packing ring 74, the lower seal 66, the collar 70, the upper seal 64, and finally against the shoulder 68. The passage 62 around the rod 16 is sealed by the seal 64 which is being compressed between the shoulder 68 and the collar 70, and also by the seal 66 being compressed between the collar 66 and the packing ring 72. In addition to providing an upward guiding force on the seals 64, 66, the fittings 72 also provide downward guiding force to keep the ball 14 firmly on the seats 42, 44, at all times. When operating, the flow enters the body of the valve 10 through the inlet port 20 and travels horizontally in the inlet portion 24 of the flow passage 15, until it is directed upward at an angle of 45 'by the bending 76 in the inlet portion 24. the fluid continues to flow up through the annular valve seat 42 and into the arcuate flow passage 36 in the ball 14. When the fluid flows past the entry seat 42 in the arcuate flow passage 36, forces the spheroidal portion 34 of the ball member 14, against the exit seat 44, to act as a locking piston. In addition, the fluid flow has an upward force component that increases when the valve is opened so that the force between the ball 14 and the seats 42, 44 is reduced and less torque will be needed to open the valve. When the fluid flows through the ball 14, it is directed downwardly. The fluid flows from the ball 14 through the annular valve seat 44 until it redirects back through the bend 78 in the outlet portion 26 of the passageway 15. and leaves the body 10 as a horizontal flow in the outlet port 22. As illustrated in Figure 6, the passage 36 in the ball 14 can have a pronounced bend in the form of an inverted L or V instead of a U. As will be appreciated, other designs can be used for the annular valve seats 42, 44 to place the seats in the box. Figure 6 illustrates an alternative configuration for the valve seats where rings -O- 80 sit in a recess 82 in the periphery of the seats 42a, 44a to guide the seats 42a, 44a and provide a pressure seal between the seats 42a, 44a and the valve body 10. As best illustrated in Figure 6, the fittings Belleville 72 can be replaced by a helical spring 72a which will guide the ball 14 against the valve seats 42a, 44a. The included angle of the anticlinal passage 36 through the ball 14 can vary from a minimum of about 60 ° to a maximum of about 120 °. However, the included 90 ° angle of the passage 36 illustrated in the drawings represents an optimum shape between the design conditions competent for the transverse area of the passage, the diameter of the ball to locate the seat members below that diameter, and the size of the angle of the passage. For example for a given size of the cross sectional area of the passage 14, the diameter of the ball should increase when the angle of the arcuate passage 14 increases in order to allow the seats to remain around the lower spherical portion 34 of the ball 14 in accordance with the present invention. However, if the included angle of the passage decreases, then the pressure decrease increases through the valve. Thus the 90 ° angle of the passage 36 according to the preferred embodiment represents an optimal selection between those opposing considerations of the design. As illustrated in Figure 7, the inlet and outlet ports 20a, 22a of the body 10a can be in planes that are oriented at an angle to each other. This configuration allows the valve to serve immediately as an elbow for joining tubes (not shown) that are similarly oriented at an angle to each other, which in turn, reduces installation costs by eliminating the need to adjust and perform two welds. The planes where the input and output ports 20a, 22a lie are aligned with the seats 42a, 44a and are also at an angle of 45 ° to the axis of rotation of the ball and at 90 ° to each other. It will be appreciated that various materials can be used for the construction of the valve. More conveniently, the valve member and the seats can be manufactured in a hard, sinking resistant alloy, to resist frictional abrasion and erosion when the ball moves through the seats, when opening and closing the valve , and can be provided with surface coatings resistant to wear by plasma deposit or the like. Thus, it can be seen that the present invention provides a novel ball valve for operating under high pressure conditions, and that it is highly effective and reliable, durable and relatively easy and economical to manufacture, the box is provided with a top opening and ball and the valve seats are designed and configured to cooperate, so that they receive maintenance easily online, without the need to remove the valve body from the operating line where it is installed.

Claims (24)

1. REVINDI CAC IONS 1.- A valve for controlling the flow of fluid and having opening and closing positions, characterized in that it comprises: a) a box that provides a chamber in its interior and a passage of fluid flow through with portions inlet and outlet to, and from the chamber adjacent to the lower end of the box, the box also has an opening at its upper end communicating with the chamber; b) a bonnet removed over the box, sealing the opening at the upper end and having a passage extending therethrough from the chamber; c) means that fix the bonnet to the box; d) a generally hemispherical plug member that is rotatably seated in the chamber and having an axis of rotation aligned with the center of the opening in the box, the opening in the box and the plug member are cooperatively sized to allow removal of the cap member therethrough, the cap member presents: i) a spheroidal lower portion having an anticlinal fluid flow passage therethrough with inlet and outlet ends, the inlet and outlet ends of the cap member are aligned with the inlet and outlet portions of the flow passage in and out of the chamber in the open position of the valve and are offset from the inlet and outlet portions of the flow passage in the closed position of the valve , the passage flow extends through the axis of rotation; and ii) a higher portion; e) removable valve seats placed in the box within the chamber and extending around the inlet and outlet portions of the flow passage, the wall of the box chamber has annular concave recesses around the inlet portions and outlet with transverse axes extending perpendicularly to the flow axes of the adjacent end portions of the anticlinal passage inlet and outlet through the plug and of the inlet and outlet portions of the flow passage in and out of the chamber, the valve seats they are placed in the annular concave recesses and extend outward from the recesses to the chamber, the valve seats include a concave surface in sealing engagement with the surface of the lower portion of the cap member, the valve seats are sized and configured for easy insertion and easy removal from the arched annular recesses in the chamber through the opening in the box; f) means for rotating the cap member about its axis of rotation between the open and closed positions of the valve, the means for rotating have a portion disposed outwardly of the box and the bonnet and are operatively connected to the upper portion of the cap. the ball through the passage in the bonnet.
2. 2. A valve according to claim 1, wherein the anticline portion of the flow passage through the plug has an inverted U-shape and wherein the valve seats are oriented at an angle of 45 * with respect to the axis rotation of the cap.
3. 3. A valve according to claim 1, wherein the anticline part of the flow passage through the stopper has a pair of legs extending at a right angle to each other from the axis of rotation of the plug to form an L-shaped portion of the passage through the stopper, and wherein the seats are oriented at an angle of 45 ° to the axis of rotation of the stopper.
4. 4. A valve according to claim 1, wherein the means for rotating includes a valve rod that extends within the passage of the bonnet and connects at one end to the upper portion of the cap.
5. 5. A valve according to claim 4 wherein the stem of the valve is separated and coupled to the plug.
6. 6. A valve according to claim 4, wherein the valve includes elastically deflectable means that guide the plug toward the valve seats.
7. 7. A valve according to claim 6, wherein the deflectable means comprises a helical spring.
8. 8. A valve according to claim 6, wherein the elastically deflectable means comprises at least one annular member that is elastically deflectable.
9. 9. A valve according to claim 6, wherein the passage in the bonnet is configured to provide a shoulder that extends around it, and wherein the valve includes a first annular seal disposed around the rod and against the valve. The stem has a collar extending around the passage in the bonnet and disposed down and against the annular seal first, and wherein the valve also includes a second annular seal disposed below the collar and a packing collar arranged around the rod below the second annular seal, on the elastically deflectable member, that deflectable means guides the packing collar against the second seal and against the collar.
10. 10. A valve according to claim 1, wherein the valve seats have convex seating surfaces that settle into the annular concave recesses around the inlet and outlet portions of the flow passage in the box.
11. 11. A valve according to claim 1, wherein the valve seats include a groove extending around the circumference thereof and provide means for guiding the concave sealing surface against the surface of the ball.
12. 12. A valve according to claim 1, wherein the inlet portion of the flow passage extends from an inlet port, the outlet portion of the flow passage extends from an outlet port, and the ports of output and input lie in planes oriented between a certain angle.
13. 13. A valve according to claim 12, wherein the planes in which the inlet and outlet ports lie are oriented at an angle of 45 ° to the axis of rotation of the plug and at 90 ° to each other,
14. 14.- A valve for controlling fluid flow and having closed and open positions, comprising a) a box that provides a chamber inside and a passage of fluid flow therethrough with inlet and outlet portions to, and from the adjacent chamber At the lower end of the box, the box also has an opening at its upper end that communicates with the camera; b) a bonnet on the box, sealing the opening at the upper end and having a passage extending therethrough from the chamber, the passage includes a shoulder extending around; c) means that fix the bonnet to the box; d) a generally hemispherical plug member that is rotatably seated in the chamber and having an axis of rotation aligned with the center of the opening in the box, the plug member having: i) a lower spheroidal portion having a the anticlinal fluid flow passage therethrough with inlet and outlet ends, the inlet and outlet ends of the plug member are aligned with the inlet and outlet portions of the flow passage in and from the chamber in the open position of the valve and are displaced from the inlet and outlet portions of the flow passage in the closed position of the valve; and ii) a higher portion; e) a cylindrical valve stem extending within the bonnet passage, operatively connected to one end of the top portion of the plug to rotate the plug about its axis of rotation between the open and closed positions of the valve, the valve stem has a portion disposed outwardly of the box at its other end; f) means for rotating the valve stem; g) elastic deflectable means in the bonnet around the rod; h) a first annular seal disposed around the rod and against the shoulder, the valve rod has a collar extending around inside the passage in the bonnet and disposed below and against the first annular seal; i) a second annular seal disposed below and against the collar; j) a packing collar arranged around the rod below and against the second annular seal, the elastic deflectable means guides the packing collar against the second seal; and) removable valve seats placed in the box within the chamber and extending around the inlet and outlet portions of the flow passage, the wall of the box chamber has annular concave recesses around the inlet portions and output with transverse axes extending perpendicularly to the flow axes of the adjacent end portions of the anticlinal passage inlet and outlet through the plug and of the inlet and outlet portions of the flow passage in and out of the chamber, the valve seats they are placed in the annular concave recesses and extend outward from the recesses to the chamber, the valve seats include a concave surface in sealing engagement with the surface of the lower portion of the cap member, the valve seats are dimensioned and configured for easy insertion and easy removal from arched annular recesses in the chamber through the opening in the box.
15. 15. A valve according to claim 14, wherein the elastically deflectable means comprises at least one annular member that is elastically deflectable.
16. 16. In a ball valve for controlling the flow of fluid and having open and closed positions, the combination comprises: a) a box having a chamber inside and a passage of fluid flow therethrough, with portions of entrance and exit to, and from the chamber, adjacent to the lower end of the box; b) a plug member rotatably seated in the chamber and having a spherical lower portion having an anticlinal fluid flow passage therethrough with inlet and outlet ends, the inlet and outlet ends of the plug member are aligned with the inlet and outlet portions of the flow passage in and out of the chamber in the open position of the valve and are offset from the inlet and outlet portions of the flow passage in the closed position of the valve; c) valve seats placed in the box within the chamber and extending around the inlet and outlet portions of the flow passage, the wall of the box chamber has concave annular recesses around the inlet and outlet portions with transverse axes extending perpendicularly to the flow axes of the adjacent end portions of inlet and outlet of the anticlinal passage through the plug and of the inlet and outlet portions of the flow passage in and out of the flow passage chamber and the convex surface of the valve seats settle into the annular concave recesses and extend outward from the recesses towards the chamber, the valve seats being in sealing engagement with the concave surfaces of the box, and d) means for rotating the cap member about its axis of rotation between the open and closed positions of the valve, the means for rotating have a portion disposed out from the box and the bonnet and are operatively connected to the upper portion of the plug through the passage in the bonnet.
17. 17. A valve according to claim 16, wherein the valve seats include a slot around the circumference thereof and which provides means for guiding the concave sealing surface against the surface of the plug.
18. 18. A valve for controlling the flow of fluid and having open and closed positions, comprising: a) a box that provides a chamber in its interior and a passage of fluid flow through it, with portions of entry and exit to and from the camera, adjacent to the lower end of the box, the box also has an opening at its upper end that communicates with the camera; b) a bonnet in the box sealing the opening at the upper end and having a passage extending through the chamber, the passage includes a shoulder extending around it; c) fixing means of the bonnet to the box; d) a valve member rotatably seated in the chamber having an axis of rotation aligned with the center of the opening in the box, the valve member i) having a lower portion including means for allowing the flow of fluid between the portions inlet and outlet of the flow passage to and from the chamber in the open position of the valve, and means for preventing the passage of fluid between the inlet and outlet portions of the flow passage when the valve is in the closed position; and ii) a higher portion; e) a cylindrical valve stem extending within the bonnet passage, operatively connected to one end of the top portion of the plug to rotate the plug about its axis of rotation between the open and closed positions of the valve, the rod of the valve has a portion disposed away from the box at its other end; f) means for rotating the valve stem; g) elastic deflectable means in the bonnet, around the valve stem; h) a first annular seal arranged around the rod and against the shoulder; i) a collar extending around the valve stem within the passage in the bonnet and disposed below and against the first annular seal; j) a second annular seal disposed below and against the collar; and k) a packing collar arranged around the valve stem and below and against the second annular seal, the elastic deflection means guiding the packing collar against the second seal and thus the collar against the first seal.
19. 19. A valve according to claim 18 wherein the elastic deflectable means comprise at least one annular member that is elastically deflectable.
20. 20. A valve according to claim 18, wherein the valve is integral with the valve member.
21. 21. A valve according to claim 21, wherein the valve stem is a separate element and is coupled to the valve member by an intermediate coupler.
22. 22. A valve according to claim 21, wherein the coupler is movable axially with respect to the rod and the elastically deflectable means also guides the coupling member and thus the valve member down into the interior of the chamber.
23. 23. A valve according to claim 18, wherein the shoulder is adjacent to the upper end of the bonnet.
24. 24. A valve according to claim 18, wherein the valve rod is a separate member and wherein an annular member is included in the passage of the bonnet coupled with the bonnet and a second deflectable means elastically disposed against the bottom surface thereof and resting on the valve member to guide it down into the chamber, the first elastically deflectable member is disposed on the upper surface of the annular member.