Ball valve

Abstract

The present invention provides a ball valve that can exhibit high sealing performance even for a high-pressure fluid by mounting a ball seat while preventing the ball valve from slipping out of a seat retainer, and be easily replaced without damaging the ball seat.　A seat retainer 4 having a ball seat 5 is arranged in one or both sides of a ball 3 having a through-hole 3a in the body 2. The seat retainer is constituted by combining first and second retainers 31, 32, a ball seat outer diameter surface 21 is mounted in an exposed state in a seat mounting groove 36 at a distal end of the first retainer, an outer diameter surface is held on a front inner circumferential surface 42 of the second retainer, a protrusion 43 of a front inner peripheral surface of the second retainer is locked to the ball seat to prevent the ball seat from slipping forward, a rear inner circumference of the second retainer and an outer circumference of the first retainer are fixed by a fixing part 33, the fixing part is positioned at an outer diameter side from an outer diameter surface of the ball seat, and when the first and second retainers are attached and detached, an inner circumferential surface 41 of the second retainer does not interfere with the outer diameter surface of the ball seat.

Description

Ball valve

[0001] The present invention relates to a ball valve, and more particularly to a ball valve having a structure in which a ball seat is attached to a body via a seat retainer.

[0002] A known example of this type of ball valve is the trunnion ball valve. In a trunnion ball valve, a ball seat, which serves as the valve seat, is attached to the body while being held by a seat retainer. The seat retainer is resilient due to the elastic force of a spring, and the ball seat is pressed against the ball, sealing the fluid. A trunnion ball valve with this type of structure can exhibit high sealing performance and is particularly suitable for high-pressure fluids.

[0003] In a trunnion-type ball valve in which the ball seat is attached to the seat retainer as described above, there is a possibility that the ball seat may fly out or become detached from the seat retainer due to a pressure difference caused by a high-pressure fluid, etc. To prevent this, for example, Patent Document 1 discloses a ball valve. In this ball valve, a seat with a locking portion that protrudes radially outward is fitted to the tip of a seat holder (seat retainer). The seat is clamped and fixed to the tip of the seat holder with a seat retaining ring that is screwed to the seat holder. The locking portion formed on the seat retaining ring engages with the locking portion of the seat, preventing the seat from coming off.

[0004] Generally, ball seats in ball valves are wear parts, and ball seats in high-pressure trunnion valves made of resin are particularly susceptible to wear. For this reason, ball seats may need to be replaced periodically. In such cases, replacing the entire seat holder to which the ball seat is attached would be wasteful, so it is desirable to replace only the ball seat. For example, in the case of Patent Document 1, the seat can be replaced by removing the seat retainer by removing the seat retainer ring from the seat retainer.

[0005] Japanese Utility Model Publication No. 58-48441

[0006] However, in the ball valve of Patent Document 1, when the seat with the locking portion protruding radially is fitted into the seat holder and the male thread formed on the seat holder is screwed into the female thread of the seat retainer ring to secure them, the inner diameter of the rear end of the seat holder is set to be approximately equal to the outer diameter of the locking portion of the seat. Because of this structure, when attaching or detaching the seat retainer ring to the seat holder, the female thread is likely to interfere with the seat, centered on the locking portion.

[0007] As a result, when attaching or detaching the seat holder and the seat retaining ring, the seat retaining ring may damage the ball seat, and even if the ball seat is replaced with a new one, it may not be able to provide sufficient sealing performance. In particular, if the ball seat is made of a resin material, the ball seat is more likely to be damaged.

[0008] In addition, as mentioned above, in the installation direction (axial direction) of the seat holder and seat retaining ring, the threaded portion formed by the male and female threaded portions and the outer diameter of the seat's engagement portion are aligned in a straight line. Therefore, when attaching or detaching these, the female threaded portion may interfere with the ball seat, causing the seat retaining ring to be installed at an angle relative to the seat holder, or the resistance when threading may be large, making the attachment and detachment work difficult.

[0009] The present invention was developed to solve the above-mentioned problems, and its purpose is to provide a ball valve that can prevent the ball seat from flying out of the seat retainer, can easily attach and detach the ball seat and replace it without damaging it, and has high sealing properties even against high-pressure fluids after attachment.

[0010] In order to achieve the above object, the invention of claim 1 is a ball valve in which a seat retainer having a ball seat is arranged on one or both sides of a ball having a through hole in a body, the seat retainer being composed of a first retainer and a second retainer combined together, and the seat retainer is attached to a seat attachment groove formed on the tip side of the first retainer with the outer diameter surface of the ball seat exposed, the outer diameter surface being held by the front inner peripheral surface of the second retainer, and a protruding portion protruding from the tip inner peripheral surface of the second retainer is engaged with the ball seat to prevent the ball seat from jumping out forward, and the rear inner circumference of the second retainer and the outer circumference of the first retainer are fixed by a fixing portion which is positioned outer diameter side of the outer diameter surface of the ball seat, so that the inner peripheral surface of the second retainer and the outer diameter surface of the ball seat do not interfere with each other when the first retainer and the second retainer are attached or detached.

[0011] The invention of claim 2 is a ball valve in which centering surfaces of the same diameter are provided at the combined position of the outer peripheral surface of the first retainer and the inner peripheral surface of the second retainer, and each centering surface is accurately aligned.

[0012] The invention according to claim 3 is a ball valve in which a gap is provided between the outer diameter rear end of the ball seat and the outer diameter front end of the first retainer, and the gap is exposed to the outer diameter side when the second retainer is removed from the first retainer.

[0013] The invention of claim 4 is a ball valve in which a seat tapered surface that slopes toward the ball is formed on the back side of the ball seat, and a tapered surface is formed on the surface of the seat mounting groove facing this seat tapered surface, and the taper angle of the tapered surface is made larger than the taper angle of the seat tapered surface, so that the ball seat is mounted in the seat mounting groove in a wedge shape and the two form a linear seal within the seat mounting groove.

[0014] The invention of claim 5 is a ball valve in which the outer end of the seat tapered surface abuts halfway against the forward inner surface of the second retainer, and the abutment surface where the tip end surface of the first retainer abuts against the step surface between the fixed portion and the outer diameter surface extends toward the inner diameter side, forming a gap between the seat tapered surface and the abutment surface.

[0015] The invention according to claim 6 is a ball valve in which the fixed portion is fixed by threaded engagement between the female thread of the second retainer and the male thread of the first retainer.

[0016] According to the invention of claim 1, the ball seat is installed in the seat installation groove of the first retainer with its outer diameter surface exposed, and this outer diameter surface is held by the front inner circumferential surface of the second retainer, and a protrusion on the front inner circumferential surface of the second retainer engages with the ball seat to prevent the ball seat from protruding forward, so the ball seat can be installed while preventing it from protruding or coming off the seat retainer, and this ball seat installation structure using the seat retainer maintains high sealing performance even against high-pressure fluids. Moreover, the rear inner periphery of the second retainer is fixed to the outer periphery of the first retainer with a fixing part, and this fixing part is located outer diameter than the outer diameter of the ball seat, so that the inner periphery of the second retainer and the outer diameter surface of the ball seat do not interfere with each other when the first retainer and the second retainer are attached or detached. Therefore, the ball seat can be easily attached, detached, and replaced without damaging the ball seat when attached, and after attachment, high sealing performance can be achieved even against high-pressure fluids.

[0017] According to the invention of claim 2, the outer peripheral surface of the first retainer and the inner peripheral surface of the second retainer are provided with centering surfaces of the same diameter at the mating position of the respective retainers, and accurate centering is achieved by these centering surfaces, so that the rear sides of the first retainer and second retainer are fixed at their fixed positions, and they can be attached while being aligned concentrically at these fixed positions. As a result, the ball seat can be installed between the first retainer and second retainer with the ball seat accurately positioned, and this ball seat can be positioned accurately relative to the ball to ensure sealing.

[0018] According to the invention of claim 3, a gap is provided between the outer diameter side rear end of the ball seat and the outer diameter side front end of the first retainer, and this gap is exposed to the outer diameter side when the second retainer is removed from the first retainer. Therefore, when the second retainer is removed from the first retainer, the outer diameter side rear end of the ball seat, which was located in the gap, is exposed along with the exposure of the outer peripheral surface of the ball seat that was previously held by the second retainer. This makes it possible to easily remove the ball seat from the seat mounting groove of the first retainer through this outer diameter side rear end portion. Furthermore, even if the ball seat is tightly fixed by being wedged into the seat mounting groove, applying force from the exposed portion of the ball seat to the linear contact portion between the ball seat and the first retainer using the principle of leverage allows the ball seat to be easily removed with a light force, resulting in excellent maintainability.

[0019] According to the invention of claim 4, the taper angle of the tapered surface of the seat mounting groove of the first retainer is made larger than the taper angle of the seat tapered surface of the ball seat, and the ball seat is mounted in a wedge-like manner in the seat mounting groove. Therefore, when the ball seat is pressed against the ball or when fluid pressure is applied from the front side, the ball seat is pushed into the seat mounting groove in a wedge-like manner, and a linear seal with a small contact area is formed between the tapered surfaces and the seat tapered surface, which have different inclination angles, thereby improving the pressure at the time of contact and effectively suppressing fluid leakage from between the rear of the ball seat and the seat mounting groove, so-called backside leakage.

[0020] According to the fifth aspect of the present invention, the outer end of the tapered seat surface abuts against the middle of the forward inner peripheral surface of the second retainer, and the abutment surface where the distal end surface of the first retainer abuts extends radially inward relative to the step between the fixed portion of the first and second retainers and the outer diameter surface of the ball seat. This allows the distal end of the tapered seat surface to protrude forward of the distal end surface of the first retainer, thereby forming a predetermined gap between the tapered seat surface and the abutment surface. By positioning the distal end surface of the first retainer and the tapered seat surface in a predetermined positional relationship, a gap of a predetermined size can be formed. When the second retainer is removed from the first retainer, the outer peripheral surface of the ball seat that was previously held by the second retainer is exposed, and a portion of the tapered seat surface of the ball seat that was located in the gap can also be exposed. This allows the ball seat to be easily removed from the seat mounting groove of the first retainer through the gap or the exposed portion. Furthermore, even if the ball seat is tightly fixed by being wedged into the seat mounting groove, by applying force from the exposed part of the ball seat to the linear contact part between the ball seat and the first retainer, the ball seat can be easily removed with a light force using the principle of leverage, making it easy to maintain.

[0021] According to the sixth aspect of the present invention, the fixing portion is secured by a threaded engagement between the female threads of the second retainer and the male threads of the first retainer, and this fixing portion secures the rear inner periphery of the second retainer to the outer periphery of the first retainer. Therefore, the fixing portion is located on the secondary side of the ball seat relative to the valve cavity side, preventing fluid from contacting the fixing portion and improving corrosion resistance. There is no need for a separate fixing member such as a bolt to secure the second retainer to the first retainer, or for this fixing member to be treated to be corrosion-resistant. Compared to fastening with multiple bolts, the second retainer can be easily attached and detached with a single touch by rotating it relative to the first retainer, and an increase in the number of parts can be suppressed.

[0022] It is a central longitudinal cross-sectional view showing the ball valve of the present invention. It is an enlarged cross-sectional view of part A in Figure 1. It is an enlarged schematic view of Figure 2 with a partial omission. It is a schematic separated perspective view of a seat retainer and a ball seat.

[0023] An embodiment of a ball valve according to the present invention will be described in detail below with reference to the drawings. Figure 1 is a central longitudinal cross-sectional view of the ball valve of the present invention, Figure 2 is an enlarged cross-sectional view of part A in Figure 1, and Figure 3 is an enlarged schematic view of Figure 2 with a partial omission.

[0024] In the figure, the ball valve (hereinafter referred to as valve body 1) comprises a body 2, a ball 3, a seat retainer 4, a ball seat 5, a stem 6, and a coil spring 7, and is configured as a trunnion-type ball valve in which a seat retainer 4 having ball seats 5 on both sides of the ball 3 is disposed within the body 2. The valve body 1 of this embodiment is particularly suitable for use with high-pressure fluids of class (nominal pressure) 150 to 2500, more preferably class 150 to 1500, and the preferred bore size is 2 to 24 inches.

[0025] The body 2 has an annular body 10 and caps 11 attached to both sides (upstream and downstream sides) of the annular body 10, which are made of, for example, carbon steel or stainless steel. The annular body 10 and caps 11 are fastened together with bolts and nuts 12 to form the body 2, and a flow path 13 is defined inside the body 2. An attachment recess 14 for attaching the seat retainer 4 is formed on the side of the cap 11 opposite the ball 3.

[0026] A ball 3 is rotatably mounted within the body 2 via a stem 6 consisting of an upper stem 6a and a lower stem 6b, and seat retainers 4 having ball seats 5 are disposed on both the upstream and downstream sides of the ball 3 via mounting recesses 14. The ball 3 is made of stainless steel, for example, and has a through hole 3a that can communicate with the flow path 13.

[0027] The ball seat 5 is formed into an annular shape from a resin material such as PTFE (polytetrafluoroethylene), nylon, or PEEK (polyether ether ketone). On the side of the ball seat 5 that comes into contact with the ball 3, an annular sealing surface 20 with an inclined or rounded cross section that can seal with the outer circumferential surface of the ball 3 is provided. On the outer circumferential side of the ball seat 5, a flat outer diameter surface 21 is formed in an annular shape.

[0028] The back surface of the ball seat 5, i.e., the side where it is attached to the seat retainer 4, is formed with a ring-shaped seat tapered surface 22 that slopes toward the ball 3, in other words, the rear side of the seat tapered surface 22 slopes from the outer diameter side toward the inner diameter side toward the rear.

[0029] 2 to 4, the seat retainer 4 includes two retainer members: a first retainer 31 and a second retainer 32 that functions as a retainer ring, i.e., that mounts the ball seat 5 to the first retainer 31. The first retainer 31 and the second retainer 32 are formed into a generally cylindrical shape from a metal material such as carbon steel or stainless steel. The seat retainer 4 is assembled together by fastening the rear inner periphery of the second retainer 32 to the outer periphery of the first retainer 31 with a fastening portion 33. In this embodiment, the front (leading end) side of the seat retainer 4 is the side facing the ball 3, and the rear (rear end) side of the seat retainer 4 is the end opposite the leading end (leading end).

[0030] The fixing portion 33 is provided on the seat retainer 4 so as to be located on the outer diameter side of the outer diameter surface 21 of the ball seat 5. This fixing portion 33 consists of a female thread 34 formed on the inner periphery of the rear end side of the second retainer 32 and a male thread 35 formed on the outer periphery of the front end of the first retainer 31. The first retainer 31 and the second retainer 32 are fixed together by the threaded connection between the female thread 34 and the male thread 35, and the ball seat 5 is movably mounted between them.

[0031] A recessed seat mounting groove 36, into which the ball seat 5 can be mounted, is formed in an annular shape on the tip side of the first retainer 31 of the seat retainer 4, and a tapered surface 37 is formed in this seat mounting groove 36 on the surface facing the seat tapered surface 22 of the ball seat 5. The taper angle θ1 of this tapered surface 37 relative to the flow path direction is set to be larger than the taper angle θ2 of the seat tapered surface 22 relative to the flow path direction. As a result, when the ball seat 5 is mounted to the seat retainer 4, the ball seat 5 is mounted in a wedge-like shape in the seat mounting groove 36, and at the same time, after mounting, the seat tapered surface 22 and the tapered surface 37 are in annular line contact with each other, thereby forming an annular linear seal portion 38 between the ball seat 5 and the second retainer 32.

[0032] An annular centering surface 40 is provided on the outer peripheral surface of the first retainer 31 at the position where the first retainer 31 and the second retainer 32 are mated, specifically, rearward of the position of the male thread 35, so that the diameter is larger than that of the male thread 35. As described above, both the outer peripheral surface of the tip end of the first retainer 31 and the inner peripheral surface 42 (described later) of the second retainer 32 are shaped to gradually increase or decrease in diameter from the front. This allows all cylindrical surfaces to be machined without having to grip and change the grip of each component during machining, making centering of each cylindrical surface easy. Furthermore, because the centering surface 40 is located at the outermost diameter, it can be visually observed from behind the tip end of the first retainer 31, allowing confirmation that the surface 40 is properly centered. This allows the first retainer 31 and the second retainer 32 to be mated in a precisely centered state, allowing the ball seat 5 to be fixed in a precise position, resulting in particularly good sealing between the ball seat 5 and the ball 3.

[0033] On the inner surface 41 of the second retainer 32, a ring-shaped front inner surface 42 is formed on the front side where the ball seat 5 is attached, and a protrusion 43 for engaging with the ball seat 5 is formed on the tip side of this front inner surface 42 and protrudes toward the inner side.

[0034] At the position on the inner surface of the second retainer 32 where it is combined with the first retainer 31, specifically, rearward of the position of the female thread 34, an alignment surface 44 is provided which has a larger diameter than the female thread 34 and has approximately the same diameter as the alignment surface 40 of the first retainer 31.

[0035] When the female screw 34 and the male screw 35 are screwed together, the centering surface 44 of the second retainer 32 and the centering surface 40 of the first retainer 31, which have approximately the same diameter, come into close contact with each other, and the second retainer 32 and the first retainer 31 are assembled in a state where they are accurately centered at the centering surfaces 44, 40.

[0036] When combining the ball seat 5 and second retainer 32 with the above-described first retainer 31, the first retainer 31 is attached with the seat tapered surface 22 of the ball seat 5 fitted into the seat attachment groove 36 of the first retainer 31, with the outer diameter surface 21 of the ball seat 5 exposed to the outside from the seat attachment groove 36, and in this state, the second retainer 32 is assembled to the first retainer 31. At this time, the ball seat outer diameter surface 21 is held by the front inner circumferential surface 42 of the second retainer 32, and a protruding portion 43 protruding from the tip inner circumferential surface of the second retainer 32 engages with the front side of the ball seat 5 (the side facing the ball 3), preventing the ball seat 5 from jumping out forward.

[0037] After assembly, an appropriate clearance C is provided between the ball seat 5 and the first retainer 31, and the ball seat 5 is movable in the flow path direction via the clearance C. The clearance C may be formed, for example, with a length of about 0.5 to 1.2 mm in the flow path direction depending on the size of the valve.

[0038] In this case, the rear inner periphery of the second retainer 32 and the outer periphery of the first retainer 31 are fixed by a fixing portion 33 consisting of an internal thread 34 and an external thread 35, and this fixing portion 33 is positioned on the outer diameter side of the outer diameter surface 21 of the ball seat 5. This prevents interference between the inner periphery surface 41 of the second retainer 32 and the outer diameter surface 21 of the ball seat 5 when the first retainer 31 and the second retainer 32 are attached or detached.

[0039] After the ball seat 5 is attached to the seat retainer 4, the outer end 22a of the seat tapered surface 22 is arranged to abut against the middle of the forward inner circumferential surface 42 of the second retainer 32. In the second retainer 32, a step surface 50 is provided in a direction approximately perpendicular to the flow path 13 between the fixing portion 33 formed by the female thread 34 and the male thread 35 and the outer diameter surface 21 of the ball seat 5.

[0040] The first retainer 31 has an abutment surface 53 on its tip end surface that abuts against the stepped surface 50, and this abutment surface 53 extends radially inward. Because the abutment surface 53 is radially longer than the stepped surface 50, a gap S is provided between the outer diameter rear end 60 of the ball seat 5 and the outer diameter front end 61 of the first retainer 31 when the ball seat 5 is attached to the first retainer 31 and the second retainer 32. When the second retainer 32 is removed from the first retainer 31, the gap S is exposed to the outer diameter side. In this embodiment, a gap S of a predetermined size is formed in an annular shape in the region between the seat tapered surface 22 and the abutment surface 53.

[0041] Furthermore, because the stepped surface 50 and the abutment surface 53 abut against each other with their smooth surfaces, it is also possible to align the first retainer 31 and the second retainer 32 in a direction along the flow path 13. This, combined with the radial centering achieved by the centering surface 40 described above, allows the assembly of the first retainer 31 and the second retainer 32 to be performed with extremely accurate alignment, so that even though the retainer that holds the ball seat 5 is divided into two, the ball seat 5 can be held accurately and a high level of sealing with the ball 3 can be achieved.

[0042] The outer diameter surface 21 of the ball seat 5 is provided with a single or multiple communication grooves 55 that communicate with the cavity portion 51 provided in the valve body 1. In this embodiment, as shown in Figure 4, three communication grooves 55 are provided at equal intervals on the outer diameter surface 21. When the first retainer 31 and the second retainer 32 are combined, these communication grooves 55 communicate with the gap S, thereby communicating the gap S with the cavity portion 51 in the valve body 1.

[0043] The integrated seat retainer 4 is mounted on the first retainer 31 side in the mounting recess 14 of the cap 11 through the coil spring 7, and is assembled into the valve body 1 in a state where it is biased toward the ball 3 by the elastic force of the coil spring 7. With this configuration, in the valve body 1, the seat retainer 4 is elastically biased by the coil spring 7, and the seal surface 20 of the ball seat 5 mounted on the seat retainer 4 is pressed against the outer peripheral surface of the ball 3, ensuring a seal between the ball seat 5 and the ball 3 and preventing fluid leakage.

[0044] In the above embodiment, the valve body 1 is configured such that the seat retainer 4 having the ball seat 5 is disposed on both sides (first and secondary sides) of the ball 3. However, the valve body 1 may be configured such that the seat retainer 4 having the ball seat 5 is disposed on one side of the ball 3.

[0045] In a configuration in which the seat retainer 4 is constructed by attaching a ball seat 5 between the first retainer 31 and the second retainer 32, the fixing portion 33 may have a structure other than a screw connection using a female thread 34 and a male thread 35. For example, the fixing portion may be provided using an interlocking structure, and the first retainer 31 and the second retainer 32 may be fixed by this interlocking fixing portion.

[0046] The gap S may be provided between the outer diameter rear end 60 of the ball seat 5 and the outer diameter front end 61 of the first retainer 31, and by providing an appropriate combination structure for the ball seat 5 and the first retainer 31, gaps S of various shapes can be provided between the outer diameter rear end 60 of the ball seat 5 and the outer diameter front end 61 of the first retainer 31.

[0047] 2 to 4, instead of the communicating groove 55 provided in the outer diameter surface 21 of the ball seat 5 as described above, pressure equalizing holes 52, indicated by two-dot chain lines, may be provided at a predetermined interval near the outer diameter side of the stepped surface 50 of the second retainer 32. The pressure equalizing holes 52 communicate with the cavity portion 51 provided in the valve body 1. In this case, the abutment surface 53 of the first retainer 31 that abuts against the stepped surface 50 of the second retainer 32 may be provided with a single or multiple groove-like communicating portion 54, indicated by two-dot chain lines, that communicates from the inner diameter side to the outer diameter side of the abutment surface 53. By providing the communicating portion 54 with the gap S described above via the communicating portion 54 when the first retainer 31 and the second retainer 32 are assembled, the pressure equalizing hole 52 of the second retainer 32 can be connected to the gap S described above. This also allows the gap S in the valve body 1 to communicate with the cavity 51 through the communication portion 54 and the pressure equalizing hole 52. Note that in this embodiment, for the sake of convenience, the same drawing shows two structures for communicating the cavity 51 with the gap S (the back surface of the ball seat 5): one with a communication groove 55 (dashed line) and the other with a pressure equalizing hole 52 and a communication portion 54 (chain double-dashed lines), but in practice, only one of these structures may be used.

[0048] In this case, it is possible to easily attach and detach the second retainer 32 relative to the first retainer 31 by inserting an appropriate jig into one of the pressure equalizing holes 52 provided at multiple locations and using the jig to rotate the second retainer 32 relative to the first retainer 31. Even if pressure equalizing holes 52 are not provided in this manner, it is possible to form a non-through jig hole 56 shown in Figure 4 in the tip surface of the second retainer 32 and use this to easily rotate the second retainer 32 with a jig.

[0049] As long as the taper angle θ1 of the tapered surface 37 is greater than the angle θ2 of the seat tapered surface 22, these taper angles θ1 and θ2 can be set as desired. This allows the linear seal portion 38 to be positioned at any radial location depending on the diameter of the valve body 1, the magnitude of fluid pressure, and other factors. In this case, a shorter distance from the center of the flow path 13 to the seal portion 38 is preferable because a greater force acts on the ball seat 5 when pressure is applied thereto, making the ball seat 5 more likely to pop out. Furthermore, the protrusion 43 of the second retainer 32 prevents the ball seat 5 from popping out. To effectively prevent this pop-out, the wider the engagement width of the protrusion 43 over the ball seat 5, the better. However, to avoid interference with the movement of the ball 3, it is preferable for the protrusion 43 to be approximately one-third the radial thickness of the ball seat 5.

[0050] Next, the operation of the valve body 1 in the above embodiment of the present invention will be described. Referring to Figures 1 to 3, the valve body 1 in this embodiment is configured so that the protrusion 43 formed on the second retainer 32 engages with the front side of the ball seat 5 to prevent the ball seat 5 from protruding forward. This allows for the use of a prefabricated ball seat without the need for special processing on the ball seat 5, such as a step for engaging with the second retainer 32. After the ball seat 5 is attached to the seat retainer 4, it is reliably prevented from protruding or slipping out. Therefore, even when high-pressure fluid flows through the valve body 1, the ball seat 5 can be maintained attached to the seat retainer 4, ensuring high sealing performance.

[0051] In this case, when fluid pressure is applied to the flow path 13 side when the valve is open, the fluid will try to flow from the gap S to the cavity portion 51 side. This fluid pressure and the pressure during sealing act on the ball seat 5 in an upward left direction as shown by the arrow in Figures 2 and 3, and this force F acts as vectors in the X and Y directions due to forces Fx and Fy. This is an example of a force applied to the sealing point of the ball seat 5, and fluid pressure is applied to all other parts of the ball seat 5 that come into contact with the fluid.

[0052] As described above, because clearance C is provided between ball seat 5 and first retainer 31, force Fx presses ball seat 5 leftward (toward the rear) relative to first retainer 31. This causes strong pressure contact between seat tapered surface 22 and tapered surface 37 in seal portion 38, forming a linear seal point that prevents fluid from leaking from the seat back surface side toward cavity portion 51.

[0053] At this time, a force Fy is applied from the outer diameter surface 21 of the ball seat 5 in the direction of the forward inner peripheral surface 42 of the second retainer 32, but the outer diameter surface 21 and the forward inner peripheral surface 42 abut by surface contact, and since force does not act locally from the ball seat 5 on the second retainer, there is no risk of the area around the outer diameter surface 21 of the ball seat 5 being scratched or damaged.

[0054] Furthermore, according to this embodiment, the outer diameter surface 21 of the ball seat 5 can be held by the front inner peripheral surface 42 of the second retainer 32 with a uniform peripheral surface that has no steps in the depth direction, so that it can effectively withstand forces in the Fy direction and can also suppress twisting in the upper left direction that is likely to occur in the ball seat 5, which is more advantageous in preventing the ball seat 5 from popping out and allows the ball seat 5 to be positioned more accurately.

[0055] The fixing portion 33 that fixes the rear inner periphery of the second retainer 32 to the inner periphery of the first retainer 31 is located radially outward of the outer periphery 21 of the ball seat 5, preventing interference between the inner periphery 41 of the second retainer 32 and the outer periphery 21 of the ball seat 5 when the first retainer 31 and the second retainer 32 are attached or detached. This eliminates the risk of the second retainer 32 scratching or damaging the area near the outer periphery 21 of the ball seat 5. This allows the ball seat 5 to be formed from a resin material to ensure high sealing performance, and allows the ball seat 5 to be replaced while maintaining this functionality. In this way, it is necessary to replace only the ball seat 5 of the seat retainer 4, and there is no need to replace the first retainer 31 or the second retainer 32. Therefore, the first and second retainers 31, 32 can be reused.

[0056] As described above, the inner surface 41 of the second retainer 32 and the outer diameter surface 21 of the ball seat 5 are positioned at a radial offset, so when the second retainer 32 is screwed into the first retainer 31, its inner surface 41 (female thread 34) comes into contact with the ball seat 5, preventing the second retainer 32 from being installed in an inclined state, and no unnecessary resistance is applied when screwing, resulting in excellent maintainability.

[0057] When the first retainer 31 and the second retainer 32 are fixed together, the centering surface 40 of the first retainer 31 and the centering surface 44 of the second retainer 32 come into close contact, and these centering surfaces 40, 44 absorb any radial play caused by the engagement of the male thread 35 and the female thread 34, preventing radial misalignment and rattle while the first retainer 31 and the second retainer 32 are integrated while being accurately centered. Therefore, the ball seat 5 attached to the seat retainer 4 can be positioned in a centered state with respect to the ball 3, and the accurate contact position between the ball seat 5 and the ball 3 is maintained throughout the operation of the valve body 1 from valve closing to valve opening, providing excellent sealing performance.

[0058] In a ball valve, it is important to accurately determine the contact position between the ball 3 and the ball seat 5 in order to obtain a reliable seal. To achieve this, it is important that the ball seat be held in an accurate position by a seat retainer or the like. Typically, a seat retainer is constructed from a single member, making it easy to form a ball seat retaining portion that will not come loose. In this embodiment, the ball seat 5 is held by two members, the first retainer 31 and the second retainer 32, and positioning the ball seat 5 is usually not easy. In contrast, as described above, in this embodiment, the first retainer 31 and the second retainer 32 can be accurately positioned by the centering surface 40 and the surface contact between the stepped surface 50 and the abutment surface 53, so that the ball seat 5 can also be held in the correct position.

[0059] This is an installation structure for the ball seat 5, in which the ball seat 5 is attached so as to be sandwiched between the first retainer 31 and the second retainer 32. As described above, this ball seat 5 is an off-the-shelf part, and therefore there is no need to process a special shape such as a step. When fluid pressure is applied, there is no risk of the force being concentrated on one part of the ball seat 5, as would be the case if a step or the like were provided. This prevents deformation or damage to the ball seat 5 and maintains sealing properties, and also makes it easy to remove the ball seat 5 from the first retainer 31 and the second retainer 32.

[0060] The tapered seat surface 22 is formed on the back side of the ball seat 5, and the tapered surface 37 is formed in the seat mounting groove 36. The taper angle θ1 of the tapered surface 37 is made larger than the taper angle θ2 of the seat tapered surface 22, and the ball seat 5 is mounted in the seat mounting groove 36 in a wedge shape. This firmly mounts the ball seat 5 to the first retainer 31 by a wedge action, and the ball seat 5 and the first retainer 31 form a linear seal portion 38 in the seat mounting groove 36, which can improve the surface pressure. Moreover, since the sealing pressure of the seal portion 38 improves as the fluid pressure increases, leakage of fluid from the back side of the ball seat 5, or so-called back leakage, can be reliably prevented even for high-pressure fluids.

[0061] The outer end 22 a of the seat tapered surface 22 abuts partway on the forward inner circumferential surface 42 of the second retainer 32, and the abutment surface 53 where the tip end surface of the first retainer 31 abuts extends radially inward relative to the step surface 50 between the fixing portion 33 and the outer diameter surface 21, forming a gap S in the region between the seat tapered surface 22 and the abutment surface 53. This allows the gap S to be shaped to widen toward the outer diameter. By providing the gap S in this manner, the gap S is exposed to the outer diameter side when the second retainer 32 is removed from the first retainer 31. As a result, even if the ball seat 5 is pressed into the seat mounting groove 36 of the first retainer 31 by fluid pressure, the ball seat 5 can be easily removed by removing the second retainer 32 from the first retainer 31 and easily hooking a fingertip or a tool on the exposed portion of the ball seat 5 through the exposed gap S.

[0062] A stepped surface 50 is provided on the second retainer 32, and the gap S is connected to the cavity portion 51 inside the valve body 1. Therefore, even if pressure infiltrates the back side of the ball seat 5 from between the ball seat 5 and the second retainer 32 when the valve is fully open, the pressure in the gap S on the back side of the ball seat 5 can be kept equal to the pressure inside the cavity portion 51, preventing the accumulation of pressure on the back side of the ball seat 5 and preventing the generation of a force in the pushing direction on the ball seat 5 due to the accumulation of this fluid pressure, thereby reliably preventing the ball seat 5 from popping out.

[0063] The fixing portion 33 is fixed by a screw connection between the female thread 34 of the second retainer 32 and the male thread 35 of the first retainer 31. Therefore, by temporarily attaching the ball seat 5 to the second retainer 32 and then attaching the first retainer 31 to the second retainer 32 by a screw connection, the ball seat 5 can be positioned in a predetermined position relative to the seat retainer 4, and the two can be accurately integrated.

[0064] The above describes in detail the embodiments of the present invention, but the present invention is not limited to the description of the above embodiments, and various modifications can be made within the scope of the spirit of the invention described in the claims of the present invention.

[0065] REFERENCE SIGNS LIST 1 valve body 2 body 3 ball 3a through hole 4 seat retainer 5 ball seat 21 outer diameter surface of ball seat 22 seat tapered surface 22a outer end of seat tapered surface 31 first retainer 32 second retainer 33 fixing portion 34 female thread 35 male thread 36 seat mounting groove 37 tapered surface 38 seal portion 40, 44 centering surface 41 inner peripheral surface of second retainer 42 front inner peripheral surface of second retainer 43 protrusion 50 step surface 51 cavity portion 52 pressure equalizing hole 53 abutment surface 54 communicating portion 60 outer diameter side rear end 61 outer diameter side front end S clearance θ1 taper angle of tapered surface θ2 taper angle of seat tapered surface

Claims

1. A ball valve in which a seat retainer having a ball seat is disposed on one or both of a ball having a through hole within a body, the seat retainer being constructed by combining a first retainer and a second retainer, the seat retainer being mounted in a seat mounting groove formed on the tip side of the first retainer with the outer diameter surface of the ball seat exposed, the outer diameter surface being held by the inner peripheral surface at the front of the second retainer, and a protruding portion protruding from the inner peripheral surface at the front of the second retainer engaging with the ball seat to prevent the ball seat from jumping out forward, the rear inner circumference of the second retainer and the outer circumference of the first retainer being fixed by a fixing portion which is positioned on the outer diameter side of the outer diameter surface of the ball seat, so that the inner peripheral surface of the second retainer and the outer diameter surface of the ball seat do not interfere with each other when the first retainer and the second retainer are attached or detached.

2. A ball valve as described in claim 1, in which the outer peripheral surface of the first retainer and the inner peripheral surface of the second retainer are provided with respective centering surfaces of the same diameter at the mating position, and accurate centering is achieved at each centering surface.

3. A ball valve as described in claim 1 or 2, in which a gap is provided between the outer diameter side rear end of the ball seat and the outer diameter side front end of the first retainer, and the gap is exposed to the outer diameter side when the second retainer is removed from the first retainer.

4. A ball valve as described in claim 1 or 2, in which a seat taper surface is formed on the back side of the ball seat which slopes toward the ball, and a taper surface is formed on the surface of the seat mounting groove opposite this seat taper surface, and the taper angle of the taper surface is made larger than the taper angle of the seat taper surface, so that the ball seat is mounted in the seat mounting groove in a wedge shape and the two form a linear seal within the seat mounting groove.

5. A ball valve as described in claim 4, wherein the outer end of the seat tapered surface abuts halfway against the forward inner circumferential surface of the second retainer, and the abutment surface where the tip surface of the first retainer abuts against the step surface between the fixed portion and the outer diameter surface is extended toward the inner diameter side, thereby forming the gap in the area of ​​the seat tapered surface and the abutment surface.

6. A ball valve as set forth in claim 1, wherein said fixed portion is fixed by a threaded connection between the female thread of said second retainer and the male thread of said first retainer.

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