Hard sealing lifting rod ball valve

Abstract

The utility model discloses a hard sealing lifting rod ball valve, the surface of a ball body is provided with a circular convex ring structure which is coaxial with a valve seat, the surface of the circular convex ring structure is a ball body sealing surface which abuts against the valve seat, and the ball body sealing surface is an arc surface; a lower joint head is fixed to the bottom of the ball, the side face of the lower joint head is an ellipsoid, the bottom face of the lower joint head is an arc face located on the same spherical face with the sealing face of the ball, and the spherical face and the ball are concentric. According to the utility model, the integral valve seat is matched with the ball body to form hard sealing, so that the problem of leakage of a sealing pair possibly caused by adopting a combined valve seat structure can be avoided; the sealing surface of the ball body and the bottom surface of the joint head at the lower part of the ball body share the same spherical surface with the same radius, so that the center of the matching surface of the valve seat and the ball body is distributed on the center line of a valve runner, and the height of the ball center of the ball body does not change when the ball body moves close to the valve seat; and therefore, the sealing performance of the hard sealing lifting rod ball valve is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of valve equipment, in particular to a hard-sealed rising-stem ball valve. Background Art

[0002] High-temperature hard-seal rising-stem ball valves are often used in molecular sieve dehydration of fluids in the petroleum, natural gas, and chemical industries, and their operating temperatures can reach 250-350°C. Under high-temperature conditions, it is inevitable that fine solid particles of the desiccant will leak out of the drying tower and into the valve. When these hard, fine solid particles are pressed between the valve seat and the ball sealing surface, they will adversely affect the valve's sealing performance, thereby affecting the dehydration performance of the molecular sieve and subsequent performance.

[0003] At present, hard seal rising stem ball valves are mostly used Figure 7 The modular valve seat structure shown in FIG. comprises a metal outer ring 810, a metal inner ring 820, and a metal hollow ring 830 disposed between the valve body 100 and the ball 300. The metal outer ring 810, the metal inner ring 820, and the metal hollow ring 830 all form an interference fit, as does the metal outer ring and the valve body 100. A disadvantage of this modular valve seat structure is that fine particles in the medium can easily damage the sealing pair formed by the ball sealing surface and the metal hollow ring, causing valve leakage. Furthermore, under high-temperature operating conditions, the differential thermal expansion between the metal outer ring, the metal inner ring, the metal hollow ring, and the valve seat hole in the valve body can cause leakage in the sealing pair formed by these components. Utility Model Content

[0004] The technical problem to be solved by the utility model is to provide a hard-sealed rising-stem ball valve capable of improving the sealing performance.

[0005] In order to solve the above technical problems, the technical solution adopted by the utility model is as follows: a hard-sealed rising-stem ball valve, comprising a valve body, a valve seat, a ball, a valve stem and a valve cover. A valve cavity is provided inside the valve body, and upstream and downstream flow channels communicating with the valve cavity are provided at both ends of the valve body respectively. The valve seat is provided at the junction of the valve cavity and the downstream flow channel. A ball sealing surface is provided on the surface of the ball which can abut against the valve seat to form a hard seal. The ball is rotatably provided in the cavity of the valve body, a through-channel is provided in the center of the ball, and the valve cover is detachably connected to the top of the valve body. The upper end of the valve stem is connected to a lifting rod extending out of the valve cover, and the lifting rod drives the valve stem to rise and fall synchronously while driving the ball to rotate. The surface of the sphere is provided with a circular convex ring structure coaxially arranged with the valve seat. The surface of the circular convex ring structure is the sphere sealing surface abutting the valve seat, and the sphere sealing surface is an arc surface; the bottom of the sphere is fixed with a lower joint head, the side surface of the lower joint head is an ellipsoidal surface, and the bottom surface of the lower joint head is an arc surface on the same sphere as the sphere sealing surface, and the spherical surface is concentric with the sphere.

[0006] As an improvement to the above solution: an upper boss is fixed on the top of the sphere, the upper boss is provided with a matching through hole, the lower end of the valve stem is inserted into the matching through hole and forms a circumferential limit fit with the matching through hole.

[0007] As an improvement to the above scheme: a horizontally arranged ball disengagement pin and a ball sealing pin are fixed in the mating through hole, the ball disengagement pin and the ball sealing pin are parallel to each other, the ball disengagement pin is arranged in a position away from the ball sealing surface in the mating through hole, and the ball sealing pin is arranged in a position close to the ball sealing surface in the mating through hole; two inclined surfaces are provided on the circumferential surface of the lower end of the valve stem, which form a sliding fit with the ball disengagement pin and the ball sealing pin respectively, and the two inclined surfaces are parallel to each other; when the valve stem rises with the lifting rod, the inclined surface cooperating with the ball disengagement pin squeezes the ball disengagement pin upward to make the ball translate in the direction away from the valve seat; when the valve stem descends with the lifting rod, the inclined surface cooperating with the ball sealing pin squeezes the ball sealing pin downward to make the ball translate in the direction toward the valve seat.

[0008] As an improvement to the above solution: two limit pins are also threadedly connected to the upper boss, the limit pins are horizontally arranged and one end of the limit pins extends into the matching through hole, and the ends of the two limit pins are respectively abutted against two planes arranged on the circumference of the lower end of the valve stem.

[0009] As an improvement to the above solution: the matching surfaces of the valve seat and the valve body are both conical surfaces, and the valve seat and the valve body form an interference fit through the conical surfaces; the outer diameter of the valve seat gradually decreases from the end close to the sphere toward the end close to the downstream flow channel.

[0010] As an improvement to the above solution: the surface where the valve seat abuts the sphere sealing surface is the valve seat sealing surface, and both the valve seat sealing surface and the sphere sealing surface are formed by hard alloy surfacing, the hard alloy forming the sphere sealing surface has a thermal expansion coefficient that is the same as or similar to that of the sphere, and the hard alloy forming the valve seat sealing surface has a thermal expansion coefficient that is the same as or similar to that of the valve seat; the valve seat is also provided with an elastic groove, which is an annular groove concentric with the valve seat, and the elastic groove is arranged on the inner annular surface of the valve seat.

[0011] As an improvement to the above scheme: two horizontally arranged and coaxially opposed guide pins are fixed on the valve cover, and two guide grooves corresponding to the guide pins are provided on the upper end circumference of the valve stem, and the end heads of the guide pins are inserted into the corresponding guide pins to form a sliding fit; the guide groove is composed of an upper straight groove section, a first spiral groove section, a second spiral groove section and a lower straight groove section connected in sequence, the upper straight groove section and the lower straight groove section extend vertically along the axial direction of the valve stem, and the first spiral groove section and the second spiral groove section extend spirally along the axial direction of the valve stem; the two guide grooves are centrally symmetrical with respect to the central axis of the valve stem; a group of guide curved surfaces matching the guide grooves are provided on both sides of the circumference of the end head of the guide pin, and the guide curved surfaces include a first spiral curved surface and a second spiral curved surface connected to each other, the first spiral curved surface is matched with the side surface of the first spiral groove section, and the second spiral curved surface is matched with the side surface of the second spiral groove section.

[0012] As an improvement to the above scheme: the pitch of the first spiral groove segment and the second spiral groove segment is different; the distance between the two first spiral surfaces in the two groups of guide surfaces on the guide pin shaft is equal to or less than the pitch of the first spiral groove segment, and the distance between the two second spiral surfaces is equal to or less than the pitch of the second spiral groove segment.

[0013] The beneficial effects of the present invention are as follows: the present invention directly adopts an integral valve seat and a ball to form a hard seal, thereby avoiding the problem of leakage of the sealing pair caused by the use of a combined valve seat structure in the prior art; the present invention sets the spherical sealing surface and the bottom surface of the lower joint head of the sphere to a co-spherical relationship with the same radius, so that the center of the valve seat and the sphere matching surface is distributed on the center line of the valve flow channel, the height of the sphere center will not change during the movement of the sphere close to the valve seat, and the sealing cooperation between the sphere and the valve seat is more accurate and stable, thereby effectively improving the sealing cooperation effect between the sphere and the valve seat, thereby improving the sealing performance of the hard-seal rising stem ball valve. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a cross-sectional view of the utility model;

[0015] Figure 2 This is a cross-sectional view of the matching structure of the ball and the valve seat in the utility model;

[0016] Figure 3 It is a top axonometric view of the sphere in the present invention;

[0017] Figure 4 This is a bottom-up axonometric drawing of the sphere in the present invention;

[0018] Figure 5 This is an axonometric view of the valve stem in the present utility model;

[0019] Figure 6 This is an axonometric drawing of the guide pin shaft in the present utility model;

[0020] Figure 7 It is a cross-sectional view of the matching structure of the ball and the valve seat in the prior art.

[0021] Marked in the figure: 100-valve body, 110-upstream flow channel, 120-downstream flow channel, 200-valve seat, 210-valve seat sealing surface, 220-elastic groove, 300-sphere, 310-sphere sealing surface, 320-lower joint head, 330-upper boss, 340-matching through hole, 350-sphere disengagement pin, 360-sphere sealing pin, 370-limit pin, 400-valve stem, 410-inclined surface, 420-guide groove, 421-upper straight groove section, 422-first spiral groove section, 423-second spiral groove section, 424-lower straight groove section, 500-valve cover, 600-lifting rod, 700-guide pin, 710-first spiral surface, 720-second spiral surface, 810-metal outer ring, 820-metal inner ring, 830-metal hollow ring. DETAILED DESCRIPTION

[0022] In order to facilitate understanding of the present invention, the present invention will be further described below with reference to the accompanying drawings.

[0023] In the description of the present invention, it should be noted that the terms "front", "rear", "left", "right", "up", "down", "inside", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of description. They do not indicate or imply that the device or component referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they cannot be understood as limitations on the present invention.

[0024] like Figure 1As shown, the hard-seal rising-stem ball valve disclosed in the present invention includes a valve body 100, a valve seat 200, a ball 300, a valve stem 400, a valve cover 500, and a lifting rod 600. The interior of the valve body 100 defines a valve cavity, which communicates with an upstream flow channel 110 and a downstream flow channel 120 disposed at either end of the valve body 100 for medium transport. The valve seat 200 is an annular structure coaxially arranged with the flow channel of the valve body 100. In the present invention, only one valve seat 200 is used, located at the junction of the valve cavity and the downstream flow channel 120. The ball 300 is movably mounted within the valve cavity of the valve body 100. A through-channel is defined at the center of the ball 300. The ball 300's rotation changes the direction of the through-channel. When the ball 300 rotates until the through-channel aligns with the flow path of the valve body 100, the valve is fully open. When the ball 300 rotates until the through-channel is completely offset from the flow path of the valve body 100, the valve is fully closed. A ball sealing surface 310 is defined on the surface of the ball 300, which abuts against the valve seat sealing surface 210 of the valve seat 200 to form a hard seal. The valve cover 500 is detachably mounted on the top of the valve body 100 by means of bolts or other fasteners; the lower end of the valve stem 400 is connected to the ball 300, and the upper end of the valve stem 400 is connected to the lifting rod 600 extending to the outside of the valve cover 500; the lifting rod 600 can move vertically up and down, and during the process of vertical lifting of the lifting rod 600, the valve stem 400 will be driven to rise and fall together, and the valve stem 400 will drive the ball 300 to rotate during the lifting process, thereby realizing the opening or closing of the valve.

[0025] like Figures 1 to 3As shown, to enhance the sealing effect between the ball 300 and the valve seat 200, the present invention utilizes a monolithic valve seat 200. The structure of the ball 300 is also improved, with a lower joint head 320 provided at the bottom of the ball 300. A circular convex ring structure is also provided on the surface of the ball 300. The surface of the circular convex ring structure serves as the ball sealing surface 310, which is an arc-shaped surface. When the ball 300 and the valve seat 200 are in contact, the circular convex ring structure and the valve seat 200 are coaxially aligned. Because the ball sealing surface 310 is provided on the circular convex ring structure protruding from the surface of the ball 300, the ball 300 may press against or release from the valve seat 200 during rotation. The side surface of the lower joint head 320 is an ellipsoidal surface. A limiting protrusion is provided at the bottom of the valve cavity in the valve body 100 where it mates with the lower joint head 320. This limiting protrusion forms a vertical limiting fit with the side surface of the lower joint head 320. The bottom surface of the lower joint head 320 is an arc surface that is on the same sphere as the ball sealing surface 310. This spherical surface is concentric with the ball 300, that is, the ball sealing surface 310 and the bottom arc surface of the lower joint head 320 have the same radius. Due to the above structure, the height of the center of the ball sealing surface 310 of the ball 300 does not change during the process of pressing or releasing the ball 300 from the valve seat 200. Therefore, the ball 300 can be accurately aligned when it abuts the valve seat 200 to form a sealing fit, and misalignment will not occur, which can effectively improve the sealing effect between the ball 300 and the valve seat 200.

[0026] Further, such as Figure 2 As shown, in the present invention, the fitting relationship between the valve seat 200 and the valve body 100 is configured as a conical fit, that is, the contact surfaces of the valve seat 200 and the valve body 100 are both conical surfaces, and the outer diameter of the valve seat 200 gradually decreases from the end close to the ball 300 toward the end close to the downstream flow channel 120, so that the valve seat 200 and the valve body 100 form an interference fit through the conical surface. The interference fit between the valve seat 200 and the valve body 100 through the matching conical surface can improve the installation stability between the valve seat 200 and the valve body 100 by relying on the interference. At the same time, when the ball 300 presses against the valve seat 200, the force applied by the ball 300 on the valve seat 200 is transmitted to the matching conical surface of the valve seat 200 and the valve body 100, thereby facilitating sealing by establishing a sealing pressure ratio on the matching conical surface. When assembling the valve seat 200 with the valve body 100, the valve seat 200 is first immersed in liquid nitrogen to cool and shrink. The valve seat 200 is then placed in the tapered mating hole of the valve body 100 and allowed to naturally warm to room temperature. The thermal expansion of the valve seat 200 allows the valve seat 200 to be secured. The thermal expansion coefficient of the material used to make the valve seat 200 is preferably greater than that of the material used to make the valve body 100. This ensures that the thermal expansion tendency of the mating tapered surface of the valve seat 200 is greater than that of the mating tapered surface of the valve body 100 under high-temperature operating conditions, thereby meeting sealing requirements under high-temperature operating conditions.

[0027] The part of the sphere 300 that abuts the valve seat 200 is the sphere sealing surface 310, and the part of the valve seat 200 that abuts the sphere 300 is the valve seat sealing surface 210. The utility model forms the sphere sealing surface 310 and the valve seat sealing surface 210 by surfacing hard alloy. The hard alloy can be made of any alloy material with high temperature resistance and wear resistance. The hard alloy forming the sphere sealing surface 310 is limited to have a thermal expansion coefficient that is the same as or similar to that of the sphere 300, and the hard alloy forming the valve seat sealing surface 210 is limited to have a thermal expansion coefficient that is the same as or similar to that of the valve seat 200, thereby avoiding the defect of cracking of the surfacing layer due to the large difference in thermal expansion coefficient between the surfacing layer and the surfacing base material at high temperature. The utility model also provides an elastic groove 220 on the valve seat 200. The elastic groove 220 is provided on the inner ring surface of the valve seat 200. The elastic groove 220 is an annular groove concentric with the valve seat 200. By providing the elastic groove 220, the elastic adaptability of the valve seat sealing surface 210 and the spherical sealing surface 310 when they are matched under pressure can be increased.

[0028] like Figure 1 and Figure 3 As shown, the utility model provides an upper boss 330 on the top of the sphere 300. The upper boss 330 is provided with a matching through hole 340 for the lower end of the valve stem 400 to be inserted to provide a movable space for the lifting and lowering movement of the valve stem 400. The lower end of the valve stem 400 forms a limited fit with the matching through hole 340 on the circumference to realize the driving of the valve stem 400 to rotate the sphere 300. Specifically, two horizontally spaced pins are provided in the matching through hole 340, namely the sphere disengagement pin 350 and the sphere sealing pin 360. The sphere disengagement pin 350 and the sphere sealing pin 360 are parallel to each other. The sphere disengagement pin 350 is provided in the matching through hole 340 at a position away from the sphere sealing surface 310, and the sphere sealing pin 360 is provided in the matching through hole 340 at a position close to the sphere sealing surface 310; in coordination, as shown in FIG. Figure 1 and Figure 5 As shown, two parallel inclined surfaces 410 are provided on the circumference of the lower end of the valve stem 400. The two inclined surfaces 410 form a sliding fit with the ball disengagement pin 350 and the ball sealing pin 360, respectively. When the valve stem 400 rises with the lifting rod 600, the ball disengagement pin 350 receives the thrust applied by the rising valve stem 400. The inclined surfaces 410, which cooperate with the ball disengagement pin 350, press the ball disengagement pin 350 upward, causing the ball 300 to translate away from the valve seat 200 and disengage from the valve seat 200. When the valve stem 400 descends with the lifting rod 600, the ball sealing pin 360 receives the thrust applied by the descending valve stem 400. The inclined surfaces, which cooperate with the ball sealing pin 360, press the ball sealing pin 360 downward, causing the ball 300 to translate toward the valve seat 200 and press the valve seat 200.

[0029] Further, such as Figure 3 As shown, two stopper pins 370 are threadedly connected to the upper boss 330. Both stopper pins 370 are fully threaded. The stopper pins 370 are arranged horizontally, with one end extending into the mating through-hole 340. The ends of the two stopper pins 370 respectively abut against two flat surfaces provided on the circumferential surface of the lower end of the valve stem 400. The stopper pins 370 form a circumferential stopper with the lower end of the valve stem 400, so that rotation of the valve stem 400 can drive the ball 300 to rotate together. The end of the stopper pin 370 located in the mating through-hole 340 can be threadedly connected to a nut for further locking, and the nut can also be used to adjust the extension length of the stopper pin 370.

[0030] In the present invention, the valve stem 400 can simultaneously perform both lifting and rotational actions. The lifting action of the valve stem 400 is driven by the lifting action of the lifting rod 600, and the rotation of the valve stem 400 is achieved by the cooperation of the guide pin 700 provided on the valve cover 500 and the guide groove 420 provided on the valve stem 400. Figure 1 and Figure 5 As shown, two horizontally arranged and coaxially opposed guide pins 700 are fixed to the valve cover 500. Two guide grooves 420 corresponding to the guide pins 700 are provided on the upper circumference of the valve stem 400. The ends of the guide pins 700 are inserted into the corresponding guide pins 700 to form a sliding fit. When the lifting rod 600 drives the valve stem 400 to rise and fall, the guide pins 700 inserted into the guide grooves 420 serve as a guide and limiter for the valve stem 400. Since the guide pins 700 are fixed, the guide pins 700 slide along the guide grooves 420, causing the valve stem 400 to rotate as it rises and falls, thereby driving the ball 300 to rotate as well.

[0031] Specifically, the guide groove 420 in the present invention is composed of an upper straight groove section 421, a first spiral groove section 422, a second spiral groove section 423 and a lower straight groove section 424 connected in sequence. The upper straight groove section 421 and the lower straight groove section 424 extend vertically along the axial direction of the valve stem 400, and the first spiral groove section 422 and the second spiral groove section 423 extend spirally along the axial direction of the valve stem 400; the two guide grooves 420 are centrally symmetrical with respect to the central axis of the valve stem 400; a group of guide curved surfaces matching the guide grooves 420 are provided on both sides of the circumferential surface of the end of the guide pin shaft 700, and the guide curved surfaces include a first spiral curved surface 710 and a second spiral curved surface 720 connected to each other, the first spiral curved surface 710 is matched with the side of the first spiral groove section 422, and the second spiral curved surface 720 is matched with the side of the second spiral groove section 423. In the prior art, a guide pin with multiple planes on its circumference is often used to cooperate with the spiral groove provided on the valve stem. However, since the side surface of the spiral groove is a spiral curved surface, the spiral curved surface of the spiral groove and the plane on the guide pin can never be completely aligned, resulting in no surface contact between the side surface of the spiral groove and the plane of the guide pin. Only line contact can be formed between the two. The contact portion between the guide pin and the side surface of the spiral groove is the intersection line between the adjacent planes, which will make the contact area between the guide pin and the spiral groove approach zero. When the guide pin slides along the spiral groove, even if it is only affected by Even a very small force will generate great contact stress, which is much greater than the strength of the contact part, so the contact part is very prone to wear. In addition, the guide pin remains stationary during the lifting and lowering of the valve stem, and the contact part between the guide pin and the side of the spiral groove remains unchanged. What occurs on the guide pin is continuous wear, while the contact part between the side of the spiral groove and the guide pin will change with the lifting and lowering of the valve stem. What occurs on the side of the spiral groove of the valve stem is instantaneous wear, which will eventually cause the wear degree of the guide pin to be more serious than the wear degree of the side of the spiral groove on the valve stem. The present invention improves the structure of the guide groove 420 on the valve stem 400 so that the guide groove 420 has two spiral sections, a first spiral groove section 422 and a second spiral groove section 423, and provides a guide curved surface with a first spiral surface 710 and a second spiral surface 720 on the circumferential surface of the end of the guide pin shaft 700. When the guide pin shaft 700 and the guide groove 420 slide relative to each other, the first spiral curved surface 710 on the guide pin shaft 700 can fit into surface contact with the side surface of the first spiral groove section 422 in the guide groove 420, and the second spiral curved surface 720 on the guide pin shaft 700 can also fit into surface contact with the side surface of the second spiral groove section 423 in the guide groove 420, thereby increasing the contact area between the guide pin shaft 700 and the guide groove 420, thereby effectively reducing the contact stress between the guide pin shaft 700 and the guide groove 420, improving the wear of the two, and effectively extending the service life of the guide pin shaft 700 and the valve stem 400.

[0032] Furthermore, in the present invention, the pitches of the first spiral groove section 422 and the second spiral groove section 423 are set to be different, with the helix angle of the second spiral groove section 423 being greater than the helix angle of the first spiral groove section 422. Furthermore, in the two sets of guide curved surfaces on the guide pin 700, the distance between the two first spiral curved surfaces 710 is set to be equal to or less than the pitch of the first spiral groove section 422, and the distance between the two second spiral curved surfaces 720 is set to be equal to or less than the pitch of the second spiral groove section 423. The guide groove 420 of the valve stem 400 has two spiral groove sections with different pitches, which effectively reduces the axial travel of the entire guide groove 420, thereby shortening the lifting stroke of the valve stem 400. This allows the use of a linear pneumatic actuator with a shorter stroke to drive the valve, thereby reducing the cost of the valve assembly.

Claims

1. A hard-sealed rising stem ball valve, comprising a valve body (100), a valve seat (200), a ball (300), a valve stem (400) and a valve cover (500). A valve cavity is provided inside the valve body (100). An upstream flow channel (110) and a downstream flow channel (120) communicating with the valve cavity are provided at both ends of the valve body (100). The valve seat (200) is provided at the junction of the valve cavity and the downstream flow channel (120). The surface of the ball (300) is provided with a valve seat (200) that can abut against the valve seat (200) to form a valve. The spherical sealing surface (310) is matched with a hard seal, the spherical body (300) is rotatably arranged in the cavity of the valve body (100), a through channel is provided in the center of the spherical body (300), the valve cover (500) is detachably connected to the top of the valve body (100), the upper end of the valve stem (400) is connected to a lifting rod (600) extending out of the valve cover (500), and the lifting rod (600) drives the valve stem (400) to rise and fall synchronously while driving the spherical body (300) to rotate, characterized in that: The surface of the sphere (300) is provided with a circular convex ring structure coaxially arranged with the valve seat (200), and the surface of the circular convex ring structure is a sphere sealing surface (310) abutting against the valve seat (200), and the sphere sealing surface (310) is an arc surface; a lower joint head (320) is fixed to the bottom of the sphere (300), the side surface of the lower joint head (320) is an ellipsoidal surface, and the bottom surface of the lower joint head (320) is an arc surface on the same sphere as the sphere sealing surface (310), and the spherical surface is concentric with the sphere (300).

2. The hard-sealed rising-stem ball valve according to claim 1, characterized in that: An upper boss (330) is fixed on the top of the sphere (300), and the upper boss (330) is provided with a matching through hole (340). The lower end of the valve stem (400) is inserted into the matching through hole (340) and forms a circumferential limit fit with the matching through hole (340).

3. The hard-sealed rising-stem ball valve according to claim 2, characterized in that: A horizontally arranged ball detachment pin (350) and a ball sealing pin (360) are fixed in the matching through hole (340). The ball detachment pin (350) and the ball sealing pin (360) are parallel to each other. The ball detachment pin (350) is arranged in a position away from the ball sealing surface (310) in the matching through hole (340), and the ball sealing pin (360) is arranged in a position close to the ball sealing surface (310) in the matching through hole (340). The lower end circumference of the valve stem (400) is provided with two pins which are respectively connected to the ball detachment pin (350) and the ball sealing pin (360). The sealing pin (360) forms a slidingly fitting inclined surface (410), and the two inclined surfaces (410) are parallel to each other; when the valve stem (400) rises along with the lifting rod (600), the inclined surface matched with the ball separation pin (350) squeezes the ball separation pin (350) upwards to make the ball (300) move in a direction away from the valve seat (200); when the valve stem (400) descends along with the lifting rod (600), the inclined surface matched with the ball sealing pin (360) squeezes the ball sealing pin (360) downwards to make the ball (300) move in a direction toward the valve seat (200).

4. The hard-sealed rising-stem ball valve according to claim 2, characterized in that: Two limit pins (370) are also threadedly connected to the upper boss (330). The limit pins (370) are arranged horizontally and one end of the limit pins (370) extends into the matching through hole (340). The ends of the two limit pins (370) are respectively in contact with two planes arranged on the circumference of the lower end of the valve stem (400).

5. The hard-sealed rising-stem ball valve according to claim 1, characterized in that: The matching surfaces of the valve seat (200) and the valve body (100) are both conical surfaces, and the valve seat (200) and the valve body (100) form an interference fit through the conical surfaces; the outer diameter of the valve seat (200) gradually decreases from the end close to the sphere (300) toward the end close to the downstream flow channel (120).

6. The hard-sealed rising-stem ball valve according to claim 5, characterized in that: The surface where the valve seat (200) contacts the spherical sealing surface (310) is the valve seat sealing surface (210). Both the valve seat sealing surface (210) and the spherical sealing surface (310) are formed by surfacing welding of hard alloys. The hard alloy forming the spherical sealing surface (310) has a thermal expansion coefficient that is the same as or similar to that of the sphere (300). The hard alloy forming the valve seat sealing surface (210) has a thermal expansion coefficient that is the same as or similar to that of the valve seat (200). The valve seat (200) is also provided with an elastic groove (220). The elastic groove (220) is an annular groove concentric with the valve seat (200). The elastic groove (220) is arranged on the inner annular surface of the valve seat (200).

7. The hard-sealed rising-stem ball valve according to claim 1, characterized in that: Two horizontally arranged and coaxially opposed guide pins (700) are fixed on the valve cover (500), and two guide grooves (420) corresponding to the guide pins (700) are provided on the upper end circumference of the valve stem (400), and the ends of the guide pins (700) are inserted into the corresponding guide pins (700) to form a sliding fit; the guide groove (420) is composed of an upper straight groove section (421), a first spiral groove section (422), a second spiral groove section (423) and a lower straight groove section (424) connected in sequence, and the upper straight groove section (421) and the lower straight groove section (424) are vertically extended along the axial direction of the valve stem (400). The first spiral groove section (422) and the second spiral groove section (423) extend in a spiral shape along the axial direction of the valve stem (400); the two guide grooves (420) are centrally symmetrical with respect to the central axis of the valve stem (400); a group of guide curved surfaces adapted to the guide grooves (420) are provided on both sides of the circumference of the end of the guide pin shaft (700), and the guide curved surfaces include a first spiral curved surface (710) and a second spiral curved surface (720) connected to each other, the first spiral curved surface (710) being adapted to the side surface of the first spiral groove section (422), and the second spiral curved surface (720) being adapted to the side surface of the second spiral groove section (423).

8. The hard-sealed rising-stem ball valve according to claim 7, characterized in that: The pitches of the first spiral groove section (422) and the second spiral groove section (423) are different; the distance between the two first spiral curved surfaces (710) in the two groups of guide curved surfaces on the guide pin shaft (700) is equal to or less than the pitch of the first spiral groove section (422), and the distance between the two second spiral curved surfaces (720) is equal to or less than the pitch of the second spiral groove section (423).

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