FLUOROPLASTIC BUTTERFLY VALVE STRUCTURE

Abstract

The present invention relates to a fluoroplastic butterfly valve structure, including a valve body, a butterfly disc, a lining, and a back-up ring. The butterfly disc has a disc-like structure and includes an inner metallic butterfly disc and an outer fluoroplastic material enclosing the metallic butterfly disc. The butterfly disc is provided with a valve shaft and includes two bulging portions for connecting with the valve shaft. The butterfly disc has a board-like or cone-like cross section. The valve shaft is mounted in a shaft hole portion of the valve body, enabling rotation of the butterfly disc for adjusting flow amount or opening/closing the valve. The back-up ring and the fluoroplastic lining are mounted on an inner peripheral surface of the valve body. An outer rim of the butterfly disc and an inner surface of the lining are tightly pressed against each other by interference fit. The back-up ring is provided between the inner peripheral surface of the valve body and the lining and is made of high temperature resistance rubber in order for bearing the pressing pressure of deformation resulted from said interference fit, thereby meeting the requirement of working with a high-temperature (200 degree Celsius) and high-pressure fluid. The butterfly disc has a complex sealing structure, which includes an unequal-width conical surface and an unequal-width curved surface. The unequal-width curved surface is disposed in a closing direction of the butterfly disc for preventing interference sliding thereof with respect to the inner surface of the lining, thereby reducing deformation of lining and reducing torque. The unequal-width curved surface is composed of arc curves. A portion of the unequal-width curved surface which is at a position near the valve shaft has a longer arc, while a portion of the unequal-width conical surface which is at a position near the valve shaft has a smaller width, said smaller width exceeding 50 percent of a thickness of the outer rim of the inner metallic butterfly disc. Take a 3-inch butterfly disc as an example, where a thickness of the butterfly disc is 8 mm, a sealing width of the butterfly disc is greater than 4 mm. A portion of the unequal-width curved surface which is at a largest-diameter region of a central of the butterfly disc has a shortest arc, while a portion of the unequal-width conical surface which is at the largest-diameter region of the central of the butterfly disc has a largest width, said largest width exceeding 70 percent of the thickness of an outer rim of the inner metallic butterfly disc of the butterfly disc.

Claims

1. A fluoroplastic butterfly valve structure comprising a valve body, a butterfly disc, a lining, and a back-up ring, said valve body being formed in a circular ring shape and being horizontally divided into an upper valve body and a lower valve body each being formed in a semicircular shape, said upper valve body and said lower valve body being fastened together to become united, said upper valve body and said lower valve body being installed in an axial direction, said valve body having an inner peripheral surface, a groove with a trapezoidal cross section being formed in said inner peripheral surface; said butterfly disc being formed in a disc-like shape and including a butterfly disc outer rim, respective horizontal sealing end surfaces being formed at two axial ends of said butterfly disc outer rim, said horizontal sealing end surface and an annular curved surface of said butterfly disc outer rim being connected at a place where an arc-shaped side cutting edge is formed, a valve shaft and a bulging portion being respectively disposed on said horizontal sealing end surface at said two axial ends of said butterfly disc outer rim, said valve shaft and said bulging portion being concentric, a shaft sealing surface and a protuberant sealing ring being disposed on said bulging portion; said shaft sealing surface, said side cutting edge and said annular curved surface being connected to form a butterfly disc sealing surface; said lining disposed in correspondence with said valve body and being formed in a circular ring shaped, said lining having an inner diametral side and an outer diametral side, two ends of said lining each including a radial flange, said lining including a tubular portion, an inner diametral side of said tubular portion being an inner surface of said lining, two axial ends of said lining each being formed with a horizontal sealing plane, a thickness of said horizontal sealing plane being larger than a thickness of said tubular portion, said thickness being defined to cover said inner diametral side and said outer diametral side of said lining, a shaft hole and a shaft hole surface being formed on said horizontal sealing plane, said shaft hole surface being formed on said inner diametral side and said outer diametral side around an outer periphery of said shaft hole, an inner diametral side of said horizontal sealing plane and said inner diametral side of said tubular portion being connected at a place where an arc-shaped joint edge is formed, a sealing recess being formed on said shaft hole surface which is located on said inner diametral side; said shaft hole surface located on said inner diametral side, said joint edge, and said inner surface of said lining being connected to form a lining sealing surface, said lining being installed in said inner peripheral surface of said valve body; and said back-up ring being an elastic body with a trapezoidal cross section, said back-up ring being installed in said groove and fitting snugly with an outer diametral side of said tubular portion; wherein with respect to said butterfly disc sealing surface and said lining sealing surface, said shaft hole surface is formed in correspondence with said shaft sealing surface, said annular curved surface of said butterfly disc outer rim is formed in correspondence with said inner surface of said lining, said sealing ring is located in correspondence with said sealing recess, and said joint edge is formed in correspondence with said side cutting edge, the above parts being tightly pressed against each other to form a continuous and smooth sealing surface, an included angle at which said butterfly disc is orientated with respect to a central axis being 0 degrees when said butterfly disc is fully open, an included angle at which said butterfly disc is orientated with respect to said central axis being 90 degrees when said butterfly disc is fully closed, said central axis being an axis perpendicular to said axial direction and passing a center of said shaft hole, when said butterfly disc is changed from a full open state to a closed state, a portion of said butterfly disc outer rim near said valve shaft is in contact with inner surface of said lining first and then the contact between said butterfly disc outer rim and said inner surface of said lining moves from said portion near said valve shaft to a middle portion of said butterfly disc, a joint line being defined between a contact point where said butterfly disc outer rim and said inner surface of said lining meet and an axial center of rotation, a contact angle () being formed between said joint line and said central axis, different contact angles () being generated by any of contact points where said butterfly disc outer rim and said inner surface of said lining meet, when there is an interference sliding between said butterfly disc outer rim and said inner surface of said lining, a sliding surface being formed on a contact surface where said butterfly disc outer rim is in contact with a lining deformation () of said lining, a sliding angle () being formed between a tangent of said sliding surface and a tangent of said inner surface of said lining perpendicular to said valve shaft, said annular curved surface including a complex sealing structure which has an unequal-width conical surface and an unequal-width curved surface, a portion of said unequal-width conical surface near said valve shaft having a smaller sealing width, while a portion thereof near a middle portion of said butterfly disc having a largest sealing width, said sealing width of said portion of said unequal-width conical surface near said valve shaft exceeding 50 percent (50%) of a thickness of an outer rim of an inner metallic butterfly disc of said butterfly disc, said sealing width of said portion thereof near said middle portion of said butterfly disc exceeding 70 percent (70%) of said thickness of said outer rim of said metallic butterfly disc, said unequal-width curved surface extending from a superficial face of said butterfly disc to said butterfly disc outer rim, a portion of said unequal-width curved surface near said valve shaft having a longest smooth arc, while a portion thereof near said middle portion of said butterfly disc having a shortest smooth arc, said unequal-width curved surface being disposed in a closing direction of said butterfly disc, said interference sliding being generated between said unequal-width curved surface and said inner surface of said lining while closing or opening said butterfly disc.

2. The fluoroplastic butterfly valve structure according to claim 1, wherein said butterfly disc has said metallic butterfly disc and a fluoroplastic encapsulation, said metallic butterfly disc being enclosed by said fluoroplastic encapsulation, said annular curved surface being located on said fluoroplastic encapsulation, said outer rim of said metallic butterfly disc having a corresponding curved surface structure, an unequal-width conical surface, and an unequal-width curved surface, a portion of said unequal-width curved surface near said valve shaft having a longest smooth arc, while a portion thereof near said middle portion of said butterfly disc having a shortest smooth arc, said unequal-width curved surface being disposed in said closing direction of said butterfly disc.

3. The fluoroplastic butterfly valve structure according to claim 1, wherein when said butterfly valve is 3 inches, said butterfly disc is 8 mm in thickness, said sealing width of said portion of said butterfly disc outer rim near said valve shaft is above 4 mm, and said sealing width of said portion thereof near said middle portion of said butterfly disc is above 5.6 mm.

4. The fluoroplastic butterfly valve structure according to claim 1, wherein a compression ratio of said sealing surface is a number of a packing amount compared to a thickness of said back-up ring, said compression ratio ranging from 15 percent (15%) to 20 percent (20%).

5. The fluoroplastic butterfly valve structure according to claim 1, wherein said bulging portions disposed at said two ends divide said butterfly disc into two butterfly disc flanks, said butterfly disc flank having a board-like cross section or a cone-like cross section.

6. The fluoroplastic butterfly valve structure according to claim 1, wherein a projecting ring is disposed on a bottom of said groove, a projecting height of said projecting ring being smaller than a groove depth of said groove, an expansion room being defined when said back-up ring is installed in said groove, a projecting width of said projecting ring ranging from 1.5 to 2 times a thickness of said inner metallic butterfly disc of said metallic butterfly disc but being smaller than a bottom width of said groove.

7. The fluoroplastic butterfly valve structure according to claim 1, wherein an inner diameter of said back-up ring is substantially equal to an inner diameter of said valve body, and an outer diameter of said tubular portion is substantially equal to said inner diameter of said valve body.

8. The fluoroplastic butterfly valve structure according to claim 1, wherein said smooth arc of said unequal-width curved surface is analogous to an elliptical curve.

9. A fluoroplastic butterfly valve structure comprising a valve body, a butterfly disc, a lining, and a back-up ring, said valve body being formed in a circular ring shape and being horizontally divided into an upper valve body and a lower valve body each being formed in a semicircular shape, each of said upper valve body and said lower valve having a fastening portion and a shaft hole portion, said upper valve body and said lower valve body being fastened together to become united, said upper valve body and said lower valve body being installed in an axial direction, said valve body including an inner peripheral surface, a groove with a trapezoidal cross section being formed in said inner peripheral surface; said butterfly disc being formed in a disc-like shape and including a butterfly disc outer rim, respective horizontal sealing end surfaces being formed at two axial ends of said butterfly disc outer rim, said horizontal sealing end surface and an annular curved surface of said butterfly disc outer rim being connected at a place where an arc-shaped side cutting edge is formed, a valve shaft and a bulging portion being respectively disposed on said horizontal sealing end surface at said two axial ends, said bulging portion and said valve shaft being concentric, a shaft sealing surface and a protuberant sealing ring being disposed on said bulging portion; said shaft sealing surface, said side cutting edge and said annular curved surface being connected to form a butterfly disc sealing surface; said lining being formed in a circular ring shape and disposed in correspondence with said valve body, said lining having an inner diametral side and an outer diametral side, two ends of said lining each including a radial flange, said lining including a tubular portion, an inner diametral side of said tubular portion being an inner surface of said lining, two axial ends of said lining each being formed with a horizontal sealing plane, a thickness of said horizontal sealing plane being larger than a thickness of said tubular portion, said thickness being defined to cover said inner diametral side and said outer diametral side of said lining, a shaft hole and a shaft hole surface being formed on said horizontal sealing plane, said shaft hole surface being formed on said inner diametral side and said outer diametral side around an outer periphery of said shaft hole, an inner diametral side of said horizontal sealing plane and said inner diametral side of said tubular portion being connected at a place where an arc-shaped joint edge is formed, a sealing recess being formed on said shaft hole surface which is located on said inner diametral side; said shaft hole surface located on said inner diametral side, said joint edge, and said inner surface of said lining being connected to form a lining sealing surface, said lining being installed in said inner peripheral surface of said valve body; and said back-up ring being an elastic body with a trapezoidal cross section, said back-up ring being installed in said groove and fitting snugly with an outer diametral side of said tubular portion; wherein with respect to said butterfly disc sealing surface and said lining sealing surface, said shaft hole surface is formed in correspondence with said shaft sealing surface, said annular curved surface of said butterfly disc outer rim is formed in correspondence with said inner surface of said lining, said sealing ring is located in correspondence with said sealing recess, and said joint edge is formed in correspondence with said side cutting edge, the above parts being tightly pressed against each other to form a continuous and smooth sealing surface; wherein reinforcement portions are respectively formed on an outer diametral side of said horizontal sealing plane and located on two sides of said shaft hole along said tubular portion, a width of said reinforcement portion exceeding two times a thickness of an inner metallic butterfly disc of said butterfly disc to thereby allow said thicknesses of said horizontal sealing plane and said tubular portion to be smoothly varied.

10. The fluoroplastic butterfly valve structure according to claim 9, wherein said reinforcement portion smoothens a thickness of said joint edge.

11. A fluoroplastic butterfly valve structure comprising: a valve body; and a butterfly disc pivotally connected to said valve body by a valve shaft, a pivotal rotation of said valve shaft allowing said butterfly disc to open or close said valve body; wherein said butterfly disc has a butterfly disc outer rim, said butterfly disc outer rim having an annular curved surface, said annular curved surface including an unequal-width conical surface, a sealing width of said unequal-width conical surface increasing progressively from said valve shaft to a middle portion of said butterfly disc, a sealing width of a portion of said unequal-width conical surface near said valve shaft exceeding 50 percent (50%) of a thickness of an outer rim of an inner metallic butterfly disc, a sealing width of a portion of said unequal-width conical surface near said middle portion of said butterfly disc exceeding 70 percent (70%) of said thickness of said outer rim of said metallic butterfly disc.

12. The fluoroplastic butterfly valve structure according to claim 11, wherein said annular curved surface further includes a complex sealing structure which has an unequal-width curved surface and an unequal-width conical surface, said unequal-width curved surface extending from a superficial face of said butterfly disc to said butterfly disc outer rim, a smooth arch of said unequal-width curved surface narrowing progressively from said valve shaft to said middle portion of said butterfly disc, said unequal-width curved surface being disposed in a closing direction of said butterfly disc.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0144] FIG. 1 is a schematic view showing the appearance and installation of a fluoroplastic butterfly valve of this invention;

[0145] FIG. 2A is a cross-section view showing a lining with reinforcement portions;

[0146] FIG. 2B is a plan view showing the sealing of the lining with reinforcement portions;

[0147] FIG. 3 is a schematic view showing the combination of the lining and a back-up ring;

[0148] FIG. 4A is a top plan view showing a butterfly disc of this invention in an axial direction;

[0149] FIG. 4B is a side elevational view of the butterfly disc of this invention;

[0150] FIG. 4C is a perspective view showing an unequal-width conical surface and an unequal-width curved surface of the butterfly disc of this invention;

[0151] FIG. 4D is a perspective showing a metallic butterfly disc of the butterfly disc of this invention;

[0152] FIG. 5Ai is a schematic view showing the contact points where the butterfly disc and the inner surface of the lining of this invention meet along the cross-sectional line c-c;

[0153] FIG. 5Aii is a schematic view showing the contact point where the butterfly disc and the inner surface of the lining of this invention meet along the cross-sectional line b-b;

[0154] FIG. 5Aiii is a schematic view showing the contact point where the butterfly disc and the inner surface of the lining of this invention meet along the cross-sectional line a-a;

[0155] FIG. 5B is a schematic view showing the sealing status where the butterfly disc of this invention is in contact with the lining and adds press forces to cause the lining and the back-up ring to become deformed;

[0156] FIG. 5C is a top plan view showing the butterfly disc of this invention in an axial direction;

[0157] FIG. 5D is a cross-sectional view showing the contact point where the butterfly disc of this invention is in contact with the inner surface of the lining along the cross-sectional line a-a;

[0158] FIG. 5E is a cross-sectional view showing the interference sliding of the butterfly disc of this invention;

[0159] FIG. 6A is a schematic view showing a slit passage of the butterfly valve of this invention;

[0160] FIG. 6Bi is a curve diagram of the flow coefficient Cv of the butterfly valve of this invention at different opening degrees;

[0161] FIG. 6Bii is a curve diagram of the flow coefficient Cv of 3-inch butterfly valve of Reference 10 at different opening degrees;

[0162] FIG. 6Biii is a curve diagram of the flow coefficient Cv of 3-inch butterfly valve of Reference 11 at different opening degrees;

[0163] FIG. 7A is a schematic view showing an appearance of a conventional fluoroplastic butterfly valve;

[0164] FIG. 7B is a perspective view showing the structure of a conventional fluoroplastic-encapsulated butterfly disc;

[0165] FIG. 7C is a schematic view showing the combination of a lining and a back-up ring of the conventional fluoroplastic butterfly valve;

[0166] FIG. 7D is a cross-sectional view showing a tubular portion of the lining of the conventional fluoroplastic butterfly valve;

[0167] FIG. 7E is a schematic view showing the required torque when the conventional butterfly disc closes the butterfly valve;

[0168] FIG. 7F is a schematic view showing the required torque when the conventional butterfly disc opens the butterfly valve to form a slit passage;

[0169] FIG. 8Ai is a schematic view showing the contact points where a ribbon sealing butterfly disc of the conventional fluoroplastic butterfly valve and the inner surface meet along the cross-sectional line c-c;

[0170] FIG. 8Aii is a schematic view showing the contact point where a ribbon sealing butterfly disc of the conventional fluoroplastic butterfly valve and the inner surface meet along the cross-sectional line b-b;

[0171] FIG. 8Aiii is a schematic view showing the contact point where a ribbon sealing butterfly disc of the conventional fluoroplastic butterfly valve and the inner surface meet along the cross-sectional line a-a;

[0172] FIG. 8B is a schematic view showing the deformation of the sealing surface and the press pressure of the ribbon sealing of the conventional fluoroplastic butterfly valve;

[0173] FIG. 8C is a schematic view showing the shape of the sealing surface of the ribbon sealing of the conventional fluoroplastic butterfly valve;

[0174] FIG. 8D is a cross-sectional view showing the contact point where the ribbon sealing of the conventional fluoroplastic butterfly disc and the inner surface meet along the cross-sectional line a-a;

[0175] FIG. 8E is a cross-sectional view showing the interference sliding of the ribbon sealing of the conventional fluoroplastic butterfly valve;

[0176] FIG. 9Ai is a schematic view showing the contact points where a conventional linear sealing butterfly disc and the inner surface meet along the cross-sectional line c-c;

[0177] FIG. 9Aii is a schematic view showing the contact point where a conventional linear sealing butterfly disc and the inner surface meet along the cross-sectional line b-b;

[0178] FIG. 9Aiii is a schematic view showing the contact point where a conventional linear sealing butterfly disc and the inner surface meet along the cross-sectional line a-a;

[0179] FIG. 9B is a schematic view showing the deformation of the sealing surface and the press pressure of the linear sealing of the conventional fluoroplastic butterfly valve;

[0180] FIG. 9C is a schematic view showing the shape of the sealing surface of the linear sealing of the conventional fluoroplastic butterfly valve;

[0181] FIG. 9D is a cross-sectional view showing the contact point where the linear sealing of the conventional fluoroplastic butterfly valve and the inner surface meet along the cross-sectional line a-a; and

[0182] FIG. 9E is a cross-sectional view showing the interference sliding of the linear sealing of the conventional fluoroplastic butterfly valve.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0183] Referring to FIGS. 1, 2A, 2B, 3, 4A, 4B, 4C and 4D, a fluoroplastic symmetrical butterfly valve 1 includes a valve body 2, a lining 3, a back-up ring 4 and a butterfly disc 5.

[0184] The valve body 2 is formed in a circular ring shape and is horizontally divided into a semicircular-shaped two-piece part, namely an upper valve body 21 and a lower valve body 22. Two fasteners are used to fasten the two valve bodies together to become united. The upper valve body 21 and the lower valve body 22 are installed in an axial direction. The upper valve body 21 has a fastening portion 211 and a shaft hole portion 212 disposed thereon, and the lower valve 22 has a fastening portion 221 and a shaft hole portion 222 disposed thereon. An inner peripheral surface 23 of the valve body 2 is formed to allow an installation of the fluoroplastic lining 3. The inner peripheral surface 23 forms a groove 232 with a trapezoidal cross section which defines an included angle 233(), serving to receive the back-up ring 4 having a trapezoidal cross section 42 and defining an included angle 43(), as shown in FIG. 3. A projecting ring 234 is disposed on a bottom of the groove 232. A height 239(s2) of the projecting ring 234 is smaller than a groove depth 237(s1) of the groove 232. A width 236(t2) of the projecting ring 234 ranges from 1.5 to 2 times a thickness 631(t1) of an inner metallic butterfly disc 51 of the butterfly disc 5 but is smaller than a bottom width 238(t3), as shown in FIG. 4A.

[0185] The lining 3, disposed in correspondence with the valve body 2, is formed in a circular ring shape. The lining 3 has an inner diametral side and an outer diametral side. Two ends of the lining 3 each form a radial flange 32. The lining includes a tubular portion 31. An outer diameter 315 of the tubular portion 31 is installed on the inner peripheral surface 23 of the valve body 2. While closing, a butterfly disc outer rim 53 of the butterfly disc 5 presses against a cylindrical inner surface 311 of the lining of the tubular portion 31, supported by the valve body 2 and the back-up ring 4, in order to close the flow of fluid and bear the fluid pressure and temperature. Two axial ends of the lining 3 each are formed with a horizontal sealing plane 632. A thickness of the horizontal sealing plane 632 is larger than a thickness of the tubular portion 31. The horizontal sealing planes 632 are set by a flat structure on the inner diametral side and the outer diametral side to allow a diametral distance between the two horizontal sealing planes 632 to be smaller than an inner diameter of the tubular portion 31. An inner diametral side of the horizontal sealing plane 632 of the lining 3 and an inner diametral side of the tubular portion 31 of the lining 3 are connected, and the connection forms a joint edge 633 which is formed in an arc shape. A shaft hole 312 is formed on the horizontal sealing plane 632, and the inner diametral side and an outer diametral side of the horizontal sealing plane 632 each form a shaft hole surface 634 which surrounds an outer periphery of the shaft hole 312 for press sealing. A sealing recess 634a is formed on the shaft hole surface 634 and located on the inner diametral side. The shaft hole surface 634 located on the inner diametral side, the joint edge 633 and the inner surface 311 of the lining are connected to construct a full sealing surface 6. On the outer diametral side of the horizontal sealing plane 632 are respectively formed reinforcement portions 318 which are located on two sides of the shaft hole 312 and arranged along a central axis 25. A width of the reinforcement portion 318 exceeds two times the thickness 631(t1) of the inner metallic butterfly disc 51 of the butterfly disc 5, thereby allowing smooth variations in the thicknesses of the horizontal sealing plane 632 and the tubular portion 31 to solve the leakage of the joint edge 633. The central axis 25 is an axis perpendicular to the axial direction and passing a center of the shaft hole 312.

[0186] Referring to FIG. 3, the back-up ring 4 is an elastic body made of rubber and is installed between the groove 232 of the inner peripheral surface 23 of the valve body 2 and the tubular portion 31 of the fluoroplastic lining 3. A shaft hole portion 46 is disposed according to the demand for a valve shaft 55 of the butterfly disc 5. An inner diameter 41 of the back-up ring 4 is basically equal to an inner diameter of the valve body 2. When the back-up ring 4 is installed inside the groove 232, an expansion room 235 is defined to supply the need of heat expansion under high temperatures. When the back-up ring 4 is tightly pressed, more than 80 percent (80%) of the expansion room 235 can be filled, and the whole room is almost filled by the heat expansion under high temperatures. The outer diameter 315 of the tubular portion 31 is basically equal to the inner diameter of the valve body 2. The inner diameter 41 of the back-up ring and the inner surface 311 of the lining is slightly small and protrudes inwards because of shrinkage during the manufacturing process. A thickness 45(s3) of the back-up ring plus the height 239(s2) of the projecting ring 234 equals the depth 237(s1) of the groove 232. However, the shrinkage and the deformation occurred in the manufacturing process may cause the thickness 45(s3) of the back-up ring 4 to be slightly large and render the inner diameter of the back-up ring 4 slightly smaller than the inner diameter of the valve body 2. The inner surface 311 of the lining also protrudes inwards because of the aforementioned shrinkage to cause the cross section of the inner surface 311 of the lining to have a swelling curve 66a. These arrangements need a process control whereby a swelling height 66b(h) is set within a reasonable range. Because the installation of the butterfly disc 5 in the tubular portion 31 of the lining 3 needs to generate a sufficient packing amount 65() in order to attain the sealing effect, the swelling height 66b(h) needs to be controlled and included in the calculation of the packing amount 65() during the manufacturing process. The packing amount 65() is shown in FIG. 5A.

[0187] Referring to FIGS. 4A, 4B, 4C, and 4D, the butterfly disc 5 is formed in a disc-like shape, and the butterfly disc 5 has a butterfly disc outer rim 53. The butterfly disc outer rim 53 has an annular curved surface 531. Two axial ends of the butterfly disc 5 each form a horizontal sealing end surface 635. The horizontal sealing end surface 635 is formed in correspondence with the horizontal sealing plane 632 of the lining 3. The horizontal sealing end surface 635 and the annular curved surface 531 are connected, and the connection forms a side cutting edge 636 which is formed in an arc shape. The side cutting edge 636 is formed in correspondence with the joint edge 633 located on the inner diametral side of the lining 3 for sealing. The horizontal sealing end surface 635 and the horizontal sealing plane 632 are axially and perpendicularly pressed against each other for sealing. The sealing between the side cutting edge 636 and the joint edge 633 is changed from a vertical sealing to a radial sealing. Because the reinforcement portion 318 smoothens the thickness, the tight press becomes even and no fluid leaks out of the valve shaft 55. A bulging portion 54 and the valve shaft 55 are disposed on the horizontal sealing end surface 635. The valve shaft 55 and the bulging portion 54 are concentric. The valve shaft 55 includes a long upper valve shaft 55a and a short lower valve shaft 55b. The valve shaft 55 passes two shaft holes 312 of the lining 3 and is installed in the shaft hole portion 212 of the upper valve body 21 and the shaft hole portion 222 of the lower valve body 22, so the butterfly disc 5 can rotate to adjust the flow amount or open and close the valve. The bulging portions 54 divide the butterfly disc 5 into two butterfly disc flanks 56. The butterfly disc flank 56 can have a board-like cross section or a cone-like cross section. For example, a large-sized butterfly valve uses a cone-like cross section, as shown in FIG. 7E, and a small-sized butterfly valve uses a board-like cross section, as shown in FIG. 4A.

[0188] An outer diameter of the butterfly disc outer rim 53 of the butterfly disc 5 is slightly larger than an inner diameter of the inner surface 311 of the lining, and half of the difference between them is the packing amount 65() for a unilateral radius, as shown in FIG. 5A. A compression ratio of the sealing surface 6 is a number of the packing amount 65() compared to the thickness 45(s3) of the back-up ring 4. According to the adopted material of the back-up ring 4 and the demand for pressure resistance and temperature resistance, the compression ratio ranges from 15 percent (15%) to 22 percent (22%), and the thickness 631(t1) of the metallic butterfly disc 51 at the outer rim of the butterfly disc flank 56 can provide a complex sealing with a sealing width larger than or equal to 4 mm, namely 4 mm while taking a 3-inch butterfly disc as an example, as shown in FIG. 4A.

[0189] Referring to FIG. 1, on a shaft sealing surface 637 of the bulging portion 54 of the horizontal sealing end surface 635 is disposed a protuberant sealing ring 637a capable of sealing the sealing recess 634a of the shaft hole surface 634 and reducing an outer diameter of the bulging portion 54. Accordingly, the press sealing between the butterfly disc outer rim 53 and the inner surface 311 of the lining is also connected to the shaft sealing surface 637 and the shaft hole surface 634 to thereby form a continuously reliable sealing surface 6, including the sealing between the horizontal sealing end surface 635 and the horizontal sealing plane 632.

[0190] Referring to FIGS. 4A, 4B, 4C, and 4D, the butterfly disc outer rim 53 has a complex sealing structure 67 capable of resisting high temperatures and high pressure, attaining low torque and having a good service life. The complex sealing structure 67 includes: the annular curved surface 531 of the butterfly disc outer rim 53 is a smooth curved surface comprised of an unequal-width conical surface 532 and an unequal-width curved surface 533. The unequal-width curved surface 533 is disposed in a closing direction 791 of the butterfly disc 5, as shown in FIG. 5D. Respective positions along cross-sectional lines a-a, b-b and c-c are the same as the positions along the cross-sectional lines of the conventional butterfly valve shown in FIG. 7A. A portion of the unequal-width conical surface 532 along the line a-a having a smaller sealing width 63(B), a portion thereof along the line b-b has a larger sealing width 63(B), and a portion thereof along the line c-c has a largest sealing width 63(B). In other words, the structure widens progressively from the portion near the valve shaft 55 towards the portion near the middle portion of the butterfly disc 5, and the unequal-width conical surface 532 is constructed as a part of the sealing surface 6. A side of the unequal-width conical surface 532 opposite to the unequal-width curved surface 533 forms a corner edge 535 having a small arc radius connected to a superficial face of the butterfly disc flank 56. The corner edge 535 is disposed in an opening direction of the butterfly disc 5. The corner edge 535 and the inner surface 311 of the lining generate an extreme small interference sliding 7. The unequal-width curved surface 533 extends from the superficial face of the butterfly disc flank 56 to the outer rim 53. The portion of the unequal-width curved surface 533 along the line a-a has a longest smooth arc 533a, the portion thereof along the line b-b has a shorter smooth arc 533b, and the portion thereof along the line c-c has a shortest smooth arc 533c. In other words, the structure narrows progressively from the portion near the valve shaft 55 towards the portion near the middle portion of the butterfly disc 5. The unequal-width curved surface 533 makes an interference sliding 7 with the inner surface 311 of the lining. The longest smooth arc 533a, the shorter smooth arc 533b and the shortest smooth arc 533c are formed in a curve analogous to an elliptical curve. The short diameter of the ellipse is perpendicular to the superficial face of the butterfly disc flank 56. These curves can be constructed by multiple arcs. An outer rim 511 of the inner metallic butterfly disc 51 of the butterfly disc 5 also has a corresponding curved structure including butterfly disc flanks 516, bulging portions 517, horizontal sealing end surfaces 518 and side cutting edges 519, as shown in FIG. 4D. An unequal-width conical surface 514 is also provided, and an unequal-width curved surface 515 has a longest arc 515a along the cross-sectional line a-a and a shortest arc 515c along the cross-sectional line c-c.

[0191] Referring to FIG. 4A, the complex sealing structure 67 can fulfill the resistance to high temperatures and high pressure. It is herein taken as an example that a butterfly valve whose caliber is 3 inches, the thickness of the outer rim of the metallic butterfly disc 51 is 8 mm, the sealing width 63(B) of the portion of the unequal-width conical surface 532 along the line a-a exceeds 50 percent (50%) of the thickness 631(t1) of the outer rim of the inner metallic butterfly disc 51, and the sealing width thereof is above 4 mm. Further, the sealing width 63(B) of the portion of the unequal-width conical surface 532 along the line c-c exceeds 70 percent (70%) of the thickness 631(t1) of the outer rim of the inner metallic butterfly disc 51, and the sealing width thereof is above 5.6 mm. The unequal-width conical surface 532 and the inner surface 311 of the lining are pressed against each other to define the continuously reliable sealing surface 6, and the press sealing is also connected to the shaft sealing surface 637 and the shaft hole surface 634, as shown in FIG. 2A and FIG. 4C. The sealing surface 6 has the largest radius and bears the largest moment of static pressure at the portion along the line c-c to attain the largest sealing width 63(B) whereby the higher pressure resistance and the better airtight capability are provided. This sealing width 63(B) is not smaller than the width of the conventional ribbon sealing 62.

[0192] Referring to FIGS. 5Ai, 5Aii, and 5Aiii, the complex sealing structure 67 shown in FIGS. 4A through 4D can fulfill the low torque and have a good life time because the portion of the unequal-width curved surface 533 along the line a-a has a smaller contact angle 71() and decreases the sliding distance greatly, and the contact angle 71() of the unequal-width curved surface 533 approaches the contact angle 71() of the conventional linear sealing.

[0193] Referring to FIGS. 5Ai, 5Aii, 5Aiii, 5B, 5C, 5D and 5E, the complex sealing structure 67 shown in FIGS. 4A through 4D can fulfill the low torque and have a good life time. More specifically, in terms of the portion of the complex sealing structure 67 along the line a-a during the closing operation, there is an interference sliding 7 generated between the unequal-width curved surface 533 and the inner surface 311 of the lining, and the unequal-width curved surface 533 slides forwards at a sliding angle 74() so that a friction force 75(F) can impinge on the inner surface 311 of the lining, cause a depression at a place to which the press is added, and cause a lining deformation 68() which protrudes forwards on a frontal side of the butterfly disc outer rim 53. The material of the inner surface 311 of the lining having the lining deformation 68() bears the press, and the magnitude of deformation varies according to the value of the packing amount 65(). The material of the inner surface 311 of the lining on the rear side of the butterfly disc outer rim 53 bears the tension. The sliding angle 74() and the lining deformation 68() of the complex sealing structure 67 are smaller than those of the ribbon sealing 62 and the linear sealing 61. When the sliding angle 74() and the lining deformation 68() become larger, it is more unfavorable for using at high temperatures. In other words, materials of the inner surface 311 of the lining and the external fluoroplastic encapsulation 69 of the butterfly disc 5 suffer more creep and friction forces 75(F).

[0194] Referring to FIG. 6 A, when the butterfly disc 5 is open or closed, the butterfly disc 5 forms a certain opening degree whereby a flow passage 8 forms a slit passage 81, and a sharply widening flow passage 814 and a gradually reducing flow passage 815 are respectively generated on both sides of the butterfly disc 5, as arrowed by a streamline 811 in the figure. When fluid flows, a circulation zone 812 appears at the back side of the butterfly disc 5. The unequal-width curved surface 533 of the butterfly disc outer rim 53 of the butterfly disc 5 can provide the slit passage 81 with more flow areas, i.e. a slit width 813(W) becomes larger. This arrangement benefits an increase in the flow amount and Cv value of the butterfly disc 5 in a small-angled position and also reduces a fluid torque 792(Th).

[0195] The torque for closing the butterfly valve of this invention is 40 Ntm under an atmospheric pressure, and this torque is required when a 3-inch butterfly valve is adopted and set in a state of near 90 degrees. Torque which is less than 30 Ntm (<30 Ntm) is needed from 0 degrees to 80 degrees, and torque which is less than 20 Ntm (<20 Ntm) is needed while opening. These results show that the interference sliding 7 which the inner surface 311 of the lining experiences occurs smoothly, and the suffered friction force 75(F) is reduced. Particularly, when the required torque is reduced during the opening operation, the friction force 75(F) is largely decreased, and the service life of the butterfly valve 1 is prolonged.

[0196] In a preferred embodiment of this invention, tests are executed on a standard platform. Angles of the butterfly disc 5 are set at 0 degrees, 18 degrees, 36 degrees, 54 degrees, 72 degrees, and 90 degrees. When the angle is 0 degrees, a full open state is presented. When the angle is 90 degrees, a full closed state is presented. Table 1 is a result of the preferred embodiment showing the flow coefficient Cv. Table 2 is a result of Reference 10 showing the Cv value, and Table 3 is a result of Reference 11 showing the Cv value. FIGS. 6Bi, 6Bii and 6Biii are curve diagrams showing a curve A, a curve B, and a curve C at different opening degrees. The comparison between the butterfly valve of this invention and these two references is described as follows: [0197] 1. The linearity of the curve of the flow coefficient Cv of the butterfly disc of this invention is better than those of Reference 10 and Reference 11. [0198] 2. The flow coefficient Cv % is 16% when the butterfly disc of this invention has a low opening degree at 36 degrees. The Cv % is 9% when Reference 10 has an opening degree at 35 degrees. The Cv % is 11% when Reference 11 has an opening degree at 40 degrees. [0199] 3. The flow coefficient Cv % is 34% when the butterfly disc of this invention has a middle opening degree at 54 degrees. The Cv % is 23% when Reference 10 has an opening degree at 55 degrees. The Cv % is 26% when Reference 11 has an opening degree at 60 degrees.

TABLE-US-00001 TABLE 1 3 lined Butterfly Valve (the embodiment) Open degree 0 18 36 54 72 90 Cv 0 10.7 60.3 127.2 271 377.2 Cv % 0% 3% 16% 34% 72% 100%

TABLE-US-00002 TABLE 2 Reference 10 CN100376828C-Valve body of miter valve Open degree 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 Cv 0 0 11.8 27 35.7 46.9 61.9 75.1 90.1 117.3 153.9 193.7 243.9 319.2 393.3 508.6 625 805.8 830.7 CV % 0% 0% 1% 3% 4% 6% 7% 9% 11% 14% 19% 23% 29% 38% 47% 61% 75% 97% 100%

TABLE-US-00003 TABLE 3 Reference 11 Tomoe Valves USA catalog-846t-847t-847q-20150601 lined 3butterfly valve Open degree 0 20 30 40 50 60 70 80 90 Cv 0 9 25 56 85 130 225 396 500 Cv % 0% 2% 5% 11% 17% 26% 45% 79% 100%

DESCRIPTIONS OF ELEMENTS

[0200] 1 symmetrical butterfly valve [0201] 2 valve body [0202] 21 upper valve body [0203] 211 fastening portion [0204] 212 shaft hole portion [0205] 22 lower valve body [0206] 221 fastening portion [0207] 222 shaft hole portion [0208] 23 inner peripheral surface [0209] 232 groove [0210] 233() trapezoidal included angle [0211] 234 projecting ring [0212] 235 expansion room [0213] 236(t2) width of the projecting ring [0214] 237(s1) groove depth [0215] 238(t3) bottom width [0216] 239(s2) height of the projecting ring [0217] 24 fastening hole [0218] 25 central axis [0219] 3 lining [0220] 31 tubular portion [0221] 311 inner surface of the lining [0222] 312 shaft hole [0223] 315 outer diameter of the tubular portion [0224] 318 reinforcement portion [0225] 32 radial flange [0226] 4 back-up ring [0227] 41 inner diameter of the back-up ring [0228] 42 trapezoidal cross section [0229] 43() trapezoidal included angle [0230] 45(s3) thickness [0231] 46 shaft hole portion [0232] 5 butterfly disc [0233] 51 metallic butterfly disc [0234] 511 outer rim [0235] 513 linking hole [0236] 514 unequal-width conical surface [0237] 515 unequal-width curved surface [0238] 515a longest arc [0239] 515c shortest arc [0240] 516 butterfly disc flank [0241] 517 bulging portion [0242] 518 horizontal sealing end surface [0243] 519 side cutting edge [0244] 53 butterfly disc outer rim [0245] 531 annular curved surface [0246] 532 unequal-width conical surface [0247] 533 unequal-width curved surface [0248] 533a longest smooth arc [0249] 533b shorter smooth arc [0250] 533c shortest smooth arc [0251] 54 bulging portion [0252] 544 shaft hole [0253] 55 valve shaft [0254] 55a upper valve shaft [0255] 55b lower valve shaft [0256] 56 butterfly disc flank [0257] 57 outer diameter of the butterfly disc [0258] 6 sealing surface [0259] 61 linear sealing [0260] 62 ribbon sealing [0261] 63(B) sealing width [0262] 631(t1) thickness of the metallic butterfly disc [0263] 632 horizontal sealing plane [0264] 633 joint edge [0265] 634 shaft hole surface [0266] 634a sealing recess [0267] 635 sealing end surface [0268] 636 side cutting edge [0269] 637 shaft sealing surface [0270] 637a sealing ring [0271] 64(p) press pressure [0272] 65() packing amount [0273] 66 inward protrusion [0274] 66a swelling curve [0275] 66b(h) swelling height [0276] 67 complex sealing [0277] 68() lining deformation [0278] 69 fluoroplastic encapsulation [0279] 69a encapsulation deformation [0280] 7 interference sliding [0281] 71() contact angle [0282] 72 contact point [0283] 73(R) rotary moment arm [0284] 74(%) sliding angle [0285] 75(F) friction force [0286] 79(T) torque [0287] 791 rotational direction [0288] 792(Th) fluid torque [0289] 793(Tp) static pressure torque [0290] 794(Tf) friction torque [0291] 8 flow passage [0292] 81 slit passage [0293] 811 streamline [0294] 812 circulation zone [0295] 813(W) slit width [0296] 814 sharply widening flow passage [0297] 815 gradually reducing flow passage [0298] 82(Ps) static pressure [0299] 9 fluoroplastic butterfly valve [0300] 91 valve body [0301] 911 inner peripheral surface [0302] 912 groove [0303] 913 upper shaft hole portion [0304] 914 lower shaft hole portion [0305] 92 butterfly disc [0306] 92a linear sealing butterfly disc [0307] 92b ribbon sealing butterfly disc [0308] 92c metallic butterfly disc [0309] 921 butterfly disc flank [0310] 922 butterfly disc outer rim [0311] 923 annular curved surface [0312] 923a corner [0313] 924 conical curved surface [0314] 927 butterfly disc protrusion [0315] 928 shaft hole [0316] 929 diametral connection [0317] 93 lining [0318] 931 tubular portion [0319] 932 radial flange [0320] 933 inner surface of the lining [0321] 937 shaft hole [0322] 94 back-up ring [0323] 941(t4) thickness [0324] 95 valve shaft