Valve element for butterfly valve

Abstract

To make a structure where an incident angle of a valve element with respect to a seat ring is small, to prevent wear of the seat ring and increase in opening / closing torque and to make it possible to recover seal performance when leakage occurs due to aging.SOLUTION: A valve element for a butterfly valve has the same edge shape of respective cross sections in an axial direction of the valve element to reduce an incident angle of the valve element with respect to a seat ring and the edge shape of the valve element is made so as to be connected with two circular arcs with a linear line.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a valve body of a butterfly valve, and more particularly to a valve body of a butterfly valve which reduces wear on a seat ring and reduces opening and closing torque, and which is capable of recovering sealing performance by closing the valve blades further in the closing direction from the fully closed position. [Background technology]

[0002] Conventionally, there has been proposed a central type butterfly valve in which the outer peripheral surface of a disk-shaped valve body is pressed into the inner peripheral surface of a seat ring made of an elastic sealing material to obtain sealing surface pressure for opening and closing the valve, and in which the entire outer peripheral surface, including the boss portion of the valve body, is formed of the same curved surface with a radius smaller than the outer peripheral radius of the valve body, making the sealing surface pressure uniform all around the valve body, making the sealing performance uniform all around the valve body, and ensuring stable sealing performance with the minimum necessary amount of squeezing, making it possible to open and close the valve body with less torque, and also improving the durability of the seat ring by reducing the load on the seat ring (Patent Document 1).

[0003] However, when the entire outer circumferential surface of the disc, including the boss, is formed with the same curved surface, the edge shape of the disc changes in the height direction of the disc, as shown in Fig. 12. As the edge shape of the disc becomes elliptical, the aspect ratio of the disc increases, and the angle (incidence angle) between the cylindrical surface of the seat ring and the seat contact point of the disc increases. This causes the seat ring to deform when the disc bites into the seat ring, preventing the disc from biting into the seat ring smoothly, and increases the wear of the seat ring and the opening and closing torque. In addition, as the outer circumferential surface of the disc is formed with the same curved surface, the compression of the seat ring is maximized at the position of the disc where the valve opening is 0 degrees (fully closed position). Therefore, when leakage occurs due to aging, the compression of the seat ring decreases regardless of whether the disc is rotated in the open or closed direction, making it impossible to restore the sealing performance. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 3121527 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has a structure in which the valve disc radius shape is the same for each cross section in the valve axis direction and the incidence angle of the valve disc with respect to the seat ring is reduced. By reducing the incidence angle, deformation of the seat ring is suppressed when the valve disc bites into the seat ring, allowing the valve disc to bite into the seat ring smoothly, preventing wear on the seat ring and increasing opening and closing torque. In addition, by shaping the edge portion of the valve disc in an edge shape that connects two radii with a straight line, the maximum compression position of the seat ring is shifted in the closing direction from the fully closed position of the valve disc, making it possible to restore sealing performance in the event of leakage due to aging. [Means for solving the problem]

[0006] In order to solve the above problems, the inventors have taken measures to design the edge radius shape of the valve disc such that two radii (R) are connected by a straight line, and the edge shape of each cross section in the valve axis direction is the same shape, thereby reducing the angle of incidence of the valve disc with respect to the seat ring and shifting the maximum compression position of the seat ring in the closing direction from the fully closed position of the valve disc.

[0007] The valve body has an edge portion on the entry side that is a circular arc equal to or larger than the edge portion on the exit side, and a straight line portion on the entry side that is equal to or smaller than the straight line portion on the exit side. Effect of the Invention

[0008] According to the present invention, the disc edge radius shape is the same for each cross section in the valve axis direction, so that the incidence angle of the disc with respect to the seat ring can be reduced, and by reducing the incidence angle, deformation of the seat ring is suppressed when the disc bites into the seat ring, and the disc bites into the seat ring smoothly, preventing wear of the seat ring and an increase in opening and closing torque. In addition, the shape of the disc edge portion is an edge shape in which two radii are connected by a straight line, so that when the disc is closed further in the closing direction from the fully closed position, the flat portion of the disc formed by the straight line connecting the two radii bites into the seat ring. By the disc biting into the seat ring more than the fully closed position, it is possible to create a more closed state than the fully closed position, and even if valve leakage occurs in the fully closed position due to aging, the seal performance can be restored by closing the valve blade difference further in the closing direction from the fully closed position, and it is possible to eliminate valve leakage. [Brief description of the drawings]

[0009] [Figure 1] A perspective view of the valve body [Diagram 2] Front view of valve body [Diagram 3] Figure 2B-B line cross section [Figure 4] A perspective view of a butterfly valve in a fully open state. [Diagram 5] Central cross section of butterfly valve in fully open state [Figure 6] Central cross section of butterfly valve at the start of sealing [Figure 7] Central cross-sectional view of butterfly valve when fully closed (valve opening 0 degrees) [Figure 8] Central cross section of butterfly valve at 3 degrees overrun from fully closed [Figure 9] 1 is a diagram showing cross sections of a valve body at different positions in the valve axis direction; [Figure 10] Schematic diagram showing the definition of the valve disc size range [Figure 11] Schematic diagram showing the state of engagement between the valve disc and the seat ring when the valve disc is fully closed and at 3 degrees overrun [Figure 12] 1A and 1B are cross-sectional views of a conventional valve body taken at different positions in the valve axis direction; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] A preferred embodiment of the present invention will be described in detail below with reference to the drawings. In the drawings, (1) is a butterfly valve body, on whose inner circumferential surface is attached a seat ring (2) made of an elastic sealing material such as fluororesin or rubber. (3) is a disk-shaped valve body that contacts the inner circumferential surface of the seat ring (2) to provide a seal, and is rotatably supported on the valve body (1) by a valve stem (4).

[0011] The present invention is characterized in that the edge shape of the valve body (3) is made uniform for each cross section in the valve axis direction, the angle of incidence of the valve body with respect to the seat ring (2) is made small, and the edge shape of the valve body (3) is made into a shape that connects two circular arcs and a straight line.

[0012] That is, as shown in Fig. 9 and Fig. 10, the edge shape of the valve disc (3) is the same at both cross sections 1 and 2 in the valve axis direction. The edge shape is such that the arc (Ra) on the entry side of the valve disc (3) into the seat ring (2), i.e., the side where contact with the seat ring begins, is the same as or larger than the arc (Rb) on the end of contact with the seat ring, and the two arcs (Ra, Rb) on the entry side and exit side are connected by a straight line (Ya, Yb).

[0013] The valve body (3) of the present invention is suitable for butterfly valves with a valve diameter (2Rd) of preferably 40 mm small diameter to 300 mm medium diameter, but is not limited thereto. The thickness (T) of the valve body is preferably in the range of 3 to 36 mm so as to have the strength to withstand the fluid pressure and not to impede the flow when fully open. In addition, if the difference between the valve body radius (Rd) and the seat ring inner radius (Rs) is small, sealing is not performed, and if it is too large, the valve opening and closing torque increases. Therefore, the seat ring inner diameter (2Rs) is designed to be slightly smaller than the valve body diameter (2Rd), and the difference between the two, Rd-Rs, is preferably in the range of 0.1 to 2.0 mm. The seal portion that compresses the seat ring of the valve body is composed of straight lines (Ya, Yb) as shown in Figures 9 and 10. This allows the seal performance to be restored when the valve body is rotated further in the closing direction than the fully closed position. The linear distance (Ya+Yb) of the seal portion is preferably 1.0 to 15.6 mm. If the radius (Rb) of the edge portion of the valve body (3) on the outlet side is too small, the opening resistance increases, so the minimum value is set to 0.5 mm. In the valve body of the present invention, the inlet radius (Ra) is set so that the above valve body radius (Rd), seat ring radius (Rs), and linear portion (Ya) satisfy the following formula 1, and the inlet radius (Ra) is set to be equal to or larger than the outlet radius (Rb), and the dimensions of each portion are set so that the linear portion (Ya) on the inlet side from the center of the valve body is equal to or smaller than the linear portion (Yb) on the outlet side.

[0014] TIFF2025012007000002.tif24119

[0015] By providing the straight sections (Ya, Yb) on the edge of the valve disc (3), when the valve disc (3) is closed further from the fully closed position, the flat section formed by the straight section (Yb) on the outlet side is bitten into by the seat ring, as shown in Figure 11. As a result, even if leakage occurs due to aging, etc., it is possible to restore the sealing performance by closing the valve blade difference further in the closing direction from the fully closed position. [Explanation of symbols]

[0016] 1 Valve body 2 seat ring 3 Valve body 4-port shaft

Claims

1. A center-type butterfly valve in which the outer peripheral surface of a disk-shaped valve body is pressed into the inner peripheral surface of a seat ring made of an elastic sealing material to obtain sealing surface pressure, wherein the edge shape of the valve body in each cross section in the valve axial direction is made uniform, the angle of incidence of the valve body with respect to the seat ring is made small, and the edge shape of the valve body is formed by connecting two arcs and a straight line.

2. 2. A butterfly valve according to claim 1, wherein the arc of the edge of the valve body on the entry side is equal to or larger than the arc on the exit side.

3. 3. A butterfly valve according to claim 1, wherein the straight line portion on the inlet side of the edge of the valve body is the same as or smaller than the straight line portion on the outlet side.

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