Gasket and joint structure

Abstract

To eliminate a dead space between a gasket and a flange.SOLUTION: Provided is a gasket 30 having an annular shape, mounted between planar seal surfaces 12x of opposing flange parts 12. The gasket includes a step formed between a radially inner surface 30b and a radially outer surface 30c, both of which are continuous with an inner circumferential surface. The radially inner surface 30b is located on an axially outer side from the radially outer surface 30c. The radially inner surface 30b and the radially outer surface 30c each form a plane orthogonal to an axial direction. After the radially inner surface 30b comes into contact with the seal surfaces 12x, the radially outer surface 30c comes into contact with the seal surfaces 12x.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a gasket and a joint structure using the gasket. [Background technology]

[0002] As shown in Patent Document 1, a conventional pipe joint includes first and second joint parts having fluid passages that communicate with each other, and a gasket interposed between the butt end faces of the first and second joint parts, with annular seal projections formed on the butt end faces (sealing surfaces) of the first and second joint parts. In this pipe joint, the annular seal projections bite into the axial end face of the gasket, thereby improving the adhesion between them.

[0003] However, in a structure in which the gasket is crushed by the sealing protrusions formed on the sealing surface, a dead space may be formed between the gasket and the sealing surface on the gas-contacting side of the gasket (radially inward from the sealing protrusions). This dead space causes gas to accumulate in the dead space. For example, if a pipe fitting with this structure is used in a semiconductor manufacturing process, high-purity material gas will accumulate in the dead space between the gasket and the sealing surface, adversely affecting the concentration control of the high-purity material gas. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-17381 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made to solve the above problems, and its main object is to reliably eliminate the dead space between the gasket and the flange portion. [Means for solving the problem]

[0006] That is, the gasket according to the present invention is a ring-shaped gasket that is fitted between the planar sealing surfaces of opposing flange portions, and is characterized in that a step is formed between both radially inner axial end faces (hereinafter referred to as radial inner surfaces) that are continuous with the inner peripheral surface and both radially outer axial end faces (hereinafter referred to as radial outer surfaces), the radially inner surfaces are located axially outward of the radially outer surfaces, the radially inner surfaces and the radially outer surfaces each have a planar shape perpendicular to the axial direction, and the radially inner surfaces come into contact with the sealing surfaces before the radially outer surfaces come into contact with the sealing surfaces.

[0007] With a gasket configured in this manner, when the flanges are fastened together, the radially inner surface comes into contact with the sealing surface and undergoes plastic deformation, and then the radially outer surface comes into contact with the sealing surface. This results in the highest sealing performance on the gas-contacting side (the radially inner side) of the gasket, ensuring the elimination of dead space between the gasket and the flanges. Furthermore, because the gas-contacting side is the part with the highest sealing performance, any dead space that forms will be detected as a leak. Therefore, the presence or absence of dead space can be detected by a leak test, such as a helium leak test.

[0008] In order to ensure that when the radially inner surface undergoes plastic deformation, the deformation escapes radially outward rather than radially inward (toward the flow path), it is desirable that a groove be formed along the circumferential direction between the radially inner surface and the radially outer surface.

[0009] In a specific embodiment of the gasket, the dimension of the step along the axial direction is preferably 0.03 to 0.09 mm.

[0010] Furthermore, a joint structure according to the present invention is a joint structure in which opposing flange portions are fastened together with an annular gasket sandwiched between the planar seal surfaces of the flange portions, wherein a step is formed between each of the radially inner axial end faces (hereinafter referred to as radially inner surfaces) that are continuous with the inner peripheral surface and each of the radially outer axial end faces (hereinafter referred to as radially outer surfaces), the radially inner surfaces are located axially outward of the radially outer surfaces, the radially inner surfaces and the radially outer surfaces each have a planar shape perpendicular to the axial direction, and the radially inner surfaces come into contact with the seal surfaces before the radially outer surfaces come into contact with the seal surfaces.

[0011] In order to improve the sealing performance between the gasket and the sealing surface, it is desirable that when the flange portions are fastened together, at least the radially inner surface undergoes plastic deformation, and the radially inner surface and the radially outer surface become flush with each other.

[0012] In order to improve the sealing performance between the gasket and the sealing surface and the number of repeated uses, it is desirable that the sealing surface be subjected to a mirror finish. [Effects of the Invention]

[0013] According to the present invention described above, it is possible to reliably eliminate the dead space between the gasket and the flange portion. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a partial cross-sectional view of a joint structure according to an embodiment of the present invention. [Figure 2] 4 is a view showing the clamp joint of the embodiment in a fastened state as viewed from the axial direction. FIG. [Figure 3] FIG. 2 is a view showing the clamp joint of the embodiment in an unfolded state as viewed from the axial direction. [Figure 4] FIG. 2 is a plan view of the clamp joint of the embodiment in an unfolded state. [Figure 5]FIG. 2 is a perspective view of a central clamping element in the same embodiment. [Figure 6] 2A and 2B are a cross-sectional view and a partially enlarged cross-sectional view schematically illustrating the configuration of the gasket of the embodiment. [Figure 7] 4 is a cross-sectional view schematically showing the sealing mechanism of a joint structure using the gasket of the embodiment. FIG. [Figure 8] FIG. 10 is a cross-sectional view of a joint structure according to a modified embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] <One embodiment of the present invention> An embodiment of a joint structure according to the present invention will be described below with reference to the drawings. Note that, for ease of understanding, all of the drawings shown below are drawn in a schematic manner with appropriate omissions or exaggerations. Identical components are designated by the same reference numerals, and their description will be omitted where appropriate.

[0016] 1, the joint structure 100 of this embodiment is formed by connecting a pair of pipe members 10 with a clamp joint 20. Specifically, the joint structure 100 includes the clamp joint 20 that connects the pair of pipe members 10 in an opposing state, and an annular gasket 30 that is interposed between the pair of pipe members 10, and is a structure that connects the pair of pipe members 10 in an airtight manner.

[0017] The pipe member 10 has a pipe main body 11 with a linear flow path formed therein and a flange portion 12 provided at the end of the pipe main body 11. A flat sealing surface 12x that comes into close contact with a gasket 30 is formed on the tip surface of the flange portion 12. This sealing surface 12x is flat and perpendicular to the axial direction. The sealing surface 12x is mirror-finished. Furthermore, an inclined surface 14 whose diameter increases toward the tip is formed on the back surface of the flange portion 12 opposite the opposing surface (tip surface). Furthermore, a step portion 15 with a decreasing diameter is formed on the outer circumferential surface of the flange portion 12. A holder 50 that holds the gasket 30 is attached to this step portion 15. Furthermore, a ring-shaped dustproof protector 60 may be attached to the outer periphery of the step portion 15 as needed.

[0018] The clamp joint 20 is fitted onto the opposing flange portions 12 to tightly fasten them together. Specifically, as shown in Figures 1 to 4, the clamp joint 20 has a clamp body 21 having a recessed groove 211 formed on its inner peripheral surface so as to extend in the circumferential direction, and a fastening mechanism 22 that tightens the clamp body 21 so as to reduce its inner diameter.

[0019] The clamp body 21 has a series of clamp elements 21a-21c in which adjacent ones are rotatably connected to each other. Specifically, the clamp body 21 has one central clamp element 21a and a pair of outer clamp elements 21b, 21c rotatably connected to both ends of the central clamp element 21a. Each of the clamp elements 21a-21c is made of stainless steel, such as SUS630 or SUS316.

[0020] 1 and 4, a circumferentially extending groove 211 is formed on the inner peripheral surface of each of the clamp elements 21a to 21c. The groove 211 has a width that allows it to fit onto the outer peripheral edges of the pair of opposing flange portions 12. An inclined surface 213 corresponding to the inclined surface 14 of the flange portions 12 is formed on the inner surface of a pair of side wall portions 212 that form the groove 211. The groove 211 of each of the clamp elements 21a to 21c has a depth that allows the bottom surface of the groove 211 to not come into contact with the outer peripheral surface of the flange portions 12 when the inclined surface 213 of the side wall portions 212 is in contact with the inclined surface 14 of the flange portions 12.

[0021] These clamp elements 21a to 21c are rotatably connected by a hinge pin 214. The hinge pin 214 is preferably made of stainless steel such as SUS630, SUS316, or SUS304, and is preferably made of a material having strength equal to or greater than that of the material of each of the clamp elements 21a to 21c.

[0022] As shown in FIG. 4, a first connecting portion 215 having an insertion hole H1 through which the hinge pin 214 is inserted is formed at one end of each of the pair of outer clamp elements 21b, 21c that is connected to the central clamp element 21a.

[0023] The first connecting portion 215 is configured by a protrusion that protrudes toward the central clamp element 21a at one end of the outer clamp elements 21b, 21c. The width (axial dimension) of the protrusion is smaller than the distance between the pair of side wall portions 212 that form the recessed groove 211 (the width of the bottom surface of the recessed groove 211) (see FIG. 4).

[0024] Furthermore, a pair of second connecting portions 216 are formed at both ends of the central clamp element 21a, sandwiching the first connecting portions 215 of the outer clamp elements 21b and 21c and having fixing holes H2 to which the hinge pins 214 are fixed. The hinge pins 214 are fixed in the fixing holes H2 by caulking, press-fitting, or the like.

[0025] The pair of second connecting portions 216 sandwich the convex portion, which is the first connecting portion 215, from both sides in the axial direction, with a small gap between them. Recesses into which the convex portions, which are the first connecting portions 215, fit with a small gap between them, are formed at each end of the central clamp element 21a, and the wall portions along the axial direction that form these recesses serve as the second connecting portions 216. The pair of second connecting portions 216 are located circumferentially on extensions of the pair of side wall portions 212 that form the recessed groove 211 (see FIG. 4).

[0026] 2 to 5, the upper surface portions 212a of the pair of side wall portions 212 provided on the central clamp element 21a are formed in the circumferential direction from the pair of second connecting portions 216 on one end side to the pair of second connecting portions 216 on the other end side. In other words, the side wall portions 212 are formed so that the upper surface portions 212a of the side wall portions 212 are connected to both the second connecting portions 216 on one end side and the second connecting portions 216 on the other end side. In this embodiment, the upper surface portions 216a of the second connecting portions 216 and the upper surface portions 212a of the side wall portions 212 are linearly continuous when viewed from the axial direction. In addition, an inclined surface 213 corresponding to the inclined surface 14 of the flange portion 12 is formed on the entire inner surface of the pair of side wall portions 212 of the central clamp element 21a.

[0027] Furthermore, in terms of the relationship between the central clamp element 21a and the outer clamp elements 21b and 21c, a shape that avoids interference between the side wall portion 212 of the central clamp element 21a and the side wall portions of the outer clamp elements 21b and 21c is different from conventional shapes. In this embodiment, the gap formed between the side wall portion 212 of the central clamp element 21a and the side wall portions of the outer clamp elements 21b and 21c does not extend from the hinge pin 214 toward the axial center, but extends in a direction perpendicular to the radial direction from the axial center (the left-right direction in FIG. 2, which is the arrangement direction of the two hinge pins 214).

[0028] The fastening mechanism 22 fastens the free ends of the pair of outer clamp elements 21b, 21c together. Specifically, as shown in FIGS. 1 to 4, the fastening mechanism 22 has a bolt member 221 rotatably provided in a through hole H3 formed in the free end of one of the outer clamp elements 21b, and a female screw hole 222 formed in the free end of the other outer clamp element 21c. By threading the bolt member 221 into the female screw hole 222, the pair of outer clamp elements 21b, 21c are connected and the inner diameter of the clamp body 21 can be expanded or contracted. The bolt member 221 is made of stainless steel, such as SUS304 or SUS316.

[0029] 4, the through hole H3 formed in the free end of one of the outer clamp elements 21b has an elliptical shape extending along the radial direction. This elliptical through hole H3 is configured to absorb any inclination of the bolt member 221 relative to one of the outer clamp elements 21b when the bolt member 221 is screwed into the female screw hole 222. In addition, a stopper ring 223 prevents the bolt member 221 from coming out of the through hole H3.

[0030] Furthermore, when the free ends of the pair of outer clamp elements 21b, 21c are fastened together, the stopper ring 223 does not come into contact with the other outer clamp element 21c (see FIG. 2). Specifically, the thickness of the stopper ring 223 is smaller than the dimension of the gap formed between the free ends of the pair of outer clamp elements 21b, 21c when these free ends are fastened together. This configuration ensures a sufficient tightening margin for the bolt member 221, making it possible to manage the torque of the bolt member 221.

[0031] The gasket 30 is fitted between the planar sealing surfaces 12x of the opposing flange portions 12, and is annular in shape with an inner diameter that is the same as or slightly larger than the inner diameter of the flow passages of the pair of pipe members 10. The gasket 30 is made of high-cleanliness stainless steel, such as SUS316 or SUS316L.

[0032] Specifically, as shown in FIG. 6, the gasket 30 has radially inner axial end faces (hereinafter referred to as radially inner surface 30b) that are continuous with the inner peripheral surface 30a, radially outer axial end faces (hereinafter referred to as radially outer surface 30c), and a step 30d formed between them.

[0033] The radially inner surface 30b has an annular shape and is flat, perpendicular to the axial direction. The radially outer surface 30c has an annular shape that is larger than the radially inner surface 30b and is flat, perpendicular to the axial direction. The radially inner surface 30b is positioned axially outward of the radially outer surface 30c. In other words, the radially inner surface 30b protrudes axially outward relative to the radially outer surface 30c. In this embodiment, the radially inner surface 30b protrudes axially outward relative to the radially outer surface 30c by 0.03 to 0.09 mm.

[0034] Furthermore, the step 30d is annular and formed between the radially inner surface 30b and the radially outer surface 30c. The dimension of this step 30d along the axial direction is 0.03 to 0.09 mm. In this embodiment, an annular groove 30M is formed along the circumferential direction between the step 30d, i.e., between the radially inner surface 30b and the radially outer surface 30c. This groove 30M can absorb the deformed portion of the radially inner surface 30b that undergoes plastic deformation. The cross-sectional shape of this groove 30M perpendicular to the axial direction is not limited to an arc shape, but may be a V-shape or a rectangle.

[0035] Next, a method for connecting a pair of pipe members 10 using the clamp joint 20 of this embodiment and a sealing mechanism of the joint structure using the gasket 30 will be described with reference to FIG.

[0036] The flange portions 12 of a pair of pipe members 10 are placed opposite each other with a gasket 30 sandwiched between them. At this time, as shown in FIG. 7(a), a holder 50 holding the gasket 30 is attached to the step portion 15 formed on the flange portion 12 of one of the pipe members 10. Then, the gasket 30 is sandwiched between the flange portion 12 of the other pipe member 10.

[0037] In this state, the clamp body 21 is attached so as to surround the pair of flange portions 12. At this time, the recessed grooves 211 of each of the clamp elements 21a to 21c fit onto the outer peripheral edges of the pair of flange portions 12. Then, the bolt members 221 are threaded into the female screw holes 222 to fasten the free ends of the pair of outer clamp elements 21b, 21c together. This reduces the inner diameter of the clamp body 21, causing the inclined surfaces 213 of each of the clamp elements 21a to 21c to press against the inclined surfaces 14 of the flange portions 12, and the axial component force generated at this time crimps the flange portions 12 together.

[0038] When the flange portions 12 are crimped and joined together, the sealing surfaces 12x of the flange portions 12 first come into surface contact with the radially inner surface 30b of the gasket 30, as shown in FIG. 7(b). Then, as the flange portions 12 are crimped and joined together, the radially inner surface 30b undergoes plastic deformation while remaining in surface contact with the sealing surfaces 12x, as shown in FIG. 7(c). The portion deformed by this plastic deformation enters the groove 30M formed in the step 30d. Furthermore, the sealing surfaces 12x of the flange portions 12 not only come into surface contact with the radially inner surface 30b of the gasket 30, but also come into surface contact with the radially outer surface 30c of the gasket 30. As a result, when the flange portions 12 are fastened together, the radially inner surface 30b and the radially outer surface 30c are flush with each other.

[0039] In this way, by tightening the fastening mechanism 22, the radially inner surface 30b is plastically deformed until it becomes flush with the radially outer surface 30c, and the gasket 30 is in close contact with almost the entire sealing surface 12x. The surface pressure of the plastically deformed radially inner surface 30b is greater than that of the radially outer surface 30c, completely sealing the sealing portion (between the radially inner surface 30b and the sealing surface 12x) without any gaps. In addition, the inner peripheral surface 30a of the gasket 30 and the inner peripheral surface formed by the flow path of each pipe member 10 become almost flush with each other. In the joint structure 100 of this embodiment, by tightening the fastening mechanism 22, the surface pressure σ of the radially inner surface 30b is reduced to σ=350 N / mm 2 and the surface pressure σ on the radially outer surface 30c is σ=250 N / mm 2As a metal flat seal, the required surface pressure σ>180N / mm 2 Sealing performance is ensured (JIS standard).

[0040] <Effects of this embodiment> In the clamp joint 20 of this embodiment configured as described above, when the flange portions 12 are tightened, the radially inner surface 30b comes into surface contact with the sealing surface 12x and undergoes plastic deformation, and then the radially outer surface 30c comes into contact with the sealing surface 12x. Therefore, when the flange portions 12 are tightened together, the sealing performance is highest on the gas-contacting side (radially inner side) of the gasket 30, and dead space between the gasket 30 and the sealing surface 12x of the flange portions can be reliably eliminated. Furthermore, because the gas-contacting side is the part with the highest sealing performance, any dead space that forms will detect a leak. Therefore, the presence or absence of dead space can be detected by a leak test, such as a helium leak test.

[0041] Furthermore, in this embodiment, the upper surface portions 212a of the pair of side wall portions 212 provided on the central clamp element 21a are formed circumferentially from the pair of second connecting portions 216 on one end side to the pair of second connecting portions 216 on the other end side, thereby improving the mechanical strength of the central clamp element 21a in the clamp joint 20. As a result, the mechanical strength of the entire clamp joint 20 can be improved, and there is no risk of the clamp joint 20 being damaged even if the clamp joint 20 is tightened to the point where the radially inner surface 30b is plastically deformed. In addition, the mechanical strength of the central clamp element 21a can also be improved by fixing the hinge pin 214 in the fixing hole of the central clamp element 21a by, for example, crimping or press-fitting. As a result, even greater safety can be achieved for the clamp joint 20.

[0042] <Other embodiments> The present invention is not limited to the above-described embodiment.

[0043] For example, in the above embodiment, the inclined surface 213 was formed on the entire inner surface of the side wall portion 212 of the central clamp element 21a, but the inclined surface 213 may be formed on only a portion of the inner surface of the side wall portion 212 of the central clamp element 21a.

[0044] Furthermore, in the above embodiment, when viewed from the axial direction, the upper surface portion 216a of the second connecting portion 216 and the upper surface portion 212a of the side wall portion 212 are continuous in a straight line, but as long as the upper surface portion 212a of the side wall portion 212 is configured to be continuous with the second connecting portion 216, these upper surface portions 212a, 216a do not have to be continuous in a straight line.

[0045] Furthermore, the fastening mechanism 22 may be configured to screw the bolt member 221 into the female threaded hole 222 formed in the outer clamp element 21c, or may be configured to form a through hole in the free end of the other outer clamp element 21c through which the bolt member 221 is inserted, and to screw a nut member onto the bolt member 221 extending from the through hole.

[0046] Although the gasket 30 in the above embodiment has a configuration in which the groove 30M is provided in the step 30d, the gasket 30 may have a configuration in which the groove 30M is not provided in the step 30d.

[0047] The connection structure 100 in the above embodiment is configured to fasten the flange portions 12 together using a clamp joint 20, but as shown in Figure 7, the pipe joint may also be configured to include a first nut member 71 that is fitted onto the outer periphery of one pipe member 10 and has a male threaded portion formed on its outer periphery, and a second nut member 72 that is fitted onto the outer periphery of the other pipe member 10 and has a female threaded portion formed on its inner periphery that screws into the male threaded portion, and to connect a pair of pipe members 10 by screwing together the male threaded portion of the first nut member 71 and the female threaded portion of the second nut member 72.

[0048] More specifically, the tip portion 711 of the first nut member 71 presses the flange 12 of one of the tubular members 10 from the back side. The second nut member 72 is provided with an accommodation recess 721 that accommodates the flange 12 of each of the pair of tubular members 10, and is configured so that the bottom surface of this accommodation recess 721 receives the flange 12 of the other tubular member 10 from the back side. With this configuration, by threading the male thread portion of the first nut member 71 and the female thread portion of the second nut member 72 together, the first nut member 71 presses the flange 12 of one of the tubular members 10 from the back side, and the second nut member 72 receives the flange 12 of the other tubular member 10 from the back side, and the sealing surface 12x comes into surface contact with the gasket 30, as in the above embodiment, to airtightly connect the pair of tubular members 10.

[0049] Furthermore, the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications are possible without departing from the spirit of the present invention. [Explanation of symbols]

[0050] 100···Joint structure 12 Flange part 12x sealing surfaces 30 Gasket 30a...Inner circumferential surface 30b...Radial inner surface 30c...Radial outer surface 30d... step 30M...Groove

Claims

1. A ring-shaped gasket that is fitted between the planar sealing surfaces of opposing flange portions, a step is formed between both axial end faces (hereinafter referred to as radially inner side faces) on the radially inner side that are continuous with the inner peripheral surface and both axial end faces (hereinafter referred to as radially outer side faces) on the radially outer side, The radially inner surface is located axially outward of the radially outer surface, The radially inner surface and the radially outer surface each have a planar shape perpendicular to the axial direction, The gasket wherein the radially inner surface contacts the sealing surface, and then the radially outer surface contacts the sealing surface.

2. The gasket according to claim 1 , wherein a groove is formed along a circumferential direction between the radially inner surface and the radially outer surface.

3. 3. The gasket according to claim 1, wherein the dimension of the step along the axial direction is 0.03 to 0.09 mm.

4. A joint structure in which opposing flanges are fastened together with an annular gasket sandwiched between planar sealing surfaces of the flanges, The gasket has a step formed between both axial end faces (hereinafter referred to as radially inner side faces) on the radially inner side that are continuous with the inner peripheral surface and both axial end faces (hereinafter referred to as radially outer side faces) on the radially outer side, The radially inner surface is located axially outward of the radially outer surface, The radially inner surface and the radially outer surface each have a planar shape perpendicular to the axial direction, A joint structure in which the radially inner surface contacts the seal surface, and then the radially outer surface contacts the seal surface.

5. The joint structure according to claim 4, wherein, in a state in which the flange portions are fastened together, at least the radially inner surface is plastically deformed, and the radially inner surface and the radially outer surface become flush with each other.

6. 6. The joint structure according to claim 4, wherein the sealing surface is mirror-finished.

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