JP2019178695A - Pipe joint - Google Patents

Abstract

To provide an excellent pipe joint in which sealability is hardly degraded by temperature change.SOLUTION: In a pipe joint 1A for connecting joint members 2, 3 having fluid passages 2a, 3a, a cylindrical gasket 6, a male screw member 4 disposed on one of the joint members, and a female screw member 5 disposed on the other joint member, an annular recessed portion is formed on a butt end surface of at least one of both joint members to form an annular space 9 when both joint members are kept into contact with each other, the gasket 6 is housed in the annular space 9 so that an inner peripheral surface of the gasket is kept into contact with an inner peripheral surface of the recessed portion and includes an annular back ring 7, the back ring 7 is housed in the annular space while kept into contact with an outer peripheral surface of the gasket 6 and an outer peripheral surface of the recessed portion, and an axial width d1 of the back ring 7 is larger than an axial width d2 of the annular space. When the joint members are connected, the back ring 7 is expanded in the radial direction and presses the gasket 6 to a radial inner side to seal the same.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pipe joint, and more particularly to a pipe joint that prevents a decrease in sealing performance when temperature changes.

  The pipe joint includes, for example, a pair of joint members having fluid passages communicating with each other and an annular gasket interposed between the butted end surfaces of the pair of joint members. There is known one in which a pair of joint members are coupled to each other by a male screw member provided in the joint member and a female screw member provided in the other joint member.

  In Patent Document 1, as shown in FIG. 10, a cylindrical sleeve 23 in which a fluid passage 23 a and an outward flange 23 d are formed, an annular joint member 22 in which a fluid passage 22 a and a male screw 22 b are formed, and a sleeve 23. And a gasket 26 supported by a retainer 27 interposed between opposing end surfaces of the annular joint member 22 is disclosed. The female screw member 25 has an inward flange 25 a that faces the outward flange 23 d of the sleeve 23, and is a nut that is fitted into the sleeve 23.

  A thrust bearing 28 for preventing rotation is provided between the outward flange 23d and the inward flange 25a.

  An annular protrusion 22C and an annular protrusion 23C are respectively formed on the opposing end surfaces of the tubular joint member 22 and the sleeve 23, and a male screw 22b formed on the annular joint member 22 and a female screw 25b formed on the female screw member 25 are screwed together. When tightened, the annular protrusions 22c and 23C press the gasket 26, and the gasket 26 is plastically deformed to be sealed.

JP 2007-155044 A

  The above-described conventional pipe joint is excellent in sealing performance by plastically deforming a gasket and performing surface sealing, and is used in various applications. When the outside air temperature decreases or when the fluid to flow is a cryogenic fluid, the surface pressure applied to the sealing member such as a gasket may decrease due to thermal contraction of the joint member or the piping material, and the sealing performance may deteriorate.

  For example, in a hydrogen station, since cryogenic gas of about minus 200 ° C. passes through the fluid passage of the pipe joint in the pipe, the pipe joint and the entire pipe to which the pipe joint is connected are cooled and heat shrinkage occurs. As a result, the axial surface pressure between the annular protrusion and the gasket is lowered, and there is a concern that the sealing performance is lowered.

  The present invention has been made in view of the above points, and an object of the present invention is a pipe joint for connecting joint members to each other. The object is to provide a pipe joint with excellent sealing performance that does not cause leakage.

  The pipe joint according to the present invention (1), which has been made to solve the above-mentioned problems, is either a pair of joint members having a fluid passage in at least one of them, a cylindrical gasket that seals a butt portion of both joint members, or one of them. In the pipe joint in which the male screw provided in the joint member or the male screw member and the female screw member provided in the other joint member are coupled, an annular recess is provided in at least one butt end surface of both the joint members, An annular space is formed when the joint members are brought into contact with each other. The gasket is accommodated in the annular space so that the inner peripheral surface of the gasket is along the inner peripheral surface of the recess. An annular buckling that is an elastic body that presses the gasket radially inward, and the buckling is in contact with the outer peripheral surface of the gasket and the outer peripheral surface of the recess. The axial width of the buckling that is housed in between and before the pipe joint is coupled is larger than the axial width of the annular space, and the pair of joint members are the male screw or the male screw. When combined with a member and the female screw member, the buckling extends in the radial direction and presses the gasket inward in the radial direction.

  According to the pipe joint of the present invention (1), an annular buckling that is an elastic body that presses the gasket radially inward is provided, and the buckling is in contact with the outer circumferential surface of the gasket and the outer circumferential surface of the recess. And accommodated in the annular space.

  The axial width of the buckling before the pipe joint is joined is larger than the axial width of the annular space, and when the pair of joint members are joined by the male screw or the male screw member and the female screw member The buckling extends in the radial direction and presses the gasket inward in the radial direction.

  With the pipe joint of the present invention (1), the force with which the buckling presses the gasket inward in the radial direction is orthogonal to the axial direction. However, since the surface pressure that presses the gasket inward in the radial direction does not decrease, it is possible to obtain a pipe joint that has excellent sealing properties against environmental changes due to temperature changes.

  This pipe joint according to the present invention (2) is the pipe joint according to the present invention (1), wherein the recess is provided in both of the pair of joint members.

  When both of the pair of annular joint members are formed into sleeves by the pipe joint of the present invention (2), it is only necessary to provide an annular recess of the same shape on both end faces, so the types of members are reduced. Can do.

  The pipe joint of the present invention (3) is the pipe joint of the present invention (1), wherein the recess is provided in one joint member, and the end surface of the other joint member is a flat surface.

  In the pipe joint of the present invention (3), it is only necessary to provide an annular recess only on one side of the pipe joint, so that the manufacturing cost can be reduced.

  The pipe joint of the present invention (4) is characterized in that the recess is provided in one joint member, and an end surface of the other joint member is provided with an annular convex portion facing the recess. It is a pipe joint of the present invention (1).

  In the pipe joint of the present invention (4), an annular recess is provided in one joint member, and an annular convex portion facing this recess is provided on the end face of the other joint member. The sealing property can be increased and the sealing property can be further improved.

  In the pipe joint of the present invention (5), the buckling is composed of one or a plurality of ring bodies, and the ring body has a radial cross-sectional shape with one end surface bulging with respect to the axial direction and the other end surface recessed. The one end surface and the other end surface are the pipe joints according to the present invention (1) to (4) that are smoothly connected.

  Since the back ring is composed of a plurality of ring bodies, the surface pressure directed radially inward can be generated at a plurality of locations at the interface with the gasket, so that the sealing performance can be further improved. In addition, the one end face is swollen with respect to such an axial direction, the other end face is recessed, and the one end face and the other end face are smoothly connected to each other. Can be easily converted to a force toward the surface, and a radial surface pressure can be generated.

  According to the pipe joint of the present invention, it is possible to provide a pipe joint having excellent sealing performance that does not cause fluid leakage even when the seal surface pressure in the axial direction is reduced due to a temperature change of the joint member or the like.

FIG. 1 is a longitudinal sectional view showing a first embodiment of a pipe joint according to the present invention. FIG. 2 is a longitudinal sectional view showing the vicinity of the seal portion before the pipe joint is joined in the first embodiment of the pipe joint according to the present invention. FIG. 3 is a longitudinal sectional view showing the vicinity of the seal portion after the pipe joint is joined in the first embodiment of the pipe joint according to the present invention. FIG. 4 is a longitudinal sectional view showing the vicinity of the seal portion before the pipe joint is joined in the second embodiment of the pipe joint according to the present invention. FIG. 5 is a longitudinal sectional view showing the vicinity of the seal portion after the pipe joint is joined in the second embodiment of the pipe joint according to the present invention. FIG. 6 is a longitudinal sectional view showing the vicinity of the seal portion before the pipe joint is joined in the third embodiment of the pipe joint according to the present invention. FIG. 7 is a longitudinal sectional view showing the vicinity of the seal portion after the pipe joint is joined in the third embodiment of the pipe joint according to the present invention. FIG. 8 is a diagram showing stress vectors generated around the seal portion generated after fastening of the pipe joint in the pipe joint of the first embodiment of the pipe joint according to the present invention. FIG. 9 is a diagram showing a stress vector generated around the seal portion generated after fastening of the pipe joint in the conventional pipe joint. FIG. 10 is a longitudinal sectional view of the pipe joint described in Patent Document 1.

  Embodiments of the present invention will be described below with reference to the drawings. In the following description, up, down, left, and right refer to up, down, left, and right in the drawings.

  FIG. 1 shows a first embodiment of a pipe joint according to the present invention, and this pipe joint 1A has a joint member 2 having a fluid passage 2a (hereinafter also referred to as a sleeve 2) and a fluid passage 3a. The joint member 3 (hereinafter also referred to as a sleeve 3), a female screw member 5 that is fitted from the right side of the sleeve 2, and a male screw member 4 that is fitted from the left side of the sleeve 3 are configured. The joint member 3 and the male screw member 4 may have an integral structure. Further, the joint member 3 integrally structured with the male screw member 4 may not be provided with the fluid passage 3a but may be a so-called closing plug integrated with the male screw member.

  A male screw 4a is formed at the right end of the male screw member 4, a female screw 5a is formed at the inner surface of the left end of the female screw member 5, and an inward flange 5b is formed at the right end. The pipe joint 1A is coupled by screwing the male screw 4a and the female screw 5a and fastening them. A thrust ring 8 for preventing rotation is provided between the outward flange 2b and the inward flange 5b. An outward flange 3 b is also formed at the butt end of the sleeve 3.

  As shown in FIG. 2, annular recesses 2c and 3c are formed on the butted end surfaces of the sleeve 2 and the sleeve 3, respectively, and both the recesses 2c and 3c have the same shape. An annular space 9 is formed by the recesses 2c and 3c.

  A gasket 6 and a back ring 7 are accommodated in an annular space 9. In the first embodiment shown in FIG. 1, as shown in FIG. 2, the buckling 7 is composed of a pair of ring bodies 7a and 7b, and these ring bodies 7a and 7b are arranged so that the concave surface sides face each other. However, the present invention is not limited to this, and the convex surfaces may be arranged so as to face each other.

  The ring bodies 7a and 7b have the same shape, and in the radial cross-sectional shape, one end surface is a gently convex surface bulging with respect to the axial direction, the other end surface is a concave concave surface, and the one end surface and the other end surface Is connected smoothly.

  The axial width d1 (see FIG. 2) of the back ring 7 before the pipe joint 1A is coupled is the width of the annular space when the sleeves 2 and 3 are brought into contact with each other. 3)).

  FIG. 3 shows the vicinity of the seal portion when the sleeves 2 and 3 are joined by tightening the male screw 4a and the female screw 5a from the state of FIG. As a result of this fastening, the ring bodies 7a and 7b are elastically deformed, and the cross-sectional side shape is flat.

  In FIG. 2, the ring bodies 7a and 7b constituting the back ring 7 have a lower end (inner peripheral side end) in contact with the outer peripheral surface of the gasket 6 and an upper end (outer peripheral side end) in contact with the outer peripheral surface of the recesses 2c and 3c. ing. When the sleeves 2 and 3 are coupled as shown in FIG. 3, the buckling 7 is shortened in the axial direction and expanded in the radial direction, and contact stress is generated inward and outward in the radial direction. The contact stress generated inward in the radial direction presses the gasket and is in contact with the inner peripheral surface of the gasket 6 and the lower ends (inner peripheral surfaces) of the recesses 2c and 3c in FIG. Contact stress is generated. In addition, the gasket 6 is compressed in the radial direction to extend in the axial direction and exhibits a sealing property in the axial direction.

  The gasket 6 is made of a nickel alloy and is silver-plated as necessary. As the material of the gasket 6, austenitic stainless steel, copper, an aluminum alloy, or the like is appropriately employed. The gasket can also be made of resin. In this case, a resin gasket can be disposed further inside the gasket 6 made of a metal such as a nickel alloy, so that the load in the radial direction of the backup ring 7 is received and the occurrence of stress relaxation is suppressed.

  The material of the back ring 7 is not particularly limited as long as the linear expansion coefficient is smaller than that of iron, but an invar alloy whose main component is an alloy of iron and nickel is preferable. According to this alloy, the linear expansion coefficient is about 1/10 of that of iron, and the amount of shrinkage is small even when cooled to a very low temperature. Therefore, the decrease in contact stress generated in the radial direction can be extremely small. it can. As described above, the shape of the backup ring 7 is such that one end surface is a convex surface and the other end surface is a concave surface, and this shape and dimensions are such that sufficient contact stress is applied to the gasket 6 even with slight heat shrinkage. It is designed to have a working shape and size.

  FIG. 4 shows the vicinity of the seal portion before the pipe joint is joined in the second embodiment. The difference from the first embodiment is that the annular recess 3 c is formed only in the sleeve 3, the butted end surface of the sleeve 2 is flat, and there is one back ring 7.

  In the second embodiment, it is only necessary to form the recess only in the sleeve on one side and only one buckling is required, so that the manufacturing cost can be reduced. Of course, a pair of bucklings 7 may be provided in the annular space 9 of the second embodiment as in the first embodiment. Note that the relationship between the width d1 shown in FIG. 4 and the width d2 shown in FIG. 5 is the same as that in the first embodiment. Also in the second embodiment, as in the first embodiment, the contact stress can be generated in the radial direction.

  FIG. 6 shows the vicinity of the seal portion before the pipe joint is joined in the third embodiment. The difference from the first embodiment is that an annular recess 3c is formed only in the sleeve 3, and an annular convex portion 2d that is fitted to face the recess 3c is provided on the butt end surface of the sleeve 2. The number of bucklings 7 is one.

  In the third embodiment, since the annular protrusion 2d fitted to the recess 3c is provided, the sealing performance of the annular space 9 is improved, and the sleeves 2 and 3 are coupled as shown in FIG. And the sealing performance can be further improved. Of course, a pair of bucklings 7 can be provided in the annular space 9 of the third embodiment as in the first embodiment. The relationship between the width d1 shown in FIG. 6 and the width d2 shown in FIG. 7 is the same as that in the first embodiment. In the third embodiment as well, the contact stress can be generated in the radial direction as in the first embodiment.

  FIG. 8 shows a contact stress vector generated around the seal portion after fastening of the pipe joint in the pipe joint according to the first embodiment of the present invention using the FEM analysis means.

  From this figure, it can be seen that radial contact stress is generated at six locations surrounded by a dotted circle. This axial contact stress is not significantly affected even when piping and joints are cooled to extremely low temperatures and thermally contracted, so that the sealing performance against temperature changes can be improved compared to conventional joints. it can.

  FIG. 9 shows a contact stress vector generated around the seal portion after fastening of the pipe joint in the conventional pipe joint pipe joint shown in FIG. 10 using the FEM analysis means.

  As can be seen from the diagram, the contact stress generated in the seal part is in the axial direction or close to the axial direction. It cannot be said that the seal against changes is good.

  As described above, the present invention can provide a pipe joint having a good sealing property by the contact stress generated in the radial direction even when the contact stress in the axial direction is reduced due to the temperature change.

1A: Pipe fitting (first embodiment)
1B: Pipe joint (second embodiment)
1C: Pipe joint (third embodiment)
2: Sleeve (joint member)
2a: Fluid passage 2c: Recess 3: Sleeve (joint member)
3a: Fluid passage 3b: Outward flange 3c: Recess 4: Male screw member 4a: Male screw
5: Female thread member 5a: Female thread 5b: Inward flange 6: Gasket 7: Buck ring 7a: Ring body 7b: Ring body 8: Thrust ring 9: Annular space

Claims (5)

A pair of joint members having a fluid passage on at least one side;
A cylindrical gasket that seals the butted portion of both joint members;
In a pipe joint in which a male screw provided in any one of the joint members or a male screw member and a female screw member provided in the other joint member are coupled,
An annular recess is provided in at least one butt end surface of the joint members, and an annular space is formed when the joint members are brought into contact with each other.
The gasket is accommodated in the annular space so that the peripheral surface of the gasket is along the inner peripheral surface of the recess,
An annular buckling that is an elastic body that presses the gasket radially inward is provided, and the buckling is accommodated in the annular space in contact with the outer circumferential surface of the gasket and the outer circumferential surface of the recess. ,
The axial width of the buckling before the pipe joint is joined is made larger than the axial width of the annular space,
When the pair of joint members are joined by the male screw or the male screw member and the female screw member, the buckling extends in the radial direction and presses the gasket inward in the radial direction.   The pipe joint according to claim 1, wherein the recess is provided in both of the pair of joint members.   The pipe joint according to claim 1, wherein the recess is provided in one joint member, and an end surface of the other joint member is a flat surface.   2. The pipe joint according to claim 1, wherein the recess is provided in one joint member, and an annular convex portion facing the recess is provided on an end surface of another joint member. The buckling is composed of one or a plurality of ring bodies, and the ring body has a radial cross-sectional shape with one end surface bulging with respect to the axial direction and the other end surface recessed, and the one end surface and the other end surface are The pipe joint of Claims 1-4 connected smoothly.

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