Pipe joint

Abstract

To provide a pipe joint that stably exerts strong anti-pipe drawing force and does not break locally.SOLUTION: A number of pipe-digging small irregularity parts 6 are formed in a region Y near an axial position L9 of a farther tip 9A of a recess groove 9 in an inner peripheral surface 7A of a sleeve 7.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a pipe joint. [Background technology]

[0002] The pipe fittings with the structures shown in Figures 12 to 14 are used for refrigerant piping because they are easy to connect and can reliably prevent external leakage of refrigerant gas, and are therefore popular and widely used in the industry (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5736499 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the conventional pipe joints shown in Figs. 12 to 14 have the following problems. That is, the outer peripheral grooves 59A, 59B of the sleeve 62 have sharp corners shaped like a baseball home base. In particular, the corners 60 at the innermost tips of the grooves 59A, 59B have a sharp shape (see FIG. 14). 12 and 14, the pipe connection is completed as shown in FIG. 13. However, cracks may occur at the original sharp corners 60. In particular, there is a risk of fatigue cracks occurring after long-term use. In addition, the angular home plate shape of the nut 40 causes the plastic deformation of the grooves 59A, 59B near the corners 60 when they bite into the outer circumferential surface of the pipe P, which is somewhat problematic.

[0005] Therefore, an object of the present invention is to solve these problems and prevent cracks from occurring in the innermost part of the sleeve groove during sleeve compression or even after a long period of use (after connection is complete.) Another object of the present invention is to provide a pipe fitting in which the groove smoothly undergoes plastic deformation while reliably biting into the outer circumferential surface of the pipe, thereby stably exerting a large pull-out resistance force. [Means for solving the problem]

[0006] The present invention comprises a fitting body with an external thread, a cap nut that is screwed onto the external thread of the fitting body, and a sleeve that is stored in the internal storage space of the cap nut and is compressively plastically deformable as the cap nut is screwed in; the sleeve has a groove with a home plate-shaped cross section on its outer surface; the innermost tip of the groove is formed in an arc shape with a predetermined radius; and the inner surface of the sleeve has a number of small irregularities for pipe engagement formed in an area near the axial position of the innermost tip of the groove.

[0007] Furthermore, if the groove width dimension of the groove is W9, the inner end of the nearby region in which the small uneven portion is formed is set at an axially inward position of 0.6·W9 to 1.0·W9 from the axial position of the deepest tip of the groove; and the outer end of the nearby region is set at an axially outward position of 0.1·W9 to 0.5·W9 from the axial position of the deepest tip of the groove.

[0008] In addition, the small uneven portion for pipe engagement comprises a parallel thread portion on the axial inner side with a constant thread groove depth and a tapered thread portion on the axial outer side with a thread groove depth that gradually decreases toward the tip; the boundary position between the parallel thread portion and the tapered thread portion is set to coincide with the axial position of the innermost tip of the groove, or to an axial inner position within twice the thread pitch.

[0009] In addition, the cross-sectional shape of the home plate-shaped groove is asymmetrical left and right, with the dimension to the inner side edge on the base end side of the sleeve set larger than the dimension to the outer side edge on the tip end side of the sleeve, based on the left and right dividing imaginary line passing through the deepest point of the innermost tip.

[0010] The cross-sectional shape of the grooves of the small uneven portion for pipe engagement is arc-shaped, and the cross-sectional shape of the projections is like Mount Fuji with a flat top. [Effects of the Invention]

[0011] According to the present invention, it is possible to prevent cracks from occurring from the inner peripheral surface of the sleeve to the tip of the recessed groove when the sleeve is compressed and deformed, thereby maintaining an excellent sealing state for a long period of time. Furthermore, since a large number of small uneven portions for cutting into the pipe are formed in the area near the axial position of the innermost tip of the groove, the large number of small uneven portions cut into the outer surface of the pipe (as the groove compresses), thereby exerting a stable force to prevent the pipe from being pulled out. In particular, by having many small uneven parts bite into the outer surface of the pipe (rather than one or two edges as in the past), the pull-out resistance force is distributed and borne, cleverly avoiding stress concentration and preventing cracks from occurring in the sleeve. Moreover, the pipe pull-out resistance force is the sum of the many protrusions that have bitten into the pipe, and can exhibit a value equal to or greater than the pull-out resistance force exerted by the conventional one or two edges. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a cross-sectional view showing one embodiment of the present invention, in which the upper half shows a state during connection with the sleeve uncompressed, and the lower half shows a state after connection has been completed with the sleeve compressed. [Figure 2] FIG. 2 is an enlarged view of the main part of the upper half of FIG. [Figure 3] FIG. 2 is an enlarged cross-sectional view of a main part of the sleeve. [Figure 4] FIG. 4 is a further enlarged cross-sectional view of a main part of the sleeve. [Figure 5] 10 is an enlarged cross-sectional view illustrating a main portion of a sleeve capable of compressive plastic deformation during construction. FIG. [Figure 6] FIG. 10 is an enlarged cross-sectional view of a main portion showing a state immediately before the completion of compressive deformation of the sleeve. [Figure 7] 1A to 1C are enlarged cross-sectional views of essential parts showing two specific examples of small uneven portions for pipe biting according to the present invention. [Figure 8] FIG. 10 is an enlarged cross-sectional view of a main part showing a comparative example of a sleeve. [Figure 9] 10 is an enlarged cross-sectional view of a main portion of a comparative example sleeve showing a state in which the sleeve is undergoing deformation while being subjected to a compressive force. FIG. [Figure 10] 10 is an enlarged cross-sectional view of a main part showing a state in which the sleeve of the comparative example is further deformed from the state of FIG. 9. FIG. [Figure 11] 11 is an enlarged cross-sectional view of a main part showing a state in which the sleeve of the comparative example is compressed and deformed from the state shown in FIG. 10, causing a defect. [Figure 12] FIG. 10 is a cross-sectional view showing a conventional example in an untightened state of the cap nut. [Figure 13] FIG. 10 is a cross-sectional view showing a conventional example in a state where the cap nut has been tightened. [Figure 14] 13A and 13B are enlarged views of a conventional example, in which (A) is an enlarged view of a main part of FIG. 12, and (B) is an enlarged view of a main part of (A). DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention will be described in detail below based on the illustrated embodiments. FIG. 1 shows one embodiment of the present invention, in which the upper half of the area above the axial line (center line) L0 shows the sleeve in an uncompressed state, and the lower half of the area below the axial line L0 shows the sleeve in a compressed state, indicating that the connection is complete. 2 is an enlarged view of the upper half of FIG. 1, and FIG. 3 shows only the sleeve 7 shown in FIG.

[0014] In Figures 1 to 3, the pipe fitting according to the present invention comprises a fitting body 1 with a male thread 2, a cap nut 3 that is screwed onto the male thread 2, and a metal compression plastic deformation sleeve 7 that is stored in the internal storage space 10 of the cap nut 3. The sleeve 7 has a single groove 9 having a home plate-shaped cross section on the outer peripheral surface 5 near the tip. In other words, while the conventional example (FIGS. 12 to 14) has two grooves 59A and 59B, the present invention reduces this to half (see FIG. 1).

[0015] The innermost tip 9A of the recessed groove 9 is formed in a rounded shape with a predetermined radius R1. Furthermore, L9 indicates the axial position of the deepest tip 9A of the recessed groove 9. On the inner circumferential surface 7A of the sleeve 7, a small uneven portion 6 for pipe engagement is formed in an area Y near the axial position L9.

[0016] Here, the cross-sectional shape of the home plate-shaped groove 9 will be described. The dimension W to the inner side edge 36 of the base end of the sleeve 7 is determined based on a left-right dividing imaginary line L9 (which may be referred to as the "axial position L9" in the description of the present invention) that passes through the deepest point Z9 of the innermost tip 9A of the innermost part. L The dimension W to the outer side edge 37 of the tip side of the sleeve 7 R In other words, W R <W L By setting the above, the cross-sectional shape of the recessed groove 9 is made asymmetrical.

[0017] Next, the vicinity region Y will be specifically described below. As shown in Figures 3, 4 and 7, the inner end 11 (in the axial direction) of the vicinity region Y is set to be located at an axially inward position of 0.6·W9 to 1.0·W9 from the axial position L9 of the innermost tip 9A of the recessed groove 9. That is, in Figure 4, 0.6·W9≦L 11 ≦ 1.0·W9 (W9 is the groove width dimension of the recessed groove 9.)

[0018] Furthermore, the outer end 12 (in the axial direction) of the vicinity region Y is set to be present at an axially outer position of 0.1·W9 to 0.5·W9 from the axial position L9 of the innermost tip 9A of the recessed groove 9. That is, 0.1·W9≦L 12 ≦ 0.5·W9. As described above, the vicinity region Y where the small concave and convex portions 6 are formed is unevenly distributed in the axial direction (from the axial position L9 of the innermost tip 9A of the recessed groove 9).

[0019] The small uneven portion 6 for pipe insertion is formed, for example, with a (pipe insertion) thread portion 20, and furthermore, is composed of a parallel thread portion 21 and a tapered thread portion 22. In FIG. 11 -ΔL) is the dimension range in which the parallel thread portion 21 is formed, and (L 12 +ΔL), a tapered thread portion 22 is formed.

[0020] The tapered thread portion 22 differs from a normal tapered thread. That is, the diameter of the thread groove bottom of the tapered thread portion 22 tapers, gradually decreasing axially outward. However, as is clear from Figures 4 and 7, the inner diameter of the tapered thread portion 22 does not change in the axial direction and is set to be the same as the inner peripheral surface 7A of the sleeve 7. In other words, the tapered thread portion 22 of the present invention has a thread depth that gradually decreases toward the tip.

[0021] The reason for providing the tapered thread portion 22, in which the thread groove depth gradually decreases toward the tip, will now be explained. That is, it is desired to reduce the diameter of the axial inner region first, using the axial position L9 as the reference, but to achieve this, it is not desirable to form grooves in the axial outer region. However, if grooves are only formed in the axial inner region, the pipe pull-out force resistance (force to prevent pipe coming out) will be insufficient. Therefore, it is unavoidable to form grooves in the axial outer region as well.

[0022] Therefore, a "tapered thread portion 22" is provided, in which the depth of the thread groove gradually decreases toward the tip (outward). Then, the boundary position B between the parallel thread portion 21 and the tapered thread portion 22 is set at an axially inner position with a minute dimension ΔL within twice the thread pitch P, or the boundary position B is made to coincide with the axial direction position L9.

[0023] It is desirable to cut and form the parallel thread portion 21 and the tapered thread portion 22 continuously. When cutting and forming the parallel thread portion 21 and the tapered thread portion 22, cutting is started with a cutting tool (cutting blade) from the parallel thread groove 21A at the left end shown in Figures 4 and 7(A), and the parallel thread portion 21 is cut to the boundary position B while feeding in the radial outward direction, and then the tapered thread portion 22 is cut and formed up to the outer end 12 (while gradually retracting the cutting tool).

[0024] 4 and 5, (desirably) the cross-sectional shape of the groove 20N of the small uneven portion 6 for pipe engagement is arc-shaped, and the cross-sectional shape of the convex portion 20T is a Mount Fuji shape with a flat top. When a compressive force F (F') is applied to the sleeve 7, as shown in FIGS. 5 and 6, the groove 9 undergoes compressive deformation, and the small convex portions 20T with a Mount Fuji cross-section engage the pipe 30. The sharp corners of the peaks of these small convex portions 20T engage the pipe 30, generating a stable and strong pipe pull-out resistance force.

[0025] When a compressive force F' is applied to the approximately home plate-shaped groove 9 as shown in Figure 5 when no external force is applied in the axial direction, the groove 9 is compressed in the axial direction, and ultimately reaches the state shown in Figure 6. That is, the area from the midpoint 9M of the depth of the compressed groove 9 to the tip 9A of the innermost portion forms an orthogonal plane perpendicular to the axis of the pipe 30. Moreover, the most reduced diameter portion (bottom dead center) T0 of the inner circumferential surface 7A of the sleeve 7 and the tip 9A of the innermost portion are positioned in the axial direction of the sleeve 7 (axial position).

[0026] As is clear from FIG. 6, the parallel thread portion 21 (see FIG. 4) corresponds to the inclined surface 15 axially inward of the narrowest diameter portion (bottom dead center) T0. On the other hand, as shown in FIGS. 4 and 6, a tapered thread portion 22 corresponds (is arranged) axially outward from the narrowest diameter portion (bottom dead center) T0.

[0027] In the comparative example shown in FIGS. 8 to 11, a sharp large edge 33 was present in the vicinity of the most reduced diameter portion (bottom dead center) T0, so when a large external force (compressive force) F was applied, a crack 34 formed in the direction of the arrow N as shown in FIG. 34 There was a problem where the following occurred: In the present invention, the occurrence of cracks is reliably prevented by having a large number of small protrusions 20T dig into the pipe 30 (to disperse stress) and avoiding stress concentration.

[0028] Next, the cross-sectional shape of the recessed groove 9 will be described. The recessed groove 9 shown in FIGS. 2 to 4 has the following cross-sectional shape. That is, the groove 9 has a home plate-shaped cross section, and the tip 9A of the innermost portion thereof is rounded with a predetermined radius R1. Furthermore, the opening angle of the tip 9A of the innermost portion is 90° to 120°. Further, at each of the side corners 25, 25 of the home plate-shaped groove 9, a small side recess 26 (cut-out shape) is formed.

[0029] It may be preferable to omit the small lateral recesses 26, 26 of the groove 9 (although not shown). Also, the cross-sectional shape of the groove 9 may be freely modified, for example, by forming the left and right gradient lines 9L, 9L leading to the innermost tip 9A of the groove 9 in a curved convex shape.

[0030] 7(B) shows another embodiment in which a plurality of independent annular grooves 24 are arranged in parallel instead of the parallel thread portion 21 described in FIG. 7(A). That is, the independent annular grooves 24 are shaped in a plane perpendicular to the axis and are arranged independently at a predetermined pitch. In addition, in FIG. 7(B), similarly to FIG. 7(A), the tapered thread portion 22 is provided in series.

[0031] As described above, the present invention comprises a fitting body 1 with a male thread 2, a cap nut 3 threaded onto the male thread 2 of the fitting body 1, and a sleeve 7 housed in the internal storage space 10 of the cap nut 3 and compressively plastically deformable as the cap nut 3 is threaded. The sleeve 7 has a groove 9 with a home plate-shaped cross section on its outer surface 5, the innermost tip 9A of the groove 9 is curved with a predetermined radius R1, and the inner surface 7A of the sleeve 7 has numerous small pipe-engaging irregularities 6 formed in an area Y near the axial position L9 of the innermost tip 9A of the groove 9. The engagement of the numerous small irregularities 6 reliably prevents cracks 34 due to stress concentration, as shown in Figures 8 to 11 of the conventional fitting. Moreover, even though the pullout-prevention force of each small irregularity 6 is small, the numerous protrusions collectively exert a strong (pipe) pullout resistance force.

[0032] Furthermore, in the present invention, when the groove width dimension of the groove 9 is W9, the inner end 11 of the nearby region Y where the small uneven portion 6 is formed is set at an axially inward position of 0.6·W9 to 1.0·W9 from the axial position L9 of the innermost tip 9A of the groove 9, and the outer end 12 of the nearby region Y is set at an axially outward position of 0.1·W9 to 0.5·W9 from the axial position L9 of the innermost tip 9A of the groove 9. Therefore, as shown in Figure 6, the small uneven portion 6 most effectively bites into the outer peripheral surface of the pipe 30. As a result, the inner slope 15 exhibits a strong pipe pull-out resistance force, as shown in Figure 6. Furthermore, by forming the outer end 12 of the small uneven portion 6 in a narrow range of 0.1·W9 to 0.5·W9, the biting deformation when deforming from FIG. 5 to FIG. 6 is smoothly carried out.

[0033] Furthermore, the small uneven portion 6 for pipe engagement comprises a parallel thread portion 21 on the axial inner side, which has a constant thread groove depth, and a tapered thread portion 22 on the axial outer side, which has a thread groove depth that gradually decreases toward the tip; the boundary position B between the parallel thread portion 21 and the tapered thread portion 22 is aligned with the axial position L9 of the innermost tip 9A of the groove 9, or is set at an axially inner position within twice the thread pitch P. Therefore, when the sleeve 7 is compressed as shown in Figure 6, a single parallel thread portion 21 with a large thread groove depth exists corresponding to the inner inclined surface 15, and strong pipe pull-out resistance can be effectively exerted.

[0034] The cross-sectional shape of the home plate-shaped groove 9 is determined by the dimension W from the left-right dividing imaginary line L9 passing through the deepest point Z9 of the innermost tip 9A of the innermost portion 9A to the inner side edge 36 of the base end of the sleeve 7. L The dimension W to the outer side edge 37 of the tip side of the sleeve 7 R Since the cross-sectional shape of the groove 9 is asymmetrical, the inner peripheral surface 7A of the axially inner portion of the pipe 30 is reduced in diameter and moves more rapidly than the inner peripheral surface 7A of the axially outer portion of the pipe 30, based on the imaginary dividing line L9. As a result, the parallel thread portion 21 is firmly (deeply) inserted into the pipe 30 (as shown in FIG. 6), and a strong pull-out resistance force is exerted.

[0035] Furthermore, the cross-sectional shape of the grooves 20N of the small uneven portion 6 for pipe engagement is arc-shaped, and the cross-sectional shape of the convex portions 20T is a Mount Fuji shape with a flat top, so the corners at the top of the convex portions 20T act as sharp edges and powerfully bite into the pipe 30. This provides a strong pull-out resistance. Moreover, cutting the grooves 20N into an arc shape is reliable and easy. [Explanation of symbols]

[0036] 1. Joint body 2 male threads 3 Cap nuts 5 Outer surface 6 Small uneven part for pipe insertion 7 Sleeve 7A Inner surface 9 Groove 9A Inner tip 10. Interior storage space 11 Inner end 12 Outer end 21 Parallel thread 21A Parallel thread groove at innermost position 22 Tapered thread 36 Inner side 37 Outer side B Boundary position L9 axial position (left and right dividing imaginary line) P thread pitch W9 groove width dimension W L ,W R size Y Neighborhood Z9 deepest point

Claims

1. The joint body (1) has a male thread (2), a cap nut (3) that is screwed onto the male thread (2) of the joint body (1), and a sleeve (7) that is housed in an internal housing space (10) of the cap nut (3) and is compressively plastically deformable as the cap nut (3) is screwed in. The sleeve (7) has a groove (9) on its outer circumferential surface (5) that has a cross section shaped like a home plate. The innermost tip (9A) of the recessed groove (9) has a predetermined radius (R 1 ) is formed in an arc shape, On the inner peripheral surface (7A) of the sleeve (7), the axial position (L 9 ) in a region (Y) adjacent to the first end (Y) of the pipe joint, a large number of small uneven portions (6) for pipe engagement are formed.

2. The groove width dimension of the recessed groove (9) is (W 9 ) then, The inner end (11) of the vicinity region (Y) where the small uneven portion (6) is formed is located at the axial position (L 9 ) to 0.6 W 9 or 1.0 W 9 is set at the axial inner position of The outer end (12) of the vicinity region (Y) is located at the axial position (L 9 ) to 0.1 W 9 or less than 0.5 W 9 The axial outward position of 2. The pipe joint of claim 1.

3. The small uneven portion (6) for pipe feeding has a parallel thread portion (21) on the axial inner side, which has a constant thread groove depth, and a tapered thread portion (22) on the axial outer side, which has a thread groove depth that gradually decreases toward the tip, The boundary position (B) between the parallel thread portion (21) and the tapered thread portion (22) is set at the axial position (L 9 ) or set at an axial inner position within twice the thread pitch (P) 3. A pipe joint according to claim 1 or 2.

4. The cross-sectional shape of the home plate-shaped groove (9) is such that the deepest point (Z 9 ) passing through the left and right dividing imaginary line (L 9 ) as a standard, The dimension (W) of the sleeve (7) to the inner side edge (36) on the base end side Ｌ ) to the outer side edge (37) at the tip end of the sleeve (7) (W Ｒ 4. A pipe joint according to claim 1, 2 or 3, wherein the cross-sectional shape of said recessed groove (9) is asymmetrical.

5. 5. A pipe joint according to claim 1, 2, 3 or 4, wherein the cross-sectional shape of the groove (20N) of the small uneven portion (6) for pipe engagement is arc-shaped, and the cross-sectional shape of the convex portion (20T) is Mount Fuji-shaped with a flat top.

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