JP4982447B2 - Resin pipe fitting - Google Patents

Description

  The present invention relates to a resin pipe joint having a structure in which a tube as a fluid transfer path is expanded (flared) and connected, and more specifically, in various technical fields such as semiconductor manufacturing, medical / pharmaceutical manufacturing, food processing, chemical industry, etc. It is also suitable for piping of high-purity liquid and ultrapure water handled in the manufacturing process, and relates to a resin pipe joint used as a connecting means of a tube that is a fluid device such as a pump, a valve, a filter, or a fluid transfer path. .

  As this type of resin pipe joint, a tube joint disclosed in Patent Document 1 is known. That is, the tube 1 made of synthetic resin is forcibly pushed into the inner tube portion 5 of the joint body 4 or, as shown in FIG. It fits in part 5. Then, the union nut 6 fitted in the tube in advance is screwed into the joint body, and is tightened to forcibly move in the axial direction of the joint body 4, so that the enlarged root portion 2 a of the tube 1 is edged. This is a structure in which the portion 6 a is pressed strongly in the axial direction to seal between the tube 1 and the inner cylinder portion 5.

  As the structure similar to the above-described structure, the one disclosed in FIGS. 8 and 9 of Patent Document 2 and the resin pipe joint disclosed in FIG. 6 of Patent Document 3 are known. As described above, the joint structure in which the tip of the tube is expanded (flared), fitted to the joint body, and fastened with a nut is the structure disclosed in FIG. 5 of Patent Document 2, FIG. 5 of Patent Document 3, and the like, Compared to a three-part tube fitting in which the tube end, which is externally expanded on the inner ring of the dedicated part, is fitted into the tubular receptacle of the joint body and fastened with a union nut, the joint body and union nut are fewer parts There is an advantage that a good sealing function can be obtained while economically constituting a pipe joint with two points.

  However, in the conventional resin pipe joint composed of two parts as described above, the tube end is expanded and firmly fitted, and the expanded root portion is tightened with a union nut. There was a tendency for the force to pull out the tube from the joint body to be relatively weak, probably because it was for the purpose of functioning. Although the tube itself is pulled out and moved, there is also a problem that the sealing point due to the pressing of the edge portion is also shifted and the sealing performance is adversely affected. In particular, when the resin pipe joint is formed of a resin material having a large expansion coefficient such as a fluororesin so as to handle a high temperature fluid of 100 ° C. or higher, those problems become more prominent.

Therefore, as disclosed in Patent Document 4, a drawing-proof means having a structure in which a C-shaped split ring is interposed between the tube enlarged portion and the union nut in a state of being fitted in the circumferential groove of the tube enlarged portion. It is known to provide a resin pipe joint that is strong not only for the sealing function but also for pulling out the tube. However, the resin pipe joint disclosed in Patent Document 4 requires a pre-treatment for forming a circumferential groove in the tube enlarged portion in advance, and the number of parts is increased to 3 parts. A new problem arises that the economic efficiency is impaired. Therefore, there is still room for further improvement in making the resin pipe joint consisting of the joint body and the union nut strong against pulling out without causing new problems. .
Noto 3041899 gazette Japanese Patent Laid-Open No. 7-27274 JP 2002-357294 A Noto 2587449 gazette

  In view of the above circumstances, an object of the present invention is a resin pipe that can achieve both a pull-out resistance and a good sealing property while being economical, consisting of a joint body and a union nut. The point is to provide a joint.

According to the first aspect of the present invention, in the resin pipe joint, the inner tube portion 4 that can be fitted and fitted by expanding the diameter of the end portion of the synthetic resin tube 3, and the tube 3 on the inner back side of the inner tube portion 4. A synthetic resin joint body 1 including a cover portion 6 having a radial gap m that allows entry, and a male screw portion 5; and
A female threaded portion 8 that can be screwed into the male threaded portion 5, and a sealing pressing portion that can act on the small diameter side portion of the expanded diameter changing region 9 in the expanded diameter portion 3 </ b> A that is externally fitted to the inner cylinder portion 4 of the tube 3 10 and a hook part 11 having a retaining pressing part 13 projecting so as to be displaceable in the radially inward direction and acting on the expanded diameter part 3A.
The joint body 1 of the union nut 2 in which the female screw portion 8 is screwed into the male screw portion 5 in a state where the tube 3 is externally fitted to the inner cylinder portion 4 to form the enlarged diameter portion 3A. The small diameter side portion of the diameter expansion change region 9 is pressed in the direction of the axis P by the seal pressing portion 10 and the hook portion 11 of the cover portion 6 is screwed in the direction of the shaft center P. The diameter-enlarged portion 3 </ b> A is set so as to be pushed radially by the retaining pressing portion 13 by entering the inside of the diameter and the male screw portion 8 is formed on the outer periphery of the cover portion 6. Is also formed.

According to a second aspect of the present invention, in the resin pipe joint according to the first aspect, the cover portion 6 has a flared inner peripheral surface 18 whose diameter increases toward the opening side end, and the radial gap. m is formed in the cover cylinder part which becomes a circumferential groove, and the hook part 11 has a pointed edge extending in the axial center P direction and facing the inner diameter of the tip part as the retaining pressing part 13. Formed in the arc-shaped hook portion 11A,
Due to the screwing of the union nut 2, the tip edge 13 bites into the enlarged diameter portion 3 </ b> A due to the inclined component force of the cantilevered arc-shaped hook portion 11 </ b> A coming into contact with the pointed inner peripheral surface 18. Thus, it is set so as to be pressed inward in the diameter.

  According to a third aspect of the present invention, in the resin pipe joint according to the first or second aspect, the inner cylindrical portion 4 includes a distal tapered portion 4A for gradually expanding the diameter of the tube 3, and the distal tapered portion. A straight cylinder portion 4B formed on the large diameter side of the cylindrical portion 4A, and a portion of the tube 3 where the diameter-enlargement changing region 9 covers the distal tapered portion 4A. In addition, the retaining pressing portion 13 is configured to act on the diameter-enlarging straight portion 12 fitted on the straight barrel portion 4B in the diameter-enlarging portion 3A. is there.

The invention according to claim 4 is the resin pipe joint according to claim 3, wherein the straight barrel portion 4B includes a first straight barrel portion 23 that continues to the large diameter side of the tip-constricted barrel portion 4A; A second straight cylinder part 24 having a diameter larger than that of the first straight cylinder part 23 and continuing to the anti-tip tapered cylinder part 4A side;
Due to the screwing of the union nut 2, the large-diameter straight that is externally fitted to the second straight cylinder portion 24 from the small-diameter straight portion 26 that is externally fitted to the first straight barrel portion 23 in the enlarged diameter portion 3 </ b> A. It is configured that the retaining pressing portion 13 is in contact with the diameter-expansion changing region 28 to the portion 27.

  The invention according to claim 5 is the resin pipe joint according to any one of claims 1 to 4, wherein both the joint body 1 and the union nut 2 are made of a fluororesin.

  According to the first aspect of the present invention, the seal portion is formed at the tip end portion of the inner cylinder portion, and will be described between the inner cylinder portion and the enlarged diameter portion. The tube and the joint body can be satisfactorily sealed without entering. As the union nut is tightened, the retaining pressing portion presses the expanded diameter portion in the radial direction, so that the expanded diameter portion is strongly held between the inner cylindrical portion and the retaining pressing portion and held. As a result, the function of effectively restricting the movement of the enlarged diameter portion in the direction of coming out of the inner cylinder portion in the axial direction is generated. As a result, it is possible to provide a resin pipe joint that can achieve both sufficient pull-out resistance and good sealing performance while being economical, consisting of two points of a joint body and a union nut.

  According to the first aspect of the present invention, the male screw portion and the insertion portion of the tube into the inner tube portion can be made to overlap each other in the axial direction, so that the union nut and the joint main body are screwed and connected. In addition, it is possible to provide a resin pipe joint having an advantage that the axial length can be reduced.

  According to the invention of claim 2, since the hook portion is displaced toward the inner diameter side as the union nut is tightened, the pointed edge presses so that the enlarged diameter portion bites into the outer peripheral portion. There exists an advantage that the said effect by invention of Claim 1 can be show | played, so that force may be strengthened more.

  According to the invention of claim 3, it is easy to carry out external fitting to the inner cylinder part by expanding the diameter of the tube using the tapered part of the tip, and the effect on the diameter expansion change region of the pressing part for sealing. The location and the location where the pressing portion for retaining the portion acting on the diameter change region are separated from each other in the axial direction, making it easier to clearly demonstrate the sealing function and the retaining function, respectively. There is an advantage that the effect of the invention of 2 can be strengthened

  According to the invention of claim 4, as will be described in detail in the section of the embodiment, the tip of the pressing portion for retaining in the expanded diameter changing region to the large diameter straight portion in the expanded diameter portion by screwing of the union nut. It is possible to provide a resin pipe joint that can be brought into a state where the side is brought into contact with each other and the diameter straight portion is firmly pressed in the radial direction by the retaining pressing portion, and the pull-out force can be further enhanced. it can.

  According to the invention of claim 5, since both the joint body and the union nut are formed of a fluorine-based resin having characteristics excellent in chemical resistance and heat resistance, even if the fluid is a chemical liquid or a chemical liquid, Or even if it is a high-temperature fluid, a joint structure part does not deform | transform and it becomes easy to leak, and favorable sealing property and drawing-out force can be maintained now. Note that the fluorine-based resin is preferable in that it is stable at high temperatures, excellent in water repellency, has a small coefficient of friction, has extremely high chemical resistance, and has high electrical insulation.

  Embodiments of a resin pipe joint according to the present invention will be described below with reference to the drawings. 1 is a cross-sectional view of a resin pipe joint according to Example 1, FIG. 2 is an enlarged cross-sectional view of the main part of the resin pipe joint of FIG. 1, FIG. 3 is a cross-sectional view of a resin pipe joint according to Example 2, and FIG. It is an expanded sectional view which shows the principal part of this resin pipe joint. The “inner back side” in the present specification is a definition of the back side in the direction of the axis P from the reference part (or part), and the axis in the object (eg, joint body 1). The central position in the direction of the heart P is not necessarily the deepest.

[Example 1]
As shown in FIGS. 1 and 2, the resin pipe joint A according to Example 1 includes a tube 3 made of a fluororesin (an example of a synthetic resin typified by PFA, PTFE, etc.), a fluid device such as a pump and a valve, A joint body 1 made of fluororesin (an example of a synthetic resin typified by PFA, PTFE, etc.) and a fluororesin (synthetic resin typified by PFA, PTFE, etc.) are connected to tubes of different diameters or the same diameter. An example) It is comprised by two parts with the union nut 2 made from. Each figure shows an assembled state in which the union nut 2 is tightened by a predetermined amount.

  As shown in FIGS. 1 and 2, the joint body 1 has an inner cylinder portion 4 at one end that can be externally fitted by expanding the diameter of the end portion of the tube 3, and an outer peripheral side of the inner back side portion of the four inner cylinder portion. A cover cylinder portion (an example of a cover portion) 6 having a circumferential groove (an example of a “radial gap”) m extending in the axis P direction so as to allow the tube 3 to enter, a male screw portion 5, It is formed in the cylindrical member provided with the taper external thread part (illustration omitted) of the other end, and the cylindrical space-like fluid path | route 7 with the axial center P. As shown in FIG. The inner cylinder part 4 has a straight shape having a tip tapered cylinder part 4A for gradually expanding the diameter of the tube 3 and a straight cylinder part 4B formed on the large diameter side of the tip tapered cylinder part 4A. Is formed.

  In the circumferential groove m, the outer peripheral surface that is the inner peripheral surface of the diameter is the outer peripheral surface 4b of the straight barrel portion 4B, and the inner peripheral surface that is the outer peripheral surface of the diameter is the inner peripheral surface 15 of the cover cylindrical portion 6. is there. A joint flange 1A is formed at a position away from the inner peripheral surface 21 of the circumferential groove m in the axial center P direction by a predetermined length, and the outer peripheral surface of the end portion of the cover cylinder portion 6 from the substantially root portion of the joint flange 1A. A male screw portion 5 is formed over the entire area. The tip surface of the inner cylinder part 4 is formed with a reverse taper angle that is closer to the inner inner side (the inner side in the direction of the axis P) toward the inner side in the radial direction. The shape of the liquid reservoir peripheral portion 17 due to the inner peripheral surface of the tube 3 being expanded and displaced toward the enlarged diameter portion (flare portion) is defined as the inner peripheral side expanded shape, and the fluid is stored in the liquid peripheral portion. 17 is difficult to stay. The cut surface 16 is formed so that the maximum diameter thereof is a substantially intermediate value between the inner diameter and the outer diameter of the tube 3 in the natural state, but this is not particularly concerned.

  In addition to the male threaded portion 5, the cover tube portion 6 is externally fitted with a radial gap to the enlarged straight portion 12 surrounded by the straight barrel portion 4B having a constant diameter in the enlarged diameter portion 3A (free outer fit). ) And a straight inner peripheral surface 15 parallel to the axis P, a pre-expanded inner peripheral surface (tip inner peripheral surface) 18 whose diameter increases toward the opening side end, and an outer peripheral side of the pre-expanded inner peripheral surface 18 And it has the small-diameter front-end | tip outer peripheral surface 19 following the tip of the external thread part 5. FIG.

  As shown in FIGS. 1 and 2, the union nut 2 includes an internal thread portion 8 that can be screwed into the external thread portion 5, and an expanded diameter changing region 9 in an expanded diameter portion 3 </ b> A that is externally fitted to the inner cylindrical portion 4 of the tube 3. A peripheral edge for sealing (an example of a pressing portion for sealing) 10 that can act on a small-diameter side end portion (an example of a “small-diameter side portion”), and a protrusion projecting so as to be displaceable in the radially inward direction. The hook portion 11 having a possible retaining pressing portion 13, the fitting inner peripheral surface 20 that fits inside the tip outer peripheral surface 19 of the cover tube portion 6, and the tube 3 following the sealing peripheral edge 10 And a guide tube portion 14 that surrounds a predetermined length in the P direction. The sealing peripheral edge 10 has an inner diameter substantially equal to the outer diameter of the tube 3, and the pressing surface 10 a is a side peripheral surface orthogonal to the axis P.

  The hook portion 11 extends in the axial direction following the pressing surface 10a of the peripheral edge 10 for sealing, and has a cantilevered arc-shaped hook portion 11A having a pointed edge 13 facing the inside of the diameter of the tip as a pressing portion for retaining. It is formed with a plurality. That is, for example, an arc-shaped hook that is arcuate when viewed in the direction of the axis P divided into eight locations in the circumferential direction at equal angles around the axis P so as to facilitate the oscillating displacement in the radial direction. The hook portion 11 is formed of eight portions 11A. The number of divisions may be other plural numbers, or may be the hook portion 11 composed of one cantilevered arc-shaped hook portion 11A that exhibits a C shape when viewed in the axial direction. Further, the hook portion 11 having a continuous circumferential shape that is not divided may be used as long as the diameter can be sufficiently reduced. Although not shown, the hook portion 11 when the union nut 2 is in a free state is in a posture that slightly swings outward from the state shown in FIGS. 1 and 2, and has a pointed edge 13 in its basic posture. Is set in a positional relationship slightly closer to the outer diameter than the outer peripheral surface of the tube 3 that is forcibly fitted to the inner cylinder portion 4, that is, the expanded diameter portion 3A.

  Each arcuate hook portion 11 </ b> A has a tapered outer peripheral surface 22 that can come into contact with the expanded inner peripheral surface 18, and the tapered hook portion 11 </ b> A is tapered due to screwing in the axial center P direction by tightening the union nut 2. The outer peripheral surface 22 expands and contacts the inner peripheral surface 18. As a result, the cantilevered arc-shaped hook portion 11A is oscillatingly displaced inwardly by the inclined component force caused by contact with the forwardly expanding inner peripheral surface 18, and the pointed edge 13 bites into the enlarged diameter portion 3A. It is pressed inward, thereby preventing the diameter-expanded portion 3A, that is, the tube 3 from pulling out from the inner cylinder portion 4 due to an external tensile force, etc. Means N are configured.

  Next, in order to externally insert and insert the end of the tube 3 into the inner cylinder portion 4, the tube 3 is forcibly pushed in at room temperature to expand the diameter, or it is easily heated and expanded using a heat source. Then, the tube end 3t is moved as shown in FIG. 1 by pushing it in, or by enlarging the tube end in advance using a diameter expander (not shown) and then pushing it into the inner cylinder part 4. Insert until it reaches almost the back side peripheral surface 21. As shown in FIGS. 1 and 2, the enlarged-diameter portion 3A that is externally fitted to the inner cylinder portion 4 includes an enlarged-diameter changing region 9 that is fitted on the outer peripheral surface 4a of the cylindrical portion 4A. It consists of the diameter-expanded straight part 12 fitted on the outer peripheral surface 4b of the barrel part 4B.

  That is, as shown in FIGS. 1 and 2, the joint main body 1 is formed by tightening the union nut 2 by screwing the female screw portion 8 with the male screw portion 5 in a state in which the tube 3 is externally fitted to the inner cylinder portion 4. The inner peripheral surface 20 is fitted on the outer peripheral surface 19 of the tip, and immediately after that, the outer peripheral surface 22 begins to bend forward and comes into contact with the inner peripheral surface 18. The sealing peripheral edge 10 starts to contact the end portion on the small diameter side of the diameter expansion change region 9. The arcuate hook portion 11A starts to swing radially inward with the base of the arcuate hook portion 11A as a fulcrum by the contact of the flared inner peripheral surface 18 with the tapered outer peripheral surface 22, and the pointed edge 13 moves in the radially inward direction. Start to move.

  Further, by performing screwing by tightening the union nut 2, as shown in FIG. 1 and FIG. 2, the retaining means N acts, and the arc-shaped hook portion 11A is largely displaced inwardly in the diameter. The pointed edge 13 strongly presses the enlarged diameter portion 3A into the outer peripheral surface 3a. Thereby, the state by which extraction from the inner cylinder part 4 of 3 A of enlarged diameter parts is prevented is obtained. At the same time, the end portion on the small diameter side of the diameter expansion change region 9 is strongly pressed in the direction of the axis P by the sealing peripheral edge 10, and the seal portion S that prevents leakage of fluid from between the tube 3 and the inner cylinder portion 4. Is formed. Note that the diameter of the fluid transfer path 3W of the tube 3 and the diameter of the fluid path 7 are set to be the same diameter in order to obtain a smooth fluid flow, but may be different from each other.

  That is, the axial center P direction of the joint body 1 of the union nut 2 in which the female screw portion 8 is screwed into the male screw portion 5 in a state where the tube 3 is externally fitted to the inner cylinder portion 4 to form the enlarged diameter portion 3A. The small diameter side portion of the diameter expansion change region 9 is pressed in the direction of the axis P by the sealing peripheral edge 10 and the hook portion 11 enters the inside diameter of the cover tube portion 6 due to the screwing to the inside. It is set so that the expanded diameter portion 3 </ b> A is pressed by the pointed edge 13 in the radial direction.

  As described above, only by performing the tightening operation of the union nut 2, excellent sealing performance by the seal portion S and excellent pull-out resistance by the retaining means N can be obtained. As a result, the flare-type resin pipe joint A composed of the joint body 1 and the union nut 2 can be easily assembled by a nut operation in a state where the tube is mounted on the inner cylinder portion, and has excellent assemblability. Thus, it has been realized as an improved structure that can achieve both excellent sealing performance by the seal portion S and excellent pull-out resistance by the retaining means N.

  Further, the retaining pressing portion 13 such as a pointed edge portion, which is a portion which is strongly in contact with the enlarged diameter portion 3A and is relatively easily worn or deformed, is not attached to the union nut 2 having a small figure but the joint body 1 having a large figure. Since it is formed, it has the following effects. That is, when replacement of parts due to inconvenience such as deformation of the retaining pressing portion 13 is necessary, the smaller part of the two parts constituting the resin pipe joint A, that is, the cheaper part. There is a rational and economical advantage that only the union nut 2 needs to be replaced.

[Example 2]
As shown in FIGS. 3 and 4, the resin pipe joint A according to the second embodiment is the resin pipe of the first embodiment except that the fitting portion between the inner cylindrical portion 4 and the enlarged diameter portion 3 </ b> A is a two-stage flare. It is the same as the joint A, and the same parts are denoted by the same reference numerals and the description thereof is made. The resin pipe joint A according to the second embodiment is intended to further enhance the pull-out resistance as a two-stage flare structure. Next, the differences will be described.

  That is, the straight barrel portion 4B has a first straight barrel portion 23 that continues to the large diameter side of the tip portion of the cylindrical portion 4A, and has a diameter larger than that of the first straight barrel portion 23, and the opposite tip end. It has a second straight cylinder portion 24 continuing to the narrow cylinder portion 4A side, and an enlarged outer peripheral surface 25 formed between them. Thereby, the diameter-expanded straight portion 12 includes a small-diameter straight portion 26 that is externally fitted to the first straight cylinder portion 23, a large-diameter straight portion 27 that is externally fitted to the second straight cylinder portion 24, and both the straights. It is formed in a two-stage shape having a second diameter expansion change region 28 between the portions 26 and 27.

  Then, as shown in FIGS. 3 and 4, as the union nut 2 is screwed, the peripheral edge 10 for sealing presses the end portion on the small diameter side of the diameter expansion change region 9 in the axis P direction and expands the diameter. The tip inclined surface 29 of the pointed edge 13 abuts on the second diameter expansion change region 28 in the portion 3A, and the pointed edge 13 bites into the tip portion of the small-diameter straight portion 26 so that an attached state can be obtained. Is set.

  That is, since the retaining means N is configured with a contact structure between the second diameter expansion change region 28 and the tip inclined surface 29, the number of parts is increased and the number of parts is increased as compared with the resin pipe joint A of the first embodiment. The pull-out force can be clearly improved without causing an increase in man-hours, and an even better resin pipe joint A is realized.

[Another Example]
The sealing pressing portion 10 has an intermittent circumferential edge divided into a plurality in the circumferential direction, a cross-sectional shape such as an angle of 80 degrees or 100 degrees, and other than 90 degrees (right angle) shown in FIG. An angle is also acceptable. The hook portion 11 can have a longer or shorter shape in the direction of the axis P, and the shape and size of the pointed edge 13 can be variously changed. 1 to 4, the outer peripheral end portion 2 a of the union nut 2 is drawn in contact with the side surface of the joint flange 1 </ b> A in a predetermined assembled state (a set tightening amount state). Is for convenience, and in practice, there is usually a gap in the axial direction so that retightening can be performed.

  As the synthetic resin, various resins such as PEEK (polyetheretherketone) and PP (polypropylene) can be used in addition to the fluororesin. Further, as the fluororesin, various types such as PTFE, PFA, PVDF, ETFE and the like are possible.

Sectional drawing which shows the structure of the resin pipe joint by Example 1 FIG. 1 is an enlarged sectional view showing the main part of FIG. Sectional drawing which shows the structure of the resin pipe joint by Example 2 FIG. 3 is an enlarged sectional view showing the main part of FIG.

DESCRIPTION OF SYMBOLS 1 Joint main body 2 Union nut 3 Tube 3A Expanded diameter part 4 Inner cylinder part 4A Tip tapered cylinder part 4B Straight trunk cylinder part 5 Male thread part 6 Cover part 8 Female thread part 9 Expansion diameter change area 10 Sealing pressing part 11 Hook part 11A Arc-shaped hook portion 12 Expanded straight portion 13 Detachable pressing portion, pointed edge 18 Pointed inner peripheral surface 23 First straight barrel portion 24 Second straight barrel portion 26 Small diameter straight portion 27 Large diameter straight portion P Shaft center m radial gap, circumferential groove

Claims (5)

An inner cylindrical portion that can be fitted to the end of the synthetic resin tube by expanding its diameter, and a cover portion that covers the inner cylindrical portion with a radial gap that allows the tube to enter inside. , A synthetic resin joint body provided with a male screw part, and
A female threaded portion that can be screwed into the male threaded portion, a sealing pressing portion that can act on the small diameter side portion of the expanded diameter changing region of the expanded diameter portion that is externally fitted to the inner cylindrical portion of the tube, and a radially inward direction A hook portion having a retaining pressing portion that protrudes displaceably and can act on the enlarged diameter portion, and has a union nut made of synthetic resin.
The union nut is screwed in the axial direction of the joint body by screwing the female threaded portion into the male threaded portion in a state where the tube is fitted on the inner cylindrical portion to form the enlarged diameter portion. Due to the advance, the small diameter side portion of the diameter expansion change region is pressed in the axial direction by the seal pressing portion, and the hook portion is pressed radially inward by entering the inside of the cover portion. A resin pipe joint in which an enlarged diameter portion is set to be pressed in a radial direction by the retaining pressing portion, and the male screw portion is also formed on the outer periphery of the cover portion . The cover portion has a flared inner peripheral surface whose diameter increases toward the opening side end, and the radial gap is formed in a cover tube portion serving as a circumferential groove, and the hook portion is formed in the axial direction. Is formed in a cantilevered arc-shaped hook portion having a pointed edge that extends to the inside of the diameter of the tip portion and serves as the retaining pressing portion,
Due to the screwing of the union nut, the tip edge is pressed inward as the tip edge bites into the enlarged diameter portion due to the inclined component force of the cantilevered arc-shaped hook portion in contact with the enlarged inner peripheral surface. The resin pipe joint according to claim 1, wherein the resin pipe joint is set to do.   The inner cylinder part is formed to have a tip tapered cylinder part that gradually expands the diameter of the tube, and a straight cylinder part formed subsequent to the large diameter side of the tip tapered cylinder part. The diameter expansion change region of the tube is a portion that covers the cylindrical portion with the distal end constricted, and the diameter increasing straight that the pressing portion for retaining is externally fitted to the straight barrel portion in the diameter expanding portion The resin pipe joint according to claim 1, wherein the resin pipe joint is configured to act on the portion. The straight cylinder part is a first straight cylinder part that continues to the large diameter side of the tip tapered cylinder part, and has a diameter larger than that of the first straight cylinder part, and its anti-tip tapered cylinder A second straight cylinder portion that follows the portion side,
Due to the screwing of the union nut, the diameter is increased from the small-diameter straight part fitted to the first straight cylinder part in the enlarged diameter part to the large-diameter straight part fitted to the second straight cylinder part. The resin pipe joint according to claim 3, wherein the retaining pressing portion is in contact with the change region . The resin pipe joint according to any one of claims 1 to 4, wherein the joint body and the union nut are both made of a fluororesin .

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